碳保护固相合成Li_3V_2(PO_4)_3/C工艺及其电化学性能研究

在碳粉填埋保护条件下,分别以草酸、硝酸锂、磷酸二氢铵和偏钒酸铵为碳源、锂源、磷源和钒源,采用固相合成法,在900,1 000,1 100℃下制备了Li3V2(PO4)3/C正极材料。X射线衍射、扫描电子显微镜和充放电分析测试表明,900,1 000,1 100℃焙烧均可获得较纯且粒径为50 nm~3μm的Li3V2(PO4)3/C;随焙烧温度升高,合成产物中的LiVP2O7杂质相含量下降;在0.1 C充放电倍率下,900,1 000,1 100℃合成的Li3V2(PO4)3/C充放电30次后容量保持率分别为80%,98.5%和95.7%。     

聚阴离子型锂离子电池正极材料Li_3V_2(PO_4)_3的研究进展

与LiFePO4相比,单斜结构的磷酸钒锂(Li3V2(PO4)3)具有更高的Li+扩散系数和更高的放电电压、能量密度和高的比容量,已成为锂离子电池正极材料的研究热点之一。综述了近年来Li3V2(PO4)3的主要合成方法、充放电机理及其掺杂改性的研究现状,并且对Li3V2(PO4)3的发展趋势进行了展望。     

锂离子电池Li_3V_(2-x)Al_x(PO_4)_3正极材料合成及性能研究

以V_2O_5、LiOH、NH_4H_2PO_4、Al(OH)_3和柠檬酸为原料采用溶胶-凝胶法合成V位掺杂Al3+的Li_3V_(2-x)Al_x(PO_4)_3/C复合材料,仔细研究Al3+掺杂对磷酸钒锂材料电化学性能的影响,确定最佳的Al掺杂量。同时借助各种分析手段(如XRD、SEM、TG-DTA)对掺杂后Li_3V_(2-x)Al_x(PO_4)3/C材料结构变化进行探究,深入理解V位掺杂对电化学性能产生作用的内在机理。Li_3V_2-xAlx(PO_4)_3/C(x=0,0.02,0.05,0.1,0.15,0.2)首次放电比容量分别为103.7 m Ah/g,105.7 m Ah/g,108.4 m Ah/g,141.1 m Ah/g,130.1 Ah/g,124.8 m Ah/g。在一定范围内,随着Al3+量的提高,相应的Li3V2-xAlx(PO4)3/C的首次放电比容量也不断的增加。     

电池正极材料Li3V2-2x/3Mnx（PO4）3/C的制备及性能研究

以V2O5、NH4H2PO4、Li2CO3、(CH3COO)2Mn.4H2O原料,以葡萄糖和抗坏血酸为复合还原剂及碳源,通过常温还原-低温烧结法制备锂离子电池正极材料Li3V(2-2x/3)Mnx(PO4)3/C(x=0,0.03,0.06,0.09,0.12)。通过X射线衍射(XRD),扫描电镜(SEM),恒电流充放电测试对该正极材料的物相、结构、微观形貌以及电化学性能进行了表征。结果表明,Mn2+的掺杂对磷酸钒锂电化学性能的发挥影响很大,其中当锰掺杂量x=0.09时材料表现出最佳的电化学性能,0.2 C倍率条件下首次放电比容量131 mAh/g,循环50次后容量衰减仅为4.02%。     

