Jiang Yong, Song Daiyun, Wu Juan, Wang Zhixuan, Huang Shoushuang, Xu Yi, Chen Zhiwen, Zhao Bing, Zhang Jiujun
School of Environmental and Chemical Engineering , Shanghai University , Shanghai 200444 , China.
Institute for Sustainable Energy , Shanghai University , Shanghai 200444 , China.
ACS Nano. 2019 Aug 27;13(8):9100-9111. doi: 10.1021/acsnano.9b03330. Epub 2019 Jul 24.
SnS materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS/graphene/SnS (SnS/rGO/SnS) composite with ultrathin SnS nanosheets covalently decorated on both sides of reduced graphene oxide sheets C-S bonds. Owing to the graphene sandwiched between two SnS sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Å for SnS, which could facilitate the insertion/extraction of Li/Na ions with rapid transport kinetics as well as inhibit the restacking of SnS nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g for Li/Na-ion batteries even at 10 A g. No distinct morphology changes occur after 200 cycles, and the SnS nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.
硫化锡（SnS）材料因其具有高比容量的层状结构，在电化学储能领域引起了广泛关注。然而，在充放电循环过程中，其容易发生重新堆叠的特性会导致电极结构不稳定，并严重降低容量。在本文中，我们报道了一种简单的一步水热合成法，制备出硫化锡/石墨烯/硫化锡（SnS/rGO/SnS）复合材料，其中超薄的SnS纳米片共价修饰在还原氧化石墨烯片的两侧形成C-S键。由于石墨烯夹在两个SnS片层之间，该复合材料中SnS的层间距增大至约8.03 Å，这有利于Li/Na离子的嵌入/脱出，具有快速的传输动力学，同时还能抑制SnS纳米片在充放电循环过程中的重新堆叠。密度泛函理论计算揭示了这种三明治状复合材料中层间距适中时最稳定的状态。分子模拟和实验观察得到的Li/Na离子扩散系数也表明，这种状态最适合快速离子传输。此外，大量锚定在石墨烯片上的超小SnS纳米颗粒对复合材料产生了主要的赝电容贡献，特别是在大电流密度下，这保证了其优异的高倍率性能，即使在10 A g的电流密度下，Li/Na离子电池的比容量仍分别高达844和765 mAh g。经过200次循环后，复合材料的形貌没有明显变化，SnS纳米颗粒仍能恢复到原始相，且无明显团聚，这表明这种具有高倍率性能和优异循环稳定性的复合材料是锂/钠存储的有前途的候选材料。
