电池级磷酸铁的制备及性能

以铁粉和H₃PO₄为原料,采用沉淀法制备了FePO₄,并研究了反应温度、反应时间、过氧化氢加入量对FePO₄性能的影响。利用X射线衍射分析仪、扫描电子显微镜、激光粒度分析仪、TG/DTA和电感耦合等离子体发射光谱仪等对制备的磷酸铁形貌、晶体结构与化学成分进行了表征。实验结果表明,磷酸铁制备过程的最佳实验条件为：反应温度70℃,反应时间1h,H₂O₂过量10%滴加时间60min。在最佳条件下制备的磷酸铁粒径为1~4μm,结晶度好,纯度高。样品中铁的质量分数为36.37%,磷的质量分数为20.86%,铁磷物质的量比为0.97,均可达到电池级磷酸铁的标准,完全可以满足磷酸铁锂正极材料前体的要求。     

Free lewis acid effects in electrolytes for Li/SOCl2 cells

Electrolyte solutions containing lithium tetrachloroaluminate with free aluminum chloride added, have been evaluated for use in Li/SOCl₂ cells. The optimum electrolyte composition contained 1.0 M LiAlCl₄ plus 2.0 M AlCl₃ in SOCl₂. Such a solution, when used in cells in place of the more usual 1.8 M LiAlCl₄ electrolyte, results in 45% longer reaction times. This increase can only be explained in part by a two stage discharge process. The beneficial effect of free Lewis acid in the electrolyte was found to be greater for cells containing lower surface area carbon black cathodes.     

A novel promotion strategy for microstructure and electrical performance of garnet electrolytes via Li4GeO4 additive

Cubic Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (c-LLZTO) electrolyte is one of the most promising solid electrolytes. However, it is rather difficult to promote its electrical performance while reducing process parameters. Therefore, Li₄GeO₄ is applied as the additive in liquid sintering of LLZTO ceramics in this study. The LLZTO@Li₄GeO₄/Li₂O composite electrolyte sintered at 1180 °C for 3 h performs a significantly promoted microstructure and electrical performance, the ionic conductivity of which reaches 5.77 × 10⁻⁴ S cm⁻¹ at 25 °C. The Li₄GeO₄/Li₂O eutectic phase contributed prominently, in which the high concentration of Li⁺ seaming the LLZTO grains tightly. Meanwhile, Li⁺ conduction in the consecutive conductive pathways constructed by [GeO₄] groups among the grains was greatly stimulated. With the modification of the grain boundary, an improved garnet electrolytes/Li anode interface performance is produced. The Li/Au|LLZTO@Li₄GeO₄/Li₂O|Au/Li symmetrical cell is able to cycle stably for more than 500 h at the current density of 0.1 mA cm⁻² at room temperature.     

The behaviour of graphite, carbon black, and Li4Ti5O12 in LiBOB-based electrolytes

The film formation behaviour of lithium bis(oxalato)borate (LiBOB), a new electrolyte salt for lithium batteries, on graphite, carbon black and lithium titanate is reported. LiBOB is actively involved in the formation of the solid electrolyte interphase (SEI) at the anode. Part of this formation is an irreversible reductive reaction which takes place at potentials of around 1.75 V vs Li/Li⁺ and contributes to the irreversible capacity of anode materials in the first cycle. Carbon black interacts strongly with LiBOB-based electrolytes, which results in strong film formation and loss of electronic conductivity within the composite electrode. In LiBOB-based electrolytes the electrode kinetics increase in the order: carbon black << fine particulate graphite ~ metal powder, due to decreased film formation of the conductive additive. The influence of various solvents, surfactant additives, and potential impurities was also studied.     

