Exploring layered lithium-rich spinel composite cathodes for lithium-ion battery obtained by the solution combustion-mechanochemical synthesis

Abstract

In this study, layered lithium-rich oxides (LLO) cathode materials were modified with different amounts of the spinel phase to form integrated layered-layered-spinel (LLS) hetero-composites [0.5Li2MnO3 ⋅ (0.5 − x) LiNi0.5Mn0.3Co0.2O2 ⋅ xLiMn1.5Ni0.5O4 (0.05 ≤ x ≤ 0.25)] using a facile solution combustion mechanochemical synthesis method for the first time. The XRD results indicate that all the LLS materials have distinct layered and spinel phases with R3m, C2/m and Fd3m space groups. Notably, the initial coulombic efficiency of the LLS materials increased with increase in the spinel content but showed a reduction both in their charge and discharge capacities. The LLS doped with 5 % spinel content (651LLS), exhibited the best electrochemical performance compared to the ones doped with 15 % spinel (642LLS) and 25 % spinel (633LLS). The 651LLS cathode which had the lowest spinel content, gave the smallest particle size and the largest unit cell volume. Consequently, the 651LLS cell delivered the highest initial discharge capacity of 279.58 mAh g⁻¹ and a capacity retention of 84.71 % after 50 cycles at a current density of 10 mA g⁻¹ within a voltage window of 2.0 – 4.8 V. Additionally, the 651LLS cell demonstrated superior rate capability with the average capacities 275, 225, 200, 155, and 90 mAh g⁻¹ at 10, 20, 50, 100, and 200 mA g− 1. This enhanced performance is attributed to the optimised spinel amount and the smaller particle size which facilitated faster Li-ion transport during cycling. Also, the optimal electrochemical behaviour of the 651LLS cathode is linked to its optimum spinel content (~5 %) which contributed to its improved structural stability. The results show that the amount of spinel in these LLS materials must be carefully tuned in relation to the operating cycling parameters to produce optimum electrochemical performance.