CN113285056B

CN113285056B - Positive plate and battery

Info

Publication number: CN113285056B
Application number: CN202110601256.8A
Authority: CN
Inventors: 张保海; 彭冲; 李俊义
Original assignee: Zhuhai Cosmx Battery Co Ltd
Current assignee: Zhuhai Cosmx Battery Co Ltd
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2023-11-21
Anticipated expiration: 2041-05-31
Also published as: CN113285056A

Abstract

The invention provides a positive plate and a battery, wherein the positive plate comprises a positive current collector and a positive coating, the positive current collector comprises a first base material and a conductive coating, the conductive coating is arranged on two opposite side surfaces of the first base material, and the first base material comprises a polymer layer; the positive current collector includes first and second opposite sides, at least one of which has the positive electrode coating disposed thereon. The polymer layer coated with the conductive coating is used as the positive electrode current collector of the positive electrode plate, so that the risk of internal short circuit can be reduced, and the safety performance of the battery can be improved.

Description

Positive plate and battery

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a positive plate and a battery.

Background

With the continuous development and progress of society, electronic devices with various functions have been rapidly developed. The lithium battery has the advantages of high battery voltage, high energy density, good cycle performance and the like, and the application requirements of the lithium battery on various electronic devices are also increasing.

The lithium battery is used incorrectly, is impacted by sharp objects or is pierced, and the positive electrode aluminum foil and the negative electrode active material in the battery are contacted, so that the internal short circuit of the battery is caused, and when the internal short circuit is serious, the battery can be ignited or even exploded, so that the personal safety of a user is endangered. It can be seen that the existing lithium battery has a problem of high short circuit risk.

Disclosure of Invention

The embodiment of the invention aims to provide a positive plate, a battery and a preparation method of the positive plate, which solve the problem of lower safety performance of the battery in the prior art.

In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a positive electrode sheet, including a positive electrode current collector and a positive electrode coating layer, the positive electrode current collector including a first substrate and a conductive coating layer, the conductive coating layer being disposed on two opposite sides of the first substrate, the first substrate including a polymer layer; the positive current collector includes first and second opposite sides, at least one of which has the positive electrode coating disposed thereon.

Optionally, the first substrate further comprises a ceramic coating disposed on two opposite sides of the polymer layer, and the conductive coating is disposed on a side of the ceramic coating opposite the polymer layer.

Optionally, the first side and the second side are both provided with the positive electrode coating, the positive electrode current collector includes a first end and a second end that are opposite, the positive electrode coating of the first side includes a first edge and a second edge that are opposite, the first edge is close to the first end, and the second edge is close to the second end; the positive electrode coating of the second side comprises a third edge and a fourth edge which are opposite, wherein the third edge is close to the first end, and the fourth edge is close to the second end; the first side includes a first region between the second edge and the second end, the second side includes a second region between the fourth edge and the second end; the positive electrode coating is not arranged in the first area and the second area.

Optionally, the length of the first region is smaller than the length of the second region.

Optionally, the positive electrode coating comprises a first winding layer, wherein the first winding layer is a winding layer on which the positive electrode sheet is wound, and the second winding layer is a winding layer on which the positive electrode sheet is wound.

Optionally, the battery further comprises a positive electrode tab, the first side comprises a third region, the third region is located between the first edge and the first end, the second side comprises a fourth region, and the fourth region is located between the third edge and the first end; the third region and the fourth region are not provided with the positive electrode coating, and the positive electrode lug is in contact with the third region and the fourth region.

Optionally, the positive tab includes a first extension portion and a second extension portion, and an included angle between the first extension portion and the second extension portion is smaller than 180 °; the first extension part is arranged in one of the third region and the fourth region, the second extension part is arranged in the other of the third region and the fourth region, and the first extension part is electrically connected with the second extension part.

In a second aspect, an embodiment of the present invention provides a battery, including an electrical core and a housing, where the electrical core is disposed in the housing, and the electrical core is formed by sequentially laminating and winding a positive plate and a negative plate, and a diaphragm is disposed between any adjacent positive plate and negative plate, and the positive plate is the positive plate provided in the first aspect of the present invention.

Optionally, the housing is an electrically conductive shell; the first side surface and the second side surface are both provided with the positive electrode coating, and the positive electrode current collector comprises a first end and a second end which are opposite; the positive electrode coating of the first side comprises a first edge and a second edge which are opposite, the first edge is close to the first end, the second edge is close to the second end, the first side comprises a first area, and the first area is located between the second edge and the second end; the positive electrode coating of the second side comprises a third edge and a fourth edge which are opposite, the third edge is close to the first end, the fourth edge is close to the second end, the second side comprises a second area, and the second area is located between the fourth edge and the second end; the first area and the second area are not provided with the positive electrode coating, and the second area is attached to the inner wall of the shell.

Optionally, the second end is bent towards a first direction to form a bending part, the first direction is opposite to the winding direction of the battery cell, the bending part comprises a first subarea and a second subarea which are opposite to each other, the first subarea comprises the first subarea, the second subarea comprises the second subarea, and the first subarea is attached to the inner wall of the shell.

One of the above technical solutions has the following advantages or beneficial effects:

the embodiment of the invention provides a positive plate, a battery and a preparation method of the positive plate, wherein the positive plate comprises a positive current collector and a positive coating, the positive current collector comprises a first base material and a conductive coating, the conductive coating is arranged on two opposite side surfaces of the first base material, and the first base material comprises a polymer layer. The positive plate is different from a positive current collector using aluminum foil as the positive plate in the prior art, and a polymer layer coated with a conductive coating is used as the positive current collector of the positive plate. The conductive coating can ensure conductivity among positive electrode particles in the horizontal direction in the positive electrode coating, reduces the use of positive electrode aluminum foil, can reduce the risk of internal short circuit, and improves the safety performance of the battery.

Drawings

FIG. 1 is a cross-sectional view of a positive electrode sheet according to an embodiment of the present invention;

fig. 2 is a sectional view of a positive electrode current collector according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a battery cell according to an embodiment of the present invention;

FIG. 4 is a second cross-sectional view of a positive electrode sheet according to an embodiment of the present invention;

FIG. 5 is a block diagram of a positive tab according to an embodiment of the present invention;

fig. 6 is a top view of a structure of a positive plate according to an embodiment of the present invention;

FIG. 7 is a second cross-sectional view of a battery cell according to an embodiment of the present invention;

fig. 8 is a flowchart of a method for preparing a positive plate according to an embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Referring to fig. 1 to 7, an embodiment of the present invention provides a positive electrode sheet 100.

As shown in fig. 1 and 2, the positive electrode sheet 100 includes a positive electrode current collector 110 and a positive electrode coating layer 120, the positive electrode current collector 110 includes a first substrate and a conductive coating layer 111, the conductive coating layer 111 is disposed on two opposite sides of the first substrate, and the first substrate includes a polymer layer 112; the positive electrode current collector 110 includes first and second opposite sides, at least one of which has a positive electrode coating 120 disposed thereon.

