Preparation method of lithium ion battery negative electrode material, design method of preparation process and lithium ion battery

Abstract

A design method, a preparation process, and a lithium-ion battery for preparing a negative electrode material are disclosed. The design method includes: obtaining target performance parameters of the negative electrode material, the target performance parameters including at least one of the reversible specific capacity of the negative electrode material, the powder OI value of the negative electrode material, and DC impedance data of a coin cell test of a lithium-ion battery prepared using the negative electrode material; designing a first median particle size of the first powder formed from the raw material after pulverization in the pulverization step based on the reversible specific capacity; and / or designing the granulation degree of the first powder in the granulation step based on the powder OI value; and / or designing the coating amount of the coating layer formed in the coating treatment step based on the DC impedance data, the coating layer being formed on the surface of the core of the negative electrode material formed after the graphitization step.

Description

Preparation method of lithium ion battery negative electrode material, design method of preparation process and lithium ion battery Technical Field

[0001] The present application relates to the field of lithium-ion batteries, and in particular to a method for preparing a negative electrode material for a lithium-ion battery, a method for designing a process for preparing a negative electrode material for a lithium-ion battery, and a lithium-ion battery. Background Art

[0002] The development of lithium-ion batteries is in full swing, and the demand for battery applications is changing with each passing day. The demand for negative electrode materials is also gradually increasing. The industry generally requires negative electrode materials to have high energy density, excellent fast charging performance, low DC resistance (DCR) and small electrode expansion performance, etc. This puts higher requirements on the product development of negative electrode materials.

[0003] Graphite is a common negative electrode material used in lithium-ion batteries. Graphite anode raw materials primarily consist of graphite particles. Graphite is a crystalline structure composed of carbon atoms arranged in layers. Graphite anode raw materials typically come in the form of natural graphite, synthetic graphite, or graphene.

[0004] Artificial graphite negative electrode material is a material with a certain particle size distribution obtained by crushing and granulating raw materials such as needle coke, petroleum coke, and asphalt coke, and then undergoing high-temperature graphitization treatment to form a graphite flake structure.

[0005] At present, research on artificial graphite negative electrode materials mainly focuses on the research of preparation methods. It is impossible to correlate the product parameters of each step in the preparation process of graphite negative electrode materials with the performance of the final graphite negative electrode materials, and then determine whether the graphite negative electrode materials can achieve specific battery performance and functions through the product parameter indicators of graphite negative electrode materials.

[0006] Summary of the Invention

[0007] One aspect of the present application provides a design method for a preparation process of a negative electrode material for a lithium ion battery, wherein the preparation process includes the steps of crushing, granulating, graphitizing, coating, and carbonizing. The design method includes: obtaining target performance parameters of the negative electrode material, wherein the target performance parameters include at least one of the reversible gram capacity of the negative electrode material, the powder OI value of the negative electrode material, and the DC impedance data of a lithium ion battery buckle test prepared using the negative electrode material; designing the negative electrode material obtained by crushing the raw material according to the reversible gram capacity of the negative electrode material; and and / or designing the first median particle size of the first powder in the granulation step according to the powder OI value of the negative electrode material, the granulation degree of the first powder being the difference between the second median particle size of the first powder after granulation and the first median particle size before granulation; and / or designing the coating amount of the coating layer formed in the coating treatment step according to the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, the coating layer being formed on the surface of the inner core of the negative electrode material formed after the graphitization step, the coating layer being a carbon coating layer having an amorphous structure.

[0008] In some embodiments of the present application, designing the first median particle size of the first powder formed from the raw materials in the pulverizing step based on the reversible gram capacity of the negative electrode material includes: selecting raw materials for preparing the negative electrode material and obtaining the volatile matter of the raw materials; designing the first median particle size of the first powder based on the volatile matter of the raw materials and the reversible gram capacity of the negative electrode material.

[0009] In some embodiments of the present application, the first median particle size of the first powder is D150, then 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120, where T 挥发分 is the volatile matter of the raw material; M 可逆克容量 is the reversible gram capacity of the negative electrode material.

[0010] In some embodiments of the present application, the volatile matter of the raw material is 0.2% to 20%, the reversible gram capacity of the negative electrode material is 320 to 365 mAh / g, and the first median particle size of the first powder is 5 to 20 μm.

[0011] In some embodiments of the present application, designing the granulation degree of the first powder in the granulation step according to the OI value of the powder of the negative electrode material includes: recording the OI value of the powder of the negative electrode material as G OI , the granulation degree is D 造粒程度 , then 1≤100 / (D 造粒程度 +3.3×G OI )≤25.

[0012] In some embodiments of the present application, the powder OI value of the negative electrode material is 1 to 20, and the granulation degree is 1 to 10 μm.

[0013] In some embodiments of the present application, the coating amount of the coating layer formed in the coating treatment step is designed based on the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, including: DCR is the DC impedance data of the lithium-ion battery buckle test prepared by using the negative electrode material, T 包覆量 is the coating amount of the coating layer, then 2≤(13×R DCR +0.07) / T 包 覆量 ≤500.

[0014] In some embodiments of the present application, the DC impedance data of the lithium-ion battery prepared using the negative electrode material in the buckle test is 2 to 20Ω, and the coating amount is 0.5% to 4.0%, wherein the coating amount is the mass percentage of the coating layer and the core of the negative electrode material.

