Rational Regulation of High-Voltage Stability in Potassium Layered Oxide Cathodes.

Layered oxide cathode materials may undergo irreversible oxygen loss and severe phase transitions during high voltage cycling and may be susceptible to transition metal dissolution, adversely affecting their electrochemical performance. Here, to address these challenges, we propose synergistic doping of nonmetallic elements and in situ electrochemical diffusion as potential solution strategies. Among them, the distribution of the nonmetallic element fluorine within the material can be regulated by doping boron, thereby suppressing manganese dissolution through surface enrichment of fluorine. Furthermore, in situ electrochemical diffusion of fluorine from the surface into the bulk of the materials after charging reduces the energy barrier of potassium ion diffusion while effectively inhibiting irreversible oxygen loss under high voltage. The modified K0.5Mn0.83Mg0.1Ti0.05B0.02F0.1O1.9 layered oxide cathode exhibits a high capacity of 147 mAh g-1 at 50 mA g-1 and a long cycle life of 2200 cycles at 500 mA g-1. This work demonstrates the efficacy of synergistic doping and in situ electrochemical diffusion of nonmetallic elements and provides valuable insights for optimizing rechargeable battery materials.

Entropy-Tuned Layered Oxide Cathodes for Potassium-Ion Batteries.

The manganese-based layered oxides as a promising cathode material for potassium ion batteries (PIBs) have attracted considerable interest owing to their simple synthesis, high specific capacity, and low cost. However, due to the irreversible phase transition and the Jahn-Teller distortion of the Mn3+ , its application in potassium ion batteries is limited, leading to slow potassium ion kinetics and severe capacity attenuation. Here, entropy-tuning by changing the content of cathode material composition is proposed to address the above challenges. Compared to low and high entropy variants of K0.45 Mnx Co(1- x )/4 Mg(1- x )/4 Cu(1- x )/4 Ti(1- x )/4 O2 , where x = 0.8, 0.6, and 0.4, the medium entropy K0.45 Mn0.6 Co0.1 Mg0.1 Cu0.1 Ti0.1 O2 shows more balanced electrochemical properties in the PIBs. Benefiting from entropy-tuned suppression of the Jahn-Teller distortion of the Mn3+ , the K0.45 Mn0.6 Co0.1 Mg0.1 Cu0.1 Ti0.1 O2 can achieve a high K+ ion transport rate and alleviated volume variation while retaining high specific capacity. Accordingly, the medium entropy K0.45 Mn0.6 Co0.1 Mg0.1 Cu0.1 Ti0.1 O2 cathode in the full cell exhibits a high capacity of 100 mAh g-1 at 50 mA g-1 , delivers superior rate capability (65.8 mAh g-1 at 500 mA g-1 ) and cycling stability (67.8 mAh g-1 after 350 cycles at 100 mA g-1 ). The entropy-tuning strategy is expected to open new avenues in designing PIB cathode materials and beyond.

Phase-engineered cathode for super-stable potassium storage.

The crystal phase structure of cathode material plays an important role in the cell performance. During cycling, the cathode material experiences immense stress due to phase transformation, resulting in capacity degradation. Here, we show phase-engineered VO2 as an improved potassium-ion battery cathode; specifically, the amorphous VO2 exhibits superior K storage ability, while the crystalline M phase VO2 cannot even store K+ ions stably. In contrast to other crystal phases, amorphous VO2 exhibits alleviated volume variation and improved electrochemical performance, leading to a maximum capacity of 111 mAh g-1 delivered at 20 mA g-1 and over 8 months of operation with good coulombic efficiency at 100 mA g-1. The capacity retention reaches 80% after 8500 cycles at 500 mA g-1. This work illustrates the effectiveness and superiority of phase engineering and provides meaningful insights into material optimization for rechargeable batteries.

Precise Ligand Tuning Emission of Mn-Doped CsPbCl3 Nanocrystals by the Amount of Sulfonates.

Using Mn-doped CsPbCl3 nanocrystals (Mn:CsPbCl3 NCs) to improve perovskite's properties is becoming an important strategy. Here, we demonstrate a modified supersaturated recrystallization route to synthesize high-quality Mn:CsPbCl3 NCs at room temperature. Unprecedentedly, sulfonate ligands with various concentrations are shown to successfully tune the dual-color emission of Mn:CsPbCl3 NCs. Ultrafast transient absorption studies reveal that the host-to-dopant internal energy-transfer process involves the mediated traps. Interestingly, the dual-color emission is tuned via stabilizing mediated traps with a small amount of ligand (band edge (BE) emission reduces and Mn2+ emission increases), passivating the deep traps with a large amount of ligand (Mn2+ emission increases), and destroying Mn:CsPbCl3 NCs with too much ligand (both BE and Mn2+ emission is quenched). Furthermore, the ligand tuning Mn2+ emission exhibits quenching for Cu2+ with high sensitivity and selectivity. Our work provides a new strategy to tune the optical properties of Mn:CsPbCl3 NCs and presents its potential application in an optical detector.

Novel Ag/Si composite particles through galvanic displacement and its conductive application.

Here we synthesized a novel Ag/Si composite sub-micro particle using galvanic displacement by capitalizing on the active chemical surface of Si particles sludge from wafer-slicing process. Si works as chemical reactant, as well as reaction site to form composite particles. Sequent structural characterizations and analysis which include X-ray diffraction, transmission electron microscopy, scanning electron microscope, energy dispersive X-ray and electrical properties of this composite particle were done. A well-proved hetero-epitaxial growth mechanism could explain Ag nano-island/layer with a satisfactory bond property deposited on the Si surface. Since these Si are mechanically cleaved from crystal, formed conductive Ag/Si composites retain the flake shape from Si sludge particles, and narrow size distribution. They are preferred as conductive fillers, an Ag/Si composite-based conductive ink was prepared, its conductance was tested through screen printing, film thickness and resistivity were measured. The resistivity reached the µΩ cm level, even without optimizing the ink formulation. Our methods not only convert this Si sludge into highly conductive composite particles as filler for applications, but also considerably reduce the consumption of precious metal.