Observation of the structural changes of sol-gel formed Li₂MnTi₃O₈ during electrochemical reaction by in-situ and ex-situ studies

In this work, spinel Li₂MnTi₃O₈ is successfully prepared by using a simple sol-gel route and evaluated as an anode material for lithium-ion batteries. Charge-discharge tests exhibits than spinel Li₂MnTi₃O₈ can deliver an initial discharge capacity of 273.5 mAh g⁻¹ and the reversible capacity is kept at 206.1 mAh g⁻¹ after 50 cycles, corresponding to 94.5% of the initial charge capacity. The electrochemical reaction mechanism between Li₂MnTi₃O₈ and lithium is investigated based on the results of various in-situ and ex-situ observations. The result indicates that the (Li_0.505Mn_0.495)^tet(Li_0.495Mn_0.005)^octTi_1.5^octO₄ has multiple interstitials to accommodate lithium ions during the lithiation process, in which the octahedral sites (4a) would be occupied by lithium ions at high working potential and the tetrahedral sites (8c) would be occupied by lithium ions at low working potential. As a result, two two-phase transitions between three end-number phases Li₂MnTi₃O₈, Li₃MnTi₃O₈ and Li₅MnTi₃O₈ can be observed during the reversible electrochemical reaction between Li₂MnTi₃O₈ and lithium