Lithiophilic Three-Dimensional Porous Ti<sub>3</sub>C<sub>2</sub>T<i><sub>x</sub></i>-rGO Membrane as a Stable Scaffold for Safe Alkali Metal (Li or Na) Anodes.
basic_science · Level V
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- Record sourced from PubMed, PMID 31747257.
- Also identified by DOI 10.1021/acsnano.9b07729.
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Abstract
Metallic anodes have high theoretical specific capacities and low electrochemical potentials. However, short-circuit problems caused by dendritic deposition and low Coulombic efficiency limit the cyclic life and safety of metallic anode-based batteries. Herein, dendrite-free and flexible three-dimensional (3D) alkali anodes (Li/Na-Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO) are constructed by infusing molten lithium (Li) or sodium (Na) metal into 3D porous MXene Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-reduced graphene oxide (Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO) membranes. First-principles calculations indicate that large fractions of functional groups on the Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i> surface lead to the good affinity between the Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO membrane and molten alkali metal (Li/Na), and the formation of Ti-Li/Na, O-Li/Na, and F-Li/Na mixed covalent/ionic bonds is extremely critical for uniform electrochemical deposition. Furthermore, the porous structure in Li/Na-Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO composites results in an effective encapsulation, preventing dendritic growth and exhibiting stable stripping/plating behaviors up to 12 mA·cm<sup>-2</sup> and a deeper capacity of 10 mA·h·cm<sup>-2</sup>. Stable cycling performances over 300 h (750 cycles) at 5.0 mA·cm<sup>-2</sup> for Li-Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO and 500 h (750 cycles) at 3.0 mA·cm<sup>-2</sup> for Na-Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-GO are achieved. In a full cell with LiFePO<sub>4</sub> cathodes, Li-Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i>-rGO electrodes show low polarization and retain 96.6% capacity after 1000 cycles. These findings are based on 2D MXene materials, and the resulting 3D host provides a practical approach for achieving stable and safe alkali metal anodes.