CN115411225A - Winding type positive plate and secondary battery - Google Patents

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a winding type positive plate and a secondary battery. The safety coating is arranged between the positive current collector and the positive active material layer, the adhesive force of the safety coating is large, so that the positive current collector and the safety coating are firmly adhered, the positive current collector is prevented from contacting with the negative active material layer when the mechanical abuse safety test is performed on the battery cell, the mechanical abuse safety of the battery cell is improved, meanwhile, the diaphragm resistance of the positive pole piece is increased by the safety coating, the short-circuit current in the mechanical abuse safety test process is reduced, and the safety performance of the battery cell is improved.

Description

A wound positive electrode sheet and secondary battery

technical field

The invention belongs to the technical field of secondary batteries, and in particular relates to a wound positive electrode sheet and a secondary battery.

Background technique

Lithium-ion batteries are widely used in electric vehicles and other power fields, as well as mobile phones, watches, tablets, Notebook and other consumer fields.

With the gradual development of lithium-ion batteries in fields such as fast charging and high energy density, the safety issues brought about by batteries have gradually become the focus of everyone's attention. Lithium-ion battery mechanical abuse safety tests such as acupuncture, unilateral extrusion, and foreign object extrusion are a direction that everyone is paying attention to.

Lithium-ion batteries will have four total contact short circuits during acupuncture, unilateral extrusion, foreign object extrusion, etc., "positive active material and negative active material", "positive active material and negative current collector", "positive current collector" and negative electrode active material", "positive electrode current collector and negative electrode current collector". Among the four short-circuit modes, the short-circuit mode most prone to thermal runaway is the short-circuit between the positive electrode current collector and the negative electrode active material.

The existing diaphragm and electrolyte have limited ability to improve the safety of the battery cell, and are more used to improve the safety of thermal abuse such as thermal shock. They have no obvious effect on improving the safety of mechanical abuse such as acupuncture, 45° acupuncture, and foreign body extrusion. Therefore, need badly a kind of technical scheme that solves the above problems.

Contents of the invention

The purpose of the present invention is to provide a winding positive electrode sheet in view of the deficiencies of the prior art, a safety coating is provided between the positive electrode current collector and the positive electrode active material layer, and the safety coating has a relatively large adhesive force. The bond between the positive current collector and the safety coating is firm, so that the battery can avoid the contact between the positive current collector and the negative active material layer during the mechanical abuse safety test, and improve the safety of the mechanical abuse of the battery. At the same time, the safety coating increases the safety of the positive electrode The diaphragm resistance of the pole piece reduces the short-circuit current during the mechanical abuse safety test and improves the safety performance of the battery cell.

In order to achieve the above object, the present invention adopts the following technical solutions:

A wound positive electrode sheet, comprising a positive electrode current collector, a safety coating disposed on at least one side of the positive electrode current collector, and a positive active material layer disposed on the side of the safety coating away from the positive electrode current collector, the length of the safety coating being Less than or equal to the length of the positive electrode current collector, the length of the positive electrode active material layer is less than or equal to the length of the safety coating, and the adhesion of the safety coating is greater than the adhesion of the positive electrode active material layer.

Preferably, the thickness of the safety coating is smaller than the thickness of the positive electrode active material layer.

Preferably, the safety coating includes the following raw materials in parts by weight: 80-97 parts of inorganic filler, 1-10 parts of the first conductive agent, and 2-10 parts of the first binder.

Preferably, the inorganic filler includes one or more of alumina, boehmite, magnesia, titania, zirconia, silica and yttrium oxide.

Preferably, the first conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; the first binder is polyvinylidene fluoride, polyurethane, polyacrylic acid One or more combinations of sodium, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylate.

Preferably, the positive electrode active material layer includes the following raw materials in parts by weight: 90-98 parts of positive electrode active material, 1-6 parts of the second conductive agent, and 1-4 parts of the second binder.

Preferably, the positive electrode active material includes one or more combinations of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, and lithium manganate.

Preferably, the first conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; the first binder is polyvinylidene fluoride, polyurethane, polyacrylic acid One or more combinations of sodium, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylate.

