Electrolytes TPFPB, 322

In order to enhance the air electrode capacity, it was suggested to introduce certain additives into electrolyte that would enhance solubility of Li202 because of complexation. An example of such an additive is tris-(pentafluorophenyl)-borane (TPFPB). However, such additives reduce oxygen solubility in electrolyte and enhance the overpotential of the anodic process under battery charging. 

SEI through reductive decomposition of the bis (oxalate) borate anion [103, 104]. Monofluoroethylene carbonate (FEC) can improve the cycling performance of Si-based anode material due to the generation of a more fluorinated SEI layer and inhibition of LiF production [104, 105]. Tris (pentafluorophenyl) borane (TPFPB) also was reported as an electrolyte additive for silicon thin-fihn electrode due to the formation of stable SEI, which therefore suppresses the surface pulverization [106]. The same research group also disclosed another additive, succinic anhydride (SA), as an electrolyte additive for sihcon thin-fihn electrode. Similar mechanism was proposed by the authors that addition S A can prevent the decomposition of LiPFg salt the Si surface and an SEI layer with higher hydrocarbon and LijCOs contents is formed on the Si surface [107]. 

Fig. 10 Charge-discharge curves for Li/LiMn204 cells at room temperature, with various electrol3 tes a 0.4 M tris(pentafluorophenyl) borane (TPFPB) and 0.2 M LijO in PC/DMC (1 1, v/v) b 0.4 M TPFPB and 0.2 M U2O2 in PC/DMC (1 1, v/v) and c conventional LiPFg-based electrolyte. The cells were cycled between 3 and 4.3 V at 0.2 C. Reprodueed with permission [150]. Copyright 2008 Elsevier...

The behavior of the anion receptor TPEPB in a 1 M LiCl04 electrolyte in EC/DMC (1/2.5 v/v) was studied by Lee et al. [425]. The transference number of the lithium cation was enhanced by increasing the TPFPB content from 0.22 (0 M TPFPB) to 0.55 (0.1 M TPFPB), measured by the potentiostatic polarization method of Bruce and Vincent (see Section 17.4.6.4). The total ionic conductivity decreased due to the decreasing anionic conductivity, but the cationic conductivity increased. The interaction between TPFPB and Cl04, resulting in formation of a complex and advanced dissociation of LiCl04, was shown by FTIR analysis. 

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