Lithium supplement additive and preparation method thereof, multi-element lithium supplement agent and preparation method thereof, positive pole piece and lithium ion battery

Abstract

The invention relates to the technical field of batteries, and particularly provides a lithium supplement additive and a preparation method thereof, a multi-element lithium supplement agent and a preparation method thereof, a positive pole piece and a lithium ion battery. The chemical formula of the lithium supplement additive is Li2NixAl1-xO2, and x is more than 0 and less than 1. According to the invention, the LFO (at) Li2NixAl1-xO2 multi-element lithium supplement agent is formed by blending the lithium supplement additive with a positive electrode lithium supplement agent or coating the lithium supplement additive on the outer layer of LFO, so that a positive electrode plate containing the multi-element lithium supplement agent and a lithium ion battery are provided. Therefore, in practical application, the multi-element lithium supplement agent can absorb active oxygen generated during first-time charging activation of the LFO, greatly reduces gas production in circulation and storage processes, and effectively inhibits side reaction between an electrolyte and a material at the same time, so that the safety of a battery cell is greatly improved, and the cycle life of the battery cell is greatly prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and specifically provides a lithium supplement additive and a preparation method thereof, a multi-component lithium supplement agent and a preparation method thereof, a positive electrode sheet and a lithium ion battery. Background Art

[0002] With the continuous increase in the installed capacity ratio of domestic photovoltaic and wind power generation and the rising sales ratio of new energy electric vehicles, the market demand for lithium ion batteries has thus increased sharply. Lithium ion batteries have the advantages of high energy density, long life, and low cost per unit of electricity, and are currently the most widely used secondary batteries. However, with the continuous improvement of the market's demand for battery life, the traditional chemical system design has been difficult to meet the requirements. As a new type of electrode material, the lithium supplement agent can effectively improve the cycle life of the battery and is an essential part of the current long-cycle battery.

[0003] Currently, the lithium supplement agents are divided into two categories according to the lithium supplement method: positive electrode lithium supplement and negative electrode lithium supplement. The positive electrode lithium supplement directly adds the lithium supplement agent to the positive electrode slurry, which has a high compatibility with the existing production line and is currently the lithium supplement method with the highest mass production feasibility. In addition to adding the lithium supplement agent to the negative electrode slurry, the negative electrode lithium supplement can also adopt strategies such as lithium powder spraying and lithium foil rolling at the electrode sheet level. However, the negative electrode lithium supplement currently has a relatively high safety risk and a low compatibility with the existing production line, and is still in the laboratory verification stage, with a large distance from mass production.

[0004] The current positive electrode lithium supplement agents mainly include lithium ferrite, lithium nickelate, lithium oxalate, lithium squarate, etc. Among them, lithium ferrite and lithium nickelate have entered the mass production stage, while lithium oxalate and lithium squarate are still in the laboratory verification stage. The lithium ferrite lithium supplement agent has a higher capacity and a lower reversible capacity, and its lithium supplement effect is much better than that of lithium nickelate, and the theoretical material cost is also much lower than that of lithium nickelate. Therefore, lithium ferrite is the most cost-effective lithium supplement agent at the present stage.

[0005] The chemical formula of lithium ferrite is Li 5 FeO 4 (LFO), and the theoretical capacity is 867 mAh / g. Currently, the main preparation method of LFO is the high-temperature solid-phase method. For example, Chinese Patent CN118198536A mixes Fe 2 O 3 with a mixed lithium salt of LiOH and Li 2 O, grinds them together, and then performs high-temperature calcination in a nitrogen atmosphere to obtain the LFO material.

[0006] Under the existing process, when the prepared LFO is first charged and activated, theoretically 4 mol of Li + and 1 mol of O 2However, during the actual measurement of gas generation during the first charge activation, it was found that the amount of gas generated was significantly less than the theoretical value, only about half of the theoretical value. The gap between the actual gas generation and the theoretical gas generation is due to the fact that not all of the oxygen generated by the decomposition in LFO exists in the form of gas, and part of it exists in the form of active oxygen (mainly oxygen free radicals and oxygen anions). This part of the active oxygen will dissolve in the electrolyte and continuously oxidize the electrolyte to decompose and generate gas during subsequent cycles and storage, which will further lead to swelling of the battery cell, an increase in safety risks, and a dive in the cycle performance.

[0007] Correspondingly, a new technical solution is needed in the art to solve the above technical problems. Summary of the Invention

[0008] The present invention aims to solve the above technical problems, that is, to solve the problem in the prior art that the active oxygen generated by LFO during the first activation continuously oxidizes the electrolyte to decompose and generate gas during subsequent cycles and storage, thereby accelerating the failure of the battery cell.