Preferably, the resistance value of the safety coating is 0.2-4Ω.

Another object of the present invention is to address the shortcomings of the prior art and provide a secondary battery that can pass mechanical abuse safety tests such as acupuncture, unilateral extrusion, and foreign matter extrusion, and has good safety performance.

In order to achieve the above object, the present invention adopts the following technical solutions:

A secondary battery, comprising, a separator, a negative electrode sheet, an electrolyte and a casing, the separator is used to separate the positive electrode sheet and the negative electrode sheet, and the casing is used to separate the positive electrode sheet, the separator, the negative electrode sheet and the Encapsulated with electrolyte solution, the positive electrode sheet is the above-mentioned wound positive electrode sheet.

Compared with the prior art, the beneficial effect of the present invention is that: the present invention is provided with a safety coating between the positive electrode current collector and the positive electrode active material layer, and the adhesion of the safety coating is relatively large, so that the positive electrode current collector and the safety coating The bonding between the layers is firm, so that the contact between the positive current collector and the negative active material layer is reduced during the mechanical abuse safety test of the battery, and the mechanical abuse safety of the battery is improved. At the same time, the safety coating increases the membrane resistance of the positive pole piece , reduce the short-circuit current during the mechanical abuse safety test, and improve the safety performance of the battery cell.

Description of drawings

FIG. 1 is a schematic structural view of a wound positive electrode sheet according to Example 1 of the present invention.

Fig. 2 is a schematic structural view of a wound positive electrode sheet according to Example 2 of the present invention.

Fig. 3 is a schematic structural view of a wound positive electrode sheet according to Example 3 of the present invention.

FIG. 4 is a schematic structural view of a wound positive electrode sheet according to Example 4 of the present invention.

Fig. 5 is a schematic structural view of a wound positive electrode sheet according to Example 5 of the present invention.

FIG. 6 is a schematic structural view of a wound positive electrode sheet according to Example 6 of the present invention.

Fig. 7 is a schematic structural view of a wound positive electrode sheet according to Example 7 of the present invention.

Fig. 8 is a schematic structural view of a wound positive electrode sheet according to Example 8 of the present invention.

Among them: 1. Positive electrode current collector; 2. Safety coating; 3. Positive electrode active material layer.

Detailed ways

The present invention will be described in further detail below in conjunction with the specific embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

A wound positive electrode sheet, comprising a positive electrode current collector 1, a safety coating 2 disposed on at least one side of the positive electrode current collector 1, and a positive electrode active material layer 3 disposed on the side of the safety coating 2 away from the positive electrode current collector 1, the The length of the safety coating 2 is less than or equal to the length of the positive electrode current collector 1, the length of the positive electrode active material layer 3 is less than or equal to the length of the safety coating 2, and the adhesion of the safety coating 2 is greater than that of the positive electrode active material. Layer 3 adhesion. Preferably, the length of the long film surface of the positive electrode active material layer 3 is smaller than the length of the safety coating 2 on the other side.

In the present invention, a safety coating 2 is provided between the positive current collector 1 and the positive active material layer 3 to increase the sheet resistance of the positive pole piece and reduce the short-circuit current of the battery during the mechanical abuse safety test. Moreover, the safety coating 2 has good adhesion, and can not fall off during the mechanical abuse safety test of the battery, avoiding direct contact between the current collector and the negative electrode active material layer; and improving the mechanical abuse safety performance of the battery.

In some embodiments, the thickness of the safety coating 2 is smaller than the thickness of the positive electrode active material layer 3 . The safety coating 2 has a relatively thin thickness, which can cover the surface of the positive electrode current collector 1, and reduce the risk of a short circuit between the negative electrode and the positive electrode current collector 1 during the mechanical abuse test, thereby increasing the mechanical abuse safety of the battery cell, and at the same time not Occupies too much volume and has little impact on energy density.

