CN120527462A - Battery cell - Google Patents

Abstract

The application relates to the technical field of batteries, and discloses a battery which comprises an electrolyte, wherein an additive of the electrolyte comprises lithium trifluoromethane sulfonate and N-phenyl-difluoro-sulfonyl imide, and the lithium trifluoromethane sulfonate and the N-phenyl-difluoro-sulfonyl imide cooperate together, so that manganese dissolution can be inhibited at high temperature, the DCR growth rate in a high-temperature circulation process is reduced, and the high-temperature circulation performance of the battery is improved.

Description

Battery cell

Technical Field

The application relates to the technical field of batteries, in particular to a battery.

Background

With the rapid development of pure electric vehicles, intelligent home, electric tools, intelligent transportation and other markets, the performance requirements of consumers on batteries are continuously improved. The lithium ion battery has the advantages of high specific energy, long cycle life, small self-discharge and the like, and is widely applied to consumer electronic products and energy storage and power batteries. However, the manganese metal in the battery is seriously dissolved out after the current battery is cycled at high temperature, and the performance of the battery is affected.

Therefore, the current battery performance is in need of improvement.

Disclosure of Invention

In view of the above, the present application provides a battery, in which the electrolyte in the battery can inhibit the elution of manganese in the positive electrode active material at high temperature, and improve the high temperature cycle performance of the battery, to at least partially solve the above-mentioned technical problems.

In a first aspect of the present application, there is provided a battery comprising:

The positive electrode plate comprises a positive electrode active material, wherein the positive electrode active material comprises a manganese-based material;

An electrolyte comprising a first additive comprising lithium triflate and N-phenyl-difluorosulfimide.

In some embodiments, the mass ratio of lithium triflate to N-phenyl-difluoro-sulfonimide in the electrolyte is (0.005-200): 1.

In some embodiments, the mass ratio of the lithium triflate to the N-phenyl-difluoro-sulfonimide in the electrolyte is (0.1-3.33): 1.

In some embodiments, the mass content of the lithium triflate in the electrolyte is 0.01% -2%.

In some embodiments, the mass content of the lithium triflate in the electrolyte is 0.1% -1%.

In some embodiments, the mass content of the N-phenyl-difluoro-sulfonyl imide in the electrolyte is 0.01% -2%.

In some embodiments, the mass content of the N-phenyl-difluorosulfimide in the electrolyte is 0.3% -1%.

In some embodiments, the electrolyte further includes a second additive including at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

In some embodiments, the mass content of the second additive in the electrolyte is 0.1% -0.5%.

In some embodiments, the manganese-based material is selected from at least one of the following materials:

Li _aNi_bCo_cM1_dM2_eO_fR_g, wherein 1≤a≤1.2, 0.6≤b≤1, 0≤c≤1, 0≤d.1, 0≤e≤0.2, b+c+d+e≤1, 1≤f≤g≤1, f+g≤2, M1 is selected from Mn, or Mn and Al, M2 is selected from at least one of Zr, zn, cu, cr, mg, fe, V, ti, sr, sb, Y, W, nb, R is selected from at least one of N, F, S, cl;

LiMn _xFe_1－xPO₄, wherein 0< x <1.

The battery provided by the application comprises the electrolyte, wherein the additive of the electrolyte comprises lithium trifluoromethane sulfonate and N-phenyl-difluoro-sulfonyl imide, and the lithium trifluoromethane sulfonate and the N-phenyl-difluoro-sulfonyl imide cooperate together, so that manganese dissolution can be inhibited at high temperature, the growth rate of direct current resistance (Direct Current Resistance and DCR) in the high-temperature circulation process is reduced, and the high-temperature circulation performance of the battery is improved.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present application. Furthermore, it should be understood that the detailed description is presented herein for purposes of illustration and description only, and is not intended to limit the application.

In the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third and the like are used merely as labels, and do not impose numerical requirements or on the order of construction.

