Introducing high-valence elements into cobalt-free layered cathodes for practical lithium-ion batteries

The elimination of Co from Ni-rich layered cathodes is considered a priority to reduce their material cost and for sustainable development of Li-ion batteries (LIBs) as Co is becoming increasingly scarce. The introduction of 1 mol% Mo into Li(Ni0.9Mn0.1)O2 delivers 234 mAh g−1 at 4.4 V. The cycling stability of a full cell featuring the Li(Ni0.89Mn0.1Mo0.01)O2 (Mo–NM90) cathode is enhanced with a modified electrolyte; retaining 86% of its initial capacity after 1,000 cycles while providing 880 Wh kgcathode−1. The grain size refinement achieved by Mo doping dissipates the deleterious strain from abrupt lattice contraction through fracture toughening and the removal of local compositional inhomogeneities. Enhanced cation ordering induced by the presence of Mo6+ also stabilizes the delithiated structure through a pillar effect. The Mo–NM90 cathode is able to deliver a high capacity with cycling stability suitable for the long service life for electric vehicles at a reduced material cost, furthering the realization of a commercially viable Co-free cathode for LIBs.