CN115986322A - Battery with a battery cell - Google Patents
Battery with a battery cell Download PDFInfo
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- CN115986322A CN115986322A CN202310265397.6A CN202310265397A CN115986322A CN 115986322 A CN115986322 A CN 115986322A CN 202310265397 A CN202310265397 A CN 202310265397A CN 115986322 A CN115986322 A CN 115986322A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a battery, which comprises a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, wherein the diaphragm comprises a base film and a base film coating, the base film coating is arranged on the surface of the base film, and the base film coating is formed by compounding inorganic particles and organic particles; the base film coating includes first surface and second surface, and the base film setting is kept away from to the first surface, and the second surface is close to the base film setting, is equipped with organic granule on the first surface, and organic granule is formed with the depressed part, and the opening of depressed part is the first surface dorsad. According to the invention, the sunken part is arranged on the diaphragm, so that the composition of the diaphragm and the pole piece is strengthened, the stability of the electrode assembly prepared from the diaphragm and the pole piece is improved, the interface resistance is reduced, and the cycle performance of the battery is improved.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a battery, wherein a diaphragm adopted by the battery is provided with a sunken structure.
Background
In a lithium battery, a diaphragm is mainly used for separating a positive plate from a negative plate, so that the dangerous problems of deterioration of the cycle performance of the battery, explosion caused by overheating of the battery and the like caused by short circuit caused by contact of the two electrodes are prevented. The diaphragm and the pole piece are in direct contact, the temperature of the battery can rise in the using process of the lithium battery, the diaphragm can easily shrink due to the rise of the temperature of the battery, the positive pole piece and the negative pole piece are directly short-circuited, short circuits are caused, the cycle performance of the battery can be degraded, and the safety performance of the battery can be greatly influenced. In the lithium battery, in order to meet the requirement of automatic assembly of the battery, a diaphragm and a pole piece are required to be compounded together, and the good compounding of interfaces can effectively improve the structural stability of the battery cell and reduce the interface impedance. If the composite effect of the diaphragm and the pole piece is poor, the automatic battery cell entering into the shell is difficult and the interface impedance is increased.
Disclosure of Invention
In order to solve the problems and the defects in the prior art, the invention provides a battery, wherein a diaphragm adopted by the battery is provided with a sunken structure, and the sunken structure can enhance the composition of the diaphragm and a pole piece, improve the structural stability of a battery cell, reduce the interface resistance and further improve the cycle performance of the battery.
The invention provides a battery, which comprises a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, wherein the diaphragm comprises a base film and a base film coating, and the base film coating is formed by compounding inorganic particles and organic particles; the base film coating includes first surface and second surface, and the base film setting is kept away from to the first surface, and the second surface is close to the base film setting, is equipped with organic granule on the first surface, and organic granule is formed with the depressed part, and the opening of depressed part is the first surface dorsad.
In the process of assembling the battery provided by the invention, the pole piece provided with the base film coating facing the diaphragm is compounded with the base film coating of the diaphragm, on the other hand, electrolyte positioned near the diaphragm can enter a region surrounded by the concave part of the diaphragm and the pole piece, and in the process of battery charging and discharging circulation, the electrolyte stored in the region can be decomposed to generate gas, so that the formed gas escapes from the region, so that a negative pressure difference relative to the outside of the region is formed inside the region, and the concave part of the diaphragm generates an adsorption effect on the pole piece facing the opening of the diaphragm due to the existence of the negative pressure difference, so that the close compounding of the diaphragm and the pole piece is strengthened, the structural stability of an electric core component consisting of the pole piece and the diaphragm is effectively improved, and the interface impedance of the electric core component is reduced. The base film coating layer of the diaphragm comprises inorganic particles and organic particles, on one hand, the inorganic particles in the base film coating layer of the diaphragm enable the diaphragm to have high temperature resistance, even if the environmental temperature is obviously increased, the diaphragm can not shrink obviously, the situation that a positive plate and a negative plate are contacted to cause short circuit due to preheating shrinkage of the diaphragm is effectively avoided, and the battery provided by the invention has good safety performance; on the other hand, compared with inorganic particles, the organic particles are easier to shape and control, and the organic particles are used as one of the components forming the base film coating and are used for forming the concave part, so that the convenience and controllability of forming the concave part are improved.
