Synthesis Of Zinc-based Nanocomposites And Their Electrochemical Properties In Energy Storage Devices

Due to the different electrode materials,electrolyte and energy storage mechanism,rechargeable electrochemical power sources are mainly divided into organic secondary batteries represented by lithium ion batteries and aqueous batteries represented by nickel-hydrogen and lead-acid batteries.The searching for higher performance of electrochemical cells is a necessary process for the rapid development of green society,and the key to determine the performance is the electrode materials.Up to now,graphite has been widely used as an anode material for organic lithium ion batteries.Compared with graphite,zinc oxide is a promising electrode material because of its low cost,environmental friendly,high theoretical capacity and suitable operating voltage.In organic lithium batteries,ZnO,as an anode material,has a high energy density.Meanwhile,the charging and discharging platform of ZnO is lower than that of most other metal compounds,but slightly higher than that of carbon materials,which can avoid the formation of lithium dendrites.In aqueous batteries,ZnO has a highly specific capacity and highly hydrogen evolution overpotential,which can broaden the potential window and inhibit hydrogen evolution.Therefore,the main content of this paper is the modification of zinc oxide matrix composites and improving their electrochemical performance in energy storage devices:（1）Carbon coated ZnO composite（ZnO@C）was synthesized by two methods:the first one used camphor as carbon source via chemical vapor deposition method;the other one used dopamine as carbon source via two-step pyrolysis method.Compared with commercial ZnO,ZnO@C composite has a higher specific capacity and better cycle stability.The capacity of ZnO@C synthesized by chemical vapor deposition method remains at 865 m A h g^-1 after 400cycles,and the capacity of ZnO@C synthesized by two-step pyrolysis method reaches 955m A h g^-1 after 300 cycles,While the commercial ZnO only remained 54 m A h g^-1 after 250cycles.（2）The ZnO@C composite synthesized by chemical vapor deposition method was coated a layer of polyvinyl alcohol（PVA）,and then used as the anode of the nickel-zinc battery.The full battery was assembled with commercial nickel hydroxide and ZnO@C composite.The battery was tested in beaker cell、pouch cell、coin cell system.Compared with the traditional ZnO anode,the improved ZnO@C composite has better specific capacity,cycling stability and discharge platform.The composite can work in small amount of electrolyte and Zn-free electrolyte.Its specific discharge capacity can reach 500 m A h g^-1 after 200 cycles in a beaker cell,while commercial ZnO can only maintain less than 100 cycles.The capacity can still maintain more than 500 m A h g^-1 in the pouch cell after 100 cycles.