Luo Hao, Chen Yuxi, Huang Jing, Chen Zhanglong, Xia Xiaohong, Li Jin, Liu Hongbo
College of Materials Science and Engineering, Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology, Hunan University, Changsha 410082, China.
Nanoscale. 2020 Apr 3;12(13):7366-7375. doi: 10.1039/c9nr10750a.
Decreasing the particle size of nanoscaled battery materials will induce amazing enhancement effects on their charging rates, which holds a promise to overcome the common bottleneck of the low charging rates of batteries. However, the fabrication of ultrafine-sized battery materials remains a great challenge. Herein, 3.3 nm-sized anatase TiO2 particles embedded in electrically and ionically conductive carbon spheres have been designed and fabricated via the suppression of Ostwald ripening with the aim to obtain insight into the electrochemical behaviors of ultrafine-sized materials. The pseudocapacitive and diffusion-controlled intercalative characteristics of the 3.3 nm-sized TiO2/carbon hybrid spheres for Li-ion and Na-ion storage have been systematically investigated via a cyclic voltammetry (CV) method combined with a differential capacitance method that is introduced here for the first time to analyze battery materials. CV and galvanostatic voltage profiles demonstrate that pseudocapacitance dominates the charge storage and increases with cycling for both Li-ion and Na-ion storage. Capacitance accounts for >83% of the Li-ion storage. A specific pseudocapacitance of 558 F g-1 with a window voltage of ∼2 V in carbonate electrolyte has been achieved. The reversible capacity is higher than the theoretical capacity of TiO2 after 600 discharge/charge cycles at 2 C and maintains ∼60% of that of TiO2 even at 80 C (45 s for full discharge or charge). For Na-ion storage, a high cycliability of 2500 discharge/charge cycles has been obtained at 2 C. Capacitance accounts for ∼79% of the Na-ion storage with cycling. Ultrafine-sized materials are very promising electrode candidates for constructing pseudocapacitive batteries possessing both high energy and power densities.
减小纳米级电池材料的粒径会对其充电速率产生惊人的增强效果，这有望克服电池充电速率低这一常见瓶颈。然而，制备超细尺寸的电池材料仍然是一个巨大的挑战。在此，通过抑制奥斯特瓦尔德熟化设计并制备了嵌入在导电和离子导电碳球中的3.3纳米尺寸的锐钛矿型TiO₂颗粒，旨在深入了解超细尺寸材料的电化学行为。通过循环伏安法（CV）结合首次在此引入的用于分析电池材料的微分电容法，系统地研究了3.3纳米尺寸的TiO₂/碳混合球对锂离子和钠离子存储的赝电容和扩散控制的嵌入特性。CV和恒电流电压曲线表明，赝电容主导电荷存储，并且在锂离子和钠离子存储中均随循环增加。电容占锂离子存储的83%以上。在碳酸盐电解质中，在约2 V的窗口电压下实现了558 F g⁻¹的比赝电容。在2 C下经过600次充放电循环后，可逆容量高于TiO₂的理论容量，即使在80 C（全充或全放45秒）时仍保持TiO₂理论容量的约60%。对于钠离子存储，在2 C下获得了2500次充放电循环的高循环稳定性。电容在循环过程中占钠离子存储的约79%。超细尺寸材料是构建具有高能量和功率密度的赝电容电池非常有前景的电极候选材料。
