Abstract
In concern of resource sustainability and environmental friendliness, organic electrode materials for rechargeable batteries have attracted increasing attentions in recent years. However, for many researchers, the primary impression on organic cathode materials is the poor cycling stability and low energy density, mainly due to the unfavorable dissolution and low redox potential, respectively. Herein, a novel polymer cathode material, namely poly(benzoquinonyl sulfide) (PBQS) is reported, for either rechargeable Li or Na battery. Remarkably, PBQS shows a high energy density of 734 W h kg–1 (2.67 V × 275 mA h g–1) in Li battery, or 557 W h kg–1 (2.08 V × 268 mA h g–1) in Na battery, which exceeds those of most inorganic Li or Na intercalation cathodes. Moreover, PBQS also demonstrates excellent long‐term cycling stability (1000 cycles, 86%) and superior rate capability (5000 mA g–1, 72%) in Li battery. Besides the exciting battery performance, investigations on the structure–property relationship between benzoquinone (BQ) and PBQS, and electrochemical behavior difference between Li–PBQS battery and Na–PBQS battery, also provide significant insights into developing better Li‐organic and Na‐organic batteries beyond conventional Li‐ion batteries.
Highlights
Synthesis and Characterization of poly(benzoquinonyl sulfide) (PBQS)The structure of PBQS (Scheme 1b) was proposed as one of the ideal structures of quinone-based polymer cathodes, when we successfully synthesized poly(anthraquinonyl sulfide) (PAQS, Scheme 1a) and investigated it as cathode material for rechargeable Li battery in 2009.[12]
Battery technology is recognized as attentions in recent years
After carefully optimizing the reaction conditions including the stoichiometric ratio of sulfide (Li2S) to monomer, solvent and temperature, we proposed a new polymerization reaction between DCBQ and Li2S as shown in Scheme 1b
Summary
The structure of PBQS (Scheme 1b) was proposed as one of the ideal structures of quinone-based polymer cathodes, when we successfully synthesized poly(anthraquinonyl sulfide) (PAQS, Scheme 1a) and investigated it as cathode material for rechargeable Li battery in 2009.[12]. The above XPS analysis agree well with the FTIR spectra, and based on all the characterization results, we can conclude that our final PBQS product is a polymer containing benzoquinone units in the majority and hydroquinone units in the minority linked by thioether bonds, with unavoidable residual NMP and absorbed H2O in it. This is not a perfect structure as we proposed in Scheme 1b, it is still a significant progress if considering that no chemical synthesis of such kind of benzoquinone-based polymers was reported so far
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