High-Voltage and High-Temperature LiCoO2 Operation via the Electrolyte Additive of Electron-Defect Boron Compounds

Commercial LIBs have the problem of instability interface of electrolyte/cathode at high voltage and high temperature. This work reports a novel series of electron-defect boron compounds to construct stable interfaces of LCO/electrolyte. The results of theoretical calculation indicate that compounds of DPD scaffold can win in the competitive oxidation decomposition for interface regulation. F-rich and B-rich interface is designed by modifying the functional group of DPD scaffold. This strategy of in situ interface design successfully suppresses the dissolution of harmful transition metal ions and the nucleophilic reaction between electrolyte and cathode. Li/LCO cell can remain stable at high voltage (4.5 V) and high temperature (70 °C) in commercial carbonate electrolyte after DPD-F interphase formation. Meanwhile, faster Li+ extraction and insertion kinetics of DPD-F-interface make the Li/LCO cell stable at 4.6 V. Spectral characterizations and theoretical calculations uncover the secret of the forming process of this DPD-F-interface.