锂离子电池正极材料LiNi1-xCoxO2的合成及性能

以硝酸盐为原料,用sol-gel法合成锂离子电池正极材料LiNi1-xCoxO2,采用XRD、SEM和电化学测试等方法对材料的物理化学性质以及电化学性能进行表征。结果表明,经过Co掺杂后,材料具有较高的初始放电比容量和较好循环性能。在750℃下合成的LiNi0.8Co0.2O2,在3.0~4.2 V 0.2 C下经恒电流充放电测试,其首次放电容量为170.40mAh.g–1,经过30次充放电循环后放电容量为149.86 mAh.g–1,可逆容量的保持率为89.95%。     

锂离子电池混合正极材料LiNi0.5Co0.2Mn0.3O2/LiFePO4电化学性能研究

采用湿法球磨制备了锂离子电池用混合正极材料LiNi0.5Co0.2Mn0.3O2/LiFePO4。通过X射线衍射(XRD)和扫描电镜(SEM)表征了材料的结构和形貌,采用恒流充放电测试、循环伏安测试(CV)和电化学阻抗谱测试(EIS)方法研究了混合正极材料LiNi0.5Co0.2Mn0.3O2/LiFePO4的电化学性能。结果表明：混合正极材料LiNi0.5Co0.2Mn0.3O2/LiFePO4的晶体结构完好,碳包覆的纳米LiFePO4颗粒较好地包覆在LiNi0.5Co0.2Mn0.3O2表面。含质量分数15% LiFePO4的混合正极材料LiNi0.5Co0.2Mn0.3O2/LiFePO4电化学性能优良,0.2C首次充放电比容量为181.40 mAh?g–1,首次充放电效率为90.79%;1.0C循环50次后放电比容量为169.89 mAh?g–1,容量保持率为97.80%;3.0C循环5次后的放电比容量为162.22 mAh?g–1,容量保持率仍有89.43%;60 ℃高温存储7 d后,容量保持率和容量恢复率分别为86.48%和97.32%。     

镍钴酸锂的空气气氛下高温固相合成

通过改进马弗炉结构,在空气气氛下合成了LiNi0.7Co0.3O2锂离子二次电池正极材料。利用XRD、SEM和循环充放电测试等手段,研究了材料结构与电化学性能之间的关系。实验电池以C/3的电流倍率在2.7~4.2V进行恒流充放电循环,电池首次充电比容量与放电比容量分别为181mAh/g和157mAh/g,库仑效率为86.7%。经过15次循环后,放电比容量趋于稳定,库仑效率保持在98%以上。循环40次,放电比容量为122mAh/g。     

Ce4+掺杂对LiFePO4/C正极极材料微观结构和性能的影响

采用碳热还原法合成了LiFe1-2xCexPO4/C(0≤x≤0.03)锂离子电池正极材料。利用X射线衍射、扫描电镜、恒流充放电、循环伏安法等手段对Ce4+掺杂前后磷酸铁锂正极材料的结构和电化学性能进行了表征。结果表明,随着Ce4+掺入量的增加,LiiFe1-2xCerPO4/C材料的电化学性能,特别是较高倍率(5～1...     

V2O5(TiO2)/S复合材料作锂电池正极的性能研究

为了改善锂硫电池的循环性能,将单质硫分别与纳米金属氧化物(V2O5,TiO2)机械混合。用XRD对材料的晶体结构进行了表征。通过循环伏安、交流阻抗和电池性能的对比,对材料的电化学性能进行了分析。结果表明:采用V2O5改性的硫材料,首次放电比容量达844.68 mAh.g–1,样品循环容量衰减明显改善,30次后比容量保持在696.71 mAh.g–1。而TiO2/S复合材料,初始放电比容量为578.21 mAh.g–1,30次循环后比容量为347.71 mAh.g–1。     

