Encapsulating micro-nano Si/SiO(x) into conjugated nitrogen-doped carbon as binder-free monolithic anodes for advanced lithium ion batteries

Gamma radiation-induced nanodefects in diffusive memristors and artificial neurons

Gamma photons with an average energy of 1.25 MeV are well-known to generate large amounts of defects in semiconductor electronic devices. Here we investigate the novel effect of gamma radiation on diffusive memristors based on metallic silver nanoparticles dispersed in a dielectric matrix of silica. Our experimental findings show that after exposure to radiation, the memristors and artificial neurons made of them demonstrate much better performance in terms of stable volatile resistive switching and higher spiking frequencies, respectively, compared to the pristine samples. At the same time we observe partial oxidation of silver and reduction of silicon within the switching silica layer. We propose nanoinclusions of reduced silicon distributed across the silica layer to be the backbone for metallic nanoparticles to form conductive filaments, as supported by our theoretical simulations of radiation-induced changes in the diffusion process. Our findings propose a new opportunity to engineer the required characteristics of diffusive memristors in order to emulate biological neurons and develop bio-inspired computational technology.

Construction of porous Si/Ag@C anode for lithium-ion battery by recycling volatile deposition waste derived from refining silicon

Owing to the rapid advancement of the photovoltaic industry, a lot of photovoltaic (PV) silicon waste will be generated. Thus, the recycling and reuse of waste silicon have become particularly important, both for environmental remediation and economic benefits. In this work, a special structure of porous Si nanoparticles embedded nano-Ag and coated carbon layer (P-SiNPs/Ag@C) was produced by silver-assisted chemical etching (Ag-ACE) the deposited silicon waste. The special porous structure and carbon layer coating can effectively address the volume expansion issues during charge/discharge. The intercalated Ag nanoparticles greatly reduced the transfer impedance and enhanced the electrical conductivity of the anode material. As a result, the novel-designed P-SiNPs/Ag@C anode can maintain a prominent reversible capacity (1521 mAh·g^-1 at 0.2 A g^-1 after 50 cycles) and outstanding rate performance (1099 mAh·g^-1 at 2 A g^-1). When the current density at 1 A g^-1, the specific capacity still maintains at 706 mAh·g^-1 over 300 cycles. The superiority of the prepared P-SiNPs/Ag@C structures was further confirmed by Comsol Multiphysics software. Impressively, the synthesis route provides a novel avenue for value-added utilization of residual silicon waste resources from EB refining silicon and the preparation of high-performance lithium battery silicon-based anode.

Thermochemical Cyclization Constructs Bridged Dual-Coating of Ni-Rich Layered Oxide Cathodes for High-Energy Li-Ion Batteries

Enhancing microstructural and electrochemical stabilities of Ni-rich layered oxides is critical for improving the safety and cycle-life of high-energy Li-ion batteries. Here we propose a thermochemical cyclization strategy where heating polyacrylonitrile with LiNi_0.8Co_0.1Mn_0.1O₂ can simultaneously construct a cyclized polyacrylonitrile outer layer and a rock-salt bridge-like inner layer, forming a compact dual-coating of LiNi_0.8Co_0.1Mn_0.1O₂. Systematic studies demonstrate that the mild cyclization reaction between polyacrylonitrile and LiNi_0.8Co_0.1Mn_0.1O₂ induces a desirable "layered to rock-salt" structural transformation to create a nano-intermedium that acts as the bridge for binding cyclized polyacrylonitrile to layered LiNi_0.8Co_0.1Mn_0.1O₂. Because of the improvement of the structural and electrochemical stability and electrical properties, this cathode design remarkably enhances the cycling performance and rate capability of LiNi_0.8Co_0.1Mn_0.1O₂, showing a high reversible capacity of 183 mAh g^-1 and a high capacity retention of 83% after 300 cycles at 1 C rate. Notably, this facile and scalable surface engineering makes Ni-rich cathodes potentially viable for commercialization in high-energy Li-ion batteries.

