Lithium battery positive and negative electrode coating method and positive electrode material, negative electrode material and lithium battery

Abstract

The present invention discloses a method for coating positive and negative electrode materials for lithium batteries, comprising the following steps: S1. mixing boehmite with a lithium salt, and then subjecting it to high-speed pulverization to activation to obtain a coating mixture; S2. uniformly mixing the pre-fired positive electrode material or negative electrode material and the coating mixture to obtain a mixed powder; S3. firing the mixed powder at a temperature of 750 to 850°C for 4 to 8 hours, and cooling to obtain the coated positive electrode material or negative electrode material. The present invention discloses a positive electrode material and a negative electrode material, which are prepared using the positive and negative electrode coating method for lithium batteries disclosed in the present invention. The present invention discloses a lithium battery, wherein both the positive electrode and the negative electrode are prepared from the positive electrode material and the negative electrode material disclosed in the present invention, and the battery has high comprehensive performance and meets the requirements of use in high and low temperature environments.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials, and in particular relates to a method for coating positive and negative electrodes of a lithium battery, a positive electrode material, a negative electrode material and a lithium battery. Background Art

[0002] Lithium-ion batteries have advantages such as high energy density and long cycle life. In addition to their applications in portable electronic devices, lithium-ion batteries are also increasingly used in power and energy storage. According to existing technical solutions, some practical bottlenecks have been encountered. For example, in terms of environmental adaptability, the discharge environment of most lithium-ion batteries on the market is -20°C to +60°C. Relevant parties can meet the requirements of high-efficiency discharge at -40°C through modification or optimization of individual materials, but they will appear in high-temperature environments, or in terms of cycle life, or safety indicators. There are obvious shortcomings and poor overall performance. Some relevant parties use aluminum hydroxide to coat the positive electrode powder to further improve the electrochemical performance, but aluminum hydroxide also has related problems such as high hardness, high cost, and easy to cause serious wear and tear on equipment. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for coating the positive and negative electrodes of a lithium battery, a positive electrode material, a negative electrode material and a lithium battery, wherein the positive and negative electrode materials are coated with boehmite to improve the electrochemical properties of the positive and negative electrode materials, thereby improving the comprehensive performance of the lithium battery, so that it has higher comprehensive quality characteristics (including cycle life, charge retention ability, overcharge protection, acupuncture, etc.).

[0004] The embodiments of the present invention are achieved through the following technical solutions:

[0005] A method for coating positive and negative electrode materials of a lithium battery, comprising the following steps:

[0006] S1. The boehmite is mixed with a lithium salt and then activated by high-speed pulverization to obtain a coated mixture;

[0007] S2. The pre-fired positive electrode material or negative electrode material and the coating mixture are uniformly mixed to obtain a mixed powder;

[0008] S3. sinter the mixed powder at a temperature of 750-850° C. for 4-8 hours, and obtain the coated positive electrode material or negative electrode material after cooling.

[0009] Before step S1, the following steps are also included:

[0010] S0. Pre-treating the coated boehmite so that its particle size distribution D50 is 100 nm to 1 μm.

[0011] In the step S1, the weight ratio of the boehmite to the lithium salt is (3-5):1.

[0012] In step S2, the weight ratio of the positive electrode or negative electrode material to the coating mixture is (80-100):1.

[0013] In step S3, the coating thickness of the positive electrode material or the negative electrode material is 0.7um-2um.

[0014] The lithium salt is selected from one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate.

[0015] In step S2, the positive electrode material is one of lithium cobalt oxide, ternary lithium, and lithium iron phosphate; the negative electrode material is one of graphite and silicon carbon.

[0016] A positive electrode material is prepared by a lithium battery positive and negative electrode coating method.

[0017] A negative electrode material is prepared by a lithium battery positive and negative electrode coating method.

[0018] A lithium battery comprises a positive electrode material and a negative electrode material prepared by a positive and negative electrode coating method for a lithium battery.

