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Multi-Layer Graphene Nanoshell Si and Ge Composites and Sustainable Graphite from Biomass for Li-ion Anodes Open Access

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Smokeless pyrolysis of biomass to generate bio-oils is a nascent, albeit largely currently uneconomical, sustainable bio-energy technology. Biochar is an amorphous carbon-rich waste product of pyrolysis oil production. Turning this carbon waste into valuable carbon materials is desirable to make bio-oil economically competitive with fossil fuels, enabling market driven reduction of global CO2 emissions. The synthesis and characterization of two such value added carbon materials, graphite and multi-wall graphene nanoshells (MGNS), is presented in this thesis. Current graphite production is highly deleterious to the environment, whether obtained by mining natural deposits or by high-temperature heating of petroleum coke. In contrast, the novel photocatalytic conversion of biochar to high-purity, highly crystalline graphite is ecologically beneficial because it can be powered by a fraction of the net-zero emission electricity produced from its bio-oil co-product and graphite is an indefinitely stable carbon sequestration sink. Simple modification of the process results in MGNS which is also a net negative carbon sequestration material. The graphite and MGNS produced by this method are shown to be excellent anode materials for Li-ion batteries; the graphite is an inexpensive “drop in” replacement for commercial graphite currently used and MGNS is an alternative material for rapid charging and sub-ambient batteries, with exceptionally large energy density when made into a composite with Si or Ge nanomaterials.

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