Drawings
Fig. 1 is a schematic structural view of a separator according to the present invention, including a base film and a base film coating layer, the base film coating layer being disposed on a surface of the base film, the organic particles of the base film coating layer having a recess opening flush with a first surface;
fig. 2 is a schematic structural view of a separator according to the present invention, including a base film and a base film coating layer, the base film coating layer being disposed on a surface of the base film, the recess openings of the organic particles being higher than the first surface and the bottoms of the recesses being located below the first surface;
FIG. 3 is an SEM image of a coated surface of a base film according to the present invention;
the reference numbers in the above-described diagram 1~2 are: 11. organic particles; 111. a recessed portion; 112. a boss portion; 12. a film body; 121. a first surface; 122. a second surface; 2. a base film; H. the depth of the recess.
Detailed Description
According to a first aspect of the present invention, there is provided a battery comprising a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, wherein the separator comprises a base film and a base film coating, and the base film coating is formed by compounding inorganic particles and organic particles; the base film coating includes first surface and second surface, and the base film setting is kept away from to the first surface, and the second surface is close to the base film setting, is equipped with organic granule on the first surface, and organic granule is formed with the depressed part, and the opening of depressed part is the first surface dorsad. The arrangement mode of the concave part can comprise: the opening of the concave part is flush with the first surface or lower than the first surface, and the bottom of the concave part is lower than the first surface; the opening of the concave part is higher than the first surface, and the bottom of the concave part is positioned below the first surface; the opening and the bottom of the concave part are higher than the first surface. In the present invention, the first pole piece may be a positive pole piece or a negative pole piece, and the second pole piece may be a positive pole piece or a negative pole piece.
In the process of assembling the battery provided by the invention, the pole piece provided with the base film coating facing the diaphragm is compounded with the base film coating of the diaphragm, on the other hand, electrolyte positioned near the diaphragm can enter a region surrounded by the concave part of the diaphragm and the pole piece, and in the process of battery charging and discharging circulation, the electrolyte stored in the region can be decomposed to generate gas, so that the formed gas escapes from the region, so that a negative pressure difference relative to the outside of the region is formed inside the region, and the concave part of the diaphragm generates an adsorption effect on the pole piece facing the opening of the diaphragm due to the existence of the negative pressure difference, so that the close compounding of the diaphragm and the pole piece is strengthened, the structural stability of an electric core assembly consisting of the pole piece and the diaphragm is effectively improved, the interface impedance of the electric core assembly is reduced, and the cycle performance of the battery is improved. The base film coating layer of the diaphragm comprises inorganic particles and organic particles, on one hand, the inorganic particles in the base film coating layer of the diaphragm enable the diaphragm to have high temperature resistance, and the diaphragm can not shrink even if the environmental temperature is obviously increased, so that the situation that a positive plate and a negative plate are contacted to cause short circuit due to preheating shrinkage of the diaphragm is effectively avoided, and the battery provided by the invention has good safety performance; on the other hand, compared with inorganic particles, the shape of the organic particles is easier to regulate, and the organic particles are used as one of components forming the base film coating, and the organic particles are used for forming the concave parts, so that the convenience and controllability of concave part forming are improved.
Preferably, the distance between the bottom of the recess and the second surface is greater than 0. In other words, when the distance between the bottom of the depression and the second surface is 0, which is actually equivalent to the case of perforation of the base film coating, in this case, structural weak regions of hollow perforations are formed in the base film coating due to the excessive depth of the depression of the organic particles, and the presence of these structural weak regions easily causes chipping and peeling of the base film coating. And the bottom of the depressed part on the organic particle is spaced from the second surface by a certain distance, so that the second surface of the base film coating can be kept as flat as possible, the structural weak area cannot be formed due to the arrangement of the depressed part, the structural stability of the base film coating is improved, and the base film coating can play the application function for a long time.
Preferably, the ratio of the depth of the recessed portion to the thickness of the base film coating is 0.01 to 1.
