CN114068868A

CN114068868A - Pole piece, battery pack and manufacturing method of pole piece

Info

Publication number: CN114068868A
Application number: CN202010762272.0A
Authority: CN
Inventors: 杜思红
Original assignee: Beijing Xiaomi Mobile Software Co Ltd
Current assignee: Beijing Xiaomi Mobile Software Co Ltd
Priority date: 2020-07-31
Filing date: 2020-07-31
Publication date: 2022-02-18

Abstract

The disclosure relates to a pole piece, a battery pack and a manufacturing method of the pole piece, which comprises the following steps: the current collector, and an active layer and an adsorption layer which are positioned on the current collector; the active layer comprises one or more layers, correspondingly, the adsorption layer comprises one or more layers, and the active layer and the adsorption layer are arranged at intervals; the adsorption layer contains an adsorption material for adsorbing electrolyte. This is disclosed through increasing the adsorbed layer, utilizes the adsorption of adsorption material to electrolyte in the adsorbed layer, has increased the quantity of being preserved of pole piece to electrolyte, has promoted the cycle life of battery package. Moreover, the adsorbent layer occupies less space relative to the central wick, reducing the impact on the energy density of the battery pack.

Description

Pole piece, battery pack and manufacturing method of pole piece

Technical Field

The disclosure relates to the technical field of energy, in particular to a pole piece, a battery pack and a manufacturing method of the pole piece.

Background

With the application and popularization of lithium ion batteries in intelligent products, the durability of the lithium ion batteries becomes an important concern of people. How to improve the cycle life of the lithium ion battery pack is also a direction of research and development efforts. However, with the improvement of the energy density of the lithium ion battery pack, the compaction density of the lithium ion battery pole piece is increased, the electrolyte retention capacity of the battery pack is reduced, the capacity attenuation at the later cycle period is accelerated, and the cycle life of the battery is greatly lost.

At present, as shown in fig. 1, a central tube core 110 is arranged inside a battery cell 100, electrolyte is stored inside the central tube core 110, a plurality of through round holes are formed in the surface of the central tube core 110, and the arrangement of the central tube core 110 is that the electrolyte is communicated for circulation in the circulation process, so that the circulation life of the battery cell can be prolonged. However, this solution is complicated to manufacture, and the central die 110 occupies a large space to be unfavorable for energy density, so that it has no certain commercial opportunity.

Disclosure of Invention

The disclosure provides a pole piece, a battery pack and a manufacturing method of the pole piece.

According to a first aspect of the embodiments of the present disclosure, there is provided a pole piece, including: the current collector, and an active layer and an adsorption layer which are positioned on the current collector;

the active layer comprises one or more layers, correspondingly, the adsorption layer comprises one or more layers, and the active layer and the adsorption layer are arranged at intervals;

the adsorption layer contains an adsorption material for adsorbing electrolyte.

In some embodiments, the active layer alternating with the adsorbent layer comprises:

when the density of the active layer surface is less than or equal to 0.0020g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, both the active layer and the adsorption layer are one layer, the adsorption layer is positioned on the surface layer, and the active layer is positioned between the adsorption layer and the current collector.

when the density of the active layer surface is 0.0020-0.0027 g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, the active layer and the adsorption layer are both 2 layers, the adsorption layer is positioned on the surface layer, and the 2 active layers and the other adsorption layer are alternately arranged between the current collectors.

when the density of the active layer surface is more than or equal to 0.0027g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, at least 3 layers of the adsorption layers are selected, wherein one adsorption layer is positioned on the surface layer, and other adsorption layers and the active layer are arranged alternately.

In some embodiments, the adsorbent material is a carbon material.

In some embodiments, the adsorbent layer further comprises: a binder and a dispersant mixed with the adsorbent material.

In some embodiments, the mass ratio of the adsorption material, the binder and the dispersant is: 95-99.5 wt%: 0.5-4 wt%: 0 to 1 wt%.

In some embodiments, the total thickness of the adsorbent layer is 1-10 um.

In some embodiments, the specific surface area of the adsorbing material is 40-1000 m²/g。

In some embodiments, the current collector is a positive current collector and the active layer is a positive active layer;

or

The current collector is a negative current collector, and the active layer is a negative active layer.

