Preparation process and application of current collector with lithium supplement function

Abstract

The invention discloses a preparation process and application of a current collector with a lithium supplementing function, and relates to the technical field of functional current collectors. The preparation method of the current collector with the lithium supplementing function comprises the following steps: step 1, coating lithium supplementing slurry on the surface of a thin film substrate, and drying to obtain a lithium supplementing layer; 2, coating the surface of the lithium supplementing layer with priming slurry, and drying to obtain a priming layer; and 3, evaporating an aluminum layer on the surface of the base layer to obtain the lithium-supplementing functional current collector. The application method comprises the following steps: coating a conductive coating on the surface of a current collector with a lithium supplement function, drying and rolling to obtain a pole piece with a lithium supplement function; and assembling a battery cell by taking the lithium-supplementing functional pole piece as a positive electrode and graphite as a negative electrode, and injecting an electrolyte containing an initiator to finish the assembly.

Description

Technical Field

[0001] The present invention relates to the technical field of functional integrated fluid, and specifically to a preparation process and application of a lithium-supplementing functional integrated fluid. Background Art

[0002] A functional integrated fluid is a new type of composite foil with a "metal conductive layer - PET / PP polymer material support layer - metal conductive layer" sandwich structure, which is made by depositing metals (copper or aluminum) on both the upper and lower surfaces with polymer PET, PP and other organic polymer materials as the support layer. Composite copper foil and composite aluminum foil are used as the negative electrode current collector and the positive electrode current collector respectively to replace traditional electrolytic copper foil and rolled aluminum foil and are applied to lithium batteries.

[0003] The application of the functional integrated fluid can reduce the consumption of copper and aluminum metals, thus effectively reducing the battery mass, helping to improve the energy density of the battery, and also being helpful for the safety test of the battery core to a certain extent. However, the main function of the functional integrated fluid is to support the active material and collect current; it does not directly participate in the electrode chemical reaction and does not make a positive contribution to the battery core life.

[0004] Based on this, the present invention is designed to set a lithium-containing bottom layer on the polymer PET / PP so that it can play a role in supplementing lithium ions when the lithium ions are consumed during the battery core cycle, thereby extending the cycle life of the battery core.

[0005] In summary, the present invention will propose a preparation process and application of a lithium-supplementing functional integrated fluid, which is of great significance. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation process and application of a lithium-supplementing functional integrated fluid to solve the problems raised in the above background art.

[0007] To solve the above technical problems, the present invention provides the following technical solutions in the first aspect:

[0008] A preparation process of a lithium-supplementing functional integrated fluid includes the following steps:

[0009] Step 1: Coat a lithium-supplementing slurry on the surface of a thin film substrate and vacuum dry it at 120 - 140 °C to obtain a lithium-supplementing layer;

[0010] Step 2: Coat a bottoming slurry on the surface of the lithium-supplementing layer and vacuum dry it at 120 - 140 °C to obtain a bottoming layer;

[0011] Step 3: Evaporate a layer of aluminum on the surface of the bottoming layer to obtain a lithium-supplementing functional integrated fluid.

[0012] Further, the thin film substrate is a PET film or a PP film, and its thickness is 6 - 30 μm.

[0013] Further, the lithium supplement slurry is obtained by mixing the following components: by weight, 2-4 parts of lithium aluminum alloy, 6-10 parts of lithium-rich compound coated with silicon dioxide, 0.8-1.4 parts of polyvinylidene fluoride, and 1.2-2.3 parts of N-methylpyrrolidone.

[0014] Further, the thickness of the lithium supplement layer is 0.6-0.7 μm.

[0015] Further, the primer slurry is obtained by mixing the following components: by weight, 5-10 parts of alumina, 0.5-1 part of polyvinylidene fluoride, and 0.5-1 part of N-methylpyrrolidone.

[0016] Further, the thickness of the primer layer is 0.1-0.2 μm.

[0017] Further, the particle sizes of the lithium aluminum alloy, the lithium-rich compound coated with silicon dioxide, and the alumina are D50 0.1-0.3 μm.

[0018] Further, the process parameters of the evaporation coating are: the vacuum degree ≤ 1×10 -2 Pa, and the evaporation coating temperature is 1400-1600 °C.

[0019] Further, the total thickness of the aluminum layer, the lithium supplement layer, and the primer layer is 1 μm.

