CN113097440B

CN113097440B - Electrochemical device and electric equipment

Info

Publication number: CN113097440B
Application number: CN202110353314.XA
Authority: CN
Inventors: 翁秋燕; 张益博; 魏红梅
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2022-07-26
Anticipated expiration: 2041-03-31
Also published as: CN113097440A

Abstract

The application discloses an electrochemical device and an electric device. The adhesive force between the same pole piece and the isolation layers on the two sides of the same pole piece is different, and the positive pole piece and the negative pole piece can move relatively when expanding, so that the risks of structural deformation and current collector fracture can be reduced, and the mechanical safety performance of the battery can be improved; and the cohesive force of one side is reduced, the dynamic advantage of the battery can be maintained, the deformation rate of the battery cell is reduced, and the multiplying power performance of the battery cell is improved.

Description

Electrochemical device and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to an electrochemical device and electric equipment.

Background

In an electrochemical device (e.g., a lithium ion battery), an isolation layer is disposed between a positive electrode sheet and a negative electrode sheet, and mainly functions to: the positive plate and the negative plate are isolated, so that the situation that electrons are directly conducted between the positive plate and the negative plate to cause short circuit of the battery is avoided, and ions in the electrolyte are allowed to freely pass through.

One of the mainstream techniques for preparing the isolation layer in the industry is a diaphragm-free technique, i.e. a material for preparing the isolation layer is directly formed on the surface of the pole piece by a blade coating method. However, the separator made by the diaphragm-free technology has a large adhesive force with the pole pieces, and the positive and negative pole pieces of the electrochemical device are difficult to move relatively along the extension direction of the pole pieces after expanding in the charge-discharge cycle process, so that structural deformation or current collector fracture is easily caused.

Disclosure of Invention

In view of this, the present application provides an electrochemical device and an electrical apparatus, so as to solve the problem of low safety performance caused by large adhesion between the isolation layer and the pole piece.

A first aspect of the present application provides an electrochemical device comprising a first pole piece, a first isolation layer, a second pole piece, and a second isolation layer. The first isolation layer is positioned between the first pole piece and the second pole piece, the second pole piece is positioned between the first isolation layer and the second isolation layer, and second bonding force is formed between the first isolation layer and the second pole piece; and a third adhesive force is formed between the second isolation layer and the second pole piece, and the third adhesive force is greater than the second adhesive force.

In some embodiments, the second adhesion is F2 and the third adhesion is F3, satisfying: f2 is more than 0N/m and less than or equal to 8N/m, and F3 is more than or equal to 3N/m and less than or equal to 15N/m. Optionally, 0N/m < F2 ≦ 5N/m, 5N/m ≦ F3 ≦ 10N/m.

In some embodiments, the electrochemical device comprises a stacked structure, the stacked structure further comprising a third pole piece, the second separator layer being positioned between the second pole piece and the third pole piece, the second separator layer and the third pole piece having a fourth adhesion therebetween, the third adhesion being greater than the fourth adhesion.

In some embodiments, the electrochemical device comprises a stacked structure, the stacked structure further comprising a third separator layer, the first pole piece is positioned between the first separator layer and the third separator layer, the third separator layer and the first pole piece have a fifth adhesion force therebetween, and the first adhesion force is greater than the fifth adhesion force.

In some embodiments, the electrochemical device comprises a rolled structure, the second separator layer comprises a first region and a second region, the second pole piece is positioned between the first region and the first separator layer, the first pole piece is positioned between the second region and the first separator layer, the second region and the first pole piece have a sixth adhesion force, and the first adhesion force is greater than the sixth adhesion force.

In some embodiments, the first adhesion is greater than the second adhesion.

In some embodiments, the first and third pole pieces are both positive pole pieces and the second pole piece is a negative pole piece.

In some embodiments, the second electrode sheet includes a current collector, a first mixture layer between the current collector and the first isolation layer, and a second mixture layer between the current collector and the second isolation layer, a seventh adhesion between the first mixture layer and the current collector is F7, an eighth adhesion between the second mixture layer and the current collector is F8, and at least one of the following conditions is satisfied:

a)F3>F8；

b)F2<F7。

in some embodiments, the first separator layer has an average filament diameter a in a first predetermined thickness region adjacent to the second pole piece, and the second separator layer has an average filament diameter b in a second predetermined thickness region adjacent to the second pole piece, such that: b < a; optionally, the first predetermined thickness is 1/4 times the thickness of the first isolation layer and the second predetermined thickness is 1/4 times the thickness of the second isolation layer.

In some embodiments, the first and second spacer layers satisfy: a is more than or equal to 20nm and less than or equal to 5 mu m, and b is more than or equal to 10nm and less than or equal to 2 mu m.

In some embodiments, the first, second, and third spacer layers have a porosity of each independently α, a pore diameter of each independently Φ, and a thickness of each independently H, satisfying at least one of the following conditions:

a)30％≤α≤95％；

b)10nm≤Ф≤5μm；

c)1μm≤H≤20μm。

in some embodiments, at least one of the first separator layer, the second separator layer, and the third separator layer comprises polymeric fibers, and optionally further comprises at least one of an inorganic oxide, a lithium ion conducting inorganic, or an organic.

In some embodiments, at least one of the first barrier layer, the second barrier layer, and the third barrier layer comprises a first layer and a second layer disposed on at least one surface of the first layer; the first layer comprises polymeric fibers and optionally further comprises at least one of an inorganic oxide, a lithium ion conductive inorganic, or an organic; the second layer includes at least one of an inorganic oxide, a lithium ion conductive inorganic substance, or an organic substance.

