Insights into the electrochemical properties of Li₂FeS₂ after FeS₂ discharging

Abstract

All-solid-state lithium-sulfur batteries (ASSLSBs) have the highly reversible characteristics owing to high redox potential, high theoretical capacity, high electronic conductivity, and low Li+ diffusion energy barrier in the cathode. Monte...

First-principles study of the discharge electrochemical and catalytic performance of the sulfur cathode host Fe0.875M0.125S2 (M = Ti, V)

“…Moreover, the redox voltage of FeS 2 is 1.64–2.90 V, and has a high theoretical capacity of 894 mA h g −1 . 21,31 The mixing enthalpy (Δ H mix ) at each Li composition x is investigated to understand the Fe 0.875 M 0.125 S 2 discharge by the eqn (2). 21,32 where E indicates the total energy of the system.…”

“…21,31 The mixing enthalpy (Δ H mix ) at each Li composition x is investigated to understand the Fe 0.875 M 0.125 S 2 discharge by the eqn (2). 21,32 where E indicates the total energy of the system. Based on the mixing enthalpy considering the vacancy, the average equilibrium voltage over a full cycle ( V cell ) of the battery was calculated by using the Nernst eqn (3): 21 where n is the number of moles of electrons transferred, F is the Faraday constant, Δ G is the change of Gibbs free energy per mole, Δ E is the change of the ground state energy of the overall reaction per mole; E (Li x 2 Fe 0.875 M 0.125 S 2 ) and E (Li x 1 Fe 0.875 M 0.125 S 2 ) represent the energies of and , respectively; E (Li) is for the energy of each Li atom of Li metal.…”

“…The larger the capacity of the battery, the longer it can be used for the same discharge current. Eqn (4) calculated the theoretical capacity ( Q t ) of the sulfur cathode host: 21 where Q t means the max capacity, n is the number of moles of Li, z is the number of electrons during the discharging, F represents the Faraday constant ( F = 26.8 A h mol −1 ) and M represents the molecular mass of Li 2 Fe 0.875 M 0.125 S 2 .…”

“…The space group and lattice constant of unit cell Li 2 FeS 2 are P 3̄ m 1 and a = b = 3.41 Å, c = 6.10 Å, respectively, including one Li atom, two S atoms, and one Fe atom, which is almost consistent with ref. 21. The lattice constants of Li 2 FeS 2 with Ibam , Immm , P 3 m 1, P 2 1 / c and P 42 mcm are listed in Table S1 (ESI†).…”

“…The excellent electronic conductivity of Li 2 FeS 2 can provide a fast Li + transfer channel during the discharging, and effectively improve the electrochemical kinetics of electrode materials. 21 The different pathways are shown in Fig. S6 (ESI †).…”