Preferably, the depth of the recess is 0.2 to 4 μm. In the present invention, the depth of the recess is the vertical distance from the bottom of the recess to the farthest position of the recess in the opening direction of the recess. The depth of the depressed part is ensured to be within a certain range, on one hand, the depressed part can be ensured to provide enough electrolyte storage space, and further, the electrolyte stored in the depressed part is ensured to generate enough gas to form an effective negative pressure difference area on the base film coating so as to strengthen the compounding of the diaphragm and the pole piece; on the other hand, the sunken part can be avoided too deeply, thereby ensuring that the sunken part is not arranged to form an excessively thin structural weak area on the base film coating and ensuring the structural stability of the base film coating.
Preferably, the depth of the recess is 1.5 to 3 μm. In the battery provided by the invention, when the sunken part of the diaphragm meets the conditions, the battery has more excellent cycle performance.
Preferably, the organic particle further comprises a convex portion, the convex portion being convex with respect to the first surface. For inorganic particle, organic particle has certain viscidity, on this basis, through making organic particle form the bellying for the first surface of base film coating is bellied, can increase the area of contact of organic particle and its relative pole piece that sets up to strengthen the bonding effect of organic particle to the pole piece, improve the compound stability of diaphragm and pole piece.
Preferably, the organic particle is convex with respect to the first surface, and in the organic particle, an edge of the depression is a convex portion.
Preferably, the organic particles include at least one of an acrylic acid homopolymer, a styrene homopolymer, an acrylate ester homopolymer, an acrylic acid-styrene copolymer, an acrylic acid-acrylate ester copolymer, a styrene-acrylate ester copolymer, and an acrylic acid-styrene-acrylate ester copolymer. The organic particles prepared from the organic resin have good viscosity, so that the prepared base film coating can be tightly attached to the base film, the bonding strength of the organic particles and the inorganic particles in the base film coating can be enhanced, the base film and the base film coating are not easy to separate and the base film coating is not easy to crack under the cyclic stress in the battery charging and discharging process of the diaphragm, and the structural stability of the diaphragm is improved.
Preferably, the inorganic particles comprise at least one of boehmite, titanium oxide, silicon oxide, magnesium hydroxide, aluminum oxide. The inorganic particles and the organic particles are tightly attached to each other, so that gaps among the particles in the formed base film coating are fewer, and the improvement of the structural strength of the base film coating is facilitated.
Preferably, the inorganic particles are alumina.
Preferably, a base film coating is arranged on the surface of the base film facing the first pole piece and the surface of the base film facing the second pole piece. Being provided with based on the base film coating does benefit to the firm complex of diaphragm and pole piece, through set up the base film coating towards positive plate, negative pole piece simultaneously on the both sides surface of base film, can make the diaphragm firmly compound with positive plate, negative pole piece simultaneously.
Preferably, the preparation method of the separator comprises the following steps: s1, preparing mixed slurry by adopting organic particles with a core-shell structure and using the organic particles and inorganic particles, coating the mixed slurry on the surface of a base film, and drying the mixed slurry to form a base film coating on the surface of the base film; s2, breaking the shell of the organic particle to form a concave part on the organic particle.
Preferably, in the method for manufacturing the separator, the organic particles may form the depressions by a pyrolysis gasification method, in which the organic particles have a core/shell structure, and the inner core bodies have a better high temperature resistance than the outer shell bodies, and the outer shell bodies are pyrolyzed and gasified at a high temperature, and the inner core bodies flow out in a molten manner and then settle and spread to form the depressions.
In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.
The positive plate and the negative plate used in the following examples and comparative examples were prepared by the following methods:
preparing a positive plate: the positive electrode active material Ni 0.5 Co 0.2 Mn 0.3 O 2 The preparation method comprises the following steps of uniformly mixing Li, a conductive agent carbon black (Super P), a carbon nanotube slurry (CNT slurry) and a binder polyvinylidene fluoride (PVDF) in a proper amount of N-methylpyrrolidone (NMP) according to a mass ratio of (96).
Preparing a negative plate: the preparation method comprises the following steps of uniformly mixing the artificial graphite serving as a negative electrode active material, carbon black serving as a conductive agent (Super P), styrene Butadiene Rubber (SBR) serving as a binder and sodium carboxymethylcellulose (CMC-Na) in a proper amount of solvent deionized water according to a mass ratio of 97.8.
