互聯多孔多孔石墨烯膜電極，用于高功率長周期鋰氧電池

1成果簡介

鋰氧電池（LOBs）中的能量-功率權衡源于多孔正極中氧氣（O?）傳輸遲緩以及過氧化鋰（Li?O?）堵塞孔隙的問題。雖然提高孔隙率能增強電解質可及性并提升Li?O?儲存能力，但同時也會增加電解質需求，從而削弱電池的整體能量密度。這迫使研究者尋求替代策略，在不犧牲能量密度的前提下提升功率性能。本研究通過O?傳輸理論模擬揭示：相較于孔隙率本身，通過增強孔隙互聯性降低曲折度對O?傳輸的影響更為顯著。

基于此發現，本文，日本國立材料科學研究所Arghya Dutta、Shoichi Matsuda等研究人員在《ADVANCED SCIENCE》期刊發表名為“Interconnected Hierarchically Porous Graphene-Based Membrane Electrode for High-Power and Long-Cycle Lithium–Oxygen Battery”的論文，研究采用非溶劑誘導相分離法，以聚丙烯腈（PAN）為碳支架、聚乙二醇（PEO）為犧牲孔隙劑，制備出具有高度互聯巨孔網絡的自支撐石墨烯基電極。PEO的選擇性分解形成空間互聯的巨孔結構，有效降低了曲折度。所得電極使鋰氧電池在稀釋電解液條件下，于1.0 mA cm?2電流密度下實現>2500 mAh g?1的能量密度。僅使用3.25 g Ah?1電解液即可在4 mAh cm?2電流密度下保持穩定循環，并在1.5 mA cm?2條件下經受90次循環仍保持高倍率性能。本研究通過合理電極結構設計，為實用化鋰離子電池同時提升能量密度與功率性能提供了強有力的解決方案。

2圖文導讀

圖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.

圖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.

圖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.

圖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.

圖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小結

本研究強調了在稀薄電解液條件下運行的液態氧化物電池中，碳電極內部互聯多孔網絡與優化孔隙率的關鍵作用——其能實現高容量、長循環壽命，并在高功率運行時保持穩定性能。雖然增加電極孔隙率通常與更高容量相關，但多孔網絡的合理連接對確保電解液和氧氣的有效擴散至關重要，這是實現高功率性能的基礎。此外，孔隙體積過大且未優化的電極往往需要更大電解液容量才能維持穩定循環，反而抵消了比容量優勢。反之，當電解液容量降低時，高孔隙率電極將面臨嚴重電解液耗竭，導致顯著的電壓極化及電池過早失效。

開發具有高度互聯孔隙網絡和優化孔隙體積的電極，同時最大限度減少非活性孔隙率，為克服鋰離子電池中的能量-功率權衡提供了有前景的途徑。例如，一種具有優化孔隙結構的GMS電極在低電解液負載比（EL/C=5）下，于1.0 mA cm?2放電速率下展現出2520 mAh g?1的高放電容量。此外，該孔隙優化GMS電極在EL/C比值為4時，以4 mAh cm?2的高面積容量實現穩定循環，并在1.5 mA cm?2高倍率下持續90次循環，展現卓越的高功率循環性能。相比之下，在類似稀薄電解液條件下，孔隙體積更大但缺乏合理孔隙連通性的電極，其容量表現欠佳，循環穩定性降低，且倍率性能較弱。這些發現強調了精細調節電極孔隙結構的重要性，以在鋰氧電池中平衡容量、循環穩定性、倍率性能和電解液利用率。這些研究還為先進碳材料的設計提供了寶貴見解，為開發下一代實用鋰氧電池鋪平了道路。

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

來源：材料分析與應用