CN108598422A - Electrode, nonaqueous electrolyte battery, battery pack and vehicle - Google Patents

Abstract

According to one embodiment, a nonaqueous electrolyte battery includes a positive electrode (3), a negative electrode (4) and a nonaqueous electrolyte. The positive electrode ( 3 ) contains a compound represented by LiFe _1‑x Mn _x SO ₄ F having at least one crystal structure selected from the group consisting of hectorite and pyrosite, where 0≤x≤0.2. The negative electrode (4) contains a titanium-containing oxide.

Description

Electrodes, non-aqueous electrolyte cells, battery packs and vehicles

This application is a divisional application of the application No. 201310038915.7 and titled "Non-aqueous Electrolyte Battery and Battery Pack" submitted on January 31, 2013.

Cross References to Related Applications

This application is based on and claims priority from Japanese Patent Application No. 2012-074801 filed on March 28, 2012, the entire contents of which are incorporated herein by reference.

technical field

In general, the embodiments described herein relate to non-aqueous electrolyte cells and batteries.

Background technique

Lithium-ion batteries comprising a positive electrode containing a lithium-containing metal oxide such as LiCoO ₂ or LiMn ₂ O ₄ and a negative electrode containing a carbon-containing material that absorbs and releases lithium ion. However, batteries used in automobiles or power storage systems are required to have storage characteristics in high-temperature environments, float charge resistance, cycle life performance, high output power, safety, long-term reliability, etc. For this reason, for materials constituting positive and negative electrodes in lithium ion batteries, materials having excellent chemical stability and electrochemical stability are required. Someone has studied LiFePO ₄ as a cathode material. However, in this case, high-temperature durability and performance deterioration in a low-temperature environment become issues. For automotive applications, high performance in cold regions is also required, for example, high output performance and cycle life performance in low temperature environments (eg -40°C) are required. On the other hand, although lead storage batteries (12V) have long been widely used as batteries in automobile starters and storage systems, research has been conducted on alternatives to lead storage batteries to reduce battery weight and lead-free. However, batteries that replace lead storage batteries have not yet been realized.

Therefore, there are problems in high-temperature durability, float charge resistance, and low-temperature output performance for batteries installed in automobiles (vehicle applications) or power storage systems (stationary use) in place of lead storage batteries. It is difficult to install an existing battery instead of a lead storage battery in the engine room of a car as a starter power supply.

Contents of the invention

An object of this embodiment is to provide a nonaqueous electrolyte battery having excellent float charge resistance and low-temperature output performance.

According to one embodiment, a nonaqueous electrolyte battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode contains a compound represented by LiFe _1-x Mn _x SO ₄ F having at least one crystal structure selected from the group consisting of tavoraite and tavoraite, where 0≦x≦0.2. The negative electrode contains titanium-containing oxide.

According to this embodiment, a nonaqueous electrolyte battery having excellent float charge resistance and low-temperature output performance can be provided.

Description of drawings

FIG. 1 is a partially cutout sectional view showing a nonaqueous electrolyte battery of an embodiment;

Figure 2 is a side view showing the battery in Figure 1;

3 is a perspective view showing one embodiment of a battery module used in the battery pack of the embodiment;

4 is a graph showing the relationship between the depth of discharge and the battery voltage of the battery of Example 1 and the batteries of Comparative Examples 1, 2 and 5;

5 is a graph showing the relationship among the depth of discharge, positive electrode potential, and negative electrode potential of Examples 1 and 2 and Comparative Example 2. FIG.

Detailed ways

According to one embodiment, a nonaqueous electrolyte battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode contains a compound represented by LiFe _1-x Mn _x SO ₄ F having at least one crystal structure selected from hectorite and pyrosite, where 0≤x≤0.2. The negative electrode contains titanium-containing oxide.

Embodiments are explained below with reference to the drawings.

first embodiment

According to the first embodiment, there is provided a nonaqueous electrolyte battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte. The negative electrode contains titanium-containing oxide. Such negative electrodes have charge and discharge potential curves with high flatness, but the charge and discharge potentials suddenly change at their respective final stages. For this reason, if only an oxide having an olivine structure such as _LiFePO4 is used as a positive electrode active material, similar to the negative electrode, the charge and discharge potentials of the resulting positive electrode change abruptly at their respective final stages. Therefore, the voltage of batteries using such positive and negative electrodes also changes suddenly at the final stage of charge and the final stage of discharge, so it is difficult to detect capacity, SOC (state of charge), SOD (state of discharge), or depth of discharge from changes in battery voltage (DOD). The positive electrode in this embodiment contains a compound represented by LiFe _1-x Mn _x SO ₄ F having at least one crystal structure selected from the group consisting of a hectorite crystal structure and a pyrosite crystal structure (hereinafter referred to as lithium iron manganese compound), where 0 ≤ x ≤ 0.2, the positive electrode potential changes gradually in the last stage of charge and the last stage of discharge, respectively. When this positive electrode is combined with the negative electrode, the voltage change curve can be gentle at the last stage of charge and the last stage of discharge respectively, so it is easy to detect capacity, SOC, SOD or DOD by battery voltage change, and overcharge and overdischarge can be prevented .

According to this embodiment, it is possible to suppress the reaction between the positive electrode and the nonaqueous electrolyte in a high-temperature environment or during float charging, thereby suppressing the growth of a film produced on the surface of the positive electrode. Thereby, an increase in interfacial resistance on the positive electrode can be suppressed, and thus life performance in high-temperature charge-discharge cycles when floating charge up to 100% of SOC is performed can be improved. Also, the discharge rate performance in a low temperature environment (eg -20°C or lower) can be improved.

