Three‐Tier Hierarchical Clusters of Carbon‐Coated Li₄Ti₅O₁₂ Single Crystals as High‐Power and High‐Energy Anodes for Lithium‐Ion Batteries

Abstract

A novel three‐tier hierarchical cluster lithium‐ion battery (LIB) anode is reported here, consisting of 1) carbon‐coated Li4Ti5O12 crystals as the first nano‐tier (ca. 10 nm) for high‐rate capability; 2) submicron spheres consisting of Li4Ti5O12 crystals as the second submicron tier (100–300 nm), facilitating electrolyte infiltration and Li+ diffusion; and 3) clusters comprising Li4Ti5O12 spheres as the third micron‐sized tier (1–2 μm) to increase the packing density of active materials for high‐power LIBs. The submicron tier acts as a transition zone between the nano‐tier and micro‐tier to further benefit Li+ diffusion, electrolyte infiltration, and electron transport. The carbon coating on Li4Ti5O12 forms a uniform and continuous conductive network for fast electron transport and Li+ diffusion to address the low electronic conductivity obstacle of the Li4Ti5O12 anode. The three‐tier hierarchical clusters maximize the close contact between the electrolytes and the active materials for excellent electrochemical performance.

Challenges of Spinel Li4Ti5O12 for Lithium‐Ion Battery Industrial Applications

“…One is to introduce carbon after the synthesis of Li 4 Ti 5 O 12 , [7,23] and the other is called in situ carbon-coating, i.e., forming a carbon layer during the phase formation of the Li 4 Ti 5 O 12 . There are two primary ways to introduce carbon on the surface of Li 4 Ti 5 O 12 particles.…”

“…Bai et al [23] reported a typical three-tier hierarchical micro-/submicron-/nano-structured Li 4 Ti 5 O 12 /C cluster in which the nanosized carbon-coated Li 4 Ti 5 O 12 single crystals (ca. Furthermore, hierarchical spherical Li 4 Ti 5 O 12 /C composites can also be realized via a simple organic carbon source thermal pyrolysis process under certain conditions.…”

“…However, although almost all of the organic materials can be decomposed into carbon after pyrolysis, the conductivity and degree of graphitization are different. Common organic carbon sources used for improving the rate performance of Li 4 Ti 5 O 12 anodes include sucrose, glucose, malic acid, citric acid, pitch, ethylenediamine (EDA), certain polymers, and so forth. Nugroho et al studied the influence of organic carbon sources with different functional groups and chain lengths (including oleylamine, oleic acid, hexylamine) on the particle size, morphology, crystallinity and electrochemical properties of Li 4 Ti 5 O 12 /C composites.…”

“…There are two primary ways to introduce carbon on the surface of Li 4 Ti 5 O 12 particles. One is to introduce carbon after the synthesis of Li 4 Ti 5 O 12 , and the other is called in situ carbon‐coating, i.e., forming a carbon layer during the phase formation of the Li 4 Ti 5 O 12 . The latter synthesis method is obviously simplified, and the particle size of Li 4 Ti 5 O 12 can also be controlled in the presence of the carbon source during the calcination process.…”

Advanced composites of complex Ti-based oxides as anode materials for lithium-ion batteries

“…Organic carbon from various sources subjected to different pyrolysis shows variable degrees of graphitization. Common organic carbon sources used for Li 4 Ti 5 O 12 include glucose [99][100][101][102][103], sucrose [104][105][106][107], sugar [108,109], starch [110], melamine [111,112], malic acid [113], toluene [114], citric acid [115,116], pitch [117,118], acetonitrile [119], and polymers [120][121][122][123][124][125][126]. The differences, advantages and advanced modification approaches of inorganic and organic carbon are summarized below.…”