CN116565119A

CN116565119A - Positive electrode sheet, secondary battery, method of manufacturing the same, and device including the secondary battery

Info

Publication number: CN116565119A
Application number: CN202210112151.0A
Authority: CN
Inventors: 王亚龙; 陆雷; 李世松
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-01-29
Filing date: 2022-01-29
Publication date: 2023-08-08
Also published as: WO2023142934A1

Abstract

The application provides a positive electrode plate, a secondary battery, a preparation method thereof and a device containing the secondary battery. The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material and a gel, and after the gel is dried, a three-dimensional fiber network structure is formed in the positive electrode active material layer of the positive electrode plate. The positive electrode plate of the invention has good dynamic advantages. The positive electrode plate provided by the application can also improve the rate capability of the secondary battery.

Description

Positive electrode sheet, secondary battery, method of manufacturing the same, and device including the secondary battery

Technical Field

The application belongs to the technical field of energy storage devices, and particularly relates to a positive electrode plate, a secondary battery, a preparation method of the positive electrode plate and the secondary battery, and a device containing the secondary battery.

Background

In recent years, as the application range of lithium ion secondary batteries is becoming wider, the lithium ion secondary batteries are widely applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, and various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like. As lithium ion secondary batteries have been greatly developed, there are also demands for higher energy density, cycle performance, safety performance, and the like.

Disclosure of Invention

In order to achieve the above object, a first aspect of the present application provides a positive electrode tab for a secondary battery, the positive electrode tab including a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector,

the positive electrode active material layer comprises a positive electrode active material and a gel, and a three-dimensional fiber network structure is formed in the positive electrode active material layer after the gel is dried.

Surprisingly, it was found that by adding a gelling agent to the active material layer of the electrode sheet, the polar functional group-OH is present due to the inclusion of the functional group (c=o) in the gelling additive. The gel is self-assembled in one-dimensional direction through intermolecular hydrogen bonds, electrostatic action and Van der Waals force, a fiber structure is presented, fibers are mutually wound to form a three-dimensional network, a three-dimensional gel additive network exists in an electrode plate after the electrode plate is dried, and solvent micromolecules, dimethyl carbonate and ethylene carbonate in electrolyte enter a gel additive molecular chain to be swelled to become gel electrolyte and are filled in an electrode after the electrolyte is injected into a cell. The gel electrolyte does not contain free electrolyte solvent micromolecules, the complexation degree of lithium ions and the solvent micromolecules is reduced, and the migration number of the lithium ions is improved, so that the migration dynamics of the lithium ions in the pole piece is improved, and the thick pole piece shows good dynamics advantages. By adopting the electrode plate provided by the application, the rate performance of the secondary battery can be improved.

In any of the above embodiments, in the three-dimensional fiber network structure, the fibers have an aspect ratio of 1:20-1:500; optionally 1:50-1:400; further alternatively 1:100-1:300. the gel meets the above conditions, and in the preparation process of the electrode plate, the electrolyte infiltration performance can be further improved, the electrode plate is quickly infiltrated, the infiltration formation time in the production process of the battery cell is shortened, and the production efficiency is improved.

In any of the above embodiments, the molecular weight of the gelling agent is 100-1000; optionally 200-800; further alternatively 400-600. The gel meets the above conditions, and can obtain better performance in the preparation process of the electrode plate. The molecular weight of the gel is too low, the gel effect is insufficient, and the gel is dissolved; the gel agent has too high molecular weight, can be easily dispersed poorly in the pulping process, and can be agglomerated after drying, so that the gel factors in the pole piece are unevenly distributed, and the electrical performance of the pole piece can be affected.

In any of the above embodiments, the mass ratio of the gelling agent in the active material layer is 0.1 to 1%, optionally 0.3 to 0.8%; further alternatively 0.4-0.6%. The content of the gel is in a proper range, so that the rate performance of the battery can be further improved; meanwhile, the battery is favorable for achieving higher safety performance.

In any of the above embodiments, the positive electrode active material comprises a positive electrode active material; alternatively, the positive electrode active material includes a positive electrode active material, a conductive agent, a binder, and a gel.

In any of the above embodiments, the gelling agent may be dispersed in N-methylpyrrolidone.

