A negative electrode sheet for lithium supplementation and preparation method thereof, and a preparation method of a negative electrode sheet for a lithium ion secondary battery

Abstract

The present invention provides a negative electrode sheet for lithium replenishment, comprising a negative electrode current collector; a negative electrode active material layer composited on the negative electrode current collector; a lithium-rich layer composited on the negative electrode active material layer; and a porous substrate composited on the lithium-rich layer. The negative electrode sheet for lithium replenishment provided by the present invention has a specific structure. Before the lithium replenishment process is carried out on the negative electrode coil after the lithium-rich layer is composited, and before the pre-lithium electrode coil is rolled up, a specific porous heat dissipation layer substrate with good heat dissipation performance is attached to a single side of the pre-lithium electrode coil by a coating device. On the one hand, the substrate utilizes its good heat dissipation properties to transfer excess heat from the coil core by heat conduction; on the other hand, the porous properties of the substrate can also transfer excess heat from the coil core; at the same time, under the dense adhesion of the substrate and the spontaneous thermal effect, the surface metal lithium is effectively embedded into the negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery negative electrode preparation, and in particular to a negative electrode sheet for lithium supplementation and a preparation method thereof, and a preparation method of a negative electrode sheet for a lithium ion secondary battery. Background Art

[0002] With the increasing popularity of consumer electronics products such as laptops, mobile phones, handheld game consoles, and tablets, the demands placed on their batteries are becoming increasingly stringent. For example, batteries must be small and lightweight while also possessing high capacity, long cycle life, and stable performance. Among secondary batteries, lithium-ion batteries have long dominated the market due to their higher energy density compared to other battery types. However, with the increasing demand for battery capacity and long cycle life in electronic devices, the performance of existing lithium-ion batteries is gradually failing to meet these demands. One of the key factors determining lithium-ion battery performance is the anode material. Currently available commercial lithium-ion batteries mostly use graphite anode materials, which offer the advantages of long cycle life and low cost. However, graphite anode materials have a low theoretical capacity of only 372 mAh / g, making such a low energy density insufficient to meet the energy density requirements of increasingly advanced portable electronic devices, energy storage devices, and electric vehicles. Silicon, a negative electrode material with a high theoretical capacity, has attracted considerable attention. Reportedly, it boasts an ultra-high theoretical specific capacity (4200 mAh / g) and a low delithiation potential (<0.5V). Its voltage plateau is slightly higher than that of graphite, making it less susceptible to surface lithium deposition during charging and offering improved safety. Due to its abundant reserves, low cost, and low discharge plateau, it has become an ideal anode material for high-energy-density lithium-ion batteries.

[0003] Currently, silicon anode batteries are an important direction for improving the energy density of lithium batteries. However, silicon anode batteries have low initial coulombic efficiency and require pre-lithium replenishment to improve this initial efficiency. During the lithium replenishment process, a rapid lithium insertion reaction occurs at the silicon anode, generating a large amount of heat, which poses safety issues during production.

[0004] In actual production, the use of dry air or other physical cooling methods can reduce the temperature of the electrode during the production of silicon negative electrode lithium replenishment, but this cannot completely solve the problem and there are certain safety risks. In existing heat dissipation layer solutions, one is to set a buffer layer containing a conductive agent and a binder between the negative electrode active material layer and the lithium replenishment layer. This can slow down the diffusion rate of lithium ions into the negative electrode active material and thus reduce the heat generation rate. However, conductive agents such as conductive carbon black will adsorb lithium ions, resulting in a decrease in the utilization rate of lithium ions during the lithium replenishment process. The second is to coat the surface of the negative electrode active material layer with a buffer layer of solid cyclic sulfate, solid cyclic carbonate, solid sultone, dicyclohexylcarbodiimide and other substances, taking advantage of their advantages of increasing the resistance to pre-lithium insertion during pre-lithiation and quickly dissolving in the electrolyte after injection. However, in this solution, after the coating material on the surface of the electrode is dissolved by injection, it becomes more difficult for the surface metal lithium to be embedded in the negative electrode, which easily produces attached "dead lithium".