In the present application, "and/or" describes an association relationship of an association object, which means that there may be three relationships, for example, A and/or B, and that there is A alone, while there is A and B, and there is B alone. Wherein A, B may be singular or plural.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "one or more," "at least one of," or the like, refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (a), b, or c)", or "at least one (a, b, and c)", may each represent a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

Various embodiments of the application may exist in a range format, it being understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application, as the range format described above specifically disclosing all possible sub-ranges and individual values within the range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1,2,3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

The current research shows that under the condition of quick charge, the manganese metal is seriously dissolved out after high-temperature circulation of the battery such as the lithium iron manganese phosphate mixed high-nickel ternary battery, the high-temperature circulation capacity is seriously attenuated, the DCR growth rate is increased, and the high-temperature circulation performance of the battery is deteriorated.

In view of the above drawbacks, the present application provides a battery including a positive electrode tab and an electrolyte. The positive electrode sheet includes a positive electrode active material including a manganese-based material. The electrolyte includes a first additive including lithium triflate and N-phenyl-difluorosulfimide.

The CAS number of the lithium triflate is 33454-82-9, and the structural formula is. The CAS number of the N-phenyl-difluoro-sulfonyl imide is 1622206-83-0, and the structural formula is。

The lithium triflate and the N-phenyl-difluoro sulfimide additive are added into the electrolyte, so that the battery with the electrolyte can inhibit manganese from dissolving out at high temperature, reduce the DCR growth rate in the circulation process and improve the high-temperature circulation performance of the battery.

The triflate (CF ₃SO₃ ^-) has a strong electronegative C-F bond (bond energy 485 kJ/mol) and s=o conjugated structure, giving it a decomposition temperature higher than that of conventional lithium salt additives (lithium triflate decomposition temperature around 300 ℃). The side reaction can be effectively inhibited at high temperature, namely, HF generation caused by high-temperature disproportionation (LiPF ₆→ LiF + PF₅) of lithium salt LiPF ₆ commonly used in electrolyte is avoided, and the acid etching risk of a solid electrolyte interface (Solid Electrolyte Interface, SEI) film/positive electrode electrolyte interface (Cathode Electrolyte Interface, CEI) film is reduced; the CF ₃ radical neutralizes the O ₂ ^- free radical generated by the oxidation of the electrolyte through an electron capturing mechanism (the LUMO energy level is-1.8 eV) to block the chain decomposition reaction, so that the lithium triflate has better thermodynamic stability compared with other lithium salt additives. Therefore, lithium triflate can be used as an additive of the electrolyte to construct a stable solid electrolyte interface SEI film. Specifically, lithium triflate is reduced in the negative electrode of the battery preferentially to generate a composite SEI film containing LiF and Li ₂S_xO_y (such as Li ₂SO₃、Li₂SO₄), the flexibility of a negative electrode interface layer is further improved, the solvent decomposition of the electrolyte at high temperature and high pressure is inhibited to damage the electrode structure, the stability of the negative electrode interface film is improved, and the defect of the SEI film can be dynamically supplemented by continuous decomposition of CF ₃SO₃ ^-.

In addition, the inventors speculate that lithium triflate can also inhibit manganese dissolution of the positive electrode active material mainly because the strong Lewis basicity of CF ₃SO₃ ^- forms a stable [ Mn (CF ₃SO₃)]⁺ complex, which inhibits Mn ²⁺ from migrating to the electrolyte by steric hindrance effect) with Mn ²⁺, and under the conditions of high temperature and high pressure (> 4.3V), CF ₃SO₃ ^- is oxidized and decomposed to form a polymer passivation layer containing-SO ₂CF₃ functional groups, namely sulfonic acid groups (zeta potential-35 mV), which electrostatically repel dissolved Mn ³⁺, inhibiting the ginger-Taylor effect (Jahn-Teller) distortion, thereby reducing the amount of positive electrode manganese dissolution.

However, lithium triflate is reduced at the negative electrode to generate excessive CF ₃ (free radical) and LiF, which leads to an increase in the resistance of the SEI film, specifically:

CF ₃SO₃ ^-+ 2e^-+ 2Li⁺→ LiF+Li₂S+·CF₃ (free radical);

The addition of the N-phenyl-difluoro-sulfonyl imide can remove the byproduct free radical generated by the reduction of lithium triflate (LiOTf) at the negative electrode, block the thick SEI growing chain, generate Li ₃ N (ion conductor) to construct an ion channel, increase the ion conductivity and construct LiF (nanocrystalline) -Li ₃ N (matrix) composite SEI:

CF ₃ (free radical ）+C₆H₅N(SO₂F)₂→ C₆H₅N(SO₂F)(SO₂CF₃)+ ·F（ free radical)

