Lithium-ion secondary battery, positive electrode sheet, preparation method and electric device

Abstract

The present invention relates to a lithium-ion secondary battery, a positive electrode sheet, a preparation method and an electric device. The lithium-ion secondary battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a lithium replenishment agent and an organic solvent, at least part of the organic solvent adheres to the lithium replenishment agent, the lithium replenishment agent comprises one or more of Li3N, Li3P, Li2O2 and Li2S, the organic solvent comprises an organic solvent weak in the deintercalation of protonic hydrogen, and the organic solvent weak in the deintercalation of protonic hydrogen comprises one or more of triethyl phosphate, sulfolane and propylene carbonate. In the embodiments, only a very small amount of protonic hydrogen is deintercalated from the organic solvent, and therefore side reactions of the lithium replenishment agent are reduced, and the lithium replenishment effect of the lithium replenishment agent can be improved.

Description

Lithium-ion secondary battery, positive electrode sheet, preparation method and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 2023116072719, filed on November 27, 2023, entitled “Positive electrode sheet and preparation method, battery, and electrical equipment,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of battery technology, and in particular to a lithium-ion secondary battery, a positive electrode sheet, a preparation method and an electrical device. Background Art

[0004] This section merely provides background information related to the present application and is not necessarily prior art.

[0005] Lithium-ion batteries, as a new generation of green energy storage and conversion devices, have been widely used in portable electronic devices and electric vehicles. During the initial charge and discharge process of lithium-ion batteries, some lithium ions react with electrolyte components to form a SEI film on the surface of the negative electrode material, resulting in a loss of lithium ions and a reduction in battery energy density. To compensate for this loss, lithium supplements are often added, but the effectiveness of these supplements can be limited.

[0006] Summary of the Invention

[0007] The main technical problem solved by this application is that the lithium replenishment effect needs to be improved. In order to solve the above technical problem, this application provides a lithium-ion secondary battery, a positive electrode sheet, a preparation method and an electrical equipment, which can improve the lithium replenishment effect of the lithium replenisher.

[0008] The first aspect of the present application provides a technical solution: a lithium-ion secondary battery, including a positive electrode plate, the positive electrode plate includes a lithium supplement and an organic solvent, at least part of the organic solvent is attached to the lithium supplement, the lithium supplement includes one or more of Li3N, Li3P, Li2O2 and Li2S, the organic solvent includes an organic solvent with weak proton hydrogen removal, and the organic solvent with weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate.

[0009] In the technical solution of the embodiment of the present application, a lithium-ion secondary battery is provided. The positive electrode of the lithium-ion secondary battery includes a lithium supplement agent. The lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S. The lithium supplement agent can decompose to form lithium ions. The lithium supplement effect is achieved by adding the lithium supplement agent. Among them, Li3N as a lithium supplement agent releases nitrogen, and Li2O2 as a lithium supplement agent releases oxygen or generates strong lithium oxide. After the battery formation process, the air bag can be removed to achieve no by-product residue in the positive electrode; Li3P and Li2S as lithium supplement agents form Li x P and Li y At the same time, by using an organic solvent that releases weak proton hydrogen to disperse the lithium supplement agent, at least part of the organic solvent is attached to the surface of the lithium supplement agent when the positive electrode plate is formed, and the amount of proton hydrogen released by the organic solvent is very weak, and the amount of proton hydrogen released can be ignored, thereby reducing the probability of deprotonation-self-condensation reaction between the lithium supplement agent and the organic solvent, reducing the occurrence of side reactions of the lithium supplement agent, and improving the lithium supplement effect of the lithium supplement agent.

[0010] In the embodiment of the present application, a lithium supplement agent is added to the positive electrode plate, so that during the secondary charging of lithium ions, an external voltage is applied, causing the lithium supplement agent in the positive electrode plate to release electrons and decompose lithium ions, so that the lithium supplement agent can decompose lithium ions and achieve a lithium supplement effect.

[0011] In the embodiment of the present application, the molecular structure of triethyl phosphate, cyclopentane and propylene carbonate has a weak effect of proton hydrogen removal, and the amount of proton hydrogen removed can be ignored. It can almost be considered that no proton hydrogen is removed, and no self-condensation reaction will occur with the lithium supplement agent, which can reduce the occurrence of side reactions of the lithium supplement agent. At the same time, in the embodiment of the present application, triethyl phosphate and propylene carbonate are non-toxic or less toxic, reducing the impact of the positive electrode plate manufacturing process on the environment. In the embodiment of the present application, after the positive electrode plate is manufactured, some organic solvents with weak proton hydrogen removal still remain in the positive electrode plate. The residual organic solvent can be attached to the surface of the lithium supplement agent or located between adjacent lithium supplement agents.

[0012] In any embodiment, the particle size D50 of the lithium supplement agent is 1 μm-10 μm. In the embodiment of the present application, the particle size D50 of the lithium supplement agent is within the above range. On the one hand, the lithium supplement agent has better dispersibility and can be better dispersed in the organic solvent, so that during the production process of the positive electrode sheet, the surface of the film layer formed by coating the slurry containing the lithium supplement agent is relatively smooth; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has an extremely small particle size and a large specific surface area, which can accelerate the solvation process of the lithium supplement agent, better improve the dispersibility of the lithium supplement agent, and reduce or avoid the occurrence of lithium supplement agent agglomeration; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has a relatively high decomposition rate, which is conducive to improving the lithium supplement efficiency.

[0013] The particle size D50 represents the particle size corresponding to when the cumulative particle size distribution percentage of the test powder reaches 50%.

[0014] In any embodiment, the particle size D50 of the lithium supplement agent is 3μm-8μm. In an embodiment of the present application, the particle size D50 of the lithium supplement agent is within the above range, so that the dispersibility of the lithium supplement agent is better, and the lithium supplement agent can be well dispersed in an organic solvent. In any embodiment, the positive electrode sheet includes a positive electrode sheet layer and a current collector, and the positive electrode sheet layer is arranged on one side or both sides of the current collector, and the positive electrode sheet layer includes a first positive electrode active material layer, and the lithium supplement agent and an organic solvent are dispersed in the first positive electrode active material layer. In an embodiment of the present application, the positive electrode sheet layer includes a first positive electrode active material layer, and the lithium supplement agent is dispersed in the first positive electrode active material layer, so that in the embodiment of the present application, the production process of the positive electrode sheet is relatively simple, and the lithium supplement agent can have a lithium supplement effect.

[0015] In any embodiment, the positive electrode sheet includes a positive electrode sheet layer and a current collector, the positive electrode sheet layer being disposed on one or both sides of the current collector; the positive electrode sheet layer includes a second positive electrode active material layer and a lithium replenishing film layer, the lithium replenishing film layer being disposed on the side of the second positive electrode active material layer facing away from the current collector, and the lithium replenishing film layer including a lithium replenishing agent and an organic solvent. In the embodiment of the present application, the positive electrode sheet layer includes a second positive electrode active material layer and a lithium replenishing film layer. In the embodiment of the present application, by disposing the lithium replenishing agent as a film layer on the surface of the second positive electrode active material layer, after the positive electrode sheet is assembled into a battery, the lithium replenishing agent reacts after performing its lithium replenishing function, and does not form vacancies in the second positive electrode active material layer, thereby not affecting the charge transfer path of the battery cell, not increasing the impedance of the positive electrode sheet, and thus not affecting the long-term cycle stability of the battery cell.

[0016] In any embodiment, the first positive electrode active material layer and the second positive electrode active material layer both include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In the embodiments of the present application, a lithium replenisher is used as an additive in combination with an organic solvent that can weakly dehydrogenate protons, and can be applied to positive electrode sheets of the above-mentioned positive electrode active materials, thereby facilitating lithium replenishment.

[0017] In any embodiment, the mass ratio of the lithium replenisher to the positive electrode active material is (1-3):100. By controlling the mass ratio of the lithium replenisher to the positive electrode active material within the above range, the lithium replenisher can achieve a good lithium replenishment effect, so that when the positive electrode plate is used in a battery, the amount of lithium replenisher can meet the lithium replenishment requirements while avoiding the formation of lithium dendrites in the negative electrode caused by excessive lithium replenishment.

[0018] In any embodiment, the mass ratio of the organic solvent to the mass of the positive electrode layer is 1×10 3 ppm-9.9×10 3 ppm. In the embodiment of the present application, the organic solvent accounts for 1×10 3 ppm-9.9×10 3 The use of organic solvents that can remove weak proton hydrogen can also reduce the occurrence of side reactions of lithium supplements during the electrode manufacturing process.

[0019] In the embodiment of the present application, the organic solvent for weak proton hydrogenation is an organic solvent with a dehydrogenation energy barrier greater than 375 kcal / mol. The dehydrogenation energy barrier can be obtained by theoretical calculation.

[0020] A second aspect of the present application further provides a method for preparing a lithium-ion secondary battery, comprising:

[0021] Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2, and Li2S, and the organic solvent includes an organic solvent that undergoes weak proton hydrogen removal, and the organic solvent that undergoes weak proton hydrogen removal includes one or more of triethyl phosphate, sulfolane, and propylene carbonate;

[0022] placing a lithium supplement dispersion into a dispersion containing a positive electrode active material, mixing and stirring to disperse the mixture to obtain a slurry, and coating the slurry on a current collector to form a positive electrode sheet;

[0023] The positive electrode sheet, the separator and the negative electrode sheet are stacked to form a lithium-ion secondary battery.

[0024] In the embodiment of the present application, the lithium supplement agent is first dispersed in an organic solvent and ground, so that the lithium supplement agent has a better dispersion effect and can improve the dispersibility of the lithium supplement agent. In addition, the production steps of the embodiment of the present application are relatively few and the production is relatively simple.

[0025] In any embodiment, the mass ratio of the lithium replenisher to the positive electrode active material is (1-3):100. By controlling the mass ratio of the lithium replenisher to the positive electrode active material within the above range, the lithium replenisher can achieve a good lithium replenishment effect, so that when the positive electrode plate is used in a battery, the amount of lithium replenisher can meet the lithium replenishment requirements while avoiding the formation of lithium dendrites in the negative electrode caused by excessive lithium replenishment.

