Is Li₄Ti₅O₁₂ a Solid-Electrolyte-Interphase-Free Electrode Material in Li-Ion Batteries? Reactivity Between Li₄Ti₅O₁₂ Electrode and Electrolyte

Abstract

Li4Ti5O12 with a cubic spinel structure (space group, Fd3(_)m) has a high redox potential at around 1.5 V vs. Li+/Li with a theoretical capacity of 175 mA h g−1.2 The negligible structural difference between pristine Li4Ti5O12 and lithiated Li7Ti5O12 at the two-phase equilibrium junction guarantees an outstanding electrochemical reversibility during the charge/discharge process.3 Furthermore, the high redox potential would prevent not only the lithium metal deposition on the anode at high current conditions but also the formation of the resistive solid electrolyte interphase (SEI) layer, which may lead to an active Li-ion loss and an increase of the cell impedance.4 No SEI formation at the surface of Li4Ti5O12 is a widely accepted argument from the literature point of view. However, in our previous report regarding the electrochemical study of the carbon-free Li4Ti5O12 electrode,5 we noticed the formation and dissolution of the SEI layer through the change in the intensity of Ti 2p XPS core peaks during the charge and discharge process. This fact led us to suspect the stability of Li4Ti5O12 vis-à-vis to the electrolyte in spite of its high redox potential. Despite the interesting properties of Li4Ti5O12, only few literature studies were reported on its reactivity to the electrolyte. Based on a detailed XPS study on the electrolyte/electrode interfaces in LiMn1.6Ni0.4O4/ Li4Ti5O12 system, Dedryvère et al. have reported the formation of organic and inorganic species on the surface of Li4Ti5O12 anode after cycling.6 However, they concluded that those species were first formed at the cathode and then, adsorbed on the surface of Li4Ti5O12 either by diffusion or by migration of organic cationic species. In addition, the lower voltage limit of Li4Ti5O12 anode couldn’t be also guaranteed to be over 1 V in their study because measuring the voltage of Li4Ti5O12 itself is impossible in two-electrode full cell. He et al. also pointed out the formation of SEI film on the Li4Ti5O12 electrode cycled between 2.5 and ~ 0 V vs. Li+/Li., but they mainly focused on the SEI formation occurred below 1 V.7 Moreover, in the aforementioned studies, the results were obtained only at room temperature cycling, and the effects of carbon conducting agent contained in the conventional Li4Ti5O12electrodes were neither considered nor clarified. In this report, for the first time, the Li4Ti5O12/ electrolyte interface is investigated at room and high temperature using the carbon-free Li4Ti5O12 electrode. The new electrode concept5,8 allows us to examine the reactivity of Li4Ti5O12 to the electrolyte and avoid any kind of parasite reaction which may be induced by the high-surface-area carbon conducting additive. Chemical changes at the surface of Li4Ti5O12 were investigated using a step by step X-ray photoelectron spectroscopy (XPS) analysis during charge/discharge cycling. The time-of-flight secondary ion mass spectroscopy (ToF-SIMS) study and scanning electron microscopy (SEM) observation were carried out to examine a quantitative and qualitative change in the surface chemistry and the electrode morphology after cycling, respectively. The differences between the carbon-free and carbon-containing Li4Ti5O12electrodes in terms of stability and cyclability were also discussed. [1] S.S. Zhang, J. Power Sources, 2006, 161, 1385. [2] T. Ohzuku, A. Ueda, N. Yamamoto, J. Electrochem. Soc., 1995, 142, 1431; L. Kavan, M. Gratzel, Electrochem. Solid State Lett., 2002, 5, A39. [3] K. Zaghib, M. Simoneua, A. Armand, M. Gauthier, J. Power Sources, 1999, 81-82, 300; G. Armstrong, A. R. Armstrong, J. Canales, P. G. Bruce, Electrochem. Solid-State Lett., 2006, 9, A139; A. N. Jansen, A. J. Kahaian, K. D. Kepler, P. A. Nelson, K. Amine, D. W. Dees, D.R. Vissers, M. M. Thackeray, J. Power Sources, 1999, 81-82, 902; T. Brousse, P. Fragnaud, R. Marchand, D. M. Schleich, O. Bohnke, K. West, J. Power Sources, 1997, 68, 412; T. Ohzuku, A. Ueda, N. Yamamoto, J. Electrochem. Soc., 1995, 142, 1431. [4] J. Christensen, V. Srinivasan, J. Newman, J. Electrochem. Soc., 2006, 153, A560; M. Winter, W. K. Appel, B. Evers, T. Hodal, K. C. Moller, I. Schneider, M. Wachtler, M. R. Wagner, G. H. Wrodnigg, J. O. Besenhard, Monatsch. Chem., 2001, 132, 473. [5] M. S. Song, A. Benayad, Y. M. Choi and K. S. Park, Chem. Commun., 2012, 48, 516. [6] R. Dedryvère, D. Foix, S. Franger, S. Patoux, L. Daniel and D. Gonbeau, J. Phys. Chem. C, 2010, 114, 10999. [7] Y. B. He, F. Ning, B. Li, Q. S. Song, W. Lv, H. Du , D. Zhai, F. Su, Q. H. Yang, F. Kang, J. of Power Sources, 2012, 202, 253. [8] C. J. Kim, N. S. Norberg, C. T. Alexander, R. Kostecki and J. Cabana, Adv. Funct. Mater., 2013, 23, 1214.

Manganese in the SEI Layer of Li4Ti5O12 Studied by Combined NEXAFS and HAXPES Techniques

“…The O 1s spectra of the lithiated sample also display a corresponding peak at about 534 eV, which is equivalent to the energy of the C−O bond. 23 A similar behavior was observed by Song et al 24 and attributed to adsorption/desorption of SEI/ electrolyte decomposition species during cycling. That bulk material is clearly detected at a photon energy of 2005 eV, meaning that the SEI is not more than 20 nm thick (assuming that the SEI is a compact layer).…”

Interfacial Effects in ε-LixVOPO4 and Evolution of the Electronic Structure

“…There have been reports of surface Li 2 O formation as a solidelectrolyte interphase (SEI) constituent on electrode materials formed upon lithiation. 16,51,52 These reports all attribute this to a breakdown of the electrolyte. It is possible that this is the case here when considering the low operating voltage of the second lithium insertion.…”

Unravelling the Interface Layer Formation and Gas Evolution/Suppression on a TiNb2O7 Anode for Lithium-Ion Batteries

“…Interestingly, the similar results were also confirmed by the XPS probing depth of LTO from Benayad's work. 41 For C1s XPS profile, the peaks at 284.6 and 290.9 eV in the initial state (curve a) correspond to the C−C/C−H from carbon black and C−F bonds from PVDF, respectively, and the peak at about 286.3 eV can be attributed to the C−H bond and C−C bond of CH 2 in PVDF. 42 At the 50% lithiated state (curve b), peaks at 287.6 and 289.7 eV appear, correspond to the CO double bond of Li 2 CO 3 and ROCOOLi, respectively, which are the basic components of SEI film.…”