钇掺杂LiFePO4锂离子电池正极材料的制备与性能

用固相法合成LiFe1-xYxPO4 (x=0, 0.01, 0.02, 0.03, 0.04)锂离子电池正极材料,采用X射线衍射仪、扫描电子显微镜、粉末比电阻法和充放电性能测试表征材料的晶体结构、微观形貌、电子电导率和电化学性能。结果表明,少量的钇掺杂并未改变材料的晶体结构,但改善了材料的微观结构,提高其电子电导率,改善可逆容量和电化学性能。在10 mA/g的电流密度下,LiFe0.97Y0.03PO4首次放电容量可达146.54 mAh/g。     

Li2Fe1-xMnxSiO4正极材料的合成及电化学性能

采用真空固相法成功地合成了锂离子电池正极材料Li2Fe1-xMnxSiO4,并用FTIR、XRD和电化学性能测试对材料进行了表征.FTIR和XRD测试表明,Mn很好地崮溶到Li2FeSiO4中.电化学性能测试表明,当w≌w(Mn)=0.1%时,合成的Li2Fe1-xMnxSiO4电化学性能最佳,首次放电容量达到67.7 mAh/g,20次循环后容量仍保持在44.8 mAh/g.     

镍、锰掺杂LiFePO_4电池正极材料的合成和电化学性能研究

以Li OH·H2O,Fe SO4·7H2O,H3PO4、Ni SO4、Mn SO4为原料,采用水热法合成了Li Fe1-xNixPO4和Li Fe1-xMnxPO4。采用XRD、FESEM分析了正极材料的组成、结构及形貌,利用电池测试仪测试了正极材料的电化学性能。结果表明:镍、锰掺杂Li Fe PO4具有较好的充放电性能。Li Fe0.9Mn0.1PO4的首次充放电比容量分别为143.5、143 m Ah/g,Li Fe0.95Ni0.05PO4的首次充放电比容量分别为132、131 m Ah/g,离子掺杂能显著提高材料的充放电比容量。     

LiMn2O4/Li4Ti5O12复合材料的制备与电化学性能

以LiMn2O4、醋酸锂和钛酸四丁酯为原料,乙醇为溶剂,采用原位复合法制备LiMn2O4/Li4Ti5O12复合材料.采用X射线衍射分析、红外光谱、扫描电镜和电化学测试等手段对复合材料进行表征.结果表明,在LiMn2O4/Li4Ti5O12复合材料中晶态的LiMn2O4表面被无定形结构的Li4Ti5O12包覆,但Li4Ti5O12的存在并没有改变LiMn2O4的晶体结构.由于Li4Ti5O12的包覆,LiMn2O4的倍率性能和高温性能都得到显著提高:室温下2.0C放电时20次循环后LiMn2O4/Li4Ti5O12复合材料的可逆容量达到108.4mA·h/g,平均每次循环的容量损失只有0.053%;而55 ℃ 1.0C放电时,经60次循环后LiMn2O4/Li4Ti5O12的放电容量为109.9 mA·h/g,平均每次循环的容量损失为0.036%.     

Li2Mn1-xMgxSiO4正极材料合成与电化学性能

采用固相法合成了Li2Mn1-xMgxSiO4掺杂型正极材料,并用TG-DTA、XRD、SEM和电化学性能测试对材料进行了表征。前驱体的TG-DTA曲线和XRD物相分析表明,合成Li2MnSiO4时优化的煅烧温度为750℃。XRD测试表明Li2Mn1-xMgxSiO4具有正交结构,对应Pmn21空间群,掺镁可以提高样品主相的结晶度。掺Mg对微观形貌影响明显,适量掺杂可以得到粒径均匀、少团聚的亚微米级粉体。将Li2Mn1-xMgxSiO4组装成扣式电池进行电化学测试的结果表明,Li2Mn0.98Mg0.02SiO4样品性能最好,首次放电比容量达到124.6mAh/g,为理论容量的38%,循环20次后放电容量仍有60mAh/g。     

锂离子电池正极材料LiFe0.9Ni0.1PO4的合成与性能

采用高温固相法合成锂离子电池正极材料LiFe0.9Ni0.1PO4,研究了反应条件对合成产物的影响. 利用X射线衍射(XRD)和扫描电镜(SEM)对所得样品的晶体结构、表面形貌等进行了表征. 结果表明反应温度和时间对LiFe0.9Ni0.1PO4晶体结构及材料性能均有较大影响,其中650℃下焙烧20h合成出的样品电化学性能最佳;在20mA/g 的电流密度下进行恒流充放电时,首次放电比容量可达145mA·h/g,循环30次后比容量仍为135mA·h/g,容量衰减仅为6.9%.     

