Si Microparticles Research Articles

Enhancing the Cycle Life of Silicon Microparticle Anodes for High-Energy Density Lithium-Ion Batteries through a Reinforced Conductive Matrix

Silicon (Si) is increasingly regarded as a promising candidate for anode materials in lithium-ion batteries (LIBs) owing to its exceptional theoretical specific capacity and abundant material resources. However, widespread commercial adoption faces hurdles due to inherent challenges such as significant volume expansion and the uncontrolled growth of the solid-electrolyte interphase (SEI) during cycling. To address these obstacles, numerous strategies have been proposed, including the fabrication of nano-sized silicon structures to enhance structural stability and long cyclability. Nonetheless, reducing silicon to the nanoscale diminishes the initial coulombic efficiency (ICE) and tap density of Si nanomaterials, thereby hindering the commercialization of Si anodes. Si microparticles (SiMPs) exhibit higher ICE and volumetric capacity compared to Si nanoparticles (SiNPs), making them better suited to meet the requirements of high energy density. However, their larger particle size also increases susceptibility to pulverization during cycling. Despite numerous efforts to enhance the performance of SiMP anodes, the conventional anode structure typically comprises active materials, conductive additives, and a polymeric binder. This traditional structure is prone to damage caused by the substantial volume expansion and shrinkage of SiMPs, resulting in the isolation of electrical network. To overcome these limitations, we propose a novel electrode architecture consisting of active materials, reinforcing materials, and a conductive matrix. The reinforcing materials act as a bridge between the active materials and the conductive matrix, enhancing the electrode's elasticity. The conductive matrix integrates the functionalities of both binder and conductive additive, eliminating the need for nonconductive binders. Consequently, the issue of electrical connectivity in the SiMP electrode during repeated cycling is addressed. The conductive matrix is synthesized using a simple method involving the cyclization of polymers at a specific temperature, thereby enhancing the electrical conductivity of the polymer. Through the examination of mechanical and electrical characteristics, our proposed electrode structure demonstrates improved electrical conductivity while preserving electrode integrity when compared to the conventional SiMP electrode structure. In conclusion, our novel electrode structure presents a promising solution for enhancing the applicability of SiMPs in LIB electrode materials. This advancement holds potential for overcoming challenges associated with SiMPs, thus facilitating their broader utilization in next-generation lithium-ion batteries.

Enhancing Lithium-Ion Battery Performance of Silicon Microparticle-Embedded Wrinkled Multilayered Graphene Structures for High Areal Capacity

Even nanostructured Si electrodes have demonstrated stable electrochemical performances in lithium-ion batteries (LIBs), complex process and high-cost of nanostructured Si electrodes are far from industry standards. Thus, utilization of commercially available low-cost Si microparticles with high-performance is highly necessary for high-energy-density LIBs. In this presentation, we demonstrate a simple and scalable method to utilize commercially available Si microparticles (ca. 7 μm) with wrinkled-multilayered-graphenes (Si-WMGs) for high-areal-capacity LIBs. The WMGs provide not only mechanical flexibility for mitigating large volume change of Si microparticles during deep charge/discharge processes, but also good adhesion property to effectively coalesce Si microparticles, and high electrical conductivity, resulting in binder- and conductor-free thick electrodes. The Si-WMG electrodes showed high initial areal capacities of 12.5 mAh cm-2 at 0.1 C and 7.1 mAh cm-2 even at a very high rate of 2 C, with outstanding long-term stability with 5.3 mAh cm-2 at 2 C for over 240 cycles. Furthermore, a full cell composed of Si-WMG and lithium cobalt oxide presented 3.13 mAh cm-2 and a stable cycling performance (90.3% retention after 100 cycles) in a practical cell setting, clearly demonstrating the practical applicability of Si-WMG electrodes. Therefore, the WMG as a binder and conductor could be applicable to other electrodes with a large volume change and high mass-loading for high-areal-capacity LIBs.

