Carbon-coated Silicon Nanoparticles Research Articles

Fabrication of 3D silicon anode by inkjet printing: Opportunities and challenges

The pressing issue of climate change and the acceleration of global warming have prompted increased concerns about CO2 emissions and the need for sustainable energy solutions. The transition to electric vehicles (EVs) is crucial in achieving a sustainable and greener future for our planet. Lithium-ion batteries (LIBs) are the most common storage energy systems used in the fabrication of EVs. However, further advancements are needed to improve their energy density, power density, safety, and cost. One promising approach is to replace conventional graphite anodes with silicon, offering higher capacity and environmental friendliness. This study explores the fabrication of three-dimensional (3D) silicon anodes using drop-on-demand (DOD) inkjet printing (IJP), a promising additive manufacturing technique. The formulation of stable aqueous inks for LIB anodes is presented, highlighting their potential for scalable production. The article addresses the difficulties encountered in developing printable inks for DOD IJP and assesses the electrochemical performance of these ink formulations. Inks containing carbon-coated silicon nanoparticles and PEDOT:PSS result in electrodes that attained the cutoff lithiation capacity of 2000mAh gAM−1 with no observed capacity degradation over time. In contrast, anodes composed of pure silicon demonstrate a capacity decay after 75 cycles, proving the advantages of utilizing a Si/Carbon core-shell structure. The printability tests are presented, revealing the instabilities of the drop generation process, and the importance of particle surface chemistry. While it is possible to use IJP with the formulated anode inks, further optimization of the technology is necessary for practical implementation.

Stress level estimates in coated or uncoated silicon nanoparticles during lithiation

This work is devoted to the modeling of the mechanical behavior of coated or uncoated silicon nanoparticles, which constitute the anode active material in some lithium ion batteries, during their first lithiation at room temperature. The lithiation process induces a large volume expansion of the particles and a high level of stresses, which can lead to the fragmentation of the particles. Several approaches are proposed in order to estimate the volume expansion and the stress levels experienced by the particles. An original semi-analytical small strain model is first presented, which adapts the solution proposed by Seck et al. (2018) of the elastic-viscoplastic composite sphere problem subjected to radial loading, to the lithiated particle problem, in particular by considering the variation of phases properties during lithiation. The lithium concentration in the silicon particle is given by a sigmoid function (called logistic function) in order to mimic the reaction front between the phases. The implementation of the approach using the Hencky strain tensor Miehe et al. (2002) is proposed to take into account the large strains experienced by the particles. A complete description of the formulation is provided and the advantages are discussed. The importance of the large strains model is established by comparing it with the small strain one concerning the predictions of the pushing-out effect and the size effect of particles on their internal stresses during lithiation. Comparisons between our simulations and experimental data from Tardif et al. (2017) measuring the operando strain experienced by the pristine silicon gives the yield stress of the lithiated silicon. In addition, carbon-coated silicon nanoparticles are finally studied. We develop original closed-form expressions to predict the maximal stresses experienced by the coating at the end of the lithiation. Those expressions are used to re-estimate the fracture stress of pyrolitic carbon, considering a critical review of both pyrolitic carbon and lithiated silicon elastic properties. Finally, the mechanical effect of the coating on silicon during lithiation is studied.

Industrial waste micron-sized silicon use for Si@C microspheres anodes in low-cost lithium-ion batteries

As the energy demands of our society increase, more and more high-energy-density lithium-ion batteries (LIBs) are required to satisfy them. Silicon-based anodes are very promising for future electrical energy storage equipment. However, their commercial applications are limited by their expensiveness and the detrimental volume expansion during the battery cycling. This work describes the fabrication of low-cost silicon nanoparticles (SiNPs) by high-energy mechanical milling (HEMM) using industrial waste micron-sized Si sheets as the initial material. The produced SiNPs were encapsulated by carbon microspheres derived from sucrose. Carbon-coated SiNPs (Si@C) were incorporated as LIB anodes, which delivered high specific capacity (equal to 948 mAh g−1) even after 500 cycles at 0.5C. Even the full-cell with the prelithiated Si@C microsphere-based anode and the Li(Ni1/3Co1/3Mn1/3)O2 cathode exhibited very high energy density (equal to 439.8 Wh Kg−1) and 90% capacity retention after 300 cycles. We believe that the recycling and utilization of the solid industrial waste might play a crucial role in the next-generation energy storage applications based on low-cost Si LIB anodes.

