Effective SEI Formation via Phosphazene‐Based Electrolyte Additives for Stabilizing Silicon‐Based Lithium‐Ion Batteries (Adv. Energy Mater. 26/2023)

Multifunctional Additive Ethoxy(pentafluoro)cyclotriphosphazene Enables Safe Carbonate Electrolyte for SiOx‐Graphite/NMC811 Batteries

“…875548. The authors would like to acknowledge the work of the University of Münster, Germany, their collaboration partner in the SeNSE project, who independently conducted similar experiments and came to similar conclusions [47] . The authors thank Solvionic for providing the carbonate electrolyte and Marcel Held from Empa for providing expertise and equipment for the pouch cell experiments.…”

Molecular‐Cling‐Effect of Fluoroethylene Carbonate Characterized via Ethoxy(pentafluoro)cyclotriphosphazene on SiOx/C Anode Materials – A New Perspective for Formerly Sub‐Sufficient SEI Forming Additive Compounds

“…Further electrochemical investigations (e.g., long-term performance, gas generation, self-discharge) regarding HFPN-derivatives as electrolyte additives in NCM523 || SiO x /C multilayered pouch cells (with 10 wt.% SiO x ) have been discussed in our previous study. [5] The ∆V plot shows the difference between the mean charge and the mean discharge voltages. These can give an estimation of the cell polarization upon (dis)charging and can be correlated to the cell impedance of different electrolyte blends upon cycling.…”

“…The absence of EtPFPN decomposition peaks in the GC-MS of the STD-FEC-EtPFPN electrolyte blend (Figure 3) after SEI for-mation is notable since EtPFPN as a single additive compound without FEC is not known as an effective SEI forming additive for SiO x /C based anode materials, but rather as electrolyte stabilizing agent at high temperatures (60 °C). [5] Recently, Liu et al [4,32] demonstrated in LiNi 0.5 Mn 1.5 O 4 (LNMO) || Li metal cells that EtPFPN as a single-additive electrolyte compound contributes to the formation of a beneficial LiF-rich SEI and generates a dense, uniform, thin, and phosphorous-and nitrogen-rich CEI layer on the surface of LNMO at high cell voltages (> 4.5 V). However, in their study [4] EtPFPN decomposition product traces have only been found on the cathode side, but not on the anode side (Limetal).…”

“…[3,4] With this in line, we previously investigated fluorinated cyclic phosphazene compounds in combination with fluoroethylene carbonate (FEC) as a dual-additive approach in electrolytes to foster cell stability by effective SEI formation in LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) || SiO x /C pouch cells. [5] Investigations on the silicon anode passivation properties at the anode side and electrochemical performance measurements have also been performed. The suppression of gas formation of the dual-additive electrolyte with fluoroethylene carbonate (FEC)/hexafluorocyclotriphosphazene (HFPN)derivatives have been studied and electrochemical aspects of the synergistic effect between FEC and HFPN-derivatives have been discussed.…”

“…Considering the proposed OHCs formation mechanisms by Henschel et al [6] and Gachot et al, [9] as well as the electrochemical observations in terms of long-term performance, gas evolution, and electrode passivation properties with FEC/HFPNderivatives as dual-additive electrolyte compounds in our previous study, it is likely that there is a correlation between the improved electrochemical performance with the dual-additive electrolyte approach, the LEMC intermediate compound, and the observed reduced OHC formation. [5] Especially the role of lithium alkyl carbonates like lithium ethyl carbonate (LEC) and LEMC are mentioned to be essential for the formation of such effective SEI. LEMC as EC reductive decomposition product facilitates a relatively high Li + conductivity (>1 × 10 −6 S cm −1 ) and is mentioned as the main SEI constituent by Wang, Xu, Eichhorn, and colleagues.…”