阅读说明：本技术 一种低温锂离子电池 (low-temperature lithium ion batteries ) 是由 李红 朱坤庆 计阳 夏小勇 庞佩佩 刘露 聂灿 于 2019-10-30 设计创作，主要内容包括：本发明属于锂电池领域,尤其涉及一种低温锂离子电池,正极片包括正极集流体和正极活性物质层,正极活性物质层包括4.4V钴酸锂材料、正极导电剂和正极粘结剂；负极片包括负极集流体和负极活性物质层,负极活性物质层包括硬碳包覆二次颗粒人造石墨材料、负极导电剂、分散剂和负极粘结剂；电解液包括10～20％六氟磷酸锂、10～20％丙酸乙酯、10～20％碳酸二乙酯、15～30％碳酸乙烯酯、15～30％丙酸丙酯、3％～10％氟代碳酸乙烯酯、2～3％亚硫酸丙烯酯、0.5～2.5％乙二醇单丁醚和0.5～2.5％2,2’-二硫二吡啶。相比于现有技术,本发明的锂离子电池在低温条件下具有良好的充放电性能以及较高的能量密度。(The invention belongs to the field of lithium batteries, and particularly relates to low-temperature lithium ion batteries, wherein a positive plate comprises a positive current collector and a positive active material layer, the positive active material layer comprises a 4.4V lithium cobaltate material, a positive conductive agent and a positive binder, a negative plate comprises a negative current collector and a negative active material layer, the negative active material layer comprises a hard carbon-coated secondary particle artificial graphite material, a negative conductive agent, a dispersing agent and a negative binder, an electrolyte comprises 10-20% of lithium hexafluorophosphate, 10-20% of ethyl propionate, 10-20% of diethyl carbonate, 15-30% of ethylene carbonate, 15-30% of propyl propionate, 3-10% of fluoroethylene carbonate, 2-3% of propylene sulfite, 0.5-2.5% of ethylene glycol monobutyl ether and 0.5-2.5% of 2, 2' -dipyridyl disulfide.)

1, kinds of low temperature lithium ion battery, wherein it comprises positive plate, negative plate, diaphragm and electrolyte;

the positive plate comprises a positive current collector and a positive active substance layer arranged on the surface of the positive current collector, wherein the positive active substance layer comprises a 4.4V lithium cobaltate material, a positive conductive agent and a positive binder;

the negative plate comprises a negative current collector and a negative active substance layer arranged on the surface of the negative current collector, wherein the negative active substance layer comprises a hard carbon-coated secondary particle artificial graphite material, a negative conductive agent, a dispersing agent and a negative binder;

the electrolyte comprises 10-20% of lithium hexafluorophosphate, 10-20% of ethyl propionate, 10-20% of diethyl carbonate, 15-30% of ethylene carbonate, 15-30% of propyl propionate, 3-10% of fluoroethylene carbonate, 2-3% of propylene sulfite, 0.5-2.5% of ethylene glycol monobutyl ether and 0.5-2.5% of 2, 2' -dipyridyl disulfide.

2. The low temperature lithium ion battery of claim 1, wherein: the surface density of the positive electrode active material layer is 145-150 g/m²The positive electrode activityThe compacted density of the material layer is 3.6-4.2 g/m³。

3. The low temperature lithium ion battery of claim 1, wherein: the surface density of the negative electrode active material layer is 75-80 g/m²The compacted density of the negative electrode active material layer is 1.3-1.8 g/m³。

4. The low temperature lithium ion battery of claim 1, wherein: the mass ratio of the 4.4V lithium cobaltate material to the positive electrode conductive agent to the positive electrode binder is (95-98): 1-3): (1-2).

5. The low temperature lithium ion battery of claim 1, wherein: the mass ratio of the hard carbon-coated secondary particle artificial graphite material to the negative electrode conductive agent to the dispersing agent to the negative electrode binder is (95-98): (0.5-1.5): (1-1.5): (1-2).

6. The low temperature lithium ion battery of claim 1, wherein: the 4.4V lithium cobaltate material is formed by mixing at least two kinds of spheroidal particles with different particle diameters, the median particle diameter of the 4.4V lithium cobaltate material is 12-18 mu m, and the specific surface area is 0.25-0.3 m²The tap density is 2.5-3.0 g/cm³Wherein the particle size of the spheroidal particles with large particle size is 32-38 μm, and the particle size of the spheroidal particles with small particle size is 2-5 μm.