In some embodiments, the safety coating 2 includes the following raw materials in parts by weight: 80-97 parts of inorganic filler, 1-10 parts of the first conductive agent, and 2-10 parts of the first binder. The safety coating 2 is provided with inorganic fillers, which increases the resistance of the safety coating 2 and improves the pass rate of the mechanical abuse test, and has more weight parts of the first binder, so that the safety coating 2 has a greater bonding strength. Force, so that the positive electrode current collector 1 and the positive electrode active material layer 3 are firmly bonded, and the electrode sheet has good mechanical properties. Preferably, the safety coating 2 includes the following raw materials in parts by weight: 80-90 parts of inorganic filler, 3-10 parts of the first conductive agent, 5-8 parts of the first binder; 82-90 parts of the inorganic filler, the first 4-10 parts of conductive agent, 5-7 parts of first binder; specifically, 82 parts of inorganic filler, 6 parts of first conductive agent, 8 parts of first binder; 85 parts of inorganic filler, 7 parts of first conductive agent 9 parts, 9 parts of the first binder; 87 parts of inorganic filler, 8 parts of the first conductive agent, 7 parts of the first binder.

In some embodiments, the inorganic filler includes one or more of alumina, boehmite, magnesia, titania, zirconia, silica and yttrium oxide. Inorganic fillers have poor electrical conductivity and are added to the safety coating 2 to make the safety coating 2 have a certain resistance, thereby increasing the resistance value when the contact is short-circuited, reducing the short-circuit current and improving safety performance. Moreover, the inorganic filler is a heat-resistant material, which can increase the heat-resistant performance of the safety coating 2, thereby improving the safety performance. Preferably, the inorganic filler is boehmite.

In some embodiments, the first conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; the first binder is polyvinylidene fluoride, polyurethane , sodium polyacrylate, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylic acid ester or a combination thereof. The first binder can bond the inorganic filler and the first conductive agent to form a safety coating 2, and the first binder can be bonded with the positive electrode current collector 1, and the first binder can also be bonded with the positive active coating Bonding with the second binder in the pole piece, thereby improving the overall firmness of the pole piece. The first conductive agent can improve the electrical conductivity of the safety coating 2, and is helpful for the deintercalation of ions and the conduction of electrons.

In some embodiments, the positive electrode active material layer 3 includes the following raw materials in parts by weight: 90-98 parts of positive electrode active material, 1-6 parts of the second conductive agent, and 1-4 parts of the second binder. Compared with the safety coating 2, the positive electrode active material layer 3 uses a positive electrode active material to replace the inorganic filler, thereby increasing the capacity, and the amount of the second binder in the positive electrode active material layer 3 is less, which helps to improve the removal of ions. Embedded, thereby improving chemical performance.

In some embodiments, the positive electrode active material includes one or more combinations of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, and lithium manganate. The positive electrode active material contains lithium, which can increase the capacity.

In some embodiments, the first conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; the first binder is polyvinylidene fluoride, polyurethane , sodium polyacrylate, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylic acid ester or a combination thereof.

In some embodiments, the resistance of the security coating 2 is 0.2-4Ω.

A secondary battery can pass the mechanical abuse safety test of acupuncture, unilateral extrusion, and foreign body extrusion, and has good safety performance.

A secondary battery, comprising a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte and a casing, the separator is used to separate the positive electrode sheet and the negative electrode sheet, and the casing is used to separate the positive electrode sheet, the separator, the negative electrode sheet Sheet and electrolyte packaging, the positive electrode sheet is the above-mentioned wound positive electrode sheet.

The positive electrode sheet includes a positive electrode current collector 1 and a positive electrode active coating disposed on at least one surface of the positive electrode current collector 1, and the positive electrode current collector 1 is usually a structure or part that collects current, and the positive electrode current collector 1 can be various materials in the art. A material suitable for use as the positive electrode collector 1 of a lithium ion battery, for example, the positive electrode collector 1 may include but not limited to metal foil, and more specifically may include but not limited to aluminum foil.

