全固态锂离子电池V2O5阴极薄膜研究进展

全固态薄膜锂离子电池由于具有能量密度高、循环性能和安全性能好等优点已成为目前研究的热点.其中,V2O5薄膜是锂离子电池中一种备受重视的阴极材料.对V2O5薄膜的离子扩散系数以及结构特点做了简单介绍,重点评述了V2O5薄膜电极制备和电化学性能研究方面的发展近况,并对今后的发展方向进行了展望.     

氧化钒作锂离子电池正极材料的研究进展

V_2O_5具有独特的层状结构,适合于锂离子的存储,与传统的锰酸锂、钴酸锂、磷酸铁锂等正极材料相比,具有高的理论比容量、功率密度以及价格低廉、原材料丰富等优势,在作为锂离子电池正极材料方面备受关注。但V_2O_5低的固有电导率及锂离子扩散系数,导致其容量保持率低和倍率性能差;此外,充放电过程中反复的相变会引起结构的不稳定,而且氧化钒会部分溶于电解液,因此表现出差的循环性能。正是由于这些制约因素的存在,对V_2O_5的固有缺陷进行改性研究以提高氧化钒正极材料的电化学性能成为重要的研究热点。将氧化钒进行纳米化以增大比表面积和缩短离子扩散距离,同时通过复合、掺杂改性等方法提高材料的导电性和循环稳定性,从而使V_2O_5正极材料表现出优异的电化学性能成为可能。文章从氧化钒电极材料纳米化,在纳米化的基础上复合导电材料,调节工作电压窗口,掺杂金属离子这四类方法阐述对氧化钒电化学性能的改善,以及各种方法对电极电化学性能的影响。     

静电纺丝法制备氧化锰纳米丝电极及其电化学性能

利用静电纺丝技术成功制备了φ60～80nm的氧化锰纳米纤维丝,并构建了三维纳米丝网状结构电极,应用于锂离子二次电池. 使用扫描电子显微镜、X射线衍射、循环伏安和电池充放电等研究手段,表征了纳米纤维丝的结构和电化学性能. 研究结果发现:氧化锰构建的纳米丝在嵌锂和脱锂的过程中没有出现纳米纤维丝的结构塌陷问题,在高能量密度下表现出较大的可逆循环容量,放电容量达到160mAh/g. 经过50次循环后, 容量可达132.5mAh/g, 平均每次循环的容量衰减在1%以下. 这些结果表明了氧化锰纳米纤维丝可作为三维锂离子电池中的阴极材料.     

水溶液锂离子电池电极材料的发展概况

通过对水溶液锂离子电池电极材料的制备方法、结构、电化学性能、充放电过程等方面的论述,总结了近年来水溶液锂离子电池电极材料的研究状况,并对存在的问题进行了分析。探讨了采用不同化合物、不同制备方法和改性方法来提高其比容量和循环稳定性的可能性。     

Na+掺杂V2O5电极材料的制备及其储锌性能

针对V2O5电子传输慢、离子 扩散受阻以及循环性能不稳定等问题,通过一步水热法制备Na0.4V2O5纳米粉体材料,并作为锌离子电池正极材料。结果表明,Na0.4V2O5电极的倍率性能和循环稳定性均优于V2O5电极。Na+掺杂通过改变V2O5的层状结构,改善V2O5的电子传输和离子扩散,从而提高电极电导特性和结构稳定性。Na0.4V2O5电极是倍率性能和循环稳定性优良的电极材料。     

Mn2+掺杂对V2O5纳米材料结构与电化学性能的影响

以V2O5粉末、H2O2和Mn(CH3COO)2·4H2O为原料,采用水热法制备了纳米结构的锂离子电池阴极材料Mnx V2O5。运用X射线衍射(XRD)、X射线光电子能谱分析(XPS)和扫描电镜(SEM)测试对制备的材料进行结构和形貌表征,并利用充放电测试和交流阻抗测试研究了样品的电化学性能。结果表明:随着锰掺杂量的增加,V2O5的正交晶型层状结构未发生改变,其层间距逐渐扩大,形貌由纳米短棒状向纳米带簇状变化。电化学测试表明:Mn2+掺杂提高了V2O5的电化学性能,其首次充放电效率由70.8%提高到90%以上;Mn0.01V2O5经过90次充放电循环后,其容量仍为192.2 mAh/g。Mn2+掺杂对V2O5电极材料的离子电导率有影响,Mn0.02V2O5离子电导率由未掺杂时的6.27×10-4S/cm提高到1.58×10-3S/cm。     