F (free radical) +e ^-+ Li⁺ →LiF (nanocrystalline)

C₆H₅N(SO₂F)(SO₂CF₃)+ 3e^-+ 3Li⁺→Li₃N+LiF+ Phenyl derivatives

The lattice energy of LiF is up to 1040 kJ/mol (which is far higher than 625 kJ/mol of common CEI components such as Li ₂CO₃), a compact physical barrier is formed at high temperature, electrolyte is blocked from being in direct contact with a positive electrode, transition metal dissolution is further inhibited, O ₂ ^- free radicals can be prevented from attacking an electrode, lattice oxygen release is reduced, lithium ion conductivity of Li ₃ N can reach more than 10 ^-3 S/cm (which is 10 ⁴ times that of traditional Li ₂CO₃), interface impedance is obviously reduced, li ⁺ migration rate is improved (desolvation energy barrier is reduced to 0.15 eV), polarization problem under high multiplying power is effectively relieved, and N ^3- in Li ₃ N can capture free H ⁺ to generate NH ₄ ⁺, neutralize electrolyte acidity and delay CEI rupture.

In addition, the N-phenyl-difluoro sulfimide contains F, S, N, and can be matched with lithium triflate to comprehensively improve the high-temperature cycle performance of the battery, wherein F provides heat stability, S optimizes ion transmission and N inhibits metal dissolution.

The action mechanism of the N-phenyl-difluoro-sulfonyl imide for improving the high-temperature performance is that the C-F bond (bond energy 485 kJ/mol) of the trifluoro-methyl sulfonate and the S-F bond (bond energy 343 kJ/mol) of the N-phenyl-difluoro-sulfonyl imide form a three-dimensional network structure (the decomposition energy barrier is improved to 2.8 eV by DFT calculation of density functional theory) so as to inhibit molecular chain fracture at high temperature;

the N atom lone pair electron (LUMO energy level-2.1 eV) in the N-phenyl-difluoro sulfimide molecule and the S=O group can cooperatively capture the O ₂ ^- and OH free radicals generated by the oxidation of electrolyte, block the chain decomposition reaction and improve the high-temperature cycle performance.

In conclusion, the synergistic effect of the lithium triflate and the N-phenyl-difluoro sulfimide inhibits the dissolution of manganese, reduces the DCR growth rate in the high-temperature cycle process, improves the high-temperature cycle performance of the battery,

In some specific embodiments, the mass ratio of the lithium triflate to the N-phenyl-difluoro-sulfimide in the electrolyte is (0.005-200): 1, so that the dissolution of manganese in the battery can be inhibited, the DCR growth rate in the high-temperature cycle process can be reduced, and the high-temperature cycle performance of the battery can be improved.

The mass ratio of lithium triflate to N-phenyl-difluorosulfimide in the electrolyte may be 0.005：1、0.01：1、0.03：1、0.3：1、0.5：1、0.8：1、1：1、1.3：1、1.6：1、2：1、2.5：1、3：1、3.3：1、4：1、4.5：1、5：1、5.5：1、6：1、6.3：1、6.6：1、10：1、12：1、15：1、20：1、25：1、30：1、35：1、40：1、50：1、60：1、70：1、80：1、90：1、100：1、110：1、115：1、120：1、125：1、130：1、135：1、140：1、145：1、150：1、155：1、160：1、165：1、170：1、175：1、180：1、185：1、190：1、195：1、200：1, or a range between any two of the above.

In some examples, the mass ratio of lithium triflate to N-phenyl-difluorosulfimide in the electrolyte is (0.1-3.33): 1, for example 0.1：1、0.2：1、0.3：1、0.4：1、0.5：1、0.6：1、0.7：1、0.8：1、0.9：1、1：1、1.1：1、1.2：1、1.3：1、1.4：1、1.5：1、1.6：1、1.7：1、1.8：1、1.9：1、2：1、2.1：1、2.2：1、2.3：1、2.4：1、2.5：1、2.5：1、2.6：1、2.7：1、2.8：1、2.9：1、3：1、3.1：1、3.2：1、3.3：1、3.33：1, or a range between any two of the above values, and in this mass ratio range, the degree of attenuation of the high-temperature circulation capacity (i.e., the capacity retention rate) can be greatly reduced while effectively suppressing the elution of manganese and reducing the DCR increase rate.

