Modified lithium replenishment agent, preparation method therefor and use thereof

Abstract

A modified lithium replenishment agent, a preparation method therefor and a use thereof, relating to the technical field of lithium batteries. The surface of a lithium replenishment agent substrate is doped / coated with metal elements such as Co, Cu, Ca, Ti, Zr, Al and Mg. The elements can inhibit the decomposition reaction of the lithium replenishment agent by an electrolyte, thereby effectively reducing the gas production. By means of the modification of the lithium replenishment agent, the gas produced by batteries in storage can be significantly reduced while improvements to battery performance (such as battery capacity) achieved by ordinary lithium replenishing agents can be maintained.

Description

A modified lithium supplement and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to application number 2023107982081 filed with the Patent Office of China on June 30, 2023, entitled “A modified lithium supplement agent, its preparation method and application,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of lithium batteries, and in particular to a modified lithium supplement agent and a preparation method and application thereof. Background Art

[0004] Energy is essential to the development of human society. With the increasing shortage of traditional fossil fuels, the development of new clean energy sources has become a hot topic. Among the many new energy options being developed, lithium-ion batteries, with their high energy efficiency, long cycle life, low maintenance costs, and flexible power and energy characteristics, are very popular in automotive propulsion and energy storage.

[0005] However, with the widespread adoption of electric vehicles, the pursuit of lithium-ion batteries with higher energy density has become a common goal. Since the introduction of Sony's first-generation lithium-ion battery in 1990, advances in chemical material systems and optimization of internal and external battery structures have brought the maximum energy density of commercial lithium-ion batteries close to 300Wh / kg. However, further increases in energy density are extremely difficult under current design concepts and material systems, and such increases often come at the expense of battery safety, power, and lifespan, resulting in a low cost-to-performance ratio and high costs.

[0006] In addition to the above methods, there is another way to increase the energy density of the battery, which can be achieved by reducing the initial loss of positive and negative electrode materials, that is, by increasing the number of active lithium ions to increase the battery energy. This method is mainly achieved by adding positive or negative electrode additives, usually called lithium replenishers. Among them, the negative electrode lithium replenisher requires the introduction of metallic lithium or alkyl lithium, which has high requirements on the environment and process, and is more difficult to implement; while the positive electrode lithium replenisher only needs to mix a small amount of lithium replenisher (1-3%) into the positive electrode active material, without changing any front-end and mid-stage process equipment. The operation is very simple and easy to implement, making it the first choice of many battery companies.

[0007] Currently, the commonly used positive electrode lithium replenishers are materials such as Li5FeO4, Li2NiO2, and Li2O2, added to the cathode material during the preparation of the electrode sheet to compensate for the efficiency loss of the negative electrode during the initial charge and discharge. Taking Li5FeO4 as an example, its mechanism of action is as follows: during the initial charge process, the lithium replenisher releases a specific capacity of >600mAh / g, while the initial discharge capacity is generally 30-40mAh / g. This produces excess lithium ions to replenish the lithium loss of the graphite negative electrode during the initial charge, and releases oxygen. The Li5FeO4 lithium replenisher has two charging platforms during the initial charge process, approximately 3.5-3.6V and 3.9-4.0V. Li5FeO4 undergoes a lithium delithiation reaction at each platform, ultimately generating LiFeO2 and O2. Furthermore, the lithium replenisher generally needs to be charged to a higher voltage (>4.0V) to achieve its maximum lithium replenishment effect. This voltage is higher than the conventional voltage range of lithium iron phosphate (LFP) (approximately 2.0-3.75). Therefore, at high voltages, the electrolyte decomposes, producing other gases or irreversible gassing. Gassing primarily arises from several sources: the release of oxygen from the decomposition of lithium supplements at high voltages, and the catalytic decomposition of the electrolyte at high voltages. Gassing can cause swelling in the battery cell, severely impacting battery life. Furthermore, catalytic decomposition of the electrolyte can reduce the battery's cycle life.

[0008] Therefore, how to make the lithium supplement agent achieve the lithium supplement effect while reducing gas production, effectively reduce the DC resistance (DCR) of LFP and effectively improve the rate performance of LFP, is a technical problem that needs to be solved urgently.

[0009] In view of this, the present disclosure is proposed.

