CERAMIC COATING ON BATTERY SEPARATORS
The present invention relates generally to electrochemical energy storage devices such as Li-ion batteries, and more particularly to a method of providing uniform ceramic coatings with controlled thicknesses for separators in such storage devices. Some embodiments of the invention utilize a layer by layer coating of nano/micro-sized particles dispersed in a solvent, which can be aqueous or non-aqueous. Other embodiments of the invention utilize a dry process such as PVD for depositing a ceramic film on a porous polyolefin separator. According to certain aspects of the invention, advantages of this approach include the ability to achieve a denser more uniform film with better controlled thickness with less waste and higher yield than current ceramic coating technology. An advantage of a ceramic coated separator is increased safety of cells.
1 . A separator for a battery, comprising:
a porous battery separator material having a negative electrode facing surface and an opposite positive electrode facing surface; and
a ceramic coating that is uniformly distributed on the negative electrode facing surface.
2 . A separator according to claim 1 , wherein the porous battery separator material comprises an approximately 25 micron thick structure of polyolefin.
3 . A separator according to claim 2 , wherein the ceramic coating is about 3 microns thick.
4 . A separator according to claim 3 , wherein the ceramic coating comprises one or both of nano-particles and micro-particles.
5 . A separator according to claim 3 , wherein the ceramic coating comprises one of Al2O3 and SiO2.
6 . A separator according to claim 3 , wherein the ceramic coating comprises an ion conducting ceramic.