The Li+ charge transfer process starts from the solvated Li+ in the electrolyte to the reception of an electron (e-) from the electrode. This involves the de-solvation step of Li+ before entering into SEI and the diffusion step of Li+ through the SEI at the electrode and electrolyte interfaces before receiving an e- from the electrode at the electrode and SEI interface. Abe et al. [4-6] believe that the Li+ desolvation is the rate limiting step, which is supported by the results from the investigation of the electrolytes of different solvent systems using LiClO4 salt at HOPG, Li4Ti5O12 and Li+ solid conductors interfaces. The question is whether the de-solvation as a limiting step can be extended to the cathode-electrolyte interface. Jow et al.  examined the Li+ charge transfer kinetics at the graphite anode-electrolyte interface (SEI) and LiFePO4 (LFP) cathode-electrolyte interface (CEI) in a full cell, LFP/Gr, with Li as a reference electrode in 1 M LiPF6 in EC-DMC-MB with VC as an additive. It is found that the activation energy (Ea) at the graphite-electrolyte is about 67 kJ mol-1, which is much higher than 33 kJ mol-1 found at the LFP-electrolyte interface. It is concluded that the electrodes and their associated electrode-electrolyte interfacial layers are controlling the Li+ charge transfer kinetics.
The impact of additives such as VC, LiBOB, and LiFSI, etc. on the impedance of the anode-electrolyte and the cathode-electrolyte interfaces in LiNiCoAlO2/Gr cylindrical cells in 1.0 M LiPF6 in EC-EMC-MP (20:20:60 vol %), where MP is methyl propionate, at low temperatures was studied by Jones et al. . It is found that the additive impacts the impedance at the anode differently from that at the cathode. Further, we also found that the additives impact the Ea of Li+ charge transfer differently at the anode-electrolyte and the cathode-electrolyte interfaces. Different electrolyte components, including additives, result in different reduction and oxidation reactions during cell formation and cycling at the anode and cathode  and therefore, different and SEI and CEI layers. A discussion regarding the conditions in which the de-solvation step or the Li+ diffusion in either SEI or CEI layer is limiting the kinetics will also be provided.
Some work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA).
M. C. Smart, B. V. Ratnakumar, and S. Surampudi, J. Electrochem. Soc., 1999, 146(2), 486-492.
S. Herreyre, O. Huchet, S. Barusseau, F. Peron, J. M. Bodet, Ph. Biensan, J. Power Sources, 2001, 97-98, 576.
K. Xu, J. Electrochem. Soc., 2008, 155(10), A733-A738.
T. Abe, H. Fukuda, Y. Iriyama, Z. Ogumi, J. Electrochem. Soc., 2004, 151(8), A1120-A1123.
Y. Ishihara, K. Miyazaki, T. Fukutsuka, T. Abe, ECS Electrochemistry Lett., 3 (8) A83-A86 (2014).
T. Abe, F. Sagane, M. Ohtsuka, Y. Iriyama, and Z. Ogumi, J. Electrochem. Soc., 2005, 152(11), A2151-A2154.
T. R. Jow, M. B. Marx, J. L. Allen, J. Electrochem. Soc., 2012, 159 (5), A604-A612.
J.-P. Jones, M. C. Smart, F. C. Krause, B. V. Ratnakumar, E. J. Brandon, ECS Trans., 2017, 75, 1-11.
S. A. Delp, O. Borodin, M. Olguin, C. G. Eisner, J. L. Allen, T. R. Jow, Electrochimica Acta, 2016, 209, 498-510.