New Lithium Metal Polymer Solid State Battery for an Ultrahigh Energy: Nano C‑LiFePO₄ versus Nano Li_1.2V₃O₈

Novel lithium metal polymer solid state batteries with nano C-LiFePO₄ and nano Li_1.2V₃O₈ 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 Li_1.2V₃O₈ 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.