CN117239104B

CN117239104B - Lithium supplementing additive, positive pole piece, battery and electricity utilization device

Info

Publication number: CN117239104B
Application number: CN202311504784.7A
Authority: CN
Inventors: 吴凯; 谢浩添; 张楠楠; 景二东; 刘桓基; 林逵; 陈晓; 孙信
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-11-13
Filing date: 2023-11-13
Publication date: 2024-03-29
Anticipated expiration: 2043-11-13
Also published as: CN117239104A

Abstract

The application discloses benefit lithium additive, positive pole piece, battery, power consumption device, benefit lithium additive includes: a first lithium supplementing agent comprising a first core satisfying the chemical formula Li _a M _b O _c Wherein a is 1.5-6, b is 0-2, c is 1-6, and M comprises at least one of magnesium element, calcium element, vanadium element, chromium element, manganese element, iron element, cobalt element, nickel element, copper element, zinc element, niobium element, molybdenum element, ruthenium element, tin element, silicon element, carbon element, and boron element; a second lithium supplementing agent comprising a second core satisfying the chemical formula Li _d C _e O _f D is 1.5-6,e and 3-5, f is 1.5-6, and the mass fraction of the first lithium supplementing agent in the lithium supplementing additive is m ₁ The mass fraction of the second lithium supplementing agent in the lithium supplementing additive is m ₂ ，m ₁ :m ₂ Less than or equal to (10:1). Therefore, particle agglomeration of the lithium supplementing additive can be reduced, poor processing such as slurry gel is caused, and the lithium supplementing effect of the lithium supplementing additive can be improved.

Description

Lithium supplementing additive, positive pole piece, battery and electricity utilization device

Technical Field

The application relates to the technical field of batteries, in particular to a lithium supplementing additive, a positive pole piece, a battery and an electric device.

Background

Lithium ion batteries are widely used in portable electronic devices, electric vehicles and energy storage systems because of their high energy density, long cycle life, good rate capability and other advantages. How to further increase the energy density and cycle life of lithium ion batteries has also become a research hotspot in the battery field. Lithium depletion is a direct cause of battery degradation. For example, during the first charge and discharge of a battery, an electrolyte solution forms a solid electrolyte interface film (SEI film) on the surface of the negative electrode, and the formation of the SEI film consumes a large amount of active lithium ions, thereby resulting in low coulombic efficiency of the first cycle of the battery. In the charge-discharge cycle process of the battery, active lithium ions are consumed by cracking and crushing of positive electrode active material particles, thickening and repairing of SEI films and the like, so that the cycle performance of the battery is obviously reduced. The first-cycle efficiency, energy density and cycle life of the lithium battery can be improved by adding the lithium supplementing additive. However, the current lithium supplement additive is in an early development stage, and has a plurality of defects in production and application aspects.

It should be noted that the foregoing statements are merely to provide background information related to the present application and may not necessarily constitute prior art.

Disclosure of Invention

In a first aspect of the present application, the present application proposes a lithium supplementing additive comprising: a first lithium supplementing agent comprising a first core satisfying the chemical formula Li _a M _b O _c Wherein a is 1.5-6, b is 0-2, c is 1-6, M element comprises magnesium element, calcium element, vanadium element, chromium element, manganese element, ferrum element, cobalt element, nickel element, copper element, zinc element, niobium element, molybdenum element, ruthenium element, tin element, silicon element, and carbon elementAt least one of boron elements; a second lithium supplementing agent comprising a second core satisfying the chemical formula Li _d C _e O _f D is 1.5-6,e and f is 1.5-6, and the mass fraction of the first lithium supplementing agent in the lithium supplementing additive is m ₁ The mass fraction of the second lithium supplementing agent in the lithium supplementing additive is m ₂ ，m ₁ :m ₂ Less than or equal to (10:1). Therefore, the agglomeration of particles of the lithium supplementing additive can be reduced, poor processing such as slurry gel is caused, and the lithium supplementing effect of the lithium supplementing additive can be improved.

In some embodiments, the mass fraction of carbon element in the first lithium-supplementing agent is k ₁ The mass fraction of lithium element in the first lithium supplementing agent is q ₁ ，k ₁ /q ₁ 0-2. Thus, the lithium supplementing effect of the lithium supplementing additive can be further improved.

In some embodiments, the mass fraction of carbon element in the second lithium-supplementing agent is k ₂ The mass fraction of lithium element in the second lithium supplementing agent is q ₂ ，k ₂ /q ₂ Greater than or equal to 2.5. Therefore, particle agglomeration of the lithium supplementing additive can be reduced, poor processing such as slurry gel is caused, and the lithium supplementing effect of the lithium supplementing additive can be improved. Thus, the lithium supplementing effect of the lithium supplementing additive can be further improved.

In some embodiments, the first lithium-compensating agent includes a first core and a first cladding layer covering at least a portion of a surface of the first core, the first cladding layer including at least one of a metal fluoride, a metal oxide, a metal phosphate, a ternary lithium salt, a carbon material, poly 3, 4-ethylenedioxythiophene, polypyrrole. Thereby, the basicity of the first lithium-supplementing agent can be reduced.

In some embodiments, the second lithium-compensating agent includes a porous carbon support and a second core located within the pore structure of the porous carbon support. Thereby, the conductivity of the second lithium-supplementing agent can be improved.

In some embodiments, the first lithium-compensating agent has a particle size greater than a particle size of the second lithium-compensating agent, and at least a portion of the surface of the first core has a second coating layer comprising the second lithium-compensating agent. Thus, the process for producing the first lithium-supplementing agent can be simplified, and the basicity of the first lithium-supplementing agent can be reduced.

In some embodiments, k ₁ 0% -30%, q ₁ 7% -70%. Thus, the first lithium supplementing agent has higher lithium supplementing gram capacity.

In some embodiments, k ₂ 15% -70%, q ₂ 8% -20%. Thus, the second lithium supplementing agent has both higher conductivity and lower alkalinity.

In some embodiments, the first core satisfies at least one of the following conditions: when a is 2 and c is 2, M comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu; when a is 2 and c is 3, M comprises at least one of Si, ni, co, fe, mn, sn, cr; when a is 2 and c is 4, M comprises at least one of C, fe, mn, cr, nb; when a is 3 and c is 4, M comprises at least one of Co, fe, mn, cr, V, mo, nb; when a is 5 and c is 4, M comprises at least one of Ni, co, fe, mn, cr, mo; when a is 6 and c is 4, M comprises at least one of Ni, co, mn, fe, cu, ru. Thus, the lithium-compensating gram capacity of the first lithium-compensating agent can be further improved.

In some embodiments, the second core comprises Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₄ O ₆ At least one of them. Thereby, the basicity of the second lithium-supplementing agent can be further reduced.

