The demand for high-energy-density lithium-ion batteries (LIBs) has intensified with the rapid growth of the electric vehicle (EV) industry. Batteries must now store more energy in a compact form while maintaining long cycle life and structural integrity. However, these advancements place significant mechanical and electrochemical stress on electrode materials, leading to degradation, loss of conductivity, and eventual failure. This challenge is particularly pronounced in silicon-based anodes, where substantial volume expansion during lithiation severely impacts cycle stability.

Single wall carbon nanotubes (SWCNTs), also known as graphene nanotubes, provide a unique solution to these issues. Their high aspect ratio, exceptional conductivity, and mechanical strength enable the formation of a durable, long-range 3D conductive network within the electrode. Unlike conventional conductive additives such as multi-wall carbon nanotubes or carbon black, SWCNTs create flexible yet robust electrical pathways that remain intact even as active material particles expand and contract during cycling.

By incorporating TUBALL™ SWCNTs produced by OCSiAl, the global leader in single wall carbon nanotube technologies, silicon anodes achieve significantly improved cycle life, maintaining electrical connectivity despite material stress. Even at ultra-low concentrations (e.g., 0.05 wt.%), these nanotubes outperform alternative additives, providing stable and long-lasting performance in silicon oxide, silicon-carbon, and high-silicon-content anodes. Their ability to reinforce electrode architecture extends beyond anodes to cathode materials such as LFP and NCM, as well as emerging battery chemistries like lithium-sulfur and solid-state batteries.

This article compiles recent advancements in TUBALL™ SWCNT applications for silicon anodes, highlighting their role in mitigating failure mechanisms and enhancing the durability of next-generation LIBs.

1.1 Preserving Electron Conduction Networks in Si-Based Anodes 

A research team from the Korea Advanced Institute of Science and Technology (KAIST) and LG Energy Solution (Republic of Korea) [1] used conductive artifact-free atomic force microscopy (C-AFM) to analyze electron conduction channels in Si-based composite anodes. They identified and mitigated artifacts induced by surface morphology using statistical visualization methods and cooling cross-section polishing, validated through Pearson correlation analysis.

Comparing two composite anodes—one with single wall carbon nanotubes and another with carbon black—researchers observed a significant difference in electronic conductivity retention. After 130 cycles, the SWCNT-containing electrode maintained its average conductivity, although with increased deviation due to active material degradation. In contrast, the carbon black electrode exhibited a substantial decline in conductivity. This study correlates conductivity degradation with morphological changes, underscoring the advantages of SWCNTs in enhancing electrical and electrochemical performance.

The anodes were composed of 85 wt.% graphite and SiO (85:15), with a binder system comprising styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) at less than 4 wt.%. The conductive additives were either 0.1 wt.% SWCNTs (TUBALL™ by OCSiAl) or 1.0 wt.% carbon black (Super C65 by IMERYS).

1.2 Mitigating Pulverization and Stabilizing Volume Changes

Building on the previous work, research group from KAIST and LG Energy Solutions further investigated the role of SWCNTs in addressing the pulverization of Si-based anodes and maintaining electron-conduction stability during severe volume fluctuations [2]. Since uncontrolled expansion and contraction of Si anodes can disrupt conduction pathways and accelerate capacity fading, the study aimed to visualize how SWCNTs influence this process at the nanoscale.

Kelvin probe force microscopy revealed that anodes lacking SWCNTs exhibited uneven charge/discharge behavior, while those incorporating SWCNTs enabled uniform electron transfer to the active material, ensuring stable electrochemical reactions. This visualization demonstrated that SWCNTs contribute to more uniform volume expansion during cycling, reducing particle pulverization and enhancing electrode longevity.

The anode slurries contained 81 wt.% graphite and SiO (85:15), 3 wt.% carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and either 0.1 wt.% SWCNTs (TUBALL™ by OCSiAl) or 1.0 wt.% carbon black (Super C65 by IMERYS).

1.3 Scaling Up Si-Based Anodes with SWCNTs for Industrial Applications

Spanish researchers from the University of the Basque Country and the Basque Research and Technology Alliance explored the integration of Si-based materials into lithium-ion battery anodes to enhance energy density [3]. Their approach involved replacing part of the conventional graphite anode with 22 wt.% silicon suboxide (SiOx) and optimizing the composition of inactive materials (2 wt.% carbon black, 1 wt.% dispersant, and 3 wt.% binder). After establishing this formulation at the laboratory scale, they scaled it up to a semi-industrial electrode coating and cell assembly process.

