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Mechanism of Na‐Ion Storage in Hard Carbon Anodes Revealed by Heteroatom Doping
Author(s) -
Li Zhifei,
Bommier Clement,
Chong Zhi Sen,
Jian Zelang,
Surta Todd Wesley,
Wang Xingfeng,
Xing Zhenyu,
Neuefeind Joerg C.,
Stickle William F.,
Dolgos Michelle,
Greaney P. Alex,
Ji Xiulei
Publication year - 2017
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201602894
Subject(s) - materials science , anode , heteroatom , graphene , carbon fibers , doping , intercalation (chemistry) , nanotechnology , ion , chemical physics , chemical engineering , inorganic chemistry , composite material , optoelectronics , electrode , ring (chemistry) , composite number , chemistry , organic chemistry , engineering
Hard carbon is the leading candidate anode for commercialization of Na‐ion batteries. Hard carbon has a unique local atomic structure, which is composed of nanodomains of layered rumpled sheets that have short‐range local order resembling graphene within each layer, but complete disorder along the c ‐axis between layers. A primary challenge holding back the development of Na‐ion batteries is that a complete understanding of the structure–capacity correlations of Na‐ion storage in hard carbon has remained elusive. This article presents two key discoveries: first, the characteristics of hard carbons structure can be modified systematically by heteroatom doping, and second, that these structural changes greatly affect Na‐ion storage properties, which reveals the mechanisms for Na storage in hard carbon. Specifically, via P or S doping, the interlayer spacing is dilated, which extends the low‐voltage plateau capacity, while increasing the defect concentrations with P or B doping leads to higher sloping sodiation capacity. The combined experimental studies and first principles calculations reveal that it is the Na‐ion‐defect binding that corresponds to the sloping capacity, while the Na intercalation between graphenic layers causes the low‐potential plateau capacity. The understanding suggests a new design principle of hard carbon anode: more reversibly binding defects and dilated turbostratic domains, given that the specific surface area is maintained low.