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Enabling Stable Cycling of 4.2 V High‐Voltage All‐Solid‐State Batteries with PEO‐Based Solid Electrolyte
Author(s) -
Qiu Jiliang,
Liu Xinyu,
Chen Rusong,
Li Qinghao,
Wang Yi,
Chen Penghao,
Gan Luyu,
Lee SangJun,
Nordlund Dennis,
Liu Yijin,
Yu Xiqian,
Bai Xuedong,
Li Hong,
Chen Liquan
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201909392
Subject(s) - materials science , electrolyte , electrochemistry , cathode , chemical engineering , oxide , battery (electricity) , quasi solid , oxidizing agent , electrode , electrochemical window , fast ion conductor , ionic conductivity , metallurgy , chemistry , organic chemistry , power (physics) , physics , quantum mechanics , engineering , dye sensitized solar cell
Abstract Poly(ethylene oxide) (PEO)‐based solid electrolytes are expected to be exploited in solid‐state batteries with high safety. Its narrow electrochemical window, however, limits the potential for high voltage and high energy density applications. Herein the electrochemical oxidation behavior of PEO and the failure mechanisms of LiCoO 2 ‐PEO solid‐state batteries are studied. It is found that although for pure PEO it starts to oxidize at a voltage of above 3.9 V versus Li/Li + , the decomposition products have appropriate Li + conductivity that unexpectedly form a relatively stable cathode electrolyte interphase (CEI) layer at the PEO and electrode interface. The performance degradation of the LiCoO 2 ‐PEO battery originates from the strong oxidizing ability of LiCoO 2 after delithiation at high voltages, which accelerates the decomposition of PEO and drives the self‐oxygen‐release of LiCoO 2 , leading to the unceasing growth of CEI and the destruction of the LiCoO 2 surface. When LiCoO 2 is well coated or a stable cathode LiMn 0.7 Fe 0.3 PO 4 is used, a substantially improved electrochemical performance can be achieved, with 88.6% capacity retention after 50 cycles for Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 coated LiCoO 2 and 90.3% capacity retention after 100 cycles for LiMn 0.7 Fe 0.3 PO 4 . The results suggest that, when paired with stable cathodes, the PEO‐based solid polymer electrolytes could be compatible with high voltage operation.