Impacts of 3Li2O-2GeO2 melt on fabrication and electrical performance of novel LLZTO@Li4GeO4/Li2O composite electrolytes

Novel LLZTO@Li₄GeO₄/Li₂O composite electrolytes have been successfully produced through liquid sintering Li_6.4La₃Zr_1.4Ta_0.6O₁₂ via the 3Li₂O-2GeO₂ (LGO1.5) additive at 1140 °C for 3 h in air atmosphere. The Li-Ge-O additive performs a prominent role in fabricating compact connections among LLZTO grains and accelerating their densification procedure. Moreover, the additive acts as a bridge to promote Li⁺ transportation in the grain boundary domains. Consecutive Li⁺ conduction pathways are constructed inside the ceramics correspondingly. A considerably enhancement for the electrical performance of the garnet-type electrolytes is realized. The composite electrolyte with 2wt% LGO1.5 exhibits a high ionic conductivity of 5.57 × 10^?4 S·cm^?1 at 25 °C, the relative density of which reaches 95.8%. It is also capable of withstanding a high voltage up to 6 V (vs. Li/Li⁺) and a large critical current density of 0.65 mA·cm^?2.     

Effects of electrolytes on the electrochemical performance of Si/graphite/disordered carbon composite anode for lithium-ion batteries

The influences of LiBF₄, LiClO₄, lithium bis(oxalato) borate (LiBOB), LiPF₆ with VC and without VC, and the mixed electrolytes composed of different ratios of LiBOB and LiPF₆ or LiClO₄ on the electrochemical properties of Si/graphite/disordered carbon (Si/G/DC) composite electrode were systematically investigated by constant current charge-discharge and electrochemical impedance spectra (EIS) techniques. Scanning electron microscopy (SEM) was used to observe the change of electrodes in morphology after given cycle numbers. X-ray photoelectron spectroscopy (XPS) was employed to understand the influences of different mixed electrolytes on the composition of SEI layers. The results showed that Si/G/DC composite electrode in the mixed electrolytes presented better electrochemical performance than in single electrolyte. The compactness and compositions of SEI layers intensively influenced the cycle performance of Si/G/DC composite materials. LiBOB and additive VC had a good synergistic effect on the formation of the dense SEI layers. In particular, Si/G/DC in 0.5 M LiBOB + 0.38 M LiPF₆ electrolytes containing VC exhibited a high reversible capacity and excellent cycle performance.     

Preparation and characterization of GDC-Li2SO4/Li2CO3 nanocomposite electrolytes for applications in intermediate solid oxide fuel cells

Gd_0.1Ce_0.9O_1.95/Li₂CO₃-Li₂SO₄ (GDC/LCS) nanocomposite electrolytes were prepared through nano-powders mixing, prefiring and sintering operations. The phase components and microstructures of the as-prepared nanocomposite were characterized by XRD, FESEM, TG-DSC and IR spectroscopy. AC impedance spectroscopy and DC polarization method were utilized to measure their electrical conductivities under different conditions. It has been found that the GDC/LCS nanocomposite have a very homogeneous microstructure, where the LCS is mostly in amorphous state due to the strong interfacial interactions between the GDC and LCS. In addition, their overall electrical conductivity was found to increase with temperature in air, featured with a sharp activation energy change from 1.01 to 0.30 eV around 520 °C, and reach 108.7 mS/cm at 600 °C, while their protonic and oxide ionic conductivities were 16 mS/cm in H₂ and 5 mS/cm in air at the same temperature, respectively. The single cell built up of the GDC/LCS nanocomposite showed an open-circuit voltage of 1.01 V and peak power density of 272 mW/cm² at 600 °C.     

共生Li3PO4对LiFePO4电化学性能的影响

采用固相法制备出xLi3PO4/LiFePO4/C(x=0,0.025,0.05,0.10,0.15,0.20,0.50)复合锂离子电池阴极材料.电化学充放电测试显示,0.025Li3PO4/LiFePO4/C材料的性能优于同时制备的对比样品LiFePO4/C的.0.025Li3PO4/LiFePO4/C材料以0.1 ...     

