Lithium-selenium batteries (LSeBs) have attracted increasing attention due to their excellent electronic conductivity and high theoretical specific capacity. However, there are still difficult problems such as low utilization rate and fast capacity decay in the actual application process. Herein, a surface iodine modified three-dimensional (3D) nano hollow carbon fiber (I-NHCF) network is designed and synthesized as Se host (Se@I-NHCF) for highly stable LSeBs. The surface iodine species induce the formation of robust cathode electrolyte interface (CEI), thus preventing the transformation of amorphous selenium to low-activity crystalline selenium and enabling stable electrochemical performance. Moreover, the surface iodine species promote rapid charge transfer, enhancing the chemical reaction kinetics and improving the utilization of the active Se species. As a result, the Se@I-NHCF cathode exhibits superior specific capacity of 581.8 mAh g −1 with a high stability (0.0054% capacity decay per cycle) after 500 cycles at 1C, and an excellent rate performance of 567.6 mAh g −1 at 2C. This work addresses the problem of rapid capacity decay by the formation of uniform and robust CEI to conserve highly reactive amorphous Se species, improve Se utilization, and achieve ultra-stable Li-Se batteries with high energy and long cycle life.
Because of their high ionic conductivity, utilizing gel polymer electrolytes (GPEs) is thought to be an effective way to accomplish high-energy-density batteries. Nevertheless, most GPEs have poor adaptability to Ni-rich cathodes to alleviate the problem of inevitable rapid capacity decay during cycling. Therefore, to match LiNi0.8Co0.1Mn0.1O2 (NCM811), we applied pentaerythritol tetraacrylate (PETEA) monomers to polymerize in situ in a polyacrylonitrile (PAN) membrane to obtain GPEs (PETEA-TCGG-PAN). The impedance variations and key groups during the in situ polymerization of PETEA-TCGG-PAN are investigated in detail. PETEA-TCGG-PAN with a high lithium-ion transference number (0.77) exhibits an electrochemical decomposition voltage of 5.15 V. Noticeably, the NCM811|PETEA-TCGG-PAN|Li battery can cycle at 2C for 120 cycles with a capacity retention rate of 89%. Even at 6C, the discharge specific capacity is able to reach 101.47 mAh g–1. The combination of LiF and Li2CO3 at the CEI interface is the reason for the improved rate performance. Moreover, when commercialized LFP is used as the cathode, the battery can also cycle stably for 150 cycles at 0.5C. PETEA and PAN can together foster the transportation of Li+ with the construction of a fast ion transport channel, making a contribution to stable charge–discharge of the above batteries. This study provides an innovative design philosophy for designing in situ GPEs in high-energy-density lithium metal batteries.
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