Cost-Effective Layered Oxide - Olivine Blend Cathodes for High-Rate Pulse Power Lithium-Ion Batteries

Sustainability and supply-chain concerns require lithium-ion batteries (LIBs) free from critical minerals, such as nickel and cobalt. While recent advances provide encouraging signs that cobalt can be removed, the question remains how much Ni can be removed from Co-free layered oxide cathodes before sacrificing critical performance metrics. This study highlights the effect of reducing Ni by benchmarking several Co-free cathodes with decreasing Ni content. Keeping the energy density the same by increasing the charge voltage, cathodes below 80% Ni content exhibit worsened capacity fade due to increasing oxygen release and electrolyte decomposition. Charge transfer and diffusion kinetics are also hindered with increasing Mn content and exacerbated by resistive surface phases formed at high voltages, rendering lower-Ni, Co-free cathodes less competitive than high-Ni cathodes for high energy and power applications. It is demonstrated blending layered oxide with olivine as an effective alternative to deliver energy density and cycling stability comparable to lower-Ni cathodes with moderate charging voltages. Blending with 30 wt% olivine LiMn0.5Fe0.5PO4 (LMFP) virtually eliminates the diffusion limitation of layered oxides at low state-of-charge, with enhanced pulse power characteristics rivaling the high-Ni counterparts. Cathode blending can further reduce the overall Ni content and cost without the performance limitations of lower-Ni, Co-free cathodes. A side-by-side performance and cost assessment of cobalt-free LiNixMnyAlzO2 (NMA) cathodes reveals the nickel reduction limit and the associated performance limitations of lower-nickel (approximate to 70%) cathodes. Blending layered oxide with olivine LiFePO4 (LFP) or LiMn0.5Fe0.5PO4 (LMFP) not only delivers similar energy density and reduces Ni content further, but also provides synergistic pulse power characteristics superior to lower-Ni cathodes. image