In some embodiments, the sum of the mass percentages of the inorganic oxide, the lithium ion conducting inorganic substance, and the organic substance, based on the mass of the separator layer, is c, and satisfies: c is more than or equal to 5 percent and less than or equal to 80 percent.

In some embodiments, the polymeric fiber comprises at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof.

In some embodiments, the inorganic oxide comprises at least one of hafnium oxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, hydrated aluminum oxide, magnesium hydroxide, or aluminum hydroxide.

In some embodiments, the lithium ion conducting inorganic includes at least one of lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium metaaluminate, lithium germanium phospho-sulfur ceramic, or garnet.

In some embodiments, the organic substance includes at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof.

In a second aspect, the present application provides an electrical device comprising any one of the electrochemical devices described above.

In the electrochemical device and the electric equipment, the binding force between the same pole piece and the isolating layers on the two sides of the same pole piece is different, so that the positive pole piece and the negative pole piece can move relatively when expanding in the circulation process, the risks of structural deformation and current collector fracture are reduced, the mechanical safety performance of the battery is improved, the binding force on one side is reduced, the dynamic advantage of the battery can be maintained, the deformation rate is reduced, the multiplying power performance of the battery is improved, and the setting of the differential binding force is favorable for improving the interface performance between the pole piece and the isolating film, improving the lithium precipitation phenomenon, and favorable for timely releasing oxidizing gas generated by the positive pole piece at high temperature, and improving the safety performance;

in addition, the polymer fibers are adopted to form the isolating layer, the bonding force between the isolating layer and the pole piece can be ensured to meet the requirement by utilizing the cross-linking of the polymer fibers, the structural strength and the infiltration of electrolyte can be improved, the circular expansion phenomenon of a battery core is improved, and the energy density of the battery is favorably improved.

Drawings

Fig. 1 is a partial structural sectional view of an electrochemical device according to example 1 of the present application;

fig. 2 is a partial structural sectional view of an electrochemical device according to example 2 of the present application;

fig. 3 is a partial structural sectional view of an electrochemical device according to example 3 of the present application;

FIG. 4 is a schematic structural view of a rolled electrochemical device of the present application;

FIG. 5 is a schematic partial cross-sectional view taken along the line A-A shown in FIG. 4;

fig. 6 is a partial structural sectional view of an electrochemical device according to example 4 of the present application;

FIG. 7 is a schematic flow chart of a method of forming an isolation layer according to an embodiment of the present application;

FIG. 8 is a schematic view of a microstructure of an isolation layer according to an embodiment of the present application;

fig. 9 is a schematic view of the microstructure of an isolation layer according to another embodiment of the present application.

Detailed Description

The embodiment of the application provides an electrochemical device, and the adhesion between the same pole piece and the isolation layer on both sides thereof is different to this improves the security performance and improves energy density.

In a particular scenario, the electrochemical device includes, but is not limited to, all kinds of primary batteries, secondary batteries, fuel cells, solar cells, and capacitor (e.g., supercapacitor) batteries. The electrochemical device may preferably be a lithium ion battery including, but not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery. The electrochemical device may be in the form of a battery, a battery cell/module, or a battery module.

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments and accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present application and are not to be taken as the whole. The embodiments described below and their technical features may be combined with each other without conflict.

Referring to fig. 1, the electrochemical device includes a first pole piece 11, a second pole piece 12, a first isolation layer 13, and a second isolation layer 14. The first isolation layer 13 is located between the first pole piece 11 and the second pole piece 12, and the second pole piece 12 is located between the first isolation layer 13 and the second isolation layer 14.

According to the design of the electrochemical device having positive and negative polarities, one of the first pole piece 11 and the second pole piece 12 is a positive pole piece, and the other is a negative pole piece, and for convenience of description, the first pole piece 11 is taken as the positive pole piece, and the second pole piece 12 is taken as the negative pole piece.

Positive plate

The positive electrode sheet may include a positive electrode current collector and positive electrode active material layers formed on both surfaces of the positive electrode current collector, the positive electrode active material layers containing a positive electrode active material.

The material of the positive electrode current collector is not particularly limited, and may be any material suitable for use as a positive electrode current collector. In some examples, the positive current collector includes, but is not limited to: metal materials such as aluminum (Al), stainless steel, nickel (Ni), titanium (Ti), tantalum (Ta), and the like; carbon cloth, carbon paper, and the like.

In some examples, the positive electrode active material layer may be one or more layers, each of which contains the same or different positive electrode active materials. The positive electrode active material is a material capable of reversibly inserting and extracting metal ions such as lithium ions. Preferably, the chargeable capacity of the positive electrode active material layer is smaller than the discharge capacity of the negative electrode active material layer to prevent metal ions (lithium ions) in the electrolytic solution from being precipitated on the negative electrode sheet at the time of charging.

The kind of the positive electrode active material is not limited in the present application, and any material may be used as long as it can electrochemically occlude and release ions. In some application scenarios, the positive electrode active material may be a material containing lithium and at least one transition metal. The positive active material includes, but is not limited to: lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds, transition metals including but not limited to: vanadium (V), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and the like.

A substance having a different composition from the positive electrode active material may be attached to the surface of the positive electrode active material. Such attachment substances include, but are not limited to: oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; carbon, and the like.

Methods of attaching substances to the surface of the positive active material include, but are not limited to: a method of dissolving or suspending an adhesion substance in a solvent, infiltrating the adhesion substance into the positive electrode active material, and drying the positive electrode active material; a method in which the adherent substance is dissolved or suspended in a solvent, and the adherent substance is added to the positive electrode active material after infiltration, and then the reaction is carried out by heating or the like; a method of adding the precursor to the positive electrode active material and simultaneously firing the precursor. In the example of attaching carbon, a method of mechanically attaching carbon material (e.g., activated carbon or the like) may be used.

