Si Anode Research Articles

Hybrid 2D/3D carbon framework confined Si with optimized reaction kinetics for highly stable Li-Ion storage

Three-dimensional (3D) conductive skeletons can optimize electron/Li-ion migration kinetics and alleviate stress accumulation for silicon (Si)-based electrodes. In this study, the modified carbon nanotubes (MCNs) are used as a stress-buffering and high-speed conducting framework, and a hierarchical structure of 3D MCNs interspersed with flour-derived 2D N-doped C layer is designed for Si anode via molecular self-assembly and in-situ carbonization strategies. Experimental and theoretical calculations show that the charge redistribution occurred in the fabricated SiOx and N-doped C interfaces, which induced an electric field response and increased the interfacial electron/Li-ion transfer rate. Multiphysics simulations show that the 2D/3D hierarchical structures of carbon can optimize the physicochemical properties, such as a favorable local electronic environment, flexible stress dissipation mechanisms and good thermal stability. The prepared electrode with 77.1 wt% Si@SiOx shows a low volume expansion rate of 23 % and has an excellent Li-ion storage capability (972.1 mAh g−1 at 4000 mA g−1). Moreover, the structural stability of fabricated Si-based electrodes is enhanced, achieving 0.04 % per cycle capacity decay for 500 cycles at 2000 mA g−1. Such integrating the 2D/3D carbon framework to manipulate Si interfacial properties provides fundamental research for other electrodes plagued by significant volume expansion.

A Polysaccharide Binder with Carbon Quantum Dots for Improved Flexibility of Si Anodes in Lithium–Ion Batteries

A Polysaccharide Binder with Carbon Quantum Dots for Improved Flexibility of Si Anodes in Lithium–Ion Batteries

Performance Degradation Mechanism of the Si@N, S-Doped Carbon Anode in Sulfide-Based All-Solid-State Batteries.

Silicon (Si) anode is a promising anode material for all-solid-state lithium batteries with ultra-high theoretical specific capacity and low lithium dendrite risk. However, the inevitable vast volume expansion of Si anode during charge/discharge is recognized as a major limitation preventing its commercial application. Herein, an N, S self-doped amorphous carbon layer coated on porous micron-sized Si (p-mSi@C) is designed to construct an electron/ion conducting network while ensuring structural and interfacial stability. Uneven distribution of von mises stresses during p-mSi lithiation leads to irregular volume expansion and even fragmentation. Meanwhile, the growth of by-products at the interface between p-mSi and electrolyte contact leads to a rapid capacity decay. Compared to p-mSi anode, p-mSi@C reduces the risk of fragmentation thanks to the stress-absorbing effect of amorphous carbon, delivering excellent electrochemical performance (2679.65 mAh g-1 at 0.2 mA cm-2 with initial coulombic efficiency of 84%). More importantly, the chemical failure mechanisms of p-mSi and p-mSi@C composite anodes are revealed through structural characterization, chemical analysis, and simulation, which provides the necessary theoretical guidance for practicalization.

Electrochemical in-situ lithiated Li2SiO3 layer promote high performance silicon anode for lithium-ion batteries

Si anode is considered to be one of the most promising candidates for the next-generation lithium-ion batteries (LIBs). However, the severe volume variation of Si (> 300%) during the lithiation/delithiation process results in unstable interface and thus contributes to poor cycling stability. Moreover, the relatively low conductivity derived from the semiconductor nature of Si leads to inferior rate performance. Herein, Li2SiO3 layer with fast lithium-ions transport capability and high mechanical property was formed on Si surface in an in-situ electrochemical method. The relationships between the valence of SiOx and LixSiOy constituents were readily studied. Fortunately, the as-prepared Si@ES-LSO showed great potential to mitigate the expansion and high lithium-ions diffusion coefficient. When employed as anode materials for LIBs, the modified Si anode delivered a specific capacity of 2074.8 mAh g−1 at 1000 mA g−1 with a retention ratio of 98.9% after 100 cycles, demonstrating superior electrochemical performance. This work provides a facial and efficient strategy for the roadmap of Si anode application.

