The research group of Professor Yaqian Lan, which comes from the School of Chemistry and Materials Science, Nanjing Normal University made significant breakthrough on the research of using polyoxometalates-based metal–organic frameworks (POMOFs) as new generation electrode materical for lithium-ion batteries (LIBs). This discovery provides new insights into the design of synthesized new electrode materials for LIBs with high performance and the understanding of the relations between its structure and performance.
Faced with the decreasing non-renewable energy resource and the increasingly serious environmental problems, the development of a renewable new energy which is highly-efficient, safe, clean brooks no delay. Currently, the two major Electrochemical energy storage (EES) devices are supercapacitors and LIBs. But due to the differences on the energy storage mechanism, supercapacitors enable high rate performances but with low energy density, while LIBs provides high energy density but without high rate performances. Hence, it is of great significance to design one single EES device which combines battery-like energy and supercapacitor-like rate performances.
Professor Lan’s research group tactfully take advantage of POMOFs/reduced graphene oxide (RGO) as the battery cathode material for LIBs, and get synthesized POMOFs/RGO nanocomposites namely NENU-9/RGO by a facile one-pot method. The POMOFs shares the advantages of both Metal-organic frameworks (MOFs) and polyoxometalates (POMs). MOFs provide regular arranged pores which could mechanically buffer the volume change caused by the insertion andextraction of lithium-ion particles during the charge-discharge process and ensure good cycling stabilities. The reversible redox reaction of metal ion ( Mo and V ) in the single POMs can store 22 metal ions at maximum. At the same time, RGO can effectively increase the electronic conductivity of the electrode materials. Therefore, NENU-9/RGO, when used as cathode material for LIBs and charges/discharges at a current density of 50 mA g−1, the reversible capacities is over 1000mAh g-1. Moreover, the capacity retention of NENU-9/RGO is nearly 105% after 400 cycles’ charge-discharge processes at a high current density of 3000 mA g-1.Its capacity and rate performances are almost the best compared to the reported pristine MOFs and POMs based materials.
Based on theoretical and experimental approach, it is proved that such excellent performance is benefited from the cooperative capacity of battery-supercapacitor behavior among which the capacitive contribution makes up about 69.0%
The related achievements are published on Nano Energy entitled as“POM-Based Metal-Organic Framework/Reduced Graphene Oxide Nanocomposites with Hybrid Behavior of Battery-Supercapacitor for Superior Lithium Storage”(2017, 34, 205-214; DOI: 10.1016/j.nanoen.201702028). For more information, you can visit http://dx.doi.org/10.1016/j.nanoen.2017.02.028.Nano Energy is a top journal in the field of nano energy whose impact factor is 11.553 in 2016. The first author of this research is Tao Wei, a post-doctor in the School of Chemistry and Materials Science, and the joint first author is Mi Zhang, a graduate student in the School of Chemistry and Materials Science. This is the first time that NNU has published a research paper in Nano Energy.