Electrostatic Interactions Leading to Hierarchical Interpenetrating Electroconductive Networks in Silicon Anodes for Fast Lithium Storage

Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter‘s agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h⁻¹ even tested at 10 A g⁻¹), cycling stability (stable reversible capacity of 547 mA h g⁻¹ after 200 cycles at 1 A g⁻¹) and applicability (a high reversible capacity of 101 mA h g⁻¹ after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability.     

降低“死锂”残留，提高硅负极首圈库仑效率

正锂离子电池硅负极的理论容量(4200m Ah·g~(-1))超过商用石墨负极的十倍(372 m Ah·g~(-1)),但循环中巨大的体积变化制约了其发展~(1,2)。过去十多年,随着各种纳米硅负极结构的提出,极大地缓解了体积膨胀带来的问题。但纳米硅负极的高比表面积同时也带来了较低的首圈库仑效率(50%–85%)的问题~(3,4),制约了其商业化应用进程。     

Synthesis and Comparative Investigation of Silicon Transition Metal Silicide Composite Anodes for Lithium Ion Batteries

A significant increase in energy density of lithium ion batteries (LIBs) can be achieved by using high‐capacity, silicon (Si)‐based negative electrode materials. Several challenges arise from the enormous volumetric changes of Si during lithiation/delithiation, such as disintegration/pulverization of the active material and the electrode as well as ongoing electrolyte decomposition, leading to rapid capacity fading. Here, we synthesize and comparatively investigate three different porous transition metal‐Si‐carbon composite materials that are composed of an active Si phase and the corresponding inactive metal‐silicide phases. In this material design, the inactive phases, as well as the pores serve as a buffer to attenuate the previously mentioned detrimental effects. The synthesized materials are studied with respect to their structural and surface properties and are characterized electrochemically regarding their rate performance, and long‐term charge/discharge cycling stability. Thereby, the composite materials show a promising rate capability and a high specific capacity. Their low initial Coulombic efficiency, due to the porous structure, can be partially compensated by pre‐lithiation. This is demonstrated by the application of the synthesized materials in a LIB full‐cell set‐up vs. NMC‐111 cathodes, where the amount of lithium is confined due to anode/cathode capacity balancing.     

Fluorescence Probing of Active Lithium Distribution in Lithium Metal Anodes

The uncontrollable growth of Li dendrites and the accumulation of byproducts are two severe concerns for lithium metal batteries, which leads to safety hazards and a low Coulombic efficiency. To investigate the deterioration of the cell, it is important to figure out the distribution of active Li species on the anode surface and distinguish Li dendrites from byproducts. However, it is still challenging to identify these issues by conventional visual observation methods. In this work, we introduce a novel fluorescent probing strategy using 9,10‐dimethylanthracene (DMA). By marking the cycled Li‐anode surface, the active Li distribution can be visualized by the fluorescence quenching of DMA reacting with active Li. The method demonstrates validity for electrolyte selection and predictive detection of uneven Li deposition on Li metal anodes. Furthermore, the location of dendrites can be clearly identified after destructive utilization of the anode, which will contribute to the development of failure‐analysis technology for Li metal batteries.     

微米级SiO合成多孔氧化硅/硅/碳储锂复合材料

以微米级SiO为原料,通过简单的高温煅烧、碳包覆和酸刻蚀制备多孔氧化硅/硅/碳复合材料,复合材料比表面积和平均孔径分别为32.9 m~2/g和3 nm。纳米硅分散在缓冲介质氧化硅多孔体系中,表面包覆一层薄而均匀的碳层。所得的复合材料具有较好的循环稳定性,在0.3 m A/g下,50次循环后可逆容量保持在645.1 m A·h/g。多孔结构、氧化硅缓解了硅在脱嵌锂过程的体积膨胀,碳层提高了复合材料的导电性和结构稳定性。     

A Freestanding Selenium Disulfide Cathode Based on Cobalt Disulfide‐Decorated Multichannel Carbon Fibers with Enhanced Lithium Storage Performance

SeS₂ shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root‐like carbon fiber network decorated with CoS₂ nanoparticles (denoted as CoS₂@LRC) has been designed and prepared as the SeS₂ host for enhancing the lithium storage performance. The integrated electrode is constructed by three‐dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS₂ (70 wt %), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g⁻¹ at 0.2 A g⁻¹. What is more, there are numerous CoS₂ nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g⁻¹.     

