Constructing unique dual-functional double-hollow architecture for enhanced high-voltage structural stability of layered oxide cathode

Elevating the working voltage has proven to be an effective strategy for enhancing the energy density of ternary layered cathode materials. However, the accelerated failure of secondary particle structure during high-voltage cycling hinders their practical application. Although some attempts have been exerted to address this issue by designing particle arrangement, these secondary structure modifications only provide the limited help to the structural failure problem. Herein, we focus on the cause and characteristic of secondary particle cracks, investigate their formation principle and development rule, and delicately propose a unique double-hollow secondary structure. The two hollow regions create an environment that facilitates the release of internal strain and reduces stress at grain boundaries, thus ensuring the homogeneous stress distribution within the secondary particles. Thereby, the formation of intergranular crack is effectively mitigated. Additionally, the hollow regions act as barrier layers to impede the crack propagation. The dual functions of this double-hollow structure efficiently maintain the tight connection among these primary particles, greatly boosting the high-voltage cycling stability. The designed material with double-hollow architecture exhibits an obvious capacity retention increase from 67.8% (conventional structure) to 84.4% at 1 C within 3.0-4.5 V after 300 cycles. This work demonstrates that the double-hollow structure can effectively address the key issues of crack occurrence and development, providing a novel structural design concept for the exploration of high-voltage cathode materials with superior stability.