[0026] In any embodiment, dispersing the lithium supplement agent in an organic solvent includes dispersing the lithium supplement agent in an organic solvent under an inert atmosphere. In the embodiment of the present application, dispersing the lithium supplement agent under an inert atmosphere can reduce the reaction of the lithium supplement agent with moisture in the outside air, thereby reducing the decomposition of the lithium supplement agent and improving the lithium supplement effect of the lithium supplement agent. In the embodiment of the present application, dispersing the lithium supplement agent in a dispersion containing a positive electrode active material can also be dispersed under an inert atmosphere to reduce the occurrence of decomposition of the lithium supplement agent.

[0027] The third aspect of the present application further provides a method for preparing a lithium-ion secondary battery, comprising:

[0028] Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2, and Li2S, and the organic solvent includes an organic solvent that undergoes weak proton hydrogen removal, and the organic solvent that undergoes weak proton hydrogen removal includes one or more of triethyl phosphate, sulfolane, and propylene carbonate;

[0029] Applying the lithium supplement agent dispersion to the side of the second positive electrode active material layer facing away from the current collector to form a positive electrode sheet;

[0030] The positive electrode sheet, the separator and the negative electrode sheet are stacked to form a lithium-ion secondary battery.

[0031] In the embodiment of the present application, a lithium replenishing agent dispersion is coated on the side of the second positive electrode active material facing away from the current collector, so that a lithium replenishing film layer is formed on the surface of the second positive electrode active material layer. After the positive electrode sheet is assembled into a lithium-ion secondary battery, the lithium replenishing agent plays a lithium replenishing role, and the lithium replenishing agent in the lithium replenishing film layer reacts without forming vacancies in the second positive electrode active material layer. Therefore, it will not affect the charge transfer path of the lithium-ion battery, will not increase the impedance of the battery cell, and will not affect the long-term cycle stability of the battery cell.

[0032] In any embodiment, dispersing the lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion includes dispersing the lithium supplement agent, a conductive agent, and an adhesive in the organic solvent to form the lithium supplement agent dispersion. In the embodiment of the present application, the addition of the conductive agent imparts conductivity to the formed lithium supplement film layer, facilitating lithium ion transport; and the addition of the adhesive facilitates film formation, allowing the lithium supplement agent to be more evenly distributed on the second positive electrode active material layer.

[0033] The fourth aspect of the present application provides a positive electrode plate, which includes a lithium supplement agent and an organic solvent, at least part of the organic solvent is attached to the lithium supplement agent, the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S, and the organic solvent includes an organic solvent with weak proton hydrogen removal, and the organic solvent with weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate.

[0034] In the technical solution of the embodiment of the present application, a positive electrode plate is provided, wherein the positive electrode plate includes a lithium supplement agent, and the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S. The lithium supplement agent can decompose to form lithium ions, and the lithium supplement effect is achieved by adding the lithium supplement agent. Among them, Li3N as a lithium supplement agent releases nitrogen, and Li2O2 as a lithium supplement agent releases oxygen or generates strong lithium oxide. After the battery formation process, the air bag can be removed to achieve no byproduct residue in the positive electrode; Li3P and Li2S as lithium supplement agents form Li x P and Li y At the same time, by using an organic solvent that releases weak proton hydrogen to disperse the lithium supplement agent, at least part of the organic solvent is attached to the surface of the lithium supplement agent when the positive electrode plate is formed, and the amount of proton hydrogen released by the organic solvent is very weak, and the amount of proton hydrogen released can be ignored, thereby reducing the probability of deprotonation-self-condensation reaction between the lithium supplement agent and the organic solvent, reducing the occurrence of side reactions of the lithium supplement agent, and improving the lithium supplement effect of the lithium supplement agent.

[0035] In the embodiment of the present application, a lithium supplement agent is added to the positive electrode plate, so that after the positive electrode plate is assembled into a battery, during the battery charging process, an external voltage is applied, causing the lithium supplement agent in the positive electrode plate to release electrons and decompose lithium ions, so that the lithium supplement agent can decompose lithium ions and achieve a lithium supplement effect.

[0036] In the embodiment of the present application, the molecular structure of triethyl phosphate, cyclopentane and propylene carbonate has a weak effect of proton hydrogen removal, and the amount of proton hydrogen removed can be ignored. It can almost be considered that no proton hydrogen is removed, and no self-condensation reaction will occur with the lithium supplement agent, which can reduce the occurrence of side reactions of the lithium supplement agent. At the same time, in the embodiment of the present application, triethyl phosphate and propylene carbonate are non-toxic or less toxic, reducing the impact of the positive electrode plate manufacturing process on the environment. In the embodiment of the present application, after the positive electrode plate is manufactured, some organic solvents with weak proton hydrogen removal still remain in the positive electrode plate. The residual organic solvent can be attached to the surface of the lithium supplement agent or located between adjacent lithium supplement agents.

[0037] In any embodiment, the particle size D50 of the lithium supplement agent is 1 μm-10 μm. In the embodiment of the present application, the particle size D50 of the lithium supplement agent is within the above range. On the one hand, the lithium supplement agent has better dispersibility and can be better dispersed in the organic solvent, so that during the production process of the positive electrode sheet, the surface of the film layer formed by coating the slurry containing the lithium supplement agent is relatively smooth; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has an extremely small particle size and a large specific surface area, which can accelerate the solvation process of the lithium supplement agent, better improve the dispersibility of the lithium supplement agent, and reduce or avoid the occurrence of lithium supplement agent agglomeration; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has a relatively high decomposition rate, which is conducive to improving the lithium supplement efficiency.

[0038] In any embodiment, the positive electrode sheet includes a positive electrode sheet layer and a current collector, the positive electrode sheet layer being disposed on one or both sides of the current collector; the positive electrode sheet layer includes a second positive electrode active material layer and a lithium replenishing film layer, the lithium replenishing film layer being disposed on the side of the second positive electrode active material layer facing away from the current collector, and the lithium replenishing film layer including a lithium replenishing agent and an organic solvent. In the embodiment of the present application, the positive electrode sheet layer includes a second positive electrode active material layer and a lithium replenishing film layer. In the embodiment of the present application, by disposing the lithium replenishing agent as a film layer on the surface of the second positive electrode active material layer, after the positive electrode sheet is assembled into a battery, the lithium replenishing agent reacts after performing its lithium replenishing function, and does not form vacancies in the second positive electrode active material layer, thereby not affecting the charge transfer path of the battery cell, not increasing the impedance of the positive electrode sheet, and thus not affecting the long-term cycle stability of the battery cell.

[0039] In any embodiment, the first positive electrode active material layer and the second positive electrode active material layer both include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In the embodiments of the present application, a lithium replenisher is used as an additive in combination with an organic solvent that can weakly dehydrogenate protons, and can be applied to positive electrode sheets of the above-mentioned positive electrode active materials, thereby facilitating lithium replenishment.

[0040] A fifth aspect of the present application further provides a method for preparing a positive electrode sheet, comprising:

[0041] Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2, and Li2S, and the organic solvent includes an organic solvent that undergoes weak proton hydrogen removal, and the organic solvent that undergoes weak proton hydrogen removal includes one or more of triethyl phosphate, sulfolane, and propylene carbonate;

[0042] The lithium supplement agent dispersion is placed in the dispersion containing the positive electrode active material, mixed and stirred to disperse to obtain a slurry, and the slurry is coated on the current collector to form a positive electrode sheet.

[0043] In the embodiment of the present application, the lithium supplement agent is first dispersed in an organic solvent and ground, so that the lithium supplement agent has a better dispersion effect and can improve the dispersibility of the lithium supplement agent. In addition, the production steps of the embodiment of the present application are relatively few and the production is relatively simple.

[0044] In any embodiment, the mass ratio of the lithium replenisher to the positive electrode active material is (1-3):100. By controlling the mass ratio of the lithium replenisher to the positive electrode active material within the above range, the lithium replenisher can achieve a good lithium replenishment effect, so that when the positive electrode plate is used in a battery, the amount of lithium replenisher can meet the lithium replenishment requirements while avoiding the formation of lithium dendrites in the negative electrode caused by excessive lithium replenishment.

[0045] In any embodiment, dispersing the lithium supplement agent in an organic solvent includes dispersing the lithium supplement agent in an organic solvent under an inert atmosphere. In the embodiment of the present application, dispersing the lithium supplement agent under an inert atmosphere can reduce the reaction of the lithium supplement agent with moisture in the outside air, thereby reducing the decomposition of the lithium supplement agent and improving the lithium supplement effect of the lithium supplement agent. In the embodiment of the present application, dispersing the lithium supplement agent in a dispersion containing a positive electrode active material can also be dispersed under an inert atmosphere to reduce the occurrence of decomposition of the lithium supplement agent.

[0046] A sixth aspect of the present application further provides a method for preparing a positive electrode sheet, comprising:

[0047] Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2, and Li2S, and the organic solvent includes an organic solvent that undergoes weak proton hydrogen removal, and the organic solvent that undergoes weak proton hydrogen removal includes one or more of triethyl phosphate, sulfolane, and propylene carbonate;

[0048] The lithium supplement agent dispersion is coated on the side of the second positive electrode active material layer facing away from the current collector to form a positive electrode sheet.

[0049] In the embodiment of the present application, a lithium replenishing agent dispersion is coated on the side of the second positive electrode active material facing away from the current collector, so that a lithium replenishing film layer is formed on the surface of the second positive electrode active material layer. After the positive electrode sheets are assembled into a battery, the lithium replenishing agent plays a role in replenishing lithium, and the lithium replenishing agent in the lithium replenishing film layer reacts, and no vacancies are formed in the second positive electrode active material layer. Therefore, the charge transfer path of the lithium-ion battery will not be affected, the impedance of the battery cell will not be increased, and the long-term cycle stability of the battery cell will not be affected.

[0050] In any embodiment, dispersing the lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion includes dispersing the lithium supplement agent, a conductive agent, and an adhesive in the organic solvent to form the lithium supplement agent dispersion. In the embodiment of the present application, the addition of the conductive agent imparts conductivity to the formed lithium supplement film layer, facilitating lithium ion transport; and the addition of the adhesive facilitates film formation, allowing the lithium supplement agent to be more evenly distributed on the second positive electrode active material layer.

