Understanding the physical picture of Li ion transport in the current ionic conductors is quite essential to further develop lithium superionic conductors for solid-state batteries. The traditional practice of directly extrapolating room temperature ion diffusion properties from the high-temperature (>600 K) ab initio molecular dynamics simulations (AIMD) simulations by the Arrhenius assumption unavoidably cause some deviations. Fortunately, the ultralong-time molecular dynamics simulation based on the machine-learning interatomic potentials (MLMD) is a more suitable tool to probe into ion diffusion events at low temperatures and simultaneously keeps the accuracy at the density functional theory level. Herein, by the low-temperature MLMD simulations, the non-linear Arrhenius behavior of Li ion was found for Li3ErCl6, which is the main reason for the traditional AIMD simulation overestimating its ionic conductivity. The 1μs MLMD simulations capture polyanion rotation events in Li7P3S11 at room temperature, in which four [PS4]3− tetrahedra belonging to a part of the longer-chain [P2S7]4− group are noticed with remarkable rotational motions, while the isolated group [PS4]3− does not rotate. However, no polyanion rotation is observed in Li10GeP2S12, β-Li3PS4, Li3ErCl6, and Li3YBr6 at 300 K during 1μs simulation time. Additionally, the ultralong-time MLMD simulations demonstrate that not only there is no paddle-wheel effect in the crystalline Li7P3S11 at room temperature, but also the rotational [PS4]3− polyanion groups have weakly negative impacts on the overall Li ion diffusion. The ultralong-time MLMD simulations deepen our understanding of the relationship between the polyanion rotation and cation diffusion in ionic conductors at room environments.
Sodium-ion batteries with evident merits in resource abundance and expenditure are emerging as a more suitable alternative to lithium-ion batteries for fulfilling the voracious energy demand of human activities. As the integral component of the battery, the exploration of anode materials suited to the electrochemical system during the last few decades has been never suspended, and the sodium metal anode successfully stands out with its high theoretical capacity and low redox potential. However, a huge gap exists between the direct usage of the sodium metal anode and the large-scale applications, as the uncontrollable sodium dendritic growth during cycling brings about serious concerns (i.e. infinite volume change, unstable solid electrolyte interphase, and safety issues) on battery performance losses. Although a few review articles on high-performance sodium metal anode have been already published, new research on solving the aforementioned challenges is still in progress. Therefore, we herein summarize the recent progress on the high-energy sodium metal anode from four aspects (protective layers, electrolyte additives, three-dimensional framework current collectors, and alloy materials) together with the detailed discussion and analysis in this Perspective. Furthermore, the potential directions and prospects of future research on constructing high-performance sodium metal anodes are also proposed.
This study adopted the latest self-developed bioabsorbable material lactide-glycolide-1,3-trimethylene carbonate (LA-GA-TMC) and applied the three-dimensional (3D) printing technique to manufacture the occluder for cardiac septal defects, so as to realize the individualized treatment of cardiac septal defects. At the same time, its biosafety was evaluated, with an aim to establish foundation for futural large-scale animal experiment and clinical trial. The traditional "one-pot synthesis" was modified, and the "two-step synthesis method" was utilized to synthesize the LA-GA-TMC terpolymer at the lactide: glycolide: trimethylene carbonate ratio of 6:1:1.7. Afterward, the synthesized terpolymer was used as the raw material to fabricate the occluder model via using 3D printing technique. Then, its biocompatibility was comprehensively evaluated through cytocompatibility, blood compatibility, and histocompatibility. The occluder made from LA-GA-TMC 3D printing had favorable ductility and recoverability; besides, it possessed the temperature-control feature, and the relative cell proliferation rates in extract liquids at various concentrations were all >70%, suggesting that it had favorable cytocompatibility. Moreover, hemolytic experiment revealed that its hemolytic rate was <5%, dynamic blood coagulation experiment demonstrated that the sample material moderately activated the blood coagulation, and the above findings suggested that it had good blood compatibility. In addition, implanting experiment in vivo revealed that its histocompatibility was superior to the traditional nitinol and the emerging poly-L-lactic acid. It is completely feasible to manufacture the cardiac septal defects occluder based on the novel absorbable material LA-GA-TMC, which has favorable biocompatibility, through 3D printing technique and it possesses broad prospects in large-scale animal experiment and clinical trial.
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