CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No. 201811367128.6, filed on Nov. 16, 2018, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This application belongs the field of electrochemical technology, and more particularly, this application relates to a battery.

BACKGROUND

Lithium-ion batteries are widely used in electric vehicles and consumer electronics because of their high energy density, high output power, long cycle life and small environmental pollution. However, lithium-ion batteries are prone to fire and explode when subjected to abnormal conditions such as crushing, bumping or puncture, causing serious harm. Therefore, the safety problem of lithium-ion batteries greatly limits the application and popularity of lithium-ion batteries.

Although researchers have proposed many ways to improve the safety of batteries, there is still no very effective means for the safety hazard caused by the puncture of the battery. In view of this, it is indeed necessary to provide a battery that has improved battery safety, especially nail penetration safety.

SUMMARY

It is an object of this application to provide a battery with improved safety, especially with improved nail penetration safety.

It is a further object of this application to provide a battery having excellent properties such as good safety, improved electrical properties, and good processibility.

This application provides a battery comprising a positive electrode plate, a separator, and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and at least two layers of positive active material coated on at least one surface of the positive electrode current collector, and wherein an underlying positive active material layer in contact with the positive electrode current collector comprises a first positive active material, a first polymer material and a first conductive material, and based on total weight of the underlying positive active material layer, the first positive active material has a content of A % by weight, the first polymer material has a content of B % by weight, and the first conductive material has a content of C % by weight; and wherein an upper positive active material layer in contact with the underlying positive active material layer and away from the positive electrode current collector comprises a second positive active material, a second polymer material and a second conductive material, and based on total weight of the upper positive active material layer, the second positive active material has a content of A′ % by weight, the second polymer material has a content of B′ % by weight, and the second conductive material has a content of C′ % by weight, wherein A %<A′ %, B %>B′ %, C %≥C′ %, and the first polymer material comprises fluorinated polyolefin and/or chlorinated polyolefin polymer material.

The battery of this application has good safety and improved electrical properties.

