用不同碳源对LiFePO_4的碳包覆改性

采用共沉淀方法结合原位碳包覆合成了LiFePO4/C复合正极材料.对碳化过程和包覆LiFePO4进行了研究.结果表明:在不同碳源的热解过程中,由于分子量和结构的不同,分解温度和碳化产物的结构也不相同;不同碳源的碳包覆对LiFePO4的晶体结构有一定的影响,而且由于碳包覆层结构的差异所包覆改性的LiFeO4表现出不同的电化学性能.文中还讨论了不同碳源对碳包覆后LiFePO4/C的电化学性能的影响.     

苯胺用量对固相法合成LiFePO_4/C电化学性能的影响

通过聚苯胺包覆法制备LiFePO4/C,研究了苯胺用量对LiFePO4/C电化学性能的影响。采用X射线衍射(XRD)测试材料结构并用扫描电镜(SEM)和透射电镜(TEM),观察材料形貌及碳层包覆情况。结果表明:该方法制得的LiFePO4结晶度高并且具有规整的球状结构,粒径在50~80nm之间,碳层厚度约为2.5nm。经电化学性能测试发现:在相同合成工艺下,苯胺用量对合成的LiFePO4/C的电化学性能有很大影响.当苯胺加入量为0.5mL时所得LiFePO4/C(6mmol)的电化学性能最佳,0.2C下首次放电比容量可达161.6mAh·g-1,5C下放电比容量可达112.2mAh·g-1,且在5C下循环300次无明显衰减。     

掺碳LiFePO4的合成及性能研究

为提高LiFePO4的电化学性能,通过固相合成法制备了掺碳的LiFePO4正极材料,并用XRD、SEM、电化学工作站及充放电测试等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,0.1C首次放电比容量为141.9mAh/g,循环50次后容量下降了11.2mAh/g,以1C倍率首次放电比容量为126.5mAh/g,循环50次后容量保持率为87.2%.     

产综研合成LiFePO4超微粒子

产业技术综合研究所和日本学术振兴会利用包覆有碳膜、有望作锂离子电池正极材料的橄榄石（结晶结构的一种）LiFePO4（磷酸铁锂）,成功合成了纳米级超微粒子。LiFePO4因价格低,作为电动汽车大型锂离子电池的正极材料备受关注,但使用这种材料的电池存在如果高倍率（短时间内通过大电流）充放电,其容量就会急剧下降的问题。     

锂离子电池正极材料Li(MnxFe1-x)PO4的合成及电化学性能的研究

采用高温固相法合成了组成为Li（MnxFe1-x）PO4（x=0、0．2、0．4、0．6、0．8、1．0）的锂离子电池正极材料。通过对合成样品的XRD、SEM及电化学性能（循环性能,大电流放电性能）的研究表明,少量Mn的掺杂未影响到LiFePO4的晶体结构,但显著改善了它的电化学性能。Li（Mn0.2Fe0.8）PO4与LiFePO4材料相比有更好的电化学性能,在低放电倍率（电流密度为20mA／g）时,放电容量为150mAh／g,当放电倍率提高到2C时,放电容量仍可达113mAh／g,且循环性能良好。     

基于铁粉还原的LiFePO4/C合成路径及其电化学性能研究

使用还原铁粉作为铁源, 通过超细球磨与喷雾干燥、高温煅烧技术制备了球形微纳米LiFePO₄/C复合材料。使用DSC/TG以及XRD对LiFePO₄/C复合材料的形成过程进行了分析; 使用SEM、穆斯堡谱仪等手段对复合材料进行分析; 使用电化学工作站、容量测试仪对其充放电行为进行分析。研究发现, 使用该合成技术路线, 在500~700℃下能够合成LiFePO₄/C复合材料。获得的LiFePO₄/C复合材料具有规则的球形外貌, 平均尺寸4~5 μm。该微米颗粒由200 nm左右细小颗粒组成, 颗粒间具有纳米尺寸微孔。穆斯堡谱仪测试结果表明, 复合材料中Fe处于+2价的价态。复合材料在1C倍率下表现出稳定的充放电行为, 平均比容量在156 mAh/g, 300次循环后, 容量保持率为92.8%。该技术制备的LiFePO₄/C复合材料具有潜在的应用价值。     

锂离子电池正极材料LiFePO4的研究进展

磷酸铁锂用作锂离子电池正极材料是当前研究热点之一,由于其性能、价格、安全和环境优势,其应用前景十分看好.首先对晶体结构进行了描述,并综述了近年来各种制备LiFePO4的方法,包括高温固相合成,机械化学法等"固相方法"以及溶胶-凝胶法等"软化学合成法",对各种方法的优缺点进行了分析对比.并且对LiFePO4的改性研究进行了简单的探讨.     