Towards a better understanding of the degradation mechanisms of Li-ion full cells using Si/C composites as anode

Carbon-coated silicon nanoparticles (40 nm diameter) were used to prepare pitch-based Si/C composites with different Si contents and a pitch and graphite-based Si/C/Gr composite. These composites were prepared by pyrolysis at 900 °C of a pitch/Si mixture obtained from the dispersion of Si particles in a solution of pitch in THF. The as-prepared composites delivered high coulombic efficiencies at the first cycle (83–86%) and stable reversible capacities (560–650 mAh g−1) versus lithium. The anodes degradation phenomena while cycling versus NMC622 in a full cell configuration were studied by simple electrochemical tests such as analysing the harvested electrodes in half-cells vs. lithium. The clear improvement on electrochemical performances due to the graphite addition was demonstrated with the suppression of the active particle's disconnection. The pitch and graphite-based composite was proven to accommodate well the silicon volume expansion and to deliver a stable electrochemical capacity of 650 mAh g−1 at the rate of C/5.

Preparation of Carbon-Coated Silicon Nanoparticles with Different Hydrocarbon Gases in Induction Thermal Plasma

Preparation of Carbon-Coated Silicon Nanoparticles with Different Hydrocarbon Gases in Induction Thermal Plasma

A controllable and byproduct-free synthesis method of carbon-coated silicon nanoparticles by induction thermal plasma for lithium ion battery

Carbon coated silicon nanoparticle is regarded as a promising anode material for the next generation of lithium ion batteries, while the development of a cost-effective and environmental-friendly preparation method is still difficult and hinders the practical implementation. In this research, a controllable and byproduct-free synthesis method is proposed for the preparation of silicon nanoparticles with amorphous hydrogenated carbon coating. The current apparatus is operated based on the application of induction thermal plasma. Plasma properties are tunable by adjusting the ratio of tangential and radial gas flow rates (T/R), which compose the plasma sheath gas. Obtained results reveal the plasma shape is shrunk with higher T/R values, which will lead to a steeper temperature gradient and lower temperature distributions in reaction chamber. Consequently, the compositions and properties of synthesized particles can be modified with T/R values. The formation of SiC, which was an intractable issue before, can be vanished at higher tangential gas flow rates in current research and the capacity of silicon anode for batteries will be improved in predict. This research is significant for a deep understanding of plasma synthesis processing and design of batteries with excellent performance.

A bilayer polymer electrolyte encompassing pyrrolidinium-based RTIL for binder-free silicon few-layer graphene nanocomposite anodes for Li-ion battery

A binder-free electrode made of polycrystalline carbon-coated silicon nanoparticles encapsulated in few-layer graphene flakes is coupled with a PEO-based crosslinked bilayer polymer electrolyte (BLPE). A soft polymer electrolyte layer enriched with a pyrrolidium-based ionic liquid (Pyr14TFSI) is deposited on top of the electrode and UV cured by an in situ process to achieve optimal interfacial contact. A hard layer consisting of a crosslinked PEO-based polymer electrolyte film with a lower amount of Pyr14TFSI is integrated with the electrode/electrolyte assembly to improve the self-standing and shape-retention abilities. Proof-of-concept lab-scale Si-C||Li-metal polymer cells demonstrate a reversible specific discharge capacity up to 1044 mAh gSi–1 at 80 °C, largely outperforming the one with Pyr14TFSI/LiTFSI liquid electrolyte under the same experimental condition. Our results highlight the beneficial effect of the crosslinked PEO-based polymer matrix on the cycling performance, despite the absence of any SEI-forming agent.

Synthesis of carbon-coated silicon nanoparticles by induction thermal plasma for lithium ion battery

Synthesis of silicon nanoparticles with carbon coating by induction thermal plasma was investigated experimentally. Crystalline silicon was injected into plasma as raw material, and nanoparticles were produced through quenching process. Ethylene was chosen as carbon source for coating and injected into plasma downstream as a counter-flow with different gas flow rates to understand the effect on products. Synthesized silicon nanoparticles were successfully coated with carbon materials, and had an average diameter around 70 nm which was independent from ethylene flow rate. Obtained carbon coating was amorphous and consisted of sp2 carbons and sp3 carbons. Molar ratio of sp2 carbons to sp3 carbons, as well as the hydrogen content, decreased with higher ethylene gas flow rate. Increased concertation of hydrogen radicals was believed as the reason for those phenomenon due to etching effect on carbon coating. The above results are significant for the better performance of lithium ion batteries.