[0051] The seventh aspect of the present application further provides an electrical device, comprising the lithium-ion secondary battery of the first aspect, or the lithium-ion secondary battery prepared by the method for preparing the lithium-ion secondary battery of the second or third aspect, or the positive electrode sheet of the fourth aspect, or the positive electrode sheet prepared by the method for preparing the positive electrode sheet of the fifth or sixth aspect. The battery of the embodiment of the present application has at least the same advantages as the lithium-ion secondary battery of the first aspect, or the same advantages as the lithium-ion secondary battery prepared by the method for preparing the lithium-ion secondary battery of the second or third aspect, or the same advantages as the positive electrode sheet of the fourth aspect, or the same advantages as the positive electrode sheet prepared by the method for preparing the positive electrode sheet of the fifth or sixth aspect, and will not be further elaborated here.

[0052] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0054] FIG1 is a schematic structural diagram of an embodiment of a positive electrode layer provided by the present application;

[0055] FIG2 is a schematic diagram of the exploded structure of a battery cell according to an embodiment of the present application;

[0056] FIG3 is a schematic diagram of the exploded structure of an embodiment of a battery provided by the present application;

[0057] FIG4 is a schematic structural diagram of an embodiment of an electrical device provided by the present application;

[0058] FIG5 is a scanning electron microscope image of an embodiment of a lithium supplement dispersion provided by the present application;

[0059] FIG6 is a scanning electron microscope image of an embodiment of a positive electrode layer provided in the present application.

[0060] Description of Figure Numbers:

[0061] 1000, electrical equipment; 100, lithium-ion secondary battery; 200, controller; 300, motor; 400, battery module; 10, battery cell; 20, housing; 21, first part; 22, second part; 11, battery cell assembly; 12, end cover; 13, housing; 12a, electrode terminal; 11a, tab; 1110, positive electrode layer; 1111, second positive electrode active material layer; 1112, lithium replenishing membrane layer; 1120, current collector. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and effect of this application clearer and more specific, the following embodiments of the technical solution of this application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0064] In the description of the embodiments of the present application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two), and "multiple pieces" refers to more than two (including two), unless otherwise clearly and specifically defined.

[0065] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0066] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0067] Amounts, ratios, and other numerical values ​​are presented herein in a range format. It should be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the values ​​explicitly specified as range limits, but also all individual values ​​or sub-ranges encompassed within the range, as if each value and sub-range were explicitly specified.

[0068] During the initial charge and discharge process of current lithium-ion batteries, some lithium ions react with electrolyte components to form an SEI film on the surface of the negative electrode material, resulting in a loss of some lithium ions and a reduction in the battery's energy density. To compensate for this loss, a lithium replenisher is usually added to the positive electrode sheet. During the production of the positive electrode sheet, N-methylpyrrolidone (NMP) is generally used as a solvent to disperse the positive electrode active material, conductive agent, and binder to produce the positive electrode slurry. When the lithium replenisher is added to the N-methylpyrrolidone solvent, the N-methylpyrrolidone solvent will release proton hydrogen, and the lithium replenisher will attack the N-methylpyrrolidone, causing the N-methylpyrrolidone to undergo a self-condensation reaction, resulting in the decomposition of the lithium replenisher, which greatly reduces the lithium replenishment effect.

[0069] The first aspect of the present application provides a technical solution: a lithium-ion secondary battery, the lithium-ion secondary battery including a positive electrode plate, the positive electrode plate including a lithium replenisher and an organic solvent, at least part of the organic solvent is attached to the lithium replenisher, the lithium replenisher includes one or more of Li3N, Li3P, Li2O2 and Li2S, the organic solvent includes a weak proton hydrogen release organic solvent, and the weak proton hydrogen release organic solvent includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate.

[0070] In the technical solution of the embodiment of the present application, a lithium-ion secondary battery is provided, and the positive electrode plate of the lithium-ion secondary battery includes a lithium supplement. In the technical solution of the embodiment of the present application, the lithium supplement includes one or more of Li3N, Li3P, and Li2O2, wherein the theoretical capacity of Li3N reaches 2300mAh / g, the theoretical capacity of Li3P reaches 1616mAh / g, the theoretical capacity of Li2O2 reaches 1168mAh / g, and the theoretical capacity of Li2S reaches 1166mAh / g, so that in the embodiment of the present application, the lithium supplement effect can be achieved by adding a small amount of lithium supplement. In the embodiment of the present application, Li3N releases nitrogen as a lithium supplement, and Li2O2 releases oxygen or generates strong lithium oxide as a lithium supplement. After the battery formation process, the air bag can be removed to achieve no by-product residue in the positive electrode; Li3P and Li2S form Li as lithium supplements. x P and Li y In the embodiment of the present application, an organic solvent with weak proton hydrogen release is used to disperse the lithium supplement agent, so that when the positive electrode plate is formed, at least part of the organic solvent is attached to the surface of the lithium supplement agent, and the amount of proton hydrogen released by the organic solvent is very weak, and the amount of proton hydrogen released can be ignored, thereby reducing the probability of deprotonation-self-condensation reaction between the lithium supplement agent and the organic solvent, reducing the occurrence of side reactions of the lithium supplement agent, and improving the lithium supplement effect of the lithium supplement agent.

[0071] In the embodiment of the present application, a lithium replenisher is added to the positive electrode plate, so that after the positive electrode plate is assembled into a lithium-ion secondary battery, during the battery charging process, an external voltage is applied, causing the lithium replenisher in the positive electrode plate to release electrons and decompose lithium ions, so that the lithium replenisher can decompose lithium ions and achieve a lithium replenishment effect.

[0072] It should be noted that, in the positive electrode sheet in the embodiment of the present application, after being assembled into a battery at a later stage, after formation or cycling, the atomic number ratio of the Li element in the atomic number ratio of the constituent elements of Li3N may be greater than 3, or less than 3 and greater than 0, and the atomic number ratio of the N element may be greater than 1, or less than 1 and greater than 0. The atomic number ratio of the Li element in the atomic number ratio of the constituent elements of Li3P may be greater than 3, or less than 3 and greater than 0, and the atomic number ratio of the P element may be greater than 1, or less than 1 and greater than 0. The atomic number ratio of the Li element in the atomic number ratio of the constituent elements of Li2O2 may be greater than 2, or less than 2 and greater than 0, and the atomic number ratio of the O element may be greater than 2, or less than 2 and greater than 0. The atomic number ratio of the Li element in the atomic number ratio of the constituent elements of Li2S may be greater than 2, or less than 2 and greater than 0, and the atomic number ratio of the S element may be greater than 1, or less than 1 and greater than 0.

[0073] In the embodiment of the present application, the molecular structure of triethyl phosphate, sulfolane and propylene carbonate has weak proton hydrogen release, which makes it difficult to undergo self-condensation reaction with the lithium supplement agent, which can reduce the occurrence of side reactions of the lithium supplement agent. At the same time, in the embodiment of the present application, triethyl phosphate and propylene carbonate are non-toxic or have low toxicity, reducing the impact of the positive electrode plate manufacturing process on the environment. In the embodiment of the present application, triethyl phosphate or propylene carbonate can be used as an organic solvent to better disperse the lithium supplement agent. The above three organic solvents have good boiling points, heat of vaporization, viscosity and surface tension, so that the surface tension of the organic solvent in the embodiment of the present application is preferably 30dyne / cm-30.6dyne / cm, which can be coated on the surface of the lithium supplement agent; the viscosity of the organic solvent is preferably 1.38mPa·s-1.76mPa·s, which makes the organic solvent easy to stir and can better disperse the lithium supplement agent; the heat of vaporization is 55.3KJ / mol-57.4KJ / mol, which makes the organic solvent easy to volatilize during the manufacturing process of the positive electrode plate in the embodiment of the present application. In the embodiment of the present application, during the manufacturing process of the positive electrode sheet, some organic solvent from the dehydrogenation of weak protons still remains in the positive electrode sheet. The residual organic solvent may adhere to the surface of the lithium supplement agent or be located between adjacent lithium supplement agents.

[0074] In some embodiments, the particle size D50 of the lithium supplement agent is 1 μm-10 μm. In the embodiments of the present application, the particle size D50 of the lithium supplement agent is within the above range. On the one hand, the lithium supplement agent has better dispersibility and can be better dispersed in the organic solvent, so that during the production process of the positive electrode sheet, the surface of the film layer formed by coating the slurry containing the lithium supplement agent is relatively smooth; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has an extremely small particle size and a large specific surface area, which can accelerate the solvation process of the lithium supplement agent, better improve the dispersibility of the lithium supplement agent, and reduce or avoid the occurrence of lithium supplement agent agglomeration; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has a relatively high decomposition rate of the lithium supplement agent, which is conducive to improving the lithium supplement efficiency. The particle size D50 of the lithium supplement is 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., or a range consisting of any two of the above values, for example, 1 μm-3 μm, 3 μm-6 μm, 6 μm-10 μm, etc.

[0075] In some embodiments, the particle size D50 of the lithium supplement is 3 μm-8 μm. In the embodiments of the present application, the particle size D50 of the lithium supplement is within the above range, so that the dispersibility of the lithium supplement is better, and the lithium supplement can be well dispersed in the organic solvent. Among them, the particle size D50 of the lithium supplement is 3 μm, 4 μm, 4.8 μm, 5 μm, 5.6 μm, 6 μm, 7 μm, 7.4 μm, 8 μm, etc., or a range consisting of any two of the above values, for example, 3 μm-4.8 μm, 4.8 μm-5.6 μm, 5.6 μm-8 μm, etc.

[0076] In some embodiments, as shown in FIG1 , the positive electrode sheet includes a positive electrode sheet layer 1110 and a current collector 1120 . The positive electrode sheet layer 1110 is disposed on one or both sides of the current collector 1120 . The positive electrode sheet layer 1110 includes a first positive electrode active material layer, in which a lithium replenishing agent and an organic solvent are dispersed. In the embodiment of the present application, the positive electrode sheet layer 1110 includes a first positive electrode active material layer, and the lithium replenishing agent is dispersed in the first positive electrode active material layer. This makes the manufacturing process of the positive electrode sheet in the embodiment of the present application relatively simple, and the lithium replenishing agent can achieve a lithium replenishing effect. In the embodiment of the present application, the first positive electrode active material layer includes a positive electrode active material, a conductive agent, a binder, etc.

