Lithium-supplementing electrode sheet, preparation method thereof, battery and electrical equipment comprising the lithium-supplementing electrode sheet

Abstract

The present invention relates to the technical field of secondary batteries, and particularly to a lithium supplement electrode sheet and a preparation method thereof, as well as a battery and an electrical device comprising the lithium supplement electrode sheet. The lithium supplement electrode sheet includes a current collector and a coating area provided on at least one side surface of the current collector. The coating area includes at least two active layers, and a pore former is included in the at least two active layers. The two adjacent active layers including the pore former are defined as a first active layer and a second active layer respectively. The first active layer is provided on the current collector, and the second active layer is provided on the side of the first active layer away from the current collector. The porosity of the second active layer is greater than that of the first active layer. The large porosity of the second active layer close to the electrolyte side is beneficial to improving the electrolyte wettability of the second active layer, improving the efficiency of the first active layer in contacting the electrolyte, and further improving the capacity utilization of the lithium supplement agent in the first active layer, so as to improve the battery life.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a lithium-replenishing pole piece and a preparation method thereof, as well as a battery and an electrical device comprising the lithium-replenishing pole piece. Background Art

[0002] Positive electrode lithium replenishment is the addition of lithium-containing compounds with high irreversible capacity to the positive electrode of the lithium-ion battery. Depending on the type of compound, it can be divided into binary lithium-containing compounds represented by Li2O, Li2O2, and Li2S, ternary lithium-containing compounds represented by Li6CoO4 and Li5FeO4, and organic lithium-containing compounds represented by Li2DHBN and Li2C2O4.

[0003] Positive electrode lithium replenishment materials can be added directly during the homogenization process of the positive electrode slurry, without the need for additional process improvements and at a lower cost, making them more suitable for the current lithium-ion battery manufacturing process and hailed as the most promising lithium replenishment technology. Despite this, there are still some problems with the lithium replenishment process, for example, the positive electrode lithium replenishment material has difficulty in effectively exerting its capacity during the process of exerting its capacity. Summary of the invention

[0004] The main purpose of the present invention is to provide a lithium-replenishing electrode plate, aiming to improve the capacity of the lithium-replenishing agent in the lithium-replenishing electrode plate and improve the battery life.

[0005] To achieve the above-mentioned purpose, the present invention proposes a lithium replenishing electrode, which includes a current collector and a coating area arranged on at least one side of the current collector, the coating area includes at least two active layers, and the at least two active layers include a pore-forming agent. The two adjacent active layers including the pore-forming agent are defined as a first active layer and a second active layer, respectively. The first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, and the porosity in the second active layer is greater than the porosity in the first active layer.

[0006] Optionally, the porosity formed by the pore former in the second active layer is greater than the porosity formed by the pore former in the first active layer.

[0007] The present application forms different porosities in different active layers through pore-forming agents, and the large porosity of the second active layer close to the electrolyte side is beneficial to improving the electrolyte wettability of the second active layer, improving the efficiency of the first active layer contacting the electrolyte, and further improving the capacity of the lithium supplement in the first active layer to improve the battery life.

[0008] Optionally, the pore former comprises a self-sacrificial lithium salt.

[0009] In this application, a self-sacrificing lithium salt is used as a pore former, which is beneficial to improving the energy density of the electrode sheet, avoiding the occupation of the electrode sheet space by other pore formers that do not contribute to the capacity, and causing a decrease in the energy density of the electrode sheet.

[0010] Optionally, the volume change value before and after the reaction of the self-sacrificing lithium salt in the second active layer is greater than the volume change value before and after the reaction of the self-sacrificing lithium salt in the first active layer.

[0011] The self-sacrificing lithium salt generates voids after discharging its capacity or reacting. In order to make the porosity of the second active layer greater than that of the first active layer, the volume change value before and after the reaction of the self-sacrificing lithium salt in the second active layer is greater than the volume change value before and after the reaction of the self-sacrificing lithium salt in the first active layer. It can be understood that when the same self-sacrificing lithium salt is used in the first active layer and the second active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer; it can also be understood that when different self-sacrificing lithium salts are used in the first active layer and the second active layer, the larger the volume change value before and after the reaction of the self-sacrificing lithium salt, the larger the pores left, which is more suitable for the second active layer. For example, Li2C2O4, Li2O, and Li2O2 will react completely directly, with the largest volume change value, and are suitable for the second active layer. In contrast, Li2S can be applied to the first active layer to achieve a porosity difference between the two active layers.

[0012] Optionally, when at least one self-sacrificing lithium salt in the second active layer is different from at least one self-sacrificing lithium salt in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than or equal to the concentration of the self-sacrificing lithium salt in the first active layer.

[0013] Considering that there may be multiple types of self-sacrificing lithium salts in the active layer, when at least one self-sacrificing lithium salt in the second active layer is different from at least one self-sacrificing lithium salt in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than or equal to the concentration of the self-sacrificing lithium salt in the first active layer. For example, when the volume change values generated after the reaction of two different self-sacrificing lithium salts are the same, then when the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer, a porosity difference between the two active layers can be formed. When the volume change values generated after the reaction of two different self-sacrificing lithium salts are different, and the volume change value generated after the reaction of the self-sacrificing lithium salt in the second active layer is greater than the volume change value generated after the reaction of the self-sacrificing lithium salt in the first active layer, then when the concentration of the self-sacrificing lithium salt in the second active layer is equal to the concentration of the self-sacrificing lithium salt in the first active layer, a porosity difference between the two active layers can be formed.

[0014] Optionally, when the self-sacrificing lithium salt in the second active layer is of the same type as the self-sacrificing lithium salt in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer.

[0015] When the self-sacrificing lithium salt in the second active layer is of the same type as the self-sacrificing lithium salt in the first active layer, the volume change values generated after the reaction of the self-sacrificing lithium salts in the two active layers are the same. At this time, it is necessary that the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer, so that a porosity difference can be formed between the two active layers.

[0016] Optionally, in the at least two active layers, the total concentration of the self-sacrificing lithium salt is defined as x%, and the total concentration of the self-sacrificing lithium salt = (the mass of all the self-sacrificing lithium salts in each active layer ÷ the sum of the masses of all the active substances and all the self-sacrificing lithium salts in each active layer) * 100%. The range value of the total concentration x% of the self-sacrificing lithium salt is 2% - 10%.

[0017] The range value of the total concentration x% of the self-sacrificing lithium salt is 2% - 10%. For example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and the specific value is not limited.

[0018] Optionally, the concentration of the self-sacrificing lithium salt in the layer is defined as yi, and the concentration of the self-sacrificing lithium salt in the layer = (the mass of the self-sacrificing lithium salt in each active layer ÷ the sum of the masses of the active substance and the self-sacrificing lithium salt in each active layer) * 100%. The concentration of the self-sacrificing lithium salt in the layer of the second active layer is y(i + 1), where i ≥ 1, and the concentration of the self-sacrificing lithium salt in the layer of the first active layer is y(i). Then y(i + 1) - y(i) = a, where 1% ≤ a ≤ 4%.

[0019] The difference between the concentration y(i + 1) of the self-sacrificing lithium salt in the layer of the second active layer and the concentration y(i) of the self-sacrificing lithium salt in the layer of the first active layer is 1% - 4%, where i ≥ 1. This shows that the concentrations of the self-sacrificing lithium salts in adjacent two active layers are different to form different porosities. The difference in the concentrations of the self-sacrificing lithium salts in adjacent two active layers is 1% - 4%. For example, it can be 1%, 2%, 2.5%, 3%, 3.5%, 4%, etc., and the specific value is not limited.

[0020] Optionally, it is defined that the at least two active layers are sequentially provided with an A-layer active layer and a B-layer active layer from the direction close to the current collector to the direction far from the current collector. The range value of the concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is (x - 2)% - (x - 0.5)%.

[0021] At least two active layers are sequentially provided with an A-layer active layer and a B-layer active layer in the direction from close to the current collector to far from the current collector, which means that the A-layer active layer and the B-layer active layer are sequentially provided in the direction from the side close to the current collector to the side far from the current collector. That is, the A-layer active layer is the active layer containing the self-sacrificing lithium salt closest to the current collector.