A 3D flexible conductive network skeleton by SWCNT-COOH and PVA-PAA enabling high performance for Si anode

Silicon anode undergoes dramatic volume expansion during charge and discharge, causing structural and interfacial instability that severely degrades battery cycling performance. Herein, we propose a three-dimensional (3D) flexible self-standing SiMP/SWCNT-COOH@PVA/PAA anode, in which carboxylation-modified single-walled carbon nanotubes (SWCNT-COOH) construct a highly conductive and flexible skeleton to provide rapid electron transport channels for micron silicon (SiMP), while polyacrylic acid-polyvinyl alcohol (PVA-PAA) cross-linking layer forms a high-strength polymer interface to strengthen the conductive skeleton and helps to maintain the structural integrity of SiMP. The resulting electrode exhibits ultra-high electrical conductance (12406 S m−1) and exceptional mechanical characteristic (tensile strength of 46.95 MPa). More importantly, it demonstrates extremely stable electrochemical properties, with an impressive maximum capacity of approximately 2868.5 mAh g−1 at 0.2C, while retaining an exceptional 96.49 % of capacity even after 100 cycles. A consistent capacity of 1000 mAh g−1 at 1C throughout 1000 cycles is also realized. Furthermore, a flexible full battery based on SiMP/SWCNT-COOH@PVA/PAA anode achieves a discharge capacity of 49.5 mAh g−1 following 100 cycles, and illuminates a LED strip normally under various bending conditions. These results are expected to open a new way towards enhanced performance silicon-based electrodes within flexible LIBs.

Architecting Sturdy Si/Graphite Composite with Lubricative Graphene Nanoplatelets for High-Density Electrodes.

Densification of the electrode by calendering is essential for achieving high-energy density in lithium-ion batteries. However, Si anode, which is regarded as the most promising high-energy substituent of graphite, is vulnerable to the crack during calendering process due to its intrinsic brittleness. Herein, a distinct strategy to prevent the crack and pulverization of Si nanolayer-embedded Graphite (Si/G) composite with graphene nanoplatelets (GNP) is proposed. The thickly coated GNP layer on Si/G by simple mechanofusion process imparts exceptional mechanical strength and lubricative characteristic to the Si/G composite, preventing the crack and pulverization of Si nanolayer against strong external force during calendering process. Accordingly, GNP coated Si/G (GNP-Si/G) composite demonstrates excellent electrochemical performances including superior cycling stability (15.6% higher capacity retention than P-Si/G after 300 cycles in the full-cell) and rate capability under the industrial testing condition including high electrode density (>1.6gcm-3) and high areal capacity (>3.5mAhcm-2). The material design provides a critical insight for practical approach to resolve the fragile properties of Si/G composite during calendering process.

Enhancing Electrochemical Performance of Si@CNT Anode by Integrating SrTiO3 Material for High-Capacity Lithium-Ion Batteries

Silicon (Si) has attracted worldwide attention for its ultrahigh theoretical storage capacity (4200 mA h g−1), low mass density (2.33 g cm−3), low operating potential (0.4 V vs. Li/Li+), abundant reserves, environmentally benign nature, and low cost. It is a promising high-energy-density anode material for next-generation lithium-ion batteries (LIBs), offering a replacement for graphite anodes owing to the escalating energy demands in booming automobile and energy storage applications. Unfortunately, the commercialization of silicon anodes is stringently hindered by large volume expansion during lithiation–delithiation, the unstable and detrimental growth of electrode/electrolyte interface layers, sluggish Li-ion diffusion, poor rate performance, and inherently low ion/electron conductivity. These present major safety challenges lead to quick capacity degradation in LIBs. Herein, we present the synergistic effects of nanostructured silicon and SrTiO3 (STO) for use as anodes in Li-ion batteries. Si and STO nanoparticles were incorporated into a multiwalled carbon nanotube (CNT) matrix using a planetary ball-milling process. The mechanical stress resulting from the expansion of Si was transferred via the CNT matrix to the STO. We discovered that the introduction of STO can improve the electrochemical performance of Si/CNT nanocomposite anodes. Experimental measurements and electrochemical impedance spectroscopy provide evidence for the enhanced mobility of Li-ions facilitated by STO. Hence, incorporating STO into the Si@CNT anode yields promising results, exhibiting a high initial Coulombic efficiency of approximately 85%, a reversible specific capacity of ~800 mA h g−1 after 100 cycles at 100 mA g−1, and a high-rate capability of 1400 mA g−1 with a capacity of 800 mA h g−1. Interestingly, it exhibits a capacity of 350 mAh g−1 after 1000 lithiation and delithiation cycles at a high rate of 600 mA hg−1. This result unveils and sheds light on the design of a scalable method for manufacturing Si anodes for next-generation LIBs.

