Organic/inorganic composite separator having porous active coating layer and electrochemical device containing the same

Abstract

An organic / inorganic composite separator includes (a) a polyolefin porous substrate having pores; and (b) a porous active layer containing a mixture of inorganic particles and a binder polymer, with which at least one surface of the polyolefin porous substrate is coated, wherein the porous active layer has a peeling force of 5 gf / cm or above, and a thermal shrinkage of the separator after being left alone at 15O DEG C for 1 hour is 50% or below in a machine direction (MD) or in a transverse direction (TD). This organic / inorganic composite separator solves the problem that inorganic particles in the porous active layer formed on the porous substrate are extracted during an assembly process of an electrochemical device, and also it may prevent an electric short circuit between cathode and anode even when the electrochemical device is overheated.

Description

technical field [0001] The present invention relates to a separator for an electrochemical device such as a lithium secondary battery and an electrochemical device comprising the separator. More specifically, the present invention relates to an organic / inorganic composite separator in which a porous active layer formed of a mixture of inorganic particles and a polymer is applied to a porous substrate and an electrochemical device comprising the same face. Background technique [0002] Recently, there has been increasing interest in energy storage technologies. Batteries have been widely used as energy sources in the fields of portable phones, camcorders, notebook computers, personal computers, and electric vehicles, which has led to intensive research and development on them. In this regard, electrochemical devices are a subject of great interest. In particular, the development of rechargeable secondary batteries has been the focus of attention. Recently, in the field of...

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Problems solved by technology

However, such lithium secondary batteries have disadvantages in that the organic electrolyte used therein may cause problems regarding safety, such as fire and explosion of the battery; and that the process for manufacturing such batteries is very complicated

[0007] First, due to the stress generated in the electrochemical device assembly process such as winding, the inorganic particles can be separated from the porous active layer, and the separated inorganic particles cause local defects in the electrochemical device, which is detrimental to the stability of the electrochemical device. influences

[0008] Second, since the adhesion between the porous active layer and the polyolefin porous substrate is weak, the ability of the porous active layer to inhibit the thermal shrinkage of the polyolefin porous substrate is deteriorated.

Therefore, even when the electrochemical device is overheated, it is difficult to prevent an electrical short circuit between the cathode and anode

[0009] On the contrary, if the content of the binder polymer in the porous active layer is increased to prevent the separation of the inorganic particles, the content of the inorganic particles is relatively reduced so that it may not be easy to suppress the thermal shrinkage of the polyolefin porous substrate.

Therefore, it is difficult to prevent the electrical short circuit between the cathode and anode, and furthermore, the performance of the electrochemical device deteriorates due to the decreased porosity in the porous active layer.

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