UC San Diego

Lithium-ion batteries are central to advancing energy storage solutions, and the high-voltage spinel lithium nickel manganese oxide (LNMO) and lithium-rich layered oxide (LRLO) stand out as two promising cathode materials for next-generation lithium-ion batteries. The first half of this dissertation is on the study of LNMO for lithium-ion batteries. LNMO operates at 4.8 V and offers high energy density, yet LNMO/graphite (LNMO/Gr) full cells experience capacity fading, limiting practical applications. This work introduces a lithium metaborate (LBO) coating applied via a dry mixing method to enhance LNMO’s cycling stability. The LBO-coated LNMO, with an areal capacity of 3 mAh cm−2, exhibits superior long-term performance compared to uncoated LNMO. Characterization reveals that the 5 nm cathode electrolyte interphase (CEI) formed on LBO-coated LNMO mitigates phase transitions after extended cycling. Furthermore, the coating acts as a reservoir, dissolving into the electrolyte and reducing Nickel/Manganese dissolution and solid electrolyte interphase (SEI) formation on the anode side. The second part of this dissertation is on the study of LRLO for Lithium-ion batteries. LBO is applied to LRLO cathodes to address their challenges, such as voltage decay and poor cycling performance. The LBO-coated LRLO forms a uniform 15 nm surface layer, and when combined with lithium bis(oxalato)borate (LiBOB) as an electrolyte additive, achieves capacity retention of 82% after 400 cycles. The boron species’ interaction with PF6− anions generates BF4− and suppresses HF formation during high-voltage cycling, improving both cathode stability and electrolyte integrity. Overall, this dissertation offers surface modification through LBO stabilizes LNMO and LRLO cathodes’ surfaces and mitigates degradation mechanisms, paving the way for their practical use in advanced lithium-ion battery systems.