7. The low temperature lithium ion battery of claim 1, wherein: the hard carbon-coated secondary artificial graphite particle material has a median particle diameter of 12-18 mu m and a specific surface area of 1.0-1.4 m²The tap density is 0.8-1.2 g/cm³。

8. The low-temperature lithium ion battery according to claim 1, wherein the positive electrode conductive agent comprises at least of conductive carbon black, conductive graphite, graphene, carbon nanotubes and carbon fibers, and the positive electrode binder comprises polyvinylidene fluoride.

9. The low-temperature lithium ion battery of claim 1, wherein the negative electrode conductive agent comprises at least of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene, the negative electrode binder comprises at least of acrylonitrile multipolymer, styrene-butadiene rubber, sodium carboxymethyl cellulose and polyacrylic acid, and the dispersant is sodium carboxymethyl cellulose.

10. The low-temperature lithium ion battery of claim 1, wherein the separator comprises a base film, an adhesive layer and a ceramic layer, the ceramic layer is adhered to the surface of the base film through the adhesive layer, and the base film is at least selected from a polypropylene film, a polypropylene/polyethylene/polypropylene composite film, nylon cloth, glass fiber, a polyvinyl alcohol film and asbestos paper.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to low-temperature lithium ion batteries.

Background

At present, the low-temperature performance of the lithium ion battery is relatively poor, and particularly in a low-temperature environment below-20 ℃, the charging of the lithium ion battery becomes extremely difficult, lithium dendrites are precipitated, the internal of the battery can be short-circuited, the discharge performance of the battery is greatly reduced, and the subsequent electrochemical performance is greatly reduced, so that the research on the use of the lithium ion battery in a cold environment is urgent.

, the main reasons for the poor performance of the battery in low temperature environment are 1) the viscosity of the electrolyte increases and even the icing phenomenon occurs in low temperature environment, and the conductivity is greatly reduced, 2) the migration speed of lithium ions in the anode and cathode materials is slowed, and 3) the diffusion on the electrode/electrolyte interface and the charge transfer rate are slowed, that is, the transmission rate of lithium ions may be reduced due to the properties of the anode material, the cathode material and the electrolyte.

Disclosure of Invention

The invention aims to provide low-temperature lithium ion batteries which have good charge and discharge performance and higher energy density under low-temperature conditions aiming at the defects of the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

kinds of low temperature lithium ion battery, including positive plate, negative plate, diaphragm and electrolyte;

the positive plate comprises a positive current collector and a positive active substance layer arranged on the surface of the positive current collector, wherein the positive active substance layer comprises a 4.4V lithium cobaltate material, a positive conductive agent and a positive binder;

the negative plate comprises a negative current collector and a negative active substance layer arranged on the surface of the negative current collector, wherein the negative active substance layer comprises a hard carbon-coated secondary particle artificial graphite material, a negative conductive agent, a dispersing agent and a negative binder;

the electrolyte comprises 10-20% of lithium hexafluorophosphate, 10-20% of ethyl propionate, 10-20% of diethyl carbonate, 15-30% of ethylene carbonate, 15-30% of propyl propionate, 3-10% of fluoroethylene carbonate, 2-3% of propylene sulfite, 0.5-2.5% of ethylene glycol monobutyl ether and 0.5-2.5% of 2, 2' -dipyridyl disulfide.

The improvements of the low-temperature lithium ion battery are that the surface density of the positive electrode active material layer is 145-150 g/m²The compacted density of the positive active material layer is 3.6-4.2 g/m³. In a reasonable surface density range, the surface density is reduced, the porosity of the material is increased, the larger the electrolyte adsorption amount of active substances per unit mass is, and the solution contact resistance is reduced; the surface density is small, and the thickness of the pole piece is thickIn addition, , the thickness of the pole piece is correspondingly reduced, which is beneficial to the migration of lithium ions in active material, but when the compaction density is too high, the infiltration capacity of the material to the electrolyte is poor, the contact resistance is increased, and the negative effect on the battery performance is generated.