Example 1
1. Preparing a diaphragm:
(1) Preparation of organic particles
S1, adding agar and an emulsifier into deionized water to form a reaction solution with the solid content of 40%, keeping the stirring speed of 1700r, heating to 85 ℃, wherein the agar and the emulsifier in the reaction system form a microsphere structure together, and the microsphere structure formed by the microsphere structure is used as a biological template;
s2, adding an organic monomer and an initiator into the reaction system, wherein the organic monomer is an acrylate monomer and styrene, and polymerizing the organic monomer on the surface of the biological template under the action of the initiator for 6 hours, so that the formed polymer is coated on the surface of the biological template, and organic particles taking the biological template as an inner core and the polymer as an outer shell are formed.
In the process, the solid content and the stirring speed of the reaction solution of the S1 are regulated to control the particle size of the biological template, and the polymerization time of the S2 is regulated to control the coating amount of the polymer on the surface of the biological template so as to achieve the effect of controlling the particle size of the organic particles. In this example, the stirring rate of S1 was 1700r, which corresponds to the particle size of the produced bio-template being 2 μm, and the polymerization time of S2 was 6 hours, which corresponds to the particle size of the produced organic particles being 5 μm.
(2) Preparing slurry: with inorganic particles of aluminium oxide (Al) 2 O 3 ) Uniformly mixing the organic particles, a dispersing agent sodium carboxymethyl cellulose (CMC-Na) and a wetting agent organosilicon modified polyether in a proper amount of solvent deionized water according to the mass ratio of 70;
(3) Preparing a diaphragm: in the embodiment, a PE film is used as a base film, the slurry is coated on both surfaces of the base film by a gravure roll coating method (the slurry in a trough is brought into a mesh trough of a gravure roll by the rotation of the gravure roll, a stable thickness of the slurry is formed by the distance between the gravure roll and a doctor blade, the base film is sufficiently contacted with the gravure roll under the pressure of a rubber compression roller to transfer the slurry to both surfaces of the base film), and then the obtained semi-finished product is sent into a drying box to be dried to remove a solvent, a high-speed rotating spray head is arranged at an inlet of the drying box, atomized corrosion solvent (ethanol) is sprayed out from the spray head, and the corrosion solvent is contacted with a coating formed by the slurry to corrode an inner core (biological template) in organic particles, so that an outer shell (polymer) of the organic particles is broken to be settled or spread, a concave part is formed, and the coating is dried at 60 ℃ for 1 minute to remove the corrosion solvent, thereby preparing the diaphragm with the base film coating on the surface.
Referring to fig. 1, which is a schematic view of a separator prepared through the above-described steps, composed of a base film 2 and a base film coating layer disposed on a surface of the base film 2. Wherein, the base film coating comprises organic particle 11 and inorganic particle, and inorganic particle constitutes membrane main part 12, and organic particle 11 forms depressed part 111, and the opening of depressed part 111 is dorsad first surface 121, and depressed part 111 opening is with first surface 121 is even, and the depth of depressed part 111 is H. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 is 1.5 μm.
2. Preparation of the Battery
Compounding the positive plate, the negative plate and the diaphragm by hot pressing, wherein after hot pressing, organic particles of the base film coating generate viscosity, the diaphragm is compounded with the positive plate and the negative plate together, the diaphragm is positioned between the positive plate and the negative plate to play a role in isolation, and then winding or laminating to obtain a bare cell; and placing the bare cell in an outer packaging shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
The electrolyte in this example was prepared as follows: ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) were mixed at a mass ratio of 5 6 To form 1mol/L of electrolyte.
Example 2
In the preparation of the separator, this example is compared with example 1 except that, in (1) the preparation of the organic particles, the solid content of the reaction solution in S1 was 50%, the stirring rate was 2000r, the particle diameter of the thus-formed bio-template was 3 μm, and the polymerization time in S2 was 4 hours, thereby corresponding to the particle diameter of the prepared organic particles being 5 μm; the rest corresponds to example 1.
Referring to fig. 1, which is a schematic view of a separator prepared through the above-described steps, composed of a base film 2 and a base film coating layer disposed on a surface of the base film 2. Wherein, the base film coating comprises organic particle 11 and inorganic particle, and inorganic particle constitutes membrane main part 12, and organic particle 11 forms depressed part 111, and the opening of depressed part 111 is dorsad first surface 121, and depressed part 111 opening is with first surface 121 is even, and the depth of depressed part 111 is H. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 is 2.5 μm.
