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Micro/nano-Si flakes were obtained by a facile approach of reaction ball milling self-assembly, and then, a Si@C anode material with a carbon content of 17.7wt% was synthesized by combining the Si flakes with phenol formaldehyde resin. It was revealed that the micro/nano-Si flakes inherited the advantages of both nano-Si and bulk Si, showing not only a considerable surface area of 65.6 m 2  g −1 but also a high tap density of 0.66 g cm −3 . The Si@C anode showed outstanding electrochemical performance, particularly its high volumetric capacity, due to the formation of dual-layer SiO x /C film on the micro/nano-Si. The Si@C anode delivered a gravimetric/volumetric capacity as high as 1721.9 mAh g −1 /1239.8 mAh cm −3 at 0.05 A g −1 and preserved a large gravimetric/volumetric capacity of 1028.7 mAh g −1 /740.7 mAh cm −3 at 2.0 A g −1 . It retained 92.0% of its initial capacity after 200 cycles at 0.5 A g −1 .

Limited by the size of microelectronics, as well as the space of electrical vehicles, there are tremendous demands for lithium-ion batteries with high volumetric energy densities. Current lithium-ion batteries, however, adopt graphite-based anodes with low tap density and gravimetric capacity, resulting in poor volumetric performance metric. Here, by encapsulating nanoparticles of metallic tin in mechanically robust graphene tubes, we show tin anodes with high volumetric and gravimetric capacities, high rate performance, and long cycling life. Pairing with a commercial cathode material LiNi 0.6 Mn 0.2 Co 0.2 O 2 , full cells exhibit a gravimetric and volumetric energy density of 590 W h Kg −1 and 1,252 W h L −1 , respectively, the latter of which doubles that of the cell based on graphite anodes. This work provides an effective route towards lithium-ion batteries with high energy density for a broad range of applications. Here the authors report a tin anode design by encapsulating tin nanoparticles in graphene tubes. The design exhibits high capacity, good rate performance and cycling stability. Pairing with NMC, the full cell delivers a volumetric energy density twice as high as that for the commercial cell.

Increasing the energy density of conventional lithium‐ion batteries (LIBs) is important for satisfying the demands of electric vehicles and advanced electronics. Silicon is considered as one of the most‐promising anodes to replace the traditional graphite anode for the realization of high‐energy LIBs due to its extremely high theoretical capacity, although its severe volume changes during lithiation/delithiation have led to a big challenge for practical application. In contrast, the co‐utilization of Si and graphite has been well recognized as one of the preferred strategies for commercialization in the near future. In this review, we focus on different carbonaceous additives, such as carbon nanotubes, reduced graphene oxide, and pyrolyzed carbon derived from precursors such as pitch, sugars, heteroatom polymers, and so forth, which play an important role in constructing micrometer‐sized hierarchical structures of silicon/graphite/carbon (Si/G/C) composites and tailoring the morphology and surface with good structural stability, good adhesion, high electrical conductivity, high tap density, and good interface chemistry to achieve high capacity and long cycling stability simultaneously. We first discuss the importance and challenge of the co‐utilization of Si and graphite. Then, we carefully review and compare the improved effects of various types of carbonaceous materials and their associated structures on the electrochemical performance of Si/G/C composites. We also review the diverse synthesis techniques and treatment methods, which are also significant factors for optimizing Si/G/C composites. Finally, we provide a pertinent evaluation of these forms of carbon according to their suitability for commercialization. We also make far‐ranging suggestions with regard to the selection of proper carbonaceous materials and the design of Si/G/C composites for further development. The co‐utilization of Si and graphite has emerged as the most practical anode for high‐energy lithium‐ion batteries, but there are still significant challenges. The carbon additives play important roles in integrating the Si and graphite with tailored structure, morphology, and surface, and are discussed along with the synthesis methods and strategies to provide insights for further development and commercialization of Silicon/Graphite/Carbon (Si/G/C) anodes in the future.

To achieve both high gravimetric and volumetric energy densities of lithium–sulfur (Li–S) batteries, it is essential yet challenging to develop low‐porosity dense electrodes along with diminishment of the electrolyte and other lightweight inactive components. Herein, a compact TiO2@VN heterostructure with high true density (5.01 g cm–3) is proposed crafted by ingenious selective nitridation, serving as carbon‐free dual‐capable hosts for both sulfur and lithium. As a heavy S host, the interface‐engineered heterostructure integrates adsorptive TiO2 with high conductive VN and concurrently yields a built‐in electric field for charge‐redistribution at the TiO2/VN interfaces with enlarged active locations for trapping‐migration‐conversion of polysulfides. Thus‐fabricated TiO2@VN–S composite harnessing high tap‐density favors constructing dense cathodes (≈1.7 g cm–3) with low porosity (<30 vol%), exhibiting dual‐boosted cathode‐level peak volumetric‐/gravimetric‐energy‐densities nearly 1700 Wh L−1cathode/1000 Wh kg−1cathode at sulfur loading of 4.2 mg cm−2 and prominent areal capacity (6.7 mAh cm−2) at 7.6 mg cm−2 with reduced electrolyte (<10 µL mg−1sulfur). Particular lithiophilicity of the TiO2@VN is demonstrated as Li host to uniformly tune Li nucleation with restrained dendrite growth, consequently bestowing the assembled full‐cell with high electrode‐level volumetric/gravimetric‐energy‐density beyond 950 Wh L−1cathode+anode/560 Wh kg−1cathode+anode at 3.6 mg cm−2 sulfur loading alongside limited lithium excess (≈50%). A high‐density fibrous TiO2@VN heterostructure mediator with built‐in electric fields is constructed via an ingenious selective nitridation from biotemplate‐derived twinborn hybrid titanium/vanadium oxide fibers, which can synchronously serve as carbon‐free, dual‐capable hosts of both sulfur and lithium for practical high‐energy‐density Li–S full batteries.

