Deintercalation-type Vanadium-based Anode Materials For Electrochemical Energy Storag

Conventional internal combustion engine powered vehicles cause serious environmental problems.As a result,battery electric vehicles（BEVs）become more and more popular in recent years.Lithium-ion batteries（LIBs）own better electrochemical performance than other secondary batteries,thereby being regarded as ideal power sources for BEVs.Nevertheless,the current LIBs for BEVs suffer from unsatisfactory energy density,power density,safety,cyclability and cost.Especially,both energy and power densities are poor at low temperature（LT）,and rapidly decrease at high temperature（HT）,limiting the use of BEVs in cold（such as high altitudes and high latitudes）and hot（such as tropical regions and summer periods）situations.The anode,as one of the core components of LIBs,has not fulfilled the high performance requirements for BEVs so far.（1）VPO₅compound was synthesized by ball milling solid state reaction.Through Rietveld refinement,it is determined that VPO₅has orthogonal crystal structure（Pnma space group）.The evolution of crystal structure at different temperatures was studied by in-situ XRD,in-situ TEM,ex-situ XPS and ex-situ HRTEM.VPO₅has a developed crystal structure,which makes it have a large lithium-ion diffusion coefficient（even at low temperature）.At the same time,the inactive PO₄tetrahedron surrounds the active VO₆octahedron,which caches the volume strain and makes it have the characteristics of"zero strain"（even at high temperature）.Therefore,the structural advantages of VPO₅make it have good electrochemical performance in the whole temperature range.In different temperature ranges of 25/-20/60℃,VPO₅shows a large reversible capacity of 246/181/334m Ah·g^-1at 0.1C.At the same time,it shows excellent rate performance at 10C/2C/10C,128/85/127 m Ah·g^-1,and excellent cycle performance of 100.1%/109.4%/151.4%for 10000/3000/1000 cycles respectively.（2）We designed a Na₂Sr V₄O₁₂compound as a new type of intercalation-type anode material,and successfully prepared nanowires with an average diameter of about 200-300 nm by electrospinning and low temperature calcination.On the one hand,Na₂Sr V₄O₁₂exhibits a large reversible capacity(420 m Ah·g^-1at 0.05 A·g^-1)at a safe working potential of～1 V.On the other hand,as a material with"zero strain"characteristics,Na₂Sr V₄O₁₂not only shows good cycling performance at room temperature(150.9%capacity retention over 800 cycles at 4 A·g^-1),but also is found that the"zero strain"material at high temperature has significant advantages.Compared with room temperature,Na₂Sr V₄O₁₂shows excellent rate performance(132m Ah·g^-1at 4 A·g^-1)and excellent cycle stability(190.1%capacity retention after1000 cycles at 4 A·g^-1current density)at high temperature.