Silicon Waste Research Articles

Conversion of waste photovoltaic silicon into silicon-carbon nanocages for lithium batteries anodes preparation

As the global demand for renewable energy surges, the mass decommissioning and disposal of photovoltaic (PV) modules pose significant environmental and economic challenges. In particular, the accumulation of waste silicon from these modules calls for efficient recycling solutions. Silicon possesses a large volume expansion problem during repeated de-embedding of lithium, we instead utilize electrospinning technology to encapsulate the waste silicon in nanocages and introduce titanium dioxide and silver into the structure. A one-step calcination process produces nanoparticle-loaded nanofiber cages, with in situ TiO2 and Ag particles enhancing structural integrity. The silicon-carbon nanofiber (SATCNF) composite exhibits outstanding electrochemical performance, retaining a reversible capacity of 466.3 mAh/g after 50 cycles at a current density of 0.1 A/g. Furthermore, it demonstrates robust stability during high-rate charge and discharge cycles, maintaining substantial capacity even under elevated current densities. This work not only provides a pathway for mitigating the environmental burden of waste silicon but also contributes to advancements in LIB technology for sustainable energy storage.

Simultaneous Recovery of Red Mud and Diamond Wire Saw Silicon Waste for Si–Fe Alloy Preparation

Simultaneous Recovery of Red Mud and Diamond Wire Saw Silicon Waste for Si–Fe Alloy Preparation

Recycled industrial waste silicon steel as high-performance electrode for oxygen evolution reaction using electroless plating surface modification

Exploring the large-area, cost-effective, and high-performance electrocatalyticoxygen evolution reaction (OER) electrode for water splitting is of great significance. Inspiring from the ‘waste to resource’ toward the circular economy, herein, the waste silicon steels (SS) were transformed into high-performance CoxFe3-xP/SS OER electrode through a facile electroless plating method. The plating layer of CoxFe3-xP not only endows the CoxFe3-xP/SS with outstanding electrocatalytic OER activity but also improves the corrosion resistance and stability of CoxFe3-xP/SS. The obtained Co2Fe1P/SS electrode exhibits the lowest overpotential of 244 mV at a current density of 10 mA/cm2 in 1 M KOH with a low Tafel slope of 48.7 mV/dec. Even at high current densities and in 6 M KOH and alkaline seawater (seawater + 1 M KOH), the Co2Fe1P/SS electrode also shows relatively low overpotentials, as well as high long-term durability. Specially, a large-area Co2Fe1P/SS OER electrode(40 × 40 cm2)was successfully prepared via the electroless plating approach. Toward the CoxFe3-xP/SS, the bimetallic Co-Fe synergies and phosphating effect promote the exposure of active sites and charge transfer. In addition, generated M(OH)x/MOOH (M = Co or Fe) species during OER activation could synergize with CoxFe3-xP and contribute excellent catalytic activity and stability.

Vapor-phase conversion of waste silicon powders to silicon nanowires for ultrahigh and ultra-stable energy storage performance

Silicon nanowires (SiNWs) have been used in a wide variety of applications over the past few decades due to their excellent material properties. The only drawback is the high production cost of SiNWs. The preparation of SiNWs from photovoltaic waste silicon (WSi) powders, which are high-volume industrial wastes, not only avoids the secondary energy consumption and environmental pollution caused by complicated recycling methods, but also realizes its high-value utilization. Herein, we present a method to rapidly convert photovoltaic WSi powders into SiNWs products. The flash heating and quenching provided by carbothermal shock induce the production of free silicon atoms from the WSi powders, which are rapidly reorganized and assembled into SiNWs during the vapor-phase process. This method allows for the one-step composite of SiNWs and carbon cloth (CC) and the formation of SiC at the interface of the silicon (Si) and carbon (C) contact to create a stable chemical connection. The obtained SiNWs-CC (SiNWs@CC) composites can be directly used as lithium anodes, exhibiting high initial coulombic efficiency (86.4%) and stable cycling specific capacity (2437.4 mA h g−1 at 0.5 A g−1 after 165 cycles). In addition, various SiNWs@C composite electrodes are easily prepared using this method.