纳米复合β-Ni(OH)2电极材料的制备与电化学性能

氢氧化镍(Ni(OH)2)是碱性二次电池的正极材料,本文采用化学沉淀法制备了纳米Ni(OH)2超微粉体,XRD检测证实晶型为β相，用TEM对粉体进行形貌分析，结果表明所得产物是颗粒状纳米晶，粒径20nm左右．将纳米Ni(OH)2粉以10％的比例掺杂到常规球镍中制得纳米复合β-Ni(OH)2电极材料，其电化学容量和放电平台较常规球镍有很大提高，大电流放电时，纳米复合β—Ni(OH)2电极材料的电化学容量比常规球镍提高达40．9％。     

纳米硅/还原氧化石墨烯复合纤维材料及其负极结构锂离子超级电容器

通过湿法纺丝工艺成功制备了纳米硅/还原氧化石墨烯复合纤维材料,并对其进行形貌表征与电化学性能测试。纳米硅颗粒嵌入石墨烯层间褶皱的结构具有限制硅材料在储锂过程中体积膨胀的作用,适于作为锂离子电容器负极。同时,研究了锂离子电容器多孔活性炭正极材料的双电层电容特性,通过组装成对称超级电容器,对其电化学性能进行测试,并结合材料的形貌,分析其作为锂离子电容器正极的合理性。为使正负极电荷匹配,分别对负极硅碳纤维和正极活性炭材料组装的锂离子半电池的倍率、循环稳定性、电化学阻抗等电化学性能进行了测试。结果表明,纳米硅/还原氧化石墨烯复合纤维材料的比容量最高可达826.2 mA·h/g(在电流密度为0.2 A/g时),活性炭比容量可达39.9 mA·h/g。组装成的锂离子电容器在合理的匹配条件下,充放电首圈循环比容量可达58.2 mA·h/g (在电流密度为0.2 A/g时),能量密度为26.8 W·h/kg,循环100圈后,比容量保持率降至41.7%。     

碳改性锂离子电池正极材料LiMn2O4的电化学性能

采用高温固相法合成了锂离子电池正极材料LiMn2O4微粉,并采用热裂解法在其表面进行了碳包覆。通过XRD、SEM、TGA分析和充放电测试研究了包覆后粉体的晶体结构、形貌、包覆量和电化学性能。测试结果表明:合成的碳包覆LiMn2O4材料为单一的尖晶石型结构,碳包覆有效降低了Jahn-Teller畸变和锰在电解液中的溶解,提高了材料的电化学性能。以0.1C倍率充放电时碳包覆LiMn2O4的初始充放电比容量为123.1 mAh/g,循环20次后容量保持率为96%。     

掺杂和碳包覆对锂离子电池负极材料Li_4Ti_5O_(12)性能的影响

采用固相法首次合成了碳包覆的掺杂不同金属离子的锂离子电池负极材料Li3.9M0.1Ti5O12/C(M=Mn、Cu、Mg),对材料进行了循环伏安测试及恒电流充放电测试。结果表明:金属掺杂未改变材料的晶体尖晶石结构,由于金属离子对Li4Ti5O12的晶胞内部的掺杂和C对其外部的包覆,使复合材料的锂离子扩散速率、大电流循环稳定性和可逆容量都明显提高。在1C充放电循环时,Li3.9Mn0.1Ti5O12/C、Li3.9Cu0.1Ti5O12/C、Li3.9Mg0.1Ti5O12/C首次放电容量分别达到156.6,162.4和169.8 mAh/g;50次循环后,容量分别保持在155.4,159.6和169.7 mAh/g,展示了优良的电化学特性。     

尖晶石型LiMn_(2-x)Ga_xO_4的合成及电化学性能研究

为了提高锂离子电池尖晶石锰酸锂正极材料的循环性能和倍率性能,采用柠檬酸辅助溶胶-凝胶法制备了LiMn2–xGaxO4(x=0,0.02,0.05,0.07)正极材料。研究了Ga掺杂对所制材料性能的影响。结果表明:制得的LiMn2–xGaxO4具有单一的尖晶石结构。当Ga3+掺杂量为x=0.05时,LiMn2–xGaxO4首次放电比容量为117.1 mAh/g,经过95次循环后,放电容量保持率高达97.9%;在高倍率4C条件下,首次放电比容量为100.9 mAh/g,30次循环后放电比容量为102.4 mAh/g,具有优异的倍率性能。     

