Lithium ion battery and isolating film

Abstract

The invention provides an isolating membrane for a Li-ion battery and the thickness d, the porosity Rho r and the aperture Rho s thereof respectively meet the following conditions: d is more than or equal to 5 microns and less than or equal to 50 microns, Rho r is more than or equal to 15 percent and less than or equal to 35 percent, and Rho s is more than or equal to 0.05 micron and less than or equal to 0.08 micron. The isolating membrane for the Li-ion battery has smaller porosity and aperture. When the Li-ion battery is fully charged and the short circuit happens, the isolating membrane is capable of reducing the discharging current and decreasing the continuous discharge capacity of the battery, thus controlling the magnitude of the short circuit current and the continuous time of the current and improving the safety; and when the battery is overcharged, has high temperature, or suffers improper use such as poking of a nail, squeezing and the like, the isolating membrane can rapidly shut off a micropore at fusion temperature, cut off an ion path, cause the Li to stop migrating from the anode to the cathode so as to stop the lattice collapse of anode materials and the oxidation of an electrolytic solution, thus protecting a battery cell from burning or exploding.

Description

technical field [0001] The invention relates to a lithium ion battery and its isolation film, in particular to a lithium ion battery and its isolation film which can effectively avoid fire or even explosion when used improperly. Background technique [0002] When a lithium-ion battery is charging, Li + It is deintercalated from the positive electrode and embedded in the negative electrode through the electrolyte and separator. The negative electrode is in a lithium-rich state, and the positive electrode is in a lithium-poor state. At the same time, the electronic compensation charge is supplied from the external circuit to the carbon negative electrode to ensure the charge balance of the negative electrode; the opposite is true during discharge. + It is deintercalated from the negative electrode and inserted into the positive electrode through the electrolyte and separator, and the positive electrode is in a lithium-rich state. For example, with LiCoO 2 When graphite is us...

AI Technical Summary

Problems solved by technology

Since the existing separator cannot close the micropores and stop the migration of Li+ from the positive electrode to the negative electrode before thermal runaway, it cannot prevent the lattice collapse of the positive electrode material and the oxidation of the electrolyte, and cannot protect the battery. core will not catch fire or explode

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