Concentrated electrolytes usually demonstrate good electrochemical performance and thermal stability, and are also supposed to be promising when it comes to improving the safety of lithium-ion batteries due to their low flammability. Here, we show that LiN(SO2F)2-based concentrated electrolytes are incapable of solving the safety issues of lithium-ion batteries. To illustrate, a mechanism based on battery material and characterizations reveals that the tremendous heat in lithium-ion batteries is released due to the reaction between the lithiated graphite and LiN(SO2F)2 triggered thermal runaway of batteries, even if the concentrated electrolyte is non-flammable or low-flammable. Generally, the flammability of an electrolyte represents its behaviors when oxidized by oxygen, while it is the electrolyte reduction that triggers the chain of exothermic reactions in a battery. Thus, this study lights the way to a deeper understanding of the thermal runaway mechanism in batteries as well as the design philosophy of electrolytes for safer lithium-ion batteries.
Localized high-concentration electrolytes (LHCEs) provide
a new
way to expand multifunctional electrolytes because of their unique
physicochemical properties. LHCEs are generated when high-concentration
electrolytes (HCEs) are diluted by antisolvents, while the effect
of antisolvents on the lithium-ion solvation structure is negligible.
Herein, using one-dimensional infrared spectroscopy and theoretical
calculations, we explore the significance of antisolvents in the model
electrolyte lithium bis(fluorosulfonyl)imide/dimethyl carbonate (LiFSI/DMC)
with hydrofluoroether. We clarify that the role of antisolvent is
more than dilution; it is also the formation of a low-dielectric environment
and intensification of the inductive effect on the C=O moiety of DMC
caused by the antisolvent, which decrease the binding energy of the
Li+···solvent and Li+···anion
interactions. It also has beneficial effects on interfacial
ion desolvation and Li+ transport. Furthermore, antisolvents
also favor reducing the lowest unoccupied molecular orbital (LUMO)
energy level of the solvated clusters, and FSI– anions
show a decreased reduction stability. Consequently, the influence
of antisolvents on the interfacial chemical and electrochemical activities
of solvation structures cannot be ignored. This finding introduces
a new way to improve battery performance.
Electric vehicles (EVs) are being endorsed as the uppermost successor to fuel-powered cars, with timetables for banning the sale of petrol-fueled vehicles announced in many countries. However, the range and charging times of EVs are still considerable concerns. Fast charging could be a solution to consumers’ range anxiety and the acceptance of EVs. Nevertheless, it is a complicated and systematized challenge to realize the fast charging of EVs because it includes the coordinated development of battery cells, including electrode materials, EV battery power systems, charging piles, electric grids, etc. This paper aims to serve as an analysis for the development of fast-charging technology, with a discussion of the current situation, constraints and development direction of EV fast-charging technologies from the macroscale and microscale perspectives of fast-charging challenges. If the problem of fast-charging can be solved, it will satisfy consumers’ demand for 10-min charging and accelerate the development of electric vehicles. This paper summarized the development statuses, issues, and trends of the macro battery technology and micro battery technology. It is emphasized that to essentially solve the problem of fast charging, the development of new battery materials, especially anode materials with improved lithium ion diffusion coefficients, is the key. Finally, it is highlighted that red phosphorus is one of the most promising anodes that can simultaneously satisfy the double standards of high-energy density and fast-charging performance to a maximum degree.
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