以重組蜘蛛絲提升聚環氧乙烷電解質性能應用於全固態鋰離子電池

Abstract

對於固態鋰電池而言，探索高性能固態電解質是至關重要的，其中以研究聚環氧乙烷固態電解質最為廣泛。然而，其性能需要在降低結晶度及提高機械性質間做取捨，破壞聚環氧乙烷結晶度的同時，也代表著機械性質的下降，這是聚環氧乙烷固態電解質面臨的一大挑戰。本研究利用生物工程所合成的蜘蛛絲與聚環氧乙烷進行混摻後，製備出固態電解質，結果表明蜘蛛絲能夠同時增強機械性質以及離子傳導度。添加蜘蛛絲於聚環氧乙烷後，抗拉強度以及斷裂伸長率都有顯著地提升，使其韌性與純聚環氧乙烷相比，高出八倍。此外，我們發現蜘蛛絲可以透過與聚環氧乙烷所產生的氫鍵作用力有效地抑制聚環氧乙烷結晶的形成，以增加非晶區結構並增強聚環氧乙烷鏈段的移動性。離子傳導度的量測結果顯示，添加20 %蜘蛛絲的聚環氧乙烷固態電解質有最高的離子傳導度，在30 °C下所測得的值為3.0 * 10^–4 S cm^–1。除此之外，由於聚環氧乙烷的低結晶度以及蜘蛛絲結構中具有大量極性官能基，以至於電解質具有強黏附性，使得電解質與電極間的介面能夠更加密合，因此介面的電阻也將大幅降低。在鋰鋰對充長循環測試中，在電流密度為0.2 mA cm^–2下可以充放長達4000小時，且維持低過電位，顯示出添加蜘蛛絲的固態電解質具有極強的抗鋰枝晶能力。在全電池的充放電測試中，併入蜘蛛絲的聚環氧乙烷電解質電池展現出極佳的充放電穩定性及電容量保持率，在0.2 C下充放電，其最初的電容量可達168 mAh g^–1，且在經歷150圈充放後仍維持97 %的充電容量。上述結果展現混摻蜘蛛絲後的聚環氧乙烷電解質對於全固態鋰離子電池有實際應用的潛力。

Exploring high-performance solid electrolytes is essential for the practical application of solid-state lithium-ion batteries. The performance of widely studied PEO-based solid polymer electrolytes is hindered by the trade-off between mechanical properties and lower crystallinity, which remains an ongoing challenge to be addressed. In this work, two bio-engineered major ampullate spidroins, MaSp1 and MaSp2, are incorporated into PEO-based electrolytes, enhancing both mechanical properties and ionic conductivity simultaneously. The addition of the spider silks, particularly the more flexible MaSp2, significantly increases the tensile strength and elongation of PEO, resulting in a maximum toughness eight times greater than that of pure PEO. Additionally, the spider silks inhibit PEO crystallization through intermolecular hydrogen bonding interactions, thereby increasing the amorphous regions and enhancing the mobility of PEO segments. This leads to a maximum ionic conductivity of 3.0 * 10^–4 S cm^–1 at 30 °C for the P/Li/MA2-20 SPE. Furthermore, the originally poor PEO electrolyte/electrode solid-solid interface is substantially improved by strong interfacial adhesion due to lower crystallinity of PEO and the presence of polar groups on the spider silks, resulting in lower interfacial impedance. In galvanostatic plating/stripping tests, Li|Li symmetric batteries can be cycled at a current density of 0.2 mA cm^–2 for 4000 hours with an overpotential of 100 mV, manifesting excellent performance in inhibiting the formation of lithium dendrites. The Li|LiFePO4 full battery exhibits superior cycling and rate properties, with an initial charge capacity of 168 mAh g^–1 at 0.2 C and 97 % capacity retention after 150 cycles. These results demomstrate that PEO-based electrolytes blended with recombinant spider silks holds significant practical application potential for all-solid-state lithium-ion batteries.