[0020] Further, the preparation method of the lithium-rich compound coated with silicon dioxide is as follows:

[0021] (1) Add the lithium-rich compound and a 0.05-0.1 mol / L sodium hydroxide solution to absolute ethanol, stir and mix to obtain a lithium-rich compound dispersion;

[0022] (2) Add tetraethyl orthosilicate to an 85-90 wt% ethanol solution, stir and mix to obtain a tetraethyl orthosilicate dispersion;

[0023] (3) At 70-90 °C, slowly add the tetraethyl orthosilicate dispersion to the lithium-rich compound dispersion, continuously stir while dropping, and continue to stir until the solvent is completely evaporated to obtain a precursor of the lithium-rich compound coated with silicon dioxide;

[0024] (4) Heat the precursor of the lithium-rich compound coated with silicon dioxide to 550-700 °C at a heating rate of 5-10 °C / min, and keep it warm for 3-9 h to obtain the lithium-rich compound coated with silicon dioxide.

[0025] Further, the proportional relationship among the lithium-rich compound, the sodium hydroxide solution, and the absolute ethanol is 1 g: (0.5-1) mL: (99-99.5) mL.

[0026] Further, the proportional relationship between tetraethyl orthosilicate and the ethanol solution is (0.3 - 0.9) g: 100 mL.

[0027] Further, the volume ratio of the tetraethyl orthosilicate dispersion to the lithium-rich compound dispersion is 1:1.

[0028] Further, the lithium-rich compound includes but is not limited to any one of lithium iron phosphate, lithium fluoride, lithium cobalt phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0029] In the present invention, a lithium supplementation slurry and a primer slurry are sequentially sprayed on a polymer film to obtain a primer lithium supplementation layer; under the action of an initiator, the primer lithium supplementation layer can be separated from the polymer film, thereby releasing lithium ions, realizing lithium supplementation during the charge and discharge cycles of the battery cell, so as to achieve the purpose of extending the cycle life of the battery cell.

[0030] The lithium supplementation materials in the primer lithium supplementation layer include lithium aluminum alloy and the silica-coated lithium-rich compound prepared in the present invention. The two can cooperate to supplement lithium ions to the battery cell during the charge and discharge cycles of the battery cell. The action periods of the two lithium supplementation materials are different. Among them, under the action of the initiator contained in the electrolyte, the lithium aluminum alloy will expose and release lithium ions to supplement the battery cell after about 20 cycles; while the silica-coated lithium-rich compound will release slowly. The reason is that: in the early stage of the electrochemical cycle, the silica shell of the silica-coated lithium-rich compound will slowly react with the initiator, and then a porous structure will be formed on the silica shell, enabling the lithium-rich compound in the silica-coated lithium-rich compound to be slowly released, and only then can the lithium supplementation effect be exerted. At this time, part of the lithium aluminum alloy will also be consumed, and the speed of its lithium ion release will slow down. The release of the lithium-rich compound at this time can make up for this point. That is, under the synergistic action of the lithium aluminum alloy and the silica-coated lithium-rich compound, efficient lithium supplementation of the battery cell can be comprehensively realized, which can greatly extend the cycle life of the battery cell. At the same time, the silica-coated lithium-rich compound can also prevent more hydrogen fluoride from being decomposed from the electrolyte and can further improve the electrochemical performance of the battery cell.

[0031] In the preparation of the silica-coated lithium-rich compound, adding an appropriate amount of sodium hydroxide to the lithium-rich compound dispersion can improve the subsequent coating effect of silica, and can also have a certain cleaning effect on the residual impurities of the lithium-rich compound. However, the amount of sodium hydroxide should not be too much, otherwise it will react with silica and affect its coating; and in the present invention, the thickness of the silica coating shell can be controlled by controlling the addition amount of tetraethyl orthosilicate, so as to control the release speed of the lithium-rich compound in the follow-up.

[0032] The second aspect of the present invention provides the following technical solution:

[0033] Application of a lithium - supplementing functional current collector, and the application method is as follows: Coat a conductive coating on the surface of the lithium - supplementing functional current collector, vacuum - dry at 120 - 140 °C, and roll - press to obtain a lithium - supplementing functional electrode sheet; Use the lithium - supplementing functional electrode sheet as the positive electrode, graphite as the negative electrode, assemble into an electric core, and inject a lithium hexafluorophosphate electrolyte containing an initiator to complete the assembly.

[0034] Further, the coating amount of the conductive coating is 350 - 450 g / m 2 。

[0035] Further, the conductive coating is obtained by uniformly mixing lithium nickel cobalt manganate, polyvinylidene fluoride, and carbon black in a mass ratio of 9:1:1, and then adding them to N - methylpyrrolidone for mixing and preparation; its solid content is 85 - 90 wt%.