One-pot solution synthesis of carbon-coated silicon nanoparticles as an anode material for lithium-ion batteries.

Carbon-coated silicon nanoparticles were in situ synthesized via a facile one-pot solution synthesis method, which delivered an excellent cycling performance with a retained discharge capacity of 1120 mA h g-1 and almost no capacity decay after 500 cycles at 2 A g-1 when evaluated as an anode material in lithium ion batteries.

Protective carbon-coated silicon nanoparticles with graphene buffer layers for high performance anodes in lithium-ion batteries

Silicon is a promising anode material for use in lithium-ion batteries (LIBs). However, its volume expansion problem can cause critical issues that deteriorate efficiency, cycle life, and result in sudden breakage of battery cells. Herein, polyethylene glycol derived thin carbon-coated Si nanoparticles (Si/c-PEG) and graphene wrapping were used to block electrolyte contact and buffer volume changes, respectively. The hierarchical graphene-wrapped Si/c-PEG (Si/c-PEG/G) exhibited outstanding performance with a gravimetric capacity of ∼1820 mAh/g at 0.1 A/g and 99.5% Coulombic efficiency at the 10th cycle. Moreover, the full-cell configuration using Si/c-PEG/G anodes with commercial lithium cobalt oxides (LiCoO2, LCO) cathodes demonstrated stable operation during repeated charge/discharge cycles at 0.1 and 1 C rates. Micelle coating of PEG with graphene layers was a useful method for minimizing the exposed area of silicon to the electrolyte during lithium-ion storage.

Multi-core yolk-shell like mesoporous double carbon-coated silicon nanoparticles as anode materials for lithium-ion batteries

Various techniques have been developed to mitigate the volume expansion of silicon-based materials and improve their conductivity in lithium ion batteries (LIBs). Here, we have synthesized a novel cobalt and nitrogen co-doped double carbon coated silicon/carbon/metal-organic framework (MOF) multi-core yolk-shell like mesoporous materials through sol-gel and MOF self-template methods. The structure and morphology of the sample was characterized by X-ray diffraction and electron microscopy. The results show that the prepared composite is made up of multiple phenolic resin-based carbon-coated silicon embedded in MOF-derived carbon framework. The composite exhibits excellent lithium storage performance with a reversible capacity of 1107 mA h g−1 at 0.5 A g−1 after 100 cycles and cycling stability capacity of 852 mA h g−1 at a current density of 1 A g−1 over 300 cycles. The improved electrochemical performance could be attributed to double carbon coated multi-core yolk-shell mesoporous structure in conjunction with cobalt and nitrogen co-doping, which can improve electrical conductivity and the cycle performance of silicon. Moreover, as the electrolyte blocking layer, the double-layer carbon coating is beneficial to the formation of stable solid electrolyte interphase films, and empty space inside the MOF-derived carbon multi-core yolk-shell structure can effectively mitigate the volume change of silicon during the lithiation/delithiation process.

Low-cost open-space scaffold structure for high-capacity silicon anode

One of the causes of capacity fading in cells containing silicon anodes is the growth of a secondary SEI. A possible way of solving this problem is to create an anode with a highly porous three-dimensional structure, in which the growing SEI could be accommodated without blocking conduction pathways inside the anode. We evaluated this approach by building a 3D carbon-fiber (CF) scaffold matrix made by the pyrolysis of cotton wool. Anodes fabricated from bare and carbon-coated silicon nanoparticles, were studied from the viewpoint of the influence of anode structure and LixSi phase transformations on prolonged cycling of Li/Si cells. Analysis of the mechanisms of degradation of silicon anodes in lithium-ion batteries provides possible ways of elimination of the negative effect of the growth of the SEI on capacity fading. It will be noted that all the anodes containing cotton-carbon fiber matrix exhibit much more stable cycle life than do CF-free anodes. The synthesis of the carbon-fiber (CF) scaffold matrix is simple and easy to scale up to industrial production.

