CN116356281A - A method and application of preparing a composite negative electrode material comprising an artificial SEI film - Google Patents

Abstract

The invention provides a method and application for preparing a composite negative electrode material comprising an artificial SEI film. The method includes the following steps: first, put the negative electrode material into the reaction chamber of the atomic layer deposition system, and adjust the temperature and pressure in the reaction chamber; then perform atomic layer deposition to obtain the composite negative electrode material, the steps of each cycle It is: using an inert gas as a carrier, repeatedly pulse the lithium source and H ₂ O into the reaction chamber in sequence, after each pulse of the lithium source and H ₂ O, inject an inert gas for pulse cleaning; repeatedly inject the aluminum source and H ₂ O is sequentially pulsed into the reaction chamber, and after each pulse of aluminum source and H ₂ O is completed, an inert gas is injected for pulse cleaning. The invention uses the atomic layer deposition technology to prepare the artificial solid electrolyte interface thin film.

Description

A method and application of preparing a composite negative electrode material comprising an artificial SEI film

technical field

The invention belongs to the technical field of SEI film materials, and in particular relates to a method and application for preparing a composite negative electrode material containing an artificial SEI film.

Background technique

In the production process of lithium-ion batteries, the duration of the battery in the formation phase is long, the energy consumption is high, and the cost is correspondingly high. The main purpose of battery formation is to form a stable solid electrolyte interfacial film (SEI film), so as to ensure the cycle stability of the battery during subsequent use. The formation process of the SEI film is obtained by reducing and decomposing the electrolyte on the surface of the negative electrode during the charging process. The above process will consume lithium ions in the electrolyte, thereby reducing the reversible cycle capacity of the battery. In addition, the above-mentioned side reactions generated by the decomposition of the electrolyte consume lithium ions and generate gases such as CO ₂ , CO, C ₂ H ₄ , and H ₂ , which ultimately affect the service life of the battery. At present, supplementing lithium to the negative electrode and setting an artificial SEI film are common methods to solve the above problems. However, although the lithium supplementation technology can compensate for the consumption of lithium ions during the formation of the SEI film, it is difficult to avoid the problem of gas production caused by the formation of the SEI film.

In recent years, methods for preparing artificial SEI films mainly include magnetron sputtering, chemical vapor deposition, physical vapor deposition, or electroplating. Atomic layer deposition (ALD) is a method of preparing nano-films, because of its self-limitation, sub-layer atoms can be plated on the surface of the substrate layer by layer. The principle is to sequentially introduce different gaseous precursors into the reaction chamber, form a monoatomic layer through the reaction between different precursors, and repeat the above steps to form sub-layers or multi-layer films of required thickness. The thickness of the film can be controlled by adjusting the number of cycles, and its precision can reach sub-nanometer level. It can coat ultra-thin films with uniform thickness on the surface of materials with complex structures, and can precisely control the thickness of the film. In addition, atomic layer deposition technology can prepare thin films with ideal composition by adjusting the type and content of precursors.

Regarding the material of the artificial SEI film, it needs to have good electrochemical stability, ionic conductivity and electronic insulation. The prior art discloses the preparation of artificial SEI films such as aluminum oxide, lithium phosphorus oxynitride, zinc oxide, titanium dioxide and hafnium dioxide by atomic layer deposition. Compared with other types of thin films, the manufacturing cost of aluminum oxide thin films is lower and the process is more mature, and it has good electrochemical inertness. However, if the thickness of the aluminum oxide film is too thin, the electronic insulation of the film will deteriorate, which will lead to the decomposition of the electrolyte; otherwise, the ionic conductivity of the film will be reduced, and the overall performance of the battery will eventually be reduced.

Therefore, in this field, there is an urgent need to develop a method for preparing an artificial SEI film with good electrochemical stability, high ionic conductivity and electronic insulation, which can not only control the thickness and composition, but also avoid the Excessive consumption of lithium ions and gas production caused by film formation.

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide a method and application for preparing a composite negative electrode material containing an artificial SEI film. The invention utilizes the atomic layer deposition technology to prepare an artificial solid electrolyte interface film (SEI film) with uniform thickness and compactness on the surface of the negative electrode material. The above-mentioned SEI film can effectively solve the problems of excessive consumption of lithium ions and gas production caused by the decomposition of the electrolyte on the surface of the negative electrode.