[0077] In some embodiments, the positive electrode sheet includes a positive electrode sheet layer 1110 and a current collector 1120, and the positive electrode sheet layer 1110 is arranged on one side or both sides of the current collector 1120; the positive electrode sheet layer 1110 includes a second positive electrode active material layer 1111 and a lithium replenishing film layer 1112, and the lithium replenishing film layer 1112 is arranged on the side of the second positive electrode active material layer 1111 away from the current collector 1120, and the lithium replenishing film layer 1112 includes a lithium replenishing agent and an organic solvent. In one embodiment of the present application, the positive electrode sheet layer includes a second positive electrode active material layer 1111 and a lithium replenishing film layer 1112. In this embodiment of the present application, by disposing the lithium replenishing agent as a film layer on the surface of the second positive electrode active material layer 1111, after the positive electrode sheet is assembled into a battery, the lithium replenishing agent reacts after replenishing lithium, and does not form vacancies in the second positive electrode active material layer 1111. Therefore, it does not affect the charge transfer of the lithium-ion battery, does not increase the impedance of the positive electrode sheet, and does not affect the electrochemical stability of the lithium-ion battery. In this embodiment of the present application, the first positive electrode active material layer and the second positive electrode active material layer 1111 are only used to distinguish the positive electrode active material layer, and both belong to the positive electrode active material layer. The second positive electrode active material layer 1111 may also include positive electrode active material, conductive agent, binder, etc.

[0078] In some embodiments, the lithium-replenishing film layer 1112 further includes a conductive agent and a binder. In this embodiment, the inclusion of the conductive agent in the lithium-replenishing film layer 1112 enhances its conductivity, facilitating the transport of active ions. In this embodiment, the inclusion of the binder in the lithium-replenishing film layer 1112 facilitates interaction with the lithium-replenishing agent, thereby enhancing the film-forming properties of the lithium-replenishing film layer 1112.

[0079] In some embodiments, the thickness of the lithium-replenishing film layer 1112 ranges from 5 μm to 20 μm. By controlling the thickness of the lithium-replenishing film layer 1112 within the above range, the lithium-replenishing agent in the lithium-replenishing film layer in the embodiments of the present application is released more effectively, which is beneficial for lithium replenishment. The thickness of the lithium-replenishing film layer 1112 is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, etc., or a range consisting of any two of the above values, for example, 5 μm-9 μm, 9 μm-13 μm, 13 μm-20 μm, etc.

[0080] In some embodiments, in the lithium replenishing film layer 1112, the mass ratio of the lithium replenishing agent, the conductive agent and the binder is (60-90): (5-30): (5-10). By controlling the mass ratio range of the lithium replenishing agent, the conductive agent and the binder in the lithium replenishing film layer 1112, the lithium replenishing film layer 1112 has better lithium replenishing effect, better conductive layer and film forming properties. Among them, the mass ratio of the lithium supplement agent, the conductive agent and the binder is 60:5:5, 60:30:5, 60:30:10, 70:5:5, 80:5:5, 90:5:5, 60:10:5, 60:20:5, 60:5:8, 60:20:9, etc., or a range consisting of any two of the above values, for example, (60-70):(5-10):(5-8), (70-80):(10-20):(8-9), (80-90):(20-30):(9-10), etc.

[0081] In some embodiments, both the first positive electrode active material layer and the second positive electrode active material layer 1111 include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In the embodiments of the present application, the positive electrode active material can be one or more of the above materials. In the embodiments of the present application, the lithium replenisher is combined as an additive with an organic solvent that can remove weak proton hydrogen, and can be applied to the positive electrode sheets of the above positive electrode active materials, thereby facilitating lithium replenishment. The embodiments of the present application are not limited to the above positive electrode active materials and may also be applicable to other positive electrode active materials.

[0082] In any embodiment, the mass ratio of the lithium supplement agent to the positive electrode active material is (1-3):100. By controlling the mass ratio of the lithium supplement agent to the positive electrode active material within the above range, the lithium supplement agent can achieve a better lithium supplement effect, so that when the positive electrode plate is used in the battery, the amount of the lithium supplement agent can meet the lithium supplement demand while avoiding the formation of negative electrode lithium dendrites. Among them, the mass ratio of the lithium supplement agent to the positive electrode active material is 1:100, 1.5:100, 1.8:100, 2:100, 2.4:100, 2.6:100, 3:100, etc., or a range consisting of any two of the above values, for example, (1-1.8):100, (1.8-2.4):100, (2.4-3):100, etc.

[0083] In an embodiment of the present application, the organic solvent capable of weak proton hydrogenation has a dehydrogenation barrier greater than 375 kcal / mol. The dehydrogenation barrier can be determined by theoretical calculation. In an embodiment of the present application, the dehydrogenation barrier of triethyl phosphate is 396 kcal / mol, the dehydrogenation barrier of sulfolane is 380 kcal / mol, and the dehydrogenation barrier of propylene carbonate is 384 kcal / mol.

[0084] In some embodiments, based on the mass of the positive electrode layer 1110, the mass ratio of the organic solvent is 1×10 3 ppm-9.9×10 3 ppm. In the embodiment of the present application, the organic solvent accounts for 1×10 of the mass of the positive electrode layer 1110. 3 ppm-9.9×10 3 ppm, the content of organic solvent can be measured by gas chromatography. In the embodiment of the present application, in the process of manufacturing the positive electrode sheet, the organic solvent is used as a reagent to disperse the lithium replenisher. After the positive electrode sheet is coated, after the baking step, some organic solvent still remains in the positive electrode sheet. In the process of manufacturing the positive electrode sheet, the lithium replenisher is dispersed in the organic solvent. In the embodiment of the present application, the use of an organic solvent that can be extracted with weak proton hydrogen can also reduce the occurrence of side reactions between the lithium replenisher and water vapor in the air during the production of the sheet. Among them, the organic solvent accounts for 1×10 of the mass of the positive electrode sheet layer 1110. 3 ppm, 2×10 3 ppm, 3×10 3 ppm, 5×10 3 ppm, 6×10 3 ppm, 6.052×10 3 ppm, 7×10 3 ppm, 8×10 3 ppm, 9×10 3 ppm, 9.5×10 3 ppm, 9.9×10 3ppm, etc., or a range consisting of any two of the above values, for example, 1×10 3 ppm-5×10 3 ppm, 5×10 3 ppm-8×10 3 ppm, 8×10 3 ppm-9.9×10 3 ppm, etc.

[0085] A second aspect of the present application further provides a method for preparing a lithium-ion secondary battery, comprising:

[0086] S110, dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, and Li2O2, and the organic solvent includes an organic solvent with weak proton hydrogen removal, and the organic solvent with weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane, and propylene carbonate.

[0087] In one embodiment of the present application, the lithium supplement agent is ground and dispersed in an organic solvent with weak proton hydrogen removal, which can improve the dispersion effect of the lithium supplement agent and reduce the occurrence of agglomeration of the lithium supplement agent.

[0088] S120 , placing the lithium supplement agent dispersion into the dispersion containing the positive electrode active material, dispersing to obtain a slurry, and coating the slurry on the current collector 1120 to form a positive electrode sheet.

[0089] In one embodiment of the present application, a method for preparing a dispersion containing a positive electrode active material includes dispersing the positive electrode active material, a conductive agent, a binder and any other components in an organic solvent with weak proton hydrogen extraction to form a dispersion of the positive electrode active material.

[0090] In related technologies, directly dispersing the lithium supplement agent in the dispersion of the positive electrode active material will cause the lithium supplement agent to agglomerate. In order to solve the above technical problems, in the embodiment of the present application, the lithium supplement agent is first dispersed in an organic solvent and ground, so that the lithium supplement agent has a better dispersion effect and can improve the dispersibility of the lithium supplement agent; then the lithium supplement agent dispersion is mixed and dispersed with the dispersion containing the positive active material, which can reduce the occurrence of lithium supplement agent agglomeration. In addition, the production steps of the embodiment of the present application are relatively few and the production is relatively simple.

[0091] S130 , stacking the positive electrode sheet, the separator, and the negative electrode sheet to form a lithium-ion secondary battery.

[0092] In the embodiment of the present application, the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in a shell, the above-mentioned electrolyte is added, and after packaging, standing, formation, aging and other processes, a lithium-ion secondary battery is obtained.

[0093] In some embodiments, the mass ratio of the lithium supplement agent to the positive electrode active material is (1-3):100. In the embodiment of the present application, by controlling the mass ratio of the lithium supplement agent to the positive electrode active material within the above range, the lithium supplement agent can achieve a better lithium supplement effect in the embodiment of the present application, so that when the positive electrode plate is used in the battery, the amount of the lithium supplement agent can meet the lithium supplement demand, while not excessively precipitating on the negative electrode plate, thereby reducing the formation of lithium dendrites. Among them, the mass ratio of the lithium supplement agent to the positive electrode active material is 1:100, 1.5:100, 1.8:100, 2:100, 2.4:100, 2.6:100, 3:100, etc., or a range consisting of any two of the above values, for example, (1-1.8):100, (1.8-2.4):100, (2.4-3):100, etc.

[0094] In some embodiments, dispersing the lithium supplement agent in an organic solvent includes dispersing the lithium supplement agent in an organic solvent under an inert atmosphere. In the embodiments of the present application, dispersing the lithium supplement agent under an inert atmosphere can reduce the reaction of the lithium supplement agent with moisture in the outside air, thereby reducing the decomposition of the lithium supplement agent and improving the lithium supplement effect of the lithium supplement agent. In the embodiments of the present application, dispersing the lithium supplement agent in a dispersion containing a positive electrode active material can also be performed under an inert atmosphere to reduce the occurrence of decomposition of the lithium supplement agent.

[0095] The third aspect of the present application further provides a method for preparing a positive electrode sheet, comprising:

[0096] S210, dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, and Li2O2, and the organic solvent includes an organic solvent capable of weak proton hydrogen removal, and the organic solvent capable of weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane, and propylene carbonate.

[0097] S220 , coating a lithium supplement dispersion on the side of the second positive electrode active material layer 1111 facing away from the current collector 1120 to form a positive electrode sheet.

