Fast charging is restricted primarily by the risk of lithium(Li)plating,a side reaction that can lead to the rapid capacity decay and dendrite-induced thermal runaway of lithium-ion batteries(LIBs).Investigation on th...Fast charging is restricted primarily by the risk of lithium(Li)plating,a side reaction that can lead to the rapid capacity decay and dendrite-induced thermal runaway of lithium-ion batteries(LIBs).Investigation on the intrinsic mechanism and the position of Li plating is crucial to improving the fast rechargeability and safety of LIBs.Herein,we investigate the Li plating behavior in porous electrodes under the restricted transport of Li^(+).Based on the theoretical model,it can be concluded that the Li plating on the anodeseparator interface(ASI)is thermodynamically feasible and kinetically advantageous.Meanwhile,the prior deposition of metal Li on the ASI rather than the anode-current collector interface(ACI)is verified experimentally.In order to facilitate the transfer of Li^(+)among the electrode and improve the utilization of active materials without Li plating,a bilayer asymmetric anode composed of graphite and hard carbon(GH)is proposed.Experimental and simulation results suggest that the GH hybrid electrode homogenizes the lithiated-rate throughout the electrode and outperforms the pure graphite electrode in terms of the rate performance and inhibition of Li plating.This work provides new insights into the behavior of Li plating and the rational design of electrode structure.展开更多
In order to overcome the problem that the low conductivity and high content of graphitic N will lead to serious irreversible capacity loss,magnesiothermic denitriding method was employed to fabricate nitrogen deficien...In order to overcome the problem that the low conductivity and high content of graphitic N will lead to serious irreversible capacity loss,magnesiothermic denitriding method was employed to fabricate nitrogen deficient g-C3N4 (ND-g-C3N4).By controlling the reaction conditions,ND-g-C3N4-675 with optimal electrochemical properties was obtained.The ND-g-C3N4-675 has thinner two-dimensional porous structure,with high specific surface area and good conductivity.The ND-g-C3N4-675 showed superior cyclic stability and rate capability (After 500 cycles under 1 000 mA·g-1,2 264.9 mAh·g-1 was obtained).Moreover,it presented high initial coulombic efficiency (42.2%).展开更多
Lithium-ion hybrid supercapacitors(Li-HSCs) and dual-ion batteries(DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in d...Lithium-ion hybrid supercapacitors(Li-HSCs) and dual-ion batteries(DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in device structure, tendency for ion migration, and energy storage mechanisms at the negative electrode. However, these devices have differences in energy storage mechanisms and working potentials at the positive electrode. Here, we first realize the integration of a Li-HSC and a DIB to form a dual-ion hybrid supercapacitor(DIHSC), by employing mesocarbon microbead(MCMB)-based porous graphitic carbon(PGC) with a partially graphitized structure and porous structure as a positive electrode material. The MCMB-PGC-based DIHSC exhibits a novel dual-ion battery-capacitor hybrid mechanism: it exhibits excellent electronic double-layer capacitor(EDLC) behavior like a Li-HSC in the low-middle wide potential range and anion intercalation/de-intercalation behavior like a DIB in the high-potential range. Two types of mechanisms are observed in the electrochemical characterization process, and the energy density of the new DIHSC is significantly increased.展开更多
Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for...Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFxwas modified by using acetylene/argon mixture plasma combined with MnO_(2)particles.The CF_(x)/C/MnO_(2)composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CF_(x).The excellent rate performance of CF_(x)/C/MnO_(2)was due to the high electrochemical activity provided by the atomicscale conductive carbon layer and ultrafine MnO_(2)particles.Compared with pristine CF_(x),the charge transfer resistance of the optimized CF_(x)/C/MnO_(2)decreased from 218.5 to 48.2Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g^(-1),The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CF_(x)discharge,and the high electrochemical activity of the ultrafine MnO_(2)particles provided a faster lithium-ion diffusion rate.展开更多