[0022] Based on the fact that the self-sacrificing lithium salt in the active layer closest to the current collector is not easily able to exert its capacity, therefore, the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is lower than that in other active layers. The range of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is (x - 2)% - (x - 0.5)%. For example, it can be (x - 2)%, (x - 1.5)%, (x - 1)%, (x - 0.5)%, etc., and specific values are not limited. Among them, the range of x is 2 - 10 as described above. For example, x can take values such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., and specific values are not limited.

[0023] Optionally, the range value of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is 2% - 5%;

[0024] And / or, the range value of the in-layer concentration y2 of the self-sacrificing lithium salt in the B-layer active layer is 5% - 7%;

[0025] And / or, it is defined that at least two active layers are sequentially provided with an A-layer active layer, a B-layer active layer and a C-layer active layer in the direction from close to the current collector to far from the current collector. The range value of the in-layer concentration y3 of the self-sacrificing lithium salt in the C-layer active layer is 7% - 10%.

[0026] It is defined that at least two active layers are sequentially provided with an A-layer active layer, a B-layer active layer and a C-layer active layer in the direction from close to the current collector to far from the current collector. The A-layer active layer is closest to the current collector. Then, the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is lower than that in other active layers. The range of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is 2% - 5%. For example, it can be 2%, 3%, 4%, 5%, etc., and specific values are not limited. The range of the in-layer concentration y2 of the self-sacrificing lithium salt in the B-layer active layer is 5% - 7%. For example, it can be 5%, 6%, 7%, etc., and specific values are not limited. The range of the in-layer concentration y3 of the self-sacrificing lithium salt in the C-layer active layer is 7%, 8%, 9%, 10%, etc., and specific values are not limited. And, a concentration difference is formed in each active layer.

[0027] Optionally, in the at least two active layers, it is defined that the total porosity of the active layer is p. The total porosity of the active layer = (the total pore volume in each active layer ÷ the sum of the volumes of each active layer) * 100%. The range value of the total porosity p of the active layer is 20% - 30%.

[0028] The total porosity of the active layer refers to the volume of all pores in each active layer of the lithium-supplemented electrode divided by the sum of the volumes of each active layer in the lithium-supplemented electrode. The range of the total porosity p of the active layer is 20% - 30%. For example, it can be 20%, 22%, 25%, 27%, 30%, etc., and no specific limitation is made. It can be understood that the porosity is related not only to the concentration of the self-sacrificing lithium salt but also to the compaction density.

[0029] Optionally, define the porosity of each active layer as n. The porosity of each active layer = (the volume of pores in each active layer ÷ the volume of each active layer) * 100%. The porosity of the second active layer is n(i + 1), where i ≥ 1, and the porosity of the first active layer is ni. Then n(i + 1) - n(i) = b, where 2% ≤ b ≤ 8%.

[0030] The porosity of each active layer refers to the volume of pores in each active layer of the lithium-supplemented electrode divided by the volume of each active layer. The difference between the porosity of the second active layer and the porosity of the first active layer is 2% - 8%, indicating that the porosity of the second active layer is higher than that of the first active layer, which helps the electrolyte infiltrate into the first active layer through the second active layer. For example, the difference between the porosity of the second active layer and the porosity of the first active layer can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., and no specific limitation is made.

[0031] Optionally, define that the at least two active layers are sequentially provided with an A-layer active layer and a B-layer active layer from the direction close to the current collector to the direction far from the current collector. The range of the porosity n1 of the A-layer active layer is 20% - 25%.

[0032] The A-layer active layer is closest to the current collector. The porosity of the A-layer active layer is lower than that of other active layers. The porosity of the A-layer active layer is 20% - 25%. For example, it can be 20%, 21%, 22%, 23%, 24%, 25%, etc., and no specific limitation is made.

[0033] Optionally, the self-sacrificing lithium salt includes at least one of Li2C2O4, Li2M1O2, Li2M2O3, Li5Fe x M3 (1-x) O4 and Li6Mn y M4 (1-y) O4; where M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru.

[0034] In this application, the lithium supplement material is not limited, and the cathode lithium supplement materials reported in the current literature can all be applied to this application, including at least one of Li2C2O4, Li2M1O2, Li2M2O3, Li5Fe x M3 (1-x) O4 and Li6Mn y M4 (1-y) O4; where M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru.

[0035] Optionally, the structural general formula of the cathode material in the at least two active layers is LiMn x Fe y M (1-x-y) PO4, where 0 ≤ x ≤ 0.8; 0.1 ≤ y ≤ 0.6; 0 ≤ 1 - x - y ≤ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge;

[0036] And / or, the structural general formula of the cathode material is LiNi a Co b N (1-a-b) O2, where N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, and where 0.35 ≤ a < 1.0, 0 ≤ b ≤ 0.35, and 0 ≤ 1 - a - b ≤ 0.35.

[0037] In the application, the cathode material is not limited. For example, the structural general formula of the cathode material is LiMn x Fe y M (1-x-y) PO4, where 0 ≤ x ≤ 0.8; 0.1 ≤ y ≤ 0.6; 0 ≤ 1 - x - y ≤ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge; the structural general formula of the cathode material is LiNi a Co b N (1-a-b) O2, where N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, and where 0.35 ≤ a < 1.0, 0 ≤ b ≤ 0.35, and 0 ≤ 1 - a - b ≤ 0.35.

[0038] Optionally, the cathode active materials in the at least two active layers are the same.

[0039] Considering the problem of low energy efficiency in the case of heterogeneous cathode layer coating, in this application, the cathode active materials in the at least two active layers are the same, and the same cathode coating forms different porosities, avoiding the problem of low energy efficiency.

[0040] Optionally, the active layer of the lithium supplement electrode sheet further includes a conductive agent and a binder. The conductive agent includes at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene;

[0041] The binder includes at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene.

[0042] The conductive agent is used to improve the conductivity of the active layer. This application does not limit the conductive agent. The conductive agent includes at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. For example, it can be selected from at least one of SP, KS - 6, acetylene black, branched - chain structure Ketjen black ECP, SFG - 6, vapor - grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene and their composite conductive agents.

[0043] This application does not limit the binder. The binder uses the commonly used binders in the art. The binder includes at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene.

[0044] This application provides a method for preparing a lithium supplement electrode sheet, including the following steps:

[0045] Coating at least two slurries including a pore - forming agent on a current collector, drying and cold - pressing to obtain a lithium supplement electrode sheet. Among them, the at least two slurries including the pore - forming agent form at least two active layers. One active layer is disposed on the current collector, and the other active layer is disposed on the side of one active layer away from the current collector. The porosity of the other active layer is greater than the porosity of one active layer.

[0046] The porosity of the other active layer is greater than the porosity of one active layer. The large porosity of the other active layer close to the electrolyte side is beneficial to improving the electrolyte wettability of the other active layer, improving the efficiency of one active layer contacting the electrolyte, and further improving the capacity utilization of the lithium supplement agent in one active layer to improve the battery life.

[0047] Optionally, the porosity formed by the pore - forming agent in the other active layer is greater than the porosity formed by the pore - forming agent in one active layer.

[0048] In the present application, different porosities are formed in different active layers by using a pore-forming agent, and the large porosity of the other active layer closer to the electrolyte side is beneficial to improving the electrolyte wettability of the other active layer, enhancing the efficiency of the first active layer in contacting the electrolyte, and further improving the capacity utilization of the lithium supplement agent in the first active layer, so as to improve the battery life.

[0049] Optionally, the pore-forming agent includes a self-sacrificial lithium salt.

[0050] In the present application, using a self-sacrificial lithium salt as the pore-forming agent is beneficial to improving the energy density of the electrode sheet, avoiding the occupation of the electrode sheet space by other pore-forming agents that do not contribute to capacity, and preventing the reduction of the energy density of the electrode sheet.

[0051] The present application provides a battery, including: a negative electrode sheet, a positive electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet is the lithium supplement electrode sheet as described above.

[0052] The service life of the battery using the above lithium supplement electrode sheet is improved.

[0053] The present application provides an electrical device, and the electrical device includes the above battery.

[0054] The performance of the electrical device using the above battery is improved.