[0015] Another aspect of the present application provides a method for preparing a negative electrode material for a lithium-ion battery, comprising: a pulverizing step of pulverizing a raw material to form a first powder having a first median particle size, wherein the first median particle size is designed based on the reversible gram capacity of the negative electrode material; a granulating step of granulating the first powder to form a second powder having a second median particle size, wherein the second median particle size is the sum of the first median particle size and a granulation degree, wherein the granulation degree is designed based on the powder OI value of the negative electrode material; graphitization of the second powder to convert it into a core of the negative electrode material; a coating step of forming a coating layer on the surface of the core of the negative electrode material, wherein the coating amount of the coating layer is designed based on DC impedance data of a buckle test of a lithium-ion battery prepared using the negative electrode material; and a carbonization step of further carbonizing the coating layer to form a carbon coating layer having an amorphous structure.

[0016] In some embodiments of the present application, the first median particle size is designed based on the reversible gram capacity of the negative electrode material, including: selecting raw materials and obtaining the volatile matter of the raw materials; and designing the first median particle size of the first powder based on the volatile matter of the raw materials and the reversible gram capacity of the negative electrode material.

[0017] In some embodiments of the present application, the first median particle size of the first powder is D150, then 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容 Quantity / 372≤120, where T 挥发分 is the volatile matter of the raw material; M 可逆克容量 is the reversible gram capacity of the negative electrode material.

[0018] In some embodiments of the present application, the volatile matter of the raw material is 0.2% to 20%, the reversible gram capacity of the negative electrode material is 320 to 365 mAh / g, and the first median particle size of the first powder is 5 to 20 μm.

[0019] In some embodiments of the present application, the granulation degree is designed based on the OI value of the powder of the negative electrode material, including: recording the OI value of the powder of the negative electrode material as G OI , the granulation degree is D 造粒程度 , then 1≤100 / (D 造粒程度 +3.3×G OI )≤25.

[0020] In some embodiments of the present application, the powder OI value of the negative electrode material is 1 to 20, and the granulation degree is 1 to 10 μm.

[0021] In some embodiments of the present application, the coating amount of the coating layer is designed based on the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, including: DCR is the DC impedance data of the lithium-ion battery buckle test prepared by using the negative electrode material, T 包覆 量 is the coating amount, then 2≤(13×R DCR +0.07) / T 包覆量 ≤500.

[0022] In some embodiments of the present application, the DC impedance data of the lithium-ion battery prepared using the negative electrode material in the buckle test is 2 to 20Ω, and the coating amount is 0.5% to 4.0%, wherein the coating amount is the mass percentage of the coating layer and the core of the negative electrode material.

[0023] In some embodiments of the present application, the raw material includes at least one of needle coke, petroleum coke and pitch coke, and the negative electrode material is a graphite negative electrode material.

[0024] The present application also provides a lithium ion battery negative electrode material, which is prepared using any of the above-mentioned methods for preparing lithium ion battery negative electrode materials, and includes a core and a carbon coating layer with an amorphous structure that covers the core.

[0025] Compared with the prior art, the present application provides a method for designing a process for preparing negative electrode materials for lithium-ion batteries, which can design the preparation process according to the target performance parameters of the negative electrode material, so that the formed negative electrode material meets the target performance requirements of the lithium-ion battery cell, and can meet the requirements of the lithium-ion battery for energy density and fast charging performance, and can also meet the requirements of the negative electrode material for low expansion performance.

[0026] The present application also provides a process for further preparing the lithium-ion battery negative electrode material according to the designed method. DETAILED DESCRIPTION

[0027] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content of this application. Various local modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but is intended to be of the widest scope consistent with the claims.

[0028] On the one hand, an embodiment of the present application provides a method for designing a process for preparing a negative electrode material for a lithium-ion battery. The process for preparing a negative electrode material for a lithium-ion battery includes the steps of crushing, granulating, graphitizing, coating, and carbonizing. The design method includes:

[0029] Obtaining target performance parameters of the negative electrode material, the target performance parameters comprising at least one of a reversible gram capacity of the negative electrode material, a powder OI value of the negative electrode material, and DC impedance data of a lithium-ion battery buckle test prepared using the negative electrode material;

[0030] Designing a first median particle size of the first powder formed by pulverizing the raw material in the pulverizing step according to the reversible gram capacity of the negative electrode material; and / or

[0031] Designing the granulation degree of the first powder in the granulation step according to the OI value of the powder of the negative electrode material, wherein the granulation degree is the difference between the second median particle size of the first powder after granulation and the first median particle size before granulation; and / or

[0032] The coating amount of the coating layer formed in the coating treatment step is designed based on the DC impedance data of the lithium-ion battery buckle test prepared using the negative electrode material. The coating layer is formed on the surface of the core of the negative electrode material formed after the graphitization step. The coating layer is a carbon coating layer with an amorphous structure.

[0033] Lithium-ion battery negative electrode materials can include graphite negative electrode materials. Graphite negative electrode materials are primarily composed of graphite particles and have a crystalline structure composed of carbon atoms arranged in layers. Graphite negative electrode materials typically exist in the form of natural graphite, artificial graphite, or graphene. The graphite negative electrode materials described in the embodiments of the present application can be artificial graphite or natural graphite.

[0034] In some embodiments of the present application, the preparation process of the graphite negative electrode material may include process steps such as a crushing step, a granulation step, a graphitization step, a coating step, a carbonization step, and a finished product processing step.