[0098] In one embodiment of the present application, the preparation method of the second positive electrode active material layer 1111 includes dispersing the positive electrode active material, the conductive agent, the binder and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector 1120, and after drying and other processes, forming the second positive electrode active material layer 1111 on the current collector 1120. In the implementation of the present application, the lithium replenisher dispersion is coated on the side of the second positive electrode active material layer 1111 away from the current collector 1120 to form a lithium replenisher film layer 1112, and then forming a positive electrode sheet. In the embodiment of the present application, the solvent for dispersing the positive electrode active material, the conductive agent, the binder and any other components in the preparation process of the second positive electrode active material layer 1111 is different from the solvent for dispersing the lithium replenisher. In other embodiments, the two can also be the same, for example, both are organic solvents for weak proton hydrogen extraction.

[0099] In an embodiment of the present application, a lithium replenisher dispersion is applied to the side of the second positive electrode active material facing away from the current collector 1120, thereby forming a lithium replenisher film layer 1112 on the surface of the second positive electrode active material layer 1111. After the positive electrode sheet is assembled into a battery, the lithium replenisher in the lithium replenisher film layer 1112 reacts after replenishing lithium, without forming vacancies in the second positive electrode active material layer 1111. Therefore, the charge transfer of the lithium-ion battery and the electrochemical stability of the lithium-ion battery are not affected. In an embodiment of the present application, the lithium replenisher is dispersed in an organic solvent that has weak proton hydrogen desorption. The lithium replenisher does not attack the organic solvent, and the organic solvent does not undergo self-condensation reaction or the amount of self-condensation reaction that occurs is very weak, thereby reducing the occurrence of side reactions of the lithium replenisher and improving the lithium replenishment effect of the lithium replenisher.

[0100] In some embodiments, dispersing the lithium replenisher in an organic solvent to form a lithium replenisher dispersion includes dispersing the lithium replenisher, a conductive agent, and an adhesive in an organic solvent to form a lithium replenisher dispersion. In this embodiment, the addition of the conductive agent imparts conductivity to the lithium replenisher film layer 1112 formed in this embodiment, facilitating lithium ion transport. In this embodiment, the addition of the adhesive facilitates the formation of the lithium replenisher film layer 1112, uniformly covering the surface of the second positive electrode active material layer 1111.

[0101] S230 , stacking the positive electrode sheet, the separator, and the negative electrode sheet to form a lithium-ion secondary battery.

[0102] In the embodiment of the present application, the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in a shell, the above-mentioned electrolyte is added, and after packaging, standing, formation, aging and other processes, a lithium-ion secondary battery is obtained.

[0103] In a fourth aspect, the present application provides a lithium-ion secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a lithium replenisher and an organic solvent, at least a portion of the organic solvent being attached to the lithium replenisher, the lithium replenisher comprising one or more of Li3N, Li3P, Li2O2, and Li2S, the organic solvent comprising a weak proton hydrogen release organic solvent, the weak proton hydrogen release organic solvent comprising one or more of triethyl phosphate, cyclopentane sulfone, and propylene carbonate.

[0104] In the technical solution of the embodiment of the present application, a positive electrode plate is provided, and the positive electrode plate includes a lithium supplement. In the technical solution of the embodiment of the present application, the lithium supplement includes one or more of Li3N, Li3P, and Li2O2, wherein the theoretical capacity of Li3N reaches 2300mAh / g, the theoretical capacity of Li3P reaches 1616mAh / g, the theoretical capacity of Li2O2 reaches 1168mAh / g, and the theoretical capacity of Li2S reaches 1166mAh / g, so that in the embodiment of the present application, the lithium supplement effect can be achieved by adding a small amount of lithium supplement. In the embodiment of the present application, Li3N releases nitrogen as a lithium supplement, and Li2O2 releases oxygen or generates strong lithium oxide as a lithium supplement. After the battery formation process, the air bag can be removed to achieve no by-product residue in the positive electrode; Li3P and Li2S form Li as lithium supplements. x P and Li y In the embodiment of the present application, an organic solvent with weak proton hydrogen release is used to disperse the lithium supplement agent, so that when the positive electrode plate is formed, at least part of the organic solvent is attached to the surface of the lithium supplement agent, and the amount of proton hydrogen released by the organic solvent is very weak, and the amount of proton hydrogen released can be ignored, thereby reducing the probability of deprotonation-self-condensation reaction between the lithium supplement agent and the organic solvent, reducing the occurrence of side reactions of the lithium supplement agent, and improving the lithium supplement effect of the lithium supplement agent.

[0105] In the embodiment of the present application, a lithium supplement agent is added to the positive electrode plate, so that after the positive electrode plate is assembled into a battery, during the battery charging process, an external voltage is applied, causing the lithium supplement agent in the positive electrode plate to release electrons and decompose lithium ions, so that the lithium supplement agent can decompose lithium ions and achieve a lithium supplement effect.

[0106] In the embodiment of the present application, the molecular structure of triethyl phosphate, sulfolane and propylene carbonate has weak proton hydrogen release, which makes it difficult to undergo self-condensation reaction with the lithium supplement agent, which can reduce the occurrence of side reactions of the lithium supplement agent. At the same time, in the embodiment of the present application, triethyl phosphate and propylene carbonate are non-toxic or have low toxicity, reducing the impact of the positive electrode plate manufacturing process on the environment. In the embodiment of the present application, triethyl phosphate or propylene carbonate can be used as an organic solvent to better disperse the lithium supplement agent. The above three organic solvents have good boiling points, heat of vaporization, viscosity and surface tension, so that the surface tension of the organic solvent in the embodiment of the present application is preferably 30dyne / cm-30.6dyne / cm, which can be coated on the surface of the lithium supplement agent; the viscosity of the organic solvent is preferably 1.38mPa·s-1.76mPa·s, which makes the organic solvent easy to stir and can better disperse the lithium supplement agent; the heat of vaporization is 55.3KJ / mol-57.4KJ / mol, which makes the organic solvent easy to volatilize during the manufacturing process of the positive electrode plate in the embodiment of the present application. In the embodiment of the present application, during the manufacturing process of the positive electrode sheet, some organic solvent from the dehydrogenation of weak protons still remains in the positive electrode sheet. The residual organic solvent may adhere to the surface of the lithium supplement agent or be located between adjacent lithium supplement agents.

[0107] In some embodiments, the particle size D50 of the lithium supplement agent is 1 μm-10 μm. In the embodiments of the present application, the particle size D50 of the lithium supplement agent is within the above range. On the one hand, the lithium supplement agent has better dispersibility and can be better dispersed in the organic solvent, so that during the production process of the positive electrode sheet, the surface of the film layer formed by coating the slurry containing the lithium supplement agent is relatively smooth; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has an extremely small particle size and a large specific surface area, which can accelerate the solvation process of the lithium supplement agent, better improve the dispersibility of the lithium supplement agent, and reduce or avoid the occurrence of lithium supplement agent agglomeration; on the other hand, the lithium supplement agent with a particle size D50 of 1 μm-10 μm has a relatively high decomposition rate of the lithium supplement agent, which is conducive to improving the lithium supplement efficiency. The particle size D50 of the lithium supplement is 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., or a range consisting of any two of the above values, for example, 1 μm-3 μm, 3 μm-6 μm, 6 μm-10 μm, etc.

[0108] In some embodiments, as shown in FIG1 , the positive electrode sheet includes a positive electrode sheet layer 1110 and a current collector 1120 . The positive electrode sheet layer 1110 is disposed on one or both sides of the current collector 1120 . The positive electrode sheet layer 1110 includes a first positive electrode active material layer, in which a lithium replenishing agent and an organic solvent are dispersed. In the embodiment of the present application, the positive electrode sheet layer 1110 includes a first positive electrode active material layer, and the lithium replenishing agent is dispersed in the first positive electrode active material layer. This makes the manufacturing process of the positive electrode sheet in the embodiment of the present application relatively simple, and the lithium replenishing agent can achieve a lithium replenishing effect. In the embodiment of the present application, the first positive electrode active material layer includes a positive electrode active material, a conductive agent, a binder, etc.

[0109] In some embodiments, the positive electrode sheet includes a positive electrode sheet layer 1110 and a current collector 1120, and the positive electrode sheet layer 1110 is arranged on one side or both sides of the current collector 1120; the positive electrode sheet layer 1110 includes a second positive electrode active material layer 1111 and a lithium replenishing film layer 1112, and the lithium replenishing film layer 1112 is arranged on the side of the second positive electrode active material layer 1111 away from the current collector 1120, and the lithium replenishing film layer 1112 includes a lithium replenishing agent and an organic solvent. In one embodiment of the present application, the positive electrode sheet layer includes a second positive electrode active material layer 1111 and a lithium replenishing film layer 1112. In this embodiment of the present application, by disposing the lithium replenishing agent as a film layer on the surface of the second positive electrode active material layer 1111, after the positive electrode sheet is assembled into a battery, the lithium replenishing agent reacts after replenishing lithium, and does not form vacancies in the second positive electrode active material layer 1111. Therefore, it does not affect the charge transfer of the lithium-ion battery, does not increase the impedance of the positive electrode sheet, and does not affect the electrochemical stability of the lithium-ion battery. In this embodiment of the present application, the first positive electrode active material layer and the second positive electrode active material layer 1111 are only used to distinguish the positive electrode active material layer, and both belong to the positive electrode active material layer. The second positive electrode active material layer 1111 may also include positive electrode active material, conductive agent, binder, etc.

[0110] In some embodiments, the lithium-replenishing film layer 1112 further includes a conductive agent and a binder. In this embodiment, the inclusion of the conductive agent in the lithium-replenishing film layer 1112 enhances its conductivity, facilitating the transport of active ions. In this embodiment, the inclusion of the binder in the lithium-replenishing film layer 1112 facilitates interaction with the lithium-replenishing agent, thereby enhancing the film-forming properties of the lithium-replenishing film layer 1112.

[0111] In some embodiments, the thickness of the lithium-replenishing film layer 1112 ranges from 5 μm to 20 μm. By controlling the thickness of the lithium-replenishing film layer 1112 within the above range, the lithium-replenishing agent in the lithium-replenishing film layer in the embodiments of the present application is released more effectively, which is beneficial for lithium replenishment. The thickness of the lithium-replenishing film layer 1112 is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, etc., or a range consisting of any two of the above values, for example, 5 μm-9 μm, 9 μm-13 μm, 13 μm-20 μm, etc.