[0010] Summary of the Invention

[0011] The purpose of the present disclosure is to provide a modified lithium supplement agent and its preparation method and application, aiming to reduce gas production while ensuring that the lithium supplement agent significantly improves the specific capacity of the battery.

[0012] The present disclosure is achieved as follows:

[0013] In a first aspect, the present disclosure provides a modified lithium supplement agent, including a lithium supplement agent substrate, wherein the surface of the lithium supplement agent substrate contains a metal element, and the metal element is selected from at least one of Co, Cu, Ca, Ti, Zr, Al and Mg.

[0014] In an optional embodiment, in the modified lithium supplement agent, the doping amount of the metal element is 1000ppm-20000ppm;

[0015] Optionally, the lithium supplement base material is selected from at least one of Li5FeO4, Li2NiO2 and Li2O2.

[0016] In an optional embodiment, it further includes a conductive carbon material, wherein the conductive carbon material is selected from at least one of graphene and carbon nanotubes;

[0017] Optionally, the conductive carbon material accounts for 0.5 wt% to 5 wt% of the modified lithium supplement.

[0018] Optionally, the particle size of the conductive carbon material is 1 nm-10 nm, and the length is 5 μm-50 μm.

[0019] In a second aspect, the present disclosure provides a preparation method of any one of the aforementioned modified lithium supplement agents, wherein a metal element is doped on the surface of a lithium supplement agent substrate.

[0020] In an optional embodiment, the method includes: sintering a mixture formed by a lithium supplement base material, a metal oxide, and a conductive carbon material;

[0021] Wherein, the metal oxide is selected from Co3O4, CuO, CaO2, Al(OH)3, Mg(OH)2, Li 1+x Al x Ti 2-x (PO4)3、Li 3+x La3Zr2O 12 He Li 3+x La3Zr 2-y Ti y O 12 At least one of the following: wherein the value of x is 1≤x<2, and the value of y is 0.5-2;

[0022] Optionally, the mass ratio of the metal oxide, the conductive carbon material and the lithium supplement agent substrate is (0.1-2):(0.5-5):100.

[0023] In an optional embodiment, the preparation process of the mixture includes: ball milling the metal oxide raw material to obtain a powder with a particle size of 0.1 μm-1 μm, then ball milling it with the lithium supplement base material for a second time, and mixing the mixture obtained after the second ball milling with the conductive carbon material;

[0024] Optionally, the milling time of the first ball milling and the second ball milling is 1 h to 20 h;

[0025] Optionally, the solvent added during the first ball milling process is selected from at least one of ethanol, ethylene glycol and acetone.

[0026] In an optional embodiment, the sintering temperature is 300° C.-800° C., and the sintering time is 1 h-20 h;

[0027] Optionally, during the sintering process, the heating rate is controlled to be 1°C / min-10°C / min;

[0028] Optionally, the method further comprises: crushing the material obtained after sintering.

[0029] In a third aspect, the present disclosure provides a positive electrode sheet slurry, comprising a lithium iron phosphate active material and a modified lithium supplement agent, wherein the modified lithium supplement agent is the modified lithium supplement agent of any one of the aforementioned embodiments or the modified lithium supplement agent prepared by any one of the preparation methods of the aforementioned embodiments;

[0030] Optionally, the positive electrode sheet slurry includes, by mass: 95-98 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement agent, 0.5-3 parts of conductive agent and 0.5-2 parts of binder;

[0031] Optionally, the conductive agent is selected from at least one of conductive carbon black (SP), carbon nanotubes (CNTs) and Ketjen black;

[0032] Optionally, the binder is selected from at least one of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA).

[0033] In a fourth aspect, the present disclosure provides a positive electrode sheet, comprising a positive electrode current collector and an active coating attached to the surface of the positive electrode current collector, wherein the active coating is prepared from the positive electrode sheet slurry of the aforementioned embodiment.

[0034] In a fifth aspect, the present disclosure provides a lithium battery comprising the positive electrode sheet of the aforementioned embodiment.

[0035] The present disclosure has the following beneficial effects: by incorporating metal elements such as Co, Cu, Ca, Ti, Zr, Al, and Mg on the surface of the lithium supplement substrate, these elements can inhibit the electrolyte's reaction and decomposition of the lithium supplement, effectively reducing gas production. By modifying the lithium supplement, it is possible to significantly reduce battery storage gas production while maintaining the improved battery performance (such as battery capacity) achieved by conventional lithium supplements.