In any of the above embodiments, the gelling agent is selected from one or more of saccharide gelling agents, amide gelling agents, and cholesterol gelling agents;

optionally, the saccharide gel is selected from 2,4- (3, 4-dichlorobenzyl) -D-sorbitol and/or 2,4- (2, 3-dimethylbenzylidene) -D-sorbitol;

alternatively, the amide-based gel is selected from (E) -1- (4- ((4- ((1-amino-4, 7, 10-trioxo-14-azoctadec-18-yl) oxy) phenyl) diazinoyl) phenyl) ethan-1-one and/or 1,1'- ((1E, 1' E) - (((1,4,10,13-tetraoxo-7, 16-diazacyclooctadecane-7, 16-diacyl) bis (butane-4, 1-diacyl)) bis (oxy) bis (4, 1-phenylene) bis (diazene-2, 1-diacyl)) bis (4, 1-phenylene) bis (ethan-1-one);

optionally, the cholesterol gel is selected from (2- (naphthalen-2-yl) acetyl) -L-phenylalanine and/or (2- (naphthalen-2-yl) acetyl) -D-phenylalanine. The proper gel is adopted, so that the rate performance of the battery can be improved better.

The second aspect of the application provides a secondary battery, which comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate is the electrode plate provided by the application.

The secondary battery can obtain higher multiplying power performance due to the electrode plate.

A third aspect of the present application provides a method for manufacturing a secondary battery, comprising manufacturing a positive electrode tab of the secondary battery by: providing a slurry comprising a positive electrode active material and a gelling agent; coating the slurry on at least one surface of a positive electrode current collector, and drying and cold pressing to obtain a positive electrode plate; and after the gel is dried, a three-dimensional fiber network structure is formed in the positive electrode active material layer of the positive electrode plate.

In the secondary battery obtained by the preparation method, the gel is added into the active material layer of the positive electrode plate, the migration dynamics of lithium ions in the positive electrode plate is improved, and the thick electrode plate shows good dynamics advantages. The positive electrode plate provided by the application can also improve the rate capability of the secondary battery.

A fourth aspect of the present application provides an apparatus comprising the secondary battery of the second aspect of the present application, and/or the secondary battery obtained according to the production method of the third aspect of the present application.

The device of the present application includes the secondary battery provided by the present application, and thus has at least the same or similar advantages as the secondary battery.

Drawings

Fig. 1 is a schematic view of an embodiment of a positive electrode sheet of the present invention.

Fig. 2 is an SEM image of the positive electrode sheet of example 1 of the present invention.

Fig. 3 is an SEM image of the positive electrode sheet of example 4 of the present invention.

Fig. 4 is an SEM image of the positive electrode sheet of example 10 of the present invention.

Fig. 5 is an SEM image of a comparative example of a positive electrode sheet of the present invention.

Fig. 6 is a schematic view of an embodiment of a secondary battery.

Fig. 7 is an exploded view of fig. 6.

Fig. 8 is a schematic diagram of an embodiment of a battery module.

Fig. 9 is a schematic diagram of an embodiment of a battery pack.

Fig. 10 is an exploded view of fig. 9.

Fig. 11 is a schematic view of an embodiment of an apparatus in which a secondary battery is used as a power source.

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 a top cover assembly;

101 is a metal current collector; 102 is a conductive agent; 103 is a gel agent for forming a three-dimensional fiber network; 104 is an active substance

Detailed Description

Hereinafter, embodiments of a method of manufacturing a battery tab of the present application, a secondary battery using the battery tab of the present application, a battery module, a battery pack, and an electrical device 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, unless specifically stated otherwise.

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

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.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

The pole piece of the lithium ion secondary battery consists of active particles, a conductive agent and a binder. The active material and the conductive agent are bonded by the adhesive and simultaneously bonded to the surface of the metal current collector. In order to pursue high weight and volume energy density of the battery cell, the thickness of the pole piece needs to be further increased, and the use of inactive ingredients such as a metal current collector is reduced. However, as the thickness of the pole piece is increased, and after rolling, the porosity is reduced, the tortuosity in the pole piece is higher, and the lithium ion migration path is longer, so that the energy density of the battery core is not effectively increased under the condition of thick coating of the pole piece, but is reduced.

Positive electrode plate

The inventor has made a great deal of research and provides a novel positive electrode plate, and the positive electrode plate comprises a gel agent, so that the problems are effectively solved, the positive electrode plate, especially a thick electrode plate, is ensured, lithium ions have high mobility in an electrode in a high-voltage density state, and the battery cell shows good electrochemical performance under the condition of ensuring a thick coated electrode.

