Silicon nitride composite membrane and a preparation method

The present invention relates to a composite membrane of silicon nitride and its preparation method, the process comprising the steps of: at a temperature of -150 ℃ ~ -130 ℃, soaked with the liquid silane diaphragm 5 to 30 minutes, and then the liquid ammonia soaking the diaphragm 10 to 120 minutes, the membrane of silicon nitride deposited on the surface, and finally dried in vacuo to give a composite membrane of silicon nitride. The present invention is by one-step synthesis, the effective evenly distributed in the surface membrane of silicon nitride. Since no binder and high temperature sintering method, the silicon nitride composite membrane according to the present invention has excellent heat resistance and less dusting, thereby improving safety of the battery. Further, the present invention is the whole preparation process is simple, low cost raw materials, easy to achieve mass production.