In some specific embodiments, the mass content of the lithium triflate in the electrolyte is 0.01% -2%, and in the above range, the lithium triflate can ensure that the electrolyte maintains good electrochemical performance at high temperature, prolongs the service life of the battery, is beneficial to forming a uniform and stable SEI film, and simultaneously effectively inhibits precipitation of manganese metal.

The mass content of lithium triflate in the electrolyte may be 0.01%、0.03%、0.08%、0.1%、0.2%、0.3%、0.4%、0.5%、0.6%、0.7%、0.8%、0.9%、1%、1.1%、1.2%、1.3%、1.4%、1.5%、1.6%、1.7%、1.8%、1.9%、2%, or a range between any two of the above values, for example.

In some embodiments, the mass content of the lithium triflate in the electrolyte is 0.1% -1%, for example, may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range between any two of the above values. When the mass content of lithium triflate is within the above range, the degree of attenuation of the high-temperature cycle capacity (i.e., the capacity retention rate can be improved) can be further effectively reduced.

In some specific embodiments, the mass content of the N-phenyl-difluoro-sulfonyl imide in the electrolyte is 0.01% -2%, and the mass content of the N-phenyl-difluoro-sulfonyl imide is in the range, so that the decomposition of the electrolyte can be effectively inhibited, the generation of gas in the circulation process is reduced, and meanwhile, the formation of a uniform and stable CEI film is facilitated, and the DCR growth rate in the high-temperature circulation process is reduced.

The mass content of the N-phenyl-difluorosulfimide in the electrolyte may be 0.01%、0.03%、0.08%、0.1%、0.2%、0.3%、0.4%、0.5%、0.6%、0.7%、0.8%、0.9%、1%、1.1%、1.2%、1.3%、1.4%、1.5%、1.6%、1.7%、1.8%、1.9%、2%, or a range between any two of the above values, for example.

In some embodiments, the mass content of the N-phenyl-difluorosulfimide in the electrolyte is 0.3% -1%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range between any two of the above values. When the mass content of the N-phenyl-difluorosulfimide is within the above range, the DCR increase rate during the high temperature cycle can be further reduced, and the degree of attenuation of the high temperature cycle capacity (i.e., the capacity retention rate can be improved) can be further reduced.

In some embodiments, the manganese-based material of the positive electrode active material may be selected from at least one of the following materials ：Li_aNi_bCo_cM1_dM2_eO_fR_g、LiMn_xFe_1-xPO₄.

Wherein 1≤a≤1.2, 0.6≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤0.2, b+c+d+e=1, 1≤f≤1, 0≤g≤1, f+g=2, 0≤x≤1, M1 is selected from Mn, or Mn and Al, M2 is selected from at least one of Zr, zn, cu, cr, mg, fe, V, ti, sr, sb, Y, W, nb, R is selected from at least one of N, F, S, cl.

The manganese-based material can improve gram capacity of the positive electrode active material and reduce cost of the positive electrode active material. The energy density of the battery can be effectively improved by increasing the gram capacity of the positive electrode active material and the charging voltage of the battery, but it was found in practical use that the cycle performance and the high-temperature storage performance of the battery are seriously impaired when the energy density of the battery is improved through the above-described approach. Specifically, taking the positive electrode active material as a high-nickel ternary and lithium iron manganese phosphate positive electrode active material as an example, the energy density of the battery can be obviously improved by improving the nickel and manganese content of the positive electrode active material, but the structural stability of the positive electrode active material is poor due to the increase of the manganese content, the irreversible phase change of the positive electrode active material in the charge-discharge cycle process is increased, and the defects such as transition metal dissolution, active site deletion and the like of the positive electrode active material are caused. In the cycling process, mn ²⁺ is deposited on the surface of the negative electrode graphite, so that the SEI film on the surface of the graphite is continuously decomposed and regenerated, and active lithium is continuously consumed. The SEI film is thickened, so that the electrolyte is continuously consumed, and meanwhile, a large amount of byproducts are generated and block the lithium ion deintercalation channel, so that the polarization of the battery is increased. Meanwhile, the anode material generates a manganese-deficient phase and a ginger Taylor effect of Mn ³⁺ due to manganese dissolution, so that lattice distortion and structural stability are reduced, diffusion of lithium ions in a subsequent charge and discharge process is hindered, and polarization of the battery is increased and high-temperature circulation capacity loss is increased. As the amount of active lithium back-intercalated into the positive electrode is reduced, the low-intercalated lithium graphite of the negative electrode is increased, the disorder degree of the graphite surface is increased, and the SEI film regeneration reaction is promoted. And the dissolution of manganese, the decomposition and regeneration of SEI films can promote the decomposition of electrolyte, so that the high-temperature circulating manganese dissolution of the high-nickel ternary mixed manganese ferric lithium phosphate battery is serious, the high-temperature circulating capacity is attenuated, and the DCR growth rate is high. In contrast, the lithium triflate and the N-phenyl-difluoro sulfimide in the battery provided by the embodiment of the application cooperate together, so that the dissolution of manganese can be inhibited at high temperature, the DCR growth rate in the high-temperature circulation process is reduced, and the high-temperature circulation performance of the battery is improved.

