Separator for electrochemical element

Abstract

The present invention provides a separator for an electrochemical element such that excellent protective properties against dendrite-induced short circuits are demonstrated. The separator for an electrochemical element according to the present invention comprises a nonwoven substrate having internal gaps in which inorganic particles are adhered to nonwoven constituent fibers via polymer binders, with polyelectrolytes being in the gaps formed by the nonwoven constituent fibers, the inorganic particles, and the polymer binders. It is preferable that the amount of polyelectrolytes is 2 to 18 mass% of the entire separator for an electrochemical element; the inorganic particles are made up of silica or alumina; the nonwoven substrate is made up of a composite of nonwoven fabrics where short fibers and / or pulp fibers enter the gaps in the base nonwoven fabric; and the nonwoven constituent fibers include heat resistant fibers having a melting point or a decomposition temperature of 180 DEG Cor greater.

Description

technical field [0001] The invention relates to a separator for electrochemical elements. Background technique [0002] In recent years, along with the miniaturization and weight reduction of electronic equipment, the demand for miniaturization, weight reduction, and high energy density of batteries as their power sources has also become strong. Since lithium ion secondary batteries have high energy density, batteries that can meet such demands are expected. [0003] As a separator of such a lithium ion secondary battery, a polyolefin microporous membrane is generally used. This is considered to be because the polyolefin microporous membrane has a function that when an abnormally large current flows due to an external short circuit of the battery, etc., the temperature of the battery rises significantly, in order to prevent the generation of combustible gas, the rupture of the battery, or the fire , the heat shrinks or melts the polyolefin microporous membrane to block the...

AI Technical Summary

Problems solved by technology

[0005] However, since a separator coated with inorganic particles in this way has poor adhesion to electrodes, a separator has been proposed, which includes: a porous substrate; and a porous organic-inorganic coating, the porous organic-inorganic A coating is formed on at least one surface of the porous substrate and comprises a mixture of inorganic particles and a first binder polymer comprising a copolymer comprising: (a ) a first monomeric unit which contains at least one amino group or at least one amide group or both on its side chain, and (b) a second monomeric unit which is a C1-C14 an alkyl (meth)acrylate; and an organic coating formed by dispersing a second binder polymer on the surface of the porous organic-inorganic coating and leaving dispersed uncoated regions Formation (Patent Document 1)

Although the separator is thought to increase the adhesion to the electrodes, it does not prevent lithium dendrites during overdischarge and, in another sense, short circuits.

[0006] As other electrochemical elements, there is a lithium ion capacitor, for example. As the negative electrode active material, it is preferable to dope lithium from the viewpoint of sufficiently lowering the potential of the negative electrode. However, lithium dendrites may grow due to charge and discharge, and internal short circuits may easily occur.

As mentioned above, even in electrochemical elements other than lithium-ion secondary batteries, there is a problem that dendrites cannot be prevented and short circuits are likely to occur

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