CN115832462A

CN115832462A - Core-shell material, coating, secondary battery, battery module, battery pack, and electric device

Info

Publication number: CN115832462A
Application number: CN202210042773.0A
Authority: CN
Inventors: 武新战; 杨子钰; 李振华
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-01-14
Filing date: 2022-01-14
Publication date: 2023-03-21

Abstract

The application relates to the technical field of secondary batteries, in particular to a core-shell material, a coating, a secondary battery, a battery module, a battery pack and an electric device. The core-shell material comprises a core and a coating layer coated on the surface of the core, wherein the core is a lithium-embeddable material; the coating layer is made of insulating materials. This application is through adopting can inlay lithium material as kernel, insulating material as the coating to constitute nuclear shell structure, wherein, insulating material is used for leading through ion and separation electron, can inlay the lithium material and be used for absorbing the lithium dendrite that produces when taking place to analyse lithium on battery negative pole piece surface, and then prevent that lithium dendrite from penetrating barrier film and influencing secondary battery's performance.

Description

Core-shell material, coating, secondary battery, battery module, battery pack, and electric device

Technical Field

The application relates to the technical field of batteries, in particular to a core-shell material, a coating, a secondary battery, a battery module, a battery pack and an electric device.

Background

The secondary battery has the advantages of high energy density, long cycle life, no memory effect, environmental friendliness and the like, and is widely applied to portable electronic products, energy storage equipment and new energy automobiles.

The separator is an important component of the secondary battery, and mainly plays a role in preventing the contact of the positive and negative electrodes and allowing ion conduction. Currently, the separator used in commercial secondary batteries is mainly a polyolefin-based separator material having a microporous structure, such as a single-layer or multi-layer film of Polyethylene (PE), polypropylene (PP). In order to reduce the thermal shrinkage of the separator at high temperature and improve the safety performance of the battery cell, a layer of ceramic is generally coated on the surface (single side or double sides) of the separator. The existing ceramic isolating membrane has better improvement effect on high temperature, acupuncture and short circuit, but has limited improvement on overcharge of higher voltage. The reason is that the negative electrode of the battery cell can seriously precipitate lithium in the overcharging process to form a large amount of lithium dendrites, and on one hand, the lithium dendrites can pierce the isolating membrane to cause internal short circuit and cause thermal runaway; on the other hand, the temperature of the battery cell is increased by joule heat, reaction heat and polarization heat generated in the overcharging process, lithium dendrite and electrolyte can generate violent reaction at higher temperature, the temperature of the battery cell is rapidly increased to more than 200 ℃, then a series of reactions occur, and finally the thermal runaway of the battery cell is caused.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide a core-shell material, a coating layer, a secondary battery, a battery module, a battery pack, and an electric device, which can solve internal short circuit and thermal runaway caused by penetration of lithium dendrite through a separator; the problem that the temperature of the battery cell is increased to cause thermal runaway of the battery cell due to Joule heat, reaction heat and polarization heat generated in the overcharging process can be solved.

In order to achieve the above object, the present application provides a core-shell material, a coating layer, a secondary battery, a battery module, a battery pack, and an electric device.

The first aspect of the application provides a core-shell material, which comprises a core and a coating layer, wherein the core is a lithium-embeddable material; the coating layer is made of insulating material; wherein, the coating layer is coated on the surface of the inner core.

From this, this application is through adopting can inlay lithium material as kernel, insulating material as the coating to constitute nuclear shell structure, wherein, insulating material is used for leading through ion and separation electron, can inlay lithium material and be used for absorbing the lithium dendrite that produces when battery negative pole piece surface takes place to analyse lithium, and then prevent that lithium dendrite from penetrating the barrier film and influencing secondary battery performance.

In any embodiment, the mass percent of the core relative to the total mass of the core-shell material is 30% to 90%, and/or the mass percent of the coating relative to the total mass of the core-shell material is 10% to 70%. Through the respective mass percentage of rationally setting up kernel and coating for the coating can wrap up the kernel uniformly completely, and the thickness of coating is moderate, can play the biggest effect.

In any embodiment, the Dv50 of the core is from 0.05 μm to 40 μm. If the Dv50 of the core is too small, the quantity of lithium-embeddable materials which can react with the lithium dendrites is small, i.e. the consumption speed of the lithium-embeddable materials is high, the lithium dendrites cannot be completely reacted, and the secondary battery cannot be effectively protected; if the Dv50 of the inner core is too large, the lithium precipitation preventing coating occupies a large amount of the space inside the secondary battery, resulting in a decrease in the weight energy density and the volume energy density; therefore, the Dv50 of the inner core is set to be 0.05-40 mu m, the coating uniformity of the coating can be ensured, enough lithium embeddable materials can consume lithium dendrites, the coating occupies a proper internal space of the secondary battery, the weight energy density and the volume energy density cannot be reduced, and the lithium precipitation prevention performance of the secondary battery is improved.

In any embodiment, the thickness of the coating layer is 0.05 μm to 20 μm. When the secondary battery does not generate lithium separation or the lithium separation degree is not serious, the coating layer is contacted with the negative active material on the negative pole piece, and the inner core does not play a role, so that the phenomenon that the lithium separation prevention coating fails and the performance of the battery core is influenced due to the lithium intercalation of the lithium intercalation materials in the lithium separation prevention coating when the secondary battery is circulated or stored is avoided.

In any embodiment, the lithium intercalatable material is Lithium Titanate (LTO), titanium niobate (TiNb) ₂ O ₇ ) Lithium niobate (LiNbO), chromium (Cr), silicon (Si), tin (Sn), iron phosphate (FePO) ₄ ) Or a combination of two or more thereof. The application adopts Lithium Titanate (LTO) and titanium niobate (TiNb) ₂ O ₇ ) Lithium niobate (LiNbO), chromium (Cr), silicon (Si), tin (Sn), iron phosphate (FePO) ₄ ) One or the combination of more than two of the lithium dendrites is used as the lithium embeddable material, when the lithium dendrites penetrate through the insulating material and enter the inside to be contacted with the lithium embeddable material, the lithium dendrites and the lithium embeddable material generate lithium embeddable reaction, thereby consuming the lithium dendrites and improving the safety performance of the secondary battery.

In any embodiment, the insulating material is an inorganic insulating material or an organic insulating material. According to the lithium ion battery, the inorganic insulating material or the organic insulating material is used as the insulating material, so that the insulating material is ensured to only allow lithium ions to pass through but not allow electrons to pass through, namely, the direct contact between the internal lithium embeddable material and the active substance of the negative pole piece is isolated.

In any embodiment, the inorganic insulating material is selected from boehmite (AlOOH) or/and alumina (Al) ₂ O ₃ ). The application adopts boehmite (AlOOH) and aluminum oxide (Al) ₂ O ₃ ) As an insulating material, the insulating material is ensured to only allow lithium ions to pass through, and not allow electrons to pass through, namely, the direct contact between the internal lithium-embeddable material and the active substance of the negative pole piece is isolated.