The substance is attached to the surface of the positive electrode active material, and thus the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, which is advantageous for improving the life of the electrochemical device. In the description herein, the positive electrode active material and the material attached to the surface thereof may also be referred to as a positive electrode active material layer.

Negative plate

The negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer formed on both surfaces of the negative electrode current collector, the negative electrode active material layer containing a negative electrode active material.

In some examples, the negative current collector includes, but is not limited to: metal foils, metal films, metal meshes, stamped metal plates, foamed metal plates, and the like; a conductive resin plate.

In some examples, the anode active material layer may be one or more layers, and each of the multiple layers of the anode active material may contain the same or different anode active materials. The negative electrode active material is any material capable of reversibly inserting and extracting metal ions such as lithium ions.

The kind of the negative electrode active material is not limited in the present application, and any material may be used as long as it can electrochemically occlude and release metal ions. In some examples, the negative active material includes, but is not limited to: carbon materials such as graphite, hard carbon, soft carbon, and secondary carbon microbeads (MCMB), silicon (Si), and SiO _x (0 < x < 2) a silicon-containing compound such as silicon oxide, metallic lithium, a metal alloyed with lithium and an alloy thereof, an amorphous compound mainly composed of an oxide such as tin dioxide, and lithium titanate.

The width of the negative plate can be larger than that of the positive plate, that is, along the width direction of the negative plate, an extending region, also called as a/C overlap, is generated in the region of the negative plate, which exceeds the positive plate.

Insulating layer

The first separator 13 and the second separator 14, both referred to as separators, are disposed between the positive electrode sheet and the negative electrode sheet, for example, between the positive electrode active material layer and the negative electrode active material layer, and the separators separate the positive electrode sheet and the negative electrode sheet so that electrons in the electrochemical device cannot pass therethrough, while allowing ions in the electrolyte to pass therethrough freely. The positive electrode tab, the negative electrode tab, and the first and second separation layers 13 and 14 are wound or stacked to form an electrode assembly of the electrochemical device.

As shown in fig. 1, the first isolation layer 13 is located between the first pole piece 11 and the second pole piece 12, and the second pole piece 12 is located between the first isolation layer 13 and the second isolation layer 14.

The first pole piece 11 and the first isolation layer 13 have a first adhesive force F1 therebetween, the first isolation layer 13 and the second pole piece 12 have a second adhesive force F2 therebetween, the second isolation layer 14 and the second pole piece 12 have a third adhesive force F3 therebetween, and F3 is greater than F2.

It can be seen that the adhesion force between the second pole piece 12 and the isolation layers on both sides is different, and when any pole piece expands in the circulation process, the second pole piece 12 can move relative to the first isolation layer 13 with smaller adhesion force, so as to move relative to the first pole piece 11, thereby realizing the relative movement between the positive pole piece and the negative pole piece, and reducing the risk of structural deformation and current collector fracture.

In addition, the bonding force of one side of the second pole piece 12 is reduced, which is beneficial to increasing the interface performance of the isolation layer (such as the first isolation layer 13) and the second pole piece 12, improving the lithium precipitation phenomenon, improving the rate capability, and being beneficial to timely releasing the gas generated by the pole piece, thereby improving the safety performance.

In some specific scenarios, the second adhesion force F2 and the third adhesion force F3 may satisfy the relationship: f2 is more than 0N/m and less than or equal to 8N/m, and F3 is more than or equal to 3N/m and less than or equal to 15N/m. Preferably, 0N/m < F2 ≦ 5N/m, 5N/m ≦ F3 ≦ 10N/m.

The adhesive force is within the range, so that the adhesive strength can meet the requirement on the basis of realizing the beneficial effects, and the rate characteristic and the safety performance of the electrochemical device are ensured.

In some examples, the first adhesion may be greater than the second adhesion, i.e., F1 > F2, and the adhesion between the first separator 13 and the pole pieces on both sides (i.e., the first pole piece 11 and the second pole piece 12) may be different, so that when any one of the pole pieces expands during the cycle, the second pole piece 12 with smaller adhesion may move relative to the first separator 13, further improving the movement of the first pole piece 11 relative to the second pole piece 12, and thus improving the relative movement between the positive and negative pole pieces.

It is to be understood that the electrochemical device may have a stacked structure or a wound structure.

Taking the stacking structure as an example, the electrochemical device comprises a positive plate, an isolation layer and a negative plate which are stacked in sequence, wherein the number of the positive plate and the isolation layer is determined according to the requirement. Accordingly, it can be seen that the electrochemical device comprises a plurality of sequentially stacked sub-structures, a single sub-structure comprising three pole pieces and two separator layers as shown in fig. 2, or two pole pieces and three separator layers as shown in fig. 3.

Referring to fig. 2, the three pole pieces are a first pole piece 11, a second pole piece 12 and a third pole piece 16, and the two isolation layers are a first isolation layer 13 and a second isolation layer 14. The second isolation layer 14 is located between the second pole piece 12 and the third pole piece 16, and the fourth adhesion force between the second isolation layer 14 and the third pole piece 16 is F4.

In some examples, the third adhesion force is greater than the fourth adhesion force, i.e., F3 > F4, and the adhesion force between the second separator layer 14 and the pole pieces on both sides thereof (i.e., the second pole piece 12 and the third pole piece 16) is different, so that when any one pole piece expands during the circulation process, the third pole piece 16 with smaller adhesion force can move relative to the second separator layer 14, and the third pole piece 16 can also move relative to the second pole piece 12, so that the relative movement between the positive and negative pole pieces is realized.

