锂掺杂对石墨电化学性能的影响

研究了掺杂锂元素对用作锂离子电池负极的石墨材料的结构与性能的影响. XRD及元素分析结果表明 锂以化合物的形式存在于石墨材料中, 由于缺陷结构的增加, 掺杂后石墨材料的BET比表面积略有增大. 电化学测试结果表明 预先掺锂能够有效减少首次充放电过程中的不可逆容量, 使石墨电极的可逆容量增加. 与未掺杂的热处理石墨比较, 可逆嵌锂容量由304.5 mA*h/g增加到312.2 mA*h/g, 首次充放电不可逆容量由66.4 mA*h/g减少到52.9 mA*h/g. 以掺锂改性石墨为负极制作成063448型锂离子电池后, 电池的容量和循环稳定性均得到改善, 以1C倍率充放电时, 放电容量可达845 mA*h, 循环200次后的容量保持率为91.65%.     

天然石墨中的嵌/脱锂离子过程

研究了锂离子在天然石墨中的嵌入 /脱出过程 ,以及电流密度对锂离子嵌入石墨过程的影响。非现场XRD结果显示 ,石墨的层间距随锂的嵌入与脱出发生先膨胀后收缩复原的变化 ;SEM结果显示 ,小电流密度下石墨表面的SEI膜较致密、均匀 ,而大电流密度下的则疏松、不均一 ;恒电流充放电测试结果显示 ,在相同的嵌锂电位下锂与微晶石墨和鳞片石墨所形成的层间化合物 (Li GICs)不完全相同 ;合理的充放电制度有利于小幅度改善材料的大电流充放电性能。     

天然石墨／锑复合材料作为锂离子电池负极材料嵌／放锂性能研究

研究了用简单混杂和球磨方法制备的天然石墨／锑复合材料作为锂离子电池负极材料的嵌／放锂性能以及循环过程中嵌／放锂容量衰减机理。复合材料中的锑以独立的可逆嵌／放锂反应参与吸／放锂过程并显著提高复合材料的嵌／放锂容量。较大颗粒的锑在嵌／放锂过程中体积剧变导致颗粒破碎、电接触恶化而渐渐失去嵌／放锂活性，因此由简单混杂所获得石墨／锑复合材料在循环过程中容量逐渐降低；采用球磨方法在天然石墨颗粒表面形成弥散分布的小颗粒锑则能获得具有较高可逆容量和较好的循环稳定性的石墨／锑复合锂离子电池负极材料。     

金属间化合物CoSb3的电化学嵌锂特性研究

研究了金属间化合物CoSb3作为锂离子电池阳极材料在1MLiPF6/EC+DMC(1∶1)电解液中的电化学性能.具有skutterudite结构的CoSb3和不具有此种结构的CoSb3最大可逆容量分别为573mAh*g-1和444mAh*g-1,10个循环内可逆容量分别保持在400mAh*g-1和220mAh*g-1以上,采用非原位XRD方法研究二者嵌锂机理,发现skutterudite结构虽然不起储锂作用,但它破坏后形成的微观结构却有利于循环过程.加入10%(质量分数,下同)微碳球MCMB后CoSb3电化学性能大大提高,最大可逆容量达715mAh*g-1,循环20次后可逆容量保持在500mAh*g-1以上.     

Co掺杂LiFePO4/C的共沉淀——微波合成及电化学性能

采用共沉淀-微波法制备了Co掺杂的锂离子电池正极材料LiFe1-xCoxPO4/C(x=0.00、0.01、0.03、0.05、0.07、0.09).研究了微波时间、柠檬酸量、掺Co量等因素对材料结构、形貌和电性能的影响.XRD、SEM和电化学测试表明:该方法制备的样品为橄榄石型非晶结构,粒径尺寸为0.5～5 μm,颗粒分布比较均匀.微波15 min、柠檬酸量为20wt％时,LiFePO4/C电化学性能最优,0.1C倍率放电可达124 mA·h/g,第20次循环的比容量为117mA·h/g.掺杂Co在很大程度上可以提高LiFePO4/C的电化学性能,当Co含量为5wt％时,LiFe0.95Co0.05PO4/C的比容量为最大值,0.1C倍率放电可达136 mA·h/g,第20次循环的比容量为125 mA· h/g,容量保持率为91.9％.     

