CN115986322A - Battery with a battery cell - Google Patents

Abstract

The invention provides a battery, comprising a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, the diaphragm comprises a base film and a base film coating, and the base film coating is arranged on The surface of the base film, the base film coating is composed of inorganic particles and organic particles; the base film coating includes a first surface and a second surface, the first surface is set away from the base film, and the second surface is set close to the base film. One surface is provided with organic particles, the organic particles form a depression, and the opening of the depression faces away from the first surface. The present invention strengthens the recombination of the diaphragm and the pole piece by providing the concave part on the diaphragm, improves the stability of the cell assembly prepared by the diaphragm and the pole piece, reduces the interface resistance, and thus improves the cycle performance of the battery.

Description

a battery

technical field

The invention relates to the field of lithium batteries, in particular to a battery in which a diaphragm used in the battery has a concave structure.

Background technique

In a lithium battery, the main function of the diaphragm is to separate the positive and negative electrodes to prevent short-circuiting of the two poles, resulting in deterioration of battery cycle performance, causing dangerous problems such as battery overheating and explosion. The diaphragm and the pole piece are in direct contact. During the use of the lithium battery, the temperature of the battery will rise, and the rise in battery temperature will cause the diaphragm to shrink easily, causing the positive and negative pole pieces to be directly shorted, causing a short circuit. Not only will it deteriorate the cycle performance of the battery, but it will also have a major impact on the safety performance of the battery. In lithium batteries, in order to meet the automatic assembly of batteries, the diaphragm and the pole piece need to be combined together. The good combination of the interface can effectively improve the stability of the battery structure and reduce the interface impedance. If the composite effect of the diaphragm and the pole piece is poor, it will make it difficult for the battery to automatically enter the shell and the interface impedance will increase.

Contents of the invention

In order to solve the problems and deficiencies in the prior art, the present invention provides a battery. The diaphragm used in the battery has a concave structure, and the concave structure can strengthen the recombination of the diaphragm and the pole piece, improve the structural stability of the battery cell, and reduce the Interface resistance, thereby improving battery cycle performance.

The invention provides a battery, comprising a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, the diaphragm comprises a base film and a base film coating, and the base film coating is made of inorganic Particles and organic particles are compounded; the base film coating includes a first surface and a second surface, the first surface is set away from the base film, the second surface is set close to the base film, organic particles are arranged on the first surface, and the organic particles form There is a depression, the opening of which faces away from the first surface.

In the process of assembling the battery provided by the present invention, the pole piece that is provided with the base film coating on the diaphragm is compounded with the base film coating of the diaphragm. On the other hand, the electrolyte near the diaphragm can enter the recessed part of the diaphragm and In the area surrounded by the pole piece, during the battery charge and discharge cycle, the electrolyte stored in the above area will decompose and produce gas, and the gas thus formed escapes from the area, so that the inside of the area is formed relatively The negative pressure difference outside it, the existence of negative pressure difference makes the concave part of the diaphragm absorb the pole piece facing its opening, and then strengthens the close combination of the diaphragm and the pole piece, thus effectively improving the connection between the pole piece and the pole piece. The structural stability of the cell assembly composed of the diaphragm reduces the interface impedance of the cell assembly. It is worth noting that the base film coating included in the diaphragm of the present invention is composed of inorganic particles and organic particles. On the one hand, the inorganic particles in the diaphragm base film coating make the diaphragm have high temperature resistance, even if the ambient temperature rises significantly , the separator will not shrink significantly, effectively avoiding the short circuit caused by the contact between the positive electrode sheet and the negative electrode sheet caused by the preheating shrinkage of the separator, so that the battery provided by the present invention has good safety performance; on the other hand, compared to For inorganic particles, it is easier to control the morphology of organic particles. By using organic particles as one of the components of the base film coating and using organic particles to form depressions, it is beneficial to improve the convenience of forming depressions and Controllability.

