The morphology, thermal stability, impedance, and rate performance of germanium nanoparticle (Ge-NP) based lithium ion battery electrodes that incorporate single-walled carbon nanotube (SWCNT) conductive additives has been systematically studied for varying SWCNT loadings (1-3% w/w SWCNT) and electrode areal capacities (4-12 mA h cm À2 ). Scanning electron microscopy (SEM) was used to characterize the surface coverage for carbon black and SWCNT conductive additives. Differential scanning calorimetry (DSC) analysis shows a 30% reduction in exothermic release with SWCNT conductive additives, which demonstrates improved thermal stability for Ge-NP electrodes. Electrochemical impedance spectroscopy (EIS) indicates that the charge transfer impedance can be reduced roughly 2.5Â when comparing 5% carbon black to #3% SWCNT conductive additive. Electrochemical cycling and rate testing demonstrate that SWCNT conductive additives provide significantly improved specific capacities (1100 mA h g À1 with 1% SWCNT) and rate performance (80% capacity retention at effective 1 C rate) over traditional carbon black conductive additives when using Ge-NP active material. In addition to the benefits for thermal stability, impedance, and rate performance, predicted energy density gains from Ge-NP anodes can be up to 20-25% in full batteries.

Single wall carbon nanotubes (SWCNTs) were incorporated into lithium ion battery anodes as conductive additives in mesocarbon microbead (MCMB) composites and as a free-standing support for silicon active materials. In the traditional MCMB composite, 0.5% w/w SWCNTs were used to replace 0.5% w/w SuperP conductive additives. The composite with 0.5% SWCNTs had nearly three times the conductivity which leads to improved electrochemical performance at higher discharge rates with a 20% increase in capacity at greater than a C/2 rate. The thermal stability and safety was measured using differential scanning calorimetry (DSC), and a 35% reduction in exothermic energy released was measured using the highly thermally conductive SWCNTs as an additive. Alternatively, free-standing SWCNT papers were coated with increasing amounts of silicon using a low pressure chemical vapor deposition technique and a silane precursor. Increasing the amount of silicon deposited led to a significant increase in specific capacity (>2000 mAh/g) and coulombic efficiency (>90%). At the highest silicon loading, the surface area of the electrode was reduced by over an order of magnitude which leads to lower solid electrolyte interface formation and improved safety as measured by DSC.