Wherein the first side surface may be understood as an upper side surface as shown in fig. 1, and is an inner side of the winding when the positive electrode sheet 100 is wound; the second side surface may be understood as a lower side surface as shown in fig. 1, which is an outer side of the winding when the positive electrode sheet 100 is wound.

In embodiments of the present invention, the polymer layer 112 may include one or more of a polyethylene monolayer film, a polypropylene monolayer film, and a polyethylene and polypropylene multilayer composite film. Moreover, the polymer layer 112 has a pore path that can conduct the first side and the second side of the polymer layer 112, and in the case where the first side and the second side are both provided with the positive electrode coating, lithium ions in the positive electrode coating on the first side can move into the positive electrode coating on the second side through the pore path, or lithium ions in the positive electrode coating on the second side can move into the positive electrode coating on the first side through the pore path, so that the overall lithium ions of the positive electrode sheet are more balanced, polarization is reduced, and the cycle life of the lithium ions is improved. It should be noted that, after the conductive coating 111 is disposed, the pore canal still conducts the first side and the second side of the positive current collector 110.

In specific implementation, the hole may be a through hole or a curved hole, which may be specifically determined according to practical situations, and is not limited herein. Optionally, the porosity of the polymer layer 112 is 35% to 60%, and the porosity of the positive electrode current collector 110, i.e., the polymer layer 112 after being coated with the conductive coating 111 is 30% to 50%, wherein the porosity is a percentage of the volume of the pore channels to the entire volume. Alternatively, the polymer layer 112 has a stretching ratio of 75% to 210%, and the positive electrode current collector 110, i.e., the polymer layer 112 after being coated with the conductive coating 111 has a stretching ratio of 90% to 230%.

In the embodiment of the present invention, unlike the prior art, in which aluminum foil is used as the positive current collector of the positive electrode sheet, the polymer layer 112 coated with the conductive coating 111 is used as the positive current collector 110 of the positive electrode sheet 100. On the one hand, since the polymer layer 112 is externally coated with the conductive coating 111, the conductive coating 111 can be fully contacted with the active material in the positive electrode coating 120, so that the conductivity between the positive electrode particles in the positive electrode coating 120 in the horizontal direction can be ensured, and the current generated by the positive electrode particles in the positive electrode coating 120 is collected to form the current to be output to the outside. On the other hand, due to the fact that the aluminum foil is reduced, the aluminum foil can be effectively prevented from being contacted with the negative electrode active material, the risk of internal short circuit is reduced, and the whole lithium ions of the positive electrode plate 100 can be more balanced based on the pore channel structure of the polymer layer 112, so that the cycle life of the lithium ions is prolonged. In addition, the polymer layer 112 has good mechanical strength and flexibility, and can effectively prevent the powder falling phenomenon caused by the bending of the pole piece due to improper operation during the battery assembly.

Optionally, as shown in fig. 2, the first substrate further includes a ceramic coating 113, the ceramic coating 113 being disposed on two opposite sides of the polymer layer 112, and the conductive coating 111 being disposed on the ceramic coating 113.

In practical applications, after the slurry of the positive electrode coating 120 is coated on at least one side of the positive electrode current collector 110, the slurry needs to be dried at a high temperature. Since the positive electrode current collector 110 uses the polymer layer 112 as a base material, shrinkage may occur when it is heated. Specifically, alternatively, the polymer layer 112 may have a thermal shrinkage of 2% to 5% at 90 ℃ to 105 ℃ before the ceramic coating 113 is coated, and may have a thermal shrinkage of 70% to 93% above 130 ℃, and the positive electrode current collector 110, i.e., the polymer layer 112 may have a thermal shrinkage of 10% to 18% at 125 ℃ to 145 ℃ after the polymer layer 112 is coated with the conductive coating 111.

In this embodiment, a ceramic coating 113 may be applied to two opposite sides of the polymer layer 112, and the conductive coating 111 is disposed on the side of the ceramic coating 113 facing away from the polymer layer 112. The presence of the ceramic coating 113 can effectively increase the heat shrinkage resistance of the polymer layer 112, preventing the polymer layer 112 from thermal shrinkage during the high temperature baking process.

In particular, when the conductive paste is coated on the ceramic coating 113 to form the conductive coating 111, the conductive paste penetrates through gaps between ceramic particles in the ceramic coating 113, so that the ceramic particles and the conductive paste are connected to each other in the ceramic coating 113 to form a mesh-like weave, and thus the adhesion between the conductive coating 111 and the ceramic coating 113 and the conductivity in the vertical direction of the ceramic coating 113 can be improved. It is understood that the penetration of the conductive paste in the ceramic coating 113 decreases sequentially from the surface layer to the bottom layer of the ceramic coating 113.

Alternatively, the first substrate, i.e., the polymer layer 112, has a thermal shrinkage of 3% to 6% at 125 ℃ to 145 ℃ after being coated with the ceramic coating 113, and the positive electrode current collector 110, i.e., the polymer layer 112, has a thermal shrinkage of 2% to 7% at 125 ℃ to 145 ℃ after being coated with the ceramic coating 113 and the conductive coating 111. Alternatively, the porosity of the first substrate, i.e., the polymer layer 112, after the ceramic coating 113 is applied is 40% to 65%, and the porosity of the positive electrode current collector 110, i.e., the polymer layer 112, after the ceramic coating 113 and the conductive coating 111 are applied is 33% to 57%. Alternatively, the first substrate, i.e., the polymer layer 112, has a stretching ratio of 60% to 130% after the ceramic coating 113 is applied, and the positive electrode current collector 110, i.e., the polymer layer 112, has a stretching ratio of 85% to 140% after the ceramic coating 113 and the conductive coating 111 are applied.

Optionally, as shown in fig. 1, the first side and the second side are provided with a positive electrode coating, where the positive electrode coating of the first side is denoted as a positive electrode coating 121, and the positive electrode coating of the second side is denoted as a positive electrode coating 122 for convenience of reading; positive electrode current collector 110 includes opposing first and second ends, positive electrode coating 121 includes opposing first and second edges, the first edge being proximate to the first end and the second edge being proximate to the second end; the positive electrode coating 122 includes opposing third and fourth edges, the third edge being proximate the first end and the fourth edge being proximate the second end; the first side includes a first region between the second edge and the second end, the second side includes a second region between the fourth edge and the second end; the positive electrode coating is not arranged in the first area and the second area.

Wherein the first end may be understood as a left end as shown in fig. 1, which is a wound head when the positive electrode sheet 100 is wound; the second end may be understood as the right end as viewed in fig. 1, which is the tail of the winding when the positive electrode sheet 100 is wound. The first edge may be understood as the left side edge of the positive electrode coating 121 as shown in fig. 1, and the second edge may be understood as the right side edge of the positive electrode coating 121 as shown in fig. 1; the third edge may be understood as the left edge of the positive electrode coating 122 as shown in fig. 1, and the fourth edge may be understood as the right edge of the positive electrode coating 122 as shown in fig. 1. The first region may be understood as a region of the upper side right side of the non-coated positive electrode coating 121 as shown in fig. 1, and the second region may be understood as a region of the lower side right side of the non-coated positive electrode coating 122 as shown in fig. 1.