磷酸亚铁锂核壳结构材料的制备和电化学性能

制备热解炭/磷酸亚铁锂和纳米炭纤维/磷酸亚铁锂核壳结构材料,研究了电化学性能,结果表明,热解炭和纳米炭纤维包覆层能有效地降低磷酸亚铁锂材料的电阻率,大大提高材料的充放电容量和循环稳定性,与热解炭相比,纳米炭纤维具有一维结构和优异的力学性能,更适于作为磷酸亚铁锂电极材料的高效导电剂.     

不同锂源水热法合成LiFePO4的研究进展

LiFePO4具有较高的能量密度、较好电化学性能和热力学稳定性而成为最为热门、应用最为广泛的锂离子电池正极材料。其合成方法有很多,其中的水热法具有反应快、操作简单、产品形貌易于控制且颗粒粒径小等优点而备受关注。用不同的锂源合成出来的产品的形貌和性能也不一样。现分别以磷酸锂、碳酸锂、醋酸锂、氢氧化锂等化合物为锂源对水热法合成LiFePO4进行了一定探讨,并综述了各自利用水热法合成磷酸铁锂的研究进展情况。     

A review for the synthesis methods of lithium vanadium phosphate cathode materials

Monoclinic Lithium vanadium phosphate [Li₃V₂(PO₄)₃, LVP] has been extensively studied because of its attractive electrochemical properties including high specific energy, high specific capacity (133 mAh g^?1 in 3.0–4.3 V, 197 mAh g^?1 in 3.0–4.8 V), high working voltage (4.0 V), good cycle stability and low price used in rechargeable lithium ion batteries (LIBs). However, the inherent defects such as low conductivity still restrict its practical application in high performance LIBs. Various synthesis methods have been developed in order to improve electrochemical performances of LVP. The results show that the different synthesis methods have great influence on the properties of LVP cathodes for LIBs, so the study on the synthesis method of high performance LVP will continue to be in great demand. This review briefly introduces the present synthesis methods of LVP, such as high-temperature solid-state method, sol–gel method, hydrothermal method, etc. Apart from already established conventional routes, the novel preparation technologies are also mentioned. Moreover, the synthesis mechanism and electrochemical performances of Li₃V₂(PO₄)₃ cathode materials synthesized by each synthetic method are reviewed. Finally, the directions for further research and prospective applications for the LVP materials are proposed.     

正极材料磷酸铁锂的改性研究进展

介绍了锂离子电池正极材料磷酸铁锂的改性方法,综述了近年来锂离子电池正极材料磷酸铁锂的研究进展.重点叙述了金属粒子掺杂改性及碳包覆改性方面的研究成果.在综述各改性方式方面进展的基础上,指出了现阶段研究上对改性方式的理论体系建立方面所存在的问题,并结合作者研究小组的研究,对磷酸铁锂材料的未来研究方向进行了展望.     

新型锂电池正极材料——蒽醌/介孔炭寄生型复合物

将9,10-蒽醌（AQ）通过升华法填充在介孔炭（MC）的孔中,制备出蒽醌/介孔炭寄生型复合物。用TG/DSC、SEM、氮吸附等方法对介孔炭及复合材料进行了表征,应用恒流充放电、循环伏安法、交流阻抗等测试手段对复合材料的电化学性能进行了测试。结果表明炭/醌复合电极的比容量和循环性能较蒽醌电极有了很大程度的提高。其中蒽醌填充量为75%的复合材料首次放电比容量达到216mAh/g,50次循环之后,比容量仍有76mAh/g,是蒽醌电极比容量的2倍。     

A new sodium iron phosphate as a stable high-rate cathode material for sodium ion batteries

Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications. However, due to the large size of Na⁺, most Na⁺ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation, resulting in unsatisfactory rate and cycling performances. Herein, we report a new type of sodium iron phosphate (Na_0.71Fe_1.07PO₄), which exhibits an extremely small volume change (~ 1%) during desodiation. When applied as a cathode material for SIBs, this new phosphate delivers a capacity of 78 mA·h·g^?1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C. In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging. The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.

Open image in new window

     

溶胶-凝胶法合成磷酸铁锂正极材料

以FePO4·4H2O、LiOH·H2O、草酸为原料,以葡萄糖为碳源,采用溶胶-凝胶法合成磷酸铁锂正极材料。利用X射线衍射(XRD)、扫描电镜(SEM)等方法进行表征,并将材料组装成电池研究其电化学性能。结果表明:以葡萄糖为碳源,采用溶胶-凝胶法合成磷酸铁锂正极材料具有单一的橄榄石型晶体结构,充放电平台平稳。葡萄糖添加量为5.9%时,材料的充放电比容量和循环性能较高,室温下,0.1C和0.2C首次放电比容量达143.3mA·h/g和133.7mA·h/g,循环50次后仍保持在134.2mA·h/g和124.5mA·h/g。     

