Structure and electrochemical performance of Ba Li_(2-x)Na_xTi_6O_(14)(0≤x≤2) as anode materials for lithium-ion battery

锂离子电池BaLi_(2-x)Na_xTi_6O_(14)(0≤x≤2)负极材料的结构与电化学性能（英文）

A series of Ba Li_（2-x）NaxTi_6O_（14）（0≤x≤2） compounds as lithium storage materials were synthesized by a facile solidstate method. X-ray diffraction Rietveld refinement shows that the Bragg positions correspond to the Ba Li_2Ti_6O_（14）, indicating a successful preparation. The Na＋ions doped Ba Li_2-Ti_6O_（14） compounds have larger unit-cell volume than the pristine one because ionic radius of Na＋ion is 55% larger than that of Li＋ion. SEM shows that the Ba Li_2-xNaxTi_6O_（14）（x=0, 0.5 and1） powders show similar irregular shaped particles between500 and 1000 nm. However, Ba Li_2-xNaxTi_6O_（14）（x=1.5 and 2）powders show similar rod-like shape. CV reveals that the passivating film is mainly formed during the first insertion process, and the solid electrolyte interface film on the surface of Ba Li_2-xNaxTi_6O_（14）（0≤x≤2） is formed below 0.7 V in the first cycle. Compared with other samples, Ba Li_0.5Na1.5Ti_6O_（14） exhibits higher reversible capacity, better rate capability and superior cyclability. Ba Li_0.5Na1.5Ti_6O_（14） delivers the delithiation capacities of 162.1 mAhg^-（1）at 50 m A g^-（1）, 158.1 mAhg^-（1）at 100 m A g^-（1）, 156.7 mAhg^-（1）at 150 m A g^-（1）, 152.2 mAhg^-（1）at 200 m A g^-（1）, 147.3 mAhg^-（1）at 250 m A g^-（1）and 142 mAhg^-（1）at 300 m A g^-（1）, respectively. An interesting thing is that Ba Na2Ti_6O_（14） as anode also shows an acceptable electrochemical performance. All these improved electrochemical performances of Ba Li_0.5Na1.5Ti_6O_（14） are attributed to the lowest polarization and the highest lithium ion diffusion coefficient among all samples.Hence, Ba Li_0.5Na1.5Ti_6O_（14） with excellent cycling performance,simple synthesis route and wide discharge voltage range can be a possible anode candidate for lithium-ion batteries.

本文采用简单的高温固相法制备了BaLi_(2-x)NaxTi_6O_(14)(0≤x≤2)系列化合物作为储锂材料.XRD Rietveld精确表明Bragg点与Ba Li2Ti6O14相对应,由于Na+的半径比Li+的半径大55%,因此Na+掺杂的BaLi_2-xNaxTi_6O_(14)化合物具有比纯Ba Li2Ti6O1 4更大的晶胞体积.SEM测试结果表明,BaLi_2-xNaxTi_6O_(14)(x=0,0.5,1)粉末呈相似的不规则的颗粒状,粒径大约在500到1000 nm之间.但是,BaLi_2-xNaxTi_6O_(14)(x=1.5,2)展示了棒状的形貌.循环伏安结果表明,钝化膜主要在第一次嵌锂过程时形成,BaLi_(2-x)NaxTi_6O_(14)(0≤x≤2)表面的SEI膜主要在第一次循环且电位在0.7 V以下时形成.相对于其他样品,Ba Li0.5Na1.5Ti6O14具有较高的可逆容量,较好的倍率性能和优异的循环性能.电流密度为50、100、150、200、250和300mAg-1时,Ba Li0.5Na1.5Ti6O14的脱锂容量分别为162.1、158.1、156.7、152.2、147.3和142 mAhg(-1).有趣的是,Ba Na2Ti6O14作为阳极也展示了可接受的电化学性能.Ba Li0.5Na1.5Ti6O14所提高的电化学性能可以归因于其最小的极化和最高的锂离子扩散系数.因具有优异的循环性能、简单的合成路线和宽的放电区间,Ba Li0.5Na1.5Ti6O14可作为锂离子电池负极候选材料.