Voltage, Stability and Diffusion Barrier Differences between Sodium-ion and Lithium-ion Intercalation Materials

To evaluate the potential of Na-ion batteries, we contrast in this work the difference between Na-ion and Li-ion based intercalation chemistries in terms of three key battery properties—voltage, phase stability and diffusion barriers. The compounds investigated comprise the layered AMO2 and AMS2 structures, the olivine and maricite AMPO4 structures, and the NASICON A3V2(PO4)3 structures. The calculated Na voltages for the compounds investigated are 0.18–0.57 V lower than that of the corresponding Li voltages, in agreement with previous experimental data. We believe the observed lower voltages for Na compounds are predominantly a cathodic effect related to the much smaller energy gain from inserting Na into the host structure compared to inserting Li. We also found a relatively strong dependence of battery properties on structural features. In general, the difference between the Na and Li voltage of the same structure, ΔVNa–Li, is less negative for the maricite structures preferred by Na, and more negative for the olivine structures preferred by Li. The layered compounds have the most negative ΔVNa–Li. In terms of phase stability, we found that open structures, such as the layered and NASICON structures, that are better able to accommodate the larger Na+ ion generally have both Na and Li versions of the same compound. For the close-packed AMPO4 structures, our results show that Na generally prefers the maricite structure, while Li prefers the olivine structure, in agreement with previous experimental work. We also found surprising evidence that the barriers for Na+ migration can potentially be lower than that for Li+ migration in the layered structures. Overall, our findings indicate that Na-ion systems can be competitive with Li-ion systems.United States. Office of Naval Research (Contract N00014-11-1-0212)United States. Dept. of Energy (Contract DE-FG02 96ER45571)United States. Dept. of Energy (BATT program under Contract DE-AC02-05CH11231

Lithium vanadium phosphate as cathode material for lithium ion batteries

Lithium vanadium phosphate (Li₃V₂(PO₄)₃) has been extensively studied because of its application as a cathode material in rechargeable lithium ion batteries due to its attractive electrochemical properties, including high specific energy, high working voltage, good cycle stability, and low price. In this review, the preparation of technology, structure, Li⁺ insertion/extraction mechanism, and electrochemical properties of Li₃V₂(PO₄)₃ are introduced, and with particular focus on the relationship of these topics each other. The synthetic techniques of Li₃V₂(PO₄)₃, such as high-temperature solid-state method, sol–gel method, hydrothermal method, etc. And progress of techniques in modification, such as coating and elemental doping, is reviewed. Finally, the directions for further development and prospective applications for the material are proposed.Du Tao, Shengping Wang, Yongchao Liu, Yu Dai, Jingxian Yu, Xinrong Le