Carbon-Coated, Diatomite-Derived Nanosilicon as a High Rate Capable Li-ion Battery Anode

Abstract

Silicon is produced in a variety of ways as an ultra-high capacity lithium-ion battery (LIB) anode material. The traditional carbothermic reduction process required is expensive and energy-intensive; in this work, we use an efficient magnesiothermic reduction to convert the silica-based frustules within diatomaceous earth (diatomite, DE) to nanosilicon (nanoSi) for use as LIB anodes. Polyacrylic acid (PAA) was used as a binder for the DE-based nanoSi anodes for the first time, being attributed for the high silicon utilization under high current densities (up to 4C). The resulting nanoSi exhibited a high BET specific surface area of 162.6 cm2 g−1, compared to a value of 7.3 cm2 g−1 for the original DE. DE contains SiO2 architectures that make ideal bio-derived templates for nanoscaled silicon. The DE-based nanoSi anodes exhibit good cyclability, with a specific discharge capacity of 1102.1 mAh g−1 after 50 cycles at a C-rate of C/5 (0.7 A gSi−1) and high areal loading (2 mg cm−2). This work also demonstrates the fist rate capability testing for a DE-based Si anode; C-rates of C/30 - 4C were tested. At 4C (14.3 A gSi−1), the anode maintained a specific capacity of 654.3 mAh g−1 – nearly 2x higher than graphite’s theoretical value (372 mAh g−1).

Highly Stretchable Conductive Glue for High‐Performance Silicon Anodes in Advanced Lithium‐Ion Batteries

“…Figure c discloses the cyclic voltammetry (CV) curves of Si‐CG acquired at a scanning rate of 0.1 mV s −1 in the potential window between 0.01 and 1 V versus Li/Li + . The peak at 0.10 V reflects the cathodic process corresponding to conversion of Si to the Li x Si phase and the two peaks at 0.397 and 0.5 V in the anodic process are ascribed to delithiation of amorphous a‐Li x Si to a‐Si. [24a,25] The two broad peaks at 0.53 and 0.7 V in the first cycle (Figure S11, Supporting Information) vanish from the following cycles on account of SEI formation.…”

“…The peak at 0.10 V reflects the cathodic process corresponding to conversion of Si to the Li x Si phase and the two peaks at 0.397 and 0.5 V in the anodic process are ascribed to delithiation of amorphous a‐Li x Si to a‐Si. [24a,25] The two broad peaks at 0.53 and 0.7 V in the first cycle (Figure S11, Supporting Information) vanish from the following cycles on account of SEI formation. [3a,26] The peak current increases from 1st to 6th cycles before stabilizing indicative of a gradual activation process during the beginning cycles.…”

Multiple Routes to Smart Nanostructured Materials from Diatom Microalgae: A Chemical Perspective

“…Si replicas resulting from magnesiothermal reduction and acid treatment can be further chemically modified by other methods to tailor their features for various specific applications ranging from biomolecular sensing to energy conversion and storage . For example, Chandrasekaran et al functionalized the surface of Si replicas of Aulacoseira frustules with thiol groups by a hydrosilylation reaction with allyl mercaptan to enable their stable binding to a gold‐plated glass slide that was used as the working electrode in a photoelectrochemical cell for solar‐energy conversion ( Figure ).…”

“…Campbell et al coated the nanostructured silicon, resulting from magnesiothermal reduction and HCl treatment of diatomaceous earth, with carbon via chemical vapor deposition of ethylene. They deposited a mixture of the C‐coated Si nanostructures with polyacetylene black (AB) and poly(acrylic acid) (PAA) binders, on a copper foil electrode and used it as the anode in a Li‐ion battery . The highly porous C‐coated silicon exhibited a specific surface area higher than pristine DE (162.6 vs 7.4 cm 2 g −1 ) and good cyclability, with high specific discharge capacity (1102.1 mA h g −1 ) even after 50 cycles, was found for the C/Si‐based anode.…”

Nanostructured porous graphene and its composites for energy storage applications

“…Graphite is the most widely used anode material in LIBs because of its good reversibility and stability [ 99 , 109 , 110 ]. In graphite anodes, maximum one Li atom can be stored per six C atoms (LiC 6 ) based on the intercalation of Li, which gives a theoretical maximum capacity of 372 mAh/g [ 124 , 125 ]. In the case of graphene, two Li atoms can be stored per six C (Li 2 C 6 ) because both sides of graphene are able to store lithium ions, giving a theoretical capacity of 744 mAh/g [ 24 , 126 , 127 ].…”