Leveraging Entropy for Enhanced Energy Density in Cathode-Active Materials for Li-ion Batteries

Cathode-active materials (CAMs) play a crucial role in enhancing the energy density and reducing the cost of Li-ion battery cells. This improvement can be realized in commercially-relevant layered oxides LiNi _x Mn _y Co _z O ₂ , known as NMCs, by maximizing the nickel content at the expense of cobalt. While higher nickel content boosts energy density by increasing both potential and capacity, it can result in lower capacity retention compared to first-generation NMC CAMs with x = y = z = 1 or even with z = 1 and x = y = 0. To address this challenge, the high-entropy concept is being explored as a means to improve the material’s structural stability during battery operation, thereby enhancing capacity retention and extending cycle life. This study presents evidence through calculations of the mixing entropy ( ∆S _mix = -nR∑xlnx ) effect on CAMs and suggests rational design methods for next-generation CAMs. The mixing entropy is calculated for commercial CAMs and estimated for potential CAMs to achieve better energy density in layered oxide types such as LiNi _0.7 Mn _0.15 Co _0.15 O ₂ or LiNi _0.7 Mn _0.25 Al _0.05 O ₂ . The findings underscore the potential of 70% nickel and cobalt-free CAMs, utilizing entropy as a design principle.