With the increasing demand for efficient and economic energy storage, advanced rechargeable batteries with high-energy and high-power densities have attracted more and more attention [1].  Nanostructured materials are currently of interest as high performance anodes and cathodes for rechargeable batteries because of their novel size effects and significantly enhanced kinetics, which address much enhanced capacities, high rate performance, capacity retention abilities, and new electrochemical energy storage mechanisms found in nano-systems. However, their practical applications suffer from the problems of low thermodynamic stability and high surface reactions due to their high specific surface area and high surface energy. Electrode materials with nano/micro hierarchical structures are the best systems of choice because they can take both the advantages of nanometer-sized building blocks and micro- or submicrometer-sized assemblies. While the former provides negligible diffusion times and possible new energy storage mechanisms and hence is the key to the favorable kinetics and high capacities, the latter guarantees good stability and easy of fabrication. This contribution highlights some recent developments in this field mainly by using work of the author for illustration, especially focus on nanometer size effects of electrode materials for Li-ion batteries and post systems, including the following aspects:

(i)  Li-ion batteries: nanostructured anode and cathode materials [2-6];

(ii) Metallic Li secondary batteries: nanocomposite cathode materials for Li-S and Li-Se batteries [7-9];

(iii) Na-ion batteries and room-temperature Na-S batteries: cathode, anode and electrochemistry [10-12];

(iv) Mg-ion batteries: a highly reversible, low strain Mg-ion insertion anode material for rechargeable Mg-ion batteries and its nanosize effects [13,14].