Enhancing the Electrode Gravimetric Capacity of Li_1.2Mn_0.4Ti_0.4O₂ Cathode Using Interfacial Carbon Deposition and Carbon Nanotube-Mediated Electrical Percolation

Mn-based cation-disordered rocksalt oxides (Mn-DRX) areemergingas promising cathode materials for next-generation Li-ion batteriesdue to their high specific capacities and cobalt- and nickel-freecharacteristic. However, to reach the usable capacity, solid-state synthesized Mn-DRX materials require activation via postsyntheticball milling, typically incorporating more than 20 wt % conductivecarbon that adversely reduces the electrode-level gravimetric capacity.To address this issue, we first deposit amorphous carbon on the surfaceof the Li1.2Mn0.4Ti0.4O2 (LMTO) particles to increase the electrical conductivity by 5 ordersof magnitude. Although the cathode material gravimetric first chargecapacity reaches 180 mAh/g, its highly irreversible behavior leadsto a first discharge capacity of 70 mAh/g. Subsequently, to ensurea good electrical percolation network, the LMTO material is ball-milledwith a multiwall carbon nanotube (CNT) to obtain a 78.7 wt % LMTOactive material loading in the cathode electrode (LMTO-CNT). As aresult, a 210 mAh/g cathode electrode gravimetric first charge and165 mAh/g first discharge capacity values are obtained, compared tothe respective capacity values of 222 and 155 mAh/g for the LMTO materialball-milled with 20 wt % SuperP C65 electrode (LMTO-SP). After 50cycles, LMTO-CNT delivers a 121 mAh/g electrode gravimetric dischargecapacity, largely outperforming the value of 44 mAh/g of LMTO-SP.Our study demonstrates that while ball milling is necessary to achievea significant amount of capacity of LMTO, a careful selection of additives,such as CNT, effectively reduces the required carbon quantity to achievea higher electrode gravimetric discharge capacity.