In this embodiment, as shown in fig. 1, the upper and lower sides of the positive current collector 110 are both provided with positive electrode coatings, and the two sides of the tail of the positive plate 100 are both exposed to the positive current collector 110, because the positive current collector 110 includes the conductive coating 111, the positive current collector 110 can be in contact with the inner wall of the conductive battery case to serve as the positive electrode tab of the battery after winding is completed, and the positive electrode tab is not required to be provided on the positive plate 100.

In one implementation, as shown in fig. 3, after the positive electrode sheet 100 is wound, the positive electrode current collector 110 exposed at the tail of the positive electrode sheet 100 may surround at least the outermost turn of the wound cell for one full revolution. The second side of the exposed positive electrode current collector 110, i.e., the second region, may be in close contact with the inner wall of the conductive battery case, improving the conductive stability of the positive electrode tab 100.

In one implementation, the first edge is flush with the third edge.

Further optionally, the length of the first region is smaller than the length of the second region.

In this embodiment, the positive electrode sheet 100 is near the second end, that is, there is a portion of the tail of the positive electrode sheet 100 where only the single-sided coating is provided. As shown in fig. 3, when the positive electrode sheet 100 and the negative electrode sheet 200 are laminated and wound, a separator sheet is provided between the positive electrode sheet 100 and the negative electrode sheet 200 to facilitate the flow of lithium ions and to perform an insulating function. In the latter half of the winding, the negative electrode sheet 200 is not already present between the positive electrode sheet 100 and the battery case. If the second side surface is further provided with a positive electrode coating, lithium ions in the positive electrode coating cannot reach the negative electrode plate after being separated, and lithium precipitation can occur on the battery shell. Thus, at the tail of the positive electrode sheet 100, the outside, i.e., the second side surface, around which the positive electrode current collector 110 is wound is not provided with a positive electrode coating.

Further optionally, the positive electrode sheet 100 further includes a gummed paper 130, a part of the gummed paper 130 is attached to the positive electrode coating 122, another part of the gummed paper 130 is attached to the second area, and the length of the gummed paper 130 attached to the second area is greater than or equal to the perimeter of the first winding layer, where the first winding layer is a winding layer where the gummed paper 130 is located after the positive electrode sheet is wound.

In this embodiment, since the positive electrode current collector 110 uses the polymer layer 112 as a base material, and there is a portion of the positive electrode sheet 100 with only one coating layer, lithium ions in the positive electrode coating layer 121 can penetrate through the polymer layer 112 to reach the lower side of the positive electrode current collector 110 at the tail portion of the positive electrode sheet 100, i.e., the right end as shown in fig. 1. Meanwhile, as described above, in the latter half of the winding of the positive electrode sheet 100, the negative electrode sheet 200 does not exist between the positive electrode sheet 100 and the battery case, and thus lithium ions penetrating onto the positive electrode coating layer 122 may cause a lithium precipitation. Thus, the jelly-roll 130 may be attached to a portion of the lower side surface of the positive electrode current collector 110 where the positive electrode coating 122 is not provided to prevent precipitation of lithium ions. The gummed paper 130 can surround the whole circle of the winding layer to prevent the lithium ions at any position of the winding layer from being separated out.

In addition, a part of the gummed paper 130 is attached to the positive electrode coating 122, so that the negative electrode coating adjacent to the positive electrode coating 122 can completely cover the positive electrode coating in the latter half of winding, and the tail of the positive electrode coating 122 can be prevented from generating burrs during charging to pierce the polymer layer 112 so as to cause lithium precipitation. It should be noted that, a piece of gummed paper may be attached to the tail of the positive electrode coating 121 to avoid the tail of the positive electrode coating 121 from generating burrs to pierce the polymer layer 112 and cause lithium precipitation.

In specific implementation, the length of the gummed paper 130 may be the length of the positive electrode coating 121-the length of the positive electrode coating 122+10 mm-15 mm; the extent of the partial adhesive paper 130 attached to the positive electrode coating 122 may be 2mm to 5mm, and may be specifically determined according to practical situations, and is not limited herein.

Optionally, as shown in fig. 4, the positive electrode tab 100 further includes a positive electrode tab 140, the first side includes a third region, the third region is located between the first edge and the first end, the second side includes a fourth region, and the fourth region is located between the third edge and the first end; the third region and the fourth region are not provided with the positive electrode coating 120, and the positive electrode tab 140 is in contact with both the third region and the fourth region.

Wherein the third region may be understood as a region where the upper side left side of the positive electrode coating 121 is not coated as shown in fig. 4, and the fourth region may be understood as a region where the lower side left side of the positive electrode coating 122 is not coated as shown in fig. 4.

In the present embodiment, as shown in fig. 4, a tab installation region is provided on the left side of the positive electrode tab 100, and the positive electrode tab 140 may be installed in the tab installation region. The positive current collector 110 is exposed at two sides of the tail of the positive plate 100, and when the part of positive current collector 110 contacts with the inner wall of the conductive battery shell to serve as the first positive tab of the battery after winding is completed, the positive tab 140 can serve as the second positive tab of the positive plate 100, and the setting of the bipolar tab can improve the charging speed of the battery and further improve the quick charging capability of the battery.

In particular, since the positive electrode current collector 110 includes the polymer layer 112, the upper and lower sides of which are not electrically conductive, the positive electrode tab 140 needs to be in contact with both the third and fourth regions to ensure the electrical conductivity of the positive electrode tab 100.

In this embodiment, in one implementation manner, as shown in fig. 5, the positive tab 140 includes a first extension portion 141 and a second extension portion 142, and an included angle between the first extension portion 141 and the second extension portion 142 is smaller than 180 °; the first extension 141 is disposed at one of the third region and the fourth region, the second extension 142 is disposed at the other of the third region and the fourth region, and the first extension 141 is electrically connected to the second extension 142.

Wherein the first extension 141 includes a portion covering the upper side of the positive electrode current collector 110 as shown in fig. 5; the second extension 142 includes a portion covering the lower side of the positive electrode current collector 110 as shown in fig. 5.

In this implementation, as shown in fig. 5, the positive tab 140 is an "eight" shaped clamping tab. The first extension 141 and the second extension 142 may be electrically conductive by welding through the positive electrode current collector 110, or may be electrically conductive by filling the active material of the conductive coating 111 into the pores to thereby electrically conduct the first extension 141 and the second extension 142. It should be noted that, for convenience of packaging, an insulating member 150 may be disposed at a portion of the positive electrode tab 140 not in contact with the positive electrode current collector 110. Further, as shown in fig. 6, the width of the portion of the positive electrode tab 140 that does not contact the positive electrode current collector 110 is identical to the width of the portion of the positive electrode tab 140 that contacts the positive electrode current collector 110, and the conductivity between the positive electrode tab 140 and the positive electrode current collector 110 can be further improved.

In summary, the positive plate provided by the embodiment of the invention is different from the positive current collector using aluminum foil as the positive plate in the prior art, and the polymer layer coated with the conductive coating is used as the positive current collector of the positive plate, so that the risk of internal short circuit can be reduced, and the safety performance of the battery can be improved.