[0009] In a first aspect, the present invention provides a lithium supplement additive, and the chemical general formula of the lithium supplement additive is Li 2 Ni x Al 1-x O 2 , where 0 < x < 1.

[0010] In a preferred technical solution of the above lithium supplement additive, x is 0.3 - 0.7.

[0011] In a second aspect, the present invention provides a preparation method of the above lithium supplement additive, wherein the preparation method includes:

[0012] Providing Ni x Al 1-x (OH) 2 ;

[0013] Mixing Ni x Al 1-x (OH) 2 with a lithium source and calcining to obtain the lithium supplement additive.

[0014] In a preferred technical solution of the preparation method of the above lithium supplement additive, the providing of Ni x Al 1-x (OH) 2 is:

[0015] Obtaining Ni x Al 1-x (OH) 2 by coprecipitation.

[0016] In the preferred technical solution of the preparation method of the above lithium supplement additive, the calcination temperature is 680-720 °C, the calcination time is 4-8 h, and the heating rate to the calcination temperature is 3-8 °C / min.

[0017] In a third aspect, the present invention provides a multi-component lithium supplement agent, wherein the multi-component lithium supplement agent includes a cathode lithium supplement agent and a lithium supplement additive, and the lithium supplement additive is the above lithium supplement additive or the lithium supplement additive prepared by the above preparation method of the lithium supplement additive.

[0018] In the preferred technical solution of the above multi-component lithium supplement agent, the multi-component lithium supplement agent includes a cathode lithium supplement agent and a lithium supplement additive coating the surface of the cathode lithium supplement agent.

[0019] In the preferred technical solution of the above multi-component lithium supplement agent, the mass ratio of the lithium supplement additive to the cathode lithium supplement agent is (0.3-2.5):100.

[0020] In the preferred technical solution of the above multi-component lithium supplement agent, the cathode lithium supplement agent is an inorganic lithium supplement agent.

[0021] In the preferred technical solution of the above multi-component lithium supplement agent, the inorganic lithium supplement agent is Li 5 FeO 4 .

[0022] In a fourth aspect, the present invention provides a preparation method of the multi-component lithium supplement agent. The preparation method is as follows:

[0023] Mix the lithium supplement additive and the cathode lithium supplement agent evenly;

[0024] Or, after mixing the lithium supplement additive and the cathode lithium supplement agent evenly, sinter and pulverize them.

[0025] In the preferred technical solution of the preparation method of the above multi-component lithium supplement agent, the sintering temperature is 630-670 °C, the sintering time is 2-4 h, and the heating rate to the sintering temperature is 3-8 °C / min.

[0026] In a fifth aspect, the present invention provides a positive electrode sheet, and the positive electrode sheet includes the above multi-component lithium supplement agent or the multi-component lithium supplement agent prepared by the above preparation method of the multi-component lithium supplement agent.

[0027] In a sixth aspect, the present invention provides a lithium-ion battery, including a positive electrode sheet, a separator and a negative electrode sheet, and the positive electrode sheet is the above positive electrode sheet.

[0028] This application has the following technical effects:

[0029] The present invention provides a lithium supplement additive, which is used in a co-blended manner with a cathode lithium supplement agent or a multi-component lithium-rich metal oxide Li 2 Nix Al 1-x O 2 , to form LFO@Li 2 Ni x Al 1-x O 2 A multi-component lithium supplement, and further provide a positive electrode sheet and a lithium ion battery containing the multi-component lithium supplement. In this way, in practical applications, the multi-component lithium supplement can absorb the active oxygen generated during the first charge activation of LFO, greatly reduce the gas generation during cycling and storage, and at the same time effectively inhibit the side reaction between the electrolyte and the material, thereby greatly improving the safety and cycle life of the battery cell. Detailed implementation manners

[0030] The following describes the preferred implementation manners of the present invention. Those skilled in the art should understand that these implementation manners are only used to explain the technical principle of the present invention and are not intended to limit the protection scope of the present invention.

[0031] In this application, the term "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and back associated objects.

[0032] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following items (pieces)" or its similar expressions refer to any combination of these items, including any combination of single items (pieces) or plural items (pieces). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0033] It should be understood that in various embodiments of this application, the magnitude of the sequence numbers of the above processes does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0034] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms of "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0035] In the description of the embodiments of the present application, the weight of the relevant components mentioned not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the description of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the description of the embodiments of the present application. Specifically, the mass described in the description of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0036] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX. Similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0037] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0038] Based on the problem in the prior art pointed out in the background art that the reactive oxygen species generated during the first activation of LFO continuously oxidize the electrolyte to decompose and generate gas during subsequent cycles and storage processes, thereby accelerating the failure of the battery cell.