Description of drawings

Fig. 1 is the structural representation of diaphragm in the present invention, comprises base film and base film coating, and base film coating is positioned at the surface of base film, and in the organic particle of base film coating, the depression opening of organic particle is flat with the first surface together;

Fig. 2 is the structural representation of membrane in the present invention, comprises base film and base film coating, and base film coating is positioned at the surface of base film, and the recessed part opening of organic particle is higher than first surface and the bottom of recessed part is positioned at first surface the following;

Fig. 3 is the physical SEM figure of base film coating surface among the present invention;

The reference signs in the above-mentioned Figures 1-2 are: 11. Organic particles; 111. Depression; 112. Protrusion; 12. Film main body; 121. First surface; 122. Second surface; 2. Base film; H. Depth of depression.

Detailed ways

According to a first aspect of the present invention, a battery is provided, including a first pole piece, a second pole piece, and a diaphragm arranged between the first pole piece and the second pole piece, and the diaphragm includes a base film and a base film coating , the base film coating is composed of inorganic particles and organic particles; the base film coating includes a first surface and a second surface, the first surface is set away from the base film, the second surface is set close to the base film, and the first surface is set There are organic particles, the organic particles form a depression, the opening of the depression faces away from the first surface. The setting method of the above-mentioned recessed part may include: the opening of the recessed part is flush with or lower than the first surface, the bottom of the recessed part is lower than the first surface; the opening of the recessed part is higher than the first surface and the bottom of the recessed part is located at Below the first surface; the opening and the bottom of the recess 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 present invention, the pole piece that is provided with the base film coating on the diaphragm is compounded with the base film coating of the diaphragm. On the other hand, the electrolyte near the diaphragm can enter the recessed part of the diaphragm and In the area surrounded by the pole piece, during the battery charge and discharge cycle, the electrolyte stored in the above area will decompose and produce gas, and the gas thus formed escapes from the area, so that the inside of the area is formed relatively The negative pressure difference outside it, the existence of negative pressure difference makes the concave part of the diaphragm absorb the pole piece facing its opening, and then strengthens the close combination of the diaphragm and the pole piece, thus effectively improving the connection between the pole piece and the pole piece. The structural stability of the cell assembly composed of the diaphragm reduces the interface impedance of the cell assembly, thereby improving the cycle performance of the battery. It is worth noting that the base film coating included in the diaphragm of the present invention is composed of inorganic particles and organic particles. On the one hand, the inorganic particles in the diaphragm base film coating make the diaphragm have high temperature resistance, even if the ambient temperature rises significantly , the diaphragm will not shrink, which effectively avoids the short circuit caused by the contact between the positive electrode sheet and the negative electrode sheet due to the preheating shrinkage of the diaphragm, so that the battery provided by the present invention has good safety performance; on the other hand, compared with inorganic particles In general, it is easier to control the morphology of organic particles. By using organic particles as one of the components of the base film coating and using organic particles to form depressions, it is beneficial to improve the convenience and controllability of the formation of depressions. sex.

Preferably, the distance between the bottom of the recessed portion and the second surface is greater than zero. In other words, when the distance between the bottom of the depression and the second surface is 0, it is actually equivalent to the case where the base film coating is perforated. Hollow and perforated structurally weak areas are formed in the layer, and the existence of these structurally weak areas can easily lead to the collapse and peeling of the base film coating. And making the bottom of the depression on the organic particles and the second surface have a certain distance between them, it can ensure that the second surface of the base film coating is kept as smooth as possible, and the above-mentioned structural weak zone will not be formed due to the setting of the depression, so as to improve The structural stability of the base film coating is ensured, so that the base film coating can play its application function for a long time.

Preferably, the ratio of the depth of the depressed portion to the thickness of the base film coating is 0.01˜1.

Preferably, the depth of the depressed portion is 0.2-4 μm. In the present invention, the depth of the recessed portion is the vertical distance from the bottom of the recessed portion to the farthest point of the recessed portion along the opening direction of the recessed portion. Ensuring that the depth of the recessed part is within a certain range, on the one hand, it can ensure that the recessed part can provide enough electrolyte storage space, and then ensure that the electrolyte stored in the recessed part is gas-generated enough to form an effective negative electrode on the base film coating. In order to strengthen the recombination of the diaphragm and the pole piece; on the other hand, it can avoid the recessed part from being too deep, thus ensuring that the setting of the recessed part will not form an overly thin structural weak area on the base film coating, ensuring Structural stability of base film coatings.

