Study on Enhanced Properties of 343/442/541NCM Cathode Materials Derived from (Na0.25K0.15)Ni2.6-kMnk[Co(CN)6]2 Prussian Blue Analogues for Lithium-ion Batteries.

Abstract

It is technologically important to develop LiNixCoyMnzO2 (NCM) cathode materials for Li-ion batteries with the higher energy density. However, Li+/Ni2+ cation mixing phenomenon is a critical problem and makes Li ion kinetics poor, preventing the commercialization by widening an operating voltage window. Here, we report a new method of LiNixCoyMnzO2 synthesis by using (Na0.25K0.15)Ni2.6-kMnk[Co(CN)6]2 (PBA) and interesting physicochemical aspects for advanced Li-ion batteries. A chemical lithiation process of the PBAs is invented for an alkali metal/transition metal layered structure, which enables an effective transition to the NCM phase at a relatively low calcination temperature. As-prepared NCM retains a LiO2 slab space of 2.637 Å (an ideal value of 2.64 Å). In addition, It shows ~1 at.% of an suppressed Li+/Ni2+ mixing, resulting in a lowered barrier energy of 20–30 meV and an improved reversibility of a and c lattice constant during cycling. In addition, a chemical densification process is developed to sustain well-defined cubic morphology even at a high calcination temperature over 700 ℃. Resultant NCM microcubes demonstrates rate capability and superior cyclability in a broad potential windows of 2.7–4.5 V versus Li/Li+. Our results indicate that an importance of suppressing the Li+/Ni2+ cation mixing in LiNixCoyMnzO2 for a development of Li-ion batteries with the higher energy density.