Fabrication of silicon microparticle dispersion as terahertz wave refractive index control material

Optical systems utilizing terahertz waves hold significant potential across various fields; however, the materials for the optical elements that constitute such systems are currently scarce and the range of refractive indices that can be handled is limited. In the visible light region, there are refractive index control materials made of nanocomposites with dispersed dielectric nanoparticles. However, few technologies for refractive index control materials exist in the terahertz wave region. In this study, we developed an Si microparticle dispersion in which Si microparticles are dispersed in a cycloolefin polymer (COP) matrix as a high refractive index material for terahertz waves. Results showed that a material with a refractive index between that of Si and COP can be designed by changing the volume fraction of the Si cube, a subwavelength structural particle, in the dispersion. A method in which Si cubes werefabricated by dicing with COP and using a mold was implemented to produce four types of Si microparticle dispersions with Si concentrations of 1 vol%, 5 vol%, 15 vol%, and 25 vol%. The effective refractive index was evaluated, and results demonstrated that in the 0.1–0.2 THz range, including the D band of the Beyond 5G/6G communication band, the effective refractive index values were according to the concentration, achieving control in the range of 1.53–1.96. Additionally, the Si cubes were uniformly dispersed in the dispersion with random orientations in three dimensions, making them an optical material with minimal polarization dependence. The proposed Si microparticle dispersion can be used as a new refractive index control material in the terahertz band.

Intense pulsed light-induced millisecond selective heat treatment for high-performance silicon anodes

Silicon, which is gaining prominence as a potential anode material, exhibits long-term cycle stability issues owing to volume changes during cycling. This study presents a meticulously designed Si anode that employs intense pulsed light (IPL) technology to simultaneously reduce carbon additives and construct an effective carbon quantum dot (CQD)-derived binder system. IPL, as a light-material interaction technique, offers a novel approach for selective heat treatment with remarkably short processing durations on the order of milliseconds. By comprehensively considering the geometric structure, optical characteristics, and thermal properties of each electrode component, heat transfer bridge (HTB) materials are introduced to ensure a homogeneous depth-directional heat treatment and to minimize binder decomposition in the IPL process. By employing HTB materials, the binder can reach a controlled target temperature for the condensation reaction between poly (acrylic acid) and the CQDs. Simultaneously, higher heat generation in the conductive carbon than in the binder leads to selective additional carbon reduction. This unique approach provides selective heat treatment, which cannot be achieved using conventional methods, resulting in a Si anode with excellent cyclic stability and rate capability. The versatility of the IPL technology is further demonstrated by applying it to relatively inexpensive Si microparticles.

Enhanced Cycleability of Micron‐Size Silicon Anode by In Situ Polymerized Polymer Electrolyte

AbstractSilicon is widely recognized as an ideal anode material due to its high specific capacity, low lithiation potential, high abundance, and environmental friendliness. Nevertheless, the immense volume expansion during the lithiation leads to pulverization of silicon particles, which causes electrode failure with a rapid capacity decay. Herein, the polymerized 1, 3‐dioxolane (PDOL) electrolyte is used to stabilize the micro‐silicon Si anode via in situ polymerization route. The conformality of the quasi‐solid electrolyte suppresses the pulverization of the Si microparticles (SiMPs) effectively and thus alleviates the capacity decay. The SiMPs/PDOL anode shows an excellent initial CE of 97.5% and maintains a reversible capacity of 1837.1 mAh g−1 at 500 mA g−1 after 100 cycles. The Si/PDOL/LiFePO4 full cells also exhibit a stable cycling performance with a capacity retention of 76.3% after 300 cycles. This work provides a new and easy path for the practical application of silicon anode at low cost.

Assembled MXene-Liquid Metal Cages on Silicon Microparticles as Self-Healing Battery Anodes.

In pursuit of higher energy density in lithium-ion batteries, silicon (Si) has been recognized as a promising candidate to replace commercial graphite due to its high theoretical capacity. However, the pulverization issue of Si microparticles during lithiation/delithiation results in electrical contact loss and increased side reactions, significantly limiting its practical applications. Herein, we propose to utilize liquid metal (LM) particles as the bridging agent, which assemble conductive MXene (Ti3C2Tx) sheets via coordination chemistry, forming cage-like structures encapsulating mSi particles as self-healing high-energy anodes. Due to the integration of robust Ti3C2Tx sheets and deformable LM particles as conductive buffering cages, simultaneously high-rate capability and cyclability can be realized. Post-mortem analysis revealed the cage structural integrity and the maintained electrical percolating network after cycling. This work introduces an effective approach to accommodate structural change via a resilient encapsulating cage and offers useful interface design considerations for versatile battery electrodes.

