Electron Bottleneck in the Charge/Discharge Mechanism of Lithium Titanates for Batteries

Abstract

The semi-solid flow battery (SSFB) is a promising storage energy technology featured by employing semi-solid fluid electrodes containing conductive additive and active Li-ion battery materials. The state of art anode material for SSFB is Li4Ti5O12 (LTO). This work shows that LTO improves drastically the performance in fluid electrode via hydrogen annealing manifesting the importance of the electrical conductivity of the active material in SSFBs. On the other hand, the properties of fluid electrodes allow the contributions of ionic and electrical resistance to be separated in operando. The asymmetric overpotential observed in Li4Ti5O12 and TiO2 is proposed to originate from the so-called electron bottleneck mechanism based on the transformation from electrically insulator to conductor upon (de-)lithiation, or vice versa, which should be considered when modelling, evaluating or designing advanced materials based on Li4Ti5O12, TiO2 or others with insulating-conducting behavior materials.

Redox‐Targeting‐Based Flow Batteries for Large‐Scale Energy Storage

“…Among those new developments, the semisolid flow battery (SSFB), which breaks the solubility limit of redox species by employing a flowable slurry of lithium‐ion battery (LIB) materials, presents an interesting approach to enhance the energy density. However, the high viscosity and large quantity of conducting additives engender complex fluid dynamics and reduce volumetric energy density, thereby compromising the energy efficiency and imposing challenges in scaling up the system and maintenance. Another approach that breaks the boundary for liquid and solid energy storage is redox‐targeting‐based flow batteries .…”

Solid electrochemical energy storage for aqueous redox flow batteries: The case of copper hexacyanoferrate

“…5 However, this approach requires the use of highly conducting additives, leading to complex fluid dynamics and drop of the volumetric energy density. [6][7][8] Alternatively, Wang et al studied in 2006 the so-called redox-targeting flow battery that combines the concept of charge storage of solid batteries and the electrochemical properties of soluble redox species. 9 Typically, the insoluble solid energy storage material (LiFePO4) is stored in the electrolyte composed of a Li-salt and one or more soluble redox active molecules acting as 'redox mediators'.…”

Hydrogen‐Treated Rutile TiO2 Shell in Graphite‐Core Structure as a Negative Electrode for High‐Performance Vanadium Redox Flow Batteries

“…[24,25] In this scenario, TiO 2 is au seful materialf or photocatalysis, [26] gas sensors, [27][28][29] Li-ion batteries, [30,31] and catalysis. [24,25] In this scenario, TiO 2 is au seful materialf or photocatalysis, [26] gas sensors, [27][28][29] Li-ion batteries, [30,31] and catalysis.…”

“…It is well-known that many metal oxidesh ave good resistance to corrosion and offer outstanding catalytic properties. [24,25] In this scenario, TiO 2 is au seful materialf or photocatalysis, [26] gas sensors, [27][28][29] Li-ion batteries, [30,31] and catalysis. [32,33] In addition, TiO 2 is wells uited to work at low pH values and shows interesting electrochemical properties as well as stability to corrosion,e specially concerning the HER.…”