Nanostructured transition metal oxides,employed as anode materials for lithium-ion batteries,exhibit a higher capacity than the theoretical capacity based on the conversion reaction.To date,the reasons behind this phe...Nanostructured transition metal oxides,employed as anode materials for lithium-ion batteries,exhibit a higher capacity than the theoretical capacity based on the conversion reaction.To date,the reasons behind this phenomenon are unclear.For the one-step evolution of anode material for lithium-ion batteries,it is essential to understand the lithium storage reaction mechanism of the anode material.Herein,we provide a detailed report on the lithium storage and release mechanism of MnO2,using synchrotron-based X-ray techniques.X-ray diffraction and X-ray absorption spectroscopy results indicate that during the first discharge,MnO2 is reduced in the order of MnO2→LixMnO2(1<X<2)→MnO→Mn metal,followed by a reversible reaction between Mn metal and Mn3O4.Furthermore,soft X-ray absorption spectroscopy results indicate that additional reversible formation-decomposition of the electrolyte-derived surface layer occurs and contributes to the reversible capacity of MnO2 after the first discharge.These findings contribute to further understanding of the reaction mechanism and additional lithium storage of MnO2 and suggest practical strategies for developing high energy density anode materials for next-generation Li batteries.展开更多
Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dend...Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.展开更多
Lithium rich layered oxide(LRLO) has been considered as one of the promising cathodes for lithium-ion batteries(LIBs). The high voltage and large capacity of LRLO depend on Li2MnO_(3)phase. To ameliorate the electroch...Lithium rich layered oxide(LRLO) has been considered as one of the promising cathodes for lithium-ion batteries(LIBs). The high voltage and large capacity of LRLO depend on Li2MnO_(3)phase. To ameliorate the electrochemical performance of Li2MnO_(3), also written as Li(Li1/3Mn2/3)O_(2), we propose a strategy to substitute Mn4+and Li+in Mn/Li transition metal layer with Ti4+, which can stabilize the structure of Li2MnO_(3)by inhibiting the excessive oxidation of O_(2)-above 4.5 V. More significantly, the unequal-valent substitution brings about the emergence of interlayer Li vacancies, which can promote the Li-ion diffusion based on the enlarged interlayer and increase the capacity by activating the Mn3+/4+redox. We designed Li0.7[Li1/3Mn2/3]0.7Ti0.3O_(2)with high interlayer Li vacancies, which presents a high capacity(290 m Ah/g at 10 m A/g) and stable cycling performance(84% over 60 cycles at 50 m A/g). We predict that this strategy will be helpful to further improve the electrochemical performance of LRLOs.展开更多
因放电产物对有机电解液具有高攻击性,使得锂-氧电池能量效率低和循环稳定性差的问题一直限制着其实际应用.与典型放电产物过氧化锂相比,氢氧化锂(LiOH)具有更好的化学和电化学稳定性.本文通过在碳纸上原位生长嵌有纳米银的花状二氧化...因放电产物对有机电解液具有高攻击性,使得锂-氧电池能量效率低和循环稳定性差的问题一直限制着其实际应用.与典型放电产物过氧化锂相比,氢氧化锂(LiOH)具有更好的化学和电化学稳定性.本文通过在碳纸上原位生长嵌有纳米银的花状二氧化锰作为锂-氧电池的正极(Ag/δ-MnO_(2)@CP),并证明了它能催化LiOH的可逆生成和分解.原位拉曼测试和理论计算表明Ag/δ-MnO_(2)催化放电中间体LiO2*与水分子解离的H+反应最终生成LiOH.以Ag/δ-MnO_(2)@CP为正极的锂-氧电池在潮湿氧气环境下表现出更高的比容量和放电平台.在电流密度为200 mA g^(−1)时,锂-氧电池的过电位仅为0.5 V,在500 mA h g^(−1)的限制比容量下可循环867圈.该工作为研究固相催化剂在锂-氧电池中的作用提供了新的思路,并将促进基于LiOH放电产物的锂-氧电池的实际应用.展开更多
基金supported by the Samsung Reserach Funding & Incubation Center of Samsung Electronics under Project Number MA1401-52。
文摘Nanostructured transition metal oxides,employed as anode materials for lithium-ion batteries,exhibit a higher capacity than the theoretical capacity based on the conversion reaction.To date,the reasons behind this phenomenon are unclear.For the one-step evolution of anode material for lithium-ion batteries,it is essential to understand the lithium storage reaction mechanism of the anode material.Herein,we provide a detailed report on the lithium storage and release mechanism of MnO2,using synchrotron-based X-ray techniques.X-ray diffraction and X-ray absorption spectroscopy results indicate that during the first discharge,MnO2 is reduced in the order of MnO2→LixMnO2(1<X<2)→MnO→Mn metal,followed by a reversible reaction between Mn metal and Mn3O4.Furthermore,soft X-ray absorption spectroscopy results indicate that additional reversible formation-decomposition of the electrolyte-derived surface layer occurs and contributes to the reversible capacity of MnO2 after the first discharge.These findings contribute to further understanding of the reaction mechanism and additional lithium storage of MnO2 and suggest practical strategies for developing high energy density anode materials for next-generation Li batteries.