To achieve this purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for preparing a composite negative electrode material comprising an artificial SEI film, the method comprising the following steps:

(1) Putting the negative electrode material into the reaction chamber of the atomic layer deposition system, then vacuumizing the reaction chamber, and adjusting the temperature and pressure in the reaction chamber;

(2) 1 to 500 cycles of atomic layer deposition are carried out to obtain the composite negative electrode material comprising an artificial SEI film, and the steps of each cycle are:

Using an inert gas as a carrier, pulse the lithium source and H ₂ O into the reaction chamber sequentially, after each pulse of the lithium source and H ₂ O, inject an inert gas for pulse cleaning, and repeat the above steps to obtain a lithium-rich sub-layer;

Then the aluminum source and H ₂ O are sequentially pulsed into the reaction chamber, and after each pulse of the aluminum source and H ₂ O is finished, an inert gas is injected for pulse cleaning, and the above steps are repeated to obtain an aluminum-rich sub-layer.

In the present invention, an artificial solid electrolyte interface film (SEI film) with uniform thickness and compactness is prepared by using atomic layer deposition technology on the surface of the negative electrode material. Aluminum as an example. On the one hand, the thickness of the SEI thin film is uniform and dense, and at the same time, the SEI thin film has good electrochemical stability, ion conductivity and electronic insulation. On the other hand, the present invention deposits the above-mentioned artificial SEI film on the surface of the negative electrode, so that the interface stability between the electrolyte and the negative electrode is enhanced, avoiding the occurrence of side reactions, and then solving the excessive consumption of lithium ions and gas production. , which can ultimately improve the electrochemical performance of lithium-ion batteries. In addition, the preparation method provided by the present invention can save the pre-charging process of forming the SEI film in the formation process of the battery, thereby improving the production efficiency of the battery and reducing the production cost of the battery.

(CH ₃ ) ₃ COLi+H ₂ O→Li-O+(CH ₃ ) ₃ COH↑

Al(CH ₃ ) ₃ +H ₂ O→Al-O+CH ₄ ↑

On the one hand, compared with other thin film preparation methods disclosed in the prior art, the thickness of the thin film prepared by atomic layer deposition technology is more uniform and dense, and the thickness is smaller and can be precisely controlled. The uniformity and compactness of the above film can ensure that the electrolyte cannot be decomposed on the surface of the negative electrode, thereby avoiding problems such as consumption of lithium ions in the electrolyte and gas generation. The ultra-thin film prepared by it can alleviate the decrease of battery energy density caused by the side reaction caused by the SEI film.

On the other hand, the addition of lithium source can improve the ionic conductivity of the traditional artificial SEI film, and at the same time provide an additional lithium source, thereby improving the cycle performance of the battery.

Preferably, the negative electrode material in step (1) includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

Preferably, the negative electrode active material layer includes any one or a combination of at least two of graphite, silicon carbon, pure silicon, silicon oxide, tin or tin oxide.

Preferably, the inert gas in step (2) includes nitrogen or argon.

Preferably, the flow rate of the inert gas in step (2) is 10 to 10000 sccm, such as 10 sccm, 50 sccm, 100 sccm, 500 sccm, 1000 sccm, 5000 sccm, 10000 sccm, the specific inert gas flow depends on the size of the cavity and the size of the pipeline .

Preferably, the lithium source in step (2) includes any one or a combination of at least two of lithium tert-butoxide, lithium hexamethyldisilazide or lithium bis(trimethylsilyl)amide.

Preferably, the time for sequentially pulsed lithium source and H ₂ O into the reaction chamber in step (2) is 10 ms-1 s, for example, 10 ms, 30 ms, 50 ms, 80 ms, 1 s, the specific time depends on the chamber and the flow rate Depends on size.

In the present invention, the ionic conductivity of the prepared artificial SEI membrane is further regulated by regulating the time for sequentially pulsed lithium source and H ₂ O into the reaction chamber.

Preferably, the temperature in the reaction chamber in step (1) is 200-250°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.; the pressure is not more than 10mbar, such as It can be 1mbar, 2mbar, 4mbar, 6mbar, 8mbar, 10mbar, etc.

Preferably, the aluminum source in step (2) includes trimethylaluminum.

Preferably, the time for sequentially introducing the aluminum source and H ₂ O into the reaction chamber in step (2) is 10ms to 1s, for example, 10ms, 30ms, 50ms, 80ms, 1s, and the specific time depends on the chamber and the flow rate. Depends on size.

In the present invention, the thickness uniformity and density of the prepared artificial SEI film are adjusted by adjusting the time for sequentially pulsed aluminum source and H ₂ O into the reaction chamber.

In a second aspect, the present invention provides a composite negative electrode material, which is prepared by the method for preparing a composite negative electrode material containing an artificial SEI film according to the first aspect.