The intermediate voltage of the battery of this embodiment is about 2 V, which is almost equal to the value obtained for lead-acid batteries. Therefore, the battery of this embodiment has excellent compatibility with a lead storage battery, and a battery pack using a battery module in which 6 batteries of this embodiment are connected in series can realize a voltage of 12V, which can replace a lead storage battery. When the battery pack is installed in an engine room of an automobile instead of a lead storage battery, a smaller and lighter engine with a longer life can be obtained than in the case of using a lead storage battery.

In order to improve the output performance at low temperature, it is preferable to reduce the particle diameter of the lithium iron manganese compound. However, when the particle size of the lithium iron manganese compound decreases, the reactivity between the nonaqueous electrolyte and moisture becomes large. When at least a part of the surface of the lithium-iron-manganese compound particles is covered with a coating comprising at least one material selected from carbon materials, phosphorus compounds, fluorides, and metal oxides, the non-aqueous electrolyte can be reduced in the case of particle size reduction. Reactivity with moisture. Therefore, it is possible to suppress the oxidative decomposition reaction of the nonaqueous electrolyte and the reaction with moisture in the air in float charging up to 100% of SOC. When lithium-iron-manganese compound particles are used, this can greatly improve the cycle life performance of the battery and therefore the discharge rate performance of the battery at low temperature environments (eg –20°C or lower).

The positive electrode, negative electrode, nonaqueous electrolyte, separator, and container are explained below.

positive electrode

The positive electrode has a positive electrode current collector and a positive electrode material layer (layer containing a positive electrode active material), which is formed on one or both sides of the current collector, and contains a positive electrode active material, a conductive substance, and a binder.

The positive electrode active material comprises a compound represented by LiFe _1-x Mn _x SO ₄ F having at least one crystal structure selected from the group consisting of a hectorite crystal structure and a phosphosite crystal structure (lithium iron manganese compound), where 0≤ x≤0.2.

When the range of x exceeds 0.2, the properties of high-temperature durability, float charge resistance, and low-temperature output performance deteriorate. When x is in the range of 0≦x≦0.1, the hectorite crystal structure can be easily obtained. When x is in the range of 0.1<x≦0.2, the garlandite crystal structure can also be easily obtained. The lithium iron manganese compound with hectorite crystal structure can adjust the lithium absorption potential to 3.55V (vs. Li/Li ⁺ ). The lithium iron manganese compound with the phosphosidengite crystal structure can adjust the lithium absorption potential to 3.85 V (vs. Li/Li ⁺ ). The lithium absorption potential of lithium titanium oxide having a spinel structure represented by Li _4/3+x Ti _5/3 O ₄ is 1.55 V (vs. Li/Li ⁺ ), where 0≦x≦1. When a negative electrode containing a lithium titanium oxide having a spinel structure is combined with a positive electrode containing a lithium iron manganese compound having a hectorite crystal structure, an intermediate voltage of about 2 V can be realized, and thus a battery having an excellent performance with that of a lead storage battery can be realized. compatible batteries. Therefore, when the hedolithite crystal structure is employed, a battery having excellent high-temperature durability, float charge resistance, low-temperature output performance, and compatibility with lead storage batteries can be realized.

Preferably, the average primary particle diameter of the primary particles of the lithium iron manganese compound is in the range of 0.05 μm or more to 1 μm or less. Its more preferable range is 0.01 μm or more to 0.5 μm or less. When the primary particle diameter is in this range, the diffusion resistance of lithium ions in the active material can be reduced, thereby obtaining improved output performance. The lithium iron manganese compound may contain secondary particles in which primary particles are aggregated, with a size of 10 μm or less.

The lithium iron manganese compound can be synthesized by, for example, the following method.

FeSO ₄ .7H ₂ O and MnSO ₄ .H ₂ O are mixed in a predetermined stoichiometric ratio, and the mixture is dehydrated in vacuum at a temperature of 80° C. or higher to 150° C. or lower. Then, LiF was added thereto at a predetermined stoichiometric ratio, and the mixture was compression-molded into pellets. Then, the pellets are subjected to heat treatment at a temperature of 200° C. or higher to 350° C. or lower under a nitrogen atmosphere. The obtained product was pulverized into particles of a predetermined particle size under a dry atmosphere, thereby obtaining a lithium iron manganese compound. In this synthesis method, when x, that is, the molar ratio of Mn, is adjusted to a range of 0≤x≤0.1, a hectorite crystal structure can be obtained. Moreover, when x is adjusted to the range of 0.1<x≤0.2, the garlandite crystal structure can be obtained.

At least a part of the surface of the lithium iron manganese compound particles may be covered with a coating comprising at least one type of material selected from carbon materials, phosphorus compounds, fluorides, and metal oxides. The particles may be in any state of primary particles and secondary particles. The carbon material may include a carbonaceous material having a d ₀₀₂ of 0.344 nm or greater. The phosphorus compound may include lithium phosphate (Li ₃ PO ₄ ), aluminum phosphate (AlPO ₄ ), SiP ₂ O ₇ , and the like. The fluoride may include lithium fluoride (LiF), aluminum fluoride (AlF ₃ ), iron fluoride (FeF _x , where 2≦x≦3), and the like. Metal oxides may include Al ₂ O ₃ , ZrO ₂ , SiO ₂ , TiO ₂ , and the like.

The shape of the coating may include particles, layers, and the like. When the coating is in the form of particles, its particle diameter is preferably 0.1 μm or less, more preferably 0.01 μm or less. When the coating is layered in shape, its thickness is preferably 0.1 μm or less, more preferably 0.01 μm or less.