Preferably, the depth of the depressed portion is 1.5-3 μm. In the battery provided by the present invention, when the concave part of the separator satisfies the above conditions, the battery can have more excellent cycle performance.

Preferably, the organic particle further includes a raised portion, and the raised portion protrudes relative to the first surface. Compared with the inorganic particles, the organic particles have a certain viscosity. Based on this, by making the organic particles form a convex portion that is raised relative to the first surface of the base film coating, the pole piece that the organic particles are opposite to it can be enlarged. contact area, thereby strengthening the bonding effect of organic particles to the pole piece, and improving the stability of the composite of the diaphragm and the pole piece.

Preferably, the organic particle is raised relative to the first surface, and in the organic particle, the edge of the depression is a raised part.

Preferably, the organic particles include acrylic acid homopolymer, styrene homopolymer, acrylate homopolymer, acrylic-styrene copolymer, acrylic-acrylate copolymer, styrene-acrylate copolymer, acrylic-styrene- At least one of acrylate copolymers. The organic particles prepared from the above-mentioned organic resins have good viscosity, so that the prepared base film coating can be closely attached to the base film, and can also enhance the combination of organic particles and inorganic particles in the base film coating itself. Strength, so that the base film and the base film coating are not easy to separate during the charging and discharging process of the battery, and ensure that the base film coating is not easy to crack under cyclic stress, and improve the structural stability of the separator.

Preferably, the inorganic particles include at least one of boehmite, titanium oxide, silicon oxide, magnesium hydroxide, and aluminum oxide. The above-mentioned inorganic particles and organic particles adhere closely to each other, so that there are fewer gaps between particles in the formed base film coating, which is conducive to improving the structural strength of the base film coating.

Preferably, the inorganic particles are alumina.

Preferably, a base film coating is provided on both the surface of the base film facing the first pole piece and the surface facing the second pole piece. The setting based on the base film coating is conducive to the firm compounding of the separator and the pole piece. By setting the base film coating facing the positive electrode and the negative electrode on both sides of the base film at the same time, the separator can be combined with the positive and negative electrodes at the same time. Strong compound.

Preferably, the preparation method of the diaphragm includes the following steps: S1. Using organic particles with a core-shell structure, preparing a mixed slurry with organic particles and inorganic particles, coating the mixed slurry on the surface of the 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 particles to form depressions on the organic particles.

Preferably, in the preparation method of the diaphragm, the method of forming the depression by the organic particles also includes a pyrolysis gasification method. In this method, the organic particles have a core/shell structure, and the inner core has better high temperature resistance than the outer shell. , at high temperature, the outer shell is pyrolyzed and gasified, and the inner core body flows out in the form of melting and then settles and spreads to form a depression.

In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the present invention, rather than Full examples.

The positive electrode sheet and the negative electrode sheet used in the following examples and comparative examples are all prepared by the following methods:

Preparation of positive electrode sheet: the positive electrode active material Ni _0.5 Co _0.2 Mn _0.3 O ₂ Li, conductive agent carbon black (Super P), carbon nanotube slurry (CNT slurry), binder polyvinylidene fluoride (PVDF) According to the mass ratio of 96:1.8:1.2:1, mix it evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) to obtain the positive electrode slurry, and coat the positive electrode slurry on the positive electrode current collector copper foil, through drying, Cold pressing, slitting, and cutting processes to obtain the positive electrode sheet.

Preparation of negative electrode sheet: Negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose sodium (CMC-Na) in a mass ratio of 97:0.8 : 1.2: 1 mixed evenly in an appropriate amount of solvent deionized water to obtain negative electrode slurry, and coated the negative electrode slurry on the copper foil of the current collector of the negative electrode machine, and obtained the negative electrode through drying, cold pressing, slitting, and cutting processes piece.

Example 1

1. Preparation of diaphragm:

(1) Preparation of organic particles

S1. Add agar and emulsifier to deionized water to form a reaction solution with a solid content of 40%, keep the stirring rate at 1700r, and heat to 85°C. At this time, the agar and emulsifier in the reaction system form a microsphere structure together , using the thus formed microsphere structure as a biological template;

S2. then add organic monomer and initiator in reaction system, organic monomer is acrylate monomer and styrene, under the effect of initiator, organic monomer polymerizes on the surface of biological template, polymerization time is 6 hours, The resulting polymer coats the surface of the biotemplate, forming organic particles with the biotemplate as the inner core and the polymer as the outer shell.