Based on this, this application provides a positive plate, and it includes positive plate current collector and set up in positive plate active material layer on at least one surface of positive plate current collector, wherein, positive plate active material layer includes positive plate active material and gel, after the gel is dry, form three-dimensional fiber network structure in the active material layer of positive plate.

In some embodiments, the gelling agents of the present application may be dispersed in a solvent of the electrode slurry, for example, the gelling agents may be dispersed in N-methylpyrrolidone (NMP). Therefore, the electrode sheet contains the gelling agent in a state in which the gelling agent is dissolved in the solvent, wherein the gelling agent refers to a low molecular material capable of forming a three-dimensional fiber network structure in the solvent.

In the positive electrode sheet of the present application, there is a three-dimensional fiber network, and as a mechanism of gelation, the following reasons can be considered: as described in the "recent trend of polymer gels" (CMC publication, release 2004), low-molecular gels are crosslinked by weak secondary bonds such as hydrogen bonding, van der waals interactions, hydrophobic interactions, electrostatic interactions, pi-pi interactions, and the like, to form a three-dimensional fiber network structure in a mesh shape. After the cell is injected, solvent small molecules in the electrolyte, such as dimethyl carbonate, ethylene carbonate and the like, enter a molecular chain of the gel additive to be swelled, become gel electrolyte and are filled in the electrode. The gel electrolyte does not contain free electrolyte solvent micromolecules, so that the complexation degree of lithium ions and solvent micromolecules is reduced, the migration number of the lithium ions is improved, the migration dynamics of the lithium ions in the pole piece is improved, and the thick-coated pole piece shows good dynamics advantages.

By adopting the positive pole piece provided by the application, the multiplying power performance of the secondary battery can be improved, and the capacity retention rate of the secondary battery in the circulation process is further improved, so that the circulation performance of the secondary battery is improved.

In the positive electrode sheet of the present application, the positive electrode active material layer may be coated with a positive electrode slurry containing a positive electrode active material and a gelling agent, and dried and cold-pressed. The solvent of the positive electrode slurry may be a solvent known in the art. For example, the solvent may be selected from N-methylpyrrolidone (NMP) and the like.

In some embodiments, in the three-dimensional fiber network structure, the fibers have an aspect ratio of 1:20-1:500; optionally 1:50-1:400; further alternatively 1:100-1:300. the gel meets the above conditions, and in the preparation process of the positive electrode plate, the electrolyte infiltration performance can be further improved, the positive electrode plate is quickly infiltrated, the infiltration formation time in the production process of the battery cell is shortened, and the production efficiency is improved.

In this application, the aspect ratio of the fiber is determined by SEM test, and the pure gel factor particle size diameter is characterized as D ₁ The diameter of the gel factor fiber in the characterization pole piece is D ₂ Because of conservation of mass, the gel factor fiber length L in the pole piece is (4/3 pi (D ₁ /2) ³ )/(π(D ₂ /2) ² ) Long, longThe diameter ratio is L/(D) ₂ /2)。

In some embodiments, the gellant is a low molecular weight gellant that is itself capable of solidifying the whole into a gel by small additions to an organic or other solvent, a wide variety of low molecular weight gellants being known. As used herein, a low molecular weight gelator refers to a low molecular weight material capable of forming a three-dimensional fiber network in a solvent. Therefore, unlike a high molecular weight polymer gel (e.g., a polymer such as sodium polyacrylate) having a crosslinking point by chemical bonding, the gel used in the present application is associated by physical bonding, and thus the self-organized three-dimensional fiber network is excellent in flexibility, and the flexibility of the gel can be appropriately set. And also differs from so-called tackifiers (e.g., n-octanediamine and 1, 4-dibenzoyl butane) which have a function of increasing viscosity without gelation based on self-organized three-dimensional fiber formation.

The three-dimensional fiber network can be confirmed by a transmission electron microscope or a scanning electron microscope. As shown in fig. 2-4 of the present application, the three-dimensional fiber network formed in the positive electrode sheet of the present application is a scanning electron microscope photograph. Fig. 5 is a scanning electron microscope photograph of a positive electrode sheet containing no gelling agent according to the prior art.

