Research Of High Energy Cathode Material In Sodium Ion Battery

Sodium ion batteries have the same high energy density comparing with lithium ion batteries, on the other hand sodium ion batteries have low cost due to the high content in nature?appropriate energy density and redoxpotential?Ey?Na+/Na?=-2.71 V only 0.3 V above that of lithium?,so it has great prospect to develop and attracts us. But the radius of sodium ion is larger than lithium ion, the capacity of sodium ion battery is lower than lithium ion battery for the same cathode material in theory. Sodium cathode materials are under developing. The purpose of this paper is to develop high-energy positive electrode material for sodium ion battery. NaV₃O₈·xH₂ O and Na Ni_1/3Co_1/3Mn_1/3O₂ are the purpose of this paper, because they have high discharge capacity.This paper uses hydrothermal method and sol-gel method to synthesis NaV₃O₈·xH₂ O cathode material. The method of hydrothermal methodhas been optimized: 1. The calcining temperature, respectively, 300 ?, 400 ? and 500?was studied, and then the constant current charge and discharge are used to test their electrochemical characterization. Finally we find that the optimalcalcining temperature is 300 ?. Discharge capacity can reach almost 180 m Ah/g at a current density of 10 m A/g, and it is concluded that high temperature can damage the crystalline structure of NaV₃O₈·xH₂ O. 2. SDBS is used to guide the morphologyof NaV₃O₈·xH₂ O, so as to change the electrochemical properties. And we find the optimal addition amount. 3. SDBS can guide the growth of NaV₃O₈·xH₂ O in one dimensional direction. The electrochemical properties show that: When adding 0.04 mol/LSDBS, the first discharge capacity of NaV₃O₈·xH₂ O cathode material can develop from 179.39 to 227.5 m Ah/g comparing withthe blank NaV₃O₈·xH₂ O at a current density of 10 m A/g.The cathode material NaV₃O₈·xH₂ O is modified by doping anion and cation. Cation Mn³⁺ and Fe³⁺are doped. After doping Mn³⁺, rate performance is not improved especially in high current. The cycle performance also is improved slightly. After doping Fe³⁺, althoughrate performance is improved, cycle performance is unimproved. Anion F and Cl are doped. SEM shows that doping F can make nano-NaV₃O₈·xH₂ O grow in one dimensional direction and distribution more uniform. The constant current charge and discharge characterization results show that when doping 0.05 F and Cl, the cycle performance and rate performance is the best.The cathode material of NaV₃O₈·xH₂ O is coated by MgO, ZnO. It's the best coating amount is explored. The results of characterization of materialand electrochemical propertiesshow that:?1? With the increasing of the amount of ZnO, MgO, nano-NaV₃O₈·xH₂ O grows in one dimensional direction, so as to shorten the diffusion path?1%wt MgOand 1.5%wt ZnO is best??2? With the increasing of the amount of ZnO?MgO, NaV₃O₈·xH₂ O can improve the discharge capacity of NaV₃O₈·xH₂ O and reduce the impedance?1%wt MgOand 1.5%wt ZnO is best?. And the cathode material of NaV₃O₈·xH₂ O is coated using C by hydrothermal synthesis and find out the optimal adding amount to improve its discharge capacity and cycle performance successfully.Na Ni_1/3Co_1/3Mn_1/3O₂ cathode materials are synthesized in coprecipitation method for the first time, and find the best synthesis method is: coprecipitation method?tabletting, 260? calcination 2 h, 260? for 12 h burning, metal drops 8- hydroxyquinoline?.