Co-Inlaid Carbon-Encapsulated SiOx Anodes via a Self-Assembly Strategy for Highly Stable Lithium Storage

SiO_x is a promising anode material for next-generation lithium-ion batteries, with high energy density and low cost. However, several issues, such as poor cycling stability, should be overcome before practical application. Here, gum arabic, a well-known natural gum with low cost, is used as a carbon source to form a uniform Co-inlaid carbon coating on SiO_x by a facile and scalable self-assembly method using Co²⁺ as a "bridge", during which Co²⁺ plays a key role. After carbonization treatment, the Co-inlaid carbon coating can effectively mitigate volume effects, enhance electrical conductivity, boost deep delithiation processes, and guarantee the structural integrity of SiO_x-Co@C. Because of the unique Co-inlaid carbon coating, the SiO_x-Co@C electrode displays much improved lithium-storage properties. The charging capacity of the SiO_x-Co@C electrode at the 250th cycle is 1010.8 mA h g^-1 with 84% capacity retention at 200 mA g^-1. This work presents a facile and efficient strategy to construct a uniform multifunctional coating for improved electrochemical properties.

Fabrication of amorphous hollow mesoporous Si@SiOx nanoboxes as an anode material for enhanced lithium storage performance

Hollow mesoporous Si@SiOx nanoboxes are synthesized successfully by a simple sol–gel reaction of triethoxysilane using Fe2O3 nanocubes as the template, followed by a thermal reduction process and subsequent acid treatment process.

Green and Scalable Fabrication of Sandwich-like NG/SiOx/NG Homogenous Hybrids for Superior Lithium-Ion Batteries

SiOx is considered as a promising anode for next-generation Li-ions batteries (LIBs) due to its high theoretical capacity; however, mechanical damage originated from volumetric variation during cycles, low intrinsic conductivity, and the complicated or toxic fabrication approaches critically hampered its practical application. Herein, a green, inexpensive, and scalable strategy was employed to fabricate NG/SiOx/NG (N-doped reduced graphene oxide) homogenous hybrids via a freeze-drying combined thermal decomposition method. The stable sandwich structure provided open channels for ion diffusion and relieved the mechanical stress originated from volumetric variation. The homogenous hybrids guaranteed the uniform and agglomeration-free distribution of SiOx into conductive substrate, which efficiently improved the electric conductivity of the electrodes, favoring the fast electrochemical kinetics and further relieving the volumetric variation during lithiation/delithiation. N doping modulated the disproportionation reaction of SiOx into Si and created more defects for ion storage, resulting in a high specific capacity. Deservedly, the prepared electrode exhibited a high specific capacity of 545 mAh g-1 at 2 A g-1, a high areal capacity of 2.06 mAh cm-2 after 450 cycles at 1.5 mA cm-2 in half-cell and tolerable lithium storage performance in full-cell. The green, scalable synthesis strategy and prominent electrochemical performance made the NG/SiOx/NG electrode one of the most promising practicable anodes for LIBs.

Recycling of photovoltaic silicon waste for high-performance porous silicon/silver/carbon/graphite anode

The rapid development photovoltaic industry has generated a huge amount of waste ultra-fine silicon cutting powder. The management and value-added recovery of silicon cutting waste is highly important for both environmental remediation and economic efficiency. In this work, silicon waste was used as a cost-effective raw material for the preparation of silicon/graphite anode for lithium-ion batteries. First, porous Si embedded with Ag particles (pSi/Ag) was produced by silver-assisted chemical etching (Ag-ACE). Then, pSi/Ag was loaded on a micron-sized graphite matrix (pSi/Ag/G), and organic carbon (C) produced by the pyrolysis of polyvinylpyrrolidone (PVP) acted as a link to closely connect pSi/Ag and graphite to form the pSi/Ag/C/G composite. The incorporated Ag particles and the porous structure improve electron transfer and mitigate the volume expansion effect of silicon. The novel design and structure of the anode can maintain the integrity of the electrode during cycling, and thus strongly improve cycling stability. The prepared pSi/Ag/C/G composite exhibited a large initial discharge capacity of 2353 mAh/g at 0.5 A/g and good initial coulombic efficiency of 83%, delivering a high capacity of 972 mAh/g at 1 A/g after 200 cycles. This work confirmed the possibility of the preparation of lithium battery silicon-carbon anode from silicon waste and provides a promising new avenue for value-added utilization of silicon cutting waste materials.

