Authors: Anton Buzlukov Guillaume Gerbaud Carole Bourbon Sabine Hediger Gaël De Paëpe Sébastien Patoux Michel Bardet
Publish Date: 2013/02/01
Volume: 17, Issue: 5, Pages: 1421-1427
Abstract
Different synthesis batches of LiFePO4/C materials were prepared and their electrochemical properties as positive cathodes for lithiumion batteries were evaluated Using standard solidstate NMR conditions such as a 7mm magicanglespinning probe performing at low spinning rates information on both intercalated and nonintercalated stored on the grain boundaries lithium was obtained A sharp signal assigned to nonintercalated lithium could be observed by diluting the active material in silica Correlations could be thus obtained between the amount of each type of lithium and the electrochemical history and state of the material revealing that the relative amount of surface lithium in a pristine LiFePO4/C material is rather constant and cannot be used as a criterion for its further specification However a drastic increase of this surface lithium was observed in the cathode materials of outoforder batteries As the cathode material recovered from the batteries after electrochemical testing was carefully washed before analysis we can conclude that the nonintercalated lithium is strongly bound to the active material probably inside the socalled solid electrolyte interface layer at the surfaces of LiFePO4 particles This work illustrates that solidstate lithium NMR can allow rapid characterization and testing of LiFePO4/C cathode materials
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