Integrating Superlattice to Regulate P2‐O2 Phase Transition and Improve Cycling Stability in Sodium‐Ion Batteries

Abstract P2‐Na 2/3 Ni 1/3 Mn 2/3 O 2 is a promising cathode material for sodium‐ion batteries (SIBs), but it faces the rapid capacity decay due to P2‐O2 phase transition. The superlattice is a stable structure, compositing it can effectively eliminate the P2‐O2 phase transition. Based on superlattice of NaLi 1/3 Mn 2/3 O 2 , a series of x NaLi 1/3 Mn 2/3 O 2 ⋅ (1‐ x )Na 2/3 Ni 1/3 Mn 2/3 O 2 ( x =0, 0.3, 0.4, 0.5) were first synthesized by compounding NaLi 1/3 Mn 2/3 O 2 into Na 2/3 Ni 1/3 Mn 2/3 O 2 in this article. The XRD and SAED show that special superlattice guarantees the structure stable of materials, resulting in a first order phase transformation to a solid solution reaction in high voltage. The composite cathode materials realize excellent cycle performance and discharge specific capacity. When x =0.4, the capacity retention rate is 82.64 % after 100 cycles, which is greatly improved compared with 30.60 % of Na 2/3 Ni 1/3 Mn 2/3 O 2 . This paper provides a new idea for using superlattice to stabilize the structure and improve the electrochemical performance for SIBs.