Hu Pu, Wang Xiaofang, Wang Tianshi, Chen Lanli, Ma Jun, Kong Qingyu, Shi Siqi, Cui Guanglei
Qingdao Industrial Energy Storage Research Institute Qingdao Institute of Bioenergy and Bioprocess Technology Chinese Academy of Sciences Qingdao 266101 P. R. China; University of Chinese Academy of Sciences Beijing 100049 P. R. China.
School of Materials Science and Engineering Shanghai University Shanghai 200444 P. R. China; Materials Genome Institute Shanghai University Shanghai 200444 P. R. China.
Adv Sci (Weinh). 2016 Aug 2;3(12):1600112. doi: 10.1002/advs.201600112. eCollection 2016 Dec.
The development of excellent performance of Na-ion batteries remains great challenge owing to the poor stability and sluggish kinetics of cathode materials. Herein, B substituted NaVP B O (0 ≤ ≤ 1) as stable cathode materials for Na-ion battery is presented. A combined experimental and theoretical investigations on NaVP B O (0 ≤ ≤ 1) are undertaken to reveal the evolution of crystal and electronic structures and Na storage properties associated with various concentration of B. X-ray diffraction results indicate that the crystal structure of NaVP B O (0 ≤ ≤ 1/3) consisted of rhombohedral NaV(PO) with tiny shrinkage of crystal lattice. X-ray absorption spectra and the calculated crystal structures all suggest that the detailed local structural distortion of substituted materials originates from the slight reduction of V-O distances. NaVPBO significantly enhances the structural stability and electrochemical performance, giving remarkable enhanced capacity of 100 and 70 mAh g when the C-rate increases to 5 C and 10 C. Spin-polarized density functional theory (DFT) calculation reveals that, as compared with the pristine NaV(PO), the superior electrochemical performance of the substituted materials can be attributed to the emergence of new boundary states near the band gap, lower Na diffusion energy barriers, and higher structure stability.
由于阴极材料稳定性差和动力学迟缓，钠离子电池优异性能的发展仍然面临巨大挑战。在此，提出了B取代的NaVPBO（0≤≤1）作为钠离子电池的稳定阴极材料。对NaVPBO（0≤≤1）进行了实验和理论相结合的研究，以揭示晶体和电子结构的演变以及与不同B浓度相关的钠存储性能。X射线衍射结果表明，NaVPBO（0≤≤1/3）的晶体结构由菱面体NaV(PO)组成，晶格有微小收缩。X射线吸收光谱和计算得到的晶体结构均表明，取代材料详细的局部结构畸变源于V-O距离的轻微减小。NaVPBO显著提高了结构稳定性和电化学性能，当C速率增加到5C和10C时，容量显著提高，分别达到100和70mAh g。自旋极化密度泛函理论（DFT）计算表明，与原始的NaV(PO)相比，取代材料优异的电化学性能可归因于带隙附近新边界态的出现、更低的钠扩散能垒和更高的结构稳定性。