The study demonstrated that incorporating SWCNTs (TUBALL™ by OCSiAl) into the electrode formulation improved adhesion strength, as measured by peel tests, which showed an increase from 9.2 ± 2.7 N·m⁻¹ to 17.3 ± 1.3 N·m⁻¹. This result indicates that SWCNTs form an effective conductive network, enhancing the cohesion between coating particles and the current collector. Electrochemical testing in 1 Ah lithium-ion pouch cells revealed that among several commercial electrolytes tested, EL2 provided the highest capacity retention, extending the cycle life by 48% beyond the 80% state-of-health threshold.

The anode formulation consisted of 66 wt.% graphite, 22 wt.% SiOx, 2 wt.% carbon black (Super C65), 3 wt.% sodium carboxymethyl cellulose (Na-CMC), 1 wt% dispersant (LFC-1), and 6 wt.% styrene-butadiene rubber (SBR). SWCNTs were introduced as an additional conductive additive.

1.4 Optimizing Si Anode Performance Through Charge State Control

Researchers from National Yang Ming Chiao Tung University (Taiwan) studied how different state-of-charge (SoC) ranges and capacity control strategies influence the electrochemical behavior of Si anodes in lithium-ion batteries [4]. Their anode formulation included 70 wt% active material, 10 wt.% conductive carbon black (Super P), 10 wt.% carboxymethyl cellulose (CMC), 10 wt.% styrene-butadiene rubber (SBR), and an additional 0.5 wt.% SWCNTs (TUBALL™ by OCSiAl).

The study identified critical SoC windows that significantly impact cycle life. Anodes that remained predominantly lithiated (0.01–0.5 V, SoC 65%–100%) exhibited superior cycle performance with low impedance. Conversely, anodes that were either mostly lithiated (0.01–0.32 V, SoC 75%–100%) or mostly delithiated (0.23–1.5 V, SoC 0%–25%) experienced rapid degradation. The best cycle life was achieved when anodes underwent full lithiation followed by delithiation at 1200 mAh g⁻¹ within an SoC range of 65%–100%. These findings provide key insights into optimizing Si anode operation through controlled SoC management.

2.1 Reinforcing Silicon Anodes with Single Wall Carbon Nanotubes

A research team investigated the role of carbon nanotubes (CNTs) in enhancing the electrochemical and mechanical stability of silicon-graphite composite (SGC) anodes in lithium-ion batteries [5]. They compared CNTs with conventional conductive agents, focusing on their impact on strain-induced interfacial reactions and the formation of the solid electrolyte interphase (SEI) layer during cycling. The study demonstrated that CNTs provide mechanical reinforcement by reducing particle-level cracking, enhancing electron pathways, and controlling electrode expansion. These effects significantly mitigate pulverization and swelling, addressing key challenges in high-density silicon-based anodes used in industrial applications.

Experimental results showed that SGC blended with graphite exhibited superior electrochemical performance compared to conventional graphite anodes, particularly in low-temperature cycling, fast charging, and rate capability tests. In a 1 Ah pouch-type full cell, the SGC@CNT anode achieved a 94.6% capacity retention over 100 cycles. In situ thickness measurement (TMS) analysis revealed that the electrode swelling ratio of the CNT-containing anode (~27%) was significantly lower than that of the carbon black-containing anode (~170%) after the first full charge. These findings highlight CNTs as a critical component in stabilizing silicon-rich anodes and advancing their commercialization for next-generation lithium-ion batteries.

The SGC anode was synthesized using a chemical vapor deposition (CVD) process, in which a Si layer was deposited onto a substrate composed of spherical natural graphite and carbon nanoparticles. This was achieved through the thermal decomposition of high-purity monosilane gas (99.9999%) at 475°C for 60 minutes. The material was then coated with 5 wt.% pitch-based carbon and annealed at 900°C. The single wall carbon nanotubes (TUBALL™) used as the conductive agent were produced by OCSiAl.

2.2 Characterizing Structure and Electrochemical Properties of Advanced Si/C Anode Materials

With the growing commercial interest in silicon-based anode materials for lithium-ion batteries, researchers have developed advanced structural designs to improve cycling stability [6]. This study investigates commercial silicon/carbon (Si/C) composite anodes, where nano-silicon clusters are embedded within a carbon matrix. Structural characterization was performed using X-ray diffraction (XRD) and Debye scattering formalism (DEBUSSY) to determine the size of silicon and carbon nanoclusters. Additionally, morphology, surface area, porosity, and density measurements were conducted to evaluate the material’s physical properties and their influence on electrochemical performance.

