| Supercapacitors(SCs)are recognized as promising next-generation energy storage devices owing to their high power density,ultra-fast rate capability,and long-term stability.Currently,the huge technological challenge of supercapacitors is focused on promoting energy density without diminishing their power density and cyclic life span.Developing high performance electrode materials is the key to realizing high performance SCs.Vanad-based materials are widely used as electrode materials for supercapacitors because of their characteristics of easy synthesis,low cost and higher theoretical specific capacitance value.In this paper,a novel vanad-based material was developed by designing a mild synthesis route,adjusting the electronic structure and interface modification through controlled phase transformation,and the intercalation mechanism was applied to SCs,a new energy storage mechanism is proposed to achieve high electrochemical capacity and wide voltage window,and successfully improve the energy density of three different components of the assembled aqueous symmetrical/allsolid micro/potassium ion hybrid supercapacitors.The details of the study are as follows:1.Based on controllable phase change engineering,a layered VO(PO3)2 selfsupporting electrode material was prepared by sol-gel method.In-situ XRD revealed that the phosphorus vacancy induced the multiphase phase transition reaction(NaV0.66P0.34O3)of VO(PO3)2 electrode in neutral electrolyte.Based on the energy competition relationship between intercalation and water electrolysis,multiphase phase transformation inhibits the OER and HER processes,and increases the over-potential to broaden the voltage.A 2.8 V symmetric aqueous supercapacitor was further assembled with an energy density of 123.1 Wh kg-1 at the power density of 580 W kg1,which is much superior to those of all reported V-base supercapacitors.The underlying mechanisms of the VO(PO3)2 on ultrahigh voltage window and charge storage are further elucidated,which provide the fundamental guidance for structuring VPO-based electrodes used for commercial energy storage devices.2.Based on heterojunction engineering,the reaction kinetics of electrode materials are enhanced by constructing the electronic structure of composite materials controlled by transverse and longitudinal heterostructure.Embed V2O3 and nano-carbon into VPO4 by one-step in-situ growth(V2O3@VPO4-NC)Induced charge redistribution at the heterojunction interface.Examined as the supercapacitor electrode,the V2O3@VPO4-NC manifests superior electrochemical properties in terms of an ultrahigh specific capacitance of 2797.3 F g-1 at 1 A g-1,excellent rate performance(54%)as well as an ultralong cycle life over 10000 cycles(91.9%).In parallel,an all-solid-state interdigital micro-supercapacitors with water-in-LiCl electrolyte achieves a record operating voltage of 1.8 V,delivering a dual-boosted volumetric/areal energy density of 4637.6 Wh/L and 97.7 mWh cm-2.This work underpins the importance of lateral and vertical heterostructures for future miniaturized and integrated electronics.3.Based on grafting engineering,the surface capping groups of V2CTx materials were precisely controlled by grafting with polyionic liquid(PIL).V2CTx(K+-V2CTxPIL)with "customized surface" structure was successfully prepared by using KOH as the alkalizing agent of V2CTx and inducing ionic liquid to undergo in-situ polymerization on the alkalized V2CTx by "one-step high-pressure injection method".Benefitting by the K+/vacancy disorder structure during energy storage,K+-V2CTxPIL obtains a continuous K+diffusion channel and more active storage sites,thus achieving a high specific capacity of 476.1 mAh g-1.As the anode for potassium-ion hybrid supercapacitors(K+-V2CTx-PIL//22M KCF3SO3//activated carbon(AC)),stable capacity of 476.1 mAh g-1 can display a high energy density of 193 Wh kg-1,an ultrahigh power output of 12.6 kW kg-1 at an energy density of 43.6 Wh kg-1.This work may open a new avenue for the design of MXene materials and promote their practical application in energy storage field. |