[0005] Therefore, how to find a more suitable way to solve the problem of large amounts of heat generated during the lithium replenishment process of the silicon negative electrode without affecting the utilization rate of lithium ions and the performance of the silicon negative electrode is the focus and difficulty of the current research on silicon-based negative electrode materials, and is also one of the problems that many R&D manufacturers in this field urgently need to solve. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a negative electrode sheet for lithium replenishment and a preparation method thereof, and a preparation method of a negative electrode sheet for a lithium-ion secondary battery. The negative electrode sheet for lithium replenishment provided by the present invention can effectively solve the problem of excessively high electrode temperature caused by large amounts of heat generated by the negative electrode sheet during the lithium replenishment process, and can also effectively solve the problem of residual metallic lithium on the surface of the pre-lithium electrode sheet. At the same time, the process is simple and easy to control, and is more suitable for promotion and application in large-scale industrial production.

[0007] The present invention provides a negative electrode sheet for replenishing lithium, comprising a negative electrode current collector;

[0008] A negative electrode active material layer composited on the negative electrode current collector;

[0009] A lithium-rich layer composited on the negative electrode active material layer;

[0010] A porous substrate is composited on the lithium-rich layer.

[0011] Preferably, the negative electrode active material of the negative electrode active material layer includes one or more of silicon, tin, silicon oxide, tin oxide, a composite material of silicon and carbon, a composite material of tin and carbon, a silicon halide, and a tin halide;

[0012] The thickness of the negative electrode active material layer is 1 to 300 μm;

[0013] The material of the lithium-rich layer includes lithium powder and / or lithium foil;

[0014] The thickness of the lithium-rich layer is 1 to 10 μm.

[0015] Preferably, the porous substrate comprises a metal porous substrate;

[0016] The porous substrate is a porous substrate with heat dissipation function;

[0017] The pore size of the porous substrate is 1 to 100 μm;

[0018] The cleanliness of the surface of the porous substrate is less than or equal to 30 mg / m 2 .

[0019] Preferably, the porous substrate is a metal strip;

[0020] The metal strip includes a stainless steel strip and / or a copper strip;

[0021] The thickness of the porous substrate is 1 to 50 μm;

[0022] The negative electrode active material includes graphite and / or amorphous carbon.

[0023] Preferably, the negative electrode sheet comprises a silicon negative electrode sheet;

[0024] The negative electrode sheet is a negative electrode sheet for lithium-ion batteries;

[0025] The porous substrate is composited on at least one side of the lithium-rich layer.

[0026] The present invention provides a method for preparing a negative electrode sheet for lithium supplementation, comprising the following steps:

[0027] The pre-lithium electrode roll with the lithium-rich layer and the porous substrate are compounded to obtain a negative electrode sheet for lithium supplementation.

[0028] Preferably, the compounding method includes rolling;

[0029] The roller pressing pressure is 1 to 50 tons;

[0030] The rotation speed of the roller pressing is 1 to 300 m / min.

[0031] The present invention also provides a method for preparing a negative electrode sheet for a lithium ion battery, comprising the following steps:

[0032] Under vacuum conditions, the negative electrode sheet for lithium replenishment described in any one of the above technical solutions or the negative electrode sheet for lithium replenishment prepared by the preparation method described in any one of the above technical solutions is left to stand at room temperature to replenish lithium, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium-ion battery negative electrode sheet.

[0033] Preferably, the vacuum pressure is 1Pa to 0.1MPa;

[0034] The room temperature is 15-40°C;

[0035] The standing time is 1 to 24 hours.

[0036] Preferably, the standing still is natural standing still without the need for auxiliary cooling equipment;

[0037] The removal method includes removal by unwinding and transferring;

[0038] The preparation method can also include the following steps:

[0039] The negative electrode sheet for lithium replenishment described in any of the above technical solutions or the negative electrode sheet for lithium replenishment prepared by the preparation method described in any of the above technical solutions can also be wound to obtain an electrode roll, and then allowed to stand under vacuum conditions and at room temperature to replenish lithium to obtain a lithium-ion battery negative electrode sheet electrode roll, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium-ion battery negative electrode sheet.