In some embodiments of the present application, the gelling agent has a molecular weight of 100-1000; optionally 200-800; further alternatively 400-600. The molecular weight is determined by determining the structure by various spectroscopic analyses such as NMR. The gel meets the above conditions, and can obtain better performance in the preparation process of the electrode plate. The molecular weight of the gel is too low, the gel effect is insufficient, and the gel is dissolved; the gel agent has too high molecular weight, can be easily dispersed poorly in the pulping process, and can be agglomerated after drying, so that the gel factors in the pole piece are unevenly distributed, and the electrical performance of the pole piece can be affected.

In this application, the functional group characterization method is as follows: and preparing a xerogel sample by adopting an infrared spectrometer, a model FTS-3000 type infrared spectrometer and a KBr tabletting method. The resolution of the infrared spectrum test is set to 4cm ^-1 The scanning range is set to 1000-4000cm ^-1 。

In this application, the molecular weight measurement method is as follows: the nuclear magnetic resonance spectrum of the gel of 0.5wt% was measured by a Varian Bruker-400 hydrogen nuclear magnetic resonance spectrometer using heavy water as solvent.

The melting point of the gelling agent used in the present application is preferably 80℃or higher, more preferably 100℃or higher, and still more preferably 120℃or higher. The upper limit is preferably 300℃or lower, more preferably 200℃or lower. The melting point of the gelling agent is preferably higher than the drying temperature of the electrode sheet, more preferably at least +30℃, and still more preferably at least +50℃. The melting point can be measured by DSC (Differential scanning calorimetry, differential scanning calorimeter). In this application, the measurement is made using German relaxation resistance, STA 449Jupiter,1 ℃/min, temperature range-50℃to 400 ℃.

In some embodiments, the mass ratio of the gelling agent in the active material layer is 0.1-1%, optionally 0.3-0.8%; further alternatively 0.4-0.6%. The content of the gel is in a proper range, so that the rate performance of the battery can be further improved; meanwhile, the battery is favorable for achieving higher safety performance.

In some embodiments, the positive electrode active material includes a positive electrode active material, a conductive agent, a binder, and a gel.

In some embodiments, the gelling agent may be dispersed in N-methylpyrrolidone.

In some embodiments, the gelling agent is selected from one or more of saccharide gelling agents, amide gelling agents, and cholesterol gelling agents;

optionally, the cholesterol gel is selected from (2- (naphthalen-2-yl) acetyl) -L-phenylalanine and/or (2- (naphthalen-2-yl) acetyl) -D-phenylalanine.

In some embodiments, the positive current collector may be a metal foil or a composite current collector (a metal material may be disposed on a polymeric substrate to form a composite current collector). As an example, the positive electrode current collector may employ aluminum foil.

In some embodiments, the mass ratio of the positive electrode active material in the positive electrode active material layer may be 70% -95%, for example 70% -95%,75% -90%, or 80% -90%, or the like. The positive electrode active material layer has a higher positive electrode active material ratio, and can enable the battery to obtain higher energy density.

In some embodiments, the binder generally comprises a fluorinated polyolefin-based binder. Water is generally a good solvent relative to the fluorinated polyolefin-based binder, i.e., the fluorinated polyolefin-based binder generally has good solubility in water. For example, the fluorinated polyolefin-based binder may be a modified (e.g., carboxylic acid, acrylic acid, acrylonitrile, etc. modified) derivative or the like including, but not limited to, polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer, etc. or the like. In the positive electrode active material layer, the mass percentage content of the binder may be, for example, 0.1wt% to 10wt%,0.2wt% to 8wt%0,0.3wt% to 6wt%, or 0.5wt% to 3wt%. The amount of binder used cannot be too high because of the poor conductivity of the binder itself. Optionally, the mass percentage of the binder in the positive electrode active material layer is 0.5-3 wt% so as to obtain lower pole piece impedance.

In some embodiments, the conductive agent of the positive electrode sheet may be various conductive agents suitable for lithium ion (secondary) batteries in the art, for example, may be a combination including, but not limited to, one or more of acetylene black, conductive carbon black, carbon fiber (VGCF), carbon Nanotubes (CNT), ketjen black, and the like. The weight of the conductive agent may be 0.5wt% to 10wt% of the total mass of the positive electrode active material layer. Optionally, the weight ratio of the conductive agent to the positive electrode active material in the positive electrode sheet is 1.0wt% to 5.0wt%.

In the electrode tab cell of the present application, the active material layer may be disposed on one surface of the current collector, or may be disposed on both surfaces of the current collector at the same time.