Electrochemical tests demonstrated that restricting silicon cluster sizes to sub-nanometer dimensions within a porous carbon matrix reduces surface area while achieving a specific capacity of approximately 2000 mAh g⁻¹. This design also improves tap density (~1 g cm⁻³), minimizes reversible stack growth, and prevents particle cracking, leading to enhanced cycling stability. Anode coatings were prepared with an active material-to-binder-to-conductive additive ratio of 92:4:4. The slurry composition consisted of 92 wt.% Si/C composite, 3.5 wt.% carbon black (Super-S, TIMCAL), 0.5 wt.% single wall carbon nanotubes (TUBALL™ by OCSiAl), 1.42 wt.% carboxymethyl cellulose (CMC), and 2.58 wt.% styrene-butadiene rubber (SBR).

Si/C anodes demonstrated stable cycling in half-cells, single-layer pouch cells, and multi-layer pouch cells. Si/C_1, with a 50% silicon weight ratio, delivered a specific capacity close to 2000 mAh g⁻¹, while Si/C_2, with 35–40% silicon content, achieved approximately 1500 mAh g⁻¹. Both materials exhibited an initial irreversible capacity loss exceeding 10% and voltage hysteresis. However, the composite structure effectively confined silicon expansion, reducing reversible pressure variations during cycling and preventing irreversible stack pressure growth. Post-cycling SEM images confirmed the formation of a stable SEI layer without signs of particle cracking or pulverization. These findings validate the structural advantages of Si/C composites for high-energy-density commercial applications.

2.3 Optimization of Si-containing and SiO based Anodes with Single Wall Carbon Nanotubes for High Energy Density Applications

To mitigate silicon severe expansion, silicon (Si) and silicon monoxide (SiO) must be combined with more stable materials such as graphite, as was stated by the group of scientists led by Jeff Dahn, research partner of Tesla [7].

The study demonstrates the role of single wall carbon nanotubes as an effective conductive additive for Si-based composite anodes. The high tensile strength and electrical conductivity of SWCNTs enhance particle interconnectivity, enabling stable cycling even with simple binders like carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The impact of SWCNTs was evaluated in 92% active SiO electrodes with varying CNT concentrations (0, 0.25, 0.5, and 0.75 wt.%). Scanning electron microscopy (SEM) imaging confirmed that SWCNTs bridge active silicon particles and conductive carbons, forming a robust conductive network that counteracts mechanical degradation. The nanotubes, with diameters of approximately 1.6 ± 0.4 nm and lengths exceeding 5 µm, effectively wrap around active particles, reinforcing electrode integrity during cycling.

Electrochemical testing revealed that even small amounts of SWCNTs significantly improve capacity retention. SiO/Gr and SiO-only electrodes maintained stable cycling performance over 100 cycles without severe capacity loss. The addition of just 0.2 wt.% SWCNTs enabled the use of cost-effective binders while maintaining capacity retention. In high-loading Si/Gr electrodes containing up to 30 wt.% metallurgical silicon, SWCNTs facilitated stable cycling when paired with CMC/SBR binders. Furthermore, the strong electrical connectivity provided by SWCNTs is crucial for mitigating lithium diffusion limitations, reducing voltage fluctuations, and improving long-term stability. These findings highlight SWCNTs as a practical and scalable solution for enhancing the performance of Si-based anodes in high-energy-density lithium-ion batteries.

2.4 Investigation of Failure Mechanisms in Li-Ion Pouch Cells with Si/Graphite Composite Anodes and Single Wall Carbon Nanotube Conductive Additives

The next study conducted by the same research group [8] investigates the failure mechanisms of silicon-graphite (Si/Gr) anodes containing carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) binders in combination with single wall carbon nanotubes. The high mechanical strength and electrical conductivity of SWCNTs are expected to enhance particle interconnectivity, preserving the electrochemical activity of the electrode despite repeated expansion and contraction. Through differential voltage (dV/dQ) analysis and in situ pressure monitoring, pouch cells with Si/Gr composite anodes were shown to exhibit minimal active mass loss in both electrodes. However, capacity loss was observed due to continuous SEI growth, leading to lithium inventory depletion and shift loss.

To optimize anode performance, various formulations of CMC/SBR binders and SWCNT (by OCSiAl) loadings were tested in half-cell configurations, with silicon content ranging from 15% to 50%. Scanning electron microscopy (SEM) imaging confirmed a uniform distribution of SWCNTs, effectively enveloping active silicon particles and reinforcing electrical conductivity. dV/dQ fitting further demonstrated that SWCNTs reduced active material loss during cycling. 