The notorious shuttle effect has long been obstructing lithium-sulfur(Li-S) batteries from yielding the expected high energy density and long lifespan.Herein,we develop a multifunctional polysulfide barrier reinforced...The notorious shuttle effect has long been obstructing lithium-sulfur(Li-S) batteries from yielding the expected high energy density and long lifespan.Herein,we develop a multifunctional polysulfide barrier reinforced by the graphitic carbon nitride/carbon nanotube(g-C_3 N_4/CNT) composite toward inhibited shuttling behavior and improved battery performance.The obtained g-C_3 N_4 delivers a unique spongelike architecture with massive ion transfer pathways and fully exposed active interfaces,while the abundant C-N heteroatomic structures impose strong chemical immobilization toward lithium polysulfides.Combined with the highly conductive agent,the g-C_3 N_4/CNT reinforced separator is endowed with great capability of confining and reutilizing the active sulfur within the cathode,thus contributing to an efficient and stable sulfur electrochemistry.Benefiting from these synergistic attributes,Li-S cells based on g-C_3 N_4/CNT separator exhibit an excellent cyclability with a minimum decay rate of 0.03% per cycle over 500 cycles and decent rate capability up to 2 C.Moreover,a high areal capacity of 7.69 mAh cm^(-2)can be achieved under a raised sulfur loading up to 10.1 mg cm^(-2).demonstrating a facile and efficient pathway toward superior Li-S batteries.展开更多
As the anode materials of lithium-ion battery, the hard carbon has the higher power performance while the graphite has the higher energy performance, respectively. In this work, novel mixed hard carbon/graphite anodes...As the anode materials of lithium-ion battery, the hard carbon has the higher power performance while the graphite has the higher energy performance, respectively. In this work, novel mixed hard carbon/graphite anodes are presented showing the coupling effect of power and mixed anodes was investigated at the varying charging rates, showing the tunable behaviors dependent on the hard carbon/graphite ratios. By studying the specific capacity evolution in different split potential ranges, we found that the mixed anodes with a higher proportion of hard carbon were advantageous when working in the cut-off potential greater than 0.10 V. The electrochemical impedance spectroscopy was measured at various anode potentials, which depicted the evolution of cell resistance with the state of charge. With the aid of electrochemical impedance spectroscopy, we found that the capacity evolution with mixed ratio is attributed to the lithiation-level induced difference of charge transfer resistance and Warburg resistance. A coupling effect was discovered showing a great potential in balancing the power-energy performance of mixed anode by simply controlling the ratio of hard-carbon/graphite.展开更多
硅负极材料因具有较高的理论容量(Li22Si5合金相对应4200 mAh/g)、较低的工作电压(0.2~0.3 V vs Li/Li+)和地球上丰富的原材料储备,成为代替石墨负极的理想材料之一。但是,低电导率及在循环过程中发生剧烈体积膨胀导致电极失效问题限制...硅负极材料因具有较高的理论容量(Li22Si5合金相对应4200 mAh/g)、较低的工作电压(0.2~0.3 V vs Li/Li+)和地球上丰富的原材料储备,成为代替石墨负极的理想材料之一。但是,低电导率及在循环过程中发生剧烈体积膨胀导致电极失效问题限制了硅负极材料的进一步发展。因此,本工作通过物理法利用壳聚糖和石墨对纳米硅实现碳包覆和复合,制备壳聚糖/石墨@纳米硅复合材料(C/G@Si复合材料),对C/G@Si复合材料的结构、形貌和电化学性能进行研究。结果表明:随着石墨添加量的提高,C/G@Si复合材料的可逆比容量略微下降,循环性能和导电性能显著提高。当添加50%(质量分数)石墨时,在100 mA/g的电流密度下,C/G@Si复合材料的首次放电比容量为1136.1 mAh/g,循环充放电100次后剩余容量保持在658.5 mAh/g,展示出优异的电化学性能,对进一步推广硅碳负极材料具有一定的参考价值。展开更多
For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC...For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.展开更多
基金supported by the National Natural Scientific Foundation of China (22109083,22379014)Beijing Natural Science Foundation (L233004)。
文摘Fast charging is restricted primarily by the risk of lithium(Li)plating,a side reaction that can lead to the rapid capacity decay and dendrite-induced thermal runaway of lithium-ion batteries(LIBs).Investigation on the intrinsic mechanism and the position of Li plating is crucial to improving the fast rechargeability and safety of LIBs.Herein,we investigate the Li plating behavior in porous electrodes under the restricted transport of Li^(+).Based on the theoretical model,it can be concluded that the Li plating on the anodeseparator interface(ASI)is thermodynamically feasible and kinetically advantageous.Meanwhile,the prior deposition of metal Li on the ASI rather than the anode-current collector interface(ACI)is verified experimentally.In order to facilitate the transfer of Li^(+)among the electrode and improve the utilization of active materials without Li plating,a bilayer asymmetric anode composed of graphite and hard carbon(GH)is proposed.Experimental and simulation results suggest that the GH hybrid electrode homogenizes the lithiated-rate throughout the electrode and outperforms the pure graphite electrode in terms of the rate performance and inhibition of Li plating.This work provides new insights into the behavior of Li plating and the rational design of electrode structure.
