互联多孔多孔石墨烯膜电极，用于高功率长周期锂氧电池

1成果简介

锂氧电池（LOBs）中的能量-功率权衡源于多孔正极中氧气（O₂）传输迟缓以及过氧化锂（Li₂O₂）堵塞孔隙的问题。虽然提高孔隙率能增强电解质可及性并提升Li₂O₂储存能力，但同时也会增加电解质需求，从而削弱电池的整体能量密度。这迫使研究者寻求替代策略，在不牺牲能量密度的前提下提升功率性能。本研究通过O₂传输理论模拟揭示：相较于孔隙率本身，通过增强孔隙互联性降低曲折度对O₂传输的影响更为显著。

基于此发现，本文，日本国立材料科学研究所Arghya Dutta、Shoichi Matsuda等研究人员在《ADVANCED SCIENCE》期刊发表名为“Interconnected Hierarchically Porous Graphene-Based Membrane Electrode for High-Power and Long-Cycle Lithium–Oxygen Battery”的论文，研究采用非溶剂诱导相分离法，以聚丙烯腈（PAN）为碳支架、聚乙二醇（PEO）为牺牲孔隙剂，制备出具有高度互联巨孔网络的自支撑石墨烯基电极。PEO的选择性分解形成空间互联的巨孔结构，有效降低了曲折度。所得电极使锂氧电池在稀释电解液条件下，于1.0 mA cm−2电流密度下实现>2500 mAh g−1的能量密度。仅使用3.25 g Ah−1电解液即可在4 mAh cm−2电流密度下保持稳定循环，并在1.5 mA cm−2条件下经受90次循环仍保持高倍率性能。本研究通过合理电极结构设计，为实用化锂离子电池同时提升能量密度与功率性能提供了强有力的解决方案。

2图文导读

图1、Variation of the effective diffusion coefficient (Deff) of oxygen (O2) with a) porosity (ε) and b) tortuosity (τ). c–h) Contour plots of normalized O2 concentration across the electrode thickness under different current densities.

图2、chematic illustration of the structural differences among various carbon electrodes depending on the fabrication approach. The top panel depicts a particle-based porous carbon electrode fabricated using a binder, where pores are primarily confined within individual particles. The middle panel shows a nonideal meso-macroporous carbon membrane in which macropores exist but remain spatially isolated, limiting mass transport. The bottom panel illustrates the ideal architecture, a freestanding carbon membrane featuring a continuous network of interconnected macropores that facilitate efficient electrolyte infiltration and gas diffusion. Small white circles denote mesopores, while large white circles indicate macropore. The micropores and interconnectivity through microporous channels are not shown.

图3、a) Transmission electron micrograph (TEM) of GMS powder sample. Cross-section scanning electron micrograph (SEM) of b) GMS and c) iGMS membranes. d) Schematic representation of the electrode fabrication processes following NIPS method with and without using PEO. e) Thermogravimetric analysis (TGA) data of PAN and PEO under a helium atmosphere. Pore size distribution curves of GMS and iGMS membranes measured by f) N2 adsorption/desorption and g) Hg porosimetry.

图4、Galvanostatic discharge profiles of LOB cells with GMS and iGMS electrodes at a) 0.4 mA cm−2 and b) 1.0 mA cm−2 up to 2.0 V versus Li/Li⁺. c) Average discharge voltages at 1.0 mA cm−2. Cycling profiles of d) GMS and e) iGMS at 0.4 mA cm−2 with 4 mAh cm−2 capacity under EL/C = 6, and f) corresponding cycle lives. Cycling profiles of g) GMS and h) iGMS under EL/C = 4, and i) corresponding cycle lives. High-rate cycling of j) GMS and k) iGMS electrodes. l) Comparison of high-rate cycling stabilities of iGMS electrode with previously reported cells cycled at current densities ≥ 0.8 mA cm−2 and limited capacities.

图5、Galvanostatic discharge/charge profiles and O2 evolution rates during charging for the a) 1st and b) 5th cycles using KB, GMS, and iGMS electrodes. Comparison of O2 yield in different electrodes for the c) 1st and d) 5th cycles.

3小结

本研究强调了在稀薄电解液条件下运行的液态氧化物电池中，碳电极内部互联多孔网络与优化孔隙率的关键作用——其能实现高容量、长循环寿命，并在高功率运行时保持稳定性能。虽然增加电极孔隙率通常与更高容量相关，但多孔网络的合理连接对确保电解液和氧气的有效扩散至关重要，这是实现高功率性能的基础。此外，孔隙体积过大且未优化的电极往往需要更大电解液容量才能维持稳定循环，反而抵消了比容量优势。反之，当电解液容量降低时，高孔隙率电极将面临严重电解液耗竭，导致显著的电压极化及电池过早失效。

开发具有高度互联孔隙网络和优化孔隙体积的电极，同时最大限度减少非活性孔隙率，为克服锂离子电池中的能量-功率权衡提供了有前景的途径。例如，一种具有优化孔隙结构的GMS电极在低电解液负载比（EL/C=5）下，于1.0 mA cm⁻²放电速率下展现出2520 mAh g⁻¹的高放电容量。此外，该孔隙优化GMS电极在EL/C比值为4时，以4 mAh cm⁻²的高面积容量实现稳定循环，并在1.5 mA cm⁻²高倍率下持续90次循环，展现卓越的高功率循环性能。相比之下，在类似稀薄电解液条件下，孔隙体积更大但缺乏合理孔隙连通性的电极，其容量表现欠佳，循环稳定性降低，且倍率性能较弱。这些发现强调了精细调节电极孔隙结构的重要性，以在锂氧电池中平衡容量、循环稳定性、倍率性能和电解液利用率。这些研究还为先进碳材料的设计提供了宝贵见解，为开发下一代实用锂氧电池铺平了道路。

文献
:https://doi.org/10.1002/advs.202519091

来源：材料分析与应用