CN117525750A

CN117525750A - Battery cell, battery and electricity utilization device

Info

Publication number: CN117525750A
Application number: CN202311685498.5A
Authority: CN
Inventors: 吴凯; 肖志蔚; 魏满想; 徐�明; 张鹏; 杨建瑞
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-12-08
Filing date: 2023-12-08
Publication date: 2024-02-06

Abstract

The application discloses a battery monomer, a battery and an electric device, wherein the battery monomer comprises a negative electrode plate and a separation film, the separation film comprises a porous substrate and a coating arranged on at least one surface of the porous substrate, and the coating comprises nanocellulose and granular filler; the width of the isolating film is marked as A, the width of the negative electrode plate is marked as B, the units are all mm, and A-B is more than 0 and less than or equal to 5mm. The battery unit can have high energy density, high reliability and good processability.

Description

Battery cell, battery and electricity utilization device

Technical Field

The application relates to a battery cell, a battery and an electric device.

Background

With the increasing demands of high energy density batteries, ultra-thin separator films are beginning to be applied in a wide range. However, the existing ultrathin isolation film cannot achieve both low thickness and high heat resistance. The existing ultrathin isolating film is easy to shrink after being heated, so that in order to fully separate the positive electrode and the negative electrode, the battery is prevented from being short-circuited between the positive electrode and the negative electrode due to shrinkage of the isolating film under a heated condition, and the width of the isolating film is required to be larger than that of the negative electrode pole piece. In general, the difference between the widths of the separator and the negative electrode tab needs to be greater than 6mm, and thus, in the battery production process, the separator is prone to problems of local redundancy, folding or breakage, thereby affecting the processability of the battery. In order to obtain a high-energy-density battery, the width of the negative electrode plate is increased to reduce the difference between the widths of the isolating film and the negative electrode plate, and the isolating film is easy to cause short circuit after heat shrinkage in a high-temperature environment or a heat abuse environment of the battery. Therefore, it is difficult for the existing battery to have a combination of high energy density, high reliability and good processability.

Disclosure of Invention

The application provides a battery cell, a battery and an electric device, which can have high energy density, high reliability and good processing performance.

A first aspect of the present application provides a battery cell comprising a negative electrode sheet and a separator comprising a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating comprising nanocellulose and a particulate filler; the width of the isolating film is marked as A, the width of the negative pole piece is marked as B, and the units are mm, and A-B is more than 0 and less than or equal to 5mm.

The difference between the width of the isolating film and the width of the negative electrode plate of the battery monomer are smaller than or equal to 5mm. The difference between the widths of the isolating film and the negative electrode plate is reduced, so that the probability of local redundancy, folding or crushing problems of the isolating film in the process of assembling the battery cells is reduced, and the battery cells can have good processing performance; meanwhile, when the internal spaces of the battery cells are the same and the widths of the isolating films are the same, the coating widths of the negative electrode plate and the positive electrode plate are increased due to the fact that the difference between the widths of the isolating films and the negative electrode plate is reduced, and therefore the battery cells can have high volume energy density.

The coating of the isolating film used for the battery monomer provided by the embodiment of the application comprises nanocellulose and granular filler. The nanocellulose has good high-temperature resistance, and the volume change is smaller after being heated, so that the heat resistance of the isolating film can be improved; the density of the nanocellulose is smaller, so that the quality of the battery monomer can be reduced, and the quality energy density of the battery monomer can be improved; in addition, the nanocellulose itself contains a large amount of hydroxyl groups, so that the nanocellulose can be mutually overlapped to form a three-dimensional framework structure, and further, the mechanical strength and the puncture resistance of the isolating membrane can be improved through matching with granular fillers. The nano cellulose contains a large amount of hydroxyl groups, and can be connected with granular fillers, porous substrates and the like through acting forces such as hydrogen bonds, van der Waals forces and the like, so that the bonding strength between the granular fillers in the coating and between the coating and the porous substrates can be enhanced, the powder dropping problem is reduced, and the processability of the isolating film and the battery monomer is improved. Therefore, the battery cell provided by the embodiment of the application can also have high reliability.

In some embodiments, 2 mm.ltoreq.A-B.ltoreq.4 mm, alternatively 2.5 mm.ltoreq.A-B.ltoreq.3.5 mm. Thereby being beneficial to further improving the volume energy density and the processing performance of the battery monomer.

In some embodiments, the nanocellulose has an average length of 100nm to 1200nm, alternatively 200nm to 1000nm.

The average length of the nanocellulose is adjusted within the range, so that the nanocellulose is favorably overlapped to form a three-dimensional skeleton structure, and the three-dimensional skeleton structure and granular filler are favorably overlapped to form an integrated coating, thereby being favorable for improving the heat resistance of the isolating film, further being favorable for reducing the risk of short circuit failure in the use process of the battery monomer, and being favorable for improving the cycle performance of the battery monomer. By adjusting the average length of the nanocellulose within the above range, it is also advantageous for the coating slurry to have a suitable viscosity, thereby facilitating coating, and also facilitating promotion of uniformity and consistency of the coating.

In some embodiments, the nanocellulose has an average diameter of 11nm to 40nm, alternatively 15nm to 32nm.

The average diameter of the nanocellulose is adjusted within the range, so that the nanocellulose is favorably lapped to form a three-dimensional skeleton structure, the formed three-dimensional skeleton structure and granular filler are favorably lapped to form an integrated coating, the heat resistance of the isolating film is favorably improved, the short circuit failure risk in the use process of the battery monomer is favorably reduced, and the cycle performance of the battery monomer is favorably improved.

In some embodiments, the nanocellulose has an aspect ratio of 5 to 60, alternatively 12 to 35.

The length-diameter ratio of the nanocellulose is adjusted within the range, so that the nanocellulose is favorably overlapped to form a three-dimensional skeleton structure, the formed three-dimensional skeleton structure and the granular filler are favorably overlapped to form an integrated coating, the heat resistance of the isolating film is favorably improved, the short circuit failure risk in the use process of the battery monomer is favorably reduced, and the cycle performance of the battery monomer is favorably improved. By adjusting the length-diameter ratio of the nanocellulose within the range, the electrolyte wettability of the isolating membrane is also facilitated to be improved, so that ion transmission is facilitated, and dendrite reduction is also facilitated.

In some embodiments, the nanocellulose includes modifying groups including at least one of amine groups, carboxyl groups, aldehyde groups, sulfonic acid groups, or phosphoric acid groups, optionally including at least one of sulfonic acid groups or phosphoric acid groups.

When the nanocellulose has the specific modified group, on one hand, the heat resistance of the isolating film can be effectively improved, the thermal stability of the battery monomer is improved, and the short circuit failure risk in the use process of the battery monomer is reduced; on the other hand, the bonding strength between the coating and the porous substrate can be improved. When the nanocellulose has the specific modified group, the nanocellulose and the granular filler are lapped to form an integrated coating, so that the coating has a stable space network structure, the wettability and the liquid retention of the electrolyte of the isolating film are improved, and the ion transmission characteristic and the voltage breakdown resistance characteristic of the isolating film are improved; and the method is also beneficial to matching with high-voltage positive electrode active materials and further improving the energy density of the battery cell.

In some embodiments, the nanocellulose includes hydroxyl groups and modifying groups, and the molar ratio of modifying groups to hydroxyl groups is 1:4 to 4:1, alternatively 2:3 to 7:3.

When the molar ratio of the modified group to the hydroxyl is in the above range, the heat resistance, the ion transmission characteristic, the electrolyte wettability and the liquid retention property of the isolating film can be further improved, so that the risk of short circuit failure in the use process of the battery monomer can be reduced, and the cycle performance of the battery monomer can be improved.

In some embodiments, the nanocellulose is present in the coating in an amount of 5wt% to 60wt%, alternatively 7wt% to 45wt%.

In some embodiments, the particulate filler is present in the coating in an amount greater than 38wt%, alternatively 53wt% to 91wt%.

The mass content of the nanocellulose and the granular filler is in the range, so that the isolating film has high heat resistance and good ion transmission property, and further the battery monomer has good cycle performance; the coating slurry is also beneficial to having proper viscosity and being beneficial to coating; the high bonding strength between the coating and the porous substrate is also facilitated, and the structural stability of the isolating membrane is improved; the method is also beneficial for the nanocellulose and the granular filler to overlap to form an integrated coating, so that the coating has a more stable space network structure.

In some embodiments, the porous substrate has a thickness of 5 μm or less, optionally 3 μm to 4.5 μm.

In some embodiments, the porous substrate has an average pore size of 10nm to 60nm, alternatively 20nm to 40nm.

In some embodiments, the porous substrate has a porosity of 20% to 60%, alternatively 30% to 50%.

In some embodiments, the porous substrate comprises a polyolefin, optionally polyethylene.

In some embodiments, the porous substrate has a puncture strength of 390gf or more, optionally 400gf to 480gf.

The higher the puncture strength of the porous base material is, the better the puncture resistance is, and the short circuit between the anode and the cathode caused by the puncture of the anode particles and the metal foreign particles through the isolating membrane can be effectively avoided. Therefore, the puncture strength of the porous base material is in the range, so that the passing rate of the short circuit test of the battery cell can be improved, and the reliability of the battery cell can be improved.

In some embodiments, the porous substrate has a longitudinal heat shrinkage of less than 3%, alternatively 1% to 2.5%, at 105 ℃ for 1 hour.

In some embodiments, the porous substrate has a transverse heat shrinkage of less than 2%, alternatively 1% to 1.8%, at 105 ℃ for 1 hour.

The heat shrinkage rate of the porous base material is reduced, and the heat resistance of the porous base material is good, so that the short circuit test passing rate of the battery cell can be improved, and the reliability of the battery cell can be improved.

In some embodiments, the porous substrate has a machine direction tensile strength of 2700kgf/cm or greater ² Optionally 2800kgf/cm ² -3500kgf/cm ² 。

In some embodiments, the porous substrate has a transverse tensile strength of 2500kgf/cm or greater ² Optionally 2600kgf/cm ² -3200kgf/cm ² 。

In some embodiments, the particulate filler comprises one or more of organic particles, inorganic particles, organic-inorganic composites.

In some embodiments, the particulate filler includes a first component of secondary particle morphology and a second component of primary particle morphology.

The first component in the shape of the secondary particles can better overlap with the three-dimensional skeleton structure formed by the nanocellulose to form an integrated effect, so that the coating has a more stable space network structure, the heat resistance of the isolating film can be further improved, and the thermal stability of the battery monomer is improved. The second component of the primary particle morphology is beneficial to reducing the moisture content of the coating and improving the ion transmission characteristics of the coating, thereby helping to improve the cycle performance of the battery cell.

In some embodiments, the average particle size of the first component of the secondary particle morphology is less than the average particle size of the second component of the primary particle morphology.

Thereby facilitating better functioning of the first component of the secondary particle morphology and the second component of the primary particle morphology. The first component of the secondary particle morphology has smaller particle size and better affinity with the nanocellulose, and the nanocellulose can be lapped in gaps among the primary particles in the first component forming the secondary particle morphology, so that the nanocellulose and the first component of the secondary particle morphology can be lapped to form an integrated coating, the coating has a more stable space network structure, and the heat resistance of the isolating film can be further improved. The second component with the primary particle morphology has larger particle size and higher strength, so that the framework supporting effect can be better exerted in the coating, the thermal shrinkage of the isolating film is reduced, and the heat resistance of the isolating film is improved; and the coating has more pore canal structure and lower moisture content, so that the ion transmission property of the isolating membrane can be further improved.

In some embodiments, the average particle size of the first component of the secondary particle morphology is less than 200nm, optionally 80nm to 180nm.

The average particle size of the first component with the secondary particle morphology is in the range, so that the first component has higher specific surface area, and can be better matched with a three-dimensional framework structure formed by nanocellulose and overlap-connected to form an integrated effect, so that the heat resistance of the isolating membrane and the infiltration and retention characteristics of the isolating membrane to electrolyte can be increased, and the heat stability and the cycle performance of the battery monomer can be improved.

In some embodiments, the average particle size of the second component of the primary particle morphology is from 200nm to 600nm, alternatively from 300nm to 500nm.

The average particle size of the second component with the primary particle morphology is in the range, so that the supporting effect of the second component with the primary particle morphology can be better exerted, the stable pore channel structure of the coating can be maintained in the long-term charge and discharge process, the moisture content of the isolating membrane can be reduced, the ion transmission can be promoted, and meanwhile, the heat resistance of the isolating membrane can be improved.

