碳包覆空心Fe3O4纳米粒子作为锂离子电池负极材料的电化学性能研究

以二茂铁为铁源,石油渣油为碳源,通过加压热解和空气氧化制备了碳包覆空心Fe3O4纳米粒子。采用X射线衍射(XRD)、透射电镜(TEM)以及高倍透射电镜(HRTEM)等测试方法对样品的形貌和结构进行表征。采用恒流充放电和交流阻抗方法测试碳包覆空心Fe3O4纳米粒子作为锂离子电池负极材料的电化学性能。在电流密度为0.2mA/cm2时,首次放电比容量高达1294.7mAh/g,30次循环之后其放电比容量为392.1mAh/g;电流密度为1mA/cm2时,首次放电比容量为216.3mAh/g,30次循环之后其放电比容量为113mAh/g。     

石墨烯负载金属钌用于锂-空气电池的正极材料

通过溶液法制备钌/石墨烯(Ru/G)复合材料,用作锂-空气电池的正极材料。通过充放电测试、循环伏安(CV)和电化学阻抗(EIS)研究了锂-空气电池的电化学性能。结果表明:Ru/G复合材料作为锂-空气电池的正极材料,明显提高了氧化还原反应的催化活性,改善了电化学反应性能。在电流密度为500mA·g-1时,首次充放电比容量分别为13136mAh·g-1和13578mAh·g-1,充放电的过电位降低了约0.35V。当固定充放电比容量为1000mAh·g-1,采用恒流充放电模式,可稳定循环30次。     

尖晶石钛酸锂的三乙醇胺辅助溶胶-凝胶法合成及其性能

以三乙醇胺为配位剂,Ti(OC4H9)4和LiAc·2H2O为原料,通过溶胶-凝胶法制备锂离子电池负极材料尖晶石Li4Ti5O12。通过X射线衍射、扫描电子显微镜、循环伏安、电化学阻抗和恒流充放电分析检测产物的结构、形貌及电化学性能。结果表明:配位剂的用量对Li4Ti5O12结构及电化学性能有显著影响,其中三乙醇胺与Ti摩尔比为0.8时,Li4Ti5O12具有良好的的电化学性能。1.0C下,其首次放电容量为153.0mAh·g-1,35次循环后放电容量仍为139.9mAh·g-1,容量保持率为91.5%。     

PAn/DMcT复合膜电极的电化学性能

PAn/DMcT复合膜电极的氧化还原峰电位差和电化学阻抗比DMcT的小得多,这表明PAn对DMcT具有电催化性能,使DMcT的氧化还原反应速度大大提高.而且DMcT使几乎所有的PAn都能保持电化学活性,复合膜电极的CV曲线经过100次循环几乎没有变化.PAn/DMcT复合膜电极的首次充放电比容量分别为275mAh·g-1和200mAh·g-1,首次充放电效率为72.7%.和粉末混合法制备的复合膜相比,溶液法制备的PAn/DMcT复合膜电极具有较高的放电比容量和优良的循环稳定性.     

LiCo0.1Mn1.9O4的溶胶-凝胶法制备及电化学性能研究

采用溶胶-凝胶法制备了锂离子蓄电池正极材料尖晶石LiCo0.1Mn1.9O4粉体,考察了烧结温度对其结构及电化学性能的影响.随着烧结温度的升高,尖晶石型结构越来越完整,首次放电比容量增大,但循环性能却逐渐变差.700℃时烧结12h得到了性能较好的LiCo0.1Mn1.9O4粉体,在电流密度0.1mA/cm2,截止电压3.5～4.4V条件下,首次放电比容量为123mAh/g,稳定放电比容量达113mAh/g.     

Co~(2+)掺杂石墨烯/LiFePO_4锂离子电池复合正极材料的制备与表征

使用溶胶凝胶原位碳热还原制备了Co2+掺杂石墨烯/LiFePO4锂离子电池复合正极材料(石墨烯/LiCo0.03Fe0.97PO4),以期获得比容量高、充放电速率快和循环性能优良的锂离子电池正极材料。结构和形貌表征结果显示:石墨烯/LiCo0.03Fe0.97PO4复合材料具有三维导电网络结构,颗粒在石墨烯片层间生长均匀,粒径在200nm左右。电化学测试结果显示:石墨烯/LiCo0.03Fe0.97PO4复合材料具有高的可逆比容量和优异的循环倍率性能。2.0~4.0V充放电下0.1C时的首次放电比容量为159mA·h·g-1,在10.0C下首次放电比容量也有74mA·h·g-1;0.5C下循环100次,比容量保持率为99.7%。石墨烯/LiCo0.03Fe0.97PO4复合材料电化学性能提高的原因主要为Co2+掺杂和石墨烯包覆的协同作用。     