Secondary battery

A second aspect of the present application provides a secondary battery comprising the positive electrode tab provided in the first aspect of the present application.

In the secondary battery provided in the present application, it should be noted that the secondary battery may be a supercapacitor, a lithium ion secondary battery, a lithium metal battery, or a sodium ion battery. In the embodiments of the present application, only the embodiment in which the secondary battery is a lithium ion secondary battery is shown, but the present application is not limited thereto.

Fig. 1 shows a schematic view of an embodiment of an electrode sheet of the present application. The electrode pole piece sequentially comprises a metal current collector 101, a conductive agent 102, a gel agent 103 and an active substance 104, wherein the gel agent 103 presents a three-dimensional fiber structure on the electrode pole piece.

The secondary battery has the corresponding beneficial effects due to the electrode plate. The secondary battery can obtain higher cycle performance, higher first discharge specific capacity and first charge and discharge efficiency.

In the lithium ion secondary battery, the lithium ion secondary battery can comprise a positive electrode plate, a negative electrode plate, an isolating film and electrolyte, wherein the isolating film and the electrolyte are arranged between the positive electrode plate and the negative electrode plate, and the positive electrode plate can be the positive electrode plate provided by the first aspect of the application. Methods of preparing lithium ion secondary batteries should be known to those skilled in the art, for example, each of the positive electrode tab, the separator, and the negative electrode tab may be a laminate so as to be cut to a target size and then sequentially stacked, and may be wound to a target size for forming a battery cell, and may be further combined with an electrolyte to form a lithium ion secondary battery.

In a lithium ion secondary battery, a negative electrode tab may generally include a negative electrode current collector and a negative electrode active material layer on a surface of the negative electrode current collector, and the negative electrode active material layer generally includes a negative electrode active material. The negative electrode active material may be any of a variety of materials suitable for use in a lithium ion secondary battery in the art, and may be, for example, a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming alloys with lithium, and the like. Wherein, the graphite can be selected from one or a combination of more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from one or a combination of a plurality of simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material may be selected from one or more of elemental tin, tin oxide, and tin alloys. The negative electrode current collector is generally a structure or a part for collecting current, and may be various materials suitable for use in the art as a negative electrode current collector of a lithium ion secondary battery, for example, the negative electrode current collector may be a metal foil or the like including but not limited to, more specifically, a copper foil or the like.

In the lithium ion secondary battery, the separator may be a material suitable for a lithium ion secondary battery separator in the art, and for example, may be a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.

In a lithium ion secondary battery, the electrolyte may generally include an electrolyte and a solvent, and suitable electrolytes suitable for use in a lithium ion secondary battery should be known to those skilled in the art, for example, the electrolyte may generally include a lithium salt or the like, more specifically, the lithium salt may be an inorganic lithium salt and/or an organic lithium salt or the like, and particularly may include, but is not limited to, liPF ₆ 、LiBF ₄ 、LiN(SO ₂ F) ₂ (LiFSI)、LiN(CF ₃ SO ₂ ) ₂ (LiTFSI)、LiClO ₄ 、LiAsF ₆ 、LiB(C ₂ O ₄ ) ₂ (LiBOB)、LiBF ₂ C ₂ O ₄ (LiDFOB) et alA combination of one or more of (a) and (b); for another example, the concentration of the electrolyte may be between 0.8mol/L and 1.5 mol/L; as another example, the solvent used in the electrolyte may be any of a variety of solvents suitable for use in electrolytes for lithium ion secondary batteries in the art, typically nonaqueous solvents, alternatively may be organic solvents, and specifically may include, but are not limited to, ethylene carbonate, propylene carbonate, butylene carbonate, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, and the like, or combinations of one or more of their halogenated derivatives.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. Fig. 6 shows a square secondary battery 5 as an example. As shown in fig. 7, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The electrode assembly 52 is enclosed in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the secondary battery 5 may be one or several, and may be adjusted according to the need.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.

Fig. 8 is a battery module 4 as an example. As shown in fig. 8, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the battery modules may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

Fig. 9 and 10 are battery packs 1 as an example. As shown in fig. 9 and 10, a battery box and a plurality of battery modules 4 provided in the battery box may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

The application also provides a preparation method of the secondary battery, which comprises the following steps of preparing a positive electrode plate of the secondary battery: providing a slurry comprising a positive electrode active material and a gelling agent; coating the slurry on at least one surface of a positive electrode current collector, and drying and cold pressing to obtain a positive electrode plate; and after the gel is dried, a three-dimensional fiber network structure is formed in the positive electrode active material layer of the positive electrode plate.