According to a second aspect of the embodiments of the present disclosure, there is provided a battery pack including:

a housing;

an electrolyte within the housing;

the pole piece of any embodiment, wherein the pole piece is wound or stacked to form a cell, and the cell is located in the housing and soaked in the electrolyte.

According to a third aspect of the embodiments of the present disclosure, a method for manufacturing a pole piece is provided, including:

forming an active layer on a current collector; and coating an adsorption material containing an adsorption electrolyte on at least one active layer to obtain an adsorption layer.

In some embodiments, an active layer is formed on a current collector; coating an adsorption material containing adsorption electrolyte on at least one active layer to obtain an adsorption layer, comprising:

when the active layer and the adsorption layer are both plural; the active layer and the adsorption layer are formed by layering.

The technical scheme provided by the embodiment of the disclosure can have the following beneficial effects:

according to the above embodiment, this disclosure utilizes adsorption of adsorption material to electrolyte in the adsorbed layer through increasing the adsorbed layer, has increased the quantity of being preserved of pole piece to electrolyte, has promoted the cycle life of battery package. The tube core at the center of the battery can be replaced by the introduction of the adsorption layer, and the adsorption layer occupies a smaller space, so that the negative influence on the energy density of the battery pack is reduced, and the battery pack or the battery cell with smaller volume can have larger battery capacity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure.

Fig. 1 is a schematic structural view of a battery pack;

FIG. 2 is one of the schematic structural diagrams of a pole piece shown in accordance with an exemplary embodiment;

FIG. 3 is a second schematic diagram illustrating the structure of a pole piece according to an exemplary embodiment;

FIG. 4 is a graph comparing charge and discharge cycle data for example one, example two and a comparative example.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the exemplary embodiments below are not intended to represent all implementations consistent with the present disclosure. Rather, they are merely examples of devices consistent with certain aspects of the present disclosure, as detailed in the appended claims.

In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the battery pack in the manufacturing process or the orientation or positional relationships shown in the drawings. These relative terms are used for descriptive convenience only and are not intended as limitations on the present disclosure.

The pole piece that this disclosure provided includes: current collector 10 and active layer 20 and adsorption layer 30 on current collector 10;

the active layer 20 comprises one or more layers, correspondingly, the adsorption layer 30 comprises one or more layers, and the active layer 20 and the adsorption layer 30 are arranged alternately;

the adsorption layer 30 contains an adsorbent for adsorbing the electrolyte.

The pole pieces can be the pole piece of the battery anode and the pole piece of the battery cathode. The positive pole piece of the battery may be referred to as the positive pole piece. A negative pole piece of the battery negative pole.

In the charging and discharging process of the battery pack, ions are transferred through the electrolyte to realize the exchange of charges between the positive pole piece and the negative pole piece, so that the wettability of the electrolyte on the pole pieces directly influences the cycle performance of the battery pack. Particularly, for the battery cell formed by winding the pole piece, the electrochemical reaction of the battery pack is unbalanced due to the difference between the inner layer and the outer layer of the battery cell caused by the temperature field and the like, so that the decomposition speed of the electrolyte is inconsistent, and the cycle life of the battery cell is locally shortened due to the lack of the electrolyte. This disclosed embodiment utilizes adsorption material to electrolyte in the adsorbed layer 30, for the storage of electrolyte provides more spaces, has ensured the supply of electrolyte, even at the circulation later stage, still can effectively guarantee the electrolyte reserve of pole piece, has improved the cyclicity ability of battery package.

Compared with the scheme of fig. 1 in which the central tube core is disposed, the adsorption layer 30 in the embodiment of the present disclosure occupies a smaller space, and also reduces the negative impact on the energy density of the battery pack, so that a smaller-sized battery pack or battery cell may have a larger battery capacity.

In order to improve the cycle performance of the battery pack, improvement is also performed by optimizing the proportion of the active layer 20 in the pole piece at present, but the scheme only limits the positive active layer material or the negative active layer material with specific components, has poor adaptability and is not suitable for application of consumer product battery packs pursuing high volume energy density. In the present disclosure, the active layer 20 is used to adsorb the electrolyte to improve the performance of the battery pack, the components of the active layer 20 are not limited, and the performance of the battery pack can be improved for different types of active layers 20, so that the adaptability is strong.

In practical application, the production process and production equipment of the original pole piece do not need to be changed, only the adsorption layer 30 needs to be added, and popularization and application are facilitated.

