Mitigating Mechanical Stress by the Hierarchical Crystalline Domain for High-Energy P2/O3 Biphasic Cathode Materials
Xu Zhu, Haojie Dong, Yi‐Feng Liu, Yi‐Hu Feng, Yongwei Tang, Lianzheng Yu, Shaowen Xu, Guang‐Xu Wei, Shuai Sun, Mengting Liu, Bing Xiao, Rong Xu, Yao Xiao, Shulei Chou, Pengfei Wang
Abstract
Sodium-ion batteries (SIBs) have captured widespread attention for grid-scale energy storage owing to the wide distribution and low cost of sodium resources. Delivery of high energy density with stable retention remains a challenge in developing cathode candidates for rechargeable SIBs. Inspired by the concept of “cationic potential”, here, we present a hierarchical crystalline domain in hexagonal particles with target chemical composition (Na 0.8 Li 0.03 Mg 0.05 Ni 0.28 Fe 0.05 Mn 0.54 Ti 0.05 O 2 ) from the inner bulk O3 phase (71.1 wt %) to the outer P2-type shell (28.9 wt %) of the structure. Benefiting from the mitigated mechanical stress of the predominant bulk O3 phase under the protection of the surficial P2 crystalline domain at the microscale during Na + (de)intercalation, the brittle fracture, plastic yielding, and structural damage of the bulk O3 phase are effectively prohibited during battery cycling, thereby achieving good structural integrity. As a consequence, the biphasic P2/O3–Na 0.8 Li 0.03 Mg 0.05 Ni 0.28 Fe 0.05 Mn 0.54 Ti 0.05 O 2 material exhibits satisfactory electrochemical properties, with a high energy density of 506 Wh kg –1 and good capacity retention of 85.5% over 200 cycles. This work highlights the importance of tailoring the crystalline domain to mitigate the reaction-induced stress and particle fracture of layered biphasic cathode materials for high-energy SIBs.