[0036] It should be added that the inventors speculate that the reason why the introduction of the above metal elements can reduce gas production may be due to the following two reasons: (1) by introducing metal elements, the lattice of the material can be changed to a certain extent. After introducing different metal elements, different band gaps may be formed, which may increase the voltage of the lithium supplement agent for decomposing oxygen; (2) by introducing metal elements, the contact between the lithium supplement agent and the electrolyte can be effectively reduced, thereby achieving the purpose of reducing gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, 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 disclosure 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 creative work.

[0038] FIG1 is a SEM image of the lithium supplement agent of Comparative Example 1;

[0039] FIG2 is a SEM image of the modified lithium supplement agent prepared in Example 1;

[0040] Figure 3 is a graph showing the full battery capacity test results;

[0041] FIG4 is a test result diagram of the gas production growth rate of the battery after adding a lithium supplement;

[0042] Figure 5 shows the DCR curves of the battery without lithium supplement and with two lithium supplements (DCR test was performed by discharging at 0.33C to an unused SOC, measuring the changes in voltage and current within 30 seconds, at a test temperature of 25°C).

[0043] Figure 6 shows the DCR curves of the battery without adding a lithium supplement and with adding two lithium supplements (the DCR test was performed by discharging at 0.33C to an unused SOC, measuring the changes in voltage and current within 30 seconds, and the test temperature was -10°C).

[0044] FIG7 shows the cycle curves of the case where no lithium supplement agent is added and two lithium supplement agents are added (test conditions: current 1C / 1C, test temperature 25° C.). DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0046] The present disclosure provides a method for preparing a modified lithium supplement agent. The lithium supplement agent base material is doped or coated with metal elements. The metal elements on the surface can inhibit the electrolyte from reacting and decomposing the lithium supplement agent, effectively reducing gas production. The specific preparation process includes:

[0047] S1. Metal oxide pretreatment

[0048] The metal oxide is pretreated to form nanometer-scale powder for later use.

[0049] Metal oxides are selected from Co3O4, CuO, CaO2, Al(OH)3, Mg(OH)2, Li1+x Al x Ti 2-x (PO4)3、Li 3+x La3Zr2O 12 He Li 3+x La3Zr 2-y Ti y O 12 At least one of the above can be any one or more of the above; wherein the value of x is 1-2, and the value of y is 0.5-2;

[0050] In some embodiments, the metal oxide raw material can be ball-milled once to obtain a powder with a particle size of 0.1 μm to 1 μm, so that the metal oxide can be evenly mixed with the lithium supplement base material. The particle size after ball milling can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1.0 μm, etc.

[0051] Furthermore, the ball milling time is not limited and can be 1 h to 20 h, as long as the particle size meets the requirements, and can be specifically 1 h, 5 h, 10 h, 15 h, 20 h, etc.

[0052] In some embodiments, wet ball milling can be used, and the solvent added during the ball milling process is selected from at least one of ethanol, ethylene glycol and acetone, and can be any one or more of the above, with no limit on the amount. The mass ratio of the solvent to the metal oxide can be controlled to be 100-500:100.

[0053] S2. Raw material mixing

[0054] The lithium supplement base material, metal oxide, and conductive carbon material are mixed, and the mass ratio of metal oxide, conductive carbon material, and lithium supplement base material is controlled to be (0.1-2):(0.5-5):100. This ensures the modification effect and can significantly reduce gas production without affecting the lithium supplement effect of the lithium supplement agent.

[0055] In some embodiments, the lithium supplement base material is selected from at least one of Li5FeO4, Li2NiO2 and Li2O2, and can be any one or more of the above, preferably Li5FeO4.

[0056] In some embodiments, the conductive carbon material is selected from at least one of graphene and carbon nanotubes, and may be any one or a mixture of the above. The conductive carbon material has a particle size of 1 nm to 10 nm and a length of 5 μm to 50 μm. Using a smaller particle size allows the conductive carbon material to be evenly dispersed in the product.

[0057] In actual operation, the powder material obtained in S1 can be mixed with the lithium supplement base material by secondary ball milling, and the mixture obtained after the secondary ball milling can be mixed with the conductive carbon material. The secondary ball milling time is not limited, and can be 1 hour to 20 hours, such as 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, etc., based on the mixing.

