Superior electrochemical performance of LiCoO2 electrodes enabled by conductive Al2O3-doped ZnO coating via magnetron sputtering

• Conductive AZO thin film was directly coated on as-prepared LiCoO2 electrodes.
• AZO thin film was fabricated via radio frequency magnetron sputtering method.
• The AZO-coated LiCoO2 electrodes exhibit superior rate and cycling performances.
• The AZO coating improved the interface between the electrode and electrolyte.

A conductive Al2O3-doped ZnO (AZO) layer is coated directly on the LiCoO2 (LCO) porous composite electrode by magnetron sputtering of an AZO target, offering more efficient electron transfer and a stabilized interface layer. Up to 90% of the initial capacity of the AZO-coated electrode can be retained (173 mAh g−1) after 150 cycles between 3.0 and 4.5 V vs. Li/Li+. Meanwhile, the rate performance is remarkably improved showing a reversible capacity of 112 mAh g−1 at 12 C. The formation of amorphous solid electrolyte interface (SEI) observed on the uncoated LCO electrode is effectively impeded on the AZO-coated one. Acting as an intermediate barrier, the AZO layer can prevent chemical dissolution of the active materials by forming a thin passivation layer on the electrode surface containing some metal fluorides which are chemically inactive and ionically conductive. The positive role of the AZO coating is still effective under a more severe condition tested with an upper cut-off potential of 4.7 V.