PSi@SiOx/Nano-Ag composite derived from silicon cutting waste as high-performance anode material for Li-ion batteries

Integration of photovoltaic (PV) power generation and energy storage has been widely believed to be the ultimate solution for future energy demands. Herein, an ingenious method was reported to make full use of photovoltaic silicon cutting waste (SiCW) natural characters fabricating PSi@SiOx/Nano-Ag composite as anode material for high-performance lithium-ion batteries. The sheet-like structure with nano/micropores and native SiOx layer addressed the volume expansion issues of Si material. Ag nanoparticles greatly enhanced electrical conductivity of composite and promoted Li⁺/e^- transport. Synergistic effect of the designed PSi@SiOx/Nano-Ag composite contributed outstanding cyclic performance with reversible capacity of 1409mAhg^-1 after 500 cycles. Notably, full LIBs with PSi@SiOx/Nano-Ag anode and commercial Li[Ni_0.6Co_0.2Mn_0.2]O₂ (NCM622) cathode delivered stable capacity of 137.5mAhg^-1 at current density of 200 mA g^-1, accompanying with a high energy density of 438 Wh kg^-1. Furthermore, electrochemical Li⁺ storage behavior of this PSi@SiOx/Nano-Ag electrode was studied, and reaction mechanism and crystal structure evolution during cycles were also revealed by in-situ XRD analysis. The synthesis method is facile and cost-effective, which paves a novel way towards high-performance Si-based anodes and promising markets for both solar photovoltaic and lithium-ion battery industries.

A Low-Cost and Scalable Carbon Coated SiO-Based Anode Material for Lithium-Ion Batteries

Silicon monoxide (SiO) is considered as one of the most promising alternative anode materials thanks to its high theoretical capacity, satisfying operating voltage and low cost. However, huge volume change, poor electrical conductivity, and poor cycle performance of SiO dramatically hindered its commercial application. In this work, we report an affordable and simple way for manufacturing carbon-coated SiO-C composites with good electrochemical performance on kilogram scales. Industrial grade SiO was modified by carbon coating using cheap and environment friendly polyvinyl pyrrolidone (PVP) as carbon source. High-resolution transmission electron microscopy (HRTEM) and Raman spectra results show that there is an amorphous carbon coating layer with a thickness of about 40 nm on the surface of SiO. The synthesized SiO-C-650 composite shows great electrochemical performance with a high capacity of 1491 mAh.g-1 at 0.1 C rate and outstanding capacity retention of 67.2 % after 100 cycles. The material also displays an excellent performance with a capacity of 1100 mAh.g-1 at 0.5 C rate. Electrochemical impedance spectroscopy (EIS) results also prove that the carbon coating layer can effectively improve the conductivity of the composite and thus enhance the cycling stability of SiO electrode.

In Situ Construction of High-Performing Compact Si-SiOx-CNx Composites from Polyaminosiloxane for Li-Ion Batteries

Great efforts have been made to design high-performing Si/C composite anodes for Li-ion batteries to improve their energy density and cycling life. However, challenges remain in achieving fast electrical conductivity while accommodating significant electrode volumetric changes. Here, we report a unique Si/C-based anode architecture, a Si-SiO_x-CN_x composite, which is simultaneously constructed via the pyrolysis of a polyaminosiloxane precursor. The obtained structure features high-purity Si nanocrystals embedded in an amorphous silica matrix and then embraced by N-doped carbon layers. Notably, in this structure, all three components derived from the polyaminosiloxane precursor are linked by chemical bonding, forming a compact Si-SiO_x-CN_x triple heterostructure. Because of the improvement in the volumetric efficiency for accommodating Si active materials and electrical properties, this anode design enables promising electrochemical performance, including excellent cycle performance (830 mAh g^-1 after 100 cycles at 0.1 A g^-1) and outstanding rate performance (400 mAh g^-1 at 5 A g^-1). Moreover, this composite anode demonstrates great potential for high-energy Li-ion batteries, where a Si-SiO_x-CN_x//LiNi_0.9Co_0.1O₂ full-cell shows a high capacity of 180 mAh g^-1 as well as stable cycle performance (150 mAh g^-1 after 200 cycles at 0.19 A g^-1).

