New Electrolyte Design And Modification Of Anode For Aqueous Zinc Ion Batteries

With the high-speed development of the world economy,the increasingly severe energy crisis and environmental pollution have become global challenges.The development of clean and green renewable energy has become a consensus,and its matching scale storage technology has become the key.Among the many energy storage batteries,zinc-ion batteries based on metal zinc and aqueous electrolytes have attracted widespread attention due to their safety,reliability,low cost,environmental friendliness,and the potential advantages of high power and high energy density.However,this system faces many problems to be solved,such as material dissolution,corrosion,and hydrogen evolution caused by highly active aqueous electrolytes,difficult-to-control zinc ion deposition and dendrites.Based on this,this thesis builds a research line around the core issues of zinc deposition/stripping efficiency,ion deposition characteristics,and interfacial reactions.Through the modification of anode,new inorganic colloidal electrolytes,organic-inorganic composite electrolytes,and high-concentration dual-ion electrolytes are constructed to explore the development law and relationship around core issues.Based on the decay mechanism of zinc-based batteries,targeted solutions are proposed.The main conclusions are as follows:（1）A metal-zinc anode（Zn@Zn O-3D）with three-dimensional structure Zn O modification was synthesized in one step by liquid deposition method,and the structural regulation and functionalization of the zinc anode interface were unified.The Zn@Zn O-3D modified zinc anode exhibits up to 99.55%deposition/stripping efficiency and high reversible cycling stability up to 1000 times.Characterized by nucleation energy barrier,exchange current density and activation energy during Zn deposition,Zn@Zn O-3D was found to exhibit faster kinetic behavior of Zn ion deposition/migration reaction,hydrogen evolution inertness and lower desolvation energy(51.0 k J mol^-1).First-principles calculations show that Zn@Zn O-3D has lower ion adsorption energy and additional charge induction,which makes Zn@Zn O-3D preferentially adsorb Zn²⁺and realize the guiding effect of zinc ion deposition,so as to reduce the dehydration of hydrated zinc ions and dendrite suppression.The Zn/Mn O₂battery based on this Zn anode shows that the Zn@Zn O-3D anode exhibits better rate performance and cycling stability,maintaining nearly 93.99%capacity after 500 cycles at 500 m A g^-1,with a specific capacity of 212.9 m Ah g^-1.（2）A novel inorganic bentonite-based inorganic functional colloid electrolyte（Ben-colloid）was constructed to replace the conventional liquid electrolyte.The stable colloidal properties（-30.7 m V,Zeta potential）and layered structure（1.45 nm）exhibited by the Ben-colloid colloidal electrolyte endow the ordered ion transport channels.The results of zinc deposition exfoliation show that the use of Ben-colloid colloidal electrolyte can achieve uniform exfoliation and ordered deposition（Zn/Ti battery）,avoid dendrites,and maintain the reciprocating zinc deposition/stripping process for up to 2500 h(0.5 m Ah cm^-2).In addition,the functional ion confinement of the electrolyte and Zn/Mn ion-exchange characteristics enable the adjustment of the Mn concentration,thereby reducing the equilibrium deposition potential of Mn O₂to stimulate more two-electron Mn⁴⁺/Mn²⁺deposition-dissolution reactions.Based on this electrolyte,the Zn/Mn O₂battery achieves nearly twice the capacity release(480.7 m Ah g^-1),and the cycle capacity retention rate is 94.3%after 500 cycles,and it can withstand high temperature cycling at 80 ^oC.Even in cathode-free cells,this electrolyte induces self-dissolution/deposition redox reactions,maintaining good reversibility.（3）An in-situ programmable electrolyte preparation method was proposed for the first time to prepare a zinc alginate（Alg）-palygorskite composite organic-inorganic colloidal electrolyte.Metallic zinc was oxidized to Zn²⁺by electrochemical oxidation and ionically cross-linked with the carboxylic acid group of alginate in situ,accompanied by inorganic colloidal palygorskite material（5 wt%）to grow in situ on the surface of zinc metal.Then a layered organic-inorganic composite electrolyte（Alg-5）was formed.The electrolyte combines the flexibility of the gel electrolyte and the highly reversible zinc deposition/stripping of the inorganic colloidal electrolyte,which not only realizes the improvement of the reversibility of the zinc anode,but also retains the flexible and wearable characteristics of the gel electrolyte.Based on the coordination guidance effect of carboxylic acid groups in the electrolyte on Zn²⁺and the ion enhancement effect of inorganic colloidal electrolytes,a more stable zinc ion migration process is formed,achieving up to99.65%zinc deposition/stripping efficiency and long-term cycling stability of over 500 h.Based on this method,a composite electrolyte with a thickness of about 219μm can be obtained in situ on a 1.2 mm Zn wire in only 80 s,and a wire-shaped Zn/Alg-5/Mn O₂full cell was successfully prepared,showing good electrochemical performance,and has excellent high flexibility and stability.（4）The decay mechanism of vanadium-based material NH₄V₄O₁₀was explored,and high-concentration Mg SO₄-Zn SO₄double-ion saturated electrolytes（Mg Zn-bh）were designed to suppress V dissolution in a targeted manner.The vanadium-based materials with NH₄V₄O₁₀as the positive electrode have serious vanadium dissolution phenomenon both in the static state and during the battery cycle,and the higher the p H,the greater the solubility,even in the Zn SO₄electrolyte with a p H of 6.5for 24 h.A large amount of aggregation and deposition of Zn₃（OH）₂（V₂O₇）（H₂O）₂was detected.In the actual battery cycle,the dissolved vanadium will also shuttle to the negative electrode side,resulting in the formation of vanadium-zinc hydroxide in both the positive and negative electrodes,which promotes the continuous decay of the battery.It is found that the use of Mg Zn-bh electrolyte can effectively suppress the continuous decay of Zn/NH₄V₄O₁₀cells,especially at small current densities.On the one hand,the Mg Zn-bh electrolyte can effectively reduce the activity of free water and increase the hydrogen evolution potential,thereby realizing the inhibition of the increase of electrolyte p H,and essentially solving the dissolution of the active V in the vanadium-based system.At the same time,it has both functional preferential adsorption and too low effective reduction potential to realize the directional deposition of zinc ions,and obtain a（101）preferential deposition layer,which avoids zinc dendrites.Using this electrolyte,the Zn/Mg Zn-bh/NH₄V₄O₁₀full cell maintained 94.3%capacity retention even at a low current density of 100 m A g^-1for up to 15 day.The capacity retention rate of 3000 cycles at 5 A g^-1is close to 100%,achieving the purpose of functionally guiding deposition and avoiding vanadium dissolution from the electrolyte aspect.There are 69 pictures,9 tables and 255 references.