Application Of In-situ Strategy Of MXene For Aqueous Zinc-ion Batteries

In 2019,MXene material was first reported to be used in aqueous zinc-ion storage devices.After several years of development,its related reports gradually increased,showing huge development potential.Systematically dividing and summarizing relevant reports,building a bridge between MXene’s regulation ideas and its practical application,is of great significance for promoting further development in this field.Here,we first summarize the progress of MXene materials in aqueous zinc-ion storage devices based on the different control methods of MXene.All modification schemes of MXene can be categorized into in situ or ectopic strategies.In the review work,we systematically explored the advantages,disadvantages,and research necessity of the current in-situ strategy of MXene.In the following experimental research work,based on the in-situ strategy of MXene,we regulate the vanadium oxide cathode materials and develop a series of in situ derivation strategies including V₂C MXene as source material,Ti₃C₂MXene as substrate and Ti₃C₂MXene as additive.We have demonstrated the advantages of the current in-situ strategy and further compensated for its shortcomings,gradually expanding the application of MXene in-situ strategy in aqueous zinc ion batteries.The specific research content is as follows:1.In the review section,we classify the application of MXene in the field of aqueous zinc storage as pure MXene material,MXene-based derivative material and MXene-based hybrid material.We elaborate the design concepts of the three types of regulatory ideas mentioned above,list the related reports and summarize the various modification schemes of MXene.Pure MXene materials do not have Faraday active normally in aqueous zinc ion batteries and are more suitable for conductive substrates because their oxidizable properties,which can be modified by in situ derivation and hybrid materials,which can be constructed by heterotopic binding or in situ growth strategies considering their special surface chemical environment.Based on the systematic summary and discussion of MXene regulation ideas,as the background for our subsequent research work,we conducted three subsequent experimental research works.2.In the first research,we constructed VO₂@V₂C 1D/2D heterostructure using V₂C in situ derivation strategy and synthesized pure phase VO₂for comparison,the test results showed that the rate performance of the derived VO₂was significantly improved.The mechanism of increasing the rate performance was explained from the micro and macro perspective,and the VO₂@V₂CO_xheterojunction structure was further constructed by using electrochemical oxidation strategy to activate V₂C to increase the capacity of the electrode materials.In this work,we propose a one-step in situ derivation scheme that is different from the traditional multi-step synthesis and modification scheme for VO₂materials.We demonstrate the advantages of the in situ derivation strategy in terms of experimental simplicity and easy regulation,and systematically explain the reasons for the poor rate performance of VO₂.We reveal the mechanism of improving rate performance by heterostructure,providing a new perspective for improving rate performance strategies and construction schemes of electrode materials.3.In the second research,we propose a liquid-phase in-situ nucleation growth strategy to construct a-HVO@Ti₃C₂amorphous heterostructure.It is found that the heterogeneous interfaces connected by V-O-Ti bonds have strong interfacial interactions,which will significantly change the HVO growth mode and construct amorphous a-HVO structure.The synergistic effect introduced by amorphous structure a-HVO and high conductivity ex-Ti₃C₂MXene substrate significantly improves the cyclic stability and power performance of the electrode materials.The strong V-O-Ti bonds can also inhibit the electrochemical oxidation of MXene to protect it from high voltage windows.In addition,due to the directionality of the built-in electric field at the heterogeneous interface,which will lead to the contradiction of inhibiting ion migration during charging.Based on relevant literature reports,we propose a possible mechanism of the field inversion at the heterogeneous interface based on the fact that MXene does not have Faraday activity.In this work,we propose and elaborate in situ nucleation growth strategies,which make up for the deficiencies of current mainstream in situ derivation strategies limited by precursors.Furthermore,liquid in situ nucleation growth strategies break through the limitations of traditional in situ growth strategies limited by special reaction environments and expand the development of MXene in situ strategies.4.In the third research,we found that the above liquid-phase in situ nucleation strategy works equally well for a very small number of MXenes,and proposed an in situ strategy of MXene as a heterogeneous nucleation-inducing additive to induce lattice growth to construct a structure rich in doubly coordinate oxygen defects.The capacity and rate performance of V₅O₁₂·6H₂O was further improved by constructing T-HVO|O_dstructure.Here we call this strategy in situ induction growth strategy,and describe the mechanism of lattice induced growth by combining various characterizations and DFT calculations to simulate nucleation growth process.The mechanism of electrochemical performance improvement is discussed.In particular,in dynamic analysis,we introduce a dynamic correction process and use MATLAB to perform a matrix operation to achieve a non-linear fitting step,which distinguishes the physical capacitance from the pseudo capacitance of the electrode materials.We demonstrate that the physical and pseudo capacitance of the modified electrode material are both increased due to the unique mesh structure of T-HVO|O_dstructure and the large number of oxygen defects inside.In addition,we also found that the above in situ induction strategy has some universality,and graphene materials can also be used for this in situ induction strategy,which can further construct G-HVO|O_dmaterials to prove this conclusion.In this work,we propose a new MXene in situ induction growth strategy,which can introduce oxygen defects safely and efficiently in the lattice growth process and significantly improve the electrochemical performance of the electrode materials,further expanding the development of MXene in situ strategy.