Achieving high volumetric energy density in graphite anodes through polymer coating with improved electrolyte impregnation

Abstract

The increasing demand for electric vehicles (EVs) has prompted extensive research in the development of lithium-ion batteries (LIBs) with high volumetric energy density. The graphite anode possesses a tap density of 2.25 g cc⁻¹, resulting in a volumetric energy density of over 770 W h L⁻¹. However, the practical electrode density of 1.4–1.6 g cc⁻¹ leads to a lower volumetric energy density of ∼550 W h L⁻¹, and increasing electrode density beyond 1.6 g cc⁻¹ is limited owing to the pore closure and poor electrolyte penetration, which leads to an imbalance in the N/P ratio resulting in Li metal plating. Hence, enhancing the electrolyte permeation into the densely packed graphite electrode is the crucial aspect for achieving high volumetric energy density. In this research, we coated a functional polymer (cyanoethyl polyvinyl alcohol), which has a high electrolyte absorption capability on a conventional graphite anode to enhance the electrolyte penetration into the highly densified graphite. As a result, the electrode demonstrated a high cycle stability under a high electrode density of 1.9 g cc⁻¹ without any Li plating, and drastic degradation of capacity retention resulted in a remarkable volumetric energy density exceeding 650 W h L⁻¹.