Abstract:

In previous decades, lithium-ion batteries (LIBs) were the most commonly used energy storage systems for powering portable electronic devices because LIBs exhibit reliable cyclability. However, owing to the low specific capacity of graphite used in the anode, further increase in the energy density of LIBs was limited. The Li metal anode is promising for the construction of next-generation high-energy-density batteries because of its ultrahigh theoretical capacity (3860 mAh·g^-1) and low redox potential (-3.04 V vs. standard hydrogen electrode). However, the high activity of Li causes dendritic growth during cycling, which leads to cracking of the solid-electrolyte interphase (SEI), increase in side reactions, and formation of dead Li. Several strategies have been proposed to address these issues, including use of electrolyte additives, high-concentration electrolytes, protection of the Li metal surface with various coatings, use of solid-state electrolytes, and design of a three-dimensional (3D) "Li host" for regulating the nucleation and deposition of Li metal. Among them, the design of a 3D "Li host" has proven to be a simple and effective strategy. However, the commonly used 3D "Li hosts" include nanostructured carbons, which are lithiophobic and, thus, provide limited interaction sites with Li⁺ ions, leading to the deposition of Li metal on the "Li host" surface. Therefore, it is necessary to design a 3D "Li host" with enhanced interaction with Li⁺ ions to achieve uniform deposition. Herein, we develop a soft-hard templating route to synthesize 3D macro-/mesoporous C-TiC (denoted as 3DMM C-TiC) nanocomposites, which has been used in Li metal batteries. The as-synthesized materials possess high surface areas (~510 m²·g^-1), ordered structures, large pore volumes, and excellent conductivity. The continuous plating and stripping of Li metal and the formation of the hierarchically porous structure with sufficient volume to allow uniform Li deposition result in the alleviation of the volume change. The high specific surface area significantly decreases the local current density and suppresses dendrite growth. Consequently, ultrasmall TiC nanoparticles are uniformly distributed in the 3D macro-/mesoporous framework, which improves conductivity, enhances their interaction with Li⁺ ions, and promotes the uniform deposition of Li metal. Therefore, the fabricated 3DMM C-TiC||Li battery displays stable cycling performance with improved Coulombic efficiency (98%) over 300 cycles. Moreover, when the 3DMM C-TiC based Li metal anode is assembled with a LiFePO₄ (LFP) cathode, the resultant full cells exhibit high specific capacity and excellent cycling stability. This study provides insight for the effective design of a 3D "Li host" for dendrite-free Li metal anodes.

Key words: Lithium metal anode, Macro-/mesoporous structure, TiC, Lithium dendrites