In the above process, the particle size of the biological template can be controlled by adjusting the solid content and stirring rate of the reaction solution of S1, and the coating amount of the polymer on the surface of the biological template can be controlled by adjusting the polymerization time of S2, thereby controlling the particle size of the organic particle. diameter effect. In this embodiment, the stirring rate of S1 is 1700r, which corresponds to the particle size of the prepared biological template being 2 μm, and the polymerization time of S2 is 6 hours, thus corresponding to the particle size of the obtained organic particles being 5 μm.

(2) Preparation of slurry: use inorganic particles of aluminum oxide (Al ₂ O ₃ ), the above-mentioned organic particles, dispersant sodium carboxymethylcellulose (CMC-Na) and wetting agent silicone modified polyether according to the mass The ratio is 70:20:8:1:1 and mixed uniformly in an appropriate amount of solvent deionized water to obtain a slurry for forming a base film coating;

(3) Preparation of diaphragm: In this example, PE film is used as the base film, and the above-mentioned slurry is coated on both surfaces of the base film by gravure roll coating (the slurry in the trough is brought to the surface by the rotation of the gravure roll In the grid groove of the version roller, the distance between the version roller and the scraper forms a stable thickness of the material liquid, and under the pressure of the rubber roller, the base film and the gravure roll are fully contacted to transfer the slurry to the two surfaces of the base film), Then the semi-finished product thus obtained is sent into a drying box for drying to remove the solvent. A high-speed rotating nozzle is installed at the entrance of the drying box, and an atomized corrosion solvent (ethanol) is sprayed from the nozzle, and the corrosion solvent contacts the slurry. After the formed coating corrodes the inner core (biological template) in the organic particle, the outer shell (polymer) of the organic particle is broken and settles or spreads to form a depression, and then it is dried at 60°C for 1 minute to remove the corrosion solvent. This results in a separator provided with a base film coating on the surface of the base film.

Referring to FIG. 1 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed part 111, and the opening of recessed part 111 faces away from the first surface 121, and the opening of recessed part 111 and the first surface 121 are flush with each other, and the depth of the recessed portion 111 is H. In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 1.5 μm.

2. Preparation of battery

The positive electrode sheet, negative electrode sheet and separator are composited by hot pressing. After hot pressing, the organic particles of the base film coating become sticky, and the separator is combined with the positive electrode sheet and the negative electrode sheet. The separator is between the positive and negative electrode sheets. The role of isolation, and then winding or stacking to obtain bare cells; put the bare cells in the outer packaging, dry and inject electrolyte, after vacuum packaging, standing, forming, shaping and other processes, to obtain lithium-ion batteries.

The electrolyte in this example is prepared in the following manner: mix ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a mass ratio of 5:3:2, and then add LiPF ₆ to form a 1mol/L electrolyte.

Example 2

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 50%, and the stirring rate is 2000r. The particle size of the template is 3 μm, and the polymerization time in S2 is 4 hours, corresponding to the particle size of the obtained organic particles is 5 μm; the rest is consistent with Example 1.

Referring to FIG. 1 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed part 111, and the opening of recessed part 111 faces away from the first surface 121, and the opening of recessed part 111 and the first surface 121 are flush with each other, and the depth of the recessed portion 111 is H. In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 2.5 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 3

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 42%, and the stirring rate is 1700r. The particle size of the template is 2 μm, and the polymerization time in S2 is 7 hours, which corresponds to the particle size of the obtained organic particles is 6 μm, and the organic monomers used in S2 are acrylic monomers, styrene and acrylate monomers. body; in (2) the process of preparing the slurry, the inorganic particles used are boehmite; in (3) the preparation of the diaphragm, the slurry is coated on both surfaces of the base film by wire bar coating (Through the rotation of the wire rod in the trough, the slurry is evenly brought up and formed into a stable thickness, and the base film is fully contacted with the wire rod under the pressure of the rubber 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 thus obtained is consistent with the embodiment 1; the rest is consistent with the embodiment 1.