[0019] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0020] The present invention provides a method for coating positive and negative electrode materials of lithium batteries, which uses boehmite (Y-AlOOH) and lithium salt (Li + ) The positive and negative electrode materials are coated. The lithium batteries made of the coated positive and negative electrode materials have obvious performance improvements in low-temperature discharge, high-temperature storage, safety, first reversible capacity, overcharge, cycle life, etc., and have excellent cost-effectiveness, which is convenient for large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Flowchart of the method for coating positive and negative electrode materials of lithium batteries provided by the present invention;

[0023] Figure 2 This is the high temperature capacity test result of the battery pack of the present invention;

[0024] Figure 3 This is the low-temperature capacity test result of the battery pack of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0028] In the description of the present invention, it should be noted that if the terms "inside" and "outside" appear to indicate an orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings, or are the orientation or positional relationship in which the product of the invention is usually placed when in use. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0029] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "dispose," "install," "configure," and "connect" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] Please refer to Figure 1 A method for coating positive and negative electrode materials of a lithium battery comprises the following steps:

[0031] S0. The coating boehmite (Y-AlOOH) was pretreated to a particle size distribution D50 of 100nm~1um;

[0032] S1. Boehmite (Y-AlOOH) and lithium salt (Li +) are mixed in a weight ratio of (3-5):1, and then activated by high-speed pulverization to obtain a coating mixture;

[0033] S2. The pre-fired positive electrode material or negative electrode material and the coating mixture are uniformly mixed in a weight ratio of (80 to 100): 1 to obtain a mixed powder;

[0034] S3. sinter the mixed powder at a temperature of 750-850° C. for 4-8 hours, and obtain a coated positive electrode material or negative electrode material after cooling. The coating thickness of the positive electrode material or negative electrode material is 0.7 μm-2 μm.

[0035] The lithium salt (Li + ) is selected from one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate.

[0036] In step S2, the positive electrode material is one of lithium cobalt oxide, ternary lithium, and lithium iron phosphate; the negative electrode material is one of graphite and silicon carbon.

[0037] Example 1

[0038] Preparation of positive electrode materials:

[0039] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 3:1, and then activated by high-speed crushing to obtain a coating mixture; the pre-fired positive electrode material lithium cobalt oxide and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.7um.

[0040] Preparation of negative electrode materials:

[0041] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 3:1, and then activated by high-speed crushing to obtain a coated mixture; the pre-fired negative electrode material graphite and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.7um.

[0042] Preparation of lithium batteries:

[0043] The positive electrode is made by mixing the prepared positive electrode material with a conductive agent and a binder to form a slurry, which is then coated on aluminum foil. The negative electrode is made by mixing the prepared negative electrode material with a binder to form a slurry, which is then coated on copper foil. The positive and negative electrode sheets and separator are wound together to form a battery cell, which is then installed in a battery case, baked, injected with electrolyte, welded and sealed, and then subjected to formation and aging to complete the battery.

[0044] Example 2

[0045] Preparation of positive electrode materials:

[0046] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coating mixture; the pre-fired positive electrode material lithium cobalt oxide and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.8um.

[0047] Preparation of negative electrode materials:

[0048] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coated mixture; the pre-fired negative electrode material graphite and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.7um.

[0049] Preparation of lithium batteries:

[0050] The positive electrode is made by mixing the prepared positive electrode material with a conductive agent and a binder to form a slurry, which is then coated on aluminum foil. The negative electrode is made by mixing the prepared negative electrode material with a binder to form a slurry, which is then coated on copper foil. The positive and negative electrode sheets and separator are wound together to form a battery cell, which is then installed in a battery case, baked, injected with electrolyte, welded and sealed, and then subjected to formation and aging to complete the battery.

[0051] Example 3

[0052] Preparation of positive electrode materials:

[0053] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 5:1, and then activated by high-speed crushing to obtain a coating mixture; the pre-fired positive electrode material lithium cobalt oxide and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.8um.