The cell in this example was prepared in accordance with example 1.
Example 3
In the preparation of the separator, this example was compared with example 1 except that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 was 42%, the stirring rate was 1700r, the particle diameter of the thus-formed bio-template was 2 μm, the polymerization time in S2 was 7 hours, and thus the particle diameter of the corresponding organic particles was 6 μm, and the organic monomers used in S2 were acrylic acid monomers, styrene, and acrylate monomers; in the process of preparing the slurry in the step (2), the adopted inorganic particles are boehmite; in the preparation of the diaphragm in (3), the wire rod coating method is selected to coat the slurry on two surfaces of the base film (the wire rod rotates in the trough to uniformly carry the slurry and form stable thickness, the base film is fully contacted with the wire rod under the pressure of the rubber compression roller to transfer the slurry to the two surfaces of the base film), and after the slurry is coated on the base film, the subsequent treatment process of the semi-finished product obtained by the method is consistent with that of the embodiment 1; the rest corresponds to example 1.
Referring to fig. 2, which is a schematic view of the separator prepared through the above steps, it is composed of a base film 2 and a base film coating layer disposed on the surface of the base film 2. The base film coating is composed of organic particles 11 and inorganic particles, the inorganic particles form a film main body 12, the organic particles 11 form concave portions 111, openings of the concave portions 111 face away from the first surface 121, the openings of the concave portions 111 are higher than the first surface 121, bottoms of the concave portions 111 are located below the first surface 121, the depth of the concave portions 111 is H, and portions, higher than the first surface 121, of the organic particles 11 are convex portions 112. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 is 1.5 μm.
The cell in this example was prepared in accordance with example 1.
Example 4
In the preparation of the separator, this example was compared with example 1 except that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 was 40%, the stirring rate was 1200r, the particle diameter of the thus-formed bio-template was 1 μm, and the polymerization time in S2 was 8 hours, thereby corresponding to the particle diameter of the organic particles obtained being 6 μm; the rest corresponds to example 1.
Referring to fig. 2, which is a schematic view of the separator prepared through the above steps, it is composed of a base film 2 and a base film coating layer disposed on the surface of the base film 2. The base film coating is composed of organic particles 11 and inorganic particles, the inorganic particles form a film main body 12, the organic particles 11 form concave portions 111, openings of the concave portions 111 face away from the first surface 121, the openings of the concave portions 111 are higher than the first surface 121, bottoms of the concave portions 111 are located below the first surface 121, the depth of the concave portions 111 is H, and portions, higher than the first surface 121, of the organic particles 11 are convex portions 112. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 is 0.2 μm.
The cell in this example was prepared in accordance with example 1.
Example 5
In the preparation of the separator, this example was compared with example 1 except that in (1) the preparation of the organic particles, the solid content of the reaction solution in S1 was 55%, the stirring rate was 1400r, the particle diameter of the thus-formed bio-template was 3.5 μm, the polymerization time in S2 was 5 hours, the particle diameter of the thus-prepared organic particles was 6 μm, and the organic monomers used in S2 were acrylic acid monomers, styrene, and acrylate monomers; in the process of preparing the slurry in the step (2), the adopted inorganic particles are boehmite; the rest corresponds to example 1.
Referring to fig. 2, which is a schematic view of the separator prepared through the above steps, it is composed of a base film 2 and a base film coating layer disposed on the surface of the base film 2. Wherein, the base film coating comprises organic particles 11 and inorganic particles, the inorganic particles form the film main body 12, the organic particles 11 form the concave parts 111, the opening of the concave part 111 faces away from the first surface 121, the opening of the concave part 111 is higher than the first surface 121, the bottom of the concave part 111 is positioned below the first surface 121, the depth of the concave part 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the convex part 112. In the present embodiment, the average depth of the concave portions 111 of the organic particles 11 is 3 μm.
The cell in this example was prepared in accordance with example 1.