Referring to fig. 3, two pole pieces are a first pole piece 11 and a second pole piece 12, respectively, and three isolation layers are a first isolation layer 13, a second isolation layer 14, and a third isolation layer 15, respectively. The first pole piece 11 is located between the first isolation layer 13 and the third isolation layer 15. A fifth adhesion between the third separator layer 15 and the first pole piece 11 is F5.

The first adhesion may be greater than the fifth adhesion, i.e., F1 > F5, with the first pole piece 11 having a different adhesion to the separator layers on either side thereof (i.e., the first separator layer 13 and the third separator layer 15).

Taking the winding structure as an example, the electrochemical device includes two pole pieces and two isolation layers, as shown in fig. 4 and 5, the two pole pieces are respectively a first pole piece 11 and a second pole piece 12, and the two isolation layers are respectively a first isolation layer 13 and a second isolation layer 14. The second isolation layer 14 comprises a first region 14a and a second region 14b, the second pole piece 12 being located between the first region 14a and the first isolation layer 13, and the first pole piece 11 being located between the second region 14b and the first isolation layer 13. A sixth adhesion between the second region 14b and the first pole piece 11 is F6.

In some examples, the first adhesion is greater than the sixth adhesion, i.e., F1 > F6, and the adhesion between the first pole piece 11 and the separator layers on both sides thereof (i.e., the second regions of the first separator layer 13 and the second separator layer 14) is different, so that when either pole piece expands during cycling, movement of the first pole piece 11 relative to the second pole piece 12, and thus relative movement of the positive and negative pole pieces, is achieved.

It will be appreciated that the adhesion to the separator layer may be the same or different for different pole pieces of the same polarity. For example, referring to fig. 2, the polarities of the first pole piece 11 and the third pole piece 16 are the same, the adhesion between the first pole piece 11 and the one-side isolation layer is F1, the adhesion between the third pole piece 16 and the one-side isolation layer is F4, and F1 may be greater than, equal to, or less than F4.

In an electrochemical device, a mixture layer may be disposed between a current collector and an isolation layer of a pole piece. In some embodiments, the mixture layer includes an active material layer, a conductive agent, and a binder.

Referring to fig. 6, the second electrode sheet 12 includes a current collector 121, a first mixture layer 122 and a second mixture layer 123. The first mixture layer 122 and the second mixture layer 123 are respectively disposed on both side surfaces of the current collector 121, the first mixture layer 122 is located between the current collector 121 and the first separator 13, and the second mixture layer 123 is located between the current collector 121 and the second separator 14.

A seventh adhesion between the first mixture layer 122 and the current collector 121 is F7, and an eighth adhesion between the second mixture layer 123 and the current collector 121 is F8, and at least one of the following characteristics is satisfied:

a)F3>F8；

b)F2>F7。

in this way, the adhesive force between each mixture layer and the structural layers (the isolation layer and the current collector respectively) on the two sides of the mixture layer is different, so that the mixture layer and the structural layer with smaller adhesive force can move relatively under extreme environments such as battery deformation, and the like, thereby improving the safety performance of the battery.

The above-mentioned isolation layers are mutually independent structural layers, for example, the first isolation layer 13, the second isolation layer 14 and the third isolation layer 16 are respectively independent structural layers, the porosity α of any one layer is respectively independent, the aperture Φ is respectively independent, and the thickness H is respectively independent. In some specific scenes, alpha is more than or equal to 30% and less than or equal to 95%; phi is more than or equal to 10nm and less than or equal to 5 mu m; h is more than or equal to 1 mu m and less than or equal to 20 mu m, and ions in the electrolyte can freely pass through the electrolyte on the premise that electrons cannot freely pass through the electrolyte.

In some examples, the average filament diameter of a first predetermined thickness region of the first separator layer 13 adjacent to the second pole piece 12 is a, and the average filament diameter of a second predetermined thickness region of the second separator layer 14 adjacent to the second pole piece 12 is b, such that: b < a. Herein, the average filament diameters of the isolation layers on the two sides of the second pole piece 12 are different, and the adhesive force between the second pole piece 12 and the isolation layers on the two sides is different, which is beneficial to generating relative movement between the isolation layers and the second pole piece 12.

In some specific scenarios, 20nm & lta & lt 5 μm & gt, 10nm & ltb & lt 2 μm & gt. Further preferably, the first predetermined thickness is 1/4 a of the thickness of the first spacer layer 13 and the second predetermined thickness is 1/4 a of the thickness of the second spacer layer 14.

The embodiment of the application further provides a preparation method of the isolation layer, which is used for preparing at least one of the isolation layers. Hereinafter, a method for manufacturing an isolation layer will be described by taking an example in which the material of the isolation layer at least includes polymer fibers, as shown in fig. 7.

S11: and spraying a solution at least containing a polymer on at least one surface of the positive plate or the negative plate by adopting a spinning process, and drying to form an isolation layer.

S12: and assembling the positive plate and the negative plate into the electrochemical device after predetermined treatment.

The preparation process and materials of the positive plate and the negative plate are not limited in the embodiments of the present application.

In some examples, the negative active material graphite, the conductive carbon black (Super P), and the Styrene Butadiene Rubber (SBR) may be mixed at a weight ratio of 96:1.5:2.5, deionized water is added as a solvent, and the mixture is blended into a slurry with a solid content of 0.7, and the slurry is uniformly stirred, and then the slurry is uniformly coated on one surface of the negative current collector, and dried at 110 ℃ to obtain a negative active material layer, and then another negative active material layer is formed on the other surface of the negative current collector by using the same process. And further, cutting the sheet and welding a tab to obtain the negative plate.