[0036] Further, the thickness of the lithium - supplementing functional electrode sheet is 150 - 200 μm.

[0037] Further, the initiator is hydrogen fluoride, and its concentration is 800 - 1200 ppm.

[0038] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0039] (1) The present invention uses the synergy of lithium - aluminum alloy and silicon - dioxide - coated lithium - rich compound to supplement lithium ions to the electric core during the charge - discharge cycle of the electric core.

[0040] (2) The acting periods of the lithium - supplementing materials in the lithium - supplementing slurry of the present invention are different. The lithium - aluminum alloy releases lithium for supplementing first, and the silicon - dioxide - coated lithium - rich compound releases it slowly, comprehensively realizing long - term and efficient lithium supplementation for the electric core.

[0041] (3) The lithium - supplementing current collector prepared by the present invention provides an efficient lithium - supplementing behavior when the electric core consumes lithium ions during cycling, thereby extending the cycle life of the electric core. Specific Embodiments

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0043] It should be noted that the following parts are by weight. There are no special restrictions on the purchase manufacturers of all the raw materials involved in the present invention. Exemplarily, they include:

[0044] In the following embodiments, the PET film, with a thickness of 10 μm and a model of XR40H, is purchased from Toray Polyester Film Co., Ltd.

[0045] Lithium aluminum alloy, 20Li80Al, CAS No.: 87871-87-2, battery grade; lithium iron phosphate, CAS No.: 15365-14-7, battery grade; lithium nickel cobalt manganese oxide, CAS No.: 346417-97-8, battery grade; lithium hexafluorophosphate electrolyte, article number: L741803; all of the above were purchased from Merck & Co., Inc.;

[0046] Polyvinylidene fluoride, article number: 768737; aluminum oxide, purity 99%, particle size D50 0.1 - 0.3 μm; both were purchased from Macklin Biochemical Co., Ltd.;

[0047] The rest were all purchased commercially; each portion in the following examples was 10 g.

[0048] Example 1: Preparation process and application of a lithium - supplementing current collector:

[0049] (I) Preparation process:

[0050] Step 1: 1. Preparation of silicon dioxide - coated lithium iron phosphate: (1) Add 10 parts of lithium iron phosphate and 75 mL of 0.075 mol / L sodium hydroxide solution to 9.925 L of absolute ethanol, stir and mix to obtain a lithium iron phosphate dispersion; (2) Add 6 parts of tetraethyl orthosilicate to 10 L of 87.5 wt% ethanol solution, stir and mix to obtain a tetraethyl orthosilicate dispersion; (3) At 80 °C, slowly add 10 L of the tetraethyl orthosilicate dispersion to 10 L of the lithium iron phosphate dispersion, continuously stir while dropping, and after dropping, continue to stir until the solvent is completely evaporated to obtain a silicon dioxide - coated lithium iron phosphate precursor; (4) Heat the silicon dioxide - coated lithium iron phosphate precursor to 620 °C at a heating rate of 7.5 °C / min, hold for 6 h to obtain silicon dioxide - coated lithium iron phosphate;

[0051] 2. Preparation of the lithium - supplementing slurry: Grind the lithium aluminum alloy and silicon dioxide - coated lithium iron phosphate to a particle size of D50 0.2 μm, and then mix them evenly with polyvinylidene fluoride and N - methylpyrrolidone to obtain the lithium - supplementing slurry;

[0052] The lithium - supplementing slurry includes the following components: by weight, 3 parts of lithium aluminum alloy, 8 parts of silicon dioxide - coated lithium - rich iron phosphate, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N - methylpyrrolidone;

[0053] 3. Coating the lithium - supplementing slurry: Coat the lithium - supplementing slurry on the surface of a 10 - μm - thick PET film and dry it under vacuum at 130 °C to obtain a 0.65 - μm - thick lithium - supplementing layer;

[0054] Step 2: 1. Prepare the primer slurry: Grind alumina to a particle size of D50 0.2 μm, and then mix it evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain the primer slurry;

[0055] The primer slurry includes the following components: by weight, 8 parts of alumina, 0.8 parts of polyvinylidene fluoride, and 0.8 parts of N-methylpyrrolidone;

[0056] 2. Coat the primer slurry: Coat the primer slurry on the surface of the lithium supplement layer and dry it in vacuum at 130 °C to obtain a primer layer with a thickness of 0.15 μm;

[0057] Step 3: Evaporate a 0.2-μm-thick aluminum layer on the surface of the primer layer to obtain a lithium supplement functional current collector;

