Oxygenated carbon nitride-based high-energy-density lithium-metal batteries

Abstract

Lithium (Li)-metal batteries with polymer electrolytes are promising for high-energy-density and safe energy storage applications. However, current polymer electrolytes suffer either low ionic conductivity or inadequate ability to suppress Li dendrite growth at high current densities. This study addresses both issues by incorporating two-dimensional oxygenated carbon nitride (2D OCN) into a polyvinylidene fluoride (PVDF)-based composite polymer electrolyte and modifying the Li anode with OCN. The OCN nanosheets incorporated PVDF electrolyte exhibits a high ionic conductivity (1.6 × 10⁻⁴ S cm⁻¹ at 25°C) and Li⁺ transference number (0.62), wide electrochemical window (5.3), and excellent fire resistance. Furthermore, the OCN-modified Li anode in situ generates a protective layer of Li₃N during cycling, preventing undesirable reactions with PVDF electrolyte and effectively suppressing Li dendrite growth. Symmetric cells using the upgraded PVDF polymer electrolyte and modified Li anode demonstrate long cycling stability over 2500 h at 0.1 mA cm⁻². Full cells with a high-voltage LiNi_0.8Co_0.1Mn_0.1O₂ cathode exhibit high energy density and long-term cycling stability, even at a high loading of 8.2 mg cm⁻². Incorporating 2D OCN nanosheets into the PVDF-based electrolyte and Li-metal anode provides an effective strategy for achieving safe and high-energy-density Li-metal batteries.