阅读说明：本技术 一种高能量高安全性能锂离子电池 (High-energy high-safety lithium ion battery ) 是由 王永琛 朱华君 程凯 *** 于 2019-11-13 设计创作，主要内容包括：本发明公开了一种高能量高安全性能锂离子电池,包括负极片、隔膜、正极片叠片或卷绕而成的电芯,其中正极片中含有正极集流体、正极活性材料、正极导电剂、正极粘结剂与正极添加剂；负极片中含有负极集流体、负极活性物质、负极导电剂、负极粘结剂与负极添加剂；其特征在于：正极集流体表面两侧涂覆层为PTC材料、铝粉和碳纳米管；正极添加剂为PTC材料、铝粉和石墨烯组成的混合体；正极片表面两侧涂覆层为PTC材料和石墨烯；负极集流体表面两侧涂覆层为PTC材料、铜粉和碳纳米管；负极添加剂为PTC材料、铜粉和石墨烯组成的混合体；负极片表面两侧涂覆层为PTC材料和石墨烯。本发明获得了高安全性能,保证安全的同时提高了电池的能量密度,提高了电池的电学性能并提高了生产制程过程水平。(The invention discloses a high-energy high-safety lithium ion battery, which comprises a negative plate, a diaphragm, a positive plate lamination or a winding battery core, wherein the positive plate contains a positive current collector, a positive active material, a positive conductive agent, a positive binder and a positive additive; the negative plate contains a negative current collector, a negative active substance, a negative conductive agent, a negative binder and a negative additive; the method is characterized in that: the coating layers on the two sides of the surface of the positive current collector are made of PTC materials, aluminum powder and carbon nano tubes; the positive electrode additive is a mixture consisting of a PTC material, aluminum powder and graphene; the coating layers on the two sides of the surface of the positive plate are made of PTC materials and graphene; the coating layers on the two sides of the surface of the negative current collector are made of PTC materials, copper powder and carbon nanotubes; the negative electrode additive is a mixture consisting of a PTC material, copper powder and graphene; the coating layers on the two sides of the surface of the negative plate are made of PTC materials and graphene. The invention has high safety performance, improves the energy density of the battery while ensuring the safety, improves the electrical performance of the battery and improves the production process level.)

1. A high-energy high-safety lithium ion battery comprises a battery cell formed by laminating or winding a negative plate, a diaphragm and a positive plate; the method is characterized in that: the positive plate is composed of a positive current collector foil in the center, a positive current collector coating, a positive slurry coating and a positive plate surface coating, wherein the positive current collector coating, the positive slurry coating and the positive plate surface coating are sequentially arranged on two sides of the positive current collector foil;

the negative pole piece comprises the negative pole mass flow body paper tinsel of negative pole by central authorities, the negative pole mass flow body coating, negative pole slurry coating and the negative pole piece surface coating that set gradually that are located negative pole mass flow body paper tinsel both sides, the negative pole mass flow body coating comprises PTC material, copper powder and carbon nanotube, and negative pole slurry coating comprises negative pole active material, negative pole conductive agent, negative pole binder and negative pole additive, the negative pole additive is the mixture that PTC material, copper powder and graphite alkene constitute, negative pole piece surface coating is PTC material and graphite alkene.

2. The high energy high safety performance lithium ion battery of claim 1, wherein: the weight ratio of the PTC material, the aluminum powder and the carbon nano tubes in the positive current collector coating is (990-995) to 1 to (4-9), and the weight ratio of the PTC material, the copper powder and the carbon nano tubes in the negative current collector coating is (990-995) to 1 to (4-9).

3. The high energy high safety performance lithium ion battery of claim 1, wherein: the weight ratio of the PTC material, the aluminum powder and the graphene in the positive electrode additive is (990-995) to 1 to (4-9), and the weight ratio of the PTC material, the copper powder and the graphene in the negative electrode additive is (990-995) to 1 to (4-9).

4. The high energy high safety performance lithium ion battery of claim 1, wherein: in the positive plate surface coating and the negative plate surface coating, the weight ratio of the PTC material to the graphene is (991-996) to (4-9).

5. The high energy high safety performance lithium ion battery of claim 1, wherein: the particle size D50 of the PTC materials in the positive electrode current collector coating, the positive electrode plate surface coating, the negative electrode current collector coating and the negative electrode plate surface coating is less than or equal to 0.1 mu m, and the particle size D50 of the PTC materials in the positive electrode additive and the negative electrode additive is 1-20 mu m; the PTC material is one or more of niobium titanate, tantalum titanate, strontium titanate, barium titanate and lead titanate which are doped or not doped with one or more elements of niobium, tantalum, strontium, barium and lead.

