Lithium battery foil and preparation method thereof

Abstract

The invention provides a lithium battery foil and a preparation method thereof, and belongs to the technical field of new materials. According to the lithium battery foil and the preparation method thereof provided by the invention, the lithium supplement effect can be remarkably improved, uniform lithium supplement and surface coating with full-surface nanometer precision are realized, and the large-scale mass production requirement is met. Through the specific method, the atmosphere inert protective film is deposited on the basis of front lithium supplementation, on one hand, dead lithium loss occurring in the initial charging and discharging process is eliminated, long-term charging and discharging performance stability and energy storage density improvement of the lithium battery are achieved, on the other hand, a lithium battery production line does not need to be greatly changed, and the production cost is reduced. According to the method provided by the invention, nano-precision uniform lithium supplementation and surface coating of the whole surface of the lithium battery foil are realized, the large-scale mass production requirement can be met, and the method has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a lithium battery foil and a preparation method thereof. Background Art

[0002] Energy storage capacity and energy storage density are key indicators for measuring the performance of lithium batteries. The core factor affecting the energy storage capacity and energy storage density of lithium batteries is the number of lithium ions that can freely shuttle between the positive and negative electrodes of lithium batteries. Because of the structural defects inside the active material crystals, as well as the gaps or impurity defects between the active powder particles generated during the formation of slurry, coating on the substrate, and subsequent drying, electrolyte injection and aging of the active material powder, after the completion of the lithium battery, during the first, first few, and dozens of charge and discharge processes, the lithium ions that should have been able to shuttle are adsorbed and fixed, and no longer participate in the charge and discharge process of the lithium battery, forming dead lithium, resulting in a significant decrease in the energy storage capacity and energy density of the lithium battery. Adding excess lithium in advance on the surface of the copper foil or aluminum foil substrate used for the collector of the lithium battery, or on the surface of the lithium battery pole coated with active material, the so-called lithium supplementation, is considered to be an effective means to offset the dead lithium that appears in the early charge and discharge process of the lithium battery, resulting in a decrease in energy storage capacity and energy density.

[0003] There are various lithium replenishment schemes in the prior art. For example, Chinese patent CN118099563A discloses an electrode lithium replenishment method and a lithium battery preparation method, wherein the electrode lithium replenishment method includes the following steps: S1: pre-lithiation of the negative electrode sheet: in an inert gas atmosphere, the negative electrode sheet is placed in an electrolyte with a water content of less than 200 ppm for charging, the current rate of the negative electrode sheet during charging is 0.1C to 3C and the water content in the inert gas atmosphere is less than 500 ppm, so that a SEI film is formed on the surface of the negative electrode sheet; S2: film pressing of the negative electrode sheet: after the negative electrode sheet is dried, the surface of the negative electrode sheet is coated with a film.

[0004] However, the lithium replenishment effect and electrode performance in the existing technology need to be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a lithium battery foil and a preparation method thereof, which can significantly improve the lithium replenishment effect, achieve uniform lithium replenishment and surface coating with nanometer precision on the entire surface, and meet the needs of large-scale mass production.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a lithium battery foil, comprising the following steps:

[0008] Using metal foil as a substrate for film coating to obtain lithium battery foil;

[0009] The first target material used in the coating contains lithium-based metal and is used to prepare the middle layer of the lithium battery foil;

[0010] The second target material used in the coating contains non-metallic elements and is used to prepare the surface layer of the lithium battery foil;

[0011] The coating is carried out by one or more of magnetron sputtering, multi-arc ion plating, electron beam or laser evaporation.

[0012] Preferably, the metal foil is copper foil or aluminum foil.

[0013] Preferably, the target material contains 1 to 100% lithium.

[0014] Preferably, the lithium-based metal is a lithium-based alloy, and the lithium-based alloy is one or more of a lithium-magnesium alloy, a lithium-aluminum alloy, a lithium-titanium alloy, a lithium-copper alloy, a lithium-zinc alloy, a lithium-nickel alloy, a lithium-manganese alloy, a lithium-containing ternary alloy, or a lithium-containing quaternary alloy.

