Boosting stable lithium deposition via Li3N-Enriched inorganic SEI induced by a polycationic polymer layer.

Lithium (Li) metal is a promising anode material for future high-energy rechargeable batteries due to its remarkable properties. Nevertheless, excess Li in traditional lithium metal anodes (LMAs) reduces the energy density of batteries and increases safety risks. Electrochemical pre-lithiation is an effective technique for regulating the lithium content of the anodes. However, Cu foil or other non-Li based substrates used for pre-lithiation often have inhomogeneous surfaces and high nucleation barrier, leading to uneven tip deposition of lithium metal and fragile SEI. Herein, we have designed an interfacial layer composed of nano-Si particles and cationic polymer (poly (diallyldimethylammonium chloride)) (denoted as Si@PDDA) to induce the formation of Li3N-rich inorganic SEI and regulate the homogeneous plating/stripping of lithium. The uniformly dispersed nano-Si particles can decrease the Li+ nucleation overpotential through alloying reaction with lithium. The surface of Si nano-particles modified by PDDA contains numerous cationic sites, providing an electrostatic shielding layer to seeding the growth of Li metal and inhibiting dendrites formation. More promisingly, PDDA adsorbs electrolyte anions while transporting Li+, significantly accelerating the decomposition kinetics of inorganic salts within the electrolyte. Therefore, a SEI film rich in Li3N was formed on the anodes, ensuring the excellent interfacial stability and electrochemical cycling performance of LMAs. The symmetrical cells exhibit a cycle life of 900 h at 1 mA cm-2. Moreover, the practical full cells operate at a low negative/positive (N/P) capacity ratio (∼3) for over 160 cycles.

Comparison of soil addition, foliar spraying, seed soaking, and seed dressing of selenium and silicon nanoparticles effects on cadmium reduction in wheat (Triticum turgidum L.).

Wheat cadmium (Cd) contamination is a critical food security issue worldwide, and selenium (Se) and silicon (Si) are widely reported to reduce Cd accumulation in cereal crops. However, few studies have compared the most effective pathway to reduce Cd accumulation in crops using Se nanoparticles (nano-Se), Si nanoparticles (nano-Si), and their mixtures. Here, we investigated the concentrations of Cd in wheat using four application modes: soil addition, foliar spraying, seed soaking, and seed dressing combined with three different materials. The concentration of Cd in wheat grains can be significantly reduced by 31.30-62.99% and 36.96-51.04% through four applications of nano-Se and soil application and seed soaking of nano-Si, respectively. However, all treatments involving mixtures of nano-Si and nano-Se did not show a reduction in Cd concentration. The applications of both nano-Se and nano-Si can enhance antioxidant enzyme systems and regulate Cd-related gene expression to safeguard wheat tissues from Cd stress. Downregulation of the influx transporter from soil to root (TaNramp5) and from root to shoot (TaLCT1), along with the upregulation of the efflux transporter from cytoplasm to vacuole (TaHMA3), contributed to the nano-Si/nano-Se dependent Cd transport and reduced Cd accumulation in wheat grains. Overall, the application of nano-Se instead of nano-Si, and soil addition rather than foliar spraying, seed soaking, and seed dressing, can be efficiently utilized to reduce grain Cd accumulation from Cd-contaminated soils.

Effect of Graphene on the Performance of Silicon-Carbon Composite Anode Materials for Lithium-Ion Batteries.

(Si/graphite)@C and (Si/graphite/graphene)@C were synthesized by coating asphalt-cracked carbon on the surface of a Si-based precursor by spray drying, followed by heat treatment at 1000 °C under vacuum for 2h. The impact of graphene on the performance of silicon-carbon composite-based anode materials for lithium-ion batteries (LIBs) was investigated. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) images of (Si/graphite/graphene)@C showed that the nano-Si and graphene particles were dispersed on the surface of graphite, and thermogravimetric analysis (TGA) curves indicated that the content of silicon in the (Si/graphite/graphene)@C was 18.91%. More bituminous cracking carbon formed on the surface of the (Si/graphite/graphene)@C due to the large specific surface area of graphene. (Si/Graphite/Graphene)@C delivered first discharge and charge capacities of 860.4 and 782.1 mAh/g, respectively, initial coulombic efficiency (ICE) of 90.9%, and capacity retention of 74.5% after 200 cycles. The addition of graphene effectively improved the cycling performance of the Si-based anode materials, which can be attributed to the reduction of electrochemical polarization due to the good structural stability and high conductivity of graphene.

Stress Mitigation of Nanosilicon Anode to Achieve Energy-Dense and Highly-Stable Full Cell.