Nanoporous silicon is a promising anode material for high energy density batteries due to its high cycling stability and high tap density compared to other nanostructured anode materials. However, the high cost of synthesis and low yield of nanoporous silicon limit its practical application. Here, we develop a scalable, low-cost top-down process of controlled oxidation of Mg 2 Si in the air, followed by HCl removal of MgO to generate nanoporous silicon without the use of HF. By controlling the synthesis conditions, the oxygen content, grain size and yield of the porous silicon are simultaneously optimized from commercial standpoints. In situ environmental transmission electron microscopy reveals the reaction mechanism; the Mg 2 Si microparticle reacts with O 2 to form MgO and Si, while preventing SiO 2 formation. Owing to the low oxygen content and microscale secondary structure, the nanoporous silicon delivers a higher initial reversible capacity and initial Coulombic efficiency compared to commercial Si nanoparticles (3,033 mAh/g vs. 2,418 mAh/g, 84.3% vs. 73.1%). Synthesis is highly scalable, and a yield of 90.4% is achieved for the porous Si nanostructure with the capability to make an excess of 10 g per batch. Our synthetic nanoporous silicon is promising for practical applications in next generation lithium-ion batteries.

Compared to nanostructured Si/C materials, micro-sized Si/C anodes for lithium-ion batteries (LIBs) have gained significant attention in recent years due to their higher volumetric energy density, reduced side reactions and low costs. However, they suffer from more severe volume expansion effects, making the construction of stable micro-sized Si/C anode materials crucial. In this study, we proposed a simple wet chemistry method to obtain porous micro-sized silicon (μP-Si) from waste AlSi alloys. Then, the μP-Si@carbon nanotubes (CNT)@C composite anode with high tap density was prepared by wrapping with CNT and coated with polyvinylpyrrolidone (PVP)-derived carbon. Electrochemical tests and finite element (FEM) simulations revealed that the introduction of CNTs and PVP-derived carbon synergistically optimize the stability and overall performance of the μP-Si electrode via construction of tough composite interface networks. As an anode material for LIBs, the μP-Si@CNT@C electrode exhibits boosted reversible capacity (∼ 3500 mAh·g −1 at 0.2 A·g −1 ), lifetime and rate performance compared to pure μP-Si. Further full cell assembly and testing also indicates that μP-Si@CNT@C is a highly promising anode, with potential applications in future advanced LIBs. It is expected that this work can provide valuable insights for the development of micro-sized Si-based anode materials for high-energy-density LIBs.

Hard carbons are promising anode materials for sodium‐ion batteries. To meet practical requirements, searching for durable and conductive carbon with a stable interface is of great importance. Here, we prepare a series of vanadium‐modified hard carbon submicrospheres by using hydrothermal carbonization followed by high‐temperature pyrolysis. Significantly, the introduction of vanadium can facilitate the nucleation and uniform growth of carbon spheres and generate abundant V–O–C interface bonds, thus optimizing the reaction kinetic. Meanwhile, the optimized hard carbon spheres modified by vanadium carbide, with sufficient pseudographitic domains, provide more active sites for Na ion migration and storage. As a result, the HC/VC‐1300 electrode exhibits excellent Na storage performance, including a high capacity of 420 mAh g−1 at 50 mA g−1 and good rate capability at 1 A g−1. This study proposes a new strategy for the synthesis of hard carbon spheres with high tap density and emphasizes the key role of pseudographitic structure for Na storage and interface stabilization. The HC/VC materials were synthesized by using hydrothermal carbonization followed by high‐temperature pyrolysis. The HC/VC‐1300 material has abundant V–O–C interface bonds and sufficient pseudographitic domains to provide more active sites for Na ion migration and storage, optimizing the reaction kinetics, resulting in good structural stability and excellent Na storage properties.

Due to excellent conductivity, oxidation resistance and low electrochemical mobility of gold itself, gold conductor pastes were widely used in electronic technology. However, the application of gold conductor pastes was limited by irregular morphology, wide particle size distribution, and low tap density of gold powders, which were usually prepared by the traditional liquid-phase reduction method. In this work, gold powders with high crystallinity and average particle size of 1.5 μm were prepared by seed-mediated synthesis. The as-prepared gold powders exhibited uniform size distribution, regular morphology, and intact crystal structure. Owe to proper particle diameter and extraordinary dispersion, the tap density of gold powders was as high as 10.2 g/cm3. Gold particles were tightly packed during sintering of paste, promoting densification of sintered body and improving the conductivity of thick film circuit. Gold powders with high tap density and crystallinity served as a fundamental material for high-performance electronic pastes, which exhibited significant application potential in precision sensor electrodes.

Powder characterisation is critical for developing high-quality, consistent powder metallurgy processes and materials. Internationally standardised tests have been developed to measure specific powder characteristics that are relevant to specific powder metallurgy manufacturing techniques. Dynamic tap density is a new characterisation method for granular materials that has not yet been applied to metal powders. In this study, the dynamic tap density of different metal powders is measured and compared to standard powder characteristics. The results support the theoretical assumption that observing the dynamic tap density can give you further information on the powder characteristics and whether the powder will be suitable for a specific powder metallurgy process.

Utilization of LiFePO 4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO 4 , which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO 4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO 4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO 4 , compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a ‘carbon additive free’ cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO 4 /FePO 4 has been understood with density functional theory calculations. Nanonization of battery electrode particles is a usual way to enhance their conductivity, but the decreased tap density is detrimental to battery performance. Here, the authors coat micron-sized lithium iron phosphate with a conducting polymer layer and demonstrate some excellent electrochemical properties.