基金the National Natural Science Foundation of China(No.21473128)。
文摘In order to overcome the problem that the low conductivity and high content of graphitic N will lead to serious irreversible capacity loss,magnesiothermic denitriding method was employed to fabricate nitrogen deficient g-C3N4 (ND-g-C3N4).By controlling the reaction conditions,ND-g-C3N4-675 with optimal electrochemical properties was obtained.The ND-g-C3N4-675 has thinner two-dimensional porous structure,with high specific surface area and good conductivity.The ND-g-C3N4-675 showed superior cyclic stability and rate capability (After 500 cycles under 1 000 mA·g-1,2 264.9 mAh·g-1 was obtained).Moreover,it presented high initial coulombic efficiency (42.2%).
基金supported by the National Natural Science Foundation of China (grant no. 51672151).
文摘Lithium-ion hybrid supercapacitors(Li-HSCs) and dual-ion batteries(DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in device structure, tendency for ion migration, and energy storage mechanisms at the negative electrode. However, these devices have differences in energy storage mechanisms and working potentials at the positive electrode. Here, we first realize the integration of a Li-HSC and a DIB to form a dual-ion hybrid supercapacitor(DIHSC), by employing mesocarbon microbead(MCMB)-based porous graphitic carbon(PGC) with a partially graphitized structure and porous structure as a positive electrode material. The MCMB-PGC-based DIHSC exhibits a novel dual-ion battery-capacitor hybrid mechanism: it exhibits excellent electronic double-layer capacitor(EDLC) behavior like a Li-HSC in the low-middle wide potential range and anion intercalation/de-intercalation behavior like a DIB in the high-potential range. Two types of mechanisms are observed in the electrochemical characterization process, and the energy density of the new DIHSC is significantly increased.
基金financially supported by the National Natural Science Foundation of China(No.51972045)the Fundamental Research Funds for the Chinese Central Universities,China(No.ZYGX2019J025)。
文摘Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFxwas modified by using acetylene/argon mixture plasma combined with MnO_(2)particles.The CF_(x)/C/MnO_(2)composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CF_(x).The excellent rate performance of CF_(x)/C/MnO_(2)was due to the high electrochemical activity provided by the atomicscale conductive carbon layer and ultrafine MnO_(2)particles.Compared with pristine CF_(x),the charge transfer resistance of the optimized CF_(x)/C/MnO_(2)decreased from 218.5 to 48.2Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g^(-1),The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CF_(x)discharge,and the high electrochemical activity of the ultrafine MnO_(2)particles provided a faster lithium-ion diffusion rate.