[0055] The lithium supplement electrode sheet of the present application includes a current collector and a coating area provided on at least one side surface of the current collector. The coating area includes at least two active layers, and the at least two active layers include a pore-forming agent. Define the two adjacent active layers including the pore-forming agent as the first active layer and the second active layer respectively. The first active layer is provided on the current collector, and the second active layer is provided on the side of the first active layer away from the current collector. The porosity of the second active layer is greater than that of the first active layer. The large porosity of the second active layer closer to the electrolyte side is beneficial to improving the electrolyte wettability of the second active layer, enhancing the efficiency of the first active layer in contacting the electrolyte, and further improving the capacity utilization of the lithium supplement agent in the first active layer, so as to improve the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0057] Figure 1 It is a schematic flow chart of the preparation method of the lithium supplement electrode sheet of the present invention;

[0058] Figure 2Schematic structural diagram of a lithium - supplementing electrode sheet according to an embodiment of the present invention;

[0059] Figure 3 Schematic structural diagram of a lithium - supplementing electrode sheet according to an embodiment of the present invention;

[0060] Figure 4 Schematic diagram of a secondary battery according to an embodiment of the present application;

[0061] Figure 5 is Figure 4 Exploded view of the secondary battery according to an embodiment of the present application shown in;

[0062] Figure 6 Schematic diagram of a battery module according to an embodiment of the present application;

[0063] Figure 7 Schematic diagram of a battery pack according to an embodiment of the present application;

[0064] Figure 8 is Figure 7 Exploded view of the battery pack according to an embodiment of the present application shown in;

[0065] Figure 9 Schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0066] Explanation of the reference numerals in the drawings:

[0067] Label Name Label Name 100 Lithium supplement electrode 3 Lower box 10 Current collector 4 Battery module 20 A-layer active layer 5 Secondary battery 30 B-layer active layer 51 Shell 40 C-layer active layer 52 Electrode assembly 1 Battery pack 53 Top cover assembly 2 Upper box

[0068] The realization of the object of the present invention, functional features and advantages will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0069] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0070] Hereinafter, embodiments of the binder of the present application, its preparation method, and a separator, a secondary battery, a battery module, a battery pack, and an electric device including the binder will be specifically described in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0071] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include or exclude the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0072] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0073] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0074] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0075] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application mean open-ended, and can also be closed-ended. For example, the terms "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0076] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0077] The batteries mentioned in the art can be classified into primary batteries and rechargeable batteries according to whether they are rechargeable. Currently, common types of rechargeable batteries are: lead-acid batteries, nickel-metal hydride batteries, and lithium-ion batteries. Lithium-ion batteries are currently widely used in pure electric vehicles and hybrid vehicles. The lithium-ion batteries used for this purpose have a relatively slightly lower capacity, but have a larger output and charging current, and also have a longer service life, but the cost is higher.

[0078] The batteries described in the embodiments of this application refer to rechargeable batteries. Hereinafter, lithium-ion batteries will be mainly used as an example to describe the embodiments disclosed in this application. It should be understood that the embodiments disclosed in this application are applicable to any other suitable type of rechargeable battery. The batteries mentioned in the embodiments disclosed in this application can be directly or indirectly applied to a suitable device to supply power to the device.

[0079] The batteries mentioned in the embodiments disclosed in this application refer to a single physical module including one or more battery cells to provide a predetermined voltage and capacity. A battery cell is the basic unit in a battery. Generally, according to the packaging method, it can be divided into: cylindrical battery cells, cuboid battery cells, and soft-pack battery cells. Hereinafter, it will mainly focus on cuboid battery cells. It should be understood that the embodiments described hereinafter are also applicable to cylindrical battery cells or soft-pack battery cells in some aspects.

[0080] The battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. The lithium-ion battery cell mainly operates by the movement of lithium ions between the positive electrode plate and the negative electrode plate. In a cylindrical battery cell, the thin film structure of the three-layer material is wound into an electrode assembly in a cylindrical shape, while in a cuboid battery cell, the thin film structure is wound or stacked into an electrode assembly with a generally cuboid shape.

[0081] In a typical battery cell structure, the battery cell includes a housing, an electrode assembly, and an electrolyte. The electrode assembly is accommodated in the housing of the battery cell. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The housing includes a casing and an end cap. The casing includes an accommodation cavity formed by a plurality of walls and an opening. The end cap is arranged at the opening to close the accommodation cavity. In addition to the electrode assembly, an electrolyte is also accommodated in the accommodation cavity. The positive electrode plate and the negative electrode plate in the electrode assembly include electrode tabs. To ensure that a large current can pass through without fusing, the number of positive electrode tabs is multiple and they are stacked together, and the number of negative electrode tabs is multiple and they are stacked together. The electrode tabs are electrically connected to electrode terminals located outside the battery cell through connecting members. The electrode terminals generally include a positive electrode terminal and a negative electrode terminal. For a cuboid battery cell, the electrode terminals are generally arranged at the end cap part. Multiple battery cells are connected in series and / or in parallel via the electrode terminals for various applications.

[0082] In some high-power applications such as electric vehicles, the application of the battery includes three levels: battery cell, battery module, and battery pack. The battery module is formed by electrically connecting a certain number of battery cells together and placing them in a frame to protect the battery cells from external impacts, heat, vibrations, etc. The battery pack refers to the final state of the battery system installed in an electric vehicle. The battery pack generally includes a box body for encapsulating one or more battery cells. The box body is generally composed of a cover body and a box shell.

[0083] A plurality of mounting points for connecting to the vehicle body are provided on the border of the box body or in the middle of the box shell. To improve the stability of the connection between the vehicle body and the battery, mounting parts are often provided at the mounting points.

[0084] In some battery production and processing technologies, first, a plurality of battery cells are integrated into a battery module, and then the battery module is encapsulated in the box body of the battery pack to form a battery pack / battery box.

[0085] A common battery module generally includes two end plates. A plurality of battery cells are arranged between the two end plates. The end plate provided with the battery module output pole is also called the output end plate, and the end plate not provided with the battery module output pole is also called the non-output end plate.

[0086] A battery pack may contain multiple battery modules in one row or multiple rows. The arrangement of multiple rows of multiple battery modules may be double rows and multiple columns, multiple rows and double columns, multiple rows and multiple columns, etc. Taking a battery pack containing double rows and multiple columns of battery modules as an example, the first end plate of each column is generally a head output extreme plate, the two adjacent end plates between two rows of battery modules are middle non-output extreme plates, the last end plate of each column is a tail non-output extreme plate, the head output extreme plate and one of the middle non-output extreme plates belong to the first row of battery modules, and one of the middle non-output extreme plates and the tail output extreme plate belong to the second row of battery modules.

[0087] The battery module needs to be packaged into the battery box with the help of tooling, which is generally equipped with a clamping mechanism for clamping the battery module, such as a clamping claw, a suction cup, etc. When a tooling with a clamping claw is used to package the battery module, a clamping claw groove that matches the clamping claw is generally provided on the side of the end plate away from the battery cell, so that the clamping claw can be inserted to clamp and transport the battery module.

[0088] The development of battery technology must take into account many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate and other performance parameters. In addition, the production cost and processing technology of the battery must also be considered to improve the quality and production efficiency of the battery.

[0089] Lithium replenishing materials release Li + In the process, there needs to be a certain space and medium to hold Li + Theoretically, the closer the lithium-supplementing material is to the electrolyte, the more conducive it is to releasing Li. + , supplement Li + Similarly, the lithium supplement material close to the current collector is farther away from the electrolyte, the electrolyte infiltration is poor, the ion conduction is poor, which is not conducive to Li + Release, which makes it difficult to fully utilize the capacity of the lithium supplement material.

[0090] To this end, the present application provides a lithium replenishing electrode, which includes a current collector and a coating area arranged on at least one side of the current collector, the coating area includes at least two active layers, and at least two active layers include a pore former. The two adjacent active layers including the pore former are defined as a first active layer and a second active layer, respectively. The first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, and the porosity in the second active layer is greater than the porosity in the first active layer.

