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

초록

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<middle dot>cm-2 and a low voltage hysteresis of 110 mV at 10.0 mA<middle dot>cm-2. In full cells paired with a LiFePO4 cathode, the lithium predeposited CNT50-Ca50 electrode (Li@CNT50-Ca50) delivers 144.0 mAh<middle dot>g-1 at 1.0 C initially, retaining 80% capacity after 130 cycles with an average Coulombic efficiency of 99.6%.

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