The preparation and characterization of high-performance mesoporous carbon from a highly π-conjugated polybenzoxazine precursor

This work focusing on the effects of chemical structure can broaden the study of functional mesoporous carbon.

Binder-Free Electrodes and Their Application for Li-Ion Batteries

Lithium-ion batteries (LIB) as energy supply and storage systems have been widely used in electronics, electric vehicles, and utility grids. However, there is an increasing demand to enhance the energy density of LIB. Therefore, the development of new electrode materials with high energy density becomes significant. Although many novel materials have been discovered, issues remain as (1) the weak interaction and interface problem between the binder and the active material (metal oxide, Si, Li, S, etc.), (2) large volume change, (3) low ion/electron conductivity, and (4) self-aggregation of active materials during charge and discharge processes. Currently, the binder-free electrode serves as a promising candidate to address the issues above. Firstly, the interface problem of the binder and active materials can be solved by fixing the active material directly to the conductive substrate. Secondly, the large volume expansion of active materials can be accommodated by the porosity of the binder-free electrode. Thirdly, the ion and electron conductivity can be enhanced by the close contact between the conductive substrate and the active material. Therefore, the binder-free electrode generally exhibits excellent electrochemical performances. The traditional manufacture process contains electrochemically inactive binders and conductive materials, which reduces the specific capacity and energy density of the active materials. When the binder and the conductive material are eliminated, the energy density of the battery can be largely improved. This review presents the preparation, application, and outlook of binder-free electrodes. First, different conductive substrates are introduced, which serve as carriers for the active materials. It is followed by the binder-free electrode fabrication method from the perspectives of chemistry, physics, and electricity. Subsequently, the application of the binder-free electrode in the field of the flexible battery is presented. Finally, the outlook in terms of these processing methods and the applications are provided.

Hollow Boron-Doped Si/SiOx Nanospheres Embedded in the Vanadium Nitride/Nanopore-Assisted Carbon Conductive Network for Superior Lithium Storage

SiO_x-based anode materials with high capacity and outstanding cycling performance have gained numerous attentions. Nevertheless, the poor electrical conductivity and non-negligible volume change hinder their further application in Li-ion batteries. Herein, we propose a new strategy to construct a hollow nanosphere with boron-doped Si/SiO_x decorated with vanadium nitride (VN) nanoparticles and embedded in a nitrogen-doped, porous, and partial graphitization carbon layer (B-Si/SiO_x@VN/PC). Benefiting from such structural and compositional features, the B-Si/SiO_x@VN/PC electrode exhibits a stable cycling capacity of 1237.1 mA h g^-1 at a current density of 0.5 A g^-1 with an appealing capacity retention of 87.0% after 300 cycles. Additionally, it delivers high-rate capabilities of 1139.4, 940.7, and 653.4 mA h g^-1 at current densities of 2, 5, and 10 A g^-1, respectively, and ranks among the best SiO_x-based anode materials. The outstanding electrochemical performance can be ascribed to the following reasons: (1) its hollow structure makes the Li⁺ transportation length decreased. (2) The existing nanopores facilitate the Li⁺ insertion/desertion and accommodate the volume variation. (3) The nitrogen-doped partial graphitization carbon enhances the electrical conductivity and promotes the formation of stable solid electrolyte interface layers during the repetitive Li⁺ intercalation/extraction process.

Green Synthesis of Dual Carbon Conductive Network-Encapsulated Hollow SiO x Spheres for Superior Lithium-Ion Batteries

