A Li₃P nanoparticle dispersion strengthened ultrathin Li metal electrode for high energy density rechargeable batteries

Achievement of lithium (Li) metal anode with thin thickness (e.g., ≤ 30 µm) is highly desirable for rechargeable high energy density batteries. However, the fabrication and application of such thin Li metal foil electrode remain challenging due to the poor mechanical processibility and inferior electrochemical performance of metallic Li. Here, mechanico-chemical synthesis of robust ultrathin Li/Li₃P (LLP) composite foils (~ 15 µm) is demonstrated by employing repeated mechanical rolling/stacking operations using red P and metallic Li as raw materials. The in-situ formed Li⁺-conductive Li₃P nanoparticles in metallic Li matrix and their tight bonding strengthen the mechanical durability and enable the successful fabrication of free-standing ultrathin Li metal composite foil. Besides, it also reduces the electrochemical Li nucleation barrier and homogenizes Li plating/stripping behavior. When matching to high-voltage LiCoO₂, the full cell with a low negative/positive (N/P) capacity ratio of ~ 1.5 offers a high energy density of ~ 522 W·h·kg⁻¹ at 0.5 C based on the mass of cathode and anode. Taking into account its facile manufacturing, potentially low cost, and good electrochemical performance, we believe that such an ultrathin composite Li metal foil design with nanoparticle-dispersion-strengthened mechanism may boost the development of high energy density Li metal batteries.