[0058] The process parameters of the evaporation are: the vacuum degree is 1×10 -3 Pa, and the evaporation temperature is 1500 °C;

[0059] (2) Application:

[0060] 1. Prepare the conductive slurry: Mix lithium nickel cobalt manganese oxide, polyvinylidene fluoride, and carbon black in a mass ratio of 9:1:1 evenly, and then add them to N-methylpyrrolidone to mix and prepare it. The solid content is 87.5 wt%;

[0061] 2. Coat the conductive coating on the surface of the lithium supplement functional current collector, and the coating amount is 400 g / m 2 , dry it in vacuum at 130 °C and roll it to obtain a lithium supplement functional electrode sheet with a thickness of 180 μm; Use the lithium supplement functional electrode sheet as the positive electrode and graphite as the negative electrode to assemble a 71173204-type square battery cell, and inject a lithium hexafluorophosphate electrolyte containing hydrogen fluoride with a concentration of 1000 ppm to complete the assembly.

[0062] Example 2: A preparation process and application of a lithium supplement functional current collector:

[0063] (1) Preparation process:

[0064] Step 1: 1. Preparation of lithium iron phosphate coated with silica: (1) Add 10 parts of lithium iron phosphate and 75 mL of 0.05 mol / L sodium hydroxide solution to 9.95 L of anhydrous ethanol, stir and mix to obtain a lithium iron phosphate dispersion; (2) Add 3 parts of tetraethyl orthosilicate to 10 L of 87.5 wt% ethanol solution, stir and mix to obtain a tetraethyl orthosilicate dispersion; (3) At 80 °C, slowly add 10 L of the tetraethyl orthosilicate dispersion to 10 L of the lithium iron phosphate dispersion, continuously stir while dropping, and after dropping, continue to stir until the solvent is completely evaporated to obtain a lithium iron phosphate coated with silica precursor; (4) Heat the lithium iron phosphate coated with silica precursor to 620 °C at a heating rate of 7.5 °C / min, and keep it at this temperature for 6 h to obtain lithium iron phosphate coated with silica;

[0065] 2. Preparation of lithium supplement slurry: Grind lithium aluminum alloy and lithium iron phosphate coated with silica to a particle size of D50 0.2 μm, and then mix them evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain a lithium supplement slurry;

[0066] The lithium supplement slurry includes the following components: by weight, 3 parts of lithium aluminum alloy, 6 parts of lithium iron phosphate coated with silica, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N-methylpyrrolidone;

[0067] 3. Coating the lithium supplement slurry: Coat the lithium supplement slurry on the surface of a 10 μm thick PET film, and dry it in vacuum at 130 °C to obtain a 0.65 μm thick lithium supplement layer;

[0068] Step 2: 1. Preparation of primer slurry: Grind alumina to a particle size of D50 0.2 μm, and then mix it evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain a primer slurry;

[0069] The primer slurry includes the following components: by weight, 8 parts of alumina, 0.8 parts of polyvinylidene fluoride, and 0.8 parts of N-methylpyrrolidone;

[0070] 2. Coating the primer slurry: Coat the primer slurry on the surface of the lithium supplement layer, and dry it in vacuum at 130 °C to obtain a 0.15 μm thick primer layer;

[0071] Step 3: Evaporate a 0.2 μm thick aluminum layer on the surface of the primer layer to obtain a lithium supplement functional current collector;

[0072] The process parameters of the evaporation are: the vacuum degree is 1×10 -3 Pa, and the evaporation temperature is 1400 °C;

[0073] (2) Application:

[0074] 1. Prepare conductive paste: Mix lithium nickel cobalt manganese oxide, polyvinylidene fluoride, and carbon black evenly at a mass ratio of 9:1:1, then add them to N-methylpyrrolidone and mix to prepare it, with a solid content of 87.5 wt%.

[0075] 2. Coat the conductive coating on the surface of the lithium supplement functional current collector, with a coating amount of 400 g / m 2 , vacuum dry at 130 °C and roll to obtain a lithium supplement functional electrode sheet with a thickness of 180 μm; Use the lithium supplement functional electrode sheet as the positive electrode and graphite as the negative electrode to assemble a 71173204 type square battery cell, and inject a lithium hexafluorophosphate electrolyte containing 800 ppm hydrogen fluoride to complete the assembly.