The amount of the coating is preferably 0.001% by weight or more and 3% by weight or less based on the amount of the lithium iron manganese compound. When the amount of the coating is 0.001% by weight or more, an increase in positive electrode resistance can be suppressed, resulting in improved output performance. On the other hand, when the amount of the coating is 3% by weight or less, an increase in interfacial resistance between the positive electrode and the nonaqueous electrolyte can be suppressed, resulting in improved output performance. The amount of coating is more preferably 0.01% by weight or more and 1% by weight or less.

The positive active material may contain materials other than the lithium iron manganese compound. Examples of other positive electrode active materials are various oxides and sulfides including, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide, lithium nickel composite oxide (such as Li _x NiO ₂ ), lithium cobalt composite oxide (such as Li _x CoO ₂ ), lithium nickel cobalt composite oxide (such as LiNi _1-yz Co _y M _z O _{2 )} , wherein M is at least one element selected from Al, Cr and Fe , 0≤y≤0.5 and 0≤z≤0.1), lithium manganese cobalt composite oxide (such as LiMn _1-yz Co _y M _z O ₂ , wherein M is at least one element selected from Al, Cr and Fe, 0 ≤y≤0.5 and 0≤z≤0.1), lithium manganese nickel composite compound (such as LiMn _x Ni _x M _1-2x O ₂ , wherein M is at least one element selected from Co, Cr, Al and Fe, and 1 /3≤x≤1/2, such as LiMn _1/3 Ni _1/3 Co _1/3 O ₂ or LiMn _1/2 Ni _1/2 O ₂ ), spinel lithium manganese nickel composite oxide (Li _x Mn _2-y Ni _y O ₄ ), lithium metal phosphorus oxide with olivine structure, iron sulfate (such as Fe ₂ (SO ₄ ) ₃ ), vanadium oxide (such as V ₂ O ₅ ), etc. In addition, it may also include conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, sulfur (S), organic materials such as carbon fluoride, and inorganic materials. When preferred ranges of x, y, and z are not described, a range of 0 or more to 1 or less is preferred. The positive active material may be applied alone or as a mixture of two or more thereof.

The conductive substance may include, for example, acetylene black, carbon black, graphite, carbon fiber, and the like.

The binder may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, and the like.

The mixing ratio of the active material, the conductive substance and the binder in the positive electrode is preferably such that the ratio of the positive electrode active material is in the range of 80 to 95% by weight, the ratio of the conductive substance is in the range of 3 to 19% by weight, and the binder The proportion of the mixture is in the range of 1 to 7% by weight.

The positive electrode can be obtained by, for example, suspending a positive electrode active material, a conductive substance, and a binder in a suitable solvent, coating an aluminum foil or an aluminum alloy foil of a current collector with the resulting suspension, drying it, and pressing it. The specific surface area of the positive electrode material in the BET method refers to the surface area per g of the positive electrode material layer (excluding the current collector weight), and it is preferably in the range of 0.1 m ² /g or more to 2 m ² /g or less.

The current collector may include aluminum foil, aluminum alloy foil, and the like. The thickness of the current collector is 20 μm or less, more preferably 15 μm or less.

negative electrode

The negative electrode has a negative electrode current collector and a negative electrode material layer supported on one or both sides of the current collector, and contains an active material, a conductive substance, and a binder.

The negative electrode active material contains lithium titanium oxide. Lithium titanium oxide may include lithium titanium oxide having a spinel structure represented by Li _4/3+x Ti _5/3 O ₄ , where 0≤x≤1; lithium titanium oxide having a bronze structure represented by Li _x TiO ₂ ( B) or titanium oxide of anatase structure, wherein 0≤x≤1 (composition before charging is TiO ₂ ); niobium titanium oxide represented by Li _x Nb _a TiO ₇ , wherein 0≤x, more preferably 0 ≤x≤1, and 1≤a≤4; and Li _2+x Ti ₃ O ₇ (0≤x≤1) with orthorhombite structure; Li _{1+ x} Ti ₂ O ₄ , where 0≤x≤1 ; Li _1.1+x Ti _1.8 O ₄ , where 0≤x≤1; Li _1.07+x Ti _1.86 O ₄ , where 0≤x≤1; etc. Preferred peptide oxides represented by Li _x TiO ₂ include TiO ₂ having an anatase structure and TiO ₂ (B) having a bronze structure. Low-crystalline oxides heat-treated at a temperature of 300 to 600° C. are also preferred. In addition to the above compounds, compounds in which a part of the Ti component in the lithium titanium oxide is substituted with at least one element selected from Nb, Mo, W, P, V, Sn, Cu, Ni and Fe may be used.

The average primary particle diameter of the primary particles of the negative electrode active material is in the range of 0.001 μm or more to 1 μm or less. Good properties can be obtained with particles of any shape, such as particles or fibers. The fiber diameter of the particles is preferably 0.1 μm or less.

Desirable negative electrode active materials have an average particle diameter of 1 μm or less and a specific surface area of 3 to 200 m ² /g, which is measured by N ₂ adsorption according to the BET method. This can further enhance the affinity of the negative electrode with the non-aqueous electrolyte.

The specific surface area (excluding the current collector) of the negative electrode material layer measured according to the BET method can be adjusted from 3 m ² /g or more to 50 m ² /g or less. The specific surface area is more preferably in the range of 5 m ² /g or more and 50 m ² /g or less.

The negative electrode (excluding the current collector) preferably has a porosity in the range of 20 to 50%. This can provide a negative electrode with high affinity with nonaqueous electrolyte and high density. The porosity is more preferably in the range of 25 to 40%.

The negative electrode current collector is preferably formed of aluminum foil or aluminum alloy foil.

The aluminum foil or aluminum alloy foil has a thickness of 20 μm or less, more preferably 15 μm or less.

The aluminum foil preferably has a purity of 99.99% by weight or greater.