In any embodiment, the organic insulating material is selected from one or more of Polyvinylidene Fluoride (PVDF), styrene Butadiene Rubber (ASTM, BS, SBR), polyacrylic acid (PAA), polyphthalamide (PPA), phenol-formaldehyde resin (PF), polyethylene (PE), polypropylene (PP), or hydroxymethyl cellulose (CMC).

A second aspect of the present application provides a coating comprising the core-shell material of any of the above embodiments, wherein the core-shell material comprises a core and a coating layer, the core is used for absorbing lithium dendrites, and the core is a lithium-embeddable material; the coating layer is used for conducting ions and blocking electrons, and is made of an insulating material; wherein, the coating layer is coated on the surface of the inner core.

Therefore, the coating is arranged into a core-shell structure, specifically a coating layer and an inner core positioned in the coating layer. The coating layer is used for conducting ions and blocking electrons, namely, the coating layer is used for blocking direct contact between the inner core and active materials on the battery negative pole piece; the inner core is used for absorbing lithium dendrite generated when lithium precipitation occurs on the surface of the negative pole piece of the secondary battery, and further preventing the lithium dendrite from penetrating through the isolating membrane to influence the performance of the secondary battery.

In addition, the coating is arranged into a core-shell structure, and the coating is coated on the negative pole piece of the secondary battery or/and one side of the secondary battery isolating membrane close to the negative pole piece. When the secondary battery does not generate lithium separation or the lithium separation degree is not deep, the coating layer is contacted with the active substance on the negative pole piece, so that the lithium separation prevention coating layer can be prevented from losing efficacy and influencing the performance of the secondary battery due to lithium intercalation generated when the secondary battery is circulated or stored; when lithium is separated from the surface of the negative pole piece of the secondary battery, the lithium dendrite penetrates through the coating layer to reach the surface or the inside of the lithium-embeddable material in the kernel, and the lithium dendrite and the lithium-embeddable material are subjected to a rapid lithium-embeddable reaction, so that the lithium dendrite is prevented from penetrating through the isolating membrane, and the performance of the secondary battery is further influenced.

In any embodiment, the core-shell material is 80% to 100% by mass relative to the total mass of the coating. If the mass percentage of the core-shell material is too low, the lithium-embeddable material inside the core positioned in the cladding layer directly contacts with the active material due to coating leakage or other defects, so that lithium dendrites cannot be completely reacted, and the secondary battery cannot be effectively protected.

In any embodiment, the coating has a thickness of 0.1 μm to 50 μm. If the coating is too thin, the lithium-embeddable material in the inner core in the cladding layer can be directly contacted with the active substance due to coating leakage or other defects, so that the lithium dendrite cannot be completely reacted, and the secondary battery cannot be effectively protected; if the coating is too thick, a large amount of space inside the secondary battery is occupied, resulting in a decrease in the weight energy density and the volume energy density; therefore, the thickness of the coating is set to be 0.1-50 mu m, the coating uniformity of the coating can be ensured, the coating occupies the appropriate internal space of the secondary battery, the weight energy density and the volume energy density can not be reduced, the lithium dendrite can be effectively prevented from entering the isolating membrane, and the lithium precipitation prevention performance of the secondary battery is greatly improved.

A third aspect of the present application provides a secondary battery, including a positive electrode plate, a negative electrode plate, a coating and an isolating film, where the coating is disposed on the negative electrode plate or/and on a side of the isolating film close to the negative electrode plate, and the coating is the coating of any of the above embodiments.

Therefore, the coating is coated on the negative pole piece or/and one side of the isolating membrane close to the negative pole piece, the coating comprises a coating layer and a kernel arranged in the coating layer, wherein the coating layer is used for conducting ions and blocking electrons, and the kernel is used for absorbing lithium dendrites generated when lithium is separated on the surface of the negative pole piece of the battery due to reasons such as quick charge, overcharge and electric quantity super-separation lithium window. When the secondary battery does not generate lithium separation or the lithium separation degree is not deep, the coating layer is contacted with the active substance on the negative pole piece, and the kernel does not play a role, so that the lithium separation prevention coating is prevented from losing efficacy and influencing the battery core performance due to lithium intercalation of the lithium-intercalatable material in the lithium separation prevention coating when the secondary battery is circulated or stored; when lithium is separated on the surface of the negative pole piece of the secondary battery due to reasons such as quick charge, overcharge and electric quantity super lithium separation windows, the lithium dendrite penetrates through the coating layer to reach the surface or the interior of the lithium-embeddable material of the kernel, and the lithium dendrite and the lithium-embeddable material spontaneously generate a quick lithium-embeddable reaction, so that the lithium dendrite is absorbed to prevent the penetration of the isolating membrane to influence the performance of the secondary battery.

A fourth aspect of the present application provides a battery module including the secondary battery of any one of the above embodiments.

A fifth aspect of the present application provides a battery pack including the battery module of any one of the above embodiments.

A sixth aspect of the present application provides an electric device including at least one of the secondary battery of any one of the above embodiments, the battery module of any one of the above embodiments, and the battery pack of any one of the above embodiments.

Through adopting foretell technical scheme, the beneficial effect of this application is:

(1) The coating is arranged into a core-shell structure, specifically a coating layer and an inner core positioned in the coating layer. The coating layer is used for conducting ions and blocking electrons, namely, the coating layer is used for blocking direct contact between the inner core and active materials on the battery negative pole piece; the inner core is used for absorbing lithium dendrite generated when lithium is separated on the surface of the battery negative pole piece, and further preventing the lithium dendrite from penetrating through the isolating membrane to influence the performance of the secondary battery.

(2) This application is through rationally setting up the particle diameter of cladding layer thickness and kernel in the coating, can guarantee the coated degree of consistency of coating, and the coating occupies secondary battery inner space suitable, can not lead to weight energy density and volume energy density to descend, and can obstruct lithium dendrite effectively and get into the barrier film in, improved secondary battery's security performance greatly, prolonged secondary battery's life.

(3) The coating is arranged into a core-shell structure, and the coating is coated on the negative pole piece of the secondary battery or/and one side of the secondary battery isolating membrane close to the negative pole piece. When the secondary battery does not generate lithium separation or the lithium separation degree is not deep, the coating layer is contacted with the active substance on the negative pole piece, so that the lithium separation prevention coating layer can be prevented from losing efficacy and influencing the performance of the secondary battery due to lithium intercalation generated when the secondary battery is circulated or stored; when lithium is separated from the surface of the negative pole piece of the secondary battery, the lithium dendrite penetrates through the coating layer to reach the surface or the inside of the lithium-embeddable material in the kernel, and the lithium dendrite and the lithium-embeddable material are subjected to a rapid lithium-embeddable reaction, so that the lithium dendrite is prevented from penetrating through the isolating membrane, and the performance of the secondary battery is further influenced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Clearly, such objects and other objects of the present application will become more apparent from the detailed description of the preferred embodiment as illustrated in the various figures and drawings.