[0039] The present invention provides a lithium supplement additive. By blending it with a cathode lithium supplement agent or coating the lithium supplement additive on the outer layer of a cathode lithium supplement agent such as LFO, it can absorb the reactive oxygen species generated during the first charging activation of LFO, greatly reduce the gas generation during cycling and storage, and at the same time effectively inhibit the side reaction between the electrolyte and the material, thereby greatly improving the safety and cycle life of the battery cell.

[0040] Specifically, in the first aspect, the present invention provides a lithium supplement additive, and the chemical general formula of the lithium supplement additive is Li 2 Ni x Al 1-x O 2 , where 0 < x < 1.

[0041] The present invention provides a compound with the general formula Li 2 Ni x Al 1-x O 2 (abbreviated as LN x A 1-xThe lithium supplement additive of (O) is a multi-component lithium-rich metal oxide, which can be coated on the outer layer of LFO to form a new lithium supplement agent. Through this solution, when the multi-component lithium-rich metal oxide coated on the outer layer of the lithium supplement agent is activated during the first charging of LFO, the +2-valent Ni in it can absorb the active oxygen generated by the decomposition of LFO, inhibit the dissolution of the active oxygen in the electrolyte, and then continuously oxidize the electrolyte to generate gas during subsequent cycles and storage; the Al element can inhibit the side reaction between the electrolyte and the electrode material and improve the structural stability of the electrode material. The combination of the above two can greatly improve the safety and cycle life of the battery cell.

[0042] In some specific embodiments, x is 0.3 to 0.7.

[0043] In some preferred embodiments, x is 0.3, 0.5 or 0.7, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0044] Specifically, in some specific embodiments, the lithium supplement additive is Li 2 Ni 0.3 Al 0.7 O 2 (abbreviated as LN 0.3 A 0.7 O), Li 2 Ni 0.5 Al 0.5 O 2 (abbreviated as LN 0.5 A 0.5 O), or Li 2 Ni 0.7 Al 0.3 O 2 (abbreviated as LN 0.7 A 0.3 O), etc.

[0045] In the present invention, the above-mentioned lithium supplement additives are collectively referred to as LNAO, also known as LNAO multi-component lithium-rich metal oxide.

[0046] The present invention provides a preparation method of the above-mentioned lithium supplement additive in a second aspect, wherein the preparation method includes:

[0047] Provide Ni x Al 1-x (OH) 2 ;

[0048] Mix Ni x Al 1-x (OH) 2 with a lithium source and calcine to obtain the lithium supplement additive.

[0049] In some specific embodiments, the providing of Nix Al 1-x (OH) 2 is:

[0050] Ni is obtained by co - precipitation method x Al 1-x (OH) 2 .

[0051] The co - precipitation method means that there are two or more cations in the solution, which exist in the solution in a homogeneous phase. After adding a precipitating agent and through a precipitation reaction, precipitates with uniform components can be obtained. It is an important method for preparing ultrafine powders of composite oxides containing two or more metal elements.

[0052] It should be noted that this application does not impose any restrictions on the specific operation of the co - precipitation method. In practical applications, those skilled in the art can adjust it according to the actual situation.

[0053] In some specific embodiments, the co - precipitation method is as follows: First, NaOH is added to the aqueous solutions of nickel source and aluminum source, and then ammonia water is added to adjust the pH value to alkaline. After stirring and reacting, it is washed with water and dried to obtain Ni x Al 1-x (OH) 2 .

[0054] In some specific embodiments, the nickel source and the aluminum source are proportioned according to the molar ratio of Ni, Al as n(Ni):n(Al)=x:(1 - x).

[0055] In some specific embodiments, the nickel source is one of NiSO 4 ·6H 2 O, NiCl 2 or Ni(NO 3 ) 2 ;

[0056] and / or, the aluminum source is one of Al 2 (SO 4 ) 3 , AlCl 3 or Al(NO 3 ) 3 .

[0057] In some specific embodiments, the Ni x Al 1-x (OH) 2 and the lithium source are proportioned according to the molar ratio of Ni, Li as n(Ni):n(Li)=x:2.

[0058] In some specific embodiments, the lithium source is LiOH·H 2 O, Li2 CO 3 、LiNO 3 or CH 3 COOLi.

[0059] In some specific embodiments, the calcination temperature is 680 - 720 °C, the calcination time is 4 - 8 h, and the heating rate to the calcination temperature is 3 - 8 °C / min.

[0060] In some preferred embodiments, the calcination temperature is 700 °C, the calcination time is 6 h, and the heating rate to the calcination temperature is 5 °C / min.

[0061] In some specific embodiments, the calcination is carried out in an O 2 atmosphere.

[0062] In some specific embodiments, after calcination, a pulverization process is further included, and there is no limitation on the pulverization method. For example, it can be grinding pulverization.

[0063] It should be noted that there is no limitation on the particle size after pulverization in the present invention, and it only needs to be pulverized into powder.