镍离子掺杂对LiFePO4结构和性能的影响

为提高LiFePO4的充放电性能,用Ni2 对LiFePO4进行掺杂.采用电化学方法测量了Li1-xNixFePO4的充放电性能,用X射线衍射和里特沃尔特方法表征了掺杂LiFePO4的晶体结构.固相反应可制备单相Li1-xNixFePO4(x=0.00、0.01、0.02、0.03、0.05和0.07,摩尔分数).研究表明:少量镍离子掺杂能有效地提高LiFePO4的比容量和循环性能,其中Li0.97Ni0.03FePO4具有更好的电化学性能,放电比容量高出LiFePO4约30mA·h/g,其主要原因是镍离子掺杂不仅改变了晶体中原子间距离和位置,引起晶胞收缩;而且增加了LiFePO4中Fe3 /Fe2 共存态的浓度,提高了材料的导电能力.     

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。     

金属间化合物CoSb_3的电化学嵌锂特性研究

研究了金属间化合物 Co Sb3作为锂离子电池阳极材料在 1ML i PF6 /EC+ DMC( 1∶ 1)电解液中的电化学性能。具有 skutterudite结构的 Co Sb3和不具有此种结构的 Co Sb3最大可逆容量分别为 5 73 m Ah· g- 1 和 4 4 4 m Ah·g- 1 ,10个循环内可逆容量分别保持在 4 0 0 m Ah· g- 1和 2 2 0 m Ah·g- 1以上 ,采用非原位 XRD方法研究二者嵌锂机理 ,发现 skutterudite结构虽然不起储锂作用 ,但它破坏后形成的微观结构却有利于循环过程。加入 10 % (质量分数 ,下同 )微碳球 MCMB后 Co Sb3电化学性能大大提高 ,最大可逆容量达 715 m Ah· g- 1 ,循环 2 0次后可逆容量保持在 5 0 0 m Ah· g- 1 以上。     

锂离子电池极材料钽掺杂钛酸锂的制备及电化学性能

通过固相合成制备了钽掺杂材料Li4Ti4.95Ta0.05O12。通过XRD和SEM来表征Li4Ti4.95Ta0.05O12的结构和形貌。钽掺杂并没有改变本体材料的结构和形貌,而且显著提高了材料的循环性能和倍率性能。Li4Ti4.95Ta0.05O12在10C和30C倍率时的放电容量分别是116.1mA.h/g和91.0mA.h/g。Ta掺杂取代了Li4Ti5O12中的Ti的位置,产生了Ti4＋/Ti3＋混合价态,从而提高了钛酸锂的电导率。故具有优异的高倍率性能,是一种优异的锂离子电池负极材料。.     

Effect of graphite content on electrochemical performance of Sn-SnSb/graphite composite powders

Sn-SnSb alloy was synthesized by reducing a aqueous solution containing Sn（Ⅱ） and Sb（Ⅲ） salts with NaBH4 in the presence of sodium citrate. The product was characterized by X-ray diffractometry（XRD） and scanning electron microscopy（SEM）. Sn-SnSb/graphite composite powders were prepared by mechanical milling and the mass fraction of graphite was increased from 20% to 50%. The effect of graphite content on the electrochemical performance of Sn-SnSb/graphite composite electrode was investigated. The results show the increase of graphite content is in favor of enhancing the first charge-discharge efficiency and improving the cycle performance, but the capacity of the composite electrode decreases with increasing content of graphite.     

Effects of modification on performance of natural graphite coated by SiO2 for anode of lithium ion batteries

A stable silicon dioxide film was coated on the surface of natural graphite anode by sol-gel method with Si（OCH2CH3）4, and effects of modification on performance of natural graphite were investigated. The structure and properties of graphite samples were determined by X-ray diffi＇actometry（XRD）, scanning electron microscopy（SEM）, energy-dispersive X-ray spectroscopy（EDS） and electrochemical measurements. The modified graphite shows mainly the layer structure, and silicon dioxide film is amorphous. Compared with the pure natural graphite, the modified graphite exhibits the higher specific capacity of 366 mA-h/g. After 40 charge-discharge cycles, the capacity retention ratio of the modified graphite reaches 99.55%, while that of natural graphite is only 83.04%. The results indicate that the surface modification of natural graphite by SiO2 is effective for improving the electrochemical performance of the natural graphite anode for lithium ion batteries.     

Li1+x(Fey/2Niy/2Mn1-y)1-xO2正极材料的合成及电化学性能

采用低温共沉淀-水热-煅烧法合成了锂离子电池Fe-Ni-Mn体系正极材料Li1+x(Fey/2Niy/2Mn1-y)1-xO2,并用XRD、SEM、ICP光谱和电化学性能测试对材料进行了表征.XRD测试和ICP分析表明,Fe、Ni取代Li2MnO3中的部分Mn,形成很好的固溶结构yLiFe1/2Ni1/2O2-(1-y)Li2MnO3 (y=0.l,0.2,0.3,0.4,0.5).SEM测试表明,取代量y不同,材料的表观形貌有所不同,y=0.4时材料的颗粒粒径均匀、较小,呈类球形结构.电化学性能测试表明,当y=0.4时,循环稳定性最好,充放电50次后放电比容量仍可维持在195.0 mAh/g,放电中值电压为3.5 V,y=0.4时样品在大倍率放电下的电化学性能表现良好.     