Tailored Yolk-Shell Design to Silicon Microparticles via Scalable and Template-Free Synthesis for Superior Lithium Storage.

Micrometer-sized Si particles are beneficial to practical lithium-ion batteries in regard to low cost and high volumetric energy density in comparison with nanostructured Si anodes. However, both the issues of electrical contact loss and overgrowth of solid electrolyte interface for microscale Si induced by colossal volume change still remain to be addressed. Herein, a scalable and template-free method is introduced to fabricate yolk-shell structured Si anode from commercially available Si microparticles. The void is created via a one-step alkali etching process with the remaining silicon core as the yolk, and a double-walled shell is formed from simultaneous in situ growth of the conformal native oxide layer and subsequent carbon coating. In this configuration, the well-defined void spaces allow the Si core to expand without compromising structural integrity, while the double-walled shell acts as a static capsule to confine silicon fragments despite likely particle fracture. Therefore, electrical connectivity is maintained on both the particle and electrode level during deep galvanostatic cycling, and the solid-electrolyte interface is stabilized on the shell surface. Owing to the benefits of tailored design, excellent cycling stability (capacity retention of 95% after 100 cycles) and high coulombic efficiency (99.5%) are realized in a practical full-cell demonstration.

A Rapid, Scalable Laser-Scribing Process to Prepare Si/Graphene Composites for Lithium-Ion Batteries.

Silicon has gained significant attention as a lithium-ion battery anode material due to its high theoretical capacity compared to conventional graphite. Unfortunately, silicon anodes suffer from poor cycling performance caused by their extreme volume change during lithiation and de-lithiation. Compositing silicon particles with 2D carbon materials, such as graphene, can help mitigate this problem. However, an unaddressed challenge remains: a simple, inexpensive synthesis of Si/graphene composites. Here, a one-step laser-scribing method is proposed as a straightforward, rapid (≈3min), scalable, and less-energy-consuming (≈5W for a few minutes under air) process to prepare Si/laser-scribed graphene (LSG) composites. In this research, two types of Si particles, Si nanoparticles (SiNPs) and Si microparticles (SiMPs), are used. The rate performance is improved after laser scribing: SiNP/LSG retains 827.6mAhg-1 at 2.0AgSi+C -1, while SiNP/GO (before laser scribing) retains only 463.8mAhg-1. This can be attributed to the fast ion transport within the well-exfoliated 3D graphene network formed by laser scribing. The cyclability is also improved: SiNP/LSG retains 88.3% capacity after 100 cycles at 2.0AgSi+C -1, while SiNP/GO retains only 57.0%. The same trend is found for SiMPs: the SiMP/LSG shows better rate and cycling performance than SiMP/GO composites.

Formulating Electron Beam-Induced Covalent Linkages for Stable and High-Energy-Density Silicon Microparticle Anode.

High-capacity silicon (Si) materials hold a position at the forefront of advanced lithium-ion batteries. The inherent potential offers considerable advantages for substantially increasing the energy density in batteries, capable of maximizing the benefit by changing the paradigm from nano- to micron-sized Si particles. Nevertheless, intrinsic structural instability remains a significant barrier to its practical application, especially for larger Si particles. Here, a covalently interconnected system is reported employing Si microparticles (5 µm) and a highly elastic gel polymer electrolyte (GPE) through electron beam irradiation. The integrated system mitigates the substantial volumetric expansion of pure Si, enhancing overall stability, while accelerating charge carrier kinetics due to the high ionic conductivity. Through the cost-effective but practical approach of electron beam technology, the resulting 500 mAh-pouch cell showed exceptional stability and high gravimetric/volumetric energy densities of 413 Wh kg-1, 1022 Wh L-1, highlighting the feasibility even in current battery production lines.

