Construction Of The Novel Aqueous Zinc Batteries And Their Electrochemical Performance

With the gradual scarcity of traditional fossil fuel and the ensuing environmental problems,the application of renewable energy such as wind energy and solar energy is being seriously taken by mankind.Due to the intermittent nature and geographical constraints of renewable energy,energy storage devices are needed to achieve continuous supply of electrical energy to meet the requirements of users.Rechargeable battery technology is considered to be one of the most promising large-scale energy storage devices due to their advantages of fast-response,no terrain constraints,and lowcost.Among them,aqueous zinc(Zn)batteries with the advantages of high-safety,lowcost and long-life,are of great interest in large-scale energy storage.However,aqueous Zn batteries suffer from many issues such as unstable Zn anode,lack of highperformance cathode,low-areal capacity,and low-utilization of active material,which severely limited their cycle stability,energy density and industrialization.This thesis focuses on the design of Zn anode,electrolyte,Br2 and MnO2 cathodes for aqueous Zn battery systems with commercialization potential.The design of the novel Zn anode achieves 100%active Zn utilization and matches it with the Br2 cathode for the Zn-Br2 battery;the design of the electrolyte achieves in-situ regulation of the Br2 cathode and Zn anode to obtain a high-performance Zn-Br2 battery;the halogen redox mediators regulate the MnO2 cathode to achieve a Zn-MnO2 battery with high areal capacity and high reversibility.The main research work is as follows:1.Designing a robust two-dimensional metal/metal-zinc alloy heterostructured interface to regulate Zn plating,achieving high performance Zn-Br2 battery.This section takes the module of Sb/Sb2Zn3 heterojunction interface(Sb/Sb2Zn3-HI),benefiting from the stronger adsorption and uniform electric field distribution at the Sb/Sb2Zn3-HI in Zn plating,a dendritic-free Zn plating/stripping was achieved.The Sb/Sb2Zn3-HI coated Cu foil(Sb/Sb2Zn3-HI@Cu)substrate can achieve an ultrahigh areal capacity of 200 mAh cm-2 for Zn plating,which also enables dendrite-free Zn plating/stripping over 550 h at 10 mAh cm-2.An anode-free Zn-Br2 battery using the Sb/Sb2Zn3-HI@Cu anode can stably cycle over 800 times at 10 mAh cm-2,which also displays an attractive energy density of 274 Wh kg-1 and 62 Wh kg-1 practical energy density.The scaled-up Zn-Br2 battery in a capacity of 500 mAh can operate stably over 400 cycles.Furthermore,the Zn-Br2 battery module in an energy of 9 Wh(6 V,1.5 Ah)is integrated with a photovoltaic panel,demonstrating a practical renewable energy storage capability.2.Electrolyte design of Zn-Br2 batteries with in-situ modulation of Zn anode and Br2 cathode to further improve their electrochemical performance.Based on the design of the Sb/Sb2Zn3-HI,Zn plating/stripping were stabilized in-situ by the introduction of tetrapropylammonium bromide(TPABr)additive in the electrolyte.With the TPABr additive,the Zn semisymmetric cell can cycle stably for over 1500 h at 10 mAh cm-2 and near 400 h even at high areal capacity of 100 mAh cm-2.The TPABr additive can also inhibit the diffusion of the bromine cathode,enable the Zn-Br2 batteries to achieve a high areal capacity of 40 mAh cm-2 and stably cycle near 1200 cycles at an areal capacity of 15 mAh cm-2.In addition,the 400 mAh Zn-Br2 pouch cell can stably cycle over 3400 h at 100%DoD and 700 stable cycles at 25%DoD.The cell exhibits a practical energy density of 76 Wh kg-1 with highly sfatety,meanwhile it can be further expanded to a capacity of 5000 mAh with a Coulombic efficiency of over 98%and a discharge voltage of over 1.5 V at 0.1 C.3.High-performance cathode materials are essential to enhance the energy density of Zn batteries.Electrolytic MnO2 cathode with MnO2/Mn2+ deposition/dissolution chemistry has the advantages of high voltage(1.99 V vs.Zn2+/Zn)and high theoretical capacity(616 mAh g-1),which is a new cathode material for aqueous Zn batteries.However,the poor conductivity of MnO2 limits its reversibility at high areal capacities.We demonstrated a high areal capacity electrolytic Zn-MnO2 batteries by introducing halogen redox mediators into the electrolyte.Due to the oxidation potentials of the halogen redox mediators(Br3-/Br-,I3-/I-)are lower than the reduction potentials of MnO2,they can effectively dissolve the residual MnO2 and participate in the discharging of the battery,thus extening its capacity and reversibility.As results,the Zn-MnO2/Br2 battery exhibits a discharge voltage of 1.98 V and a rate performance of 20 C in the bromine mediator additive electrolyte.It can stably cycle 600 times at an areal capacity of 6.7 mAh cm-2 and displays an energy retention of-94%.In addition,Zn-MnO2/Br2 can be further scaled up to 1.2 Ah and stably cycle over 100 times,while the optimized battery exhibits a practical energy density of～32.4 Wh kg-1.If the electrolyte concentration and utilization are further improved,the Zn-MnO2/Br2 battery is expected to achieve a real energy density of 245.6 Wh kg-1.In addition,Zn-MnO2/I2 can reach a high areal capacity of 20 mAh cm-2 in mild electrolyte with iodine mediator.It can also stably cycle over 950 times at an areal capacity of 10 mAh cm-2.The enlarged Zn-MnO2/I2 battery exhibits a practical energy density of about 37 Wh kg-1.The successful design of high-performance aqueous Zn-Br2 and Zn-MnO2 batteries provides an important theoretical and experimental basis for exploring the next generation of high-performance aqueous Zn batteries,which will promote the application of aqueous Zn batteries in large-scale energy storage.