In some embodiments, the first lithium supplement has a Dv50 particle size d ₁ The Dv50 particle size of the second lithium supplementing agent is d ₂ ，d ₁ /d ₂ Greater than or equal to 2. Therefore, the porosity of the positive electrode plate can be improved by adding the lithium supplementing additive, and the infiltration effect of the electrolyte on the positive electrode plate is improved.

In a second aspect of the present application, the present application proposes a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material and a lithium supplementing additive comprising the aforementioned lithium supplementing additive. Therefore, the positive electrode plate has all the characteristics and advantages of the lithium supplementing additive and is not described herein.

In some embodiments, the mass fraction of the lithium supplementing additive in the positive electrode active material layer is 0.1% -10%. Therefore, the energy density and electrolyte wettability of the positive electrode plate can be improved.

In some embodiments, the positive electrode active material layer further includes a binder including at least one of polyvinylidene fluoride, sodium alginate, polyvinyl alcohol, polymethyl methacrylate, hydrogenated nitrile rubber, polytetrafluoroethylene, and polyacrylic acid. Thereby, the adhesion effect between the positive electrode active material layer and the positive electrode current collector can be improved.

In a third aspect of the present application, a battery is provided that includes the aforementioned positive electrode tab. Therefore, the battery has all the characteristics and advantages of the positive electrode plate, and the details are not repeated here.

In a fourth aspect of the present application, the present application proposes an electrical device comprising the aforementioned battery. Therefore, the power utilization device has all the characteristics and advantages of the battery and is not described in detail herein.

Drawings

The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a battery cell according to an embodiment of the present application;

fig. 2 is an exploded view of a battery cell according to an embodiment of the present application shown in fig. 1;

FIG. 3 is a schematic view of a battery module according to an embodiment of the present application;

FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application;

FIG. 5 is an exploded view of the battery pack of one embodiment of the present application shown in FIG. 4;

fig. 6 is a schematic diagram of an electrical device in which a battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5, a battery cell;

51 a housing; 52 electrode assembly; 53 top cap assembly.

Detailed Description

Embodiments of the lithium supplement additive, the method for producing the same, the positive electrode sheet, the battery, and the electric device of the present application are specifically disclosed below in detail with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers 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 listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; unless otherwise indicated, the numerical values of the parameters set forth in this application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of this application).

In the description of the present application, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The "first feature" and "second feature" may include one or more of the features.

In the description of the present application, the meaning of "plurality" is two or more.

In the description of the present application, "a and/or B" may include any of the cases of a alone, B alone, a and B, wherein A, B is merely for example, which may be any technical feature of the present application using "and/or" connection.

On the one hand, the lithium supplementing agent can supplement active lithium ion loss caused when SEI is formed in the first charge and discharge process, so that the battery has enough reversible active lithium ions in the subsequent cycle process, and the energy density of the battery is improved; on the other hand, the lithium supplementing agent can also be used for compensating lithium consumption in the cycling process and improving the cycling performance of the battery. The positive electrode lithium-supplementing agent and the negative electrode lithium-supplementing agent can be classified according to the position of action of the lithium-supplementing agent in the battery. The positive electrode lithium supplementing agent can form positive electrode slurry together with a positive electrode active material, a binder and the like, and then is coated on the surface of a positive electrode current collector to form a positive electrode active material layer. The lithium supplementing agent releases lithium ions in the first charging process of the battery, and supplements active lithium ion loss caused by SEI and other phenomena. In order to improve the lithium supplementing effect, a lithium-rich material with higher lithium ion content is generally used as a lithium supplementing additive.

The lithium-rich material has stronger alkalinity, and when the lithium-rich material is excessively strong in alkalinity, the lithium-rich material reacts with an acidic binder, for example, when the binder polyvinylidene fluoride (PVDF) is taken as an example, and when the PVDF is mixed with the lithium-supplementing agent, the strong-alkalinity lithium-supplementing agent can attack carbon-carbon bonds of the PVDF, so that the PVDF is decomposed and hydrogen fluoride molecules are removed, the chemical gel defect of the positive electrode slurry is caused, the binding force between the positive electrode active material layer and the positive electrode current collector is reduced, and the problems that the positive electrode active material layer is easily peeled off from the surface of the positive electrode current collector and the like are solved.

In the application, the first alkaline lithium supplementing agent and the second acidic lithium supplementing agent are mixed, the composite lithium supplementing additive is slightly alkaline, and when the mixed lithium supplementing additive is mixed with the acidic binder, the alkaline of the lithium supplementing additive is weak, so that the damage to the acidic binder is less, the occurrence of poor chemical gel of the positive electrode slurry is reduced, and the processing performance of the positive electrode slurry is effectively improved; meanwhile, the lithium supplementing additive can better exert the lithium supplementing performance and improve the cycle performance of the battery.

In a first aspect of the present application, the present application proposes a lithium supplementing additive comprising: a first lithium supplementing agent comprising a first core, the first core satisfying the chemical formula Li _a M _b O _c Wherein a is 1.5-6, B is 0-2, C is 1-6, M element comprises at least one of magnesium element (Mg), calcium element (Ca), vanadium element (V), chromium element (Cr), manganese element (Mn), iron element (Fe), cobalt element (Co), nickel element (Ni), copper element (Cu), zinc element (Zn), niobium element (Nb), molybdenum element (Mo), ruthenium element (Ru), tin element (Sn), silicon element (Si), carbon element (C), boron element (B), and the average valence state of M element in the first core is less than or equal to Equal to the highest oxidation state of the M element.

As examples, a may be 1.5, 2, 3, 4, 5 or 6.

As examples, b may be 0, 1 or 2.

When b is 0, the first core is a binary lithium-containing compound, which may include, as an example, li ₂ O、Li ₂ O ₂ 。

As examples, c may be 1, 2, 3, 4, 5, or 6.

The lithium supplementing gram capacity of the lithium supplementing additive can be effectively improved by adding the first lithium supplementing agent.

As an example, the first core may include Li ₂ C ₂ O ₄ 、Li ₂ CO ₃ 、Li ₂ SiO ₃ Or Li (lithium) ₃ BO ₃ 。

In the above chemical formulas, when M is two or more elements, the above definition of the numerical range of b is not only a definition of the stoichiometric number of each element as M but also a definition of the sum of the stoichiometric numbers of the elements as M, unless otherwise specified. For example, when M includes two or more elements M1, M2, M3 … … Mn, the respective stoichiometric numbers b1, b2, b3 … … bn of M1, M2, M3 … … Mn each need to fall within the numerical range defined for b in the present application, and the sum of b1, b2, b3 … … bn also needs to fall within the numerical range.

