Yuhan Lin,Zhichuan Shen,Junqiao Huang,Junli Zhu,Shiyong Jiang,Shiying Zhan,Yu Xie,Jiahong Chen,Zhicong Shi
Gel polymer electrolytes (GPEs) play a crucial role in promoting the development of lithium metal batteries , as they combine the high ionic conductivity of liquid electrolytes with the enhanced safety provided by solid electrolytes . However, traditional polymer electrolytes are typically poured using non-in-situ methods, which results in poor electrode-electrolyte contact and compromises their performance. In this paper, in situ thermal polymerization is utilized to incorporate di-pentaerythritol pentaacrylate (DPPA) and 3,3,4,4,5,5,6,6,7,7,8,8-tridecafluorooctyl acrylate (TFOA) into PAN spinning porous membranes. Application of TFOA reduces the crystallinity of GPEs and thus enhancing the Li + transport capability, which enables the newly constructed GPEs to exhibit an ionic conductivity of 2.52 × 10 −3 S cm −1 and a lithium-ion transport number of 0.61 at 30 °C. Simultaneously, fluoro-containing groups actively contribute to the formation of a negative solid electrolyte interphase (SEI) film full of LiF, ensuring the stable operation of Li symmetrical batteries for over 2000 h at a current density of 0.40 mA cm −2 . The capacity retention rate of lithium metal batteries (LMBs) with commercial NCM811 cathodes reaches 88.2% after 300 cycles. We firmly believe that our newly designed gel polymer electrolytes (GPEs) can offer a viable solution for high-voltage and high-rate LMBs.
Polymer electrolytes (PEs) synthesized from an in situ polymerization strategy are considered as promising candidates to improve interfacial compatibility. However, most in situ formed PEs still suffer from problems such as low lithium-ion transference number (tLi+) and insufficient ionic conductivity at room temperature (RT). Herein, a series of copolymer electrolytes (CPEs) consisting of 1,3-dioxolane (DOL) and 1,3,5-trioxane (TXE) monomers are synthesized. Due to the additive of succinonitrile (SN), and the promoted dissociation of lithium salt, the obtained polymer electrolyte (SN-CPE) exhibits an excellent ionic conductivity (4.06 × 10−4 S cm−1) and a high lithium-ion transference number (tLi+ = 0.881) at RT, as well as a high voltage oxidation window of 5.1 V. Thanks to the in situ formed intimate contacted electrode/electrolyte interface, the symmetric Li/Li cell can achieve long-term cycling stability over 1500 h without a short circuit. A LiF-rich organic–inorganic composite layer is formed on both the solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) as demonstrated by XPS, TEM, and SEM analyses. Thereafter, the LiFePO4/Li cell has a high capacity retention of 84.1% after 900 cycles at RT, and it can still work effectively at high temperatures (e.g. 80 °C). Furthermore, SN-CPE exhibits excellent electrochemical performance and safety in the LiCoO2/Li cell and LiFePO4/graphite pouch cell, which again supports the promising application of SN-CPE.
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