Investigation of Electrochemically Li-Ion Active Materials for Li-Ion Batteries
Being the battery of the 21st century, Li-ion batteries have been making headway towards replacing traditional medium to large scale energy storage devices. Recent applications ranging from EVs to grid-level energy storage, have driven the design criteria of Li-ion batteries to evolve at a rapid pace. Three major goals are low cost, high electrochemical performance, and improved safety. New targets set by the DOE to make Li-ion batteries more competitive in their new market sectors have been to decrease cost to US$ 125 kWh-1 and increase gravimetric and volumetric energy density to 235 Wh kg-1 and 500 Wh L-1, respectively . This thesis presents works on the three major components of a Li-ion battery: sustainable wheat derived-carbon anodes, high capacity V2O5:Graphene-nanoplatelets (GNPs) composite cathodes, and rare earth nickelates (specically SmNiO3 as a potential solid-state electrolyte for improved safety. Systematic solid-state processing, structural, and electrochemical studies were conducted on wheat-derived carbons. Coupling carbonization temperatures and structural evolution of biomass-derived carbons (in this case wheat), lithium insertion properties can be tuned, to create a high capacity and sustainable anode material. An optimal condition presents itself at a carbonization temperature of 600˚C with a stable lithiation capacity of 390 mAh g-1. In the Li-ion cell, the limiting factor in the total output capacity (mAh g-1) is governed mainly by the cathode materials, as cathode materials tend to be lithium based transitional metal oxides (high density compared to anode materials). Having one of the highest lithium storage capacity, V2O5 is a cathode material that suffers from low electronic conductivity and particle fragmentation upon continuous lithium insertion and extraction. In this work, sonochemistry is utilized in the synthesis of V2O5:Graphene-nanoplatelets (GNPs) composites to improve electronic conductivity and kinetics of lithium-insertion and extraction. Surface modification of the graphene nanoplatelets during sonication of GNPs allows for in situ growth of V2O5 nanoparticles. With the size reduction of the V2O5 particles and the conductive GNPs backbone, the composite achieved 248 mAh g-1 specific cathode capacity; retaining 83% of initial capacity after 50 cycles. Part 1 and 2 of this study illustrate strategies to create a low-cost and high electrochemical performance Li-ion battery via sustainable material implementation, structural and morphology control, and composite formation. The third part studies the electrochemical properties of perovskite rare-earth nickelates (specifically SmNiO3) and its' integration as a solid-state electrolyte in an all-solid-state lithium-ion battery. Upon insertion of Li+ ion, SmNiO3 undergoes Mott-transition, simultaneously allowing for a large amount of mobile Li+ to be stored at the interstitial sites (approaching a ratio of one dopant per unit-cell). The combination of a lattice expansion (~10% increase) and the interstitial doping creates a perfect condition for fast Li+ conduction with reduced activation energy. Initial efforts to integrate LiSmNiO3 in a solid-state-cell with LiCoO2:LiSmNiO3:Si configuration results with initial charging capacity of 1338 mAh g-1.
Youngblood, Purdue University.
Off-Campus Purdue Users:
To access this dissertation, please log in to our