Mesocrystallizing Nanograins for Enhanced Li+ Storage

The morphology and crystallinity of electrode materials have a major effect on their charge carrier storage properties when applied in rechargeable batteries. While nanosizing electrode particles (with larger surface area) and maintaining electrode integrity are both good for performance enhancement, they seem to contradict each other and are challenging to balanced. Herein, electrode particles consisting of numerous nanograins with uniform crystalline orientation are designed to guarantee both high surface area and high structural integrity, allowing the significant improvement of Li+ storage kinetics and performance. Applying this “mesocrystallizing” strategy to an NiCo2O4‐based anode, results in various degrees of pseudocapacitance response, the long‐term cyclability and rate performance of this material are also significantly enhanced. Impressively, the mesocrystalline NiCo2O4 electrode exhibits a high specific capacity of 1403 mAh g–1 after 200 cycles at 1.6 A g–1 (a rate of 1.8 C). The growth mechanism of mesocrystalline materials with different morphologies is identified to be a topotactic structural transition process featuring a gradual edge‐to‐core corrosion process. This work presents an important synthetic clue to balance the morphology and crystallinity of battery electrode materials for their performance optimization and is expected to inspire future structural design for battery materials beyond the one prototyped here. Mesocrystalline NiCo2O4 nanorods with high structural integrity are obtained and applied in lithium ion storage. One mesocrystalline NiCo2O4 nanorod is composed of numerous nanograins with a uniform crystalline orientation. These nanograins, although presenting grain‐to‐grain boundaries, are aligned along the same crystalline orientation.