纳米Al2O3包覆LiFePO4/C正极材料的结构和电化学性能（英文）

主要研究了纳米氧化铝包覆对LiFePO4/C复合正极材料结构和电化学特性的影响。采用溶胶凝胶方法把纳米氧化铝包覆在商业LiFePO4/C颗粒表面。研究了Al2O3包覆层的量对LiFePO4电极在室温和高温充放电性能的影响。结果显示:2wt%Al2O3包覆层能有效增加电池的循环容量,能延缓电池在高温条件下充放电的容量衰减,减小电极的界面阻抗。这归因于氧化铝包覆层对磷酸铁锂晶粒的表面起保护作用,减少电解液对磷酸铁锂晶粒表面的腐蚀,从而改善循环过程中磷酸铁锂的表面结构的完整和稳定,确保锂离子扩散通道的畅通。     

Si基锂离子电池负极材料的纳米化和合金化

Si作为一种新型锂离子电池负极材料,具有理论比容量高、来源丰富、成本低廉、安全性能好等优点,近年来备受关注。但其在充放电过程中会产生巨大的体积变化而使得材料粉化严重,导致循环过程中容量迅速衰退,难以满足实用化的需求。纳米化和合金化是改善Si负极材料的有效途径,纳米化能够有效缓解材料嵌脱锂过程中体积变化造成的机械应力、缩短锂离子的迁移距离,从而明显改善Si基材料的电化学循环稳定性能;合金化可以减小材料在脱嵌锂过程的体积变化率、提高材料的电导率,也可以延长Si基材料的循环寿命。此外,Si合金的振实密度高、制备工艺简单,有利于规模化应用。在简要综述最近5年在Si基锂离子电池负极材料的纳米化和合金化方面的研究进展的同时,重点关注了不同纳米结构和合金化方法对其电化学储锂容量、倍率性能和循环稳定性能的影响。     

锂离子电池负极材料球形钛酸锂的合成及性能

以3.98mol/L的四氯化钛为前驱体溶液,采用内凝胶法制备了具有尖晶石结构的球形钛酸锂(Li4Ti5O12)粉末。通过XRD、SEM及电化学性能测试等分析手段表明,合成的Li4Ti5O12材料均为纳米一次粒子(晶粒)组成的球形二次粒子(颗粒),且具有较大的比表面积。以这种流动性好、粒径分布均匀、结晶度好的球形钛酸锂为正极材料和Li片为负极材料组成的锂离子电池具有平稳的充放电电压平台和优异的循环性能。在1.0~2.5V充放电,其首次放电容量为173.8mAh/g,经30次充放电循环后,其放电比容量仍有170.2mAh/g。     

纳米磷酸铁锂的研究进展

锂离子电池磷酸铁锂(LiFePO4)正极材料具有比能量大、工作电压高、循环寿命长、无记忆效应、对环境友好等突出优点,但LiFePO4本身低的电子电导率和锂离子扩散系数阻碍了其在生产生活中的大规模应用,而制备纳米LiFePO4作为电极材料并进行改性可以改善其电化学性能。本文主要综述了国内外合成纳米LiFePO4的不同方法及其电化学性能,并介绍了当前LiFePO4发展所遇到的问题,指出了锂离子电池今后发展的主要方向。     

High‐Performance Aqueous Zinc–Ion Battery Based on Layered H2V3O8 Nanowire Cathode

Rechargeable aqueous zinc–ion batteries have offered an alternative for large‐scale energy storage owing to their low cost and material abundance. However, developing suitable cathode materials with excellent performance remains great challenges, resulting from the high polarization of zinc ion. In this work, an aqueous zinc–ion battery is designed and constructed based on H₂V₃O₈ nanowire cathode, Zn(CF₃SO₃)₂ aqueous electrolyte, and zinc anode, which exhibits the capacity of 423.8 mA h g⁻¹ at 0.1 A g⁻¹, and excellent cycling stability with a capacity retention of 94.3% over 1000 cycles. The remarkable electrochemical performance is attributed to the layered structure of H₂V₃O₈ with large interlayer spacing, which enables the intercalation/de‐intercalation of zinc ions with a slight change of the structure. The results demonstrate that exploration of the materials with large interlayer spacing is an effective strategy for improving electrochemical stability of electrodes for aqueous Zn ion batteries.     