These and other objects, features and advantages of the present application will become more apparent from the following detailed description of one or more preferred embodiments, which is to be read in connection with the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and not to limit the application.

In the drawings, like parts are designated with like reference numerals, and the drawings are schematic and not necessarily drawn to scale.

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only one or several embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic structural diagram of a core-shell material according to some embodiments of the present application;

fig. 2 is a schematic structural view of a battery module according to some embodiments of the present disclosure;

fig. 3 is a schematic structural view of a battery pack according to some embodiments of the present application;

fig. 4 is an exploded view of a battery pack according to some embodiments of the present application;

fig. 5 is a schematic structural diagram of an electric device according to some embodiments of the present application.

Description of the main reference numerals:

1, coating;

11 a coating layer; 12 a core;

2, a battery module;

3, a battery pack;

31, loading the box body;

32 a lower box body;

4, a power utilization device.

Detailed Description

Hereinafter, the core-shell material, the coating layer, the battery module, the battery pack, and the electric device according to the present invention are specifically disclosed in detail with reference to the drawings as appropriate. But a detailed description thereof will be omitted. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the description below and to facilitate understanding by those skilled in the art. The 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.

As disclosed herein, a "range" is defined in terms of lower and upper limits, with a given range being defined by the selection of one lower limit and one upper limit, which define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may 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 stated, 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, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.

In the description of the embodiments of the present application, the technical terms "first", "second", and the like are used only for distinguishing different objects, and are not to be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary-secondary relationship of the technical features indicated. In the description of the embodiments of the present application, "a plurality" means two or more unless specifically defined otherwise.

In the description of the embodiments of the present application, the term "and/or" is only one kind of association relation describing an associated object, and means that three kinds of relations may exist, for example, a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" in this document generally indicates that the former and latter associated objects are in an "or" relationship. The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that additional components not listed may also be included or included, or that only listed components may be included or included.

In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).

In the description of the embodiments of the present application, the term "plurality" means two or more (including two), and similarly, "plural sets" means two or more (including two sets), "plural pieces" means two or more (including two pieces).

In the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "up", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate the orientations and positional relationships indicated in the drawings, and are only for convenience of describing the embodiments of the present application and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the embodiments of the present application.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.

All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

At present, secondary batteries are increasingly widely used in view of the development of market conditions. The secondary battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles and the like, and a plurality of fields such as military equipment and aerospace. As the field of application of secondary batteries is continuously expanded, the demand of the market is also continuously expanded.

The separator is an important component of the secondary battery, and mainly plays a role in preventing the contact of the positive and negative electrodes and allowing ion conduction. Currently, the separator used in commercial secondary batteries is mainly a polyolefin-based separator material having a microporous structure, such as a single-layer or multi-layer film of Polyethylene (PE), polypropylene (PP). In order to reduce the thermal shrinkage of the separator at high temperature and improve the safety performance of the battery cell, a layer of ceramic is generally coated on the surface (single side or double sides) of the separator. The existing ceramic isolating membrane has better improvement effect on high temperature, acupuncture and short circuit, but has limited improvement on overcharge of higher voltage.

The reason for this is that: during the overcharge process of the battery core, the negative pole can seriously precipitate lithium, and a large amount of lithium dendrites are formed. On one hand, lithium dendrites may pierce the isolating membrane to cause internal short circuit, and thermal runaway is caused; on the other hand, joule heat, reaction heat and polarization heat generated during overcharge raise the temperature of the secondary battery, while lithium dendrite reacts violently with the electrolyte at a higher temperature, the temperature of the secondary battery rises rapidly to over 200 ℃, and then a series of reactions occur, finally leading to thermal runaway of the secondary battery.

In the existing market, lithium titanate is coated on the surface of a battery cathode, the problem of lithium precipitation of the cathode is solved by utilizing the high lithium intercalation potential and the quick charging capability of the lithium titanate, and when the lithium precipitation occurs to the battery, the lithium titanate and silicon can react with lithium dendrites in a contact manner to consume the lithium dendrites, so that the lithium dendrites are prevented from puncturing an isolation membrane to generate short circuit, and the overcharge performance of the secondary battery is improved. However, in the practical application process, the performance of the secondary battery added with the coated lithium titanate is not improved, and since the lithium titanate or the silicon-based material (such as a silicon simple substance and a silicon oxide) in the coating layer can also be used as a negative electrode active material of the lithium ion secondary battery, the coating layer is equivalent to a part of the active material after being directly contacted with the negative electrode, and the lithium ion is reacted with the safe coating layer when the lithium ion intercalation is not excessive, so that the effect of safety protection is not achieved; and on the contrary, the cycle performance of the battery is further deteriorated due to the serious problem of gas generation of lithium titanate.

In order to alleviate the above problems, the applicant has conducted extensive research and unexpectedly found a coating composition, wherein the coating composition is formed by coating an insulating material on a rapid lithium intercalation material, and then the coating composition is sprayed or coated on the surface of a negative electrode plate or on the side of a separator close to the surface of the negative electrode plate, so as to achieve the purpose of absorbing lithium dendrites and preventing the lithium dendrites from penetrating through the separator, thereby further improving the cycle performance and overcharge performance of the battery.

Based on the above consideration, in order to solve the cycle performance and overcharge performance of the secondary battery, the applicant has found that the lithium-embeddable material is coated in the insulating material to improve the cycle performance best through experimental screening of the composition, the proportion, the particle size and the like of the coating composition, and the lithium-embeddable material is simple in preparation method, low in production cost and is an optimum improvement scheme.

In further experiments, the applicant finds that the coating composition is coated on the surface of the negative pole piece or the surface of the isolating membrane close to the negative pole, so that the lithium dendrite can be effectively absorbed, the lithium dendrite is prevented from penetrating through the isolating membrane, and the cycle performance of the secondary battery is improved.

Referring to fig. 1, according to some embodiments of the present application, fig. 1 is a schematic structural diagram of a core-shell material according to some embodiments of the present application. The present application provides a core-shell material. The core-shell material comprises a core 12 and a coating layer 11 coated on the surface of the core 12, wherein the core 12 comprises a lithium-embeddable material, and the coating layer 11 comprises an insulating material.

The lithium-intercalatable material refers to a material for absorbing lithium dendrites generated when lithium precipitation occurs in the battery 11.

Insulating material is a substance which does not conduct or conducts very little electricity under the action of a DC voltage and has a resistivity generally greater than 10 ¹⁰ Omega.m. In some embodiments of the present application, the insulating material is primarily used to conduct ions and block electrons.

From this, this application is through adopting can inlay lithium material as kernel 12, insulating material as coating 11 to constitute nuclear shell structure, wherein, insulating material is used for leading on ion and separation electron, can inlay lithium material and be arranged in absorbing secondary battery negative pole piece surface because fast charge, overcharge, electric quantity super analyse lithium window etc. reason when taking place to analyse lithium and the lithium dendrite that produces prevents that lithium dendrite from piercing through the barrier film and influencing electric core performance.