Porous SiO2–Si3N4 Composite Ceramics Sintered by Carbothermal Nitridation of Diamond-Wire Sawing Silicon Waste

Porous SiO2–Si3N4 Composite Ceramics Sintered by Carbothermal Nitridation of Diamond-Wire Sawing Silicon Waste

Thermal conductivity enhancement of epoxy by a 3D Si3N4 crystal rod/grain skeleton fabricating from photovoltaic silicon waste

Silicon nitride (Si3N4) is one of the preferred fillers for the preparation of high thermal conductivity polymer composites because of its intrinsic high thermal conductivity and good electrical insulation. To maximize the thermal conductivity enhancement effect of the fillers in the composites, it is necessary to pre-construct a three-dimensional (3D) thermally conductive filler network. Herein, surfactant foaming was applied to pre-construct a 3D Si-containing framework from photovoltaic silicon waste (PSW), which was subsequently transformed into a porous skeleton consisting of Si3N4 rods and grains by in-situ nitridation reaction sintering. And finally, thermal conductive Si3N4/epoxy (EP) composites were fabricated after infiltrating EP into the network skeleton. When the filler content of Si3N4 was 41.00 vol%, the obtained Si3N4/EP composite showed the highest thermal conductivity of 2.99 W·m-1·K-1, which was 13.95 times higher than that of pure EP. Tests on running CPU and heating table showed that the Si3N4/EP substrate had excellent heat dissipation performance compared to the pure EP substrate. The 3D continuous network formed by "bridging" between two different morphologies of Si3N4 microcrystals contributed to providing effective multi-directional heat transfer paths and thereby improving the thermal conductivity of the composites. Overall, the low cost of raw silicon source originating from industrial waste as well as the simple and practical construction of heat-conducting filler network demonstrate the promising application of the Si3N4/EP composites fabricated in our work.

Simultaneous preparation of high-purity Si and eutectic Si-Nd alloy utilizing Nd2O3-containing waste slag and diamond-wire sawing silicon waste

Nd2O3-containing waste slag (NCWS) and diamond-wire sawing silicon waste (DSSW) are important rare earth and Si secondary resources, respectively. Currently, NCWS and DSSW are recycled respectively by at least two different routes, which is not efficient and increases the burden on the environment. The present study proposed a novel technical route for preparing high-purity bulk Si and eutectic Si-Nd alloy simultaneously using NCWS and DSSW as raw materials, depending on the concept of using waste to treat waste. The new technical route has only two steps: initially, raw Si-Nd alloys were obtained by extracting Nd from NCWS utilizing DSSW as a low-cost reductant, and the impurity, oxygen, in the DSSW was effectively removed utilizing NCWS; the highest extraction rate of Nd from NCWS reached 68.3%, and the oxygen removal rate in DSSW was 99.89%; in the subsequent step, the obtained raw Si-Nd alloys were separated and purified to produce high-purity bulk Si (＞99.98%) and eutectic Si-Nd alloy (＞99%) through a physical and clean method-electromagnetic directional crystallization. This novel route is considered effective and environmentally-friendly for the sustainability of rare earth and Si resources, because no gas and liquid wastes discharged throughout the whole route, and two high value products can be prepared simultaneously using two wastes.

Preparation of Si/TiSi2 as high-performance anode material for lithium-ion batteries by molten salt electrolysis

The photovoltaic industry has generated a large amount of silicon cutting waste (SiCW), whose disposal presents an urgent environmental issue. In this study, micron-sized flaky silicon cutting waste was transformed into silicon nanowires, and Si/TiSi2 nanocomposites were synthesized through molten salt electrolysis using photovoltaic SiCW and TiO2 as precursors. Lithium-ion batteries using the resulting composites as an anode exhibited an initial discharge specific capacity of 1936.1 mAh g⁻¹ and an initial Coulombic efficiency (ICE) of 83.99 %. After 200 cycles, its reversible specific capacity reached 1133.8 mAh g⁻¹, surpassing that of the molten salt electrolytic pre-oxidized SiCW (535.5 mAh g⁻¹) and untreated SiCW (385.0 mAh g⁻¹). This study presents a novel approach for modifying silicon-based anode materials while offering a sustainable and environmentally friendly method for recycling photovoltaic silicon waste.

Constructing Si@CN@MXene from silicon waste as high-performance lithium-ion battery anodes

Silicon represents one of the most attractive materials for anodes in lithium-ion batteries (LIBs) due to highest theoretical specific capacity. Thus, there is a most urgent need to prepare Si-based nano materials in a very efficient way, and develop some reasonable approaches for their modification in order to resolve the short-falls of Si anode, which include both low conductivity and huge volume changes during intercalation of lithium ions. In this work, the kerf loss silicon (KL Si) from the photovoltaic industry has been used as an inexpensive Si source for the synthesis of the Si@CN@MXene (SCM) composite to be applied as an anode material. Meanwhile, the chitosan works as the charge bridge in sequence with the Si and MXene nanosheets under electrostatic force during composite preparation. The MXene nanosheet and N-doped carbon layer that build up during chitosan calcination can be attributed to forming a hierarchical high-speed conductive network over the surface of silicon, which contributed to alleviate the volume expansion of silicon. The SCM electrode discharge capacity was obtained at a stable value of 900.8 mAh g−1 at 0.5 A g−1, 861.9 mA g−1 at 1 A g−1 and 657.6 mA g−1 even at 2 A g−1 after 100 cycles. The SCM electrode also exhibited good rate performance from 0.2 to 5 A g−1. Therefore, this study recommends that the method is very promising for producing the silicon anode material for LIBs from KL Si.