The positional relationship of the active layer 20 and the adsorption layer 30 on the current collector 10 is not a limitation of the present disclosure. For example, as shown in fig. 1, the active layer 20 may be located between the current collector 10 and the adsorption layer 30, and the active layer 20 may also be located between two adsorption layers 30.

The number of active layers 20 and adsorbent layers 30 is not intended to limit the present disclosure. For example, as shown in fig. 2, the pole piece has three active layers 20 and three adsorption layers 30, and the active layers 20 and the adsorption layers 30 are arranged alternately in layers. Alternatively, as shown in fig. 3, the pole piece has one adsorption layer 30 and one active layer 20, and the active layer 20 is located between the current collector 10 and the adsorption layer 30.

The active layer 30 includes an active material capable of absorbing and releasing lithium, and further, the active layer 30 further includes at least one additive including, but not limited to, a binder and a conductive agent. The adhesive is used for ensuring the interface adhesive force and the firmness of the active substance attached on the current collector. The conductive agent is used to ensure the transfer of charge.

For example, for a lithium battery, the positive active layer 20 on the positive electrode sheet includes a positive active material capable of absorbing and releasing lithium, and the positive active material includes, but is not limited to, one or a combination of more of lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, or lithium titanate. The negative active layer on the negative pole piece comprises a negative active material capable of absorbing and releasing lithium, and the negative active material comprises but is not limited to one or more combinations selected from transition metal oxide NaxMO2(M is transition metal, such as one or more of Mn, Fe, Ni, Co, V, Cu and Cr, and x is more than 0 and less than or equal to 1) or polyanion materials (phosphate, fluorophosphate, pyrophosphate and sulfate) and the like.

The binder may be selected from one or more of polyvinylidene fluoride (PVDF), polyurethane, copolymers of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, or styrene butadiene rubber. The conductive agent can also be one or more of carbon nano tube, carbon fiber, conductive carbon black, acetylene black, graphene or Ketjen black.

Fig. 2 and 3 only exemplarily show an example of forming the active layer 20 and the adsorption layer 30 on one side of the current collector 10, and in other examples, the active layer 20 and the adsorption layer 30 may be formed on both sides of the current collector 10 at the same time.

When the pole piece and the electrolyte are manufactured to form the battery pack, the adsorption layer 30 improves the wettability of the electrolyte to the active layer 20, the active layer 20 is in contact with the electrolyte to generate current, and the current collector 10 can collect the current generated by the active layer 20 and output large current to the outside of the battery pack. Therefore, the adsorption layer 30 has conductivity in addition to adsorption to ensure transfer of charges between the electrolyte, the active layer 20, and the current collector 10.

The number of adsorbent layers 30 can be selected based on the areal density of the active layer 20, and the compaction density of the pole pieces.

In other alternative embodiments, alternating the active layer 20 and the adsorbent layer 30 includes:

when the surface density of the active layer 20 is less than or equal to 0.0020g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, the active layer 20 and the adsorption layer 30 are both one layer, the adsorption layer 30 is positioned on the surface layer, and the active layer 20 is positioned between the adsorption layer and the current collector.

One adsorption layer 30 is used as the surface layer of the pole piece, and compared with the adsorption layer 30 between two active layers 20, the adsorption layer 30 on the surface layer can increase the total area infiltrated with the electrolyte, increase the retention amount of the electrolyte, and further improve the cycle performance of the battery pack.

In other alternative embodiments, the alternating arrangement of the active layer and the adsorbent layer comprises:

when the surface density of the active layer 20 is 0.0020-0.0027 g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, the active layer 20 and the adsorption layer 30 are both 2 layers, the adsorption layer 30 is positioned on the surface layer, and the 2 active layers 30 and the other adsorption layer 30 are alternately arranged between the current collector 10.

when the density of the active layer surface is more than or equal to 0.0027g/cc and the compacted density of the pole piece is less than or equal to 4.25g/cc, at least 3 layers of the adsorption layers 30 are selected, wherein one adsorption layer 30 is positioned on the surface layer, and other adsorption layers 30 and the active layer 20 are arranged at intervals.

Fig. 3 exemplarily shows a structural diagram of a pole piece having 3 adsorption layers 30 and 3 active layers 20, wherein the active layers 20 and the adsorption layers 30 are alternately arranged on the current collector 10 from bottom to bottom in sequence.