In some embodiments, optionally, the mass percentage of the inner core 12 relative to the total mass of the core-shell material is between 30% and 90%, and/or the mass percentage of the coating layer 11 relative to the total mass of the core-shell material is between 10% and 70%. Through reasonably setting respective mass percentages of the inner core 12 and the coating layer 11, the coating layer 11 can uniformly wrap the inner core 12, the maximum protection strength can be provided for the inner core 12, and the stability of the core-shell structure is greatly enhanced. Here, "uniform" means that the insulating material in the coating layer 11 is not a layer in which particles are stacked, but exists in a uniform and dense layer structure.

Alternatively, the core 12 may be 89%, 87%, 85%, 83%, 81%, 79%, 77%, 75%, 73%, 71%, 49%, 47%, 45%, 43%, 41%, 39%, 37%, 35%, 33%, 31% by mass or any combination thereof within the range defined by the above values.

Alternatively, the mass percentage of the coating layer 11 is 69%, 67%, 65%, 63%, 61%, 59%, 57%, 55%, 53%, 51%, 29%, 27%, 25%, 23%, 21%, 19%, 17%, 15%, 13%, 11% or a value thereof is within a range obtained by combining any two of the above values.

In some embodiments, optionally, the inner core 12 has a diameter of 0.05 μm to 40 μm.

If the diameter of the core 12 is less than 0.05 μm (i.e., the core 12 is too thin), the quantity of lithium-embeddable material available for reaction with lithium dendrites in the core 12 is small, the consumption speed of the lithium-embeddable material is high, and all lithium dendrites cannot be completely consumed by reaction, so that the secondary battery cannot be effectively protected; if the diameter of the core 12 is larger than 40 μm (i.e., the core 12 is too thick), the lithium precipitation preventing coating 1 occupies too much space inside the secondary battery, so that the gravimetric energy density and the volumetric energy density are lowered. Therefore, the diameter of the inner core 12 is set to be 0.05-40 μm, the coating uniformity of the coating 1 can be guaranteed, enough lithium embeddable materials and lithium dendrite reaction can be provided, lithium dendrite can be completely consumed, the coating 1 occupies the inner space of the secondary battery and is just suitable, the weight energy density and the volume energy density can not be reduced, and the lithium precipitation prevention performance of the secondary battery is greatly improved.

Alternatively, the diameter of the core 12 is 39 μm, 38 μm, 37 μm, 36 μm, 35 μm, 34 μm, 33 μm, 32 μm, 31 μm, 30 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, 0.09 μm, 0.08 μm, 0.07 μm, 0.06 μm, or a value within a range obtained by combining any two of the foregoing values.

In some embodiments, optionally, the coating layer 11 has a thickness of 0.05 μm to 20 μm. The thickness of the clad layer 11 refers to the distance from the outer surface of the core 12 to the outer surface of the clad layer 11.

If the thickness of the coating layer 11 is less than 0.05 mu m (namely the coating layer 11 is too thin), the insulating material in the coating layer 11 is less, and the comprehensive electron blocking cannot be ensured, so that the insulating material is quickly consumed after being contacted with a negative active substance on a negative pole piece, the route of lithium dendrite entering the internal medicine is shortened, and the lithium precipitation prevention performance is greatly reduced; if the thickness of the clad layer 11 is more than 20 μm (i.e., if the clad layer 11 is too thick), the lithium precipitation preventing coating 1 occupies too much space inside the secondary battery, so that the gravimetric energy density and the volumetric energy density are lowered. According to the lithium ion battery, the thickness of the coating layer 11 is set to be 0.05-20 microns, so that when the lithium ion of the secondary battery is not generated or the lithium ion degree is not deep, the coating layer 11 is in contact with the negative active material on the negative pole piece, the inner core 12 does not play a role, and the problem that the lithium ion deposition prevention coating layer 1 is invalid and the battery core performance is influenced due to the fact that the lithium ion deposition of the lithium-embeddable material in the lithium ion deposition prevention coating layer 1 occurs when the secondary battery is circulated or stored is avoided.

Alternatively, the coating layer 11 has a thickness of 19 μm, 18 μm, 17 μm, 16 μm, 15 μm, 14 μm, 13 μm, 12 μm, 11 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, 0.09 μm, 0.08 μm, 0.07 μm, 0.06 μm or a value within a range obtained by combining any two of the above values.

In some embodiments, optionally, the lithium intercalatable material is Lithium Titanate (LTO), titanium niobate (TiNb) ₂ O ₇ ) Lithium niobate (LiNbO), chromium (Cr), silicon (Si), tin (Sn), iron phosphate (FePO) ₄ ) One or a combination of two or more of them. The application adopts Lithium Titanate (LTO) and titanium niobate (TiNb) ₂ O ₇ ) Lithium niobate (LiNbO), chromium (Cr), silicon (Si), tin (Sn), iron phosphate (FePO) ₄ ) As the lithium-embeddable material, when the lithium dendrites penetrate the insulating materialAfter the lithium dendrite is fed into the interior of the lithium intercalation material, the lithium dendrite can be contacted with the lithium intercalation material to produce lithium intercalation reaction, so that the aim of consuming the lithium dendrite can be achieved.

In some embodiments, optionally, the insulating material is an inorganic insulating material or an organic insulating material. This application has guaranteed that insulating material only allows lithium ion to pass through as insulating material through adopting inorganic insulating material or organic insulating material, does not allow electron to pass through, can inlay lithium material and negative pole piece active material's direct contact promptly completely cut off inside.

Further, the inorganic insulating material is boehmite (AlOOH), alumina (Al) ₂ O ₃ ). The application adopts boehmite (AlOOH) and aluminum oxide (Al) ₂ O ₃ ) As an insulating material, the insulating material is ensured to only allow lithium ions to pass through, and not allow electrons to pass through, namely, the direct contact between the internal lithium-embeddable material and the active substance of the negative pole piece is isolated.

Further, the organic insulating material is Polyvinylidene Fluoride (PVDF), styrene Butadiene Rubber (ASTM, BS, SBR), polyacrylic acid (PAA), polyphthalamide (PPA), phenol-formaldehyde resin (PF), polyethylene (PE), polypropylene (PP), or hydroxymethyl cellulose (CMC), and the present application ensures that the active material does not pass through the inside of the insulating material by using Polyvinylidene Fluoride (PVDF), styrene Butadiene Rubber (PP), polystyrene-formaldehyde Rubber (ASTM, BS, SBR), polyacrylic acid (PAA), polyphthalamide (PPA), or CMC.

According to some embodiments of the present application, there is provided a coating 1. The coating 1 comprises a core-shell material, the core-shell material comprises a core 12 for absorbing lithium dendrites and a coating layer 11 for conducting ions and blocking electrons and coated on the core 12, the core 12 comprises a lithium-embeddable material, and the coating layer 11 comprises an insulating material.

