Na3-xLixV2(PO4)3正极材料的制备与电化学性能研究

Study on the Preparation and Electrochemical Performance of Lithium-doped Na3-xLixV2(PO4)3 Cathode Material

通过溶胶-凝胶法合成了锂离子掺杂的磷酸钒钠(Na3-xLixV2(PO4)3)正极材料,探究了不同锂离子掺杂量对材料组成、结构及电化学性能的影响和离子传输机理。研究结果表明,锂离子的引入并不改变Na3V2(PO4)3的主晶相,但是会造成晶胞体积的减小。锂离子通过激活Na3V2(PO4)3中的Na(1)位点来提高电化学性能。具有蜂窝状结构的Na2.96Li0.04V2(PO4)3具有较好的电化学性能,在30 C下首次放电比容量达到104.9 mAh·g^-1,经过350次循环后其放电比容量为77.52 mAh·g^-1;库伦效率接近100%;其钠离子的扩散系数为2.02×10^-13 cm^2·s^-1。

In this paper,lithium ion-doped sodium vanadium phosphate(Na3-xLixV2(PO4)3)cathode material was synthesized by sol-gel method,and the effects of different amounts of lithium ion doping on the composition,structure,and electrochemical performance of the material and the mechanism of ion transport were explored.The results showed that the introduction of lithium ions did not change the main crystal phase of Na3V2(PO4)3,but it could cause the reduction of the unit cell volume.Lithium ions improved the electrochemical performance by activating Na(1)sites in Na3V2(PO4)3.The porous sample Na2.96Li0.04V2(PO4)3 has the best electrochemical performance,and the specific discharge capacity at 30 C can reach 104.9 mAh·g^-1.At the same time,the specific discharge capacity was 77.52 mAh·g^-1 and the Coulombic efficiency was close to 100%after 350 cycles at 30 C.The diffusion coefficient of sodium ion is 2.02×10-13 cm^2·s^-1 in Na2.96Li0.04V2(PO4)3.