基于铜基底的TiO2纳米管阵列储锂性能

研究了基于铜基底的TiO2纳米管阵列直接作为锂离子电池电极的储锂性能。以铜基底上生长的Cu(OH)2纳米棒阵列为模板,采用自牺牲模板法,通过外向包覆与内向刻蚀,制备了非晶态的TiO2纳米管阵列,然后将其在500℃下退火处理4 h,获得锐钛矿型TiO2纳米管阵列。采用X射线衍射、场发射扫描电镜、透射电镜、热重分析对样品进行表征;采用恒电流充放电、循环伏安和交流阻抗谱测试对退火前后TiO2纳米管阵列的电化学性能进行研究。结果表明:与非晶态的TiO2纳米管阵列相比,锐钛矿型TiO2纳米管阵列吸附水的含量低,结晶度高,电荷迁移阻力小,锂离子扩散系数大,结构稳定,具有更好的循环性能和倍率性能;在0.2C下,其首次放电比容量为353 mAh·g-1,经过40次循环后的放电比容量仍为243 mAh·g-1,在8C下的放电比容量为90 mAh·g-1。     

基于铜基底的TiO2纳米管阵列储锂性能

研究了基于铜基底的TiO₂纳米管阵列直接作为锂离子电池电极的储锂性能。以铜基底上生长的Cu(OH)₂纳米棒阵列为模板, 采用自牺牲模板法, 通过外向包覆与内向刻蚀, 制备了非晶态的TiO₂纳米管阵列, 然后将其在500℃下退火处理4 h, 获得锐钛矿型TiO₂纳米管阵列。采用X射线衍射、场发射扫描电镜、透射电镜、热重分析对样品进行表征;采用恒电流充放电、循环伏安和交流阻抗谱测试对退火前后TiO₂纳米管阵列的电化学性能进行研究。结果表明:与非晶态的TiO₂纳米管阵列相比, 锐钛矿型TiO₂纳米管阵列吸附水的含量低, 结晶度高, 电荷迁移阻力小, 锂离子扩散系数大, 结构稳定, 具有更好的循环性能和倍率性能;在0.2 C下, 其首次放电比容量为353 mAh·g^-1, 经过40次循环后的放电比容量仍为243 mAh·g^-1, 在8C下的放电比容量为90 mAh·g^-1。     

Flexible Amalgam Film Enables Stable Lithium Metal Anodes with High Capacities

Dendrite formation is a critical challenge for the applications of lithium (Li) metal anodes. In this work a new strategy is demonstrated to address this issue by fabricating an Li amalgam film on its surface. This protective film serves as a flexible buffer that affords repeated Li plating/stripping. In symmetric cells, the protected Li electrodes exhibit stable cycling over 750 hours at a high plating current and capacity of 8 mA cm^?2 and 8 mAh cm^?2, respectively. Coupled with high‐loading cathodes (ca. 12 mg cm^?2) such as LiFePO₄ and LiNi_0.6Co_0.2Mn_0.2O₂, the protected hybrid anodes demonstrate significantly improved cell stability, indicating its reliability for practical development of Li metal batteries. Interfacial analyses reveal a unique plating‐alloying synergistic function of the protective film, where Li beneath the film is actively involved in the electrode reactions upon cycling. Lithium amalgams enrich the alloy anode family and provide new perspectives for the rational design of dendrite‐free anodes.     

Engineering of Silicon Core-Shell Structures for Li-ion Anodes

The amount of silicon in anode materials for Li-ion batteries is still limited by the huge volume changes during charge-discharge cycles. Such changes lead to the loss of electrical contacts, as well as mechanical and surface electrolyte interphase (SEI) instabilities, strongly reducing the cycle life. Core-shell structures have attracted a vast research interest due to the possibility of modifying some properties with a judicious choice of the shell. It is, for example, possible to improve the electronic conductivity and ionic diffusion, or buffer volume variations. This review gives a comprehensive overview of the recent developments and the different strategies used for the design, synthesis and electrochemical performance of silicon-based core-shells. It is based on a selection of the main types of silicon coatings reported in the literature, including carbon, inorganic, organic and double-layer coatings, Finally, a summary of the advantages and drawbacks of these different types of core-shells as anode materials for Li-ion batteries and some insightful suggestions in regards to their use are provided.     

Highly Reversible Lithium Storage in Hierarchical Ca2Ge7O16 Nanowire Arrays/Carbon Textile Anodes

Aligned Ca₂Ge₇O₁₆ nanowire arrays were successfully grown on carbon textiles to form hierarchical 3D structures by using a facile hydrothermal method on a large scale. Typical Ca₂Ge₇O₁₆ nanowires are single crystals that show preferred growth along the [001] direction. The 3D hierarchical structures were used as binder‐free anodes for lithium‐ion batteries, which showed the features of highly reversible capacity (900–1100 mA h g^?1 at a current density of 300 mA g^?1), remarkable cycling stability, even over 100 cycles, and good rate capability, with a capacity of about 500 mA h g^?1 at 3 A g^?1. Furthermore, highly bendable full cells were also fabricated, which showed high flexibility, with little voltage change after bending 600 times, and superior temperature tolerance within the range 4–60 °C, thus demonstrating their promising potential for applications in high‐performance lithium‐ion batteries.     