Thus, the present application provides the coating 1 as two layers, a cladding layer 11, and an inner core 12 within the cladding layer 11. The coating layer 11 serves to conduct ions and block electrons, in other words, it serves to block the direct contact between the core 12 and the active material on the negative electrode plate of the battery 1; the core 12 is used for absorbing lithium dendrites generated when lithium is separated on the surface of the negative pole piece of the secondary battery due to reasons such as quick charge, overcharge and electric quantity super lithium separation windows, and the like, and preventing the lithium dendrites from penetrating through the isolating membrane to influence the performance of the battery core.

In addition, the coating 1 is arranged to be the coating layer 11 and the inner core 12, and the coating 1 is coated on the negative pole piece of the secondary battery or/and one side of the secondary battery isolation film close to the negative pole piece. When the secondary battery does not generate lithium separation or the lithium separation degree is not deep, the coating layer 11 is contacted with the active substance on the negative pole piece, and at the moment, the kernel 12 does not play a role, so that the lithium separation prevention coating layer 1 is prevented from losing efficacy and influencing the battery core performance due to lithium intercalation of the lithium-intercalatable material in the kernel 12 during the cycle or storage of the secondary battery; when lithium is separated on the surface of the negative pole piece of the secondary battery due to reasons such as quick charge, overcharge and electric quantity super-lithium separation windows, the lithium dendrite penetrates through the coating layer 11 to reach the surface or the inside of the lithium-embeddable material in the kernel 12, and the lithium dendrite and the lithium-embeddable material spontaneously generate a quick lithium-embedding reaction, so that the lithium dendrite is absorbed to prevent the lithium dendrite from penetrating through the isolating membrane to influence the performance of the battery core.

In some embodiments, optionally, the mass percentage of the core-shell material is 80% to 100% based on the total mass of the coating 1. If the mass percentage of the core-shell material is too low, the lithium-embeddable material inside the core positioned in the cladding layer directly contacts with the active material due to missing coating or other defects, so that lithium dendrite cannot be completely reacted, and the secondary battery cannot be effectively protected.

Optionally, the core-shell material has a mass percentage of 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81% or a value within a range obtained by combining any two of the above values.

In some embodiments, optionally, the thickness of the coating 1 is 0.1 μm to 50 μm.

If the thickness of the coating 1 is less than 0.1 μm (i.e. the coating 1 is too thin), the lithium-intercalatable material inside the core 12 in the coating layer 11 directly contacts with the active material due to coating leakage or other defects, and at this time, the lithium-segregation preventing coating 1 becomes a part of the negative electrode material (i.e. graphite mixed with other lithium-intercalatable materials) and has poor lithium segregation preventing effect, and the secondary battery cannot be effectively protected; if the thickness of the coating layer 1 is more than 50 μm (i.e., the coating layer 1 is too thick), it may cause the lithium precipitation preventing coating layer 1 composition to occupy too much space inside the secondary battery, resulting in a decrease in the gravimetric and volumetric energy densities. Therefore, this application sets the thickness of coating 1 to 0.1 mu m ~ 50 mu m, can guarantee the 1 coated degree of consistency of coating, and coating 1 occupies secondary battery inner space just suitable, can not lead to weight energy density and volume energy density to descend, and can obstruct lithium dendrite entering barrier film effectively in, improved secondary battery greatly and prevented out lithium performance.

Alternatively, the thickness of the coating 1 is 49 μm, 48 μm, 47 μm, 46 μm, 45 μm, 44 μm, 43 μm, 42 μm, 41 μm, 1 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm or a value within a range obtained by combining any two of the above values.

According to some embodiments of the present application, there is provided a method of preparing a coating 1, comprising the steps of:

s1, preparation of a coating layer 11 solution: dissolving an insulating material in deionized water, and stirring at the rotating speed of 600-1000 rpm for 25-35 min at the temperature of 22-28 ℃ to obtain a coating layer 11 solution;

s2, preparing a coating 1: adding the lithium-intercalatable material into the coating layer 11 solution, and stirring at the rotating speed of 600-1000 rpm for 4-6 h at the temperature of 22-28 ℃ to obtain the coating layer 1.

Therefore, the insulating material is added into the deionized water and uniformly stirred at normal temperature to obtain a uniform colloidal solution (namely the coating layer 11 solution), the lithium-embeddable material is added into the uniform colloidal solution (namely the coating layer 11 solution), and the stirring is continued to be uniform to obtain a uniform mixed system (namely the coating layer 1). The preparation method is simple, special procedures and conditions are not needed, the production cost is low, the production effect is high, the prepared coating 1 can effectively prevent lithium dendrites generated when lithium separation occurs on the surface of the negative pole piece of the battery 1 due to quick charge, overcharge, electric quantity over lithium separation windows and other reasons from penetrating into the isolating membrane, and therefore the performance of the battery core is affected.

In some embodiments, optionally, the mass ratio of the insulating material to the deionized water is 1 to 2. By reasonably configuring the proportion between the insulating material and the deionized water, the concentration and the consistency of the solution of the coating layer 11 can effectively play a role in conducting ions and blocking electrons, and the lithium-embeddable material in the inner core 12 in the coating layer 1 can be better prevented from being in direct contact with the negative pole piece of the secondary battery.

In some embodiments, optionally, the mass ratio of the insulating material to the lithium intercalatable material is 16 to 18. The mass ratio of the insulating material to the lithium embeddable material is reasonably configured, so that the grain diameters of the coating layer 11 and the inner core 12 are more suitable, the coating layer and the inner core can respectively play the roles of the coating layer and the inner core, excessive space in the secondary battery cannot be occupied, and the weight energy density and the volume energy density of the secondary battery are ensured.

According to some embodiments of the present application, there is provided a secondary battery. The secondary battery comprises a positive pole piece, a negative pole piece, a coating 1 and an isolating membrane, wherein the coating 1 is arranged on the negative pole piece or/and one side of the isolating membrane close to the negative pole piece, and the coating 1 is the coating 1 of any one of the above embodiments.

From this, this application is at the negative pole piece or/and the barrier film is coated with coating 1 on being close to one side of negative pole piece, and this coating 1 includes coating 11, sets up kernel 12 within coating 11, and wherein, coating 11 is used for leading in ion and separation electron, and kernel 12 is used for absorbing the lithium dendrite that secondary cell negative pole piece surface produced when taking place to analyse lithium because reasons such as fast charge, overcharge, electric quantity super analysis lithium window. When the secondary battery does not generate lithium separation or the lithium separation degree is not deep, the coating layer 11 is contacted with the active substance on the negative pole piece, and the inner core 12 does not play a role, so that the lithium separation prevention coating 1 is prevented from being invalid and the performance of the battery cell is prevented from being influenced due to the lithium intercalation of the lithium-intercalatable material in the lithium separation prevention coating 1 during the circulation or storage of the secondary battery; when lithium is separated on the surface of the negative pole piece of the secondary battery due to reasons such as quick charge, overcharge and electric quantity super-lithium separation windows, the lithium dendrite penetrates through the coating layer 11 to reach the surface or the inside of the lithium-embeddable material of the kernel 12, and the lithium dendrite and the lithium-embeddable material spontaneously generate a quick lithium-embeddable reaction, so that the lithium dendrite is absorbed to prevent the lithium dendrite from penetrating through the isolating membrane to influence the performance of the battery core.