[0076] Example 3: A preparation process of a lithium supplement functional current collector and its application:

[0077] (I) Preparation process:

[0078] Step 1: 1. Prepare lithium iron phosphate coated with silicon dioxide: (1) Add 10 parts of lithium iron phosphate and 100 mL of 0.1 mol / L sodium hydroxide solution to 9.95 L of absolute ethanol, stir and mix to obtain a lithium iron phosphate dispersion; (2) Add 9 parts of tetraethyl orthosilicate to 10 L of 87.5 wt% ethanol solution, stir and mix to obtain a tetraethyl orthosilicate dispersion; (3) At 80 °C, slowly add 10 L of the tetraethyl orthosilicate dispersion to 10 L of the lithium iron phosphate dispersion, continuously stir while dropping, and continue to stir until the solvent completely evaporates to obtain a lithium iron phosphate coated with silicon dioxide precursor; (4) Heat the lithium iron phosphate coated with silicon dioxide precursor to 620 °C at a heating rate of 7.5 °C / min and hold for 6 h to obtain lithium iron phosphate coated with silicon dioxide;

[0079] 2. Prepare lithium supplement paste: Grind lithium aluminum alloy and lithium iron phosphate coated with silicon dioxide to a particle size of D50 0.2 μm, then mix them evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain lithium supplement paste;

[0080] The lithium supplement paste includes the following components: by weight, 3 parts of lithium aluminum alloy, 10 parts of lithium iron phosphate coated with silicon dioxide, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N-methylpyrrolidone;

[0081] 3. Coat the lithium supplement paste: Coat the lithium supplement paste on the surface of a 10 μm thick PET film, and vacuum dry at 130 °C to obtain a 0.65 μm thick lithium supplement layer;

[0082] Step 2: 1. Prepare a primer paste: Grind alumina to a particle size of D50 0.2 μm, then mix it evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain a primer paste;

[0083] The primer slurry comprises the following components: by weight, 8 parts of alumina, 0.8 part of polyvinylidene fluoride, and 0.8 part of N-methylpyrrolidone;

[0084] 2. Coating the primer slurry: Coating the primer slurry on the surface of the lithium supplement layer and drying it under vacuum at 130 °C to obtain a primer layer with a thickness of 0.15 μm;

[0085] Step 3: Evaporating a 0.2-μm-thick aluminum layer on the surface of the primer layer to obtain a lithium supplement functional current collector;

[0086] The process parameters for evaporation are as follows: the vacuum degree is 1×10 -3 Pa, and the evaporation temperature is 1600 °C;

[0087] (II) Application:

[0088] 1. Preparing the conductive slurry: Mixing lithium nickel cobalt manganese oxide, polyvinylidene fluoride, and carbon black in a mass ratio of 9:1:1 evenly, and then adding them to N-methylpyrrolidone for mixing and preparation. The solid content is 87.5 wt%;

[0089] 2. Coating the conductive coating on the surface of the lithium supplement functional current collector, with a coating amount of 400 g / m 2 , drying under vacuum at 130 °C, and rolling to obtain a lithium supplement functional electrode sheet with a thickness of 180 μm; Using the lithium supplement functional electrode sheet as the positive electrode and graphite as the negative electrode, assembling a 71173204-type square battery cell, and injecting a lithium hexafluorophosphate electrolyte containing hydrogen fluoride with a concentration of 1200 ppm to complete the assembly.

[0090] The following is based on Example 1 to set up control experiments, specifically Comparative Examples 1 to 3:

[0091] Comparative Example 1: Comparative Example 1 is based on Example 1 and adjusted as follows: Without adding lithium iron phosphate coated with silica, and other processes remain unchanged. Specifically:

[0092] A preparation process and application of a lithium supplement functional current collector:

[0093] (I) Preparation process:

[0094] Step 1:

[0095] 1. Preparing the lithium supplement slurry: Grinding the lithium aluminum alloy to a particle size of D50 0.2 μm, and then mixing it evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain the lithium supplement slurry;

[0096] The lithium supplement slurry comprises the following components: by weight, 11 parts of lithium aluminum alloy, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N-methylpyrrolidone;

[0097] 2. Coating the lithium - supplementing slurry: Coat the lithium - supplementing slurry on the surface of a 10 - μm - thick PET film and vacuum - dry it at 130°C to obtain a lithium - supplementing layer with a thickness of 0.65 μm;

[0098] Step 2: 1. Prepare the primer slurry: Grind alumina to a particle size of D50 0.2 μm, and then mix it evenly with polyvinylidene fluoride and N - methylpyrrolidone to obtain the primer slurry;