[0054] Preparation of negative electrode materials:

[0055] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 5:1, and then activated by high-speed crushing to obtain a coated mixture; the pre-fired negative electrode material graphite and the coating mixture are uniformly mixed in a weight ratio of 80:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 0.8um.

[0056] Preparation of lithium batteries:

[0057] The positive electrode is made by mixing the prepared positive electrode material with a conductive agent and a binder to form a slurry, which is then coated on aluminum foil. The negative electrode is made by mixing the prepared negative electrode material with a binder to form a slurry, which is then coated on copper foil. The positive and negative electrode sheets and separator are wound together to form a battery cell, which is then installed in a battery case, baked, injected with electrolyte, welded and sealed, and then subjected to formation and aging to complete the battery.

[0058] Example 4

[0059] Preparation of positive electrode materials:

[0060] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coating mixture; the pre-fired positive electrode material lithium cobalt oxide and the coating mixture are uniformly mixed in a weight ratio of 90:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 860nm.

[0061] Preparation of negative electrode materials:

[0062] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coated mixture; the pre-fired negative electrode material graphite and the coating mixture are uniformly mixed in a weight ratio of 90:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 750°C for 4h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 915nm.

[0063] Preparation of lithium batteries:

[0064] The positive electrode is made by mixing the prepared positive electrode material with a conductive agent and a binder to form a slurry, which is then coated on aluminum foil. The negative electrode is made by mixing the prepared negative electrode material with a binder to form a slurry, which is then coated on copper foil. The positive and negative electrode sheets and separator are wound together to form a battery cell, which is then installed in a battery case, baked, injected with electrolyte, welded and sealed, and then subjected to formation and aging to complete the battery.

[0065] Example 5

[0066] Preparation of positive electrode materials:

[0067] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coating mixture; the pre-fired positive electrode material lithium cobalt oxide and the coating mixture are uniformly mixed in a weight ratio of 100:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 850°C for 8h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 1100nm.

[0068] Preparation of negative electrode materials:

[0069] The coated boehmite (Y-AlOOH) was pretreated to make its particle size distribution D50 100, and then the boehmite (Y-AlOOH) was mixed with lithium salt (Li + ) are mixed in a weight ratio of 4:1, and then activated by high-speed crushing to obtain a coated mixture; the pre-fired negative electrode material graphite and the coating mixture are uniformly mixed in a weight ratio of 100:1 to obtain a mixed powder; the mixed powder is fired at a temperature of 850°C for 8h, and after cooling, the coated positive electrode material is obtained, and the coating thickness of the positive electrode material is measured to be 1005nm.

[0070] Preparation of lithium batteries:

[0071] The positive electrode is made by mixing the prepared positive electrode material with a conductive agent and a binder to form a slurry, which is then coated on aluminum foil. The negative electrode is made by mixing the prepared negative electrode material with a binder to form a slurry, which is then coated on copper foil. The positive and negative electrode sheets and separator are wound together to form a battery cell, which is then installed in a battery case, baked, injected with electrolyte, welded and sealed, and then subjected to formation and aging to complete the battery.

[0072] like Figure 2 and Figure 3 As shown, the present invention tested the high temperature capacity and low temperature capacity of the lithium batteries prepared in Examples 1 to 5, and the test results were all qualified.

[0073] The safety of the battery was tested using the following method. Examples 1-5 of the present invention all passed the following tests:

[0074] External short circuit: Hold a full charge at 20±5°C and 55±5°C for 8 hours. Use a wire with a resistance of less than 50mΩ to short-circuit the positive and negative terminals of the battery cell for 24 hours. The battery should not catch fire, deflagrate, or explode.

[0075] Overcharge: For fully discharged cells, connect the positive and negative electrodes to a constant current and voltage source at 20±5°C. Adjust the current to 1C5A and charge to 1.2 times the cut-off voltage. Then switch to constant voltage charging for a total charging time of 7 hours. The battery should not catch fire, deflagrate, or explode.

