Composite separator for lithium ion batteries

A battery separator for a lithium-ion battery comprising:

• a nonwoven fiber mat having a thickness of between 0.1 and 20 mils, the nonwoven fiber mat being composed of a plurality of entangled microfibers having an average fiber diameter less than 6 microns;
• a binder that binds the microfibers together;
• and
• a polymer component that is dispersed homogeneously through the plurality of entangled microfibers such that the polymer component is uniformly distributed throughout the nonwoven fiber mat and is not concentrated in any area within the nonwoven fiber mat, the nonwoven fiber mat, binder, and polymer component forming a single layered component;
• wherein the polymer component has a melting temperature of between about 90 and 150 degrees Celsius such that the polymer component melts within the nonwoven fiber mat when exposed to a sufficiently high heat in order to effectively interrupt an electro-chemical process of the lithium-ion battery and thereby prevent overheating of the battery;
• wherein the plurality of entangled microfibers includes glass microfibers having an average fiber diameter of between 150 and 550 nanometers;
• and
• wherein the plurality of entangled microfibers also includes glass microfibers having an average fiber diameter of between 0.6 and 6 microns.

A method of manufacturing a battery separator for a lithium-ion battery, the method comprising:

• dispersing glass microfibers in a liquid to form an aqueous slurry of the glass microfibers;
• dispersing a polymer component within the aqueous slurry of the glass microfibers so that the polymer component is homogenously or uniformly distributed throughout the aqueous slurry;
• distributing the aqueous slurry onto a screen and removing a liquid from the aqueous slurry so as to form a nonwoven fiber mat that is composed of entangled glass microfibers and the polymer component, wherein the polymer component is homogenously or uniformly distributed throughout the entangled glass microfibers;
• applying a binder to the entangled glass microfibers to bond the glass microfibers together with the polymer component homogenously distributed there through;
• and
• drying the entangled glass microfibers to form a nonwoven fiber mat having a thickness of between 0.1 and 20 mils;
• wherein the polymer component has a melting temperature of between about 90 and 150 degrees Celsius such that the polymer component melts within the nonwoven fiber mat when exposed to a sufficiently high heat in order to effectively interrupt an electro-chemical process of the lithium-ion battery and thereby prevent overheating of the battery;
• wherein dispersing the glass microfibers in the liquid comprises:
• dispersing between 20 and 70 weight percentage of smaller sized glass microfibers in the liquid, the smaller sized glass microfibers having an average fiber diameter of between 150 and 550 nanometers;
• and
• dispersing between 1 and 10 weight percentage of larger sized glass microfibers within the liquid, the larger sized glass microfibers having an average fiber diameter of between 0.6 and 6 microns, the smaller sized glass microfibers and larger sized glass microfibers being homogenously or uniformly distributed within the aqueous slurry.