This work aimed to prepare the spinel phase Li4Ti5O12 by a combination of the low-temperature precipitation technique and assisted calcination step. X-ray diffraction (XRD) revealed that the intermediated phase was Li2TiO3, and the spinel phase could be evidently formed at 700°C for 12 to 20 hours. The morphology of spinel powder, determined by SEM and TEM, exhibited a good distribution at the submicrometric scale that promoted a fast kinetic of Li migration and an excellent performance at the high-rate cycling test. The stable performances were achieved in the charge-discharge test at different current densities: 80 mA/g (165 mAh/g), 320 mA (160 mAh/g), and 1600 mA (145 mAh/g) upon 100 cycles. Moreover, we observe a capacity retention of 48% (corresponding 80 mA/g) at a high rate of 5000 mAh/g. The cyclic voltammetry measurement displayed a reversible system and revealed the lithium diffusion coefficient of 1.15 × 10−11 cm2/s.
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.
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