| 1. |
- Brant, William R., et al.
(författare)
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Local structure transformations promoting high lithium diffusion in defect perovskite type structures
- 2023
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 441
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Tidskriftsartikel (refereegranskat)abstract
- Defect perovskites, AxBO3 such as (Li3xLa2/3-x)TiO3, are attracting attention as high capacity electrodes in lithium-ion batteries. However, the mechanism enabling high lithium storage capacities has not been fully investigated. In this work, the reversible insertion and removal of lithium up to an average A-site cavity occupancy of 1.71 in the defect perovskite (Li0.18Sr0.66)(Ti0.5Nb0.5)O3 is investigated. It was shown that subtle lithium reorganization during lithiation has a significant impact on enabling high capacity. Contrary to previous studies, lithium was coordinated to triangular faces of Ti/Nb oxygen octahedra and offset from O4 windows between A-site cavities in the as-synthesised material. Upon electrochemical lithiation Li-Li repulsion redistributes of all the lithium towards the O4 window position resulting in a loss of lithium mobility. Surprisingly, the mobility is regained during over-lithiation and following multiple electrochemical cycles. It is suggested that lithium reorganisation into the center of the O4 window alleviates the Li-Li repulsion and modifies the diffusion behavior from site percolation to bond percolation. The results obtained provide valuable insight into the chemical drivers enabling higher capacities and enhanced diffusion in defect perovskites. More broadly the study delivers fundamental understanding on the non-equilibrium structural transformations occurring within electrode materials during repeated electrochemical cycles.
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| 2. |
- Saadoune, Ismael, et al.
(författare)
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Electrode Materials Based On Phosphates For Lithium Ion Batteries As An Efficient Energy Storage System
- 2015
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Ingår i: Proceedings of the TMS Middle East - Mediterranean Materials Congress on Energy and Infrastructure Systems (MEMA 2015). - Hoboken, NJ, USA : WILEY-BLACKWELL. - 9781119090427 - 9781119065272 ; , s. 343-349
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Konferensbidrag (refereegranskat)abstract
- Co0.5TiOPO4 and LiFe0.4Mn0.6PO4 phosphates present the electrochemical features of anode and cathode of lithium ion batteries, respectively. The cobalt oxyphosphate exhibits a high capacity and a working potential around 1.5 V. During the first discharge, an irreversible lithiation reaction occurs while during the subsequent cycles, a good reversibility of the charge/discharge process was obtained with a stable specific capacity approaching 280 mAh/g even at high rate. For the LiFe0.4Mn0.6PO4 olivine, the electrochemical process occurs in two steps involving separately two redox couples: Mn3+/Mn2+ and Fe3+/Fe2+. The electrochemical lithiation/delithiation occur without significant changes in the structure. Even if the obtained capacity ( 110 mAh/g), is lower that the theoretical one, the coulombic storage efficiency is rather good ( 95%).
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