Triphenylphosphine Oxide as Highly Effective Electrolyte Additive for Graphite/NMC811 Lithium Ion Cells

• DOI: 10.1021/acs.chemmater.8b00413
• Publication Date: 2018-03-28T21:49:55Z
• Authors: Kolja Beltrop; Sven Klein; Roman Nölle; Andrea Wilken; Juhyon J. Lee; Thomas K.-J. Köster; Jakub Reiter; Liang Tao; Chengdu Liang; Martin Winter; Xin Qi; Tobias Placke
• Keywords: 01 natural sciences; 7. Clean energy; 0104 chemical sciences; 3. Good health

Nickel-rich layered oxide materials (LiNixMnyCo1–x–yO2, x ≥ 0.8, LiNMC) attract great interest for application as positive electrode in lithium ion batteries (LIBs) due to high specific discharge capacities at moderate upper cutoff voltages below 4.4 V vs Li/Li+. However, the comparatively poor cycling stability well inferior safety characteristics prevent this material class from commercial so far. Against background, new electrolyte formulations including additives are a major prerequisite sufficient electrochemical performance of Ni-rich NMC materials. In work, we introduce triphenylphosphine (TPPO) additive graphite/LiNi0.8Mn0.1Co0.1O2 (NMC811) cells. The addition only 0.5 wt % TPPO into carbonate-based (LiPF6 EC:EMC) significantly increases first cycle Coulombic efficiency reversible capacity and improves retention LIB full cell cycled between 2.8 4.3 V. Electrochemical results indicate that fade is predominantly caused by active loss negative electrode. contribution, X-ray photoelectron spectroscopy inductively coupled plasma-mass spectrometry analysis confirm participation solid interphase formation on cathode electrode, thus, effectively reducing during cycling. Furthermore, compared literature known triphenylphosphine, vinylene carbonate, diphenyl carbonate demonstrating outstanding working ability graphite/NMC811