Co掺杂对Na3V2(PO4)2F3材料结构和电化学性能的影响

首次采用溶胶-凝胶法制备Co掺杂Na_3V_(2-x)Co_x(PO_4)_2F_3(x=0.00,0.05,0.1,0.2)钠离子电池正极材料。使用XRD、FE-SEM、恒流充放电和交流阻抗测试分析了Co掺杂对Na_3V_2(PO_4)_2F_3材料的结构和电化学性能的影响。结果表明,Co~(2+)取代V~(3+)可在Na_3V_2(PO_4)_2F_3晶格内产生V~(3+/4+)混合电价从而提高Na_3V_2(PO_4)_2F_3材料的电子电导率,具有更大离子半径的Co~(2+)替换V~(3+)可增大Na_3V_2(PO_4)_2F_3晶胞体积,扩宽钠离子传输通道,从而提高其离子电导率。此外,Co掺杂可有效减小Na_3V_2(PO_4)_2F_3电极的电荷转移阻抗。电化学测试结果表明,x=0.1时的Na_3V_(1.9)Co_(0.1)(PO_4)_2F_3电极展现出了最优异的电化学性能,0.1C时的首次放电比容量为111.3mAh·g~(-1),5C时首周可逆容量为91.9mAh·g~(-1),循环80次的容量保持率为70%。     

以溶液法制备的钠掺杂锂离子电池正极材料Li3-xNaxV2(PO4)3/C

以溶液法为制备方法、以葡萄糖为碳源合成了一种钠离子掺杂的锂离子电池正极材料Li_3-xNa_xV₂（PO₄）₃/C（x=0、0.01、0.03、0.05、0.07）。XRD结果显示组成相为单斜晶型,与标准Li₃V₂（PO₄）₃衍射峰完全一致。微量钠掺杂并未改变产物的相组成与晶体结构,但使得晶胞参数有所变化,这种变化有利于提高锂离子的扩散系数。SEM与TEM谱图显示材料颗粒基本为近似椭圆形,粒径分布均匀,碳包覆层完整。充放电测试显示Li_2.97Na_0.03V₂（PO₄）₃/C试样的倍率性能最好,在12C倍率下放电比容量约为100mAh/g,循环伏安测试也证明该试样的锂离子扩散系数较高,比纯相Li₃V₂（PO₄）₃提高了约2个数量级。     

碳保护固相合成Li3V2（PO4）3/C工艺及其电化学性能研究

在碳粉填埋保护条件下,分别以草酸、硝酸锂、磷酸二氢铵和偏钒酸铵为碳源、锂源、磷源和钒源,采用固相合成法,在900,1 000,1 100℃下制备了Li3V2（PO4）3/C正极材料。X射线衍射、扫描电子显微镜和充放电分析测试表明,900,1 000,1 100℃焙烧均可获得较纯且粒径为50 nm~3μm的Li3V2（PO4）3/C;随焙烧温度升高,合成产物中的LiVP2O7杂质相含量下降;在0.1 C充放电倍率下,900,1 000,1 100℃合成的Li3V2（PO4）3/C充放电30次后容量保持率分别为80%,98.5%和95.7%。     

HPW/Ti_3(PO_4)_4的制备及其催化酯化性能

制备了系列磷酸钛原位负载不同含量x(wt%)磷钨酸H3PW12O40(HPW)的酯化催化剂HPW-x/Ti3(PO4)4,通过催化丙酸与正戊醇的酯化反应考察了其催化酯化性能,并采用IR分析对催化剂进行了表征。结果表明,300℃焙烧2h条件下,磷钨酸含量15%的催化剂HPW-15/Ti3(PO4)4具有最佳的催化活性,催化合成低碳链羧酸酯丙酸戊酯的适宜条件为:0.2mol丙酸,催化剂用量0.4g,n(正戊醇)∶n(丙酸)=1.6∶1,反应时间4h,酯化率达97.7%。该催化剂循环利用6次酯化率减小幅度不足7.5%。该催化剂对长碳链羧酸酯庚酸戊酯的合成循环利用6次酯化率为93.2%～83.5%。     

NaTi2(PO4)3的合成及电化学性能测试

以Na_2CO_3、TiO_2和NH_4H_2PO_4为原料,采用球磨和高温烧结的方法合成了NaTi_2(PO_4)_3材料,研究发现烧结温度对于材料的生成和结晶性具有显著影响,烧结温度越高,所合成的NaTi_2(PO_4)_3相越纯,得到的产率也越高。测试了制备的NaTi_2(PO_4)_3材料作为钠离子电池负极材料的电化学性能,其比容量0.1 C倍率下可达到107 mAh/g。     

