磷酸铁锂前驱体磷酸铁的研究进展

磷酸铁锂具有原料来源广、安全性能高、环境友好等独特的优势,成为锂离子电池正极材料的研究热点之一。前驱体磷酸铁与磷酸铁锂具有类似的结构,在合成磷酸铁锂时具有独特的优势,并且磷酸铁同时提供了铁源和磷源,合成过程中只需要添加锂源便可制备出磷酸铁锂,工艺条件简单可控。其合成方法主要有沉淀法、水热法、溶胶凝胶法等。介绍了不同方法的研究现状、优缺点及下一步的展望。     

锂离子电池正极材料磷酸铁锂的研究进展

磷酸铁锂（LiFePO₄）具有高温稳定性较好、循环性能良好、环保等特点,已成为锂离子动力电池正极材料之一。但由于磷酸铁锂电导率低及锂离子扩散速率慢等缺点,制约其在动力电池行业的发展。因此主要从包覆碳材料对磷酸铁锂进行表面改性、对磷酸铁锂进行掺杂、制备亚微米或纳米级的磷酸铁锂或制备特殊形貌的磷酸铁锂3方面进行综述,分析改善磷酸铁锂性能最优的方法,对其未来的发展趋势进行了预测。     

磷酸铁锂正极材料与电解液的相容性研究

在锂离子电池使用过程中磷酸铁锂正极材料会与电解液发生许多副反应,导致铁的溶解,造成正极材料与电解液相容性差。为了研究磷酸铁锂正极材料与电解液的相容性及其对电池搁置性能的影响,先利用电感耦合等离子发射光谱对不同磷酸铁锂正极材料在不同电解液中的溶铁量进行了表征,后又对制备的电池进行了常温及高温搁置性能测试。结果表明：磷酸铁锂正极材料对电解液具有选择性,并且正极材料在电解液中的溶铁量越大,其相容性越差,对锂离子电池性能影响越大。     

高温固相法制备磷酸铁锂的原料专利技术分析

锂离子电池是目前应用最广的充电电池,磷酸铁锂是锂离子电池中占比最大的正极材料,高温固相法是制备磷酸铁锂最主要的方式,而原料对磷酸铁锂的性能具有很大的影响。通过对高温固相法制备磷酸铁锂的专利技术进行分析,具体分析了制备过程中所采用的原料种类和粒径,以期为后续研究者提供一些技术参考。     

磷酸铁锂正极材料的制备及性能强化研究进展

橄榄石型磷酸铁锂是目前应用十分广泛的锂离子电池正极材料之一,具有成本低、安全性高、环境友好、循环寿命长和工作电压稳定的特点。近年来,随着CTP技术、刀片电池技术等取得的突破性进展,磷酸铁锂的商业化程度得到了大幅提高。但磷酸铁锂存在电子导电性较差和离子扩散系数低的缺陷,严重限制了锂离子电池的电化学容量,因此开展磷酸铁锂制备工艺和性能强化研究对磷酸铁锂的性能提升具有重要意义。对比了磷酸铁锂电池与其他正极材料锂离子电池的性能差异和发展现状,系统总结了磷酸铁锂正极材料制备与强化的改性方法及相关研究进展与挑战,并提出了未来的发展方向与研究思路。     

锂离子电池正极材料磷酸铁锂的研究进展

橄榄石结构的LiFePO4因为其有高比容量、低成本、环保等优点而被认为最有前景的锂离子电池正极材料,但是其电导率和锂离子扩散速率比较慢.本文综迷了磷酸铁锂作为锂离子电池正极材料在应用方面的优缺点,近几年来磷酸铁锂常用的制备方法,各种制备方法的优缺点以及对磷酸铁锂在电化学方面的改性研究,并指出今后研究的重点是对磷酸铁锂在...     