[0099] The primer slurry includes the following components: by weight, 8 parts of alumina, 0.8 parts of polyvinylidene fluoride, and 0.8 parts of N - methylpyrrolidone;

[0100] 2. Coat the primer slurry: Coat the primer slurry on the surface of the lithium - supplementing layer and vacuum - dry it at 130°C to obtain a primer layer with a thickness of 0.15 μm;

[0101] Step 3: Evaporate - deposit an aluminum layer with a thickness of 0.2 μm on the surface of the primer layer to obtain a lithium - supplementing functional current collector;

[0102] The process parameters of the evaporation - deposition are: the vacuum degree is 1×10 -3 Pa, and the evaporation - deposition temperature is 1500°C;

[0103] (2) Application:

[0104] 1. Prepare the conductive slurry: Mix lithium nickel cobalt manganese oxide, polyvinylidene fluoride, and carbon black in a mass ratio of 9:1:1 evenly, and then add them to N - methylpyrrolidone and mix and prepare to obtain it, and its solid content is 87.5 wt%;

[0105] 2. Coat the conductive coating on the surface of the lithium - supplementing functional current collector, and the coating amount is 400 g / m 2 , vacuum - dry it at 130°C, and roll - press it to obtain a lithium - supplementing functional electrode sheet with a thickness of 180 μm; Use the lithium - supplementing functional electrode sheet as the positive electrode and graphite as the negative electrode to assemble a 71173204 - type square battery cell, and inject a lithium hexafluorophosphate electrolyte containing hydrogen fluoride with a concentration of 1000 ppm to complete the assembly.

[0106] Comparative Example 2: Based on Example 1, Comparative Example 2 adjusted: did not coat lithium iron phosphate, and other processes remained unchanged. Specifically:

[0107] A preparation process and application of a lithium - supplementing functional current collector:

[0108] (1) Preparation process:

[0109] Step 1: 1. Prepare the lithium - supplementing slurry: Grind lithium aluminum alloy and lithium iron phosphate to a particle size of D50 0.2 μm, and then mix it evenly with polyvinylidene fluoride and N - methylpyrrolidone to obtain the lithium - supplementing slurry;

[0110] The lithium supplement slurry includes the following components: by weight, 3 parts of lithium aluminum alloy, 8 parts of lithium iron phosphate, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N-methylpyrrolidone;

[0111] 2. Coating the lithium supplement slurry: Coating the lithium supplement slurry on the surface of a 10-μm-thick PET film and drying it in vacuum at 130 °C to obtain a lithium supplement layer with a thickness of 0.65 μm;

[0112] Step 2: 1. Preparing the primer slurry: Grinding alumina to a particle size of D50 0.2 μm, and then mixing it evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain the primer slurry;

[0113] The primer slurry includes the following components: by weight, 8 parts of alumina, 0.8 parts of polyvinylidene fluoride, and 0.8 parts of N-methylpyrrolidone;

[0114] 2. Coating the primer slurry: Coating the primer slurry on the surface of the lithium supplement layer and drying it in vacuum at 130 °C to obtain a primer layer with a thickness of 0.15 μm;

[0115] Step 3: Evaporating a 0.2-μm-thick aluminum layer on the surface of the primer layer to obtain a lithium supplement functional current collector;

[0116] The process parameters for evaporation are: the vacuum degree is 1×10 -3 Pa, and the evaporation temperature is 1500 °C;

[0117] (II) Application:

[0118] 1. Preparing the conductive slurry: Mixing lithium nickel cobalt manganese oxide, polyvinylidene fluoride, and carbon black in a mass ratio of 9:1:1 evenly, and then adding them to N-methylpyrrolidone for mixing and preparation. Its solid content is 87.5 wt%;

[0119] 2. Coating the conductive coating on the surface of the lithium supplement functional current collector, with a coating amount of 400 g / m 2 , drying it in vacuum at 130 °C, and rolling it to obtain a lithium supplement functional electrode sheet with a thickness of 180 μm; Using the lithium supplement functional electrode sheet as the positive electrode and graphite as the negative electrode, assembling a 71173204-type square battery cell, and injecting a lithium hexafluorophosphate electrolyte containing hydrogen fluoride with a concentration of 1000 ppm to complete the assembly.