Al掺杂Li_2MnSiO_4锂离子电池正极材料的合成和电化学性能

以Li2SiO3、Mn(CH3COO)2.4H2O和Al(OH)3为原料,用传统高温固相合成法成功制备出Li2Al0.1Mn0.9SiO4锂离子电池正极材料。采用XRD、FESEM分析了正极材料的相组成、结构和形貌,利用电池测试仪测试了正极材料的电化学性能。研究结果表明,固相合成的产物主相为Li2Al0.1Mn0.9SiO4,同时存在少量的杂质,产物表面形貌为非球形颗粒,颗粒尺寸为100～500 nm。实验结果表明,Al掺杂后,正极材料的可逆容量和循环寿命都得到提高。正极材料电化学性能提高的机理在于Al掺杂稳定了Li2MnSiO4正极材料的结构。     

LiFePO4／C复合正极材料的制备及其电化学性能研究

采用高温固相碳热还原法（CTR，Carbothermal Reduction）合成了LiFePO4／C复合正极材料。采用XRD，SEM以及BET等方法对产物进行表征。结果表明，所得LiFeP04／C材料有着单一的橄榄石型晶体结构。750℃下制备产物的BET比表面积为39．7002m^2／g。利用恒流充放电，循环伏安法（CV），电化学阻抗谱（EIS）等电化学手段研究了LiFePO4／C材料的电化学性质。结果表明：750℃下制备的LiFePO4／C复合材料在25℃工作温度下，有着优异的循环稳定性和大倍率充放电性能，使用850ma／g（5C）的电流密度对电池充放电90次后，电池放电比容量仍能保持11lmAh／g。在55℃工作温度下1C充放电倍率时，首次和第90次循环的放电比容量分别为14513mAh／g和142．9mAh／g。     

LiFePO4包覆LiCoO2的结构及性能

采用固相法在锂离子电池正极材料LiCoO2表面包覆一层LiFePO4;研究了LiFePO4包覆量对材料性能的影响;采用X射线衍射仪和扫描电镜分析样品的晶体结构和表面形貌.研究结果表明:样品具备LiCoO2的α-NaFeO2型层状结构,但随着包覆量的增加,XRD衍射谱显示样品存在多种杂相;合成的样品电化学性能良好,当LiFePO4的包覆量为1%时,在室温下以0.1C倍率充放电,首次放电比容量达145.9 mA·h/g,纯相LiCoO2放电比容量为146.2 mA·h/g.样品采用1C倍率放电时,首次放电比容量达138.9 mA·h/g,循环性能较好,经过20次循环放电比容量仅衰减4.97%.     

固相法合成LiFePO4/C正极材料的电化学性能

以廉价原材料FeSO4·7H2O为铁源,以蔗糖为碳源,采用固相法合成了锂离子电池正极材料--LiFePO4/C复合材料.用X射线衍射(XRD)、扫描电镜(SEM)和电化学测试技术对不同铁源合成的LiFePO4/C复合材料的结构、形貌和电化学性能进行研究.结果表明:合成的样品具有均一的橄榄石型结构,以FeSO4·7H2O为铁源合成的LiFePO4/C复合材料的循环性能和高倍率放电性能均优于以FeC2O4·2H2O为铁源合成的LiFePO4/C复合材料的;由FeSO4·7H2O合成的LiFePO4/C复合材料的5C倍率放电比容量为105.9 mA-h/g,经循环30次后,容量仍高达105.2 mA-h/g.     

Preparation, characterization and electrochemical properties of mesoporous LiFe0.99Mo0.01PO4/C

A mesoporous LiFe0.99Mo0.01PO4/C composite was synthesized by the sol-gel method using (NH4)2MoO4 as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneously in the prepared material. The characterizations of crystal structures and microstructures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), extended X-ray-absorption free-structure (EXAFS) and X-ray-absorption near-structure spectroscopy (XANES), while the surface area was determined using N2 adsorption techniques. Cyclic voltammetry (CV) and charge-discharge cycling performance were used to characterize its electrochemical properties. The sample possessed uniformly distributed mesopores with an average pore size of 4 nm and the specific surface area was about 69.368 m2/g. The results show that the reversible capacity of mesoporous LiFe0.99Mo0.01PO4/C is about 160 mAh/g at 0.1C, 135 mAh/g at 1C and 90 mAh/g at 5C, respectively. The capacity fading is neglectable.     

