LiBF4-based electrolyte

The impedance response with frequency can be closely simulated by the equivalent circuit shown in Figure 27a, where Re, Ra, Cdi, Rad, and Cad represent the resistance or capacitance for the electrolyte solution, charge-transfer, double layer, and adsorbed layer, respectively. An interesting correlation was found between the passivating ability of various anions and the resistances of the two impedance components R and Rad, which are high for LiPFe-and LiBF4-based electrolytes and low for LiTf- or Lilm-based electrolytes. Using the rationale proposed by the authors, the former component (Ret) is... 

By EIS analysis of the corresponding lithium ion cells, Zhang et al. showed that the impact of SEI resistance on total cell impedance was rather negligible, and hence, they attributed the superior low-temperature behavior of LiBF4-based electrolytes to the lower resistance associated with the so-called charge-transfer processes , which are usually represented in impedance spectra by the semicircle at the lower frequency region. This suggestion could be viewed as a further extension of the conclusion... 

S. S. Zhang, K. Xu, T. R. Jow, J. Solid State Electrochem. 2003,7,147-151. Low-temperature performance of Li-ion cells with a LiBF4-based electrolyte. 

Figure 10. Integrated irreversible capacities of LiC in y-butyrolactone based electrolytes without (full symbols) and with (open symbols) C02 as electrolyte additive using various electrolyte salts LiCl04 (top, left), LiBF4 (top, right), LiPF6 (bottom, left), LiN(S02CF3)2 (bottom, right). Carbon Lonza KS44 synthetic graphite, i = 10 pA mg 1, cut-off 0-1.5 V vs. Li/Li+ [12],...

Very similar to the case of LiC104, an SEI formed from LiAsFe-based electrolytes, either on a lithium or carbonaceous anode, mainly consists of alkyl carbonates or Li2COs rather than LiF, as one would expect from the behavior of its close structural brothers LiPFe or LiBF4. This can be attributed to the much less labile As—F bond that is resistive to hydrolysis. 

Like LiAsFe, LiBF4 is a salt based on an inorganic superacid anion and has moderate ion conductivity in nonaqueous solvents (Table 3). It was out of favor in the early days of lithium battery research because the ether-based electrolytes containing it were found to result in poor lithium cycling efficiencies, which decayed rapidly with cycle number. ° The reactivity of LiBF4 with lithium was suspected as discoloration occurred with time or heating. 

In another work unrelated to the low-temperature electrolytes, Mohamedi et al. characterized the spray-deposited thin film of spinel cathode material by means of EIS and studied the correlation between electrolyte composition and the impedance components. Among the three lithium salts investigated, the lowest Ret and Rfwere obtained in a LiBF4-based... 

Lithium trifluoroalkoxyborate salts (Fig. 1.17j) are liquid at room tanperature with a neat salt conductivity on the order of 10 S cm- [202]. Carbonate-based electrolytes (EC PC DMC 1 1 3 v v v) with these salts have a conductivity >3 mS cm" at 20 °C (higher than comparable electrolytes with LiBF4) [202]. 

Li/CFx-SVO uses both CFx and SVO (Ag2V40n) as the cathode [8]. The cathode can be prepared as a mixture of CFx and SVO or as discrete CFx and SVO layers bonded to the current collector [13, 14]. The ratio of CFx to SVO can be tailored to suit specific applications. Electrolytes used in Li/CFx-SVO are typically LiBF4 in GBL-based electrolytes or LiAsFg in PC/DME-based electrolyte. The choice of electrolyte depends on the power requirement of the... 

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