The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material. , carbon fibers, mesocarbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from one of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys One or more kinds; the tin-based material can be selected from one or more of simple tin, tin oxide compounds, and tin alloys. The negative electrode current collector is usually a structure or part that collects current. The negative electrode current collector can be a variety of materials suitable for use as a lithium ion battery negative electrode collector in the art. For example, the negative electrode current collector can include but is not limited to Metal foil etc., more specifically may include but not limited to copper foil etc. The negative electrode active material layer further includes a binder and a conductive agent, and the binder is polyvinylidene fluoride.

The separator can be a variety of materials suitable for lithium-ion battery separators in the art, for example, it can include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polyethylene One or more combinations of tetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

The material of the housing is one of aluminum-plastic film and stainless steel.

Example 1

(1) Add boehmite, conductive carbon, and polyvinylidene fluoride to the stirring tank in sequence according to the mass ratio of 92:5:3. The viscosity of the slurry after stirring is 1550mpa.s, and the slurry after stirring is passed through the gravure Apply uniform coating on both sides of the positive electrode current collector 1 to obtain a safety coating 2, and at this time, the coating length of the safety coating 2 on both sides is equal to the length of the pole piece, as shown in Figure 1. The thickness of the current collector is 9 μm, the coating surface density is 14 mg/1540.25 mm ² , the measured sheet resistance is 0.8Ω, and the Mohs hardness is 7.

(2) Lithium cobaltate, conductive carbon black, and binder polyvinylidene fluoride are uniformly mixed at a mass ratio of 96:2.5:1.5 to make a lithium-ion battery cathode slurry with a certain viscosity, and the slurry is coated on a On the aluminum foil of the positive electrode current collector 1 of the safety coating 2 , the coating length of the positive electrode active material layers 3 on both sides is shorter than that of the safety coating 2 , as shown in FIG. 1 . That is to make a winding positive electrode sheet, the length of the positive active material layer 3 in the short film side of the winding positive electrode sheet is less than the length of the safety coating 2, and the positive active material layer in the long film surface of the winding positive electrode sheet The length of 3 is less than the length of safety coating 2, and the length of safety coating 2 on both sides is equal to the length of positive electrode current collector 1. At this time, the diaphragm resistance of the positive electrode sheet is 2.0Ω, and the positive electrode sheet is cold pressed; then trimmed, cut into pieces, and slitting, and after slitting, dry at 110°C for 4 hours under vacuum conditions, weld the tabs, and make into a lithium-ion battery positive plate.

(3) Preparation of lithium ion battery:

The above-mentioned positive electrode sheet, diaphragm and negative electrode sheet are wound into a cell, the diaphragm is located between the positive electrode sheet and the negative electrode sheet, the positive electrode is led out by spot welding of aluminum tabs, and the negative electrode is drawn out by spot welding of nickel tabs; then the cell is placed in the aluminum The electrolyte is injected into the plastic packaging bag, and the lithium-ion battery is made into a lithium-ion battery through processes such as packaging, formation, and capacity.

Example 2

The difference from Example 1 is that the length of the positive active material layer 3 on the side of the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the positive active material layer 3 on the long film surface of the wound positive electrode sheet The length of 3 is equal to the length of safety coating 2, and the length of safety coating 2 on both sides is equal to the length of positive current collector 1. Figure 2.

All the other are identical with embodiment 1.

Example 3

The difference from Example 1 is that the length of the positive electrode active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is equal to the length of the positive electrode active material layer 3. The length of the positive active material layer 3 on the long film surface of the paper-type positive electrode sheet is equal to the length of the safety coating 2 , and the length of the safety coating 2 is shorter than the length of the positive current collector 1 . Figure 3.

All the other are identical with embodiment 1.

Example 4

The difference from Example 1 is that the length of the positive active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive active material layer 3; The length of the positive active material layer 3 in the long film surface of the roll-type positive electrode sheet is equal to the length of the safety coating 2, the length of the safety coating 2 is less than the length of the positive current collector 1, and the lengths of the safety coating 2 on both sides are equal . Figure 4.

All the other are identical with embodiment 1.