Polyacrylonitrile and aluminum metal dual functionalization interconnected network for superior lithium storage in silicon anode

Currently, silicon-based anode is one of the most promising anode materials that can be applied in next-generation lithium-ion batteries. However, the high activity of the electrode–electrolyte interface and low electronic conductivity of Si anode during the cycling process greatly limits its large-scale application. Aluminum (Al) is the metallic current collector known to promote electronic conductivity and lithium-ion transfer at low cost. However, to our knowledge, scalable interface engineering incorporating Al with carbonized polymer has not been reported. Herein, a polyacrylonitrile (PAN) and aluminum metal dual functionalization interconnected network is achieved via a simple sol-gel method followed by high-temperature calcination to obtain a stable solid electrolyte interphase (SEI) while allowing fast Li+ transmission. The calculated diffusion energy barrier for lithium ions in Al is 0.2198 eV, significantly lower than that in Cu and Fe. Benefiting from the enhanced interfacial protection and kinetics of Si with polyacrylonitrile/Al, the prepared Si@Al@CPAN anode exhibits high lithium storage capacity (2034.90 mAh/g after 150 cycles at 0.84 A/g). At the same time, the prepared Si@Al@CPAN anode outperforms the pure Si anode in rate performance at 12.6 A/g (1116.75 mAh/g vs. 2.84 mAh/g). The present work delivers new design ideas for high-performance Si anode with a multi-functionalization interface.

Dramatic Enhancement Enabled by Introducing TiN into Bread-like Porous Si-Carbon Anodes for High-Performance and Safe Lithium Storage.

Doping modifications and surface coatings are effective methods to slow volume dilatation and boost the conductivity in silicon (Si) anodes for lithium-ion batteries (LIBs). Herein, using low-cost ferrosilicon from industrial production as the energy storage material, a bread-like nitrogen-doped carbon shell-coated porous Si embedded with the titanium nitride (TiN) nanoparticle composite (PSi/TiN@NC) was synthesized by simple ball milling, etching, and self-assembly growth processes. Remarkably, the porous Si structure formed by etching the FeSi2 phase in ferrosilicon alloys can provide buffer space for significant volume expansion during lithiation. Highly conductive and stable TiN particles can act as stress absorption sites for Si and improve the electronic conductivity of the material. Furthermore, the nitrogen-doped porous carbon shell further helps to sustain the structural stability of the electrode material and boost the migration rate of Li-ions. Benefiting from its unique synergistic effect of components, the PSi/TiN@NC anode exhibits a reversible discharge capacity up to 1324.2 mAh g-1 with a capacity retention rate of 91.5% after 100 cycles at 0.5 A g-1 (vs fourth discharge). Simultaneously, the electrode also delivers good rate performance and a stable discharge capacity of 923.6 mAh g-1 over 300 cycles. This research can offer a potential economic strategy for the development of high-performance and inexpensive Si-based anodes for LIBs.

