Effect Of Metal Oxide On Thermodynamic And Electrochemical Properties Of TeO₂-V₂O₅ Glasses

Considering the advantages of the oxide glasses applied as the anodes for lithium ion batteries,i.e.,the unique random network structure and the absence of grain boundaries which can facilitate the transport and storage of lithium ions,we mainly studied on the electrochemical properties and the thermal dynamic behavior of ternary Al₂O₃-TeO₂-V₂O₅?AVT?glasses.Since the existence of polyvalence vanadium ions which could affect the electronic conductivity of the glasses,we also studied the effects of both the heat treatment atmosphere and the heat treatment time on the electrochemical properties of the AVT glasses at crystallization temperature.In addition,this paper also studied on the electrochemical properties and the thermal dynamic behavior of quaternary Li₂O-Nb₂O₅-TeO₂-V₂O₅ glasses,as well as the influence of heat treatment on their electrochemical properties.The paper will be divided into three parts:?1?We investigated the effect of Al₂O₃ doping on the physical,thermal and electrochemical properties of the V₂O₅-TeO₂ glass anode.To do so,we prepared the glass samples with the composition of x Al₂O₃-?100-x??TeO₂-V₂O₅??x=0,2,5,and 7 mol%??AVT?.The results show 2AVT glass anode exhibits the lowest T_g value due to a decrease in the network connectivity.The component has the low thermal stability,that is,the difference between T_c and T_g is the smallest,implying that the glass has the least number of constraints,i.e.,the highest degree of atomic freedom.There exists a critical Al₂O₃content,i.e.,2 mol%Al₂O₃,which gave Li Bs the highest capacity of 202 m Ah g^-1 after1000 cycles of discharging/charging under the current density of 1000 m A g^-1 and the lowest charge-transfer resistance before cycling.The disorder-order transition was found to take place in the AVT glass anodes,accompanied by formation of tellurium nanocrystals after 1000 cycles at 1 A g^-1.Both the Te nanocrystals and the glass matrix synergistically enhanced the capacity and the cycling stability of the AVT glass anode.It is mainly due to the nanocrystal could suppress the propagation of micro-cracks generated by volume changes in glass matrix.?2?2AVT glass was chosen as a study object due to its best electrochemical performance.The characteristic temperatures including glass transition temperature T_gand the crystallization temperature T_c were determined from the DSC curve.2AVT glass was heat treated at T_c under different atmosphere for different time.It was found that the crystallization phase from 2AVT glass is irrelevant to the treatment time but strongly depends on the atmosphere.The precipitation crystals were identified as V₂O₅ when 2AVT glass were heated treatment at 601 K for 5 min,2 h and 8 h,respectively.However,the crystals precipitated from the samples heated in argon and hydrogen atmosphere were Te₄O₉ and Te VO₄,respectively.It was found when 2AVT glass was heated in air atmosphere for 5 min,i.e.,the h5m2AVT glass sample exhibits the highest capacity of284 m Ah g^-1.When 2AVT glass was heat treated in argon atmosphere for two hours,the it delivers a higher capacity of 243 m Ah g^-1 after 1000 discharging/charging cycles under the current density of 1000 mA g^-1,which is higher than that of the sample treated in hydrogen and air atmosphere under the same conditions.In a word,both the heat treatment atmosphere and the time have certain influence on the crystallization types and electrochemical properties of 2AVT glass.?3?We investigated the effect of Nb₂O₅ and Li₂O doping on the electrochemical properties of the V₂O₅-TeO₂ glass anode?LNVT30?.The result showed that with the increase of the content of Li₂O and Nb₂O₅,the structure of the glass network became more and more loose.The[TeO₄]trigonal bipyramid?tbp?transformed to[TeO₃]trigonal pyramid?tp?,and VO₄ gradually turns into VO₅.As the cathode material of lithium ion battery,LNVT30 glass showed the highest reversible capacity of 131 m Ah g^-1 at 2000cycles of charging and discharging under the current density of 1000 m A g^-1.LNVT30 glass on the crystallization temperature of heat 0.5 h,1 h,4 h and 12 h.The crystal is Nb₁₈V₄O₅₅.At 2000 cycles of charging and discharging under the current density of 1000 m A g^-1 the maximum capacity of h12h LNVT30 glass was 215 m Ah g^-1.Precipitation of crystal and the rest of the glass phase in the process of charge/discharge cycle to keep the cycle stability of the anode materials and their synergy makes lithium ion batteries with high capacity and good cycle stability.We systematically studied the effect of metal oxides on the physical,thermal dynamic and electrochemical properties of V₂O₅-TeO₂ glass and studied the electrochemical properties of glass-ceramics obtained under different conditions.There was a strong dependence between the components and the electrochemical properties of glass anode with microstructure.In addition,with the dualistic V₂O₅-TeO₂ glass negative,negative charge and discharge will also induce AVT glass a disorderly and orderly transformation.This shows that the disorderly and orderly transformation may be a common phenomenon in the cathode glass,just the nanocrystalline types of precipitation and the composition of raw glass has a lot of dependencies.That is to say,the glass in the process of charging and discharging the cathode of the redox reaction process strongly depends on the chemical composition,revealed the relationship between need further experiment.It is explained that the interaction of glass phase and crystal lithium ion battery have higher capacity and excellent cycling stability.