国家纳米科学中心EcoMat：这个host厉害了，同时提高锂硫电池正、负极性能！

成果简介

具有高能量密度的锂硫 (Li-S) 电池是下一代储能体系有前景的候选者。多硫化物的穿梭效应和锂枝晶生长阻碍了锂硫电池的实际应用。鉴于此，国家纳米科学中心魏志祥团队在EcoMat发表了题为“Nitrogen-doped nanoarray-modified 3D hierarchical graphene as a cofunction host for high-performance flexible Li-S battery”的研究论文，构建了N掺杂纳米阵列修饰的3D分级石墨烯自支撑宿主材料，同时提升了锂负极和硫正极的性能。由于N掺杂纳米阵列具有高导电性、强亲和力且锂离子传输路径得到优化，本工作中的宿主材料可有效促进锂的均匀沉积和硫转化。特别地，额外的石墨烯层可有效抑制硫正极的穿梭效应。因此，锂负极显示出长循环寿命和出色的锂沉积性能，S正极显示出高容量和超高的容量保持率，并具有良好的多硫化物固定性。更重要的是，集成的锂硫电池表现出长循环稳定性和良好的柔韧性，这对未来的应用很重要。

内容详情

Figure 1 Schematic of fabrication procedure. A, Uniform dispersion of graphene oxide (GO) solution. B,C, 3D hierarchical RGO/PANI-BL and RGO/PANI. D,E, 3DRGO/NC and 3DRGO/NC-BL after three-step pyrolysis calcination. F,G, 3DRGO/NC@Li anode and 3DRGO/NC-BL@S cathode. H, The schematic of aligned vertical PANI nanoarrays on graphene sheets. I, N-doped nanoarrays without morphology change after calcination

Figure 2 A, SEM image of the 3DRGO/NC film cross section, with the inserted image showing the flexibility of the film. B,C, Surface morphology of 3DRGO/NC film under different magnifications. D, SEM image of the 3DRGO/NC-BL film cross section, with the inserted image showing the flexibility of the film. E,F, Surface morphology of barrier layer of 3DRGO/NC-BL film under different magnifications. G, Raman spectrum. H, High-resolution N 1 second spectra with peak deconvolution of 3DRGO/NC. I, Elemental mapping showing the distribution of N element

Figure 3 SEM images of 3DRGO, 3DRGO/NC, and 3DRGO/NC-BL after plating 1 mA h/cm2 Li at 1 mA/cm2. A,B, Surface morphology of 3DRGO under different magnifications. C, Cross-section of 3DRGO. D,E, Surface morphology of 3DRGO/NC under different magnifications. F, Cross-section of 3DRGO/NC. G,H, Surface morphology of 3DRGO/NC-BL under different magnifications. I, Cross-section of 3DRGO/NC-BL

Figure 4 A, Galvanostatic cycling performances with a cycling capacity of 1 mA h/cm2 at 1 mA/cm2 in Li|3DRGO@Li, Li|3DRGO/NC@Li and Li|3DRGO/NC-BL@Li symmetric cells. B, Galvanostatic rate performances with a cycling capacity of 1 mA h/cm2 at 0.5, 1, 2, 5, and 10 mA/cm2 in Li|3DRGO@Li, Li|3DRGO/NC@Li, and Li|3DRGO/NC-BL@Li symmetric cells. C, Coulombic efficiency of 3DRGO, 3DRGO/NC, and 3DRGO/NC-BL electrodes with a cycling capacity of 1 mA h/cm2 at 0.5 mA/cm2. D, Voltage profiles of Li plating on 3DRGO and 3DRGO/NC electrodes at 0.5 mA/cm2. E, Typical galvanostatic discharge-charge profiles of the 3DRGO/NC electrode with a cycling capacity of 1 mA h/cm2 at 0.5 mA/cm2

Figure 5 A, Three Li-S battery structures based on S/C cathode. 3DRGO/NC@S (cell A), 3DRGO/NC-BL@S with porous side in contact with the separator (cell B) and 3DRGO/NC-BL@S with the barrier layer in contact with the separator (cell C). B, Elemental mapping showing the distribution of S element. C, CV curves at scan rate of 0.1 mV/s in the potential range of 1.5 V to 3 V for cell C. D, Galvanostatic charge-discharge profiles during the first, 100th, 200th, 300th, 400th, and 500th cycles at 0.5 C with a potential window of 1.5-3 V of the cell C. E, Rate capability, F, Capacity retention and CE of cell A, cell B, and cell C over 500 cycles at 0.5 C

Figure 6 Schematic illustrations showing the performance of 3DRGO/NC and 3DRGO/NC-BL for Li anode and S cathode

Figure 7 A, Capacity retention and CE of two different Li-S coin cells over 400 cycles at 0.5C. B, Rate capability of flexible Li-S soft-pack battery. C, Capacity retention of the flexible battery over 200 cycles at 0.5 C at the bending radius of 1.25 cm. D-F, Experimental demonstration showing that the prototype of soft-pack battery can light up 25 green LEDs under flat, D, bent, E, and even rolled states, F

结论

总之，本工作通过设计N掺杂纳米阵列修饰的分层石墨烯为锂金属和S正极构建了3D多孔共功能宿主。通过结构设计和形貌优化，由于化学相互作用和物理作用，Li-S电池的性能得到改善。其中化学相互作用源于均匀分布的异质原子N对金属锂和多硫化物的强烈影响。物理效应来自纳米阵列对锂离子通量的限制，以及保护层对多硫化物的阻挡。3DRGO/NC表现出平滑的锂沉积行为，具有低成核过电位、超长循环寿命、高库仑效率和优异的倍率性能。3DRGO/NC-BL@S正极具有高比容量、良好的倍率性能和良好的循环性能。更重要的是，全柔性器件的进一步成功示范也证明了这种材料在柔性电子器件中的实际应用。因此，该材料在柔性储能体系的开发中显示出巨大的应用潜力。

文章信息

Ruichao Lu, Meng Cheng, Lijuan Mao, Miao Zhang, Hongxin Yuan, Kamran Amin, Chen Yang, Yueli Cheng, Yuena Meng,* Zhixiang Wei*, Nitrogen-doped nanoarray-modified 3D hierarchical graphene as a cofunction host for high-performance flexible Li-S battery, EcoMat. 2020;2:e12010.

原文链接：https://doi.org/10.1002/eom2.12010

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