Example 6
In the preparation of the separator, this example was compared with example 1 except that in (1) the preparation of the organic particles, the solid content of the reaction solution in S1 was 60%, the stirring rate was 1600r, the particle diameter of the thus-formed bio-template was 3.9 μm, the polymerization time in S2 was 4.5 hours, and the particle diameter of the thus-prepared organic particles was 6 μm, and the organic monomers used in S2 were acrylic acid monomers, styrene and acrylate monomers; in the process of (2) preparing the slurry, the adopted inorganic particles are boehmite; the rest corresponds to example 1.
Referring to fig. 2, which is a schematic view of the separator prepared through the above steps, it is composed of a base film 2 and a base film coating layer disposed on the surface of the base film 2. Wherein, the base film coating comprises organic particles 11 and inorganic particles, the inorganic particles form the film main body 12, the organic particles 11 form the concave parts 111, the opening of the concave part 111 faces away from the first surface 121, the opening of the concave part 111 is higher than the first surface 121, the bottom of the concave part 111 is positioned below the first surface 121, the depth of the concave part 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the convex part 112. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 was 3.2 μm.
The cell in this example was prepared in accordance with example 1.
Example 7
In the preparation of the separator, this example was compared with example 1 except that in (1) the preparation of the organic particles, the solid content of the reaction solution in S1 was 47%, the stirring rate was 1200r, the particle diameter of the thus-formed bio-template was 2.5 μm, the polymerization time in S2 was 6.5 hours, and the particle diameter of the thus-prepared organic particles was 6 μm, and the organic monomers used in S2 were acrylic acid monomers, styrene, and acrylate monomers; in the process of (2) preparing the slurry, the adopted inorganic particles are boehmite; the rest corresponds to example 1.
Referring to fig. 2, which is a schematic view of the separator prepared through the above steps, it is composed of a base film 2 and a base film coating layer disposed on the surface of the base film 2. The base film coating is composed of organic particles 11 and inorganic particles, the inorganic particles form a film main body 12, the organic particles 11 form concave portions 111, openings of the concave portions 111 face away from the first surface 121, the openings of the concave portions 111 are higher than the first surface 121, bottoms of the concave portions 111 are located below the first surface 121, the depth of the concave portions 111 is H, and portions, higher than the first surface 121, of the organic particles 11 are convex portions 112. In the present embodiment, the average depth of the depressed portions 111 of the organic particles 11 is 2 μm.
The cell in this example was prepared in accordance with example 1.
Example 8
In the preparation of the separator, this example was compared with example 3 except that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 was 43%, the stirring rate was 1200r, the particle diameter of the thus-formed bio-template was 2 μm, and the polymerization time in S2 was 7 hours, thereby corresponding to the particle diameter of the organic particles obtained being 6 μm; the rest is identical with example 3; the structural view of the finally obtained separator was similar to that of example 3, and the average depth of the depressed portions 111 of the organic particles 11 was also 1.5 μm.
The cell preparation in this example was identical to that of example 3.
Comparative example 1
In the preparation of the separator, this comparative example is different from example 1 in that, in (2) the slurry was prepared, the inorganic particles used were boehmite; in (3) preparing the diaphragm, coating the slurry on a base film by a wire rod coating method (refer to the wire rod method in example 3), after coating the slurry on the base film, drying the semi-finished product at 60 to 90 ℃ for 10 to 60s to prevent a concave part and a convex part from being formed on the surface of the coating (the organic particle inner core (biological template) is not corroded by a corrosive solvent, and the organic particle shell is not cracked, settled or spread, so that the organic particle does not form a concave part and a convex part relative to the first surface), and thus the diaphragm with the base film coating on the surface of the base film is prepared; the rest corresponds to example 1.
The method of manufacturing the battery in this comparative example was identical to that of example 1.
Comparative example 2
In the preparation of the separator, this comparative example is different from example 1 in that (1) the preparation of organic particles is omitted, i.e., organic particles are not used, and thus, in (2) the process of preparing the slurry, organic particles are not added; in (3) preparing a separator, a paste was applied to a base film by a wire bar coating method (see the wire bar coating method in example 3), after the paste was applied to the base film, the semi-finished product thus obtained was dried at 60 to 90 ℃ for 10 to 60s, and a base film coating layer was formed on the surface of the coating layer without forming a depression and a protrusion (without organic particles, a depression and a protrusion with respect to the first surface were not formed); the rest corresponds to example 1.
