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 µm) 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 µm) and high‐capacity LiNi 0.8 Co 0.1 Mn 0.1 O 2 (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.