Solvent-Free Mechano-Fusion Assisted Carbon Coatings for High Capacity Cathode - a Practically Feasible Approach

Abstract

Spinel LiMn2O4 (LMO) has emerged attractive as well as a potential alternative candidate to toxic LiCoO2 for high energy applications because of its relative abundance, low cost and environmentally benign. Although LMO has several advantages, it suffers from immense polarization, severe capacity decay and Mn dissolution resulting in Jahn-teller distortion with 6.5 % increased unit cell volume. Various strategies have already been proposed to alleviate these detrimental issues such as heteroatom doping, surface blocking coatings, and functional electrolyte additives. However, the surface coating is one of the promising techniques to improve the kinetics and long-term cycling performance over others. Herein, a simple and cost effective Mechano-thermal fusion was proposed because of its practical feasibility. The strong centrifugal force followed by a high shear and compression force fuse the guest molecule (super P) over the host (LMO), which ensures the uniform innate coating as like core-shell structure. Further, the fused carbon coating not only helps to reduce the polarization by improved conductivity but also acts as a barrier layer to control the Mn dissolution. The core-shell material delivered a specific capacity of 125 mAh g-1 at the initial and decreased to 103 mAh g-1 after 1000 cycles with 82 % of capacity retention at 0.75 C. Similarly, the above material exhibits excellent rate capability behaviour. The improved kinetics of the core-shell material has further been confirmed by heterogenous rate calculation and found to be 3.9 to 4.1. Further, the core-shell material exhibits stable cycling performance while couple to MCMB anode (full-cell) with above 70 % retention for the studied 1000 cycles.