[0040] The present invention provides a negative electrode sheet for lithium replenishment, comprising a negative electrode current collector; a negative electrode active material layer composited onto the negative electrode current collector; a lithium-rich layer composited onto the negative electrode active material layer; and a porous substrate composited onto the lithium-rich layer. Compared to existing technologies, the present invention addresses the safety issues associated with the substantial heat generated during the actual lithium replenishment process of existing lithium-ion battery silicon negative electrodes. Traditional physical cooling methods cannot fully address this issue and pose certain safety risks. Furthermore, other methods have drawbacks such as low lithium ion utilization during the replenishment process, increased difficulty in embedding metallic lithium into the negative electrode, and the susceptibility to adherent "dead lithium."

[0041] The present invention provides a negative electrode sheet for replenishing lithium with a specific structure, namely a pre-lithium negative electrode sheet, comprising a negative electrode current collector, a negative electrode active material layer and a porous heat dissipation layer. The present invention is based on the research that starting from the structure of the electrode sheet, increasing the heat dissipation path is a relatively easy method to implement and reduces safety risks. The present invention uses a negative electrode coil (pre-lithium electrode coil) after a lithium powder or lithium foil composite lithium-rich layer is used. Before the lithium replenishment process, before the pre-lithium electrode coil is rolled up, a specific porous heat dissipation layer substrate with good heat dissipation performance is attached to a single side of the pre-lithium electrode coil through a coating device. On the one hand, its good heat dissipation characteristics are used to transfer the excessive heat inside the coil core by heat conduction. On the other hand, the porous characteristics of the substrate can also transfer the excessive heat inside the coil core. At the same time, under the dense bonding effect of the substrate and the spontaneous thermal effect, the metallic lithium on the surface is effectively embedded in the negative electrode material. This invention effectively solves the problem of excessive heat generation during lithium replenishment of the negative electrode, which leads to excessive electrode temperature, and the problem of residual metallic lithium on the surface of the pre-lithiation electrode. It improves the initial coulombic efficiency of lithium-ion secondary batteries using this negative electrode without any negative impact on the battery's chemical system. Furthermore, the process is simple and easy to control, making it more suitable for promotion and application in large-scale industrial production.

[0042] Experimental results show that, by using the negative electrode sheet for lithium replenishment and the preparation method of the negative electrode sheet for lithium-ion secondary batteries provided by the present invention, the pre-lithium electrode coil after composite porous heat dissipation strip has significantly reduced the residual metallic lithium content on the surface of the electrode coil compared with the pre-lithium electrode coil without heat dissipation treatment, and the effective utilization rate of metallic lithium is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the structure of the equipment for preparing a negative electrode sheet for lithium supplementation provided by the present invention;

[0044] Figure 2 This is a SEM photo of one of the strips with a porous structure provided by the present invention;

[0045] Figure 3 Surface photos of the pre-lithiation electrode coils in the embodiments of the present invention and the comparative examples are shown. DETAILED DESCRIPTION

[0046] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0047] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0048] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity requirements in the field of lithium-ion battery negative electrode manufacturing.

[0049] The present invention provides a negative electrode sheet for replenishing lithium, comprising a negative electrode current collector;

[0050] A negative electrode active material layer composited on the negative electrode current collector;

[0051] A lithium-rich layer composited on the negative electrode active material layer;

[0052] A porous substrate is composited on the lithium-rich layer.

[0053] The negative electrode sheet for replenishing lithium according to the present invention, namely the pre-lithium negative electrode sheet, comprises a negative electrode active material layer.

[0054] In the present invention, the negative electrode active material of the negative electrode active material layer preferably includes one or more of silicon, tin, silicon oxide, tin oxide, a composite material of silicon and carbon, a composite material of tin and carbon, a silicon halide, and a tin halide, more preferably includes one or more of silicon, tin, silicon oxide, tin oxide, a composite material of silicon and carbon, a composite material of tin and carbon, a silicon halide, and a tin halide, more preferably includes silicon, tin, silicon oxide, tin oxide, a composite material of silicon and carbon, a composite material of tin and carbon, a silicon halide, or a tin halide. In the present invention, the negative electrode active material preferably further includes graphite and / or amorphous carbon, more preferably graphite or amorphous carbon.

[0055] In the present invention, the thickness of the negative electrode active material layer is preferably 1 to 300 μm, more preferably 10 to 280 μm, more preferably 50 to 250 μm, and more preferably 100 to 200 μm.

[0056] The negative electrode sheet for replenishing lithium of the present invention comprises a lithium-rich layer.