Role of the Anion on the Transport and Structure of Organic Mixed Conductors

Organic mixed conductors are increasingly employed in electrochemical devices operating in aqueous solutions that leverage simultaneous transport of ions and electrons. Indeed, their mode of operation relies on changing their doping (oxidation) state by the migration of ions to compensate for electronic charges. Nevertheless, the structural and morphological changes that organic mixed conductors experience when ions and water penetrate the material are not fully understood. Through a combination of electrochemical, gravimetric, and structural characterization, the effects of water and anions with a hydrophilic conjugated polymer are elucidated. Using a series of sodium‐ion aqueous salts of varying anion size, hydration shells, and acidity, the links between the nature of the anion and the transport and structural properties of the polymer are systematically studied. Upon doping, ions intercalate in the crystallites, permanently modifying the lattice spacings, and residual water swells the film. The polymer, however, maintains electrochemical reversibility. The performance of electrochemical transistors reveals that doping with larger, less hydrated, anions increases their transconductance but decreases switching speed. This study highlights the complexity of electrolyte‐mixed conductor interactions and advances materials design, emphasizing the coupled role of polymer and electrolyte (solvent and ion) in device performance.     

In Situ Construction of “Anchor‐Like” Structures in FeNCN for Long Cyclic Life in Sodium‐Ion Batteries

Iron carbodiimide (FeNCN) is a high‐reactivity anode material for sodium‐ion batteries. However, strict synthesis technology and poor electrochemical stability limit its application. FeNCN polyhedrons are prepared using a facile one‐step pyrolysis process. In these polyhedrons, many “anchor‐like” structures are in situ constructed with Fe? C bonds. These Fe? C bonds connect the FeNCN polyhedrons closely. The FeNCN polyhedrons with “anchor‐like” structures exhibit good electrochemical stability, that is, high capacity retention of 79.9% (408 mAh g^?1) at 0.5 A g^?1 after 300 cycles. Further analysis suggests that the Fe? C bond plays an important role to improve the structural stability of FeNCN polyhedrons. The “anchor‐like” structures with Fe? C bonds can hold FeNCN polyhedrons closely when Na⁺ intercalates, avoiding structural breakage with obvious capacity loss. This work provides a novel synthesis technology of FeNCN and helps related researcher to deepen the understanding of this material, as well as provide inspirations as to improving the electrochemical stability of related materials.     

Electrochemical Properties of Si‐Ge Heterostructures as an Anode Material for Lithium Ion Batteries

Si‐Ge composites have recently been explored as an anode material for lithium‐ion batteries due to their stable cycle performance and excellent rate capability. Although previous reports show the benefits of Si‐Ge composites on electrochemical performance, the specific mechanism and structural effects have been overlooked. Here, the structural effect of Si‐Ge heterogeneous nanostructures on both mechanics and kinetics is systematically studied through theoretical analysis and detailed experimental results. Si‐Ge and Ge‐Si core–shell nanowires are employed for this study. The Si‐Ge core–shell nanowires show a much improved electrochemical performance, especially cycle performance and rate capability, when compared to those of the Ge‐Si core–shell nanowires electrode. On the basis of the detailed experimental results and associated theoretical analysis, its is demonstrated that the strain distribution and Li diffusivity and/or diffusion path are significantly affected by the Si‐Ge heterostructure, which induce different mechanics and kinetics associated with lithium.     