[0064] The present invention provides a multi-component lithium supplement agent in the third aspect. Among them, the multi-component lithium supplement agent includes a cathode lithium supplement agent and a lithium supplement additive, and the lithium supplement additive is the above-mentioned lithium supplement additive or the lithium supplement additive prepared by the above-mentioned preparation method.

[0065] It should be noted that in practical applications, the multi-component lithium supplement agent of the present invention can absorb the active oxygen generated during the first charge activation of LFO, reduce the gas generation during cycling and storage, and at the same time inhibit the side reaction between the electrolyte and the material, thereby improving the safety and cycle life of the battery cell.

[0066] In some preferred embodiments, the multi-component lithium supplement agent includes a cathode lithium supplement agent and a lithium supplement additive coating the surface of the cathode lithium supplement agent.

[0067] When the lithium supplement additive of the present invention coats the surface of the cathode lithium supplement agent, the absorption effect on the active oxygen generated during the first charge activation of LFO is better, which can greatly reduce the gas generation during cycling and storage, and at the same time effectively inhibit the side reaction between the electrolyte and the material, thereby greatly improving the safety and cycle life of the battery cell.

[0068] In some specific embodiments, the mass ratio of the lithium supplement additive to the cathode lithium supplement agent is (0.3 - 2.5):100.

[0069] In some specific embodiments, the cathode lithium supplement agent is an inorganic lithium supplement agent.

[0070] In some specific embodiments, the inorganic lithium supplement includes, but is not limited to, Li 5 FeO 4 (LFO).

[0071] However, as a preferred embodiment, the cathode lithium supplement is LFO.

[0072] In the present invention, by coating the outer layer of LFO with Li 2 Ni x Al 1-x O 2 lithium supplement additive, a multi-component lithium supplement LFO@Li 2 Ni x Al 1-x O 2 is formed. This multi-component lithium supplement can absorb the active oxygen generated during the first charge activation of LFO, greatly reduce the gas generation during cycling and storage, and at the same time effectively inhibit the side reaction between the electrolyte and the material, thereby greatly improving the safety and cycle life of the battery cell.

[0073] In some specific embodiments, the multi-component lithium supplement is LFO@LN 0.5 A 0.5 O multi-component lithium supplement, LFO@LN 0.7 A 0.3 O multi-component lithium supplement or LFO@LN 0.3 A 0.7 O multi-component lithium supplement.

[0074] In the present invention, LFO can be prepared by existing methods, such as the method described in CN118198536A.

[0075] As a preferred embodiment of the present invention, LFO is prepared by the following method:

[0076] Mix Fe 2 O 3 and LiOH·H 2 O, grind them, and then perform high-temperature calcination in an N 2 atmosphere. After the calcination is completed, the product is ground and pulverized to obtain LFO.

[0077] The present invention provides a method for preparing the above multi-component lithium supplement in the fourth aspect.

[0078] Specifically, the preparation method is as follows:

[0079] Mix the lithium supplement additive and the cathode lithium supplement evenly;

[0080] Or, mix the lithium supplement additive and the cathode lithium supplement evenly, then perform sintering and pulverization.

[0081] In some specific embodiments, the sintering temperature is 630 - 670 °C, the sintering time is 2 - 4 h, and the heating rate to the sintering temperature is 3 - 8 °C / min.

[0082] In some preferred embodiments, the sintering temperature is 650 °C, the sintering time is 3 h, and the heating rate to the sintering temperature is 5 °C / min.

[0083] In some specific embodiments, the sintering is carried out in an O 2 atmosphere.

[0084] It should be noted that in the present invention, there is no limitation on the pulverization method. Those skilled in the art can carry out pulverization according to the conventional methods in the art. For example, in some specific embodiments, the pulverization method of grinding is adopted. And for the particle size after pulverization, there is also no limitation in the present invention, as long as it is pulverized into powder.

[0085] The present invention provides a positive electrode plate in the fifth aspect, and the positive electrode plate includes the above-mentioned multi-component lithium supplement agent.

[0086] It should be noted that the present invention does not impose any restrictions on the preparation method of the positive electrode plate. In practical applications, those skilled in the art can prepare it according to the conventional methods in the art.

[0087] As a preferred embodiment of the present invention, the positive electrode plate of the present invention is prepared by a method including the following steps:

[0088] (1) Mix lithium iron phosphate (purchased from Hunan Yuneng New Energy Co., Ltd.), the above-mentioned multi-component lithium supplement agent, PVDF, and conductive carbon black evenly according to a mass ratio of 96:2:1:1, and add NMP and continuously stir until the viscosity of the slurry is 8000 mPa·s.