[0035] The pulverization step described in the embodiment of the present application is a raw material processing step, which may include heat treatment and pulverization and shaping. The heat treatment, for example, heat treats raw materials such as needle coke, petroleum coke, and pitch coke at a temperature of 0 to 1400°C to cause certain changes in the structure and physical and chemical properties of the raw materials. The raw materials after heat treatment can be pulverized and shaped by mechanical grinding or roller grinding to form a first powder. The first median particle size D150 is used to mark the uniformity and particle size of the first powder formed after the pulverization step. The definition of the first median particle size D150 refers to the particle size of 50% of the particles in the particulate matter of the first powder.

[0036] The granulation step described in the embodiment of the present application is usually carried out under high temperature. The equipment for carrying out the granulation step includes a horizontal reactor, a vertical reactor, and a continuous rotary reactor. The process of the granulation step is, for example, to add a certain amount of asphalt or resin material to the first powder having a first median particle size of D150 to carry out the granulation process. During the granulation process, the particles of the first powder are bonded together and converted into a second powder having a second median particle size of D250. The second median particle size D250 is larger than the first median particle size D150. The difference between the second median particle size D250 and the first median particle size D150 is defined as the granulation degree D 造粒程度 . For example, after the granulation step, the first median particle size of the first powder increases from 8.5 microns to a second median particle size of 14 microns, and the degree of granulation is 5.5 microns. The asphalt and resin bonding materials can be used as adhesives in the granulation process. In some embodiments of the present application, the addition amount (mass percentage content) of the asphalt or resin material is less than or equal to 30%. Optionally, the addition amount (mass percentage content) of the asphalt or resin material is less than or equal to 20%, for example, 15%, 10%, 8%, 6%, 3%, etc. The addition amount of the asphalt or resin material can also be 0.

[0037] The graphitization step described in the embodiment of the present application pyrolyzes the second powder having the second median particle size D250 generated after the granulation step at a high temperature to form a graphite structure with a high degree of crystallinity. This graphite structure is the core of the negative electrode material described in the embodiment of the present application. During the graphitization step, the structure of the graphite material changes: the molecular distance is reduced, and the lattice structure is more ordered. This structural change gives the graphite material better electrical conductivity and cycle stability. After the graphitization step, the core of the negative electrode material mainly includes carbon elements and may also include a trace amount of O elements. In the embodiment of the present application, the equipment for performing the graphitization step is not limited to a crucible furnace, a box furnace, an inner series furnace, etc., and the reaction temperature of the graphitization step is 2800-3200°C.

[0038] The coating treatment steps described in the embodiments of the present application include solid-phase coating treatment and liquid-phase coating treatment, that is, the coating agents used include solid-phase coating agents and liquid-phase coating agents. The solid-phase coating treatment directly coats the surface of the core of the negative electrode material with asphalt or resin-based materials as coating agents to form a coating layer; the liquid-phase coating treatment can heat and melt the asphalt or resin-based coating agent in a horizontal reactor or a vertical reactor and then coat it on the surface of the core of the negative electrode material to form a coating layer; the liquid-phase coating treatment can also use a solvent with a low coking value to prepare a coating agent that is liquid at room temperature, and then use a fusion machine to coat the surface of the core of the negative electrode material to form a coating layer.

[0039] In the embodiments of the present application, the coating formed can be a carbon coating. Compared to the carbon coating, the graphite core of the negative electrode material is more ordered, and the carbon coating can improve the fast charging performance of the negative electrode material. When the carbon coating is amorphous carbon, the amorphous carbon can increase the embedding speed of lithium ions in the negative electrode surface layer, thereby improving the pulse charging performance of the negative electrode material. Therefore, by specifically designing the coating amount of the coating layer, the pulse charging requirements of the battery cell made of the negative electrode material can be met.

[0040] The carbonization treatment step described in the embodiment of the present application can use carbonization equipment such as a roller kiln or a tunnel kiln. Under the protection of an inert gas, the temperature of the reaction chamber of the carbonization equipment is heated to 900-1500°C. The coating layer is further carbonized at a temperature of 900-1500°C to form a carbon coating layer with an amorphous structure, thereby improving the electrochemical properties of the carbon coating layer.

[0041] After performing the carbonization treatment step, in order to better realize industrialization and mass production, the method described in the embodiment of the present application may also include a finished product processing step, that is, completing the processing of the finished product stage through screening and demagnetization treatment to meet the requirements for shipment.

[0042] Based on the above-mentioned lithium-ion battery negative electrode material preparation process, the design method includes:

[0043] First, the target performance parameters of the negative electrode material are obtained, and the target performance parameters include at least one of the reversible gram capacity of the negative electrode material, the powder OI value of the negative electrode material, and the DC impedance data of the lithium ion battery prepared using the negative electrode material during a buckle test. The lithium ion battery is prepared using the negative electrode material described in the embodiment of the present application, and the present application does not limit the preparation method of the lithium ion battery. The target performance parameters can be a numerical range set according to the performance requirements of the lithium ion battery.

[0044] Gram capacity refers to the ratio of the amount of charge released by the active material within a battery to the mass of the active material. Reversible gram capacity refers to the ratio of the amount of charge released by the active material during the charge and discharge process in a battery or supercapacitor to the mass of the electrode, in other words, the reversibility of the charge during the charge and discharge process. It is usually expressed in units of mAh / g or Ah / kg. Reversible gram capacity reflects the charge loss of a battery or supercapacitor during the charge and discharge process and is one of the important indicators for evaluating the performance of batteries or supercapacitors.