Referring to FIG. 2 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed portion 111, and the opening of recessed portion 111 faces away from the first surface 121, and the opening of recessed portion 111 is higher than first surface 121. The surface 121 and the bottom of the depression 111 are located below the first surface 121 , the depth of the depression 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the protrusion 112 . In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 1.5 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 4

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 40%, and the stirring rate is 1200r, the resulting biological The particle size of the template is 1 μm, and the polymerization time in S2 is 8 hours, so the corresponding particle size of the obtained organic particles is 6 μm; the rest is consistent with Example 1.

Referring to FIG. 2 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed portion 111, and the opening of recessed portion 111 faces away from the first surface 121, and the opening of recessed portion 111 is higher than first surface 121. The surface 121 and the bottom of the depression 111 are located below the first surface 121 , the depth of the depression 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the protrusion 112 . In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 0.2 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 5

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 55%, and the stirring rate is 1400r. The particle size of the template is 3.5 μm, and the polymerization time in S2 is 5 hours, which corresponds to the particle size of the obtained organic particles is 6 μm, and the organic monomers used in S2 are acrylic monomer, styrene and acrylate monomer; in (2) the process of preparing the slurry, the inorganic particles used are boehmite; the rest are consistent with Example 1.

Referring to FIG. 2 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed portion 111, and the opening of recessed portion 111 faces away from the first surface 121, and the opening of recessed portion 111 is higher than first surface 121. The surface 121 and the bottom of the depression 111 are located below the first surface 121 , the depth of the depression 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the protrusion 112 . In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 3 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 6

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 60%, and the stirring rate is 1600r, the resulting bio The particle size of the template is 3.9 μm, and the polymerization time in S2 is 4.5 hours, so the particle size of the corresponding organic particles is 6 μm, and the organic monomers used in S2 are acrylic monomer, styrene and acrylate monomer; in (2) the process of preparing the slurry, the inorganic particles used are boehmite; the rest are consistent with Example 1.

Referring to FIG. 2 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed portion 111, and the opening of recessed portion 111 faces away from the first surface 121, and the opening of recessed portion 111 is higher than first surface 121. The surface 121 and the bottom of the depression 111 are located below the first surface 121 , the depth of the depression 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the protrusion 112 . In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 3.2 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 7

In the preparation of the diaphragm, the difference between this example and Example 1 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 47%, and the stirring rate is 1200r, the resulting biological The particle size of the template is 2.5 μm, and the polymerization time in S2 is 6.5 hours, which corresponds to the particle size of the obtained organic particles is 6 μm, and the organic monomers used in S2 are acrylic monomer, styrene and acrylate monomer; in (2) the process of preparing the slurry, the inorganic particles used are boehmite; the rest are consistent with Example 1.

Referring to FIG. 2 , it is a schematic diagram of a diaphragm prepared through the above steps, which is composed of a base film 2 and a base film coating disposed on the surface of the base film 2 . Wherein, base film coating is made of organic particle 11 and inorganic particle, and inorganic particle forms film main body 12, and organic particle 11 forms recessed portion 111, and the opening of recessed portion 111 faces away from the first surface 121, and the opening of recessed portion 111 is higher than first surface 121. The surface 121 and the bottom of the depression 111 are located below the first surface 121 , the depth of the depression 111 is H, and the part of the organic particles 11 higher than the first surface 121 is the protrusion 112 . In this embodiment, the average depth of the depressions 111 of the organic particles 11 is 2 μm.

The preparation of the battery in this example is consistent with Example 1.

Example 8

In the preparation of the diaphragm, the difference between this example and Example 3 is that in (1) the preparation of organic particles, the solid content of the reaction solution in S1 is 43%, and the stirring rate is 1200r, the resulting biological The particle size of the template is 2 μm, and the polymerization time in S2 is 7 hours, so the particle size of the corresponding organic particles obtained is 6 μm; the rest is consistent with Example 3; the structural schematic diagram of the finally obtained diaphragm is similar to that of Example 3, The average depth of the depressed portions 111 of the organic particles 11 was also 1.5 μm.

The preparation of the battery in this example is consistent with Example 3.