[0091] The current collector refers to the structure or part that collects current. In lithium-ion batteries, it mainly refers to metal foil, such as copper foil and aluminum foil. The current collector is used as a substrate to attach the positive or negative active material, and plays the role of collecting the current generated by the active material and outputting a large current to the outside. Generally, aluminum foil is used as the positive current collector, and copper foil is used as the negative current collector.

[0092] The active layer refers to a layered structure including active materials, wherein the active material refers to the positive electrode active material involved in the positive electrode. The positive electrode active material can be used to reversibly embed and de-embed Li + of compounds.

[0093] Pore-forming agent is an additive that creates a pore structure in the material.

[0094] The two adjacent active layers including the pore former are respectively the first active layer and the second active layer, which refers to the two adjacent active layers containing the pore former, which are respectively the first active layer and the second active layer. It can be understood that the first active layer and the second active layer can be two active layers in contact, and a third active layer not containing the pore former can also be arranged between the first active layer and the second active layer, that is, the active layer not containing the pore former separates the two active layers containing the pore former.

[0095] The first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, which means that the first active layer is closer to the current collector than the second active layer. It can be understood that the first active layer is directly arranged on the current collector. It can also be understood that an active layer not containing a lithium supplement agent is arranged between the first active layer and the current collector.

[0096] In order to facilitate the infiltration of the electrolyte into the active layer near the current collector side, the porosity of the second active layer near the electrolyte side is made higher than the porosity of the first active layer near the current collector side, so as to facilitate the infiltration of the electrolyte from the second active layer to the first active layer and improve the capacity of the lithium replenisher distributed in the first active layer. In other words, the Li of the lithium replenisher material near the current collector side is convenient. + Release it.

[0097] Furthermore, the porosity formed by the pore former in the second active layer is greater than the porosity formed by the pore former in the first active layer.

[0098] The present application forms different porosities in different active layers through pore-forming agents, and the large porosity of the second active layer close to the electrolyte side is beneficial to improving the electrolyte wettability of the second active layer, improving the efficiency of the first active layer contacting the electrolyte, and further improving the capacity of the lithium supplement in the first active layer to improve the battery life.

[0099] like Figure 2As shown in the figure, it is a schematic structural diagram of an embodiment of the lithium - supplementing electrode of the present application. There are two active layers on the current collector 10, namely the A - layer active layer and the B - layer active layer. The A - layer active layer is closer to the current collector. Pore - forming agents are provided in both the A - layer active layer and the B - layer active layer. Moreover, the porosity formed by the pore - forming agent in the B - layer active layer is greater than the porosity formed by the pore - forming agent in the A - layer active layer. In this way, the ability of the A - layer active layer to infiltrate the electrolyte is improved, which is beneficial to the release of Li of the lithium - supplementing material in the A - layer active layer + to be released, enabling the lithium - supplementing agent to effectively exert its capacity and improving the battery life.

[0100] Furthermore, the pore - forming agent includes self - sacrificial lithium salts.

[0101] Self - sacrificial lithium salts, that is, lithium - supplementing materials, refer to pore - forming agents that can provide lithium ions. That is, after the self - sacrificial lithium salts exert their capacity, voids are left. It can be understood that after the lithium - supplementing materials exert their capacity, the material density decreases significantly (for example, Li2S becomes S), or is directly completely reacted (lithium oxalate generates CO2), and unlike the repeated expansion and contraction during the cycling of the positive - electrode active material, permanent voids can be left in the electrode.

[0102] In the present application, using self - sacrificial lithium salts as pore - forming agents is beneficial to improving the energy density of the electrode, avoiding the occupation of electrode space by other pore - forming agents that do not exert their capacity and causing a decrease in the energy density of the electrode.

[0103] Furthermore, the volume change value of the self - sacrificial lithium salt in the second active layer before and after the reaction is greater than the volume change value of the self - sacrificial lithium salt in the first active layer before and after the reaction.

[0104] Voids are generated after the self - sacrificial lithium salts exert their capacity or react. In order to make the porosity of the second active layer greater than that of the first active layer, the volume change value of the self - sacrificial lithium salt in the second active layer before and after the reaction is greater than the volume change value of the self - sacrificial lithium salt in the first active layer before and after the reaction. It can be understood that when the same self - sacrificial lithium salt is used in the first active layer and the second active layer, the concentration of the self - sacrificial lithium salt in the second active layer is greater than that in the first active layer; it can also be understood that when different self - sacrificial lithium salts are used in the first active layer and the second active layer, the larger the volume change value of the self - sacrificial lithium salt before and after the reaction, the larger the pores left, and it is more suitable for the second active layer. For example, Li2C2O4, Li2O, and Li2O2 will directly react completely and have the largest volume change value, which is suitable for the second active layer. In contrast, Li2S can be applied to the first active layer to achieve a porosity difference between the two active layers.

[0105] Furthermore, when at least one type of self-sacrificing lithium salt in the second active layer is different from at least one type of self-sacrificing lithium salt in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than or equal to the concentration of the self-sacrificing lithium salt in the first active layer.

[0106] Considering that there may be multiple types of self-sacrificing lithium salts in the active layer, when at least one type of self-sacrificing lithium salt in the second active layer is different from at least one type of self-sacrificing lithium salt in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than or equal to the concentration of the self-sacrificing lithium salt in the first active layer. For example, when the volume change values generated after the reaction of two different self-sacrificing lithium salts are the same, then when the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer, a porosity difference can be formed between the two active layers. When the volume change values generated after the reaction of two different self-sacrificing lithium salts are different, and the volume change value generated after the reaction of the self-sacrificing lithium salt in the second active layer is greater than the volume change value generated after the reaction of the self-sacrificing lithium salt in the first active layer, then the concentration of the self-sacrificing lithium salt in the second active layer can be equal to the concentration of the self-sacrificing lithium salt in the first active layer, and a porosity difference can be formed between the two active layers.

[0107] Furthermore, when the type of self-sacrificing lithium salt in the second active layer is the same as that in the first active layer, the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer.

[0108] When the type of self-sacrificing lithium salt in the second active layer is the same as that in the first active layer, the volume change values generated after the reaction of the self-sacrificing lithium salts in the two active layers are the same. At this time, it is necessary that the concentration of the self-sacrificing lithium salt in the second active layer is greater than the concentration of the self-sacrificing lithium salt in the first active layer, so that a porosity difference can be formed between the two active layers.

[0109] Furthermore, in at least two active layers, the total concentration of the self-sacrificing lithium salt is defined as x%, and the total concentration of the self-sacrificing lithium salt = (the mass of all self-sacrificing lithium salts in each active layer ÷ the sum of the mass of all active substances and all self-sacrificing lithium salts in each active layer) * 100%, and the range value of the total concentration x% of the self-sacrificing lithium salt is 2% - 10%.

[0110] The mass of all self-sacrificing lithium salts in each active layer refers to the sum of the masses of the self-sacrificing lithium salts in each active layer of the lithium supplement electrode sheet. For example, if the lithium supplement electrode sheet has two active layers, an A-layer active layer (98 g of active substance, 2 g of self-sacrificing lithium salt) and a B-layer active layer (96 g of active substance, 4 g of self-sacrificing lithium salt), then the mass of all self-sacrificing lithium salts in each active layer is 2 g + 4 g = 6 g.

[0111] The sum of the masses of all active substances and all self-sacrificing lithium salts in each active layer refers to the sum of the masses of the active substances and self-sacrificing lithium salts in each active layer of the lithium supplement electrode sheet. For the A-layer active layer (98 g of active substance and 2 g of self-sacrificing lithium salt) and B-layer active layer (96 g of active substance and 4 g of self-sacrificing lithium salt) mentioned above, the sum of the masses of all active substances and all self-sacrificing lithium salts in each active layer is 98 + 2 g + 96 + 4 g = 200 g.

[0112] The total concentration of the self-sacrificing lithium salt refers to the total concentration of the self-sacrificing lithium salt in the lithium supplement electrode sheet. For the A-layer active layer (98 g of active substance and 2 g of self-sacrificing lithium salt) and B-layer active layer (96 g of active substance and 4 g of self-sacrificing lithium salt) mentioned above, the total concentration of the self-sacrificing lithium salt is (6 g / 200 g) * 100% = 3%.