[0045] The powder orientation index (OI) of the negative electrode material is abbreviated as the powder OI value. The powder OI value represents the expansion level of the battery cell's negative electrode and reflects the isotropy of the various crystalline phases of the negative electrode material at the electrode sheet level. The smaller the powder OI value, the better the isotropy of the various crystalline phases at the electrode sheet level, and the lower the expansion level of the battery cell's negative electrode. Therefore, by designing the degree of granulation of the negative electrode material, the OI value of the battery cell's negative electrode made from the formed negative electrode material can be made to meet the target requirements, thereby satisfying the battery end's requirements for the expansion level of the electrode sheet and battery cell.

[0046] In the embodiment of the present application, the powder OI value of the negative electrode material can be marked as G OI , then G OI =S004 / S110, wherein S004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction spectrum of the negative electrode material, and S110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction spectrum of the negative electrode material.

[0047] The lithium-ion battery button test is a method for evaluating the capacity and performance of lithium-ion batteries. Taking button batteries as an example, the manufacturing method of button batteries is to mix the negative electrode material and conductive carbon, carboxymethyl cellulose CMC and styrene-butadiene rubber SBR to prepare a battery slurry, and after the battery slurry is coated on the current collector to form a negative electrode sheet, the negative electrode sheet, electrolyte, lithium sheet and battery shell are combined into a button battery. By measuring the voltage change of the button battery under specific conditions, the capacity of the button battery can be determined, and the performance and life of the button battery can be evaluated. The button battery is first activated and cycled for one week, and then adjusted to 50% SOC for the lithium-ion battery button test. The DC resistance (DCR) data of the lithium-ion battery button test can be marked as R DCR The test conditions are to adjust the charge and discharge rate of the lithium-ion battery to 1C, discharge for 10 seconds, and calculate the DCR of the lithium-ion battery by the voltage relaxation during the rest time before and after the discharge of the lithium-ion battery. Usually, the DCR test time is less than 30 seconds.

[0048] Then, the first median particle size of the first powder formed by crushing the raw material in the crushing step is designed according to the reversible gram capacity of the negative electrode material; and / or the granulation degree of the first powder in the granulation step is designed according to the powder OI value of the negative electrode material, and the granulation degree is the difference between the second median particle size of the first powder after granulation and the first median particle size before granulation; and / or the coating amount of the coating layer formed in the coating treatment step is designed according to the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, and the coating layer is formed on the surface of the inner core of the negative electrode material formed after the graphitization step.

[0049] In some embodiments of the present application, designing the first median particle size of the first powder formed from the raw materials in the pulverizing step based on the reversible gram capacity of the negative electrode material includes: selecting raw materials for preparing the negative electrode material and obtaining the volatile matter of the raw materials; designing the first median particle size of the first powder based on the volatile matter of the raw materials and the reversible gram capacity of the negative electrode material.

[0050] The raw materials for preparing the negative electrode material include at least one of needle coke, petroleum coke and pitch coke.

[0051] Volatile matter refers to the mass percentage of the released substances, minus the water content, when the raw materials are heated at a certain temperature in an airtight state. In some embodiments of the present application, the volatile matter of the raw materials is 0.2% to 20%, preferably 0.2% to 15%, for example, 1%, 3%, 5%, 6%, 8%, 9%, 12%, 16%, 18%, etc.

[0052] In some embodiments of the present application, the first median particle size of the first powder formed after the pulverization step is marked as D150, then 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120, where T 挥发分 is the volatile matter of the raw material; M 可逆克容量 The reversible gram capacity of the negative electrode material, i.e., the target reversible gram capacity, is set based on the performance requirements of the lithium-ion battery. Based on the set reversible gram capacity and the volatile matter of the raw material, the first median particle size of the first powder formed in the pulverization step can be designed.

[0053] Optional, 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤100.

[0054] In some embodiments of the present application, the volatile content of the raw material is 0.2% to 20%, and the reversible gram capacity of the negative electrode material set by the target parameter is 320 to 365 mAh / g. Then, by 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120, it can be obtained that the first median particle size of the first powder is 5 to 20 μm.

[0055] In some embodiments of the present application, the volatile matter of the raw material is 0.2% to 15%, and the reversible gram capacity of the negative electrode material set by the target parameter is 335 to 360 mAh / g. Then, by 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤100, it can be obtained that the first median particle size of the first powder is 7 to 15 μm.

[0056] In some embodiments of the present application, the pulverization step adopts physical pulverization, and the first median particle size of the first powder is measured by using a laser diffraction particle size distribution measuring instrument (for example: Mastersizer3000), according to the particle size distribution laser diffraction method (specific reference GB / T19077-2016), to measure the particle size distribution, and use the median value of the volume distribution to represent the first median particle size. The volatile matter of the raw material can be detected using a muffle furnace, and the test result of burning the raw material at 900°C for 1 hour is recorded as T 挥发分 .

[0057] In some embodiments of the present application, designing the granulation degree of the first powder in the granulation step according to the OI value of the powder of the negative electrode material includes: recording the OI value of the powder of the negative electrode material as GOI , the granulation degree is D 造粒程度 , then 1≤100 / (D 造粒程度 +3.3×G OI )≤25. Optional, 2≤100 / (D 造粒程度 +3.3×G OI )≤15.

