The role of the oxide shell on the stability and energy storage properties of MWCNT@TiO ₂ nanohybrid materials used in Li-ion batteries

Core@shell nanohybrids as MWCNT@TiO₂ are a reliable alternative in the use of electrode materials for Li-ion batteries, since the specific capacity is enhanced as compared to pristine MWCNT and TiO₂. Shell thickness and the degree of disorder appear to play an important role in such behavior at the graphene interface/oxide. We performed molecular dynamics and DFT calculations to understand the nature of bonding at the nanohybrid interface and the degree of disorder caused by the bonding of the oxide on the graphene surface. Growing of shell thickness with increasing number of TiO₂ nanoparticles was simulated using a reactive force field, and an optimum configuration was found. Shell size plays a dominant role in the rising of enhanced electronic states around the Fermi level, increasing chemical capacity. Interestingly, at the optimum shell thickness, stability of the MWCNT is not compromised and the value of the density of states at the Fermi level is the largest. This provides the structural features to improve the design of core@shell materials for Li-ion batteries. It may be of particular relevance to synthesize composites based on MWCNT to improve performance of several materials for Li-ion storage, since the same trend can be expected to other systems.