[0057] In the present invention, the material of the lithium-rich layer preferably includes lithium powder and / or lithium foil, and more preferably lithium powder or lithium foil.

[0058] In the present invention, the thickness of the lithium-rich layer is preferably 1 to 10 μm, more preferably 3 to 8 μm, and even more preferably 5 to 6 μm.

[0059] The lithium-replenishing negative electrode sheet of the present invention comprises a porous substrate. Specifically, the porous substrate may be a porous substrate having a heat dissipation function. In the present invention, the porous substrate preferably comprises a macroscopically porous material and / or a microscopically porous material. In the present invention, the porous substrate is preferably composited onto at least one side of the lithium-rich layer.

[0060] In the present invention, the porous substrate preferably includes a metal porous substrate, more preferably a metal strip, that is, a porous metal strip, specifically a stainless steel strip and / or a copper strip.

[0061] In the present invention, the pore diameter of the porous substrate is preferably 1 to 100 μm, more preferably 10 to 80 μm, and even more preferably 30 to 60 μm.

[0062] In the present invention, the cleanliness of the surface of the porous substrate is preferably less than or equal to 30 mg / m 2 , more preferably less than or equal to 25 mg / m 2 , more preferably less than or equal to 20 mg / m 2 .

[0063] The heat dissipation device provided by the present invention is a porous substrate with excellent heat dissipation properties, and has good heat dissipation performance, chemical stability, thermal stability, structural stability, easy processing, low price, and non-magnetic properties. In the present invention, the heat dissipation layer can also be attached to both sides of the pre-lithium negative electrode coil.

[0064] In the present invention, the negative electrode sheet preferably comprises a silicon negative electrode sheet. Specifically, the negative electrode sheet is preferably a negative electrode sheet for lithium-ion batteries.

[0065] In the present invention, the composite method preferably includes one or more of bonding, rolling, coating and spraying.

[0066] The present invention provides a method for preparing a negative electrode sheet for lithium supplementation, comprising the following steps:

[0067] The pre-lithium electrode roll with the lithium-rich layer and the porous substrate are compounded to obtain a negative electrode sheet for lithium replenishment.

[0068] In the present invention, the compounding method includes rolling.

[0069] In the present invention, the rolling pressure is preferably 1 to 50 tons, more preferably 5 to 45 tons, and even more preferably 15 to 35 tons.

[0070] In the present invention, the rotation speed of the roller pressing is preferably 1 to 300 m / min, more preferably 10 to 250 m / min, more preferably 50 to 200 m / min, and more preferably 100 to 150 m / min.

[0071] After compounding the negative electrode active material layer, the present invention further compounds the negative electrode active material layer with a lithium-rich layer for lithium supplementation, and finally covers it with a heat dissipation layer.

[0072] See also Figure 1 , Figure 1 This is a schematic diagram of the equipment structure for preparing a negative electrode sheet for lithium replenishment provided by the present invention.

[0073] Among them, 1-porous strip unwinder; 2-lithium-rich electrode coil; 3-equipment roller; 4-composite roller device; 5-winding machine.

[0074] The present invention also provides a method for preparing a negative electrode sheet for a lithium ion battery, comprising the following steps:

[0075] Under vacuum conditions, the negative electrode sheet for lithium replenishment described in any one of the above technical solutions or the negative electrode sheet for lithium replenishment prepared by the preparation method described in any one of the above technical solutions is left to stand at room temperature to replenish lithium, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium-ion battery negative electrode sheet.

[0076] In the present invention, the vacuum pressure is preferably 1 Pa to 0.1 MPa, more preferably 10 Pa to 0.01 MPa, more preferably 100 Pa to 1000 Pa, and more preferably 300 to 800 Pa.

[0077] In the present invention, the room temperature is preferably 15 to 40°C, more preferably 20 to 35°C, and even more preferably 25 to 30°C.

[0078] In the present invention, the standing time is preferably 1 to 24 hours, more preferably 4 to 21 hours, more preferably 7 to 18 hours, and more preferably 10 to 15 hours.

[0079] In the present invention, the standing still is preferably natural standing still without the need for auxiliary cooling equipment.

[0080] In the present invention, the removal method preferably includes removal by unwinding and transferring.