Anion-tethered Single Lithium-ion Conducting Polyelectrolytes through UV-induced Free Radical Polymerization for Improved Morphological Stability of Lithium Metal Anodes

Single Li⁺ ion conducting polyelectrolytes (SICs), which feature covalently tethered counter-anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li⁰) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single-step UV polymerization approach. The resulting electrolyte exhibited a high Li⁺ transference number (t₊) of 0.85 and demonstrated good Li⁺ conductivity (6.3×10⁻⁵ S/cm at room temperature), which is comparable to that of a benchmark dual ion conductor (DIC, 9.1×10⁻⁵ S/cm). Benefitting from the high transference number of SIC, it displayed a three-fold higher critical current density (2.4 mA/cm²) compared to DIC (0.8 mA/cm²) by successfully suppressing concentration polarization-induced short-circuiting. Additionally, the t₊ significantly influenced the deposition behavior of Li⁰, with SIC yielding a uniform, compact, and mosaic-like morphology, while the low t₊ DIC resulted in a porous morphology with Li⁰ whiskers. Using the SIC electrolyte, Li⁰||LiFePO₄ cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C.     

Unique Ordered TiO2 Superstructures with Tunable Morphology and Crystalline Phase for Improved Lithium Storage Properties

Unique ordered TiO₂ superstructures with tunable morphology and crystalline phase were successfully prepared by the use of different counterions. Dumbbell‐shaped rutile TiO₂ and nanorod‐like rutile mesocrystals constructed from ultrathin nanowires, and quasi‐octahedral anatase TiO₂ mesocrystals built from tiny nanoparticle subunits were achieved. Interestingly, the obtained anatase mesocrystals have a fine microporous structure and a large surface area. The influence of the counterions in the reaction system is discussed and possible mechanisms responsible for the formation of the unique ordered TiO₂ superstructures with different morphologies and crystalline phases are also proposed based on a series of experimental results. The obtained TiO₂ superstructures were used as anode materials in lithium ion batteries, and exhibited higher capacity and improved rate performance; this is attributed to the intrinsic characteristics of the mesoscopic TiO₂ superstructures, which have a single‐crystal‐like and porous nature.     

An Extremely Simple Method for Protecting Lithium Anodes in Li‐O2 Batteries

Rechargeable Li‐O₂ batteries have aroused much attention for their high energy density as a promising battery technology; however, the performance of the batteries is still unsatisfactory. Lithium anodes, as one of the most important part of Li‐O₂ batteries, play a vital role in improving the cycle life of the batteries. Now, a very simple method is introduced to produce a protective film on lithium surface via chemical reactions between lithium metals and 1,4‐dioxacyclohexane. The film is mainly composed of ethylene oxide monomers and endows Li‐O₂ batteries with enhanced cycling stability. The film could effectually reduce the morphology changes and suppress the parasitic reactions of lithium anodes. This simple approach provides a new strategy to protect lithium anodes in Li‐O₂ batteries.     

追踪锂金属负极的压力与形貌变化（英文）

采用高载量氧化物正极(>4mAh·cm^-2)和超薄锂金属负极(<50μm)可以构建高比能锂金属二次电池。然而,该类电池的循环寿命和安全性受到锂金属不可控沉积的严重制约。高比表面积的锂枝晶和锂“苔藓”导致了较低的库伦效率,前者有一定可能穿刺隔膜,造成电池内短路,是亟待解决的安全隐患。因此,提升锂金属二次电池的循环寿命和安全性的关键在于实现锂金属的致密沉积。文献中已有多种化学方法可达到这样的效果。由于锂金属较软,受力容易发生形变,对锂金属电池施加机械压力是另一种促进锂金属致密沉积和提高循环性能的方法。然而,机械压力、锂金属形态的演变、和循环性能之间的关系尚未被完全理解。本文报道了一种基于薄膜压力传感器的电池压力测量装置,可以实时跟踪纽扣型锂金属电池内部的压力变化,并且探究外加机械压力对电池循环性能的影响。研究发现,在纽扣电池和高比能的软包电池(5 Ah,>380 Wh·kg^-1)中,一定程度的压力可以促进锂金属的致密沉积,改善电池循环性能;而过大的压力则会导致锂金属向负极内部沉积,造成负极变形和电池性能恶化。我们的研究结果凸显了...     

锂离子电池锡基合金体系负极研究

综述了锂离子电池锡基金属间化合物和复合物负极的研究进展。介绍了锡基合金体系作锂离子电池负极的优势, 指出了锡金属负极的不足,提出了采用锡基合金及其复合物是克服锡金属负极主体材料尺寸稳定问题的解决办法。概述了各种锡基合金和其复合物的结构、电化学性能、相应的加工方法和某些反应机理,总结了这些材料的优点和缺点,提出了改进这些材料性能的一些建议,如采用分散形态的纳米颗粒结构或用非晶合金并控制形态结构的转变,着重指出多相锡基锂合金复合物是最有前景的负极材料。     

多孔聚合物在锂金属负极保护中的研究进展

锂金属负极具有极高的理论比容量和最低的还原电位,因此锂金属电池被认为是最具潜力的高比能储能器件之一.然而,充放电过程中不受控制的枝晶生长、不稳定的界面反应与巨大的体积变化导致锂金属负极库伦效率低与循环稳定性差,同时枝晶刺穿隔膜也会带来安全隐患,这些问题极大地制约着锂金属电池的实际应用.多孔聚合物由于比表面积大、密度低、...