The practical application of lithium-sulfur(Li-S)batteries,as promising next-generation batteries,is hindered by their shuttle effect and the slow redox kinetics.Herein,a tungsten and molybdenum nitride heterostructur...The practical application of lithium-sulfur(Li-S)batteries,as promising next-generation batteries,is hindered by their shuttle effect and the slow redox kinetics.Herein,a tungsten and molybdenum nitride heterostructure functionalized with hollow metal-organic framework-derived carbon(W_(2)N/Mo_(2)N)was proposed as the sulfur host.The hollow spherical structure provides storage space for sulfur,enhances electrical conductivity,and inhibits volume expansion.The metal atoms in the nitrides bonded with lithium polysulfides(Li PSs)through Lewis covalent bonds,enhancing the high catalytic activity of the nitrides and effectively reducing the energy barrier of Li PSs redox conversion.Moreover,the high intrinsic conductivity of nitrides and the ability of the heterostructure interface to accelerate electron/ion transport improved the Li+transmission.By leveraging the combined properties of strong adsorption and high catalytic activity,the sulfur host effectively inhibited the shuttle effect and accelerated the redox kinetics of Li PSs.High-efficiency Li+transmission,strong adsorption,and the efficient catalytic conversion activities of Li PSs in the heterostructure were experimentally and theoretically verified.The results indicate that the W_(2)N/Mo_(2)N cathode provides stable,and long-term cycling(over 2000 cycles)at 3 C with a low attenuation rate of 0.0196%per cycle.The design strategy of a twinborn nitride heterostructure thus provides a functionalized solution for advanced Li-S batteries.展开更多
Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ioni...Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ionic conductivity and slow Li+transference.Herein,based on the“binary electrolytes”of poly(vinylidene fluoride-chlorotrifluoroethylene)(P(VDF-CTFE))and lithium salt(LiTFSI),a kind of eutectogel hybrid electrolytes(EHEs)with high Li+transference number was developed via tuning the spontaneous coupling of charge and vacated space generated by Li-cation diffusion utilizing the Li6.4La3Zr1.4Ta0.6O12(LLZTO)dopant.LLZTO doping promotes the dissociation of lithium salt,increases Li+carrier density,and boosts ion jumping and the coordination/decoupling reactions of Li+.As a result,the optimized EHEs-10%possess a high Li-transference number of 0.86 and a high Li+conductivity of 3.2×10–4 S·cm–1 at room temperature.Moreover,the prepared EHEs-10%composite solid electrolyte presents excellent lithiumphilic and compatibility,and can be tested stably for 1,200 h at 0.3 mA·cm–2 with assembled lithium symmetric batteries.Likewise,the EHEs-10%films match well with high-loading LiFePO4 and LiCoO2 cathodes(>10 mg·cm–2)and exhibit remarkable interface stability.Particularly,the LiFePO4//EHEs-10%//Li and LiCoO2//EHEs-10%//Li cells deliver high rate performance of 118 mAh·g–1 at 1 C and 93.7 mAh·g–1 at 2 C with coulombic efficiency of 99.3%and 98.1%,respectively.This work provides an in-depth understanding and new insights into our design for polymer electrolytes with fast Li+diffusion.展开更多
The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur(Li-S)batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries.Heterostru...The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur(Li-S)batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries.Heterostructure engineering is an effective strategy to accelerate catalytic conversion and suppress the dissolution of polysulfides.Herein,we report a Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure composite as a bi-functional modified separator that not only achieves effective protection for lithium metal but also accelerates the polysulfides redox kinetics process.This heterostructure possesses efficient chemical anchoring and abundant active sites to immobilize polysulfides by synergistic effect,which endows a stable long cycling performance for Li-S batteries.This corresponds to an initial high capacity of 801.9 mAh g^(–1) at 1 C with a decay rate of 0.086%for 500 cycles.Due to its high Young’s modulus(up to 384 GPa),Ta_(4)C_(3) contributes to forming a protective layer on the Li metal surface to inhibit the growth of Li dendrites.Accordingly,the symmetrical cell has a stable overpotential for 700 cycles at 20 mA cm^(–2)/20 mAh cm^(–2).So,this“one stone two birds”design affords a novel perspective for high-energy Li-S battery storage system design and Li metal protection.展开更多
