The composite anode, assembled in a standard CR2032 3-volt half-cell, delivered a specific capacity of 3,412.44 milliampere-hours per gram at a rate of 0.56 C, with an energy density of 204.74 watt-hours per kilogram. The initial capacity of the half-cell, 3,103.42 milliampere-hours per gram, declined to 1,674.53 milliampere-hours per gram after 200 cycles at 2.57 C. Those numbers may not sound like a complete victory, but in the silicon anode field, where pristine silicon electrodes often collapse within a few dozen cycles, the retention of more than half the initial capacity over 200 cycles at a demanding rate is a meaningful achievement. The team attributes the resilience to a dual charge-storage mechanism that blends faradaic bulk reactions with pseudocapacitive surface processes.

The structural analysis reveals why the material behaves the way it does. X-ray diffraction showed sharp crystalline silicon peaks at 28.91, 47.76, 56.69, 69.69, and 76.97 degrees, corresponding to the (111), (220), (311), (400), and (331) planes, alongside a broad amorphous silicon dioxide hump near 14 degrees. Using the Scherrer equation, the team calculated an average crystallite size of 96.75 nanometers, closely matching the roughly 100-nanometer particle size supplied by the manufacturer. The amorphous silicon dioxide layer, far from being a defect, acts as a passivation shell that protects the crystalline core from further oxidation and helps absorb the mechanical strain of repeated lithium insertion and extraction.

Fourier-transform infrared spectroscopy confirmed the surface chemistry. Broad silanol bands between 3,300 and 3,500 inverse centimeters, together with Si-O-Si asymmetric stretching vibrations at 1,192.31, 1,084.17, and 885.56 inverse centimeters, revealed a hydrated, siloxane-rich surface. The team notes that these silanol groups enhance wettability, improving electrolyte penetration and lithium-ion diffusion during cycling. Notably, the absence of carbon-hydrogen stretching peaks in the 2,852 to 2,924 inverse centimeter region indicated high material purity with minimal organic contamination, while residual Si-H stretching modes at 1,868 and 2,258 inverse centimeters pointed to some surface hydride bonds.

Brunauer-Emmett-Teller and Barrett-Joyner-Halenda analysis painted a picture of a mesoporous architecture with a specific surface area of 61.89 square meters per gram and an average pore diameter of 38.50 nanometers. Field-emission scanning electron microscopy showed porous spherical clusters formed by aggregated particles ranging from 50 to 200 nanometers. Raman spectroscopy found a sharp first-order silicon-silicon vibration peak at 523 inverse centimeters, confirming a highly ordered crystalline lattice with minimal defects and low residual stress. Perhaps most strikingly, a water contact angle measurement showed the electrode surface to be superhydrophilic, with droplets spreading completely at a zero-degree angle, ensuring uniform electrolyte contact across the entire coating.

Cyclic voltammetry between 0.0 and 3.0 volts at scan rates from 20 to 200 millivolts per second revealed redox peaks near 1.5 and 1.0 volts corresponding to lithium insertion and deinsertion. The absence of a distinct intercalation peak between 1.0 and 0.5 volts suggested that lithium storage in this voltage window proceeds through surface-dominated faradaic processes rather than classical bulk intercalation. When the team measured stability at 200 millivolts per second across 700 cycles, the voltammetric profiles barely changed, indicating sustained redox activity and preserved electrochemical performance over long-term operation.

The charge-storage kinetics were dissected using a power-law relation between peak current and scan rate. The analysis showed that the anode stores the majority of its charge through diffusion-controlled bulk redox reactions, with a capacitive contribution of 37.79 percent at 200 millivolts per second. As the scan rate decreased, the diffusion-controlled contribution increased, driving higher specific capacity. The team suggests that the increased film thickness of the coated electrode allows deeper penetration of the LiPF6 electrolyte, promoting bulk redox activity throughout the active material rather than confining reactions to the surface.

Galvanostatic charge-discharge measurements across a wide range of C-rates, from 0.56 C all the way to 2,155.69 C, showed discharge plateaus associated with electrolyte decomposition and solid electrolyte interface formation at all current densities. The lithium-silicon alloy phases evolved systematically during cycling: Li15Si4 formed in the initial stage, transitioning to Li21Si5 as capacity declined, and later to Li13Si4. Despite the gradual capacity fade, structural integrity was maintained throughout the 200-cycle stability test, and the reversible recovery of capacitance and capacity when the rate was lowered back to 0.56 C demonstrated the material’s ability to withstand expansion-induced strain without catastrophic degradation.

Electrochemical impedance spectroscopy before and after cycling showed that the addition of activated charcoal and carbonized sucrose powder reduced the film resistance of the anode. These carbon additives stabilized the solid electrolyte interface, reduced continuous electrolyte decomposition, and helped form a relatively thin and conductive interphase layer. The team notes that the impedance spectra contained both semicircles and oblique lines, with the low-frequency linear region associated with lithium-ion diffusion into the electrode and the high-frequency semicircle reflecting charge-transfer resistance at the interface.

The study, published in Frontiers in Batteries and Electrochemistry, offers a pathway that sidesteps the expensive raw materials, complex synthesis routes, and harsh reaction conditions that have limited many previous silicon anode strategies. By combining commercially available porous silicon nanoparticles with two carbon sources that cost pennies, the researchers have assembled an anode that balances high conductivity, structural stability, and scalable fabrication. The work does not claim to have solved every problem facing silicon anodes, and the capacity fade over 200 cycles remains substantial. But the demonstration that a simple three-component composite can deliver over 3,400 milliampere-hours per gram with meaningful cycle life suggests that the road to practical high-energy silicon anodes may be paved with ingredients as ordinary as table sugar and charcoal.

Subject of Research: Dual mechanism enhanced capacitive storage and diffusion kinetics in hierarchically porous spherical cluster silicon nanoparticles-carbonized sucrose-activated charcoal anode enable high energy in lithium-ion CR2032 half-cell

Article Title: Dual mechanism enhanced capacitive storage and diffusion kinetics in hierarchically porous spherical cluster silicon nanoparticles-carbonized sucrose-activated charcoal anode enable high energy in lithium-ion CR2032 half-cell

Article References: Thombare, S., Humane, R., Kalubarme, R., Jadhav, H., Malavekar, D., Shaikh, S., & Lokhande, C. (2026). Dual mechanism enhanced capacitive storage and diffusion kinetics in hierarchically porous spherical cluster silicon nanoparticles-carbonized sucrose-activated charcoal anode enable high energy in lithium-ion CR2032 half-cell. Frontiers in Batteries and Electrochemistry, 5, Article 1913828. https://doi.org/10.3389/fbael.2026.1913828

Image Credits: AI Generated

DOI: 10.3389/fbael.2026.1913828

Keywords: Dual, mechanism, enhanced, capacitive, storage, diffusion, kinetics, hierarchically, porous, spherical, cluster, silicon