Fabrication And Properties Of Vanadium-based Oxide Cathodes Materials Of Aqueous Zinc-Ion Batteries For Energy Storage

Ships are the main source of marine and offshore atmospheric pollution.With the implementation of Chinses"peak carbon dioxide emissions"in 2030 and"carbon neutrality"in2060,we will vigorously develop new energy power propulsion system ships,and adding energy storage systems into the marine power grid can improve generator efficiency and load balance,and realize energy saving and emission reduction of the marine system.Aqueous zinc-ion batteries（ZIBs）have the advantages of low cost,high safety,large capacity,and non-polluting,which are very advantageous in the application of marine power intelligent microgrid energy storage battery system.The development of aqueous ZIBs is still in its infancy,and vanadium oxides are one of the cathode materials of choice due to their high theoretical capacity,flexible and versatile crystal structure,and abundant resources,but vanadium oxides as cathode materials for ZIBs are prone to collapse of the layered structure and dissolution of vanadium in the compounds after charge/discharge cycles,which affect their electrochemical performance and stability.Aiming at the above problems,in this thesis,the layered structure of vanadium-based oxide cathode materials,including crystal plane spacing,oxygen vacancy concentration,and electrochemical activation,to improve the dissolution and structural stability of vanadium oxide through guest pre-intercalation and coating strategies.The electrochemical properties and energy storage mechanism are further investigated.The main conclusions obtained from the study are as follows:（1）Mg_0.17V₂O₅·1.7H₂O（Mg VOH）,Ca_0.18V₂O₅·1.3H₂O（Ca VOH）,and Sr_0.19V₂O₅·1.6H₂O（Sr VOH）nanobelt cathode materials are prepared by a one-step hydrothermal method using a cation pre-intercalation strategy with the selection of alkaline earth metals Mg,Ca,and Sr with small to large ionic radii,respectively,in layered V₂O₅·n H₂O（VOH）.The pre-intercalation of alkaline earth metal ions in the VOH layers as"pillars"increased the crystalline spacing,and the crystalline spacing of the prepared Mg VOH,Ca VOH,and Sr VOH nanomaterials（001）increased from 1.14 nm to 1.30 nm,1.26 nm,and 1.35 nm for VOH,respectively.The crystalline spacing of the intercalated ions tends to decrease and then increase with the increase of the radius of the alkaline earth metal ions.The results show that the pre-intercalation of alkaline earth metal ions,which widens the ion diffusion channel and lowers the Zn²⁺migration energy barrier,as well as the partial reduction of V⁵⁺to V⁴⁺in VOH,leads to a significant improvement of the structural stability and electrical conductivity of the intercalated vanadium oxides.The prepared VOH,Mg VOH,Ca VOH,and Sr VOH vanadium-based oxide materials exhibit specific capacities of 332,382,397,and 350 m Ah g^-1 at a current density of 0.1 A g^-1with areal capacities of 0.40,0.46,0.48,and 0.42 m Ah cm^-2.（2）V₂O₅·n H₂O@PANI（VOH@PANI）nanobelts cathode materials are synthesized by self-polymerization at room temperature based on the organic molecule pre-intercalation strategy.PANI can increase the interplanar spacing of VOH（001）planes,and at the same time,PANI coats VOH and inhibits the dissolution of cathode electrode materials in weakly acidic electrolytes.Moreover,oxygen vacancies（V（?））are generated on the surface of the VOH@PANI composite,which modulates the electronic structure and surface chemistry of the composite,triggering rapid electron transfer,and PANI itself also can store zinc,thereby improving the electrochemical performance of the electrode.Therefore,the VOH@0.5PANI electrode material exhibits a high specific capacity of 413 m Ah g^-1 and an areal capacity of 0.50 m Ah cm^-2 at a current density of 0.1 A g^-1,indicating the potential of Zn//V₂O₅·n H₂O@PANI batteries.Zn²⁺intercalation/deintercalation storage mechanism.（3）At room temperature,the more conductive poly（3,4-ethylenedioxythiophene）（PEDOT）is pre-intercalation into commercial V₂O₅ by a one-step self-polymerization method,which realized the increase of the interplanar spacing of V₂O₅ and the regulation of the concentration of V（?）.Control material morphology and electrochemical performance.The prepared V（?）-V₂O₅-PEDOT-20.3%cathode exhibits a high specific capacity of 449 m Ah g^-1 and an areal capacity of 0.54 m Ah cm^-2 at a current density of 0.2 A g^-1,even at a current density of 10 A g^-1 After6000 cycles,the capacity retention rate is still 94.3%.The preparation method is simple to operate and can scale up production.（4）To obtain the material morphology with high areal capacity,the micro-flower morphology Ca V₄O₉ cathode material with high tap density is prepared by hydrothermal method,and the current collector-free Ca V₄O₉/carbon nanotube（Ca V₄O₉/CNTs）film is prepared by spraying method.The research shows that Ca V₄O₉ undergoes phase transformation during the first cycle of charging,and is transformed into amorphous V₂O₅·n H₂O,which improves the electrochemical performance of the material.The Ca V₄O₉/CNTs film electrode achieves a high areal capacity of 10.5 m Ah cm^-2 at a high loading of 50 mg cm^-2.Soft-packed flexible Zn//Ca V₄O₉/CNT batteries exhibit the reliable electrochemical performance of～295m Ah g^-1(1 A g^-1)in different deformation states.