Robust 3D Network binder for Stable and High‐Performance Si‐Based Lithium‐Ion Battery Anodes

AbstractSilicon (Si) is becoming one of the most promising candidates for lithium‐ion batteries (LIBs) owing to its high theoretical capacity, ultralow lithiation/delithiation voltage, non‐flammability, abundant natural reserves, etc. However, Si particles undergo violent volume expansion/contraction during the charge/discharge cycles, resulting in a series of serious problems such as Si particle pulverization, solid electrolyte interphase film overgrowth, and electrode structure collapse, which severely hinders the application of silicon‐based LIBs. Herein, a composite binder crosslinked by polyacrylic acid and p‐toluene sulfonic acid protonated polyaniline is proposed to improve the electrochemical performance of Si‐based anodes. The cross‐linked composite binder processes 3D networks, fast self‐healing features, and excellent mechanical strength, which can alleviate the damage caused by the expansion of Si particles to the electrodes and protect the structural integrity of the Si‐based electrodes. As a result, the Si‐based anodes with the composite binder present excellent cycle stability (2092.9 mAh g−1 after 300 cycles at 400 mA g−1). In addition, the novel binder reveals well compatibility with commercial Si microparticles. More importantly, the self‐healing Si anode is firstly equipped in an all‐solid‐LIB with solvate ionic liquid‐based quasi‐solid electrolyte and shows excellent cycling stability as well as rate capability.

Dendrimer Based Binders Enable Stable Operation of Silicon Microparticle Anodes in Lithium-Ion Batteries.

High-capacity anode materials (e.g., Si) are highly needed for high energy density battery systems, but they usually suffer from low initial coulombic efficiency (CE), short cycle life, and low-rate capability caused by large volume changes during the charge and discharge process. Here, a novel dendrimer-based binder for boosting the electrochemical performance of Si anodes is developed. The polyamidoamine (PMM) dendrimer not only can be used as binder, but also can be utilized as a crosslinker to construct 3D polyacrylic acid (PAA)-PMM composite binder for high-performance Si microparticles anodes. Benefiting from maximum interface interaction, strong average peeling force, and high elastic recovery rate of PAA-PMM composite, theSi electrode based on PAA-PMM achieves a high specific capacity of 3590 mAh g-1 with an initial CE of 91.12%, long-term cycle stability with 69.80% retention over 200 cycles, and outstanding rate capability (1534.8 mAh g-1 at 3000mA g-1 ). This work opens a new avenue to use dendrimer chemistry for the development of high-performance binders for high-capacity anode materials.

The pursuit of commercial silicon-based microparticle anodes for advanced lithium-ion batteries: A review

Silicon (Si) is one of the most promising anode materials for high-energy lithium-ion batteries. However, the widespread application of Si-based anodes is inhibited by large volume change, unstable solid electrolyte interphase, and poor electrical conductivity. During the past decade, significant efforts have been made to overcome these major challenges toward industrial applications. This review summarizes the recent development of microscale Si-based electrodes fabricated by Si microparticles or other industrial bulk materials from the perspective of industrialization. First, the challenges for microscale Si anodes are clarified. Second, structural design strategies of stable micro-sized Si materials are discussed. Third, other critical practical metrics, such as robust binder construction and electrolyte design, are also highlighted. Finally, future trends and perspectives on the commercialization of Si-based anodes are provided.

High reversible capacity silicon anode by segregated graphene-carbon nanotube networks for lithium ion half/full batteries

Micron-sized Si-based materials have gained much attention recently in the pursuit of high-performance and low-cost lithium-ion battery (LIBs). However, huge volume variation and poor conductivity induce a rapid performance decline of Si microparticles. Herein, porous silicon microsphere segregated in graphene and carbon nanotube network (pSi/HCNT/rGO) is constructed by one-step hybrid and reduction self-assembly strategy. Carbon nanotubes provide the “safety belt” for the entire structure to block aggregation between rGO layers. The hierarchical porous structure composed by intrinsic pore structure of pSi and flexible carbon network effectively buffers the volume expansion and ensures the structural and interface stability in the lithium storage process, which also delivers multiple conductive pathways to boost Li+/e− migration efficiency. Proper configuration design leads to high charging capacity of 2319 mAh g−1 at 0.1 A g−1, exceptional initial Coulombic efficiency of 87.5 % (vs pSi of 55.8 %) and stable long cycle performance of 583 mAh g−1 after 400 cycles at 5 A g−1 when pSi/HCNT/rGO applying in half battery. The pSi/HCNT/rGO||LiFePO4 (LFP) full battery also shows the capacity maintenance of 96 % after 150 cycles at 1 C.