磷酸铁锂材料在水溶液中嵌锂行为研究

应用扫描循环伏安法研究LiFePO4材料在LiNO3水溶液体系中的脱/嵌锂过程,该扫描曲线是一个完整的、闭合的氧化/还原峰曲线,峰型尖锐,说明LiFePO4材料在水溶液体系中具有良好的电化学可逆性。对LiFePO4材料在LiNO3水溶液中进行恒电位嵌锂,对嵌锂后的LiFePO4材料进行恒电位脱锂,将嵌入材料中的Li+释放到去离子水溶液中,成为含Li+水溶液。以紫外分光光度法测定其中Li+的吸光度,对照标准Li+吸光度~浓度(g/L)曲线,对应的浓度即为溶液中Li+浓度。计算出LiFePO4材料的嵌锂效率约为35%。说明LiFePO4材料可以作为含Li+水溶液的嵌锂材料进行提锂。但是提锂效率低。     

锂离子电池正极材料磷酸亚铁锂的改性进展

橄榄石型结构的磷酸亚铁锂(L iFePO4)作为一种新型的锂离子电池正极材料,具有材料来源广泛、价格便宜、理论比容量高(约170 mA.h/g)、热稳定性好、无吸湿性、对环境友好等优点,可望成为新一代首选的可替代钴酸锂(L iCoO2)的锂离子二次电池正极材料。分析了锂离子电池正极材料橄榄石型磷酸亚铁锂的结构特点和锂离子在充放电时的脱嵌模型,评述了近年来国内外对于改善磷酸亚铁锂的电化学性能所进行的改性研究,重点介绍了优化合成工艺、提高离子扩散效率、添加导电材料等方法对锂离子电池正极材料磷酸亚铁锂的影响,并对其发展方向作了展望。     

The i.r. analysis of water traces in electrolytes for Li/SOCl2 cells

It is established that the absorbance of the SOCl₂/LiAlCl₄ electrolyte solutions at 2800 cm^–1 is due the HCl, generated in the solution as a result of the hydrolysis reaction of SOCl₂. A slow self-desiccation reaction of the hydrated AlOHCl₂ is also postulated to occur in these solutions.     

基于Li3PO4水热法制备LiFePO4及其改性

以自制Li3PO4为前驱体,在水热条件下与FeSO4.7H2O反应制备得到纯相LiFePO4,并通过碳包覆和Cu2+掺杂对其进行了有效改性,获得了适合高电流密度放电的LiFePO4正极材料。采用X射线衍射(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)对产物进行了物相和形貌表征。实验研究了水热反应温度对产物的形貌及其电化学性能的影响,同时探讨了掺杂Cu2+对材料常温和低温电化学性能的影响。结果表明:在200℃、24h水热条件下制得的产物,经碳包覆后的复合材料LiFePO4/C(LFP200/C),以1C(150mA.g-1)电流放电,放电比容量达140.7mAh.g-1;对材料进行Cu2+掺杂得到的Cu-LFP200/C材料的放电比容量及倍率性能得到进一步提高,常温下1C倍率的放电比容量为150.3mAh.g-1,10C倍率的放电比容量为108.7mAh.g-1,在-30℃条件下的放电比容量依然达到97mAh.g-1。     

高密度LiFePO4正极材料的合成与性能

以高温固相法制备了高密度的LiFePO4正极材料,利用XRD、SEM、粒度分析、交流阻抗以及充放电测试等方法研究了前驱体Li3PO4和FePO4的比例与LiFePO4的物理性能和电化学性能的关系。其中,在Li3PO4与FePO4物质的量比为3：2时,制备的LiFePO4正极材料振实密度高达1.4g／cm^3,以0.1C放充电时,其首次放电比容量为159.0mA·h／g,体积比容量为222.6A·h／L,循环25次后,容量保持率达94.0％。     

磷酸铁锂高温循环性能的改善

磷酸铁锂结构稳定、循环性能优异,但是随着主机厂家对质保要求的不断提升,磷酸铁锂仍面临着高温循环性能不能满足客户要求的情况。以磷酸铁锂正极锂离子电池为研究对象,分别对比了基础电解液体系和改善电解液体系[在基础电解液中添加二氟二草酸硼酸锂（LiODFB）]对电池高温循环性能的影响。对循环后的电池采用直流内阻（DCIR）、电化学交流阻抗谱（EIS）、d Q/d U（恒定的电压间隔内电池容量的变化）曲线等无损分析方式进行数据对比,结果表明改善电解液体系电池的电荷转移阻抗进一步降低。通过对电池进行解剖,对两种电解液体系的电池极片进行了厚度分析、X射线衍射（XRD）分析、扫描电镜（SEM）分析、电感耦合等离子体发射光谱（ICP）元素分析等,结果表明改善电解液体系的电池在抑制负极表面副反应、减少正极铁溶出方面具有明显的效果,因此电池的高温循环性能更好。     

