Optimization of high potential cathode materials and lithium conducting hybrid solid electrolyte for high-voltage all-solid-state batteries

LiMn0.8Fe0.2PO4 (LMFP) as high potential cathode is synthesized by a modified mechanical activation method and tested for use in all-solid-state high-voltage rechargeable lithium ion batteries. The influence of synthesis condition on the atomic structure, particle size, morphology, surface area, and electrochemical performance of the active material is investigated. A high dielectric constant ceramic (Al2O3) is composited in Li1.3Al0.3Ge1.7P3O12 (LAGP)-based lithium conducting hybrid solid electrolyte, and a higher lithium ion transference number is observed owing to the anion scavenging effect of Al2O3. An all-solid-state LMFP battery is constructed with a graphite anode and the hybrid solid electrolyte. At current densities of 0.1, 1, 3, and 10 C, initial discharge capacities of 156.3, 133.7, 111.8, and 71.4 mAh g−1 (91.9, 78.6, 65.8, and 42% of theoretical capacity) are obtained with low corresponding capacity fade of 0.001, 0.02, 0.01, and 0.013% per cycle evaluated over 300 cycles, even after charging to 4.5 V.