The positive electrode active material lithium cobaltate (LiCoO) ₂ ) Mixing conductive carbon black and polyvinylidene fluoride (PVDF) according to a weight ratio of 97.5:1.0:1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing into slurry with a solid content of 0.75, uniformly stirring, uniformly coating the slurry on one surface of a positive current collector, and drying at 90 ℃ to obtain a positive active material layer. And then, another positive active material layer is formed on the other surface of the positive current collector by adopting the same process. Further, the anode plate is obtained through cutting and welding of the electrode lugs。

The separation layer may be formed on one or both surfaces of the positive electrode sheet, or may be formed on one or both surfaces of the negative electrode sheet, which is not limited in the embodiments of the present application.

The present embodiments also do not limit the types of polymer fibers, which in some specific scenarios include, but are not limited to, at least one of: polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof.

The present application forms the separation layer by polymer fibers, and as shown in fig. 8, the separation layer includes a polymer fiber layer having a pore size and porosity satisfying the passage of ions.

Referring to fig. 9, the isolating layer may be further provided with particles, and the pore size and porosity of the isolating layer may be further adjusted by the arrangement of the particles.

In some examples, the particles may be disposed within the polymeric fiber layer.

In other examples, the particles may be disposed on a layer of polymeric fibers, i.e., the barrier layer comprises a two-layer structure, a first layer comprising polymeric fibers and a second layer comprising particles. Or the isolation layer comprises a three-layer structure, the first layer comprises polymer fibers, and the second layer and the third layer both comprise particles and are respectively arranged on two sides of the first layer.

The particle layer (i.e., the second layer and the third layer) has a porosity of α 0, a pore diameter of Φ 0, a thickness of H0, a resistivity of ρ, and an ionic conductivity of σ, and satisfies at least one of the following conditions:

a)10％≤α0≤40％；

b)0.1nm≤Ф0≤1μm；

c)0.1μm≤H0＜20μm；

d)ρ＞107Ω·m；

e)10 ^-2 S/cm≤σ≤10 ^-8 S/cm。

the particle layers (i.e., the second layer and the third layer) having the porosity α 0, the pore diameter Φ 0, and the thickness H0 within the above ranges can contribute to improving free passage of reactive ions such as lithium ions in the electrolytic solution.

In some examples, the material of the particles includes at least one of inorganic oxides, lithium ion conductive inorganic substances, and organic substances. Optionally, based on the mass of the isolation layer, the mass percentage content of the particles is c, and the requirement that c is more than or equal to 5% and less than or equal to 80% is met, so that the adhesive force between the isolation layer and the pole piece can meet the requirement.

Inorganic oxides include, but are not limited to, at least one of the following: hafnium oxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, hydrated aluminum oxide, magnesium hydroxide, aluminum hydroxide.

Lithium ion conducting inorganics include, but are not limited to, at least one of: lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS ₂ Glass, P ₂ S ₅ Glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium metaaluminate, lithium germanium phosphorus sulfur ceramic, or garnet.

Organic matter includes, but is not limited to, at least one of the following: polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof.

In another embodiment, an electrical device includes a load and the electrochemical device of any of the above embodiments, and the electrochemical device is configured to supply power to the load.

The powered device may be implemented in various specific forms, such as a drone, an electric cleaning tool, an energy storage product, an electric car, an electric bicycle, an electric navigation tool, a backup power source, an electric motor, a large household battery, and a lithium ion capacitor, among others.

It will be appreciated by those skilled in the art that the aforementioned electrochemical device can be applied to stationary type electric equipment, in addition to elements particularly for mobile purposes.

Since the electric device has the electrochemical device according to any one of the foregoing embodiments, the electric device can produce the beneficial effects of the electrochemical device according to the corresponding embodiment.

Without further limitation, an element identified by the phrase "comprising an … …" does not exclude the presence of additional identical elements in processes, methods, articles, or devices that comprise the element, and elements, components, features, or elements having the same designation in different embodiments may have the same meaning or different meanings as defined in the description of the particular embodiment or in the context of the particular embodiment.

In addition, although the terms "first, second, third, etc. are used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well. The terms "or" and/or "are to be construed as inclusive or meaning any one or any combination. An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

The technical solution of the present application is exemplarily described below by specific embodiments:

example 1

(1) Preparing a negative plate: mixing a negative electrode active material graphite, conductive carbon black and styrene butadiene rubber according to a weight ratio of 96:1.5:2.5, adding deionized water, preparing into slurry with solid content of 0.7, uniformly stirring, uniformly coating the slurry on one surface of a negative electrode current collector (such as copper foil), drying at 110 ℃ to obtain a negative electrode active material layer, and forming another negative electrode active material layer on the other surface of the negative electrode current collector by adopting the same process. And further, cutting the sheet and welding a tab to obtain the negative plate.

(2) Preparing a positive plate: mixing the positive active material lithium cobaltate, the conductive carbon black and the polyvinylidene fluoride according to the weight ratio of 97.5:1.0:1.5, adding N-methyl pyrrolidone as a solvent, preparing into slurry with the solid content of 0.75, uniformly stirring, uniformly coating the slurry on a positive current collector aluminum foil, and drying at 90 ℃ to obtain a positive active material layer. Then, another positive electrode active material layer is formed on the other surface of the positive electrode collector using the same process. And further, cutting the sheet and welding the tab to obtain the positive plate.