Aluminum alloys containing at least one element selected from magnesium, zinc and silicon are preferred. However, it is preferable to adjust the content of transition metals such as iron, copper, nickel, or chromium to 100 ppm by weight or less.

The conductive substance may include, for example, acetylene black, carbon black, coke, carbon fiber, graphite, metal compound powder, metal powder, etc., and they may be used alone or as a mixture thereof. More preferable conductive substances may include coke, which is heat-treated at a temperature of 800° C. to 2000° C. and has an average particle diameter of 10 μm or less; graphite; acetylene black; and TiO, TiC, TiN, Al, Ni, Cu, Fe, etc. of metal powder.

Adhesives may include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, acrylic rubber, styrene butadiene rubber, core-shell adhesives, and the like.

The mixing ratio of the active material, the conductive substance and the binder in the negative electrode is preferably such that the proportion of the negative electrode active material is in the range of 80 to 95% by weight, the proportion of the conductive substance is in the range of 1 to 18% by weight, and the binder The proportion of the mixture is in the range of 2 to 7% by weight.

The negative electrode can be prepared by, for example, suspending the negative electrode active material, conductive substance, and binder in a suitable solvent, coating a current collector with the resulting suspension, drying it, and hot pressing.

non-aqueous electrolyte

The nonaqueous electrolyte may include a liquid nonaqueous electrolyte prepared by dissolving an electrolyte in an organic solvent; a gel nonaqueous electrolyte in which an organic solvent and a polymeric material are combined; and a solid nonaqueous electrolyte in which a lithium salt electrolyte and a polymeric material are combined. Room-temperature molten salts containing lithium ions (in an ionic state) can also be used as nonaqueous electrolytes. Polymeric materials may include, for example, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

As the liquid nonaqueous electrolyte, organic electrolyte solutions and room temperature molten salts (ionic liquids) having a solidification point of -20°C or lower and a boiling point of 100°C or higher are preferable.

The liquid nonaqueous electrolyte is prepared by dissolving the electrolyte in an organic solvent at a concentration of 0.5 to 2.5 mol/L.

The electrolyte may include, for example, LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , Li(CF ₃ SO ₂ ) ₃ C , LiB[(OCO) ₂ ] ₂ and so on. The kind of electrolyte used may be one kind or two or more kinds. An electrolyte including at least one of LiPF ₆ and LiBF ₄ is preferred. Such electrolytes enhance the chemical stability of organic solvents, can reduce film resistance on the negative electrode, and can significantly improve low-temperature performance and cycle-life performance.

Organic solvents can include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC) and methyl ethyl carbonate Esters (MEC); linear ethers, such as dimethoxyethane (DME) and diethoxyethane (DEE); cyclic ethers, such as tetrahydrofuran (THF) and dioxane (DOX); ester (GBL), acetonitrile (AN) and sulfolane (SL). These organic solvents may be used alone or in admixture of two or more. Organic solvents containing at least one solvent selected from propylene carbonate (PC), ethylene carbonate (EC) and γ-butyrolactone (GBL) are preferred because the nonaqueous electrolyte has a boiling point of 200° C. or higher and thus is in It has high thermal stability when used. When the organic solvent contains at least one solvent selected from the group consisting of γ-butyrolactone (GBL), diethoxyethane (DEE) and diethyl carbonate (DEC), lithium salts can be used in high concentrations, thus enhancing Output performance in low temperature environment. The lithium salt is preferably dissolved at a concentration ranging from 1.5 to 2.5 mol/L relative to the organic solvent. This concentration range provides high output power even in low temperature environments.

A room temperature molten salt refers to a salt at least a portion of which exhibits a liquid state at room temperature, and room temperature refers to a temperature range in which a power source can generally be regarded as operating. A power supply can generally be considered to operate in a temperature range that has an upper limit of about 120°C, sometimes about 60°C, and a lower limit of about -40°C, sometimes about -20°C. Among them, a range of -20°C or higher to 60°C or lower is suitable. The room temperature molten salt (ionic melt) is preferably formed of lithium ions, organic substance cations and organic substance anions. In addition, the room temperature molten salt is desirably in a liquid state at room temperature or lower.

Organic substance cations include alkylimidazolium ions having a skeleton shown in Chemical Formula 1 below, and quaternary ammonium ions.

Preferred alkylimidazolium ions may include dialkylimidazolium ions, trialkylimidazolium ions, tetraalkylimidazolium ions. Preferred dialkylimidazolium may include 1-methyl-3-ethylimidazolium ion (MEI ⁺ ). Preferred trialkylimidazolium ions may include 1,2-diethyl-3-propylimidazolium ions (DMPI ⁺ ). Preferred tetraalkylimidazolium ions may include 1,2-diethyl-3,4(5)-dimethylimidazolium ions.

Preferred quaternary ammonium ions may include tetraalkylammonium ions and cyclic ammonium ions. Preferred tetraalkylammonium ions may include dimethylethylmethoxyethylammonium, dimethylethylmethoxymethylammonium, dimethylethylethoxyethylammonium, and trimethylammonium propylammonium ion.

When alkylimidazolium ions or quaternary ammonium ions (especially tetraalkylammonium ions) are used, the melting point can be adjusted to 100°C or lower, more preferably 20°C or lower, and the reactivity with the negative electrode can be further reduced .

The concentration of lithium ions is preferably 20 mol% or less, more preferably 1 to 10 mol%. When the concentration is adjusted to the above range, a liquid room temperature molten salt can be easily obtained even at a low temperature such as 20° C. or lower. In addition, the viscosity can be reduced even at room temperature or lower, leading to enhanced ionic conductivity.

