The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion ba...The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion batteries.Thus,stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries.Surface coating is regarded as one of the most effective strategies for high voltage cathodes.The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously.However,commonly reported coating materials are unable to balance these functions well.Herein,a new type of coating material,La_(2)CuO_(4)was introduced to mitigate the surface issues of LROs for the first time,due to its superb electronic conductivity(26-35 mS·cm^(-1))and lithium-ionic diffusion coefficient(10^(-12)-10^(-13)cm^(2)·s^(-1)).After coating with the La_(2)CuO_(4),the capacity retention of Li_(1.2)Ni_(0.54)Co_(0.13)Mn_(0.13)O_(2)cathode was increased to 85.9%(compared to 79.3%of uncoated cathode)after 150 cycles in the voltage range of 2.0-4.8 V.In addition,only negligible degradations on the deliverable capacity and rate capability were observed.展开更多
Nasicon materials （sodium superionic conductors） such as Li1.5A10.5Ge1.5（PO4）3 （LAGP） and Li1.4Al0.4Til.6（PO4）3 （LATP） have been considered as important solid electrolytes due to their high ionic conductivit...Nasicon materials （sodium superionic conductors） such as Li1.5A10.5Ge1.5（PO4）3 （LAGP） and Li1.4Al0.4Til.6（PO4）3 （LATP） have been considered as important solid electrolytes due to their high ionic conductivity and chemical stability. Compared to LAGP, LATP has higher bulk conductivity around 10^-3 S/cm at room temperature; however, the apparent grain boundary conductivity is almost two orders of magnitude lower than the bulk, while LAGP has similar bulk and grain boundary conductivity around the order of 10-4 S/cm. To make full use of the advantages of the two electrolytes, pure phase Li1.5A10.5Ge1.5（PO4）3 and Li1.4A10.4Ti1.6（PO4）3 were synthesized through solid state reaction, a series of composite electrolytes consisting of LAGP and LATP with different weight ratios were designed. XRD and variable temperature AC impedance spectra were carried out to clarify the crystal structure and the ion transport properties of the composite electrolytes. The results indicate that the composite electrolyte with the LATP/LAGP weight ratio of 80：20 achieved the highest bulk conductivity which shall be due to the formation of solid solution phase Li1.42Alo.42Geo.3Ti1 .28（PO4）3, while the highest grain boundary conductivity appeared at the LATP/LAGP weight ratio of 20：80 which may be due to the excellent interfacial phase between Li1＋xAlxGeyTi2-x-y（PO4）3/LATE All the composite electrolytes demonstrated higher total conductivity than the pure LAGP and LATE which highlights the importance of heterogeneous interface on regulating the ion transport properties.展开更多
Silicon–graphite(Si–Gr)composite anodes are attractive alternatives to replace Gr anodes for lithium-ion batteries(LIBs)owing to their relatively high capacity and mild volume change.However,it is difficult to under...Silicon–graphite(Si–Gr)composite anodes are attractive alternatives to replace Gr anodes for lithium-ion batteries(LIBs)owing to their relatively high capacity and mild volume change.However,it is difficult to understand electrochemical interactions of Si and Gr in Si–Gr composite anodes and internal polarization of LIBs with regular experiment methods.Herein,we establish an electrochemical-mechanical coupled model to study the effect of rate and Si content on the electrochemical and stress behavior in a Si–Gr composite anode.The results show that the composites of Si and Gr not only improve the lithiation kinetics of Gr but also alleviate the voltage hysteresis of Si and decrease the risk of lithium plating in the negative electrode.What's more,the Si content is a tradeoff between electrode capacity and electrode volume variation.Further,various internal polarization contributions of cells using Si–Gr composite anodes are quantified by the voltage decomposition method.The results indicate that the electrochemical polarization of electrode materials and the electrolyte ohmic over-potential are dominant factors in the rate performance of cells,which provides theoretical guidance for improving the rate performance of LIBs using Si–Gr composite anodes.展开更多
The composite quasi solid state electrolytes（CQSE） is firstly synthesized with quasi solid state electrolytes（QSE） and lithium-ion-conducting material Li1.4Al0.4Ti1.6（PO4）3（LATP）, and the QSE consists of [LiG4...The composite quasi solid state electrolytes（CQSE） is firstly synthesized with quasi solid state electrolytes（QSE） and lithium-ion-conducting material Li1.4Al0.4Ti1.6（PO4）3（LATP）, and the QSE consists of [LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE is droped to 60%, its conductivity can also reach 1.39 × 10^-4S/cm at 20℃. Linear sweep voltammetry（LSV） is conducted on each composite electrolyte.The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li^＋1. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/Li Mn2O4 and Li/CQSE/Li Mn2O4 batteries is evaluated and shows good electrochemical characteristics at 60℃.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFE0100200)the National Natural Science Foundation of China(Grant No.U1964205)the Beijing Municipal Science and Technology Commission(Grant No.Z191100004719001)。