In some embodiments, the electrolyte further includes a second additive including at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), and vinyl sulfate (DTD). The addition of the second additive can improve the film formation of SEI and improve the film formation uniformity of SEI.

In some embodiments, the mass content of the second additive in the electrolyte is 0.1% -0.5%, for example, may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a range between any two of the above values. When the mass content of the second additive is within the above range, the storage stability of the electrolyte can be effectively improved while improving the film formation uniformity of the SEI.

In some embodiments, the electrolyte further comprises a solvent. The solvent should have a high solubility of lithium salt as a main component of the electrolyte so that the electrolyte lithium salt has a high ionic conductivity. The cycle life, charge-discharge rate, high temperature performance, low temperature performance and energy density of the battery can be improved by selecting a suitable solvent. In some examples, the solvent may include at least one of a carbonate solvent and a carboxylate solvent. In the electrolyte, the above solvent can improve dispersion uniformity and ion conductivity of the electrolyte.

Exemplary solvents include one or more of ethylene carbonate, propylene carbonate, methylethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, gamma-butyrolactone, sulfolane, methyltrifluoroethyl carbonate. In other examples, the solvent may include at least two of the solvents listed above.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in a mass ratio of 1 (0.5-2): (0.5-2). For example, the mass ratio of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate may be 1:0.5:0.5、1:0.5:1、1:0.5:1.5、1:0.5:2、1:1:0.5、1:1:1、1:1:1.5、1:1:2、1:1.5:0.5、1:1.5:1、1:1.5:1.5、1:1.5:2、1:2:0.5、1:2:1、1:2:1.5 or 1:2:2.

In some embodiments, the electrolyte further comprises an electrolyte lithium salt. The electrolyte lithium salt can release lithium ions after being dissolved in the solvent of the electrolyte, and the lithium ions and the solvent form a solvation structure, thereby being beneficial to the rapid migration of the lithium ions. In some examples, the electrolyte lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorosulfonimide, lithium tetrafluoroborate, lithium bistrifluoromethane sulfonimide, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate.

The electrolyte lithium salt may be lithium bis-fluorosulfonyl imide, for example. The lithium bis (fluorosulfonyl) imide contributes to reducing the generation of hydrogen fluoride in the electrolyte and reducing the manufacturing cost.

In some embodiments, the molar concentration of the lithium salt of the electrolyte in the electrolyte may be 0.8 mol/L to 2 mol/L. For example 0.8 mol/L、0.9 mol/L、1.0 mol/L、1.1 mol/L、1.2 mol/L、1.3 mol/L、1.4 mol/L、1.5 mol/L、1.6 mol/L、1.7 mol/L、1.8 mol/L、1.9 mol/L、2 mol/L, or a range between any two of the values mentioned above. Since the electrolyte lithium salt occupies a relatively high total cost (about 60%) of the electrolyte, when the molar concentration of the electrolyte lithium salt in the electrolyte is within the above range, the electrolyte lithium salt can be sufficiently dissolved in the solvent while the electrolyte has both a relatively high ionic conductivity and a relatively low manufacturing cost.