In some embodiments, the primary particles in the first component comprising the secondary particle morphology have a particle size of 15nm to 45nm, optionally 20nm to 35nm.

The particle size of the primary particles in the first component forming the appearance of the secondary particles is in the range, so that the first component has good appearance of the secondary particles, and the three-dimensional framework structure formed by the first component and the nanocellulose is better in lap joint to form an integrated effect.

In some embodiments, the specific surface area of the first component of the secondary particle morphology is greater than the specific surface area of the second component of the primary particle morphology.

Thereby facilitating better functioning of the first component of the secondary particle morphology and the second component of the primary particle morphology.

In some embodiments, the specific surface area of the first component of the secondary particle morphology is greater than 20m ² /g, optionally 30m ² /g-80m ² /g。

The specific surface area of the first component with the appearance of the secondary particles is in the range, the affinity with the nanocellulose is better, the three-dimensional framework structure formed by the nanocellulose can be better matched and overlapped to form an integrated effect, and therefore the heat resistance of the isolating membrane and the infiltration and retention characteristics of the isolating membrane to electrolyte can be improved, and the heat stability and the cycle performance of the battery monomer can be improved.

In some embodiments, the specific surface area of the second component of the primary particle morphology is 20m or less ² /g, optionally 5m ² /g-15m ² /g。

The specific surface area of the second component in the form of primary particles is within the above range, which is advantageous for reducing the moisture content of the barrier film and for improving the heat resistance of the barrier film.

In some embodiments, the mass content of the first component of the secondary particle morphology in the coating is greater than the mass content of the second component of the primary particle morphology in the coating.

In some embodiments, the first component of the secondary particle morphology is present in the coating in an amount of 10wt% to 85wt%, alternatively 20wt% to 75wt%.

The mass content of the first component with the secondary particle morphology is in the range, so that the coating slurry has proper viscosity and is more favorable for coating; in addition, the three-dimensional skeleton structure formed by the nano cellulose is lapped to form an integrated effect, so that the coating has a more stable space network structure, and the heat resistance and the ion transmission characteristic of the isolating film are improved.

In some embodiments, the second component of the primary particle morphology is present in the coating in an amount of 5wt% to 70wt%, alternatively 7wt% to 60wt%.

The mass content of the second component with the primary particle morphology is in the range, so that the supporting effect of the second component with the primary particle morphology can be better exerted, the stable pore channel structure of the coating can be maintained in the long-term charge and discharge process, and the moisture content of the isolating membrane can be reduced and the ion transmission can be promoted. The mass content of the second component in the morphology of the primary particles is in the above range, and the bulk density of the whole granular filler can be improved, and further the heat resistance and the puncture resistance of the isolating film can be improved.

In some embodiments, the coating further comprises a non-particulate binder. Optionally, the non-particulate binder is present in the coating in an amount of 3wt% or less based on the total mass of the coating.

In some embodiments, the release film further comprises an adhesive layer disposed on at least a portion of the surface of the coating. Optionally, the adhesive layer comprises a particulate adhesive. Optionally, the binder comprises at least one of an acrylate monomer homo-or copolymer, an acrylic monomer homo-or copolymer, a fluoroolefin monomer homo-or copolymer.

In some embodiments, the thickness of the coating is 0.2 μm to 2 μm, alternatively 0.4 μm to 1 μm. The thickness of the coating layer is in the above range, so that the battery cell can have high energy density, and the isolating film can have low thermal shrinkage, so that the battery cell has high reliability.

In some embodiments, the total thickness of the barrier film is 4 μm to 10 μm, alternatively 4.5 μm to 8.5 μm. The total thickness of the separator is within the above range, so that the battery cell can have high energy density, and the separator can have low thermal shrinkage, so that the battery cell has high reliability.

In some embodiments, the barrier film has a longitudinal heat shrinkage of 3% or less at 150 ℃ for 1 hour.

In some embodiments, the barrier film has a transverse heat shrinkage of 2% or less at 150 ℃ for 1 hour.

The separator has a low thermal shrinkage rate at high temperature, whereby the battery cell can have high reliability.

In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material including a carbon material. Optionally, the carbon material comprises one or more of artificial graphite and natural graphite.

In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material including a silicon-based material. Optionally, the silicon-based material further comprises one or more of alkali metal elements and alkaline earth metal elements, optionally one or more of Li, mg. Optionally, the mass ratio of the silicon-based material in the anode active material is greater than or equal to 5wt%, and is optionally 8wt% to 20wt%. Thus, the battery cell has both high energy density and long cycle life.

In some embodiments, the upper limit cutoff voltage of the battery cell is greater than or equal to 4.25V, optionally 4.30V-4.45V.

In some embodiments, the battery cell further includes a positive electrode sheet including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material including a layered lithium-containing transition metal oxide, and the positive electrode active material having a volume distribution particle diameter Dv50 of 6 μm or less, optionally 2 μm to 5 μm.

The positive electrode plate provided by the embodiment of the application adopts the positive electrode active material with smaller volume distribution particle diameter Dv50, so that the diffusion path of lithium ions in the positive electrode active material can be shortened, and further, lithium ions transmitted to the positive electrode from the negative electrode through the isolating film can be rapidly consumed. At this time, the difference in lithium ion concentration between the negative electrode side and the positive electrode side of the separator becomes large, and the driving force of lithium ions transmitted from the negative electrode to the positive electrode becomes large, so that the low temperature performance and cycle performance of the battery cell can be improved.

In some embodiments, the positive electrode active material has a volume distribution particle size Dv90 of 14 μm or less, optionally 4.5 μm to 13.5 μm.

By further adjusting the volume distribution particle diameter Dv90 of the positive electrode active material, the diffusion path of lithium ions in the positive electrode active material can be further shortened, thereby further increasing the concentration difference of lithium ions on the negative electrode side and the positive electrode side of the separator, increasing the driving force of lithium ions transmitted from the negative electrode to the positive electrode, and further improving the low temperature performance of the battery cell. By further adjusting the volume distribution particle diameter Dv90 of the positive electrode active material, the side reaction of the battery can be reduced, and the capacity fading rate of the battery can be reduced, thereby being beneficial to improving the cycle performance of the battery monomer. By further adjusting the volume distribution particle diameter Dv90 of the positive electrode active material, the positive electrode plate can also have higher compaction density, thereby being beneficial to improving the energy density of the battery cell.

In some embodiments, the positive electrode active material has a volume distribution particle size Dv10 of 3 μm or less, optionally 1 μm to 2 μm.

By further adjusting the volume distribution particle diameter Dv10 of the positive electrode active material, the side reaction of the battery can be reduced, and the capacity fading rate of the battery can be reduced, so that the cycle performance of the battery monomer can be improved, the positive electrode plate can be provided with higher compaction density, and the energy density of the battery monomer can be improved.

In some embodiments, the particle size distribution (Dv 90-Dv 10)/Dv 50 of the positive electrode active material is 0.8-2.5, optionally 1.3-2.3.

By further adjusting the particle size distribution (Dv 90-Dv 10)/Dv 50 of the positive electrode active material within the above range, the compaction density of the positive electrode plate can be improved, the space utilization rate of the positive electrode active material can be improved, and further the energy density of the battery cell can be improved. By further adjusting the particle size distribution (Dv 90-Dv 10)/Dv 50 of the positive electrode active material within the above-described range, the contact resistance between the particles of the positive electrode active material can also be reduced, the resistance of the battery cell can be reduced, and further the low-temperature performance of the battery cell can be improved.

In some embodiments, the positive electrode active material comprises a layered lithium-containing transition metal oxide in a single crystalline morphology, or both a layered lithium-containing transition metal oxide in a single crystalline morphology and a layered lithium-containing transition metal oxide in a polycrystalline morphology.

In some embodiments, the volume distribution particle size Dv50 of the layered lithium-containing transition metal oxide of single crystal morphology is 5 μm or less, optionally 2 μm to 4 μm.

In some embodiments, the volume distribution particle size Dv90 of the layered lithium-containing transition metal oxide of single crystal morphology is 10 μm or less, optionally 4.5 μm to 8 μm.

In some embodiments, the volume distribution particle size Dv10 of the layered lithium-containing transition metal oxide of single crystal morphology is 3 μm or less, optionally 1 μm to 2 μm.

The particle size of the layered lithium-containing transition metal oxide with the single crystal morphology is reduced, so that the diffusion path of lithium ions in the positive electrode active material can be further shortened, the positive electrode active material rapidly consumes lithium ions in the electrolyte, the concentration difference of the lithium ions on the negative electrode side and the positive electrode side of the isolating membrane can be further increased, the driving force of the lithium ions transmitted from the negative electrode to the positive electrode is increased, and the low-temperature performance of the battery cell can be further improved; however, the cycle performance of the battery cell may be somewhat degraded.

The volume distribution particle sizes Dv50, dv90 and/or Dv10 of the layered lithium-containing transition metal oxide with the single crystal morphology are adjusted within the above range, so that the battery cell has good low-temperature performance and good cycle performance.

In some embodiments, the layered lithium-containing transition metal oxide of single crystal morphology has a particle size distribution (Dv 90-Dv 10)/Dv 50 of 0.8-2.5, optionally 1.3-1.5.

The compaction density of the positive electrode plate can be improved by adjusting the particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide with the single crystal morphology within the range, so that the space utilization rate of the positive electrode active material is improved, and the energy density of the battery monomer is improved; the contact resistance among the particles of the positive electrode active material can be reduced, the impedance of the battery cell is reduced, and the low-temperature performance of the battery cell is further improved.

In some embodiments, the volume distribution particle size Dv50 of the layered lithium-containing transition metal oxide of the polycrystalline morphology is 7 μm to 12 μm, optionally 8 μm to 10 μm.

In some embodiments, the volume distribution particle size Dv90 of the layered lithium-containing transition metal oxide of the polycrystalline morphology is 12 μm to 20 μm, optionally 13 μm to 18 μm.

In some embodiments, the volume distribution particle size Dv10 of the layered lithium-containing transition metal oxide of the polycrystalline morphology is from 2 μm to 6 μm, optionally from 3 μm to 5 μm.

The volume distribution particle sizes Dv50, dv90 and/or Dv10 of the layered lithium-containing transition metal oxide with the polycrystalline morphology are adjusted within the above range, so that the battery cell has the advantages of high energy density, good low-temperature performance, good cycle performance and low manufacturing cost.

In some embodiments, the layered lithium-containing transition metal oxide of the polycrystalline morphology has a particle size distribution (Dv 90-Dv 10)/Dv 50 of 1.1-1.5, alternatively 1.2-1.4.

The compaction density of the positive electrode plate can be improved by adjusting the particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide with the polycrystalline morphology within the range, the space utilization rate of the positive electrode active material is improved, and the energy density of the battery monomer is improved; the contact resistance among the particles of the positive electrode active material can be reduced, the impedance of the battery cell is reduced, and the low-temperature performance of the battery cell is further improved.

A second aspect of the present application provides a battery comprising the battery cell of the first aspect of the present application.

A third aspect of the present application provides an electrical device comprising the battery of the second aspect of the present application.

The power utilization device comprises the battery provided by the application, and therefore has at least the same advantages as the battery.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the drawings that are required to be used in the embodiments of the present application. It is apparent that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained from the drawings without inventive work for those of ordinary skill in the art.

Fig. 1 is a schematic view of a battery cell provided in some embodiments of the present application.

Fig. 2 is a schematic diagram of an electrical device provided in some embodiments of the present application.

In the drawings, the drawings are not necessarily to scale. The reference numerals are explained as follows: 5. and (3) a battery cell.

Detailed Description

Hereinafter, embodiments of a battery cell, a battery, and an electric device of the present application are specifically disclosed 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, and such solutions should be considered to be included in the disclosure of the present application, 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, if not specifically stated, and such technical solutions should be considered as included in the disclosure of the present application.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "first," "second," and the like, herein, are used for distinguishing between different objects and not for describing a particular sequential or sub-relationship, unless otherwise indicated.

In the present application, the terms "plurality" and "a plurality" refer to two or more.

In the description of the embodiments of the present application, a first feature "on" or "under" a second feature may be the first and second features being in direct contact, or the first and second features being in indirect contact via an intermediary, unless otherwise specified. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art.

Unless otherwise indicated, the values of the parameters mentioned in the present application may be determined by various test methods commonly used in the art, for example, may be determined according to the test methods given in the examples of the present application. The test temperature for each parameter was 25 ℃ unless otherwise indicated.

