| 摘要: | 隨著人類科技的發展，必然會追求更好的儲能技術。傳統鋰電池使用的碳負極雖然有著高安全性、穩定度高、循環壽命長等優點，但低的理論電容量嚴重限制了鋰電池儲能技術的上限，故人們將目光轉向各種矽基材料。矽基材料有著高的理論電容量、自然蘊藏量高等優點，但缺點也顯而易見，矽基材料電極在充放電循環中會有劇烈的體積變化，導致固態電解質界面(Solid Electrolyte Interface, SEI)的反覆生成，進而消耗過多的活性鋰離子、初始庫倫效率(ICE)降低。因此，本研究的目標是在第一次充放電循環前補償不可逆的活性鋰離子損失，提高初始庫倫效率(ICE)和充放電容量。我們使用化學浸泡方法來預鋰化矽基負極。在此預鋰化過程中，我們使用了數種不同的芳香族化合物，包含聯苯(BP)、1-甲基萘(MeNP)、2-苯基酚(BPOH)以及三種溶劑2-甲基四氫呋喃(MTHF)、四氫呋喃(THF)、二甲醚(DME)與鋰金屬製備化學預鋰化溶液。
在初步的預鋰化過程中，我們先嘗試適合的預鋰化載劑、載劑濃度、鋰源濃度、溶劑以及浸泡時間。我們選擇使用聯苯(BP)化合物作為預鋰化溶液的載劑，經過1 M BP/MTHF預鋰化浸泡5分鐘後，ICE由57.9%增加至84.5%，開路電壓(OCV)由2.66 V降低至0.36 V，在200 mA/g下充放電容量由1100 mAh/g增加至1300 mAh/g。
我們嘗試改良此化學預鋰化溶液，我們的首要目標為減緩鋰-芳香烴錯合物的生成速率，促使整個預鋰化反應更加溫和。首先我們使用2-苯基酚(BPOH)作為添加劑，希冀透過OH基對鋰離子的吸引力來達成目的。爾後我們改為使用雙載劑-聯苯(BP)及1-甲基萘(MeNP)。因為兩種預鋰化載劑會彼此競爭生成鋰-芳香烴錯合物，故也能達成目的。經過比較我們發現使用雙載劑的效果最佳。在使用0.7 M BP和0.3 M MeNP反應10分鐘後，ICE增加至87.1%，同時可逆容量在不同充放電速率下皆有增加，在高速充放電速率5000 mA/g時，表現出160 mAh/g的可逆電容量。
;With the advancement of human technology, the pursuit of improved energy storage technologies has become inevitable. Although traditional lithium-ion batteries commonly use carbon-based anodes due to their high safety, excellent stability, and long cycle life, their low theoretical capacity severely limits the overall energy density of lithium-ion batteries. Consequently, attention has shifted toward silicon-based materials, which offer significantly higher theoretical capacities and abundant natural reserves. However, silicon-based anodes suffer from substantial volume changes during charge–discharge cycling, leading to repeated formation and breakdown of the solid electrolyte interphase (SEI). This not only consumes excessive amounts of active lithium ions but also significantly lowers the initial coulombic efficiency (ICE).
The objective of this study is to compensate for the irreversible loss of active lithium ions prior to the first charge–discharge cycle, thereby improving both ICE and charge–discharge capacity. Referring to previous literature, we adopted a chemical prelithiation approach for silicon-based anodes. During this process, we prepared various chemical prelithiation solutions using aromatic compounds—including biphenyl (BP), 1-methylnaphthalene (MeNP), and 2-phenylphenol (BPOH)—along with solvents such as 2-methyltetrahydrofuran (MTHF), tetrahydrofuran (THF), and dimethyl ether (DME), in the presence of lithium metal.
In the preliminary prelithiation experiments, we first explored suitable prelithiation carriers, carrier concentrations, lithium source concentrations, solvents, and soaking times. Biphenyl (BP) was selected as the carrier compound for the prelithiation solution. After soaking in 1 M BP/MTHF for 5 minutes, the initial coulombic efficiency increased from 57.9% to 84.5%, the open-circuit voltage (OCV) decreased from 2.66 V to 0.36 V, and the charge–discharge capacity at 200 mA/g improved from 1100 mAh/g to 1300 mAh/g.
To address this issue, we focused on moderating the formation rate of lithium–aromatic complexes to make the reaction milder. Initially, 2-phenylphenol (BPOH) was used as an additive, leveraging its hydroxyl group’s affinity for lithium ions. Subsequently, we employed a dual-carrier strategy using both BP and MeNP. The competitive formation of lithium–aromatic complexes between the two carriers effectively slowed the reaction rate. Among the various approaches tested, the dual-carrier system demonstrated the best performance. Using a solution of 0.7 M BP and 0.3 M MeNP with a 10-minute soaking duration, the ICE increased to 87.1%. The reversible capacity improved across all charge–discharge rates, delivering 160 mAh/g even at a high rate of 5000 mA/g. |