In some embodiments, the first core satisfies at least one of the following conditions: when a is 2 and c is 2, M comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu; when a is 2 and c is 3, M comprises at least one of Si, ni, co, fe, mn, sn, cr; when a is 2 and C is 4, M comprises at least one of C (carbon element) and Fe, mn, cr, nb; when a is 3 and c is 4, M comprises at least one of Co, fe, mn, cr, V, mo, nb; when a is 5 and c is 4, M comprises at least one of Ni, co, fe, mn, cr, mo; when a is 6 and c is 4, M comprises at least one of Ni, co, mn, fe, cu, ru. Thus, the lithium-compensating gram capacity of the first lithium-compensating agent can be further improved. When the first core meets at least one of the chemical formulas, the first core contains two or more lithium ions, has higher irreversible capacity and better stability in air. Through the collocation of different elements, the decomposition potential of the inner core can be regulated and controlled, which is beneficial to better release of active lithium ions.

It is understood that when the M element includes a metal element, li _a M _b O _c The M element in the lithium supplementing agent is not completely in the highest oxidation valence state, namely the average valence state is smaller than the highest oxidation valence state, so that the lithium supplementing agent can release lithium ions through the valence change of the M element.

It will be appreciated that the above description of the first core is merely exemplary, and that the person skilled in the art may adapt the composition of the substances of the first core to the actual situation, e.g. the first core may be made of LiMn ₂ O ₄ With Li ₂ MnO ₃ Obtained by blending in any proportion, or the first core may also be, for example, li ₄ Ti ₅ O ₁₂ And the lithium-rich material with special structure.

In some embodiments, the second core satisfies the formula Li _d C _e O _f (C is carbon element), d is 1.5-6,e is 3-5, and f is 1.5-6.

As examples, d may be 1.5, 2, 3, 4, 5 or 6.

As examples, e may be 3, 4 or 5.

As examples, f may be 1.5, 2, 3, 4, 5, or 6.

The alkalinity of the first lithium-supplementing agent can be effectively reduced by blending the second lithium-supplementing agent with the first lithium-supplementing agent.

In some embodiments, the first and second lithium-supplementing agents may be added to the positive electrode slurry separately and blended in the positive electrode slurry, or the first and second lithium-supplementing agents may be pre-blended and then added to the positive electrode slurry together.

In some embodiments, the second core may include Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₄ O ₆ At least one of them.

The lithium supplementing agent is Li _x C _y O _z For example, based on the acid-base proton theory, lithium belongs to alkali metal, lithium oxalate is strong alkali weak acid salt and is alkaline; when Li _x C _y O _z The acidity of the lithium-supplementing agent increases when the proportion of medium carbon increases, and when Li _x C _y O _z When the proportion of the lithium is increased, the alkalinity of the lithium supplementing agent is enhanced. From this, it is known that, as the mass fraction of lithium increases, the lithium supplementing gram capacity of the lithium supplementing agent increases, and the alkalinity of the lithium supplementing agent increases at the same time; accordingly, as the mass fraction of carbon increases, the basicity of the lithium-compensating agent decreases correspondingly, while the lithium-compensating gram capacity of the lithium-compensating agent decreases correspondingly. Therefore, the capacity of the lithium supplementing gram of the lithium supplementing additive can be improved and the lithium supplementing effect can be improved by adding the first lithium supplementing agent with higher lithium mass fraction; the acid-base property of the lithium supplement additive can be improved by adding the second lithium supplement agent with higher carbon mass fraction, so that the lithium supplement additive is slightly alkaline, and the defects of anode slurry gel and the like caused by over-strong alkalinity of the lithium supplement additive are reduced. By using the first lithium supplementing agent and the second lithium supplementing agent together as the lithium supplementing additive, the lithium supplementing effect of the lithium supplementing additive can be improved, and the processing performance of the positive electrode slurry containing the lithium supplementing additive can be improved.

In some embodiments, the mass fraction of carbon element in the first lithium-supplementing agent is k ₁ The mass fraction of lithium element in the first lithium supplementing agent is q ₁ ，k ₁ /q ₁ 0-2; a second lithium supplementing agent, wherein the mass fraction of carbon element in the second lithium supplementing agent is k ₂ The mass fraction of the lithium element in the second lithium supplementing agent is q ₂ ，k ₂ /q ₂ Greater than or equal to 2.5.

As an example, k ₁ /q ₁ May be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 1.9 or 2.

As an example, k ₂ /q ₂ May be 2.5-12. Specifically, k ₂ /q ₂ May be 2.5, 2.8, 3.0, 3.2, 3.5, 3.8, 4.0, 4.2, 4.5, 4.8, 5.0, 5.2, 5.5, 5.8, 6.0, 6.2, 6.5, 6.8, 7.0, 7.2, 7.5, 7.8, 8.0,8.2, 8.5, 8.8, 9.0, 9.2, 9.5, 9.8, 10.0, 10.2, 10.5, 10.8, 11.0, 11.2, 11.5, 11.8 or 12.0.

In some embodiments, the first lithium-compensating agent includes a first core and a first cladding layer covering at least a portion of a surface of the first core, the first cladding layer including at least one of a metal fluoride, a metal oxide, a metal phosphate, a ternary lithium salt, a carbon material, poly 3, 4-ethylenedioxythiophene, polypyrrole.

As an example, the metal fluoride may include AlF ₃ The method comprises the steps of carrying out a first treatment on the surface of the The metal oxide may include V ₂ O ₅ 、Al ₂ O ₃ 、ZrO ₂ 、TiO ₂ 、ZnO、Co ₃ O ₄ 、SiO ₂ At least one of (a) and (b); the metal phosphate may comprise AlPO ₄ 、FePO4、Co ₃ (PO ₄ ) ₂ 、Ni ₃ (PO ₄ ) ₂ At least one of (a) and (b); the ternary lithium salt may include Li ₃ PO ₄ 、Li ₂ MnO ₃ 、LiAlO ₂ 、Li ₂ TiO ₃ 、Li ₂ ZrO ₃ At least one of (a) and (b); the carbon material may include at least one of graphene and carbon nanotubes.

In some embodiments, the first cladding layer may include a first sub-cladding layer and a second sub-cladding layer disposed in a stack, wherein the first sub-cladding layer is disposed on a side proximate to the first inner core, and the first sub-cladding layer may include Al ₂ O ₃ 、Li ₃ PO ₄ The second sub-coating layer may include at least one of polyethylene glycol modified poly 3, 4-ethylenedioxythiophene, polypyrrole, and a carbon material.

As an example, the first sub-cladding layer is Al ₂ O ₃ When the second sub-coating layer is polyethylene glycol modified poly (3, 4-ethylenedioxythiophene); the first sub-coating layer is Li ₃ PO ₄ In this case, the second subcoating layer is polypyrrole.

