Laiqiang Xu,Jiayang Li,Wentao Deng,Lin Li,Guoqiang Zou,Hongshuai Hou,Lanping Huang,Xiaobo Ji
Poly(ethylene oxide) (PEO)-based polymer electrolytes are extensively investigated, and they have rapidly developed in all-solid-state batteries (ASSBs) over recent years for their good interface contact with electrodes, easy shaping and decent flexibility. However, their low ionic conductivity remains a serious issue to be solved urgently. Researchers have found that the addition of fillers can improve the ionic conductivity via creating more amorphous regions conducive to ion transport in PEO. Here, we adopted waste eggshell as a precursor to prepare a sub-micron filler, which is mainly CaO, and it was added into the PEO electrolyte to get a composite polymer electrolyte. Close contact via Lewis base-acid interaction between CaO and PEO can be obtained, as CaO is an effective filler with strong alkalinity. To the best of our knowledge, this is the first time it is applied in the PEO electrolyte. The filler significantly decreases the crystallinity of PEO, and hence, boosted ionic conductivity of the composite polymer electrolyte is observed, which is about 4.5 times higher than that of the polymer reference electrolyte. It additionally brings a higher tensile strength along with a more stable electrochemical window (up to 5 V) to the composite electrolyte. Therefore, as expected, the all-solid-state Li/Na battery with this composite electrolyte exhibits long cycling life and excellent rate performances. The corresponding Li/LiFeO4 battery has a stable capacity of 142.8 mA h g−1 at 1C after 200 cycles, and the corresponding solid-state Na/Na3V2(PO4)3 battery gives a reversible capacity of 101.2 mA h g−1 at 0.5C after 100 cycles.
Xiaodong Bai,Chaoliang Zheng,Heng Zhang,Jian Liu,Panpan Wang,Baojia Xia,Jianling Li
PEO-based all-solid-state electrolytes are extensively utilized and researched owing to their exceptional safety, low-mass-density, and cost-effectiveness. However, the low oxidation potential of PEO makes the interface problem with the high-voltage cathode extremely severe. In this work, the impedance of PEO-based all-solid-state batteries with high-voltage cathode (NCM811) was studied at different potentials. The Nyquist plots displayed a gyrate arc at low-frequencies for NCM811/PEO interface. Based on the kinetic modeling, it was deduced that there is a decomposition reaction of PEO-matrix in addition to de-embedded reaction of NCM811, and the PEO intermediate product (dehydra-PEO) adsorbed on the electrode surface leading to low-frequency inductive arcs. Furthermore, the distribution of relaxation time shows the dehydra-PEO results in the kinetic tardiness of the charge transfer process in the temporal dimension. Hence, an artificial interface layer (CEI x ) was modified on the surface of NCM811 to regulate the potential of cathode/electrolyte interface to prevent the high-voltage deterioration of PEO. NCM/CEI x /PEO batteries exhibit capacity retentions of 96.0%, 84.6%, and 76.8% after undergoing 100 cycles at cut-off voltages of 4.1, 4.2, and 4.3 V, respectively. Therefore, here the failure mechanism of high-voltage PEO electrolyte is investigated by EIS and a proposed solving strategy is presented.
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