Comparative example 1

In the preparation of the diaphragm, the difference between this comparative example and Example 1 is that in (2) the process of preparing the slurry, the inorganic particles used are boehmite; in (3) in the preparation of the diaphragm, the The wire bar coating method applies the slurry on the base film (refer to the wire bar method in Example 3), after coating the slurry on the base film, the semi-finished product thus obtained is placed at 60~90°C and dried for 10 ~60s, so that no depressions and protrusions are formed on the surface of the coating (the organic particle core (biological template) is not corroded by the corrosive solvent, the shell of the organic particles does not break, and does not settle or spread, so the organic particles do not form depressions, nor No protrusions are formed relative to the first surface), thereby obtaining a separator with a base film coating on the surface of the base film; the rest are consistent with Example 1.

The preparation method of the battery in this comparative example is consistent with that of Example 1.

Comparative example 2

In the preparation of the diaphragm, the difference between this comparative example and Example 1 is that (1) the preparation of organic particles is omitted, that is, organic particles are not used, thus, in the process of (2) preparing the slurry, no Organic particles; in the preparation of (3) separator, the slurry is coated on the base film by wire bar coating method (refer to the wire bar coating method in Example 3), after coating the slurry on the base film, The semi-finished product thus obtained is dried at 60-90°C for 10-60 seconds, and no depressions and protrusions are formed on the surface of the coating (no organic particles, so no depressions are formed, and no protrusions are formed relative to the first surface. Starting part), thus preparing a separator with a base film coating on the surface of the base film; the rest are consistent with Example 1.

The preparation method of the battery in this comparative example is consistent with that of Example 1.

test case

1. Experimental construction method

(1) Cut the cross-section of the diaphragm prepared in Example 1~Example 8, Comparative Example 1~Comparative Example 2 through an argon ion polisher, observe the surface structure of the base film coating in a scanning electron microscope, and measure the organic For the depth of the particle depressions 111, the average depth of the depressions 111 was calculated.

(2) Test the battery cycle performance of the batteries prepared in Examples 1 to 8 and Comparative Example 1 to Comparative Example 2; the test method for the battery cycle performance is as follows: the voltage range is 2.75-4.35V, to charge Charge with a current of 1C to 4.35V, then charge with a constant voltage until the current drops to 0.05C, discharge with a constant current of 1C to 2.75V; repeat the above procedure 2000 times.

2. Experimental results

In the test subjects of this test example, there are depressions on the base film coatings of the diaphragms provided in Examples 1 to 8, wherein the base film coatings of the diaphragms provided in Examples 3 to 8 The layer is also provided with protrusions. In these embodiments, the method used to form depressions on the surface of the membrane is the biotemplate method. In the process of preparing the base film coating, the biotemplate with a suitable particle size is mainly selected. On the base film coating of the diaphragm, a depression with a desired depth is formed, on the other hand, mainly by selecting organic particles with a suitable particle size to control whether the above-mentioned protrusions are formed on the surface of the base film coating of. For the convenience of comparison, the specific operations used to affect the size of biological templates and organic particles and the corresponding biological templates, organic Particle size information, as well as the size information of the features on the base film coatings produced in these examples.

Table 1. Embodiment 1 ~ embodiment 8 are used to prepare the raw material size information involved in the base film coating

The analysis results of the base film coating surface of the diaphragm prepared in Examples 1 to 8, Comparative Examples 1 to 2, and the batteries prepared in Examples 1 to 8, and Comparative Examples 1 to 2 The cycle performance results are shown in Table 2.

Table 2. The surface analysis results of the base film coating of the test objects and the cycle performance results of the battery