[0058] In some embodiments of the present application, the powder OI value of the negative electrode material is 1-20, then according to 1≤100 / (D 造粒程度 +3.3×G OI )≤25, the granulation degree can be 1-10 μm, such as 3 μm, 5 μm, 6 μm, 8 μm, etc. In some embodiments of the present application, the powder OI value of the negative electrode material is 1.5-10, according to 2≤100 / (D 造粒程度 +3.3×G OI )≤15, the granulation degree can be obtained to be 1 to 7 μm.

[0059] In some embodiments of the present application, the coating amount of the coating layer formed in the coating treatment step is designed based on the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, including: DCR is the DC impedance data of the lithium-ion battery buckle test prepared by using the negative electrode material, T 包覆量 is the coating amount of the coating layer, then 2≤(13×R DCR +0.07) / T 包 覆量 ≤500, optional, 5≤(13×R DCR +0.07) / T 包覆量 ≤400.

[0060] In some embodiments of the present application, the DC impedance data of the lithium-ion battery prepared by the negative electrode material is 2 to 20Ω, then according to 2≤(13×R DCR +0.07) / T 包覆量 ≤500 can be obtained that the coating amount is 0.5% to 4.0%, wherein the coating amount is the mass percentage of the coating layer and the core of the negative electrode material. In other embodiments of the present application, the DC impedance data of the lithium ion battery prepared by the negative electrode material is 3 to 15Ω in the buckle test. Then according to 5≤(13×R DCR +0.07) / T 包覆量 ≤400, and the coating amount is 0.75% to 3.5%.

[0061] The design method for the preparation process of the negative electrode material for a lithium-ion battery described in this embodiment is adopted, and the preparation parameters of the preparation process are designed according to the target performance parameters of the negative electrode material. For example, the first median particle size of the first powder formed in the pulverization step is obtained according to the reversible gram capacity of the negative electrode material, the granulation degree in the granulation step is obtained according to the powder OI value of the negative electrode material, and the coating amount of the coating layer in the coating step is obtained according to the DC impedance data of the buckle test of the lithium-ion battery prepared by using the negative electrode material, so as to realize the parameter design of the negative electrode material preparation process.

[0062] Another aspect of the present application provides a method for preparing a negative electrode material for a lithium ion battery, comprising:

[0063] S1: Executing a pulverization step to pulverize the raw materials to form a first powder having a first median particle size, wherein the first median particle size is designed based on the target reversible gram capacity of the negative electrode material. Specifically, designing the first median particle size based on the target reversible gram capacity of the negative electrode material includes: selecting raw materials and obtaining a volatile matter content of the raw materials; and designing the first median particle size of the first powder based on the volatile matter content of the raw materials and the target reversible gram capacity of the negative electrode material.

[0064] In some embodiments of the present application, the raw material of the negative electrode material includes at least one of needle coke, petroleum coke and pitch coke, the negative electrode material is graphite, and the coating layer is an amorphous carbon coating layer. 挥发分 is the volatile matter of the raw material, M 可逆克容量 is the target reversible gram capacity of the negative electrode material, the first median particle size of the first powder is D150, then 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120.

[0065] In some embodiments of the present application, the volatile matter of the raw material is 0.2% to 20%, and the target reversible capacity of the negative electrode material is 320 to 365 mAh / g. Then, 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120, it can be obtained that the first median particle size of the first powder is 5 to 20 μm.

[0066] In some embodiments of the present application, the volatile matter of the raw material is 0.2% to 15%, and the target reversible capacity of the negative electrode material is 335 to 360 mAh / g. Then, 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤100, it can be obtained that the first median particle size of the first powder is 7 to 15 μm.

[0067] S2: performing a granulation step to granulate the first powder to form a second powder having a second median particle size, where the second median particle size is the sum of the first median particle size and a granulation degree, wherein the granulation degree is designed based on the OI value of the powder of the negative electrode material;

[0068] The second median particle size of the second powder is D250, wherein D250=D150+D 造粒程度 ; 1≤100 / (D 造粒程度 +3.3×G OI )≤25. Among them, the powder OI value G OI =S004 / S110, wherein S004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction spectrum of the powder of the negative electrode active material, and S110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction spectrum of the powder of the negative electrode active material.

[0069] In some embodiments of the present application, the powder OI value of the negative electrode material is 1-20, then according to 1≤100 / (D 造粒程度 +3.3×G OI )≤25, the granulation degree can be obtained to be 1-10 μm, for example, 3 μm, 5 μm, 6 μm, 8 μm, etc. When the first median particle size D150 of the first powder is 5-20 μm, the second median particle size D250 of the second powder can be obtained to be 6-30 μm.

[0070] In some embodiments of the present application, the powder OI value of the negative electrode material is 1.5 to 10, according to 2≤100 / (D 造粒程度 +3.3×G OI )≤15, the granulation degree can be obtained to be 1-7 μm, when the first median particle size D150 of the first powder is 7-15 μm, the second median particle size D250 of the second powder is 8-22 μm.

[0071] S3: performing a graphitization step to convert the second powder into the core of the negative electrode material,

[0072] S4: Continue to perform the coating step to form a coating layer on the surface of the core of the negative electrode material, wherein the coating amount of the coating layer is designed based on the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material.

[0073] In some embodiments of the present application, the coating amount of the coating layer is designed based on the DC impedance data of the lithium ion battery buckle test prepared by using the negative electrode material, including: DCRis the DC impedance data of the lithium-ion battery buckle test prepared by using the negative electrode material, T 包覆 量 is the coating amount of the coating layer, then 2≤(13×R DCR +0.07) / T 包覆量 ≤500, optional, 5≤(13×R DCR +0.07) / T 包覆量 ≤400.