[0015] Preferably, the non-metallic element includes one or more of carbon, silicon, oxygen, hydrogen, sulfur or phosphorus.

[0016] Preferably, the magnetron sputtering is performed in a vacuum environment, and the vacuum degree of the vacuum environment is 10 -4 ~100Pa.

[0017] Preferably, the magnetron sputtering is accompanied by a process gas atmosphere, and the process gas includes one or more of argon, oxygen, hydrogen, nitrogen or carbon-containing gas.

[0018] Preferably, the coating has a thickness of 1 to 100 nm or 2 to 200 nm.

[0019] Preferably, the conditions of the magnetron sputtering include:

[0020] Substrate routing speed 0.01~100m / min;

[0021] Vacuum coating plasma energy 10~1000eV;

[0022] Energy density 0.1mA / cm 2 ~10A / cm 2 .

[0023] The invention also provides a lithium battery foil prepared by the preparation method.

[0024] Beneficial effects of the present invention:

[0025] The present invention achieves the deposition of an atmospherically inert protective film based on pre-lithium replenishment through a specific method, which can effectively prevent the lithium film from chemically reacting in the air, eliminate the loss of dead lithium in the initial charge and discharge process, and achieve long-term stable charge and discharge performance and improved energy storage density of lithium batteries. The method provided by the present invention achieves uniform lithium replenishment and surface coating of the entire surface of lithium battery foil with nanometer precision, can meet the needs of large-scale mass production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the system structure for realizing the method of the present invention, in which 1 is a vacuum chamber, 2 represents vacuuming, 3 represents process gas input, 4 is a foil unwinding shaft, 5 is a foil winding shaft, 6 and 6' are foil support shafts, 7 and 7' are lithium supplementary coating sources and pole piece material layer deposition sources, 8 represents a collector foil in a lithium battery or a pole piece after being coated with an active material, and 9 and 9' are lithium-containing particles and pole piece active material particles evaporated or sputtered from the lithium supplementary coating source;

[0027] Figure 2 This is a schematic diagram of the structure of the lithium battery foil prepared by the present invention, in which: 1. Carbon-based film layer, thickness 2 to 200 nm; 2. Lithium-based film layer, thickness 1 to 100 nm; 3. Current collector (copper foil or aluminum foil) or pole piece, thickness 1 to 200 microns. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a lithium battery foil, comprising the following steps:

[0029] Using metal foil as a substrate for film coating to obtain lithium battery foil;

[0030] The first target material used in the coating contains lithium-based metal and is used to prepare the middle layer of the lithium battery foil;

[0031] The second target material used in the coating contains non-metallic elements and is used to prepare the surface layer of the lithium battery foil;

[0032] The coating is performed by one or more of magnetron sputtering, multi-arc ion plating, electron beam or laser evaporation, preferably magnetron sputtering.

[0033] In the present invention, preferably, the metal foil is copper foil or aluminum foil; preferably, the lithium content of the target material is 1 to 100%; preferably, the lithium-based metal is a lithium-based alloy, and the lithium-based alloy is one or more of lithium-magnesium alloy, lithium-aluminum alloy, lithium-titanium alloy, lithium-copper alloy, lithium-zinc alloy, lithium-nickel alloy, lithium-manganese alloy, lithium-containing ternary alloy or lithium-containing quaternary alloy; preferably, the non-metallic element includes one or more of carbon, silicon, oxygen, hydrogen, sulfur or phosphorus; further preferably, the second target material is a target material made of high-purity graphite with a purity of more than 4 9, or a target material made of a silicon-carbon composite material, or a target material made of a pole piece material to be coated on the basis of the lithium-supplemented substrate.

