Mitigating Twin Boundary-Induced Cracking for Enhanced Cycling Stability of Layered Cathodes

Twin boundaries (TBs) as a common defect in layered cathodes play multiple roles in affecting materials' performance, which requires a deep understanding and an effective regulation method to realize rational design of superior layered cathodes. Herein, by virtue of advanced electron microscopy, we demonstrate that TBs can be quantitatively estimated and characterized, and we further validate that TBs can initiate massive cracks upon electrochemical cycling, which aggravates the performance decay of LiNiO2. Adjusting the synthesis conditions cannot avoid TB formation for the solid-state method, but fortunately, we find that a coprecipitation method can effectively eliminate TBs; thus, the improved cycling stability of LiNiO2 is achieved. We further validate that TB-free LiCoO2 can also be synthesized by the coprecipitation method, which demonstrates improved cycling stability.