The Synthesis And The Research Of Electrochemical Properties Of The Pyrolytic Hard Carbon Anode Of Na-ion Batteries

With the development of human industrialization process, the traditional fossil fuel decreasing, the global environment deteriorating, environmental pollution and energy crisis have threaten to people’s survival and health. So, in order to achieve the sustainable development and pursuit green life, human beings must develop new energy, and the secondary batteries is considered to be a way to solve the problems. However, with the further application of Li-ion battery, it faces inevitable challenges: lithium resources and cost. In recent years, Na-ion battery has drawn much interest as a power source for large-scale grid energy storage, because the low cost and abundant resources of sodium. Therefore, low-cost, long-life and room-temperature Na-ion battery will be promising for application in large-scale energy storage system in the future. So, in this paper, we discuss the key anode material of hard carbon of Na-ion battery.(1) In this paper, hard carbon materials were synthesized through pyrolysis of PVC nanofibers from 600℃ to 800℃, where the PVC nanofibers precursor were prepared by an electrospinning method. For comparison, another hard carbon was synthesized by direct pyrolysis of commercial PVC particles. The as-prepared hard carbon samples were used as anode materials for Na-ion batteries at room temperature. The hard carbon obtained from PVC nanofibers can achieve a high reversible capacity of 271 mAh/g, as well as an initial coulombic efficiency of 70%, which are much superior to those of the later, namely, a reversible capacity of 206 mAh/g and an initial coulombic efficiency of 60%. In addition, the hard carbon originated from the PVC nanofibers also showed good cycling stability and rate performance. Namely, the initial discharge capacities are 389, 228, 194, 178, 147 mAh/g at the current density of 12, 24, 60, 120 and 240 mA/g, respectively; and retain 211 mAh/g after 150 cycles. The excellent cycle performance, high reversible capacity and good rate capability enable this hard carbon to be a promising anode candidate for Na-ion battery.(2) We also studied the effects of sugar isomers(i.e. glucose and fructose, maltose and sucrose) of the two groups as precursors on the electrochemical performances. Pyrolysis temperature was obtained by thermogravimetric analysis; The morphology of the pyrolysis hard carbon was characterization by scanning electron microscopy(SEM); Through charge-discharge, cyclic test, rate capability test, the electrochemical characteristics of the as-prepared samples for Na-ion batteries were evaluated and discussed. Finding the best pyrolysis temperature, respectively is 1000℃,1000℃,1000℃,1100℃;and we compared with the hard carbon from isomers, finding that electrochemical performance of glucose is better than that of fructose, and under low current density, maltose’s electrochemical performance is excellent, however, the sucrose has better performance in ratio. Therefore, when choosing carbon source, its isomer can be given first.