Example 5

The difference from Example 1 is that the length of the positive active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive active material layer 3; The length of the positive electrode active material layer 3 in the long film surface of the rolled paper type positive electrode sheet is less than the length of the safety coating 2, the length of the safety coating 2 is equal to the length of the positive electrode current collector 1, and the length of the positive electrode active material layer 3 in the long film surface The length is equal to the length of the security coating 2 in the short film face. Figure 5.

All the other are identical with embodiment 1.

Example 6

The difference from Example 1 is that the length of the positive active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive active material layer 3; The length of the positive electrode active material layer 3 in the long film surface of the roll-type positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive electrode current collector 1, and the lengths of the safety coating 2 on both sides are equal . Figure 6.

All the other are identical with embodiment 1.

Example 7

The difference from Example 1 is that the length of the positive active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive active material layer 3; The length of the positive active material layer 3 in the long film surface of the roll-type positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive current collector 1, and the length of the safety coating 2 on the short film surface is less than the length of the safety coating 2. Less than the length of the security coating 2 on the other side. Figure 7.

All the other are identical with embodiment 1.

Example 8

The difference from Example 1 is that the length of the positive active material layer 3 in the short film surface of the wound positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive active material layer 3; The length of the positive active material layer 3 in the long film surface of the roll-type positive electrode sheet is less than the length of the safety coating 2, and the length of the safety coating 2 is less than the length of the positive current collector 1, and the length of the safety coating 2 on the short film surface is less than the length of the safety coating 2. greater than the length of the security coating 2 on the other side. Figure 8.

All the other are identical with embodiment 1.

Example 9

The difference from Example 1 is that the safety coating 2 includes the following raw materials in parts by weight: 90 parts of inorganic filler, 5 parts of first conductive agent, and 5 parts of first binder.

All the other are identical with embodiment 1.

Example 10

The difference from Example 1 is that the safety coating 2 includes the following raw materials in parts by weight: 88 parts of inorganic filler, 8 parts of first conductive agent, and 4 parts of first binder.

All the other are identical with embodiment 1.

Example 11

The difference from Example 1 is that the safety coating 2 includes the following raw materials in parts by weight: 85 parts of inorganic filler, 9 parts of the first conductive agent, and 6 parts of the first binder.

All the other are identical with embodiment 1.

Example 12

The difference from Example 1 is that the safety coating 2 includes the following raw materials in parts by weight: 83 parts of inorganic filler, 9 parts of first conductive agent, and 8 parts of first binder.

All the other are identical with embodiment 1.

Example 13

The difference from Example 1 is that the positive electrode active material layer 3 includes the following raw materials in parts by weight: 95 parts of positive electrode active material, 3 parts of the second conductive agent, and 2 parts of the second binder.

All the other are identical with embodiment 1.

Example 14

The difference from Example 1 is that the positive electrode active material layer 3 includes the following raw materials in parts by weight: 96 parts of positive electrode active material, 3 parts of the second conductive agent, and 1 part of the second binder.

All the other are identical with embodiment 1.

Example 15

The difference from Example 1 is that the positive electrode active material layer 3 includes the following raw materials in parts by weight: 98 parts of positive electrode active material, 1 part of the second conductive agent, and 1 part of the second binder.

All the other are identical with embodiment 1.

Example 16

The difference from Example 1 is that the positive electrode active material layer 3 includes the following raw materials in parts by weight: 92 parts of positive electrode active material, 5 parts of the second conductive agent, and 3 parts of the second binder.

All the other are identical with embodiment 1.

Example 17

The difference from Example 1 is that the positive electrode active material layer 3 includes the following raw materials in parts by weight: 90 parts of positive electrode active material, 6 parts of the second conductive agent, and 4 parts of the second binder.

All the other are identical with embodiment 1.

Comparative example 1

The difference from Example 1 is that the wound positive electrode sheet does not have a safety coating 2 .

The rest are the same as in Embodiment 1, and will not be repeated here.

The positive electrode sheet and the secondary battery prepared in the above-mentioned Examples 1-17 and Comparative Example 1 were subjected to foreign body extrusion, acupuncture and 45° acupuncture tests, and the test results are recorded in Table 1.