[0112] In some embodiments, in the lithium replenishing film layer 1112, the mass ratio of the lithium replenishing agent, the conductive agent and the binder is (60-90): (5-30): (5-10). By controlling the mass ratio range of the lithium replenishing agent, the conductive agent and the binder in the lithium replenishing film layer 1112, the lithium replenishing film layer 1112 has better lithium replenishing effect, better conductive layer and film forming properties. Among them, the mass ratio of the lithium supplement agent, the conductive agent and the binder is 60:5:5, 60:30:5, 60:30:10, 70:5:5, 80:5:5, 90:5:5, 60:10:5, 60:20:5, 60:5:8, 60:20:9, etc., or a range consisting of any two of the above values, for example, (60-70):(5-10):(5-8), (70-80):(10-20):(8-9), (80-90):(20-30):(9-10), etc.

[0113] In some embodiments, both the first positive electrode active material layer and the second positive electrode active material layer 1111 include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In the embodiments of the present application, the positive electrode active material can be one or more of the above materials. In the embodiments of the present application, the lithium replenisher is combined as an additive with an organic solvent that can remove weak proton hydrogen, and can be applied to the positive electrode sheets of the above positive electrode active materials, thereby facilitating lithium replenishment. The embodiments of the present application are not limited to the above positive electrode active materials and may also be applicable to other positive electrode active materials.

[0114] A fifth aspect of the present application further provides a method for preparing a positive electrode sheet, comprising:

[0115] S310, dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, and Li2O2, and the organic solvent includes an organic solvent capable of weak proton hydrogen removal, and the organic solvent capable of weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane, and propylene carbonate.

[0116] In one embodiment of the present application, the lithium supplement agent is ground and dispersed in an organic solvent with weak proton hydrogen removal, which can improve the dispersion effect of the lithium supplement agent and reduce the occurrence of agglomeration of the lithium supplement agent.

[0117] S320 , placing the lithium supplement agent dispersion into the dispersion containing the positive electrode active material, dispersing to obtain a slurry, and coating the slurry on the current collector 1120 to form a positive electrode sheet.

[0118] In one embodiment of the present application, a method for preparing a dispersion containing a positive electrode active material includes dispersing the positive electrode active material, a conductive agent, a binder and any other components in an organic solvent with weak proton hydrogen extraction to form a dispersion of the positive electrode active material.

[0119] In related technologies, directly dispersing the lithium supplement agent in the dispersion of the positive electrode active material will cause the lithium supplement agent to agglomerate. In order to solve the above technical problems, in the embodiment of the present application, the lithium supplement agent is first dispersed in an organic solvent and ground, so that the lithium supplement agent has a better dispersion effect and can improve the dispersibility of the lithium supplement agent; then the lithium supplement agent dispersion is mixed and dispersed with the dispersion containing the positive active material, which can reduce the occurrence of lithium supplement agent agglomeration. In addition, the production steps of the embodiment of the present application are relatively few and the production is relatively simple.

[0120] In some embodiments, the mass ratio of the lithium supplement agent to the positive electrode active material is (1-3):100. In the embodiment of the present application, by controlling the mass ratio of the lithium supplement agent to the positive electrode active material within the above range, the lithium supplement agent can achieve a better lithium supplement effect in the embodiment of the present application, so that when the positive electrode plate is used in the battery, the amount of the lithium supplement agent can meet the lithium supplement demand, while not excessively precipitating on the negative electrode plate, thereby reducing the formation of lithium dendrites. Among them, the mass ratio of the lithium supplement agent to the positive electrode active material is 1:100, 1.5:100, 1.8:100, 2:100, 2.4:100, 2.6:100, 3:100, etc., or a range consisting of any two of the above values, for example, (1-1.8):100, (1.8-2.4):100, (2.4-3):100, etc.

[0121] In some embodiments, dispersing the lithium supplement agent in an organic solvent includes dispersing the lithium supplement agent in an organic solvent under an inert atmosphere. In the embodiments of the present application, dispersing the lithium supplement agent under an inert atmosphere can reduce the reaction of the lithium supplement agent with moisture in the outside air, thereby reducing the decomposition of the lithium supplement agent and improving the lithium supplement effect of the lithium supplement agent. In the embodiments of the present application, dispersing the lithium supplement agent in a dispersion containing a positive electrode active material can also be performed under an inert atmosphere to reduce the occurrence of decomposition of the lithium supplement agent.

[0122] A sixth aspect of the present application further provides a method for preparing a positive electrode sheet, comprising:

[0123] S310, dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, and Li2O2, and the organic solvent includes an organic solvent capable of weak proton hydrogen removal, and the organic solvent capable of weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane sulfone, and propylene carbonate.

[0124] S320 , coating a lithium supplement dispersion on the side of the second positive electrode active material layer 1111 facing away from the current collector 1120 to form a positive electrode sheet.

[0125] In one embodiment of the present application, the preparation method of the second positive electrode active material layer 1111 includes dispersing the positive electrode active material, the conductive agent, the binder and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector 1120, and after drying and other processes, forming the second positive electrode active material layer 1111 on the current collector 1120. In the implementation of the present application, the lithium replenisher dispersion is coated on the side of the second positive electrode active material layer 1111 away from the current collector 1120 to form a lithium replenisher film layer 1112, and then forming a positive electrode sheet. In the embodiment of the present application, the solvent for dispersing the positive electrode active material, the conductive agent, the binder and any other components in the preparation process of the second positive electrode active material layer 1111 is different from the solvent for dispersing the lithium replenisher. In other embodiments, the two can also be the same, for example, both are organic solvents for weak proton hydrogen extraction.

[0126] In an embodiment of the present application, a lithium replenisher dispersion is applied to the side of the second positive electrode active material facing away from the current collector 1120, thereby forming a lithium replenisher film layer 1112 on the surface of the second positive electrode active material layer 1111. After the positive electrode sheet is assembled into a battery, the lithium replenisher in the lithium replenisher film layer 1112 reacts after replenishing lithium, without forming vacancies in the second positive electrode active material layer 1111. Therefore, the charge transfer of the lithium-ion battery and the electrochemical stability of the lithium-ion battery are not affected. In an embodiment of the present application, the lithium replenisher is dispersed in an organic solvent that has weak proton hydrogen desorption. The lithium replenisher does not attack the organic solvent, and the organic solvent does not undergo self-condensation reaction or the amount of self-condensation reaction that occurs is very weak, thereby reducing the occurrence of side reactions of the lithium replenisher and improving the lithium replenishment effect of the lithium replenisher.

[0127] In some embodiments, dispersing the lithium replenisher in an organic solvent to form a lithium replenisher dispersion includes dispersing the lithium replenisher, a conductive agent, and an adhesive in an organic solvent to form a lithium replenisher dispersion. In this embodiment, the addition of the conductive agent imparts conductivity to the lithium replenisher film layer 1112 formed in this embodiment, facilitating lithium ion transport. In this embodiment, the addition of the adhesive facilitates the formation of the lithium replenisher film layer 1112, uniformly covering the surface of the second positive electrode active material layer 1111.

[0128] The seventh aspect of the present application further provides an electrical device, comprising the lithium-ion secondary battery of the first aspect, or the lithium-ion secondary battery prepared by the method for preparing the lithium-ion secondary battery of the second or third aspect, or the positive electrode sheet of the fourth aspect, or the positive electrode sheet prepared by the method for preparing the positive electrode sheet of the fifth or sixth aspect. The battery of the embodiment of the present application has at least the same advantages as the lithium-ion secondary battery of the first aspect, or the same advantages as the lithium-ion secondary battery prepared by the method for preparing the lithium-ion secondary battery of the second or third aspect, or the same advantages as the positive electrode sheet of the fourth aspect, or the same advantages as the positive electrode sheet prepared by the method for preparing the positive electrode sheet of the fifth or sixth aspect, and will not be further elaborated here.

[0129] In addition, the positive electrode sheet, battery cell, battery and electrical equipment of the present application will be described below with appropriate reference to the drawings.

[0130] In the embodiment of the present application, a battery cell refers to the smallest unit that makes up a battery. The battery cell also includes an electrolyte and a separator. The separator is set between the positive electrode and the negative electrode. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through. During the battery charge and discharge process, the active ions Li + The electrolyte is embedded and released back and forth between the positive electrode and the negative electrode, and plays the role of conducting ions between the positive electrode and the negative electrode.

[0131] In some embodiments, the current collector included in the positive electrode plate is a positive electrode current collector, and the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] In some embodiments, the first positive electrode active material layer and the second positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0133] In some embodiments, the first positive electrode active material layer and the second positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes the negative electrode active material of the above embodiment.

[0135] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0136] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0137] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0138] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na).

[0140] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0141] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0142] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0143] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0144] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0145] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0146] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0147] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0148] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into a battery cell assembly through a winding process or a lamination process.

[0149] In some embodiments, as shown in FIG2 , the battery cell 10 may include an outer packaging. The outer packaging may be used to encapsulate the battery cell assembly 11 and the electrolyte. The outer packaging includes an end cap 12 , a housing 13 , and other functional components.

[0150] The end cap 12 refers to a component that covers the opening of the shell 13 to isolate the internal environment of the battery cell 10 from the external environment. Without limitation, the shape of the end cap 12 can be adapted to the shape of the shell 13 to match the shell 13. Optionally, the end cap 12 can be made of a material with a certain hardness and strength (such as an aluminum alloy). In this way, the end cap 12 is not easily deformed when squeezed or collided, so that the battery cell 10 can have a higher structural strength and improved safety performance. Functional components such as electrode terminals 12a can be provided on the end cap 12. The electrode terminals 12a can be used to electrically connect to the battery cell assembly 11 for outputting or inputting electrical energy into or out of the battery cell 10. In some embodiments, the end cap 12 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 10 reaches a threshold. The material of the end cap 12 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this. In some embodiments, an insulating member (not shown) may be provided inside the end cap 12 to isolate the electrical connection components in the housing 13 from the end cap 12 to reduce the risk of short circuits. For example, the insulating member may be made of plastic, rubber, or the like.

