Sulfurized polyacrylonitrile (SPAN) is regarded as an attractive cathode candidate of lithium-sulfur (Li-S) batteries for its non-dissolution mechanism and effective alleviation of polysulfides shuttling issue in Li-S batteries, displaying high utilization of cathode active material, outstanding cycle stability and structural stability. However, the relation between cyclization degree and cycle stability of SPAN is still unveiled. In this work, SPAN-C-V composites were synthesized by co-introduction of CuSO₄ and zinc n-ethyl-n-phenyldithiocarbamate (ZDB) in the co-heating of sulfur and polyacrylonitrile. The co-introduction of CuSO₄ and ZDB reduced the cyclization reaction onset temperature of PAN while increased the C—C/C=C within SPAN-C-V, thus led to an increase in the degree of cyclization of SPAN-C-V, achieving excellent electrochemical performance by simultaneously improving the cyclization degree and increasing the content of sulfur. The SPAN-C-V exhibited an initial reversible capacity of 805 mAh·g^-1 and 601 mAh·g^-1 after 100 cycles with the capacity retention rate of 93% at 0.2 C (1 C = 600 mAh·g^-1). The focus on the cyclization degree of SPAN provides an enlightenment of advanced cathode material.

Lithium (Li) metal anode holds great promise for high-energy-density rechargeable batteries. However, it suffers from the Li dendrites growth and uncontrollable side reactions with electrolyte due to the unstable solid electrolyte interphase (SEI) layer. Herein, we propose a facile strategy for the in-situ fabricate of organic-inorganic composite artificial SEI layers on Li surfaces, which consist of organic fluorinated siloxane and inorganic LiF-rich phases. The hybrid artificial SEI endows high mechanical strength (13.1 GPa) and Li⁺ transfer number (0.62). Such robust SEI protective layers can not only guide uniform nucleation and deposition of Li metal by facilitating uniform Li-ion distribution, but also prevent unfavourable side reactions. Accordingly, the protected metallic lithium anode (PMTFPS-Li) anode enables stable Li plating/stripping performance in symmetric cells for more than 300 h at 4 mA ·h/cm² under a high areal capacity of 4 mA/cm². Moreover, the PMTFPS-Li/S cells could maintain more than 300 stable cycles at 0.5C and the PMTFPS-Li/LFP cells present excellent cycling performance (400 cycles at 1C) and enhanced rate capability (110.4 mA·h/g at 3 C). This work will inspire the design of artificial SEI on Li anodes for advanced Li metal batteries.