[0081] In the present invention, the preparation method may further specifically include the following steps:

[0082] The negative electrode sheet for lithium replenishment described in any of the above technical solutions or the negative electrode sheet for lithium replenishment prepared by the preparation method described in any of the above technical solutions can also be wound to obtain an electrode roll, and then allowed to stand under vacuum conditions and at room temperature to replenish lithium to obtain a lithium-ion battery negative electrode sheet electrode roll, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium-ion battery negative electrode sheet.

[0083] See also Figure 2 , Figure 2 This is a SEM photograph of one of the tapes with a porous structure provided by the present invention.

[0084] The above steps of the present invention provide a negative electrode sheet for replenishing lithium and a method for preparing the same, as well as a method for preparing a negative electrode sheet for a lithium-ion secondary battery. The present invention provides a negative electrode sheet for replenishing lithium with a specific structure, namely a pre-lithium negative electrode sheet, comprising a negative electrode current collector, a negative electrode active material layer, and a porous heat dissipation layer. The present invention is based on research that increasing the heat dissipation path from the structure of the electrode sheet is a relatively easy-to-implement method that reduces safety risks. The present invention uses a negative electrode coil (pre-lithium electrode coil) after a lithium powder or lithium foil composite lithium-rich layer is used. Before the lithium replenishment process is carried out, before the pre-lithium electrode coil is rolled up, a specific porous heat dissipation layer substrate with good heat dissipation performance is attached to a single side of the pre-lithium electrode coil by a coating device. On the one hand, the good heat dissipation properties of the substrate are used to transfer the excess heat inside the coil core by heat conduction. On the other hand, the porous properties of the substrate can also transfer the excess heat inside the coil core. At the same time, under the dense adhesion of the substrate and the spontaneous thermal effect, the surface metal lithium is effectively embedded in the negative electrode material. This invention effectively solves the problem of excessive heat generation during lithium replenishment of the negative electrode, which leads to excessive electrode temperature, and the problem of residual metallic lithium on the surface of the pre-lithiation electrode. It improves the initial coulombic efficiency of lithium-ion secondary batteries using this negative electrode without any negative impact on the battery's chemical system. Furthermore, the process is simple and easy to control, making it more suitable for promotion and application in large-scale industrial production.

[0085] Experimental results show that, by using the negative electrode sheet for lithium replenishment and the preparation method of the negative electrode sheet for lithium-ion secondary batteries provided by the present invention, the pre-lithium electrode coil after composite porous heat dissipation strip has significantly reduced the residual metallic lithium content on the surface of the electrode coil compared with the pre-lithium electrode coil without heat dissipation treatment, and the effective utilization rate of metallic lithium is significantly improved.

[0086] To further illustrate the present invention, the following describes in detail a negative electrode sheet for lithium supplementation and a preparation method thereof, and a preparation method of a negative electrode sheet for a lithium-ion secondary battery provided by the present invention in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0087] Example 1

[0088] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0089] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0090] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 10um stainless steel substrate with good heat dissipation properties on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0091] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0092] Example 2

[0093] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0094] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0095] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 10um copper tape substrate with good heat dissipation properties on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0096] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0097] Example 3

[0098] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0099] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0100] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 20um stainless steel strip substrate with good heat dissipation properties on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0101] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0102] Example 4

[0103] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0104] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0105] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 20um copper tape substrate with good heat dissipation properties on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0106] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0107] Example 5

[0108] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0109] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0110] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 10um stainless steel strip substrate with good heat dissipation properties and porosity on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0111] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0112] Example 6

[0113] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0114] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0115] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 10um copper tape substrate with good heat dissipation properties and porosity on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0116] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0117] Example 7

[0118] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0119] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0120] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 20um stainless steel strip substrate with good heat dissipation properties and porosity on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0121] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0122] Example 8

[0123] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0124] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0125] Treatment and placement of lithium-rich negative electrode sheets: The lithium replenishment process is carried out by attaching a layer of 20um copper tape substrate with good heat dissipation properties and porosity on both sides of the lithium-rich negative electrode sheet, then winding it into a roll and leaving it at room temperature under vacuum conditions for 24 hours.

