Rutile-TiO₂ Nanocoating for a High-Rate Li₄Ti₅O₁₂ Anode of a Lithium-Ion Battery

Abstract

Well-defined Li(4)Ti(5)O(12) nanosheets terminated with rutile-TiO(2) at the edges were synthesized by a facile solution-based method and revealed directly at atomic resolution by an advanced spherical aberration imaging technique. The rutile-TiO(2) terminated Li(4)Ti(5)O(12) nanosheets show much improved rate capability and specific capacity compared with pure Li(4)Ti(5)O(12) nanosheets when used as anode materials for lithium ion batteries. The results here give clear evidence of the utility of rutile-TiO(2) as a carbon-free coating layer to improve the kinetics of Li(4)Ti(5)O(12) toward fast lithium insertion/extraction. The carbon-free nanocoating of rutile-TiO(2) is highly effective in improving the electrochemical properties of Li(4)Ti(5)O(12), promising advanced batteries with high volumetric energy density, high surface stability, and long cycle life compared with the commonly used carbon nanocoating in electrode materials.

High‐Density Microporous Li4Ti5O12 Microbars with Superior Rate Performance for Lithium‐Ion Batteries

“…The specific capacity and capacity retention are among the highest values ever reported for LTO spheres with loosely packed primary particles (Table S1, Supporting Information). It is also worth noting that the (dis)charge overpotentials for the LTO‐P‐N at 10 and 30 C are 0.204 and 0.321 V, respectively, very similar to that of LTO nanosheets 22. This small polarization demonstrates that LTO‐P‐N microbars have a small internal resistance for electron and Li‐ion transport responsible for the excellent lithiation and delithiation behavior during the high rate cycling.…”

“…For instance, metal, carbon, and graphene coating have been shown to increase the surface electronic conductivity of LTO. Nanosized LTO possesses high Li‐ion ionic conductivity, for instance, nanoparticles,3, 19 nanofibers,20, 21 nanosheets,9, 22 nanotubes,23 nanowires,24 nanoarrays,23, 24 and nanoscopic porous frameworks 25. Unfortunately, as LTO particle size decreases to the nanoscale, the specific surface area of the materials increased greatly, which significantly introduces irreversible reactions with the electrolyte solution 26, 27.…”

“…Mesoporous LTO hollow spheres present a remarkable high rate capability and stable long‐term cycling capacity,27 while above structures are easily destroyed during application in full LTO‐based power battery. In addition, a disadvantage of the porous LTO hollow spheres is that they are generally prepared by spray‐drying and hydrothermal processes, which require complex multi‐step processes that consume a large amount of energy 22, 23…”

A Facile Surface Reconstruction Mechanism toward Better Electrochemical Performance of Li4Ti5O12 in Lithium‐Ion Battery

“…Thus, under the condition of high‐power charge rates, lithium plating is prone to occur on the surface of the anode due to an extensive polarization of carbon materials, then potentially triggering thermal runaway when some lithium dendrites penetrate into the separator. Also, the reduction of electrolyte and formation of solid electrolyte interphase (SEI) layer on the carbon anode, which usually occurs around 1.0 V versus Li + /Li, can result in a considerable consumption of electrolyte and cyclable lithium, showing reduced cycle and calendar life 7, 8…”

“…One strategy is to fabricate a nano‐ or porous structure, which enlarges the specific surface area (over 200 m 2 g −1 ), and shortens the ion and electron diffusion lengths 16. The other strategy is the construction of a conductive network by adding conducting agent (such as carbon nanotubes, graphene, and other conductive carbon),17, 18, 19, 20 or doping,11, 21 or coating 8, 22. Although these approaches have been reported effective in terms of excellent high rate capabilities, the nanosizing compromises the tap density and colloidal stability, and the complicated preparation procedures are accompanied by high costs, making this strategy difficult to apply in practice 5…”