[0151] The housing 13 is a component that cooperates with the end cap 12 to form the internal environment of the battery cell 10. This internal environment can be used to accommodate the battery cell assembly 11, electrolyte, and other components. The housing 13 and the end cap 12 can be separate components. An opening can be provided in the housing 13, and the end cap 12 is placed over the opening to form the internal environment of the battery cell 10. Alternatively, the end cap 12 and the housing 13 can be integrated. Specifically, the end cap 12 and the housing 13 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 13 needs to be enclosed, the end cap 12 is placed over the housing 13. The housing 13 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 13 can be determined based on the specific shape and size of the battery cell assembly 11. The housing 13 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0152] The housing 13 may contain one or more battery cell assemblies 11. The portions of the positive and negative electrode sheets that do not contain active material each form a tab 11a. The positive and negative tabs may be located together at one end of the main body or separately at opposite ends. During the battery's charge and discharge processes, the positive and negative active materials react with the electrolyte, and the tabs 11a connect to the electrode terminals to form a current circuit.

[0153] Please refer to Figure 3, which is a schematic diagram of the exploded structure of an embodiment of the lithium-ion secondary battery 100 provided in this application. The lithium-ion secondary battery 100 includes a housing 20 and a battery cell 10, and the battery cell 10 is accommodated in the housing 20. The housing 20 is used to provide a storage space for the battery cell 10, and the housing 20 can adopt a variety of structures. In some embodiments, the housing 20 may include a first portion 21 and a second portion 22, and the first portion 21 and the second portion 22 cover each other, and the first portion 21 and the second portion 22 jointly define a storage space for accommodating the battery cell 10. The second portion 22 may be a hollow structure with one end open, and the first portion 21 may be a plate-like structure, and the first portion 21 covers the open side of the second portion 22, so that the first portion 21 and the second portion 22 jointly define a storage space; the first portion 21 and the second portion 22 may also be hollow structures with one side open, and the open side of the first portion 21 covers the open side of the second portion 22. Of course, the box body 20 formed by the first part 21 and the second part 22 can be in various shapes, such as a cylinder, a cuboid, etc.

[0154] In a lithium-ion secondary battery 100, there may be multiple battery cells 10, and the multiple battery cells 10 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 10. The multiple battery cells 10 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire structure formed by the multiple battery cells 10 is housed within the housing 20. Of course, the lithium-ion secondary battery 100 may also be a battery module formed by first connecting the multiple battery cells 10 in series, in parallel, or in a hybrid connection, and then the multiple battery modules are further connected in series, in parallel, or in a hybrid connection to form an entire structure, which is then housed within the housing 20. The lithium-ion secondary battery 100 may also include other structures, for example, the lithium-ion secondary battery 100 may further include a busbar component for electrically connecting the multiple battery cells 10.

[0155] The lithium-ion secondary battery 100 in the embodiment of the present application includes a lithium-ion battery as a battery cell 10. In other embodiments, the lithium-ion secondary battery 100 may further include any one or more of a lithium-sulfur battery, a sodium-ion battery, and a magnesium-ion battery, but is not limited thereto. The battery cell 10 may be cylindrical, flat, rectangular, or in other shapes.

[0156] In some embodiments, the lithium-ion secondary batteries 100 can be assembled into a battery module. The number of lithium-ion secondary batteries 100 contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0157] In addition, the present application also provides an electrical device, which includes at least one of the battery cells and / or lithium-ion secondary batteries 100 provided in the present application. The battery cells or lithium-ion secondary batteries 100 can be used as power sources for electrical devices, or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0158] As an electric device, a battery cell and / or a lithium-ion secondary battery 100 may be selected according to its usage requirements.

[0159] FIG4 shows an electric device as an example. The electric device is a vehicle such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A structural schematic diagram of an electric device 1000 is specifically provided. A lithium-ion secondary battery 100 is provided inside the electric device 1000, and the lithium-ion secondary battery 100 can be provided at the bottom, head, or tail of the electric device 1000. The lithium-ion secondary battery 100 can be used to power the electric device 1000. For example, the lithium-ion secondary battery 100 can serve as an operating power source for the electric device 1000. The electric device 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the lithium-ion secondary battery 100 to power the motor 300, for example, to meet the power requirements of the electric device 1000 during startup, navigation, and driving.

[0160] In some embodiments of the present application, the lithium-ion secondary battery 100 can not only serve as an operating power source for the electrical device 1000, but also serve as a driving power source for the electrical device 1000, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1000.

[0161] The beneficial effects of the present application are further illustrated below with reference to the examples.

[0162] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0163] Example 1

[0164] 1.1) Preparation of positive electrode sheet:

[0165] S111 , 4.85 g of lithium iron phosphate, a positive electrode active material, 0.115 g of conductive carbon black, and 0.0375 g of polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added and stirred to form a dispersion of the positive electrode active material.

[0166] S112, 0.0485g of lithium supplement agent Li3N is dispersed in 2g of organic solvent triethyl phosphate (TEP) to form a lithium supplement agent dispersion. The processing environment is an argon glove box, the humidity is 0.02ppm-0.06ppm, specifically 0.04ppm; the oxygen content is 0.05ppm-4.5ppm, specifically 0.1ppm; the mass of TEP is 41.24 times the mass of lithium nitride. In other embodiments, the mass of TEP is 41-76 times the mass of lithium nitride; the grinding time is 3min-7min, and the specific grinding time in the embodiment of the present application is 5min. The Li3N particle size D50 is 3.75μm. As shown in Figure 5, the Li3N particles after mixed wet grinding have no obvious agglomeration and the particle size is 2μm-4μm.

[0167] S122: Add the lithium replenisher dispersion to the positive electrode active material dispersion and stir for 10 minutes at a speed of 2000 rpm to form a positive electrode slurry. The mass ratio of the lithium replenisher in the lithium replenisher dispersion to the positive electrode active material in the positive electrode active material dispersion is 1:100. The positive electrode slurry is coated on the surface of the current collector aluminum foil, dried, cold pressed, and slit to obtain positive electrode sheets.

[0168] In other embodiments, steps S111 and S112 may be performed in different orders or simultaneously.

[0169] In an embodiment of the present application, the positive electrode plate includes a current collector and a positive electrode plate layer arranged on one side or both sides of the current collector, the positive electrode plate layer includes a first positive electrode active material layer, the first positive electrode active material layer includes lithium iron phosphate, conductive carbon black and polyvinylidene fluoride, Li3N is dispersed in the first positive electrode active material layer, and the organic solvent triethyl phosphate (TEP) is partially attached to Li3N.

[0170] 1.2) Preparation of negative electrode sheet.

[0171] Using styrene-butadiene rubber as a binder and conductive carbon as a conductive agent, the negative electrode active material, styrene-butadiene rubber, and conductive carbon were mixed in a mass ratio of 96:2:2 to prepare a negative electrode slurry. The negative electrode slurry was applied to the surface of the negative electrode current collector copper foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0172] 1.3) Isolation membrane.

[0173] Use polyethylene release film.

[0174] 1.4) Electrolyte.

[0175] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 3:7, LiPF6 was then uniformly dissolved in the solution, and fluoroethylene carbonate (FEC) was added to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L, and the mass percentage of fluoroethylene carbonate was 2%.

[0176] 1.5) Assembly of lithium-ion secondary batteries.

[0177] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in a shell, and the above-mentioned electrolyte is added. After packaging, standing, formation, aging and other processes, a battery cell is obtained.

[0178] 2. The relevant parameter test methods are as follows:

[0179] 2.1) Particle size D50 test.

[0180] After weighing 5-10g of lithium supplement agent and pouring it into the dry sampler of the MS300 laser particle size analyzer, the air flow is turned on to blow the sample into the test optical path system. Under the irradiation of the laser beam, the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light. The light shielding degree is: 8-12%. After deducting the blank background, the software calculates and analyzes the particle size D50 of the lithium supplement agent.

[0181] 2.2) Lithium-ion secondary battery cycle performance test.

[0182] The prepared lithium-ion secondary battery is charged at a constant current of 0.01C for formation, with the aim of achieving the first cycle SEI of conventional battery cells while completing the decomposition and release of lithium from the lithium supplement.

[0183] Under a constant temperature environment, charge the lithium-ion secondary battery at a constant current rate of 0.33C to a voltage of 3.65V, and then discharge it at a constant current rate of 0.33C to a voltage of 2.0V. This is a charge-discharge cycle. The discharge capacity of this cycle is recorded as the discharge capacity of the lithium-ion secondary battery in the first cycle. Perform the lithium-ion secondary battery charge-discharge test n times (n ≥ 2) according to the above method, and record the discharge capacity of the nth cycle.

[0184] The capacity retention rate (CR) of a lithium-ion secondary battery after n cycles = discharge capacity at the nth cycle / discharge capacity at the 1st cycle × 100%. In the embodiment of the present application, the capacity retention rate of the lithium-ion secondary battery after 200 cycles is specifically recorded.

[0185] 2.3) Determination of organic solvent content.

[0186] A standard sample was created using AR99.99% triethyl phosphate (TEP) reagent using gas chromatography. After drying, the electrode was sheared and placed in a vial. A certain amount of N,N-dimethylformamide (DMF) was added and ultrasonically dissolved for 12 hours to dissolve the active material on the surface of the positive electrode. A 0.4-1μL sample was injected to determine the residual organic solvent in the positive electrode.

[0187] Example 2

[0188] The difference from Example 1 is that 1.1) the preparation of the positive electrode sheet is the same as Example 1. Specifically, 1.1) the preparation of the positive electrode sheet includes the following steps:

[0189] S211, 4.85g of positive electrode active material lithium iron phosphate, 0.115g of conductive carbon black, and 0.0375g of polyvinylidene fluoride are mixed, N-methylpyrrolidone (NMP) is added and stirred to form a positive electrode slurry, the positive electrode slurry is coated on the surface of the current collector aluminum foil, and dried to form a second positive electrode active material layer on the current collector aluminum foil.

[0190] S212, 0.0485g of lithium supplement Li3N, 0.0027g of conductive carbon black and 0.0027g of polyvinylidene fluoride are dispersed in 2g of organic solvent triethyl phosphate (TEP) to form a lithium supplement dispersion. The mass ratio of lithium supplement Li3N, conductive carbon black and polyvinylidene fluoride is 90:5:5. The processing environment is an argon glove box with a humidity of 0.02ppm-0.06ppm, specifically 0.04ppm; the oxygen content is 0.05ppm-4.5ppm, specifically 0.1ppm; the mass of TEP is 41.24 times the mass of lithium nitride. In other embodiments, the mass of TEP is 41-76 times the mass of lithium nitride; the grinding time is 3min-7min, and the specific grinding time in the embodiment of the present application is 5min. The Li3N particle size D50 is 3.75μm. As shown in Figure 5, the Li3N particles after mixed wet grinding have no obvious agglomeration and the particle size is 2μm-4μm.