6. The high energy high safety performance lithium ion battery of claim 1, wherein: the particle size D50 of the aluminum powder is 40 +/-2 nm, and the particle size D50 of the copper powder is 40 +/-2 nm.

7. The high energy high safety performance lithium ion battery of claim 1, wherein: in the positive electrode coating, the mass of the positive electrode additive accounts for 0.5-1% of the total mass of the positive electrode coating, and in the negative electrode coating, the mass of the negative electrode additive accounts for 0.5-1% of the total mass of the negative electrode coating.

8. The high energy high safety performance lithium ion battery of claim 1, wherein: the thickness of the single-side coating of the positive current collector coating is 0.5-1 mu m; the single-side coating thickness of the negative current collector coating is 0.5-1 mu m; the thickness of the single-side coating of the surface coating of the positive plate is 0.1-0.2 mu m; the single-side coating thickness of the surface coating of the negative plate is 0.1-0.2 mu m.

9. The high energy high safety performance lithium ion battery of claim 1, wherein: the number of graphene layers is 1-15, 6-10 layers of additive graphene are preferred, and 10-15 layers of coating layer graphene are preferred.

10. The high energy high safety performance lithium ion battery of claim 1, wherein: the length and the width of the positive current collector coating are respectively smaller than those of the positive current collector foil and are respectively larger than those of the positive slurry coating so as to completely separate the positive current collector foil from the positive slurry coating; the length and width of the negative current collector coating are respectively less than the length and width of the negative current collector foil, and simultaneously are respectively greater than the length and width of the negative slurry coating so as to completely separate the negative current collector foil and the negative slurry coating.

Technical Field

The invention relates to a lithium ion battery, in particular to a lithium ion battery with high energy density and high safety performance.

Background

In the process of replacing the traditional fuel vehicle by the electric vehicle, the lithium ion battery plays an important role. The battery is used as one of three electric systems of the electric automobile, and the endurance mileage and the safety of the electric automobile are restricted. The occupation ratio of the new energy automobile in the automobile is very small at present, and the reasons are mainly that the number of charging piles is small, and the anxiety and the safety of a consumer on the endurance mileage are high. With the increasing sophistication of charging station charging piles and other infrastructure, charging difficulties have been addressed from a hardware standpoint. In order to improve the endurance mileage of the electric vehicle in the early days, the state subsidies the battery system with high energy density from the administrative aspect, and with the improvement of the energy density of the battery cell, the endurance mileage of the new energy vehicle is finally increased from one or two hundred kilometers to more than three or four hundred kilometers. However, some battery enterprises pursue energy density excessively, neglect battery safety, and cause fire accidents of some electric vehicles, which deserves deep thinking and training.

High energy density materials such as high nickel ternary have a lower thermal decomposition temperature than low nickel ternary, and therefore are less safe. As such, many enterprises that mass-produce 811 and NCA system batteries put their products on the market in 2018 of the original plan are delayed. With the exit of the national subsidies, the consumer market and battery technology will return to rationality. Therefore, the high-energy high-safety lithium ion battery is more and more emphasized, the endurance mileage of the electric automobile is ensured by the high energy density, and the high safety is the bottom line of the product.

The currently accepted mainstream technical route in the industry is to use a high nickel ternary material system to improve the energy density of the battery. The increase in nickel content in the ternary can increase the charge gram capacity of the material, meaning that higher energy densities can be achieved, but the safety performance will also decrease. It is a difficult and significant mission for battery developers to increase energy density while simultaneously maintaining safety.

The invention of Chinese patent application CN104425795B discloses a high-energy high-safety lithium ion power battery, wherein two sides of a battery core are respectively provided with a puncture-proof safety structure, the puncture-proof safety structure is formed by sequentially overlapping a PET plate, an aluminum foil, the PET plate, a copper foil and the PET plate from outside to inside, the aluminum foil is connected with an anode leading-out end through an anode lug, and the copper foil is connected with a cathode leading-out end through a cathode lug. According to the invention, the copper aluminum foils are additionally arranged outside the battery cell, and the PET plate structure is arranged between the copper aluminum foils, so that the battery cell has a needling prevention function. In practice, however, PET has electrical insulation and cannot be contained in the cell, so that this invention is to use PET outside the cell. Strictly speaking, the scheme belongs to a battery core-module workshop section and does not belong to the internal scope of the battery core, and the added structure and the battery core do not have integrity, so that the result of testing the single battery core according to the national standard is disputed. In addition, the energy density of the cell is only 200Wh/kg due to the increased copper-aluminum foil, and the energy density of the soft package cell in commercial mass production at present reaches 280-300 Wh/kg.

