Electrolyte additives play a critical role in enhancing the performance and longevity of lithium-ion batteries. While single-additive systems have been extensively studied, recent research has shifted toward multifunctional additive blends that leverage synergistic interactions to improve cell behavior. Among these, combinations such as vinylene carbonate (VC) and lithium difluoro(oxalato)borate (LiDFOB) demonstrate how complementary mechanisms can address multiple failure modes simultaneously.

The design of effective additive blends follows several key principles. First, additives must target distinct degradation pathways without interfering with each other’s function. VC, for example, forms a stable solid electrolyte interphase (SEI) on the anode, while LiDFOB preferentially modifies the cathode-electrolyte interface. Second, the additives should exhibit electrochemical compatibility, ensuring that their redox reactions occur within the operational voltage window of the cell. Third, the concentration ratio must be optimized to balance competing effects—excessive VC may increase impedance, while insufficient LiDFOB may fail to suppress transition metal dissolution.

Performance benefits of VC + LiDFOB blends are evident across multiple metrics. In high-voltage NMC811 cells, the combination reduces capacity fade by 30% compared to cells with VC alone. This improvement stems from dual interfacial stabilization: VC’s polymeric SEI prevents lithium inventory loss, while LiDFOB’s borate-rich cathode layer inhibits oxygen release and structural degradation. The blend also enhances thermal stability, raising the onset temperature for exothermic reactions by 15°C due to LiDFOB’s ability to scavenge hydrofluoric acid (HF) and VC’s role in reinforcing the SEI.

Case studies illustrate these advantages in practical applications. A 4.5V-class lithium-ion pouch cell with 1% VC and 0.5% LiDFOB retained 92% capacity after 800 cycles, outperforming single-additive formulations by 12%. Post-mortem analysis revealed minimal cathode cracking and a thinner, more uniform SEI. In low-temperature operation (-20°C), the blend reduced charge transfer resistance by 40%, attributed to LiDFOB’s facilitation of lithium-ion desolvation and VC’s preservation of interfacial kinetics.

Gas evolution, a common issue in high-energy cells, is also mitigated. The VC + LiDFOB system reduces ethylene and CO2 generation by 60% during formation cycling, as LiDFOB suppresses solvent oxidation while VC limits reductive decomposition. This synergy is particularly valuable in prismatic and pouch cells where gas accumulation can lead to swelling.

Mechanistic studies reveal that the additives interact at a molecular level. LiDFOB decomposes to form LiF and borate species, which incorporate into VC-derived polycarbonate networks, creating a hybrid SEI with higher ionic conductivity and mechanical resilience. On the cathode, LiDFOB’s oxalate groups chelate dissolved nickel, while VC’s radical scavenging properties reduce oxidative electrolyte breakdown.

Despite these benefits, challenges remain in optimizing additive blends for diverse cell chemistries. In silicon-dominant anodes, higher VC concentrations (2-3%) are needed to accommodate volume expansion, but this necessitates adjustments to LiDFOB dosing to avoid excessive impedance growth. Similarly, high-nickel cathodes may require additional additives to address unique degradation modes like microcracking.

The VC + LiDFOB system exemplifies how multifunctional additive blends can transcend the limitations of single-component approaches. By combining interfacial stabilization, HF scavenging, and gas suppression, such formulations enable higher energy density, longer cycle life, and improved safety—critical advancements for next-generation batteries. Future work will focus on expanding these principles to novel additive combinations and broader operational conditions.

In summary, the strategic pairing of VC and LiDFOB demonstrates the power of synergistic electrolyte design. Through targeted multi-mechanism action, these blends address interfacial, thermal, and kinetic challenges simultaneously, offering a template for further innovation in advanced battery systems.