Synthesis and electrochemical characterization of LiNi_0.8Co_0.2O₂ as cathode material for aqueous rechargeable lithium batteries

Abstract

LiNi_0.8Co_0.2O₂ cathode material for lithium ion batteries is synthesized by reaction under autogenic pressure at elevated temperature (RAPET) method. The simple synthesis procedure is time and energy saving, and thus is promising for commercial application. The structure and stability of the material have been characterized by means of XRD and TG-DTA. The electrochemical properties of the LiNi0.8Co0.2O2 cathode are investigated in 2 M Li₂SO₄ aqueous electrolyte and they are compared to that in an organic electrolyte. A battery cell consisting of LiNi_0.8Co_0.2O₂ as cathode in 2 M Li₂SO₄ solution is constructed in combination with LiTi₂ (PO₄)₃ as anode. The cell retained almost constant discharge capacity over hundred cycles. The electrochemical impedance spectral (EIS) studies in aqueous and nonaqueous electrolytes revealed that the mechanism of lithium ion intercalation and deintercalation processes in LiNi_0.8Co_0.2O₂ electrode follow almost similar mechanism in both aqueous and nonaqueous electrolytes. The chemical diffusion coefficient was calculated from slow scan rate cyclic voltammetry and EIS.