表面活性剂优化酸铁锂正极材料的进展

磷酸铁锂因稳定的橄榄石结构、资源丰富、价格便宜、安全、无污染,比容量高、电压平稳等优点,成为目前应用广泛的锂离子电池正极材料之一。本论文简要介绍磷酸铁锂结构、合成方法、物质性能和化学性能,对比不同表面活性剂对磷酸铁锂正极材料的电化学性能的影响。     

磷酸铁锂正极材料中锂离子扩散系数的测定

通过碳热还原法制备了磷酸铁锂正极材料,并采用恒电位阶跃法测定了磷酸铁锂正极材料在不同电位和循环次数下的锂离子扩散系数,通过XRD对循环前后磷酸铁锂材料的晶体结构进行了表征,并对磷酸铁锂材料的失效模式进行了简单的分析。结果表明:LiFePO4在充放电过程中锂离子扩散系数随Li含量的增大,呈现先增大后略微降低的规律。随着充放电循环次数的增多,LiFePO4中Li+的固相扩散系数值明显下降。     

LiFePO_4正极材料制备过程研究进展

基于磷酸铁锂正极材料的动力锂离子电池是近年来最受关注的电动汽车动力电源之一。由于原料路线差异,磷酸铁锂正极材料制备工艺有多种。本文回顾了上海交通大学在磷酸铁锂正极材料制备过程设计与研究中所取得的进展。在国家重点基础研究发展计划(国家973计划)支持下,重点研究了磷酸铁锂正极材料制备过程及其充放电倍率特性,还提出了如何改善磷酸铁锂正极材料在不同环境温度下性能的解决途径。最后,介绍了LiFePO4/C正极材料制备过程中涉及的还原过程、碳源选择和制备过程装备等过程工程特性问题。     

磷酸铁的研究进展

近年来,磷酸铁锂（LiFePO4）因具有突出优势已成为锂离子电池正极材料研究热点,磷酸铁与磷酸铁锂结构非常相似而成为正极材料的一种重要前躯体。介绍了磷酸铁的结构、制备方法研究现状和最新进展。     

The effect of bilayer regions on the response of epitaxial graphene devices to environmental gating

The effect of a bilayer area on the electronic response to environmental gating of a monolayer graphene Hall bar device is investigated using room temperature magnetotransport and scanning Kelvin probe microscopy measurements in a controlled environment. The device is tuned through the charge neutrality point with n–p–n-junctions formed. Scanning Kelvin probe measurements show that the work function of the monolayer graphene decreases more than that of the bilayer area however magnetotransport measurements show a larger change in carrier concentration for bilayer graphene with environmental gating. Interface scattering at the boundary between the monolayer and bilayer regions also affects device response with field-dependent suppression of the conductivity observed near the charge neutrality point. Simultaneous electronic and environmental scanning Kelvin probe measurements are used to build nano-scale maps of the work function of the device surface revealing the areas of greatest work function change with environmental gating.     

Sonoprocessing of LiFePO4 nanoparticles and nanocomposites for cathode material in lithium ion batteries

Lithium iron phosphate (LiFePO₄) nanoparticles and lithium iron phosphate/halloysite (inorganic nanotubes) (LiFePO₄/INT) nanocomposites were prepared by ultrasound‐assisted synthesis in an aqueous solution of lithium hydroxide containing ammonium dihydrogen phosphate and ferrous chloride and used as cathode materials in lithium ion batteries. The performance of the cathode material was measured using cyclic voltammetry. The oxidation potential for LiFePO₄ polyaniline/nanotubes/anode cell was found to be in the range of −1.12 to 1.063 V while the reduction potential for lithium iron phosphate cell was in the range of −1.03 to 1.15 V. POLYM. COMPOS., 37:1874–1880, 2016. © 2015 Society of Plastics Engineers     

Stacking of water molecules in hydrophilic graphene oxides characterized by Kelvin probe force microscopy

We directly measured local surface potentials of graphene oxide and poly (sodium 4-styrenesulfonate) intercalated graphene oxide (PSSGO) films, as a function of humidity, using Kelvin probe force microscopy. Our results showed a decrease in the work function of the graphene oxide (GO) film as the humidity increased. This behavior was explained using the first-principle calculation in which water molecules stacked onto the GO film, resulting in a lower local work function and ripples of the surface potential. The ripples directly measured by Kelvin Probe Force microscopy were consistent with the calculation. While the PSSGO film did not show the ripples as the humidity increased. Our results directly showed that absorbed water molecules on the films change the local surface potential and the work function such that its performance in many applications will be affected.     

