Novel lithium metal polymer solid state batteries with nano C-LiFePO4 and nano Li1.2V3O8 counter-electrodes (average particle size 200 nm) were studied for the first time by in situ SEM and impedance during cycling. The kinetics of Li-motion during cycling is analyzed self-consistently together with the electrochemical properties. We show that the cycling life of the nano Li1.2V3O8 is limited by the dissolution of the vanadium in the electrolyte, which explains the choice of nano C-LiFePO4 (1300 cycles at 100% DOD): with this olivine, no dissolution is observed. In combination with lithium metal, at high loading and with a stable SEI an ultrahigh energy density battery was thus newly developed in our laboratory.
Keywords: Lithium metal polymer battery; in situ SEM; nano C-LiFePO4; nano Li1.2V3O8.