In the present application, the terms "single crystal morphology layered lithium-containing transition metal oxide", "polycrystalline morphology layered lithium-containing transition metal oxide" are all in the meaning well known in the art.

"single crystal morphology layered lithium-containing transition metal oxide" also includes quasi-single crystal (also known as monocrystalline) morphology layered lithium-containing transition metal oxide, which is a meaning well known in the art and generally refers to particles agglomerated from a small number (e.g., 2-5) of primary particles. The layered lithium-containing transition metal oxide with the polycrystalline morphology refers to a layered lithium-containing transition metal oxide with a secondary particle morphology formed by agglomerating a plurality of primary particles.

The "layered lithium-containing transition metal oxide of single crystal morphology" and the "layered lithium-containing transition metal oxide of polycrystalline morphology" can be distinguished by scanning electron microscopy.

The Dv10, dv50, dv90 of the material are all within the meaning known in the art and can be measured using instrumentation and methods known in the art. For example, reference may be made to GB/T19077-2016 for convenient measurement using a laser particle size analyzer (e.g. Malvern Mastersizer 3000). The physical definition of Dv90 is the particle size corresponding to the material when the cumulative volume distribution percentage reaches 90%; the physical definition of Dv50 is the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%; the physical definition of Dv10 is the particle size corresponding to a material cumulative volume distribution percentage of 10%. During testing, a proper amount of sample to be tested (ensuring 8% -12% of shading degree) can be taken, 20ml of deionized water is added, and the external temperature is exceeded for 5 minutes (for example, 53 KHz/120W) at the same time so as to enable the sample to be tested to be completely dispersed.

The specific surface area of a material is within the meaning well known in the art and can be measured using instruments and methods known in the art. For example, reference may be made to GB/T19587-2017, which is determined by a nitrogen adsorption specific surface area analysis test method and calculated by BET (BrunauerEmmett Teller). Alternatively, the nitrogen adsorption specific surface area analysis test may be performed by a Tri-Star 3020 type specific surface area pore size analysis tester from Micromeritics Inc. of America.

It should be noted that, the embodiment of the application is aimed at various parameter tests of the isolating film, the positive electrode plate, the negative electrode plate and the like, and the parameter tests can be carried out in the preparation process of the battery monomer, or can be carried out after each component is disassembled from the prepared battery monomer.

The battery referred to in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in the present application may include a battery cell, a battery module, a battery pack, or the like. The battery cell is the smallest unit constituting the battery, and it alone can realize the charge and discharge functions. When a plurality of battery cells are provided, the plurality of battery cells are connected in series, in parallel or in series-parallel through the converging component. In some embodiments, the battery may be a battery module; when a plurality of battery cells are provided, the plurality of battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack including a case and a battery cell, the battery cell or battery module being housed in the case. In some embodiments, the tank may be part of the chassis structure of the vehicle. For example, a portion of the tank may become at least a portion of a floor of the vehicle, or a portion of the tank may become at least a portion of a cross member and a side member of the vehicle.

In some embodiments, the battery may be an energy storage device. The energy storage device comprises an energy storage container, an energy storage electric cabinet and the like.

The battery cells mentioned in the embodiments of the present application may include lithium ion battery cells.

The battery monomer may be in a cuboid structure or a soft package structure, which is not limited in this embodiment. Fig. 1 shows a rectangular parallelepiped battery cell 5 as an example.

The battery cell includes an electrode assembly and an outer package. The electrode assembly comprises a positive electrode plate, a negative electrode plate and a separation film. The isolating film is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the positive pole and the negative pole from being short-circuited, and can enable ions to pass through freely to form a loop.

In some embodiments, the electrode assembly may be a wound structure or a lamination structure.

The outer package is used for packaging the electrode assembly. In some embodiments, the overwrap may be a soft pack material or a hard shell material. The soft package material can be one or more of plastic, such as aluminum plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). The hard shell material may include, but is not limited to, a hard plastic shell, an aluminum shell, or a steel shell.

In some embodiments, the outer package may be a hard shell material.

The overpack may include a housing and an end cap assembly. The case may be a hollow structure having one side open, and the cap assembly is covered at the opening of the case and forms a sealing connection to form a receiving chamber for receiving the electrode assembly.

The outer package may further include a case having a hollow structure with opposite sides open, and two end cap assemblies, one of which is correspondingly covered at one opening of the case and forms a sealing connection, so as to form a receiving cavity for receiving the electrode assembly.

The end cap assembly may include an end cap that covers the opening of the housing. The end cap may be of various structures, for example, a plate-like structure, a hollow structure with one end open, or the like. The end caps may be made of an insulating material (e.g., plastic) or may be made of a conductive material (e.g., a metallic material). When the end cap is made of a conductive material, the end cap assembly may further include an insulating member at a side of the end cap facing the electrode assembly to insulate the end cap from the electrode assembly.

The end cap assembly may further include an electrode terminal mounted to the end cap. The electrode terminals may be two, which are defined as a positive electrode terminal and a negative electrode terminal, respectively, each of which is electrically connected to the electrode assembly to output electric power generated by the electrode assembly. The positive electrode terminal and the negative electrode terminal may be located at the same end of the battery cell or may be located at opposite ends of the battery cell.

The electrode assembly includes a main body portion and a tab portion extending from the main body portion. In some embodiments, the number of tab portions may be two. The two tab portions are defined as a positive tab portion and a negative tab portion, respectively. The two tab portions may extend from the same end of the main body portion of the electrode assembly, e.g., the two tab portions extend from an end of the main body portion of the electrode assembly adjacent to the end cap assembly. The two tab portions may also extend from opposite ends of the main body portion of the electrode assembly, for example, from opposite ends of the main body portion of the electrode assembly in the length direction of the battery cell. The positive electrode tab portion and the negative electrode tab portion can thereby be made wider (i.e., larger in size in the non-extending direction of the main body portion), thereby facilitating enhancement of the electron conductivity of the electrode sheet. When the two tab portions extend from opposite ends of the main body portion of the electrode assembly, the electrode terminals may be located at the same end of the battery cell or at opposite ends of the battery cell.

The main body part is a core part of the electrode assembly for realizing the charge and discharge functions, and the lug part is used for leading out the current generated by the main body part. The main body part comprises a positive electrode current collecting part of the positive electrode current collector, a positive electrode film layer, a negative electrode current collecting part of the negative electrode current collector, a negative electrode film layer, a separation film and the like. The positive electrode tab portion may include a plurality of positive electrode tabs, and the negative electrode tab portion may include a plurality of negative electrode tabs.

The tab portion is electrically connected to the electrode terminal. The tab portion may be directly connected to the electrode terminal by welding or the like, or may be indirectly connected to the electrode terminal by other members. For example, the electrode assembly further includes a current collecting member for electrically connecting the electrode terminal and the tab portion. The number of the current collecting members may be two, and the two current collecting members are defined as a positive current collecting member for electrically connecting the positive electrode terminal and the positive electrode tab portion and a negative current collecting member for electrically connecting the negative electrode terminal and the negative electrode tab portion, respectively. When the battery cell is provided with a plurality of electrode assemblies, the positive electrode current collecting members of the plurality of electrode assemblies may be integrally provided, and the negative electrode current collecting members of the plurality of electrode assemblies may be integrally provided.

The separator includes a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating including nanocellulose and a particulate filler.

The width of the isolating film is marked as A, the width of the negative electrode plate is marked as B, the units are all mm, and A-B is more than 0 and less than or equal to 5mm.

The difference between the width of the isolating film and the width of the negative electrode plate of the battery monomer are smaller than or equal to 5mm. The difference between the widths of the isolating film and the negative electrode plate is reduced, so that the probability of local redundancy, folding or crushing problems of the isolating film in the process of assembling the battery cells is reduced, and the battery cells can have good processing performance; meanwhile, when the internal spaces of the battery cells are the same and the widths of the isolating films are the same, the coating widths of the negative electrode plate and the positive electrode plate are increased due to the fact that the difference between the widths of the isolating films and the negative electrode plate is reduced, and therefore the battery cells can have high volume energy density. In addition, after the volume energy density of the battery monomer is improved, the design space of the battery module and the battery pack can be further increased, and further the service life and the reliability of the whole battery can be better improved, for example, some components for improving the reliability of the whole battery can be arranged in the limited space of the battery module and the battery pack.

A-B is more than 0 and less than or equal to 5mm. For example, A-B may be 2mm, 2.5mm, 2.7mm, 3.1mm, 3.5mm, 3.8mm, 4mm, 4.5mm, 5mm, or a range of any of the above values.

Alternatively, 2 mm.ltoreq.A-B.ltoreq.4 mm, more alternatively, 2.5 mm.ltoreq.A-B.ltoreq.3.5 mm. Thereby being beneficial to further improving the volume energy density and the processing performance of the battery monomer.

[ isolation Membrane ]

The ultrathin isolating film adopted at present uses polyolefin resin as a main raw material, the melting point of the polyolefin resin is lower, so that the isolating film has better processing performance, but the thermal shrinkage of the isolating film prepared by the method is generally larger, and when the isolating film is applied to a battery monomer, the width of the isolating film needs to be designed larger, so that the assembling difficulty of the battery monomer is increased. The porous substrate provided by the embodiment of the application can also have higher strength and higher heat resistance on the premise of having smaller thickness, so that the isolating film is facilitated to have low thickness and high heat resistance, and the battery monomer is also facilitated to have high energy density, good processing performance and high reliability.

In some embodiments, the thickness of the porous substrate may be less than or equal to 5 μm, optionally 3 μm to 4.5 μm.

In some embodiments, the puncture strength of the porous substrate may be 390gf or more, alternatively 400gf-480gf.

In some embodiments, the porous substrate may have a Machine Direction (MD) heat shrinkage of less than 3%, alternatively 1% -2.5%, at 105 ℃ for 1 h.

In some embodiments, the porous substrate may have a Transverse Direction (TD) heat shrinkage of less than 2%, alternatively 1% -1.8%, at 105 ℃ for 1 h.

The thermal shrinkage of the porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test may be performed with reference to GB/T36363-2018.

In some embodiments, the porous substrate may have a machine direction tensile strength of 2700kgf/cm or greater ² Optionally 2800kgf/cm ² -3500kgf/cm ² 。

In some embodiments, the porous substrate may have a transverse tensile strength of 2500kgf/cm or greater ² Optionally 2600kgf/cm ² -3200kgf/cm ² 。

The tensile strength of the porous base material is increased, so that positive and negative electrode particles are effectively coated, further, the short circuit between the positive electrode and the negative electrode can be effectively reduced, and the reliability of the battery cell is improved.

The tensile strength of the porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test may be performed with reference to GB/T36363-2018.

In some embodiments, the porous substrate may have an average pore size of 10nm to 60nm, alternatively 20nm to 40nm.

The average pore size of the porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test may be performed using a capillary flow pore size analyzer, which may be a PMIPorometer pore size tester.

In some embodiments, the porous substrate may have a porosity of 20% to 60%, alternatively 30% to 50%.

The porosity of the porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test may be performed with reference to GB/T36363-2018.

The coating comprises nanocellulose and particulate filler. In some embodiments, the mass content of nanocellulose in the coating may be 5wt% to 60wt%, alternatively 7wt% to 45wt%. In some embodiments, the particulate filler may be present in the coating in an amount of 38wt% or more, alternatively 53wt% to 91wt%.

In some embodiments, the nanocellulose may have an average length of 100nm to 1200nm, alternatively 200nm to 1000nm,200nm to 800nm,200 to 600nm,300 to 600nm.

In some embodiments, the nanocellulose may have an average diameter of 11nm to 40nm, alternatively 15nm to 32nm.

In some embodiments, the nanocellulose can have an aspect ratio of 5-60, alternatively 12-35.

The average length and average diameter of nanocellulose can be determined by the following method: cutting a sample with the thickness of 3.6mm multiplied by 3.6mm from an optional area in the isolating membrane, mapping the microstructure of the coating in the sample by utilizing a scanning electron microscope (such as ZEISS Sigma 300), selecting a high vacuum mode, and obtaining an SEM image, wherein the working voltage is 3kV and the magnification is 3 ten thousand times; selecting a plurality of (e.g. more than 5) test areas according to the obtained SEM image for length statistics, wherein the size of each test area is 0.5 μm multiplied by 0.5 μm, and then taking the average value of the lengths of the nanocellulose obtained by each test area as the average length of the nanocellulose; according to the obtained SEM image, a plurality of (for example, more than 5) test areas are selected for diameter statistics by using Nano Measurer particle size distribution statistical software, the size of each test area is 0.5 μm×0.5 μm, and then the average value of the diameters of nanocellulose obtained from each test area is taken as the average diameter of nanocellulose.