Table 1

It can be concluded from the above Table 1 that the wound positive electrode sheet of the present invention has better mechanical abuse performance and good safety performance than the positive electrode sheet of the prior art. The pass rate of the stress test is over 90%. From the comparison of Example 1 and Comparative Example 1, it can be concluded that the safety coating can significantly improve the foreign body extrusion test of the pole piece. Therefore, the safety coating 2 has a certain mechanical strength, which can improve the impact resistance of the pole piece and avoid In the foreign matter extrusion test, the positive electrode active coating is directly in contact with the positive electrode current collector 1, and at the same time, the safety coating 2 has a strong adhesive force, which can firmly bond the positive electrode active material layer 3 to the positive electrode current collector 1, avoiding Coating peels off during foreign object extrusion testing, improving mechanical abuse performance.

From the comparison of Examples 1 and 9-12, it can be concluded that when the safety coating 2 is set to include the following raw materials in parts by weight: 92 parts of inorganic filler, 5 parts of the first conductive agent, and 5 parts of the first binder, the prepared The secondary battery has better mechanical abuse performance and better safety.

From the comparison of Examples 1 and 13-17, it can be concluded that when the positive electrode active material layer 3 is set to include the following raw materials in parts by weight: 98 parts of the positive electrode active material, 1 part of the second conductive agent, and 1 part of the second binder, it is prepared The secondary battery has better mechanical abuse performance and better safety.

According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also change and modify the above embodiment. Therefore, the present invention is not limited to the above-mentioned specific implementation manners, and any obvious improvement, substitution or modification made by those skilled in the art on the basis of the present invention shall fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

1. A winding positive electrode sheet, characterized in that, comprises a positive electrode current collector, a safety coating arranged on at least one side of the positive electrode current collector and a positive electrode active material layer arranged on the safety coating away from the positive electrode current collector side, The length of the safety coating is less than or equal to the length of the positive electrode current collector, the length of the positive active material layer is less than or equal to the length of the safety coating, and the adhesion of the safety coating is greater than the adhesion of the positive active material layer . 2 . The wound positive electrode sheet according to claim 1 , wherein the thickness of the safety coating layer is smaller than the thickness of the positive electrode active material layer. 3 . 3. The wound positive electrode sheet according to claim 1 or 2, wherein the safety coating comprises the following raw materials in parts by weight: 80-97 parts of inorganic filler, 1-10 parts of the first conductive agent, 2-10 parts of the first binder. 4. The wound positive electrode sheet according to claim 3, wherein the inorganic filler comprises one or more of aluminum oxide, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide and yttrium oxide. Several kinds. 5. The wound positive electrode sheet according to claim 3, wherein the first conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; The first binder is one or more combinations of polyvinylidene fluoride, polyurethane, sodium polyacrylate, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylate. 6. The wound positive electrode sheet according to claim 1 or 2, wherein the positive electrode active material layer comprises the following raw materials in parts by weight: 90 to 98 parts by weight of the positive electrode active material, 1 to 6 parts by weight of the second conductive agent parts, 1 to 4 parts of the second binder. 7. The wound positive electrode sheet according to claim 6, wherein the positive electrode active material comprises one or more combinations of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, and lithium manganate. 8. The wound positive electrode sheet according to claim 6, wherein the second conductive agent is one or more combinations of conductive graphite, conductive carbon black, carbon nanotubes, and carbon nanofibers; The second binder is one or more combinations of polyvinylidene fluoride, polyurethane, sodium polyacrylate, styrene-butadiene rubber, sodium carboxymethyl cellulose, and acrylate. 9 . The wound positive electrode sheet according to claim 1 , wherein the safety coating has a resistance value of 0.2-4Ω. 10. A secondary battery, characterized in that, comprises a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte and a casing, the separator is used to separate the positive electrode sheet and the negative electrode sheet, and the casing is used to separate the positive electrode sheet sheet, separator, negative electrode sheet and electrolyte package, and the positive electrode sheet is the wound positive electrode sheet described in any one of claims 1-9.

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