When the number of the adsorption layers 30 and the number of the active layers 20 are each at least 2, the number of the adsorption layers 30 and the number of the active layers 20 may be independently set, respectively. As shown in fig. 2, the first adsorption layer 30 is the outermost layer, that is, the adsorption layer 30 is the surface layer of the electrode plate, and the adsorption layer 30 on the surface layer can increase the area wetted with the electrolyte, increase the amount of the electrolyte, and further improve the cycle performance of the battery pack. Among the plurality of active layers 20, a portion of the active layer 20 may be located between the two adsorption layers 30, and the active layer 20 located at the lowermost layer may be directly formed on the current collector 10.

In other alternative embodiments, the adsorbent material includes, but is not limited to, a carbon material.

The carbon material has both conductivity and adsorptivity, and can improve the adsorption effect on the electrolyte while effectively ensuring charge transfer.

Carbon materials include, but are not limited to, carbon black, carbon nanotubes, graphene, or porous activated carbon, among others, in one or more combinations.

In other alternative embodiments, the absorbent layer 30 further comprises: a binder and a dispersant mixed with the adsorbent material.

The adhesive can provide sufficient interfacial adhesion, ensure the firmness of the adsorption material and the dispersant on the current collector 10, and reduce the risk of the adsorption layer 30 falling off in the use process of the battery pack. The dispersing agent is used for reducing agglomeration of the adsorbing material and the adhesive, improving the dispersion uniformity of the adsorbing material and the dispersion uniformity of the adhesive, and enabling the adsorbing material and the adhesive to be uniformly distributed at different parts of the current collector 10.

Adhesives include, but are not limited to, rubber adhesives. For example, the binder is a combination of one or more of polyvinylidene fluoride (PVDF), polyurethane, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, or styrene butadiene rubber.

Dispersants include, but are not limited to, polyvinylpyrrolidone (PVP), N-methylpyrrolidone (NMP), polyvinyl alcohol, polyethylene glycol, or a combination of one or more of sodium dodecyl sulfate, and the like.

In other alternative embodiments, the mass ratio of the adsorption material, the binder and the dispersant is as follows: 95-99.5 wt%: 0.5-4 wt%: 0 to 1 wt%.

In some specific examples, the weight ratio of the adsorbent material is approximately 95.0 wt%, 95.1 wt%, 95.3 wt%, 95.5 wt%, 96.0 wt%, 96.6 wt%, 97.0 wt%, 98.0 wt%, 99.0 wt%, 99.1 wt%, or 99.5 wt%, or the weight ratio of the adsorbent material is approximately in the range of any two of these compositions, based on the total weight of the adsorbent layer 30.

In some specific examples, the weight ratio of the binder is approximately 0.5 wt%, 0.7 wt%, 1.0 wt%, 1.2 wt%, 1.8 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 3.8 wt%, or 4.0 wt%, or the weight ratio of the binder is approximately in a range of any two of these compositions, based on the total weight of the absorbent layer 30.

In some specific examples, the weight ratio of the dispersant is approximately 0 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%, or the weight ratio of the dispersant is approximately in the range of any two of these values, based on the total weight of the adsorbent layer 30.

In other alternative embodiments, the total thickness of the adsorption layer 30 is 1-10 um.

The larger the thickness of the adsorption layer 30 is, the larger the adsorption amount to the electrolyte is, but at the same time, the thickness of the coating on the surface of the current collector 10 is also increased, so that the coating is likely to be peeled off, and the transfer resistance of electric charges is also increased. Therefore, the thickness of the adsorption layer 30 is 1-10 um.

In some specific examples, the thickness of the dispersant is approximately 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, or 10um, or the thickness of the dispersant is approximately a range of any two of these compositions.

In other optional embodiments, the specific surface area of the adsorbing material is 40-1000 m²/g。

The larger the specific surface area of the adsorbent material, the more favorable the adsorption of the electrolyte.

In some examples, the specific surface area of the adsorbent material is approximately 40m²/g、80m²/g、100m²/g、200m²/g、400m²/g、500m²/g、650m²/g、800m²/g、900m²In g or 1000m²In the case of the specific surface area of the adsorbent material, the specific surface area is approximately within the range of any two of these values.