[0058] S3, sintering

[0059] The mixture of lithium supplement agent substrate, metal oxide and conductive carbon material is sintered. During the sintering process, a certain amount of Co, Cu, Ca, Ti, Zr, Al, Mg and other elements will be doped / coated into the lithium supplement agent substrate. These elements can inhibit the reaction and decomposition of the lithium supplement agent by the electrolyte, etc., and effectively reduce the gas production. At the same time, the addition of conductive carbon material can improve the conductive properties of the material.

[0060] In some embodiments, the sintering temperature is 300° C. to 800° C., and the sintering time is 1 hour to 20 hours. The sintering temperature and time can be controlled within the above ranges to achieve effective doping of metal elements. Specifically, the sintering temperature can be 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., etc., and the sintering time can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 13 hours, 15 hours, 18 hours, 20 hours, etc.

[0061] Furthermore, during the sintering process, the heating rate is controlled to be 1°C / min-10°C / min, such as 1°C / min, 3°C / min, 5°C / min, 7°C / min, 10°C / min, etc. After the sintering is completed, the temperature can be naturally cooled.

[0062] In some embodiments, the process further includes: crushing the material obtained after sintering, and the crushing can be performed by grinding to reduce particle aggregation.

[0063] The present disclosure provides a modified lithium supplement agent, including a lithium supplement agent base material. The lithium supplement agent base material contains a metal element, wherein the metal element is selected from at least one of Co, Cu, Ca, Ti, Zr, Al, and Mg, and may be any one or more of the above metal elements. In actual operation, the preparation method of the present disclosure can be used to prepare the modified lithium supplement agent.

[0064] In some embodiments, the doping amount of the metal element in the modified lithium supplement is 1000ppm-20000ppm. By controlling the doping amount of the metal element to ensure the lithium supplement effect of the lithium supplement, gas production is reduced while ensuring battery capacity and other performance.

[0065] In some embodiments, the modified lithium supplement further includes a conductive carbon material, and the conductive carbon material accounts for 0.5 wt% to 5 wt% of the modified lithium supplement, so as to improve the conductivity without affecting other electrochemical properties of the battery.

[0066] The embodiment of the present disclosure provides a positive electrode plate slurry, including lithium iron phosphate active material and a modified lithium supplement agent, the modified lithium supplement agent is the modified lithium supplement agent provided in the embodiment of the present disclosure, and the slurry is used to form a coating on the positive electrode current collector.

[0067] In some embodiments, the positive electrode sheet slurry includes, by mass, 95-98 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement agent, 0.5-3 parts of conductive agent and 0.5-2 parts of binder; in addition to the lithium iron phosphate active material and the modified lithium supplement agent, the slurry also contains conventional raw materials such as conductive agent and binder, and the binder is used to form a good fit between the other components and the positive electrode current collector to form a stable coating.

[0068] Specifically, the content of lithium iron phosphate active material can be 92 parts, 95 parts, or 98 parts, the content of modified lithium supplement agent can be 0.5 parts, 1.0 parts, 2.0 parts, 3.0 parts, 4.0 parts, 5.0 parts, etc., and the content of conductive agent can be 0.5 parts, 1.0 parts, 2.0 parts, 3.0 parts, etc.

[0069] In some embodiments, the conductive agent is selected from at least one of conductive carbon black (SP), carbon nanotubes (CNTs), and Ketjen black; and the binder is selected from at least one of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA). The raw materials for the conductive agent and the binder can be selected from the above raw materials, and can be any one or more of the above raw materials.

[0070] It should be added that, during the preparation process of the positive electrode plate slurry provided in the embodiment of the present disclosure, the mixing order and mixing method of the raw materials are not limited. The lithium iron phosphate active material, conductive agent, and binder can be mixed in a certain proportion first, homogenized by a stirring device, and a lithium supplement can be added during the stirring period.

[0071] An embodiment of the present disclosure provides a positive electrode plate, comprising a positive electrode current collector and an active coating attached to the surface of the positive electrode current collector, wherein the active coating is prepared from the positive electrode plate slurry of the aforementioned embodiment.

[0072] In actual operation, the positive electrode plate slurry provided in the embodiment of the present disclosure is coated on a positive electrode current collector (such as aluminum foil, etc.) and dried to form a coating.