Discrete–variational Xα calculations of graphite and alkali–metal graphite intercalation compounds

First-principles molecular orbital calculations using discrete–variational (DV)-Xα method are carried out on the model clusters of graphite and alkali–metal graphite intercalation compounds MC_x(M=Li, Na, K, Rb, and Cs). Results of the calculations are used so as to simulate the experimentally observed near-edge X-ray-absorption fine-structures (XANES) and ultraviolet photoelectron spectra. For the clusters of graphite and KC_x, the calculated partial electronic densities of states (PDOSs) are in good agreement with the experimental C K-edge and K K-edge XANES spectra, respectively. Furthermore, the accordance between the calculated DOSs and the observed UPS spectra of graphite and RbC_x is also satisfactory. It is shown that the Fermi level is pushed up into the conduction band of graphite by doping alkali metals.     

Synthesis and characterization of layered Li（Ni1/3Mn1/3CO1/3）O2 cathode materials by spray-drying method

Spherical Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 ℃ , Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 attains a reversible capacity of 153 mA·h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.     

新型负极添加剂对MH/Ni电池性能的影响

用过渡金属氧化物作为ＭＨ／Ｎｉ电池的负极添加剂,研究了它对ＭＨ／Ｎｉ电池容量、放电电压、电池内压和循环性能的影响。加人２％的新型负极添加剂,可以在保证电池容量不受影响的前提下,使ＭＨ／Ｎｉ电池的放电中值电压升高约２０ｎＶ,以１Ｃ倍率电流充电时的最大电池内压减少０．４ＭＰＡ,并显著提高电池循环性能。以１Ｃ倍率快速充放测试徨４００次时,其容量保持率在９０％以上,放电中值电压变１．２１６Ｖ。     

Transformation/dissolution studies on the release of iron and chromium from particles of alloys compared with their pure metals and selected metal oxides

Transformation/dissolution (T/D) data for different Cr‐ and Fe‐based alloys (a FeCr alloy, stainless steel AISI 316L, an alloy side product (SP) from stainless steel production) compared with their pure metals (Cr, Fe) and selected metal oxides (Cr₂O₃, Fe₃O₄) was generated and is used throughout the entire REACH assessment documentation of chromium metal and ferrochromium alloys to derive conclusions regarding their acute and chronic ecotoxicity hazard classification. Short and long term tests were conducted to assess data for acute and chronic aquatic toxicity following the recognized standardized T/D protocol. Tests were performed in media of different pH (pH 6.0 and pH 8.0), time periods, and solution composition, also investigating the effect of different experimental parameters. Generated data elucidates the complexity of the metal release process and its dependence on many interacting material‐, surface‐, and experimental factors as well as on the chemistry of the metal–water system being metal species specific. It is evident that the extent of metal release cannot be predicted by either the bulk or the surface composition, and that metal speciation measurements of released metals are essential to assess aquatic toxicity induced by metal/alloy particles. Observed released Fe and Cr concentrations were significantly lower than reported acute and chronic ecotoxicological endpoints.     

前处理工艺对Li[Ni1/3Mn1/3Co1/3]O2正极材料结构、形貌和电化学性能的影响（英文）

以[Ni1/3Co1/3Mn1/3]3O4和氢氧化锂为原料,分别采用球磨法和液相法前处理工艺制备层状正极材料Li[Ni1/3Mn1/3Co1/3]O2。采用X？射线衍射（XRD）、场发射扫描电镜（FESEM）、恒流充放电等手段对材料的物理和电化学性能进行表征。结果表明：采用不同前处理工艺制备出的Li[Ni1/3Mn1/3Co1/3]O2材料在结构、形貌和电化学性能上有较大差异;与球磨处理法制备的材料相比,采用液相法前处理工艺制备的Li[Ni1/3Mn1/3Co1/3]O2不但保持了前驱体较好的球形形貌,同时还具有较好的循环稳定性和倍率性能;该样品在20mA/g电流密度下,首次放电容量为178mA·h/g,50次循环后,容量保持率达98.7%;在1000mA/g电流密度下,样品容量为135mA·h/g。