[0113] The range value of the total concentration x% of the self-sacrificing lithium salt is 2% - 10%. For example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and specific values are not limited.

[0114] Furthermore, define the in-layer concentration of the self-sacrificing lithium salt as yi. The in-layer concentration of the self-sacrificing lithium salt = (the mass of the self-sacrificing lithium salt in each active layer ÷ the sum of the masses of the active substance and self-sacrificing lithium salt in each active layer) * 100%. The in-layer concentration of the self-sacrificing lithium salt in the second active layer is y(i + 1), where i ≥ 1, and the in-layer concentration of the self-sacrificing lithium salt in the first active layer is y(i). Then y(i + 1) - y(i) = a, where 1% ≤ a ≤ 4%.

[0115] The in-layer concentration of the self-sacrificing lithium salt refers to the concentration of the self-sacrificing lithium salt in each active layer of the lithium supplement electrode sheet. For example, if the lithium supplement electrode sheet has two active layers, an A-layer active layer (98 g of active substance and 2 g of self-sacrificing lithium salt) and a B-layer active layer (96 g of active substance and 4 g of self-sacrificing lithium salt), then the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is (2 g / 100 g) * 100% = 2%; the in-layer concentration y2 of the self-sacrificing lithium salt in the B-layer active layer is (4 g / 100 g) * 100% = 4%.

[0116] The difference between the in-layer concentration y(i + 1) of the self-sacrificing lithium salt in the second active layer and the in-layer concentration y(i) of the self-sacrificing lithium salt in the first active layer is 1% - 4%, where i ≥ 1. This indicates that the concentrations of the self-sacrificing lithium salts in adjacent active layers are different to form different porosities. The difference in the concentrations of the self-sacrificing lithium salts in adjacent active layers is 2% - 4%. For example, it can be 1%, 2%, 2.5%, 3%, 3.5%, 4%, etc., and specific values are not limited.

[0117] Meanwhile, the concentration of the self-sacrificing lithium salt in the second active layer closer to the electrolyte side is greater than that in the first active layer closer to the current collector side, which facilitates the capacity utilization of the self-sacrificing lithium salt in the second active layer. Because the second active layer is closer to the electrolyte, the electrolyte has good wetting and good ion conduction, and the high-concentration self-sacrificing lithium salt can effectively utilize its capacity. Moreover, after the self-sacrificing lithium salt utilizes its capacity, pores are left in the active layer, that is, the porosity of the second active layer closer to the electrolyte side is high, and the porosity of the first active layer closer to the current collector side is low. The electrolyte can effectively wet the first active layer with low porosity through the second active layer with high porosity, improving the rate performance.

[0118] It can be understood that due to the high concentration of the lithium supplementing material in the second active layer and the low concentration of the lithium supplementing material in the first active layer, through this structural arrangement, not only can the lithium supplementing material in the second active layer utilize its capacity, but also the distribution of the porosity of the active layer can be changed, improving the wetting effect of the first active layer, thereby contributing to improving the capacity utilization of the lithium supplementing material in the first active layer and the rate performance.

[0119] Further, it is defined that at least two active layers are sequentially arranged with an A-layer active layer and a B-layer active layer from the side closer to the current collector to the side farther from the current collector, and the range value of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is (x - 2)% - (x - 0.5)%.

[0120] At least two active layers are sequentially arranged with an A-layer active layer and a B-layer active layer from the side closer to the current collector to the side farther from the current collector, which means that the A-layer active layer and the B-layer active layer are sequentially arranged from the side closer to the current collector side to the side farther from the current collector side. That is, the A-layer active layer is the active layer closest to the current collector containing the self-sacrificing lithium salt.

[0121] Based on the fact that the self-sacrificing lithium salt in the active layer closest to the current collector is not easily able to utilize its capacity, therefore, the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is lower than that in other active layers. The range of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is (x - 2)% - (x - 0.5)%. For example, it can be (x - 2)%, (x - 1.5)%, (x - 1)%, (x - 0.5)%, etc., and specific values are not limited. Among them, the range of x is 2 - 10 as described above. For example, x can take values such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., and specific values are not limited.

[0122] Further, the range of the in-layer concentration y1 of the self-sacrificing lithium salt in the A-layer active layer is 2% - 5%; and / or, the range of the in-layer concentration y2 of the self-sacrificing lithium salt in the B-layer active layer is 5% - 7%; and / or, it is defined that at least two active layers are sequentially arranged with an A-layer active layer, a B-layer active layer and a C-layer active layer from the side closer to the current collector to the side farther from the current collector, and the range of the in-layer concentration y3 of the self-sacrificing lithium salt in the C-layer active layer is 7% - 10%.

[0123] As shown Figure 3 in the figure, it is defined that at least two active layers are arranged in sequence from the direction close to the current collector to the direction far from the current collector, including an A-layer active layer, a B-layer active layer, and a C-layer active layer. The A-layer active layer is closest to the current collector. Then, the concentration y1 of the self-sacrificial lithium salt in the layer of the A-layer active layer is lower than that in other active layers. The concentration y1 of the self-sacrificial lithium salt in the layer of the A-layer active layer ranges from 2% to 5%. For example, it can be 2%, 3%, 4%, 5%, etc., and no specific limitation is made. The concentration y2 of the self-sacrificial lithium salt in the layer of the B-layer active layer ranges from 5% to 7%. For example, it can be 5%, 6%, 7%, etc., and no specific limitation is made. The concentration y3 of the self-sacrificial lithium salt in the layer of the C-layer active layer ranges from 7%, 8%, 9%, 10%, etc., and no specific limitation is made. Moreover, a concentration difference is formed in each active layer.

[0124] Furthermore, in at least two active layers, the total porosity of the active layer is defined as p, and the total porosity of the active layer = (the total pore volume in each active layer ÷ the sum of the volumes of each active layer) * 100%. The range value of the total porosity p of the active layer is 20% - 30%.

[0125] The porosity calculation formula is P = [V / V0] * 100%. V0 is the volume of the material in the natural state, and V is the total volume of all voids in the material.

[0126] The total porosity of the active layer refers to the total pore volume in each active layer of the lithium supplement electrode sheet divided by the sum of the volumes of each active layer in the lithium supplement electrode sheet. The range value of the total porosity of the active layer is 20% - 30%. For example, it can be 20%, 22%, 25%, 27%, 30%, etc., and no specific limitation is made. It can be understood that the porosity is not only related to the concentration of the self-sacrificial lithium salt but also related to the compaction density.

[0127] Furthermore, the porosity of each active layer is defined as n, and the porosity of each active layer = (the pore volume in each active layer ÷ the volume of each active layer) * 100%. The porosity of the second active layer is n(i + 1), where i ≥ 1, and the porosity of the first active layer is n(i). Then, n(i + 1) - n(i) = b, where 2% ≤ b ≤ 8%.

[0128] The porosity of each active layer refers to the pore volume in each active layer of the lithium supplement electrode sheet divided by the volume of each active layer. The difference between the porosity of the second active layer and the porosity of the first active layer is 2% - 8%, indicating that the porosity of the second active layer is higher than that of the first active layer, which helps the electrolyte to infiltrate into the first active layer through the second active layer. For example, the difference between the porosity of the second active layer and the porosity of the first active layer is 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., and no specific limitation is made.

[0129] Furthermore, it is defined that at least two active layers are sequentially arranged with an A-layer active layer and a B-layer active layer from the direction close to the current collector to the direction away from the current collector, and the range of the porosity n1 of the A-layer active layer is 20% - 25%.

[0130] The A-layer active layer is closest to the current collector. The porosity of the A-layer active layer is lower than that of other active layers. The porosity of the A-layer active layer is 20% - 25%. For example, it can be 20%, 21%, 22%, 23%, 24%, 25%, etc., and specific values are not limited.

[0131] Furthermore, the self-sacrificial lithium salt includes at least one of Li2C2O4, Li2M1O2, Li2M2O3, Li5Fe x M3 (1-x) O4 and Li6Mn y M4 (1-y) O4; wherein, M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru.

