Synthesis and properties of some electrolyte additives and electrode materials for lithium-ion batteries

Abstract

Acceptable energy storage technologies are needed for the transition from fossil fuels to renewable energy sources, which can be expected to take place over the next 30 years. Lithium-ion batteries are used extensively but are limited by safety, cycle life, and the availability of materials. This study was aimed at contributing to the development of lithium-ion power sources by synthesizing bifunctional organic electrolyte additives and electrode materials. The bifunctional organic electrolyte additives 2-((2,2-dimethyl-3,6,9,12-tetraoxa-2silatetradecan-14-yl)oxy)-1,3-dihydrobenzo[d][1,3,2]diazaphosphole 2-oxide (DTSDP) and 2-phenylbenzo[d][1,3,2]dioxaborole were characterized by NMR spectroscopy; using these additives will be advantageous in improving the safety of the lithium-ion batteries (LIBs). Because of the presence of groups such as phosphate which is known to have fire retardant properties, and nitrogen within the structure which at high temperature will produce by-product N2 providing thermal insulation. Li3VO4 (LVO) was doped with five different metal ions (i.e., silver (Ag+), cerium (Ce3+), chromium (Cr3+), magnesium (Mg2+), and zinc (Zn2+)) at doping levels 0.05 ≤ x ≤ 0.5 using sol-gel methodology, and characterized by XRD, SEM, and EDX. Incorporation of dopants into the LVO orthorhombic crystal structure at low concentration (x ≤ 0.1) was successful for all the metal ions. However, for the ions Ag(I), Ce(III), Mg(II), and Zn(II) with ionic radii greater than that of V(V) (0.355 Å) doping with x ≥ 10% was not beneficial for LVO as phase purity deteriorated, as shown by their XRD showing dopant oxide peaks. Chromium doping was the most successful since it did not show any secondary phase; even at high concentrations it was well incorporated in the orthorhombic crystal structure. Microstructures seen in the SEM showed that the size of particles decreases with increased concentration of the dopants and particles become more defined and uniform at high dopant concentration.