In some examples, the battery further includes a negative electrode tab. The negative electrode plate comprises a negative electrode current collector, a negative electrode active material, a negative electrode binder and a negative electrode conductive agent. The negative electrode active material includes at least one of natural graphite, artificial graphite, silicon-carbon composite material, silicon-oxygen-carbon material, and silicon-oxygen material. The negative electrode binder may be at least one selected from styrene-butadiene rubber (SBR), polyvinylidene fluoride, aqueous acrylic resin (water-basedacrylic resin), polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polyacrylate, ethylene-vinyl acetate copolymer (EVA), polyvinyl ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), carboxymethyl cellulose (CMC-Na), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB). The negative electrode conductive agent may be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, ketjen black, carbon dots, conductive graphite, carbon nanotubes, super P (SP), and carbon nanofibers.

In some embodiments, the positive electrode sheet further comprises a positive electrode current collector, a positive electrode binder, and a positive electrode conductive agent. The positive electrode binder may be at least one selected from styrene-butadiene rubber (SBR), polyvinylidene fluoride, aqueous acrylic resin (water-basedacrylic resin), polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polyacrylate, ethylene-vinyl acetate copolymer (EVA), polyvinyl ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB). The positive electrode conductive agent may be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, ketjen black, carbon dots, conductive graphite, carbon nanotubes, super P (SP), and carbon nanofibers.

In some examples, the battery further comprises a separator. The separator material may be selected from a known porous material separator film with good chemical and mechanical stability, the separator film may be at least one selected from non-woven fabrics, glass fibers, polytetrafluoroethylene, polyethersulfone, polypropylene, polyolefin, aromatic polyamide and polyethylene, and the separator film may be a single-layer or multi-layer composite film.

Based on the battery, the application also provides an electric device comprising the battery in any embodiment.

The application is not limited to the specific type of the power utilization device, and can comprise any equipment which needs batteries to supply power for the power utilization device, such as an electric automobile, a mobile phone, an intelligent home, a robot, an unmanned aerial vehicle, an electronic cigarette, a sound box and the like.

Hereinafter, a battery provided by the present application will be described in detail by way of specific examples.

Example 1

(1) The preparation of the electrolyte comprises the following steps:

In a glove box filled with argon (moisture <10 ppm, oxygen content <1 ppm), mixing ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate according to a mass ratio of 3:5:2 to obtain a base solvent, and then adding dried lithium hexafluorophosphate, lithium trifluoromethane sulfonate, N-phenyl-difluoro-sulfimide, fluoroethylene carbonate (FEC) and ethylene sulfate (DTD) into the base solvent, and fully and uniformly mixing to obtain an electrolyte. Wherein in the electrolyte, the molar concentration of lithium hexafluorophosphate is 1 mol/L, the mass content of lithium trifluoromethane sulfonate is 0.5%, the mass content of N-phenyl-difluoro-sulfonyl imide is 0.3%, the mass content of fluoroethylene carbonate (FEC) is 1.0%, the mass content of ethylene sulfate (DTD) is 0.5%, and the balance is a base solvent.

(2) The preparation of the positive pole piece comprises the following steps:

mixing positive electrode active materials NCM811 (nickel cobalt lithium manganate, liNi _0.8Co_0.1Mn_0.1O₂) and LMFP (lithium manganese iron phosphate, liMn _0.6Fe_0.4PO₄), positive electrode binder polyvinylidene fluoride (PVDF), positive electrode conductive agent carbon black and carbon nano tube according to the mass ratio of 93:2.3:2:0.7, adding N-methyl pyrrolidone (NMP) as a solvent to obtain a mixed system, stirring the mixed system in vacuum until the mixed system is uniformly mixed to obtain positive electrode slurry, uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 12 mu m, wherein the coating density is 35 g/m ², sequentially drying and cold pressing the coated positive electrode slurry at 85 ℃, trimming, cutting pieces, splitting, drying at the vacuum condition and 85 ℃ for 4 hours after splitting, and welding the electrode lugs to obtain the positive electrode sheet.

(3) The preparation of the negative electrode plate comprises the following steps:

mixing graphite as a negative electrode active material, carbon black as a conductive agent, sodium carboxymethylcellulose (CMC-Na) as a binder and styrene-butadiene rubber (SBR) according to the mass ratio of 95:1.5:1:2.5, adding deionized water as a solvent to obtain a mixed system, stirring the mixed system in vacuum until the mixed system is uniformly mixed to obtain negative electrode slurry, uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector, wherein the coating density is 20 g/m ², sequentially drying and cold pressing the coated negative electrode slurry at 85 ℃, trimming, cutting pieces, splitting, drying for 4 hours at the vacuum condition and 85 ℃ after splitting, and welding the electrode lugs to obtain the negative electrode plate.