As the anion, preferably at least one selected from BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , (FSO ₂ ) Anions of ₂ N ^– , N(CF ₃ SO ₂ ) ₂ ^– , N(C ₂ F ₅ SO ₂ ) ₂ ^– and (CF ₃ SO ₂ ) ₃ C ^– . When multiple types of anions coexist, a room-temperature molten salt having a melting point of 20° C. or lower can be easily formed. More preferred anions may include BF ₄ ⁻ , (FSO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ^{2 −} , N(CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ^– and (CF ₃ SO ₂ ) ₃ C ^– . When these anions are used, room temperature molten salts can be more easily obtained at 0°C or lower.

diaphragm

A separator may be located between the positive electrode and the negative electrode. As the separator, for example, a synthetic resin nonwoven fabric, a cellulose nonwoven fabric, or a polyolefin porous film (for example, a polyethylene porous film and a polypropylene porous film) can be used. Preferred separators include polyolefin porous films and cellulose fiber non-woven fabrics.

The separator preferably has a porosity of 50% or less.

Preferably, the separator has a thickness of 10 to 100 μm and a density of 0.2 to 0.9 g/cm ³ .

When the physical properties are within the above ranges, a good balance between increase in mechanical strength and decrease in battery resistance can be obtained, and a battery having properties of high output power and reduced internal short circuit can be provided. Thermal shrinkage in a high-temperature environment is small, and good high-temperature storage characteristics can be obtained.

Cellulose fiber membranes with a porosity greater than 60% are preferably used. The separator may be in the state of nonwoven fabric, film, paper, or the like with a fiber diameter of 10 μm or less. In particular, a cellulose fiber separator having a porosity of 60% or more has good impregnation ability with electrolytes, and can exhibit high output performance at low to high temperatures. A more preferred range is 62% to 80%. In addition, in long-term storage, the cellulose fiber separator with a porosity of 60% or more does not react with the negative electrode in the charged state, float charge, and overcharge, and can prevent dendrite deposition caused by lithium metal. internal short circuit. Also, when the fiber diameter is 10 μm or less, the affinity with the nonaqueous electrolyte is improved, resulting in reduced battery resistance. The fiber diameter is more preferably 3 μm or less.

container

A container formed of a metal or a thin film can be used as a container for accommodating a positive electrode, a negative electrode, and a nonaqueous electrolyte.

A container formed of aluminum, aluminum alloy, iron, or stainless steel and having a rectangular or cylindrical shape can be used as the metal container. The desired plate thickness of the container is 0.5 mm or less, more preferably 0.3 mm or less.

The sheet film may include, for example, a multilayer film in which an aluminum foil is covered with a resin film or the like. Examples of resins may include polymers such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The thickness of the thin film is preferably 0.2 mm or less. The aluminum foil preferably has a purity of 99.5% by weight or higher.

It is preferable to form a metal can of an aluminum alloy from an alloy containing at least one element selected from manganese, magnesium, zinc and silicon and having a purity of 99.8% by weight or more of aluminum. The strength of metal cans made of aluminum alloys can be significantly increased, so that their wall thickness can be reduced. Thereby, a thin and light battery with high output power and excellent heat radiation properties can be realized.

A rectangular secondary battery according to an embodiment of the present invention is shown in FIGS. 1 and 2 . As shown in FIG. 1 , an electrode group 1 is placed in a rectangular cylindrical metal container 2 . The electrode group 1 has a structure in which a positive electrode 3, a negative electrode 4, and a separator 5 interposed therebetween are spirally wound so that the resulting product has a planar shape. A non-aqueous electrolyte (not shown in the figure) is placed in the electrode group 1 . As shown in FIG. 2 , portions of the edge of the positive electrode 3 located on the edge face of the electrode group 1 are each electrically connected to a strip-shaped positive electrode lead 6 . Also, portions of the edge of the negative electrode 4 located on this edge face are each electrically connected to a strip-shaped negative electrode lead 7 . A plurality of positive lead wires 6 are bundled together in a group, which is electrically connected to a positive conductive contact 8 . The positive terminal is formed by a positive lead 6 and a positive conductive contact 8 . Negative lead wires 7 are bundled together in a group, which are electrically connected to negative conductive contacts 9 . The negative terminal is formed by a negative lead 7 and a negative conductive joint 9 . The metal sealing plate 10 is fixed to the opening of the metal container 2 by welding or the like. The positive-electrode conductive tab 8 and the negative-electrode conductive tab 9 are each pulled out through holes provided in the sealing plate 10 . The inner circumferential surface of each hole in the sealing plate 10 is covered with an insulating member to avoid a short circuit caused by contact with the positive electrode conductive tab 8 or the negative electrode conductive tab 9 .

The type of battery is not limited to a rectangular battery, and various types of batteries including cylindrical batteries, thin batteries, coin-shaped batteries, and the like can be prepared. In addition, the shape of the electrode group is not limited to a planar shape, and may be formed in a cylindrical shape, a sheet shape, or the like.

The first embodiment explained above _includes a _negative electrode comprising a titanium- _containing oxide; A compound of a crystal structure of ferromanganese crystal structure, in which 0≤x≤0.2, so it is possible to provide a nonaqueous electrolyte battery which has excellent high-temperature durability, float charge resistance, and low-temperature output performance, and has compatibility with lead-acid batteries , its capacity, SOC, SOD and DOD can be easily detected.

second embodiment

The battery pack of the second embodiment includes one or more of the nonaqueous electrolyte batteries of the first embodiment. A battery pack may have a battery module including a plurality of batteries. The batteries may be connected in series or in parallel, and n groups (n is an integer of 1 or more) of 6 batteries connected in series are particularly preferred. When using _a positive electrode comprising a compound having a hectorite crystal structure represented by _{LiFe1- xMnxSO4F} where 0≤x≤0.1 and a negative electrode comprising lithium titanium oxide having a spinel structure, it is possible to obtain A battery with an intermediate voltage of 2V. In this case, if n groups of 6 cells are connected in series and the value of n is 1, the voltage of the group of 6 cells in series becomes 12V, thereby significantly improving the compatibility with the lead storage battery group. In addition, the voltage curve of the battery using the above-mentioned positive and negative electrodes has an appropriate slope, so its capacity, SOC, SOD, and DOD can be easily detected only by monitoring the voltage, similar to the lead storage battery. Therefore, even in a battery pack in which the number of battery series is n times six, the influence of variations between points can be reduced, and it is possible to control the battery only by monitoring the voltage.