[0034] In the present invention, preferably, the magnetron sputtering is performed in a vacuum environment, and the vacuum degree of the vacuum environment is 10 -4 ~100Pa; preferably, the magnetron sputtering is accompanied by a process gas atmosphere, and the process gas includes one or more of argon, oxygen, hydrogen, nitrogen or carbon-containing gas; preferably, the conditions of the magnetron sputtering include: substrate line speed 0.01~100m / min; vacuum coating plasma energy 10~1000eV; energy density 0.1mA / cm 2 ~10A / cm 2 ; Preferably, the thickness of the coating is 1 to 100 nm or 2 to 200 nm, and further preferably, the thickness of the middle layer of the lithium battery foil is 1 to 100 nm; the thickness of the surface layer of the lithium battery foil is 2 to 200 nm.

[0035] The present invention also provides a lithium battery foil prepared by the preparation method, wherein the lithium battery foil comprises a surface layer, an intermediate layer and a bottom layer, as shown in the schematic diagram Figure 2 As shown; in the present invention, preferably, the surface layer is replaced by a carbon-based film layer or other newly developed negative electrode materials, such as a silicon-carbon film layer or a positive electrode material film layer, such as a film layer formed by lithium iron phosphate, nickel-cobalt-manganese ternary positive electrode materials, etc.; the surface layer of the present invention can protect the lithium-based film layer from being oxidized and corroded by the environment on the one hand, and can achieve excellent bonding with subsequent material film layers on the other hand; the carbon-based film layer of the present invention refers to a film layer mainly composed of carbon elements, wherein the structural characteristics are carbon with different structural forms such as crystalline graphite, amorphous chaotic carbon structure, amorphous diamond structure, and the presence of carbon doped with gas phase substances such as nitrogen, oxygen, hydrogen or solid phase substances such as lithium, magnesium, aluminum, etc., the introduction of impurity elements, or intentional independent introduction, such as gas phase elements, or mixed deposition introduction, such as lithium, magnesium and other elements.

[0036] The schematic diagram of the system structure for implementing the method of the present invention is as follows: Figure 1As shown, it includes: a vacuum chamber 1, a vacuum pumping system 2, a process gas input 3, a metal foil unwinding 4, a foil rewinding 5, a foil support shaft 6, a lithium replenishing coating source 7, a foil in a process object lithium battery 8, and lithium-containing particles 9 evaporated or sputtered from the lithium replenishing coating source; on the whole, the lithium replenishing system is composed of a vacuum chamber and a vacuum unit, a lithium battery foil and its routing mechanism, a lithium replenishing coating source and its dedicated power supply, a coating target and a process gas input, and a control system. The vacuum chamber provides the process environment required for lithium replenishment of the lithium battery foil. Under the action of the routing mechanism, the lithium battery foil is unwound, passes through the coating lithium replenishing area, and is rewound in the vacuum chamber. The lithium replenishing coating source is opposite to the foil unfolding area, and the evaporated or sputtered lithium-containing substance is deposited on the foil surface.

[0037] In the present invention, the vacuum chamber is a single chamber or multiple chambers; when it is multiple chambers, unwinding, lithium replenishment plating, and winding are completed in three chambers respectively, and the chambers are vacuum isolated. The foil routing mechanism is realized by driving the unwinding and winding shafts to rotate, and the driving mode is either an external gear plus an intermediate sealing ring sealing drive, or a magnetic fluid sealing drive; as needed, the unwinding and winding shafts can be operated in reverse motion. The foil surface lithium replenishment plating source is located directly in front of the foil lithium replenishment area. The lithium replenishment plating source can be a resistance evaporation source, a magnetron sputtering source, an arc evaporation source, or a laser evaporation source. The distance between the lithium replenishment plating source and the lithium battery foil is between 1 cm and 1 m.

[0038] When the system of the present invention is used for product processing, it can be applied without major changes to the lithium battery production line, and the application scenarios are more extensive.

