An electro-chemical energy conversion and storage device includes an enclosure, a first electrode operatively connected to the enclosure, a second electrode operatively connected to the enclosure, a nanofluid or particle suspension in the enclosure, a heat transfer unit, and a circulation system for circulating the nanofluid or particle suspension to the heat transfer unit. The nanofluid includes nanoparticles plus a dielectric or ionic fluid. The particle suspension includes particles plus a dielectric or ionic fluid. A wide range of nanoparticles or particles can be used. For example the following nanoparticles or particles can be used: metal and metal alloy particles for anodic dissolution and thermal transport; hydrides as source of hydrogen ions; lithium and lithium alloys; intercalated graphite and carbon aerogel as Li source (anodic material); intercalated transition metal oxide as Li sink (cathodic material); and semiconductors for photovoltaic conversion in photo-electrochemical or hybrid electrochemical cell.