Lower-voltage plateau Zn-substituted Co₃O₄ submicron spheres anode for Li-ion half and full batteries

Carbonaceous materials are used as the anode for rechargeable lithium-ion batteries (LIBs), however, lithium dendrites are easily formed during cycling due to the low lithium insertion potential (~0.1 V versus Li⁺/Li). As alternative anodes, transition metal oxides based on conversion mechanism have attached much attention. But the high lithiation potential (>1.0 V vs. Li⁺/Li) usually leads to a low output voltage and energy density when used in a full cell configuration. Herein, Zn-substituted Co₃O₄ submicron spheres are successfully synthesized by a facile solvothermal reaction and subsequent calcination method. When used as the anode for LIB, the optimized sample shows a specific capacity of 686 mAh g⁻¹ at 0.8 A g⁻¹ after 500 cycles, and a specific capacity of 692.9 mAh g⁻¹ at a higher current density of 3.2 A g⁻¹ in a half-cell. Thanks to the controlled Zn substitution, the discharge voltage plateau is 0.16 V lower than that of the pure Co₃O₄ anode at a current density of 0.4 A g⁻¹. Further investigation of the 0.5Zn-Co₃O₄//LiCoO₂ full cells also displays a high capacity (400.7 mAh g⁻¹ after 200 cycles at 0.4 A g⁻¹) and an excellent rate capability (658.1 mAh g⁻¹ at 1.6 A g⁻¹) compared with the Co₃O₄//LiCoO₂ full cells. This work confirms that substituting suitable metal elements into sub-micron conversion based anodes can reduce the voltage plateau, which is of great significance for the practical applications in high performance energy storage devices.