The embodiment of the invention also provides a battery, as shown in fig. 3 and 7, which comprises a battery core and a housing 300, wherein the battery core is arranged in the housing 300, the battery core is formed by sequentially laminating and winding a positive plate 100 and a negative plate 200, a diaphragm (not shown in the drawings) is arranged between any adjacent positive plate 100 and negative plate 200, and the positive plate 100 is the positive plate 100 provided by the embodiment of the invention.

It should be noted that, in the embodiment of the present invention, the battery includes all the technical features of the positive electrode sheet 100 provided in the embodiment of the present invention, and all the technical effects of the positive electrode sheet 100 provided in the embodiment of the present invention may be achieved, so that repetition is avoided and no further description is given here.

Alternatively, as shown in FIG. 3, the housing 300 is a conductive shell; the first side includes a first region between the second edge and the second end; the second side includes a second region proximate the second end, the second region being located between the fourth edge and the second end; the positive electrode coating is not disposed in the first region and the second region, and the second region is attached to the inner wall of the housing 300.

In this embodiment, as shown in fig. 3, the positive current collector 110 exposed at two sides of the tail of the positive electrode sheet 100 has a conductive coating 111, and the positive current collector 110 may contact with the inner wall of the conductive housing 300 to be used as the positive tab of the battery after winding, and the negative tab of the negative electrode sheet 200 may be connected with the bottom cover of the conductive housing 300 to be used as the negative tab 210 of the battery, so that insulation between the inner wall of the conductive housing 300 and the bottom cover needs to be ensured.

In this embodiment, preferably, the inner wall of the conductive case 300 may be provided with a conductive coating to reduce contact resistance between the inner wall of the conductive case 300 and the positive electrode current collector 110, further enhancing conductivity.

In this embodiment, as shown in fig. 3, the second end is bent in a first direction to form a bending portion, the first direction is opposite to the winding direction of the electrical core, the bending portion includes a first sub-area and a second sub-area opposite to each other, the first area includes the first sub-area, the second area includes the second sub-area, and the first sub-area is attached to the inner wall of the conductive housing 300.

The first direction is opposite to the winding direction of the battery cell, and, for example, as shown in fig. 3 and 7, the winding direction of the positive electrode sheet 100 is clockwise, and the first direction is counterclockwise.

As can be seen from the above embodiments, the second area, that is, the tail of the upper side of the positive electrode current collector 110 is attached to the inner wall of the case 300 to realize electrical conduction. Since the positive electrode current collector 110 includes a polymer layer, the upper and lower sides of the polymer layer are not conductive, and therefore, in order to ensure the conductivity of the positive electrode tab, the tail portion of the lower side of the positive electrode current collector 110 needs to be attached to the inner wall of the conductive housing 300 to achieve conductivity. In this way, in this embodiment, as shown in fig. 3, the tail portion of the positive electrode current collector 110 may be bent backward, so that the tail portion of the lower side surface of the positive electrode current collector 110, that is, the first sub-region) may also be attached to the inner wall of the housing 300 to achieve electrical conduction.

In one embodiment, as shown in fig. 7, the positive electrode tab 100 further includes a positive electrode tab 140, the first side includes the third region, the second side includes the fourth region, and the positive electrode tab 140 contacts both the third region and the fourth region.

In this embodiment, as shown in fig. 7, the battery structure is the positive current collector 110 exposed at two sides of the tail of the positive electrode sheet 100, and since the positive current collector 110 includes the conductive coating 111, the positive current collector 110 can be in contact with the inner wall of the conductive housing 300 to serve as the first positive electrode tab of the battery after winding is completed, the positive electrode tab 140 can be electrically connected with the top cover of the conductive housing 300 to serve as the second positive electrode tab of the battery, and the negative electrode tab of the negative electrode sheet 200 can be connected with the bottom cover of the conductive housing 300 to serve as the negative electrode tab 210 of the battery, at this time, insulation between the top cover, the inner wall and the bottom cover of the conductive housing 300 needs to be ensured. The bipolar lug can improve the charging speed of the battery, so that the quick charging capacity of the battery is improved.

In summary, the battery provided by the embodiment of the invention includes the positive electrode plate which is different from the positive electrode current collector using the aluminum foil as the positive electrode plate in the prior art, and the polymer layer coated with the conductive coating is used as the positive electrode current collector of the positive electrode plate, so that the risk of internal short circuit can be reduced, and the safety performance of the battery can be improved.

Referring to fig. 8, fig. 8 is a flowchart of a method for preparing a positive plate according to an embodiment of the invention. As shown in fig. 8, the preparation method of the positive plate includes:

step 801, forming a first substrate, the first substrate comprising a polymer layer;

step 802, coating conductive coating slurry on two opposite side surfaces of the first substrate and drying to obtain a positive current collector, wherein the conductive coating slurry is formed by mixing a conductive agent and a solvent;

and 803, coating the positive electrode coating slurry on at least one side surface of the positive electrode current collector, and drying to obtain a positive electrode plate, wherein the positive electrode coating slurry is formed by mixing a positive electrode active material, a conductive agent, a binder and a solvent.

The first substrate in the embodiment of the present invention is described below.

In the embodiment of the present invention, the first substrate includes a polymer layer, and the polymer layer is formed with a pore canal, and the implementation manner of the pore canal may refer to the description in the foregoing embodiment, which is not repeated herein.

The conductive coating in the embodiment of the present invention is described below.

In the embodiment of the invention, the conductive coating slurry of the conductive coating can be formed by mixing a conductive agent and a solvent. Further, the conductive coating paste may further include, but is not limited to, a binder, a tackifier, a heat stabilizer, a curing agent, a dispersing agent, and a solvent, which are not limited herein. Wherein, by adding a heat stabilizer, the heat stability of the conductive coating can be enhanced.

Wherein, the conductive agent can comprise one or more of carbon black particles, carbon nanotubes, carbon fibers, graphene, carbon nanofibers (Vapor Grown Carbon Fiber, VGCF), conductive glass fibers.

The curing agent may include one or more of isocyanate, methylimidazole, 3 to aminopropylimidazole, 2 to ethyl to 4 to methylimidazole, dimethylaniline, methyltetrahydrophthalic anhydride, dodecylmaleic anhydride, methyltetrahydrophthalic anhydride, toluene diisocyanate, diphenylmethane diisocyanate, phenyl to dimethylurea, 2 monoethylimidazole, 2 monophenyl imidazole, dicyandiamide, triethylamine, 1 to cyanoethyl to 2 to ethyl to 4 to methylimidazole, phthalic anhydride, pyromellitic dianhydride, 308 tung oil anhydride, methyl endo-methyltetrahydrophthalic anhydride, maleic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, metaphenylene diamine, 651 low molecular weight polyamide, T31 phenolic modified amine.

