Electrodes And Electrolytes Of Zinc-based Energy Storage Devices:Controlled Fabrication And High/Low-temperature Performance

With the development of economy and society,deep sea,deep ground,deep space and other fields have put forward higher requirements for the high-and-low-temperature performance of electrochemical energy storage devices.However,the current electrochemical energy storage technology can not meet practical applications.It is urgent to develop electrochemical energy storage systems for extreme-temperature environments.In recent years,Zn-based energy storage devices have received extensive attention due to their low cost and high safety.However,the current research on the high-and-low-temperature performance of Zn-based energy storage devices is still in the early stage.The frozen electrolytes and sluggish kinetics at low temperatures,the unclear failure mechanism at high temperatures and dendrite growth severely hinder their further developments.It is of great significance to clarify the failure mechanism of Zn-based energy storage devices under extreme-temperature conditions and improve their electrochemical performances.In this thesis,from the design of electrode materials to the construction of electrode structures,from the regulation of liquid electrolyte to the application of gel electrolyte,we have systematically investigated the issues of Zn-based energy storage devices under extreme-temperature conditions.The main contents are as follows:1.Aimming at the sluggish kinetics of oxygen reduction reaction at the cathode site of Zn-air batteries at low temperatures,a large-scale synthesis of Fe,N-doped carbon nanotube networks(Fe-N-CNNs)catalysts was carried out through a simple template method.Thanks to the abundant active sites,three-dimensional interconnection network structure,high specific surface area and hierarchical porous structure,the Zn-air battery exhibits excellent electrochemical performance at-40°C.Specifically,the working voltage can reach 1.23 V at 1 m A cm^-2.This work provides new ideas for the design of high-performance low-temperature-resistant Zn-air batteries.2.Aiming at the dendrite growth and freezing of aqueous electrolytes at subzero temperatures,an electrolyte based on water/glycol hybrid solvent has been developed.Compared with the aqueous electrolyte,the addition of glycol in the hybrid-solvent electrolyte can regulate the deposition behavior of zinc ions,thereby inhibiting the growth of zinc dendrite and improving the stability of zinc anode.Using this electrolyte,the Zn/Zn symmetrical cell can be reversibly cycled for 5400 h,and the cyclability of the Zn-ion capacitor is improved.In addition,the electrolyte can remain liquid at-50°C due to the hydrogen bonding between glycol and water molecules.The Zn/Zn symmetrical cell can be cycled for 1000 h at-20°C,and the Zn-ion capacitor can still work at the low temperature of-40°C.This research lay a foundation for the design of Zn-based energy storage devices with long life and low temperature resistance.3.Aimming at the low energy density of Zn-ion capacitor,based on the water/glycol hybrid solvent electrolyte,a bi-material capacitor/battery electrode of Fe-N-CNNs/V₂O₅has been further constructed.It is found that Fe-N-CNNs can improve the wettability of V₂O₅ to the electrolyte,and V₂O₅ can enhance the specific capacity of the electrode.Due to the synergistic effect between the two active materials,the assembled Zn battery achieves high energy density while maintaining the long life and high power density of Zn-ion capacitors.At room temperature,the energy density of the battery is 104.9 Wh kg^-1.Even at-20°C,the energy density can still be maintained at 79.4 Wh kg^-1.In addition,after 1,000cycles at 1 A g^-1 under such a low temperature,the battery can maintain 80%of the initial capacity.This study provides a new strategy for improving the electrochemical performance of Zn-based energy storage devices.4.Aiming at the inferior high-temperature performance and unclear failure mechanism of Zn-ion batteries under high temperatures,an ionogel electrolyte has been developed for Zn/V₂O₅ batteries.The results show that the electrolyte not only exhibits good thermal stability,but also can inhibit the growth of zinc dendrite and the dissolution of V₂O₅.The Zn/V₂O₅ battery assembled with this electrolyte can maintain 82%of the initial capacity after 200 cycles at 55°C.However,the capacity decays at 80°C.It is found that the growth of dendrites and the formation of the Zn O passivation layer at the Zn anode are the main reasons for the failure.This work provides guidance for further improving the high-temperature performance of Zn-based energy storage devices.