[0120] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustment: hydrogen fluoride is not added to the lithium hexafluorophosphate electrolyte, and other processes remain unchanged. Specifically:

[0121] A preparation process and application of a lithium supplement functional current collector:

[0122] (I) Preparation process:

[0123] Step 1: 1. Preparation of lithium iron phosphate coated with silica: (1) Add 10 parts of lithium iron phosphate and 75 mL of 0.075 mol / L sodium hydroxide solution to 9.925 L of absolute ethanol, stir and mix to obtain a lithium iron phosphate dispersion; (2) Add 6 parts of tetraethyl orthosilicate to 10 L of 87.5 wt% ethanol solution, stir and mix to obtain a tetraethyl orthosilicate dispersion; (3) At 80 °C, slowly add 10 L of tetraethyl orthosilicate dispersion to 10 L of lithium iron phosphate dispersion, continuously stir while dropping, after dropping, continue to stir until the solvent is completely evaporated to obtain a lithium iron phosphate coated with silica precursor; (4) Heat the lithium iron phosphate coated with silica precursor to 620 °C at a heating rate of 7.5 °C / min, hold for 6 h to obtain lithium iron phosphate coated with silica;

[0124] 2. Prepare the lithium supplement slurry: Grind the lithium aluminum alloy and lithium iron phosphate coated with silica to a particle size of D50 0.2 μm, and then mix evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain the lithium supplement slurry;

[0125] The lithium supplement slurry includes the following components: by weight, 3 parts of lithium aluminum alloy, 8 parts of lithium iron phosphate rich in silica, 1.1 parts of polyvinylidene fluoride, and 1.8 parts of N-methylpyrrolidone;

[0126] 3. Coat the lithium supplement slurry: Coat the lithium supplement slurry on the surface of a 10 μm thick PET film, and dry it in vacuum at 130 °C to obtain a 0.65 μm thick lithium supplement layer;

[0127] Step 2: 1. Prepare the primer slurry: Grind alumina to a particle size of D50 0.2 μm, and then mix evenly with polyvinylidene fluoride and N-methylpyrrolidone to obtain the primer slurry;

[0128] The primer slurry includes the following components: by weight, 8 parts of alumina, 0.8 parts of polyvinylidene fluoride, and 0.8 parts of N-methylpyrrolidone;

[0129] 2. Coat the primer slurry: Coat the primer slurry on the surface of the lithium supplement layer, and dry it in vacuum at 130 °C to obtain a 0.15 μm thick primer layer;

[0130] Step 3: Evaporate a 0.2 μm thick aluminum layer on the surface of the primer layer to obtain a lithium supplement functional current collector;

[0131] The process parameters of the evaporation are: the vacuum degree is 1×10 -3 Pa, and the evaporation temperature is 1500 °C;

[0132] (2) Application:

[0133] 1. Preparation of conductive paste: Lithium nickel cobalt manganate, polyvinylidene fluoride, and carbon black are mixed evenly in a mass ratio of 9:1:1, and then added to N-methylpyrrolidone for mixing and preparation, with a solid content of 87.5 wt%;

[0134] 2. Coating the conductive coating on the surface of the lithium-supplementing functional current collector, with a coating amount of 400 g / m 2 , followed by vacuum drying at 130 °C and rolling to obtain a lithium-supplementing functional electrode sheet with a thickness of 180 μm; Using the lithium-supplementing functional electrode sheet as the positive electrode and graphite as the negative electrode, a 71173204-type square battery cell is assembled, and a lithium hexafluorophosphate electrolyte is injected to complete the assembly.

[0135] Performance test: Electrochemical performance tests are carried out on the 71173204-type square battery cells assembled in Examples 1 to 3 and Comparative Examples 1 to 3, as follows:

[0136] (1) Battery internal resistance test: Use a multimeter to test the internal resistance of the battery;

[0137] (2) Charge-discharge cycle performance test: Test its capacity retention rate after 1000 charge-discharge cycles at a rate of 1C at 25 °C;

[0138] The specific test results of the above test items are shown in Table 1 below:

[0139] Table 1

[0140] Sample Internal resistance (mΩ) Capacity retention rate (%) Example 1 0.6 86.6 Example 2 0.7 81.7 Example 3 0.6 83.4 Comparative Example 1 1.5 71.5 Comparative Example 2 1.2 73.2 Comparative Example 3 0.9 79.8

[0141] Result analysis: It can be seen from the data in Table 1 above that for the square battery cells assembled in the examples, after 1000 charge-discharge cycles at a rate of 1C, their capacity retention rate still remains above 80%, indicating that the lithium-supplementing current collector prepared by the present invention can play a good role in lithium supplementation during the charge-discharge cycle of the battery cell. By comparing the examples and comparative examples, it can be known that through the synergistic effect of lithium-aluminum alloy and silicon dioxide-coated lithium-rich compounds, combined with a hydrofluoric acid initiator, the lithium-supplementing material can be well controlled for lithium supplementation release, comprehensively achieving long-term and efficient lithium supplementation for the battery cell and extending the cycle life of the battery cell.

