Ag Nanoparticle-Decorated Mesocarbon Microbeads for Homogeneous Lithium Deposition toward Stable Hybrid Anodes

Transforming conventional Li-ion batteries into lithium-ion/lithium metal hybrid batteries by curtailing the N/P (anode lithiation capacity/cathode delithiation capacity) ratio is an effective approach to improve the energy density. The lower N/P ratio brings more capacity in the form of lithium metal, leading to more serious inhomogeneous plating/stripping of Li and active Li consumption. Therefore, it is of great importance to regulate uniform Li plating/stripping in the low N/P ratio condition for improving the reversibility of the batteries. This work proposes the surface modification of mesocarbon microbeads (MCMBs) with Ag nanoparticles as lithiophilic seeds that are capable of diminishing the nucleation overpotential of lithium and directing uniform and conformal Li deposition on the surface of MCMB particles, which prevents dendrite growth and agglomeration of dead Li on top of the anode. As a result, the hybrid anode using Ag-modified MCMBs can remain stable for more than 150 charge/discharge cycles in half-cells under an ultra-low N/P ratio of 0.33. Meanwhile, the full cell using this hybrid anode maintains 80.1% capacity after 130 cycles at 0.5 C under a low N/P ratio of 0.67, while the capacity retention of the cell using bare MCMBs quickly drops to 13.2% only after 100 cycles.