Nanosilicon (nano-Si) anode is subjected to significant stress concentration, which is caused by extrusion deformation of expanded Si nanoparticles with uneven distribution. The low-strength binder and adhesive interface are unable to withstand the stress, resulting in exfoliation and impeding the use of nano-Si anodes. This work aims to mitigate stress in a Si anode with flexible copper (Cu) skeletons that are metallurgically bonded to uniformly distributed Si nanoparticles. It is worth noting that the proposed porous Si-Cu anode exhibits improved high-load cycling performance and promising potential in the full cell, with an energy density of 463 Wh kg-1 at 0.5 C and retention of 81% after 500 cycles at 2 C. Chemo-mechanical simulation and in (ex) situ observation demonstrate that expansion stress is reduced and more evenly distributed in the anode due to uniform distribution of Si nanoparticles, flexible Cu skeletons, and adequate pores. More importantly, the stress is primarily distributed in the flexible Cu skeletons and bonding interface, preventing anode exfoliation, and ensuring efficient lithium ion/electron transference. This work sheds light on the structure construction of an alloy-type anode.

Carbon-Free Conversion of SiO2 to Si via Ultra-Rapid Alloy Formation: Toward the Sustainable Fabrication of Nanoporous Si for Lithium-Ion Batteries.

Silicon has the potential to improve lithium-ion battery (LIB) performance substantially by replacing graphite as an anode. The sustainability of such a transformation, however, depends on the source of silicon and the nature of the manufacturing process. Today's silicon industry still overwhelmingly depends on the energy-intensive, high-temperature carbothermal reduction of silica─a process that adversely impacts the environment. Rather than use conventional thermoreduction alone to break Si-O bonds, we report the efficient conversion of SiO2 directly to Mg2Si by a microwave-induced Mg plasma within 2.5 min at merely 200 W under vacuum. The underlying mechanism is proposed, wherein electrons with enhanced kinetics function readily as the reductant while the "bombardment" from Mg cations and electrons promotes the fast nucleation of Mg2Si. The 3D nanoporous (NP) Si is then fabricated by a facile thermal dealloying step. The resulting hierarchical NP Si anodes deliver stable, extended cycling with excellent rate capability in Li-ion half-cells, with capacities several times greater than graphite. The microwave-induced metal plasma (MIMP) concept can be applied just as efficiently to the synthesis of Mg2Si from Si, and the chemistry should be extendable to the reduction of multiple metal(loid) oxides via their respective Mg alloys.

Silicon inhibits the upward transport of Cd in the first internode of different rice varieties in a Cd stressed farm land.

Silicon spraying on leaves can reduce the accumulation of cadmium (Cd) in rice grain. However, it has been found that not all rice varieties decrease in Cd content after silicon (Si) application. A field study was conducted to check the performance of Si on the accumulation and transport of Cd in four rice varieties. TY390 and YXY2, having 51.5%- 60.6% Cd content of grain was inhibited by foliar Si, were classified as CRS varieties; BXY9978 and YXYLS, having Cd content of grain is nonresponsive with Si, were classified as CNS varieties. The Cd contents were mainly accumulated in stem, especially in the first stem node. While foliar Si reported no changes in the Cd content of first node in four different rice varieties. Comparing the correlation between Si and Cd contents in the above part of the first internode of CRS and CNS, as well as the relative expression of Cd transport genes in the first internode suggested that first internode was the key site to effect Cd transport through Si application, and OsZIP7 is a key Cd transporter protein responsive to Si, leading to different response of Cd transport and accmulation between the CRS and the CNS varieties of rice.

Si@nitrogen-doped porous carbon derived from covalent organic framework for enhanced Li-storage.

Due to ultra-high theoretical capacity (4200 mAh g-1), silicon (Si) is an excellent candidate for the anode of lithium-ion batteries (LIBs). However, the application of Si is severely limited by its volume expansion of approximately 300% during the charge/discharge process. Herein, nitrogen-doped porous carbon (NC) capped nano-Si particles (Si@NC) composites with a core-shell structure were obtained by calcination of covalent organic frameworks (COFs) encapsulated nano-Si. COFs is a crystalline material with well-ordered structures, adjustable and ordered pores and abundant N atoms. After carbonization, the well-ordered pores and frameworks were kept well. Compared with other Si@NC composites, the well-ordered NC framework shell derived from COFs possesses high elasticity and well-ordered pores, which provides space for the volume expansion of nano-Si, and a channel to transfer Li+. The core-shell Si@NC composite exhibited good performances when applied as the anode of LIBs. At a current density of 100 mA g-1, it exhibited a discharge-specific capacity of 1534.8 mAh g-1 after 100 cycles with a first-coulomb efficiency of 69.7%. The combination of COFs with nano-Si is a better strategy for the preparation of anode materials of LIBs.

Constructing an artificial boundary to regulate solid electrolyte interface formation and synergistically enhance stability of nano-Si anodes.

