無鋰金屬電池 (Lithium-Free Battery) 負極因擁有高能量密度 (3860 mAh/g) 與相對鋰金屬電池來說更低的安全疑慮使之成為下世代電池中最具競爭力的候選者，但銅箔與電解液之間的低親和力使得鋰枝晶於循環過程更易生成，因枝晶鋰所增加的比表面積會加速電解液的消耗、形成更多的固態電解質介面膜 (SEI) 、並增加鈍化層的厚度，再者，不可逆的容量損耗與循環過程所產生的體積變化降低了其被實際應用的可能性。因此，本研究透過靜電紡絲技術製造了一層高親鋰性的聚丙烯腈/二氧化鈦複合保護層於銅箔上使電鍍鋰金屬更為均勻，從結果來說，我們使用相對更高的 0.5C 充電 1C 放電速率，達到了於 100 圈下 51.8%的高容量維持率 (無保護層的為40.3%) ，另外，相對於研究保護層對於正負極所產生的影響而使用的半電池二極式系統來說 (e.g. Li||Cu, LFP||Li) ，我們使用三極式系統，直接的量測於無鋰金屬電池 (LFP||Cu) 充放電過程當中，兩極分別的電位變化情形，並透過所蒐集的結果提出對於 LFP||Cu 充放電機制的解釋，總體而言，我們除了提供一個高電流密度保護層的新思路外，還展現了一個研究無鋰金屬電池的新角度。

Lithium-free batteries are considered to be a promising candidate for the next generation lithium batteries due to their higher energy density (3860 mAh/g) and reduced safety concerns. However, because of the low affinity of copper substrates to the electrolyte, lithium dendrites are easily generated during the charge-discharge cycling process. The enhanced surface area, due to the lithium dendrite formation, accelerates the electrolyte consumption to generate solid electrolyte interface (SEI) on the newly born Li surface, and further thickens the passivation layer. In addition, both the irreversible capacity loss and infinite volume change during the charge-discharge cycling may hinder its commercial application. Herein, we construct a lithiophilic nanofibrous membrane consisting of polyacrylonitrile (PAN) and titanium dioxide (TiO2) via an electrospinning process on the copper foil to deposit lithium uniformly. As a result, we achieved higher retention rate (51.8%) and greater discharge capacity (77.32 mAh/g) compared with the unprotected copper foil (40.3% retention rate, 52.73mAh/g discharge capacity) in the 0.5C-charge-1C-discharge program for 100 cycles in the lithium-free battery. Besides, rather than the approaches using the two-electrode cell configurations (e.g., Li||Cu, LFP||Li), we directly decouple the potential variations of each electrode in LFP||Cu to gain the understanding on both electrodes within the charge-discharge mechanisms in a three-electrode system. Lastly, this work not only constructs an effective modified electrode, allowing the high current density operation, but also demonstrates a broad scope for studying the lithium-free battery mechanism.

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