Preferably, the composite anode material includes an anode material and a nano-modified layer deposited on the surface of the anode material, the thickness of the nano-modified layer is 10-1000nm, for example, 10nm, 50nm, 100nm, 500nm, 1000nm.

In the present invention, by adjusting the thickness of the nano-modified layer, the nano-modified layer can be applied to different lithium ion battery systems.

In a third aspect, the present invention provides a lithium ion battery, the lithium ion battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, and the negative electrode sheet includes the composite negative electrode material according to the second aspect.

Compared with the prior art, the present invention has the following beneficial effects:

The invention provides a method for preparing a composite negative electrode material comprising an artificial SEI film, which prepares a uniform and dense artificial solid electrolyte interface film (SEI film) by using atomic layer deposition technology on the surface of the negative electrode material. On the one hand, the SEI The thickness of the film is uniform and dense, and the SEI film has good electrochemical stability, ion conductivity and electronic insulation. On the other hand, the present invention deposits the above-mentioned artificial SEI film on the surface of the negative electrode, so that the interface stability between the electrolyte and the negative electrode is enhanced, avoiding the occurrence of side reactions, and then solving the excessive consumption of lithium ions and gas production. , which can ultimately improve the electrochemical performance of lithium-ion batteries. In addition, the preparation method provided by the present invention can save the pre-charging process of forming the SEI film in the formation process of the battery, thereby improving the production efficiency of the battery and reducing the production cost of the battery.

Description of drawings

Fig. 1 is the preparation flowchart of the nano-modified layer that embodiment 1 provides;

Fig. 2 is the top view of the scanning electron microscope of the nano-modified layer provided by embodiment 1, and its scale is 500nm;

FIG. 3 is a scanning electron microscope cross-sectional view of the nano-modified layer provided in Example 1, and the scale bar is 1 μm.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments. It should be clear to those skilled in the art that the examples are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1

This embodiment provides a graphite composite negative electrode material comprising an artificial SEI film and a preparation method thereof, as shown in Figure 1, the graphite composite negative electrode material includes a graphite negative electrode material and a nano-modified layer deposited on the surface of the graphite negative electrode material, as shown in Figure 2 -3, the thickness of the nano-modified layer is 160nm, and the preparation method comprises the following steps:

(1) Put the graphite negative electrode material into the reaction chamber of the atomic layer deposition system (volume is 80L), then vacuumize the reaction chamber, and adjust the temperature in the reaction chamber to 200°C, and the pressure is lower than 1mbar;

(2) Carry out 40 cycles of atomic layer deposition to obtain graphite composite negative electrode material, the steps of each cycle are:

Using nitrogen gas as the carrier, the flow rate of nitrogen gas is 100sccm, pulse lithium tert-butoxide and H ₂ O into the reaction chamber sequentially for 100ms, and after each pulse of lithium tert-butoxide and H ₂ O is completed, nitrogen gas is then injected for 100ms. Cleaning, repeating the above steps 20 times to obtain a lithium-rich sub-layer with a thickness of 2nm; then pulse trimethylaluminum and H ₂ O into the reaction chamber in sequence for 100s, after each pulse of trimethylaluminum and H ₂ O , blowing nitrogen gas for 100 ms for cleaning, and repeating the above steps 20 times to obtain an aluminum-rich sub-layer with a thickness of 2 nm.

Example 2

This embodiment provides a graphite composite negative electrode material comprising an artificial SEI film and a preparation method thereof. The graphite composite negative electrode material includes a graphite negative electrode material and a nano-modified layer deposited on the surface of the graphite negative electrode material. The thickness of the nano-modified layer is 200nm. Described preparation method comprises the following steps:

(1) Put the graphite negative electrode material into the reaction chamber of the atomic layer deposition system, then vacuumize the reaction chamber, and adjust the temperature in the reaction chamber to 220°C, and the pressure is lower than 2mbar;

(2) Carry out 50 cycles of atomic layer deposition to obtain graphite composite negative electrode material, the steps of each cycle are:

Using nitrogen gas as the carrier, the flow rate of nitrogen gas is 100sccm, pulse lithium tert-butoxide and H ₂ O into the reaction chamber sequentially for 100ms, and after each pulse of lithium tert-butoxide and H ₂ O is completed, nitrogen gas is then injected for 100ms. Cleaning, repeating the above steps 20 times to obtain a lithium-rich sublayer with a thickness of 2nm; then pulse trimethylaluminum and H ₂ O into the reaction chamber for 100ms in sequence, after each pulse of trimethylaluminum and H ₂ O, Nitrogen was blown in for 100 ms for cleaning, and the above steps were repeated 20 times to obtain an aluminum-rich sublayer with a thickness of 2 nm.