In some embodiments, optionally, the secondary battery comprises a positive electrode plate, a negative electrode plate, a coating 1 and a separation film, wherein the coating 1 is disposed on the negative electrode plate, and the coating 1 is the coating 1 disclosed in some embodiments of the present application. The preparation method of the secondary battery comprises the following steps:

[ preparation of coating 1 ]

Preparation of coating layer 11 solution: dissolving the material of the coating layer 11 in deionized water, and stirring at the rotating speed of 600-1000 rpm for 25-35 min at the temperature of 22-28 ℃ to obtain a solution of the coating layer 11; adding the core 12 material into the coating layer 11 solution, and stirring at the rotating speed of 600-1000 rpm for 4-6 h at the temperature of 22-28 ℃ to obtain a coating layer 1; continuously stirring the coating 1 at the temperature of 22-28 ℃ at the speed of 15-25 rpm to prevent the gel from settling.

[ PREPARATION OF POSITIVE ELECTRODE PIECE ]

The positive pole piece comprises a positive current collector and a positive pole film layer arranged on at least one surface of the positive current collector, and the positive pole film layer comprises a positive active material.

As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.

In some embodiments, the positive electrode 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 polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive active material may employ a positive active material for a secondary battery, 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 positive electrode active material of a secondary battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g., liNiO) ₂ ) Lithium manganese oxides (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 (may also be abbreviated as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may also be abbreviated as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may also be abbreviated as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (may also be abbreviated as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxides (e.g., liNi) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, 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 referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) Composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate and manganese phosphateAt least one kind of composite material of lithium iron and carbon.

In some embodiments, the positive electrode film layer further optionally includes 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 fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes 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: dispersing the above components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

In some embodiments, the positive electrode sheet may be prepared by: preparing a nickel-cobalt-manganese (NCM) ternary material, a conductive agent carbon black, a binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) according to a weight ratio of 97:1.5:1.5:70, stirring and mixing uniformly to obtain anode slurry; and then uniformly coating the positive electrode slurry on a positive electrode current collector, and then drying, cold pressing and cutting to obtain the positive electrode piece.

[ PREPARATION OF NEGATIVE ELECTRODE PIECE ]

The negative pole piece includes the negative pole mass flow body and sets up the negative pole rete on the negative pole mass flow body at least one surface, and the negative pole rete includes negative pole active material.

As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode 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 can be used. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative active material may employ a negative active material for a secondary battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material may be selected from at least one of elemental silicon, silicon oxy-compounds, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative active material of the battery 1 may be used. The negative electrode active material may be used alone or in combination of two or more.

In some embodiments, the anode film layer further optionally includes a binder. The binder may be at least one selected from 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 negative electrode film layer further optionally includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet can be prepared by: dispersing the components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.

In some embodiments, the negative electrode sheet can be prepared by: the active substance artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), and thickening agent sodium carboxymethylcellulose (CMC) are mixed according to the weight ratio of 96.2:0.8:0.8:1.2 dissolving in solvent water, and uniformly mixing to prepare cathode slurry; and uniformly coating the negative electrode slurry on the copper foil of the negative current collector once or for multiple times, and drying and cold-pressing to obtain the negative electrode piece.

[ coating of coating layer 1 ]

And coating the prepared coating 1 on the surface of the negative pole piece by using a transfer coating machine, and then drying and die-cutting to obtain the negative pole piece with the lithium precipitation prevention coating 1.

[ preparation of electrolyte ]

The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The electrolyte is not particularly limited in kind, and can be selected according to the requirement. 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 may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may 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, dimethylsulfone, methylethylsulfone, and diethylsulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery 1, such as an additive for improving overcharge properties of the battery 1, an additive for improving high-temperature or low-temperature properties of the battery 1, and the like.

In some embodiments, the electrolyte may be prepared by: in an argon atmosphere glove box (H) ₂ O<0.1ppm，O ₂ <0.1 ppm), mixing organic solvent Ethylene Carbonate (EC)/Ethyl Methyl Carbonate (EMC) uniformly according to the volume ratio of 3/7, adding 12.5% LiPF ₆ And dissolving the lithium salt in the organic solvent, and uniformly stirring to obtain the electrolyte.

[ preparation of isolation film ]

The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.

In some embodiments, the material of the isolation film may be at least one selected from 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.

[ Assembly of Secondary Battery ]

And assembling the positive pole piece and the negative pole piece into a battery cell, and performing processes of liquid injection, formation, aging, K measurement, capacity test and the like to obtain the secondary battery.

In some embodiments, optionally, the secondary battery includes a positive electrode plate, a negative electrode plate, a coating 1, and a separator, the coating 1 is disposed on a side of the separator close to the negative electrode plate, and the coating 1 is the coating 1 disclosed in some embodiments herein. The preparation method of the secondary battery comprises the following steps:

[ preparation of coating 1 ]

[ PREPARATION OF POSITIVE ELECTRODE PIECE ]

In some embodiments, the positive active material may be a positive active material for the battery 1, 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 the positive electrode active material of the battery 1 may be used. These positive electrode active materials may be used alone or in combination of two or more kinds thereof. Among them, examples of the lithium transition metal oxide 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 (may also be abbreviated as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may also be abbreviated as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may also be abbreviated as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (may also be abbreviated as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxides (e.g., liNi) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, 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 referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

[ PREPARATION OF NEGATIVE ELECTRODE PIECE ]

The negative pole piece includes the negative current collector and sets up the negative pole rete on the negative current collector at least one surface, and the negative pole rete includes negative active material.

In some embodiments, the negative active material may be one known in the art for use in the battery 1. As an example, the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material may be selected from at least one of elemental silicon, silicon oxy-compounds, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative active material of the battery 1 may be used. The negative electrode active material may be used alone or in combination of two or more.

In some embodiments, the negative electrode sheet can be prepared by: the active substance artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), and thickening agent sodium carboxymethylcellulose (CMC) are mixed according to the weight ratio of 96.2:0.8:0.8:1.2 dissolving in solvent water, and preparing into negative electrode slurry after uniformly mixing; and uniformly coating the negative electrode slurry on the copper foil of the negative current collector once or for multiple times, and drying and cold-pressing to obtain the negative electrode piece.

[ preparation of electrolyte ]

In some embodiments, the electrolyte may be prepared by: in an argon atmosphere glove box (H) ₂ O<0.1ppm，O ₂ <0.1 ppm), mixing organic solvent Ethylene Carbonate (EC)/Ethyl Methyl Carbonate (EMC) at volume ratio of 3/7, adding LiPF 12.5% ₆ And dissolving the lithium salt in the organic solvent, and uniformly stirring to obtain the electrolyte.

[ preparation of isolation film ]

[ coating of coating 1 ]

And (3) coating the prepared coating 1 on one side of the isolating film close to the negative pole piece by using a transfer coater to form the isolating film with the lithium precipitation preventing coating 1.