It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate(BST)films for microwave tunable application because these two properties change simultaneously.Herein,a nov...It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate(BST)films for microwave tunable application because these two properties change simultaneously.Herein,a novel composite of strontium titanate(ST)and potassium-doped BST(KBST)has been designed as ST/KBST/ST sandwich-type film with various ST and KBST layers.X-ray diffraction patterns show that the film exhibits cubic perovskite polycrystalline structure composed of BST and ST phase,mainly grow along(110)crystal plane with average grain size of less than 20 nm and decreasing BST phase/ST phase ratio with increasing film thickness.Scanning electron microscope shows that no interfacial layer can be observed,indicating that ST and KBST are fully compounded.Low dielectric loss and high tunability at-10-10 V and stable and excellent dielectric properties at 1 GHz are achieved,meeting the needs of microwave tunable application at high frequency.The surface structures are also studied by other analysis methods,and ST/MgBST/ST sandwich-type film is compared.展开更多
基金supported by the National Natural Science Foundation of China (52202104)the China Postdoctoral Science Foundation (2021T140433,2020M683408)+6 种基金the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China (LZY23B030002)the Quzhou Science and Technology Bureau Project (2021D006)the International Cooperation Projects of Sichuan Provincial Department of Science and Technology (2021YFH0126)the Fundamental Research Funds for the Central Universities (ZYGX2020ZB016)the Key Research and Development Program of Yunnan Province China (202103AA080019)the Yunnan Major Scientific and Technological Projects (202202AG050003)the Foundation of Key Laboratory of Advanced Technique&Preparation for Renewable Energy Materials,Ministry of Education,Yunnan Normal University (OF2022-04)。
文摘The practical application of lithium-sulfur(Li-S)batteries,as promising next-generation batteries,is hindered by their shuttle effect and the slow redox kinetics.Herein,a tungsten and molybdenum nitride heterostructure functionalized with hollow metal-organic framework-derived carbon(W_(2)N/Mo_(2)N)was proposed as the sulfur host.The hollow spherical structure provides storage space for sulfur,enhances electrical conductivity,and inhibits volume expansion.The metal atoms in the nitrides bonded with lithium polysulfides(Li PSs)through Lewis covalent bonds,enhancing the high catalytic activity of the nitrides and effectively reducing the energy barrier of Li PSs redox conversion.Moreover,the high intrinsic conductivity of nitrides and the ability of the heterostructure interface to accelerate electron/ion transport improved the Li+transmission.By leveraging the combined properties of strong adsorption and high catalytic activity,the sulfur host effectively inhibited the shuttle effect and accelerated the redox kinetics of Li PSs.High-efficiency Li+transmission,strong adsorption,and the efficient catalytic conversion activities of Li PSs in the heterostructure were experimentally and theoretically verified.The results indicate that the W_(2)N/Mo_(2)N cathode provides stable,and long-term cycling(over 2000 cycles)at 3 C with a low attenuation rate of 0.0196%per cycle.The design strategy of a twinborn nitride heterostructure thus provides a functionalized solution for advanced Li-S batteries.
基金This work was supported by the International Cooperation Projects of Sichuan Provincial Department of Science and Technology(No.2021YFH0126)Quzhou Science and Technology Bureau Project(No.2021D006)+2 种基金the Fundamental Research Funds for the Central Universities(No.A030202063008029)The China Postdoctoral Science Foundation(Nos.2021T140433,2020M683408)the Natural Science Foundation of Shaanxi Province(No.2021JQ-538).
