A lithium battery negative electrode and preparation method thereof, and a lithium battery

Abstract

The present invention provides a lithium battery negative electrode and a preparation method thereof, and a lithium battery, wherein the preparation method comprises the steps of: providing lithium carbide particles; mixing the lithium carbide particles with graphene in a binder solution to obtain a mixed solution; coating the mixed solution on a metal sheet to form a coating; coating the lithium battery negative electrode material on the coating to obtain the lithium battery negative electrode. The present invention provides a coating between the metal sheet and the lithium battery negative electrode material, wherein the coating includes lithium carbide particles and graphene, which is equivalent to pre-storing some lithium ions in the negative electrode. During the charging process of the lithium battery negative electrode, a large number of electrons are generated, which makes the lithium carbide in the coating easily split into carbon and lithium ions, thereby effectively replenishing some lithium ions lost due to crystallization, so that the lithium ion battery can maintain a high power level for a longer time.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrodes, and in particular to a lithium battery negative electrode and a preparation method thereof, and a lithium battery. Technical Background

[0002] When preparing the two electrodes of a battery product, polar materials are usually coated on metal sheets, which are bonded together with adhesives, and then connected with wires to make the two electrodes of the battery. In order to increase the conductivity of the electrode, before the polar materials are coated on the metal sheets, a layer of conductive material with strong conductivity and much smaller particles than the electrode material is pre-coated on the metal sheets to form a pre-coating layer.

[0003] However, lithium batteries will encounter the problem of battery capacity decay during long-term use. This is usually because lithium ions form lithium crystals in the process of traveling between the positive and negative electrodes, causing the lithium ions traveling between the positive and negative electrodes to gradually decrease after a period of use, resulting in a faster battery capacity decay.

[0004] As an example, for lithium iron phosphate batteries, its positive and negative electrode reaction equations are as follows:

[0005] Positive electrode reaction:

[0006] Negative electrode reaction:

[0007] Once the lithium in a lithium battery forms crystals, fewer and fewer lithium ions will circulate in the battery, eventually causing a decrease in power.

[0008] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0009] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a lithium battery negative electrode and a preparation method thereof, and a lithium battery, aiming to solve the problem of rapid power decay of existing lithium batteries.

[0010] The technical solution of the present invention is as follows:

[0011] A method for preparing a negative electrode of a lithium battery, comprising the steps of:

[0012] Providing lithium carbide particles;

[0013] Mixing the lithium carbide particles and graphene in a binder solution to obtain a mixed solution;

[0014] coating the mixed solution on a metal sheet to form a coating;

[0015] A lithium battery negative electrode material is coated on the coating to obtain the lithium battery negative electrode.

[0016] A method for preparing a negative electrode of a lithium battery, wherein the mass ratio of the lithium carbide particles to the graphene is 1:99-3:7.

[0017] The method for preparing the negative electrode of a lithium battery, wherein the binder solution is an aqueous solution of acrylic resin.

[0018] The method for preparing the negative electrode of a lithium battery, wherein the negative electrode material of the lithium battery is metallic lithium or a lithium alloy.

[0019] The method for preparing the negative electrode of a lithium battery, wherein the lithium carbide particles are prepared by the reaction of graphene and lithium.

[0020] A lithium battery negative electrode comprises a metal sheet, a coating coated on the metal sheet, and a lithium battery negative electrode material coated on the coating, wherein the material of the coating comprises lithium carbide particles, graphene and a binder solution.

[0021] A lithium battery comprises a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode, characterized in that the negative electrode is a lithium battery negative electrode prepared by the preparation method of the lithium battery negative electrode of the present invention.

[0022] The lithium battery, wherein the positive electrode includes at least one of LiCoO2, LiFePO4, nickel-cobalt-aluminum ternary positive electrode material, and nickel-cobalt-manganese ternary positive electrode material.

[0023] Beneficial effects: The present invention provides a method for preparing a negative electrode of a lithium battery, wherein a coating is provided between a metal sheet and a negative electrode material of a lithium battery, wherein the coating includes lithium carbide particles and graphene, which is equivalent to pre-storing a portion of lithium ions in the negative electrode. During the charging process of the negative electrode of the lithium battery, a large number of electrons are generated, which makes it easy for the lithium carbide in the coating to split into carbon and lithium ions, thereby effectively replenishing a portion of lithium ions lost due to crystallization, so that the lithium ion battery can maintain a high power level for a longer period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of a lithium battery negative electrode and a preparation method thereof.

[0025] Figure 2 It is a schematic diagram of the battery negative electrode structure without a pre-coating layer in the prior art.