[ Assembly of Secondary Battery ]

And assembling the positive pole piece and the negative pole piece into a battery cell, and carrying out processes of liquid injection, formation, aging, K measurement, capacity test and the like to obtain the secondary battery.

Referring to fig. 2, fig. 2 is a schematic structural view of a battery module 2 according to some embodiments of the present disclosure. The present application provides a battery module 2. The battery module 2 includes the secondary battery provided in the present application. The number of the secondary batteries included in the battery module 2 may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module 2.

In the battery module 2, a plurality of secondary batteries may be arranged in series along the longitudinal direction of the battery module 2. Of course, the arrangement may be in any other manner. The plurality of secondary batteries may be further fixed by a fastener.

Alternatively, the battery module 2 may further include a case having an accommodating space in which a plurality of secondary batteries are accommodated.

Referring to fig. 3-4, according to some embodiments of the present disclosure, fig. 3 is a schematic structural view of a battery pack 3 according to some embodiments of the present disclosure; fig. 4 is an exploded view of the battery pack 3 according to some embodiments of the present application. The present application provides a battery pack 3. The battery pack 3 includes the battery module 2 provided in the present application. The number of the battery modules 2 included in the battery pack 3 may be one or more, and the specific number may be selected by those skilled in the art according to the application and the capacity of the battery pack 3.

The battery pack 3 may include a battery case and a plurality of battery modules 2 disposed in the battery case. The battery box includes an upper box 31 and a lower box 32, and the upper box 31 can be covered on the lower box 32 and forms a closed space for accommodating the battery module 2. The plurality of battery modules 2 may be arranged in the battery box in any manner.

Referring to fig. 5, according to some embodiments of the present application, fig. 5 is a schematic structural diagram of an electric device 4 according to some embodiments of the present application. The present application provides an electric device 4. The electric device 4 includes at least one of the secondary battery, the battery module 2, and the battery pack 3 provided in the present application. The secondary battery, the battery module 2, and the battery pack 3 may be used as a power source of the electric device 4, or may be used as an energy storage unit of the electric device 4. The powered device 4 may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

As the electric device 4, a secondary battery, the battery module 2, or the battery pack 3 may be selected according to the use requirement thereof.

Please refer to fig. 5 again. The electric device 4 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, or the like. In order to satisfy the demand of the electric device 4 for high power and high energy density of the secondary battery, the battery pack 3 or the battery module 2 may be used.

In some embodiments, the powered device 4 may be a mobile phone, a tablet computer, a notebook computer, or the like. The electric device 4 is generally required to be thin and light, and a secondary battery can be used as a power source.

Examples

Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

The coating comprises a core-shell material, the core-shell material comprises a core and a coating layer coated on the core, the core is lithium titanate, and the coating layer is aluminum oxide. Wherein, the Dv50 of the core is 20 μm, the thickness of the coating layer is 10 μm, the mass percent of the core is 60 percent and the mass percent of the coating layer is 40 percent relative to the total mass of the core-shell material.

The preparation method of the core-shell material comprises the following steps:

[ preparation of coating solution ]

Dissolving alumina in deionized water, and stirring at 25 deg.C and 800rpm for 30min to obtain coating layer solution.

[ preparation of core-Shell Material solution ]

Adding lithium titanate into the coating layer solution, and stirring at the rotating speed of 800rpm for 5 hours at 25 ℃ to obtain a core-shell material solution.

[ PREPARATION OF CORE-SHELL MATERIAL ]

And drying the core-shell material solution to obtain the core-shell material.

The preparation method of the secondary battery comprises the following steps:

[ PREPARATION OF POSITIVE ELECTRODE PIECE ]

LiNi as positive electrode active material _0.5 Co _0.2 Mn _0.3 O ₂ And after fully stirring and uniformly mixing the anode plate with a conductive agent Super P and a binder polyvinylidene fluoride (PVDF) in an N-methyl pyrrolidone solvent according to a weight ratio of 96.

[ PREPARATION OF NEGATIVE ELECTRODE PIECE ]

The method comprises the following steps of fully stirring and uniformly mixing artificial graphite serving as a negative active material, a conductive agent Super P, a binder Styrene Butadiene Rubber (SBR) and a thickening agent sodium carboxymethyl cellulose (CMC) in a deionized water solvent system according to a weight ratio of 97.5.

[ preparation of coating ]

And coating the prepared core-shell material solution on the surface of the negative pole piece by using a transfer coating machine to form a coating with the thickness of 30 mu m, and then drying and die-cutting to obtain the negative pole piece with the lithium precipitation prevention coating.

[ preparation of isolation film ]

The isolating membrane is made of polypropylene.

[ Assembly of Secondary Battery ]

And overlapping the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole and the negative pole to play an isolating role, and winding to obtain the bare cell. And placing the bare cell in a corresponding aluminum shell, injecting electrolyte and packaging to obtain the secondary battery.

Example 2

The present example differs from example 1 in that: the inner core is titanium niobate.

Example 3

This example differs from example 1 in that: the inner core is lithium niobate.

Example 4

This example differs from example 1 in that: relative to the total mass of the core-shell material, the mass percent of the core is 30%, the mass percent of the coating layer is 70%, and the thickness of the coating layer is 15 μm.

Example 5

This example differs from example 1 in that: relative to the total mass of the core-shell material, the mass percent of the core is 90%, the mass percent of the coating layer is 10%, and the thickness of the coating layer is 0.50 μm.

Example 6

This example differs from example 1 in that: the Dv50 of the core was 0.05. Mu.m.

Example 7

The present example differs from example 1 in that: the Dv50 of the core was 40 μm.

Example 8

This example differs from example 1 in that: the coating layer is polyacrylic acid.

Example 9

This example differs from example 1 in that: the coating layer is polyethylene.

Example 10

This example differs from example 1 in that: the thickness of the coating layer was 0.05. Mu.m.

Example 11

This example differs from example 1 in that: the thickness of the coating layer was 20.00. Mu.m.

Example 12

This example differs from example 1 in that: the preparation method of the secondary battery comprises the following steps:

[ PREPARATION OF POSITIVE ELECTRODE PIECE ]

[ PREPARATION OF NEGATIVE ELECTRODE PLATE ]

[ preparation of isolation film ]

The isolating membrane is made of polypropylene, the prepared core-shell material solution is coated on the surface of one side, close to the negative pole piece, of the isolating membrane by using a transfer coating machine to form a coating with the thickness of 30 micrometers, and then the isolating membrane with the lithium precipitation preventing coating is obtained after drying and die cutting.

[ preparation of coating ]

And coating the prepared core-shell material solution on the surface of one side, close to the negative pole piece, of the isolation film by using a transfer coating machine, and then drying and die-cutting to obtain the negative pole piece with the lithium precipitation preventing coating.

[ Assembly of Secondary Battery ]

Comparative example 1

The comparative example differs from example 1 in that: the core-shell material includes only the core and no cladding.