An embodiment of a battery module for a battery pack is shown in FIG. 3 . The battery module 21 shown in FIG. 3 has a plurality of rectangular secondary batteries 22 ₁ to 22 ₅ of the first embodiment. The positive conductive joint 8 of the secondary battery 22 ₁ is electrically connected to the negative conductive joint 9 of the secondary battery 22 ₂ adjacent to the battery 22 ₁ through a lead wire 23 . In addition, the positive conductive terminal 8 of this secondary battery 22 ₂ is electrically connected to the negative conductive terminal 9 of the secondary battery 22 ₃ adjacent to the battery 22 ₂ through a lead wire 23 . The secondary batteries 22 ₁ to 22 ₅ are connected in series in this way.

As a case for accommodating a battery module, a metal can formed of aluminum alloy, iron, or stainless steel, and a plastic container may be used. The container preferably has a plate with a thickness of 0.5 mm or more.

The embodiment of the battery pack can be freely changed according to the application. The battery pack is preferably used for a battery pack expected to have cycle performance at a large current. In particular, it is preferably used for a power source of a digital camera, and for automotive use such as, for example, a 2-wheel to 4-wheel hybrid electric vehicle, a 2-wheel to 4-wheel electric vehicle, or a moped. It is preferably used in automotive applications.

The second embodiment has the non-aqueous electrolyte battery of the first embodiment, so it is possible to realize a battery pack which is excellent in high-temperature durability, float charge resistance, and low-temperature output performance, and has compatibility with a lead storage battery pack, Its capacity, SOC (state of charge), SOD (state of discharge) or DOD (depth of discharge) can be easily detected.

Example

Embodiments are explained in detail below with reference to the accompanying drawings.

Example 1

After FeSO ₄ .7H ₂ O and MnSO ₄ .H ₂ O were mixed in a predetermined stoichiometric ratio and the mixture was vacuum dehydrated at 90° C., LiF in a predetermined stoichiometric ratio was added thereto, and the mixture was compression-molded into pellets. Then, the pellets were treated at 290° C. for 24 hours in a nitrogen atmosphere, thereby obtaining LiFe _0.95 Mn _0.05 SO ₄ F having a hectorite crystal structure and an average primary particle diameter of 0.3 μm. The crystal structures of the synthesized compounds were identified by the Rietveld method and X-ray diffraction patterns.

The positive electrode was prepared using LiFe _0.95 Mn _0.05 SO ₄ F obtained in the following method. Carbon particles having an average particle diameter of 0.005 μm were bonded to the surface of the LiFe _0.95 Mn _0.05 SO ₄ F particles in a bonding amount of 0.1% by weight (based on 100% by weight of LiFe _0.95 Mn _0.05 SO ₄ F). 5% by weight (based on the amount of the positive electrode) of graphite powder as a conductive substance and 5% by weight (based on the amount of the positive electrode) of PVdF were mixed with the obtained positive electrode active material, and the mixture was dispersed in N-methylpyrrolidone (NMP) solvent to prepare a slurry. Both surfaces of an aluminum alloy foil (purity: 99% by weight) having a thickness of 15 μm were coated with the obtained slurry, dried, and after a pressing step, a positive electrode was prepared having positive electrode material layers each having a thickness of 43 μm and The electrode density was 2.2 g/cm ³ . The specific surface area of the positive electrode material layer was 5 m ² /g.

Respectively, Li _4/3 Ti _{5/ 3} O ₄ powder with an average primary particle diameter of 0.8 μm and a BET specific surface area of 10 m ² /g, graphite powder with an average particle diameter of 6 μm were used as conductive substances, and PVdF was used as The binder was mixed in a weight ratio of 95:3:2, and the mixture was dispersed in N-methylpyrrolidone (NMP), and the dispersion was stirred with a ball mill at a speed of 1000 rpm and a stirring time of 2 hours to prepare slurry. An aluminum alloy foil (purity: 99.3% by weight) with a thickness of 15 μm was coated with the obtained slurry, dried, and after a hot pressing step, an anode was prepared having an anode material layer each having a thickness of 59 μm and an electrode density of 2.2 g/cm ³ . The negative electrode porosity excluding the current collector was 35%. The BET specific surface area (surface area per g of the negative electrode material layer) of the negative electrode material layer was 5 m ² /g.

Methods for measuring the particles of the positive electrode active material and the negative electrode active material are as follows.

The particle measurement of the active material was carried out using a laser diffraction particle size analyzer (Shimadzu SALD-300) by the following method: first, about 0.1 g of the sample, a surfactant, and 1 to 2 mL of distilled water were added to a beaker; the mixture was stirred well; the mixture was poured into a stirred bath; measure the distribution of luminescence intensity 64 times at 2 second intervals; and analyze the particle size distribution data.

The BET specific surface area was measured by _N2 adsorption under the following conditions.

As samples, 1 g of powdered active material or 2 × 2 ^cm slices of two electrodes (positive or negative) were used. A BET specific surface area measuring device manufactured by Yuasa-Ionics Co., Ltd. was used, and nitrogen gas was used as an adsorption gas.

