Design Of High-performance Electrode Materials And Their Application In Aqueous Zinc Ion Batteries

With the depletion of traditional energy sources and the environmental degradation caused by fossil fuel combustion,there is an increasing demand for renewable and clean energy.In order to cope with the occasional need,efficient electrochemical energy storage systems are needed to realize energy conversion and storage.Among various energy storage systems,lithium-ion batteries,as the most classical rechargeable batteries with high output voltage and energy density,occupy the main position in the energy field of modern society.However,the scarcity of lithium ore resources and strict battery assembly conditions have raised the production cost of lithium-ion batteries.More importantly,the high activity of lithium metal itself and the flammability and toxicity of organic electrolyte have raised a series of safety issues,limiting the large-scale application of lithium-ion batteries.Therefore,there is an urgent need to develop efficient,clean and safe rechargeable batteries as an alternative solution to achieve large-scale energy storage and utilization.Considering the inherent safety and environmental friendliness of aqueous electrolytes,cost advantages,and high ionic conductivity,rechargeable batteries based on aqueous electrolytes offer a promising alternative for grid-level energy storage.Among them,aqueous zinc ion batteries with zinc anodes can achieve higher capacity and energy density.However,electrode materials still face several problems that limit the electrochemical performance of full batteries.First,vanadium oxide,the most prevalent cathode material,has the advantages of high theoretical capacity and large layer spacing;however,its own low electronic/ionic conductivity and slow kinetics lead to limited rate performance and electrochemical activity.Vanadium oxides also face vanadium dissolution and collapse of the laminate structure,which severely reduces cycle life.In addition,Zn anodes suffer from dendrites and side reactions in aqueous electrolytes,reducing the reversibility of the Zn anode.In order to extend the cycle life of the anode,excess Zn is often used which leads to a decrease in overall energy density and an increase in cost.This paper addresses these issues and proposes strategies for improving the cathode design and anode interface of high-performance aqueous zinc ion batteries to effectively improve battery energy/power density and cycle stability and further promote the development and application of aqueous rechargeable batteries.The paper is organized around the following aspects.1.Mixed electronic-ionic conducting network intercalated V₂O₅ cathode for high-rate and high-loading-capacity aqueous zinc ion batteryA mixed conductor intercalation strategy was used to design and prepare a V₂O₅ cathode（Zn VO）intercalated by a mixed conducting polymer,using the mixed electronic-ionic conducting polymer as a transport vehicle for the charge carriers(Zn²⁺and e^-)of the V₂O₅layers.The mixed conducting polymer can promote electron/ion transfer,accelerate cathodic reaction kinetics and stabilize the layer structure.In addition,their own inherent electronic/ionic conductivity can eliminate mass transfer limitations,thus improving electrochemical reactivity.As a result,the Zn VO cathode provides high capacity and high-rate performance(380.2/206.1 m Ah g^-1 at 0.3/10 A g^-1)at a mass loading of 2 mg cm^-2,exhibiting excellent stability(85.4%capacity retention after 400 cycles at 0.3 A g^-1;90.3%retention after5000 cycles at 5 A g^-1).Even under a high mass loading of 10 mg cm^-2,it provides a high area capacity of 2.6 m Ah cm^-2 and an energy density of 2.0 m Wh cm^-2.The homemade pouch battery is capable of providing 25 m Ah capacity and 82.2%capacity retention after 100 cycles at 1 A g^-1,effectively driving a small fan.2.Metal-induced layered conducting solid electrolyte interface for high-rate and long-life Zn anodeUsing in-situ welding and charge enrichment strategies,a mixed conducting polymer solid electrolyte interface（SEI）with a layered nanocrystal structure and fast ion transport channels was induced in-situ on the Zn anode surface to develop the high-rate and long-life dendrite-free Zn anode（PZn）.The mixed conducting polymer layer not only facilitates charge concentration enrichment,but also homogenizes the electric field and ion flux and promotes the desolvation of hydrated zinc ions.In addition,the layer structure is able to regulate the diffusion behavior of Zn²⁺,thus achieving uniform Zn deposition.As a result,the PZn symmetric cell exhibits dendrite-free behavior and has excellent rate performance(current rate up to 20 m A cm^-2)and ultra-long cycle life(1 m A cm^-2,4000 h;10 m A cm^-2,2000 h;20 m A cm^-2,1500 h)with cumulative plating capacity up to 15 Ah cm^-2.When the PZn anode is assembled with K_xMn O₂ cathode towards aqueous zinc ion batteries,they are able to provide high energy density(412.2/191.0 Wh kg^-1 at 0.2/3 A g^-1 based on the mass of the cathode)with excellent cycling stability,and 80.1%of capacity retention after 1000 cycles at 1 A g^-1.When the optimized capacity ratio of anode/cathode is 2.7/1,the full cell can provide a high energy density of 168 Wh kg^-1（based on the mass of two electrodes）.3.Interfacial reversible electric field regulated by amphoteric charged protein-based coating towards high-rate and stable Zn anodeThe interfacial p H-regulated amphoteric charged silk fibroin（SF）coating is utilized to construct an adaptive electric field direction to homogenize and accelerate the Zn²⁺flux on the anode surface.In addition to the acceleration of Zn plating/stripping kinetics by the interfacial electric field,the hydrophobicβ-sheet acts as a water barrier to suppress side reactions of hydrogen evolution.Experimental analysis and theoretical calculations show that the surface polar group of SF（-CO-NH-）accelerates the desolvation of hydrated zinc ions and provides nucleation sites for homogeneous Zn deposition.As a result,the symmetric cell shows a low polarization voltage(83 m V at 20 m A cm^-2)and a long lifetime(1500 h at 1 m A cm^-2 and 500h at 10 m A cm^-2)with a cumulative plating capacity of 2.5 Ah cm^-2.The full cell assembled with the Zn_xV₂O₅·n H₂O cathode exhibits a specific energy of 270.5/150.6 Wh kg^-1(0.5/10 A g^-1)and 80.3%of capacity retention after 3000 cycles at 5 A g^-1.When the optimized capacity ratio of anode/cathode is 2.8/1,the full cell can provide a high energy density of 101 Wh kg^-1（based on the mass of two electrodes）.4.Preliminary exploration of catechol-grafted conducting polymer cathodes for fast-charging all-polymer aqueous proton batteryAn all-polymer aqueous proton battery with excellent electrochemical performance was developed using a catechol-based cathode（PTC）and an anthraquinone-based anode（PUQ）.Using a charge separation strategy,the cathode potential enhancement was achieved by introducing a catechol pendant to the PEDOT backbone to provide a significant electron delocalization.The charge separation of the redox pendant and the conjugated backbone facilitates pseudocapacitive charge storage,resulting in excellent rate performance.Diffusion-type anodes with hard and soft sections can increase the overpotential of hydrogen evolution reaction and reduce the electrode rupture caused by volume change,thus improving the cycling stability.DFT theoretical calculations and ex-situ characterization clarifies that the PTC cathode has a dual ion(H⁺and SO₄^2-)inserted mechanism.Combining the capacitive-type cathode and diffusion-type anode,the aqueous proton cell exhibits a high voltage（0.72V）,high-rate capacity(50.8 m Ah g^-1 at 25 A g^-1),excellent energy density/power density(56.2Wh kg^-1/360 W kg^-1)and superior cycling stability(80%capacity retention after 1000 cycles at 2 A g^-1).These results highlight the feasibility of the rational design of high-performance polymer electrodes for fast-charging energy storage systems.