Tris borane TPFPB

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. 

It was shown recently that the addition of tris(pentafluorophenyl)borane (TPFPB) enhanced thermal stability of the graphite anode interface due to a reduced amount of lithium fluoride in the SEI by this complexation. Ethyltriacetoxysilane (ETAS) was used for the same purpose. ... 

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...

Another concept for anion receptors comprises bases on boron. It is possible to obtain highly conducting liF solutions in nonaqueous solvents hy means of boron additives, such as tris(pentafluorophenyl)borane (TPFPB) (see Figure 17.15) [423, 424], Solubihty of LiF can be increased by 6 orders of magnitude up to 1 mol- solutions. This observation can be exclusively attributed to Equation 17.27 Moreover, 1 molL solutions of LiF and boron-based anion receptors show good electrochemical stabiHty up to 5 V vs Li. Therefore, full battery systems... 

Figure 17.15 Structure of the anion receptor and Lewis acid tris(pentafluorophenyl)borane (TPFPB).

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