Without limitation, in the pore diameter of the adsorbing material in the embodiment of the disclosure, the ratio of mesopores (pore diameter of 2nm to 50nm) is more than or equal to 40% by the number of pores; macropores (the aperture is larger than 50nm) account for less than or equal to 20 percent.

In other alternative embodiments, current collector 10 is a positive current collector and active layer 20 is a positive active layer;

or

The current collector 10 is a negative electrode current collector, and the active layer 20 is a negative electrode active layer.

In practical applications, the positive electrode plate forming the cell may have the adsorption layer 30, or the negative electrode plate forming the cell may have the adsorption layer 30. Or, both the positive electrode plate and the negative electrode plate forming the battery cell may have the adsorption layer 30.

The positive electrode current collector may be selected from aluminum foil or nickel foil. Of course, other materials may also be employed as the positive electrode current collector.

The negative electrode current collector may be selected from copper foil or nickel foil. Of course, other materials may also be employed as the negative electrode current collector.

The embodiment of the present disclosure further provides a battery pack, including:

a housing;

an electrolyte within the housing;

in the pole piece according to any of the embodiments, the pole piece is wound or stacked to form a battery cell, and the battery cell is located in the casing and soaked in the electrolyte.

The housing may be a metal housing or a plastic housing, for example, an aluminum-plastic film.

Further, the battery pack further comprises an isolating membrane, in practical application, the positive pole piece, the isolating membrane and the negative pole piece can be sequentially wound, folded or stacked to form a battery cell, the battery cell is arranged in the shell, electrolyte is injected, and then the procedures of vacuum packaging, standing, formation, shaping and the like are carried out, so that the lithium ion battery is obtained.

Generally, the electrolyte includes a solvent, and a lithium salt dispersed and dissolved in the solvent. Further, lithium salts include, but are not limited to LiPF₆、LiBF₄、LiAsF₆、LiClO₄、LiB(C₆H₅)₄、LiCH₃SO₃、LiCF₃SO₃、LiN(SO₂CF₃)₂、LiC(SO₂CF₃)₃Or LiSiF₆One or more of the above. The solvent includes, but is not limited to, a combination of one or more of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents. For example: ethylene carbonate, propylene carbonate, dimethyl sulfoxide,N-methyl-2-pyrrolidone, formamide, or dimethylformamide.

The isolating membrane is a porous structure for ions to pass through. The release film includes, but is not limited to, a combination of one or more of a polyolefin, a polyamide, a polyimide, a polyester, or an aramid.

An embodiment of the present disclosure further provides an electronic device including the battery pack according to any one of the above embodiments.

Electronic devices include, but are not limited to, laptops, desktops, tablets, electronic book players, cell phones, televisions, calculators, backup power sources, automobiles, motorcycles, mopeds, lighting fixtures, wearable devices, game consoles, clocks, power tools, or cameras, and the like.

The embodiment of the present disclosure further provides a manufacturing method of a pole piece, including:

forming an active layer 20 on the current collector 10; an adsorption material containing an electrolyte is coated on at least one of the active layers 20 to obtain an adsorption layer 30.

The pole piece in the method disclosed by the invention comprises the pole piece in any one of the embodiments.

In practical application, the method can be used without changing the production process and production equipment of the original pole piece, for example, as shown in fig. 3, after the original pole piece without the adsorption layer 30 is manufactured, the pole piece of the embodiment of the disclosure can be manufactured by only adding the adsorption layer 30 on the surface of the active layer 20, and is convenient to popularize and apply.

In the preparation of the electrode sheet, after the active layer 20 is formed and then the roll is formed, the electrolyte adsorption layer 30 is coated and dried to prepare the electrolyte adsorption layer 30.

The active layer 20 and the adsorption layer 30 are formed separately. Without limitation, the active layer 20 and the adsorption layer 30 may be respectively formed by coating.

For example, as shown in fig. 3, when both the adsorption layer 30 and the active layer 20 are formed as one layer, the active layer 20 may be coated on the current collector 10, the active layer 20 may be rolled, the coating material for the adsorption layer 30 may be further coated on the active layer 20, and the adsorption layer 30 may be formed after drying.

In other alternative embodiments, active layer 20 is formed on current collector 10; coating an adsorption material containing an adsorbed electrolyte on at least one active layer 20 to obtain an adsorption layer 30, comprising:

when the active layer 20 and the adsorption layer 30 are both plural; the active layer 20 and the adsorption layer 30 are formed by layering.

