Zhu Kaiyue, Wu Tao, Huang Kevin
Department of Mechanical Engineering , University of South Carolina , Columbia , South Carolina 29201 , United States.
ACS Nano. 2019 Dec 24;13(12):14447-14458. doi: 10.1021/acsnano.9b08039. Epub 2019 Nov 27.
Aqueous Zn-ion batteries (ZIBs) are promising candidates for grid-scale energy storage because they are intrinsically safe, cost competitive, and energy intense. However, the development of ZIBs is currently challenged by the performance of cathode materials. Herein, we report on CaVO·3.5HO (CaVO) nanobelts as a type of ZIB cathode with a discharge capacity of 466 mAh g (equivalent to an energy density of 345.6 Wh kg) at 0.1 A g and a capacity retention rate of 100%, 95%, and 74% at 5.0 A g for 500, 1000, and 2000 cycles, respectively. Through a combined theoretical and experimental study, we reveal that the outstanding energy and power performances of CaVO are deeply rooted in its Zn-transport friendly, bilayer ρ-type VO structure, and the structure-derived reversibility in single-phase Zn-intercalation/deintercalation process. We also uncover that Ca as a structural stabilizer in CaVO undergoes a fast, performance-harmless ion-exchange with Zn in the electrolyte and the entire Zn-intercalation/deintercalation process is accompanied by a counter migration of solvent water. Last, we show that a successful synthesis of CaVO depends critically on pH value of the precursor solution and the structural stability of CaVO is controlled by the co-presence of Ca/Zn and structural water.
水系锌离子电池（ZIBs）因其本质安全、成本具有竞争力且能量密度高，是电网规模储能的理想候选者。然而，目前ZIBs的发展受到阴极材料性能的挑战。在此，我们报道了CaVO·3.5HO（CaVO）纳米带作为一种ZIB阴极，在0.1 A g时放电容量为466 mAh g（相当于能量密度为345.6 Wh kg），在5.0 A g下500、1000和2000次循环时的容量保持率分别为100%、95%和74%。通过理论与实验相结合的研究，我们揭示了CaVO优异的能量和功率性能深深植根于其对锌传输友好的双层ρ型VO结构，以及在单相锌嵌入/脱嵌过程中由结构衍生的可逆性。我们还发现，CaVO中作为结构稳定剂的Ca在电解液中与Zn发生快速且对性能无害的离子交换，并且整个锌嵌入/脱嵌过程伴随着溶剂水的反向迁移。最后，我们表明CaVO的成功合成关键取决于前驱体溶液的pH值，并且CaVO的结构稳定性由Ca/Zn和结构水的共同存在所控制。
