A large-area lithium metal–carbon nanotube film for precise contact prelithiation in lithium-ion batteries

Abstract

Prelithiation is a method to improve the energy density and cycle life of lithium-ion batteries, and contact prelithiation of the graphite anode using thin lithium foil is a promising technique. However, producing thin lithium foil below 5 μm is extremely challenging, making it difficult to achieve precise prelithiation with lithium metal. Additionally, pure thin Li foil suffers from drawbacks such as low lithium utilization, debris formation, and scalability issues. To address these challenges, we developed a straightforward doctor blade method to cast molten lithium onto a carbon nanotube (CNT) film, resulting in a thin and ultra-light Li-CNT film. The increasing lithiophilicity of the CNT film induced by lithiation enables the uniform casting of molten lithium onto its surface. The method enables adjustable lithium capacities ranging from 0.1 to 1.12 mA h cm⁻² or higher by controlling the amount of cast lithium. The Li-CNT films show high specific capacities and nearly 100% lithium utilization owing to their exceptional conductive network, porous structure, and electrolyte-philic nature, which facilitates the efficient transport of both electrons and lithium ions. To achieve prelithiation of the graphite anode when paired with commercial LFP electrodes of ∼3.3 mA h cm⁻², our Li-CNT film significantly enhances the initial Coulombic efficiency of the LFP||Gr full cell from 89% to 100%, fully compensating for the initial loss of active lithium ions caused by solid electrolyte interface formation. Furthermore, the Li-CNT film has superior mechanical properties, positioning it as a viable candidate for practical applications in lithium-ion batteries.