Zinc borates have merits of low voltage polarization and suitable redox potential, but usually suffer from low rate capability and poor cycling life, as an emerging anode candidate for Na+ storage. Here, a new intercalator-guided synthesis strategy is reported to simultaneously improve rate capability and stabilize cycling life of N, B co-doped carbon/zinc borates (CBZG). The strategy relies on a uniform dispersion of precursors and simultaneously stimulated combustion activation and solid-state reactions capable of scalable preparation. The Na+ storage mechanism of CBZG is studied: 1) ex situ XRD and XPS demonstrate two-step reaction sequence of Na+ storage: Zn6O(OH)(BO3)3+Na++e−↔3ZnO+Zn3B2O6+NaBO2+0.5H2 ①, Zn3B2O6+6Na++6e−↔3Zn+3Na2O+B2O3 ②; reaction ① is irreversible in ether-based electrolyte while reversible in ester-based electrolyte. 2) Electrochemical kinetics reveal that ether-based electrolyte possesses faster Na+ storage than ester-based electrolyte. The composite demonstrates an excellent capacity of 437.4 mAh g−1 in a half-cell, together with application potential in full cells (discharge capacity of 440.1 mAh g−1 and stable cycle performance of 2000 cycles at 5 A g−1). These studies will undoubtedly provide an avenue for developing novel synthetic methods of carbon-based borates and give new insights into the mechanism of Na+ storage in ether-based electrolyte for the desirable sodium storage.
All Science Journal Classification (ASJC) codes
- Medicine (miscellaneous)
- Chemical Engineering(all)
- Materials Science(all)
- Biochemistry, Genetics and Molecular Biology (miscellaneous)
- Physics and Astronomy(all)