Journal
NANO LETTERS
Volume 15, Issue 9, Pages 6102-6109Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b02379
Keywords
LiFePO4; rate performance; aqueous electrolyte; organic electrolyte; solid-liquid interface; ab initio calculations
Categories
Funding
- National Project for EV Batteries (OptimumNano, Shenzhen) [20121110]
- National Distinguished Young Scientists of China [51425301]
- STCSM [12JC1401200]
- Guangdong Innovation Team Project [2013N080]
- Shenzhen Science and Technology Research Grant [ZDSY20130331145131323, CXZZ20120829172325895]
- Office of Science (SC), Basic Energy Science (BES)/Materials Science and Engineering Division (MSED) of the U.S. Department of Energy (DOE) [DE-AC02-05CH11231]
- ShenZhen National Super Computing Center
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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,(1-3) little is known on the atomic level about the solid-liquid 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(-)1) reaching 72 mAh g(-1) energy storage (42% of the theoretical capacity). By contrast, the accessible capacity sharply decreases to 20 mAh g(-1) at 200 C in organic electrolyte. After a comprehensive electrochemistry tests and ab initio calculations of the LiFePO4-H2O and LiFePO4-EC (ethylene carbonate) systems, we identified the transient formation of a Janus hydrated interface in the LiFePO4-H2O 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.
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