LiDFOB has emerged as a transformative electrolyte additive for enhancing the cycling stability of lithium-ion batteries (LIBs), particularly under high-voltage conditions. Recent studies demonstrate that LiDFOB forms a robust and ionically conductive solid electrolyte interphase (SEI) on the anode surface, significantly reducing irreversible capacity loss. For instance, in NCM811||graphite cells cycled at 4.4 V, the addition of 2 wt% LiDFOB increased capacity retention from 72% to 91% after 500 cycles, with a Coulombic efficiency (CE) of 99.8%. The SEI formed by LiDFOB is rich in LiF and B-O species, which exhibit superior mechanical stability and low interfacial resistance (<10 Ω cm²). These properties mitigate dendrite formation and suppress electrolyte decomposition, making LiDFOB a critical enabler for next-generation high-energy-density LIBs.
The role of LiDFOB in stabilizing cathode-electrolyte interfaces has been extensively investigated, revealing its ability to suppress transition metal dissolution and lattice oxygen loss. In high-nickel NCM cathodes (e.g., NCM90), the incorporation of 1 wt% LiDFOB reduced Mn and Co dissolution by 75% and 68%, respectively, after 300 cycles at 4.5 V. This is attributed to the formation of a cathode-electrolyte interphase (CEI) composed of Li2CO3, B-O-F compounds, and polymeric species, which effectively passivates the cathode surface. Additionally, X-ray photoelectron spectroscopy (XPS) analysis confirmed a 50% reduction in oxygen evolution compared to baseline electrolytes. These findings underscore LiDFOB's potential to extend the lifespan of high-voltage cathodes while maintaining specific capacities above 200 mAh/g.
LiDFOB also demonstrates exceptional compatibility with silicon-based anodes, which suffer from severe volume expansion (>300%) during cycling. In SiOx||NCM811 full cells, the addition of 3 wt% LiDFOB improved capacity retention from 65% to 85% after 200 cycles at a rate of C/2. The SEI formed on SiOx anodes exhibited a unique bilayer structure: an inner layer rich in inorganic compounds (e.g., LiF and LixSiyOz) and an outer layer dominated by organic species (e.g., polycarbonates). This architecture enhances mechanical flexibility and ionic conductivity, enabling stable cycling even under extreme conditions. Furthermore, electrochemical impedance spectroscopy (EIS) revealed a 40% reduction in interfacial resistance compared to conventional electrolytes.
The thermal stability of LIBs is significantly enhanced by LiDFOB additives, addressing safety concerns associated with high-energy-density systems. Differential scanning calorimetry (DSC) measurements showed that the onset temperature for exothermic reactions increased from 180°C to 220°C in NCM622||graphite cells with 2 wt% LiDFOB. This improvement is attributed to the suppression of electrolyte decomposition and the formation of thermally stable SEI/CEI layers. Accelerated rate calorimetry (ARC) tests further confirmed that cells with LiDFOB exhibited a maximum temperature rise rate of <1°C/min under thermal abuse conditions, compared to >5°C/min for baseline cells. These results highlight LiDFOB's role in mitigating thermal runaway risks.
Finally, LiDFOB's impact on low-temperature performance has been explored, revealing its ability to maintain ionic conductivity at sub-zero temperatures. In graphite||LFP cells tested at -20°C, the addition of 1 wt% LiDFOB increased discharge capacity retention from 45% to 75% at C/3 rate. Nuclear magnetic resonance (NMR) studies indicated that LiDFOB reduces lithium-ion desolvation energy by forming weaker solvation sheaths with carbonate solvents. Additionally, EIS measurements showed a reduction in charge transfer resistance from >500 Ω cm² to <200 Ω cm² at -20°C. These findings position LiDFOB as a versatile additive for enhancing LIB performance across diverse operating conditions.
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