[0089] (2) Use a blade coater to evenly coat the above slurry on both sides of the carbon-coated aluminum foil, and the coating surface density per side is 18 mg / cm 2 , and then dry the foil with the slurry in a vacuum oven to obtain the positive electrode plate.

[0090] The present invention provides a lithium-ion battery in the sixth aspect, which includes a positive electrode plate, a separator, and a negative electrode plate, and the positive electrode plate is the above-mentioned positive electrode plate.

[0091] According to the embodiment of the present invention, the negative electrode plate is prepared by a method including the following steps:

[0092] (1) Graphite anode (purchased from Shanghai Shanshan Technology Co., Ltd.), conductive carbon black, styrene-butadiene rubber, polyacrylic acid, and carboxymethyl cellulose were mixed uniformly in a mass ratio of 96:1:1:1:1, and deionized water was added and stirred continuously until the slurry viscosity reached 6000 mPa·s.

[0093] (2) Use a scraper coater to evenly apply the above slurry on both sides of the carbon-coated copper foil, with a single-side surface density of 9 mg / cm 2 Then, the foil with the slurry is dried in a vacuum oven to obtain the negative electrode sheet.

[0094] According to an embodiment of the present invention, the lithium-ion battery is assembled from a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte. For example, the positive electrode sheet, the negative electrode sheet and the separator are assembled into a battery cell by winding or stacking in a common manner in the industry, and then packaged by an aluminum-plastic film, and then sequentially subjected to baking, electrolyte injection, formation, and secondary sealing processes to obtain a lithium-ion battery.

[0095] According to an embodiment of the present invention, by mixing with a positive electrode lithium supplement or coating the LFO outer layer with a multi-lithium-rich metal oxide Li 2 Ni x Al 1-x O 2 , forming LFO@Li 2 Ni x Al 1-x O 2 A multi-element lithium supplement is provided, and a positive electrode plate and a lithium-ion battery containing the multi-element lithium supplement are provided. Thus, in practical applications, the multi-element lithium supplement can absorb the active oxygen generated when the LFO is first charged and activated, greatly reducing the gas generation during the cycle and storage process, and effectively inhibiting the side reaction between the electrolyte and the material, thereby greatly improving the safety and cycle life of the battery cell.

[0096] The lithium supplement additive, multi-component lithium supplement agent, positive electrode plate and lithium ion battery of the present application are described in detail below through several specific embodiments.

[0097] In the following examples and comparative examples, LFO was prepared by the following method:

[0098] Weigh 80gFe 2 O 3 and 220 g LiOH·H 2 O, ground in a ball mill, and then calcined in a tube furnace at a high temperature of 800°C for 10 h. The rate of heating to the calcination temperature was 3°C / min. N 2 After calcination, the product is ground and crushed to obtain LFO.

[0099] Example 1

[0100] This embodiment provides LN 0.5 A 0.5 O lithium supplement additive, LFO@LN obtained from this lithium supplement additive 0.5 A 0.5 O multi-component lithium supplement agent, positive electrode sheet and lithium ion battery.

[0101] [LN 0.5 A 0.5 O lithium supplement additive]

[0102] The LN provided by this embodiment 0.5 A 0.5 The preparation method of the O lithium supplement additive is as follows:

[0103] S1. Weigh 6.6 g of NiSO 4 ·6H 2 O and 8.6 g of Al 2 (SO 4 ) 3 , place them in 100 mL of clear water, and stir to dissolve both. Then add 4 g of flaky NaOH to the solution, stir evenly, continue to add 1 M ammonia water solution, adjust the pH = 11, and continue to stir for 6 h until the reaction is completed. Filter, wash with water, separate the product, and dry to obtain Ni 0.5 Al 0.5 (OH) 2 .

[0104] S2. Weigh 2.1 g of LiOH·H 2 O, mix it evenly with the obtained Ni 0.5 Al 0.5 (OH) 2 , and then carry out high-temperature calcination in a tubular furnace. The calcination temperature is 700 °C, the calcination time is 6 h, and the heating rate is 5 °C / min. Oxygen is passed through during the calcination process. 2 . After the calcination is completed, the product is ground and pulverized to obtain Li 2 Ni 0.5 Al 0.5 O 2 (abbreviated as: LN 0.5 A 0.5 O) multi-component lithium-rich metal oxide, that is, the lithium supplement additive.

[0105] [LFO@LN 0.5 A 0.5 O multi-component lithium supplement agent]

[0106] Furthermore, the above lithium supplement additive is prepared into an LFO@LN 0.5 A 0.5 O multi-component lithium supplement agent, and the preparation method is as follows:

[0107] LN 0.5 A 0.5 The lithium supplement additive and LFO were mixed evenly in a high-speed mixer and sintered in a tube furnace at a high temperature of 650°C for 3 h. The rate of heating to the sintering temperature was 5°C / min. During the sintering process, O 2 After sintering, the product was ground and crushed to obtain LFO@LN 0.5 A 0.5 O Multi-lithium supplement.