(3) Preparing an isolation layer: 95% of polyvinylidene fluoride (PVDF), 4.5% of acrylonitrile and 0.5% of boron trifluoride are dispersed in a solvent with a weight ratio of dimethylformamide to acetone of 7:3, and the mixture is uniformly stirred until the viscosity of the slurry is stable, so that a solution A with the mass fraction of 25% is obtained. Dispersing 95% of polyethylene oxide (PEO), 4.5% of acrylonitrile and 0.5% of boron trifluoride in a solvent with a weight ratio of dimethylformamide to acetone of 7:3, and uniformly stirring until the viscosity of the slurry is stable to obtain a solution B with the mass fraction of 40%.

On the first surface of the positive electrode sheet, a polymer fiber layer having a thickness of 10 μm was prepared using the solution a as a raw material by a combination of an electrospinning process and a gas spinning process with a filament diameter of 500 nm. And then preparing a polymer fiber layer with the filament diameter of 500nm and the thickness of 10 mu m on the second surface of the positive plate by using the solution B and adopting the same process.

(4) Preparation of electrode assembly: and (3) relatively stacking and winding the negative plate and the positive plate integrating the isolation layer, then, drying in vacuum at 40 ℃ to remove the solvent, and then, raising the temperature to 80 ℃ for heat treatment for 6 hours to complete the crosslinking process, thereby obtaining the negative plate with the isolation layers on both sides.

(5) Preparing an electrolyte: mixing organic solvents of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 30:50:20 in a dry argon environment, and adding lithium salt of lithium hexafluorophosphate (LiPF) ₆ ) Dissolving and mixing uniformly to obtain LiPF ₆ Electrolyte with the concentration of 1.15 mol/L.

(6) Preparing a lithium ion battery: and placing the lithium ion battery in an outer packaging foil, and performing processes such as liquid injection, packaging and the like to obtain the lithium ion battery.

Test method

And (3) testing the adhesive force: cutting the pole piece (including the isolation layer on the two side surfaces) into strips with the width of 2cm, peeling the isolation layers on the two sides from the surface of the pole piece, pulling the bonding area of the isolation layer at a constant speed of 50mm/min by using an universal tensile machine at an angle of 180 degrees, and measuring the obtained force y, wherein the bonding force y1 is y/2 cm.

And (3) testing the deformation rate: the lithium ion battery is rested for 5 minutes at 25 ℃, then is charged to 4.4V by a constant current of 0.5C, is charged to 0.05C by a constant voltage of 4.4V, and is rested for 5 minutes. The lithium ion battery determines three positions, determines the thicknesses of points of the three positions, and takes an average value as H0. Then the lithium ion battery is discharged to 3.0V by constant current of 0.5C and is static for 5 minutes. Repeating the charge-discharge cycle for 300 times, selecting the same measurement position, measuring the thickness of the lithium ion battery by using the same measurement tool, and taking an average value H.

Measured position Change ratio (H-H0)/H0X 100%

And then averaging the calculation results of different positions to obtain the deformation rate of the lithium ion battery.

And (3) rate performance test: charging the lithium ion battery to a voltage of 4.4V at a constant current of 0.5C, then charging to a current of 0.05C at a constant voltage of 4.4V, then discharging to a voltage of 3.0V at a constant current of 1C, and recording the discharge capacity during 1C discharging; charging the lithium ion battery at a constant current of 0.5C until the voltage is 4.4V, then charging at a constant voltage of 4.4V until the current is 0.05C, then discharging at a constant current of 3C until the voltage is 3.0V, and recording the discharge capacity during 3C discharging; rate performance is the discharge capacity at 3C discharge/discharge capacity at 1C discharge × 100%.

And (3) drop test: fixing the lithium ion secondary battery in a drop test fixture by using double-sided adhesive tape, sequentially numbering 6 surfaces of the fixture as 1, 2, 3, 4, 5 and 6, and sequentially numbering four corners of the fixture as C1, C2, C3 and C4; placing the fixture on a test bench with the height of 1.5m at the temperature of 25 ℃, sequentially dropping the lithium ion secondary batteries according to the sequence of the numbers 1-6, then sequentially dropping the lithium ion secondary batteries according to the sequence of the numbers C1-C4, circulating for 6 times, and finishing a dropping test; measuring and recording the voltage of the electrochemical device after each round of test is finished, checking the appearance of the electrochemical device, stopping drop test when the electrochemical device leaks and catches fire, and recording as not passing the sample; and (4) disassembling the lithium ion secondary battery, observing whether the diaphragm is inverted or not, and if the diaphragm is inverted, recording that the sample does not pass through.

And taking 10 lithium ion batteries for drop test, and recording the number of the lithium ion batteries passing the test. Drop test pass rate is the number of lithium ion batteries that pass the test/10.

Example 2

The difference from example 1 is that: the polymer fiber on the second surface of the positive electrode sheet is Polyimide (PI). The second surface is the surface of the positive plate attaching solution B, and the first surface and the second surface are arranged oppositely.

Examples 3 to 5

The difference from example 1 is that: the two polymer fiber slurries (e.g., the second surface in example 3) were blended on one of the surfaces of the positive electrode sheet to provide a composite polymer fiber layer.

Comparative example 1

The differences from examples 1 to 5 are: as shown in table 1, conventional Polyethylene (PE) was used as a separator on both the first surface and the second surface of the positive electrode sheet.

	First surface polymer material	Second surface polymer material
			Comparative example 1	PE	PE
Example 1	PVDF	PEO
			Example 2	PVDF	PI
Example 3	PVDF	PVDF+PI
			Example 4	PI+PVDF	PEO
Example 5	PVDF	PI+PEO

TABLE 1

TABLE 2

As shown in table 2, the electrochemical devices according to examples 1 to 5 of the present application have the following characteristics, compared to the conventional separator (comparative example 1): through the adjustment to barrier film polymer fiber material, change the adhesion stress of pole piece both sides to showing the deformation rate that has reduced lithium ion battery and increasing, promoted the multiplying power performance of battery. Meanwhile, the battery drop test passing rate shows that the mechanical safety performance of the battery is also obviously improved by the differentiated binding force arrangement on the two sides of the pole piece. The battery combination property is obviously improved by arranging the two sides of the pole piece and the isolating layer with different binding power.