文摘Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ionic conductivity and slow Li+transference.Herein,based on the“binary electrolytes”of poly(vinylidene fluoride-chlorotrifluoroethylene)(P(VDF-CTFE))and lithium salt(LiTFSI),a kind of eutectogel hybrid electrolytes(EHEs)with high Li+transference number was developed via tuning the spontaneous coupling of charge and vacated space generated by Li-cation diffusion utilizing the Li6.4La3Zr1.4Ta0.6O12(LLZTO)dopant.LLZTO doping promotes the dissociation of lithium salt,increases Li+carrier density,and boosts ion jumping and the coordination/decoupling reactions of Li+.As a result,the optimized EHEs-10%possess a high Li-transference number of 0.86 and a high Li+conductivity of 3.2×10–4 S·cm–1 at room temperature.Moreover,the prepared EHEs-10%composite solid electrolyte presents excellent lithiumphilic and compatibility,and can be tested stably for 1,200 h at 0.3 mA·cm–2 with assembled lithium symmetric batteries.Likewise,the EHEs-10%films match well with high-loading LiFePO4 and LiCoO2 cathodes(>10 mg·cm–2)and exhibit remarkable interface stability.Particularly,the LiFePO4//EHEs-10%//Li and LiCoO2//EHEs-10%//Li cells deliver high rate performance of 118 mAh·g–1 at 1 C and 93.7 mAh·g–1 at 2 C with coulombic efficiency of 99.3%and 98.1%,respectively.This work provides an in-depth understanding and new insights into our design for polymer electrolytes with fast Li+diffusion.
基金supported by the National Natural Science Foundation of China(Nos.52202104,51875330,51975342)the China Postdoctoral Science Foundation(Nos.2021T140433,2020M683408)+1 种基金the Natural Science Foundation of Shaanxi Province(Nos.2019JZ-24,2021JQ-538)the Natural Science Foundation of Zhejiang Province(LZY23B030002).
文摘The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur(Li-S)batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries.Heterostructure engineering is an effective strategy to accelerate catalytic conversion and suppress the dissolution of polysulfides.Herein,we report a Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure composite as a bi-functional modified separator that not only achieves effective protection for lithium metal but also accelerates the polysulfides redox kinetics process.This heterostructure possesses efficient chemical anchoring and abundant active sites to immobilize polysulfides by synergistic effect,which endows a stable long cycling performance for Li-S batteries.This corresponds to an initial high capacity of 801.9 mAh g^(–1) at 1 C with a decay rate of 0.086%for 500 cycles.Due to its high Young’s modulus(up to 384 GPa),Ta_(4)C_(3) contributes to forming a protective layer on the Li metal surface to inhibit the growth of Li dendrites.Accordingly,the symmetrical cell has a stable overpotential for 700 cycles at 20 mA cm^(–2)/20 mAh cm^(–2).So,this“one stone two birds”design affords a novel perspective for high-energy Li-S battery storage system design and Li metal protection.
基金financially supported by the Key Project of National Natural Science Foundation of China(No.11832007)the Applied Basic Research Program of Sichuan(No.19YYJC1846)the Science and Technology Achievement Transfer and Transformation of Sichuan(No.20ZHSF0154)。
文摘It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate(BST)films for microwave tunable application because these two properties change simultaneously.Herein,a novel composite of strontium titanate(ST)and potassium-doped BST(KBST)has been designed as ST/KBST/ST sandwich-type film with various ST and KBST layers.X-ray diffraction patterns show that the film exhibits cubic perovskite polycrystalline structure composed of BST and ST phase,mainly grow along(110)crystal plane with average grain size of less than 20 nm and decreasing BST phase/ST phase ratio with increasing film thickness.Scanning electron microscope shows that no interfacial layer can be observed,indicating that ST and KBST are fully compounded.Low dielectric loss and high tunability at-10-10 V and stable and excellent dielectric properties at 1 GHz are achieved,meeting the needs of microwave tunable application at high frequency.The surface structures are also studied by other analysis methods,and ST/MgBST/ST sandwich-type film is compared.