Understanding and Strategies for High Energy Density Lithium‐Ion/Lithium Metal Hybrid Batteries

Abstract A pressing need for high‐capacity anode materials beyond graphite is evident, aiming to enhance the energy density of Li‐ion batteries (LIBs). A Li‐ion/Li metal hybrid anode holds remarkable potential for high energy density through additional Li plating, while benefiting from graphite's stable intercalation chemistry. However, limited comprehension of the hybrid anode has led to improper utilization of both chemistries, causing their degradation. Herein, this study reports an effective hybrid anode design considering material properties, the ratio of intercalation‐to‐plating capacity, and Li‐ion transport phenomena on the surface. Mesocarbon microbeads (MCMB) possesses desirable properties for additional Li plating based on its spherical shape, lithiophilic functional group, and sufficient interparticle space, alongside stable intercalation‐based storage capability. Balancing the ratio of intercalation‐to‐plating capacity is also crucial, as excessive Li plating occurs on the top surface of the anode, eventually deactivating the intercalation chemistry by obstructing upper pores. To address this issue, electrospun polyvinylidene fluoride (PVDF) is introduced to prevent Li metal accumulation on the upper surface, leveraging its non‐conductive, polar nature, and high dielectric constant. By implementing these strategies, a LiNi_0.8Co_0.15Al_0.05O₂ (NCA)‐paired pouch cell delivers an outstanding energy density of 1101.0 Wh L⁻¹, highlighting its potential as an advanced post‐LIBs with practical feasibility.