| 摘要: | 在固態鋰金屬電池研究中，本研究旨在解決LLZTO固態電解質的兩大挑戰：固-固界面接觸不良和晶界漏電流。研究中分別採用Pulsed laser和PEALD技術對LLZTO表面進行修飾。
首先，利用雷射技術修飾LLZTO表面，並探討不同雷射功率對電池性能的影響。結果顯示，使用2.5 W雷射修飾的LLZTO為最佳條件。SEM分析發現，LLZTO表面的孔隙被有效修補，XRD和Raman光譜則證實未生成LZO相。Li∣IL∣LLZTO(HCl)@L2.5∣IL∣Li電池的臨界電流密度(CCD)明顯提高至1.7 mA/cm²（相較於原先的0.4 mA/cm²）。在長時間循環測試中，極化電壓可穩定維持100小時（原本僅0.5小時即發生短路）。長時間循環後的SEM分析顯示，LLZTO橫截面上的鋰絲沉積顯著減少。
針對Li∣IL∣LLZTO(HCl)@L2.5∣IL∣LFP全電池，其在0.1、0.2、0.5、1、2 C梯度倍率下的比電容量分別為137、135、130、124、120 mAh/g，明顯優於原先的123、121、119、115、108 mAh/g，同時高倍率性能下的容量衰退亦顯著受到抑制。
接下來，應用PEALD技術在LLZTO表面沉積氧化鋁作為氧化保護層，並探討不同沉積循環數及後處理方式對電池性能的影響。最佳條件為在LLZTO表面沉積25個循環數的氧化鋁，並結合退火及酸蝕處理。XPS分析顯示，PEALD沉積氧化鋁薄膜的同時，會形成碳酸鋰和偏氧酸鋁。退火處理可降低碳酸鋰和氧化鋁的比例，並提高偏鋁酸鋰的比例；Raman分析則證實，酸蝕處理能有效移除表面的碳酸鋰。
在此條件下，Li∣IL∣LLZTO(HCl)@AA25AE∣IL∣Li電池的CCD提高至1.2 mA/cm²（原先為0.8 mA/cm²），且長時間循環測試中，極化電壓穩定維持100小時（原本僅0.5小時即短路）。長時間循環後，SEM分析亦顯示LLZTO橫截面上的鋰絲沉積程度減輕。
綜上所述，經修飾的LLZTO能有效實現充放電過程中的電流均勻分布，大幅提升鋰對稱電池的臨界電流密度和長時間循環性能，同時顯著提高全電池在倍率性能下的比電容量，這是固態鋰金屬電池發展中的重要技術突破。;This study focuses on addressing two critical challenges in solid-state electrolyte lithium metal batteries with LLZTO solid electrolytes: poor solid-solid interfacial contact and grain boundary leakage currents. Surface modifications of LLZTO were carried out using pulsed laser and PEALD techniques. Initially, laser technology was employed to modify the LLZTO surface, and the impact of various laser power levels on battery performance was investigated. The LLZTO modified with a 2.5 W laser demonstrated optimal properties. SEM analysis confirmed that surface pores were effectively repaired, while XRD and Raman spectroscopy verified the absence of LZO.
The Li∣IL∣LLZTO(HCl)@L2.5∣IL∣Li cell exhibited a significant increase in the critical current density (CCD), reaching 1.7 mA/cm² compared to the initial CCD of 0.4 mA/cm². During long-term cycling, the polarization voltage remained stable for 100 hours, a substantial improvement over the 0.5 hours observed before short-circuiting. Post-cycling SEM analysis revealed a marked reduction in lithium filament deposition on the LLZTO cross-section.
For the Li∣IL∣LLZTO(HCl)@L2.5∣IL∣LFP cell, the specific capacities at 0.1, 0.2, 0.5, 1, and 2 C were 137, 135, 130, 124, and 120 mAh/g, respectively, surpassing the original values of 123, 121, 119, 115, and 108 mAh/g. Furthermore, the capacity fade under high-rate performance was significantly suppressed.
The application of PEALD technology involves depositing aluminum oxide as an oxidation protection layer on LLZTO surfaces and examining the effects of deposition cycles and post-treatment methods on battery performance. Optimal conditions were achieved with 25 PEALD cycles, combined with annealing and acid etching. XPS analysis revealed that PEALD forms lithium carbonate and aluminum hydroxide, while annealing reduced these and increased lithium aluminate. Raman analysis confirmed that acid etching effectively removed surface lithium carbonate.
Under these conditions, the CCD of the Li∣IL∣LLZTO(HCl)@AA25AE∣IL∣Li cell increased to 1.2 mA/cm² (from 0.8 mA/cm²), and the polarization voltage remained stable for 100 hours during cycling (vs. 0.5 hours in the original configuration). SEM analysis post-cycling showed reduced lithium filament deposition on the LLZTO cross-section.
In conclusion, modified LLZTO achieved uniform current distribution during charge-discharge, significantly enhancing critical current density, long-term cycling performance, and specific capacity under high c-rate conditions. This marks a key breakthrough in solid-state lithium-metal battery development. |