[0108] [Positive electrode]

[0109] The multi-element lithium supplement agent is further prepared into a positive electrode plate, and the preparation method comprises the following steps:

[0110] (1) Lithium iron phosphate (purchased from Hunan Yuneng New Energy Co., Ltd.) and the LFO@LN prepared above were added. 0.5 A 0.5 The multi-component lithium supplement agent, PVDF and conductive carbon black were uniformly mixed in a mass ratio of 96:2:1:1, and NMP was added and stirred continuously until the slurry viscosity reached 8000 mPa·s.

[0111] (2) Use a knife coater to evenly coat the slurry on both sides of the carbon-coated aluminum foil. The surface density of the coated surface is 18 mg / cm 2 Then, the foil with the slurry is dried in a vacuum oven to obtain the positive electrode sheet.

[0112] [Lithium-ion battery]

[0113] (1) Preparation of negative electrode sheet

[0114] Graphite anode (purchased from Shanghai Shanshan Technology Co., Ltd.), conductive carbon black, styrene-butadiene rubber, polyacrylic acid, and carboxymethyl cellulose were mixed in a mass ratio of 96:1:1:1:1, and deionized water was added and stirred continuously until the slurry viscosity reached 6000mPa·s. Then, a blade coater was used to evenly coat the slurry on both sides of the carbon-coated copper foil, and the surface density of the coated single side was 9mg / cm 2 Then, the foil with the slurry is dried in a vacuum oven to obtain the negative electrode sheet.

[0115] (2) Preparation of lithium-ion batteries

[0116] The positive electrode sheet, negative electrode sheet, and separator (purchased from Yunnan Enjie New Materials Co., Ltd.) are wound into a soft-pack full battery, and an electrolyte (purchased from Guangzhou Tianci High-tech Materials Co., Ltd.) is injected. The soft-pack full battery is then subjected to chemical conversion at high temperature to obtain a lithium-ion battery.

[0117] Example 2

[0118] This embodiment provides LN 0.7 A 0.3 O lithium supplementation additive, LFO@LN obtained from this lithium supplementation additive 0.7 A 0.3 O multi-component lithium supplement, positive electrode sheet and lithium-ion battery.

[0119] The LN provided by this embodiment 0.7 A 0.3 The preparation method of the O lithium supplementation additive refers to Example 1. The difference from Example 1 is that the NiSO 4 ·6H 2 O used is 9.2 g, and the Al 2 (SO 4 ) 3 used is 5.1 g.

[0120] Furthermore, the above lithium supplementation additive is prepared into LFO@LN 0.7 A 0.3 O multi-component lithium supplement, positive electrode sheet and lithium-ion battery, and the method is the same as that in Example 1.

[0121] Example 3

[0122] This embodiment provides LN 0.3 A 0.7 O lithium supplementation additive, LFO@LN obtained from this lithium supplementation additive 0.3 A 0.7 O multi-component lithium supplement, positive electrode sheet and lithium-ion battery.

[0123] The LN provided by this embodiment 0.3 A 0.7 The preparation method of the O lithium supplementation additive refers to Example 1. The difference from Example 1 is that the NiSO 4 ·6H 2 O used is 3.9 g, and the Al 2 (SO 4 ) 3 used is 12.0 g.

[0124] Furthermore, the above lithium supplementation additive is made into LFO@LN 0.3 A 0.7 O multi-component lithium supplement, positive electrode sheet and lithium-ion battery, and the method is the same as that in Example 1.

[0125] Example 4

[0126] Referring to Example 1, the difference from Example 1 is that the NiSO 4 ·6H 2 O is replaced by NiCl2 , the used Al 2 (SO 4 ) 3 is replaced with AlCl 3 .

[0127] Example 5

[0128] Referring to Example 1, the difference from Example 1 is that the used NiSO 4 ·6H 2 O is replaced with Ni(NO 3 ) 2 , and the used Al 2 (SO 4 ) 3 is replaced with Al(NO 3 ) 3 .

[0129] Example 6

[0130] Referring to Example 1, the difference from Example 1 is that during the preparation process of [LN 0.5 A 0.5 O lithium supplement additive], the calcination temperature is 680 °C, the calcination time is 8 h, and the heating rate to the calcination temperature is 3 °C / min.

[0131] Example 7

[0132] Referring to Example 1, the difference from Example 1 is that during the preparation process of [LN 0.5 A 0.5 O lithium supplement additive], the calcination temperature is 720 °C, the calcination time is 4 h, and the heating rate to the calcination temperature is 8 °C / min.