[0039] When the above system is used for application, the process parameters and operations are preferably as follows:

[0040] Step 1: Install and fix the metal foil coil on the reel and test whether the reel moves normally;

[0041] Step 2: Close the vacuum chamber door and start the vacuum pumping system. At this time, the minimum vacuum is controlled to be no greater than 10Pa, and the ultimate vacuum is 10 -4 Pa;

[0042] Step 3: Process gas is introduced into the vacuum chamber, and the vacuum of the vacuum chamber is maintained at 100-0.01Pa;

[0043] Step 4, start the reeling and unreeling shaft to rotate;

[0044] Step 5, starting the lithium supplementation plating source to complete the plating according to the preparation method provided by the present invention;

[0045] Step 5: After the whole roll of lithium battery foil is processed, the lithium replenishment coating source, process gas input, metal foil reel routing movement, and vacuum system exhaust are turned off in sequence. Then, the vacuum chamber is vented to atmospheric pressure, and the lithium battery foil that has completed the lithium replenishment treatment is taken out to complete the process.

[0046] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] Example 1

[0048] The copper foil is 400 mm wide, 6 microns thick and 30 kg in weight. The reel, unreel, and support shafts 4, 5, 6, and 6' are all stainless steel rollers with a height of 600 mm. They are fixed to the wall of the vacuum chamber 1 through an insulating and dynamically sealed sealing sleeve. The vacuum chamber 1 is made of stainless steel. The vacuum system adopts a three-stage cascade form of mechanical pump, Rhodes pump, and molecular pump to obtain 5×10 -4 The ultimate vacuum is Pa, and the process gas input adopts a three-way gas mass flow meter. The process gases that can be input are argon, oxygen, nitrogen and hydrogen.

[0049] The support shaft 6 is located between the winding shaft and the unwinding shaft, and the center line is located at a position 20mm above the two shaft connection line to ensure close contact between the support shaft and the copper foil. The spacing between the support shaft and the winding and unwinding shafts is 400mm. The winding shaft, unwinding shaft and the negative support shaft are all driven to rotate by magnetic fluid, thereby driving the copper foil to move and align. The achievable alignment rate ranges from 0.01m / min to 100m / min.

[0050] Opposite to the supporting shaft, on the wall of the vacuum chamber, a rectangular magnetron sputtering coating source is installed, and the effective width of the magnetron sputtering coating source is 200 mm and the height is 600 mm.

[0051] Lithium-magnesium alloy (50%:50% mass ratio) and high-purity graphite are used as magnetron sputtering targets. The magnetron sputtering power supply is characterized by a DC high-voltage power supply with a maximum suspension voltage of 1000V and a maximum process current of 20A.

[0052] The vacuum chamber has an internal space height of 800 mm and an overall cylindrical body with a diameter of 1000 mm.

[0053] The process of copper foil surface magnetron sputtering coating lithium replenishment is as follows: 1. The vacuum chamber is evacuated to the ultimate vacuum of 5×10 - 4Pa, 2. Input process gas argon, and the vacuum degree of the vacuum chamber reaches 0.5Pa, 3. Start the copper foil routing system with a routing speed of 1m / min, 4. Start the lithium-based metal target and high-purity graphite target magnetron sputtering coating source power supply in turn, and adjust the process voltage to 500V and the current to 10A, 5. Stabilize the above conditions and work continuously until the lithium replenishment coating treatment of the entire roll of copper foil is completed (the part whose heads and tails are always fixed on the winding and unwinding shafts is not counted), 6. Stop magnetron sputtering, process gas input, vacuum pumping, etc., let the atmosphere into the vacuum chamber, take out the copper foil that has completed the lithium replenishment treatment, and the lithium replenishment process of the surface coating of a batch of copper foil is completed.