Modified solid-state reaction synthesized cathode lithium iron phosphate (LiFePO4) from different phosphate sources

A modified solid-state method was used to prepare LiFePO4. With the aid of deionized water, a mixture containing Fe2O3, NH4H2PO4 (or (NH4)2HPO4), LiOH, glucose and oxalic acid was prepared into fluffy powders, which were heated in a carbon-coated crucible at 700 degrees C for 3 hours to synthesize LiFePO4 without any inert gas flow. For the first time, the roles of NH4H2PO4 and (NH4)2HPO4 on the preparation of LiFePO4 were systematically investigated. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), revealing that the crystallinity of the LiFePO4 sample prepared from NH4H2PO4 is superior to that prepared from (NH4)2HPO4 and the particle size of the sample prepared from NH4H2PO4 is smaller than that prepared from (NH4)2HPO4. The specific capacity, cycle property and rate capabilities were also compared between the as-prepared LiFePO4 samples. A better electrochemical performance was observed in the sample prepared from NH4H2PO4.     

稀土元素掺杂对LiFePO4正极材料电导率和电化学性能的影响

橄榄石型LiFePO4因其安全性能突出、价格低廉、绿色环保、循环性能优良等优点已成为最具应用潜力的新一代锂离子电池用正极材料。由于LiFePO4电子导电能力较低，因此其充放电容量有待进一步改进。采用水热合成法制备了纯LiFePO4和稀土元素La、Ce、Nd掺杂的LiFePO4纳米粉末。研究表明，掺杂后材料的电导率比未掺杂试样高2-3个数量级。电化学测试显示掺杂后LiFePO4的首次充放电容量提高2-5倍，其中掺Nd的效果最好。水热合成产物经高温碳包覆后，掺杂的LiFePO4/C复合材料也比纯的LiFePO4/C复合材料的放电容量高，表明掺杂稀土元素能有效提高橄榄石型LiFePO4的充放电容量。     

A multiphase sodium vanadium phosphate cathode material for high-rate sodium-ion batteries

The unsatisfactory rate capability and poor cycling stability at high rate of sodium-ion batteries(SIBs) have impeded their practical applications. Herein, a Na₃V₂(PO₄)₃/Na₃V₃(PO₄)₄ multiphase cathode materials for high-rate and long cycling SIBs was successfully synthesized by regulation the stoichiometric ratio of raw materials. The combined experiment and simulation results show that the multiphase materials consisted of NASICON structural phase Na3V2(PO4)3 and layered structure phase Na₃V₃(PO₄)₄, possess abundant phase boundaries. Electrochemical experiments demonstrate that the multiphase materials maintain a remarkable reversible capacity of 69.0 mA h g^-1 even at an ultrahigh current density of 100 C with a high capacity retention of 81.25 % even after 10,000 cycles. Na₃V₂(PO₄)₃/Na₃V₃(PO₄)₄ electrode exhibits a higher working voltage, superior rate capability and better cycling stability than Na₃V₂(PO₄)₃ electrode, which indicates that the introduction of second phase can be an effective strategy for the development of novel cathode materials for SIBs.     

水热合成磷酸铁锂粉体的形貌控制

以氢氧化锂、硫酸亚铁、磷酸为原料,采用水热法合成磷酸铁锂.研究了表面活性剂,加料温度、降温速度对产物形貌及性能的影响.用X射线衍射(XRD)、扫描电子显微镜(SEM)和激光粒度仪、恒流充放电测试表征材料的性能.结果表明:表面活性剂选择CTAB,40℃加料,降温速度选择5℃·min-1,可以得到平均粒径为1.5μm的粉体,在30℃的环境温度下,材料0.2C、1C和5C首次充放电比容量分别为157、152和136mAh·g-1,经过35次5C倍率充放电循环后,比容量无衰减.     

Electrosprayed polyaniline as cathode material for lithium secondary batteries

Doped polyaniline with LiPF₆ is electrosprayed onto aluminum foil using electrospinning technique, and evaluated as cathode active material for application in room-temperature lithium batteries. Doping level is characterized using FTIR and UV-vis spectroscopy. In FTIR Spectra, characteristic peaks of PANI are shifted to lower bands as a result of doping which indicates the effectiveness of doping. Doping level is also confirmed by UV-vis spectra. Surface morphology of the cathode is studied using scanning electron microscope. Electrochemical evaluation of the cell using electrosprayed PANI as cathode show good cycling properties. The cell delivers a high discharge value of 142.5 mAh/g which is about 100% of theoretical capacity, and the capacity is lowered during cycle and reached 61% of theoretical capacity after 50 cycles. The cell delivers a stable but lower discharge capacity at higher C-rates.