[0191] S122: Under an argon atmosphere, apply a lithium replenisher dispersion to the side of the second positive electrode active material layer facing away from the current collector aluminum foil. After drying, cold pressing, and slitting, a positive electrode sheet is obtained. The mass ratio of the lithium replenisher in the lithium replenisher dispersion to the positive electrode active material in the positive electrode active material dispersion is 1:100. As shown in Figure 6, the second positive electrode active material layer and the lithium replenisher membrane layer are included.

[0192] In an embodiment of the present application, as shown in FIG1 , the positive electrode plate includes a current collector 1120 and a positive electrode plate layer 1110 arranged on one side or both sides of the current collector 1120. The positive electrode plate layer 1110 includes a second positive electrode active material layer 1111 and a lithium replenishing film layer 1112. The second positive electrode active material layer 1111 includes lithium iron phosphate, conductive carbon black and polyvinylidene fluoride. The lithium replenishing film layer includes Li3N, triethyl phosphate (TEP), conductive carbon black and polyvinylidene fluoride. The organic solvent triethyl phosphate (TEP) is partially attached to Li3N.

[0193] The specific target ingredients of each embodiment and comparative example are shown in Table 1.

[0194] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

[0195] Table 1 Sample parameters and performance test results of various embodiments and comparative examples.

[0196] Note: D50 represents the particle size D50 of the lithium supplement agent; mass ratio represents the mass ratio of the lithium supplement agent to the positive electrode active material; mass proportion represents the mass proportion of the organic solvent in the positive electrode layer; dehydrogenation energy barrier represents the dehydrogenation energy barrier of the organic solvent; setting method represents the setting method of the lithium supplement agent in the positive electrode layer, method 1 represents that the lithium supplement agent is dispersed in the first positive electrode active material layer, and method 2 represents that the lithium supplement film layer formed by the lithium supplement agent is located on the second positive electrode active material layer; cycle performance represents the cycle capacity retention rate.

[0197] The results show that in Comparative Examples 1 and 2, the organic solvent is NMP, which has a dehydrogenation capacity of less than 375 kcal / mol and is not an organic solvent for weak proton hydrogen removal. Based on Comparative Examples 1 and 2, Examples 1 to 15 of the present application use organic solvents such as triethyl phosphate, cyclopentane, and propylene carbonate that are weak proton hydrogen removal as organic solvents for solvent lithium replenishers. The batteries formed therefrom have a cycle capacity retention rate of 90.6%-96.4% after 1000 cycles, which is significantly improved compared to the cycle capacity retention rates of 89.1% and 89.3% of Comparative Examples 1 and 5. The cycle capacity retention rates of Examples 1 to 15 are also significantly improved compared to Comparative Examples 4 and 5. This shows that the embodiment of the present application uses organic solvents that are weak proton hydrogen removal to disperse lithium replenishers, which can improve the lithium replenishment effect and improve the cycle stability of lithium-ion secondary batteries.

[0198] Based on Examples 1 to 4, it can be seen that in the embodiments of the present application, the cycle capacity retention rates of Examples 2 and 4 are higher than those of Examples 1 and 3, indicating that the lithium replenisher is made into a lithium replenisher film layer and is arranged on the side of the second positive electrode active material layer away from the current collector. After the lithium replenisher plays a role in replenishing lithium, the lithium replenisher reacts and will not form vacant batteries in the second positive electrode active material layer, will not affect the charge transfer path of the battery cell, and will not increase the impedance of the positive electrode sheet, so that its cycle capacity retention rate is higher.

[0199] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A lithium ion secondary battery, characterized in that: The invention comprises a positive electrode plate, wherein the positive electrode plate comprises a lithium supplement agent and an organic solvent, wherein at least a part of the organic solvent is attached to the lithium supplement agent, wherein the lithium supplement agent comprises one or more of Li3N, Li3P, Li2O2 and Li2S, wherein the organic solvent comprises an organic solvent for weak proton hydrogen release, and wherein the organic solvent for weak proton hydrogen release comprises one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate.

2. The lithium ion secondary battery according to claim 1, characterized in that: The particle size D50 of the lithium supplement agent is 1 μm-10 μm.

3. The lithium ion secondary battery according to claim 1 or 2, characterized in that: The particle size D50 of the lithium supplement agent is 3 μm-8 μm.

4. The lithium ion secondary battery according to any one of claims 1 to 3, characterized in that: The positive electrode sheet comprises a positive electrode sheet layer and a current collector, wherein the positive electrode sheet layer is arranged on one side or both sides of the current collector; The positive electrode sheet layer includes a first positive electrode active material layer, in which the lithium supplement agent and the organic solvent are dispersed.

5. The lithium ion secondary battery according to any one of claims 1 to 3, characterized in that: The positive electrode sheet comprises a positive electrode sheet layer and a current collector, wherein the positive electrode sheet layer is arranged on one side or both sides of the current collector; The positive electrode layer includes a second positive electrode active material layer and a lithium replenishing film layer, wherein the lithium replenishing film layer is arranged on the side of the second positive electrode active material layer away from the current collector, and the lithium replenishing film layer includes the lithium replenishing agent and the organic solvent. Optionally, the lithium replenishing film layer also includes a conductive agent and a binder.

6. The lithium ion secondary battery according to claim 4 or 5, characterized in that: The first positive electrode active material layer and the second positive electrode active material layer both include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

7. The lithium ion secondary battery according to claim 6, characterized in that: The mass ratio of the lithium supplement agent to the positive electrode active material is (1-3):

100.

8. The lithium ion secondary battery according to any one of claims 4 to 7, characterized in that: Based on the mass of the positive electrode layer, the mass proportion of the organic solvent is 1×10 3 ppm-9.9×10 3 ppm.

9. The lithium ion secondary battery according to any one of claims 1 to 8, characterized in that: The dehydrogenation energy barrier of the organic solvent for weak proton hydrogenation is greater than 375 kcal / mol.

10. A method for preparing a lithium ion secondary battery as claimed in any one of claims 1 to 4 and 6 to 9, characterized in that: include: Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S, and the organic solvent includes an organic solvent for weak proton hydrogen removal, and the weak proton hydrogen removal organic solvent includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate; placing the lithium supplement agent dispersion in a dispersion containing a positive electrode active material, mixing, stirring and dispersing to obtain a slurry, and coating the slurry on a current collector to form the positive electrode sheet; The positive electrode sheet, the separator and the negative electrode sheet are stacked to form a lithium-ion secondary battery.

11. A method for preparing a lithium ion secondary battery according to any one of claims 1 to 3 and 5 to 9, characterized in that: include: Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S, and the organic solvent includes an organic solvent for weak proton hydrogen removal, and the organic solvent for weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate; Applying the lithium supplement agent dispersion on the side of the second positive electrode active material layer away from the current collector to form the positive electrode sheet; The positive electrode sheet, the separator and the negative electrode sheet are stacked to form a lithium-ion secondary battery.

12. The method for preparing a lithium ion secondary battery according to claim 11, characterized in that: The step of dispersing the lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion comprises: The lithium supplement agent, the conductive agent and the adhesive are dispersed in the organic solvent to form a lithium supplement agent dispersion.

13. A positive electrode sheet, characterized in that: The positive electrode plate includes a lithium supplement and an organic solvent, at least part of the organic solvent is attached to the lithium supplement, the lithium supplement includes one or more of Li3N, Li3P, Li2O2 and Li2S, the organic solvent includes an organic solvent for weak proton hydrogen release, and the organic solvent for weak proton hydrogen release includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate.

14. The positive electrode sheet according to claim 13, characterized in that: The particle size D50 of the lithium supplement agent is 1 μm-10 μm.

15. The positive electrode sheet according to claim 13 or 14, characterized in that: The positive electrode sheet comprises a positive electrode sheet layer and a current collector, wherein the positive electrode sheet layer is arranged on one side or both sides of the current collector; The positive electrode sheet layer includes a first positive electrode active material layer, in which the lithium supplement agent and the organic solvent are dispersed.

16. The positive electrode sheet according to claim 13 or 14, characterized in that: The positive electrode sheet comprises a positive electrode sheet layer and a current collector, wherein the positive electrode sheet layer is arranged on one side or both sides of the current collector; The positive electrode layer includes a second positive electrode active material layer and a lithium replenishing film layer, wherein the lithium replenishing film layer is arranged on the side of the second positive electrode active material layer away from the current collector, and the lithium replenishing film layer includes the lithium replenishing agent and the organic solvent. Optionally, the lithium replenishing film layer also includes a conductive agent and a binder.

17. The positive electrode sheet according to claim 15 or 16, characterized in that: The first positive electrode active material layer and the second positive electrode active material layer both include positive electrode active materials, and the positive electrode active materials include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

18. A method for preparing a positive electrode sheet battery as claimed in any one of claims 13 to 15 and 17, characterized in that: include: Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S, and the organic solvent includes an organic solvent for weak proton hydrogen removal, and the weak proton hydrogen removal organic solvent includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate; The lithium supplement agent dispersion is placed in a dispersion containing a positive electrode active material, mixed, stirred and dispersed to obtain a slurry, and the slurry is coated on a current collector to form the positive electrode sheet.

19. A method for preparing a lithium ion secondary battery according to any one of claims 13-14, 16-17, characterized in that: include: Dispersing a lithium supplement agent in an organic solvent to form a lithium supplement agent dispersion, wherein the lithium supplement agent includes one or more of Li3N, Li3P, Li2O2 and Li2S, and the organic solvent includes an organic solvent for weak proton hydrogen removal, and the organic solvent for weak proton hydrogen removal includes one or more of triethyl phosphate, cyclopentane sulfone and propylene carbonate; The lithium supplement agent dispersion is coated on the side of the second positive electrode active material layer away from the current collector to form the positive electrode sheet.

20. An electrical equipment, characterized in that: Including the lithium ion secondary battery as described in any one of claims 1 to 9, or the lithium ion secondary battery prepared by the method for preparing a lithium ion secondary battery as described in any one of claims 10 to 12, or the positive electrode sheet as described in any one of claims 13 to 17, or the positive electrode sheet prepared by the method for preparing a positive electrode sheet as described in any one of claims 18 to 19.

Images