[0054] Example 2

[0055] The negative electrode sheet with a width of 400mm and a thickness of 100 microns, which has been coated, dried and compacted with graphite material, adopts a multi-chamber coating and lithium replenishment system. Its unwinding, lithium replenishment coating, carbon-based coating and winding are respectively in different chambers. Each chamber has an independent vacuum system, which adopts a three-stage cascade form of mechanical pump, Rhodes pump and molecular pump to obtain 5×10 -4 The ultimate vacuum of Pa is 1.58kPa. The two coating chambers are connected to the process gas input. A three-way gas mass flow meter is used. The process gases that can be input are argon, oxygen, nitrogen and hydrogen.

[0056] A synchronous motor is used to drive the negative pole pieces in different chambers to move forward at a uniform speed, and the routing rate obtained is adjustable from 0.01m / min to 100m / min.

[0057] In the coating chamber, a rectangular multi-arc ion coating source is installed on the wall of the vacuum chamber opposite to the supporting shaft. The effective width of the multi-arc ion coating source is 200 mm and the height is 600 mm.

[0058] Lithium-magnesium alloy (50%:50% mass ratio) and high-purity graphite are used as magnetron sputtering targets. The multi-arc ion plating power supply is characterized by a low-voltage and high-current power supply, with a maximum suspension voltage of 100V and a maximum process current of 200A.

[0059] The process of magnetron sputtering coating and lithium replenishment on the surface of the negative electrode is as follows: 1. The vacuum chamber is evacuated to the ultimate vacuum of 5×10 -4Pa, 2. Input process gas argon, and the vacuum degree of the vacuum chamber reaches 0.5Pa, 3. Start the electrode routing system with a routing speed of 1m / min, 4. Start the multi-arc ion plating source power supply of lithium-based metal targets and high-purity graphite targets in turn, and adjust the process voltage to 20V and the current to 100A, 5. Stabilize the above conditions and work continuously until the lithium replenishment plating process of the entire roll of copper foil is completed (the part that is always fixed on the winding and unwinding shafts at the beginning and end is not counted), 6. Stop multi-arc ion plating, process gas input, vacuum pumping, etc., let the atmosphere into the winding chamber, take out the negative electrode piece that has completed the lithium replenishment treatment, and the lithium replenishment process of the surface coating of a batch of negative electrode pieces is completed.

[0060] Example 3

[0061] The positive electrode sheet with a width of 400mm and a thickness of 100 microns has been coated, dried and compacted with 8 series ternary positive electrode materials. It adopts a multi-chamber coating and lithium replenishment system. Its unwinding, lithium replenishment coating, carbon-based coating and winding are respectively in different chambers. Each chamber has an independent vacuum system, which adopts a three-stage cascade form of mechanical pump, Rhodes pump and molecular pump to obtain 5×10 -4 The ultimate vacuum of Pa is 1.58kPa. The two coating chambers are connected to the process gas input. A three-way gas mass flow meter is used. The process gases that can be input are argon, oxygen, nitrogen and hydrogen.

[0062] A synchronous motor is used to drive the negative pole pieces in different chambers to move forward at a uniform speed, and the routing rate obtained is adjustable from 0.01m / min to 100m / min.

[0063] In the coating chamber, a rectangular electron beam evaporation coating source is installed on the wall of the vacuum chamber opposite to the supporting axis. The effective width of the electron beam evaporation coating source target is 200 mm and the height is 600 mm.

[0064] Lithium-magnesium alloy (50%:50% mass ratio) and high-purity graphite are used as coating targets. Electron beams are scanned and evaporated on the surface of the target to achieve coating, and the maximum power of the electron beam output is 10kW.

[0065] The process of electron beam evaporation coating of positive electrode to replenish lithium is as follows: 1. The vacuum chamber is evacuated to the ultimate vacuum of 5×10 -4 Pa, 2. Input process gas argon, vacuum chamber vacuum to 0.005Pa, 3. Start the electrode routing system, the routing rate is 1m / min, 4. Start the lithium-based metal target and high-purity graphite target electron beam power supply in turn, adjust the process voltage to 5kV, the target surface is electron beamed at 1m 2 / s rate uniform scanning, 5. Stabilize the above conditions and work continuously until the whole roll of copper foil is treated with lithium replenishment (the part whose head and tail are always fixed on the winding and unwinding shafts is not counted), 6. Stop the electron beam evaporation, process gas input, vacuum pumping and other operations, let the atmosphere into the winding chamber, take out the positive electrode sheets that have completed the lithium replenishment treatment, and the lithium replenishment process of the surface coating of a batch of positive electrode sheets is completed.