我国磷酸铁锂改性技术的进展与应用前景

介绍了新型锂离子电池正极材料磷酸铁锂制备与改性技术,特别介绍了我国磷酸铁锂纳米化、离子掺杂、碳包覆等改性技术和水热合成、溶胶—凝胶法等磷酸铁锂制备技术,阐明了改性技术有利于进一步改进电池电化学性能,以适应混合动力汽车与电动汽车动力电池和风能、太阳能储能设备等对锂离子电池要求。基于磷酸铁锂正极材料发展前景,提出了我国传统磷化工行业调整产品结构,对接新能源材料的发展思路。     

锂离子电池正极材料磷酸铁锂的研究进展

对锂离子电池正极材料磷酸铁锂的制备方法进行了介绍。首先介绍了固相合成法的基本过程、研究改进情况以及优缺点,其次介绍了液相合成法即水热法、溶胶-凝胶法和共沉淀法的基本原理及研究进展,然后从非晶相掺杂和晶相掺杂两个方面对锂离子电池材料的性能改进研究情况进行了介绍,最后对材料的发展方向进行了展望。     

锂电正极材料的生命周期评价

在生命周期评价的基础上,本文通过对锂电正极材料五个阶段对环境的影响进行评估,提出了锂电正极材料LCA计算方法,并用该方法分析比较了磷酸铁锂和锰酸锂两种正极材料对环境的影响。结果表明:锰酸锂相对于磷酸铁锂具有更大的环境效益。该结果为市场以及锂电正极材料生产厂商选择动力电池用正极材料提供一定的参考。     

Depth profiles of the Fermi level at an amorphous-carbon nitride/SiO2/n-type-Si heterojunction interface obtained by Kelvin probe force microscopy

To explore the work function of a typical amorphous-CN film containing a nitrogen concentration of 23.5 at.%, surface potential images were acquired using Kelvin probe force microscopy. Based on the Fermi level of the n-type Si and the contact potential difference between the amorphous-CN film and the n-Si substrate, the work function of the amorphous-CN film was estimated to be 5.2 ± 0.2 eV below its vacuum level. Using the surface potential depth profile for an etched amorphous-CN film, energy diagrams of the amorphous-CN/SiO₂/n-Si interface were constructed based on the positional relationship of the Fermi level. These band diagrams showed that band bending occurred at the amorphous-CN/SiO₂/n-Si interface despite the Fermi level pinning effect of surface trapping due to the SiO₂ insulator layer.     

Negative electron affinity on polycrystalline diamond surface induced by lithium fluoride deposition

Lithium fluoride (LiF) was deposited on hydrogenated and oxygenated polycrystalline diamond surfaces. Lowering of the work function induced by the dipole effect of LiF was clearly observed using UV photoemission spectroscopy and Kelvin probe. The decrease of the work function was sufficiently large so that negative electron affinity was induced. This shows that the LiF overlayer on diamond acts as an effective dipole layer to lower the surface work function of the diamond film.     

Lithium Ion Diffusion Mechanism in Lithium Lanthanum Titanate Solid‐State Electrolytes from Atomistic Simulations

Perovskite‐structured lithium lanthanum titanate (LLT, La_2/3–xLi_3xTiO_3, 0 <  x < 0.16) is a promising solid electrolyte with high lithium ion conductivity and a good model system to understand lithium ion diffusion behaviors in solids. Molecular dynamics (MD) and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism as a function of composition in LLT solid‐state electrolytes. The effect of defect concentration on the structure and lithium ion diffusion behaviors in LLT was systematically studied using MD simulations and molecular static calculations with the goal to obtain fundamental understanding of the diffusion mechanism of lithium ions in these materials. The simulation results show that there exists an optimal vacancy concentration at around x = 0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static nudged elastic band calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8%–10% when lithium ions pass through. By designing perovskite structures with larger bottleneck sizes can be a means of further improving lithium ion conductivities in these materials.     

Ion migration in anodic barrier oxide films on iron in acidic phosphate solutions

A kinetic study was carried out of the ionic current in the anodic barrier oxide layer on iron at the steady state in the passive potential region in acidic phosphate solutions. It is found that the ionic current follows the classical high field ion conduction equation in which the current is expressed as an exponential function of the electric field in the barrier layer. From the kinetic constants appearing in this equation and their temperature dependence, the diffusion coefficient and the activation energy for diffusion of moving ions in the layer were estimated and compared with those of high temperature diffusion in iron oxides. It is suggested that the ionic current is carried by oxygen ions than by iron ions in the barrier oxide film.