The binder may include one or more of polyvinylidene fluoride, polyvinylidene fluoride to trifluoroethylene, polyvinylidene fluoride to tetrafluoroethylene, polyvinylidene fluoride to hexafluoroethylene, polyvinylidene fluoride to hexafluoropropylene, styrene-acrylic emulsion, polyethyl acrylate, polymethyl methacrylate, polybutyl methacrylate, polyvinyl alcohol, ethylene to vinyl acetate copolymer, polyvinyl acetate, polyurethane.

The tackifier may comprise a resin-based binder including phenolic resin, polyacrylic resin, polyurethane resin, epoxy resin. Wherein the epoxy resin may include any one of the following: bisphenol a glycidyl ether type, bisphenol F type epoxy resin, glycidyl epoxy resin, aliphatic epoxy resin, and aliphatic epoxy resin.

The heat stabilizer may include one or more of 2,6 to t-butyl to 4 to methylphenol, triphenyl phosphite, and trisnonylphenyl phosphite.

The solvent may include one or more of toluene, xylene, methanol, ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone, NMP, and water.

In the embodiment of the invention, the components can be fused according to the preset proportion to obtain the conductive coating slurry. The preset proportion can be 10 to 45 parts of conductive agent, 1 to 5 parts of dispersing agent, 5 to 15 parts of binder, 0.5 to 3 parts of heat stabilizer, 30 to 70 parts of tackifier, 1 to 7 parts of curing agent and 100 parts of solvent. Preferably, the preset proportion may be 10 to 30 parts of conductive agent, 1 to 3 parts of dispersing agent, 5 to 10 parts of binder, 0.5 to 1.5 parts of heat stabilizer, 40 to 55 parts of tackifier, 1 to 4 parts of curing agent and 100 parts of solvent. Preferably, 10 to 30 parts of conductive agent, 1 to 3 parts of dispersing agent, 5 to 10 parts of binder, 0.5 to 1.5 parts of heat stabilizer, 40 to 55 parts of tackifier, 1 to 4 parts of curing agent and 100 parts of solvent.

In particular, the conductive coating paste may be prepared according to the following steps:

1) And adding 50% of solvent into the conductive agent and the dispersing agent, fully stirring, and simultaneously performing ultrasonic dispersion. Then, a binder is added to the above solution to be sufficiently stirred, and simultaneously ultrasonic dispersion is performed. After that, the above solution was heated to 30℃to 60℃to obtain a solution A.

2) Adding tackifier and heat stabilizer into the rest 50% solvent, stirring thoroughly at 60-90 deg.C, and simultaneously performing ultrasonic dispersion. After the components in the solution are uniformly dispersed, the temperature of the solution is reduced to 30-60 ℃ to obtain the solution B.

3) And adding the solution A into the solution B, fully stirring, and simultaneously performing ultrasonic dispersion. Throughout the process, the temperature was maintained at 30 ℃ to 60 ℃ to obtain a C solution.

4) And adding a curing agent into the solution C, and then fully stirring to obtain the conductive coating slurry.

In specific implementation, the positive electrode current collector may be prepared according to the following steps:

the positive electrode current collector is prepared by first coating the conductive coating paste on opposite sides of the polymer layer using an extrusion coater, which may have a thickness of 1 to 10 μm, preferably 1 to 5 μm, and then drying at 70 deg.c for 0.5 to 3 hours.

The positive electrode coating in the embodiment of the present invention is described below.

In the embodiment of the invention, the positive electrode coating slurry of the positive electrode coating can be formed by mixing a positive electrode active material, a conductive agent, a binder and a solvent. The positive electrode active material may be lithium cobaltate, and the conductive agent, the binder and the solvent may be determined with reference to the above description of the conductive agent, the binder and the solvent, and will not be described herein. Preferably, the conductive agent may be conductive carbon nanotubes, the binder polyvinylidene fluoride, and the solvent may be an N-methylpyrrolidone NMP solvent.

In specific implementation, the positive electrode sheet may be prepared according to the following steps:

1) Lithium cobaltate is used as an anode active material, conductive carbon nano-tubes are used as a conductive agent, polyvinylidene fluoride is used as an adhesive, the conductive carbon nano-tubes are added into a stirring tank according to the mass ratio of 97.2:1.5:1.3, then N-methylpyrrolidone (NMP) solvent is added, the mixture is fully stirred according to a batching process in the prior art, and the mixture is filtered through a 200-mesh screen to prepare anode slurry, wherein the solid content of the anode slurry is 70-75%.

2) The slurry was coated onto the positive electrode current collector using a coater. And then drying at 120 ℃ to obtain the positive plate.

The preparation method of the positive plate provided by the embodiment of the invention is different from the positive current collector taking aluminum foil as the positive plate in the prior art, wherein the polymer layer coated with the conductive coating is taken as the positive current collector of the positive plate, and then the positive current collector is coated with positive coating slurry to prepare the positive plate. The conductivity between the positive electrode particles in the positive electrode coating can be ensured through the conductive coating, and the contact between the aluminum foil and the negative electrode active material can be effectively avoided due to the reduction of the use of the aluminum foil, so that the risk of internal short circuit is reduced.

Optionally, the forming the first substrate includes:

forming a polymer layer;

coating ceramic coating slurry on two opposite sides of the polymer layer and drying to obtain the first substrate, wherein the ceramic coating slurry is formed by mixing ceramic and a solvent;

the conductive coating slurry is coated on two opposite side surfaces of the first substrate and dried to obtain a positive current collector, which comprises the following components:

and coating the conductive coating slurry on the side surface of the ceramic coating, which is opposite to the polymer layer, and drying to obtain the positive electrode current collector.

In this embodiment, in the preparation of the positive electrode current collector, a layer of ceramic coating slurry may be coated on two opposite sides of the polymer layer, and the ceramic coating may be formed after drying. The existence of the ceramic coating can effectively increase the heat shrinkage resistance of the polymer layer and prevent the polymer layer from thermal shrinkage during the high-temperature baking process. And then coating the conductive coating slurry on the ceramic coating to obtain the positive electrode current collector.

The ceramic coating in the embodiments of the present invention is described below.

In the embodiment of the invention, the ceramic coating slurry of the ceramic coating can be formed by mixing ceramic particles, a binder, a thickener, a dispersing agent and the like with a solvent. Wherein the ceramic particles may comprise one or more of alumina, magnesia, silica, titania, zirconia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, or calcium carbonate. The median diameter D50 of the ceramic particles may be from 0.1 μm to 11 μm, preferably from 0.5 μm to 3 μm.

The binder may include one or more selected from styrene-butadiene rubber, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, styrene-acrylic emulsion, polyethyl acrylate, polymethyl methacrylate, polybutyl methacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane.

The dispersant may include one or more of fluoroalkyl methoxyl alcohol ether, polyoxyethylene alkylamine, sodium butylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate, sodium alkyl sulfate, sodium polyacrylate, sodium polymetaphosphate, sodium silicate, and sodium dodecyl sulfate.

The thickener may be sodium carboxymethyl cellulose and/or lithium carboxymethyl cellulose.