Reversible silicon anodes enabled by fluorinated inorganic-organic hybrid coating

Silicon anodes deliver batteries with energy densities much higher than those based on today’s dominant graphite anodes. However, they commonly exhibit huge volume variations and unfavorable interface stability, causing a gradually diminishing capacity on extended cycling. Most Si-based batteries consisting Si/C composites in industry can only use a very limited amount of Si (<30 % by weight). Exploiting molecular layer deposition (MLD) technique, a fluorine-rich flexible inorganic–organic hybrid alucone (AlFHQ) shell is controllably deposited onto Si electrodes. Employing ex situ XPS and AFM, the AlFHQ film presents reversible electrochemical evolutions in terms of composition and morphology. The interactions the between Li+ and −O−2,3,5,6-fluorobenzene functional groups help to construct a mechanically-chemically robust LiF-rich hybrid solid electrolyte interphase (SEI) on Si anode, delivering enhanced interfacial stability and integrity of electrode. An optimized coating thickness (≈5 nm) for interfacial stabilization and Li+ transport kinetics is demonstrated, namely, Si@AlFHQ-20. The reported fluorine-rich hybrid modification technique endows (a), stable cycling of Si anode (≈3.8 mAh cm−2) with an ultrahigh initial Coulombic efficiency (ICE) of 92.3 %; (b), enhanced rate capability of 1468 mAh/g at 2.0 A g−1 and good cycling performance; and (c), overall cell (Si@AlFHQ-20//LiCoO2@Al2O3) operational stability for more than 100 cycles under stringent cathode conditions (2.68 mAh cm−2, high cutoff voltage at 4.55 V).

Selective Methylation of Cyclic Ether Towards Highly Elastic Solid Electrolyte Interphase for Silicon‐based Anodes

Silicon (Si)‐based anodes offer high theoretical capacity for lithium‐ion batteries but suffer from severe volume changes and continuous solid electrolyte interphase (SEI) degradation. Here, we address these challenges by selective methylation of 1,3‐dioxolane (DOL), thus shifting the unstable bulk polymerization to controlled interfacial reactions and resulting in a highly elastic SEI. Comparative studies of 2‐methyl‐1,3‐dioxolane (2MDOL) and 4‐methyl‐1,3‐dioxolane (4MDOL) reveal that 4MDOL, with its larger ring strain and more stable radical intermediates due to hyperconjugation effect, promotes the formation of high‐molecular‐weight polymeric species at the electrode‐electrolyte interface. This elastic, polymer‐rich SEI effectively accommodates volume changes of Si and inhibits continuous side reactions. Our designed electrolyte enables Si‐based anode to achieve 85.4% capacity retention after 400 cycles at 0.5 C without additives, significantly outperforming conventional carbonate‐based electrolytes. Full cells also demonstrate stable long‐term cycling. This work provides new insights into molecular‐level electrolyte design for high‐performance Si anodes, offering a promising pathway toward next‐generation lithium‐ion batteries with enhanced energy density and longevity.

Are Sulfide‐Based Solid‐State Electrolytes the Best Pair for Si Anodes in Li‐Ion Batteries? (Adv. Energy Mater. 40/2024)

Are Sulfide‐Based Solid‐State Electrolytes the Best Pair for Si Anodes in Li‐Ion Batteries? (Adv. Energy Mater. 40/2024)

Selective Methylation of Cyclic Ether Towards Highly Elastic Solid Electrolyte Interphase for Silicon-based Anodes.

Silicon (Si)-based anodes offer high theoretical capacity for lithium-ion batteries but suffer from severe volume changes and continuous solid electrolyte interphase (SEI) degradation. Here, we address these challenges by selective methylation of 1,3-dioxolane (DOL), thus shifting the unstable bulk polymerization to controlled interfacial reactions and resulting in a highly elastic SEI. Comparative studies of 2-methyl-1,3-dioxolane (2MDOL) and 4-methyl-1,3-dioxolane (4MDOL) reveal that 4MDOL, with its larger ring strain and more stable radical intermediates due to hyperconjugation effect, promotes the formation of high-molecular-weight polymeric species at the electrode-electrolyte interface. This elastic, polymer-rich SEI effectively accommodates volume changes of Si and inhibits continuous side reactions. Our designed electrolyte enables Si-based anode to achieve 85.4% capacity retention after 400 cycles at 0.5 C without additives, significantly outperforming conventional carbonate-based electrolytes. Full cells also demonstrate stable long-term cycling. This work provides new insights into molecular-level electrolyte design for high-performance Si anodes, offering a promising pathway toward next-generation lithium-ion batteries with enhanced energy density and longevity.

