细菌纤维素衍生的三维碳集流体用于无枝晶的锂金属负极

锂金属是下一代高能量密度电池的关键负极,然而其实用化面临着一系列问题,主要包括循环过程中体积变化大、枝晶生长等。使用三维集流体是解决这些问题的有效方法,然而现有大多数三维集流体存在重量大、体积大、表面亲锂性差、成本高等问题。针对上述问题,本文以低成本的细菌纤维素为前驱体,通过直接碳化制备出具有连通网络的轻质三维碳集流体,其表面均匀分布的含氧官能团可以促进锂离子的均匀成核和沉积,有效抑制了枝晶生长。值得注意的是,该集流体的面密度仅为0.32 mg·cm^?2,在3 mAh·cm^?2比容量的锂金属负极中质量占比仅为28.8%。电化学测试结果表明,该集流体在3 mA·cm^?2的高电流密度或4 mAh·cm^?2的高循环容量的工作条件下,稳定循环超过150次,并且在对称电池或与LiNi0.8Co0.15Al0.05匹配的全电池中也表现出良好的电化学性能。

Bacterial Cellulose-Derived Three-Dimensional Carbon Current Collectors for Dendrite-Free Lithium Metal Anodes

Lithium (Li) metal anodes are critical components for next-generation high-energy density batteries, owing to their high theoretical specific capacity (3800 mAh·g^-1) and low voltage (-3.040 V versus the standard hydrogen electrode). However, their applications are hindered by dendrite growth, which potentially induces inner short circuit and leads to safety issues. Employing three-dimensional (3D) current collectors is an effective strategy to suppress dendrite growth by decreasing the local current density. However, many of the reported 3D current collectors have a lithiophobic surface, which leads to non-uniform Li⁺ ion deposition. Thus, a complicated modification process is required to increase the lithiophilic property of the current collectors. In addition, they have a large weight or volume, which greatly lowers the energy density of the entire anode. In this work, we report a lightweight 3D carbon current collector with a lithiophilic surface by employing the direct carbonization of low-cost bacterial cellulose (BC) biomass. The current collector is composed of electrically conductive, robust, and interconnected carbon nanofiber networks, which provide sufficient void space to accommodate a large amount of Li and buffer the volume changes during Li plating and stripping. More importantly, homogeneously distributed oxygen-containing functional groups on the nanofiber surface are retained by controlling the carbonization temperature. These functional groups serve as uniform nucleation sites and help realize uniform and dendrite-free Li deposition. Notably, the areal mass density of the 3D carbon current collector was only 0.32 mg·cm^-2 and its mass ratio in the whole anode was 28.8%, with a capacity of 3 mAh·cm^-2. This 3D carbon current collector facilitates the stable working of the half cells for 150 cycles under a high current density of 3 mA·cm^-2 or a high capacity of 4 mAh·cm^-2. Symmetric cells exhibit a steady cycling life as long as 600 h under a current density of 1 mA·cm^-2 and a capacity of 1 mAh·cm^-2. Moreover, appreciable cycling performance was realized in the full cells when the anodes were paired with LiNi_0.8Co_0.15Al_0.05 cathodes. Furthermore, the low-cost raw materials and the simple preparation method promise significant potential for the future applications of the proposed 3D current collectors.