In some embodiments, the nanocellulose may include modifying groups, which may include at least one of amine groups, carboxyl groups, aldehyde groups, sulfonic acid groups, or phosphoric acid groups, optionally including at least one of sulfonic acid groups or phosphoric acid groups.

When the nanocellulose has the specific modified group, on one hand, the heat resistance of the isolating film can be effectively improved, the thermal stability of the battery monomer is improved, and the short circuit failure risk in the use process of the battery monomer is reduced; on the other hand, the bonding strength between the coating and the porous substrate can be improved.

When the nanocellulose has the specific modified group, the nanocellulose and the granular filler are lapped to form an integrated coating, so that the coating has a stable space network structure, the wettability and the liquid retention of the electrolyte of the isolating film are improved, and the ion transmission characteristic and the voltage breakdown resistance characteristic of the isolating film are improved; and the method is also beneficial to matching with high-voltage positive electrode active materials and further improving the energy density of the battery cell.

In addition, the existence of the modifying group can reduce the proportion of hydroxyl, so that the coating slurry has proper viscosity, and is more beneficial to coating, the production efficiency of the isolating film can be improved, and the uniformity and consistency of the coating are improved.

In some embodiments, the nanocellulose includes hydroxyl groups and modifying groups, and the molar ratio of modifying groups to hydroxyl groups can be 1:4 to 4:1, alternatively 2:3 to 7:3.

The type of modifying groups in nanocellulose can be determined by infrared spectrometry. For example, the material may be tested for infrared spectra, and the characteristic peaks contained therein determined, to thereby determine the type of modifying group. Specifically, the materials may be analyzed by infrared spectroscopy using instruments and methods known in the art, such as an infrared spectrometer (e.g., an IS10 type Fourier transform infrared spectrometer from Nippon high-force corporation) according to the general rules of GB/T6040-2019 infrared spectroscopy.

The molar ratio of modifying groups to surface hydroxyl groups in nanocellulose can be determined by the following method: the hydroxyl values (milligrams of potassium hydroxide equivalent to the hydroxyl content in each gram of sample) of the raw material cellulose and the nanocellulose are respectively tested according to the phthalic anhydride method in GB/T12008.3-2009, and the obtained values are in units of mg KOH/g and are converted into mmol/g to serve as the hydroxyl content. The hydroxyl content of the raw material cellulose is subtracted by the hydroxyl content of the nanocellulose to obtain the content of the modified group (namely the modified hydroxyl content), and the molar ratio of the modified group to the hydroxyl is calculated.

In some embodiments, the nanocellulose includes sulfonic acid groups, and the content of elemental sulfur may be ≡0.1wt%, alternatively 0.2wt% to 0.5wt%, based on the total mass of nanocellulose.

The content of sulfur element in nanocellulose can be tested according to the following method: the nanocellulose is dried, ground for 30min in a mortar (such as agate mortar), and then tested by using an X-ray diffractometer (such as Miniflex 600-C) to obtain the content of sulfur element. The test can be carried out by adopting a Cu target material, a Ni filter, a tube pressure of 40KV and a tube flow of 15mA, and the continuous scanning range is 5-80 degrees.

In some embodiments, the nanocellulose may have a weight average molecular weight of 10000 to 60000, alternatively 30000 to 50000.

The weight average molecular weight of the nanocellulose is in the range, so that the coating slurry has proper viscosity, and has good fluidity and wettability during coating, thereby being beneficial to improving the quality of the coating and further being beneficial to improving the heat resistance and ion transmission characteristics of the isolating membrane.

In some embodiments, nanocellulose may be obtained as follows: providing cellulose powder with whiteness of more than or equal to 80%; mixing the obtained cellulose powder with a modifying solution, reacting, washing to remove impurities, adjusting the pH value to be neutral, grinding and cutting to obtain the nanocellulose.

Alternatively, the above cellulose powder having a whiteness of 80% or more can be obtained commercially, or can be obtained by chemical methods (e.g., acidolysis method, alkali treatment method, tempo catalytic oxidation method), biological methods (e.g., enzyme treatment method), mechanical methods (e.g., ultrafine grinding, ultrasonic crushing, high-pressure homogenization), or the like. The fiber raw material used for preparing the above cellulose powder having a whiteness of 80% or more may include plant fibers such as at least one of cotton fibers (e.g., cotton fibers, kapok fibers), hemp fibers (e.g., sisal fibers, ramie fibers, jute fibers, flax fibers, hemp fibers, abaca fibers, etc.), palm fibers, wood fibers, bamboo fibers, grass fibers.

In some embodiments, the above cellulose powder having a whiteness of 80% or more may also be prepared by: after the fiber raw material is subjected to opening and deslagging, the fiber raw material is steamed by alkali liquor (such as NaOH aqueous solution with the concentration of 4-20wt%, optionally 5-15wt%) and then sequentially subjected to water washing for impurity removal (such as water washing for 3-6 times), bleaching (such as sodium hypochlorite and/or hydrogen peroxide), acid washing for impurity removal, water driving and air flow drying to obtain cellulose powder.

In some embodiments, the modifying solution may be an acid solution (e.g., aqueous sulfuric acid, aqueous phosphoric acid, aqueous acetic acid) or an alkali solution (e.g., urea-organic solvent solution). Optionally, the modifying solution is an acid solution.

Alternatively, the concentration of the acid solution may be 5wt% to 80wt%. When the aqueous sulfuric acid solution is used as the modifying solution, the concentration of the acid solution may be 40wt% to 80wt%, whereby a cellulose powder having sulfonic acid groups can be obtained. When the aqueous phosphoric acid solution is used as the modifying solution, the concentration of the acid solution may be 45 to 75wt%, whereby a cellulose powder having a phosphoric acid group can be obtained. When an aqueous acetic acid solution is used as the modifying solution, the concentration of the acid solution may be 40 to 80wt%, whereby a cellulose powder having carboxylic acid groups can be obtained.

Alternatively, the urea organic solvent solution may be a urea xylene solution, whereby cellulose powder having amine groups may be obtained.

In some embodiments, the mass ratio of cellulose powder to modifying solution may be optionally 1:2.5 to 1:50, optionally 1:5 to 1:30.

When aqueous sulfuric acid is used as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When the modifying solution is an aqueous phosphoric acid solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When aqueous acetic acid is used as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When the modifying solution is a urea organic solvent solution, the mass ratio of the cellulose powder to the urea organic solvent solution may be 1:4 to 1:40.

In some embodiments, when the modifying solution is an acid solution, the reaction may be performed at a temperature of not higher than 80 ℃, optionally at a temperature of 30 ℃ to 60 ℃, and the reaction time of the cellulose powder with the modifying solution may be 0.25h to 4h, optionally 0.5h to 3h.

In some embodiments, when the modifying solution is an alkali solution, the reaction may be performed at 100 ℃ to 145 ℃ and the reaction time of the cellulose powder and the modifying solution may be 0.5h to 5h.

In some embodiments, grinding may be performed using a grinder and cutting may be performed using a high pressure homogenizer. Nanocellulose having different average diameters and/or different average lengths can be obtained by adjusting the milling parameters of the mill (e.g. number of milling times, milling time, etc.) and the cutting parameters of the high pressure homogenizer.

In some embodiments, the particulate filler may include one or more of organic particles, inorganic particles, organic-inorganic composites.

In some embodiments, the particulate filler may include a first component of secondary particle morphology and a second component of primary particle morphology.

The first component in the shape of the secondary particles can better overlap with the three-dimensional skeleton structure formed by the nanocellulose to form an integrated effect, so that the coating has a more stable space network structure, the heat resistance of the isolating film can be further improved, and the thermal stability of the battery monomer is improved.

The second component of the primary particle morphology is beneficial to reducing the moisture content of the coating and improving the ion transmission characteristics of the coating, thereby helping to improve the cycle performance of the battery cell.

The first component of the secondary particle morphology has smaller particle size and better affinity with the nanocellulose, and the nanocellulose can be lapped in gaps among the primary particles in the first component forming the secondary particle morphology, so that the nanocellulose and the first component of the secondary particle morphology can be lapped to form an integrated coating, the coating has a more stable space network structure, and the heat resistance of the isolating film can be further improved.

The second component with the primary particle morphology has larger particle size and higher strength, so that the framework supporting effect can be better exerted in the coating, the thermal shrinkage of the isolating film is reduced, and the heat resistance of the isolating film is improved; and the coating has more pore canal structure and lower moisture content, so that the ion transmission property of the isolating membrane can be further improved.

In some embodiments, the average particle size of the first component of the secondary particle morphology is less than 200nm, optionally 80nm to 180nm. The average particle size of the first component with the secondary particle morphology is in the range, so that the first component has higher specific surface area, and can be better matched with a three-dimensional framework structure formed by nanocellulose and overlap-connected to form an integrated effect, so that the heat resistance of the isolating membrane and the infiltration and retention characteristics of the isolating membrane to electrolyte can be increased, and the heat stability and the cycle performance of the battery monomer can be improved.

In some embodiments, the primary particles in the first component that make up the secondary particle morphology may have a particle size of 15nm to 45nm, alternatively 20nm to 35nm. The particle size of the primary particles in the first component forming the appearance of the secondary particles is in the range, so that the first component has good appearance of the secondary particles, and the three-dimensional framework structure formed by the first component and the nanocellulose is better in lap joint to form an integrated effect.

In some embodiments, the average particle size of the second component of the primary particle morphology may be from 200nm to 600nm, alternatively from 300nm to 500nm. The average particle size of the second component with the primary particle morphology is in the range, so that the supporting effect of the second component with the primary particle morphology can be better exerted, the stable pore channel structure of the coating can be maintained in the long-term charge and discharge process, the moisture content of the isolating membrane can be reduced, the ion transmission can be promoted, and meanwhile, the heat resistance of the isolating membrane can be improved.

The average particle size of the first component of the secondary particle morphology, the second component of the primary particle morphology, can be tested using equipment and methods known in the art. For example, a Scanning Electron Microscope (SEM) may be used to map the microstructure of the coating in the sample (e.g., ZEISS Sigma 300), and referring to JY/T0584-2020, a Scanning Electron Microscope (SEM) picture of the coating of the barrier film may be taken, the longest diagonal length of the particles may be measured by the SEM picture and then averaged, and the number of particles selected may be greater than 100.

In some embodiments, the specific surface area of the first component of the secondary particle morphology may be greater than the specific surface area of the second component of the primary particle morphology. Thereby facilitating better functioning of the first component of the secondary particle morphology and the second component of the primary particle morphology.

In some embodiments, the specific surface area of the first component of the secondary particle morphology may be greater than 20m ² /g, optionally 30m ² /g-80m ² And/g. The specific surface area of the first component with the appearance of the secondary particles is in the range, the affinity with the nanocellulose is better, the three-dimensional framework structure formed by the nanocellulose can be better matched and overlapped to form an integrated effect, and therefore the heat resistance of the isolating membrane and the infiltration and retention characteristics of the isolating membrane to electrolyte can be improved, and the heat stability and the cycle performance of the battery monomer can be improved.

In some embodiments, the specific surface area of the second component of the primary particle morphology may be 20m or less ² /g, optionally 5m ² /g-15m ² And/g. The specific surface area of the second component in the form of primary particles is within the above range, which is advantageous for reducing the moisture content of the barrier film and for improving the heat resistance of the barrier film.

In some embodiments, the mass content of the first component of the secondary particle morphology in the coating may be greater than the mass content of the second component of the primary particle morphology in the coating. Thereby facilitating better functioning of the first component of the secondary particle morphology and the second component of the primary particle morphology.

In some embodiments, the mass content of the first component of the secondary particle morphology in the coating may be from 10wt% to 85wt%, alternatively from 20wt% to 75wt%. The mass content of the first component with the secondary particle morphology is in the range, so that the coating slurry has proper viscosity and is more favorable for coating; in addition, the three-dimensional skeleton structure formed by the nano cellulose is lapped to form an integrated effect, so that the coating has a more stable space network structure, and the heat resistance and the ion transmission characteristic of the isolating film are improved.

In some embodiments, the mass content of the second component of the primary particle morphology in the coating may be from 5wt% to 70wt%, alternatively from 7wt% to 60wt%. The mass content of the second component with the primary particle morphology is in the range, so that the supporting effect of the second component with the primary particle morphology can be better exerted, the stable pore channel structure of the coating can be maintained in the long-term charge and discharge process, and the moisture content of the isolating membrane can be reduced and the ion transmission can be promoted. The mass content of the second component in the morphology of the primary particles is in the above range, and the bulk density of the whole granular filler can be improved, and further the heat resistance and the puncture resistance of the isolating film can be improved.

