Origin and Suppression of Intragranular Cracks for Long‐Cycling High‐Ni Co‐Free Cathodes

Antiphase boundaries (APBs) are found to be widely distributed in high-Ni Co-free (NM) cathodes, and the relation between APBs gain boundaries and intragranular cracks has been established for the first time. Additionally, a charge self-balancing doping strategy is proposed to reduce the formation of APBs and optimize the generation/distribution of internal stresses, thereby suppressing intragranular cracks.

Abstract

Intragranular cracks have been identified as a direct reflection of failure in high-energy-density cathodes, especially for high-Ni Co-free cathodes with severe electrochemical–mechanical degradation. Here we show that antiphase boundaries (APBs) are prone to form in high-Ni Co-free cathodes and demonstrate their crucial role in determining the formation of intragranular cracks. The results show that the APBs grain boundaries are continuously expand during the electrochemical process, and their presence promotes the formation and accumulation of heterogeneous internal stresses within the layered structure, which in turn facilitates the nucleation and expansion of intragranular cracks. We further show that an elaborate charge self-balancing doping strategy can inhibit APBs, which not only maintains the electronic equilibrium of the oxygen framework, but also the synergistic effect of double-site modification can exhibit a “lattice-locking” effect, leading to an ordered layered structure. The present work suppresses intragranular cracks by eliminating APBs grain boundaries, and this understanding provides insights for developing long-cycling high-Ni Co-free cathodes.

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