基金funding support from the National Natural Science Foundation of China (21905151 and 51772162)the Youth Innovation and Technology Foundation of Shandong Higher Education Institutions, China (2019KJC004)+1 种基金the Outstanding Youth Foundation of Shandong Province, China (ZR2019JQ14)the Taishan Scholar Young Talent Program, Major Scientific and Technological Innovation Project (2019JZZY020405)。
文摘Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.
基金financially supported by the National Natural Science Foundation of China (Nos. 51972258 and 22109186)Open Fund by Sanya Science and Education Innovation Park of Wuhan University of Technology (No. 2021KF0021)supported by 21C Innovation Laboratory,Contemporary Amperex Technology Ltd. by Project No. 21C-OP-202002。
文摘Lithium rich layered oxide(LRLO) has been considered as one of the promising cathodes for lithium-ion batteries(LIBs). The high voltage and large capacity of LRLO depend on Li2MnO_(3)phase. To ameliorate the electrochemical performance of Li2MnO_(3), also written as Li(Li1/3Mn2/3)O_(2), we propose a strategy to substitute Mn4+and Li+in Mn/Li transition metal layer with Ti4+, which can stabilize the structure of Li2MnO_(3)by inhibiting the excessive oxidation of O_(2)-above 4.5 V. More significantly, the unequal-valent substitution brings about the emergence of interlayer Li vacancies, which can promote the Li-ion diffusion based on the enlarged interlayer and increase the capacity by activating the Mn3+/4+redox. We designed Li0.7[Li1/3Mn2/3]0.7Ti0.3O_(2)with high interlayer Li vacancies, which presents a high capacity(290 m Ah/g at 10 m A/g) and stable cycling performance(84% over 60 cycles at 50 m A/g). We predict that this strategy will be helpful to further improve the electrochemical performance of LRLOs.
基金financially supported by the High-level Talents’Discipline Construction Fund of Shandong University(31370089963078)the School Research Startup Expenses of Harbin Institute of Technology(Shenzhen)(20190037 and 20210028)+3 种基金China Postdoctoral Science Foundation(2019M661276 and 2021T140150)Guangdong Basic and Applied Basic Research Foundation(2019A1515110756)the National Natural Science Foundation of China(52002094)the Open Fund of Guangdong Provincial Key laboratory of Advanced Energy Storage Materials(AESM202107)。
文摘因放电产物对有机电解液具有高攻击性,使得锂-氧电池能量效率低和循环稳定性差的问题一直限制着其实际应用.与典型放电产物过氧化锂相比,氢氧化锂(LiOH)具有更好的化学和电化学稳定性.本文通过在碳纸上原位生长嵌有纳米银的花状二氧化锰作为锂-氧电池的正极(Ag/δ-MnO_(2)@CP),并证明了它能催化LiOH的可逆生成和分解.原位拉曼测试和理论计算表明Ag/δ-MnO_(2)催化放电中间体LiO2*与水分子解离的H+反应最终生成LiOH.以Ag/δ-MnO_(2)@CP为正极的锂-氧电池在潮湿氧气环境下表现出更高的比容量和放电平台.在电流密度为200 mA g^(−1)时,锂-氧电池的过电位仅为0.5 V,在500 mA h g^(−1)的限制比容量下可循环867圈.该工作为研究固相催化剂在锂-氧电池中的作用提供了新的思路,并将促进基于LiOH放电产物的锂-氧电池的实际应用.