Comparative example 2

This comparative example differs from example 1 in that: core shell materials are not included.

[ Battery Performance test ]

1. Battery weight energy density test

Discharging to the lower limit termination voltage by 0.33C or 1C current at 25 +/-2 ℃, standing for 1h, charging to the termination voltage by 0.33C or 1C constant current, then charging to the upper limit termination voltage by 0.05C constant voltage, standing for 1h, discharging to the lower limit termination voltage by 0.33C or 1C, and dividing the measured 0.33C or 1C discharge energy by the cell weight to obtain the cell weight energy density (unit is Wh/kg) of 0.33C or 1C.

2. Battery volumetric energy density test

Discharging to the lower limit termination voltage by 0.33C or 1C current at 25 +/-2 ℃, standing for 1h, charging to the termination voltage by 0.33C or 1C constant current, then charging to the upper limit termination voltage by 0.05C constant voltage, standing for 1h, discharging to the lower limit termination voltage by 0.33C or 1C, and dividing the measured 0.33C or 1C discharge energy by the cell volume to obtain the 0.33C or 1C cell volume energy density (the unit is Wh/L).

3. First discharge test

Discharging to the lower limit stop voltage by 0.33C or 1C current at 25 +/-2 ℃, standing for 1h, charging to the stop voltage by 0.33C or 1C constant current, charging to the upper limit stop voltage by 0.05C constant voltage, standing for 1h, discharging to the lower limit stop voltage by 0.33C or 1C, and measuring the 0.33C or 1C discharge capacity and energy.

4. Capacity Retention test after 100 weeks cycling

At the temperature of 25 +/-2 ℃,

a. taking the 0.33C capacity in the first discharge capacity test as the initial capacity value C0 of the battery core;

b. charging at 0-80% SOC 1.5C0 and 80-100% SOC 0.33C0 with constant current to upper limit termination voltage, charging at 0.05C constant voltage to upper limit termination voltage, and standing for 30min;

c. discharging to lower limit termination voltage with 0.33C0, and standing for 30min;

and C, cycling for 100 weeks, and dividing the discharge capacity at the 100 th week by the initial capacity C0 to obtain the capacity retention rate after 100-week cycling.

5. Capacity Retention test after 500 weeks cycling

At the temperature of 25 +/-2 ℃,

d. taking the 0.33C capacity in the initial discharge capacity test as a cell initial capacity value C0;

e. charging at 0-80% SOC 1.5C0 and 80-100% SOC 0.33C0 with constant current to upper limit termination voltage, charging at 0.05C constant voltage to upper limit termination voltage, and standing for 30min;

f. discharging with 0.33C0 to lower limit termination voltage, and standing for 30min;

and C, cycling for 500 weeks, and dividing the discharge capacity at 500 weeks by the initial capacity C0 to obtain the capacity retention rate after 500 weeks cycling.

The coating-related parameters and battery performance test data for the examples and comparative examples are shown in table 1.

[ data analysis ]

As can be seen from table 1, it is,

(1) The density of the lithium-embeddable material of the core is higher than that of the cladding layer, so that the energy density of the lithium-embeddable material is slightly reduced;

(2) The coating proportion has no influence on the volume of the battery, so the energy density is unchanged;

(3) The density of the core lithium-embeddable material is higher than that of the coating layer, so that the thickness of the core lithium-embeddable material Dv50 is larger than that of the coating layer, the weight of the corresponding battery is increased, and the energy density of the battery is slightly reduced;

(4) After the battery is cycled for 100 weeks, the comparative example 1 only has a lithium intercalation material without being coated by an insulating material, the battery capacity and the capacity retention rate after cycling are lowest, and the lithium intercalation material is directly contacted with an active substance and serves as a part of the active substance due to no protection of the insulating layer, so that the active lithium is consumed, and the performances of other experimental batteries are basically equivalent;

(5) After the battery is cycled for 500 weeks, the comparative example 1 only contains the lithium-embeddable material and is not coated by the insulating material, and the battery capacity and the capacity retention rate after cycling are the lowest, because the battery cycling capacity retention rates of other experimental batteries containing the coating material have smaller difference and are all better than the battery core without the coating material in the comparative example 8, and the cycling capacity retention rates of the lithium-embeddable material with the content of more than 30 percent are basically the same.

(6) Comparative example 2 shows a decrease in discharge capacity and capacity retention rate compared to other coated batteries because the lithium intercalatable layer cannot be completely coated when the coating is too thin, resulting in direct contact between the partially intercalated lithium material and the active material, charging the active material, and consumption of the active lithium, resulting in a slight decrease in performance.

The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.

Claims

1. A core-shell material, comprising:

the core is a lithium embeddable material which is one or a combination of more than two of lithium titanate, titanium niobate, lithium niobate, chromium, silicon, tin and iron phosphate;

the coating layer is made of an insulating material;

wherein the coating layer is coated on the surface of the inner core.

2. Core-shell material according to claim 1, characterized in that the mass percentage of the core relative to the total mass of the core-shell material is between 30% and 90% and/or the mass percentage of the coating layer relative to the total mass of the core-shell material is between 10% and 70%.

3. The core-shell material according to claim 1 or 2, wherein the Dv50 of the core is between 0.05 μ ι η and 40 μ ι η.

4. The core-shell material according to any one of claims 1 to 3, wherein the thickness of the coating layer is 0.05 μm to 20 μm.

5. The core-shell material according to any of claims 1-4, wherein the insulating material is an inorganic insulating material or an organic insulating material.

6. Core-shell material according to claim 5, wherein the inorganic insulating material is selected from boehmite or/and alumina.

7. The core-shell material of claim 5, wherein the organic insulating material is selected from one or more of polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, polyphthalamide, phenolic resin, polyethylene, polypropylene, hydroxymethyl cellulose.

8. A coating comprising the core-shell material of any one of claims 1-7, the core-shell material comprising:

the inner core is used for absorbing lithium dendrites, the inner core is a lithium embeddable material, and the lithium embeddable material is one or a combination of more than two of lithium titanate, titanium niobate, lithium niobate, chromium, silicon, tin and iron phosphate;

a coating layer for conducting ions and blocking electrons, the coating layer being an insulating material;

wherein the coating layer is coated on the surface of the inner core.

9. Coating according to claim 8, wherein the mass percentage of the core-shell material is 80% to 100% relative to the total mass of the coating.

10. Coating according to claim 8 or 9, characterized in that the thickness of the coating is 0.1-50 μm.

11. A secondary battery, comprising a positive electrode plate, a negative electrode plate, a coating layer and a separator, wherein the coating layer is arranged on the negative electrode plate or/and on one side of the separator close to the negative electrode plate, and the coating layer is the coating layer as claimed in any one of claims 8 to 10.

12. A battery module comprising the secondary battery according to claim 11.

13. A battery pack comprising the battery module according to claim 12.

14. An electric device comprising at least one of the secondary battery according to claim 11, the battery module according to claim 12, and the battery pack according to claim 13.