Synthesis Method and Thermodynamic Characteristics of Anode Material Li₃FeN₂ for Application in Lithium-Ion Batteries

Li₃FeN₂ material was synthesized by the two-step solid-state method from Li₃N (adiabatic camera) and FeN₂ (tube furnace) powders. Phase investigation of Li₃N, FeN₂, and Li₃FeN₂ was carried out. The discharge capacity of Li₃FeN₂ is 343 mAh g^-1, which is about 44.7% of the theoretic capacity. The ternary nitride Li₃FeN₂ molar heat capacity is calculated using the formula C = 77.831 + 0.130 × T - 6289 × T^-2, (T is absolute temperature, temperature range is 298-900 K, pressure is constant). The thermodynamic characteristics of Li₃FeN₂ have the following values: entropy S⁰₂₉₈ = 116.2 J mol^-1 K^-1, molar enthalpy of dissolution Δ_dH_LFN = -206.537 ± 2.8 kJ mol^-1, the standard enthalpy of formation Δ_fH⁰ = -291.331 ± 5.7 kJ mol^-1, entropy S⁰₂₉₈ = 113.2 J mol^-1 K^-1 (Neumann-Kopp rule) and 116.2 J mol^-1 K^-1 (W. Herz rule), the standard Gibbs free energy of formation Δ_fG⁰₂₉₈ = -276.7 kJ mol^-1.