Shi Ji-Lei, Sheng Hang, Meng Xin-Hai, Zhang Xu-Dong, Lei Dan, Sun Xiaorui, Pan Hongyi, Wang Junyang, Yu Xiqian, Wang Chunsheng, Li Yangxing, Guo Yu-Guo
CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing100190, China.
University of Chinese Academy of Sciences, Beijing100049, China.
Natl Sci Rev. 2022 Oct 19;10(2):nwac226. doi: 10.1093/nsr/nwac226. eCollection 2023 Feb.
A single-crystalline Ni-rich (SCNR) cathode with a large particle size can achieve higher energy density, and is safer, than polycrystalline counterparts. However, synthesizing large SCNR cathodes (>5 μm) without compromising electrochemical performance is very challenging due to the incompatibility between Ni-rich cathodes and high temperature calcination. Herein, we introduce Vegard's Slope as a guide for rationally selecting sintering aids, and we successfully synthesize size-controlled SCNR cathodes, the largest of which can be up to 10 μm. Comprehensive theoretical calculation and experimental characterization show that sintering aids continuously migrate to the particle surface, suppress sublattice oxygen release and reduce the surface energy of the typically exposed facets, which promotes grain boundary migration and elevates calcination critical temperature. The dense SCNR cathodes, fabricated by packing of different-sized SCNR cathode particles, achieve a highest electrode press density of 3.9 g cm and a highest volumetric energy density of 3000 Wh L. The pouch cell demonstrates a high energy density of 303 Wh kg, 730 Wh L and 76% capacity retention after 1200 cycles. SCNR cathodes with an optimized particle size distribution can meet the requirements for both electric vehicles and portable devices. Furthermore, the principle for controlling the growth of SCNR particles can be widely applied when synthesizing other materials for Li-ion, Na-ion and K-ion batteries.
与多晶正极相比，具有大粒径的单晶富镍（SCNR）正极可实现更高的能量密度，且更安全。然而，由于富镍正极与高温煅烧不相容，在不影响电化学性能的情况下合成大尺寸（>5μm）的SCNR正极极具挑战性。在此，我们引入维加德斜率作为合理选择烧结助剂的指导，成功合成了尺寸可控的SCNR正极，其中最大尺寸可达10μm。综合理论计算和实验表征表明，烧结助剂不断迁移至颗粒表面，抑制亚晶格氧释放，并降低典型暴露晶面的表面能，从而促进晶界迁移并提高煅烧临界温度。通过填充不同尺寸的SCNR正极颗粒制备的致密SCNR正极，实现了最高电极压实密度3.9 g/cm³和最高体积能量密度3000 Wh/L。软包电池展现出303 Wh/kg的高能量密度、730 Wh/L以及1200次循环后76%的容量保持率。具有优化粒径分布的SCNR正极能够满足电动汽车和便携式设备的要求。此外，控制SCNR颗粒生长的原理在合成锂离子、钠离子和钾离子电池的其他材料时可广泛应用。