[0126] Lithium-ion battery preparation: After resting, the lithium-rich negative electrode sheet is unwound and transferred to remove the porous substrate to form the negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0127] The pre-lithiation electrode rolls (lithium-rich negative electrode sheets after standing and replenishing lithium) prepared in the examples of the present invention and the comparative examples were characterized.

[0128] See also Figure 3 , Figure 3 Surface photos of the pre-lithiation electrode coils in the embodiments of the present invention and the comparative examples are shown.

[0129] Among them, A is an uncompounded porous heat dissipation belt, and B is a composite porous heat dissipation belt. Figure 3 It can be clearly seen that after the composite porous heat dissipation strip is formed, the residual metallic lithium content on the surface of the pole coil is significantly reduced.

[0130] The lithium-ion batteries prepared in the examples of the present invention and the comparative examples were measured and their performance tested.

[0131] Test method:

[0132] 1. During the lithium replenishment process, the negative electrode sheets prepared in the examples and comparative examples were rolled onto a small roll and the temperature of the sheets was measured using a multi-channel thermometer.

[0133] 2. Measure the content of active lithium on the lithium-rich negative electrode after lithium replenishment is completed by the water drainage method.

[0134] 3. Measure the amount of active lithium in the rolled-up electrode using the water displacement method and calculate it using the following formula:

[0135] Active lithium content = 2*M water*M Li*298 / Vm / m Li / 273

[0136] in:

[0137] Mwater = weight of water discharged;

[0138] Vm = molar volume of gas;

[0139] MLi = molar weight of Li;

[0140] mLi = lithium supplement weight.

[0141] First coulombic efficiency:

[0142] At room temperature, the battery is charged at a rate of 0.2C to a voltage of 4.2V, at which point the charge capacity is C0; it is discharged at a rate of 0.2C to a voltage of 2.75V, at which point the discharge capacity is D0; the first coulombic efficiency = D0 / C0.

[0143] The maximum pre-lithiation temperature, active lithium content and first efficiency of the battery cells of 10 electrodes were measured in parallel, and the average values ​​were calculated. The obtained data are shown in Table 1.

[0144] See Table 1, which shows the performance test data of the negative electrode sheets prepared in the embodiments of the present invention and the comparative examples.

[0145] Table 1

[0146] Group Pole temperature after lithium replenishment (℃) Active lithium content (%) First efficiency (%) Example 1 55 87.3 81.3 Example 2 47 88.5 83.1 Example 3 48 88.7 83.26 Example 4 44 91.5 85.8 Example 5 44 91.7 86.03 Example 6 36 93.1 87.3 Example 7 41 92.2 86.5 Example 8 31 93.5 87.7 Comparative Example 1 -- 0 77.6％ Comparative Example 2 70 85.1 79.3％

[0147] It can be seen from the results in Table 1 that, compared with Comparative Example 2, in Examples 1 to 8, with the introduction of metals with excellent heat dissipation performance, changes in the thickness of the heat dissipation substrate, and the introduction of micropores in the substrate, the temperature of the electrode gradually decreases after lithium replenishment is completed, the side reactions of metallic lithium with O2, N2, etc. gradually decrease, the active lithium content of the metallic lithium layer gradually increases, the utilization rate of metallic lithium increases, and the first coulombic efficiency of the battery also gradually increases and approaches the design value.

[0148] Comparative Example 1

[0149] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0150] Lithium-ion battery preparation: The rested lithium-rich negative electrode sheet is formed into a negative electrode sheet. The prepared positive and negative electrode sheets and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0151] Comparative Example 2

[0152] Preparation of negative electrode sheet: The negative electrode active material SiO2C 600 negative electrode is mixed with a conductive agent (SuperP), a thickener sodium carboxymethyl cellulose (CMC), and a binder styrene butadiene rubber (SBR) in a mass ratio of 90:2:4:4 to prepare a slurry, which is then coated on the current collector and dried at 85°C to obtain a surface density of 80g / m 2 The bottom diaphragm.

[0153] Preparation of lithium-rich negative electrode sheet: Cover the prepared negative electrode sheet with a metallic lithium layer with a thickness of 5um to obtain a lithium-rich negative electrode sheet.

[0154] Treatment and placement of lithium-rich negative electrode sheets: The prepared lithium-rich negative electrode sheets were directly wound and left to stand at room temperature under vacuum for 24 hours.

