Porous Co_(2)VO_(4) Nanodisk as a High-Energy and Fast-Charging Anode for Lithium-Ion Batteries

High-energy–density lithium-ion batteries(LIBs)that can be safely fast-charged are desirable for electric vehicles.However,sub-optimal lithiation potential and low capacity of commonly used LIBs anode cause safety issues and low energy density.Here we hypothesize that a cobalt vanadate oxide,Co_(2)VO_(4),can be attractive anode material for fast-charging LIBs due to its high capacity(~1000 mAh g^(−1))and safe lithiation potential(~0.65 V vs.Li^(+)/Li).The Li+diffusion coefficient of Co2VO4 is evaluated by theoretical calculation to be as high as 3.15×10^(-10) cm^(2) s^(−1),proving Co_(2)VO_(4) a promising anode in fast-charging LIBs.A hexagonal porous Co2VO4 nanodisk(PCVO ND)structure is designed accordingly,featuring a high specific surface area of 74.57 m^(2) g^(−1) and numerous pores with a pore size of 14 nm.This unique structure succeeds in enhancing Li^(+) and electron transfer,leading to superior fast-charging performance than current commercial anodes.As a result,the PCVO ND shows a high initial reversible capacity of 911.0 mAh g^(−1) at 0.4 C,excellent fast-charging capacity(344.3 mAh g^(−1) at 10 C for 1000 cycles),outstanding long-term cycling stability(only 0.024% capacity loss per cycle at 10 C for 1000 cycles),confirming the commercial feasibility of PCVO ND in fast-charging LIBs.

The lithium and sodium storage performances of phosphorus and its hierarchical structure

Recent preparation of black phosphorene and subsequent discovery of its excellent optical and electronic properties have attracted great attenti on,and ren ewed interest to phosphorus.Rece nt researches have indicated that phosphorus structures are promisi ng an odes for lithium-ion and sodium-ion batteries.A high theoretical capacity of 2,596 mAh·g^-1 was predicted for phosphorus according to the reaction of 3Li/Na+P→Li3P/Na3P.However,fast capacity degradation is accompanying with most phosphorus structures due to the low electronic conductivity and structural pulverization induced by large volume change in charging and discharging proceses.The electrochemical performances are significantly affected by the hierarchical structural design of phosphorus.A few reviews of phosphorus structures have been reported recent?However,no review about the electrochemical performances of phosphorus structures according to their hierarchical structures has been reported.First of all,phosphrus allotropes along with their structure and fundamental properties are briefly reviewed in this work.Secondly,the studies on lithiation/sodiation mechanism of red/black phosphorus are presented.Thirdly,a summary about the electrochemical performances of red/black phosphorus composites with different hierarchical structures is presented.Furthermore,the,development challenges and future perspectives of phosphorus structures as anodes for LIBs and SIBs are discussed.

Role of oxygen vacancy in rare-earth-free LiCa_(3)Mg(VO_(4))_(3) phosphor: Enhancing photoluminescence by heat-treatment in oxygen flow

As a kind of white light emitting diode(w-LED)with many advantages,rare-earth-free vanadate phosphor has attracted more and more attention.The oxygen vacancies and other surface defects in vanadate oxide have obvious effects on its structure and properties.In order to reveal the specific effects,we heat-treat the original LiCa_(3)Mg(VO_(4))_(3)(LCMV)in an oxygen flow with different time to decrease oxygen vacancies,and find that the lattice distortion of[VO_(4)]tetrahedron caused by oxygen vacancy is effectively reduced.Meanwhile,the crystallinity of the treated samples increases,the surface defects decreases,and the fluorescence intensity increases.The variation of photoluminescence quantum yield(PLQY)with oxygen treatment time is as follows:the enhancement effect firstly reaches the strongest(69.34%)within one hour,then begins to decline after two hours,and finally reaches the platform after three hours and remains basically unchanged.The reason for the enhancement of PLQY is the decrease of oxygen vacancy after one-hour treatment,and the reason for the decrease of PLQY after a further increased treatment time is that the absorption of oxygen and water in air caused by excessive surface defects introduced by oxygen treatment.