Separately, the positive electrode was covered with a regenerated cellulose fiber separator having a thickness of 30 μm, a porosity of 65%, and an average fiber diameter of 1 μm, and was formed from the pulp as a starting material, and the negative electrode was placed on the resulting positive electrode. The ratio (Sp/Sn) of the area of the positive electrode material layer (Sp) to the area of the negative electrode material layer (Sn) was 0.98, and the edge of the negative electrode material layer protruded from the edge of the positive electrode material layer. The positive electrode, the negative electrode, and the separator are wound helically, thereby producing an electrode group. At this time, the electrode width of the positive electrode material layer (Lp) was 50 mm, and the electrode width of the negative electrode material layer (Ln) was 51 mm, and Lp/Ln was 0.98.

The electrode group was pressed into a planar shape. The resulting electrode group was placed in a container of a thin metal can having a thickness of 0.25 mm and formed of an aluminum alloy (Al purity 99% by weight).

Separately, the liquid nonaqueous electrolyte (nonaqueous electrolyte solution) was prepared by dissolving 1.5 mol/L lithium tetrafluoroborate (LiBF ₄ ) as a lithium salt in propylene carbonate (PC) and γ-butyrolactone ( GBL) in a mixed solvent (volume ratio of 1:1). The boiling point of the non-aqueous electrolyte is 220°C. The nonaqueous electrolyte was poured into the electrode group in the container, thereby producing a rectangular nonaqueous electrolyte secondary battery having a thickness of 10 mm, a width of 50 mm, and a height of 90 mm, and having the structure described above in FIG. 1 .

Example 2

After mixing FeSO ₄ ·7H ₂ O and MnSO ₄ ·H ₂ O in a predetermined stoichiometric ratio, the mixture was vacuum dehydrated at 90 °C, and a stoichiometric ratio of LiF was added thereto, and the mixture was compression molded into pellets. Then, the pellets were heat-treated at 290° C. for 24 hours under a nitrogen atmosphere. The obtained product was pulverized in a dry atmosphere, thereby obtaining LiFe _0.85 Mn _0.15 SO ₄ F having a jasperite crystal structure, and the average primary particle diameter of the primary particles was 0.3 μm. The crystal structure of the synthesized compound was confirmed in the same manner as in Example 1.

Li ₃ PO ₄ particles having an average particle diameter of 0.005 μm were bonded to the surface of the obtained LiFe _0.85 Mn 0.15 SO ₄ F particles in a bonding amount of 0.1% by weight (based on 100% by weight of LiFe _0.85 Mn _{0.15 SO 4 F} ). A nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except for using the obtained positive electrode active material.

Examples 3 to 10 and Comparative Examples 1 to 4

Rectangular secondary batteries were prepared in the same manner as described in Example 1 above, except that the positive electrode active material, negative electrode active material, and nonaqueous electrolyte shown in Table 1 below were used.

Comparative Example 5

In Comparative Example 5, a commercially available lead storage battery (nominal capacity: 3.4 Ah, 12 V, 1.2 kg) was used.

When charging at 25°C with a constant current of 1C to 2.4V and at a constant voltage of 2.4V (charging time is 3 hours), and then discharging it at 1C to 1.5V, measured in Examples 1 to 10 and Comparative Example 2 The discharge capacity and intermediate voltage (battery voltage) of each secondary battery were obtained.

In Comparative Examples 1, 3 and 4, at 25°C, when charging at 1C constant current to 4.2V and at 4.2V constant voltage (charging time is 3 hours), and then discharging it at 1C to 3.0V, measured The discharge capacity and intermediate voltage (battery voltage) of the battery.

In Examples 1 to 10 and Comparative Examples 1 to 4, battery packs were obtained by preparing battery modules in which 6, 5 or 3 batteries obtained in each of Examples 1 to 10 and Comparative Examples 1 to 4 were connected in series. The number of secondary battery series in the battery pack is set to the number of secondary batteries that do not cause overcharge (more than 100% charge) at an end-of-charge voltage of 14.4V to have an end-of-charge voltage comparable to that of a 12V lead storage battery (14.4V ) compatibility.

Obtained at 50% SOD (state of discharge) by charging the battery pack with a constant current of 1C to 14.4V, charging with a constant voltage of 14.4V (charging time is 3 hours), and discharging to 50% SOD (state of discharge) at 1C The voltage of the battery pack of each of Examples 1 to 10 and Comparative Examples 1 to 4. The results are shown in Table 2.

In the high-temperature float charge test, in an environment of 60°C, the batteries of Examples 1 to 10 and Comparative Examples 2 and 5 were float-charged at a constant voltage of 2.25V (100% SOC), and the batteries of Comparative Examples 1 and 3 Each of the batteries of and 4 was charged at a constant voltage of 4.2V (100% SOC), and then discharged at 1C at 25°C to measure its battery capacity every week, and the time when the capacity maintenance rate reached 80% was defined as the durability life.

In the low-temperature performance test, the discharge capacity was measured while the battery 10C was discharged in an environment of -30°C. The capacity retention rate was obtained from the discharge capacity obtained above, and the discharge capacity obtained in the 1C discharge test at 25° C. was assumed to be 100%.

The results of these measurements are shown in Table 2. FeF _x used as the coating layer in Example 5 satisfies the range of 1≤x≤3.

Table 1

Table 2

As can be seen from Table 2, compared with Comparative Examples 1 to 5, the batteries of Examples 1 to 10 have superior durability life (cycle life) in float charge at a high temperature such as 60° C., and high-speed discharge in a low temperature environment sex.