Controlled surface oxidation of mesoporous silicon microparticles to achieve a stable Si/SiOx anode for lithium-ion batteries

Silicon (Si) is the most promising next-generation anode material for lithium-ion batteries. However, it often suffers from a fast capacity fading due to the large volume changes during the lithiation/delithiation resulting in electrical contact loss between different components of the anode and eventually in battery fading. Mesoporous structure of silicon is a potential material to overcome the issue as the pores could accommodate the volume change during the battery cycling. However, its high surface area can cause continuous parasitic electrolyte decomposition reactions, causing low initial coulombic efficiency (ICE), capacity fading, and battery safety issue. In this study, the surface passivation of mesoporous Si microparticles produced with electrochemical etching and milling was realized through thermal oxidation. The silicon oxide (SiOx) layer generated acted as a protective layer to stabilize the Si surface, thus improving Si electrode performance. Electrochemical characterization showed that the electrode performance of Si/SiOx was strongly correlated with the oxygen content. The Si/SiOx anode delivered a discharge capacity of over 2000 mAh g−1 when the oxygen content was less than 34 wt%, but a much lower capacity when there was higher oxygen content. The best sample (oxidation at 700 °C) showed ICE of 78% and a stable cycling performance for over 180 cycles with a limited capacity of 800 mAh g−1. The results indicate that the appropriate oxidation of mesoporous Si surface to get optimized surface/oxygen content enhances the electrochemical performance of Si anodes essentially.

A High-Performance Polyurethane–Polydopamine Polymeric Binder for Silicon Microparticle Anodes in Lithium-Ion Batteries

Micro silicon (Si) has been one of the most promising anode materials for lithium-ion batteries (LIBs) due to high theoretical specific capacity and material sources. Nonetheless, an unavoidable huge volume expansion of Si microparticles (SiMPs) and the uncontrolled growth of the solid–electrolyte interphase (SEI) during the cycling still inhibit its commercialization. Among the strategies to overcome these problems, the design of a polymer binder is more feasible. Herein, a binder derived from two of the most common polymers, polyurethane (PU) and polydopamine (PDA), has been synthesized by a simple heating and mixing method for SiMP anodes in LIBs. In the PU–PDA binder, the synergistic effect of PU and PDA enables it to adapt to the volume expansion of SiMPs and maintain the electrode integrity and provides excellent cycling performance and long cycle life. The SiMP anodes with the PU–PDA binder have a capacity retention above 1000 mA h g–1 after 1000 cycles at a current density of 0.2 C and could deliver a discharging specific capacity of 1399 mA h g–1 at 4 C. Our research provides a safe, simple, and efficient PU–PDA polymer binder for SiMP anodes in the next-generation LIBs.

High-areal-capacity of micron-sized silicon anodes in lithium-ion batteries by using wrinkled-multilayered-graphenes

Even nanostructured Si electrodes have demonstrated stable electrochemical performances in lithium-ion batteries (LIBs), complex process and high-cost of nanostructured Si electrodes are far from industry standards. Thus, utilization of commercially available low-cost Si microparticles with high-performance is highly necessary for high-energy-density LIBs. Herein, we demonstrate a simple and scalable method to utilize commercially available Si microparticles (ca. 7 μm) with wrinkled-multilayered-graphenes (Si-WMGs) for high-areal-capacity LIBs. The WMGs provide not only mechanical flexibility for mitigating large volume change of Si microparticles during deep charge/discharge processes, but also good adhesion property to effectively coalesce Si microparticles, and high electrical conductivity, resulting in binder- and conductor-free thick electrodes. The Si-WMG electrodes showed high initial areal capacities of 12.5 mAh cm−2 at 0.1 C and 7.1 mAh cm−2 even at a very high rate of 2 C, with outstanding long-term stability with 5.3 mAh cm−2 at 2 C for over 240 cycles. Furthermore, a full cell composed of Si-WMG and lithium cobalt oxide presented 3.13 mAh cm−2 and a stable cycling performance (90.3% retention after 100 cycles) in a practical cell setting, clearly demonstrating the practical applicability of Si-WMG electrodes. Therefore, the WMG as a binder and conductor could be applicable to other electrodes with a large volume change and high mass-loading for high-areal-capacity LIBs.