In concrete implementation, a certain amount of deionized water can be taken, a certain amount of dispersing agent is added, and a certain amount of ceramic particles are added at the same time to prepare ceramic-containing slurry, wherein the mass ratio of the dispersing agent can be 0.2-10%, and the mass ratio of the ceramic particles can be 30-70%; then, 1 to 10% by mass of a binder and 1 to 10% by mass of a thickener are added to the ceramic-containing slurry to obtain a ceramic slurry having a solid content of 32.2 to 60%.

Thereafter, the positive electrode current collector may be prepared as follows:

1) The ceramic coating paste is first coated on opposite sides of the polymer layer using an extrusion coater, and the coating thickness may be 1 to 10 μm, preferably 1 to 5 μm, and dried.

2) The conductive coating slurry is coated on the surface of the ceramic coating layer to a thickness of 1 to 10 μm, preferably 1 to 5 μm, and then dried at 70 deg.c for 0.5 to 3 hours, thereby preparing the positive electrode current collector.

The following describes 5 specific examples of the present invention and 1 comparative example:

Example 1

And step one, preparing ceramic coating slurry.

Specifically, a certain amount of deionized water is taken, a certain amount of sodium polyacrylate is added as a dispersing agent, and the dispersing agent accounts for 1% of the mass. Meanwhile, a certain amount of ceramic (alumina) is added, the ceramic accounts for 45% of the mass, and the slurry containing the ceramic is prepared. Then, polyvinylidene fluoride of 5% by mass as a binder and sodium methylcellulose of 8% by mass as a thickener were added to the above ceramic-containing slurry to obtain a ceramic coating slurry having a solid content of 59%.

And step two, preparing conductive coating slurry.

Specifically, the components are respectively weighed according to a preset proportion for later use, wherein the proportion is 30 parts of conductive agent (carbon nano tube), 1.5 parts of dispersing agent (sodium polyacrylate), 5 parts of binder (acrylic emulsion), 1 part of heat-stable (2, 6-tertiary butyl-4-methylphenol) agent, 50 parts of tackifier (polyacrylic resin), 1 part of curing agent (diphenylmethane diisocyanate) and 100 parts of solvent (acetone).

1) And adding 50% of solvent into the conductive agent and the dispersing agent, fully stirring, and simultaneously performing ultrasonic dispersion. Then, a binder is added to the above solution to be sufficiently stirred, and simultaneously ultrasonic dispersion is performed. After that, the above solution was heated to 45℃to obtain a solution A.

2) Adding tackifier and heat stabilizer into the rest 50% solvent, stirring thoroughly at 80deg.C, and simultaneously performing ultrasonic dispersion. After the components in the solution are uniformly dispersed, the temperature of the solution is reduced to 45 ℃ to obtain the solution B.

3) And adding the solution A into the solution B, fully stirring, and simultaneously performing ultrasonic dispersion. Throughout the process, the temperature was maintained at 45 ℃ to give a C solution.

4) And adding a curing agent into the solution C, and then fully stirring to obtain the conductive coating slurry. The conductive coating paste had a viscosity of 4700cps at 25 ℃ and a solid content of 47.3%.

And step three, preparing the positive current collector.

Specifically, the ceramic coating slurry prepared in the first step is coated on two opposite sides of a polyethylene single-layer base film (with the thickness of 5 μm) with the coating thickness of 1 μm by using an extrusion coater, and dried. And then, coating the conductive coating slurry prepared in the second step on the surface of the ceramic coating, wherein the coating thickness is 1 mu m. Finally, drying at 70 ℃ for 0.5 to 3 hours to prepare the positive electrode current collector.

And step four, preparing anode coating slurry.

Specifically, lithium cobaltate is used as an anode active material, conductive carbon nano-tubes are used as a conductive agent, polyvinylidene fluoride is used as a binder, the conductive carbon nano-tubes are added into a stirring tank according to the mass ratio of 97.2:1.5:1.3, N-methylpyrrolidone (NMP) solvent is added, the mixture is fully stirred according to a batching process in the prior art, and the mixture is filtered through a 200-mesh screen to prepare anode slurry, wherein the solid content of the anode slurry is 70-75%.

And fifthly, preparing the positive plate.

Specifically, the positive electrode coating slurry prepared in the fourth step is coated on the positive electrode current collector prepared in the third step by using a coating machine. And then drying at 120 ℃ to obtain the positive plate. For the positive plate of the monopole ear, as shown in fig. 1, the left side edge of the positive electrode coating of the upper side surface of the positive plate of the monopole ear, the left side edge of the positive electrode current collector and the left side edge of the positive electrode coating of the lower side surface are flush, and the positive electrode coating of the upper side surface is longer than the positive electrode coating of the lower side surface, a part of the adhesive paper is attached to the positive electrode current collector, and the length of the adhesive paper is as follows: the length of the positive electrode coating of the upper side surface-the length of the positive electrode coating of the lower side surface +7mm, and the left end of the gummed paper covers the positive electrode coating of the lower side surface for 2mm, and the right end exceeds the positive electrode coating of the upper side surface for 5mm. For the bipolar ear positive plate, as shown in fig. 4, an empty foil area is arranged on the left side of the bipolar ear positive plate, the empty foil area can be used for arranging the positive electrode ear, and the length of the empty foil area in the horizontal direction is 8mm. The left edge of the positive electrode coating of the upper side is flush with the left edge of the positive electrode coating of the lower side, and the positive electrode coating of the upper side is longer than the positive electrode coating of the lower side. The adhesive tape is partially attached to the anode coating on the lower side surface, and partially attached to the anode current collector, and the length of the adhesive tape is as follows: the length of the positive electrode coating of the upper side surface-the length of the positive electrode coating of the lower side surface +7mm, and the left end of the gummed paper covers the positive electrode coating of the lower side surface for 2mm, and the right end exceeds the positive electrode coating of the upper side surface for 5mm.

And step six, preparing negative electrode coating slurry.

Specifically, artificial graphite is used as a negative electrode active material, conductive carbon black is used as a conductive agent, styrene-butadiene rubber is used as a binder and sodium carboxymethylcellulose is used as a thickener, the materials are added into a stirring tank according to the mass ratio of 96.9:1.5:1.3:13, deionized water solvent is added, the materials are fully stirred according to the batching process in the prior art, and the materials are filtered through a 150-mesh screen, so that negative electrode coating slurry is prepared, and the solid content of the negative electrode slurry is 40-45%.

Step seven, preparing a negative plate

And D, coating the slurry on the copper foil by using a coating machine, and drying at the temperature of 100 ℃ to obtain the negative electrode plate. An empty foil area is arranged on the left side of the negative plate, and the empty foil area can be used for arranging a negative electrode lug. The length of the empty foil area in the horizontal direction is 8mm. At the rightward extending end of the negative electrode sheet, a single-sided paste-coated region having a lower side coated with a negative electrode coating and an upper side not coated with a negative electrode coating, the length of the single-sided paste-coated region in the horizontal direction being 5mm, was first provided, followed by a double-sided paste-coated region having both the upper and lower sides coated with a negative electrode coating.

And step eight, assembling the battery.

For a single positive tab battery, the assembly steps are as follows:

1) The metal shell of the cylindrical battery is taken, the conductive coating slurry is uniformly coated in the metal shell, and the metal shell is dried for 0.5 to 3 hours at 70 ℃.

