Lixiong Qian,Rui Huang,Haoran Zhang,Shengxue Yan,Shaohua Luo
Co-free Fe/Mn-based cathodes have become a popular choice for sodium-ion batteries (SIBs) due to their affordability and impressive theoretical capacity. Nevertheless, the issue of their terrible battery life and rate capability continues to be their hindrances. A set of three-factor, three-level orthogonal experiments was adopted, including the calcination temperature, calcination time, and heating rate. And two single-factor experiments were carried out to further optimize the preparation conditions. Finally, the optimal conditions were obtained as follows: the calcination temperature was 900 °C, the calcination time was 12 h, and the heating rate was 5 °C min–1. The layered oxide cathode material Co-free P2-Na2/3Fe1/2Mn1/2O2 was synthesized by the solid phase method. Under the control of the optimal conditions, the P2-Na2/3Fe1/2Mn1/2O2 cathode could yield a remarkable initial discharge specific capacity (179.3 mAh g–1, 0.1 C) and cycle stability (54.6% over 50 cycles). These findings further declared that it was feasible to design Co-free Fe/Mn-based cathode materials with superior performance, which might offer guidance for popularizing cost-effective Fe/Mn-based cathode materials in the future.
Yarn-ball-shaped P2-Na 2/3 Fe 1/2 Mn 1/2 O 2 nanofiber cathode material is synthesized by a magnetic-assisted electrospinning method. Based on the electrospinning method, an electromagnetic-field is performed to keep the nanofibers rotating to form the yarn-ball-like architecture. XRD result indicates that the sample is a pure P2-type Na 2/3 Fe 1/2 Mn 1/2 O 2 phase with good crystallization. SEM results show that the diameter of the balls is about 10–50 µm, and the balls are composed of nanofibers with a diameter of 200–400 nm. This special architecture is beneficial to increase the Na + diffusion speed and tap-density of nanofiber material. Electrochemical tests show that the sample has a high discharge specific capacity of 218.6 mAh g −1 at 0.1 C rate, and exhibits good rate capability and excellent cycling performance.
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