Enthalpy of formation and heat capacity of Li₂MnO₃

Abstract

The enthalpy of formation of Li 2 MnO 3 was measured by high temperature oxide solution calorimetry in a sodium molybdate solvent and the heat capacity of the compound was determined using differential scanning calorimetry. The enthalpy of formation of Li 2 MnO 3 from the elements is slightly less exothermic than that of the orthorhombic and monoclinic modifications of LiMnO 2 but more exothermic than that of LiNiO 2 , LiCoO 2 , the LiNi 1¹x Co x O 2 solid solutions and the Li 1+x Mn 2¹x O 4 spinels. The heat capacity of Li 2 MnO 3 is also slightly lower than the estimated heat capacity based on stoichiometric amounts of Li 2 O and MnO 2 according to the Neumann-Kopp approximation. The slight differences in heat capacities are attributed to the differences in the bonding environments of Li + ions in Li 2 MnO 3 and the constituent binary oxide Li 2 O. The thermochemical data presented here are essential for the advanced thermodynamic modeling of multicomponent electrode materials based on the promising xLi 2 MnO 3 ·(1 ¹ x)LiMO 2 nano-composite cathode system.

Doping Li-rich cathode material Li2MnO3 : Interplay between lattice site preference, electronic structure, and delithiation mechanism

“…where ∆H f is the formation enthalpy (previously calculated to be −12.30 eV per formula unit, 6 in good agreement with the experimental value 12.78 ± 0.05 eV 34 reported more recently). More realistic µ i values, however, can be identified by taking into account actual experimental conditions.…”

Analysis of the Phase Stability of LiMO2 Layered Oxides (M = Co, Mn, Ni)

“…The resulting values for the energy changes of reactions E3-E6 are reported in Table 3 for all the polymorphs of the LCO, LMO and LNO compounds. The ∆E values reported in the Table 4 can be easily combined with literature thermochemical data [54][55][56][57][58][59][60][61] reported in the Supplementary Material (Table S2) to derive the formation energy from elements (Table S3). To derive the formation thermodynamics at room temperature, thermal effects and formation entropies at 298 K are necessary.…”

“…Similarly, thermal effects at 298 K have been estimated by adopting the Kellogg and Kubaschewski semiempirical model [63]. Because the semiempirical models were unsensitive towards the crystal structure, we adopted identical thermal effects and absolute entropies (Table S4) to derive formation enthalpies and free energies at 298 K for all polymorphs of a given composition (see Table 4; Table 5 The assessed values reported in the literature of the experimental Gibbs energy of formation for the LCO, LNO and LMO phases in the hR12, mC8, oP8 lattices, respectively, are −632 ± 8, −532 ± 8 and 782 ± 8 [13,54,62,[65][66][67] and our computational determinations are in good agreement in all the three cases, with the largest difference between computational and experimental determination below 6%. On passing, one may comment that possible sources of inaccuracies in our computational estimates are (a) the thermodynamic supplementary data, largely estimated, and (b) the adopted DFT + U computational approach where a mean U value is adopted for all metals.…”

High-Throughput Description of Infinite Composition–Structure–Property–Performance Relationships of Lithium–Manganese Oxide Spinel Cathodes

“…Since there are experimental data on heat capacity of Li 2 MnO 3 in a wide temperature range, the Gibbs energy of Li 2 MnO 3 is expressed as where A and B in eqs and are the parameters to be evaluated; the coefficients C , D , and E are taken from the expression of heat capacity for solid Li 2 MnO 3 …”