[0132] In this application, the lithium supplement material is not limited. Currently, the reported cathode lithium supplement materials in the literature can all be applied to this application. Li2C2O4, Li2M1O2, Li2M2O3, Li5Fe x M3 (1-x) O4 and Li6Mn y M4 (1-y) O4; wherein, M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru.

[0133] Furthermore, the structural general formula of the cathode material in at least two active layers is LiMn x Fe y M (1-x-y) PO4, where 0 ≤ x ≤ 0.8; 0.1 ≤ y ≤ 0.6; 0 ≤ 1 - x - y ≤ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge; and / or, the structural general formula of the cathode material is LiNi a Co b N (1-a-b)O2, where N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, La, and 0.35 ≤ a < 1.0, 0 ≤ b ≤ 0.35, 0 ≤ 1 - a - b ≤ 0.35.

[0134] In the application, the cathode material is not limited. For example, the general structural formula of the cathode material is LiMn x Fe y M (1-x-y) PO4, where 0 ≤ x ≤ 0.8; 0.1 ≤ y ≤ 0.6; 0 ≤ 1 - x - y ≤ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge; the general structural formula of the cathode material is LiNi a Co b N (1-a-b) O2, where N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, La, and 0.35 ≤ a < 1.0, 0 ≤ b ≤ 0.35, 0 ≤ 1 - a - b ≤ 0.35.

[0135] Furthermore, the cathode active materials in at least two active layers are the same.

[0136] Considering the problem of low energy efficiency in the case of heterogeneous cathode layer coating, in this application, the cathode active materials in at least two active layers are the same, and the same cathode coatings form different porosities, avoiding the problem of low energy efficiency.

[0137] Furthermore, the active layer of the lithium - supplementing electrode sheet further includes a conductive agent and a binder. The conductive agent includes at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene; the binder includes at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene.

[0138] The conductive agent is used to improve the conductivity of the active layer. In this application, the conductive agent is not limited. The conductive agent includes at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. For example, it can be selected from at least one of SP, KS - 6, acetylene black, branched - chain structure Ketjen black ECP, SFG - 6, vapor - grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene and their composite conductive agents.

[0139] In this application, the binder is not limited. The binder uses the commonly used binders in the art. The binder includes at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene.

[0140] Such as Figure 1As shown, the present application provides a method for preparing a lithium supplement electrode, comprising the following steps:

[0141] At least two layers of slurry including pore formers are coated on the current collector, and the lithium replenishing electrode is obtained after drying and cold pressing, wherein the at least two layers of slurry including pore formers form at least two active layers, one active layer is arranged on the current collector, and the other active layer is arranged on the side of the active layer away from the current collector, and the porosity in the other active layer is greater than the porosity in the one active layer.

[0142] The porosity of the other active layer is greater than that of the first active layer. The large porosity of the other active layer close to the electrolyte is beneficial to improving the electrolyte wettability of the other active layer, improving the efficiency of the first active layer contacting the electrolyte, and further improving the capacity of the lithium supplement in the first active layer to improve the battery life.

[0143] Furthermore, the porosity formed by the pore former in the other active layer is greater than the porosity formed by the pore former in the one active layer.

[0144] The present application forms different porosities in different active layers through pore-forming agents, and the large porosity of the other active layer close to the electrolyte side is beneficial to improving the electrolyte wettability of the other active layer, improving the efficiency of one active layer contacting the electrolyte, and further improving the capacity of the lithium supplement agent in one active layer to improve the battery life.

[0145] Further, the pore former includes a self-sacrificial lithium salt.

[0146] In the present application, self-sacrificial lithium salt is used as a pore-forming agent, which is beneficial to improving the energy density of the electrode and avoiding other pore-forming agents that do not exert their capacity occupying the electrode space, resulting in a decrease in the energy density of the electrode.

[0147] The present application also provides a battery, including: a negative electrode plate, a positive electrode plate, a separator and an electrolyte, wherein the positive electrode plate is the lithium supplement plate as described above. Since the lithium supplement plate adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0148] The service life of the battery using the above-mentioned lithium-supplementing electrode is improved.

[0149] The present application also provides an electrical device, which includes the above-mentioned battery. Since the battery adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0150] The performance of the electrical equipment using the battery is improved.

[0151] In addition, the secondary battery, battery module, battery pack, and electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0152] In one embodiment of the present application, a secondary battery is provided.

[0153] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through. The separator is the separator improved above in the present application.

[0154] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0155] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0156] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can 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 can be formed by forming a metal material (such as 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.).

[0157] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material can be a positive electrode active material well-known in the art for lithium-ion batteries. As an example, the positive electrode active material can include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be abbreviated as NCM333 )), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 )), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 )), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 )), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 )), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of olivine-structured lithium-containing phosphates may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, composites of lithium manganese iron phosphate and carbon.

[0158] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0159] In some embodiments, the positive electrode film layer may also 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.

[0160] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, conductive agent, 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, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0161] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0162] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0163] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper 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.).

[0164] In some embodiments, the negative electrode active material can be a negative electrode active material for a battery well-known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0165] In some embodiments, the negative electrode film layer may also optionally include a binder. The binder can 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).

[0166] In some embodiments, the negative electrode film layer may also optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the negative electrode film layer may also optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0168] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet described above, 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 processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0169] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. There is no specific limitation on the type of the electrolyte in this application, and it can be selected according to requirements.

[0170] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0171] In some embodiments, the electrolyte salt can 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 difluorooxalate borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluorooxalate phosphate.

[0172] 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, methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0173] In some embodiments, the electrolytic solution may further optionally include additives. For example, the additives can include negative electrode film - forming additives, positive electrode film - forming additives, and can also include additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high - temperature or low - temperature performance of the battery, etc.

[0174] In some embodiments, the secondary battery further includes a separator. There is no particular limitation on the type of the separator in this application, and any well - known porous - structure separator with good chemical stability and mechanical stability can be selected.

[0175] 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.

[0176] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0177] In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0178] In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the secondary battery may also be a soft package, such as a pouch soft package. The material of the soft package may be plastic, and examples of the plastic may include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0179] The present application has no particular limitation on the shape of the secondary battery, and it may be cylindrical, square, or any other arbitrary shape. For example, Figure 4 is a secondary battery 5 with a square structure as an example.

[0180] In some embodiments, referring to Figure 5 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to specific actual needs.

[0181] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0182] Figure 6 is a battery module 4 as an example. Referring to Figure 6 , in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other arbitrary manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0183] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of secondary batteries 5 are received in the receiving space.

[0184] In some embodiments, the above-mentioned battery module may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0185] Figure 7 and Figure 8is the battery pack 1 as an example. Refer to Figure 7 and Figure 8 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0186] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include 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, satellites, energy storage systems, etc., but not limited thereto.

[0187] As the electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0188] Figure 9 is the electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or battery module can be adopted.

[0189] Another example of the device can be a mobile phone, tablet computer, laptop, etc. This device usually requires thin and light, and a secondary battery can be used as the power source.

[0190] Embodiment

[0191] Preparation of the lithium supplement electrode

[0192] Mix the positive active material, lithium supplement material, conductive agent (CNT), and binder (PVDF) evenly according to different mass ratios, then add NMP as a solvent, and stir under a vacuum mixer until the system becomes homogeneous to obtain the positive active paste. Coating different positive active pastes evenly on the substrate in sequence, drying and cold pressing to obtain the positive electrode, stacking the positive electrode, separator, and negative electrode in sequence, making the separator in the middle of the positive and negative electrodes to play a role in isolation, and winding to obtain a bare battery cell. Place the bare battery cell in the outer package, inject the electrolyte and encapsulate to obtain the battery cell

[0193] Preparation of the negative electrode

[0194] The active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed evenly in a deionized water solvent system according to a certain weight ratio (such as 96.5:0.7:1.8:1), and then coated on a current collector (such as copper foil), dried, and cold-pressed to obtain a negative electrode sheet.

[0195] Example 1

[0196] The lithium supplement electrode sheet including two active layers

[0197] The formulation of the A-layer active layer is 97% (98% LFP + 2% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0198] The formulation of the B-layer active layer is 97% (93% LFP + 7% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0199] In the lithium supplement electrode sheet, the mass of LFP is m, the mass of Li2C2O4 is n, and the total concentration of the self-sacrificing lithium salt x% = n / (m + n) * 100% = 4.5%. The concentration of the self-sacrificing lithium salt in the A-layer active layer is 2%, and the concentration of the self-sacrificing lithium salt in the B-layer active layer is 7%.

