Accelerating Ion Dynamics Under Cryogenic Conditions by the Amorphization of Crystalline Cathodes.

ABSTRACT

The normal operation of lithium-ion batteries (LIBs) at ultralow temperature (<-40 °C) is significant for cold-climate applications; however, their operation is plagued by the low capacity of the conventional intercalation cathodes due to their sluggish kinetics and the slow solid diffusion of Li+ in their frameworks. Here, it is demonstrated that amorphization is an effective strategy to promote the low-temperature dynamics of cathodes by relieving the blocking effect of a dense lattice structure on ion transport under cryogenic conditions. As a result, due to the decreased charge transport impedance and enhanced Li+ diffusion rate, the obtained covalent amorphous polymer (CAP) with an abundance of pyrazine and carbonyl active sites displays a remarkably outstanding specific capacity of 141 mAh g-1 at -80 °C, which is superior to its structural analog, a covalent crystalline polymer (43.8 mAh g-1 ). Furthermore, 84.7% of the initial capacity of the CAP can be retained after 500 cycles of charge and discharge at -60 °C. Molecular dynamic simulations show that the channel-rich amorphous structure is highly conducive for lithium ions to diffuse quickly in the interstitial space of organic solids. This work provides an effective strategy regarding the amorphization of crystalline cathodes to develop low-temperature (Low-T) batteries.