[0074] In some embodiments of the present application, the DC impedance data of the lithium-ion battery prepared using the negative electrode material in the buckle test is 2 to 20Ω, and the coating amount is 0.5% to 4.0%, wherein the coating amount is the mass percentage of the coating layer and the core of the negative electrode material.

[0075] In some embodiments of the present application, the DC impedance data of the lithium-ion battery prepared by the negative electrode material is 2 to 20Ω, then according to 2≤(13×R DCR +0.07) / T 包覆量 ≤500 can be obtained that the coating amount is 0.5% to 4.0%, wherein the coating amount is the mass percentage of the coating layer and the core of the negative electrode material. In other embodiments of the present application, the DC impedance data of the lithium ion battery prepared by the negative electrode material is 3 to 15Ω in the buckle test. Then according to 5≤(13×R DCR +0.07) / T 包覆量 ≤400, the coating amount is 0.75% to 3.5%

[0076] S5: performing a carbonization step to further carbonize the coating layer to form a carbon coating layer with an amorphous structure.

[0077] After performing the carbonization treatment step, in order to better achieve industrialization and mass production, the method described in the embodiment of the present application may further include an S5 finished product processing step.

[0078] In the production of lithium-ion battery negative electrode materials, in order to obtain negative electrode materials with different reversible gram capacities and compaction densities, screening and pretreatment are required at the raw material stage. The volatile content of the raw materials and the size of the first median particle size formed after the raw materials are crushed directly affect the development of the crystallite size of the core of the negative electrode material in the subsequent graphitization step, which directly affects the compaction density and reversible gram capacity of the negative electrode material in the finished product stage. The lower the volatile content of the raw materials, the larger the internal crystallites of the core of the negative electrode material will develop under the action of heat during the graphitization step. The corresponding first median particle size of the first powder is larger, providing sufficient space for the development of crystallites in the subsequent graphitization step, and the higher the reversible gram capacity of the final negative electrode material.

[0079] The preparation method of the lithium-ion battery negative electrode material of the present application can achieve target performance parameters of the formed lithium-ion battery negative electrode material by controlling the first median particle size of the first powder formed in the pulverization step, the degree of granulation in the granulation step, and the coating amount of the coating layer in the coating step, so as to ensure the application requirements of the negative electrode material at the battery cell end, and further meet the energy density and kinetic requirements of the battery cell system for the negative electrode material.

[0080] The present application also provides a lithium ion battery negative electrode material, which is prepared using any of the above-mentioned methods for preparing lithium ion battery negative electrode materials, and includes a core and a carbon coating layer with an amorphous structure that covers the core.

[0081] The following further discusses the implementation of the present application based on reference examples 1 to 18.

[0082] Examples 1 to 9:

[0083] Select raw materials with volatile content of 13.0±4.0%, such as T 挥发分 The raw materials with different volatile fraction values ​​are 9.0±1.0%, 4.0±1.0%, and 1.0±1.0%, respectively. The raw materials with different volatile fraction values ​​are respectively crushed into first powders with different first median particle sizes D150, wherein the D150 ranges are 6-8μm, 9-11μm, and 14-16μrm, respectively. The first powders are formed into second powders through granulation, and the second powders are graphitized and put into a furnace for processing to convert the second powders into the core of the negative electrode material, wherein the core of the negative electrode material is a graphite core, and then the reversible gram capacity of the graphite core is measured. The pulverization step adopts physical pulverization, and the first median particle size of the first powder is measured by using a laser diffraction particle size distribution measuring instrument (for example: Mastersizer 3000) according to the particle size distribution laser diffraction method (specific reference GB / T19077-2016) to measure the particle size distribution, and the median value of the volume distribution is used to represent the first median particle size D150; the volatile matter of the raw material is detected using a muffle furnace, and the test result of burning at 900°C for 1h is recorded as T 挥发分 The reversible gram capacity test method of the graphite core is as follows: the graphite core and carboxymethyl cellulose CMC, styrene butadiene rubber SBR, and conductive carbon black SP are prepared in a ratio of 95.5:1.5:1.5:1.5 to prepare a slurry, and then the slurry is coated on a current collector and dried to prepare a button battery. The reversible gram capacity of the graphite core is tested, which is marked as M. 可逆克容 The test data are shown in Table 1, where A = D150 × (0.71 + 0.39 × D150 / T 挥发分 )+M 可逆克容量 / 372.

[0084] Table 1

[0085] The first median particle size D150 of the powder in Examples 1 to 9 above satisfies the relationship between the volatile matter of the raw material and the reversible gram capacity of the graphite core material: 3≤D150×(0.71+0.39×D150 / T 挥发分 )+M 可逆克容量 / 372≤120; that is, A is greater than or equal to 3 and less than or equal to 120.

[0086] Examples 10-12:

[0087] The graphite core formed in Example 5 is selected, and a coating step is performed to form a coating layer on the surface of the graphite core. A roller kiln is then used as a device for the carbonization step. Under the protection of an inert gas, the temperature of the roller kiln reaction chamber is heated to 1200°C. The process is carried out at a temperature of 1200°C to further carbonize the coating layer to form a carbon coating layer having an amorphous structure, thereby making a negative electrode material. The negative electrode material comprises a graphite core and an amorphous carbon coating layer coated on the surface of the graphite core. Among them, Example 10 adopts a solid-phase coating process, directly mixing an asphalt coating agent to coat the graphite core, with a coating amount of 1%; Example 11 adopts a liquid-phase coating process, heating and melting a resin coating agent in a horizontal reactor to coat the graphite core, with a coating amount of 2%; Example 12 adopts a liquid-phase coating process, using a room-temperature liquid coating material prepared with a solvent having a low coking value, and using a fusion machine to coat the graphite core, with a coating amount of 3%.

