Tris(pentafluorophenyl) borane as an additive to improve the power capabilities of lithium-ion batteries

Tris(pentafluorophenyl) borane (TPFPB) was investigated as an electrolyte additive to improve the power capabilities of lithium-ion batteries. As discussed here, TPFPB is adopted as an anion receptor to dissolve the LiF in passivation films, which create transport problems for both electrons and lithium ions. We found that the power capabilities of lithium-ion batteries could be dramatically improved by adding a controlled amount of TPFPB. Moreover, the addition of TPFPB also improves the cycling performance of graphite/Li-1.1[Ni1/3Co1/3Mn1/3](0.9)O-2 lithium-ion cells. Although the use of TPFPB as an anion receptor has been reported to improve the ionic conductivity of the electrolyte, we demonstrate that excessive TPFPB also significantly raises the interfacial impedance of lithium-ion batteries. Therefore, high TPFPB concentrations are not recommended for high-power lithium-ion batteries. (C) 2006 The Electrochemical Society.