Introduction of natural energy and electric vehicles have been extensively progressed in order to reduce carbon dioxide emission from our human society. The emission of carbon dioxide leads to grovel warming. The electric energy without carbon dioxide emission should be produced from natural energy and utilized in vehicles. Therefore, a smart grid and electric vehicle are very important applications. In both applications, rechargeable batteries play an important role. So far, lithium ion battery has been applied to such applications. However, lithium ion battery may not be enough performances. In order to realize high performance of rechargeable batteries, new next generation batteries have been developed, extensively.

Polyvinylidene fluoride (PVDF) is an engineering plastic which has features of both fluoropolymers and general-purpose plastics: chemical resistance, thermal stability, UV-resistance and melt processability. Because of its well-balanced features, it has been used in many fields such as electronic materials, hollow fiber, fishing lines, chemical piping, and lithium-ion batteries (LIB).

Nowadays, PVDF is in high demand for LIB applications especially for electric vehicles. In the early days of LIB, PVDF was utilized as binding agent for cathode and anode because of its excellent electrochemical stability and good adhesion performance to electrode materials. The applications of PVDF in LIB have been expanded to gel-electrolyte and coated separator films for the improvement of safety and reliability of battery cells. In this article, recent work on lithium-ion dynamics in PVDF based gel-electrolyte is introduced in addition to general information of PVDF and its application for LIB.

Lithium ion battery (LIB) is a solution for the energy challenges of our planet. It becomes more and more important since it can not only be used in consumption products but can also be applied to the automobiles and family use by further performance improvement.

The “performance” which involves productivity of electrode and battery, capacity, resistance and cycle life is highly affected by the binder. In this article, we will introduce the latest technique of SBR emulsion which covers the control of interaction between binder and CMC/electrolyte and the toughness of polymer. The required property can be achieved by introducing specific functional group to the SBR. If we increase the interaction between binder and CMC/electrolyte, adhesive strength and resistance can both be improved. Furthermore, the mechanical strength can also be enhanced by modifying the functional group on SBR surface to suppress the large volume change of silicon-carbon electrode and thus extend the lifetime of battery.

Kono et al. reported bi-axial orientation of gel sheets of high molecular weight polyethylenes, by what is often referred to as the “wet process", to obtain microporous film with a uniform and fine network of micro fibrils, 3 dimensionally interconnected and relatively narrow pore size distribution in 1984. A Tonen Chemical polyethylene separator provides many advantages as separator for lithium ion rechargeable batteries (LIBs) and was used in the world's first commercial LIB by Sony in 1991.

The demand for LIBs has increased rapidly, and now they are used in electrical vehicles and energy storage systems in addition to laptops, cellular phones, smartphones, power tools and cordless cleaners.Toray and Tonen established JV in 2010 and expand the separator business now.

LIB manufacturers desire thinner separators to increase the energy density and power of LIB. Separator manufacturers need to improve heat resistance and mechanical strength of thinner such as 5micron in order to meet safety requirements.

In this paper, we would like to outline the manufacturing processes, roles and features of separators, then to introduce our commercial products and our development activities of co-extruded and coated separators.

The key material for realizing all-solid-state lithium batteries is solid electrolytes. Glassy sulfide and oxide electrolytes and composite electrolytes with high conductivity and good formability have been developed.