文摘The structural transformations,oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides(LROs)cathodes in Li-ion batteries.Thus,stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries.Surface coating is regarded as one of the most effective strategies for high voltage cathodes.The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously.However,commonly reported coating materials are unable to balance these functions well.Herein,a new type of coating material,La_(2)CuO_(4)was introduced to mitigate the surface issues of LROs for the first time,due to its superb electronic conductivity(26-35 mS·cm^(-1))and lithium-ionic diffusion coefficient(10^(-12)-10^(-13)cm^(2)·s^(-1)).After coating with the La_(2)CuO_(4),the capacity retention of Li_(1.2)Ni_(0.54)Co_(0.13)Mn_(0.13)O_(2)cathode was increased to 85.9%(compared to 79.3%of uncoated cathode)after 150 cycles in the voltage range of 2.0-4.8 V.In addition,only negligible degradations on the deliverable capacity and rate capability were observed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0100100)the National Natural Science Foundation of China(Grant Nos.52315206 and 51502334)Fund from Beijing Municipal Science&Technology Commission,China(Grant No.D171100005517001)
文摘Nasicon materials （sodium superionic conductors） such as Li1.5A10.5Ge1.5（PO4）3 （LAGP） and Li1.4Al0.4Til.6（PO4）3 （LATP） have been considered as important solid electrolytes due to their high ionic conductivity and chemical stability. Compared to LAGP, LATP has higher bulk conductivity around 10^-3 S/cm at room temperature; however, the apparent grain boundary conductivity is almost two orders of magnitude lower than the bulk, while LAGP has similar bulk and grain boundary conductivity around the order of 10-4 S/cm. To make full use of the advantages of the two electrolytes, pure phase Li1.5A10.5Ge1.5（PO4）3 and Li1.4A10.4Ti1.6（PO4）3 were synthesized through solid state reaction, a series of composite electrolytes consisting of LAGP and LATP with different weight ratios were designed. XRD and variable temperature AC impedance spectra were carried out to clarify the crystal structure and the ion transport properties of the composite electrolytes. The results indicate that the composite electrolyte with the LATP/LAGP weight ratio of 80：20 achieved the highest bulk conductivity which shall be due to the formation of solid solution phase Li1.42Alo.42Geo.3Ti1 .28（PO4）3, while the highest grain boundary conductivity appeared at the LATP/LAGP weight ratio of 20：80 which may be due to the excellent interfacial phase between Li1＋xAlxGeyTi2-x-y（PO4）3/LATE All the composite electrolytes demonstrated higher total conductivity than the pure LAGP and LATE which highlights the importance of heterogeneous interface on regulating the ion transport properties.
基金the National Key Research and Development Program of China(Grant No.2019YFE0100200)the National Natural Science Foundation of China(Grant No.U1964205)the Beijing Municipal Science and Technology Commission(Grant No.Z191100004719001)。
文摘Silicon–graphite(Si–Gr)composite anodes are attractive alternatives to replace Gr anodes for lithium-ion batteries(LIBs)owing to their relatively high capacity and mild volume change.However,it is difficult to understand electrochemical interactions of Si and Gr in Si–Gr composite anodes and internal polarization of LIBs with regular experiment methods.Herein,we establish an electrochemical-mechanical coupled model to study the effect of rate and Si content on the electrochemical and stress behavior in a Si–Gr composite anode.The results show that the composites of Si and Gr not only improve the lithiation kinetics of Gr but also alleviate the voltage hysteresis of Si and decrease the risk of lithium plating in the negative electrode.What's more,the Si content is a tradeoff between electrode capacity and electrode volume variation.Further,various internal polarization contributions of cells using Si–Gr composite anodes are quantified by the voltage decomposition method.The results indicate that the electrochemical polarization of electrode materials and the electrolyte ohmic over-potential are dominant factors in the rate performance of cells,which provides theoretical guidance for improving the rate performance of LIBs using Si–Gr composite anodes.
基金supported by the National Natural Science Foundation of China(Grant Nos.52315206 and 51502334)the Funds from the Ministry of Science and Technology of China(Grant No.2016YFB0100100)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA09010000)the Foundation from Beijing Municipal Science&Technology Commission(Grant No.D171100005517001)
文摘The composite quasi solid state electrolytes（CQSE） is firstly synthesized with quasi solid state electrolytes（QSE） and lithium-ion-conducting material Li1.4Al0.4Ti1.6（PO4）3（LATP）, and the QSE consists of [LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE is droped to 60%, its conductivity can also reach 1.39 × 10^-4S/cm at 20℃. Linear sweep voltammetry（LSV） is conducted on each composite electrolyte.The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li^＋1. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/Li Mn2O4 and Li/CQSE/Li Mn2O4 batteries is evaluated and shows good electrochemical characteristics at 60℃.
