high performance device, several factors that have pivotal impacts on the perovskite films are under intense study including the crystallization behavior, the deposition method, and the reactant components. [4,5] Several strategies have been studied to enhance the crystallinity and surface morphology of the active layer via the composition of the perovskite precursors. By replacing the lead precursor PbI 2 with PbCl 2 or Pb(CH 3 COO) 2 , the morphology of perovskite film and the device stability were strongly influenced due to decelerated crystallization kinetics and selected crystallographic orientation. [6,7] For the organic iodine precursor, methylammonium iodide (MAI) combined with methylammonium bromine or formamidine iodide (FAI) showed notable changes on energy bandgap, thermal or moisture stability, grain size, and ion migration behaviors. This was mainly due to the variation of relative ion sizes and lattice structure. [8] Besides the selection on lead and organic iodine precursors, some ligand compounds that act as electron donor (Lewis-bases) could also greatly affect the properties of perovskite films. [9] Three categories of Lewis-bases can coordinate with PbI 2 and promote the sequential deposition of perovskite film: O-donor, N-donor, and S-donor. [10] Dimethylsulfoxide (DMSO), is an O-donor, and has received much attention for having successfully grown uniform and dense perovskite films due to the formation of immediate phase MAI⋅PbI 2 ⋅DMSO, which retarded the otherwise rapid reaction between PbI 2 and organic iodide in solution. [11] Furthermore, an intramolecular exchange process between DMSO and FAI was also reported to fabricate FAPbI 3 with a flat and dense surface without volume expansion. [12] However, due to the weak coordination between O and Pb, the O-donor was easy to escape from the PbI 2 framework. This often leads to insufficient perovskite grain growth. Perovskite films with smooth surfaces and large grains are desired with effective photon capture, fast carrier transport, and suppressed ion migration. [13] Thus, more stable ligands are needed for the fabrication of perovskite films.A new perovskite precursor and a two-step antisolvent processing method were utilized to grow high-quality perovskite films. By introducing thiourea into the pristine CH 3 NH 3 PbI 3 precursor in equivalent molar ratios, the perovskite films acquired the desired morphology. Sequential ethyl acetate (EA) antisolvent processing removed the residual thiourea and opened the grain The synthesis and growth of perovskite films with controlled crystallinity and microstructure for highly efficient and stable solar cells is a critical issue. In this work, thiourea is introduced into the CH 3 NH 3 PbI 3 precursor with two-step sequential ethyl acetate (EA) interfacial processing. This is shown for the first time to grow compact microsized and monolithically grained perovskite films. X-ray diffraction patterns and infrared spectroscopy are used to prove that thiourea significantly impacts the perovskite crystallini...

Development of the next-generation, high-energy-density, low-cost batteries will likely be fueled by sodium (Na) metal batteries because of their high capacity and the abundance of Na. However, their practical application is significantly plagued by the hyper-reactivity of Na metal, unstable solid electrolyte interphase (SEI), and dendritic Na growth, leading to continuous electrolyte decomposition, low Coulombic efficiency, large impedance, and safety concerns. Herein, we add a small amount of SnCl2 additive in a common carbonate electrolyte so that the spontaneous reaction between SnCl2 and Na metal enables in situ formation of a Na–Sn alloy layer and a compact NaCl-rich SEI. Benefitting from this design, rapid interfacial ion transfer is realized and direct exposure of Na metal to the electrolyte is prohibited, which jointly achieve a nondendritic deposition morphology and a markedly reduced voltage hysteresis in a Na/Na symmetric cell for over 500 h. The Na/SnCl2-added electrolyte/Na3V2(PO4)3 full cell exhibits high capacity retention over cycling and excellent rate capability (101 mAh/g at 10 C). This work can provide an easily scalable and cost-effective approach for developing high-performance Na-metal batteries.

LiCoO2 is used as a cathode material for lithium‐ion batteries, however, cationic/anodic‐redox‐induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO2 to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg‐pillared LiCoO2. Dopant Mg ions, serving as pillars in the Li‐slab of LiCoO2, prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li‐Mg mixing structure at the surface of Mg‐pillared LiCoO2 is beneficial for eliminating the cathode‐electrolyte interphase overgrowth and phase transformation in the close‐to‐surface region. Mg‐pillared LiCoO2 exhibits a high capacity of 204 mAh g−1 at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0–4.6 V. In contrast, pristine LiCoO2 has a capacity retention of 14 % within the same voltage window.