The preferred technical characteristics or technical scheme of the electrode plate are also applicable to the preparation method of the application, and the corresponding beneficial effects are generated.

The preparation method of the present application may further include other well-known steps for preparing the secondary battery, and will not be described herein.

The present application also provides an apparatus comprising at least one of the secondary battery, the battery module, or the battery pack of the present application. The secondary battery, battery module or battery pack may be used as a power source for the device, and may also be used as an energy storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a cell phone, a 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 device may select a secondary battery, a battery module, or a battery pack according to its use requirements.

Fig. 11 is an apparatus as one example. The device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the device for the secondary battery, a battery pack or a battery module may be employed.

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

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 by weight, 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.

Wherein 2,4- (3, 4-dichlorobenzyl) -D-sorbitol is available from Aba Ding Shiji company under the trade designation O302477 and has a molecular weight of 400, and is represented by T1 in the following examples;

2,4- (2, 3-dimethylbenzylidene) -D-sorbitol was purchased from Aba Ding Shiji company under the trade designation D303957 and has a molecular weight of 400, and is represented by T2 in the following examples;

(E) -1- (4- ((4- ((1-amino-4, 7, 10-trioxo-14-azoctadec-18-yl) oxy) phenyl) diazoyl) phenyl) ethan-1-one available from a company of ala Ding Shiji, cat No. E351880, molecular weight 500, represented by X1 in the examples below;

1,1'- ((1 e,1' e) - ((1,4,10,13-tetraoxo-7, 16-diazacyclooctadecane-7, 16-diacyl) bis (butane-4, 1-diacyl)) bis (oxy) bis (4, 1-phenylene) bis (diazene-2, 1-diacyl)) bis (4, 1-phenylene) bis (ethane-1-one) was purchased from ala Ding Shiji company, cat No. S290177 molecular weight 530, represented by X2 in the following examples;

(2- (naphthalen-2-yl) acetyl) -L-phenylalanine is available from a company of alar Ding Shiji under the trade designation a276249, molecular weight 570, represented by D1 in the examples below;

(2- (naphthalen-2-yl) acetyl) -D-phenylalanine is available from Aba Ding Shiji company under the trade designation P107874 and has a molecular weight of 570, and is represented by D2 in the examples below.

Preparation and testing of secondary batteries:

example 1

Preparation of positive electrode plate

The positive active material lithium iron phosphate (LFP), PVDF (polyvinylidene fluoride), a conductive agent SP and 2,4- (2, 3-dimethylbenzylidene) -D-sorbitol (T1) are mixed according to the weight ratio of 97:1:1.8: and 0.2 dispersing the powder into an N-methyl pyrrolidone solvent system, fully stirring and uniformly mixing, coating the powder on an Al foil by using extrusion coating or transfer coating, drying and cold pressing to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material layer is 450mg/1504.25mm ²

FIG. 2 is an SEM photograph of a pole piece prepared in example 1, from which the three-dimensional fiber structure of saccharide gelling agent 2,4- (2, 3-dimethylbenzylidene) -D-sorbitol (T1) can be observed.

Preparation of negative electrode plate

Artificial graphite as a negative electrode active material, acetylene black as a conductive agent and styrene-butadiene rubber (SBR) as a binder according to the proportion of 96:2: and 2, after being fully and uniformly stirred in deionized water, the mixture is coated on a Cu foil, dried and cold-pressed to obtain the negative plate.

Preparation of electrolyte

Uniformly mixing ethylene carbonate and dimethyl carbonate according to the volume ratio of 1:1 to obtain a solvent; and dissolving lithium hexafluorophosphate serving as an electrolyte in the solvent, and uniformly mixing to obtain an electrolyte, wherein the concentration of the lithium hexafluorophosphate is 1mol/L.

Preparation of secondary battery

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, so that the isolating film is positioned in the middle of the positive electrode and the negative electrode to play a role in isolation, and winding to obtain the bare cell. And placing the bare cell in an outer package, injecting the prepared electrolyte, and packaging. PE porous polymeric film is used as a isolating film.

