UC San Diego

Renewable power plants and battery energy storage systems are expanding worldwide in many countries for eventual smart grid systems. However, the high cost of electricity generation and storage is still a barrier to the utilization of abundant renewable energy such as sunlight and wind. For instance, the levelized cost of electricity (LCOE) of concentrating solar power (CSP) plants entering service in 2019 is projected to be 24.3 [cent]/kWh, compared to nuclear power plants' LCOE of 9.6 [cent]/kWh (US EIA). For the CSP system to obtain the competitiveness, new technologies have to be developed to reduce electricity price. If new solar receivers can be operated stably at 750 °C in air, Carnot efficiency can increase by 1.5 times from the conventional CSP opertated at 500 °C. To develop solar receivers operated at 750 °C under air, 3 types of approach are carried out including 'Si boride-coated Si core-shell nanoparticles', 'tandem- structured spectrally selective coating (SSC) layers with CuO nanowires and Co₃O₄ nanoparticles' and 'tandem- structured SSC layers with CuFeMnO₄ and CuCr₂O₄ nanoparticles'. Finally 2-layered SSC with porous CuFeMnO₄ top and dense CuCr₂O₄ bottom layer can achieve 0.90 in figure of merit (efficiency of solar-to-thermal energy), assuming an operation at 750 °C and 1000 in sunlight concentrating factor. Lithium-ion batteries (LIB) with high energy density can be used for energy storage system for many applications including renewable power plants and electric vehicles capable of longer distance driving. One method to make LIB with high energy density is to use high voltage cathodes such as LiCoPO₄ (LCP, 4.6-4.8V, 800 Wh/ kg). However, LCP material has one drawback of low electrical conductivity (̃10⁻¹⁵ S/cm) which needs to be solved for LIB applications. In this research, multi-wall carbon nanotubes-embedded LCP nanocomposites (LCP-CNT) are devised in order to enhance the electrical conductance of LCP-CNT particles which can improve cell capacity by 2 times from 24.4 mAh/g for bare LCP to 52.5 mAh/g. And main important factors affecting the capacity increment are a reduced impedance of charge transfer (intercalation/de- intercalation of Li⁺) in addition to uniform distribution of MWCNTs which can be fabricated during gelation step of LiCoPO₄ in synthesis procedure