In addition, by adjusting the contents of the nanocellulose, the first component of the secondary particle morphology and the second component of the primary particle morphology within the above ranges, the coating can have a relatively thin thickness and simultaneously have highly developed pore channels, thereby further improving the electrolyte wettability of the separator.

In some embodiments, the first component of the secondary particle morphology may include one or more of inorganic particles and organic particles.

Optionally, the inorganic particles comprise boehmite (gamma-AlOOH), alumina (Al ₂ O ₃ ) Barium sulfate (BaSO) ₄ ) Magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂ ) Silicon oxygen compound SiO _x (x is more than 0 and less than or equal to 2), tin dioxide (SnO) ₂ ) Titanium oxide (TiO) ₂ ) Calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO) ₂ ) Yttria (Y) ₂ O ₃ ) Nickel oxide (NiO), hafnium oxide (HfO) ₂ ) Cerium oxide (CeO) ₂ ) Zirconium titanate (ZrTiO) ₃ ) Barium titanate (BaTiO) ₃ ) And magnesium fluoride (MgF) ₂ ) One or more of the following. More optionally, the inorganic particles comprise boehmite (gamma-AlOOH), alumina (Al ₂ O ₃ ) Barium sulfate (BaSO) ₄ ) Magnesium oxide (MgO), silicon oxide SiO _x (x is more than 0 and less than or equal to 2), titanium oxide (TiO) ₂ ) Zinc oxide (ZnO), cerium oxide (CeO) ₂ ) And barium titanate (BaTiO) ₃ ) One or more of the following.

Optionally, the organic particles comprise one or more of polystyrene and polyacrylic wax.

In some embodiments, the first component of the secondary particle morphology may include inorganic particles of the secondary particle morphology, and the crystalline forms of the inorganic particles of the secondary particle morphology include at least two of an alpha crystalline form, a theta crystalline form, a gamma crystalline form, and an eta crystalline form. Optionally, the crystalline forms of the inorganic particles of the secondary particle morphology include at least two of an alpha crystalline form, a theta crystalline form, and a gamma crystalline form.

In some embodiments, the mass content of the inorganic particles of the secondary particle morphology of the alpha crystalline form in the inorganic particles of the secondary particle morphology may be ≡ 1.2wt%, alternatively 1.2wt% to 10wt%, more alternatively 1.2wt% to 5wt%, based on the total mass of the inorganic particles of the secondary particle morphology.

In some embodiments, the mass content of the inorganic particles of the secondary particle morphology of the θ crystal form in the inorganic particles of the secondary particle morphology may be ≡ 50wt%, alternatively 60wt% to 85wt%, more alternatively 60wt% to 82.5wt%, based on the total mass of the inorganic particles of the secondary particle morphology.

In some embodiments, the mass content of the secondary particle morphology inorganic particles of the gamma crystalline form in the secondary particle morphology inorganic particles may be ≡10wt%, alternatively 15wt% to 60wt%, more alternatively 15wt% to 35wt%, based on the total mass of the secondary particle morphology inorganic particles.

In some embodiments, the mass content of the inorganic particles of the secondary particle morphology of the eta crystalline form in the inorganic particles of the secondary particle morphology may be 5wt% or less, alternatively 2wt% or less, more alternatively 1wt% or less, based on the total mass of the inorganic particles of the secondary particle morphology.

The inorganic particles with the morphology of the secondary particles of the alpha crystal form have the advantages of high hardness, good heat resistance, low dielectric constant, high safety and high true density; inorganic particles in the shape of theta-crystal secondary particles have moderate specific surface area and hardness, so that the heat resistance and ion transmission characteristics of the isolating film can be better improved at the same time; the inorganic particles with the secondary particle morphology of the gamma crystal form and the eta crystal form have the advantage of large specific surface area. Therefore, the inorganic particles of the secondary particle morphology of different crystal forms are selected to contribute to the improvement of at least one of the heat resistance, the ion transport property, the adhesive strength, and the electrolyte wettability of the separator.

In some embodiments, the first component of the secondary particle morphology may include secondary particle morphology inorganic particles, and the crystalline form of the secondary particle morphology inorganic particles includes alpha, theta, gamma, and eta crystalline forms, and the mass content of the alpha crystalline form secondary particle morphology inorganic particles in the secondary particle morphology inorganic particles may be 1.2wt% to 5wt%, the mass content of the theta crystalline form secondary particle morphology inorganic particles in the secondary particle morphology inorganic particles may be 60wt% to 82.5wt%, the mass content of the gamma crystalline form secondary particle morphology inorganic particles in the secondary particle morphology inorganic particles may be 15wt% to 35wt%, the mass content of the eta crystalline form secondary particle morphology inorganic particles in the secondary particle morphology inorganic particles may be 1wt% or less, all based on the total mass of the secondary particle morphology inorganic particles.

The X-ray diffraction pattern of the inorganic particles with the secondary particle morphology can be obtained by testing according to the following method: drying inorganic particles with secondary particle morphology, grinding for 30min in a mortar (such as agate mortar), and testing by using an X-ray diffractometer (such as Miniflex 600-C) to obtain an X-ray diffraction pattern. The test can be carried out by adopting a Cu target material, a Ni filter, a tube pressure of 40KV and a tube flow of 15mA, and the continuous scanning range is 5-80 degrees.

In some embodiments, the first component of the secondary particle morphology may include inorganic particles of the secondary particle morphology, which may be prepared as follows: the precursor solution of the inorganic particles is subjected to oxidation reaction by high-pressure sputtering, then heated at 600-900 ℃ for 1-3 hours to form small particles, and then dried and shaped at 150-250 ℃ for 30-60 minutes to obtain the inorganic particles with secondary particle morphology. The average particle diameter of the inorganic particles of the secondary particle morphology can be adjusted by adjusting sputtering parameters such as temperature, time, etc.

In some embodiments, the shape of the first component of the secondary particle morphology may include one or more of string, chain, amorphous, spherical, spheroid, pyramid.

In some embodiments, the second component of the primary particle morphology may include inorganic particles of the primary particle morphology.

Alternatively, the inorganic particles of the primary particle morphology may include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of electrochemical reaction.

Optionally, the inorganic particles having a dielectric constant of 5 or more include one or more of the following: boehmite, alumina, zinc oxide, silica, titania, zirconia, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium titanate, pb (Zr, ti) O ₃ (abbreviated as PZT), pb _1-m La _m Zr _1-n Ti _n O ₃ (abbreviated as PLZT, m is more than 0 and less than 1, n is more than 0 and less than 1), pb (Mg) ₃ Nb _2/3 )O ₃ -PbTiO ₃ (abbreviated as PMN-PT), and their respective modified inorganic particles. Alternatively, the modification of each inorganic particle may be chemical modification and/or physical modification. The chemical modification mode includes coupling agent modification (for example, silane coupling agent, titanate coupling agent, etc.), surfactant modification, polymer grafting modification, etc. The physical modification mode can be mechanical force dispersion, ultrasonic dispersion, high-energy treatment and the like. The agglomeration of inorganic particles can be reduced by modification treatment, so that the coating has a more stable and uniform spatial network structure; in addition, by selecting a compound having a specific functional group The coupling agent, the surfactant or the polymer is used for modifying the inorganic particles, and is also helpful for improving the infiltration and retention characteristics of the coating to the electrolyte and improving the cohesiveness of the coating to the porous substrate.

Optionally, the inorganic particles having ion conductivity but not storing ions include one or more of the following: li (Li) ₃ PO ₄ Lithium titanium phosphate Li _x1 Ti _y1 (PO ₄ ) ₃ Lithium aluminum titanium phosphate Li _x2 Al _y2 Ti _z1 (PO ₄ ) ₃ 、(LiAlTiP) _x3 O _y3 Glass, lanthanum lithium titanate Li _x4 La _y4 TiO ₃ Lithium germanium thiophosphate Li _x5 Ge _y5 P _z2 S _w Lithium nitride Li _x6 N _y6 、SiS ₂ Glass Li _x7 Si _y7 S _z3 And P ₂ S ₅ Glass Li _x8 P _y8 S _z4 0 < x1 < 2,0 < y1 < 3,0 < x2 < 2,0 < y2 < 1,0 < z1 < 3,0 < x3 < 4,0 < y3 < 13,0 < x4 < 2,0 < y4 < 3,0 < x5 < 4,0 < y5 < 1,0 < z2 < 1,0 < w < 5,0 < x6 < 4,0 < y6 < 2,0 < x7 < 3,0 < y7 < 2,0 < z3 < 4,0 < x8 < 3,0 < y8 < 3,0 < z4 < 7. Thereby, the ion transport property of the separation film can be further improved.

Optionally, the inorganic particles capable of undergoing an electrochemical reaction include one or more of the following: lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

In some embodiments, the second component of the primary particle morphology may include inorganic particles of the primary particle morphology, and the crystalline form of the inorganic particles of the primary particle morphology may include one or more of an alpha crystalline form and a gamma crystalline form, optionally including an alpha crystalline form. The inorganic particles with the primary particle morphology of the alpha crystal form have the advantages of high hardness, good heat resistance, low dielectric constant, high safety and high true density, thereby being capable of further improving the heat resistance of the coating.

In some embodiments, the crystalline form of the inorganic particles of primary particle morphology includes an alpha crystalline form, and the mass content of the inorganic particles of primary particle morphology of the alpha crystalline form in the inorganic particles of primary particle morphology may be ≡90wt%, optionally 95wt% to 100wt%, based on the total mass of the inorganic particles of primary particle morphology.

In some embodiments, the shape of the second component of the primary particle morphology may include at least one of spheres, dumbbells, and polygons.

The inorganic particles of the alpha crystal form have diffraction peaks at 57.48 ° ± 0.2 ° and 43.34 ° ± 0.2 ° in an X-ray diffraction spectrum measured by using an X-ray diffractometer.

The inorganic particles of the θ crystal form have diffraction peaks at 36.68°±0.2° and 31.21°±0.2° in an X-ray diffraction pattern measured by using an X-ray diffractometer.

The inorganic particles of the gamma crystal form have diffraction peaks at 66.95 ° ± 0.2 ° and 45.91 ° ± 0.2 ° of 2θ in an X-ray diffraction spectrum measured by using an X-ray diffractometer.

The inorganic particles of the eta crystal form have diffraction peaks at 31.89 DEG + -0.2 DEG and 19.37 DEG + -0.2 DEG in an X-ray diffraction pattern measured by using an X-ray diffractometer.

The X-ray diffraction pattern of the inorganic particles can be tested as follows: the inorganic particles were dried and ground in a mortar (e.g., agate mortar) for 30 minutes, and then tested using an X-ray diffractometer (e.g., miniflex 600-C) to obtain an X-ray diffraction pattern. The test can be carried out by adopting a Cu target material, a Ni filter, a tube pressure of 40KV and a tube flow of 15mA, and the continuous scanning range is 5-80 degrees.

In some embodiments, the coating further comprises a non-particulate binder. The type of the non-granular binder is not particularly limited, and any known material having good adhesion may be used, and examples thereof include a linear type binder, an emulsion type binder, and a mixed linear and emulsion type binder.

Alternatively, the non-particulate binder may have at least one polar group selected from the group consisting of: hydroxy (-OH), carboxyl (-COOH), ester (-COO-), cyano (-CN) imide group (-CO-NH-CO-), maleic anhydride group (-COOOC-), sulfonate group (-SO) ₃ H) And pyrrolidinesKeto (-NCO-).

Alternatively, the non-particulate binder may comprise a homopolymer or copolymer of monomers selected from the group consisting of: allyl polyether sulfate, acrylic acid, methacrylic acid, acrylamide, methyl acrylate, butyl acrylate, ethyl acrylate, glycidyl methacrylate, vinyl alcohol, acrylonitrile, hydroxyethyl acrylate, styrene, acetoxyethyl methacrylate, vinyltrimethoxysilane, lithium acrylate, sodium acrylate, lithium methacrylate, isobutylene, maleic anhydride.

Optionally, the non-particulate binder may include at least one of: polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polyethylene oxide, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide.

