Structural and property investigations into low-doped lithium nitridometallates Li3-x-yMxN, x = Co, Ni and Cu

Carmichael, Donald Kenneth (2011) Structural and property investigations into low-doped lithium nitridometallates Li3-x-yMxN, x = Co, Ni and Cu. PhD thesis, University of Glasgow.

Abstract

Bulk samples of the lithium nitridometallates of the general form Li3-xMxN and Li3-x-yMxN, where M = Co, Ni and Cu, x ≤ 0.1 and y = vacancy, have been synthesised. The products of the syntheses have been characterised by Powder X-ray Diffraction (PND), Constant Wavelength Powder Neutron Diffraction (CW PND), Time of Flight Powder Neutron Diffraction (ToF PND), SEM and SQUID magnetometry. The transition metal entirely substituted for the Li(1) at the interplanar site and resulted in a retention of the Li3N-type structure, P6/mmm. These materials displayed similar structural trends as seen in lithium nitridometallates with higher transition metal levels, and with vacancies, which were also dependent on reaction time and temperature at this low level. For longer reacted lithium nitridometallates a large concentration of vacancies was obtained despite a small quantity of dopant transition metal. The resultant charge was deemed too high to be solely balanced by the transition metal, as is usual in these materials. A charge compensation mechanism involving the nitrogen ion was assumed for the high-vacancy materials.
The materials displayed some interesting forms of magnetism such as spin-glass magnetic behaviour and also Pauli paramagnetism. Li2.95Ni0.05N and Li2.90Co0.1N displayed a high specific capacity upon electrochemical testing when applied as a potential anode material, and gave better charge capacities than that of the previous best lithium anode material and showed signs of improvement upon cycling.
Preliminary investigations into hydrogen adsorption of the materials had been attempted, with one particular material, Li2.95Ni0.05N, giving a hydrogen adsorption of 7.839 wt % over 90 hours with a hydrogen pressure of 20 bar and temperature of 250 oC. A corresponding 3.5 wt % loss was achieved upon desorption at the same temperature.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Lithium nitride, Anode material, Electrochemistry, Hydrogen Storage, Cycle life, Charge capacity
• Subjects: Q Science > QD Chemistry; Q Science > Q Science (General)
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Gregory, Prof. Duncan H.
• Date of Award: 2011
• Depositing User: Dr Donald Carmichael
• Unique ID: glathesis:2011-2909
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 04 Nov 2011
• Last Modified: 10 Dec 2012 14:01
• URI: https://theses.gla.ac.uk/id/eprint/2909