LiNi0.8-x Znx Co0.2 O2的合成及电化学性能研究

掺杂改性和表面修饰的LiNi0.8Co0.2O2是锂电池正极换代候选材料.采用共沉淀法制备了系列LiNi0.8-xZnxCo0.2O2材料,并对其进行X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)、电化学阻抗(EIS)和充放电循环性能(CP)测试分析.恒流循环(0.2C、3.0～4.2V)测试结果显示,Zn的掺入使材料的初始放电比容量有大幅增加,循环性能有所改善.其中LiNi0.78Zn0.02Co0.2O2的首次放电比容量达到206.37 mAh·g-1.第30循环时,放电比容量仍为204.03 mAh·g-1,不可逆容量损失仅为2.34 mAh·g-1,显示了很好的初期循环性能.     

温度对燃烧包覆LiMn2O4/ZnO及其电性能的影响

通过葡萄糖辅助低温燃烧制备ZnO包覆型LiMn2O4,利用X射线衍射仪、扫描电子显微镜、循环伏安、交流阻抗以及恒流充放电测试等手段,研究了温度对产物晶体结构、微观形貌及电化学性能的影响。XRD结果表明所有产物均为单相尖晶石型LiMn2O4结构。SEM结果表明产物的颗粒尺寸随温度的升高而增大。电化学性能测试表明400℃和500℃制备的LiMn2O4/ZnO具有相对优异的电化学性能,室温1C条件下首次放电比容量分别为119.3mAh/g、116.3mAh/g,循环100次后容量保持率分别85.6%、87.8%。尖晶石LiMn2O4电极的阻抗谱特征与温度有关,电池的电化学性能主要受电荷转移电阻(Rct)影响。     

硝尿配合法合成掺杂尖晶石LiNi0.06Cr0.1Mn1.84O4及电化学性能研究

以硝尿配合物为前驱物，合成协同掺杂尖晶石LiNi0.06Cr0.1Mn1.84O4正极材料，用XRD，SEM表征其结构与性能。结果表明，当煅烧温度为800℃烧结时间为7h时，所得产物粒度均匀，分布窄，平均粒度为60nm，呈球形颗粒。该材料具有良好的电化学性能，在4V附近首次充放电比容量为121mAh／g，循环15次之后达到最大放电比容量128mAh／g，循环50次后放电比容量仍能保持111mAh／g，容量损失率为7．5％。循环伏安曲线显示，材料具有良好的电化学可逆性与循环稳定性。     

锂离子电池复合正极材料xLiFePO4·yLi3V2(PO4)3的制备与性能研究

以FePO4·xH2O、V2O5、NH4H2PO4和Li2CO3为原料,以乙二酸为还原剂,在常温常压下经机械活化并还原嵌锂,形成无定形的5LiFePO4·Li3V2(PO4)3前驱体混合物,然后低温热处理合成出晶态的复合正极材料5LiFePO4·Li3V2(PO4)3.分别研究了复合材料的物相结构、形貌、电化学性能.SEM图像表明合成的材料粒径小、分布均匀,一次粒径为100～200nm.充放电测试结果表明,650℃烧结12h制得的复合正极材料5LiFePO4·Li3V2(PO4)3电化学性能优良,1C放电比容量高达158mAh/g,达到该复合材料的理论比容量(156.8mAh/g).复合材料具有良好的倍率性能和循环性能,在10C放电比容量高达114mAh/g,100次循环后容量几乎无衰减.循环伏安测试表明,复合材料的脱嵌锂性能优良,且明显优于单一的LiFePO4和Li3V2(PO4)3.     

Novel porous starfish-like Co<Subscript>3</Subscript>O<Subscript>4</Subscript>@nitrogen-doped carbon as an advanced anode for lithium-ion batteries

A Co-based metal-organic framework (Co-MOF) with a unique three-dimensional starfish-like nanostructure was successfully synthesized using a simple ultrasonic method.After subsequent carbonization and oxidation,a nanocomposite of nitrogen-doped carbon with a Co3O4 coating (Co3O4@N-C) with a porous starfish-like nanostructure was obtained.The final hybrid exhibited excellent lithium storage performance when evaluated as an anode material in a lithiumion battery.A remarkable and stable discharge capacity of 795 mAh·g-1 was maintained at 0.5 A·g-1 after 300 cycles.Excellent rate capability was also obtained.In addition,a full Co3O4@N-C/LiFePO4 battery displayed stable capacity retention of 95％ after 100 cycles.This excellent lithium storage performance is attributed to the unique porous starfish-like structure,which effectively buffers the volume expansion that occurs during Li+ insertion/deinsertion.Meanwhile,the nitrogendoped carbon coating enhances the electrical conductivity and provides a buffer layer to accommodate the volume change and accelerate the formation of a stable solid electrolyte interface layer.     

