Enabling Sustainable Lithium Metal Electrodes via Cholesteric Liquid Crystalline Cellulose Nanocrystal Nanomembranes

Abstract

Despite their potential as high-energy-density lithium battery electrodes, Li metals are still far from practical use mainly due to their insufficient electrochemical reliability. Here, a cholesteric liquid crystalline (cLC) cellulose nanocrystal (CNC) nanomembrane as a natural material-based mechanically robust and precisely defined ion channel strategy for sustainable Li metal electrodes is demonstrated. The cLC-CNC nanomembrane (1 mu m) is designed to achieve a self-assembled ordered nanoporous structure with optimal tortuosity. This well-defined cLC structure and high mechanical modulus of CNC, which are difficult to attain with traditional synthetic materials, allow facile/uniform Li-ion flux toward Li metal electrodes, and simultaneously prevent Li dendrite growth and mitigate volume expansion of the Li metal during Li plating/stripping cycling. Driven by these viable roles of the cLC-CNC nanomembrane, Li metal full cells (consisting of thin Li metal anodes (20 mu m) and high-capacity LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes (3.8 mAh cm(-2)), capacity excess of the Li metal over the NCM811 = 1.0) exhibit high energy density (890 Wh L-cell(-1)) along with stable cycling retention, which lie far beyond those achievable with previously reported Li protective layers.