High-Capacity, Long-Life Iron Fluoride All-Solid-State Lithium Battery with Sulfide Solid Electrolyte

Metal fluoride-lithium batteries with potentially high-energy densities are regarded as promising candidates for next-generation low-cost rechargeable batteries. However, liquid-electrolyte metal fluoride-lithium batteries suffer from sluggish reaction kinetics, high voltage hysteresis due to side reactions, poor rate capability, and rapid capacity drop during cycling. Moreover, the research on sulfide all-solid-state batteries (ASSBs) with metal fluoride cathode is still lacking. Herein, four kinds of iron fluoride materials are applied to the sulfide all-solid-state lithium battery system for the first time to investigate the best cathode and corresponding methods. Electrochemical tests showed the cycling performance at different current densities (0.1, 0.3, and 1 C) and rate performance of the four cathodes with the following rules: FeF3-HT > FeF3-RT > FeF3 center dot 0.33H(2)O > FeF3 center dot 3H(2)O. The reversible capacities of FeF3-HT AASB are 519.9 mAh g(-1) after 120 cycles at 0.3C and still maintains 340.7 mAh g(-1) after 400 cycles even at a high rate of 1 C. In addition, electro impedence spectroscopy and cyclic voltammetry tests of the above four cathodes show that different contents of crystal water, morphologies, and particle sizes have a great influence on the lithium storage mechanism of cathode. Moreover, the reason for the FeF3-HT cathode's superior specific capacity and rate performance compared with other cathodes at high current densities is revealed, according to cyclic voltammogram tests under different scan rates. The cause is that FeF3-HT has the highest proportion of the contribution capacity of the cathode surface control process. The above research opens up a new avenue for FeF3-HT, FeF3-RT, FeF3 center dot 0.33H(2)O, and FeF3 center dot 3H(2)O cathodes in sulfide ASSBs.