Highly porous carbon-coated silicon nanoparticles with canyon-like surfaces as a high-performance anode material for Li-ion batteries

Highly porous carbon-coated Si nanoparticles with canyon-like surfaces exhibit a stable cycle retention of 59.1% after 200 cycles because of sufficient free volume for expansion upon lithiation from their unique canyon-like porous surfaces and cavities formed upon MgO etching.

Conformal carbon layer coating on well-dispersed Si nanoparticles on graphene oxide and the enhanced electrochemical performance

Abstract Silicon nanoparticles (SiNPs)–graphene oxide (GO) composites are synthesized using a simple, fast, and mild ball-milling route. Uniform and conformal carbon layer is coated on the surface of SiNPs and the carbon-coated SiNPs are well-dispersed on the GO matrix by forming Si O C linkages. A high reversible capacity of 1265 mA g −1 at 50 mA g −1 after 80 cycles, good rate capability of 238 mAh g −1 at 2.5 A g −1 , and long-term cyclability of 230 mAh g −1 at 1 A g −1 after 800 cycles are resulted. The mild ball-milling can be highly promising and scalable approach for producing high-performance Si anode material.

Mechanics-based optimization of yolk-shell carbon-coated silicon nanoparticle as electrode materials for high-capacity lithium ion battery

Abstract Yolk-shell carbon-coated silicon nanoparticles (Si@void@C NPs) have been demonstrated to have a great promise in solving the problem of significant volume change of silicon-based anode materials during lithiation and delithiation cycling. However, our in situ lithiation experiments show that Si@void@C NPs may still subject to fracture upon lithiation, depending on their characteristic structural features such as the size of Si yolk, the thickness of carbon shell, and the interspace between the yolk and shell. Given the size of Si yolk, to ensure structural integrity of Si@void@C NPs during lithiation and delithiation, thicker carbon shell and larger yolk-shell interspace are preferred. On the other hand, from the perspective of attaining higher effective capacity, thinner carbon shell and smaller yolk-shell interspace are favored. To find the optimal structural design which yields the maximum capacity and meanwhile ensure the integrity of Si@void@C NPs during lithiation, mechanics-based theoretical modeling is carried out. A diagram for structural optimizations is obtained, by which the optimized Si@void@C NPs are synthesized and found to have improved capacity and capacity retention compared to the unoptimized ones. The results of this paper provide a guideline for the design of Si@void@C NPs as anode materials for high-capacity lithium ion battery.

Carbon-coated silicon nanoparticle-embedded carbon sphere assembly electrodes with enhanced performance for lithium-ion batteries

We demonstrate carbon-coated silicon nanoparticles embedded in monodisperse carbon spheres for lithium-ion batteries with high capacity retention.

Bulk Silicon/Graphite Alloy Anode Material for High Energy Density Li-Ion Batteries

Silicon anodes are an optimum alternative to traditional graphite anodes because of their higher lithium ion storage capacity. However, the massive first cycle capacity loss and large fade during cycling have hindered its commercialization. Here we present a solution for these issues in the form of commercial grade silicon/graphite alloy. A silicon-carbon alloy structure with carbon-coated silicon nanoparticles gives an ability to buffer volume changes and retain the silicon amorphous phase. The material achieved a first cycle reversible capacity of over 480 mAh/g when cycled between 0.01-1.5V at a c-rate of 0.05C, with first cycle efficiency of close to 95%. The capacity of the silicon alloy was ~30 mAh/g even at 10C after cycling, and recovered to 480 mAh/g at 0.05C. We performed further studies using galvanostatic intermittent titration (GITT) technique which showed the diffusion coefficient to be 10-9 to 10-12 cm2/sec. Nyquist plots were obtained using electrochemical impedance spectroscopy (EIS) at every 5%SOC. 95x64 mm pouch cells (2Ah) with the silicon alloy coupled with high capacity NMC cathode had impressive long term cycling, over 500 cycles, at a high c-rate (1C/1C), and stable c-rate performance at 10C. The cells were disassembled after cycling to study the SEI formation, electrode expansion and coating stability. Physical measurement of electrodes and SEM analysis of active materials showed that even after long term cycling, the coating was intact without minor cracks or paste delamination.