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The use of solid-state electrolytes to provide safer, next-generation rechargeable batteries is becoming more feasible as materials with greater stability and higher ionic diffusion coefficients are designed. However, accurate determination of diffusion coefficients in solids is problematic and reliable calculations are highly sought-after to understand how their structure can be modified to improve their performance. In this paper we compare diffusion coefficients calculated using nonequilibrium and equilibrium ab initio molecular dynamics simulations for highly diffusive solid-state electrolytes, to demonstrate the accuracy that can be obtained. Moreover, we show that ab initio nonequilibrium molecular dynamics can be used to determine diffusion coefficients when the diffusion is too slow for it to be feasible to obtain them using ab initio equilibrium simulations. Thereby, using ab initio nonequilibrium molecular dynamics simulations we are able to obtain accurate estimates of the diffusion coefficients of Li ions in Li6PS5Cl and Li5PS4Cl2, two promising electrolytes for all-solid-state batteries. Furthermore, these calculations show that the diffusion coefficient of lithium ions in Li5PS4Cl2 is higher than many other potential all-solid-state electrolytes, making it promising for future technologies. The reasons for variation in conductivities determined using computational and experimental methods are discussed. It is demonstrated that small degrees of disorder and vacancies can result in orders of magnitude differences in diffusivities of Li ions in Li6PS5Cl, and these factors are likely to contribute to inconsistencies observed in experimentally reported values. Notably, the introduction of Li-vacancies and disorder can enhance the ionic conductivity of Li6PS5Cl.

Quantum dots (QDs) of formamidinium lead triiodide (FAPbI3) perovskite hold great potential, outperforming their inorganic counterparts in terms of phase stability and carrier lifetime, for high‐performance solar cells. However, the highly dynamic nature of FAPbI3 QDs, which mainly originates from the proton exchange between oleic acid and oleylamine (OAm) surface ligands, is a key hurdle that impedes the fabrication of high‐efficiency solar cells. To tackle such an issue, here, protonated‐OAm in situ to strengthen the ligand binding at the surface of FAPbI3 QDs, which can effectively suppress the defect formation during QD synthesis and purification processes is selectively introduced. In addition, by forming a halide‐rich surface environment, the ligand density in a broader range for FAPbI3 QDs without compromising their structural integrity, which significantly improves their optoelectronic properties can be modulated. As a result, the power conversion efficiency of FAPbI3 QD solar cells (QDSCs) is enhanced from 7.4% to 13.8%, a record for FAPbI3 QDSCs. Furthermore, the suppressed proton exchange and reduced surface defects in FAPbI3 QDs also enhance the stability of QDSCs, which retain 80% of the initial efficiency upon exposure to ambient air for 3000 hours.

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The development of cost-effective and long-life rechargeable aluminium ion batteries (AIBs) shows promising prospects for sustainable energy storage applications. Here, we report a heteroatom π-conjugated polymer featuring synergistic C=O and C=N active centres as a new cathode material in AIBs using a low-cost AlCl 3 /urea electrolyte. Density functional theory (DFT) calculations reveal the fused C=N sites in the polymer not only benefit good πconjugation but also enhance the redox reactivity of C=O sites, which enables the polymer to accommodate four AlCl 2 (urea) 2 + per repeating unit. By integrating the polymer with carbon nanotubes, the hybrid cathode exhibits a high discharge capacity and a long cycle life (295 mAh g À 1 at 0.1 A g À 1 and 85 mAh g À 1 at 1 A g À 1 over 4000 cycles). The achieved specific energy density of 413 Wh kg À 1 outperforms most Al-organic batteries reported to date. The synergistic redox-active sites strategy sheds light on the rational design of organic electrode materials.