Designing hollow/porous structure is regarded as an effective approach to address the dramatic volumetric variation issue for Si-based anode materials in Li-ion batteries (LIBs). Pioneer studies mainly focused on acid/alkali etching to create hollow/porous structures, which are, however, highly corrosive and may lead to a complicated synthetic process. In this paper, a dual carbon conductive network-encapsulated hollow SiO _x (DC-HSiO _x) is fabricated through a green route, where polyacrylic acid is adopted as an eco-friendly soft template. Low electrical resistance and integrated electrode structure can be maintained during cycles because of the dual carbon conductive networks distributed both on the surface of single particles formed by amorphous carbon and among particles constructed by reduced graphene oxide. Importantly, the hollow space is reserved within SiO _x spheres to accommodate the huge volumetric variation and shorten the transport pathway of Li⁺ ions. As a result, the DC-HSiO _x composite delivers a large reversible capacity of 1113 mA h g^-1 at 0.1 A g^-1, an excellent cycling performance up to 300 cycles with a capacity retention of 92.5% at 0.5 A g^-1, and a good rate capability. Furthermore, the DC-HSiO _x//LiNi_0.8Co_0.1Mn_0.1O₂ full cell exhibits high energy density (419 W h kg^-1) and superior cycling performance. These results render an opportunity for the unique DC-HSiO _x composite as a potential anode material for use in high-performance LIBs.

Toward Mechanically Stable Silicon-Based Anodes Using Si/SiO x@C Hierarchical Structures with Well-Controlled Internal Buffer Voids

Low conductivity and structural degradation of silicon-based anodes lead to severe capacity fading, which fundamentally hinders their practical application in Li-ion batteries. Here, we report a scalable Si/SiO _x@C anode architecture, which is constructed simultaneously by sintering a mixture of SiO/sucrose in argon atmosphere, followed by acid etching. The obtained structure features highly uniform Si nanocrystals embedded in silica matrices with well-controlled internal nanovoids, with all of them embraced by carbon shells. Because of the improvement of the volumetric efficiency for accommodating Si active spices and electrical properties, this hierarchical anode design enables the promising electrochemical performance, including a high initial reversible capacity (1210 mAh g^-1), stable cycling performance (90% capacity retention after 100 cycles), and good rate capability (850 mAh g^-1 at 2.0 A g^-1 rate). More notably, the compact heterostructures derived from micro-SiO allow high active mass loading for practical applications and the facile and scalable fabrication strategy makes this electrode material potentially viable for commercialization in Li-ion batteries.

Hierarchical C/SiO x /TiO2 ultrathin nanobelts as anode materials for advanced lithium ion batteries

TiO₂-based nanomaterials are demonstrated to be a promising candidate for next generation lithium ion batteries due to their stable performance and easy preparation. However, their inherent low capacity impedes their wide application compared to commercial carbon nanomaterials. Here we present a unique in situ grafting-graphitization method to achieve a ternary nanocomposite of C/SiO _x /TiO₂ ultrathin nanobelts with a core-shell heterostructure. The obtained ternary nanocomposite integrates the merits of high specific capacity of SiO _x , the excellent mechanical stability of graphite-like carbon and the high reactivity of TiO₂. Cyclic voltammetric curves and cycling performance manifest the optimal ternary nanocomposite and deliver a very high initial specific capacity of ∼1196 mA h g^-1 with both good rate capability (∼200 mA h g^-1 up to 10 C) and especially enhanced cycle stability. Our work demonstrates that building hierarchical core-shell heterostructures is an effective strategy to improve capacity and cycling performance in other composite anodes for electrochemical energy storage materials.

Facile Synthesis of a MoS2 and Functionalized Graphene Heterostructure for Enhanced Lithium-Storage Performance

A facile strategy was designed for the in situ synthesis of MoS₂ nanospheres on functionalized graphene nanoplates (MoS₂@f-graphene) for use as lithium-ion battery anode materials. A modified Birch reduction was used to exfoliate graphite into few-layer graphene followed by modification with functional groups. Compared to the most common approach of mixing MoS₂ and reduced graphene oxide, our approach provides a way to circumvent the harsh oxidation and destruction of the carbon basal planes. In this process, alkylcarboxyl functional groups on the functionalized graphene (f-graphene) serve as sites where MoS₂ nanospheres crystallize, and thus create bridges between the MoS₂ nanospheres and the graphene layers to effectively facilitate electronic transport and to avoid both the aggregation of MoS₂ and the restacking of graphene. As anode materials, this unique MoS₂@f-graphene heterostructure has a high specific capacity of 1173 mAh g^-1 at a current density of 100 mA g^-1 and a good rate capacity (910 mAh g^-1 at 1600 mA g^-1).