Examples 2 to 3

The same as in example 1, except that the coating amounts of the positive electrode active material layers were 550mg/1504.25mm, respectively ² And 650mg/1504.25mm ² 。

Example 4

Preparation of positive electrode plate

The positive electrode active material lithium iron phosphate, PVDF (polyvinylidene fluoride), SP and amide gel (E) -1- (4- ((4- ((1-amino-4, 7, 10-trioxo-14-nitrogen octadecan-18-yl) oxy) phenyl) diazooyl) phenyl) ethane-1-ketone (X1) are mixed according to the weight ratio of 97.4:1:0.4: and 1, fully stirring and uniformly mixing the mixture in an N-methyl pyrrolidone solvent system, and then coating the mixture on an Al foil by using extrusion coating or transfer coating, drying and cold pressing to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material layer is 450mg/1504.25mm ²

FIG. 3 is a SEM photograph of a pole piece prepared in example 4, from which the three-dimensional fiber structure of the amide-based gel (E) -1- (4- ((4- ((1-amino-4, 7, 10-trioxo-14-azoctadec-18-yl) oxy) phenyl) diazoyl) phenyl) ethane-1-one (X1) can be observed.

The rest is the same as in example 1

Examples 5 to 6

The same as in example 4, except that the coating amounts of the positive electrode active material layers were 550mg/1504.25mm, respectively ² And 650mg/1504.25mm ² 。

Example 7

Preparation of positive electrode plate

The positive electrode active material lithium iron phosphate, PVDF (polyvinylidene fluoride), SP, cholesterol gel (2- (naphthalene-2-yl) acetyl) -L-phenylalanine (D1)) were mixed in a weight ratio of 97.4:1:0.4: and 1, fully kneading in an N-methyl pyrrolidone solvent system, coating the mixture on an Al foil by extrusion coating or transfer coating, drying and cold pressing to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material layer is 450mg/1504.25mm ²

The rest is the same as in example 1

Examples 8 to 9

The same as in example 7, except that the coating amounts of the positive electrode active material layers were 550mg/1504.25mm, respectively ² And 650mg/1504.25mm ² 。

Example 10

Preparation of positive electrode plate

The positive electrode active material lithium nickel cobalt manganese oxide (NCM 523), PVDF (polyvinylidene fluoride), SP and cholesterol gel (2- (naphthalene-2-yl) acetyl) -D-phenylalanine (D2) are fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent system according to the weight ratio of 98:0.7:1:0.3, and then are coated on an Al foil by extrusion coating or transfer coating, dried and cold pressed to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material layer is 380mg/1504.25mm ²

FIG. 4 is an SEM photograph of a pole piece prepared in example 10, from which the three-dimensional fiber structure of the cholesterol gel (2- (naphthalen-2-yl) acetyl) -D-phenylalanine (D2) can be observed.

Examples 11 to 12

The same as in example 10, except that the coating amounts of the positive electrode active material layers were 450mg/1504.25mm, respectively ² And 550mg/1504.25mm ² 。

Examples 13 to 17: the secondary battery was prepared similarly to example 1, except that the relevant preparation parameters of the positive electrode tab were adjusted as detailed in table 1.

Comparative example 1

Dispersing positive active materials of lithium iron phosphate, PVDF (polyvinylidene fluoride) and SP in an N-methyl pyrrolidone solvent system according to a weight ratio of 97:1: and 2, after fully stirring and uniformly mixing, coating the mixture on an Al foil by using extrusion coating or transfer coating, drying and cold pressing to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material is 450mg/1504.25mm ²

The details of the rest are shown in Table 1, as in example 1.

Comparative examples 2 to 3

The same as in comparative example 1, except that the coating amounts of the positive electrode active material layers were respectively550mg/1504.25mm ² And 650mg/1504.25mm ² . Details are shown in Table 1.

Comparative example 4:

positive electrode active material nickel cobalt lithium manganate NCM 532, PVDF (polyvinylidene fluoride) and SP according to the weight ratio of 98:0.7:1.3 fully stirring and uniformly mixing the mixture in an N-methyl pyrrolidone solvent system, and then coating the mixture on an Al foil by using extrusion coating or transfer coating, drying and cold pressing to obtain the positive electrode plate. Wherein the coating amount of the positive electrode active material layer is 380mg/1504.25mm ² The details of the rest of example 10 are shown in Table 1.

Comparative examples 5 to 6

The same as in comparative example 4, except that the coating amounts of the positive electrode active material layers were 450mg/1504.25mm, respectively ² And 550mg/1504.25mm ² . The details of the rest of example 10 are shown in Table 1.