When the first coating layer includes a carbon material, the conductive performance of the first lithium-compensating agent may be effectively improved.

Taking lithium oxalate as an example, although in lithium oxalateIs sp as carbon atom ² The carbon atoms in the lithium oxalate need to be connected with one carbon atom and two oxygen atoms, so that electron cloud density near the carbon atoms is low, conductivity is poor, and decomposition potential is high, therefore, a coating layer needs to be formed on the surface of the first inner core, ion conductivity, electron conductivity and the like of the first inner core can be improved through the arrangement of the first coating layer, and further lithium ion release capacity of the first lithium supplementing agent is improved, alkaline substances such as lithium oxide and the like remained on the surface of the first inner core can be removed, and the problems of water absorption of the first lithium supplementing agent, positive electrode slurry gel in a processing process and the like caused by over-high alkalinity of the first lithium supplementing agent are solved.

In some embodiments, the second lithium-supplementing agent may include a porous carbon support and a second core positioned within the pore structure of the porous carbon support.

As an example, the second core may be recrystallized in the pore structure of the porous carbon support by a liquid phase synthesis method, and thus the second lithium-supplementing agent in which the second core is located in the pore structure of the porous carbon support may be obtained.

The second inner core is arranged in the pore structure of the porous carbon carrier with better electrical conductivity, so that the electrical conductivity of the second lithium supplementing agent can be effectively improved, and the release of the lithium supplementing gram capacity is facilitated.

In some embodiments, the porous carbon support comprises at least one of activated carbon, carbon nanotubes, carbon nitrides, carbon nitride nanotubes.

In some embodiments, the second lithium-supplementing agent may be coated on the surface of the first lithium-supplementing agent, that is, the aforementioned lithium-supplementing additive is obtained by coating. The particle size of the first lithium supplementing agent is larger than that of the second lithium supplementing agent, at least part of the surface of the first inner core is provided with a second coating layer, and the second coating layer comprises the second lithium supplementing agent, namely, the second lithium supplementing agent at least covers part of the surface of the first inner core so as to form the second coating layer.

When the second lithium supplementing agent is arranged on the surface of the first lithium supplementing agent in the form of a coating layer, the first lithium supplementing agent and the second lithium supplementing agent can share the porous carbon carrier of the second lithium supplementing agent so as to improve the conductivity of the first lithium supplementing agent, and further, a carbon material coating layer is not required to be formed on the surface of the first inner core.

In some embodiments, k ₁ 0% -30%, q ₁ 7% -70%.

As an example, k ₁ May be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%.

In some embodiments, k ₁ May be 2% -26%.

By way of example, q ₁ 7%, 8%, 9%, 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, 67% or 70%.

In some embodiments, q ₁ May be 10% -23%.

When k is ₁ And q ₁ Within the above range, the first lithium-supplementing agent can provide a higher lithium-supplementing gram capacity.

In some embodiments, k ₂ 15% -70%, q ₂ 8% -20%.

As an example, k ₂ May be 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, 67% or 70%.

In some embodiments, k ₂ May be 35% -50%.

By way of example, q ₂ May be 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19% or 20%.

In some embodiments, q ₂ May be 8% -15%.

For the lithium supplementing agent, as the mass fraction of lithium increases, the lithium supplementing gram capacity of the lithium supplementing agent correspondingly increases, and meanwhile, the alkalinity of the lithium supplementing agent correspondingly increases; accordingly, as the mass fraction of carbon increases, the basicity of the lithium-compensating agent decreases correspondingly, while the lithium-compensating gram capacity of the lithium-compensating agent decreases correspondingly. When k is ₂ And q ₂ When the amount of the lithium-ion source is within the above range, the second lithium-ion source can effectively alleviate the strong basicity of the first lithium-ion source, so that the acid-basicity of the lithium-ion source additive is weak basicity.

The mass fraction of lithium element in both the first and second lithium-supplementing agents may be tested using methods known in the art. As an example, an inductively coupled plasma emission spectrometer (ICP-OES) can be used for testing, in particular, test conditions: and if the sample to be measured contains solid particles, the solid particles are required to be digested by adding acid or filtered. The range of the element to be measured is required to be within the range of the standard curve, and if the element to be measured exceeds the range, the sample is required to be diluted. The main operation procedure is as follows: 1. testing a standard curve; 2. diluting a sample to be tested; 3. testing the diluted sample; 4. and (5) carrying out data calculation processing to obtain the concentration of the element to be detected.

The mass fraction of carbon element in both the first and second lithium-supplementing agents may be tested using methods known in the art. As an example, an infrared sulfur carbon analyzer can be used for testing, specifically, a sample to be tested is subjected to oxygen combustion in a high-temperature furnace to generate and escape CO ₂ Gas, separation of carbon element and metal element and compound thereof is realized by the method, and then CO is measured ₂ And (3) converting the content of the carbon in the sample to be detected.

In some embodiments, the mass fraction of the first lithium-supplementing agent in the lithium-supplementing additive is m ₁ The mass fraction of the second lithium supplementing agent in the lithium supplementing additive is m ₂ ，m ₁ :m ₂ Less than or equal to (10:1).

As an example, m ₁ :m ₂ May be (1:1), (1.5:1), (2:1), (2.5:1), (3:1), (3.5:1), (4:1), (4.5:1), (5:1), (5.5:1), (6:1), (6.5:1), (7:1), (7.5:1), (8:1), (8.5:1), (9:1), (9.5:1) or (10:1).

In some embodiments, when the first and second lithium-supplementing agents are added directly to the positive electrode slurry, m ₁ :m ₂ May be (5:1) - (10:1), in which case the lithium-compensating additive has both a relatively high lithium-compensating gram capacity and is generally weakly basic, the lithium-compensating additive being relatively binder-specificThe negative effect is less, the gel defect of the positive electrode slurry can be reduced, and the processing performance of the positive electrode slurry is improved.

In some embodiments, when the second lithium-supplementing agent forms a second coating layer on the surface of the first core, m ₁ :m ₂ The content of the lithium-supplementing additive in the positive electrode slurry can be increased, so that the capacity of the lithium-supplementing additive for supplementing lithium which can be released by the lithium-supplementing additive is effectively increased.

In some embodiments, the first lithium supplement has a Dv50 particle size d ₁ The second lithium supplementing agent has a Dv50 particle diameter d ₂ ，d ₁ /d ₂ Greater than or equal to 2.