Example 6

The difference from example 2 is that: and preparing a polymer particle layer on the polymer fiber layer on the first surface of the positive plate by adopting an electrospray method to adjust the porosity of the isolation layer, wherein the polymer layer is made of PVDF (polyvinylidene fluoride).

Preparing a polymer particle layer: PVDF is added with acetone as a solvent, slurry with the solid mass percentage content of 40% is prepared, and polymer aggregates with the particle size of 500nm are sprayed on polymer fibers by an electrospray method.

Example 7

The difference from example 6 is that: the polymer particle layer is made of POSS (polyhedral oligomeric silsesquioxane).

Example 8

The difference from example 6 is that: the polymer layer is made of PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer).

Example 9

The difference from example 6 is that: when the polymer fiber layer is prepared on the first surface of the positive plate by spinning solution A, Al is filled in fiber gaps by adopting an electrospray method ₂ O ₃ Inorganic particles.

Al ₂ O ₃ Preparing inorganic particle slurry: inorganic ceramic particles of alumina (Al) with the diameter of 500nm ₂ O ₃ ) Adding N-methyl pyrrolidone (NMP) as a solvent to prepare slurry with the solid mass percentage of 40%.

Example 10

The differences from example 9 are: al (aluminum) ₂ O ₃ And the inorganic particles are filled in the polymer fiber layer on the second surface of the positive plate.

Example 11

The difference from example 9 is that: the filler particles are Al ₂ O ₃ And PVDF, the mass ratio of the mixed particles is Al ₂ O ₃ PVDF (90: 10) and the particle sizes of the particles are all 500 nm.

Comparative example 2

And pair ofThe difference in ratio 1 is that: a high-adhesion layer is arranged on the PE isolation layer and is made of PVDF oily coating (PVDF, Al) ₂ O ₃ And the mass ratio of DMF is 1:1: 8).

Comparative example 3

The difference from example 1 is that: PVDF is arranged on the PE isolation layer on the first surface, inorganic particles are arranged on the PE isolation layer on the second surface, and the material is Al ₂ O ₃ 。

TABLE 3

TABLE 4

"-" indicates that no such feature is added or present.

As shown in tables 3 and 4, the electrochemical devices of examples 6 to 11 of the present application have the following characteristics, compared to comparative examples 2 and 3: the particle layer is prepared in or on the surface of the polymer fiber layer by adopting an electrospray method, so that the differential design of the bonding force and the strength of the fiber layer can be realized, on one hand, the rigidity of the lithium ion battery can be improved, and the safety performance of the battery can be further improved; the rate capability of the battery is obviously improved through the design of differentiated interface performance; meanwhile, the self-discharge resistance can be further optimized, so that the comprehensive performance of the lithium ion battery is improved.

Examples 12 to 17

The difference from example 2 is that: the amount of the electrolyte solution injected was varied and is shown in table 5.

TABLE 5

TABLE 6

As shown in tables 5 and 6, the electrochemical devices of examples 12 to 17 of the present application have the following characteristics: through the adjustment to the liquid retaining capacity and the isolation layer parameter of battery, can promote the ionic conduction efficiency of battery, further optimize the comprehensive properties of battery.

Example 18

The difference from example 2 is that: the diameters of the polymer fibers on the first surface and the second surface are adjusted.

TABLE 7

TABLE 8

As shown in tables 7 and 8, by controlling the diameter of the spinning filaments (i.e., the diameter of the polymer fibers), differential design of the bonding force and strength of the fiber layer can be achieved, the deformation rate of the battery can be reduced, and the self-discharge resistance can be further optimized, thereby improving the overall performance of the lithium ion battery.

Example 22

The difference from example 2 is that: the porosity of each fiber layer was controlled by adjusting the compression ratio in the thickness direction of the separator layer, as shown in table 9.

	First surface polymer material	Second surface polymer material
			Example 22	PVDF	PI
Example 23	PVDF	PI
			Example 24	PVDF	PI
Example 25	PVDF	PI

TABLE 9

Watch 10

As shown in tables 9 and 10, by adjusting the porosity of the isolation layer, differential design of the bonding force and strength of the fiber layer can be achieved, the rate capability can be improved, the battery deformation rate can be reduced, and the self-discharge resistance can be further optimized, thereby improving the comprehensive performance of the lithium ion battery.

Examples 26 to 29

The difference from example 2 is that: the average pore diameters of the first and second surfaces of the pole piece were adjusted by adjusting the compression ratio in the thickness direction of the separator layer, as shown in table 11.

TABLE 11

TABLE 12

As shown in tables 11 and 12, the pore size of the isolation layer was adjusted to achieve differential design of the bonding force and strength of the fiber layer, reduce the deformation rate of the battery, and further optimize the self-discharge resistance, thereby improving the overall performance of the lithium ion battery.

Example 30

The difference from example 2 is that:

(1) preparing a negative pole piece: in the slitting step, the pole pieces were cut to a specification of (41mm × 61 mm).

(2) Preparing a positive pole piece: in the slitting step, the pole pieces are cut to a (38mm by 58mm) gauge.

(4) Preparation of electrode assembly: and sequentially stacking the negative plate and the positive plate of the integrated isolation layer.