Preparation of WSi@SiOx/Ti3C2 from photovoltaic silicon waste as high-performance anode materials for lithium-ion batteries

Silicon anodes hold promise for future lithium-ion batteries (LIBs) due to their high capacity, but they face challenges such as severe volume expansion and low electrical conductivity. In this study, we present a straightforward and scalable electrostatic self-assembly method to fabricate WSi@SiOx/Ti3C2 composites for LIBs. Silicon nanosheets and the ultra-thin oxide layer SiOx serve as sufficient buffers against volume changes, while the layered MXene enhances the electrical conductivity of the composite and promoted Li+/e- transport. Additionally, cationic surfactant-treated Ti3C2 provides more active sites for WSi@SiOx attachment and acts as an intercalating agent, enabling WSi@SiOx to enter the interlayer spaces of Ti3C2. The WSi@SiOx/Ti3C2 electrodes significantly improved electrochemical performance, achieving a capacity of 1,130 mAh g-1 after 800 charge/discharge cycles at 500 mA g-1. This study not only presents a straightforward pathway for high-value utilization of silicon waste but also offers a feasible route for preparing high-performance and cost-effective silicon-based LIBs.

Synergetic recovery of Ti and Fe from Ti-bearing blast furnace slag and red mud by diamond wire saw silicon waste

Diamond wire saw silicon waste (DWSSW), Ti-bearing blast furnace slag (TBFFS), and red mud (RM) are three types of industrial wastes that contain abundant Si, Ti, and Fe. Their recovery is vital for reducing the waste of resources, environmental protection, and sustainable industrial development. In this study, the environmentally friendly process of synergetic recovery of Ti and Fe from TBFS and RM to prepare Si-Ti-Fe alloy by using DWSSW as reducing agent was proposed. The thermodynamic and experimental determinations of the reason behind Si extracting Ti from TBFS and RM is that it decreased the activity of SiO2. The optimal conditions for recovery of Ti and Fe were that the mass ratio of RM to TBFS was 1, and the mass ratio of DWSSW to (RM+TBFS) was 1.25. The highest recovery rates of Ti and Fe are 88.67 % and 93.33 %, respectively. Further, the Si-Ti-Fe alloy was separated and purified by electromagnetic directional solidification to obtain Si and Si-Fe-Ti alloys. Through life cycle assessment (LCA), it is concluded that electricity during the recycling process has the most significant impact on the environment. This process is a green and efficient method for the recovery of DWSSW, TBFS, and RM.

Upcycling of waste photovoltaic silicon: Co-MOF derived coating layer enhanced lithium storage

Large amounts of silicon waste (W-Si) powders or ingots from the photovoltaic (PV) industry can be recycled as the improved raw negative electrode material in Lithium-ion batteries. Herein, Co-MOFs (ZIF-67) is produced in the form of small particles which turns into the uniform coating layer on the surface of micro-sized W-Si by solvent evaporation, and then ZIF-67 is carbonized to form nitrogen-doped carbon (NC) layer and carbon nanotubes (CNTs). Finally, W-Si/NC/Co/CNTs composites are formed. The continuous and uniform NC layer and CNTs formed by the catalyzation of Co on the surface of the silicon particles can inhibit the volume expansion of silicon during the charge and discharge process, showing the reversible discharge capacity of 1039 mAh g−1 after 100 cycles. The rate performance is also improved due to the high conductivity composite structure. This work can provide a choice for the composite of MOF and micro-silicon, and the meaning guidance for the application of silicon waste from PV industry.