[0088] The negative electrode materials formed in Examples 10 to 12 were made into button cells. The method for making the button cells was similar to that described in Examples 1 to 9. After initial calibration, the button cells were subjected to a DCR test. The test conditions were as follows: the SOC was adjusted to 50% SOC at a charge and discharge rate of 0.1C, and a discharge test was performed for 10 seconds. The DCR data of the corresponding button cells were calculated based on the test data. The test data are shown in Table 2, where B = (13 × R DCR +0.07) / T 包覆量 .

[0089] Table 2

[0090] As can be seen from Table 2, in the above Examples 10 to 12, T 包覆量 The value of DCR satisfies the relationship: 2≤(13×R DCR +0.07) / T 包覆量 ≤500, that is, B is greater than or equal to 2 and less than or equal to 500.

[0091] In the design of the negative electrode material in the embodiments of the present application, the negative electrode material plays a vital role in the expansion of the product, seriously affecting the processability of the negative electrode material during use and the electrochemical performance of the final finished battery. The expansion of the product is closely related to the OI value of the powder of the negative electrode material. Therefore, the relationship between the OI value of the powder of the negative electrode material and the degree of granulation is clarified in this application, with reference to Examples 13 to 18.

[0092] Examples 13 to 18

[0093] In Examples 13 to 15, the first powder having a first median particle size of D150 formed after the crushing step in Example 1 is selected, and a granulation step is performed to generate a second powder having a second median particle size of D250. The equipment selected for the granulation step is a horizontal reactor, a vertical reactor, and a continuous rotary reactor, respectively. After granulation, the second powder is subjected to a graphitization step to form a graphite core of the negative electrode material, and the powder OI value of the graphite core is tested.

[0094] In Examples 16 to 18, a first powder having a first median particle size of D150 formed after the crushing step in Example 2 is selected, and a granulation step is performed to generate a second powder having a second median particle size of D250. The equipment selected for the granulation step is a horizontal reactor, a vertical reactor, and a continuous rotary reactor, respectively. After granulation, a graphitization step is performed on the second powder to form a graphite core of the negative electrode material, and the powder OI value of the graphite core is tested.

[0095] The first median particle size D150 and the second median particle size D250 of the first powder and the second powder formed in Examples 13 to 18 are shown in Table 3, respectively. The powder OI values ​​G of the graphite core measured are respectively OI =S004 / S110, wherein S004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction spectrum of the powder of the negative electrode active material, and S110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction spectrum of the powder of the negative electrode active material, wherein C=100 / (D 造粒程度 +3.3×G OI ).

[0096] Table 3

[0097] As can be seen from Table 3, the OI value of the powders in Examples 13 to 18 and the degree of granulation satisfy the relationship: 1≤100 / (D 造粒程度 +3.3×G OI )≤25, that is, C is greater than or equal to 1 and less than or equal to 25.

[0098] Finally, it should be understood that the embodiments of the application disclosed herein are illustrations of the principles of the embodiments of the present application. Other modified embodiments are also within the scope of the present application. Therefore, the embodiments disclosed in the present application are merely examples and not limitations. Those skilled in the art can adopt alternative configurations based on the embodiments in the present application to implement the applications in the present application. Therefore, the embodiments of the present application are not limited to those embodiments that have been precisely described in the application.

Claims

1. A design method for the preparation process of a negative electrode material for a lithium-ion battery, the preparation process including steps of crushing, granulation, graphitization, coating treatment, and carbonization treatment, characterized in that, The design method includes: Obtaining target performance parameters of the negative electrode material, where the target performance parameters include at least one of the reversible specific capacity of the negative electrode material, the powder OI value of the negative electrode material, and the DC impedance data of the coin cell test of the lithium-ion battery prepared using the negative electrode material; Designing the first median particle size of the first powder formed after crushing the raw material in the crushing step based on the reversible specific capacity of the negative electrode material; and / or Designing the granulation degree of the first powder in the granulation step based on the powder OI value of the negative electrode material, where the granulation degree is the difference between the second median particle size after granulating the first powder and the first median particle size before granulation; and / or Designing the coating amount of the coating layer formed in the coating treatment step based on the DC impedance data of the coin cell test of the lithium-ion battery prepared using the negative electrode material, where the coating layer is formed on the surface of the core of the negative electrode material formed after the graphitization step, and the coating layer is a carbon coating layer with an amorphous structure.

2. The design method of the preparation process of the negative electrode material of the lithium-ion battery according to claim 1, wherein, Designing the first median particle size of the first powder formed after crushing the raw material in the crushing step based on the reversible specific capacity of the negative electrode material includes: Selecting the raw material for preparing the negative electrode material and obtaining the volatile content of the raw material; Designing the first median particle size of the first powder based on the volatile content of the raw material and the reversible specific capacity of the negative electrode material.

3. The design method of the preparation process of the negative electrode material of the lithium-ion battery according to claim 2, characterized in that, If the first median particle size of the first powder is D150, then 3 ≤ D150 × (0.71 + 0.39 × D150 / T 挥发分 ) + M 可逆克容量 / 372 ≤ 120, where T 挥 发分 is the volatile content of the raw material; M 可逆克容量 is the reversible specific capacity of the negative electrode material.