[0073] The present disclosure also provides a lithium battery, comprising the positive electrode sheet of the aforementioned embodiment and a negative electrode sheet. The negative electrode sheet can be made of existing materials, such as a graphite system.

[0074] Specifically, the process of preparing batteries from positive electrode sheet slurry is a conventional preparation process, and the batteries can be prepared through the steps of coating - rolling - slitting - lamination - assembly - liquid injection - sealing - formation and the like.

[0075] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0076] Example 1

[0077] This embodiment provides a method for preparing a modified lithium supplement agent, comprising the following steps:

[0078] (1) Metal oxide pretreatment

[0079] The metal oxide Li 1+x Al x Ti 2-x (PO4)3 and ethanol were mixed in a mass ratio of 200:100 and wet ball milled for 10 h to obtain metal oxide powder with a particle size of about 0.5 μm.

[0080] (2) Raw material mixing

[0081] The metal oxide powder and the lithium supplement agent substrate Li5FeO4 were ball-milled for 10 hours, and the ball-milled mixture was evenly mixed with graphene, and the mass ratio of the metal oxide powder, graphene and Li5FeO4 was controlled to be 0.8:2.3:100.

[0082] (3) Sintering

[0083] The mixture obtained in step (2) was placed in a sintering furnace, heated to 500°C at a heating rate of 5°C / min, sintered for 8 hours, and then cooled naturally. After sintering, the mixture was ground and pulverized to a particle size of about 8 μm.

[0084] This embodiment also provides a method for preparing a lithium battery, which uses the modified lithium supplement prepared in this embodiment to prepare a positive electrode plate slurry, and then uses conventional processes to prepare a battery. The details are as follows:

[0085] (a) Preparation of positive electrode slurry: 100 parts total of 94-96.5 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement (the main material content), 1 part of SP, and 2 parts of PVDF are mixed. The lithium iron phosphate active material, conductive agent, and binder are homogenized by stirring. The modified lithium supplement is added during stirring.

[0086] (b) Preparation of positive electrode sheet: The prepared positive electrode sheet slurry was coated on aluminum foil, and the coating amount was controlled to be 16 mg / cm 2, and then dried at 110°C to form a film.

[0087] (c) Preparation of lithium battery: Assemble the positive electrode sheet, negative electrode sheet, separator, etc. prepared in step (b), inject electrolyte, seal, and form.

[0088] Example 2

[0089] This embodiment provides a method for preparing a modified lithium supplement agent, comprising the following steps:

[0090] (1) Metal oxide pretreatment

[0091] The metal oxide Li 1+x Al x Ti 2-x (PO4)3 and ethylene glycol were mixed in a mass ratio of 100:100 and wet ball milled for 1 h to obtain metal oxide powder with a particle size of about 1.0 μm.

[0092] (2) Raw material mixing

[0093] The metal oxide powder and the lithium supplement base material Li5FeO4 were ball-milled for 1 hour, and the ball-milled mixture was evenly mixed with graphene, and the mass ratio of the metal oxide powder, graphene and Li5FeO4 was controlled to be 0.8:2.3:100.

[0094] (3) Sintering

[0095] The mixture obtained in step (2) was placed in a sintering furnace, heated to 300°C at a heating rate of 1°C / min, sintered for 20 hours, and then cooled naturally. After sintering, the mixture was ground and pulverized to a particle size of about 5 μm.

[0096] This embodiment also provides a method for preparing a lithium battery, which uses the modified lithium supplement prepared in this embodiment to prepare a positive electrode plate slurry, and then uses conventional processes to prepare a battery. The details are as follows:

[0097] Prepare the positive electrode slurry: take 94-96.5 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement agent as the main material content, 1 part of SP and 2 parts of PVDF, a total of 100 parts, mix the lithium iron phosphate active material, conductive agent and binder, and homogenize the slurry through a stirring equipment. Add the modified lithium supplement agent during stirring.

[0098] (b) Preparation of positive electrode sheet: the process is the same as in Example 1.

[0099] (c) Preparation of lithium battery: The process is the same as in Example 1.

[0100] Example 3

[0101] This embodiment provides a method for preparing a modified lithium supplement agent, comprising the following steps:

[0102] (1) Metal oxide pretreatment

[0103] The metal oxide Al(OH)3 and ethanol were mixed in a mass ratio of 200:100 and wet ball milled for 20 hours to obtain a metal oxide powder with a particle size of about 0.1 μm.

