Fig. 1

Diagram of EC-free electrolyte regulation"

Fig. 2

Network diagram of the electrolyte test set"

Fig. 3

Timeline of the development of EC-free electrolytes"

Fig. 4

Current status of electric vehicle development and thermal runaway accidents. (a) Demand for lithium-ion batteries for electric vehicles; (b) Roadmap for lithium-ion batteries for electric vehicles; (c) Lithium-ion battery accident[11]; (d) Schematic diagram of the fire and combustion of an electric vehicle in Germany"

Fig. 5

Thermal runaway reaction mechanism and chronological analysis (a) Internal characteristics of different stages of battery thermal runaway[30]; (b) Schematic diagram of chemical crosstalk between positive and negative electrodes[35]; (c) Schematic of the causes of LIB fire accidents[10];(d) Thermal runaway mechanism graph of 38 Ah battery[46]"

Fig. 6

EC-free based electrolyte lithium battery thermal safety characteristics test (a) Comparison of thermal runaway characteristics of conventional electrolytes and (b) perfluorinated electrolytes[28]; The electrical performance of SL-based batteries and conventional batteries at (c) 25 ℃ and (d) 60 ℃/70 ℃ [68]; (e) Characteristic stages of the heating test process for double-salt electrolyte batteries and (f) voltage and internal temperature changes[22]"

Fig. 7

Schematic diagram of voltage windows for different types of electrolytes"

Fig. 8

High voltage Failure Mechanisms. (a) Schematic illustration of the proposed degradation pathways for Ni-rich cathodes with EC-containing and EC-free electrolytes; (b) Mechanism of rollover fading of EC-based electrolyte[73]; (c) Schematics showing the effect of the suppressed nickel ions dissolution on the morphology of the anode SEI layer[40]"

Fig. 9

(a) Graphite negative electrode diagram after STD+Li2CO3 electrolyte is circulated 100 times at 2.8—4.5 V[107]; (b) LiDFP to NCM523|| Effect of graphite full battery cycling[105]; (c) Interactions between the components of LHCEs[100]"

Table 1

Different EC-free electrolyte formulations and properties"

Fig. 10

Schematic diagram of the melting and boiling points of different electrolyte solvents"

Fig. 11

Lithium deposition on the surface of the negative electrode at low and room temperature"

Fig. 12

Summary of low-temperature electrolyte performance (a) Comparison of the characterization of two electrolytes in the NMC532 system after 20 cycles[124]; (b) Low-temperature cycling electrical properties of PC-based electrolytes[113]; (c) Comparison network diagram of EC electrolyte and EC-free electrolyte performance[19]; (d) Discharge curves of conventional electrolytes and (e) D2-based electrolytes[93]"