基金supported by the National Natural Science Foundation of China (Nos. 21978110 and 51772126)the Natural Science Foundation of Beijing (No. L182062)+8 种基金the Organization Department of Beijing Talents Project (2018000021223ZK21)the Yue Qi Young Scholar Project of China University of Mining & Technology (Beijing) (No. 2017QN17)the Fundamental Research Funds for the Central Universities (No. 2014QJ02)the Jilin Province Science and Technology Department Program (Nos. 20200201187JC, 20190201309JC, and 20190101009JH)the ‘‘13th five-year” Science and Technology Project of Jilin Provincial Education Department (No. JJKH20200407KJ)the Jilin Province Development and Reform Commission Program (Nos. 2020C026-3 and 2019C042-1)the Jilin Province Fund for Talent Development Program (No. [2019] 874)the supports from Natural Sciences and Engineering Research Council of Canada (NSERC), the University of Waterloothe Waterloo Institute for Nanotechnology。
文摘The notorious shuttle effect has long been obstructing lithium-sulfur(Li-S) batteries from yielding the expected high energy density and long lifespan.Herein,we develop a multifunctional polysulfide barrier reinforced by the graphitic carbon nitride/carbon nanotube(g-C_3 N_4/CNT) composite toward inhibited shuttling behavior and improved battery performance.The obtained g-C_3 N_4 delivers a unique spongelike architecture with massive ion transfer pathways and fully exposed active interfaces,while the abundant C-N heteroatomic structures impose strong chemical immobilization toward lithium polysulfides.Combined with the highly conductive agent,the g-C_3 N_4/CNT reinforced separator is endowed with great capability of confining and reutilizing the active sulfur within the cathode,thus contributing to an efficient and stable sulfur electrochemistry.Benefiting from these synergistic attributes,Li-S cells based on g-C_3 N_4/CNT separator exhibit an excellent cyclability with a minimum decay rate of 0.03% per cycle over 500 cycles and decent rate capability up to 2 C.Moreover,a high areal capacity of 7.69 mAh cm^(-2)can be achieved under a raised sulfur loading up to 10.1 mg cm^(-2).demonstrating a facile and efficient pathway toward superior Li-S batteries.
文摘As the anode materials of lithium-ion battery, the hard carbon has the higher power performance while the graphite has the higher energy performance, respectively. In this work, novel mixed hard carbon/graphite anodes are presented showing the coupling effect of power and mixed anodes was investigated at the varying charging rates, showing the tunable behaviors dependent on the hard carbon/graphite ratios. By studying the specific capacity evolution in different split potential ranges, we found that the mixed anodes with a higher proportion of hard carbon were advantageous when working in the cut-off potential greater than 0.10 V. The electrochemical impedance spectroscopy was measured at various anode potentials, which depicted the evolution of cell resistance with the state of charge. With the aid of electrochemical impedance spectroscopy, we found that the capacity evolution with mixed ratio is attributed to the lithiation-level induced difference of charge transfer resistance and Warburg resistance. A coupling effect was discovered showing a great potential in balancing the power-energy performance of mixed anode by simply controlling the ratio of hard-carbon/graphite.
文摘硅负极材料因具有较高的理论容量(Li22Si5合金相对应4200 mAh/g)、较低的工作电压(0.2~0.3 V vs Li/Li+)和地球上丰富的原材料储备,成为代替石墨负极的理想材料之一。但是,低电导率及在循环过程中发生剧烈体积膨胀导致电极失效问题限制了硅负极材料的进一步发展。因此,本工作通过物理法利用壳聚糖和石墨对纳米硅实现碳包覆和复合,制备壳聚糖/石墨@纳米硅复合材料(C/G@Si复合材料),对C/G@Si复合材料的结构、形貌和电化学性能进行研究。结果表明:随着石墨添加量的提高,C/G@Si复合材料的可逆比容量略微下降,循环性能和导电性能显著提高。当添加50%(质量分数)石墨时,在100 mA/g的电流密度下,C/G@Si复合材料的首次放电比容量为1136.1 mAh/g,循环充放电100次后剩余容量保持在658.5 mAh/g,展示出优异的电化学性能,对进一步推广硅碳负极材料具有一定的参考价值。
基金the National Natural Science Foundation of China(No.51972045)the Fundamental Research Funds for the Chinese Central Universities,China(No.ZYGX2019J025)。
文摘For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.