[0026] Figure 3 The schematic diagram of the negative electrode structure of a battery is a pre-coating layer arranged between the metal sheet and the negative electrode material. DETAILED DESCRIPTION

[0027] The present invention provides a lithium battery negative electrode and a preparation method thereof, and a lithium battery. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The initial lithium battery negative electrode was made by directly coating the negative electrode material on the metal sheet, such as Figure 1 As shown, the negative electrode of this lithium battery has coarse negative electrode material particles, which results in fewer contact points between the negative electrode material and the metal sheet, resulting in a longer charging and discharging time of the lithium battery. In order to solve the problem of long charging and discharging time of the lithium battery, before coating the polar material on the metal sheet, a layer of conductive particles with strong conductivity and much smaller particles than the electrode material can be pre-coated on the metal sheet to form a pre-coating layer, such as Figure 2 As shown, the small molecule conductive particles in the pre-coating layer can increase the contact points between the electrode material and the metal sheet, thereby effectively improving the charging and discharging speed. However, the existing lithium batteries will encounter the problem of battery power decay during long-term use. This is usually due to the formation of lithium crystals in the process of lithium ions traveling back and forth between the positive and negative electrodes, which makes the lithium ions traveling back and forth between the positive and negative electrodes gradually decrease after a period of use, resulting in a faster battery power decay rate.

[0029] Based on this, the present invention provides a method for preparing a negative electrode of a lithium battery, such as Figure 3 As shown, it includes the steps of:

[0030] S10, providing lithium carbide particles;

[0031] S20, mixing the lithium carbide particles and graphene in a binder solution to obtain a mixed solution;

[0032] S30, coating the mixed solution on a metal sheet to form a coating;

[0033] S40, coating a negative electrode material of a lithium battery on the coating to obtain the negative electrode of the lithium battery.

[0034] In the present invention, a coating layer is provided between the metal sheet and the negative electrode material of the lithium battery, wherein the coating layer includes lithium carbide particles and graphene, which is equivalent to pre-storing some lithium ions in the negative electrode. During the charging process of the negative electrode of the lithium battery, a large number of electrons are generated, which makes the lithium carbide in the coating layer easy to split into carbon and lithium ions, thereby effectively replenishing some lithium ions lost due to crystallization, so that the lithium ion battery can maintain a high power level for a longer time.

[0035] In some embodiments, the mass ratio of the lithium carbide particles to the graphene is 1:99-3:7. In this embodiment, if the mass ratio of the lithium carbide particles to the graphene is too low (less than 1:99), the lithium carbide particles can provide less lithium ions, making it difficult for the lithium-ion battery to maintain a high charge level for a longer period of time; if the mass ratio of the lithium carbide particles to the graphene is too high (higher than 3:7), the lithium carbide particles have a poorer conductivity than the graphene, resulting in a longer charge and discharge time for the lithium battery.

[0036] In some embodiments, the binder solution is an aqueous solution of acrylic resin, but is not limited thereto.

[0037] In some embodiments, the negative electrode material of the lithium battery is metallic lithium or a lithium alloy, but is not limited thereto.

[0038] In some embodiments, the lithium carbide particles are prepared by reacting graphene and lithium.

[0039] In some embodiments, a lithium battery negative electrode is also provided, which includes a metal sheet, a coating coated on the metal sheet, and a lithium battery negative electrode material coated on the coating, wherein the material of the coating includes lithium carbide particles, graphene, and a binder solution.

[0040] In the present invention, a coating layer is provided between the metal sheet and the negative electrode material of the lithium battery, wherein the coating layer includes lithium carbide particles and graphene, which is equivalent to pre-storing some lithium ions in the negative electrode. During the charging process of the negative electrode of the lithium battery, a large number of electrons are generated, which makes the lithium carbide in the coating layer easy to split into carbon and lithium ions, thereby effectively replenishing some lithium ions lost due to crystallization, so that the lithium ion battery can maintain a high power level for a longer time.

[0041] In some embodiments, a lithium battery is also provided, comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode, wherein the negative electrode is a lithium battery negative electrode prepared by the method for preparing a lithium battery negative electrode of the present invention.

[0042] In some embodiments, the positive electrode includes at least one of LiCoO2, LiFePO4, a nickel-cobalt-aluminum ternary positive electrode material, and a nickel-cobalt-manganese ternary positive electrode material, but is not limited thereto.

[0043] The present invention is further explained below by specific embodiments:

[0044] Example 1

[0045] Preparation of a lithium-ion battery:

[0046] The lithium carbide particles and graphene are mixed in an acrylic resin aqueous solution at a mass ratio of 1:99 to obtain a mixed solution; the mixed solution is coated on a metal sheet to form a coating; and metallic lithium is coated on the coating to obtain a negative electrode of a lithium battery;

[0047] The negative electrode and positive electrode LiCoO2 of the lithium battery are arranged on the left and right sides of the separator, and a 1M LiPF6 EC / DEC solution is added as an electrolyte to assemble a CR2032 button battery.