Performance test of secondary battery:

(1) Liquid absorption rate test:

sucking electrolyte with the thickness of 2mm by adopting a capillary tube, vertically placing the electrolyte on the cold-pressed pole piece for standing for 200s, and observing the residual height of the electrolyte in the capillary tube;

imbibition rate = (2 mm-residual height) ×capillary cross-sectional area ×1.0g/cm ³ (electrolyte density)/time, results are shown in table 2;

(2) And (3) liquid climbing height test:

taking a pole piece after cold pressing, taking a diaphragm to clamp the pole piece in the middle, cutting the pole piece to be 10cm long and 20mm wide, adopting a hot press to simulate winding hot pressing to compress the diaphragm and the pole piece, then vertically hanging the pole piece above a plate with electrolyte, and enabling the lower end to be in contact with the electrolyte to perform a climbing experiment, and recording the height once per hour, wherein the result is shown in Table 2.

Battery cell multiplying power test

A charge-discharge tester (Shenzhen New Will electronic Co., ltd.) is adopted, and the voltage range is 2.5-4.2V.

The charge/discharge rate is a current value required for the battery to discharge its rated capacity for a predetermined period of time, and is denoted by C. 1C indicates that charging was completed for 1h, 0.33C indicates that charging and discharging was completed for 3h, and the results are shown in Table 2.

Table 1: preparation parameters of positive pole piece

Table 2: results of cycle performance test of secondary battery

As can be seen from the results of table 2, the use of the electrode sheet for the positive electrode sheet of the present application can significantly improve the cycle capacity retention rate of the secondary battery using the same, and thus the secondary battery has significantly improved cycle performance. Specifically, in the preparation process of the pole piece, the higher the pole piece gram weight is, the thicker the pole piece is, the longer the lithium ion migration path is, the electrolyte wettability is also poor, the lithium ion migration is blocked, and the transmission dynamics is deteriorated. In the application, by adding the gel in the preparation of the pole piece, the electrolyte infiltration and the liquid retaining capacity are improved, and the migration number of lithium ions in the local part of the active main material particles is increased, so that the pole piece dynamics is improved.

As can be seen from a comparison of examples 1 to 3 with comparative examples 1 to 3, in the same coated electrode sheet, after the use of the gel, the wettability of the electrolyte was significantly improved, and the liquid retention ability was also significantly improved, thereby correspondingly improving the cycle capacity retention rate of the secondary battery.

Comparative examples 1 to 6 were inferior in cycle performance due to the absence of the gelling agent.

The above description is merely a specific embodiment of the present application, but the scope of the present application is not limited thereto. Various equivalent modifications and substitutions will occur to those skilled in the art, and these are intended to be included within the scope of the present disclosure. Therefore, the protection scope of the present application shall be subject to the protection scope defined by the claims.

Claims

1. A positive electrode sheet for a secondary battery, the positive electrode sheet including a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector,

2. The positive electrode sheet according to claim 1, wherein in the three-dimensional fiber network structure, an aspect ratio of the fibers is 1:20-1:500; optionally 1:50-1:400; further alternatively 1:100-1:300.

3. the positive electrode sheet according to claim 1 or 2, wherein the molecular weight of the gel is 100-1000; optionally 200-800; further alternatively 400-600.

4. A positive electrode sheet according to any one of claims 1 to 3, wherein the mass ratio of the gelling agent in the active material layer is 0.1 to 1%, optionally 0.3 to 0.8%; further alternatively 0.4-0.6%.

5. The positive electrode sheet according to any one of claims 1 to 4, wherein the positive electrode active material includes a positive electrode active material, a conductive agent, a binder, and a gelling agent.

6. The positive electrode sheet according to any one of claims 1 to 5, wherein the gelling agent is dispersible in N-methylpyrrolidone.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein the gelling agent is selected from one or more of saccharide gelling agents, amide gelling agents and cholesterol gelling agents;

8. A secondary battery comprising a positive electrode tab and a negative electrode tab, the positive electrode tab being the electrode tab according to any one of claims 1-7.

9. A battery module comprising the secondary battery according to claim 8.

10. A battery pack comprising the secondary battery according to claim 8 or the battery module according to claim 9.

11. An electric device comprising at least one of the secondary battery according to claim 8, the battery module according to claim 9, and the battery pack according to claim 10.