Extending the High-Voltage Capacity of LiCoO2 Cathode by Direct Coating of the Composite Electrode with Li2CO3 via Magnetron Sputtering

Surface coating of composite electrode has recently received increasing attention and has been demonstrated to be effective in enhancing the electrochemical performance of lithium ion battery (LIB) materials. In this work, an electronic-insulating but ionic-conductive lithium carbonate (Li2CO3) is rationally selected as the unique coating material for commercial LiCoO2 (LCO) cathode. Li2CO3 is a well-known constitute in conventional solid electrolyte interface (SEI) layer, which can electrochemically protect the electrode. The carbonate coating layer is deposited on LCO composite electrodes via a facial magnetron sputtering approach. The sputtered Li2CO3 layer serves as an artificial SEI layer between the active material and electrolyte and can impede the formation of the primary SEI layer, which will permanently consume Li+ and reduce the reversible capacity of the electrode. After a 10 min Li2CO3 coating, the capacity retention of the composite electrode is improved from 64.4% to 87.8% when cycled at room temperature in the potential range of 3.0-4.5 V vs Li/Li+ for 60 cycles. The obtained discharge capacity is extended to 161 mAh g(-1), which is 36% higher than the uncoated one (118 mAh g(-1)). When further increasing the charging potential up to 4.7 V, or elevating the operation temperature to 55 degrees C, the Li2CO3-coated LCO electrodes still display remarkably improved cycling stability.