聚阴离子型锂离子电池正极材料Li3V2（PO4）3的研究进展

与LiFePO4相比,单斜结构的磷酸钒锂（Li3V2（PO4）3）具有更高的Li＋扩散系数和更高的放电电压、能量密度和高的比容量,已成为锂离子电池正极材料的研究热点之一.综述了近年来Li3 V2（PO4）3的主要合成方法、充放电机理及其掺杂改性的研究现状,并且对Li3V2（PO4）3的发展趋势进行了展望.     

锂离子电池正极材料磷酸钒锂的研究进展

Li3V2(PO4)3因具有优异的电化学性能,成为目前倍受关注的锂离子电池正极材料。介绍了单斜结构磷酸钒锂[α-Li3V2(PO4)3]的结构及充放电机理,概述了几种主要的制备Li3V2(PO4)3方法,包括了固相法、溶胶-凝胶法、微波法。同时阐述了几种主要方法用来对Li3V2(PO4)3电化学性能进行改性研究,对该材料的发展前景进行了展望。     

锂离子电池正极材料Li3V2（PO4）3研究进展

锂离子电池正极材料Li3V2（PO4）3具有环保、安全性能好、成本低廉、结构稳定、电化学性能较好等特点,吸引了研究者的广泛关注.本文对Li3V2（PO4）5的结构、制备方法和电化学性能的研究现状进行了综述,并对其进行了展望.Li3V2（PO4）5很有希望产业化,进而取代目前市场上的主流材料LiCoO2。     

Scalable synthesis of Na3V2(PO4)3/C with high safety and ultrahigh-rate performance for sodium-ion batteries

NASICON-type Na₃V₂(PO₄)₃ is a promising electrode material for developing advanced sodium-ion batteries. Preparing Na₃V₂(PO₄)₃ with good performance by a cost-effective and large-scale method is significant for industrial applications. In this work, a porous Na₃V₂(PO₄)₃/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method. The Na₃V₂(PO₄)₃/C cathode displayed specific capacities of 113.4 mAh·g^-1, 107.0 mAh·g^-1 and 87.1 mAh·g^-1 at 0.1 C, 1 C and 10 C, respectively. For the first time, the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na₃V₂(PO₄)₃/C electrodes are successfully fabricated. The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83% at 0 ℃ owing to the rapid sodium ion migration ability and structural stability of Na₃V₂(PO₄)₃/C. Moreover, the thermal runaway features are revealed by accelerating rate calorimetry (ARC) test for the first time. Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries. Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na₃V₂(PO₄)₃/C have a prospect of practical application in high safety requirement fields.     

焙烧条件对Na3V2(PO4)3/C的制备及储锌性能影响

采用喷雾干燥法合成了Na₃V₂(PO₄)₃(NVP)前驱体,然后经过高温煅烧得到水系锌离子电池正极复合材料Na₃V₂(PO₄)₃/C(NVP/C),考察了煅烧温度和煅烧时间对NVP/C性能的影响。通过XRD、SEM和BET对样品结构和形貌进行了表征,通过循环伏安和充放电测试了样品的电化学性能。结果表明,不同煅烧温度和煅烧时间制备样品均为纯相的NVP/C,且并没有改变NVP/C的晶体结构;煅烧温度过高或煅烧时间过长会导致晶粒尺寸增大,性能迅速衰减。NVP/C制备最佳条件为煅烧温度700℃、煅烧时间8 h,在该条件下所制备的NVP/C(记为NVP/C-700-8)形貌更为规整,结晶性良好,具有较小的阻抗以及更好的离子扩散能力,进而表现出最佳的电化学性能。在0.1 A/g电流密度下表现出最佳的放电比容量(122.4 mA·h/g)。在1.0 A/g电流密度下经过200圈循环后放电比容量仍高达103.9 mA·h/g。     