[0066] Example 4

[0067] The aluminum foil is 400 mm wide, 12 microns thick and 30 kg in weight. The reel, unreel, and support shafts 4, 5, 6, and 6' are all stainless steel rollers with a height of 600 mm. They are fixed to the wall of the vacuum chamber 1 through an insulating and dynamically sealed sealing sleeve. The vacuum chamber 1 is made of stainless steel. The vacuum system adopts a three-stage cascade form of mechanical pump, Rhodes pump, and molecular pump to obtain 5×10 -4 The ultimate vacuum is Pa, and the process gas input adopts a three-way gas mass flow meter. The process gases that can be input are argon, oxygen, nitrogen and hydrogen.

[0068] The support shafts 6 and 6' are located between the winding shaft and the unwinding shaft, and the center line is located at a position 20mm above the two shaft connection line, ensuring close contact between the support shaft and the copper foil. The spacing between the support shaft and the winding and unwinding shafts is 400mm. The winding shaft, unwinding shaft and the negative electrode support shaft are all driven to rotate by magnetic fluid, thereby driving the aluminum foil to move and walk. The available walking speed ranges from 0.01m / min to 100m / min.

[0069] Opposite to the supporting axis, on the wall of the vacuum chamber, a rectangular laser evaporation coating source is installed. The effective width of the laser evaporation source target is 200 mm and the height is 600 mm.

[0070] Lithium-magnesium alloy (50%:50% mass ratio) and high-purity graphite are used as laser evaporation targets. The laser pulse scans the target, and the target is vaporized and evaporated to achieve coating. The maximum power of the laser is 10kW.

[0071] The vacuum chamber has an internal space height of 800 mm and an overall cylindrical body with a diameter of 1000 mm.

[0072] The process of magnetron sputtering coating lithium replenishment on aluminum foil surface is as follows: 1. The vacuum chamber is evacuated to the ultimate vacuum of 5×10 - 4 Pa, 2. Input process gas argon, vacuum chamber vacuum to 0.005Pa, 3. Start the aluminum foil routing system, the routing rate is 1m / min, 4. First start the high-purity graphite target laser evaporation coating source power supply, adjust the laser output power to 5kW, the target surface is laser beam at 1m 2 / s uniform scanning rate, 5. Stabilize the above conditions and work continuously until the graphite coating of the entire roll of aluminum foil is completed (the part with the head and tail always fixed on the winding and unwinding shafts is not counted), and stop the graphite target coating work, 6. Reverse start the aluminum foil routing system, the routing rate is 1m / min, and on the basis of the unchanged argon gas, a trace amount of oxygen is introduced (the input ratio of argon to oxygen is 10:1), 7. Start the lithium-based metal target laser evaporation film source power supply, adjust the laser output power to 5kW, and the target surface is irradiated by the laser beam at a speed of 1m 2 / s uniform scanning rate, 8. Stabilize the above conditions and work continuously until the lithium-based metal coating of the entire roll of aluminum foil is completed (the part with the head and tail always fixed on the winding and unwinding shafts is not counted), stop the lithium-based metal target coating work and oxygen input, 9. Repeat the process of 3-5, that is, restart the aluminum foil routing in the forward direction, start the graphite target work, until the entire roll of aluminum foil is completely coated, 10. Stop laser evaporation, process gas input, vacuum pumping, etc., let the atmosphere into the vacuum chamber, take out the aluminum foil that has completed the lithium replenishment treatment, and the lithium replenishment process of the surface coating of a batch of aluminum foil is completed.

