1成果簡介
硅（Si）作為高能量密度鋰離子電池（LIBs）最具前景的負極材料之一，因其在循環過程中體積變化顯著而面臨商業化挑戰。將非晶硅納米顆粒（SiNP）嵌入多孔碳基體已成為緩解此問題的有效策略，特別是通過近期開發的以硅烷為前驅體的化學氣相沉積（CVD）途徑。碳骨架的結構特性——如孔徑、孔體積和比表面積——至關重要。本文，武漢理工大學屈德宇 教授、劉丹 副教授等在《ACS Appl. Energy Mater 》期刊發表名為「Optimization of Porous Structure on Carbon Host for Silicon/Carbon Anodes in High-Capacity Lithium-Ion Batteries」的論文，研究採用三種模型碳載體：具有單分散微孔的沸石模板碳（ZTC）、均勻分布4.9納米介孔的CMK-3，以及具有單分散8.3納米介孔的有序介孔碳（OMC-8）。系統研究了碳載體的多孔結構對硅/碳（Si/C）負極性能的影響。
結果表明，微孔結構能提高硅負載的孔隙利用效率，從而實現高比容量、優異的倍率性能和卓越的循環穩定性。當作為鋰離子電池負極時，嵌入ZTC的碳包覆硅（C@Si@ZTC）電極在0.1C充放電條件下展現出2175 mAh g–1的超高比容量，初始庫侖效率達87.48%。在0.2C條件下經200次充放電循環後，仍保持1825 mAh g–1的可逆容量。此外，在圓柱形18650電池配置（C@Si@ZTC/石墨||NCM811）中，該電池展現出2143 mAh的容量，並在1C條件下經400次循環後仍保持92.4%的容量保持率。
2圖文導讀
圖1. (a) SEM image of the ZTC. (b) TEM image of ZTC. (c) Nitrogen sorption isotherm and pore size distribution curve of ZTC. (d) SEM image of CMK-3. (e) TEM image of CMK-3. (f) Nitrogen sorption isotherm and pore size distribution curve of CMK-3. (g) SEM image of OMC-8. (h) TEM image of OMC-8. (i) Nitrogen sorption isotherm and pore size distribution curve of OMC-8.
圖2. (a) Schematic of silicon deposition into the porous carbon host followed by the carbon coating. HAADF-STEM-EDS elemental mapping images of (b) C@Si@ZTC. (c) C@Si@CMK-3, and (d) C@Si@OMC-8. HRTEM images of the (e) C@Si@ZTC, (f) C@Si@CMK-3, and (g) C@Si@OMC-8. (h, i) Nitrogen sorption isotherm and pore size distribution curve of C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8. (j) Percentages of each component in C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8.
圖3. Schematic of silicon deposition behavior in a carbon host with differential porosity.
圖4. (a) Cyclic performance at 0.2C (0.1C for the first cycle), (b) Initial discharge–charge voltage profiles at 0.1C, and (c) rate performance of the C@Si@ZTC, C@Si@CMK-3 and C@Si@OMC-8. (d) Nyquist plots of the C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8 electrodes after 3 cycles. (e–g) CV curves at various scan rates of C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8; (h) the relationship between the peak currents and scan rates in logarithmical format. Galvanostatic intermittent titration technique (GITT) corresponding DLi+C values as a function of (i) lithiation and (j) delithiation states.
圖5. (a, e, i) Top-view SEM images of the C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8 electrodes before and (b, f, j) after 200 cycles. (c, g, k) Cross-sectional SEM images of the C@Si@ZTC, C@Si@CMK-3, and C@Si@OMC-8 electrodes before and (d, h, l) after 200 cycles with fully charged (delithiated) state.
圖6. (a) Cyclic performances of C@Si@ZTC||NCM811, C@Si@CMK-3||NCM811, and C@Si@OMC-8||NCM811 full cells at 1C. (b) Comparison of the rate performances of the three full cells. (c) Voltage profiles of the C@Si@ZTC||NCM811 full cell in the range of 1C to 4C. (d) Cyclic performance of C@Si@ZTC/Graphite||NCM811, C@Si@CMK-3/Graphite||NCM811, and C@Si@OMC-8/Graphite||NCM811 full cells at 1C.
圖7. Electrochemical performance of C@Si@ZTC/Graphite|NCM811 cylindrical 18650 batteries. (a) Schematic illustration and digital image of cylindrical 18650 batteries. (b) Initial voltage profiles at 0.1C, (c) rate capability, and (d) cycling performance at 1C.
3小結
綜上所述，本研究系統探討了碳材料納米結構與通過化學氣相沉積法將硅沉積於多孔碳載體中形成的Si/C複合材料性能之間的關聯。研究中合成了三種多孔碳模型載體：微孔ZTC、介孔CMK-3和介孔OMC-8，並將其應用於本項研究。微孔ZTC展現出卓越的硅負載孔隙利用效率，使C@Si@ZTC複合材料相比C@Si@CMK-3和C@Si@OMC-8實現更高硅含量（60.1 wt% vs 39.0和34.6 wt%）及更均勻的硅分布。ZTC的結構優勢協同作用於最終形成的Si/C負極，顯著提升了其比容量、電化學穩定性、電化學轉換效率、循環穩定性和倍率性能。在半電池測試中，C@Si@ZTC電極在0.2C倍率下經200次循環後仍保持85.07%容量，可逆容量達1825 mAh g–1。當與NCM811正極配對時，全電池在1C倍率下經200次循環後容量保持率達79.7%。值得注意的是，採用C@Si@ZTC/石墨負極與NCM811正極的圓柱形18650電池，在1C倍率下經400次循環後仍保持2143 mAh放電容量及92.4%容量保持率。本研究為高性能硅碳複合負極設計建立了孔隙結構優化範式。
文獻：
來源：材料分析與應用
