Many components inside of a lithium battery are soft materials. Electrode binders are a critical component of lithium-ion batteries, but have not been emphasized until recently. Without polymer binder, the electrode does not function properly. The emerging high-capacity materials for lithium-ion battery have large volume-change during operation, putting high demand on functional binders. Emerging high-capacity materials require non-traditional polymer binders, causing a recent explosive growth of research activities for the electrode binders. Currently, there are intensive research and development activities in lithium-sulfur battery, where electrolyte and electrode binder may play crucial roles to improve performance. The successful applications of soft materials in all the above areas require extensive engineering effort in both composite morphology and interfaces, for an optimized system performance. This seminar will discuss our recent activities in those areas in my laboratory.