Alternatively, the non-particulate binder may be present in the coating in an amount of less than or equal to 3wt%, alternatively from 0.3wt% to 1.5wt%, based on the total mass of the coating. The nanocellulose in the coating and the granular filler and the like can form a stable space network structure, so that the isolating film can keep high bonding strength, good ion transmission property and high heat resistance on the premise of reducing the using amount of the binder.

In some embodiments, the coating may not include wetting agents, such as common acrylates, polyoxyethylene-polyoxypropylene block copolymer based wetting agents. The wetting agent is usually a compound with low surface tension and high fluidity, so that the problem of pore blocking of the porous substrate occurs in the coating slurry coating and drying process easily, and the coating of the isolating film provided by the embodiment of the application does not contain the wetting agent, so that the problem of pore blocking of the porous substrate caused by the wetting agent in the coating slurry coating and drying process can be avoided.

In some embodiments, the release film may further include an adhesive layer disposed on at least a portion of the surface of the coating. The bonding layer not only can prevent the coating from falling off and improve the reliability of the battery monomer, but also can improve the interface between the isolating film and the electrode (such as the anode and the cathode), thereby being beneficial to improving the cycle performance of the battery monomer.

In some embodiments, the adhesive layer may include an adhesive. Alternatively, the adhesive layer may comprise a particulate adhesive.

In some embodiments, the binder in the adhesive layer may include at least one of an acrylate monomer homo-or copolymer, an acrylic monomer homo-or copolymer, a fluoroolefin monomer homo-or copolymer.

The comonomer may include, but is not limited to, at least one of the following: acrylic monomers, olefin monomers, halogen-containing olefin monomers, fluoroether monomers, and the like.

Alternatively, the binder in the adhesive layer may comprise a vinylidene fluoride polymer, such as a homopolymer of vinylidene fluoride monomer (VDF) and/or a copolymer of vinylidene fluoride monomer and comonomer. The comonomer can be at least one of olefin monomer, fluorine-containing olefin monomer, chlorine-containing olefin monomer, acrylic monomer and fluoroether monomer.

Optionally, the comonomer may comprise at least one of: trifluoroethylene (VF 3), chlorotrifluoroethylene (CTFE), 1, 2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alkyl vinyl) ethers (e.g., perfluoro (methyl vinyl) ether PMVE, perfluoro (ethyl vinyl) ether PEVE, perfluoro (propyl vinyl) ether PPVE), perfluoro (1, 3-dioxole) and perfluoro (2, 2-dimethyl-1, 3-dioxole) (PDD).

In some embodiments, the binder in the adhesive layer may include at least one of: poly (perfluoroethylene), poly (vinylidene fluoride-co-hexafluoropropylene), poly (vinylidene fluoride-co-trichloroethylene), polystyrene-co-methyl methacrylate, polystyrene-co-butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide.

In some embodiments, the total thickness of the barrier film may be 4 μm to 10 μm, alternatively 4.5 μm to 8.5 μm. The total thickness of the separator is within the above range, so that the battery cell can have high energy density, and the separator can have low thermal shrinkage, so that the battery cell has high reliability.

The common ceramic coating is arranged on the porous substrate, so that the thermal shrinkage of the whole isolating film can be reduced. However, this approach tends to require a greater ceramic coating thickness, thereby sacrificing the energy density of the cell; in addition, the processability of the isolating film is sacrificed, for example, the isolating film has high probability of winding powder. In some embodiments, the thickness of the coating of the barrier film provided by embodiments of the present application may be 0.2 μm to 2 μm, alternatively 0.4 μm to 1 μm. The coating comprises nano cellulose and granular filler, so that the coating has low thickness and high heat resistance, and the battery cell has good processability. The thickness of the coating layer is in the above range, so that the battery cell can have high energy density, and the isolating film can have low thermal shrinkage, so that the battery cell has high reliability. The thickness of the coating refers to the thickness of the coating on a single side of the porous substrate.

In some embodiments, the separator film may have a Machine Direction (MD) heat shrinkage of 3% or less at 150 ℃ for 1 h.

In some embodiments, the barrier film may have a Transverse Direction (TD) heat shrinkage of 2% or less at 150 ℃ for 1 hour.

The heat shrinkage of the release film has a meaning well known in the art and can be measured using methods known in the art. For example, the test may be performed with reference to GB/T36363-2018.

The parameters (e.g., thickness, etc.) of the separator are all parameters of the porous substrate on one side. When the coating is disposed on both sides of the porous substrate, the coating parameters on either side are satisfactory for the present application, i.e., are considered to fall within the scope of the present application.

[ negative electrode sheet ]

In some embodiments, the negative electrode tab may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

The negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. As examples of the metal foil, copper alloy foil, aluminum alloy foil may be employed. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As examples, the metallic material may include one or more of copper, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

In some embodiments, the anode active material may include a carbon material. Alternatively, the carbon material may include one or more of artificial graphite and natural graphite.

In some embodiments, the anode active material may include a silicon-based material. Thereby improving the energy density of the battery cell. The silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

In some embodiments, the silicon-based material may include one or more of an alkali metal element and an alkaline earth metal element, optionally one or more of Li, mg, in addition to the silicon element. As an example, the silicon-based material may be an alkali metal and/or alkaline earth metal pre-intercalated silicon-based material, for example, may be an Li and/or Mg pre-intercalated silicon-based material.

In some embodiments, the mass ratio of the silicon-based material in the anode active material may be 5wt% or more, optionally 8wt% to 20wt%.

In some embodiments, the anode active material may include a carbon material and a silicon-based material, and the mass ratio of the silicon-based material in the anode active material may be 8wt% to 20wt%, and the mass ratio of the carbon material in the anode active material may be 80wt% or more. Thus, the battery cell has both high energy density and long cycle life.

In some embodiments, the volume distribution particle diameter Dv10 of the anode active material may be 4 μm to 8 μm, alternatively 4.5 μm to 6.5 μm.

In some embodiments, the volume distribution particle diameter Dv50 of the anode active material may be 6 μm to 15 μm, alternatively 8 μm to 13 μm.

In some embodiments, the volume distribution particle diameter Dv90 of the anode active material may be 15 μm to 30 μm, alternatively 18 μm to 25 μm.

By adjusting the volume distribution particle diameters Dv10, dv50, and/or Dv90 of the anode active material within the above-described range, the battery side reaction can be reduced, the battery cell can have a long cycle life, and the battery cell can also have good low-temperature performance.

In some embodiments, the anode film layer may further include an anode binder, for example, may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), and carboxymethyl chitosan (CMCS), which the embodiments of the present application are not limited to.

In some embodiments, the negative electrode film layer further optionally includes a negative electrode conductive agent. The kind of the negative electrode conductive agent is not particularly limited in the present application, and the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, as examples.

In some embodiments, the negative electrode film layer may also optionally include other adjuvants. As an example, other adjuvants may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

The negative electrode tab does not exclude other additional functional layers than the negative electrode film layer. For example, in some embodiments, the negative electrode tab may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) interposed between the negative electrode current collector and the negative electrode film layer, disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode tab may further include a protective layer covering the surface of the negative electrode film layer.

The negative electrode sheet can be prepared according to the following method: dispersing a negative electrode active material, an optional negative electrode binder, an optional negative electrode conductive agent and an optional other auxiliary agent in a solvent, and uniformly stirring to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and forming a negative electrode plate after the procedures of drying, cold pressing and the like. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[ Positive electrode sheet ]

In some embodiments, the upper charge cutoff voltage of the battery cell may be greater than or equal to 4.25V, optionally 4.30V-4.45V. Thereby allowing the battery cell to have a higher energy density.

In some embodiments, the positive electrode tab may include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces opposing in the thickness direction thereof, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

The positive electrode film layer includes a positive electrode active material including a layered lithium-containing transition metal oxide.

In some embodiments, the layered lithium-containing transition metal oxide may include Ni element. The molar amount of the Ni element may account for 70% or more of the total molar amount of the transition metal element in the layered lithium-containing transition metal oxide; alternatively, the molar amount of the Ni element may be 80% or more of the total molar amount of the transition metal element in the layered lithium-containing transition metal oxide; more alternatively, the molar amount of the Ni element may be 90% or more of the total molar amount of the transition metal element in the layered lithium-containing transition metal oxide.

In some embodiments, the layered lithium-containing transition metal oxide may include Li _a Ni _b Co _c M _d O _e A _f Wherein a is more than 0 and less than or equal to 1.2; b is more than or equal to 0.8 and less than 1; c is more than 0 and less than 1; d is more than 0 and less than 1; e is more than or equal to 1 and less than or equal to 2; f is more than or equal to 0 and less than or equal to 1; m includes, but is not limited to, one or more of Mn, al, zr, zn, cu, cr, mg, fe, V, ti and B; a includes, but is not limited to, one or more of N, F, S and Cl. Thereby, the energy density of the battery cell can be further improved.

In some embodiments, as an example, the layered lithium-containing transition metal oxide may include, but is not limited to, liNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.80 Co _0.15 Al _0.05 O ₂ 、LiNi _0.9 Co _0.06 Mn _0.04 O ₂ 、LiNi _0.92 Co _0.06 Mn _0.02 O ₂ 、LiNi _0.96 Co _0.02 Mn _0.02 O ₂ One or more of the following.

The higher the Ni element content in the layered lithium-containing transition metal oxide, the higher the upper limit cutoff voltage of the battery cell, and the higher the energy density of the battery cell.

In some embodiments, the positive electrode active material may include a layered lithium-containing transition metal oxide in a single crystalline morphology, or both a layered lithium-containing transition metal oxide in a single crystalline morphology and a layered lithium-containing transition metal oxide in a polycrystalline morphology.

When the types of the layered lithium-containing transition metal oxides are the same and the upper limit cutoff voltages of charging of the battery monomers are the same, the cyclic stability of the layered lithium-containing transition metal oxide with single crystal morphology is higher than that of the layered lithium-containing transition metal oxide with polycrystalline morphology; when the volume distribution particle size is the same, the specific surface area of the lamellar lithium-containing transition metal oxide with single crystal morphology is smaller than that of the lamellar lithium-containing transition metal oxide with polycrystal morphology, so that side reaction, capacity loss and gas production can be reduced. Therefore, the layered lithium-containing transition metal oxide with single crystal morphology can enable the battery monomer to have higher upper limit cutoff voltage for charging, and can enable the high-voltage battery monomer to have good cycling stability.

In some embodiments, the volume distribution particle diameter Dv50 of the positive electrode active material may be 6 μm or less, alternatively 2 μm to 5 μm.

The separator provided in the embodiments of the present application provides a coating layer comprising nanocellulose and particulate filler on at least one surface of a porous substrate. When the coating thickness is the same and the coating includes both nanocellulose and particulate filler, the porosity of the separator may become low, thereby affecting ion diffusion and thus also affecting the low temperature performance of the battery cell.

At low temperatures, the impedance of the cell increases, the discharge voltage plateau decreases, and the terminal voltage of the cell decreases rapidly, thereby causing a rapid decay in the available capacity and power of the cell.

In some embodiments, the volume distribution particle diameter Dv90 of the positive electrode active material may be 14 μm or less, alternatively 4.5 μm to 13.5 μm,4.5 μm to 11 μm,4.4 μm to 9.0 μm.

In some embodiments, the volume distribution particle diameter Dv10 of the positive electrode active material may be 3 μm or less, alternatively 1 μm to 2 μm,1.4 μm to 2 μm.

In some embodiments, the particle size distribution (Dv 90-Dv 10)/Dv 50 of the positive electrode active material may be 0.8-2.5, optionally 1.3-2.3,1.3-2.1.

In some embodiments, the volume distribution particle size Dv50 of the layered lithium-containing transition metal oxide of single crystal morphology may be 5 μm or less, alternatively 2 μm to 4 μm, more alternatively 2.3 μm to 3.5 μm.

In some embodiments, the volume distribution particle size Dv90 of the layered lithium-containing transition metal oxide of single crystal morphology may be 10 μm or less, alternatively 4.5 μm to 8 μm, and more alternatively 4.5 μm to 7 μm.

In some embodiments, the volume distribution particle size Dv10 of the layered lithium-containing transition metal oxide of single crystal morphology may be 3 μm or less, alternatively 1 μm to 2 μm, more alternatively 1.4 μm to 2 μm.

In some embodiments, the particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide in the single crystal morphology may be from 0.8 to 2.5, alternatively from 1.2 to 1.6,1.3 to 1.5.

