Nanostructured amorphous and anatase TiO2 are both considered as high rate Li-insertion/extraction electrode materials. To clarify which phase is more desirable for lithium ion batteries with both high power and high density, we compare the electrochemical properties of anatase and amorphous TiO2 by using anodic TiO2 nanotube arrays (ATNTAs) as electrodes. With the same morphological features, the rate capacity of nanostructured amorphous TiO2 is higher than that of nanostructured anatase TiO2 due to the higher Li-diffusion coefficient of amorphous TiO2 as proved by the electrochemical impedance spectra of an amorphous and an anatase ATNTA electrode. The electrochemical impedance spectra also prove that the electronic conductivity of amorphous TiO2 is lower than that of anatase TiO2. These results are helpful in the structural and componential design of all TiO2 mesoporous structures as anode material in lithium ion batteries. Moreover, all the advantages of the amorphous ATNTA electrode including high rate capacity, desirable cycling performance and the simplicity of its fabrication process indicate that amorphous ATNTA is potentially useful as the anode for lithium ion batteries with both high power and high energy density.

With the rapid iteration of portable electronics and electric vehicles, developing high-capacity batteries with ultra-fast charging capability has become a holy grail. Here we report rechargeable aluminum-ion batteries capable of reaching a high specific capacity of 200 mAh g−1. When liquid metal is further used to lower the energy barrier from the anode, fastest charging rate of 104 C (duration of 0.35 s to reach a full capacity) and 500% more specific capacity under high-rate conditions are achieved. Phase boundaries from the active anode are believed to encourage a high-flux charge transfer through the electric double layers. As a result, cationic layers inside the electric double layers responded with a swift change in molecular conformation, but anionic layers adopted a polymer-like configuration to facilitate the change in composition.

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