The method of manufacturing the battery in this comparative example was identical to that of example 1.
Test example
1. Experimental construction mode
(1) The diaphragms prepared in examples 1 to 8 and comparative examples 1 to 2 were cut in cross section by an argon ion polisher, the surface structure of the coating layer on the base film was observed in a scanning electron microscope, the depth of the depressions 111 of the organic particles was measured, and the average depth of the depressions 111 was calculated.
(2) The batteries prepared in examples 1 to 8 and comparative examples 1 to 2 were subjected to a battery cycle performance test; the method for testing the battery cycle performance comprises the following steps: the voltage interval is 2.75-4.35V, the charging current is 1C to 4.35V, then the constant voltage charging is carried out until the current is reduced to 0.05C,1C constant current discharging is carried out until 2.75V; the above procedure was repeated 2000 times.
2. Results of the experiment
In the test subjects of the present test example, the base film coating of the separator provided in examples 1 to 8 had depressed portions, and the base film coating of the separator provided in examples 3 to 8 also had raised portions, and the method for forming depressed portions on the surface of the separator in these examples was a biomatepattern method, and in the process of preparing the base film coating, depressed portions having a desired depth were formed on the base film coating of the separator mainly by selecting a biomatepattern having an appropriate particle size, and on the other hand, the above-mentioned raised portions were formed on the surface of the base film coating mainly by selecting organic particles having an appropriate particle size. For comparison, table 1 shows the detailed operations for influencing the sizes of the biological templates and the organic particles and the corresponding size information of the biological templates and the organic particles, and the size information of the features on the base film coatings prepared in these embodiments, which are adopted in the process of preparing the base film coatings in embodiments 1 to 8.
TABLE 1 EXAMPLES 1 TO 8 raw material dimensional information involved in the preparation of base film coatings
The results of analyzing the surface of the base film coating layer of the separator prepared in examples 1 to 8 and comparative examples 1 to 2 and the results of the cycle performance of the battery prepared in examples 1 to 8 and comparative examples 1 to 2 are shown in table 2.
TABLE 2 analysis results of the surface of the coating layer of the base film of the reference object, and cycle performance results of the battery
After the test is finished, the electric core assembly of the reference battery is observed, the electric core assembly provided by the comparative example 1 and the comparative example 2 has poor bonding effect of the diaphragm and the pole piece, while the electric core assembly provided by the embodiment 1~8 has a good structure, and the bonding effect of the diaphragm and the pole piece is good. The reason for this is that the diaphragm adopted in embodiment 1~8 has a recessed portion on its first surface facing the pole piece, the electrolyte near the diaphragm can enter the area enclosed by the recessed portion of the diaphragm and the pole piece, during the battery charging and discharging cycle, the electrolyte stored in the area can be converted into gas to escape, so that a negative pressure difference is formed inside the area relative to the outside of the area, and the presence of the negative pressure difference enables the recessed portion of the diaphragm to generate an adsorption effect on the pole piece facing its opening, thereby strengthening the close combination of the diaphragm and the pole piece, and enabling the electric core component manufactured in embodiment 1~8 to have good structural stability. However, the separators employed in comparative examples 1 and 2 lack the provision of microstructures similar to the above-described depressions compared to example 1~8, thereby resulting in a significant decrease in the degree of composite tightness between the separators and the pole pieces of the two comparative examples, indicating that the structural stability of the cell assemblies provided in comparative examples 1 and 2 is poor. The difference that the base film coating layer of the separator provided in comparative example 1 contains organic particles having a certain viscosity based on the organic particles so that the surface of the separator provided in comparative example 1 maintains a certain viscosity, while the base film coating layer of the separator provided in comparative example 2 is composed of only inorganic particles and does not contain adhesive particles results in that the composite tightness between the separator and the pole piece provided in comparative example 2 is poorer than that of comparative example 1, as evidenced by the occurrence of significant separation between the pole piece and the separator in the battery pack assembly of comparative example 2 at the later stage of the test. While structural stability of the cell assembly is an important factor affecting the cycling characteristics of the cell, it can be seen from the test result data shown in table 1 that the cycling retention of the cell in example 1~8 is higher relative to the reference cells provided in comparative examples 1 and 2, thus illustrating that the cycling performance of the cell provided in example 1~8 is better.
