**4. Conclusions**

In summary, the Sn-doped hydrated V2O5 ZIB cathode materials were prepared by simple one-step hydrothermal synthesis. Compared to the undoped sample, the Sn-doped hydrated V2O5 demonstrates a significant enhancement in its rate performance and cyclic stability. SnVOH shows a high initial reversible capacity of 387 mAh/g at 0.1 A/g, an excellent rate capability with 301 mAh/g even at a large current density of 10 A/g, and its retains 87.5% of its initial capacity after the cycling at 2 A/g for 2000 times. The rate and cycling performance of Sn-doped hydrated V2O5 are superior to the results from recent research on hydrated V2O5. These great improvements can be due the smaller charge transfer resistance and the higher zinc diffusion coefficient that occur after the Sn doping. Therefore, this work reveals that Sn doping is an effective strategy to improve the zinc storage performance of hydrated V2O5, and the Sn-doped hydrated V2O5 is a promising cathode material candidate to construct ZIBs of a high specific capacity, an excellent rate performance, and a high durability.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/cryst12111617/s1, Figure S1: Scheme of synthesis of SnVOH; Figure S2: The schematic crystalline structure of SnVOH; Figure S3: EDS characterization of VOH sample; Table S1: The molar ratio of different elements in SnVOH; Figure S4: Characterization of VOH and SnVOH composite cathodes; Figure S5: Electrochemical characterization of VOH-based cathode; Table S2. Electrochemical performance comparison of SnVOH with recent literature data on doped hydrated V2O5-based cathodes in ZIBs. Refs. [42–45] are cited in the Supplementary Materials file.

**Author Contributions:** Conceptualization, K.G. and N.Y.; investigation, W.C. and H.L. (Haiyuan Liu); validation, H.L. (Haiyuan Liu), W.S. and Y.W.; writing—original draft preparation, K.G.; writing—review and editing, N.Y. and J.O.; visualization, H.W., H.L. (Hanbin Li) and Z.L.; supervision, N.Y.; project administration, K.G.; funding acquisition, K.G., X.Z. and N.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China (52102214, 51702048, and 22166003), the Jiangxi Provincial Natural Science Foundation (20202BAB213008, 20202BABL213003, and 20202BABL203026), the Opening Project of Jiangxi Province Engineering Research Center of New Energy Technology and Equipment (JXNE2021-04, JXNE2021-05), State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (P2022-009), and the National (Jiangxi Province) College Students Innovation and Entrepreneurship Training Program 2020 (S202110405018, S202010405031 and S202010405018) supported this work.

**Institutional Review Board Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank Xiaoming Chen from Shiyanjia Lab (www. shiyanjia.com) for the material characterization.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**