When d ₁ /d ₂ When the lithium ion battery is more than or equal to 2, the second lithium supplementing agent is coated on the surface of the first lithium supplementing agent to form a second coating layer, so that the formation of the coating layer is facilitated; in addition, the porosity of the positive electrode plate can be improved by adding the lithium supplementing additive, specifically, after lithium ions are released by the lithium supplementing agent in the positive electrode active material layer in the first charging process, a small amount of metal salt is reserved in the rest part, so that a larger gap is formed in a hole structure occupied by the lithium supplementing agent originally; or the hole structure occupied by the lithium supplementing agent is completely vacated due to the decomposition and gas production, so that the porosity of the positive electrode plate is improved.

In some embodiments, d ₁ From 5 μm to 15 μm, and/or d ₂ 1 μm to 5 μm.

As an example, d ₁ May be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm or 15 μm.

As an example, d ₂ May be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm.

When d ₁ From 5 μm to 15 μm, and/or d ₂ At 1 μm to 5 μm, the volume average particle diameter of the lithium-supplementing additive is larger than that of the positive electrode active materialThe volume average particle diameter is, for example, larger than that of lithium iron phosphate. Therefore, the stacking structure of the lithium supplementing additive is different from that of the positive electrode active material, so that after lithium ions are released from the lithium supplementing additive in the first charging process, larger pores can be formed in the residual part, and the porosity of the positive electrode plate is further improved.

In some embodiments, the first lithium supplement has a Dv10 particle size d ₃ The second lithium supplementing agent has a Dv10 particle diameter d ₄ ，d ₃ /d ₄ Greater than or equal to 4.

When d ₃ /d ₄ When the lithium ion battery is more than or equal to 4, the processing performance of the mixed first lithium supplementing agent and second lithium supplementing agent is improved.

In some embodiments, d ₃ From 1 μm to 10 μm, and/or d ₄ 0.2 μm to 1 μm.

As an example, d ₃ May be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm.

As an example, d ₄ May be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1.0 μm.

In some embodiments, the purity of the lithium-compensating additive is greater than or equal to 90%.

As an example, the purity of the lithium supplement additive may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%.

When the purity of the lithium-supplementing additive is within the above-described range, inert impurities on the surfaces of the first and second lithium-supplementing agents, e.g., liOH, li ₂ CO ₃ Or other lithium-containing oxides, copper-containing oxides, nickel-containing oxides and the like are fewer, and the lithium supplementing effect of the lithium supplementing agent is better.

As the purity of the lithium supplement approaches 100%, both the process steps and the costs required for purification increase significantly. As an example, the purity of the lithium supplement additive may be 90% -97%.

In some embodiments, the first-time delithiation capacity of the foregoing lithium-compensating additive may be greater than 400mAh/g; the decomposition potential of the lithium supplementing additive, namely the potential for releasing lithium ions, is 2.0V-4.5V.

When the decomposition potential of the lithium-supplementing additive is 2.0V-4.5V, the lithium-supplementing additive is not easy to react with air/water, so that overdischarge is caused; meanwhile, when the lithium supplementing additive is decomposed to release lithium ions, the electrolyte cannot generate bad decomposition gas production due to over-high voltage.

As an example, when the positive electrode active material is lithium iron phosphate, the decomposition potential of the lithium supplementing material may be 3.0V to 3.75V.

In some embodiments, the first lithium-supplementing agent and the second lithium-supplementing agent may be premixed and then added to the positive electrode slurry, or the first lithium-supplementing agent and the second lithium-supplementing agent may be added to the positive electrode slurry separately and then the positive electrode slurry may be subjected to a mixing process such as stirring.

In some embodiments, the mixing process may include a ball milling process that satisfies at least one of the following conditions: the rotation speed of ball milling treatment is 600rpm-1200rpm; the ball milling treatment time is 1h-4h; the grinding aid treated by ball milling comprises graphite; the mass ratio of the first lithium supplementing agent to the second lithium supplementing agent in the mixture is (5:1) - (10:1).

The second lithium supplementing agent can be coated on the surface of the first lithium supplementing agent through ball milling treatment, and a second coating layer is formed, so that the lithium supplementing additive is obtained through a coating mode. When the second lithium supplementing agent comprises a porous carbon carrier and a second inner core, and the second inner core is positioned in the pore structure of the porous carbon carrier, the process of forming a carbon material coating layer on the surface of the first inner core of the first lithium supplementing agent can be omitted, the second lithium supplementing agent is fixed on the surface of the first inner core by utilizing a ball milling process, and the first inner core and the second inner core share the coating layer in the second lithium supplementing agent.

In a second aspect of the present application, the present application proposes a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material and a lithium supplementing additive, the lithium supplementing additive comprising the aforementioned lithium supplementing additive. Therefore, the positive electrode plate has all the characteristics and advantages of the lithium supplementing additive and is not described herein.

In some embodiments, the mass fraction of the lithium-compensating additive in the positive electrode active material layer is 0.1% -10%. In some embodiments, the mass fraction of the lithium-compensating additive in the positive electrode active material layer is 2% -7%.

As an example, the mass fraction of the lithium supplementing additive in the positive electrode active material layer may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%.

When the mass fraction of the lithium supplementing additive in the positive electrode active material layer is 0.1% -10%, a proper amount of lithium supplementing agent is contained in the positive electrode active material layer, so that the active lithium ion loss in the battery charging and discharging process can be supplemented, too little positive electrode active material in the positive electrode active material layer can not be caused due to too high lithium supplementing agent content, and then the reversible lithium intercalation vacancy in the positive electrode active material layer is insufficient, and the energy density of the battery is too low.

After the lithium supplementing additive in the positive electrode active material layer releases lithium ions in the first charging process, the rest part only retains a small amount of metal salt, so that larger gaps appear in the pore structure originally occupied by the lithium supplementing additive; or the pore structure originally occupied by the lithium supplementing additive is completely vacated due to the decomposition and gas production, so that the porosity of the positive electrode plate is improved. When the negative electrode plate expands in the charging process, the pore structure in the positive electrode plate can be extruded, so that the expansion stress on the negative electrode plate is relieved, the extrusion of electrolyte in the negative electrode plate is reduced, the electrolyte backflow of the negative electrode plate is facilitated, and the wettability of the electrolyte to the negative electrode plate is improved.

In some embodiments, the mass fraction of the first lithium-supplementing agent in the positive electrode active material layer is 0.1% -10%; the mass fraction of the second lithium supplementing agent in the positive electrode active material layer is 0.1% -5%.

As an example, the mass fraction of the first lithium supplementing agent in the positive electrode active material layer may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10%.

As an example, the mass fraction of the second lithium supplementing agent in the positive electrode active material layer may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode active material layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, 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.).

In some embodiments, when the battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries, which is well known in the art.

As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, 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 a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (alsoMay be abbreviated as NCM ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon. The modifying compound of each material can be doping modification and/or surface coating modification of the material.