Multidimension‐Controllable Synthesis of Ant Nest‐Structural Electrode Materials with Unique 3D Hierarchical Porous Features toward Electrochemical Applications

Hierarchical porous materials (HPM) have been widely used to enhance electrochemical performance in different fields of application, since their porous structures benefit electrolyte infiltration and ion diffusion. However, the realization of multidimension‐controllable synthesis of HPM, including material category, material components, supporting substrates, as well as pore sizes/distributions, is still a huge challenge. Herein, a novel concept is proposed, for the first time, on the geometry structure of HPM bioinspired by natural ant nests, which features 3D interlaced and well‐interconnected porous structures. Moreover, a facile and universal approach is developed to the multidimension‐controllable synthesis of ant nest‐structural HPM. Further investigation shows that the in situ construction of carbon‐based ant nests onto porous current collectors to fabricate the integrated electrode for supercapacitors could induce nearly 70% and 45% enhancement on the specific capacitance compared to the common powder and freestanding materials, respectively. Moreover, this synthesis route can be facilely extended to obtain the ant nest‐structural CuO_x, which exhibits fivefold enhancement in sensitivity for glucose detection. Such biomimetic hierarchical porous architectures are of great significance in the field of electrochemical applications.     

High Cycling Rate-Induced Irreversible TMO6 Slabs Glide in Co-Free High-Ni Layered Cathode Materials

Co-free high-Ni layered transition metal oxide is a promising cost-effective cathode material for high-energy Li-ion batteries, but it suffers from undesirable rate performance and rapid capacity decay upon high-rate cycling. The underlying structural changes under fast electrochemical processes remain unclear to date. In this study, atomic scale structural evolutions of Co-free high-Ni layered cathode at different cycling rates are revealed by advanced TEM characterization. It is found that the phase transition after high-rate cycling is much different from that after low-rate cycling. The low-rate cycled sample shows a typical layer-to-rock salt transition. However, O1-type stacking faults are uncovered in the high-rate cycled sample owing to irreversible TMO₆ slabs glide, which induces severe lattice distortion and structural dislocations. These findings deepen the understanding of the rate-dependent structural degradation mechanism of Co-free high-Ni layered cathodes, and have significant implications for improving current materials to withstand high-rate applications.     

Highly Reversible Anion Redox of Manganese-Based Cathode Material Realized by Electrochemical Ion Exchange for Lithium-Ion Batteries

Anion energy storage provides the possibility to achieve higher specific capacity in lithium-ion battery cathode materials, but the problems of capacity attenuation, voltage degradation, and inconsistent redox behavior are still inevitable. In this paper, a novel O2-type manganese-based layered cathode material Li_x[Li_0.2Mn_0.8]O₂ with a ribbon superlattice structure is prepared by electrochemical ion exchange, which realizes the highly reversible redox of anions and excellent cycle performance. Through low-voltage pre-cycling treatment, the specific capacity of the material can reach 230 mAh g⁻¹ without obvious voltage attenuation. During the electrochemical ion exchange, the precursor with P2 structure transforms into Li_x[Li_0.2Mn_0.8]O₂ with O2 structure through the slippage and shrink of adjacent slabs, and the special superlattice structure in Mn slab is still retained. Simultaneously, a certain degree of lattice mismatch and reversible distortion of the MnO₆ octahedron occur. In addition, the anion redox catalyzes the formation of the solid electrolyte interface, stabilizing the electrode/electrolyte interface and inhibiting the dissolution of Mn. The mechanism of electrochemical ion exchange is systematically studied by comprehensive structural and electrochemical characterization, opening an attractive path for the realization of highly reversible anion redox.     

Galvanically Replaced,Single‐Bodied Lithium‐Ion Battery Fabric Electrodes

Despite extensive research on flexible/wearable power sources, their structural stability and electrochemical reliability upon mechanical deformation and charge/discharge cycling have not yet been completely achieved. A new class of galvanically replaced single‐bodied lithium‐ion battery (LIB) fabric electrodes is demonstrated. As a proof of concept, metallic tin (Sn) is chosen as an electrode active material. Mechanically compliable polyethyleneterephthalate (PET) fabrics are conformally coated with thin metallic nickel (Ni) layers via electroless plating to develop flexible current collectors. Driven by the electrochemical potential difference between Ni and Sn, the thin Ni layers are galvanically replaced with Sn, resulting in the fabrication of a single‐bodied Sn@Ni fabric electrode (Sn is monolithically embedded in the Ni matrix on the PET fabric). Benefiting from the chemical/structural uniqueness and rationally designed bicontinuous ion/electron transport pathways, the single‐bodied Sn@Ni fabric electrode provides exceptional redox reaction kinetics and omnidirectional deformability (notably, origami‐folding boats), which lie far beyond those attainable with conventional LIB electrode technologies.     