[0155] Lithium-ion battery preparation: The rested lithium-rich negative electrode sheet is formed into a negative electrode sheet. The prepared positive electrode sheet, lithium-rich negative electrode sheet, and separator are wound or stacked to form a battery cell, with the separator positioned between the cathode and negative electrode sheets. The battery cell is then placed in a packaging bag, injected with electrolyte, and subjected to formation and capacity testing to complete the lithium-ion battery.

[0156] The above describes in detail a negative electrode sheet for lithium replenishment and its preparation method, as well as a method for preparing a negative electrode sheet for a lithium-ion secondary battery, provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above examples is intended only to facilitate understanding of the methods and core concepts of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be noted that a person skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims. The scope of patent protection for the present invention is defined by the claims and may include other embodiments that are conceivable to a person skilled in the art. If such other embodiments have structural elements that do not differ from the literal meaning of the claims, or if they include equivalent structural elements that do not differ substantially from the literal meaning of the claims, then such other embodiments are also intended to be included within the scope of the claims.

Claims

1. A negative electrode sheet for lithium supplementation, characterized in that: including a negative electrode current collector; A negative electrode active material layer composited on the negative electrode current collector; A lithium-rich layer composited on the negative electrode active material layer; A porous substrate composited on the lithium-rich layer; The porous substrate comprises a metal porous substrate; The porous substrate is a porous substrate with heat dissipation function; The thickness of the porous substrate is 1-50 μm.

2. The negative electrode sheet according to claim 1, characterized in that: The negative electrode active material of the negative electrode active material layer includes one or more of silicon, tin, silicon oxide, tin oxide, a composite material of silicon and carbon, a composite material of tin and carbon, a silicon halide, and a tin halide; The thickness of the negative electrode active material layer is 1 to 300 μm; The material of the lithium-rich layer includes lithium powder and / or lithium foil; The thickness of the lithium-rich layer is 1-10 μm.

3. The negative electrode sheet according to claim 1, characterized in that: The pore size of the porous substrate is 1 to 100 μm; The cleanliness of the surface of the porous substrate is less than or equal to 30 mg / m 2 .

4. The negative electrode sheet according to claim 1, characterized in that: The porous substrate is specifically a metal strip; The metal strip includes a stainless steel strip and / or a copper strip; The negative electrode active material includes graphite and / or amorphous carbon.

5. The negative electrode sheet according to claim 1, characterized in that: The negative electrode sheet includes a silicon negative electrode sheet; The negative electrode sheet is a negative electrode sheet for lithium-ion batteries.

6. A method for preparing a negative electrode sheet for lithium supplementation according to any one of claims 1 to 5, characterized in that: The following steps are involved: The pre-lithium electrode roll with the lithium-rich layer and the porous substrate are compounded to obtain a negative electrode sheet for lithium supplementation.

7. The preparation method according to claim 6, characterized in that The compounding method includes roller pressing; The roller pressing pressure is 1 to 50 tons; The rotation speed of the roller pressing is 1-300 m / min.

8. A method for preparing a negative electrode sheet for a lithium ion battery, characterized in that: The following steps are involved: Under vacuum conditions, the negative electrode sheet for lithium replenishment according to any one of claims 1 to 5 or the negative electrode sheet for lithium replenishment prepared by the preparation method according to any one of claims 6 to 7 is allowed to stand at room temperature to replenish lithium, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium-ion battery negative electrode sheet.

9. The preparation method according to claim 8, characterized in that The vacuum pressure is 1Pa~0.1MPa; The room temperature is 15-40°C; The standing time is 1 to 24 hours.

10. The preparation method according to claim 8, characterized in that The said static state is natural static state without auxiliary cooling equipment; The removal method includes removal by unwinding and transferring.

11. A method for preparing a negative electrode sheet for a lithium-ion battery, characterized in that: The following steps are involved: The negative electrode sheet for lithium replenishment according to any one of claims 1 to 5 or the negative electrode sheet for lithium replenishment prepared by the preparation method according to any one of claims 6 to 7 is wound to obtain an electrode roll, and then the electrode roll is obtained after standing under vacuum conditions and room temperature to replenish lithium, and then the porous substrate on the negative electrode sheet for lithium replenishment is removed to obtain a lithium ion battery negative electrode sheet.

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