2) And (3) winding the positive electrode sheet prepared in the step (V) and the negative electrode sheet prepared in the step (seventh) together with the diaphragm to form a winding cell. As shown in fig. 3, the outermost side of the winding cell is the positive current collector at the tail of the positive plate, and the positive current collector is wound around the periphery of the winding cell for one and a half turns. After winding is completed, the portion of the positive current collector may be folded back a portion.

3) The winding electric core is turned into the cylindrical battery metal shell, so that the outer ring of the winding electric core is tightly contacted with the inner wall of the metal shell, and the bent part is tightly contacted with the inner wall of the metal shell, so that the conductivity of the cylindrical battery metal shell is ensured.

4) And welding the negative electrode lug of the negative electrode plate with the bottom cover to serve as the negative electrode lug of the battery. And an insulating pad is arranged in the bottom cover to ensure insulation between the bottom cover and the cylindrical battery metal shell, and electrolyte is injected after baking to remove moisture. The electrolyte can be prepared according to the following steps: and adding lithium hexafluorophosphate LiPF6 into a solvent formed by mixing propylene carbonate PC, ethylene carbonate EC, dimethyl carbonate DMC and ethylmethyl carbonate EMC according to the weight ratio of about 1:1:0.5:1, and uniformly mixing, wherein the concentration of the lithium hexafluorophosphate LiPF6 is about 1mol/L, so that an electrolyte can be obtained after uniformly mixing.

5) The top cover and the cylindrical battery metal shell are directly welded together to serve as an anode, so that the battery provided by the embodiment of the invention is assembled.

For a double positive ear cell, the assembly steps are as follows:

2) And (3) winding the positive electrode sheet prepared in the step (V) and the negative electrode sheet prepared in the step (seventh) together with the diaphragm to form a winding cell. As shown in fig. 7, the outermost side of the winding cell is the positive current collector at the tail of the positive plate, and this part of positive current collector is wound around the periphery of the winding cell by one and a half turns. After winding is completed, the portion of the positive current collector may be folded back a portion.

3) And rotating the winding electric core into the cylindrical battery metal shell so that the outer ring of the winding electric core is tightly contacted with the inner wall of the metal shell, and tightly contacting the bent part with the inner wall of the metal shell to ensure the conductivity of the winding electric core to be used as a first positive electrode lug.

4) And welding the negative electrode lug of the negative electrode plate with the bottom cover to serve as the negative electrode lug of the battery. And an insulating pad is arranged in the bottom cover to ensure insulation between the bottom cover and the cylindrical battery metal shell, and electrolyte is injected after baking to remove moisture. The electrolyte can be prepared according to the following steps: and adding lithium hexafluorophosphate LiPF6 into a solvent formed by mixing propylene carbonate PC, ethylene carbonate EC, dimethyl carbonate DMC and ethylmethyl carbonate EMC according to the weight ratio of about 1:1:0.5:1, and uniformly mixing, wherein the concentration of the lithium hexafluorophosphate LiPF6 is about 1mol/L, so that an electrolyte can be obtained after uniformly mixing. The positive tab is then electrically connected to the top cap as a second positive tab.

5) The top cover and the cylindrical battery metal shell are directly welded together to serve as a total positive lug, and the battery provided by the embodiment of the invention is assembled.

Example 2

Example 2 differs from example 1 in that in step three, the single-layer coating thickness of the ceramic coating layer was controlled to 2 μm, and the single-layer coating thickness of the conductive coating layer was controlled to 1 μm.

Other steps may be referred to in the specific description of embodiment 1, and are not repeated here.

Example 3

Example 3 is different from example 1 in that in step three, the single-layer coating thickness of the ceramic coating layer is controlled to 3 μm and the single-layer coating thickness of the conductive coating layer is controlled to 1 μm.

Example 4

Example 4 differs from example 1 in that in step three, the single-layer coating thickness of the ceramic coating layer was controlled to 2 μm, and the single-layer coating thickness of the conductive coating layer was controlled to 2 μm.

Example 5

Example 5 differs from example 1 in that in step three, the single-layer coating thickness of the ceramic coating layer was controlled to 2 μm and the single-layer coating thickness of the conductive coating layer was controlled to 3 μm.

Comparative example 1

And step one, preparing anode coating slurry and an anode plate.

The positive electrode coating slurry was coated on an aluminum foil substrate using a coater. And then drying at 120 ℃ to obtain the conventional positive plate. In this comparative example, an empty foil region, which can be used to provide a positive electrode tab, was provided on the left side of the conventional positive electrode sheet, and the length of the empty foil region in the horizontal direction was 8mm. The left edge of the positive electrode coating of the upper side is flush with the left edge of the positive electrode coating of the lower side, and the positive electrode coating of the upper side is longer than the positive electrode coating of the lower side. The right extending end of the conventional positive plate is firstly provided with a double-sided paste coating area with the upper side and the lower side coated with positive electrode coating, then a single-sided paste coating area with the upper side coated with positive electrode coating and the lower side not coated with positive electrode coating, and finally an exposed area with both sides not coated with positive electrode coating, wherein the length of the exposed area in the horizontal direction is 12mm.

And step two, preparing negative electrode coating slurry and a negative electrode plate.

Specifically, artificial graphite is used as a negative electrode active material, conductive carbon black is used as a conductive agent, styrene-butadiene rubber is used as a binder and sodium carboxymethylcellulose is used as a thickener, the materials are added into a stirring tank according to the mass ratio of 96.9:1.5:1.3:13, deionized water solvent is added, the materials are fully stirred according to the batching process in the prior art, and the materials are filtered through a 150-mesh screen, so that negative electrode coating slurry is prepared, and the solid content of the negative electrode slurry is 40-45%. And coating the prepared negative electrode coating slurry on a copper foil substrate by using a coating machine, and drying at the temperature of 100 ℃ to obtain a negative electrode plate. In this comparative example, an empty foil region is provided on the left side of the conventional negative electrode sheet, which can be used to provide a negative electrode tab. The length of the empty foil area in the horizontal direction is 8mm. At the rightward extending end of the conventional negative electrode sheet, a single-sided pasted region having a lower side coated with a negative electrode coating and an upper side not coated with a negative electrode coating, the length of the single-sided pasted region in the horizontal direction being 5mm, was first provided, followed by a double-sided pasted region having both the upper and lower sides coated with a negative electrode coating.

And thirdly, assembling the battery.

2) And (3) winding the positive electrode sheet prepared in the first step and the negative electrode sheet prepared in the second step together with the diaphragm to form a winding cell.

3) The winding battery core is turned into the cylindrical battery metal shell, the negative electrode lug of the negative electrode plate is welded with the bottom cover to serve as the negative electrode lug of the battery, an insulating pad is arranged inside the bottom cover to ensure insulation between the bottom cover and the cylindrical battery metal shell, and electrolyte is injected after baking to remove moisture; and welding the positive electrode lug of the positive electrode plate with a top cover of the cylindrical lithium ion battery, wherein an insulating pad is arranged inside the top cover to ensure insulation between the top cover and the metal shell of the cylindrical battery, so that the battery in the comparative example is assembled.