In FIG. 4 , the 1C discharge curves of the battery packs of Example 1 and Comparative Examples 1, 2 and 5 are shown, wherein the horizontal axis represents the discharge depth (%) and the vertical axis represents the voltage (V). The discharge curve of the battery pack of Example 1 was similar to that of the lead storage battery pack of Comparative Example 5, so the battery pack of Example 1 had excellent compatibility with the lead storage battery. Also, the discharge curve of the battery pack of Example 1 was flatter than that of the lead storage battery pack of Comparative Example 5, so it was found to have high stability at a discharge voltage of 12V. On the other hand, the discharge voltages of the batteries of Comparative Examples 1 and 2 were lower than those of the lead storage battery of Comparative Example 5, and thus their compatibility with the lead storage battery was found to be poor.

The potential curves of the positive and negative electrodes of Examples 1 and 2 are shown in FIG. 5 . In FIG. 5 , the horizontal axis represents the discharge depth (%), and the vertical axis represents the potential (V, vs. Li/Li ⁺ ). The lithium absorption-release potential of the positive electrode active material of embodiment 1 is 3.55 (V, relative to Li/Li ⁺ ), the lithium absorption-release potential of the positive electrode active material of embodiment 2 is 3.85 (V, relative to Li/Li ⁺ ), and the lithium absorption-release potential of the cathode active material of Comparative Example 2 was 3.45 (V, vs. Li/Li ⁺ ). On the other hand, the lithium absorption-release potentials of the anode active materials of Examples 1 and 2 and Comparative Example 2 were 1.55 (V, vs. Li/Li ⁺ ). Therefore, the intermediate voltages (battery voltage at 50% depth of discharge) of Examples 1 and 2 and Comparative Example 2 were 2.0 V, 2.35 V, and 1.8 V, respectively. Accordingly, the intermediate voltage of the battery of Example 1 is the same as that of the lead storage battery, and thus the battery of Example 1 has the most excellent compatibility with the lead storage battery.

It can be seen from FIG. 5 that the lithium absorption potentials of the cathode active materials of Examples 1 and 2 gradually decrease after the discharge depth exceeds 80%. Since the voltage of the batteries of Examples 1 and 2 gradually decreased when the depth of discharge reached 80%, the capacity and depth of discharge (DOD) could be easily detected from the voltage change (see FIG. 4 ). On the other hand, the lithium absorption potential of the cathode active material of Comparative Example 2 remained stable even when the discharge depth exceeded 80%, and it suddenly decreased when the discharge depth approached 100%. Therefore, as shown in FIG. 4 , the voltage of the battery of Comparative Example 2 suddenly decreased when the depth of discharge exceeded 90%. Therefore, in the battery of Comparative Example 2, it was difficult to detect the capacity and the depth of discharge (DOD) with high accuracy from the voltage change.

The non-aqueous electrolyte battery of at _least one of the above-mentioned embodiments and _examples comprises a negative electrode comprising a _titanium -containing oxide; The compound of the crystal structure of lithium ironite crystal structure and heptanite crystal structure, in which 0≤x≤0.2, can therefore provide the following non-aqueous electrolyte battery, which has excellent high-temperature floating charge performance and low-temperature high-speed discharge performance and is compatible with lead The compatibility of the storage battery, and its capacity can be easily checked.

While certain embodiments have been described, these embodiments have been exemplary only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in other forms, and furthermore, various omissions, substitutions and changes in the form of the embodiments described herein are possible without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the invention.

Claims (13)

CLAIMS 1. An electrode comprising a compound represented by LiFe _1-x Mn _x SO ₄ F, wherein 0≦x≦0.2, the compound having a jasmine crystal structure. 2. The electrode according to claim 1, wherein the value of x satisfies 0.1<x≦0.2. 3. The electrode according to claim 1 or 2, wherein, further comprising a coating, the coating covers at least a part of the surface of the particles of the compound, and contains at least one selected from the group consisting of carbon materials, phosphorus compounds, fluoride compounds and metal oxide materials. 4. The electrode according to claim 3, wherein the coating comprises at least one carbonaceous material selected from the group consisting of carbonaceous materials having a d ₀₀₂ of 0.344 nm or greater, Li ₃ PO ₄ , AlPO ₄ , SiP ₂ O ₇ , LiF , AlF ₃ , FeF _x where 2≤x≤3, Al ₂ O ₃ , ZrO ₂ , SiO ₂ and TiO ₂ materials. 5. The electrode according to claim 3, wherein an amount of the coating is in a range of 0.001 to 3% by weight based on an amount of particles of the compound. 6. The electrode according to claim 3, wherein the average primary particle diameter of the compound particles is in the range of 0.05˜1 μm. 7. The electrode according to claim 1 or 2, which is a positive electrode. 8. A nonaqueous electrolyte battery comprising: Positive pole, it is the electrode described in any one in claim 1～6; a negative electrode comprising a titanium-containing oxide; and non-aqueous electrolyte. 9. The non-aqueous electrolyte battery according to claim 8, wherein the titanium-containing oxide is at least one selected from Li _4/3+x Ti _5/3 O ₄ wherein 0≤x≤1, Li _x TiO ₂ oxides where 0≤x≤1 and Li _x Nb _a TiO ₇ where 0≤x and 1≤a≤4. 10. The non-aqueous electrolyte battery according to claim 8, wherein the titanium-containing oxide is at least one selected from lithium titanium oxide with a spinel structure, titanium oxide with a bronze structure (B), titanium oxide with Oxides of titanium oxide with anatase structure, niobium-titanium oxide, and lithium-titanium oxide with orthorhombsite structure. 11. A battery pack comprising the nonaqueous electrolyte battery according to any one of claims 8 to 10. 12. A battery pack comprising a battery module comprising 6n or 5n non-aqueous electrolyte batteries according to any one of claims 8 to 10 connected in series, wherein n is 1 or more. 13. A vehicle comprising the battery pack according to claim 11 or 12.