Lithium ion batteries are being developed for use in hybrid cars and electric vehicles, and further improvements are expected in terms of increased power output and battery performance. Lithium ion batteries are composed of a cathode, anode, separator and electrolyte. Normally the anode is made from a graphite active material, but recent years have seen research into silicon (Si) active materials as next-generation anode materials that will have a higher theoretical capacity than graphite active materials. Here, we carried out SPM shape observations of binder samples held in both the electrolyte material used for actual battery operation and in N2 gas for reference. The physical properties of binder samples were also measured in electrolyte to find the binder most suited to use in batteries with an Si active material as the anode.