Comparing the data of the depths of the depressions in 3~7 of example 5363, it can be seen that the average depths of the depressions in examples 3, 5 and 7 are within the range of 1.5 to 3 μm, and the cycle efficiency of the batteries provided in examples 3, 5 and 7 is better than that in examples 4 and 6 (the average depth of the depressions is outside the range of 1.5 to 3 μm, but within the range of 0.2 to 4 μm). The reason for the above test result is that the depth of the concave part affects the amount of the electrolyte storage, on one hand, the larger the depth of the concave part is, the larger the electrolyte storage is, and the too large the electrolyte storage of the concave part can relatively reduce the electrolyte amount for soaking the pole piece, thereby affecting the effect of soaking the pole piece with the electrolyte, causing the reduction of the ion transmission performance of the pole piece, and deteriorating the cycle performance of the battery; on the other hand, the depth of the depressed part is too small, the storage amount of the electrolyte is smaller, the gas generated by the electrolyte in the depressed part in the charging and discharging process of the battery is less, the negative pressure difference formed by the depressed part and the pole piece after the gas escapes is smaller, and the composite effect of the pole piece and the diaphragm is relatively poor. In conclusion, when the depth of the concave parts on the organic particles is within the range of 1.5 to 3 μm, the firm combination between the pole piece and the diaphragm can be further strengthened, and the comprehensive performance of the battery can be further improved.
Comparing the separators obtained in examples 1 and 3, the coating layer of the base film of the separator provided in example 3 had a convex portion formed thereon with respect to the first surface, whereas the coating layer of the base film of the separator provided in example 1 did not have the convex portion formed thereon. By observing the conditions of the electric core assemblies provided by the two embodiments before and after the test, the structure retention condition of the electric core assembly provided by the embodiment 3 is better, the pole piece and the diaphragm can still be tightly compounded, and although the pole piece and the diaphragm still remain compounded after the test of the electric core assembly provided by the embodiment 1 is completed, the gap of the compound surface of the pole piece and the diaphragm is increased. The data of the test results corresponding to the above two examples shown in table 1 show that the battery provided in example 3 exhibits higher cycle efficiency. The reason for the difference is that the organic particles have certain viscosity, and the protrusions are formed by the organic particles, so that the adhesion of the diaphragm and the pole piece can be enhanced by the presence of the protrusions, and thus the adhesion reliability of the diaphragm and the pole piece can be enhanced by the protrusions and the depressions together, and the stability of the electric core assembly consisting of the diaphragm and the pole piece is further improved.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A battery comprising a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, wherein:
the diaphragm comprises a base film and a base film coating, wherein the base film coating is arranged on the surface of the base film and is formed by compounding inorganic particles and organic particles;
the base film coating includes first surface and second surface, the first surface is kept away from the base film setting, the second surface is close to the base film setting be equipped with on the first surface organic granule, organic granule is formed with the depressed part, the opening of depressed part dorsad the first surface.
2. The battery of claim 1, wherein: the distance between the bottom of the recess and the second surface is greater than 0.
3. The battery of claim 1, wherein: the ratio of the depth of the recessed portion to the thickness of the base film coating is 0.01 to 1.
4. The battery of claim 1, wherein: the depth of the concave part is 0.2 to 4 mu m.
5. The battery of claim 4, wherein: the depth of the concave part is 1.5 to 3 mu m.
6. The battery of claim 1, wherein: the organic particle also includes a raised portion that is raised relative to the first surface.
7. The battery of claim 6, wherein: the organic particle is convex with respect to the first surface, and in the organic particle, an edge of the concave portion is the convex portion.
8. The cell of claim 1~7 wherein: the organic particles comprise at least one of acrylic acid homopolymer, styrene homopolymer, acrylate homopolymer, acrylic acid-styrene copolymer, acrylic acid-acrylate copolymer, styrene-acrylate copolymer and acrylic acid-styrene-acrylate copolymer.
9. The battery of claim 1, wherein: the inorganic particles comprise at least one of boehmite, titanium oxide, silicon oxide, magnesium hydroxide and aluminum oxide.
10. The battery of claim 1, wherein: the surface of the base film facing the first pole piece and the surface of the base film facing the second pole piece are both provided with the base film coating.
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