First-Principles Study on a Layered Antiperovskite Li7O2Br3 Solid Electrolyte.

Lithium-rich antiperovskites (LiRAPs) have garnered recent attention as solid electrolytes for solid-state lithium-ion batteries (SSLIBs) with high safety and high energy density. Among them, the layered antiperovskite Li7O2Br3 exhibits superior Li+ conductivity compared to cubic antiperovskite Li3OBr. However, the pure phase of Li7O2Br3 has not been synthesized to date, impeding an in-depth investigation of its migration mechanism and electrochemical properties. Herein, we employ density functional theory (DFT) calculations to examine the physical and electrochemical properties of Li7O2Br3. Our results reveal that Li7O2Br3 is dynamically stable in its ground state, featuring electrical insulation with a wide bandgap of approximately 5.83 eV. Moreover, Li7O2Br3 exhibits improved malleability compared to Li3OBr, making it favorable for material processing. Notably, the calculated energy barrier for Li+ migration in Li7O2Br3 is 0.26 eV, lower than that in Li3OBr (0.4 eV), primarily attributed to the softened phonons of Li at the edge layers within the Li7O2Br3 lattice. We also investigated the impact of various defect types on Li+ diffusion in Li7O2Br3, with the results indicating that LiBr defects effectively facilitate Li+ mobility. Additionally, we constructed a pressure-temperature-Gibbs (PTG) free energy phase diagram for Li7O2Br3 to explore appropriate experimental synthesis conditions. These findings hold substantial promise for promoting the research and development of innovative solid electrolyte materials for advanced SSLIBs.

Bilayer Halide Electrolytes for All-Inorganic Solid-State Lithium-Metal Batteries with Excellent Interfacial Compatibility.

Inorganic solid-state electrolytes (ISSEs) have been extensively researched as the critical component in all-solid-state lithium-metal batteries (ASSLMBs). Many ISSEs exhibit high ionic conductivities up to 10-3 S cm-1. However, most of them suffer from poor interfacial compatibility with electrodes, especially lithium-metal anodes, limiting their application in high-performance ASSLMBs. To achieve good interfacial compatibility with a high-voltage cathode and a lithium-metal anode simultaneously, we propose Li3InCl6/Li2OHCl bilayer halide ISSEs with complementary advantages. In addition to the improved interfacial compatibility, the Li3InCl6/Li2OHCl bilayer halide ISSEs exhibit good thermal stability up to 160 °C. The Li-symmetric cells with sandwich electrolytes Li2OHCl/Li3InCl6/Li2OHCl exhibit long cycling life of over 300 h and a high critical current density of over 0.6 mA cm-2 at 80 °C. Moreover, the all-inorganic solid-state lithium-metal batteries (AISSLMBs) LiFePO4-Li3InCl6/Li3InCl6/Li2OHCl/Li fabricated by a facile cold-press method exhibit good rate performance and long-term cycling stability that stably cycle for about 3000 h at 80 °C. This work presents a facile and cost-effective method to construct bilayer halide ISSEs, enabling the development of high-performance AISSLMBs with good interfacial compatibility and thermal stability.

Temperature-dependent compatibility study on halide solid-state electrolytes in solid-state batteries.

All-solid-state lithium batteries (ASSLBs) have attracted much attention owing to their high safety and energy density compared to conventional organic electrolytes. However, the interfaces between solid-state electrolytes and electrodes retain some knotty problems regarding compatibility. Among the various SSEs investigated in recent years, halide SSEs exhibit relatively good interfacial compatibility. The temperature-dependent interfacial compatibility of halide SSEs in solid-state batteries is investigated by thermal analysis using simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) and X-ray diffraction (XRD). Halide SSEs, including rock-salt-type Li3InCl6 and anti-perovskite-type Li2OHCl, show good thermal stability with oxides LiCoO2, LiMn2O4, and Li4Ti5O12 up to 320 °C. Moreover, anti-perovskite-type Li2OHCl shows a chemical reactivity with other battery materials (eg., LiFePO4, LiNi0.8Co0.1Mn0.1O2, Si-C, and Li1.3Al0.3Ti1.7(PO4)3) at 320°C, which reaches the melting point of Li2OHCl. It indicated that Li2OHCl has relatively high chemical reactivity after melting. In contrast, rock-salt-type Li3InCl6 shows higher stability and interfacial compatibility. This work delivers insights into the selection of suitable battery materials with good compatibility for ASSLBs.

The thermodynamics and electronic structure analysis of P-doped spinel Co3O4.

The thermodynamics of phosphorus (P) doping to spinel Co3O4, for both bulk cases and (100) and (110) surface cases, is studied using first principles calculations. The doping energies of the P atom at different doping sites are carefully calculated and compared. It is shown that P doping at Co sites, at either tetrahedral or octahedral sites, is energetically favorable, while P doping and replacing O atoms are energetically unfavorable. The doping energy difference is large enough to conclude that P doping has a very strong preference to take the Co sites, rather than the O sites in spinel Co3O4. Even when O-vacancy is available, P doping and taking the O-vacancy site is thermodynamically unfavorable. The physical/chemical mechanism behind this phenomenon is carefully analyzed. Electronic structure analysis shows that P doping and replacing the Co atom brings excess electrons to the Co3O4 system, which is beneficial to enhance the electrochemical and catalytic performance of the spinel Co3O4. Our results clarified the misleading results of P doping and replacing O atoms in spinel Co3O4 reported in the literature.

Efficient potential-tuning strategy through p-type doping for designing cathodes with ultrahigh energy density.

Designing new cathodes with high capacity and moderate potential is the key to breaking the energy density ceiling imposed by current intercalation chemistry on rechargeable batteries. The carbonaceous materials provide high capacities but their low potentials limit their application to anodes. Here, we show that Fermi level tuning by p-type doping can be an effective way of dramatically raising electrode potential. We demonstrate that Li(Na)BCF2/Li(Na)B2C2F2 exhibit such change in Fermi level, enabling them to accommodate Li+(Na+) with capacities of 290-400 (250-320) mAh g-1 at potentials of 3.4-3.7 (2.7-2.9) V, delivering ultrahigh energy densities of 1000-1500 Wh kg-1. This work presents a new strategy in tuning electrode potential through electronic band structure engineering.

The effect of protons on the Mg2+ migration in an α-V2O5 cathode for magnesium batteries: a first-principles investigation.

The scarce inventory of cathode materials with reasonable diffusion of Mg ions is the main obstacle in the development of rechargeable magnesium batteries. In this regard, vanadium pentoxide (V2O5) has been reported to be a candidate cathode material for Mg batteries. In this study, via first-principles calculations, we showed that the Mg-ion diffusion energy barrier in α-V2O5 could be substantially decreased through hydrogenation. It is found that the Mg-ion migration energy barrier in HxV2O5 is gradually decreased with an increase in H concentration. When the H concentration x reaches 2, the migration barrier is decreased to 0.56 eV from that in α-V2O5 without hydrogenation (1.28 eV). This indicates that the Mg diffusion kinetics can be substantially improved through hydrogenation, and the resultant energy barrier makes Mg diffusion acceptable even at room temperature. The mechanism of the H-enhanced Mg-diffusion has also been studied, and it has been found that H atoms not only can expand the Mg-diffusion pathway, but also have a screening effect on the interactions between Mg ions and the α-V2O5 lattice.