Series of LiNi 0.5 Mn 1.5-x Zr x O 4 (x = 0, 0.0025, 0.005, 0.01, 0.02) samples have been prepared by a combined coprecipitationhydrothermal method followed by two-step calcination. The effects of Zr 4 + doping contents on the structure, morphology and electrochemical properties are studied. The results show that Zr 4 + doping reduces Mn 3 + content and Ni/Mn disordering degree. Additionally, Zr 4 + doping reduces primary particle size and agglomeration degree. More significantly, Zr 4 + doping leads to the appearance of higher-surface-energy {110} and/or {311} facets, while undoped sample only consists of {111} and {100} facets. But excessive Zr 4 + doping (x = 0.02) leads to the decrease of higher-surface-energy facets. Electrochemical results show that appropriate Zr 4 + doping improves the rate and cycling performances of LiNi 0.5 Mn 1.5 O 4 material. Among them, LiNi 0.5 Mn 1.495 Zr 0.005 O 4 shows the optimal electrochemical performance, which can be attributed to high phase purity, high crystallinity, appropriate primary particle size and agglomeration degree, enlarged lattice constant, and greater exposure of {110} and/or {311} facets.
An Fe3+/PO4
3– codoped LiNi0.5Mn1.4667Fe0.02P0.0133O4 sample has been prepared by a coprecipitation–hydrothermal
method followed by two-step calcination. A novel wet chemical route,
using FeSO4 rather than Fe2(SO4)3 as the Fe3+ source and NaH2PO4 as the PO4
3– source, is adopted to
obtain uniform codoping of Fe3+ and PO4
3– ions in a carbonate precursor according to the precipitation–dissolution–transformation
mechanism. For comparison, Fe3+-doped and PO4
3–-doped samples have been also synthesized via
the same route. The effects of Fe3+/PO4
3– codoping and single doping on the crystalline structure,
morphology, and electrochemical performance of LiNi0.5Mn1.5O4 are investigated. Compared with pristine and
single doped samples, the codoped sample shows better electrochemical
performance, with a specific discharge capacity of 125.2 mAh g–1 at 10 C and a capacity retention rate of 85.9% after
200 cycles at 1 C, under the synergy of Fe3+/PO4
3– codoping, including enhanced crystallinity,
decreased Mn3+ content, significantly reduced primary particle
size and secondary agglomeration, as well as the appearance of (110)
surfaces in truncated octahedral primary particles.
In order to alleviate the rapid capacity decay caused by the instability of the crystal structure and electrode/electrolyte interface, a series of Li 2 SiO 3 -coated LiNi 0.5 Mn 1.5 O 4 materials have been prepared via the lithium acetate-assisted sol−gel method followed by a short-term calcination process. During the sol−gel process, TEOS is hydrolyzed, condensed, and polymerized with the assistance of lithium acetate to form a Li + -embedded [Si−O−Si] n network structure to ensure the uniformity of the coating. By changing the amount of TEOS and lithium acetate, the coating thickness can be precisely controlled, whose effects on the structural and electrochemical properties of LiNi 0.5 Mn 1.5 O 4 materials are intensively investigated. The results show that the material with an appropriate thickness of Li 2 SiO 3 coating exhibits a larger primary particle size and reduced secondary particle agglomeration. The uniform Li 2 SiO 3 coating with appropriate thickness can not only improve Li + ion diffusion kinetics but also suppress side reactions and CEI growth at the electrode/electrolyte interface. Besides, the interaction of Li 2 SiO 3 with HF can alleviate electrode corrosion and the dissolution of transition metal ions. All the abovementioned factors together promote the significant improvement of the electrochemical performance of Li 2 SiO 3 -coated LiNi 0.5 Mn 1.5 O 4 materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.