Constructing LiF‐Enriched Solid Electrolyte Interface on Graphene Arrays with Abundant Edges on Microscale Si‐C Anodes Toward High‐Energy Lithium‐Ion Batteries

AbstractSilicon (Si) anodes offer excellent lithium storage capacity for lithium‐ion batteries but face practical limitations due to significant volume expansion and low intrinsic electrical conductivity. These issues lead to side reactions that consume the electrolyte and impede ion‐electron transport, resulting in low areal loading (&lt;2 mg cm⁻²) and restricted energy density. To address this, a scalable method is developed using spray drying of commercial graphite flakes (s‐Gr) and nanosilicon particles (n‐Si), followed by chemical vapor deposition to create microscale Si/C anodes (s‐Gr/n‐Si/VGs). Thin vertical graphene nanosheets (VGs) are grown on the surfaces and within the internal pores, forming a robust, micron‐sized Si/C spherical composite material. The VGs construct the conductive network, allowing the electrodes to operate at high areal loadings without pulverization and promoting LiF‐enriched solid electrolyte interphase for improved cycling stability. The s‐Gr/n‐Si/VGs maintain a capacity of 641.9 mAh g⁻¹ after 1000 cycles at 11.0 mg cm⁻², retaining 95.9% capacity. In pouch cells with NCM811 cathodes, the 5.0 Ah‐level cells achieved 80.0% capacity retention after 510 cycles at 1.0 C. This research provides a feasible pathway for manufacturing high‐performance, low‐cost, and scalable Si/C anodes suitable for high‐energy‐density lithium‐ion batteries.

Anodic Dissolution of Al–Fe and Al-Fe-Si Alloys in Emimcl–AlCl3 Electrolyte

To produce over 99.9% of high-purity Al from Al–Fe alloy containing Al6Fe and Al–Fe–Si alloy containing β-AlFeSi by electrorefining, their anodic dissolution and cathodic electrodeposition characteristics were investigated in an EmImCl–AlCl3 ionic liquid electrolyte at 323 K. Constant potential electrolysis showed that Fe dissolved from Al–Fe anode at 0.7 V vs Al/Al(III) and from Al–Fe–Si anode at 1.4 V, and was co-deposited with Al on the cathode. Notably, anodic dissolution potential of Fe was changed by forming β-AlFeSi, and Si did not dissolve from β-AlFeSi at either potential. A combination of controlled anodic dissolution potential and the use of the Al alloy containing β-AlFeSi further suppressed the dissolution and cathodic co-deposition of Fe, affording high-purity Al on the cathode.

Effect of precursor morphology on the electrochemical performance of porous Si anodes prepared by magnesiothermic reduction

The magnesiothermic reduction of SiO2 to Si is a promising route for preparing high-energy-density Si-based anode materials for lithium-ion batteries. However, the effect of the initial morphological properties of SiO2 on the electrochemical performance of Si remains unclear. Herein, porous Si (PSi) particles were prepared from four different SiO2 precursors, namely, spherical SiO2 particles with diameters of 0.3 and 20 μm (denoted SiO2-0.3 and SiO2-20, respectively), fumed SiO2 powder (denoted SiO2-F), and well-ordered mesoporous SiO2 particles (denoted SiO2-K). Highly crystalline PSi particles were obtained after magnesiothermic reduction and subsequent HCl and HF etching. PSi prepared from SiO2-0.3 maintained its precursor morphology to some extent, whereas highly irregular Si particles were produced from SiO2-20, SiO2-F, and SiO2-K. Among the PSi particles, those prepared from SiO2-0.3 delivered the highest reversible capacity (1427 mAh g–1 at 0.1 A g–1) after 50 discharge–charge cycles. Because of the unique hierarchically porous morphology of PSi prepared from SiO2-0.3, the expansion of its electrode thickness was suppressed below 140 %. Moreover, owing to its nanosized Si domains and good electrode wetting, PSi prepared from SiO2-0.3 demonstrated improved electrochemical properties compared with those prepared from SiO2-F and SiO2-K.

