Uniform Lithium Deposition via Optimization of the Conductive CNT-to-Insulating CaCO₃ Ratio for High-Performance...

Lithium metal batteries (LMBs) are promising for next-generation energy storage systems due to their high energy density. However, challenges such as uncontrolled lithium dendrite growth and volume expansion of lithium metal anodes (LMAs) limit their practical application, leading to capacity degradation and safety risks. To address these challenges, a composite scaffold combining conductive carbon nanotubes (CNTs) with insulating CaCO₃ is being developed. This design enhances lithium-ion adsorption at the electrode surface through the optimized CNT-to-CaCO₃ ratio, which increases the local lithium-ion concentration during deposition while balancing conductivity to suppress lithium accumulation typically induced by highly conductive CNTs. Spray pyrolysis is used to fabricate CaCO₃ and carbon composite microspheres with multivoid structures (CaCO₃/C), designed to fragment into smaller particles, minimizing agglomeration and enabling uniform mixing with CNTs. Among electrodes with varying CNTs-to-CaCO₃/C ratios, the electrode having an equal weight ratio of CNTs and CaCO₃/C (CNT50-Ca50) exhibits uniform deposition and minimizes volume expansion. In symmetric cells, this electrode demonstrates stable cycling for over 1,200 h at 1.0 mA·cm^-2 and a low voltage hysteresis of 110 mV at 10.0 mA·cm^-2. In full cells paired with a LiFePO₄ cathode, the lithium predeposited CNT50-Ca50 electrode (Li@CNT50-Ca50) delivers 144.0 mAh·g^-1 at 1.0 C initially, retaining 80% capacity after 130 cycles with an average Coulombic efficiency of 99.6%.