The battery is charged and discharged with the release and consumption of Li, and the molar contents of Li are different when the battery is discharged to different states. In the list of the positive electrode active materials in the application, the molar content of Li is the initial state of the materials, namely the state before charging, and the molar content of Li is changed after the positive electrode active materials are applied to a battery system and undergo charge and discharge cycles.

In the list of the positive electrode active materials in the application, the molar content of O is only a theoretical state value, the molar content of oxygen is changed due to lattice oxygen release, and the actual molar content of O can float.

In some embodiments, the positive electrode active material layer may further optionally include a binder.

As an example, the binder may include at least one of polyvinylidene fluoride, sodium alginate, polyvinyl alcohol, polymethyl methacrylate, hydrogenated nitrile rubber, polytetrafluoroethylene, and polyacrylic acid. Thereby, the adhesive strength between the positive electrode active material layer and the positive electrode current collector can be improved.

In some embodiments, the positive electrode active material layer may further 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.

In some embodiments, the positive electrode sheet may be prepared by: the components for preparing the positive electrode plate, such as the positive electrode active material, the lithium supplementing agent, the conductive agent, the adhesive and any other components, are dispersed in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry, the positive electrode slurry is coated on a positive electrode current collector, and the positive electrode plate can be obtained after the procedures of drying, cold pressing and the like.

In some embodiments, the positive electrode sheet may be prepared by: dispersing a positive electrode active material, a conductive agent, a binder and any other components in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, drying, cold pressing and the like to form a positive electrode active material layer, and compositing a lithium supplementing agent with the positive electrode active material layer on the surface of the positive electrode active material layer by adopting modes of spraying, secondary coating and the like.

In some embodiments, the positive electrode slurry has a solids content of 50% to 70%.

As an example, the solid content of the positive electrode slurry may be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, or 70%.

When the solid content of the positive electrode slurry is 50-70%, the solid content of the positive electrode slurry is moderate, so that components such as the positive electrode active material and the like can be fully dissolved, the solvent consumption in the positive electrode slurry can be reduced, the cost is reduced, the positive electrode slurry has proper fluidity, and the coating process is convenient to carry out.

In some embodiments, the positive electrode slurry has a solids content of 60% to 65%.

Typically, a battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing short circuit between the positive pole piece and the negative pole, and meanwhile ions can pass through the isolating film.

In some embodiments, further comprising: the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer at least positioned on one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

When the battery is charged, lithium ions are separated from the positive electrode active material, are diffused by electrolyte, migrate to the surface of the negative electrode plate and are embedded into the negative electrode active material; when the battery is discharged, lithium ions can be separated from the anode active material, then are diffused through the electrolyte and migrate to the surface of the anode plate and are embedded into the anode active material, the anode active material can undergo volume expansion due to the insertion of the lithium ions in the charging and discharging process, and undergo volume shrinkage due to the separation of the lithium ions, so that the anode active material can continuously undergo volume change in the charging and discharging cycle process of the battery. In general, the volume change of the anode active material with higher gram capacity in the charge-discharge process is larger, and taking an anode active material with larger volume expansion in the charge-discharge cycle process, such as a silicon-based anode active material as an example, an anode piece containing the silicon-based anode material has huge volume effect in the charge-discharge cycle process, so that electrolyte in the anode piece can be gradually extruded along one side of the anode piece, thereby reducing the wettability of the electrolyte to a part area of the anode piece, finally causing lithium precipitation, and obviously affecting the cycle life and capacity of a battery cell.

In the application, through the optimal design of the lithium supplementing additive in the positive electrode plate, after lithium ions are released by the lithium supplementing additive in the positive electrode active material layer in the first charging process, a small amount of metal salt is reserved in the rest part, so that a larger gap exists in a hole structure originally occupied by the lithium supplementing additive; or the pore structure originally occupied by the lithium supplementing additive is completely vacated due to the decomposition and gas production, so that the porosity of the positive electrode plate is improved. When the negative electrode plate expands in the charging process, the pore structure in the positive electrode plate can be extruded, so that the expansion stress on the negative electrode plate is relieved, the extrusion of electrolyte in the negative electrode plate is reduced, and the wettability of the electrolyte to the negative electrode plate is improved. The energy density of the battery can be effectively improved by adopting the high-gram-capacity negative electrode active material, and the wettability of the electrolyte to the negative electrode plate is improved greatly, so that the cycle performance of the battery is improved greatly.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode active material layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, 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.).

In some embodiments, the anode active material layer further optionally includes a binder. The binder comprises 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).

In some embodiments, the anode active material layer may further optionally include a conductive agent. The conductive agent comprises at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the anode active material layer may optionally further include other adjuvants, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt includes 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 difluorooxalato borate, lithium dioxaato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent comprises at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene 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.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

[ isolation Membrane ]

In some embodiments, a separator is also included in the battery. The type of the separator is not particularly limited, and any porous separator having good chemical stability and mechanical stability may be selected.

In some embodiments, the material of the isolation film comprises at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

The battery of the present application includes a battery cell form, a battery module form, and a battery pack form. The battery, the battery module, and the battery pack of the present application will be described below with reference to the drawings as appropriate.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the exterior package of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery may also be a pouch, such as a pouch-type pouch. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the battery is not particularly limited in this application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a square-structured battery cell 5 as one example.

In some embodiments, referring to fig. 2, the overpack may include a housing 51 and a cap assembly 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodating chamber, and the top cover assembly 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cells may be one or more, and those skilled in the art may choose according to specific practical requirements.

In some embodiments, the cells may be assembled into a battery module, and the number of cells contained in the battery module may be one or more, with the specific number being selectable by one of ordinary skill in the art based on the application and capacity of the battery module.

Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of battery cells may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells may further be secured by fasteners.

Alternatively, the battery module 4 may further include a housing having an accommodating space in which a plurality of battery cells are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 4 and 5 are battery packs 1 as an example. Referring to fig. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

The battery, battery module, battery pack may be used as a power source for an electrical device, or may be used as an energy storage unit for an electrical device. The power utilization device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.

As the electricity consumption device, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 6 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle and the like. To meet the high power and high energy density requirements of the power device for the battery, a battery pack or battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a battery can be used as a power source.

The following description of the present application is made by way of specific examples, which are given for illustration only and should not be construed as limiting the scope of the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

Preparing a positive electrode plate:

LiFePO as positive electrode active material ₄ (LFP), conductive agent acetylene black, binder PVDF and lithium supplementing additiveThe additive is added according to the weight ratio of 95:1:2:2, and after being fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent (NMP) system, the anode slurry is obtained, the solid content of the anode slurry is 60%, and the anode slurry is coated on an Al foil, dried and cold-pressed to obtain the anode plate. The Dv50 particle size of the LFP particles was 1.2 μm. Wherein the surface density of the positive electrode slurry on the surface of the positive electrode plate is 20g/cm ² 。

The lithium supplementing additive comprises a first lithium supplementing agent and a second lithium supplementing agent, and the mass ratio of the first lithium supplementing agent to the second lithium supplementing agent is 9:1.