Thу innovation made by Chinese scientists introduces a slurry-coated sheet-type Si−Sn hybrid electrode with 0.2 wt.% single wall carbon nanotubes (TUBALL™ by OCSiAl) as the binder, designed for all-solid-state lithium batteries (ASSLBs) [9]. The use of SWCNTs enhances the electrical conductivity and structural integrity of the electrode, as they replace traditional polymer binders, which improves the overall cycling performance of the anode. The Si−Sn hybrid, a mixed ion-electron conductor, leverages the advantages of both silicon and tin to overcome conductivity issues in individual materials. Full cells incorporating this electrode show remarkable performance, maintaining 85.9% capacity retention after 200 cycles, and even at higher cathode loadings, demonstrate strong cycling stability. This approach provides a scalable method to produce high-performance anodes for ASSLBs, pushing the boundaries of energy density and longevity in next-generation battery technology.

A novel method for enhancing Si-based anode materials in Li-ion batteries by combining less defective graphene oxide (C-GO) and highly oxidized single wall carbon nanotubes (C-SWCNTs) was introduced by Korean scientists [10]. Through spray drying and chemical reduction, Si alloy (SiA) particles are encapsulated in a conductive hybrid coating, eliminating the need for additional conductive agents while maintaining a low binder content. The integration of reduced C-SWCNTs and C-GO significantly improves capacity and cycle retention, achieving an initial capacity of 1224 mAh g⁻¹ and 82.3% retention over 100 cycles. In full-cell configurations, the SiA/NC composite electrodes demonstrate a high energy density of 350 Wh kg⁻¹ with 65% retention after 200 cycles. This pioneering approach, leveraging OCSiAl’s pristine SWCNTs, overcomes dispersion challenges in nanomaterial-enabled electrodes, paving the way for advanced energy storage solutions.

Another study tackles the challenge of rapid capacity degradation in lithium-ion batteries (LIBs) with silicon microparticle anodes by developing a nanoporous silicon (PSi) structure confined within a single wall carbon nanotube (in the form of aqueous dispersion produced by OCSiAl) segregated network [11]. This innovative design effectively mitigates silicon’s volume expansion, enhancing electrode stability. Additionally, a hierarchical porous structure, created through freeze-drying, improves rate capability and cycling performance, while a specialized mixTHF electrolyte enables the formation of a thin and uniform solid–electrolyte interface (SEI), reducing SEI breakage and improving Coulombic efficiency. As a result, the PSi-CNT composite anode achieves an impressive specific capacity of 3210.1 mAh g⁻¹ at 1/15 °C, an initial Coulombic efficiency of 87.3%, and maintains over 2000 mAh g⁻¹ with 99.5% CE after 100 cycles. With a remarkable rate performance of 2264.5 mAh g⁻¹ at 5 °C, this approach presents promising solutions for advancing the commercialization of silicon anodes.

The use of industrial waste materials—silicon powder from the photovoltaic industry and pitch from petroleum residue—to develop a silicon single wall carbon nanotube-embedded carbon composite for lithium-ion battery anodes was examined [12]. TUBALL™ SWCNTs, produced by OCSiAl, create an efficient conductive network, while the composite’s inner voids enhance conductivity and provide space to accommodate silicon’s volume expansion. A porous, pitch-based spherical composite with embedded Si and SWCNTs was synthesized through a one-step spray-drying and antisolvent precipitation process, followed by thermal treatments. The resulting anode material demonstrated high reversible specific capacities of 2001 mAh g⁻¹ at 1 A/g (0.5 C) with 66.1% retention after 100 cycles and 1682 mAh g⁻¹ with 55.6% retention after 200 cycles. These results highlight the effectiveness of pitch-derived soft carbon and TUBALL™ SWCNTs in enhancing conductivity and structural stability, paving the way for sustainable high-performance silicon anodes.

Chinese researchers study [13] presents a shearing-force-driven strategy for re-exfoliating waste MXene (Ti₃C₂Tₓ) residue, addressing key challenges in industrial-scale production. By utilizing TUBALL™ single wall carbon nanotubes from OCSiAl, along with chitosan (CS) and polyacrylamide (PAM) aqueous solutions, strong shear stress facilitates efficient exfoliation through coordination between hydroxyl groups and Ti atoms. This process not only enhances MXene’s oxidative stability by stabilizing low-valent Ti atoms but also enables the creation of CNT@MXene composites. A free-standing membrane constructed from these composites successfully encapsulates silicon nanoparticles, delivering a high and reversible capacity after 50 cycles. This approach reduces processing costs, improves MXene’s chemical stability, and opens new pathways for the commercialization of MXene-based materials, advancing their practical applications.

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