High Power-High Energy Polyanionic Sodium Cathodes
作者单位：Department of Materials Science and Engineering Sun-Yat Sen University
会议名称：《中国化学会2019能源材料和缺陷化学研讨会》
会议日期：2019年
摘 要：Developing high power-high energy electrochemical energy storage systems is an ultimate goal in energy storage field, which is even more difficult but significant for low cost sodium ion batteries. According to the transport properties of electrodes, constructing an effective mixed conducting network is very helpful to improve the rate performance. We have successully fabricated NaV(PO) with ultrahigh rate performance, whose rate capability even outperforms lithium cathodes. However, the energy density of NaV(PO) is not satisfactory. We experimentally investigate and improve the transport properties of high energy NaV(PO)F, whose the rate capability of NaV(PO)F is still not comparable to NaV(PO). Here, for the first time we proposed a two-step strategy(solvothermal plus ESD method) to construct a bicontinuous ordered network of 3 D porous Na(VO)(PO) F/rGO(NVOPF/rGO). This two-step strategy makes sure that NVOPF can be prepared by ESD, since it can avoid the loss of F element during synthesis. The obtained NVOPF particles are as small as 15 nm(the minimum size ever reported), and the carbon content is only 3.5% in the final nanocomposite. Such bicontinuous ordered network and small size of electroactive particles lead to significant contribution of pseudocapacitance effect to sodium storage, resulting in real high power-high energy sodium cathodes. The cathode exhibits excellent rate capability and cycling stability, whose rate performance is one of the best ever reported in both half cells and full cells. Moreover, this work provides a general and promising strategy for developing high power-high energy electrode materials for various electrochemical energy storage systems.