四方相Nb2O5微米球的可控合成及高负载量下的储锂性能研究

Facile formation of tetragonal-Nb2O5 microspheres for high-rate and stable lithium storage with high areal capacity

通过一种简单且可控的方法合成了四种晶型的Nb2O5微米球(TT-Nb2O5,T-Nb2O5,M-Nb2O5,H-Nb2O5).将它们作为锂离子电池负极进行电化学性能测试,相较TT-Nb2O5, T-Nb2O5和H-Nb2O5, M-Nb2O5表现出更高的可逆容量、更好的循环稳定性和优异的倍率性能. M-Nb2O5在0.2 A g^-1的电流密度下,表现出163 m Ah g^-1的比容量,循环1000圈后的容量保持率为82.3%. M-Nb2O5电极材料在充放电过程中呈现扩散控制、高度可逆的锂离子脱嵌机制,表现出更高的本征电导,在22.51 mg cm^-2的超高负载量下能够实现高达2.24 m Ah cm^-2的面积比容量.在12.12 mg cm^-2的负载量下,循环100圈后的容量保持率为95.1%,表明此材料具有良好的循环稳定性.此外,还通过电化学测试、密度泛函理论计算以及原位XRD测试进一步解释了M-Nb2O5高的电子传输和锂离子传输动力学特征.

Niobium pentoxide;Ion and electron transport;Mass loading;Areal capacity;Lithium-ion batteryNiobium pentoxide(Nb2 O5) has attracted great attention as an anode for lithium-ion battery, which is attributed to the high-rate and good stability performances. In this work, TT-, T-, M-, and H-Nb2 O5 microspheres were synthesized by a facile one-step thermal oxidation method. Ion and electron transport properties of Nb2 O5 with different phases were investigated by both electrochemical analyses and density functional theoretical calculations. Without nanostructuring and carbon modification, the tetragonal Nb2 O5(M-Nb2 O5) displays preferable rate capability(121 m Ah g^-1 at 5 A g^-1), enhanced reversible capacity(163 m Ah g^-1 at 0.2 A g^-1) and better cycling stability(82.3% capacity retention after 1000 cycles)when compared with TT-, T-, and H-Nb2 O5. Electrochemical analyses further reveal the diffusioncontrolled Li+intercalation kinetics and in-situ X-ray diffraction analysis indicates superior structural stability upon Li+intercalation/deintercalation. Benefiting from the intrinsic fast ion/electron transport, a high areal capacity of 2.24 m Ah cm^-2 is obtained even at an ultrahigh mass loading of 22.51 mg cm^-2.This work can promote the development of Nb2 O5 materials for high areal capacity and stable lithium storage towards practical applications.