[0133] Example 8

[0134] Referring to Example 1, the difference from Example 1 is that during the preparation process of [LFO@LN 0.5 A 0.5 O multi-component lithium supplement agent], the sintering temperature is 630 °C, the sintering time is 4 h, and the heating rate to the sintering temperature is 3 °C / min.

[0135] Example 9

[0136] Referring to Example 1, the difference from Example 1 is that during the preparation process of [LFO@LN 0.5 A 0.5 O multi-component lithium supplement agent], the sintering temperature is 670 °C, the sintering time is 2 h, and the heating rate to the sintering temperature is 8 °C / min.

[0137] Comparative Example 1

[0138] This comparative example provides an LFO lithium supplement, which is LFO, and the preparation method is the same as described above.

[0139] Comparative Example 2

[0140] This comparative example provides an LFO@LNO lithium supplement, which is prepared by a method including the following steps:

[0141] S1. Weigh 13.1 g of NiSO 4 ·6H 2 O, place it in 100 mL of clear water, and stir to dissolve. Then add 4 g of flaky NaOH to the solution, stir evenly, continue to add 1 M ammonia water solution, adjust the pH = 11, and continue stirring for 6 h until the reaction is completed. The product is obtained by filtration, washing with water, separating the product, and drying to obtain Ni(OH) 2 .

[0142] S2. Weigh 2.1 g of LiOH·H 2 O, mix it evenly with the obtained Ni(OH) 2 , and then carry out high-temperature calcination in a tube furnace. The calcination temperature is 700 °C, the calcination time is 6 h, the heating rate to the calcination temperature is 5 °C / min, and O 2 is passed during the calcination. After the calcination is completed, the product is ground and pulverized to obtain an LNO lithium-rich metal oxide.

[0143] S3. Mix the LNO lithium-rich metal oxide and LFO evenly in a high-speed mixer, and then carry out high-temperature sintering in a tube furnace. The sintering temperature is 650 °C, the sintering time is 3 h, the heating rate to the sintering temperature is 5 °C / min, and O 2 is passed during the sintering. After the sintering is completed, the product is ground and pulverized to obtain an LFO@LNO lithium supplement.

[0144] Comparative Example 3

[0145] This comparative example provides an LFO@LAO lithium supplement, which is prepared by a method including the following steps:

[0146] S1. Weigh 17.1 g of Al 2 (SO 4 ) 3 , place it in 100 mL of clear water, and stir to dissolve. Then add 4 g of flaky NaOH to the solution, stir evenly, continue to add 1 M ammonia water solution, adjust the pH = 11, and continue stirring for 6 h until the reaction is completed. The product is obtained by filtration, washing with water, separating the product, and drying to obtain Al(OH) 3 .

[0147] S2. Weigh 2.1 g of LiOH·H 2 O, mix it evenly with the obtained Al(OH) 3 , and then conduct high-temperature calcination in a tubular furnace at a calcination temperature of 700 °C for 6 h. The heating rate to the calcination temperature is 5 °C / min, and O 2 is introduced during the calcination process. After the calcination is completed, the product is ground and pulverized to obtain the LAO lithium-rich metal oxide.

[0148] S3. Mix the LAO lithium-rich metal oxide and LFO evenly in a high-speed blender, and then conduct high-temperature sintering in a tubular furnace at a sintering temperature of 650 °C for 3 h. The heating rate to the sintering temperature is 5 °C / min, and O 2 is introduced during the sintering process. After the sintering is completed, the product is ground and pulverized to obtain the LFO@LAO lithium supplement agent.

[0149] Test Example 1

[0150] This test example investigated the performance of the lithium-ion battery cells obtained with the lithium supplement agents of Examples 1 to 9 and Comparative Examples 1 to 3 of the present invention.

[0151] The method is as follows:

[0152] First, prepare the positive electrode sheets from the lithium supplement agents in Comparative Examples 1 to 3 according to the method of Example 1, and then prepare lithium-ion batteries;

[0153] Then, the lithium-ion battery cells of Examples 1 to 9 and Comparative Examples 1 to 3 are cycled and stored at 45 °C with a 0.5P cycle regime and at 45 °C with 100% SOC high temperature, respectively, and the gas production during cycling and storage is recorded. The test methods are as follows:

[0154] (1) Gas production during 45 °C 0.5P cycling

[0155] At 45 °C, the lithium-ion battery is left standing for 60 min, discharged to 2.5 V at a 0.5P rate, left standing for 5 min, then charged to 3.65 V at a 0.5P rate, and left standing for 5 min. The charge and discharge cycles are carried out in this way. The mass of the battery before and after the charge and discharge cycles is measured by the drainage method, and the gas production of the battery at 200 cls, 400 cls, 600 cls, 800 cls, and 1000 cls of cycling is calculated according to Archimedes' law.