Comparative example 4

Differences from example 30: in the lamination process, a Polyethylene (PE) isolation layer is arranged between the positive and negative pole pieces.

	First surface polymer material	Second surface polymer material
			Comparative example 4	PE	PE
Example 30	PVDF	PI

Watch 13

TABLE 14

As shown in tables 13 and 14, example 30 significantly improves the safety performance of the battery through differential design of the bonding force and strength of the fiber layers, and improves the rate capability of the battery while significantly improving the deformation rate of the battery, compared to the conventional laminate structure of comparative example 2, thereby achieving an improvement in the overall performance of the battery.

It should be understood that the above-mentioned embodiments are only some examples of the present application, and not intended to limit the scope of the present application, and all equivalent structural changes made by using the contents of the specification and drawings of the present application are included in the scope of the present application.

Claims

1. An electrochemical device comprising a first pole piece, a first separator layer, a second pole piece, and a second separator layer, wherein the first separator layer is located between the first pole piece and the second pole piece, the second pole piece is located between the first separator layer and the second separator layer,

a second adhesive force is formed between the first isolation layer and the second pole piece;

and a third bonding force is formed between the second isolation layer and the second pole piece, and the third bonding force is greater than the second bonding force.

2. The electrochemical device of claim 1, wherein the second adhesion is F2, the third adhesion is F3, satisfying: f2 is more than 0N/m and less than or equal to 8N/m, and F3 is more than or equal to 3N/m and less than or equal to 15N/m.

3. The electrochemical device of claim 2, wherein the second adhesion is F2, the third adhesion is F3, and satisfies: f2 is more than 0N/m and less than or equal to 5N/m, and F3 is more than or equal to 5N/m and less than or equal to 10N/m.

4. The electrochemical device according to claim 1,

the electrochemical device comprises a stacked structure, the stacked structure further comprises a third pole piece, the second isolation layer is positioned between the second pole piece and the third pole piece, a fourth adhesion force is formed between the second isolation layer and the third pole piece, and the third adhesion force is larger than the fourth adhesion force;

or, the electrochemical device comprises a stacked structure, the stacked structure further comprises a third separator layer, the first pole piece is located between the first separator layer and the third separator layer, a fifth adhesion force is provided between the third separator layer and the first pole piece, and the first adhesion force is greater than the fifth adhesion force;

alternatively, the electrochemical device comprises a wound structure, the second separator layer comprises a first region and a second region, the second pole piece is positioned between the first region and the first separator layer, the first pole piece is positioned between the second region and the first separator layer, a sixth adhesion force is provided between the second region and the first pole piece, and the first adhesion force is greater than the sixth adhesion force.

5. The electrochemical device of claim 4, wherein the first adhesion force is greater than the second adhesion force.

6. The electrochemical device according to any one of claims 1 to 5, wherein the first pole piece and the third pole piece are both positive pole pieces, and the second pole piece is a negative pole piece.

7. The electrochemical device according to claim 6, wherein the second pole piece includes a current collector, a first mixture layer between the current collector and the first separation layer, a second mixture layer between the current collector and the second separation layer,

the seventh adhesive force between the first mixture layer and the current collector is F7, the eighth adhesive force between the second mixture layer and the current collector is F8, and at least one of the following conditions is satisfied:

a)F3>F8；

b)F2>F7。

8. the electrochemical device of claim 1, wherein an average filament diameter of a first predetermined thickness region of the first separator layer adjacent to the second pole piece is a, and an average filament diameter of a second predetermined thickness region of the second separator layer adjacent to the second pole piece is b, such that: b < a.

9. The electrochemical device of claim 8, wherein the first predetermined thickness is 1/4 times the thickness of the first separator layer and the second predetermined thickness is 1/4 times the thickness of the second separator layer.

10. The electrochemical device of claim 8, wherein the first and second separator layers satisfy: a is more than or equal to 20nm and less than or equal to 5 mu m, and b is more than or equal to 10nm and less than or equal to 2 mu m.

11. The electrochemical device according to claim 4, wherein the first separator layer, the second separator layer, and the third separator layer each independently have a porosity of α, a pore diameter of Φ, and a thickness of H, and at least one of the following conditions is satisfied:

a)30％≤α≤95％；

b)10nm≤Ф≤5μm；

c)1μm≤H≤20μm。

12. the electrochemical device of claim 4, wherein at least one of the first separator layer, the second separator layer, and the third separator layer:

comprising polymer fibers and at least one of inorganic oxides, lithium ion conductive inorganic or organic.

13. The electrochemical device of claim 4, wherein at least one of the first separator layer, the second separator layer, and the third separator layer:

comprises a first layer and a second layer arranged on at least one surface of the first layer;

the first layer comprises polymeric fibers and at least one of an inorganic oxide, a lithium ion conducting inorganic or organic;

the second layer includes at least one of an inorganic oxide, a lithium ion conductive inorganic substance, or an organic substance.

14. The electrochemical device according to claim 12 or 13, wherein the sum of the mass percentages of the inorganic oxide, the lithium ion conductive inorganic substance, and the organic substance, based on the mass of the separator, is c, and satisfies: c is more than or equal to 5 percent and less than or equal to 80 percent.

15. The electrochemical device according to claim 12,

the polymer fiber includes at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof;

the inorganic oxide comprises at least one of hafnium oxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, hydrated aluminum oxide, magnesium hydroxide or aluminum hydroxide;

the lithium ion conductive inorganic substance comprises at least one of lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium metaaluminate, lithium germanium phosphorus sulfur ceramic or garnet;

the organic matter includes at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-chlorotrifluoroethylene), and derivatives thereof.

16. An electrical device comprising the electrochemical device of any one of claims 1 to 15.