[0104] (2) Raw material mixing

[0105] The metal oxide powder and the lithium supplement substrate Li5FeO4 were ball-milled for 20 hours, and the ball-milled mixture was evenly mixed with graphene, and the mass ratio of the metal oxide powder, graphene and Li5FeO4 was controlled to be 0.8:2.3:100.

[0106] (3) Sintering

[0107] The mixture obtained in step (2) was placed in a sintering furnace, heated to 800°C at a heating rate of 10°C / min, sintered for 1 hour, and then cooled naturally. After sintering, the mixture was ground and pulverized to a particle size of about 8 μm.

[0108] This embodiment also provides a method for preparing a lithium battery, which uses the modified lithium supplement prepared in this embodiment to prepare a positive electrode plate slurry, and then uses conventional processes to prepare a battery. The details are as follows:

[0109] (a) Preparation of positive electrode slurry: 100 parts total of 94-96.5 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement (the main material content), 1 part of SP, and 2 parts of PVDF are mixed. The lithium iron phosphate active material, conductive agent, and binder are homogenized by stirring. The modified lithium supplement is added during stirring.

[0110] (b) Preparation of positive electrode sheet: the process is the same as in Example 1.

[0111] (c) Preparation of lithium battery: The process is the same as in Example 1.

[0112] Example 4

[0113] The only difference from Example 1 is that the type of metal oxide is Li 3+x La3Zr 2-y Ti y O 12 .

[0114] Example 5

[0115] The only difference from Example 1 is that the type of metal oxide is Co3O4.

[0116] Example 6

[0117] The only difference from Example 1 is that the mass ratio of metal oxide powder, graphene and Li5FeO4 is 1.6:2.3:100.

[0118] Example 7

[0119] The only difference from Example 1 is that the mass ratio of metal oxide powder, graphene and Li5FeO4 is 0.4:2.3:100.

[0120] Comparative Example 1 (Base)

[0121] Base is the electrical performance test data of LFP without adding lithium supplement agent, and the specific process is the same as Example 1.

[0122] Comparative Example 2

[0123] This comparative example provides a conventional lithium supplement Li5FeO4, which is used to prepare a lithium battery.

[0124] This comparative example provides a method for preparing a lithium battery, which differs from Example 1 only in that a lithium supplement is introduced during the preparation process, no metal elements are doped / coated, and only simple carbon coating is used.

[0125] Test Example 1

[0126] The SEM image of the ordinary lithium supplement agent in comparative example 1 is shown in Figure 1, and the SEM image of the modified lithium supplement agent prepared in Example 1 is shown in Figure 2. It can be seen that the surface is relatively smooth, and the metal elements and

[0127] Test Example 2

[0128] The full battery capacity was prepared by testing Example 1 and Comparative Examples 1-2. The test conditions were: room temperature test 0.33C charge / discharge test cell capacity. The results are shown in Figure 3, where Base represents Comparative Example 1 and the ordinary lithium supplement represents Comparative Example 2.

[0129] As can be seen, the modified lithium supplement prepared in Example 1 has comparable lithium supplementation effectiveness to the conventional lithium supplement in Comparative Example 1, with roughly the same battery capacity, and both significantly improved compared to Comparative Example 2. The battery capacity using the modified lithium supplement prepared in Example 1 is 3-4 mAh / g higher than that of the Base group, and is comparable to that of the conventional lithium supplement, indicating that the new preparation method does not cause capacity loss in the lithium supplement.

[0130] Test Example 3

[0131] The volume growth rate of the full batteries prepared in Example 1 and Comparative Examples 1-2 during use was tested, and the results are shown in FIG4 , where Base represents Comparative Example 1 and the common lithium supplement represents Comparative Example 2.

[0132] Test method: The test method adopts the drainage method to conduct volume test.

[0133] As can be seen from FIG4 , the gas generation during storage of the battery using the modified lithium supplement prepared in Example 1 is significantly lower than that of the ordinary lithium supplement.

[0134] Test Example 4

[0135] In testing Example 1 and Comparative Example 1, a common lithium supplement was used to prepare a full battery cycle curve. The results are shown in Figures 5 to 7 , which respectively test DCR, low-temperature DCR, and cycle.