The layered lithium-containing transition metal oxide with the polycrystalline morphology has higher lithium ion diffusion coefficient, better electrolyte wettability and shorter lithium ion diffusion path. Therefore, when the positive electrode active material includes both the layered lithium-containing transition metal oxide of a single-crystal morphology and the layered lithium-containing transition metal oxide of a polycrystalline morphology, it contributes to the improvement of the low-temperature performance of the battery cell.

In some embodiments, the volume distribution particle size Dv50 of the layered lithium-containing transition metal oxide of the polycrystalline morphology may be 7 μm to 12 μm, alternatively 8 μm to 10 μm.

In some embodiments, the volume distribution particle size Dv90 of the layered lithium-containing transition metal oxide of the polycrystalline morphology may be 12 μm to 20 μm, optionally 13 μm to 18 μm.

In some embodiments, the volume distribution particle size Dv10 of the layered lithium-containing transition metal oxide of the polycrystalline morphology may be 2 μm to 6 μm, alternatively 3 μm to 5 μm.

The particle size of the layered lithium-containing transition metal oxide with the polycrystalline morphology is reduced, which is beneficial to improving the low-temperature performance of the battery monomer; however, the energy density of the battery cells is also reduced to some extent, and at the same time, the manufacturing cost of the battery cells is greatly increased.

In some embodiments, the particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide of the polycrystalline morphology may be from 1.1 to 1.5, alternatively from 1.2 to 1.4.

In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode film layer further optionally includes a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate-based resin.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As examples, the metallic material may include one or more of aluminum, aluminum alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

The positive electrode film layer is usually formed by coating positive electrode slurry on a positive electrode current collector, drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. In some embodiments, the electrolyte may include an electrolyte salt and a solvent.

In some embodiments, as an example, the electrolyte salt may include, but is not limited to, lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium bis (fluorosulfonyl) imide (LiLSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium difluorooxalato borate (LiBOB), lithium difluorophosphate (LiPO) ₂ F ₂ ) At least one of lithium difluorophosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

In some embodiments, as an example, the solvent may include, but is not limited to, at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), butylene Carbonate (BC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE).

In some embodiments, the electrolyte may further include additives, which may include, by way of example, but are not limited to, one or more of fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), vinylene Carbonate (VC).

Alternatively, the total mass of the additives may be 0.5wt% to 12wt%, alternatively 2wt% to 8wt%, of the total mass of the electrolyte.

Methods for preparing battery cells are well known. In some embodiments, the positive electrode tab, separator, negative electrode tab, and electrolyte may be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet may be made into an electrode assembly, the electrode assembly is placed in an outer package, dried, injected with the electrolyte, and subjected to vacuum packaging, standing, formation and other processes to obtain a battery cell. The plurality of battery cells may further constitute a battery module via series connection or parallel connection or series-parallel connection. The plurality of battery modules may also form a battery pack via series or parallel connection or series-parallel connection. In some embodiments, multiple cells may also directly make up a battery pack.

The embodiment of the application also provides an electric device, which comprises the battery provided by the embodiment of the application. The battery may be used as a power source for the electrical device or as an energy storage unit for the electrical device. The powered device may be, but is not limited to, a mobile device (e.g., a cell phone, tablet computer, notebook 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 watercraft, a satellite, an energy storage system, etc.

The power utilization device may select the type of battery, such as a battery cell, a battery module, or a battery pack, according to its use requirements.

Fig. 2 is a schematic diagram of an electrical device as one example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the power device, a battery pack or battery module may be employed.

As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. The power utilization device is required to be light and thin, and a battery unit can be used as a power supply.

Examples

The following examples more particularly describe the disclosure of the present application, which are intended as illustrative only, since numerous modifications and variations within the scope of the disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.

The porous substrate and nanocellulose used in the examples of the present application are commercially available.

Example 1

Preparation of positive electrode plate

The positive electrode active material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Mixing conductive agent acetylene black and binder polyvinylidene fluoride according to the mass ratio of 94:3:3, adding a proper amount of solvent NMP, and uniformly stirring to obtain positive electrode slurry; and coating the positive electrode slurry on two surfaces of a positive electrode current collector aluminum foil, and drying, cold pressing and cutting to obtain a positive electrode plate. Positive electrode active material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ The particle size Dv50 of the single crystal morphology and volume distribution is 2.5 mu m.

Preparation of negative electrode plate

Uniformly mixing a mixture of negative electrode active material artificial graphite and silicon oxide in a mass ratio of 90:10, a conductive agent acetylene black, a binder Styrene Butadiene Rubber (SBR) and sodium carboxymethylcellulose (CMC) in a proper amount of solvent deionized water according to a mass ratio of 95:2:2:1 to obtain negative electrode slurry; and (3) coating the negative electrode slurry on two surfaces of a negative electrode current collector copper foil, and drying, cold pressing and cutting to obtain a negative electrode plate.

Preparation of a separator film

The porous substrate was PE porous substrate having a thickness of 4 μm, a puncture strength of 450gf, a heat shrinkage in the longitudinal direction of 105 ℃/1h of 2.0% and a heat shrinkage in the transverse direction of 105 ℃/1h of 1.5%.

Uniformly mixing nanocellulose, a first component with secondary particle morphology, a second component with primary particle morphology and binder polyacrylic acid in a proper amount of solvent deionized water according to a mass ratio of 20:55:23:2 to obtain coating slurry. The average length of the nanocellulose is 420nm, the average diameter is 24nm, and the length-diameter ratio is 17.5. The first component of the secondary particle morphology adopts alumina with the secondary particle morphology, the volume distribution particle diameter Dv50 is 150nm, and the contents of alpha crystal form, theta crystal form, gamma crystal form and eta crystal form in the alumina are respectively 1.1wt%, 68.7wt%, 29.6wt% and 0.6wt%, based on the total mass of the alumina. The second component of the primary particle morphology adopts aluminum oxide of the primary particle morphology, the volume distribution particle diameter Dv50 is 350nm, the crystal form of the aluminum oxide is mainly alpha crystal form, and the content is more than 99wt percent based on the total mass of the aluminum oxide.

Uniformly mixing vinylidene fluoride monomer (VDF) homopolymer particles, polymethyl methacrylate, dispersing agent sodium carboxymethyl cellulose (CMC) and a surfactant in a proper amount of solvent deionized water according to a mass ratio of 87:8:3:2 to obtain bonding layer slurry.

Coating the prepared coating slurry on two surfaces of a PE porous substrate in a micro-gravure mode, drying, coating the adhesive layer slurry on the coating, and drying and cutting to obtain the isolating film.

Preparation of electrolyte

Mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a mass ratio of 20:80 to obtain an organic solvent, and drying the LiPF sufficiently ₆ Dissolving in the above organic solventForming an electrolyte with the concentration of 1mol/L, and then adding fluoroethylene carbonate (FEC) and 1, 3-Propane Sultone (PS), wherein the mass content of the FEC is 3wt% of the total mass of the electrolyte, and the mass content of the PS is 0.5wt% of the total mass of the electrolyte.

Preparation of a Battery

Sequentially stacking and winding the positive electrode plate, the isolating film and the negative electrode plate to obtain an electrode assembly; and placing the electrode assembly in an outer packaging aluminum shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other procedures to obtain the battery. The dimensions of the cell were 28.5mm by 148mm by 97.5mm.

In the prepared battery, the thickness of the coating layer on one side of the PE porous substrate was 0.75 μm, the total thickness of the coating layer was 1.5 μm, the thickness of the adhesive layer on the coating layer was 0.5 μm, and the total thickness of the adhesive layer in the separator was 1 μm. The total thickness of the isolating film is 6.5 mu m, the width is 91.0mm, the width of the negative pole piece is 88.0mm, and the width of the positive pole piece is 84.0mm.

Example 2

A battery was produced in a similar manner to example 1, except that the width of the negative electrode sheet was 87.2mm and the width of the positive electrode sheet was 83.2mm.

Example 3

A battery was prepared in a similar manner to example 1, except that the width of the negative electrode sheet was 89.0mm and the width of the positive electrode sheet was 85.0mm.

Example 4

A battery was produced in a similar manner to example 1, except that the width of the negative electrode sheet was 86.0mm and the width of the positive electrode sheet was 82.0mm.

Example 5

The preparation method of the battery was similar to example 1, except for the following differences.

The porous substrate is PE porous substrate with thickness of 5 μm, puncture strength of 420gf, longitudinal heat shrinkage rate of 105 ℃/1h of 2.5%, and transverse heat shrinkage rate of 105 ℃/1h of 1.8%.

In the prepared battery, the thickness of the coating layer on one side of the PE porous substrate was 0.75 μm, the total thickness of the coating layer was 1.5 μm, the thickness of the adhesive layer on the coating layer was 0.5 μm, and the total thickness of the adhesive layer in the separator was 1 μm. The total thickness of the isolating film is 7.5 mu m, the width is 91.0mm, the width of the negative pole piece is 88.0mm, and the width of the positive pole piece is 84.0mm.

Example 6

The porous substrate was PE porous substrate having a thickness of 5 μm, a puncture strength of 380gf, a heat shrinkage in the longitudinal direction of 105 ℃/1h of 2.8% and a heat shrinkage in the transverse direction of 105 ℃/1h of 2.1%.

Comparative example 1

A battery was prepared in a similar manner to example 1, except that the width of the negative electrode sheet was 84.0mm and the width of the positive electrode sheet was 80.0mm.

Comparative example 2

And uniformly mixing aluminum oxide and binder polyacrylic acid in a proper amount of solvent deionized water according to a mass ratio of 94:6 to obtain coating slurry. The alumina is in a primary particle shape, the volume distribution particle diameter Dv50 is 800nm, the crystal form of the alumina is mainly an alpha crystal form, and the mass ratio of the alpha crystal form is more than 99wt percent based on the total mass of the alumina.

Coating the prepared coating slurry on two surfaces of a PE porous substrate by using a coating machine, drying, coating the adhesive layer slurry on the coating, and drying and cutting to obtain the isolating film.

In the prepared battery, the thickness of the coating layer on one side of the PE porous substrate was 1.5 μm, the total thickness of the coating layer was 3 μm, the thickness of the adhesive layer on the coating layer was 0.5 μm, and the total thickness of the adhesive layer in the separator was 1.0 μm. The total thickness of the isolating film is 9 mu m, the width is 91.0mm, the width of the negative electrode plate is 84.0mm, and the width of the positive electrode plate is 80.0mm.

Comparative example 3

The battery was produced in a similar manner to comparative example 2, except that the width of the negative electrode tab was 88.0mm and the width of the positive electrode tab was 84.0mm.

Test part

(1) Puncture strength test of porous substrates

The sample is cut by a blade, and the length and the width of the sample are larger than 64mm. After the high-speed rail tension machine is inspected to be clean, a puncture clamp is installed, a sample is placed in the center of the clamp, and an upper cover is covered. On a computer operation panel of the high-speed rail tension machine, the test is set as sample compression, the speed is 50mm/min, the start is clicked, the puncture test is carried out in sequence, and the force-displacement curve is preserved. Each group is tested at least three times in parallel, and if there are three force-displacement curves with better repeatability, the next group of tests is performed. For accuracy, an average of 5 parallel samples can be taken as the test result.

(2) Thermal shrinkage test of porous substrates and release films

The sample was die cut into 100mm by 50mm specimens using a punch. And (3) marking the punched sample with the diameter of 100mm and 50mm at the lower right corner by using a marker pen, measuring before baking under a secondary element, setting the baking temperature and time, putting the sample into a baking oven together with a steel plate to bake after the baking oven reaches the set temperature, taking out after the baking time is set, and standing for 10min. The transverse and longitudinal dimensions of the same numbered samples after baking were measured separately, with the transverse dimension recorded as X2 and the longitudinal dimension recorded as Y2. The longitudinal heat shrinkage = (100-Y2)/100×100% and the transverse heat shrinkage = (50-X2)/50×100%, if the shrinkage of the sample edge is uneven, the maximum shrinkage position is the reference. For accuracy, an average of 5 parallel samples can be taken as the test result.

When the heat shrinkage of the porous substrate was measured, the oven temperature was set at 105℃for 1 hour.

When the heat shrinkage of the separator was measured, the oven temperature was set at 150℃for 1 hour.