[0076] Overdischarge: For fully charged cells, discharge at a constant current of 1C5A for 7 hours at 20±5℃. The battery should not catch fire, deflagrate or explode.

[0077] Thermal Abuse: Place a fully charged battery cell in an oven and heat it to 130°C ± 2°C at a rate of 5 ± 2°C / min, hold it for 30 minutes, then return to room temperature and hold it for 6 hours. The battery should not catch fire, deflagrate, or explode.

[0078] Extrusion: At 20±5°C, place a fully charged battery cell between two iron plates with the electrode surfaces parallel to the plates (front and side). Apply a pressure of 13kN±0.78kN at a speed of 15mm / s and maintain the extrusion state for 6 hours. The battery should not catch fire, deflagrate, or explode.

[0079] Heavy object impact: At 20±5°C, place a steel rod with a diameter of 15.8mm±0.2mm horizontally in the center of a fully charged battery cell, with the longitudinal axis of the rod parallel to a plane (both the front and side directions). Allow a 9.1kg±0.1kg weight to fall freely from a height of 610mm±25mm onto the rod above the center of the cell. Observe for 6 hours. The battery should not catch fire, deflagrate, or explode.

[0080] Acupuncture: At 20±5°C, use a high-temperature resistant steel needle with a diameter of 3-5mm to vertically penetrate the center of the fully charged cell (from both the front and side) at a speed of 20-30mm / s (the needle remains in the cell for 90 minutes). Observe for 6 hours after puncture. The battery should not catch fire, deflagrate, or explode.

[0081] The environmental adaptability of the battery was also tested using the following method. Examples 1-5 of the present invention all passed the following tests:

[0082] Temperature shock: After standard charging, the battery cell is kept in -55℃±2℃ and +70℃±2℃ environments for 4 hours respectively, with a switching time of 20s-60s, for 10 cycles, and then discharged at 0.2C5A to a cut-off voltage of 2.5V. The battery discharge capacity is >90%.

[0083] Constant humidity and heat: After a standard charge, place the battery in an environment of 30-60°C and 95±2% relative humidity for 24 hours. Cycle 10, then discharge at 0.2C5A to a cutoff voltage of 2.5V. Record the discharge time. Battery discharge capacity >90%.

[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for coating positive and negative electrode materials of a lithium battery, characterized in that: The following steps are involved: S1. The boehmite γ-AlOOH is mixed with a lithium salt and then subjected to high-speed pulverization to activate it to obtain a coated mixture; wherein the coated boehmite is pretreated to have a particle size distribution D50 of 100 nm to 1 μm; the weight ratio of the boehmite to the lithium salt is (3 to 5): 1; S2. The pre-fired positive electrode material or negative electrode material and the coating mixture are uniformly mixed to obtain a mixed powder; wherein the positive electrode material is one of lithium cobalt oxide and lithium iron phosphate; the negative electrode material is one of graphite and silicon carbon; S3. sinter the mixed powder at a temperature of 750-850° C. for 4-8 hours, and obtain the coated positive electrode material or negative electrode material after cooling.

2. A lithium battery positive and negative electrode coating method according to claim 1, characterized in that: In step S2, the weight ratio of the positive electrode or negative electrode material to the coating mixture is (80-100):

1.

3. The method for coating positive and negative electrodes of a lithium battery according to claim 1, wherein: In step S3, the coating thickness of the positive electrode material or the negative electrode material is 0.7um-2um.

4. The method for coating positive and negative electrodes of a lithium battery according to claim 1, wherein: The lithium salt is selected from one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate.

5. A positive electrode material, characterized in that The lithium battery positive and negative electrode coating method is used to prepare the lithium battery positive and negative electrode coating method according to any one of claims 1 to 4.

6. A negative electrode material, characterized in that The positive and negative electrodes of a lithium battery are prepared by the coating method according to any one of claims 1 to 4.

7. A lithium battery, characterized in that: The positive electrode material and the negative electrode material are prepared by the positive and negative electrode coating method for lithium batteries described in any one of items 1 to 4.

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