Evaluation of low-temperature cryolite-based electrolytes for aluminium smelting

Aluminium was smelted in a laboratory-scale cell at temperatures down to 850 °C from cryolite-based electrolytes with bath ratios in the range 0.75–1.50. Electrolyses were conducted for 1–2h using a current density of 1 A cm^–2 on 5 cm² electrodes with an anode-cathode distance of 2 cm. Current efficiencies of up to 95% were recorded. In low bath ratio electrolytes, operation at alumina concentrations of 3 wt% sometimes resulted in the aluminium deposit breaking into globules which clustered around the cathode. Under constant current conditions, the critical alumina concentration for the onset of anode effect was found to be 2 wt%. The bubble evolution characteristics (i.e., size and frequency) which affect mass transfer and cell voltage were also evaluated. Overall, low-temperature cryolite-based electrolytes may offer a viable alternative to conventional compositions for aluminium smelting.Author to whom correspondence should be addressed     

碳掺杂改善LiFePO4电化学性能

采用葡萄糖为碳源,通过固相合成法制备了掺碳的LiFePO4正极材料,并对样品的性能进行了研究分析.结果表明,少量的碳掺杂并未改变LiFePO4的晶体结构但显著改善了其电化学性能,LiFePO4/C样品的粒度较小粒径分布均匀,0.1 C首次放电比容量为141.9 mAh/g,循环50次后容量下降11.2 mAh/g,以1 C倍率首次放电比容量为126.5 mAh/g,循环50次后容量保持率为87.2%.     

锂离子电池正极材料LiFePO4的电化学性能改进

引言 随着社会的进步,人们对化学电源提出了高能量、长寿命、低成本、低环境污染的要求.虽然锂离子蓄电池目前已经实现了商品化,但正极嵌锂材料结构与性能的研究,以及如何提高容量和降低成本是锂离子蓄电池进一步被开发和应用的关键.     

磷酸铁锂电池铁溶解对电池性能的影响

研究了铁溶解对于磷酸铁锂/石墨体系电池性能的影响。对磷酸铁锂与电解液的相容性做了研究,配制了溶解了铁盐的电解液并制成已经商品化的方形电池,在0.5C下进行循环性能的测试,并在常温和55 ℃高温的情况下进行搁置实验。结果表明,铁的溶解并没有对磷酸铁锂电池容量衰减及自放电造成特别明显的影响,说明铁的溶解不是磷酸铁锂电池容量衰减及自放电大的主要原因。     

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。     

Electrochemical performance of in situ LiFePO4 modified by N-doped graphene for Li-ion batteries

LiFePO₄ modified by N-doped graphene (NG) with a three-dimensional conductive network structure was synthesized via a one-step in situ hydrothermal method. The effects of N amount of NG on the phase structure, morphology, and electrochemical properties of LiFePO₄ are investigated in this study. X-ray diffraction (XRD) results show that doping suitable N amounts in NG do not alter the crystal structure of LiFePO_4, and scanning electron microscopy (SEM) images show that NG can slightly reduce the particle size of LiFePO₄. The high-resolution transmission electron microscopy (HRTEM) results show that the LiFePO₄ particles are well covered and connected by NG. The electrochemical performance confirms that LiFePO₄ modified by 20% N-doped graphene (named LFP/NG-4) displays a perfect specific capacity of 166.6 mAh·g^?1 at a rate of 0.2C and can reach 125 mAh·g^?1 at a rate of 5 C. Electrochemical impedance spectroscopy (EIS) results illustrate that the charge transfer resistance value of the LFP/NG-4 composite is only 58.6 Ω, which is very low compared with LiFePO₄. Cyclic voltammetry (CV) tests indicate that the addition of 20% N-doped graphene can effectively reduce electrode polarization and improve reversibility. The LFP/NG-4 composite with a three-dimensional conductive network structure can be regarded as a promising cathode material for Li-ion batteries.