Facile preparation of heat-conducting ceramics/epoxy composites by pre-constructing Si3N4–SiC skeleton from photovoltaic silicon waste

As a by-product of solar panel production, photovoltaic silicon waste (PSW) is becoming a threat to the environment and human health. The classical resource recycling approaches are separating Si and SiC from PSW, most of which is costly and inefficient. In this study, the PSW acted as a silicon source was directly translated into a vertically oriented 3D Si3N4–SiC skeleton with ice-templating and in situ nitriding technology. The Si3N4–SiC/epoxy (EP) composites were successfully produced by the following vacuum epoxy infusion. Composite with 55.46 wt% filler content had the maximum thermal conductivity (TC) of 1.717 W/(m·K), 950 % higher than pure epoxy. The composite substrates showed excellent heat dissipation performance in practical applications due to their high TC, primarily attributed to the directional arrangement of ceramic powders in the Si3N4–SiC skeleton. Additionally, the Si3N4 whiskers produced in situ promoted the formation of wider continuous phonon heat transfer channels. In short, we proposed a simple and feasible approach for recycling PSW to fabricate high-value heat-conducting composites, which expands a new direction of industrial waste secondary recycling and is of great importance for the clean utilization of the resource.

Regeneration of photovoltaic industry silicon waste toward high-performance lithium-ion battery anode

Regeneration of photovoltaic industry silicon waste toward high-performance lithium-ion battery anode

Recycling of Ti and Si from Ti-bearing blast furnace slag and diamond wire saw silicon waste by flux alloying technique

Two industrial solid wastes, Ti-bearing blast furnace slag (TBFS) and diamond wire saw silicon waste (DWSSW), contain large amounts of Ti and Si, and their accumulation wastes resources and intensifies environmental pollution. In the present study, DWSSW was used as the silicon source to reduce titanium oxide in TBFS by electromagnetic induction smelting, and meanwhile Na3AlF6 was added as a flux to improve the recycling of the wastes. Ti and Si of the two wastes were simultaneously recovered in the form of alloy. The effects of different addition amount of Na3AlF6 flux in the mixture of DWSSW and TBFS on chemical composition, viscosity, basicity and structure of slag were investigated. The dissolution behavior of SiO2 in Na3AlF6 flux was theoretically deduced and experimentally verification. The optimized recovery rate of Ti and Si were obtained, and the research realizes the efficient recycling of DWSSW and TBFS simultaneously.

Recycling of waste silicon powder from the photovoltaic industry into high performance porous Si@void@carbon anodes for Li-ion battery

To enhance the performance of lithium-ion battery anodes, this study leverages recycled diamond wire-cut silicon particles, a byproduct of the photovoltaic sector. These particles undergo purification through acid wash and pyrolysis to eliminate contaminants, thereby serving as potential anode materials. The inherent challenge with silicon involves its significant volumetric expansion during lithiation and delithiation, which hampers its viability for commercial applications. Addressing this, the research introduces a facile approach by synthesizing porous silicon (pSi) via the Ag-assisted chemical etching method. Subsequently, a distinctive yolk-shell porous silicon@void@carbon (pSi@V@C) structure is created using a sacrificial template approach, ensuring the formation of voids between the porous silicon core and the carbon shell. This configuration mitigates the detrimental effects of silicon's volume expansion while enhancing electrical conductivity through the carbon shell. The pSi@V@C composite exhibits promising electrochemical performance, demonstrated by an initial discharge capacity of 1826 mAh g-1 and a Coulombic efficiency of 68.6% at 0.1 A g-1. Remarkably, it maintains a capacity of 821.8 mAh g-1 after 550 cycles at 1 A g-1, with a retention rate of 90.4%.

Si3N4 preparation from photovoltaic kerf loss silicon waste by copper collaborative nitriding method

In this work, Si3N4 powders were prepared by collaborative direct nitriding method from photovoltaic kerf loss silicon waste. The catalytic effect of copper (Cu) on the direct nitriding reaction of photovoltaic Si waste and the morphologies of the nitriding products were investigated. The quantitative analysis of XRD results and thermogravimetric results demonstrate that Cu significantly reduces the initial nitriding temperature, and Cu has a positive effect on the nitriding of silicon waste. At 1300 °C, the sample without Cu had almost no nitriding reaction, while the total conversion rate of kerf loss waste Si was 100 %, and the yield of (α+β) Si3N4 was up to 79.2 % with 8 wt% Cu additive. The thermodynamic analysis of the Si-O-N-Cu and nitriding process was carried out by FactSage software. Moreover, the morphologies of the nitride products were observed by SEM. The addition of copper promoted the generation of Si3N4 nanorods, and the number and diameter of α-Si3N4 nanorods increased with the increase in copper content. Three reaction mechanisms of Si nitridation were discussed. This work provides a feasible method to reuse and recycle the kerf lost silicon waste.

