Diagnostic analysis of electrodes from high-power lithium-ion cells cycled under different conditions

摘要: , were cycled over different ranges of depth discharge~DOD! and at temperatures. A combination electrochemical, physical, chemical diagnostic evaluations, includingRaman, nuclear magnetic resonance ~NMR!, Fourier transform infrared ~FTIR! spectroscopy, transmission electron micros-copy ~TEM!, energy-dispersive X-ray, X-ray diffraction~XRD!, carried out on the components removed from cellsto form a clear picture mechanism for capacity power fade in this important cell chemistry. Both andimpedance rise found to increase with cycling temperature span DOD. The loss cycleable Li, most likely dueto solvent reduction anode, was linear test time, room-temperature cells showed solid electrolyte interfacecomposition degree graphite disorder that roughly correlated extent Li consumption. However, electrochemicalanalysis cathode controlling performance cell. TEM NMR evidence crystallinedefects degradation Li-Ni environment, respectively, though no major new phases identified, agreement theXRD results. FTIR analysis revealed polymeric deposits particles, although bothRaman P-containing deposits. Raman mapping noticeable change active material/carbon surface concentration ratio 1000 times 100% DOD as compared 70% DOD.© 2004 Electrochemical Society. @DOI: 10.1149/1.1710514# All rights reserved.Manuscript submitted June 23, 2003; revised manuscript received November 15, 2003. Available electronically May 4, 2004.