[0156] (2) Gas production during 100% SOC 45 °C high-temperature storage

[0157] The lithium-ion battery with 100% SOC is stored at 45°C. The mass of the battery before and after storage is measured using the drainage method, and the gas generation amounts of the battery stored for 30d, 60d, 90d, 120d, and 150d are calculated according to Archimedes' law respectively.

[0158] The results are shown in Table 1 and Table 2 as follows:

[0159] Table 1

[0160] Table 2

[0161] It can be seen from the results of Table 1 and Table 2 that:

[0162] In Comparative Example 1, since the LFO lithium supplement agent has no coating of poly-rich lithium metal oxide on the outer layer, a large amount of reactive oxygen generated during formation remains in the electrolyte. During subsequent high-temperature cycling and storage, the electrolyte continues to be oxidized and decomposed to produce gas.

[0163] In Comparative Example 2, the LFO material only has an outer LNO rich lithium metal oxide coating. Although it can absorb the reactive oxygen generated by the decomposition of LFO, the H2→H3 phase transition of the LNO material itself during charge and discharge will cause the material to form a rock salt phase, resulting in the collapse of the layered structure and then severe gas generation.

[0164] In Comparative Example 3, the LFO material only has an outer LAO rich lithium metal oxide coating and cannot absorb the reactive oxygen generated by the decomposition of LFO, resulting in serious gas generation.

[0165] In the above three comparative examples, the gas generation is serious, which leads to a significant decrease in the safety performance and service life of the battery cell.

[0166] In Examples 1-9 of the present invention, the outer layer of LFO is coated with LNAO poly-rich lithium metal oxide, which can not only absorb the reactive oxygen generated by the decomposition of LFO, but also effectively isolate the side reaction between the active material and the electrolyte, resulting in a significant reduction in gas generation and ensuring the cycle life and safety performance.

[0167] So far, the technical solution of the present invention has been described in combination with the preferred embodiments. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A lithium supplement additive, characterized in that: The general chemical formula of the lithium supplement additive is Li2Ni x Al 1-x O2, where 0<x<1.

2. The lithium supplement additive according to claim 1, characterized in that: x is 0.3 to 0.

7.

3. A method for preparing the lithium supplement additive according to claim 1 or 2, characterized in that: The preparation method comprises: Provide Ni x Al 1-x (OH)2; Ni x Al 1-x (OH)2 is mixed with a lithium source and calcined to obtain the lithium supplement additive.

4. The method for preparing the lithium supplement additive according to claim 3, characterized in that: The Ni x Al 1-x (OH)2 is: Ni was obtained by coprecipitation x Al 1-x (OH)2.

5. The method for preparing the lithium supplement additive according to claim 3 or 4, characterized in that: The calcination temperature is 680-720° C., the calcination time is 4-8 hours, and the rate of heating to the calcination temperature is 3-8° C. / min.

6. A multi-component lithium supplement, characterized in that: The multi-element lithium supplement agent comprises a positive electrode lithium supplement agent and a lithium supplement additive, wherein the lithium supplement additive is the lithium supplement additive according to claim 1 or 2 or a lithium supplement additive prepared by the preparation method of the lithium supplement additive according to any one of claims 3 to 5.

7. The multi-component lithium supplement according to claim 6, characterized in that: The multi-element lithium supplement agent comprises a positive electrode lithium supplement agent and a lithium supplement additive coating the surface of the positive electrode lithium supplement agent.

8. The multi-component lithium supplement according to claim 6 or 7, characterized in that: The mass ratio of the lithium replenishing additive to the positive electrode lithium replenishing agent is (0.3-2.5):

100.

9. The multi-component lithium supplement according to claim 6 or 7, characterized in that: The positive electrode lithium supplement is an inorganic lithium supplement, and preferably the inorganic lithium supplement is Li5FeO4.

10. A method for preparing the multi-component lithium supplement according to any one of claims 6 to 9, characterized in that: The preparation method is: Mixing the lithium supplement additive and the positive electrode lithium supplement agent; Alternatively, the lithium supplement additive and the positive electrode lithium supplement agent are mixed and then sintered and crushed.

11. The method for preparing a multi-component lithium supplement according to claim 10, characterized in that: The sintering temperature is 630-670° C., the sintering time is 2-4 hours, and the rate of heating to the sintering temperature is 3-8° C. / min.

12. A positive electrode sheet, characterized in that: The positive electrode plate comprises the multi-component lithium supplement agent according to any one of claims 6 to 9 or the multi-component lithium supplement agent prepared by the preparation method of the multi-component lithium supplement agent according to claim 10 or 11.

13. A lithium ion battery, comprising a positive electrode sheet, a separator and a negative electrode sheet, characterized in that: The positive electrode sheet is the positive electrode sheet according to claim 12.

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