Scalable synthesis of high-performance anode material SiOx/C for lithium-ion batteries by employing the Rochow reaction process

The commercial application of silicon oxide (SiOx)-based anode materials in lithium-ion batteries (LIBs) is hindered by their poor electrochemical performance and difficulty in large-scale production. Here, we report a scalable synthesis of a carbon-coated SiOx composite (SiOx/C) as an excellent and stable anode material for LIBs. By employing the industrial Rochow reaction process, metallurgic grade Si microparticles first reacted with gaseous CH3OH over a Cu-based catalyst to generate alkoxysilanes (important organosilane monomers) and SiOx particles covered with organic compounds. After separation and washing, the obtained SiOx solid particles were carbonized to generate the SiOx/C composite. The prepared SiOx/C composite used as the anode material in LIBs could deliver a high reversible capacity of 581 mAh g−1 at a higher current density of 100 mA g−1 after 100 cycles and 510 mAh g−1 after 250 cycles even at a higher current density of 500 mA g−1. It is anticipated that by employing an industrial process for alkoxysilane synthesis with controlled reaction conditions, the large-scale preparation of a SiOx/C anode material becomes highly feasible.

Tag-laser-induced breakdown spectroscopy with Si, Ti, and Fe micro-particles and analysis of leptin in a phosphate buffer solution

The micro-particles composed of different chemical elements potentially can be used to yield the multi-element code for labeling of the molecules of interest. Proposed approach can recognize numerous analytes (biomarkers of diseases) of interest in parallel with minimum interfering. We report on a Laser Induced Breakdown Spectroscopy analysis of samples with known and controlled ratio of concentration of three metallic, two tags and a substrate, micro-particles, containing one of the chemical elements Ti, Si and Fe, as a function of the load of a particular element in a single or binary target sample. In addition, we report on the detection of ovarian cancer biomarker leptin in PBS buffer with 5% BSA using two metal micro-particles as Tags for LIBS with magnetic particle separation. We also show that the dual-TAG LIBS approach yields a 1.3 to 10 times enhancement in signal response obtained by the dual- over the single elemental marker approach.

Lithium Diffusion in Silicon Encapsulated with Graphene.

The model of a graphene (Gr) sheet putting on a silicon (Si) substrate is used to simulate the structures of Si microparticles wrapped up in a graphene cage, which may be the anode of lithium-ion batteries (LIBS) to improve the high-volume expansion of Si anode materials. The common low-energy defective graphene (d–Gr) structures of DV5–8–5, DV555–777 and SV are studied and compared with perfect graphene (p–Gr). First-principles calculations are performed to confirm the stable structures before and after Li penetrating through the Gr sheet or graphene/Si-substrate (Gr/Si) slab. The climbing image nudged elastic band (CI-NEB) method is performed to evaluate the diffusion barrier and seek the saddle point. The calculation results reveal that the d–Gr greatly reduces the energy barriers for Li diffusion in Gr or Gr/Si. The energy stability, structural configuration, bond length between the atoms and layer distances of these structures are also discussed in detail.

Bifunctional hydrogen-bonding cross-linked polymeric binders for silicon anodes of lithium-ion batteries

The optimization of polymeric binders has been considered as an effective strategy to accommodate the huge volume change of Si anodes during lithiation and delithiation processes. In this work, three dimensional polymeric binders (CMC/TU) with multiple hydrogen bonds were designed and fabricated through the copolymerization reaction between carboxymethylcellulose sodium (CMC) and thiourea (TU), which possess bifunctional effects on Cu current collectors and Si active materials. On the one hand, similar to the interaction mechanism at rubber-metal boundary in tire industry, the formation of dendritic CuxS layers results in physical interlocked forces to strengthen the binding forces of CMC/TU binders with Cu current collectors. On the other hand, the generation of hydrogen bonds between polymeric binders and Si oxide layers can enhance the binding forces of CMC/TU binders with Si active materials and stabilize the electrode/electrolyte interface. When served as binders to Si microparticles (1–5 μm), they exhibited initial coulomb efficiency of 89.9% and reached 1059 mAh g−1 after 150 cycles, which results from the bifunctional roles of CMC/TU binders for maintaining electrode integrity during the discharge and charge processes. The developed synthetic method provides a strategy to enhance the electrochemical properties of Si-based materials, and can be widely applied to other electrode materials.