[0142] The lithium-supplementing functional current collector prepared by the present invention has excellent charge-discharge cycle performance; Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Preparation process of a current collector with lithium supplementation function, characterized in that: It includes the following steps: Step 1: Coating a lithium - supplementing slurry on the surface of a thin - film substrate, and drying to obtain a lithium - supplementing layer; Step 2: Coating a primer slurry on the surface of the lithium - supplementing layer, and drying to obtain a primer layer; Step 3: Evaporating a layer of aluminum on the surface of the primer layer to obtain a lithium - supplementing functional current collector; Among them, the lithium - supplementing slurry is obtained by mixing the following components: by weight, 2 - 4 parts of lithium aluminum alloy, 6 - 10 parts of silica - coated lithium - rich compound, 0.8 - 1.4 parts of polyvinylidene fluoride, and 1.2 - 2.3 parts of N - methylpyrrolidone; The primer slurry is obtained by mixing the following components: by weight, 5 - 10 parts of alumina, 0.5 - 1 part of polyvinylidene fluoride, and 0.5 - 1 part of N - methylpyrrolidone.

2. The preparation process of a lithium supplement functional current collector according to claim 1, characterized in that: The preparation method of the silica - coated lithium - rich compound is as follows: (1) Adding a lithium - rich compound and a 0.05 - 0.1mol / L sodium hydroxide solution to absolute ethanol, stirring and mixing to obtain a lithium - rich compound dispersion; (2) Adding tetraethyl orthosilicate to an 85 - 90wt% ethanol solution, stirring and mixing to obtain a tetraethyl orthosilicate dispersion; (3) At 70 - 90°C, slowly adding the tetraethyl orthosilicate dispersion to the lithium - rich compound dispersion, continuously stirring while dropping, and after dropping, continuing to stir until the solvent is completely evaporated to obtain a silica - coated lithium - rich compound precursor; (4) Heating the silica - coated lithium - rich compound precursor to 550 - 700°C at a heating rate of 5 - 10°C / min, and holding for 3 - 9h to obtain the silica - coated lithium - rich compound; Among them, the proportional relationship among the lithium - rich compound, sodium hydroxide solution, and absolute ethanol is 1g:(0.5 - 1)mL:(99 - 99.5)mL; The proportional relationship between tetraethyl orthosilicate and the ethanol solution is (0.3 - 0.9)g:100mL; The volume ratio of the tetraethyl orthosilicate dispersion to the lithium - rich compound dispersion is 1:

1.

3. The preparation process of a lithium supplement functional current collector according to claim 2, characterized in that: The lithium - rich compound includes any one of lithium iron phosphate, lithium fluoride, lithium cobalt phosphate, lithium cobalt oxide, and lithium manganese oxide.

4. The preparation process of a lithium supplement functional current collector according to claim 1, wherein: The particle sizes of the lithium aluminum alloy, silica - coated lithium - rich compound, and alumina are D50 0.1 - 0.3μm.

5. The preparation process of a lithium compensation functional current collector according to claim 1, characterized in that: The process parameters of the evaporation coating are as follows: the vacuum degree ≤ 1×10 -2 Pa, and the evaporation coating temperature is 1400 - 1600 °C.

6. According to the preparation process of a lithium - supplementing functional current collector described in claim 1, it is characterized in that: The thickness of the lithium - supplementing layer is 0.6 - 0.7μm; The thickness of the primer layer is 0.1 - 0.2μm; The total thickness of the aluminum layer, lithium - supplementing layer, and primer layer is 1μm.

7. The preparation process of a lithium-compensating functional current collector according to claim 1, characterized in that: The thin - film substrate is a PET film or a PP film, and its thickness is 6 - 30μm.

8. Application of a current collector with lithium supplementation function, characterized in that: The application method is: Coating a conductive coating on the surface of the lithium - supplementing functional current collector prepared by the preparation process described in any one of claims 1 - 7, drying, and rolling to obtain a lithium - supplementing functional electrode; using the lithium - supplementing functional electrode as the positive electrode, graphite as the negative electrode, assembling into an electric core, and injecting an electrolyte containing an initiator to complete the assembly.

9. The application of a current collector with lithium supplementation function according to claim 8, wherein: The initiator is hydrogen fluoride, and its concentration is 800 - 1200ppm.