Chinese patent application CN108511761A discloses a current collector containing a PTC coating, which utilizes the temperature effect of a PTC material with positive temperature coefficient to increase the internal resistance when the temperature rises, thereby improving the needling safety performance of the battery. But the thickness of the coating is 1-10 μm, which reaches or exceeds the thickness of the current collector, and limits the improvement of the energy density of the battery.

Disclosure of Invention

The invention aims to provide a high-energy high-safety lithium ion battery, so that the obtained lithium ion battery can have both high energy density and high safety performance.

In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: a high-energy high-safety lithium ion battery comprises a battery cell formed by laminating or winding a negative plate, a diaphragm and a positive plate; the positive plate is composed of a positive current collector foil in the center, a positive current collector coating, a positive slurry coating and a positive plate surface coating, wherein the positive current collector coating, the positive slurry coating and the positive plate surface coating are sequentially arranged on two sides of the positive current collector foil;

the negative pole piece comprises the negative pole mass flow body paper tinsel of negative pole by central authorities, the negative pole mass flow body coating, negative pole slurry coating and the negative pole piece surface coating that set gradually that are located negative pole mass flow body paper tinsel both sides, the negative pole mass flow body coating comprises PTC material, copper powder and carbon nanotube, and negative pole slurry coating comprises negative pole active material, negative pole conductive agent, negative pole binder and negative pole additive, the negative pole additive is the mixture that PTC material, copper powder and graphite alkene constitute, negative pole piece surface coating is PTC material and graphite alkene.

In the technical scheme, the surface of the positive current collector foil is provided with a positive current collector coating, a positive active material, a positive conductive agent, a positive binder and a positive additive are mixed and then coated on the surface of the positive current collector coating, and PTC and graphene mixed material coatings are coated on two sides of the surface to finally form a positive plate; and the negative active material, the negative conductive agent, the negative binder and the negative additive are mixed and then coated on the surface of the negative current collector, and PTC and graphene mixed material coatings are coated on two sides to finally form the negative plate. The positive plate and the negative plate are coated, dried and pressed by a conventional method.

According to the technical scheme, the anti-needling safety performance of the battery is ensured by coating the PTC on the surface of the current collector, doping the PTC in the active material and coating the PTC on the surface of the pole piece. The PTC material, the aluminum powder (the negative electrode is copper powder) and the carbon nano tube are coated on the surface of the current collector, the coating has the anti-needling safety performance, the anti-peeling strength of the outer active substance coating can be improved, the direct contact between the electrolyte and the current collector is reduced, the electrolyte corrosion resistance of the current collector is improved, the tensile strength and the elongation percentage of the current collector are improved, the band breakage frequency of rolling after coating is reduced, the yield is improved, the internal resistance is reduced, and the cycle performance and the rate capability of the battery are improved. The positive and negative internal additive PTC material, the aluminum powder (the negative electrode is copper powder) and the graphene form a mixture, the additive has the anti-needling safety performance, and also has the functions of reducing the risk of internal short circuit caused by lithium precipitation inside the pole piece, improving the liquid retention capacity of electrolyte inside the pole piece and further improving the cycle performance, the electronic conductivity is improved by the aluminum powder and the copper powder, and the ion conductivity of the stored graphene is improved, so that the multiplying power performance of the battery is finally improved. PTC materials and graphene coatings on two sides of the surface of the pole piece have the anti-needling safety performance, and the graphene also has the liquid retention performance, so that the cycle performance of the battery is improved. Because the existence of the current collector surface coating improves the tensile strength and the elongation percentage of the current collector, a thinner current collector can be used, thereby improving the energy density of the battery.

According to the preferable technical scheme, the weight ratio of the PTC material to the aluminum powder to the carbon nano tubes in the positive current collector coating layers on the two sides of the surface of the positive current collector is (990-995) to 1 to (4-9), and the weight ratio of the PTC material to the copper powder to the carbon nano tubes in the negative current collector coating layers on the two sides of the surface of the negative current collector is (990-995) to 1 to (4-9).

The weight ratio of the PTC material, the aluminum powder and the graphene in the positive electrode additive is (990-995) to 1 to (4-9), and the weight ratio of the PTC material, the copper powder and the graphene in the negative electrode additive is (990-995) to 1 to (4-9).

The weight ratio of the PTC materials to the graphene on the coating layers on the surface of the positive plate and the surface of the negative plate is (991-996) to (4-9).

