Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries

• Published in: Nature energy Vol. 1; no. 1; p. 15004
• Main Authors: Lin, Feng, Nordlund, Dennis, Li, Yuyi, Quan, Matthew K., Cheng, Lei, Weng, Tsu-Chien, Liu, Yijin, Xin, Huolin L., Doeff, Marca M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.01.2016; Nature Publishing Group
• Subjects: 639/301/299/891; 639/638/298; 639/638/542; Absorption spectroscopy; batteries; Cathodes; Center for Functional Nanomaterials; Cycles; Economics and Management; Electrode materials; Energy; Energy Policy; Energy Storage; Energy Systems; High voltages; Lithium; Lithium batteries; Lithium-ion batteries; materials chemistry; MATERIALS SCIENCE; Pyrolysis; Rechargeable batteries; Reconstruction; Renewable and Green Energy; Soft x rays; Spray pyrolysis; Surface chemistry; Transmission electron microscopy; Voltage; X ray absorption; X-ray absorption spectroscopy
• ISSN: 2058-7546; 2058-7546
• DOI: 10.1038/nenergy.2015.4

In technologically important LiNi 1− x − y Mn x Co y O 2 cathode materials, surface reconstruction from a layered to a rock-salt structure is commonly observed under a variety of operating conditions, particularly in Ni-rich compositions. This phenomenon contributes to poor high-voltage cycling performance, impeding attempts to improve the energy density by widening the potential window at which these electrodes operate. Here, using advanced nano-tomography and transmission electron microscopy techniques, we show that hierarchically structured LiNi 0.4 Mn 0.4 Co 0.2 O 2 spherical particles, made by a simple spray pyrolysis method, exhibit local elemental segregation such that surfaces are Ni-poor and Mn-rich. The tailored surfaces result in superior resistance to surface reconstruction compared with those of conventional LiNi 0.4 Mn 0.4 Co 0.2 O 2 , as shown by soft X-ray absorption spectroscopy experiments. The improved high-voltage cycling behaviour exhibited by cells containing these cathodes demonstrates the importance of controlling LiNi 1− x − y Mn x Co y O 2 surface chemistry for successful development of high-energy lithium ion batteries. Advanced batteries require careful control over the interfacial properties of their constituent materials. This study designs hierarchically structured cathode materials that are resistant to surface reconstruction, leading to improved cycling performance.