Structural evolution of electrodes in the NCR and CGR cathode-containing commercial lithium-ion batteries cycled between
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Moshiul Alam Australian Nuclear Science and Technology Organisation, Kirrawee DC, New South Wales 2232, Australia; and School of Chemistry, UNSW Australia, Sydney, New South Wales 2052, Australia
Vanessa K. Petersonb),c) Australian Nuclear Science and Technology Organisation, Kirrawee DC, New South Wales 2232, Australia
Neeraj Sharma School of Chemistry, UNSW Australia, Sydney, New South Wales 2052, Australia (Received 31 July 2014; accepted 17 September 2014)
The dissimilar lattice-evolution of the isostructural layered Li(Ni,Co,Al)O2 (NCR) and Li(Ni,Co, Mn)O2 (CGR) cathodes in commercial lithium-ion batteries during overcharging/discharging was examined using operando neutron powder-diffraction. The stacking axis (c parameter) of both cathodes expands on initial lithiation and contracts on further lithiation. Although both the initial increase and later decrease are smaller for the CGR cathode, the overall change between battery charged and discharged states of the c parameter is larger for the CGR (1.29%) than for the NCR cathode (0.33%). We find these differences are correlated to the transition metal to oxygen bond (as measured through the oxygen positional-parameter) which is specific to the different cathode chemistries. Finally, we note the formation of and suggest a model for a LiCx intermediate between graphite and LiC12 in the anode of both batteries.
I. INTRODUCTION
Lithium-ion batteries (LIBs) have higher energy-densities, a portative design, and longer lifetimes than other battery technologies. Although LIBs meet the majority of the demands for existing smaller-scale applications (e.g., laptop computers and mobile phones), emerging larger-scale applications, such as electric vehicles and grid-scale energy storage, require improvements in safety, cost, energy density, and current performance.1,2 The first commercialized LIB by SONY Corp. in 1991 consisted of a layered LiCoO2 cathode with a graphite anode.3 Recently new cathode-chemistries have been developed and commercialized both for specialist applications such as electric vehicles and to replace the more widespread use of LiCoO2 cathodes. Such examples include LiFePO4,4 LiMn2O4,5 and the mixed transition-metal Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] c) This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www. mrs.org/jmr-editor-manuscripts/. DOI: 10.1557/jmr.2014.297 J. Mater. Res., Vol. 30, No. 3, Feb 14, 2015
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Li(Ni1/3Mn1/3Co1/3)O2 with varying Li:Ni:Co:Mn ratio, and Al-doped Li(NiCo)O2,6 with the latter two isostructural to LiCoO2.7 The cathode plays an essential role in the performance of a LIB and is often the limiting factor in the battery’s performance. The theoretical capacity of a cathode is limited by the composition, with LiMO2 (M 5 transition metal) ;270–280 mAh g1, LiFePO
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