(4) A method of making a separator comprising:

a polyethylene separator film having a thickness of 8 μm was used as the separator.

(5) A method of making a battery comprising:

And (3) sequentially preparing the prepared positive electrode plate, the diaphragm and the negative electrode plate into a laminated assembly through a lamination process, wherein the thickness of the laminated assembly is 4.7 mm, the width of the laminated assembly is 55 mm, the length of the laminated assembly is 60 mm, baking the laminated assembly under vacuum condition and at 85 ℃ for 48 h, then injecting the electrolyte prepared by the preparation process, and carrying out the procedures of vacuum packaging, standing, formation, shaping and the like to obtain the battery.

The preparation processes and structures of the batteries prepared in examples 2 to 33 and comparative examples 1 to 8 were the same as in example 1, except that the respective components and contents of the electrolytes were different, and the other components and contents were the same, except for the following table 1.

TABLE 1

The batteries prepared in examples 2 to 33 and comparative examples 1 to 8 were subjected to a high temperature cycle performance test, a DCR growth rate test and a manganese elution amount test after high temperature cycle, and the specific test results are summarized in table 2, and the test modes are as follows:

(1) High temperature cycle performance test

Placing the battery in a 45 ℃ incubator, standing for 4 hours, charging the battery at a constant current of 1 ℃ until the voltage is 4.25V (the cut-off current is 0.05C), standing for 5 minutes, discharging at a constant current of 1 ℃ until the voltage is 2.50V, recording the initial discharge capacity as C ₁, repeating the charge and discharge cycle for 500 times with one charge and discharge cycle, and recording the discharge capacity as C ₂ after the 500 th cycle. The charge-discharge cycle test instrument is a Xinwei BTS.

The high-temperature cycle performance of the lithium battery was evaluated at 45 ℃ 500-week cycle capacity retention (%) =c ₂/C₁ ×100%, and the higher the capacity retention, the better the high-temperature cycle performance of the battery was explained.

(2) DCR growth rate test

Placing the battery in a 45 ℃ environment, discharging to a cut-off voltage of 2.5V according to a constant current of 1 ℃ and standing for 5min, charging to an upper limit voltage of 4.2V with a constant current and a constant voltage of 1 ℃ and a cut-off current of 0.05 ℃, discharging for 30min according to a constant current of 1 ℃ and standing for 5min at 25 ℃ by using a constant current of 2 ℃ and discharging current of I _2C when discharging. The initial voltage V0 and the voltage V1 after 30s discharge were recorded. The calculation formula of the discharge DC internal resistance at 50% SOC is as follows, DCR (mΩ) = (V0-V1)/I _2C ×1000, the initial DCR is recorded as DCR ₁, the charge and discharge cycle is repeated for 500 times, and the DCR after the 500 th cycle is recorded as DCR ₅₀₀.

The DCR increase rate (%) = [ (DCR ₅₀₀- DCR₁)/DCR₁ ] ×100% after 500 weeks of circulation, and the DCR increase rate after 500 weeks of circulation is used for measuring the performance decline of the battery, the lower the DCR increase rate, the better the performance of the battery is maintained in the circulation process, and the higher the stability of the internal electrode materials and electrolyte components is.

(3) Manganese leaching amount test after high-temperature circulation

And (3) testing the manganese leaching amount, namely discharging the battery subjected to the 500-circle high-temperature cycle performance test to a lower limit voltage at a small multiplying power, then disassembling the battery to obtain a negative electrode plate, scraping the powder of the negative electrode plate by a ceramic knife, and testing by ICP to obtain the manganese leaching amount (ppm) on the negative electrode plate.

TABLE 2

In combination with tables 1 and 2, it can be seen that:

(1) From the experimental results of comparative examples 1 to 8 and examples 1 to 22, it can be seen that the simultaneous addition of the first additives lithium triflate and N-phenyl-difluorosulfimide to the electrolyte of the battery can effectively inhibit the elution of manganese at high temperature, reduce the DCR growth rate during high temperature cycle, and improve the high temperature cycle performance of the battery.