Example 3

This embodiment provides a graphite composite negative electrode material comprising an artificial SEI film and a preparation method thereof. The graphite composite negative electrode material includes a graphite negative electrode material and a nano-modified layer deposited on the surface of the graphite negative electrode material. The thickness of the nano-modified layer is 320nm. Described preparation method comprises the following steps:

(1) Put the graphite negative electrode material into the reaction chamber of the atomic layer deposition system, then vacuumize the reaction chamber, and adjust the temperature in the reaction chamber to 230°C, and the pressure is lower than 4mbar;

(2) Carry out 80 cycles of atomic layer deposition to obtain graphite composite negative electrode material, the steps of each cycle are:

Using nitrogen gas as the carrier, the flow rate of nitrogen gas is 100sccm, pulse lithium tert-butoxide and H ₂ O into the reaction chamber sequentially for 100ms, and after each pulse of lithium tert-butoxide and H ₂ O is completed, nitrogen gas is then injected for 100ms. Cleaning, repeating the above steps 20 times to obtain a lithium-rich sublayer with a thickness of 2nm; then pulse trimethylaluminum and H ₂ O into the reaction chamber for 100ms in sequence, after each pulse of trimethylaluminum and H ₂ O, Nitrogen was blown in for 100 ms for cleaning, and the above steps were repeated 20 times to obtain an aluminum-rich sublayer with a thickness of 2 nm.

Example 4

This embodiment provides a graphite composite negative electrode material comprising an artificial SEI film and a preparation method thereof. The graphite composite negative electrode material includes a graphite negative electrode material and a nano-modified layer deposited on the surface of the graphite negative electrode material. The thickness of the nano-modified layer is 400nm. Described preparation method comprises the following steps:

(1) Put the graphite negative electrode material into the reaction chamber of the atomic layer deposition system, then vacuumize the reaction chamber, and adjust the temperature in the reaction chamber to 240°C, and the pressure is lower than 8mbar;

(2) Carry out 100 cycles of atomic layer deposition to obtain graphite composite negative electrode material, the steps of each cycle are:

Using nitrogen gas as the carrier, the flow rate of nitrogen gas is 100sccm, pulse lithium tert-butoxide and H ₂ O into the reaction chamber sequentially for 100ms, and after each pulse of lithium tert-butoxide and H ₂ O, nitrogen gas is injected for 100ms for cleaning , repeat the above steps 20 times to obtain a lithium-rich sublayer with a thickness of 2nm; then pulse trimethylaluminum and H ₂ O into the reaction chamber for 100 ms in sequence, and after each pulse of trimethylaluminum and H ₂ O is completed, pass Nitrogen gas was injected for 100 ms for cleaning, and the above steps were repeated 20 times to obtain an aluminum-rich sub-layer with a thickness of 2 nm.

Example 5

This embodiment provides a graphite composite negative electrode material comprising an artificial SEI film and a preparation method thereof. The graphite composite negative electrode material includes a graphite negative electrode material and a nano-modified layer deposited on the surface of the graphite negative electrode material. The thickness of the nano-modified layer is 800nm. Described preparation method comprises the following steps:

(1) Put the graphite negative electrode material into the reaction chamber of the atomic layer deposition system, then vacuumize the reaction chamber, and adjust the temperature in the reaction chamber to 250°C, and the pressure is lower than 10mbar;

(2) Carry out 200 cycles of atomic layer deposition to obtain graphite composite negative electrode material, the steps of each cycle are:

Using nitrogen gas as the carrier, the flow rate of nitrogen gas is 100sccm, pulse lithium tert-butoxide and H ₂ O into the reaction chamber sequentially for 100ms, and after each pulse of lithium tert-butoxide and H ₂ O, nitrogen gas is injected for 100ms for cleaning , repeat the above steps 20 times to obtain a lithium-rich sublayer with a thickness of 2nm; then pulse trimethylaluminum and H ₂ O into the reaction chamber for 100 ms in sequence, and after each pulse of trimethylaluminum and H ₂ O is completed, pass Nitrogen gas was injected for 100 ms for cleaning, and the above steps were repeated 20 times to obtain an aluminum-rich sub-layer with a thickness of 2 nm.

Example 6

The difference between this embodiment and embodiment 1 is that the temperature in step (1) is 150° C., and the others are the same as in embodiment 1.

Example 7

The difference between this example and Example 1 is that the temperature in step (1) is 300° C., the pressure is 15 mbar, and the others are the same as Example 1.