A comparative investigation of different chemical treatments on SiO anode materials for lithium-ion batteries: towards long-term stability

In this work, we conduct a comparative study of boron-doped SiO (HB-SiO) and carbon-coated SiO (HC-SiO) to find an effective means of improving the electrochemical performances of SiO anode materials during long-cycle tests.

Two-step ball-milling synthesis of a Si/SiOx/C composite electrode for lithium ion batteries with excellent long-term cycling stability

SiO_x-based anodes have attracted tremendous attention owing to their low cost, higher theoretical capacity than graphite and lower volume expansion than pure silicon.

Facial Synthesis of Three-Dimensional Cross-Linked Cage for High-Performance Lithium Storage

Silicon/C composite is a promising anode material for high-energy Li-ion batteries. However, synthesizing high-performance Si-based materials at large scale and low cost remains a huge challenge. Here, we for the first time report the preparation of an interconnected three-dimensional (3D) porous Si-hybrid architecture by using a spray drying method. In this unique structure, the highly robust C-CNT-RGO cages not only can improve the conductivity of the electrode and buffer the volume expansion but also suppress the Si nanoparticles aggregation. As a result, the 3D Si@po-C/CNT/RGO electrode achieves long-life cycling stability at high rates (a reversible capacity of 854.9 mA h g(-1) at 2 A g(-1) after 500 cycles and capacity decay less than 0.013% per cycle) and good rate capability (1454.7, 1198.8, 949.2, 597.8, and 150 mA h g(-1) at current densities of 1, 2, 4, 10, and 20 A g(-1), respectively). Moreover, this novel electrode could deliver high reversible capacities and long-life stabilities even with high mass loading density (764.9 mA h g(-1) at 1.0 mg cm(-2) after 500 cycles and 472.2 mA h g(-1) at 1.5 mg cm(-2) after 400 cycles, respectively). This cheap and scalable strategy can be extended to fabricate other materials with large volume expansion (Sn, Ge, transition-metal oxides) and 3D porous carbon for other potential applications.

MnO2 nanotubes with a water soluble binder as high performance sodium storage materials

Well dispersed MnO₂ nanotubes were synthesized via a hydrothermal method.

SiOx and carbon double-layer coated Si nanorods as anode materials for lithium-ion batteries

SNs@SiO_x/C composite delivers a reversible capacity of 779 mA h g⁻¹ over 300 cycles at a current density of 400 mA g⁻¹.

Scalable Preparation of Ternary Hierarchical Silicon Oxide-Nickel-Graphite Composites for Lithium-Ion Batteries

Silicon monoxide is a promising anode candidate because of its high theoretical capacity and good cycle performance. To solve the problems associated with this material, including large volume changes during charge-discharge processes, we report a ternary hierarchical silicon oxide-nickel-graphite composite prepared by a facile two-step ball-milling method. The composite consists of nano-Si dispersed silicon oxides embedded in nano-Ni/graphite matrices (Si@SiOx /Ni/graphite). In the composite, crystalline nano-Si particles are generated by the mechanochemical reduction of SiO by ball milling with Ni. These nano-Si dispersed oxides have abundant electrochemical activity and can provide high Li-ion storage capacity. Furthermore, the milled nano-Ni/graphite matrices stick well to active materials and interconnect to form a crosslinked framework, which functions as an electrical highway and a mechanical backbone so that all silicon oxide particles become electrochemically active. Owing to these advanced structural and electrochemical characteristics, the composite enhances the utilization efficiency of SiO, accommodates its large volume expansion upon cycling, and has good ionic and electronic conductivity. The composite electrodes thus exhibit substantial improvements in electrochemical performance. This ternary hierarchical Si@SiOx /Ni/graphite composite is a promising candidate anode material for high-energy lithium-ion batteries. Additionally, the mechanochemical ball-milling method is low cost and easy to reproduce, indicating potential for the commercial production of the composite materials.

A plum-pudding like mesoporous SiO2/flake graphite nanocomposite with superior rate performance for LIB anode materials

A novel kind of plum-pudding like mesoporous SiO₂ nanospheres (MSNs) and flake graphite (FG) nanocomposite (pp-MSNs/FG) was designed and fabricated via a facile and cost-effective hydrothermal method.