Cathode in Rechargeable Lithium-ion Battery under Low Polarization Potential Limit*

Certain transition metal oxides-based electrode materials for Li-ion batteries (LIBs) have attracted importance due to their low cost, thermal stability, and high specific energy. In this work, sheet-like Li₄Ti₅O₁₂ (LTO) with a calculated band gap of ~3.95 eV and V₂O₅ [1] was synthesized via a solution and green approach process. The electrochemical performance of the LTO anode was studied in detail by widening its potential window. The obtained LTO suffers high polarization and intercalation plateau loss when the discharge potential limit is set below 0.5 V. In addition lowering the discharge potential leads to a considerable increase in the specific discharge capacity: 195.56 mAh/g and 241.45 mAh/g at 0.1 C-rate for 0.5 V and 0 V, respectively. Regardless of high initial capacity, it limits its potential use over long-term cycling due to severe capacity fading, primarily due to the intercalation of lithium ions in the vacant sites of the Li₇Ti₅O₁₂ after crossing the 1 V, which further leads to the formation of Li₉Ti₅O₁₂, creating hindrance and less diffusive pathways for the subsequent lithium ions. Similarly, the cell shows excellent capacity retention of 86.37% after 250 cycles under the potential window of 1-2.5 V and also suffers less plateau loss even at high C-rates (>1 C). The V2O5 cathode cell exhibits an initial discharge capacity of 143.94 mAh/g at 0.1 C-rate between 2.5-4 V but suffers high polarization and curve distortion at high scan rates (>0.2 mV/s) in the CV test. Moreover, Li₄Ti₅O₁₂||V₂O₅ full-cell assembly was carried out with the as-synthesized anode and cathode after successfully restricted electrochemical lithiation of V2O5 to 2.5 V. The full cell delivers an initial discharge capacity of 126.62 mAh/g at 0.12 C-rate with an energy density of 221.59 Wh/Kg. The above work indicates the potential use of LTO-V₂O₅ full-cell for high-power applications such as electric vehicles (EV). In addition, various ex-situ characterization (post cycling): XPS, TOF-SIMS, XRD, Raman, AFM, and FTIR, etc., were carried out to study electrode surface morphology and its interaction with electrolyte for SEI layer formation.

[1]  Green Chem., 2021,23, 8200-8211