Controllable Interface Engineering for the Preparation of High Rate Silicon Anode

AbstractSilicon (Si) is considered to be the promising candidate anode for the next generation of high‐energy‐density batteries. However, the poor initial coulombic efficiency (ICE) and rate performance severely hinder its commercial development. Here, fully exploits the 2D structure of photovoltaic silicon waste (PV‐WSi), combining with the advantage of controllable depositing layers offered by fluidized bed atomic layer deposition (FBALD), to simultaneously achieve high ICE and highrate performance of Si‐based anodes. The characteristic of Li+ embedding vertically into the plane direction of the 2D sheet‐like structure of PV‐WSi helps shorten the diffusion distance, alleviating the pulverization problem caused by volume expansion. FBALD is utilized to controllably deposit Li2O (≈1 nm) and TiO2 (≈4 nm) layers to compensate for the loss of Li sources, further suppressing the volume expansion of Si and isolating the side reactions between Si and electrolyte. The prepared Si@Li2O@TiO2 demonstrates ultrahigh ICE (90.9%) and outstanding rate performance (>900 mAh g−1 at a rate of 20 A g−1). Full cells with the Si@Li2O@TiO2 anode and LiFePO4 cathode deliver a stable capacity of 100 mAh g−1 after 300 cycles at 0.5 C. This work provides new ideas for the development of high ICE, high‐rate Si‐based anodes based on low‐cost photovoltaic waste.

Direct recycle waste silicon wafer as the charge transfer bridge to assemble a Z-scheme heterojunction for enhanced photocatalytic performance

The retirement wave of photovoltaic (PV) panels is expected to result in a significant number of discarded panels in the near future. Recycling PV silicon in a rational manner will not only help reduce the environmental impact but also lead to substantial economic gains. In this study, aaste solar silicon wafers were ball-milled to obtain recycled silicon (r-Si) powder. The TiO2/r-Si carrier was prepared through a simple hydrothermal process, followed by the creation of a novel Ag3PO4/TiO2/r-Si (APO/TIO/r-Si) ternary heterojunction composite using a co-precipitation method. The photocatalytic properties of the materials doped with different concentrations of Ag3PO4 were examined using Rhodamine B (RhB) degradation rate as a performance metric. Among them, 40 %APO/TIO/r-Si heterojunction exhibits excellent photodegradation activity under visible light irradiation. The photocatalytic degradation efficiency reached 93.0 % in 30 min, with a removal rate of 82.8 % after 5 cycles. It was found that superoxide radicals and hydroxyl radicals are the main drivers of RhB photodecomposition. The decomposition pathways of RhB dye were identified using high performance liquid chromatography mass spectroscopy (HPLC-MS), revealing N-de-ethylated intermediates as the main intermediate. The photoreaction mechanism and RhB degradation pathway over APO/TIO/r-Si were elucidated, showing a direct Z-Scheme heterojunction electron transfer pathway with r-Si acting as charge transfer center. The formation of the heterojunction not only minimizes interfacial resistance effectively but also enhances disintegration and preservation of photo-carriers, leading to improved photo-redox ability and increased photoactivity. This study presents a win–win approach for recycling waste silicon wafers from retired PV panels as potential heterojunction photocatalysts for efficient photocatalytic oxidation of dye contamination.

Effect of gas atmospheres and SiO2 content on preparation and properties of SiO2–Si3N4 composite ceramics via nitridation of diamond-wire saw silicon waste powder

Composite ceramics are applied widely nowadays by combining superior properties of different ceramic materials. In this study, SiO2–Si3N4 composite ceramics with higher mechanical properties and lower dielectric constant were successfully fabricated by nitriding diamond-wire saw silicon waste. The effect of gas atmospheres (N2, NH3, N2–H2) and SiO2 content (0%, 10%, 20%, 30%, 40%) on the microstructure and properties of composite ceramics were studied. It shows that the synthesis of SiO2–Si3N4 composite ceramics can be obtained in the NH3 atmosphere, and it is inevitable to form the Si2N2O phase in N2 and N2–H2 mixture atmospheres. Furthermore, the shrinkage rate and dielectric constant of the ceramics decreased as SiO2 content increased from 0% to 40%. As for the porosity of the sintered ceramics, it first decreased and then increased, with a minimum of 1.73% at the SiO2 content of 20%. However, the flexural strength of the sintered ceramics was the inverse of the porosity, with a maximum of 160.72 MPa at the SiO2 content of 30%. For the sintered ceramic with 30% SiO2, the shrinkage rate, dielectric constant, porosity and flexural strength are 0.3%, 4.62, 1.97% and 160.72 MPa respectively. Thus, this study provides an environment-friendly and value-added approach to recycling photovoltaic waste and reducing the cost of the reactive sintering SiO2–Si3N4 composite ceramics with excellent mechanical and dielectric properties.