NaFeTiO4 nanorod/multi-walled carbon nanotubes composite as an anode material for sodium-ion batteries with high performances in both half and full cells

NaFeTiO4 nanorods of high yields (with diameters in the range of 30-50 nm and lengths of up to 1-5 μm) were synthesized by a facile sol-gel method and were utilized as an anode material for sodium-ion batteries for the first time.The obtained NaFeTiO4 nanorods exhibit a high initial discharge capacity of 294 mA·h·g-1 at 0.2 C (1 C =177 mA·g-1),and remain at 115 mA·h·g-1 after 50 cycles.Furthermore,multi-walled carbon nanotubes (MWCNTs) were mechanically milled with the pristine material to obtain NaFeTiO4/MWCNTs.The NaFeTiO4/MWCNTs electrode exhibits a significantly improved electrochemical performance with a stable discharge capacity of 150 mA·h·g-1 at 0.2 C after 50 cycles,and remains at 125 mA·h·g-1 at 0.5 C after 420 cycles.The NaFeTiO4/MWCNTs//Na3V2(PO4)3/C full cell was assembled for the first time;it displays a discharge capacity of 70 mA·h·g-1 after 50 cycles at 0.05 C,indicating its excellent performances.X-ray photoelectron spectroscopy,ex situ X-ray diffraction,and Raman measurements were performed to investigate the initial electrochemical mechanisms of the obtained NaFeTiO4/MWCNTs.     

Simple synthesis of a porous Sb/Sb2O3 nanocomposite for a high-capacity anode material in Na-ion batteries

High-capacity anode materials are highly desirable for sodium ion batteries.Here,a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air.In the composite,Sb contributes good conductivity and Sb2O3 improves cycling stability,particularly within the voltage window of 0.02-1.5 V.It remains at a reversible capacity of 540 mAh·g-1 after 180 cycles at 0.66 A·g-L Even at 10 A·g-1,the reversible capacity is still preserved at 412 mAh.g-1,equivalent to 71.6％ of that at 0.066 A.g-1.These results are much better than Sb nanocrystals with a similar size and structure.Expanding the voltage window to 0.02-2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles.This would induce a large volume change and high structure strain/stress,deteriorating the cycling stability.The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.     

Three-dimensionally ordered,ultrathin graphitic-carbon frameworks with cage-like mesoporosity for highly stable Li-S batteries

Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur (Li-S) batteries.The ability to engineer the porosity,wall thickness,and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries,such as fast capacity decay and poor high-rate performance.In this work,highly ordered,ultrathin mesoporous graphitic-carbon frameworks (MGFs) having unique cage-like mesoporosity,derived from self-assembled Fe3O4 nanoparticle superlattices,are demonstrated to be an excellent host for encapsulating sulfur.The resulting S@MGFs exhibit high specific capacity (1,446 mAh·g-1 at 0.15 C),good rate capability (430 mAh.g-1 at 6 C),and exceptional cycling stability (～0.049％ capacity decay per cycle at 1 C) when used as Li-S cathodes.The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs.In addition to the interconnected,ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport,the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides,leading to improved capacity retention even at high current densities.     

Interface-modulated fabrication of hierarchical yolk–shell Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/C dodecahedrons as stable anodes for lithium and sodium storage