In the technical scheme, the particle size D50 of the coating layer PTC material is less than or equal to 0.1 mu m, the particle size D50 of the additive PTC material is 1-20 mu m, and the PTC material is one or more of niobium titanate, tantalum titanate, strontium titanate, barium titanate and lead titanate which are doped or undoped with one or more elements of niobium, tantalum, strontium titanate, barium titanate and lead titanate.

The particle size D50 of the aluminum powder in the positive electrode and the copper powder in the negative electrode is 40 +/-2 nm, and is consistent with the D50 of common conductive graphite.

The total mass of the positive electrode additive PTC material, the aluminum powder and the graphene accounts for 0.5-1% of the total mass of the positive electrode material, and the total mass of the negative electrode additive PTC material, the copper powder and the graphene accounts for 0.5-1% of the total mass of the negative electrode material. Too low an additive does not guarantee the safety against needle-punching, while more additive will be excessive and will reduce the effective active substance mass and thus affect the energy density.

The thickness of the single-side coating layers on the surfaces of the positive electrode current collector and the negative electrode current collector is 0.5-1 mu m. Thinner coatings do not guarantee a needle-punching resistance and impose too high a demand on the coating machine, whereas thicker coatings are superfluous and take up space dimensions and thus affect the energy density.

The thickness of the single-sided coating layers on the two sides of the surfaces of the positive and negative pole pieces is 0.1-0.2 mu m. Thinner coatings do not guarantee a needle-punching resistance and impose too high a demand on the coating machine, whereas thicker coatings are superfluous and take up space dimensions and thus affect the energy density.

The number of graphene layers is 1-15, 6-10 layers of additive graphene are preferred, and 10-15 layers of coating layer graphene are preferred. The price of 1-5 layers of graphene is high, the price of the multilayer graphene is relatively reasonable, but the conductivity of the excessive layers of graphene is poor, and the liquid storage capacity is weak.

The length and the width of the surface coating of the current collector are both smaller than those of the inner current collector, and are both larger than those of the coating of outer slurry (active material, conductive agent, binder and additive). The formation of burrs during slicing is reduced, the short circuit rate of the battery is finally reduced, the self-discharge is reduced, and the consistency is improved.

In the above technical solution, the positive electrode conductive agent and the negative electrode conductive agent are preferably one or more of conductive carbon black, conductive graphite and conductive carbon tubes. The positive electrode binder is preferably polyvinylidene fluoride (PVDF), and the negative electrode binder is preferably acrylonitrile multipolymer. The anode active substance is preferably ternary material, the thickness of the anode aluminum foil is less than or equal to 15 μm, the thickness of the cathode copper foil is less than or equal to 8 μm, and the thickness of the diaphragm is less than or equal to 18 μm.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

1. in the aspect of safety, the PTC-containing material is coated and doped in the invention, so that the anti-needling safety performance of the battery is ensured, and the risk of internal short circuit caused by internal lithium precipitation is reduced.

2. In the aspect of energy density, due to the existence of the surface coating of the current collector, the tensile strength and the elongation percentage of the current collector are improved, so that an aluminum foil below 12 micrometers and a copper foil below 6 micrometers can be used, the self weight of the current collector is reduced, and meanwhile, a space is vacated for the interior of a battery core, so that the energy density of the battery is further improved.

3. In the aspect of performance, the invention reduces the internal resistance of the battery, improves the multiplying power performance of the battery and increases the cycle performance.

4. In other aspects, the invention improves the yield of the production process, and mainly reduces the broken strip of the current collector and the short circuit rate and self-discharge caused by the cutting burr.

Drawings

FIG. 1 is a schematic cross-sectional view of a positive plate;

FIG. 2 is a schematic structural diagram of a mixture in the positive electrode additive;

FIG. 3 is a schematic cross-sectional view of a negative plate;

fig. 4 is a schematic structural diagram of a mixture in the negative electrode additive.

Wherein: 1. a positive current collector foil; 2. coating a positive current collector; 3. coating the positive electrode slurry; 4. coating the surface of the positive plate; 5. a PTC material; 6. aluminum powder; 7. graphene; 8. a negative current collector foil; 9. a negative current collector coating; 10. coating the negative electrode slurry; 11. coating the surface of the negative plate; 12. copper powder.

Detailed Description

Hereinafter, the present invention will be described in detail by description of embodiments, while making reference to the accompanying drawings for better understanding of the present invention. However, the embodiments of the present invention may be modified in various ways, and the scope of the present invention is not to be considered limited to the embodiments described below. The embodiments of the present invention are merely intended to provide a clearer and more definite description of the present invention to those skilled in the art.