Electrochemical performance of nanocrystalline Li3V2(PO4)3/carbon composite material synthesized by a novel sol–gel method

A novel sol–gel method based on V₂O₅·nH₂O hydro-gel was developed to synthesize nanocrystalline Li₃V₂(PO₄)₃/carbon composite material. In this route, V₂O₅·nH₂O hydro-gel, NH₄H₂PO₄, Li₂CO₃ and high-surface-area carbon were used as starting materials to prepare precursor, and the Li₃V₂(PO₄)₃/carbon was obtained by sintering precursor at 750 °C for 4 h in flowing argon. The sol–gel synthesis ensures homogeneity of the precursors and improved reactivity. The sample was characterized by XRD, SEM and TEM. X-ray diffraction results show Li₃V₂(PO₄)₃ sample is monoclinic structure with the space group of P2₁/n. The TEM image indicates that the Li₃V₂(PO₄)₃ particles modified by conductive carbon are about 70 nm in diameter. The Li₃V₂(PO₄)₃/carbon system showed that the discharge capacities in the first and 50th cycle are about 155.3 and 143.6 mAh/g, respectively, in the range of 3.0–4.8 V. The sol–gel method is fit for the preparation of Li₃V₂(PO₄)₃/carbon composite material which may offer some favorable properties for commercial application.     

Insight into cations substitution on structural and electrochemical properties of nanostructured Li2FeSiO4/C cathodes

Structural instability is the major obstacle in the Li₂FeSiO₄/C cathode during charge and discharge process, which can be improved by the substitution of cations in the host cage. In this study, the transition metal ions with different valence (Ag¹⁺, Zn²⁺, Cr³⁺, and Ti⁴⁺) have been substituted in Li₂FeSiO₄/C via modified sol-gel method and the impact on the structural, electrical, and electrochemical performances has been systematically explored. The Rietveld-refined XRD pattern and HR-TEM (SAED) result reveal that all the prepared samples maintain orthorhombic structure (S.G- Pmn2₁). The FE-SEM and TEM micrographs of bare and doped Li₂FeSiO₄/C display nanoparticle formation with 20-40 nm size. Among different cation-substituted silicates, Li₂Fe_0.9Ti_0.1SiO₄/C sample exhibits an excellent total conductivity of 1.20 × 10⁻⁴ S cm⁻¹ which is one order of magnitude higher than the bare Li₂FeSiO₄/C sample. The galvanostatic charge-discharge curves and cyclic voltammetric analysis reveal that the Li₂Fe_0.9Ti_0.1SiO₄/C material provides an excellent initial specific capacity of 242 mAh g⁻¹ and maintains a capacity of 226 mAh g⁻¹ after 50 cycles with capacity retention of 93.38%. The Ti doping is a promising strategy to overcome the capacity fading issues, by preventing the structural collapse during Li-ion intercalation/de-intercalation processes in the Li₂FeSiO₄/C electrode through the strong hybridization between the 3d and 4s orbitals in titanium and 2p orbital in oxygen.     

NaTi2(PO4)3纳米晶的室温固相合成及表征

以Ti(SO4)2和Na3PO4·12H2O为原料,在表面活性剂聚乙二醇(PEG)-400的存在下,进行固相反应,然后将混合物在60 ℃下保温4 h, 接着用水洗去混合物中的可溶性无机盐并于100 ℃下干燥,即得纳米晶NaTi2(PO4)3 的前驱体,将前驱体煅烧可得NaTi2(PO4)3纳米晶.前驱体和它的煅烧产物通过TG/DTA,IR,XRD和UV-vis表征.结果表明,500 ℃下煅烧2 h得到的产物为无定形结构,700 ℃下煅烧2 h得到具有高结晶度的斜方NaTi2-(PO4)3[空间群R-3c(167)],其平均一次粒径为47 nm.前驱体及煅烧产物均具有强的紫外吸收能力.     

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。