Bottom‐Up Synthesis of Advanced Carbonaceous Anode Materials Containing Sulfur for Na‐Ion Batteries

The fabrication of sulfur‐containing carbonaceous anode materials (CS) that show exceptional activity as anode material in Na‐ions batteries is reported. To do so, a general and straightforward bottom‐up synthesis of CS materials with precise control over the sulfur content and functionality is introduced. The new synthetic path combined with a detailed structural analysis and electrochemical studies provide correlations between i) the sulfur content and chemical species and ii) the structural, electronic, and electrochemical performance of the associated materials. As a result, the new CS substances demonstrate excellent activity as Na‐ion battery anode materials, reaching capacity values above 500 mAh g^?1 at a current density of 0.1 A g^?1, as well as high reversible sodium storage capabilities and excellent cycling durability. The results reveal the underlying working principles of carbonaceous materials, alongside the storage mechanism of the Na⁺ ions in these advanced sodium‐ion battery anode materials and provide a new avenue for their practical realization.     

Poly(2,5-Dihydroxy-1,4-Benzoquinonyl Sulfide) As an Efficient Cathode for High-Performance Aqueous Zinc–Organic Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted considerable attention as a promising candidate for low-cost and high-safety electrochemical energy storage. However, the advancement of ZIBs is strongly hindered by the sluggish ionic diffusion and structural instability of inorganic metal oxide cathode materials during the Zn²⁺ insertion/extraction. To address these issues, a new organic host material, poly(2,5-dihydroxy-1,4-benzoquinonyl sulfide) (PDBS), has been designed and applied for zinc ion storage due to its elastic structural factors (tunable space and soft lattice). The aqueous Zn-organic batteries based on the PDBS cathode show outstanding cycling stability and rate capability. The coordination moieties (O and S) display the strong electron donor character during the discharging process and can act as the coordination arms to host Zn²⁺. Also, under the electrochemical environment, the malleable polymer structure of PDBS permits the rotation and bending of polymer chains to facilitate the insertion/extraction of Zn²⁺, manifesting the superiority and uniqueness of organic electrode materials in the polyvalent cation storage. Finally, quasi-solid-state batteries based on aqueous gel electrolyte demonstrate highly stable capacity under different bending conditions.     

One‐Pot Synthesis of Antimony‐Embedded Silicon Oxycarbide Materials for High‐Performance Sodium‐Ion Batteries

Sodium‐ion batteries have recently attracted intensive attention due to their natural abundance and low cost. Antimony is a desirable candidate for an anode material for sodium‐ion batteries due to its high theoretical capacity (660 mA h g^?1). However, the utilization of alloy‐based anodes is still limited by their inherent huge volume changes and sluggish kinetics. The Sb‐embedded silicon oxycarbide (SiOC) composites are simply synthesized via a one‐pot pyrolysis process at 900 °C without any additives or surfactants, taking advantage of the superior self‐dispersion properties of antimony acetate powders in silicone oil. The structural and morphological characterizations confirm that Sb nanoparticles are homogeneously embedded into the amorphous SiOC matrix. The composite materials exhibit an initial desodiation capacity of around 510 mA h g^?1 and maintained an excellent capacity retention above 97% after 250 cycles. The rate capability test reveals that the composites deliver capacity greater than 453 mA h g^?1, even at the high current density of 20 C rate, owing to the free‐carbon domain of SiOC material. The electrochemical and postmortem analyses confirm that the SiOC matrix with a uniform distribution of Sb nanoparticles provides the mechanical strength without degradation in conductive characteristics, suppressing the agglomeration of Sb particles during the electrochemical reaction.