美國橡樹嶺國家實驗室ACS Nano：納米級離子傳輸增強固體聚合物陶瓷鋰電解質的電導率

【研究背景】

固態電池（SSB）是一種新興的儲能技術，其具有高能量密度和安全性。實現SSB需要材料發現和加工方面的發展。目前，使用陶瓷電解質制造 SSB 仍然具有挑戰性。從材料加工的角度來看，聚合物電解質由于其靈活性、卷對卷加工和優異的界面性能，可能成為制造 SSB 的解決方案。為此，研究人員需要設計下一代輕質、柔性、無溶劑和電化學穩定的聚合物電解質材料，其具有超快和明確的離子傳輸特性。定制與離子傳輸相關的納米結構-性能相互依賴性是預測設計具有超高電導率的聚合物電解質的可行方法。離子傳輸可以通過三個基本傳輸參數來定量表示：離子遷移率、自由離子濃度和遷移數。在不同的電解質類型中，聚合物復合電解質具有與兩相相稱的性能優勢。陶瓷氧化物相具有高導電性和抗枝晶性，而聚合物相雖然導電性較差，但提供了靈活且易于加工的基質，用于分散陶瓷相并合成與陰極和陽極具有優異界面性能的獨立薄膜電解質。目前，陶瓷相和離子傳輸機制之間的結構-性能相互依賴性仍然是 SSB 復合聚合物電解質中一個有趣的概念。

鑒于此，美國橡樹嶺國家實驗室李健林博士帶領團隊在ACS Nano上發表了題為“Nanoscale Ion Transport Enhances Conductivity in Solid Polymer-Ceramic Lithium Electrolytes”的最新研究成果。

【文章要點】

Figure 1. SEM image of the electrospun Al-LLZO platelets. The scale bar is 10 μm. The inset shows a cross-sectional SEM image of a composite PEO electrolyte filled with 15 wt% Al-LLZO. The scale bar is 4 μm.

1.在這項工作中，作者建立了陶瓷聚合物復合材料中復合材料結構、聚合物鏈段動力學和鋰離子 (Li⁺) 傳輸之間的相關性。

Figure 2. Summarized Arrhenius plot for the composite LiTFSI and LiFSI PEO electrolytes filled with Al-LLZO. The electrochemical testing was performed at 60 oC (dotted line on the plot).

2.闡明這種結構-性能關系將可以通過優化電解質的宏觀電化學穩定性來調整Li⁺電導率。作者發現通過控制聚合物/陶瓷界面的形態和功能可以增強慢聚合物鏈段動力學的離子解離。復合電解質中Li⁺鹽的化學結構與離子簇域的大小、導電機制和電解質的電化學穩定性相關。

Figure 4. Experimental SAXS patterns and model-fits of the (a, b) PEO/LiFSI electrolytes at 25 ^oC and 60 ^oC. (c, d) PEO/LiTFSI electrolytes at 25 ^oC and 60 ^oC. The SAXS model-fits were based on multiple SAXS model functions as indicated in each plot. The fitting parameters of the SAXS functions that were used to fit the scattering curves are summarized in the Supporting Information.

3.作者使用填充有雙(三氟甲磺酰基)亞胺鋰(LiTFSI)或雙(氟磺酰基)亞胺鋰(LiFSI)鹽的聚環氧乙烷(PEO)作為基質。此外，具有平面幾何形狀的石榴石電解質、鋁取代的鋰鑭鋯氧化物（Al-LLZO）被用于陶瓷納米顆粒部分。

Figure 5. Structural behavior of Li+ ions. Radial distribution function (RDF) of Li+ with respect to (a) fluorine, (b-c) oxygen of salt and oxygen of PEO at two different temperatures, 60 oC and 120 oC. (d) Li+ with nitrogen atoms of salt. (e) and (f) snapshots showing LiFSI and LiTFSI respectively. For clarity only Li+ and Li+ salts are shown.

4.作者使用介電弛豫光譜研究了強束縛和高流動性 Li⁺ 的動力學。 Al-LLZO 片晶的摻入增加了更易移動的 Li⁺ 的數量密度。

Figure 6. The mean-square-displacement (MSD) and diffusivities of the Li+, FSI/TFSI anions, and PEO chains. (a) Comparison of Li+, FSI and PEO MSDs for LiFSI samples at 50 oC. (b) Comparisons of Li+, TFSI and PEO MSDs for LiTFSI sample at 50 oC. (c) Comparison of Li+ and PEO dynamics (MSDs) for LiFSI and LiTFSI at 50 oC (solid lines) and 120 oC (dashed lines) respectively. The color schemes are shown in legends. (d) Diffusivity, calculated from Einstein’s relation, of Li+, FSI/TFSI and PEO chain. The circles (solid lines) and triangles (dashed lines) represent LiFSI and LiTFSI samples respectively.

5.作者通過小角X射線散射研究納米級離子團聚結構，同時進行分子動力學（MD）模擬研究，以獲得LiTFSI 和 LiFSI 鹽中 Li⁺ 與長 PEO 鏈去相關的基本機制。

Figure 7. Comparison of the long term galvanostatic cycling of the (a, b) LiFSI and LiTFSI electrolytes and (c, d) LiTFSI and LiTFSI composite filled with 7 wt% Al-LLZO at 60 oC and 50 μA/ cm^-2.

【文章鏈接】

Georgios Polizos et al.,?Nanoscale Ion Transport Enhances Conductivity in Solid Polymer-Ceramic Lithium Electrolytes.?ACS Nano 2024.?https://doi.org/10.1021/acsnano.3c03901.

【通訊作者簡介】

Dr. Jianlin Li (李健林) is the Energy Storage and Conversion department manager in the Applied Materials division. He leads a department devoted to creating a go-to department that sustains national leadership in advanced materials manufacturing and process scale up for energy storage and conversion applications. The department aims to be a one-stop shop covering from precursors for material development to manufacturing of final devices.

Jianlin’s research area includes materials synthesis, processing and characterization, electrode engineering, cell manufacturing and prototyping for energy storage and conversion.

He received bachelor’s degrees in Materials Chemistry and Electronic Information Engineering and a master’s degree in Materials Science from the University of Science and Technology of China. Jianlin received his doctorate in Materials Science and Engineering from the University of Florida, and was most recently a senior R&D staff member and leader of the Energy Storage and Conversion Manufacturing Group at Oak Ridge National Laboratory (ORNL). Prior to joining Argonne National Laboratory, he spent almost 14 years at ORNL where he was the leader of the Energy Storage and Conversion Manufacturing Group. He was among a small team to establish the Battery Manufacturing Facility (BMF) at ORNL in 2012.

Jianlin is also the recipient of several prestigious awards, including the 2023 UT-Battelle Outstanding Research Output team award, 2021 UT-Battelle Research Accomplishment individual award, three R&D 100 awards and two Federal Laboratory Consortium awards. He holds more than 35 patents and patent applications with 7 licensed, has authored more than 170 refereed journal articles and 11 book chapters and edited one book. Jianlin serves as an associate editor for Journal of Energy Storage and IEEE IAS Transportation Systems Committee.

Dr. Jianlin Li’ Google Scholar:

https://scholar.google.com/citations?user=n2TLDPoAAAAJ&hl=en&oi=ao