[0136] It can be seen that in Example 1, the modified lithium supplement agent prepared in Example 1 can effectively reduce the DCR of LFP and effectively improve the rate performance of LFP.

[0137] The above are merely preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations of the present disclosure are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure. Industrial Applicability

[0138] This disclosure introduces metallic elements, such as Co, Cu, Ca, Ti, Zr, Al, and Mg, onto the surface of a lithium supplement substrate. These elements inhibit the electrolyte's decomposition of the supplement, effectively reducing gas production. This modified lithium supplement significantly reduces battery storage gas production while maintaining the improved battery performance (e.g., capacity) provided by conventional lithium supplements, demonstrating promising industrial application prospects.

Claims

1. A modified lithium supplement agent, characterized in that: The invention comprises a lithium supplement substrate, the surface of which contains a metal element, and the metal element is selected from at least one of Co, Cu, Ca, Ti, Zr, Al and Mg.

2. The modified lithium supplement agent according to claim 1, characterized in that: In the modified lithium supplement, the doping amount of the metal element is 1000ppm-20000ppm; Optionally, the lithium supplement base material is selected from at least one of Li5FeO4, Li2NiO2 and Li2O2.

3. The modified lithium supplement agent according to claim 1 or 2, characterized in that: Also includes a conductive carbon material, wherein the conductive carbon material is selected from at least one of graphene and carbon nanotubes; Optionally, the conductive carbon material accounts for 0.5wt%-5wt% by mass in the modified lithium supplement agent; Optionally, the conductive carbon material has a diameter of 1 nm-10 nm and a length of 5 μm-50 μm.

4. A method for preparing the modified lithium supplement agent according to any one of claims 1 to 3, characterized in that: The metal element is doped on the surface of the lithium supplement substrate.

5. The preparation method according to claim 4, characterized in that: include: Sintering a mixture of the lithium supplementing agent substrate, the metal oxide and the conductive carbon material; Wherein, the metal oxide is selected from Co3O4, CuO, CaO2, Al(OH)3, Mg(OH)2, Li 1+x Al x Ti 2-x (PO4)3、Li 3+x La3Zr2O 12 and Li 3+x Ln3Z 2-y Ti y O 12 At least one of; wherein the value of x is 1-2, and the value of y is 0.5-2; Optionally, the mass ratio of the metal oxide, the conductive carbon material and the lithium supplement agent substrate is (0.1-2):(0.5-5):

100.

6. The preparation method according to claim 5, characterized in that: The preparation process of the mixed material includes: ball milling the raw material of the metal oxide to obtain a powder with a particle size of 0.1 μm-1 μm, then ball milling and mixing with the lithium supplement base material for a second time, and mixing the mixture obtained after the second ball milling with the conductive carbon material; Optionally, the milling time of the first ball milling and the second ball milling is 1h-20h; Optionally, the solvent added during the first ball milling process is selected from at least one of ethanol, ethylene glycol and acetone.

7. The preparation method according to claim 5 or 6, characterized in that: The sintering temperature is 300℃-800℃, and the sintering time is 1h-20h; Optionally, during the sintering process, the heating rate is controlled to be 1°C / min-10°C / min; Optionally, the method further comprises: crushing the material obtained after sintering.

8. A positive electrode sheet slurry, characterized in that: It comprises a lithium iron phosphate active material and a modified lithium supplement agent, wherein the modified lithium supplement agent is the modified lithium supplement agent described in any one of claims 1 to 3 or the modified lithium supplement agent prepared by the preparation method described in any one of claims 4 to 7; Optionally, the positive electrode sheet slurry includes, by mass: 95-98 parts of lithium iron phosphate active material, 0.5-3 parts of modified lithium supplement agent, 0.5-3 parts of conductive agent and 0.5-2 parts of binder; Optionally, the conductive agent is selected from at least one of conductive carbon black (SP), carbon nanotubes (CNT) and Ketjen black; Optionally, the binder is selected from at least one of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA).

9. A positive electrode sheet, characterized in that: It comprises a positive electrode current collector and an active coating attached to the surface of the positive electrode current collector, wherein the active coating is prepared from the positive electrode sheet slurry according to claim 8.

10. A lithium battery, characterized in that: Including the positive electrode sheet as described in claim 9.

Images