After the test, the cell assembly of the test battery was observed. In the cell assembly provided by Comparative Example 1 and Comparative Example 2, the bonding effect of the separator and the pole piece was not good, while the bonding effect of the diaphragm and the pole piece provided by Examples 1 to 8 was not good. The structure of the cell assembly remains intact, and the bonding effect of the diaphragm and the pole piece is good. The reason for the above phenomenon is that the diaphragms used in Examples 1 to 8 all have recesses formed on the first surface facing the pole piece, and the electrolyte near the diaphragm can enter the recessed part of the diaphragm and the pole piece. In the formed area, during the charge and discharge cycle of the battery, the electrolyte stored in the above area will be converted into gas and escape, so that the inside of the area will form a negative pressure difference relative to the outside. The existence of the negative pressure difference makes The concave part of the diaphragm has an adsorption effect on the pole piece facing its opening, thereby strengthening the close combination of the diaphragm and the pole piece, so that the cell assemblies prepared in Examples 1-8 all have good structural stability. However, compared with Examples 1 to 8, the separators used in Comparative Examples 1 and 2 lack the microstructure settings similar to the above-mentioned recessed parts, thus resulting in the diaphragm and pole pieces of these two Comparative Examples The composite tightness between them has obviously decreased, which shows that the structural stability of the cell assemblies provided by Comparative Example 1 and Comparative Example 2 is not good. The base film coating in the diaphragm provided in Comparative Example 1 contains organic particles, based on the organic particles have a certain viscosity, so that the surface of the diaphragm provided in Comparative Example 1 maintains a certain degree of viscosity, while the diaphragm provided in Comparative Example 2 has a certain viscosity. The base film coating is only composed of inorganic particles, and the base film coating does not contain sticky particles. The above-mentioned difference leads to that, compared with Comparative Example 1, the composite tightness between the separator and the pole piece provided by Comparative Example 2 is stronger. Poor, it shows that the pole piece and separator in the cell assembly of Comparative Example 2 have obvious separation in the later stage of the test. The structural stability of the cell assembly is an important factor affecting the cycle characteristics of the battery. It can be seen from the test result data shown in Table 1 that, compared with the test batteries provided in Comparative Example 1 and Comparative Example 2, Example 1 The cycle retention rate of the battery in ~8 is higher, which shows that the cycle performance of the battery provided by Examples 1~8 is better.

Comparing the depression depth data in Examples 3 to 7, it can be seen that the average depth of the depressions in Examples 3, 5, and 7 is within the range of 1.5 to 3 μm, compared to Examples 4 and 6 (the depth of depressions The average depth is outside the range of 1.5-3 μm, but within the range of 0.2-4 μm), the cycle efficiency of the batteries provided in Examples 3, 5, and 7 is better. The reason for the above test results is that the depth of the depression affects the storage capacity of the electrolyte. On the one hand, the greater the depth of the depression, the greater the storage capacity of the electrolyte, and if the storage capacity of the electrolyte in the depression is too large, it will be relatively reduced. The amount of electrolyte infiltrating the pole piece will affect the effect of the electrolyte infiltrating the pole piece, resulting in a decrease in the ion transmission performance of the pole piece and deteriorating the cycle performance of the battery; on the other hand, if the depth of the depression is too small, the electrolyte storage capacity will be smaller. During the charging and discharging process of the battery, the electrolyte in the concave part generates less gas, and after the gas escapes, the negative pressure difference between the concave part and the pole piece is small, and the composite effect of the pole piece and the diaphragm is relatively poor. In summary, when the depth of the depressions on the organic particles is in the range of 1.5-3 μm, it is beneficial to further strengthen the solid recombination between the pole piece and the separator, so that the overall performance of the battery is further improved.

Comparing the membranes prepared in Examples 1 and 3, the base film coating of the membrane provided in Example 3 forms a raised portion that is raised relative to the first surface, while the membrane provided in Example 1 has The above-mentioned protrusions are not provided in the base film coating. By observing the conditions of the cell assemblies provided by the above two embodiments before and after the test, it can be seen that the structure of the cell assembly provided by Embodiment 3 is better maintained, and the pole piece and the diaphragm can still be tightly compounded, while the 1. Although the pole piece and the diaphragm of the provided cell assembly are still composited after the test is completed, the gap on the composite surface of the pole piece and the diaphragm has increased. The test result data corresponding to the above two examples shown in Table 1 shows that the battery provided by Example 3 exhibits higher cycle efficiency. The reason for the above difference is that the organic particles have a certain viscosity, and the protrusions are formed by organic particles, so the existence of the protrusions can enhance the adhesion between the diaphragm and the pole piece, so that the protrusions and the depressions The part can jointly enhance the bonding reliability of the diaphragm and the pole piece, and further improve the stability of the cell assembly composed of the diaphragm and the pole piece.

The above embodiments are only used to illustrate the technical solutions of the present invention rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, but these modifications or replacements are within the protection scope of the present invention.

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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