[0073] Experimental example

[0074] The performance of the product obtained in the embodiment is tested, and the thickness of the lithium supplement coating is obtained by testing the cross section of the coating using an optical microscope and a scanning electron microscope;

[0075] The bonding strength test used a hundred-grid tape bonding and tearing method. When the original sheet was copper foil or aluminum foil, there was no peeling of the lithium supplement coating. When the original sheet was a negative electrode sheet or a positive electrode sheet, there was a peeling phenomenon of the electrode sheet coating, i.e., the graphite layer and the positive electrode material layer.

[0076] In the weather resistance test, the lithium-replenished samples were placed in the atmosphere for 48 hours, and the weight changes before and after were measured. There was no obvious change (the weight change was less than one ten-thousandth); when the original sheet was the positive electrode sheet or the negative electrode sheet, there was occasional (less than one ten-thousandth) weight change in some samples. This was caused by the uneven surface of the original sheet, the lack of full coverage of the lithium-replenished coating, and the changes in the electrode material in the environment.

[0077] Subsequent tests were also carried out on the lithium replenishment effect. For samples whose original sheets were copper foil and aluminum foil, the first step was to continue to coat graphite negative electrode materials and ternary positive electrode materials to form corresponding negative electrode sheets and positive electrode sheets, and then test them. During the test, the battery structure formed was: graphite negative electrode sheet / diaphragm / ternary positive electrode sheet.

[0078] The results are shown in Table 1 below:

[0079] Table 1 Example lithium supplement coating analysis

[0080]

[0081] The results show that compared with the lithium battery samples that have not been supplemented with lithium, the final lithium battery samples obtained in Examples 1, 2, 3, and 4 have significantly improved cycle performance, and the lithium storage capacity (calculated according to the content of the ternary positive electrode material) is also significantly improved for the lithium battery samples whose original sheets are aluminum foil and ternary positive electrode sheets.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a lithium battery foil, characterized in that: The following steps are involved: Using metal foil as a substrate for film coating to obtain lithium battery foil; The first target material used in the coating contains lithium-based metal and is used to prepare the middle layer of the lithium battery foil; The second target material used in the coating contains non-metallic elements and is used to prepare the surface layer of the lithium battery foil; The coating is carried out by one or more of magnetron sputtering, multi-arc ion plating, electron beam or laser evaporation.

2. The preparation method according to claim 1, characterized in that: The metal foil is copper foil or aluminum foil.

3. The preparation method according to claim 1, characterized in that: The target material contains 1 to 100% lithium.

4. The preparation method according to claim 3, characterized in that: The lithium-based metal is a lithium-based alloy, and the lithium-based alloy is one or more of a lithium-magnesium alloy, a lithium-aluminum alloy, a lithium-titanium alloy, a lithium-copper alloy, a lithium-zinc alloy, a lithium-nickel alloy, a lithium-manganese alloy, a lithium-containing ternary alloy, or a lithium-containing quaternary alloy.

5. The preparation method according to claim 1, characterized in that: The non-metallic elements include one or more of carbon, silicon, oxygen, hydrogen, sulfur or phosphorus.

6. The preparation method according to claim 1, characterized in that: The lithium supplementation coating is carried out in a vacuum environment, and the vacuum degree of the vacuum environment is 10 -4 ~100Pa.

7. The preparation method according to claim 6, characterized in that: The lithium-replenishing film is accompanied by a process gas atmosphere, and the process gas includes one or more of argon, oxygen, hydrogen, nitrogen or carbon-containing gas.

8. The preparation method according to claim 1, characterized in that: The thickness of the coating is 1-100 nm or 2-200 nm.

9. The preparation method according to claim 1, characterized in that: The conditions for the lithium supplementation plating include: Substrate routing speed 0.01~100m / min; Vacuum coating plasma energy 10~1000eV; The surface current density of the coating source is 0.1 mA / cm 2 ~10A / cm 2 .

10. A lithium battery foil prepared by the preparation method according to any one of claims 1 to 9.

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