[0048] Example 2

[0049] Preparation of a lithium ion battery

[0050] The lithium carbide particles and graphene are mixed in an acrylic resin aqueous solution at a mass ratio of 20:99 to obtain a mixed solution; the mixed solution is coated on a metal sheet to form a coating; and metallic lithium is coated on the coating to obtain a negative electrode of a lithium battery;

[0051] The negative electrode and positive electrode LiCoO2 of the lithium battery are arranged on the left and right sides of the separator, and a 1M LiPF6 EC / DEC solution is added as an electrolyte to assemble a CR2032 button battery.

[0052] Example 3

[0053] Preparation of a lithium ion battery

[0054] The lithium carbide particles and graphene are mixed in an acrylic resin aqueous solution at a mass ratio of 30:99 to obtain a mixed solution; the mixed solution is coated on a metal sheet to form a coating; and metallic lithium is coated on the coating to obtain a negative electrode of a lithium battery;

[0055] The negative electrode and positive electrode LiCoO2 of the lithium battery are arranged on the left and right sides of the separator, and a 1M LiPF6 EC / DEC solution is added as an electrolyte to assemble a CR2032 button battery.

[0056] Example 4

[0057] Preparation of a lithium ion battery

[0058] The lithium carbide particles and graphene are mixed in an acrylic resin aqueous solution at a mass ratio of 3:7 to obtain a mixed solution; the mixed solution is coated on a metal sheet to form a coating; and metallic lithium is coated on the coating to obtain a negative electrode of a lithium battery;

[0059] The negative electrode and positive electrode LiCoO2 of the lithium battery are arranged on the left and right sides of the separator, and a 1M LiPF6 EC / DEC solution is added as an electrolyte to assemble a CR2032 button battery.

[0060] Comparative Example 1

[0061] Preparation of a lithium ion battery

[0062] Mixing graphene in an acrylic resin aqueous solution to obtain a mixed solution; coating the mixed solution on a metal sheet to form a coating; coating metallic lithium on the coating to obtain a negative electrode of a lithium battery;

[0063] The negative electrode and positive electrode LiCoO2 of the lithium battery are arranged on the left and right sides of the separator, and a 1M LiPF6 EC / DEC solution is added as an electrolyte to assemble a CR2032 button battery.

[0064] The lithium ion batteries prepared in Examples 1-4 and Comparative Example 1 were subjected to a cycle performance test. The cycle test conditions were as follows: charging with a 2C current until the voltage reached 4.45V, with a cut-off current of 0.05C; capacity retention rate = the capacity of the cycle divided by the capacity of the initial full charge 0.2C discharge. The test results are shown in Table 1 (T in the table represents the cycle).

[0065] Table 1 Test results

[0066]

[0067]

[0068] As can be seen from Table 1, after adding lithium carbide particles to the coating of the negative electrode of the lithium battery, the lithium ions after the lithium carbide split can effectively replenish some of the lithium ions lost due to crystallization, so that the lithium-ion battery can maintain a high power level for a longer time.

[0069] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a negative electrode of a lithium battery, characterized in that: Includes steps: Providing lithium carbide particles; Mixing the lithium carbide particles and graphene in a binder solution to obtain a mixed solution; coating the mixed solution on a metal sheet to form a coating; Coating a lithium battery negative electrode material on the coating to obtain the lithium battery negative electrode; Wherein, the mass ratio of the lithium carbide particles to the graphene is 1:99-3:7; The negative electrode material of the lithium battery is metallic lithium or a lithium alloy.

2. The method for preparing a negative electrode of a lithium battery according to claim 1, characterized in that: The binder solution is an acrylic resin aqueous solution.

3. The method for preparing a negative electrode of a lithium battery according to claim 1, characterized in that: The lithium carbide particles are prepared by reaction of graphene and lithium.

4. A lithium battery negative electrode prepared by the method for preparing a lithium battery negative electrode according to any one of claims 1 to 3, characterized in that: The invention comprises a metal sheet, a coating coated on the metal sheet, and a lithium battery negative electrode material coated on the coating, wherein the material of the coating comprises lithium carbide particles, graphene and a binder solution.

5. A lithium battery comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode, characterized in that: The negative electrode is a lithium battery negative electrode prepared by the method for preparing a lithium battery negative electrode according to any one of claims 1 to 3.

6. The lithium battery according to claim 5, characterized in that: The positive electrode includes at least one of LiCoO2, LiFePO4, nickel-cobalt-aluminum ternary positive electrode material, and nickel-cobalt-manganese ternary positive electrode material.

Images