Electrochemical properties of non-stoichiometric nanocrystalline Li4Mn5O12 for hybrid capacitors

Van Man Tran, Le Thanh Nguyen Huynh, Cam Thanh Duy Ha, Thi My Van Nguyen and My Loan Phung Le

Abstract

Non-stoichiometric nanocrystalline Li₄Mn₅O₁₂ was synthesized using the sol–gel method with citric acid at a low-temperature. The effects of the pH condition on the structure, morphology and electrochemical properties were investigated. X-ray diffraction patterns and scanning electron microscopy images confirmed that all the samples crystallized in spinel structures with a particle size in the nanometric scale. Transmission electron microscopy images showed that particle size varied from 50–100 nm. The Li₄Mn₅O₁₂ was tested as an electrode material in half-cell Li/Li₄Mn₅O₁₂ and in full-cell vulcanized carbon/Li₄Mn₅O₁₂ at a high rate charge–discharge. Among the samples, Li₄Mn₅O₁₂ (prepared at pH = 9) exhibited the best electrochemical capacitive performance in an aqueous hybrid capacitor full-cell AC/Li₄Mn₅O₁₂ as well as in an non-aqueous Li/Li₄Mn₅O₁₂ half-cell. The specific sample delivered a power density of 20 F g⁻¹ at a high discharge rate of 4 A g⁻¹ and an energy density of 31.1 Wh g⁻¹