文摘
LiFePO4 has long been held as one of the most promising battery cathode for its high energy storage capacity. Meanwhile, although extensive studies have been conducted on the interfacial chemistries in Li-ion batteries,1鈭? little is known on the atomic level about the solid鈥搇iquid interface of LiFePO4/electrolyte. Here, we report battery cathode consisted with nanosized LiFePO4 particles in aqueous electrolyte with an high charging and discharging rate of 600 C (3600/600 = 6 s charge time, 1 C = 170 mAh g鈥?) reaching 72 mAh g鈥? energy storage (42% of the theoretical capacity). By contrast, the accessible capacity sharply decreases to 20 mAh g鈥? at 200 C in organic electrolyte. After a comprehensive electrochemistry tests and ab initio calculations of the LiFePO4鈥揌2O and LiFePO4鈥揈C (ethylene carbonate) systems, we identified the transient formation of a Janus hydrated interface in the LiFePO4鈥揌2O system, where the truncated symmetry of solid LiFePO4 surface is compensated by the chemisorbed H2O molecules, forming a half-solid (LiFePO4) and half-liquid (H2O) amphiphilic coordination environment that eases the Li desolvation process near the surface, which makes a fast Li-ion transport across the solid/liquid interfaces possible.
