Butyronitrile-Based Electrolytes for Fast Charging of Lithium-Ion Batteries

Enhancing the Charging Performance of Lithium-Ion Batteries by Reducing SEI and Charge Transfer Resistances

To enable the mass adoption of electric vehicles, the charging performance of Li-ion batteries needs to be significantly enhanced. The development of electrolytes with enhanced transport properties and faster interfacial reaction is one critical approach to realize fast charging within 10 min. Most current electrolyte studies are focusing on ester-based electrolytes. In this work, an ether-based electrolyte is reported, which shows remarkably better charging performance than commercial carbonate electrolytes and other reported ester-based electrolytes in both half and full cells. Electrochemical and spectroscopic characterization shows that the superior charging performance of the reported electrolyte is due to significantly reduced SEI resistance and charge transfer resistance. Cycling tests show remarkable stability in Li||graphite (gr) half cells, suggesting the potential of the electrolytes to enhance battery charging performance. LiFePO4 (LFP)||gr full cells were further tested, and it is found that the resistance of cells builds up during cycling due to gelation of the electrolyte, which limits the cycling performance of full cells. Potential strategies to address this limitation are discussed.

Understanding the Role of SEI Layer in Low-Temperature Performance of Lithium-Ion Batteries

Low-temperature electrolytes (LTEs) have been considered as one of the most challenging aspects for the wide adoption of lithium-ion batteries (LIBs) since the SOA electrolytes cannot sufficiently support the redox reactions at LT resulting in dramatic performance degradation. Although many attempts have been taken by employing various noncarbonate solvent electrolytes, there was a lack of fundamental understanding of the limiting factors for low-temperature operations (e.g., -20 to -40 °C). In this paper, the crucial role of the solid-electrolyte-interface (SEI) in LIB performance at low temperature using a butyronitrile (BN)-based electrolyte was demonstrated. These results suggested that an additive formed SEI with low resistance and low charge transfer dictates the LT performance in terms of capacity and cycle life, presenting a useful guideline in designing new electrolytes to address the LT issue.

Electrolyte Modulators toward Polarization-Mitigated Lithium-Ion Batteries for Sustainable Electric Transportation

Electric vehicles (EVs) are being adopted to replace combustion engine vehicles to reduce greenhouse gas emissions and mitigate climate change; developing batteries with high energy efficiency and long lifespan, in the context of carbon footprint and cost, are essential to ensure the successful transition. Herein, an electrolyte modulator that can effectively mitigate the polarization of lithium-ion batteries, leading to dramatically improved energy efficiency and lifespan, is reported. Under a dynamic stress test that mimics the operations of EVs, commercial pouch cells with a low concentration of electrolyte modulator (0.2 wt% of the electrolyte) exhibit enhanced energy efficiency (87.5% vs 80.4% for the first 500 testing cycles) and prolonged lifespan (fourfold improvement based on 70% energy-output retention). This work provides a simple yet effective strategy toward sustainable electrification of vehicles.

Toward adequate control of internal interfaces utilizing nitrile-based electrolytes

Methods to control internal interfaces in lithium ion batteries often require sophisticated procedures to deposit coating layers or introduce interphases, which are typically difficult to apply. This particularly holds for protection from parasitic reactions at the current collector, which reflects an internal interface for the electrode composite material and the electrolyte. In this work, electrolyte formulations based on aliphatic cyclic nitriles, cyclopentane-1-carbonitrile and cyclohexane-1-carbonitrile, are introduced that allow for successful suppression of aluminum dissolution and control of internal interfaces under application-relevant conditions. Such nitrile-based electrolytes show higher intrinsic oxidative and thermal stabilities as well as similar capacity retentions in lithium nickel-manganese-cobalt oxide LiNi_3/5Mn_1/5Co_1/5O₂ (NMC622)||graphite based full cells compared to the state-of-the-art organic carbonate-based electrolytes, even when bis(trifluoro-methane)sulfonimide lithium salt is utilized. Moreover, the importance of relative permittivity, degree of ion dissociation, and viscosity of the applied electrolyte formulations for the protection of current collector interfaces is emphasized.