Water‐Pillared Sodium Vanadium Bronze Nanowires for Enhanced Rechargeable Magnesium Ion Storage

Owing to the advantages of high safety, low cost, high theoretical volumetric capacities, and environmental friendliness, magnesium‐ion batteries (MIBs) have more feasibility for large‐scale energy storage compared to lithium‐ion batteries. However, lack of suitable cathode materials due to sluggish kinetics of magnesium ion is one of the biggest challenges. Herein, water‐pillared sodium vanadium bronze nanowires (Na₂V₆O₁₆·1.63H₂O) are reported as cathode material for MIBs, which display high performance in magnesium storage. The hydrated sodium ions provide excellent structural stability. The charge shielding effect of lattice water enables fast Mg²⁺ diffusion. It exhibits high specific capacity of 175 mAh g^?1, long cycle life (450 cycles), and high coulombic efficiency (≈100%). At high current density of 200 mA g^?1, the capacity retention is up to 71% even after 450 cycles (compared to the highest capacity), demonstrating excellent long‐term cycling performance. The nature of charge storage kinetics is explored. Furthermore, a highly reversible structure change during the electrochemical process is proved by comprehensive electrochemical analysis. The remarkable electrochemical performance makes Na₂V₆O₁₆·1.63H₂O a promising cathode material for low‐cost and safe MIBs.     

Design and synthesis of inorganic–organic hybrid microstructures

Vanadium oxide–polypyrrole (V₂O₅–PPy) hybrid aerogels were prepared using three different strategies. These approaches were focused on either sequential or consecutive polymerization of the inorganic and organic networks. The hybrid microstructure differed greatly depending on which synthesis approach was used. Microcomposite aerogels were synthesized by encapsulating a dispersion of preformed PPy in a V₂O₅ gel. In the second approach, pyrrole was polymerized and doped within the pore volume of a preformed V₂O₅ gel. The hybrid microstructure of these materials was nanometer scaled but inhomogeneous. When the inorganic and organic precursors were allowed to polymerize simultaneously, the resulting gels exhibited a nanometer-scaled microstructure with a homogeneous distribution of the PPy and the V₂O₅. Through this route, a suitable microstructure and composition for a lithium secondary battery cathode were obtained. Undoped material with a composition of [PPy]_0.8V₂O₅ exhibited a lithium intercalation capacity comparable to that of V₂O₅ aerogel. For the full benefit of the PPy phase to be achieved, a suitable doping procedure is still required to oxidize the PPy into its high conductivity state while preserving the inorganic structure.     

V2O5 Textile Cathodes with High Capacity and Stability for Flexible Lithium-Ion Batteries

Textile-based energy-storage devices are highly appealing for flexible and wearable electronics. Here, a 3D textile cathode with high loading, which couples hollow multishelled structures (HoMSs) with conductive metallic fabric, is reported for high-performance flexible lithium-ion batteries. V₂O₅ HoMSs prepared by sequential templating approach are used as active materials and conductive metallic fabrics are applied as current collectors and flexible substrates. Taking advantage of the desirable structure of V₂O₅ HoMSs that effectively buffers the volume expansion and alleviates the stress/strain during repeated Li-insertion/extraction processes, as well as the robust flexible metallic-fabric current collector, the as-prepared fabric devices show excellent electrochemical performance and ultrahigh stability. The capacity retains a high value of 222.4 mA h g⁻¹ at a high mass loading of 2.5 mg cm⁻² even after 500 charge/discharge cycles, and no obvious performance degradation is observed after hundreds of cycles of bending and folding. These results indicate that V₂O₅ HoMSs/metallic-fabric cathode electrode is promising for highly flexible lithium-ion batteries.     

LiNi0.8 Co0.15 A10.05 O2正极材料的表面包覆改性研究

LiNi_0.8 Co_0.15 A1_0.05 O₂正极材料具有容量高、价格低等优点,被认为是最具发展前景的锂离子电池正极材料之一.但LiNi 0.8Co 0.15A1 0.05O₂材料本身存在充放电过程中容量衰减较快、倍率性能差和储存性能差等缺陷,影响了其进一步发展.本文以 LiNi 0.8Co 0.15A1 0.05O₂为研究对象,采用共沉淀法制备氢氧化物前驱体,在前驱体的表面包覆一层Ni 1/3Co 1/3 Mn 1/3(OH)₂,制备成具有核壳结构的正极材料.通过XRD、SEM、EDX、电化学测试等分析手段,系统地研究了其结构、形貌以及电化学性能.分析表明:包覆改性后,LiNi 0.8Co 0.15Al 0.05O₂正极材料在0.1、0.2、0.5、1 C倍率下,材料的首次充放电比容量分别为167.6,160.1,0.4,8.5 mAhg -1.由0.1到1 C,包覆改性前后的正极材料的放电比容量衰减量由34.7 mAhg -1降为29.1 mAhg -1,容量衰减百分比由22.1%降低到17.4%.综合性能分析认为,包覆改性后电化学性能有一定的改善.     