Example 8

The difference between this embodiment and embodiment 1 is that the thickness of the nano-modified layer is 4nm, and the others are the same as embodiment 1.

Example 9

The difference between this embodiment and embodiment 1 is that the thickness of the nano-modified layer is 2000 nm, and the others are the same as embodiment 1.

Comparative example 1

The difference between this comparative example and Example 1 is that in step (2), lithium tert-butoxide is not added to the reaction chamber, only trimethylaluminum and H ₂ O are added, and the others are the same as in Example 1.

Comparative example 2

The difference between this comparative example and Example 1 is that in step (2), no trimethylaluminum is added to the reaction chamber, only lithium tert-butoxide and H ₂ O are added, and the others are the same as in Example 1.

In summary, the present invention prepares an artificial solid electrolyte interface film (SEI film) with uniform thickness and compactness by using atomic layer deposition technology on the surface of the negative electrode material. Electrochemical stability, ionic conductivity and electronic insulation. On the other hand, the present invention deposits the above-mentioned artificial SEI film on the surface of the negative electrode, so that the interface stability between the electrolyte and the negative electrode is enhanced, avoiding the occurrence of side reactions, and then solving the excessive consumption of lithium ions and gas production. , which can ultimately improve the electrochemical performance of lithium-ion batteries.

Compared with Application Example 1, Comparative Application Example 1-2 shows that the technical effect _of the present application cannot be achieved by depositing a certain seed layer alone. This is because a single aluminum-rich _Al2O3 single layer has stable electrochemical properties and can It effectively protects the electrodes, but its lithium ion conductivity is poor, which will affect the overall performance of the battery. Although a single lithium-rich monolayer has good lithium ion conductivity, it is electrochemically unstable and cannot effectively protect the electrode material.

The applicant declares that the present invention illustrates the process method of the present invention through the above examples, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the selected raw materials in the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A method of preparing a composite anode material comprising an artificial SEI film, the method comprising the steps of:

(1) Placing a cathode material into a reaction cavity of an atomic layer deposition system, vacuumizing the reaction cavity, and adjusting the temperature and pressure in the reaction cavity;

(2) And (3) performing atomic layer deposition for 1-500 cycles to obtain the composite anode material containing the artificial SEI film, wherein the steps of each cycle are as follows:

inert gas is used as carrier to make lithium source and H ₂ O is sequentially pulse-led into the reaction cavity, and each time lithium source and H ₂ After the O pulse is finished, introducing inert gas to perform pulse cleaning, and repeating the steps to obtain a lithium-rich sublayer;

subsequently combining an aluminum source with H ₂ O is sequentially pulse-led into the reaction cavity, each time the aluminum source and H ₂ And after the O pulse is finished, introducing inert gas to perform pulse cleaning, and repeating the steps to obtain the aluminum-rich sublayer.

2. The method according to claim 1, wherein the anode material in step (1) includes an anode current collector and an anode active material layer provided on at least one side of the anode current collector;

preferably, the anode active material layer includes any one or a combination of at least two of graphite, silicon carbon, pure silicon, silicon oxide, tin, or tin oxide.

3. The method according to claim 1 or 2, wherein the inert gas in step (2) comprises nitrogen or argon;

preferably, the flow rate of the inert gas in the step (2) is 10-10000 sccm.

4. A method according to any one of claims 1 to 3, wherein the lithium source in step (2) comprises any one or a combination of at least two of lithium tert-butoxide, lithium hexamethyldisilazide or lithium bis (trimethylsilyl) amide;

preferably, the method comprises the steps of,combining a lithium source with H as described in step (2) ₂ The time for leading O into the reaction cavity in sequence is 10ms-1s.

5. The method according to any one of claims 1 to 4, wherein the temperature in the reaction chamber in step (1) is 200 to 250 ℃ and the pressure is not more than 10mbar.

6. The method of any one of claims 1-5, wherein the aluminum source in step (2) comprises trimethylaluminum.

7. The method according to any one of claims 1 to 6, wherein in step (2) the aluminum source and H are combined ₂ The time for leading O into the reaction cavity in sequence is 10ms-1s.

8. A composite anode material, characterized in that the composite anode material is prepared by the method for preparing a composite anode material comprising an artificial SEI film according to any one of claims 1 to 7.

9. The composite anode material according to claim 8, wherein the composite anode material comprises an anode material and a nano-modification layer deposited on the surface of the anode material, and the thickness of the nano-modification layer is 10-1000 nm.

10. A lithium ion battery, characterized in that it comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, the negative electrode sheet comprising the composite negative electrode material according to claim 8 or 9.

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