In practical applications, as shown in fig. 2, when there are a plurality of active layers 20 and adsorption layers 30, the active layers 20 may be coated on the current collector 10, then the adsorption layers 30 may be coated on the active layers 20, then the active layers 20 may be coated again, and so on, and the active layers 20 and the adsorption layers 30 may be formed alternately. Further, in order to further improve the cycle performance of the battery pack, one of the adsorption layers 30 may be used as a surface layer of the pole piece.

The distribution of a plurality of active layers 20 can be effectual adsorb electrolyte, provides more spaces for the storage of electrolyte, is favorable to the supply of circulation later stage electrolyte, has further improved lithium ion battery's cyclicity ability.

The technical solution of the present disclosure is further described below by referring to specific examples and comparative examples, and it is understood that the present disclosure is not limited to the following examples.

Example one

Preparing a positive pole piece: mixing lithium cobaltate, conductive carbon black (SP), and PVDF (polyvinylidene fluoride) binder according to the mass ratio of 96% to 2%, mixing with NMP (N-methyl pyrrolidone) as a dispersing agent, coating the slurry on an aluminum foil of a positive current collector after the preparation of the slurry of the positive active layer is finished, wherein the density of the positive active layer is 0.0018g/cc, and drying the coating to be coated with an adsorption layer.

Preparing an adsorption layer, namely mixing carbon nanotubes and conductive carbon black according to the solid mass ratio of 80%: 20% is subjected to high-speed dispersion mixing to obtain a composite adsorbing material, and the adsorbing material and the binder are mixed according to the mass ratio of solids of 99%: after 1 percent of the mixture is mixed, a dispersing agent NMP is added to be dispersed into uniform slurry, and the uniform slurry is coated on the surface of the active layer of the positive electrode and dried.

And compacting the obtained positive pole piece with the adsorption layer by a roller press, controlling the compaction density to be 4.2g/cc, and finally preparing the positive pole piece with the required size by a striping process.

And preparing the negative pole piece in the same way, wherein the negative pole piece is not provided with an adsorption layer.

And winding the prepared positive pole piece, the prepared negative pole piece and the prepared isolating membrane into a battery cell, and preparing the lithium ion battery pack with the adsorption layer by the processes of packaging, liquid injection, formation, capacity and the like.

And placing the obtained lithium ion battery cell in an environment with the temperature of 25 to 3 ℃, and performing charge-discharge cycle test according to 1.5C charging and 0.7C multiplying power discharging.

Example two

Preparing a positive pole piece, namely mixing lithium cobaltate, conductive carbon black SP and a binder PVDF according to the mass ratio of 96% to 2%, mixing the mixture by using a dispersant NMP, coating the slurry on a positive current collector after the preparation of the positive active layer slurry is finished, wherein the surface density of the positive active layer is 0.0016g/cc, and drying the coating to be coated with an adsorption layer.

Preparation of the adsorption layer, the adsorption material is conductive carbon black and graphene, and the conductive carbon black, the graphene, the binder and the dispersant are mixed according to a solid mass ratio of 70%: 25%: 3.8%: and mixing 1.2 percent of the mixture, adding a dispersing agent NMP (N-methyl pyrrolidone) to disperse the mixture into uniform adsorption layer slurry, coating the uniform adsorption layer slurry on the surface of the positive active layer, and drying to obtain a first active adsorption layer.

And then coating the slurry of the positive active layer on two sides of the first active adsorption layer, controlling the surface density of the active coating to be 0.0010g/cc, and continuously coating the slurry of the second active adsorption layer on the surface of the active coating after drying to obtain the final composite coating.

Compacting the obtained composite positive coating pole piece by a roller press, controlling the compaction density to be 4.25g/cc, and finally preparing the positive pole piece with the required size by a striping process.

The difference between the second embodiment and the first embodiment is only the preparation of the positive electrode plate.

Comparative example

Preparing a positive pole piece, namely mixing lithium cobaltate, conductive carbon black SP and a binder PVDF according to the mass ratio of 96% to 2%, mixing slurry by using a dispersant NMP, coating the slurry on a positive current collector after the slurry is prepared, wherein the surface density is 0.0018g/cc, and drying the coating to obtain the positive pole coated pole piece.