TiO2 Feather Duster as Effective Polysulfides Restrictor for Enhanced Electrochemical Kinetics in Lithium–Sulfur Batteries

The rechargeable lithium–sulfur battery is recognized as a promising candidate for electrochemical energy storage system because of their exceptional advance in energy density. However, the fast capacity decay of sulfur cathode caused by polysulfide dissolution and low specific capacity caused by poor electrical conductivity still impede the further development of lithium–sulfur battery. To address above issues, this study reports the synthesis of feather duster‐like TiO₂ architecture by in situ growth of TiO₂ nanowires on carbon cloth and further evaluates as sulfur host material. The strong chemical binding interaction between the polysulfides and TiO₂ feather duster efficiently restrains the shuttle effect, leading to enhanced electrochemical kinetics. Besides, the in situ grown TiO₂ NWs array also supply high surface for sulfur‐loading and fast path for electron transfer and ion diffusion. As results, the novel CC/TiO₂/S composite cathode exhibits a high capacity of 608 mA h g^?1 at 1.0 C after 700 cycles corresponding to capacity decay as low as 0.045% per cycle with excellent Coulombic efficiency higher than 99.5%.     

Facile synthesis of rutile TiO2/carbon nanosheet composite from MAX phase for lithium storage

Titanium oxide (TiO₂), with excellent cycling stability and low volume expansion, is a promising anode material for lithium-ion battery (LIB), which suffers from low electrical conductivity and poor rate capability. Combining nano-sized TiO₂ with conductive materials is proved an efficient method to improve its electrochemical properties. Here, rutile TiO₂/carbon nanosheet was obtained by calcinating MAX (Ti₃AlC₂) and Na₂CO₃ together and water-bathing with HCl. The lamellar carbon atoms in MAX are converted to 2D carbon nanosheets with urchin-like rutile TiO₂ anchored on. The unique architecture can offer plentiful active sites, shorten the ion diffusion distance and improve the conductivity. The composite exhibits a high reversible capacity of 247 mA h g⁻¹, excellent rate performance (38 mA h g⁻¹ at 50 C) and stable cycling performance (0.014% decay per cycle during 2000 cycles) for lithium storage.     

Carbon-nanofiber composite electrodes for thin and flexible lithium-ion batteries

Addition of vapor-grown carbon nanofiber (VGCF) into a LiCoO₂ composite electrode increases electrode’s conductivity and adhesion strength significantly. These increases are attributed to the uniform distribution of network-like VGCF of high conductivity; VGCF not only connects the surface of the active materials, its network penetrates into and connects each active material particle. VGCF composite electrode also improves the electrochemical performance of thin and flexible lithium-ion batteries such as discharge capacity at high current densities, cycle-life stability, and low-temperature (at −20 °C) discharge capacity. These improved electrochemical properties are attributed to the well-distributed network-like carbon nanofibers, VGCF, within the cathode. The addition of VGCF reduces the electron conducting resistance and decreases the diffusion path for lithium ions, hence increases the utilization of active materials during high-current discharge and low-temperature discharge. In addition, network-like VGCF forms a more uniform cathode structure so as to have a lower deterioration rate and correspondingly better life cycle stability.     

A High‐Rate V2O5 Hollow Microclew Cathode for an All‐Vanadium‐Based Lithium‐Ion Full Cell

V₂O₅ hollow microclews (V₂O₅‐HMs) have been fabricated through a facile solvothermal method with subsequent calcination. The synthesized V₂O₅‐HMs exhibit a 3D hierarchical structure constructed by intertangled nanowires, which could realize superior ion transport, good structural stability, and significantly improved tap density. When used as the cathodes for lithium‐ion batteries (LIBs), the V₂O₅‐HMs deliver a high capacity (145.3 mAh g^‐1) and a superior rate capability (94.8 mAh g^‐1 at 65 C). When coupled with a lithiated Li₃VO₄ anode, the all‐vanadium‐based lithium‐ion full cell exhibits remarkable cycling stability with a capacity retention of 71.7% over 1500 cycles at 6.7 C. The excellent electrochemical performance demonstrates that the V₂O₅‐HM is a promising candidate for LIBs. The insight obtained from this work also provides a novel strategy for assembling 1D materials into hierarchical microarchitectures with anti‐pulverization ability, excellent electrochemical kinetics, and enhanced tap density.