Unraveling Lithium Deposition Behavior on Cobalt-Decorated 3D Carbon Textiles for High-Energy-Density Lithium Metal Batteries

Rechargeable secondary batteries have been widely used in various energy storage applications, ranging from small electronic devices to large-scale energy systems. The rapid expansion of the electric vehicle (EV) market, driven by global climate policies, has led to an unprecedented increase in the demand for lithium-ion batteries (LIBs), which currently dominate the secondary battery market. The rising demand for energy has intensified the need for batteries with higher energy densities. However, commercial LIBs utilize graphite anodes, which suffer from significant limitations of low theoretical capacity of 372 mAh g⁻1, necessitating a transition to alternative materials. Lithium metal is considered the ultimate anode material, due to its high theoretical capacity of 3860 mAh g⁻1, a low redox potential (−3.04 V vs. SHE), and low density of 0.53 g cm⁻3. Despite these advantages, Li metal anodes face several critical challenges, including unstable interface properties that lead to dendrite formation during Li plating and stripping. This can result in internal short circuits and thermal runaway. Furthermore, the accumulation of dead Li during cycling increases cell resistance, leading to rapid capacity degradation. To mitigate these issues, numerous strategies have been developed. These include electrolyte optimization and the introduction of artificial layers for interface engineering. Yet, due to the infinite volumetric expansion of Li during plating, focusing solely on interface modification is insufficient. Therefore, it is crucial to provide space for accommodating Li metal, which can be achieved by incorporating three-dimensional (3D) hosts. These 3D hosts, characterized by high surface area and porosity, can buffer the mechanical stress caused by volumetric changes by storing Li within their internal voids. Moreover, according to Sand’s time theory, 3D hosts can lower the local current density, thereby restricting the growth of Li dendrites. Among the various materials, carbon-based frameworks have demonstrated significant potential as Li metal hosts due to their lightweight nature, excellent mechanical strength, and superior electrical conductivity. Nevertheless, the inherent lithiophobic properties of carbon can lead to uneven Li growth, necessitating additional surface modifications. Strategies such as heteroatom doping or the introduction of lithiophilic metal seeds on carbon surfaces have been proposed to address these challenges. However, the non-uniform distribution of metal seeds and excessively strong Li adsorption can restrict surface diffusion of Li, leading to localized Li accumulation at lithiophilic sites. To ensure uniform Li growth, precise design aimed at achieving an even distribution of lithiophilic seeds is crucial. In addition, an in-depth understanding of the properties and interactions of lithiophilic seeds is essential for optimizing their placement and functionality. Furthermore, to maximize energy density, systems that eliminate the copper foil current collector and utilize only freestanding carbon substrates as host materials are gaining attention. These carbon substrates simultaneously function as the Li metal host and the current collector. Developing scalable and efficient methods to fabricate such carbon films is critical for their practical implementation. In this study, we adopted cost-effective cellulose-based commercial textiles as the foundational framework. The oxygen functional groups on the textile surface facilitated ion adsorption, thereby ensuring the uniform growth of cobalt-based metal-organic frameworks (MOFs). Subsequently, the material was carbonized through heat treatment, resulting in carbon textiles with uniformly distributed cobalt nanoparticles. The obtained Co@c-Textile provided an interconnected 3D electronically conductive network and sufficient internal space for Li storage, while also exhibiting flexible film properties. Additionally, we conducted a profound investigation into the Li deposition behavior at the Co-carbon composite interface. While cobalt does not form Li alloys like some other metals do, its interaction with the carbon matrix effectively redistributes charge density, thereby enhancing Li affinity. Li preferentially deposits on charge-enriched carbon sites adjacent to cobalt, enabling uniform growth along the fiber surface. This controlled and uniform Li plating behavior allowed the Co@c-Textile@Li composite to exhibit outstanding cycling performance in full-cell configurations paired with an LFP cathode. Figure 1