Self-Template Synthesis of NaCrO₂ Submicrospheres for Stable Sodium Storage

Sodium-ion batteries (SIBs) are the appropriate alternatives to lithium-ion batteries (LIBs) for the large-scale energy storage applications because of the abundant resources and wide distribution of sodium on earth. O3-NaCrO₂ is a promising cathode material for SIBs due to its stable structure and low-cost raw materials. In this paper, we design and synthesize a powder consisting of submicrometer-sized O3-NaCrO₂ spheres (s-NaCrO₂) self-assembled with nanoflakes, which exhibits faster ion migration ability and strong structure robustness. The galvanostatic intermittent titration technique test reveals the higher apparent Na⁺ diffusion coefficient of s-NaCrO₂ when compared with a normal NaCrO₂ powder with an irregular particle morphology_. The s-NaCrO₂ shows impressive electrochemical properties with a capacity of 90 mAh g^-1 at 50 C. In addition, outstanding cycling stability is shown when tested at 20 C, where a capacity of 90 mAh g^-1 is maintained with a retention of 87% after 1500 cycles. Also, s-NaCrO₂ is advantageous at high (50 °C) and low (-10 °C) temperatures. The full cells assembled employing Sb/C as the anode exhibit good rate capability with 85 mAh g^-1 obtained at 50 C.