郑州大学《Small》：基于多孔碳电催化剂的孔隙结构调控开发高能量密度锂硫电池

图1、a) Schematic depiction of the MoC-CNS synthesis pathway; SEM images of b) MoC-CNS-3 with KCl template and c,d) MoC-CNS-3; e,f,) TEM and HRTEM images of MoC-CNS-3; g) TEM image and the corresponding elemental mapping images of MoC-CNS-3; h) XRD patterns of MoC-CNS-3; i) XPS survey spectrum of MoC-CNS-3; j) Mo 3d XPS spectra of MoC-CNS-3.

图2、a) N 2 adsorption/desorption isotherms, b) corresponding pore size distribution and c) cumulative pore volume curves of MoC-C, MoC-CNS-1, MoC-CNS-3 and MoC-CNS-5; SEM images of d) MoC-C, e) MoC-CNS-1, f) MoC-CNS-3 and g) MoC-CNS-5; SEM images of the top surfaces of h) MoC-C and i) MoC-CNS-3 separators; j) Cross-sectional SEM image of MoC-CNS-3 separator; k) Contact angle of MoC-C and MoC-CNS-3separators.

图3、a) EIS plots of Li-S batteries with different modified separators; b) Rate performances from Li-S batteries with different separators at various current densities; c–e) Galvanostatic charge/discharge profiles of the Li-S batteries with different separators at 0.1, 1 and 2 C; f) Columnar comparison of Q 2 platform specific capacity of the Li-S batteries with different separators at two voltage plateaus; g) Cycle performance of Li-S batteries using various separators at 0.5 C; h) Cycle performance of Li-S batteries using various separators at high current density of 1 C.

图4、 a) Visualization of the adsorption experiment before and after treatment (from left to right are MoC-C, MoC-CNS-1, MoC-CNS-3 and MoC-CNS-5); b) UV–vis absorption spectra of MoC-C, MoC-CNS-1, MoC-CNS-3 and MoC-CNS-5; c) Chronoamperometry curves of the electrodes with Li 2 S 6 electrolyte under a constant over potential of 2.05 V; d) CV profiles for the MoC-C and MoC-CNS-3 based Li-S batteries (sulfur loading: 1.5 mg cm −2 ) at a low scan rate of 0.1 mV S −1 ; e) CV of symmetric cells with MoC-C, MoC-CNS-3 electrodes at 0.2 mol L −1 Li 2 S 6 electrolyte condition and f) 1 mol L −1 Li 2 S 6 electrolyte condition; g) SEM image of fresh Lithium; SEM images of lithium anodes assembled with h) MoC-C-3 and i) MoC-CNS separators after 100 cycles at 0.5 C with 2 mg cm −2 sulfur loading.

图5、Comparison of EIS for the electrodes with Li 2 S 6 electrolyte at a) before discharge, and b) half discharge; GITT curves of c) MoC-C d) MoC-CNS-3 modified separators; e,f) MoC-CNS-3 and h,i) MoC-C modified separator with corresponding Raman spectra selected at different potentials; g) Schematic diagram of in situ Raman test of Li-S battery.

图6、 a) Cycling performance and b) charge/discharge profiles of the Li-S batteries with various separator at 0.1 C with sulfur loading of 6 mg cm −2 and E/S = 12.5; c) Cycling performance of the Li-S batteries with various separator at 0.05 C with sulfur loading of 8 mg cm −2 and E/S = 6 and e) at 0.05 C with sulfur loading of 12 mg cm −2 and E/S = 4; d) The gravimetric energy density of sulfur loading of 6 mg cm −2 based on the total mass of the cathode including S, modified separator layer and the electrolyte in it; f) Cycling test of pouch cell with a sulfur loading of 36 mg at 1 mA.

综上所述，我们提出了一种简便的熔盐模板法，用于合成嵌有MoC电催化剂纳米粒子的层状多孔碳纳米片。通过调节前驱体中水溶性硬模板 KCl 的添加量，可以精确控制 MoC 涂层碳纳米片电催化剂的孔隙结构。在多硫化物的液固氧化还原反应中，微孔（d<2nm）和小介孔（d<20nm）对电化学性能的影响极小，而介孔（20nm 50nm）则起着关键作用。然而，较大的中孔和大孔需要更高的电解质润湿性，这反过来又会降低Li-S 电池的能量密度。为解决这一权衡问题，我们计算了改性膜层的孔隙率，并系统地研究了孔隙率与能量密度之间的关系，以确定最佳孔隙率。最佳孔隙率为均匀的 Li2S 沉积提供了足够的有效表面积，同时确保了较高的质量能量密度。因此，基于 MoC-CNS-3的Li-S电池在高硫负荷（12mg cm-2）和 4uL mg-1 的低电解质-硫（E/S）比条件下实现了50个循环的稳定运行，最终提供了高重力能量密度。这项研究的结果为提高Li-S电池的能量密度提供了一种新策略，为增强电池性能和实际应用铺平了道路。