Polycationic Polymer Layer for Air-Stable and Dendrite-Free Li Metal Anodes in Carbonate Electrolytes.
basic_science · Level V
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- Record sourced from PubMed, PMID 33543568.
- Also identified by DOI 10.1002/adma.202007428.
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Abstract
The short cycle life and safety concerns caused by uncontrollable dendrite growth have severely hindered the commercialization of lithium metal batteries. Here, a polycationic and hydrophobic polymer protective layer fabricated by a scalable tape-casting method is developed to enable air-stable, dendrite-free, and highly efficient Li metal anodes. The polymeric cations of poly(diallyl dimethyl ammonium) (PDDA) provide an electrostatic shielding effect that unifies Li<sup>+</sup> flux at the surface of the Li anode and promotes a homogeneous Li plating, while the bis(trifluoromethanesulfonyl)imide (TFSI) anions bring hydrophobic characteristics and improve moisture stability. The accumulated TFSI anions by the polycationic film also facilitate the formation of a stable solid electrolyte interphase (SEI). Steady Li plating/stripping in the carbonate electrolyte can be achieved under a high areal capacity of 10 mAh cm<sup>-2</sup> for 700 h with Li utilization efficiency up to 51.6%. LiNi<sub>0.8</sub> Mn<sub>0.1</sub> Co<sub>0.1</sub> O<sub>2</sub> and LiFePO<sub>4</sub> cells using the modified anode exhibit much improved electrochemical performance compared with the bare Li counterpart. Moreover, ultrasonic imaging shows no gas generation in the modified Li/LiFePO<sub>4</sub> pouch cell. Mechanism investigation demonstrates the stable SEI and homogeneous Li deposition derived by the polycationic layer.