First-Principles Study of Lithium Cobalt Spinel Oxides: Correlating Structure and Electrochemistry

Abstract

Embedding a lithiated cobalt oxide spinel (LiCoO, or LiCoO) component or a nickel-substituted LiCoNi O analogue in structurally integrated cathodes such as xLiMnO·(1- x)LiM'O (M' = Ni/Co/Mn) has been recently proposed as an approach to advance the performance of lithium-ion batteries. Here, we first revisit the phase stability and electrochemical performance of LiCoO synthesized at different temperatures using density functional theory calculations. Consistent with previous studies, we find that the occurrence of low- and high-temperature structures (i.e., cubic lithiated spinel LT-LiCoO; or LiCoO ( Fd3̅ m) vs trigonal-layered HT-LiCoO ( R3̅ m), respectively) can be explained by a small difference in the free energy between these two compounds. Additionally, the observed voltage profile of a Li/LiCoO cell for both cubic and trigonal phases of LiCoO, as well as the migration barrier for lithium diffusion from an octahedral (O) site to a tetrahedral site (T) in Fd3̅ m LT-LiCoO, has been calculated to help understand the complex electrochemical charge/discharge processes. A search of LiCo MO lithiated spinel (M = Ni or Mn) structures and compositions is conducted to extend the exploration of the chemical space of Li-Co-Mn-Ni-O electrode materials. We predict a new lithiated spinel material, LiNiCoO ( Fd3̅ m), with a composition close to that of commercial, layered LiNiCoAlO, which may have the potential for exploitation in structurally integrated, layered spinel cathodes for next-generation lithium-ion batteries.

Kinetic Pathways Templated by Low-Temperature Intermediates during Solid-State Synthesis of Layered Oxides

“…This conclusion is supported by previous first-principles density functional theory (DFT) calculations of relative LCO polymorph phase stability, which show that the layered LCO phase has a lower enthalpy than the spinel Li 2 Co 2 O 4 phase, 12 and additional phonon calculations revealing that layered LCO also has higher entropy than spinel Li 2 Co 2 O 4 . 13 These free-energy calculations indicate that spinel Li 2 Co 2 O 4 is metastable with respect to layered LCO at all temperatures, although it is only metastable by 8 to 20 meV/formula, which is small compared to other metastable inorganic compounds. 33 Our in situ synchrotron study reveals that the growth of spinel , the lattice parameters of the layered R3̅ m phase (being resolved from refinement) exhibit a surprisingly low c/a ratio < 4.899, as shown in Figure 3a.…”

“…8−10 Because this spinel Li 2 Co 2 O 4 phase is observed to form predominantly at LTs, it is usually referred to as LT-LCO. 11 However, first-principles investigations of LCO phase stability show that the spinel LT-LCO is actually metastable with respect to the layered phase at all temperatures, 12,13 prompting questions about the mechanistic origin of its formation. In LNO and LiNi 1−x M x O 2 , a metastable disordered layered compound with Li/Ni mixing can arise.…”

Controlling the Electrochemical Properties of Spinel Intercalation Compounds

“…An experimental voltage curve of Li x TiS 2 /Li coin cell measured by Bonnick et al is shown on (a) . The value of the voltage plateau representing the x > 0.5 region of an experimental voltage curve of Li x CoO 2 /Li coin cell measured by Kim et al is shown in (b) . An experimental voltage curve of Mg x TiS 2 /Mg coin cell measured by Sun et al is shown in (e).…”

Lithium Iron Aluminum Nickelate, LiNixFeyAlzO2—New Sustainable Cathodes for Next‐Generation Cobalt‐Free Li‐Ion Batteries

“…[ 1–8 ] Significant research efforts over the past decade have been aimed at improving the cathode materials in these systems to generate safe, low‐cost positive electrodes with high capacities. [ 9–20 ] Starting from the first commercialized cathode material—lithium cobalt oxides (LiCoO 2 ) [ 21,22 ] —to the present‐day workhorses—lithium cobalt manganese nickelates (NCM) and lithium cobalt aluminum (NCA) nickelates [ 23–26 ] —most research and development have centered around cobalt‐containing materials. A recent report from the Cobalt Development Institute indicates that 58% of global cobalt production is already used in many diverse industrial and defense applications such as super alloys, catalysts, magnets, and pigments.…”