And compacting the obtained positive coating pole piece by a roller press, controlling the compacted density to be 4.2g/cc, and finally preparing the positive pole piece with the required size by a striping process.

And winding the prepared positive pole piece, the prepared negative pole piece and the prepared isolating membrane into a battery cell, and preparing the lithium ion battery pack rich in the adsorption layer by the processes of packaging, liquid injection, formation, capacity and the like.

And placing the obtained lithium ion battery pack in an environment with the temperature of 25 to 3 ℃, and discharging according to the 1.5C charging rate and the 0.7C discharging rate to perform charge-discharge cycle test.

The comparative example is different from the first example only in the preparation of the positive electrode sheet.

A comparison of the charge and discharge cycle data for the first example, the first example and the comparative example is shown in fig. 4. Wherein, the cycle data of the example I is shown in the curve indicated by A, the cycle data of the example II is shown in the curve indicated by B, and the cycle data of the comparative example is shown in the curve indicated by C. The test conditions for a lithium ion battery pack (1.5C charge at 0.7C discharge rate under an environment of 25-/+ 3 ℃) are expressed as Cycle life @1.5C/07C @25 ℃. The abscissa is Cycle number (Cycle _ No.), the ordinate is Capacity Retention (Capacity _ Retention), and the Capacity Retention refers to discharge Capacity C of the battery pack after N charge-discharge cycles_NAnd initial discharge capacity C of the battery pack₀Percent of (a), i.e., capacity retention (%) - (C)_N/C₀)╳100％。

As can be seen from fig. 4, in the battery packs of the first and second embodiments of the present disclosure, the capacity retention rate of the battery pack still exceeds 85% at the later cycle time of 800 to 1000 cycles, while in the comparative example, the battery content retention rate has been reduced to 80% at the time of less than 900 cycles. The cell capacity retention of examples one and two was significantly higher than that of comparative example. Therefore, under the same conditions, the embodiment of the disclosure improves the cycle performance of the battery pack by adding the adsorption layer.

The methods disclosed in the several method embodiments provided in this disclosure may be combined arbitrarily without conflict to arrive at new method embodiments.

Features disclosed in several of the product embodiments provided in this disclosure may be combined in any combination to yield new product embodiments without conflict.

The features disclosed in the several method or article of manufacture embodiments provided in this disclosure may be combined in any combination to yield new method or article of manufacture embodiments without conflict.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A pole piece, comprising: the current collector, and an active layer and an adsorption layer which are positioned on the current collector;

the active layer comprises one or more layers, the corresponding adsorption layer comprises one or more layers, and the active layer and the adsorption layer are arranged at intervals;

the adsorption layer contains an adsorption material for adsorbing electrolyte.

2. The pole piece of claim 1, wherein the active layer and the absorbent layer are arranged at intervals comprising:

3. The pole piece of claim 1, wherein the active layer and the absorbent layer are arranged at intervals comprising:

4. The pole piece of claim 1, wherein the active layer and the absorbent layer are arranged at intervals comprising:

5. The pole piece of any one of claims 1 to 4, wherein the adsorbent material is a carbon material.

6. The pole piece of any one of claims 1 to 4, wherein the adsorption layer further comprises: a binder and a dispersant mixed with the adsorbent material.

7. The pole piece of claim 6, wherein the mass ratio of the adsorbing material to the adhesive to the dispersing agent is: 95-99.5 wt%: 0.5-4 wt%: 0 to 1 wt%.

8. The pole piece of any one of claims 1 to 4, wherein the total thickness of the adsorption layer is 1 to 10 um.

9. The pole piece according to any one of claims 1 to 4, wherein the specific surface area of the adsorbing material is 40-1000 m²/g。

10. The pole piece of any one of claims 1 to 4, wherein the current collector is a positive current collector and the active layer is a positive active layer;

or

11. A battery pack, comprising:

a housing;

an electrolyte within the housing;

the pole piece of any one of claims 1 to 10 wound or stacked to form a cell, said cell being located within said housing and immersed in said electrolyte.

12. A manufacturing method of a pole piece is characterized by comprising the following steps:

13. The method for manufacturing the pole piece according to claim 12, wherein an active layer is formed on the current collector; coating an adsorption material containing adsorption electrolyte on at least one active layer to obtain an adsorption layer, comprising: