Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

Abstract

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization.

A Green Method for Graphite Exfoliation Using a Mechanochemical Route

“…18.3 is an evidence of the accentuated The raw sample had a BET surface area of less than 2 that increases to 192 m 2 /g after 16 h of milling. From those results, it is clear that the milled samples show larger BET surface than the raw material that is in agreement with previous data of graphenes [1,7]. In contrast, the surface area of the milled samples increases rapidly with milling times.…”

“…In the 1990s common applications for exfoliated graphite were: seals, thermal insulators, resin composites, electrodes, lubricant supports, battlefield obscurants, molds, chemical reagents, and adsorption substrates [5,6]. Now, emerging fields are: high-speed transistors, transparent conducting films, batteries [7], structural nanocomposites, optical devices [8,9], and supercapacitors. Unfortunately, graphene is sensitive to the content of defects and functional groups and affects the performance of these devices [10].…”

Relationship between the Properties and Cycle Life of Si/C Composites as Performance-Enhancing Additives to Graphite Electrodes for Li-Ion Batteries

“…Through this route, the volume changes are expected to be buffered by the porous carbon matrix, and the electrical contact maintained during cycling. 4,5 The simplest route to embed silicon into carbon matrix is by high-energy ballmilling of silicon with a carbon material [21][22][23][24][25][26] but other approaches were also suggested. 5 One of these, enabling a better contact between silicon and carbon, is mechanical mixing or ballmilling of silicon particles with an organic carbon precursor, which is then converted into carbon by pyrolysis in inert atmosphere.…”

Lithium-silicon alloys: Phase diagram, electrochemical studies, thermodynamic properties, application in chemical power cells

“…It was suggested in [167] to use the molecular layering method for fabrication of high-capacity silicon nanocomposite. The problem of reducing the cost of carbon materials for fabrication of Si/C nanocomposites for lithium-ion batteries was considered in one of studies [168]. Data were published in [169] on the stress appearing in silicon electrodes, depending on their lithium content (Li x Si, 1.1 ≤ x ≤ 2.4), at various charging rates.…”