The electrolyte can be prepared according to the following steps: and adding lithium hexafluorophosphate LiPF6 into a solvent formed by mixing propylene carbonate PC, ethylene carbonate EC, dimethyl carbonate DMC and ethylmethyl carbonate EMC according to the weight ratio of about 1:1:0.5:1, and uniformly mixing, wherein the concentration of the lithium hexafluorophosphate LiPF6 is about 1mol/L, so that an electrolyte can be obtained after uniformly mixing.

The batteries of examples 1 to 5 and comparative example 1 described above were subjected to the nail penetration test and the cycle life test, respectively. The penetrating nail testing method comprises the following steps: the battery was charged to a voltage of 4.45V at a constant current of 1C under normal temperature, and then charged at a constant voltage until the current dropped to 0.025C, and the charging was stopped. A steel nail with a diameter of 4mm was used to vertically pass through the center of the cell at a speed of 30mm/s for 300s. If the battery does not fire or explode, it can be noted as passing. 10 lithium ion batteries are tested each time, and the passing rate of the penetrating nail test is used as an index for evaluating the safety of the batteries.

The cycle life test method comprises the following steps: the battery was placed under normal temperature conditions, charged to a voltage of 4.45V at a constant current of 1C, then charged at a constant voltage until the current dropped to 0.05C, and then stopped charging, followed by 1C discharging to 3.0V for cycling.

Finally, the results of the safety test are summarized in tables 1 and 2, table 1 being the test results of the single positive electrode ear cell and table 2 being the test results of the double positive electrode ear cell. Among them, the needling passing rate was higher and substantially all passed in examples 1 to 5, compared to comparative example 1, and the safety performance of the battery was remarkably improved. At the same time, the cycle life is substantially comparable, without attenuation. In addition, the charging speed increases significantly.

Table 1 different examples of single positive ear cell comparative example test results

Sample of	Needling pass rate	1000T capacity retention rate
			Example 1	9/10	84.27％
Example 2	10/10	83.63％
			Example 3	10/10	83.93％
Example 4	9/10	84.37％
			Example 5	10/10	85.72％
Comparative example 1	0/15	85.21％

Table 2 comparative example test results for different examples of double positive ear cell

Sample of	Needling pass rate	Charging speed 100% S0C	1000T capacity retention rate
				Example 1	10/10	87.3min	80.93％
Example 2	9/10	87.9min	80.67％
				Example 3	10/10	88.1min	80.02％
Example 4	10/10	87.3min	81.54％
				Example 5	10/10	86.9min	82.36％
Comparative example 1	0/15	96.2min	80.37％

It should be noted that, the various alternative embodiments described in the embodiments of the present invention may be implemented in combination with each other, or may be implemented separately, which is not limited to the embodiments of the present invention.

In the description of the present invention, it should be understood that the terms "upper," "lower," "left," "right," and the like indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience of description and for simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, as well as a specific orientation configuration and operation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

The embodiments described above are described with reference to the drawings, and other different forms and embodiments are possible without departing from the principle of the invention, and therefore, the invention should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention to those skilled in the art. In the drawings, component dimensions and relative dimensions may be exaggerated for clarity. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms "comprises," "comprising," and/or "includes," when used in this specification, specify the presence of stated features, integers, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, components, and/or groups thereof. Unless otherwise indicated, a range of values includes the upper and lower limits of the range and any subranges therebetween.

While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and changes can be made without departing from the principles of the present invention, and such modifications and changes are intended to be within the scope of the present invention.

Claims

1. A battery comprising a positive plate, wherein the positive plate comprises a positive current collector and a positive coating, the positive current collector comprises a first substrate and a conductive coating, the conductive coating is arranged on two opposite sides of the first substrate, and the first substrate comprises a polymer layer; the positive electrode current collector comprises a first side surface and a second side surface which are opposite to each other, and at least one of the first side surface and the second side surface is provided with the positive electrode coating;

the positive electrode current collector comprises a first end and a second end which are opposite, the positive electrode coating of the first side comprises a first edge and a second edge which are opposite, the first edge is close to the first end, and the second edge is close to the second end; the positive electrode coating of the second side comprises a third edge and a fourth edge which are opposite, wherein the third edge is close to the first end, and the fourth edge is close to the second end; the first side comprises a first region located between the second edge and the second end, the second side comprises a second region located between the fourth edge and the second end, and the positive electrode coating is not arranged in both the first region and the second region;

The length of the first region is smaller than the length of the second region;

the polymer layer has a pore canal that communicates the first side and the second side of the positive current collector;

the positive plate further comprises adhesive paper, one part of the adhesive paper is attached to the positive electrode coating, the other part of the adhesive paper is attached to the second area, the length of the adhesive paper attached to the second area is larger than or equal to the perimeter of the first winding layer, and the first winding layer is a winding layer where the adhesive paper is located after the positive plate is wound;

the battery cell also comprises a battery cell and a shell, wherein the shell is a conductive shell, and the second area is attached to the inner wall of the shell.

2. The battery of claim 1, wherein the first substrate further comprises a ceramic coating disposed on opposite sides of the polymer layer, the conductive coating disposed on a side of the ceramic coating opposite the polymer layer.

3. The battery of claim 1, wherein the positive electrode coating is disposed on both the first side and the second side.

4. The battery of claim 1, further comprising a positive tab, the first side comprising a third region located between the first edge and the first end, the second side comprising a fourth region located between the third edge and the first end; the third region and the fourth region are not provided with the positive electrode coating, and the positive electrode lug is in contact with the third region and the fourth region.

5. The battery of claim 4, wherein the positive tab comprises a first extension and a second extension, the first extension and the second extension having an included angle of less than 180 °; the first extension part is arranged in one of the third region and the fourth region, the second extension part is arranged in the other of the third region and the fourth region, and the first extension part is electrically connected with the second extension part.

6. The battery according to any one of claims 1-5, wherein the battery cell is disposed in the housing, the battery cell is formed by sequentially laminating and winding a positive electrode sheet and a negative electrode sheet, and a separator sheet is disposed between any adjacent one of the positive electrode sheet and the negative electrode sheet.

7. The battery of claim 6, wherein the positive electrode coating is disposed on both the first side and the second side, the positive electrode current collector including opposing first and second ends; the positive electrode coating of the first side comprises a first edge and a second edge which are opposite, the first edge is close to the first end, the second edge is close to the second end, the first side comprises a first area, and the first area is located between the second edge and the second end; the positive electrode coating of the second side comprises a third edge and a fourth edge which are opposite, the third edge is close to the first end, the fourth edge is close to the second end, the second side comprises a second area, and the second area is located between the fourth edge and the second end; the positive electrode coating is not arranged in the first area and the second area.

8. The battery of claim 7, wherein the second end is bent in a first direction to form a bent portion, the first direction being opposite to a winding direction of the cell, the bent portion including first and second opposite sub-regions, the first region including the first sub-region and the second region including the second sub-region, the first sub-region being in contact with an inner wall of the housing.