The synthesis method of the first lithium supplementing agent comprises the following steps:

fe is added to ₂ O ₃ And Li (lithium) ₂ And (3) carrying out solid-phase mixing on O according to the mole ratio of Li to Fe of 5.12:1, heating to 300 ℃ under argon atmosphere, maintaining for 6 hours to obtain first kernel lithium ferrite, then adding a nano aluminum oxide coating agent, wherein the mass ratio of aluminum oxide to lithium ferrite is 1:100, uniformly mixing by using a high-speed mixer, and maintaining for 8 hours at 900 ℃ to obtain the lithium ferrite with the surface coated with aluminum oxide. Then crushing the obtained lithium ferrite coated with aluminum oxide on the surface, crushing dopamine (DA, C) ₈ HNO ₂ ) Mixing the material with lithium ferrite according to the mass ratio of 1:28 to polymerize dopamine on the surface of the lithium ferrite and form a Polydopamine (PDA) nano film, and then keeping the PDA-coated material at 900 ℃ for 8 hours in an argon atmosphere to obtain a first lithium supplementing agent, wherein a first inner core of the first lithium supplementing agent is lithium ferrite, and a first sub-coating layer is Al ₂ O ₃ The second sub-coating layer is a carbon material.

The synthesis method of the second lithium supplementing agent comprises the following steps:

acid crystals (CAS: 2892-51-5) were taken and dissolved in water at a solid to liquid ratio of 1:2, according to Li ⁺ :C ₄ O ₄ ^2- Li is added in a molar ratio of 2:1 ⁺ And (3) stirring the lithium hydroxide solution with the concentration of 65g/L for 2 hours to obtain a second core, mixing the second core with the carbon nano tube solution with the mass fraction of 1wt%, keeping the mass ratio of the second core to the carbon nano tube at 6:1 in an oven for 8 hours for evaporating and crystallizing at 150 ℃ after ultrasonic treatment for 30 minutes to obtain the second lithium supplementing agent.

Preparing a negative electrode plate:

the preparation method comprises the steps of fully stirring and uniformly mixing negative active materials of artificial graphite, a conductive agent of acetylene black, a binder of styrene-butadiene rubber (SBR) and a thickener of sodium carboxymethylcellulose (CMC-Na) in a deionized water solvent system according to a weight ratio of 96.5:0.7:1.8:1 to obtain negative electrode slurry, coating the negative electrode slurry on a Cu foil, drying and cold pressing to obtain a negative electrode plate. Wherein the surface density of the negative electrode slurry on the surface of the negative electrode plate is 15g/cm ² 。

Assembling a battery:

a porous PE/PP polymer film having a thickness of 12 μm was used as a separator.

Mixing Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 50/50, and dissolving 1.1M LiPF ₆ Lithium salt to form an electrolyte.

And sequentially stacking the positive pole piece, the isolating film and the negative pole piece, so that the isolating film is positioned between the positive pole piece and the negative pole piece to play a role in isolation, and winding to obtain the bare cell. And placing the bare cell in an outer package, injecting the prepared electrolyte and packaging to obtain the battery.

Examples 2-11, comparative examples 1-2 differ from the first lithium supplement of example 1 by referring to table 1, and the second lithium supplement differs by referring to table 2. Wherein,

in example 2, the amount of dopamine added was adjusted so that the mass ratio of dopamine to lithium ferrite was 1:15.

The method of synthesizing the second lithium supplement in example 3 is as follows: ketone malonic acid (HO) ₂ C(COOH) ₂ After extraction with 100% ethanol, ketomalonic acid was reacted with LiOH in a mass ratio of 1:2.1, the product was centrifuged and washed 3 times with ethanol to remove excess alkali, followed by vacuum dehydration at 165 ℃ to give a second core Li ₂ C ₃ O ₅ And mixing the second core with a carbon nano tube solution with the mass fraction of 1wt%, wherein the mass ratio of the second core to the carbon nano tube is 6:1, carrying out ultrasonic treatment for 30min, and then, keeping the temperature in an oven at 150 ℃ for 8h for evaporative crystallization to obtain a second lithium supplementing agent.

In example 4, the second lithium-supplementing agent is coated on the surface of the first lithium-supplementing agent, and specifically includes: ball milling is carried out on the first lithium supplementing agent and the second lithium supplementing agent according to the mass ratio of 9:1, the rotation speed of ball milling is 1000rpm, the time is 3h, and the grinding aid is graphite.

In examples 5 to 9, the mass of the lithium supplement additive and the mass of the positive electrode active material in the positive electrode slurry were adjusted accordingly, the sum of the mass fraction of the lithium supplement additive and the mass fraction of the positive electrode active material was 97%, and the mass fraction of the conductive agent and the mass fraction of the binder were unchanged, as in example 1.

Embodiment 10 differs from embodiment 1 in that the first core is Li ₂ C ₂ O ₄ 。

Embodiment 11 differs from embodiment 1 in that the first core is Li ₂ NiO ₂ 。

The lithium supplementing additive in comparative example 1 uses only the first lithium supplementing additive.

The lithium supplementing additive in comparative example 2 uses only the second lithium supplementing agent.

TABLE 1

TABLE 2

The batteries of examples 1 to 11 and comparative examples 1 to 2 were subjected to the following test, and the test results are shown in Table 3.

1. And (3) testing the specific charge and discharge capacity: the battery was charged at a constant current to a charge termination voltage of 3.65V at 25℃at a rate of 0.33C, and charged at a constant voltage to 0.05C, to thereby measure a charge capacity E _c0 Using E _c0 The specific charge capacity is obtained by dividing the mass of the positive electrode active material in the battery. Namely: specific charge capacity (mAh/g) =1 st turn charge capacity/mass of positive electrode active material.

Taking the battery after charging, discharging to the discharge end voltage of 2.5V at 25 ℃ with constant current of 0.33C multiplying power, and measuring the discharge capacity to be E _d0 . Use E _d0 Divided by the positive electrode in the batteryThe mass of the active material can obtain the specific discharge capacity. Namely: specific discharge capacity (mAh/g) =1 st turn discharge capacity/mass of positive electrode active material.

The above-described test of specific charge capacity and specific discharge capacity was repeated 5 times each to average.