[0200] Example 2

[0201] The lithium supplement electrode sheet including three active layers

[0202] The formulation of the A-layer active layer is 97% (98% LFP + 2% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0203] The formulation of the B-layer active layer is 97% (93% LFP + 5% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0204] The formulation of the C-layer active layer is 97% (93% LFP + 7% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0205] In the lithium supplement electrode sheet, the mass of LFP is m, the mass of Li2C2O4 is n, and the total concentration of the self-sacrificing lithium salt x% = n / (m + n) * 100% = 4.7%. The concentration of the self-sacrificing lithium salt in the A-layer active layer is 2%, the concentration of the self-sacrificing lithium salt in the B-layer active layer is 5%, and the concentration of the self-sacrificing lithium salt in the C-layer active layer is 7%.

[0206] Example 3

[0207] The lithium supplement electrode sheet including three active layers

[0208] The formulation of the active layer of Layer A is 97% (98% LFP + 2% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0209] The formulation of the active layer of Layer B is 97% (93% LFP + 6% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0210] The formulation of the active layer of Layer C is 97% (93% LFP + 7% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0211] In the lithium - supplementing electrode, the mass of LFP is m, the mass of Li2C2O4 is n, and the total concentration of the self - sacrificial lithium salt x% = n / (m + n) * 100% = 5%. The concentration of the self - sacrificial lithium salt in the layer of the active layer of Layer A is 2%, the concentration of the self - sacrificial lithium salt in the layer of the active layer of Layer B is 6%, and the concentration of the self - sacrificial lithium salt in the layer of the active layer of Layer C is 7%.

[0212] Example 4

[0213] Lithium - supplementing electrode including two active layers

[0214] The formulation of the active layer of Layer A is 97% (98% LFP + 2% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0215] The formulation of the active layer of Layer B is 97% (93% LFP + 5% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0216] In the lithium - supplementing electrode, the mass of LFP is m, the mass of Li2C2O4 is n, and the total concentration of the self - sacrificial lithium salt x% = n / (m + n) * 100% = 3.5%. The concentration of the self - sacrificial lithium salt in the layer of the active layer of Layer A is 2%, and the concentration of the self - sacrificial lithium salt in the layer of the active layer of Layer B is 5%.

[0217] Example 5

[0218] Lithium - supplementing electrode including two active layers

[0219] The formulation of the active layer of Layer A is 97% (95% LFP + 5% Li2S) + 0.8% CNT + 2.2% PVDF;

[0220] The formulation of the active layer of Layer B is 97% (95% LFP + 5% Li2C2O4) + 0.8% CNT + 2.2% PVDF;

[0221] In the lithium - supplementing electrode sheet, the mass of LFP is m, the mass of Li2C2O is n1, the mass of Li2S is n2, and the total concentration x% of the self - sacrificial lithium salt = (n1 + n2) / (m + n1 + n2)*100% = 5%. The concentration of the self - sacrificial lithium salt in the layer of the A - layer active layer is 5%, and the concentration of the self - sacrificial lithium salt in the layer of the B - layer active layer is 5%.

[0222] Example 6

[0223] Lithium - supplementing electrode sheet including two active layers

[0224] The formula of the A - layer active layer: 97% (99.5% LFP + 0.5% Li2C2O4)+0.8% CNT + 2.2% PVDF;

[0225] The formula of the B - layer active layer: 97% (96.5% LFP + 3.5% Li2C2O4)+0.8% CNT + 2.2% PVDF;

[0226] In the lithium - supplementing electrode sheet, the mass of LFP is m, the mass of Li2C2O4 is n, the total concentration x% of the self - sacrificial lithium salt = n / (m + n)*100% = 2%. The concentration of the self - sacrificial lithium salt in the layer of the A - layer active layer is 0.5%, and the concentration of the self - sacrificial lithium salt in the layer of the B - layer active layer is 3.5%.

[0227] Example 7

[0228] Lithium - supplementing electrode sheet including two active layers

[0229] The formula of the A - layer active layer: 97% (92% LFP + 8% Li2C2O4)+0.8% CNT + 2.2% PVDF;

[0230] The formula of the B - layer active layer: 97% (88% LFP + 12% Li2C2O4)+0.8% CNT + 2.2% PVDF;

[0231] In the lithium - supplementing electrode sheet, the mass of LFP is m, the mass of Li2C2O4 is n, the total concentration x% of the self - sacrificial lithium salt = n / (m + n)*100% = 10%. The concentration of the self - sacrificial lithium salt in the layer of the A - layer active layer is 8%, and the concentration of the self - sacrificial lithium salt in the layer of the B - layer active layer is 12%.

[0232] Comparative Example 1

[0233] Lithium - supplementing electrode sheet including one active layer

[0234] The formula of the A - layer active layer: 97% (95% LFP + 5% Li2C2O4)+0.8% CNT + 2.2% PVDF;

[0235] In the lithium - supplemented electrode, the mass of LFP is m, the mass of Li2C2O4 is n, and the total concentration x% of the self - sacrificial lithium salt = n / (m + n)*100% = 5%.

[0236] Comparative Example 2

[0237] An electrode without a lithium - supplementing agent

[0238] The formulation of the active layer in Layer A: 97% LFP + 0.8% CNT + 2.2% PVDF.

[0239] Comparative Example 3

[0240] A lithium - supplemented electrode including one layer of active layer

[0241] The formulation of the active layer in Layer A

[0242] 97% (95% LFP + 3% Li2C2O4 + 2% Li2S) + 0.8% CNT + 2.2% PVDF;

[0243] In the lithium - supplemented electrode, the mass of LFP is m, the mass of Li2C2O4 is n1, the mass of Li2S is n2, and the total concentration x% of the self - sacrificial lithium salt = (n1 + n2) / (m + n1 + n2)*100% = 5%.

[0244] Table 1 List of parameters of each example

[0245]

[0246] Table 2 List of parameters of each example

[0247]

[0248] Table 3 List of parameters of each example

[0249]

[0250] Performance test

[0251] 1. Rate performance test

[0252] At 25°C, when discharging at x C to the discharge cut - off voltage with a capacity of Cx, the ratio of C2 / C0.33 can be compared with C0.33 as the base to measure the degree of rate improvement.

[0253] 2. Evaluation test of the electrolyte infiltration effect

[0254] Charge the battery (D0) to a certain voltage so that the lithium supplement material can exert its capacity, while leaving permanent voids in the electrode sheet. Then discharge the battery to the initial state (D1). After disassembling the batteries in states D0 and D1, evaporate the electrolyte in the electrode sheet, replace it with a new separator, and reassemble them into batteries E0 and E1 respectively. Test the electrolyte infiltration rates V0 and V1 of E0 and E1. In this experiment, the battery state is 3.0V.

[0255] Electrolyte infiltration rate test method: There is a liquid injection hole at the top of the battery cell, and a liquid injection cup is connected to the hole. A sufficient amount of electrolyte (100g in this experiment) is placed in the cup. After a certain time T (T = 1h in this experiment), remove the liquid injection cup, and weigh the reduction amount ▲m of the electrolyte in the liquid injection cup. The infiltration rate v = ▲m / T.

[0256] 3. Cycling performance improvement test

[0257] (1) At 45°C, charge the lithium-ion battery at a constant current of 1 / 3C to 3.65V, then charge it at a constant voltage of 3.65V until the current is 0.05C, let it stand for 5 minutes, and then discharge it at a constant current of 1 / 3C to 2.5V and record the discharge capacity C0.

[0258] (2) Then charge the lithium-ion battery at a constant current of 1.0C to 3.65V, let it stand for 5 minutes, and then discharge it at a constant current of 1 / 3C to 2.5V and record the discharge capacity C1.