(3) Hot box performance test of battery

Charging the battery to 4.25V at a constant current of 1C at 25 ℃, continuously charging at a constant voltage until the current is less than or equal to 0.05C, and standing for 5min; then each cell was tested with a jig in a DHG-9070ADHG series high temperature oven, and was raised from 25 ℃ to 60 ℃ ± 2 ℃ at a rate of 5 ℃/min, held for 30min; and then heating at a heating rate of 5 ℃ per minute, keeping the temperature for 30 minutes at each heating rate of 5 ℃, and recording the temperature of the hot box and the heat preservation time when the battery fails. The higher the hot box failure temperature of the battery, the better the thermal stability of the battery. When the heat box failure temperature of the battery is the same, the longer the heat preservation time is, the better the heat stability of the battery is. For accuracy, an average of 5 parallel samples can be taken as the test result.

(4) Volumetric energy density testing of cells

Charging the battery to 4.25V at a constant current of 0.33 ℃ at 25 ℃, and continuously charging at a constant voltage until the current is less than or equal to 0.05 ℃; after standing for 5min, the battery was discharged to 2.8V at 0.33C, giving discharge energy Q. Volumetric energy density of battery (Wh/L) =discharge energy Q/volume of battery V. For accuracy, an average of 2 parallel samples can be taken as the test result.

(5) Process rate testing of batteries

1000 cells were fabricated and subjected to an insulation withstand voltage test (Hi-port test). During testing, the coiled electrode assembly is hot-pressed for 15s at 90 ℃ and 7MPa, after hot pressing is finished, a daily internal resistance meter is used for applying 100V voltage between positive and negative electrode lugs of the electrode assembly and testing the resistance of the electrode assembly, if the resistance is less than 2MΩ, the electrode assembly is regarded as a Hi-point defective product, and otherwise, the electrode assembly passes the Hi-point test. The number of batteries passing the Hi-point test is counted, and the percentage of the total number of the batteries is calculated.

Table 1 shows the test results of the porous substrates and the separator of examples 1 to 6 and comparative examples 1 to 3.

Table 2 shows the battery test results of examples 1 to 6 and comparative examples 1 to 3.

TABLE 1

As can be seen from the test results in table 1, the separator provided in the examples of the present application can have both low thickness and low heat shrinkage.

TABLE 2

From the test results of examples 1 to 6 and comparative examples 1 to 3, it was found that the battery having high thermal stability and high process yield and high volumetric energy density was achieved by using a specific separator coating and making the difference between the widths of the separator and the negative electrode tab 5mm or less.

The difference between the widths of the separation film and the negative electrode tab in comparative examples 1 and 2 is large, and the probability of occurrence of problems of local redundancy, folding or breakage of the separation film during the battery assembly is high, thereby affecting the process yield of the battery.

As is clear from the test results of comparative examples 2 to 3, the common ceramic separator has poor heat resistance, and the difference between the widths of the separator and the negative electrode plate is reduced on the basis of the poor heat resistance, which results in poor process quality of the battery and obviously reduced Hi-pot test passing rate.

The test results of comparative examples 2 to 3 also show that the short-circuit risk of the battery can be reduced to a certain extent and the hot box failure temperature of the battery can be raised by only increasing the width difference between the common ceramic isolating film and the negative electrode plate, but the improvement degree is limited, and meanwhile, the process rate of the battery is poor.

From the test results of examples 1, 5 and 6, it is apparent that the battery using the porous substrate having higher puncture strength and lower thermal shrinkage can have better process quality on the premise of thinner thickness.

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 battery cell comprises a negative electrode plate and a separation film, and is characterized in that,

the separator comprises a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating comprising nanocellulose and particulate filler;

the width of the isolating film is marked as A, the width of the negative pole piece is marked as B, and the units are mm, and A-B is more than 0 and less than or equal to 5mm.

2. The battery cell of claim 1, wherein 2mm +.a-B +.4 mm, optionally 2.5mm +.a-B +.3.5 mm.

3. The battery cell of any one of claims 1-2, wherein the nanocellulose satisfies one or more of the following conditions (1) to (5):

(1) The average length of the nanocellulose is 100nm-1200nm, optionally 200nm-1000nm;

(2) The average diameter of the nanocellulose is 11nm-40nm, and can be 15nm-32nm;

(3) The length-diameter ratio of the nanocellulose is 5-60, and can be selected to be 12-35;

(4) The nanocellulose comprises a modifying group comprising at least one of an amine group, a carboxyl group, an aldehyde group, a sulfonic acid group, or a phosphoric acid group, optionally comprising at least one of a sulfonic acid group or a phosphoric acid group;

(5) The nanocellulose comprises hydroxyl groups and modifying groups, and the molar ratio of the modifying groups to the hydroxyl groups is 1:4 to 4:1, optionally 2:3 to 7:3.

4. The battery cell according to any one of claim 1 to 3, wherein,

the mass content of the nanocellulose in the coating is 5-60 wt%, optionally 7-45 wt%; and/or the number of the groups of groups,

the mass content of the granular filler in the coating is more than 38wt%, optionally 53wt% to 91wt%.

5. The battery cell of any one of claims 1-4, wherein the porous substrate satisfies one or more of the following conditions (1) to (9):

(1) The thickness of the porous substrate is less than or equal to 5 mu m, and can be 3 mu m to 4.5 mu m;

(2) The average pore diameter of the porous substrate is 10nm-60nm, and can be 20nm-40nm;

(3) The porosity of the porous base material is 20% -60%, optionally 30% -50%;

(4) The porous substrate is made of polyolefin, and optionally polyethylene;

(5) The puncture strength of the porous substrate is more than or equal to 390gf, and is selected to be 400gf-480gf;

(6) The longitudinal heat shrinkage rate of the porous substrate at 105 ℃ for 1h is less than 3%, and can be selected to be 1% -2.5%;

(7) The transverse heat shrinkage rate of the porous substrate at 105 ℃ for 1h is less than 2%, and can be selected to be 1% -1.8%;

(8) The porous substrate has a longitudinal tensile strength of 2700kgf/cm or more ² Optionally 2800kgf/cm ² -3500kgf/cm ² ；

(9) The porous substrate has strong transverse stretchingDegree of 2500kgf/cm or more ² Optionally 2600kgf/cm ² -3200kgf/cm ² 。

6. The battery cell of any one of claims 1-5, wherein the particulate filler comprises one or more of organic particles, inorganic particles, organic-inorganic composites.

7. The battery cell of claim 6, wherein the particulate filler comprises a first component of secondary particle morphology and a second component of primary particle morphology.

8. The battery cell of claim 7, wherein an average particle size of the first component of the secondary particle morphology is smaller than an average particle size of the second component of the primary particle morphology.

9. The battery cell according to any one of claims 7 to 8, wherein,

the average particle size of the first component in the secondary particle morphology is less than 200nm, and can be selected to be 80nm-180nm; and/or the number of the groups of groups,

the average particle size of the second component of the primary particle morphology is 200nm-600nm, optionally 300nm-500nm.

10. A battery cell according to any of claims 7-9, wherein the primary particles in the first component constituting the secondary particle morphology have a particle size of 15nm-45nm, optionally 20nm-35nm.

11. The battery cell of any one of claims 7-10, wherein the specific surface area of the first component of the secondary particle morphology is greater than the specific surface area of the second component of the primary particle morphology.

12. The battery cell according to any one of claims 7-11, wherein,

the specific surface area of the first component of the secondary particle morphology is more than 20m ² /g, optionally 30m ² /g-80m ² /g; and/or the number of the groups of groups,

the specific surface area of the second component of the primary particle morphology is less than or equal to 20m ² /g, optionally 5m ² /g-15m ² /g。

13. The battery cell of any one of claims 7-12, wherein the mass content of the first component of the secondary particle morphology in the coating is greater than the mass content of the second component of the primary particle morphology in the coating.

14. The battery cell according to any one of claims 7-13, wherein,

the mass content of the first component of the secondary particle morphology in the coating is 10-85 wt%, optionally 20-75 wt%; and/or the number of the groups of groups,

the mass content of the second component of the primary particle morphology in the coating is 5wt% to 70wt%, optionally 7wt% to 60wt%.

15. The battery cell of any one of claims 1-14, wherein the coating further comprises a non-particulate binder;

optionally, the non-particulate binder is present in the coating in an amount of 3wt% or less based on the total mass of the coating.

16. The battery cell of any one of claims 1-15, wherein the separator further comprises an adhesive layer disposed on at least a portion of a surface of the coating layer,

optionally, the adhesive layer comprises a particulate adhesive;

optionally, the binder comprises at least one of an acrylate monomer homo-or copolymer, an acrylic monomer homo-or copolymer, a fluoroolefin monomer homo-or copolymer.

17. The battery cell of any one of claims 1-16, wherein the cell comprises a plurality of cells,

The thickness of the coating is 0.2-2 μm, optionally 0.4-1 μm; and/or the number of the groups of groups,

the total thickness of the isolating film is 4-10 μm, optionally 4.5-8.5 μm; and/or the number of the groups of groups,

the longitudinal heat shrinkage rate of the isolating film at 150 ℃ for 1h is less than or equal to 3%; and/or the number of the groups of groups,

the lateral heat shrinkage rate of the isolating film is less than or equal to 2% at 150 ℃ for 1 h.

18. The battery cell of any one of claims 1-17, wherein the negative electrode tab comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material comprising a carbon material; optionally, the carbon material comprises one or more of artificial graphite and natural graphite.

19. The battery cell of any one of claims 1-18, wherein the negative electrode tab comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material comprising a silicon-based material;

optionally, the silicon-based material further comprises one or more of alkali metal elements and alkaline earth metal elements, optionally one or more of Li and Mg; and/or the number of the groups of groups,

Optionally, the mass ratio of the silicon-based material in the anode active material is greater than or equal to 5wt%, and is optionally 8wt% to 20wt%.

20. The battery cell of any one of claims 1-19, wherein the upper limit cutoff voltage of the battery cell is 4.25V or greater, optionally 4.30V-4.45V.

21. The battery cell of any one of claims 1-20, further comprising a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material comprising a layered lithium-containing transition metal oxide, and the positive electrode active material having a volume distribution particle size Dv50 of 6 μιη or less, optionally 2 μιη -5 μιη.

22. The battery cell of claim 21, wherein the positive electrode active material further satisfies one or more of the following conditions (1) to (3):

(1) The volume distribution particle diameter Dv90 of the positive electrode active material is less than or equal to 14 mu m, and is optionally 4.5 mu m-13.5 mu m;

(2) The volume distribution particle diameter Dv10 of the positive electrode active material is less than or equal to 3 mu m, and can be 1 mu m to 2 mu m;

(3) The particle size distribution (Dv 90-Dv 10)/Dv 50 of the positive electrode active material is 0.8-2.5, optionally 1.3-2.3.

23. The battery cell of any one of claims 21-22, wherein the positive electrode active material comprises a layered lithium-containing transition metal oxide of monocrystalline morphology or both a layered lithium-containing transition metal oxide of monocrystalline morphology and a layered lithium-containing transition metal oxide of polycrystalline morphology.

24. The battery cell of claim 23, wherein the layered lithium-containing transition metal oxide of single crystal morphology satisfies one or more of the following conditions (1) to (4):

(1) The volume distribution particle diameter Dv50 of the layered lithium-containing transition metal oxide with the single crystal morphology is less than or equal to 5 mu m, and can be selected to be 2 mu m-4 mu m;

(2) The volume distribution particle diameter Dv90 of the layered lithium-containing transition metal oxide with the single crystal morphology is less than or equal to 10 mu m, and is optionally 4.5 mu m-8 mu m;

(3) The volume distribution particle diameter Dv10 of the layered lithium-containing transition metal oxide with the single crystal morphology is less than or equal to 3 mu m, and can be 1 mu m to 2 mu m;

(4) The particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide with single crystal morphology is 0.8-2.5, optionally 1.3-1.5.

25. The battery cell of any one of claims 23-24, wherein the layered lithium-containing transition metal oxide of polycrystalline morphology satisfies one or more of the following conditions (1) to (4):

(1) The volume distribution particle diameter Dv50 of the layered lithium-containing transition metal oxide with the polycrystalline morphology is 7-12 mu m, and can be 8-10 mu m;

(2) The volume distribution particle diameter Dv90 of the layered lithium-containing transition metal oxide with the polycrystalline morphology is 12-20 mu m, and can be 13-18 mu m;

(3) The volume distribution particle diameter Dv10 of the layered lithium-containing transition metal oxide with the polycrystalline morphology is 2-6 mu m, and can be 3-5 mu m;

(4) The particle size distribution (Dv 90-Dv 10)/Dv 50 of the layered lithium-containing transition metal oxide with the polycrystalline morphology is 1.1-1.5, and optionally 1.2-1.4.

26. A battery comprising the battery cell of any one of claims 1-25.

27. An electrical device comprising the battery of claim 26.