A general strategy for metal compound encapsulated into network-structured carbon as fast-charging alkali-metal ion battery anode

Evolution of fast-charging alkali-metal ion battery (AIB) is of great importance, but severely limited by the high ion/electron transport resistance in the electrode structure. Carbon-based composites have demonstrated competitive results for accelerating the related technology development. However, their efficient design, versatile synthesis and diverse structural variability remain the major challenges. Herein, we propose a general and versatile protocol for synthesizing a hierarchical network structure composed of metal compound (e.g., metal oxide, metal selenide and metal sulfide) encapsulated in carbon nanoparticle unit, and demonstrate its superiority for fast-charging anode of AIB. Key to this strategy is utilization of a rational hybrid assembly comprising of chelating resin and metal ions as building blocks. The strong coordinate-covalent bond between chelating resin and metal ions not only realizes a highly homogeneous organic/inorganic interface at the molecular level, but also confines metal ions to in-situ generate metal compound nanoparticles uniformly distributed into the carbon framework after a carbonization treatment, endowing a strong binding at the carbon/non-carbon interface structure. Benefitting from the well-organized structure, the resultant network-structured metal compound@carbon composites exhibit extraordinary fast-charging alkali-metal ion storage performance. For example, the typical network-structured Fe2O3@carbon composite anode can be fully charged within 2.2 min and discharge continuously for more than 120 min with a large charge/discharge capacity of 730 mAh g(-1) in lithium ion batteries, and is able to be fully charged within 5.6 min accompanying with a long discharge time of about 110 min and a high charge/discharge capacity of 92 mAh g(-1) in potassium ion batteries.