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5072664 
Journal Article 
Chemical "Pickling" of Phosphite Additives Mitigates Impedance Rise in Li Ion Batteries 
Peebles, C; Garcia, J; Tornheim, AP; Sahore, R; Bareno, J; Liao, C; Shkrob, IA; Iddir, HH; Abraham, DP 
2018 
Yes 
Journal of Physical Chemistry C
ISSN: 1932-7447
EISSN: 1932-7455 
122 
18 
9811-9824 
WOS:000432477400010 
The use of high-voltage, high-capacity positive electrodes in lithium ion batteries presents a challenge, given their tendency to degrade organic electrolytes. To prevent this damage, electrolyte additives modifying the cathode surface are required. Tris(trimethylsilyl) phosphite (TMSPi) is one such electrolyte additive. However, the mechanism for its protective action (similar to other phosphite, borate, and boroxane compounds) remains not completely understood. In LiPF6 containing carbonate electrolytes, TMSPi undergoes reactions yielding numerous products. Here we demonstrate that one of these products, PF2OSiMe3, is responsible for mitigation of the impedance rise that occurs in aged cells during charge/discharge cycling. This same agent can also be responsible for reducing parasitic oxidation currents and transition metal loss during prolonged cell cycling. Mechanistic underpinnings of this protective action are examined using computational methods. Our study suggests that this beneficial action originates mainly through inhibition of catalytic centers for electrolyte oxidation that are present on the cathode surface, by forming capping ligands on the transition metal ions that block solvent access to such centers.