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.

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Battery safety has an ever-increasing significance and is required for consumer's safety. The high flammability of traditional organic liquid electrolyte, which consists of ethylene carbonate and highly flammable linear carbonate, is one of the major reasons for thermal runaway and battery fire events. Replacement of flammable liquid electrolyte with non-incendive one is urgently needed for safe lithium-ion batteries. A fluorinated linear sulfate paired with 1 m LiPF 6 was developed and evaluated as a solvent of non-incendive liquid electrolyte for a use in high-voltage (4.4 V) and high-temperature (45 °C) LiNi 0.82 Mn 0.07 Co 0.11 O 2 (NCM811) chemistry-based lithium-ion bat-teries. Non-incendive liquid electrolyte containing sulfate with two trifluoroethyl groups exhibited superior anodic and thermal stability and promoted cathode-electrolyte and anode-electrolyte interfacial stability, compared to flammable traditional electrolyte. Non-incendive electrolyte showed markedly improved 300 cycle performance of an industrial graph-itejjNCM811 lithium-ion pouch cell with a nominal capacity of 730 mAh under harsh conditions, and high safety of 10 V overcharge abuse tolerance, from which safe and high-performing high-energy lithium-ion batteries and battery-powered electric vehicles and energy storage system are anticipated.

State‐of‐the‐art lithium (Li)‐ion batteries employ silicon anode active material at a limited fraction while strongly relying on fluoroethylene carbonate (FEC) electrolyte additive exceeding 10 wt.% to enable stable cycling. The swelling issue of silicon in the aspect of solid electrolyte interphase (SEI) instability and a risk of safety hazards and high manufacturing cost due to FEC has motivated the authors to design a well‐working fluorinated additive substitute. High‐capacity cells employing nickel‐rich oxide cathode are pursued by operating at > 4.2 V versus Li/Li+, for which anodic stability of electrolyte is required. Herein, a highly effective new ambifunctional additive of icosafluoro‐15‐crown 5‐ether is proposed at a little fraction of 0.4 wt.% for the stabilized interfaces and reduced swelling of high capacity (3.5 mAh cm−2) 5 wt.% SiO‐graphite anode and LiNi0.88Co0.08Mn0.04O2 cathode. Utilizing together with a lowered fraction of FEC, reversible long 300 cycles at 4.35 V and 1 C (225 mA g−1) are achieved. Material characterization results reveal that such stabilization is derived from the surface passivation of both anode and cathode with perfluoro ether, LiF, and LixPFy species. The present study gives insight into electrolyte formulation design with lower cost and both‐side stabilization strategies for silicon and nickel‐rich active materials and their interfaces.

Fast charging of Li-metal battery (LMB) is a challenging issue owing to the interfacial instability of Li-metal anode in liquid electrolyte and Li-dendrites growth, resulting in fire hazard. Those issues motivated to pioneer a stabilization strategy of liquid electrolyte-derived solid electrolyte interphase (SEI) layer that enables dendrites-free Li-metal anode under extremely high current density, which solid-state battery cannot. Here, the novel electrolyte formulation is reported including trace-level pentafluoropropionic anhydride (PFPA) combined with fluoroethylene carbonate (FEC) additives, and the SEI stabilization in Li//Mn-rich LMB, achieving unprecedented ultrafast charging under simultaneous extreme conditions of 20 C (charged in 3 min), 4.8 V and 45 °C, delivering 118 mAh g −1 for long reversible 400 cycles, and unprecedented high stability of Li//Li cell under extremely high current 10 mA cm −2 (Li stripping/ plating in 6 min) for a prolonged time of 200 h. The SEI analysis results reveal that the PFPA, which has a symmetric 10 F-containing molecular structure, is a strong F source for promptly producing thin, uniform, and robust F-and organics-enriched SEI layers at both Li-metal anode and Mn-rich cathode, preventing Li-dendrites. This study provides a potential concept for ultrafast charging, long-cycled, and safer high-energy LMBs and LIBs.