4. The design method of the preparation process of the anode material for a lithium-ion battery according to claim 3, characterized in that, the volatile content of the raw material is 0.2% - 20%, the reversible specific capacity of the negative electrode material is 320 - 365 mAh / g, and the first median particle size of the first powder is 5 - 20 μm.

5. The design method of the preparation process of the negative electrode material of the lithium-ion battery according to claim 1, characterized in that, Designing the granulation degree of the first powder in the granulation step according to the OI value of the powder of the negative electrode material includes: recording the OI value of the powder of the negative electrode material as G OI , the granulation degree is D 造粒程度 , then 1 ≤ 100 / (D 造粒程度 + 3.3×G OI ) ≤ 25.

6. The design method of the preparation process of the negative electrode material of the lithium-ion battery according to claim 5, characterized in that, The powder OI value of the negative electrode material is 1 - 20, and the granulation degree is 1 - 10 μm.

7. The design method of the preparation process of the negative electrode material of the lithium ion battery according to claim 1, characterized in that, Designing the coating amount of the coating layer formed in the coating treatment step based on the DC impedance data of the coin cell test of the lithium-ion battery prepared with the negative electrode material includes: Denote R DCR as the DC impedance data of the coin cell test of the lithium-ion battery prepared with the negative electrode material, and T 包覆量 as the coating amount of the coating layer, then 2 ≤ (13×R DCR + 0.07) / T 包覆量 ≤ 500.

8. The design method of the preparation process of the negative electrode material of the lithium-ion battery according to claim 7, characterized in that, The DC impedance data of the coin cell test of the lithium-ion battery prepared using the negative electrode material is 2 - 20 Ω, and the coating amount is 0.5% - 4.0%, where the coating amount is the mass percentage of the coating layer to the core of the negative electrode material.

9. A method for preparing a negative electrode material of a lithium-ion battery, characterized in that, It includes: A crushing step of crushing the raw material to form a first powder with a first median particle size, where the first median particle size is designed based on the reversible specific capacity of the negative electrode material; A granulation step of granulating the first powder to form a second powder with a second median particle size, where the second median particle size is the sum of the first median particle size and the granulation degree, and the granulation degree is designed based on the powder OI value of the negative electrode material; A graphitization step of converting the second powder into the core of the negative electrode material; A coating step of forming a coating layer on the surface of the core of the negative electrode material, where the coating amount of the coating layer is designed based on the DC impedance data of the coin cell test of the lithium-ion battery prepared using the negative electrode material; A carbonization step of further carbonizing the coating layer to form a carbon coating layer with an amorphous structure.

10. The preparation method of the negative electrode material of the lithium ion battery according to claim 9, characterized in that, The first median particle size being designed based on the reversible specific capacity of the negative electrode material includes: Selecting the raw material and obtaining the volatile content of the raw material; Designing the first median particle size of the first powder based on the reversible specific capacity of the negative electrode material.

11. The preparation method of the negative electrode material of the lithium ion battery according to claim 10, characterized in that, The first median particle size of the first powder material is D150, then 3 ≤ D150 × (0.71 + 0.39 × D150 / T 挥发分 ) + M 可逆克容量 / 372 ≤ 120, where T 挥 发分 is the volatile content of the raw material; M 可逆克容量 is the reversible specific capacity of the negative electrode material.

12. The preparation method of the negative electrode material of the lithium ion battery according to claim 11, characterized in that, The volatile content of the raw material is 0.2% to 20%, the reversible specific capacity of the anode material is 320 to 365 mAh / g, and the first median particle size of the first powder material is 5 to 20 μm.

13. The preparation method of the negative electrode material of the lithium ion battery according to claim 9, characterized in that, The granulation degree is designed based on the OI value of the powder of the negative electrode material, including: recording the OI value of the powder of the negative electrode material as G OI , and the granulation degree is D 造粒程度 , then 1 ≤ 100 / (D 造粒程度 + 3.3 × G OI ) ≤ 25.

14. The preparation method of the negative electrode material for a lithium-ion battery according to claim 13, characterized in that, The powder OI value of the anode material is 1 to 20, and the granulation degree is 1 to 10 μm.

15. The preparation method of the negative electrode material for a lithium-ion battery according to claim 9, wherein, The coating amount of the coating layer is designed based on the DC impedance data of the coin cell test of the lithium-ion battery prepared with the negative electrode material, including: Denote R DCR as the DC impedance data of the coin cell test of the lithium-ion battery prepared with the negative electrode material, and T 包覆量 as the coating amount. Then, 2 ≤ (13 × R DCR + 0.07) / T 包覆量 ≤ 500.

16. The preparation method of the negative electrode material for a lithium ion battery according to claim 15, characterized in that, The DC impedance data of the coin cell test of the lithium-ion battery prepared with the anode material is 2 to 20 Ω, and the coating amount is 0.5% to 4.0%, where the coating amount is the mass percentage of the coating layer to the core of the anode material.

17. The preparation method of the negative electrode material of the lithium ion battery according to claim 9, characterized in that, The raw material includes at least one of needle coke, petroleum coke, and pitch coke, and the anode material is a graphite anode material.

18. A negative electrode material for a lithium-ion battery, characterized in that, Prepared by any one of the methods according to claims 9 to 17, including a core and an amorphous carbon coating layer covering the core.