UCLA

Energy storage devices, especially batteries, are indispensable in modern society, providing power for electronic devices including smartphones and electric vehicles (EVs), and storing renewable energy for the electric grid. However, batteries still have a lot of problems, such as their limited energy density, slow charging speed, high cost, short cycle life, etc. To tackle these challenges, the development of new battery materials using earth-abundant inexpensive elements prepared through facile and scalable methods is discussed in this dissertation. First, croconic acid is proposed as a new-class of high-voltage, high-capacity organic cathode materials for lithium-ion batteries (LIBs). The theoretical redox potentials are obtained through DFT calculations and the redox reaction mechanisms are investigated by CV tests limiting the potential ranges. The high-voltage redox activity (~4 V) was confirmed by assembling two-chamber cells. In chapters 3 to 5, the effect of 3D micro- and macro-structures for battery electrodes on the battery performance is discussed. The structures are mainly engineered using a 3D printer, and the 3D electrodes are applied to sodium-ion battery anodes, supercapacitors, and lithium-metal anodes for structural lithium-ion batteries (LIBs). The 3D channels were designed to allow fast ion transport through the electrodes, which enables high mass loadings up to 100 mg cm-2 without sacrificing the intrinsic battery performance. The sodium-ion storage mechanisms in carbon materials were also elucidated through ex situ XRD analysis. In chapters 6 and 7, two scalable and inexpensive synthesis methods for silicon/carbon composites, namely, laser synthesis and re-precipitation synthesis, are proposed for low-cost, high-performance LIBs. The composites prepared through these methods possess longer cycle lives compared to conventional processes. In chapter 8, zinc-ion batteries (ZIBs) are discussed as an alternative to LIBs for grid energy storage. A new synthesis method for Zn-Mn spinel nanoparticles (~5 nm in size) is proposed as an inexpensive and high-performing cathode material; this achieved one of the highest energy densities for ZIBs. The zinc-ion storage mechanisms in Zn-Mn spinel are also elucidated through materials characterizations using ex situ X-ray diffraction and operando cell pressure measurements.