The improvements of the low-temperature lithium ion battery are that the surface density of the negative electrode active material layer is 75-80 g/m²The compacted density of the negative electrode active material layer is 1.3-1.8 g/m³。

The improvements of the low-temperature lithium ion battery are that the mass ratio of the 4.4V lithium cobaltate material to the positive electrode conductive agent to the positive electrode binder is (95-98): 1-3: 1-2.

The improvements of the low-temperature lithium ion battery are that the mass ratio of the hard carbon-coated secondary particle artificial graphite material to the negative electrode conductive agent to the dispersing agent to the negative electrode binder is (95-98): (0.5-1.5): (1-1.5): 1-2.

The improvements of the low-temperature lithium ion battery are that the 4.4V lithium cobaltate material is formed by mixing at least two kinds of spheroidal particles with different particle diameters, the median particle diameter of the 4.4V lithium cobaltate material is 12-18 mu m, and the specific surface area is 0.25-0.3 m²The tap density is 2.5-3.0 g/cm³Wherein the particle size of the spheroidal particles with large particle size is 32-38 μm, and the particle size of the spheroidal particles with small particle size is 2-5 μm. The particles with different particle sizes are mixed, wherein the small particle size particles are beneficial to reducing the lithium ion transmission distance and improving the low-temperature performance, and the large particle size particles are beneficial to improving the cycle performance of the battery due to increasing the compaction density.

improvements of the low-temperature lithium ion battery provided by the invention are that the median particle size of the hard carbon-coated secondary artificial graphite particle material is 12-18 mu m, and the specific surface area of the hard carbon-coated secondary artificial graphite particle material is1.0 to 1.4m²The tap density is 0.8-1.2 g/cm³. The adoption of the hard carbon coating is favorable for improving the stability of the cathode active material under the low-temperature condition and improving the low-temperature performance of the battery.

improvements of the low-temperature lithium ion battery are that the positive electrode conductive agent comprises at least of conductive carbon black, conductive graphite, graphene, carbon nanotubes and carbon fibers, and the positive electrode binder comprises polyvinylidene fluoride.

The improvements of the low-temperature lithium ion battery are that the negative electrode conductive agent comprises at least of conductive carbon black, conductive graphite, carbon fiber, carbon nano tube and graphene, the negative electrode binder comprises at least of acrylonitrile multipolymer, styrene butadiene rubber, sodium carboxymethyl cellulose and polyacrylic acid, and the dispersant is sodium carboxymethyl cellulose.

The improvements of the low-temperature lithium ion battery comprise a base film, an adhesive layer and a ceramic layer, wherein the ceramic layer is adhered to the surface of the base film through the adhesive layer, and the base film is at least selected from a polypropylene film, a polypropylene/polyethylene/polypropylene composite film, nylon cloth, glass fiber, a polyvinyl alcohol film and asbestos paper.

Compared with the prior art, the low-temperature lithium ion battery has the beneficial effects that in the aspect of , the hard carbon coated secondary particle artificial graphite material is used as a negative electrode active substance, the direct current internal resistance (DCR) of the material is reduced, and the low-temperature performance of the battery is improved, in the aspect of , the composition and the content of each component of the electrolyte are improved, wherein propyl propionate is beneficial to infiltration and is beneficial to improvement of low-temperature discharge and low-temperature cycle lithium precipitation, ethyl propionate has low viscosity, high dielectric constant and good infiltration and is beneficial to improvement of the low-temperature charging performance of the battery core, diethyl carbonate has high dielectric constant and is beneficial to improvement of conductivity, and 2, 2' -dipyridyl disulfide is beneficial to improvement of the low-temperature charging performance, so that the conductivity and the low-temperature charging performance of the electrolyte are obviously improved.

Drawings

FIG. 1 is a diagram showing an analysis of the lithium deposition in the example of the present invention.

FIG. 2 is a diagram showing an analysis of lithium deposition in comparative example 1 of the present invention.

FIG. 3 is a diagram showing an analysis of lithium deposition in comparative example 2 of the present invention.

FIG. 4 is a diagram showing an analysis of lithium deposition in comparative example 3 of the present invention.

FIG. 5 is a graph showing the discharge rate of example 1 of the present invention.

FIG. 6 is a graph showing the cycle of example 1 of the present invention.

Detailed Description

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