Design of Fire‐Resistant Liquid Electrolyte Formulation for Safe and Long‐Cycled Lithium‐Ion Batteries

Abstract

Turning an unsafe material into a safe one without performance loss for Li-ion battery applications provides opportunities to create a new class of materials. Herein, this strategy is utilized to design a fire-resistant liquid electrolyte formulation consisting of propylene carbonate and 2,2,2-trifluoroethyl groupcontaining linear ester solvents paired with 1 m LiPF 6 salt and fluoroethylene carbonate additive for a Li-ion battery with improved safety and performance. Traditional carbonate-based electrolytes offer good performance in mild operating conditions, but are however a flammable fuel causing fire and safety hazards. It is shown that the entire replacement of linear carbonate with fluorinated linear ester yields a fire-resistant and outperforming electrolyte under the harsh condition of 4.5 V high-voltage, 45 °C and 2C rate, enabling a higher energy, longer cycle life of 500 cycles, faster charged practical graphite‖NCM622 full-cell than traditional electrolyte-based cell. The strong correlation between cathode-electrolyte and anode-electrolyte interfacial stabilization and highly reversible cycling performance is clearly demonstrated. The fire-resistant electrolyte-incorporated industrial 730 mAh graphite‖NCM811 Li-ion pouch battery achieves 82% retention after 400 cycles under 4.3 V charge voltage, 45 °C and 1C, and markedly improved safety on overcharge abuse tests. The design strategy for electrolyte formulation provides a promising path to safe and long-cycled high-energy Li-ion batteries.

Improving Compatibility between Trimethyl Phosphate and Graphite Anodes by Preconstructing a Stable Solid Electrolyte Interphase Film

“…As the main energy storage equipment of electric vehicles, lithium-ion batteries (LIBs) have been widely used for their advantages of low cost, no air pollution problems, and high energy density . However, LIBs have potential safety hazards caused by the flammability of organic carbonate electrolytes . Among them, traditional carbonate solvents with low melting point, such as ethylene carbonate (EC) and dimethyl carbonate (DMC), are not only prone to dehydrogenation when the internal temperature of the battery rises, producing hydrogen or hydroxyl free radicals (H • or • OH) with high reactivity, which further catalyzes the continuous decomposition of electrolytes and increases the potential safety hazard of LIBs in a high-temperature environment .…”

“…2 However, LIBs have potential safety hazards caused by the flammability of organic carbonate electrolytes. 3 Among them, traditional carbonate solvents with low melting point, such as ethylene carbonate (EC) and dimethyl carbonate (DMC), are not only prone to dehydrogenation when the internal temperature of the battery rises, producing hydrogen or hydroxyl free radicals (H • or • OH) with high reactivity, which further catalyzes the continuous decomposition of electrolytes and increases the potential safety hazard of LIBs in a high-temperature environment. 4 Therefore, it is necessary to solve the safety problem of traditional carbonate electrolyte.…”

Exploring fluorinated electrolyte for high‐voltage and high‐safety Li‐ion cells with Li(Ni 0. 8 Mn 0 . 1 Co 0 .1 ) O 2 cathode

“…The electrolyte formed a rich‐B and rich‐F electrode/electrolyte interface, which dominated the electrochemical feature of the cell. In 2021, An et al 29 demonstrated a fire‐resistant 1 M LiPF 6 in PC‐TFA electrolyte with 2 wt.% FEC for Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 Li‐ion cells. The chemical structures of PC and TFA are depicted in Figure 1.…”

Rejuvenating Propylene Carbonate‐based Electrolyte Through Nonsolvating Interactions for Wide‐Temperature Li‐ions Batteries

“…[10] Furthermore, it possesses high anodic stability and excellent compatibility with high-nickel cathode. [11] Therefore, rejuvenating PC-containing electrolytes with superior electrochemical compatibility and high performance is significant for developing wide-temperature LIBs.The practical switch from EC to PC in LIBs, nevertheless turns out to be unfortunate, as the formidable co-intercalation and continual decomposition of PC lead to catastrophic exfoliation of graphite and hence failure of batteries. [12,13] Currently, the most common method to tackle this tricky problem is to employ film-forming additives, [14,15] fluorinated solvent [16,17] and novel Li salts [18][19] for forming stable solid electrolyte interface (SEI) on graphite to avoid structural exfoliation.…”