The Application of Self-Assembled Hierarchical Structures in Lithium-Ion Batteries

Lithium ion batteries, which are secondary battery with the high specific energy, play an increasingly important role in the field of sustainable energy. In order to explore the next generation of lithium ion batteries with higher specific energy density, many electrode materials with high specific capacity are being researched and developed. However, these materials usually display the large volume change during lithiation and delithiation process. Therefore, it is necessary to prepare nanostructures to achieve better electrochemical performance. However, the nanostructure leads to low Coulombic efficiency, poor cycling stability and relatively low specific energy density, which can be ascribed to its high specific surface area and low tap density. The assembly of nanomaterials into a hierarchical structure can effectively reduce the overall specific surface area, and limit the consumption of lithium during the formation of solid state interphase (SEI) film, leading to the increase of the initial Coulombic efficiency. Compared with the disordered build-up of nanoparticles, the hierarchical structure has a higher accumulation density and contact area, thus leading to the decrease of porosity and the increase of build-up density of the electrode materials. Therefore, the hierarchical structure of electrode materials can further increased the specific energy density of lithium ion batteries. In this review, we mainly focus on the preparation of hierarchical structure in lithium ion batteries and its application in lithium ion batteries. In terms of preparation, solvothermal method, emulsion method, spray drying method and template method are mainly described as well as effect of various parameters on the final hierarchical structure. In terms of application, different hierarchical structures are reviewed with the purpose of improving performances of lithium ion batteries as the mainline.