Phase distribution and lattice coherency for Li-rich zero-deformation cathode design

Chemo-mechanical degradation accompanying anisotropic lattice strain and stress is one of the critical failure modes of layered cathode materials, leading to capacity loss. While “zero-strain” or “zero-volume” advanced cathode materials have shown potential in addressing this issue, design principles and rational strategies for achieving a zero-deformation property still remain elusive. Here, we demonstrate that phase distribution and lattice coherency are key factors in controlling lattice changes and isotropy at phase boundaries within layered-rocksalt intergrown Li-rich cathode materials. These parameters are influenced by kinetics of transition metal ordering from rocksalt to layered phase, as well as atomic intermixing between two phases. Our findings reveal that higher lattice coherency, enhanced by cation intermixing between layered and rocksalt phases, effectively suppresses the lattice and volume changes, promoting isotropic lattice change behavior. Consequently, we successfully designed a zero-deformation cathode with lattice and volume changes of less than 1 %, which is further validated through solid-state battery operation under low stack pressure (~1 MPa). This work introduces phase boundary design strategies for developing zero-deformation cathode materials for next-generation Li-ion and solid-state batteries.