[0259] Repeat the above step (2) 200 times, and record the discharge capacity C200 of the lithium-ion battery after the 200th cycle. The capacity retention rate P200 = C200 / C0 × 100%

[0260] 4. Test for improving the capacity utilization of the lithium supplement material

[0261] At 25°C, compare the capacity C@4.5V when the battery cell is first charged to the upper limit voltage (4.5V as follows) (control the mass of the positive active material and the positive lithium supplement material in the battery cells of different embodiments to be the same. If not, the specific capacity needs to be calculated). At the same time, the better the capacity utilization of the lithium supplement material, the better the cycling improvement will be.

[0262] Table 4 Performance parameter table of each embodiment and comparative example

[0263]

[0264] Table 1-3 shows the parameters of each example and comparative example, and Table 4 shows the performance parameter tables of each example and comparative example. It can be seen from Table 4 that Examples 1, 4, 5, 6, and 7 are two-layer active layer structures. It can be seen that as the total concentration X% of the self-sacrificing lithium salt decreases, the capacity retention rate and the capacity performance of the lithium supplement material decrease. Therefore, while maintaining a concentration gradient of the self-sacrificing lithium salt in each layer, it is still necessary to keep the total concentration of the self-sacrificing lithium salt within a certain range. It can be understood that too little lithium supplement agent results in a small improvement in cycling. Therefore, the total concentration x% of the self-sacrificing lithium salt is not less than 2%; at the same time, too much lithium supplement agent, and generally the lithium supplement agent has poor conductivity. Although it brings more pores and is beneficial to the infiltration of the electrolyte, the electronic conductivity of the electrode sheet becomes worse, the rate performance of the electrode sheet becomes worse, resulting in limited capacity performance and even no improvement or deterioration in cycling. Therefore, the total concentration x% of the sacrificial lithium salt does not exceed 10%.

[0265] Comparative Example 3 is a lithium supplement electrode sheet including one active layer. Compared with Example 5, under the same total concentration of the self-sacrificing lithium salt, the performance of the layered lithium supplement electrode sheet is better than that of the single-layer lithium supplement electrode sheet. For example, the capacity retention rate and the capacity performance of the lithium supplement material of Example 5 are higher than those of Comparative Example 3.

[0266] Examples 2 and 3 are lithium supplement electrode sheets including three active layers. Compared with Example 5, the more the number of layers, the higher the electrolyte infiltration rate and the better the rate performance.

[0267] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural transformations made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied to other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A lithium supplement electrode, characterized in that, The lithium supplement electrode includes a current collector and a coating area provided on at least one side of the current collector. The coating area includes at least two active layers, and the at least two active layers include a pore former. Define two adjacent active layers including a pore former as a first active layer and a second active layer respectively. The first active layer is provided on the current collector, and the second active layer is provided on a side of the first active layer away from the current collector. The porosity of the second active layer is greater than the porosity of the first active layer. Define the porosity of each active layer as n. The porosity of each active layer = (pore volume in each active layer ÷ volume of each active layer) × 100%. The porosity of the second active layer is n(i + 1), where i ≥ 1, and the porosity of the first active layer is n(i). Then n(i + 1) - n(i) = b, where 2% ≤ b ≤ 8%, and the range value of the porosity of the first active layer is 20% - 25%.

2. The lithium - supplementing electrode sheet according to claim 1, wherein, The porosity formed by the pore former in the second active layer is greater than the porosity formed by the pore former in the first active layer.

3. The lithium supplement electrode sheet according to claim 1, wherein, The pore former includes a self-sacrificial lithium salt.

4. The lithium supplement electrode sheet according to claim 3, wherein, The volume change value before and after the reaction of the self-sacrificial lithium salt in the second active layer is greater than the volume change value before and after the reaction of the self-sacrificial lithium salt in the first active layer.

5. The lithium supplement electrode sheet according to claim 4, characterized in that, When at least one type of self-sacrificial lithium salt in the second active layer is different from at least one type of self-sacrificial lithium salt in the first active layer, the concentration of the self-sacrificial lithium salt in the second active layer is greater than or equal to the concentration of the self-sacrificial lithium salt in the first active layer.

6. The lithium supplement electrode sheet according to claim 4, wherein, When the self-sacrificial lithium salt in the second active layer is the same as the self-sacrificial lithium salt in the first active layer, the concentration of the self-sacrificial lithium salt in the second active layer is greater than the concentration of the self-sacrificial lithium salt in the first active layer.

7. The lithium supplement electrode sheet according to claim 3, characterized in that, Among the at least two active layers, define the total concentration of the self-sacrificial lithium salt as x%. The total concentration of the self-sacrificial lithium salt = (mass of all self-sacrificial lithium salts in each active layer ÷ sum of the mass of all active substances and all self-sacrificial lithium salts in each active layer) × 100%. The range value of the total concentration x% of the self-sacrificial lithium salt is 2% - 10%.

8. The lithium supplement electrode sheet according to claim 7, wherein Define the in-layer concentration of the self-sacrificial lithium salt as yi. The in-layer concentration of the self-sacrificial lithium salt = (mass of the self-sacrificial lithium salt in each active layer ÷ sum of the mass of the active substance and the self-sacrificial lithium salt in each active layer) × 100%. The in-layer concentration of the self-sacrificial lithium salt in the second active layer is y(i + 1), where i ≥ 1, and the in-layer concentration of the self-sacrificial lithium salt in the first active layer is y(i). Then y(i + 1) - y(i) = a, where 1% ≤ a ≤ 4%.

9. The lithium supplement electrode sheet according to claim 7, wherein, Define that the at least two active layers are arranged in sequence from the side close to the current collector to the side away from the current collector as the first active layer and the second active layer. The range value of the in-layer concentration y1 of the self-sacrificial lithium salt in the first active layer is (x - 2)% - (x - 0.5)%.

10. The lithium supplement electrode sheet according to claim 9, characterized in that, The range value of the in-layer concentration y1 of the self-sacrificial lithium salt in the first active layer is 2% - 5%. And / or, the range value of the in-layer concentration y2 of the self-sacrificial lithium salt in the second active layer is 5% - 7%. And / or, it is defined that a first active layer, a second active layer, and a third active layer are sequentially arranged in a direction from near the current collector to far from the current collector, and the range value of the layer concentration y3 of the self-sacrificing lithium salt in the third active layer is 7%-10%.

11. The lithium supplement electrode sheet according to claim 1, wherein, Among the at least two active layers, the total porosity of the active layer is defined as p, and the total porosity of the active layer = (the total pore volume in each active layer ÷ the sum of the volumes of each active layer) × 100%. The range value of the total porosity p of the active layer is 20%-30%.

12. The lithium supplement electrode sheet according to claim 3, wherein, The self-sacrificial lithium salt includes at least one of Li2C2O4, Li2M1O2, Li2M2O3, Li5Fe x M3 (1-x) O4 and Li6Mn y M4 (1-y) O4; wherein, M1 includes at least one of Ni, Mn, Cu, Fe, Cr and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru and Cr, and M4 includes at least one of Ni, Fe, Cu and Ru.

13. The lithium supplement electrode sheet according to claim 1, characterized in that, The structural general formula of the positive electrode material in the at least two active layers is LiMn x Fe y M 1-x-y PO4, where 0 ≤ x ≤ 0.8; 0.1 ≤ y ≤ 0.6; 0 ≤ 1 - x - y ≤ 0.2, and M represents a doping element; and / or, the structural general formula of the positive electrode material is LiNi a Co b N (1-a-b) O2, where 0.35 ≤ a < 1.0, 0 ≤ b ≤ 0.35, and 0 ≤ 1 - a - b ≤ 0.

35.

14. The lithium supplement electrode sheet according to claim 13, characterized in that, M includes at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge.

15. The lithium supplement electrode sheet according to claim 13, wherein, N includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La.

16. The lithium supplement electrode sheet according to claim 1, wherein, The cathode active materials in the at least two active layers are the same.

17. The lithium supplement electrode sheet according to claim 16, wherein, The active layer of the lithium supplement electrode sheet further includes a conductive agent and a binder. The conductive agent includes at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. The binder includes at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene.

18. A battery, characterized in that, Comprising: A negative electrode sheet, a positive electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet is the lithium supplement electrode sheet according to any one of claims 1 to 17.

19. An electrical device, characterized in that, The electrical device includes the battery according to claim 18.

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