LiFePO_4/PANI复合材料的制备及电化学性能

通过原位聚合法,制备一系列的导电聚合物(Polyaniline,PANI)的LiFePO4/PANI复合材料。单用傅里叶红外光谱(FTIR)和高分辨透射电镜(HRTEM)表征PANI与LiFePO4之间的相互作用以及PANI对LiFePO4的包覆状况。采用四探针、电化学阻抗谱及恒电流充放电测试复合材料的电导率及其电化学性能。结果表明:当PANI含量为6.75%(质量分数)时,能在LiFePO4的表面形成均匀的包覆层,试样具有最佳的电化学性能,电荷转移电阻较小,交换电流较大,C/12倍率下首次放电容量为151.97mA·h/g,并具有较好的循环性能及倍率性能。     

NaV1-xCrxPO4F的合成及电化学性能

采用高温固相法合成掺杂改性的NaV1-xCrxPO4F(x=0,0.04,0.08)作为钠离子电池正极材料。通过红外光谱(FT-IR)、X射线衍射(XRD)和扫描电镜(SEM)等对材料的晶体结构和形貌进行表征。从材料的晶体结构、恒流充放电测试和循环性能等方面分析掺杂元素Cr在改善材料性能中的作用。结果表明:掺Cr后的材料电化学循环稳定性得到较好的改善,首次放电容量达到83.3 mA.h/g,效率高达90.3%,循环20次后可逆容量保持率仍然有91.4%。     

Synthesis and characterization of LiFe0.9Mg0.1PO4/nano-carbon webs composite cathode

LiFe_0.9Mg_0.1PO₄/nano-carbon webs composite cathode material was synthesized from nanocrystalline Fe₃O₄ through sol–gel process, followed by carbothermal reduction reaction in the presence of LiOH·H₂O and NH₄H₂PO₄. Sucrose molecule was introduced through liquid phase and used to construct carbon webs structure. FE-SEM and HR-TEM observations show that decomposed carbon can form typical carbon webs structure to connect and wrap LiFe_0.9Mg_0.1PO₄ particles. Electrochemical tests indicated that the Mg-doping at 4c site of carbon-coated LiFePO₄ did not affect the olivine structure of the lithium iron phosphate but obviously improve its discharge capacity and rate capability, which would be ascribed to the increased electronic conductivity and/or the mobility of Li⁺ ion induced by the doping method.     

Synthesis and electrochemical properties of Al-doped LiVPO4F cathode materials for lithium-ion batteries

Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.     

Synthesis and electrochemical properties of Th-doped LiMn2O4 powders for lithium-ion batteries

To improve the cycle performance of eco-friendly and cost-effective spinel LiMN2O4 as the Li secondary batteries, the Th-doped LiThxMn1-xO4 spinel powers were synthesized by solid-state method. The starting materials, Li2CO3,MnO2 and Th(NO3)4·4H2O, were mixed uniformly using a traditional ball milling, which resulted in a uniform particle size distribution in the mixed powers. Tests of X-ray diffraction, SEM, impedance spectra and charge-discharge were carried out for LiThxMn1-xO4 cathode materials. Results show that the synthesized LiTh0.01Mn1.99O4 material exhibits standard spinel structure, regular particle morphology and excellent property of charge-discharge for big current. The capacity retention of the material modified by doping Th is more than 85.1% of the first discharge specific capacity of 111.5 mAh·g -1 after 20 cycles at the current rate 1C, while the pristine LiMN2O4 is only 57% of the first discharge specific capacity of 110.2 mAh·g-1 after the same cycles at the same current rate.     

Synthesis and electrochemical properties of novel oligo-TTF donors

A series of novel oligomeric electron donors containing two to six TTF cores (5–11) were synthesized. The structures were assigned by NMR spectroscopy, infrared spectrometry and mass spectra. Their electrochemical properties were investigated by cyclic voltammetry (CV). All the compounds exhibited two pairs of nearly ideal redox waves. No distinct shift of the redox potentials was observed when TTF units increased.     

Synthesis and electrochemical properties of sol-gel derived LiMn2O4cathode for lithium-ion batteries

Spinel LiMn2O4 has been considered to be the most promising alternative cathode material for the new generation of lithium-ion batteries in terms of its low cost, non-toxicity and easy manufacture. The spinel lithium manganese mixed oxides were prepared from lithium nitrate, manganese nitrate and citric acid by asol-gel method and were characterized by thermogravimetric analysis, X-ray diffraction, cyclic voltammetry and constant current charging-discharging technique. The different sintering temperatures for different time have strong influence on the structure, initial discharge capacity and cycling performance of the lithium manganese oxide. It shows that the lithium manganese oxides sintered at 700 ℃ for 10 h have a single spinel structure and better electrochemical properties. The initial discharging capacity can be up to 125.9 mAh·g-1 , even after six cycles, it still retains 109.1 mAh·g-1 .