The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high...The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high working voltage is an appealing cathode candidate for PIBs,while the poor cycling performance and low electronic conductivity dramatically hinder the application.Herein,a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite(KVPO4F@3DC)is successfully designed in this study to tackle these problems.In the composite,KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by crosslinked large area carbon sheets.As the cathode for PIBs,the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g^-1 at 20 mA g^-1.An excellent long cycle stability with a capacity retention of 85.4%over 550 cycles at 500 mA g^-1 is achieved.In addition,it maintains 83.6%of its initial capacity at 50 mA g^-1 after 100 cycles at 55℃.The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode,successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.展开更多
锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研...锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。展开更多
钠离子电池(SIBs)的阳极材料一直备受研究关注,但缓慢的动力学行为和较大的体积变化限制了其在实际应用中的推广。为了克服这些问题,本研究利用金属有机框架和MoS_(2)的优异性能,设计并制备了具有稳定骨架结构的复合材料。以Co-ZIF为前...钠离子电池(SIBs)的阳极材料一直备受研究关注,但缓慢的动力学行为和较大的体积变化限制了其在实际应用中的推广。为了克服这些问题,本研究利用金属有机框架和MoS_(2)的优异性能,设计并制备了具有稳定骨架结构的复合材料。以Co-ZIF为前驱体,添加Mo源材料,在高温硫化烧结的过程中,构建了花状的Co_(9)S_(8)/MoS_(2)/C复合材料,探究其在不同温度条件下的结构和电化学性能。此外,通过密度泛函理论(DFT)分析了Co9S8(001)/MoS2异质结对扩散动力学的影响。结果表明,电子结构在异质结构的界面处发生了重塑,Co_(9)S_(8)/MoS_(2)表现出典型的金属性和显著增强的电子导电性。在所有样品中,700℃合成的阳极材料Co_(9)S_(8)/MoS_(2)/C具有更稳定的结构和优异的电化学性能。当电流密度从4000恢复到40 mA g^(-1)时,Co_(9)S_(8)/MoS_(2)/C-700的放电容量可以从368 mAh g^(-1)完全恢复到571 mAh g^(-1),并稳定在543 mAh g^(-1)。综上所述,本研究提供了一些关于异质结材料合理制备的思路,有助于设计高性能的金属钠离子电池负极复合材料。展开更多
基金financially supported by the National Natural Science Foundation of China(51672078 and 21473052)Hunan University State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Independent Research Project(71675004)Hunan Youth Talents(2016RS3025)。
文摘The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high working voltage is an appealing cathode candidate for PIBs,while the poor cycling performance and low electronic conductivity dramatically hinder the application.Herein,a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite(KVPO4F@3DC)is successfully designed in this study to tackle these problems.In the composite,KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by crosslinked large area carbon sheets.As the cathode for PIBs,the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g^-1 at 20 mA g^-1.An excellent long cycle stability with a capacity retention of 85.4%over 550 cycles at 500 mA g^-1 is achieved.In addition,it maintains 83.6%of its initial capacity at 50 mA g^-1 after 100 cycles at 55℃.The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode,successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.
文摘锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。
文摘钠离子电池(SIBs)的阳极材料一直备受研究关注,但缓慢的动力学行为和较大的体积变化限制了其在实际应用中的推广。为了克服这些问题,本研究利用金属有机框架和MoS_(2)的优异性能,设计并制备了具有稳定骨架结构的复合材料。以Co-ZIF为前驱体,添加Mo源材料,在高温硫化烧结的过程中,构建了花状的Co_(9)S_(8)/MoS_(2)/C复合材料,探究其在不同温度条件下的结构和电化学性能。此外,通过密度泛函理论(DFT)分析了Co9S8(001)/MoS2异质结对扩散动力学的影响。结果表明,电子结构在异质结构的界面处发生了重塑,Co_(9)S_(8)/MoS_(2)表现出典型的金属性和显著增强的电子导电性。在所有样品中,700℃合成的阳极材料Co_(9)S_(8)/MoS_(2)/C具有更稳定的结构和优异的电化学性能。当电流密度从4000恢复到40 mA g^(-1)时,Co_(9)S_(8)/MoS_(2)/C-700的放电容量可以从368 mAh g^(-1)完全恢复到571 mAh g^(-1),并稳定在543 mAh g^(-1)。综上所述,本研究提供了一些关于异质结材料合理制备的思路,有助于设计高性能的金属钠离子电池负极复合材料。