2. Cell volumetric energy density calculation:

the dimensional parameters of the internal dimensions of the battery case, length a, width b, and height c, were measured. Each cell was charged at 25℃to a voltage of 3.65V at a rate of 1C, and then discharged again to a voltage of 2.5V at a rate of 1C, and the discharge energy S was measured ₀ 。

Battery volumetric energy density = S ₀ /(a×b×c)

3. Stability of positive electrode slurry:

placing the prepared positive electrode slurry into a beaker, sealing with a preservative film, standing for 24 hours, and observing as follows:

(1) Taking out the well-settled positive electrode slurry, and recording the front mark of the beaker and the sealing condition of the beaker.

(2) Opening the preservative film, lightly stirring the surface of the positive electrode slurry by using a steel ruler, and checking whether the surface of the positive electrode slurry is abnormal or not and whether the color is changed or not.

(3) The steel rule is slowly inserted into the slurry, and the viscosity of the positive electrode slurry is primarily judged by slightly moving up and down.

(4) A part of the slurry was scooped out with a steel ruler, fluidity of the positive electrode slurry was checked, and a photograph was taken.

The gel state for the positive electrode slurry was classified into the following grades:

a. mild gel: the slurry has better fluidity, but the liquid surface has obvious reflection, and the flowing-down line of the slurry and the liquid surface are raised.

b. Medium gel: poor fluidity of the slurry and floccules; the slurry is flocculent but has no solid property; no jelly cake.

c. Severe gel: the slurry has no fluidity and is jelly-like; the slurry has solid property, no fluidity and can be lifted in a whole block.

d. Gel-free: the slurry has better fluidity and no other abnormality.

TABLE 3 Table 3

As can be seen from table 2, the lithium supplement additive in comparative example 1 only adopts the first lithium supplement agent with stronger alkalinity, which results in serious gelation of the positive electrode slurry, loss of fluidity of the slurry, unstable quality of the coating process, poor process consistency, and the like, and seriously affects the production efficiency. The mass fraction of the lithium-supplementing additive in the positive electrode slurry of the embodiment 5 is smaller, and the lithium-supplementing additive only can partially compensate lithium ion loss in the first-cycle charge and discharge process, so that the first-cycle charge specific capacity of the battery is lower, and the volumetric energy density of the battery is lower. The mass fraction of the lithium-supplementing additive in the positive electrode slurry in examples 6 to 9 is higher, the lithium-supplementing additive can effectively compensate lithium ion loss in the first-cycle charge and discharge process, the first-cycle charge specific capacity of the battery is improved, and meanwhile, the lithium-supplementing additive almost cannot provide discharge capacity due to the fact that the lithium-supplementing additive occupies a large amount in the positive electrode active material layer, and then the first-cycle discharge specific capacity and the volume energy density of the battery are lower.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A lithium supplementing additive, comprising:

a first lithium supplementing agent comprising a first core satisfying the chemical formula Li _a M _b O _c Wherein a is 1.5-6, b is 0-2, c is 1-6, M is an elementComprises at least one of magnesium element, calcium element, vanadium element, chromium element, manganese element, iron element, cobalt element, nickel element, copper element, zinc element, niobium element, molybdenum element, ruthenium element, tin element, silicon element, carbon element and boron element, wherein when M is carbon element, the first inner core is Li ₂ C ₂ O ₄ Or Li (lithium) ₂ CO ₃ ；

A second lithium supplementing agent, the second lithium supplementing agent comprising a second core, the second core comprising Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₄ O ₆ At least one of the above-mentioned materials,

the mass fraction of the first lithium supplementing agent in the lithium supplementing additive is m ₁ The mass fraction of the second lithium supplementing agent in the lithium supplementing additive is m ₂ ，m ₁ :m ₂ Less than or equal to (10:1).

2. The lithium supplement additive according to claim 1, wherein the mass fraction of carbon element in the first lithium supplement additive is k ₁ The mass fraction of lithium element in the first lithium supplementing agent is q ₁ ，k ₁ /q ₁ 0-2.

3. The lithium-supplementing additive according to claim 1 or 2, wherein the mass fraction of carbon element in the second lithium-supplementing agent is k ₂ The mass fraction of lithium element in the second lithium supplementing agent is q ₂ ，k ₂ /q ₂ Greater than or equal to 2.5.

4. The lithium supplement additive of claim 1, wherein the first lithium supplement comprises a first core and a first coating layer covering at least a portion of a surface of the first core, the first coating layer comprising at least one of a metal fluoride, a metal oxide, a metal phosphate, a ternary lithium salt, a carbon material, poly 3, 4-ethylenedioxythiophene, polypyrrole, wherein the ternary lithium salt comprises Li ₃ PO ₄ 、Li ₂ MnO ₃ 、LiAlO ₂ 、Li ₂ TiO ₃ 、Li ₂ ZrO ₃ At least one of them.

5. The lithium-compensating additive of claim 1, wherein the second lithium-compensating agent comprises a porous carbon support and a second core, the second core being located within the pore structure of the porous carbon support.

6. The lithium-compensating additive of claim 4 or 5, wherein the first lithium-compensating agent has a particle size greater than the particle size of the second lithium-compensating agent, and wherein at least a portion of the surface of the first core has a second coating layer comprising the second lithium-compensating agent.

7. The lithium supplement additive of claim 2, wherein k ₁ 0% -30%, q ₁ 7% -70%.

8. A lithium supplement additive according to claim 3, characterized in that k ₂ 15% -70%, q ₂ 8% -20%.

9. The lithium-compensating additive of claim 1, wherein the first core meets at least one of the following conditions:

when a is 2 and c is 2, M comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu;

when a is 2 and c is 3, M comprises at least one of Si, ni, co, fe, mn, sn, cr;

when a is 2 and c is 4, M comprises at least one of C, fe, mn, cr, nb;

when a is 3 and c is 4, M comprises at least one of Co, fe, mn, cr, V, mo, nb;

when a is 5 and c is 4, M comprises at least one of Ni, co, fe, mn, cr, mo;

when a is 6 and c is 4, M comprises at least one of Ni, co, mn, fe, cu.

10. The lithium supplement additive of claim 1, wherein the first lithium supplement additive has a Dv50 particle size d ₁ The Dv50 particle size of the second lithium supplementing agent is d ₂ ，d ₁ /d ₂ Greater than or equal to 2.

11. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material and a lithium supplementing additive comprising the lithium supplementing additive of any one of claims 1-10.

12. The positive electrode sheet according to claim 11, wherein the mass fraction of the lithium supplementing additive in the positive electrode active material layer is 0.1% to 10%.

13. The positive electrode sheet according to claim 11 or 12, wherein the positive electrode active material layer further comprises a binder including at least one of polyvinylidene fluoride, sodium alginate, polyvinyl alcohol, polymethyl methacrylate, hydrogenated nitrile rubber, polytetrafluoroethylene, polyacrylic acid.

14. A battery comprising the positive electrode sheet according to any one of claims 11 to 13.

15. An electrical device comprising the battery of claim 14.