Low coulombic efficiency and poor cyclic stability are two common problems for silicon anodes. Therefore, it is of great significance to improve cycling performance and initial coulombic efficiency (ICE) via rational surface engineering on nano-Si anodes. Herein, a new nano-silicon anode is obtained by straightforward constructing a multifunctional polypyrrole protective layer on the surface of silicon nanoparticles, which is further used as the inner boundary of solid electrolyte interface (SEI) film. Specifically, the Li salt decomposition reaction between the electrolyte and silicon surface is effectively inhibited under the protection of the compact artificial boundary. The transfer of Li+ for forming the SEI film is selectively slower than that of lithiation/delithiation reaction. This further reduces the amount of SEI film, leading to a high ICE of 93.2% at 0.5 A g-1 for modified nano-Si anodes. In addition, the flexible SEI precursor combined with the high proportion of organic components in SEIs not only accommodates the volume change of nano-silicon, but also suppresses accumulation of "waste SEI", so the electrode can maintain a reversible capacity of 1153.2 mAh g-1 at 1 A g-1 after 500 cycles. This work provides important guidance for surface structural optimization of alloy-type anodes with high volume change.

Micro-Mesoporous Carbons from Cyclodextrin Nanosponges Enabling High-Capacity Silicon Anodes and Sulfur Cathodes for Lithiated Si-S Batteries.

Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si-S cell.

Effects and mechanisms of foliar application of silicon and selenium composite sols on diminishing cadmium and lead translocation and affiliated physiological and biochemical responses in hybrid rice (Oryza sativa L.) exposed to cadmium and lead.

Currently, exploring effective measures to reduce multiple toxic metals accumulation in rice grains is an urgent issue to be tackled. Pot experiments were thus conducted to explore the effects and mechanisms of foliar spraying with composite sols of silicon (Si) and selenium (Se) during tillering to booting stage on diminishing cadmium (Cd) and lead (Pb) translocation to rice grains and affiliated physiological and biochemical responses in rice seedlings grown in Cd + Pb-polluted soils (positive control). Results showed that Cd and Pb contents in leaves or grains were distinctly below the positive control by the sols. Compared to the positive control, transcriptions of Cd transporter-related genes including OsLCT1, OsCCX2, OsHMA2 and OsPCR1 genes in leaves, and OsLCT1, OsCCX2, TaCNR2 and OSPCR1 in peduncles were downregulated by the increasing sols. Meanwhile, Se-binding protein 1 was evidently upregulated, together to retard Cd and Pb translocation to rice grains. The sols not only upregulated transcriptions of Lhcb1, RbcL, and OsBTF3 genes and production of psbA, Lhcb1 and RbcL proteins, but also increased the chlorophylls contents and RuBP carboxylase activities in the leaves, improving photosynthesis. The sols restrained ROS production from NADPH oxidases, but activated glutathione peroxidase, alleviating oxidative stress and damage. Additionally, Se was significantly enriched and was existed as selenomethionine in the rice grains. However, Pb transporter-related genes remain to be specified. Thus, the composite sols have potential to reduce Cd and Pb accumulation, mitigate oxidative damage, and promote photosynthesis and organic Se enrichment in rice plants under Cd and Pb combined pollution.

Effect of Silicon Nitride/Oxide on the Structure and the Thermal Conductivity of CoSi Nanocomposites.

In this work, the fabrication of nanocomposites with silicon nitride/oxide into the thermoelectric matrix of cobalt silicide is presented. The different concentrations of nano-Si3N4 were intentionally introduced by mechanical grinding while it was found that the nanocomposites also included SiO2 phase at micro- as well as at nano-scale. The structural and morphological modifications of the materials were studied by powder X-ray Diffraction, Scanning Electron Microscopy and Transmission Electron Microscopy. The nanocomposites were studied in terms of Hall Effect, Seebeck coefficient, electrical and thermal conductivity. Emphasis is given on the lattice thermal conductivity that was analyzed based on Effective Medium Theory and the contribution of each phase is taken into account.

Comprehensive Understanding of High Polar Polyacrylonitrile as an Effective Binder for Li-Ion Battery Nano-Si Anodes.

Well-defined polyacrylonitriles (PANs) with different molecular weights were synthesized through an activator regenerated by electron-transfer atom-transfer radical polymerization method and employed as binders in silicon negative electrode for lithium-ion batteries. Compared with poly(vinylidene fluoride) and carboxyl methyl cellulose as binders, the electrode performance of PANs is well-improved. Specifically, at 100 mA g(-1) from 0.01 to 1.5 V, the initial discharge capacity of PAN100-based electrode is 4147.8 mA h g(-1) and still remains about 1639.6 mA h g(-1) over 50 cycles. A comprehensive understanding on the improvement mechanism is preliminarily discussed. The results indicate that the superior performance largely depends on the higher lithium ion diffusion efficiency in PAN which results from the weak interaction between lithium ions and PAN polymer chain, and the hydrogen bonds among the nitrile group (C≡N) of PAN, Si nanoparticles, and the current collector, which will lead to an efficient coating of PAN with the Si particles and well-improved adhesion strength, synergistically depressing the structural deterioration of silicon electrodes.