(2) From the experimental results of examples 20-21 and examples 1-19, it is apparent that the manganese dissolution rate and DCR growth rate data of the batteries prepared in examples 1-19 are significantly better than those of examples 20-21, and it is apparent that the mass ratio of the lithium triflate to the N-phenyl-difluorosulfimide as the first additive in the electrolyte is in the range of (0.005-200): 1, which can further improve the manganese dissolution inhibiting effect of the batteries and reduce the DCR growth rate during high temperature cycle.

(3) From the experimental results of comparative example 1, example 9 and examples 1 to 8, it is apparent that the effect of suppressing elution of manganese is not remarkable when the addition amount of lithium triflate is too small, and it is disadvantageous to maintain the battery capacity, and to reduce the rate of increase of DCR during high temperature cycle when the addition amount is too large.

(4) As can be seen from the experimental results of comparative example 5, example 16 and examples 10 to 15, the addition of too much or too little N-phenyl-difluorosulfimide is disadvantageous in inhibiting the elution of manganese.

(5) From the experimental results of examples 2-3, 7-8, 10-11, 14-15 and examples 1, 4-6 and 12-13, it can be seen that the mass content of N-phenyl-difluoro-sulfonyl imide in the electrolyte is within the range of 0.01% -2%, the mass content of N-phenyl-difluoro-sulfonyl imide in the electrolyte is within the range of 0.3% -1%, the two can cooperate together, not only can effectively inhibit the dissolution of manganese at high temperature, but also can effectively reduce the DCR growth rate, and maintain the better cycle retention rate of the battery.

(6) From the experimental results of example 33 and examples 1, 22 to 25, 29 to 32, it can be seen that the addition of the second additive to the electrolyte having the above-described first additive is advantageous in reducing the DCR growth rate and maintaining the superior cycle retention rate of the battery.

While the battery and the power consumption device provided by the embodiments of the present application have been described in detail, specific examples are used herein to illustrate the principles and embodiments of the present application, the above examples are only for aiding in understanding the method and core concept of the present application, and meanwhile, the present application should not be construed as being limited to the embodiments and application scope of the present application, since the technical personnel in the field will change the scope of the present application according to the concept of the present application.

Claims (10)

1. A battery, comprising:

The positive electrode plate comprises a positive electrode active material, wherein the positive electrode active material comprises a manganese-based material;

An electrolyte comprising a first additive comprising lithium triflate and N-phenyl-difluorosulfimide.

2. The battery according to claim 1, wherein the mass ratio of lithium triflate to N-phenyl-difluorosulfimide in the electrolyte is (0.005-200): 1.

3. The battery according to claim 2, wherein a mass ratio of the lithium triflate to the N-phenyl-difluorosulfimide in the electrolyte is (0.1-3.33): 1.

4. A battery according to any one of claims 1 to 3, wherein the mass content of the lithium triflate in the electrolyte is 0.01% -2%.

5. The battery according to claim 4, wherein the mass content of the lithium triflate in the electrolyte is 0.1% -1%.

6. The battery according to any one of claims 1 to 3, wherein the mass content of the N-phenyl-difluorosulfonimide in the electrolyte is 0.01% -2%.

7. The battery according to claim 6, wherein the mass content of the N-phenyl-difluorosulfimide in the electrolyte is 0.3% -1%.

8. The battery of claim 1, wherein the electrolyte further comprises a second additive comprising at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

9. The battery according to claim 8, wherein the mass content of the second additive in the electrolyte is 0.1% -0.5%.

10. The battery of claim 1, wherein the manganese-based material is selected from at least one of the following materials:

Li _aNi_bCo_cM1_dM2_eO_fR_g, wherein 1≤a≤1.2, 0.6≤b≤1, 0≤c≤1, 0≤d.1, 0≤e≤0.2, b+c+d+e≤1, 1≤f≤g≤1, f+g≤2, M1 is selected from Mn, or Mn and Al, M2 is selected from at least one of Zr, zn, cu, cr, mg, fe, V, ti, sr, sb, Y, W, nb, R is selected from at least one of N, F, S, cl;

LiMn _xFe_1－xPO₄, wherein 0< x <1.