Electrochemical device and inorganic/organic composite porous membrane

Abstract

The invention discloses an inorganic / organic composite porous membrane, which comprises a porous base material and an active layer attached to the porous base material, wherein the active layer contains a mixture of inorganic granules and a bonding agent. In the inorganic / organic composite porous membrane, the defect of poor heat safety of the conventional polyolefin-base diaphragm is overcome by using the inorganic / organic composite porous membrane formed by the porous base material, the inorganic granules and the bonding agent; the inorganic / organic composite porous membrane has the high antioxidation, can prevent the diaphragm from being oxidized in a lithium battery of a high-voltage anode material system, has the absorption and infiltration capacity of electrolyte which is better than that of conventional polyolefin-base diaphragm, and can improve solve the problem of the absorption and infiltration of the electrolyte in the large-size lithium battery and the lithium precipitation of the battery effectively. Therefore, the inorganic / organic composite porous membrane can improve the performance and safety of an electrochemical device serving as the inorganic / organic composite porous membrane as the diaphragm. In addition, the invention also discloses a preparation method for the inorganic / organic composite porous membrane and the electrochemical device using the membrane.

Description

technical field [0001] The invention relates to the field of electrochemical devices, more specifically, the invention relates to an electrochemical device and its inorganic / organic composite porous film, and a preparation method of the inorganic / organic composite porous film. Background technique [0002] In recent years, with the increasing interest in energy storage technology, batteries have been widely used as energy sources in mobile phones, small camcorders, notebook computers, personal computers, and electric vehicles. Therefore, the research and development of batteries more and more widely. In this regard, electrochemical devices are the subject of great interest, and especially the development of rechargeable secondary batteries has become the focus of attention. [0003] A secondary battery is a chemical battery capable of repeated charge and discharge cycles by means of reversible interchange between chemical energy and electrical energy, and can be classified ...

AI Technical Summary

Problems solved by technology

[0006] In order to solve the above-mentioned problems related to polyolefin-based separators, various attempts have been made in the industry to develop electrolytes using inorganic materials as conventional separator substitutes, which can be roughly divided into the following two categories: Ion-conductive inorganic particles are compounded with porous substrates to obtain composite diaphragms. However, the ion conductivity of this composite diaphragm is low, and the interface resistance between inorganic particles and porous substrates is high; the second type is obtained by using organic An electrolyte obtained by mixing or not mixing lithium-ion-conducting inorganic particles with a gel polymer electrolyte formed from a porous substrate and a liquid electrolyte, however, in this case, the inorganic material introduced is larger than the total amount of the polymer and liquid electrolyte The amount is small, so it only has a supplementary function of assisting the lithium ion conductivity generated by the liquid electrolyte

[0007] As mentioned above, existing electrolytes using inorganic particles have the following common problems: First, when a liquid electrolyte is not used, interfacial resistance between inorganic particles and between inorganic particles and porous substrates increases excessively, resulting in a decrease in battery performance ; secondly, the handling of the above-mentioned electrolyte is difficult due to its brittleness when an excessive amount of inorganic material is introduced, therefore, it is difficult to assemble a battery using this electrolyte

In particular, most of the efforts made so far have been to develop composite electrolytes containing inorganic particles in the form of free-standing thin films, however, it is practically difficult to apply such electrolytes in batteries due to the poor mechanical properties (such as high brittleness) of the thin films. electrolyte

Even if the mechanical properties can be improved by reducing the content of inorganic particles, the mixture of inorganic particles and liquid electrolyte will lead to a significant decrease in mechanical properties due to the liquid electrolyte, resulting in failure of subsequent battery assembly

If the liquid electrolyte is injected after battery assembly, it takes too long for the electrolyte to disperse in the battery, and the actual wettability of the electrolyte is poor due to the high polymer content in the inorganic / organic composite film

In addition, the addition of inorganic particles in order to improve safety will lead to a significant decrease in lithium ion conductivity

In addition, the electrolyte cannot function adequately as a separator since there are no pores in the electrolyte, or if there are, only pores in the size of a few angstroms (?) and very low porosity

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