A joint team from Xiangtan University proposes a new paradigm for the design of cathode materials in sodium-ion batterie

On the 31st Mar,  a research team led by Professor Liu Li from the School of Chemistry at Xiangtan University, in collaboration with teams from Nanjing Tech University and Nankai University, made groundbreaking progress in the field of cathode materials for sodium-ion batteries. The related findings were recently published in the international journal *Journal of the American Chemical Society*.

Sodium-ion batteries, with their abundant sodium resources, are an ideal choice for large-scale energy storage. However, the complex phase transitions and voltage hysteresis during charge-discharge cycles severely limit their energy density and cycle life. Traditional modification strategies focus on in-plane design of layered oxides, making it difficult to address the issue of out-of-plane structural instability.

This time, the research team approached the issue from the perspective of crystallographic symmetry, proposing a new strategy called "out-of-plane symmetry design." By introducing charge disproportionation in the alkali metal layer, they induced monoclinic lattice distortion in P3-type layered oxides, creating unique out-of-plane symmetry. This achieved coexistence of P-type and O-type sodium ion interstitial sites, blocked long-range oxygen ion sliding, and effectively suppressed harmful phase transitions.

Tests show that the cathode material prepared based on this strategy exhibits a cycle-averaged voltage lag of only 0.16V after 100 cycles, with an energy density of 437 Wh/kg. At a current density of 100 mA/g, the capacity retention rate reaches 80.2% after 200 cycles, far surpassing that of comparative materials. This strategy demonstrates strong universality and can be extended to other layered electrode systems, providing key technological support for the industrialization of sodium-ion batteries.