不同碳源对Na_(3)V_(2)(PO_(4))_(3)正极材料储钠性能的影响

Coating a Na_(3)V_(2)(PO_(4))_(3)cathode material with carbon to improve its sodium storage

具有独特三维框架结构的钠超离子导体型磷酸钒钠是非常具有前景的钠电正极材料。在本工作中,两种碳源被选择作为原材料,通过溶胶凝胶法制备了碳包覆的磷酸钒钠。深入研究了不同炭材料对晶体结构、形貌特征、动力学特性以及电化学储钠特性的影响。结果表明柠檬酸作为碳源制备得到的磷酸钒钠,具有更大的晶胞体积和更小的粒子尺寸,导致了拓宽的离子迁移通道和缩短的离子迁移路径,进而提高动力学特性。该材料表现出优异的电化学特性,在0.1 C下可以释放112.3 mAh g^(−1)的容量。在1 C循环200圈下容量保持率接近100%。由于快速的粒子导电特性,在2 C和5 C的大倍率循环下,该材料可以释放90.0和89.1 mAh g^(−1)的初始容量,循环200圈后保持率分别为92.7%和90%。因此,这种改性的磷酸钒钠电极材料可以作为优异的正极材料应用在钠电池领域。

A sodium superionic conductor(NASICON)-type Na_(3)V_(2)(PO_(4))_(3)(NVP)with a 3D framework is a promising cathode material for sodium ion batteries.We used citric and oxalic acids as carbon sources to prepare carbon-coated NVP/C cathode materials by a sol-gel method.Their effect on the crystal structure,morphology and electrochemical performance of the coated NVP were investigated.Results indicate that compared with the NVP/C prepared from oxalic acid,NVP/C using citric acid as the carbon source has larger unit cell parameters of NVP,a smaller particle size,a thinner carbon coating layer,wider channels and shortened paths for Na^(+) migration,and superior kinetic characteristics.It had a high capacity of 112.3 mAh g^(−1) at 0.1 C and an excellent rate capability with reversible capacities of 90.0 and 89.1 mAh g^(−1) at 2 and 5 C,respectively.It also had an excellent cycling stability with capacity retention rates of nearly 100%,92.7%and 90.0%after cycling 200 times at 1,2 and 5 C,respectively.It is therefore a promising cathode material for practical use.