Overlooked challenges of interfacial chemistry upon developing high energy density silicon anodes for lithium-ion batteries

Evaluation of silicon (Si) anode performance by the assembled Si||Li half-cells is the primary approach in the development of high-energy-density lithium-ion batteries (LIBs). However, most studies focus solely on the variations of Si anode, the stability of electrolyte on the lithium (Li)-metal counter electrode has been overlooked. Herein, we discovered that the acquired cell performance not only depends on the Li+ (de-)solvation behaviors on the Si anode surface but also was affected significantly by the lithiation overpotential caused by the side reactions on the Li electrode. It is significant to identify this point, as these influences of electrolyte decomposition on the Li electrode have been previously regarded as an integral part of side reactions on the Si anode. We proposed a new perspective of the electrolyte solvation structure and electrode interfacial model to unravel the interfacial behaviors on the Si and Li electrodes respectively. The identified differences in the Li+ solvation and (de-)solvation behaviors not only provide reasons for the varied electrolyte stability in different electrolytes but also interpret the superior performance in tetrahydrofuran (THF)-based electrolytes. This study underscores the importance of understanding electrolyte behavior at the interfaces of individual electrodes to discern the reliability of electrode performance and also introduce a novel principle for designing superior electrolytes for high-energy-density LIBs.

In situ multilevel covalent crosslinking binder with high ionic conductivity for high-performance Si anodes

Silicon (Si) anode has emerged as a promising material for high-energy-density lithium-ion batteries (LIBs), thanks to its high theoretical capacity. However, the commercial application of Si anodes is hindered by inadequate cycling performance and poor interfacial stability, stemming from unfavorable stress conditions. In this study, a multiple crosslinking binder with high ionic conductivity is proposed combining high mechanical strength and high adhesion to current collector and active Si particles by coupling poly(acrylic acid), polyvinyl alcohol, and polyethylene glycol. The designed polymer binder not only efficiently dissipates the inner stress with its multiple crosslinked networks, but also establishes a fast lithium-ion conduction pathway to facilitate the electrode reaction kinetic. The resultant Si anode using the designed binder exhibits significantly improved cycling stability and superior rate performance. This work presents a straightforward yet highly effective method to alleviate the detrimental stress incurred by high-capacity anodes in high-energy LIBs.

Amide coupled Si-rGO hybrids as anode material for lithium-ion batteries

Despite silicon (Si) having a high specific capacity of 4200 mA h/g, it undergoes significant expansion in volume during lithiation. In order to alleviate the significant increase in volume that occurs in silicon nanoparticles (SiNPs) of lithium-ion batteries, herein we report covalently modified SiNP contained within reduced graphene oxide (rGO) sheets as an anode material in lithium-ion batteries (LIBs). The structural modification of SiNP could effectively mitigate the increase in volume while preserving its outstanding electrochemical properties. Graphene oxide (GO) undergoes chemical modification and functionalization by a simple and efficient method using microwave-assisted sonochemical approach. The procedure entails grafting carboxyl functionalized silicon nanoparticles (C-Si) to amine-functionalized reduced graphene oxide (NH2-rGO) to produce a Si-rGO hybrid via amide linkage. This hybrid reduces the problem of volume expansion in Si anodes by dissipating substantial changes in volume and minimizing direct contact between SiNPs and the electrolyte. The formation of a robust solid electrolyte interface (SEI) layer improves the specific capacity and durability of the anode material. We observed that the Si-rGO 2 hybrid (containing 44 wt% Si) exhibited a relatively higher specific capacity of 1604 mA h/g during the initial cycle at C/10 rate when compared to other hybrid systems, such as Si-rGO 1, Si-rGO 2, Si-rGO 3 with bare SiNP, and SRGO composite (without amide linkage). Additionally, it maintained a capacity of approximately 1000 mA h/g at C/2 rate for more than 125 cycles. Thus, enhanced specific capacity, cycling stability, electrode conductivity, and lithiation are made possible due to the structural modification of SiNPs.

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.