Transition-metal oxides (TMOs) have gradually attracted attention from researchers as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of their high theoretical capacity.However,their poor cycling stability and inferior rate capability resulting from the large volume variation during the lithiation/sodiation process and their low intrinsic electronic conductivity limit their applications.To solve the problems of TMOs,carbon-based metal-oxide composites with complex structures derived from metal-organic frameworks (MOFs) have emerged as promising electrode materials for LIBs and SIBs.In this study,we adopted a facile interface-modulated method to synthesize yolk-shell carbon-based Co3O4 dodecahedrons derived from ZIF-67 zeolitic imidazolate frameworks.This strategy is based on the interface separation between the ZIF-67 core and the carbon-based shell during the pyrolysis process.The unique yolk-shell structure effectively accommodates the volume expansion during lithiation or sodiation,and the carbon matrix improves the electrical conductivity of the electrode.As an anode for LIBs,the yolk-shell Co3O4/C dodecahedrons exhibit a high specific capacity and excellent cycling stability (1,100 mAh·g-1 after 120 cycles at 200 mA·g-1).As an anode for SIBs,the composites exhibit an outstanding rate capability (307 mAh·g-1 at 1,000 mA·g-1 and 269 mAh·g-1 at 2,000 mA·g-1).Detailed electrochemical kinetic analysis indicates that the energy storage for Li+ and Na+ in yolk-shell Co3O4/C dodecahedrons shows a dominant capacitive behavior.This work introduces an effective approach for fabricating carbonbased metal-oxide composites by using MOFs as ideal precursors and as electrode materials to enhance the electrochemical performance of LIBs and SIBs.     

原位聚合导电高分子包混对硬碳性能的影响

采用原位聚合方法对硬碳材料进行了导电聚合物包混,并测试了导电聚合物包混硬碳材料的电化学性能.利用扫描电镜,拉曼光谱,电导率仪及恒电流法研究了导电聚合物包混的硬碳材料的结构以及充放电特性.研究发现,聚苯胺、聚吡咯和聚噻吩等均能通过原位聚合包混在硬碳表面.其中,采用噻吩在硬碳表面原位聚合增强了硬碳材料的导电性.经聚噻吩包混的硬碳首次充电容量达到了385mAh g-1以上,高于未包混的硬碳(320mAh g-1).循环20周以后聚噻吩包混硬碳的容量仍保持在325 mAh g-1以上,而未包混硬碳的容量则降低到290 mAh g-1以下.     

锂离子电池斜方锰酸锂阴极材料的合成与表征

用一步固相法合成了斜方锰酸锂,对其进行了表征并确定了前驱体化合物烧结中的转变过程,以及相互化合间的烧结机制．结果表明,随着煅烧温度的升高,杂相减少,生长出主体相斜方锰酸锂．在700℃以上可以生成均一相的层状斜方类球状和棒状锰酸锂颗粒．两种颗粒的粒度分别为1～5μm和5～15μm．在充放电循环中,斜方锰酸锂结构易于向尖晶石结构转变．在2．5～4．5V范围内以20mA／g电流进行充放电循环,斜方锰酸锂的初始充电容量达到247mAh／g,放电容量为133mAh／g,50次循环后,容量保持率为92％．     

Ultrafine Sn nanocrystals in a hierarchically porous N-doped carbon for lithium ion batteries

We report a simple method of preparing a high performance,Sn-based anode material for lithium ion batteries (LIBs).Adding H2O2 to an aqueous solution containing Sn2+ and aniline results in simultaneous polymerization of aniline and oxidation of Sn2+ to SnO2,leading to a homogeneous composite of polyaniline and SnO2.Hydrogen thermal reduction of the above composite yields N-doped carbon with hierarchical porosity and homogeneously distributed,ultrafine Sn particles.The nanocomposite exhibits excellent performance as an anode material for lithium ion batteries,showing a high reversible specific capacity of 788 mAh·g-1 at a current density of 100 mA·g-1 after 300 cycles and very good stability up to 5,000 mA·g-1.The simple preparation method combined with the good electrochemical performance is highly promising to promote the application of Sn based anode materials.     

Understanding of the capacity contribution of carbon in phosphorus-carbon composites for high-performance anodes in lithium ion batteries

Phosphorus has recently received extensive attention as a promising anode for lithium ion batteries (LIBs) due to its high theoretical capacity of 2,596 mAh·g-1.To develop high-performance phosphorus anodes for LIBs,carbon materials have been hybridized with phosphorus (P-C) to improve dispersion and conductivity.However,the specific capacity,rate capability,and cycling stability of P-C anodes are still less than satisfactory for practical applications.Furthermore,the exact effects of the carbon support on the electrochemical performance of the P-C anodes are not fully understood.Herein,a series of xP-yC anode materials for LIBs were prepared by a simple and efficient ball-milling method.6P-4C and 3P-7C were found to be optimum mass ratios of x/y,and delivered initial discharge capacities of 1,803.5 and 1,585.3.mAh.g-1,respectively,at 0.1 C in the voltage range 0.02-2 V,with an initial capacity retention of 68.3％ over 200 cycles (more than 4 months cycling life) and 40.8％ over 450 cycles.The excellent electrochemical performance of the 6P-4C and 3P-7C samples was attributed to a synergistic effect from both the adsorbed P and carbon.