Manipulating Stable Layered P2-Type Cathode via a Co-Substitution Strategy for High Performance Sodium Ion Batteries

Mn-based layered transition metal oxides (TMOs) are promising cathodes for sodium ion batteries (SIBs) due to their eco-friendly character and abundant natural reserves. However, the complex phase changes and structural instability of the Mn-based layered TMO cathodes during electrochemical process are major hindrances to meet the commercial application. Cation substitution is an effective way to stabilize the structure and accelerate the Na+ kinetics of cathode materials. Herein, an intriguing layered P2-type Mn-based Na0.7Li0.06Zn0.06Ni0.21Mn0.67O2 material is reported by substitution of Li and Zn for partial Ni. The occupation of inert elements on Ni sites could well maintain the crystal structure, giving rise to a prominent cycle life and improved electrochemical kinetics. The as-prepared electrode presents an initial discharge capacity of 131.8 mA h g(-1) at 20 mA g(-1) and preserves 91.9% capacity after 100 cycles, accompanied with enexcellent rate performance (108 mA h g(-1) at 500 mA g(-1)). Furthermore, the single-phase reaction mechanism during the sodiation/desodiation process is verified by in situ X-ray diffraction. Additionally, theory computations prove the decreased migration energy barriers and enhanced Na+ kinetics ulteriorly. This dual-doping strategy inspires an effective way to produce high performance cathode materials for SIBs.

Automated summary

This study reports the synthesis of a layered P2-type Mn-based Na0.7Li0.06Zn0.06Ni0.21Mn0.67O2 material by partially substituting Ni with Li and Zn. The resulting material exhibits a stable crystal structure and shows excellent cycle life and electrochemical kinetics during the electrochemical process. It is a promising cathode material for sodium ion batteries.