Fast Charge-Transport Interface on Primary Particles Boosts High-Rate Performance of Li-Rich Mn-Based Cathode Materials

Abstract

A Li-rich Mn-based layered oxide cathode (LLO) is one of the most promising cathode materials for achieving high-energy lithium-ion batteries. Nevertheless, the intrinsic problems including sluggish kinetics, oxygen evolution, and structural degradation lead to unsatisfactory performance in rate capability, initial Coulombic efficiency, and stability of LLO. Herein, different from the current typical surface modification, an interfacial optimization of primary particles is proposed to improve the simultaneous transport of ions and electrons. The modified interfaces containing AlPO4 and carbon can effectively increase the Li+ diffusion coefficient and decrease the interfacial charge-transfer resistance, thereby achieving fast charge-transport kinetics. Moreover, the in situ high-temperature X-ray diffraction confirms that the modified interface can improve the thermal stability of LLO by inhibiting the lattice oxygen release on the surface of the delithiated cathode material. In addition, the chemical and visual analysis of the cathode–electrolyte interface (CEI) composition clarifies that a highly stable and conductive CEI film generated on the modified electrode can facilitate interfacial kinetic transmission during cycling. As a result, the optimized LLO cathode exhibits a high initial Coulombic efficiency of 87.3% at a 0.2C rate and maintains superior high-rate stability with a capacity retention of 88.2% after 300 cycles at a 5C high rate.

Separating Cationic and Anionic Redox Activity in the Lithium-Rich Antiperovskite (Li2Fe)SO

“…The recent discovery of the lithium-rich antiperovskite compounds characterized by the general formula (Li 2 TM)ChO (with TM = Fe, Mn, Co; Ch = S, Se) has significantly broadened the landscape of potential cathode materials for lithium-ion batteries (LIBs) . This novel class of materials showcases highly favorable attributes in the context of lithium-ion battery application, including cost effectiveness, utilization of environmentally benign raw materials, efficient lithium diffusion, and the ability of multielectron storage per chemical unit. − From the so far investigated antiperovskite materials Li 2 FeSO, ,,− (Li 2 Co)SO, (Li 2 Mn)SO, (Li 2 Fe 1– x Mn x )SO, ,, (Li 2 Fe 0.9 Co 0.1 )SO, (Li 2 Co)SeO, (Li 2 Mn)SeO, (Li 2 Fe)S 1– x Se x O, and (Li 2 Fe)SeO, ,, the (Li 2 Fe)SO compound captivates with the highest theoretical capacity. Despite the promises of lithium-rich antiperovskites and especially (Li 2 Fe)SO, their great potential could not be fully exploited due to poor cycling stability (only 66% capacity retention in (Li 2 Fe)SO at 0.1 C after 50 cycles) …”