Low-strain Co-free Li-rich layered cathode with excellent voltage and capacity stability

Abstract

Owing to the inherent advantages of low cost and high capacity, cobalt (Co)-free lithium (Li)-rich layered oxides have become one of the most promising cathodes for next-generation high-energy lithium-ion batteries. However, these familial cathodes suffer from serious voltage decay due to many reasons, such as oxygen release and transition metal (TM) migration, which are closely related to nanoscale strain evolution. Here, by combining the synergistic effects of surface integration, bulk doping, and concentration gradient, we successfully construct a Co-free Li-rich layered cathode with a very small volumetric strain (1.05%) between 2.0 and 4.8 V, approaching the critical value of zero strain. Various characterizations indicate that the constructed zero-strain cathode can significantly suppress the TM migration, interfacial reactions, and structural degradation including cracks, lattice defects, phase evolution, and nanovoids, leading to improved voltage stability of Co-free Li-rich layered oxides during the prolonged cycles. This work provides a strategy to eliminate the lattice strain of Li-rich layered cathodes and facilitates the up-scaled application of the as-prepared cathode materials.