Lithium Diffusion in Li_4/3Ti_5/3O₄ Particles during Insertion and Extraction

Abstract

Lithium diffusion in a small Li4/3Ti5/3O4 (LTO) particle was investigated from kinetic viewpoints of two-phase transition process based on a core-shell model by means of galvanostatic and potentiostatic measurements of thin LTO composite electrodes. High-rate galvanostatic charge (insertion) – discharge (extraction) properties of the thin LTO composite electrode showed that the insertion into the LTO particle was significantly slower than the extraction. An apparent chemical diffusion coefficient (Dapp ) of lithium in the LTO particle during the insertion and extraction was evaluated from the results of potential step chronoamperometry (PSCA) with a spherical finite diffusion model. The phase-boundary movements between the two phases in the cathodic and the anodic potential steps for a long-time region were controlled by lithium diffusion through Li7/3Ti5/3O4 rock-salt (LTO-rock-salt) and Li4/3Ti5/3O4 spinel (LTO-spinel) shell, respectively. Dapp in the LTO-rock-salt and the LTO-spinel phase were estimated to be approximately 1 × 10−12 cm2/s and 1.6 × 10−11 cm2/s, respectively. The slower insertion was mainly due to a Dapp value one order of magnitude smaller in the LTO-rock-salt than that in the LTO-spinel phase. Electrochemical kinetic properties of the LTO particle with the core-shell structure were interpreted by lithium diffusion through the LTO-rock-salt shell during the insertion and the LTO-spinel shell with the low electron conductivity during the extraction.

Enhanced Rate Capability of Oxide Coated Lithium Titanate within Extended Voltage Ranges

“…In LTO, a redox couple from Ti 4+ to Ti 3+ reversibly delivered the electron and the two-phase transition process between spinel and rock salt was occurred at 1.55 V vs. Li/Li + (Aldon et al, 2004;Takami et al, 2011). Since it has very low-volume expansion and higher working potential, LTO is an emerging anode material that can solve the above mentioned problems.…”

Overcharge Study in Li4Ti5O12Based Lithium-Ion Pouch Cell

“…6 LTO presents a nearly constant potential plateau, which indicates that LTO undergoes a phase transformation. [14][15][16][17][18][19] Therefore, in the context of these LTO || NMC cells, the LTO electrode behaves in a way reminiscent of a reference electrode. As a result, the main visible features in the cell's IC curve originate from the PEAM.…”

“…[8][9][10][11][12][13] LTO, as a negative electrode active material (NEAM), presents some unique features such as zero strain in Li intercalation and a potential plateau (1.56 V vs. Li/Li + ) over the entire stoichiometry of intercalation with Li, which is relatively high compared to that of the carbonaceous NEAM typically used in commercial LIBs today. [14][15][16][17][18][19] This high potential plateau renders it stable against conventional LIB electrolytes, with minimal solid electrolyte interphase (SEI) presence to impede intercalation kinetics (i.e. allowing a better rate capability), but at the expense of energy density.…”

Polarization Behavior of Li4Ti5O12Negative Electrode for Lithiumion Batteries

“…22) Polarization with lower carbon loading continually increases during the discharging due to the insufficient path of electron and the formation of poor conduction phase at the surface. Fig.…”