Improved Lithium Diffusion in Anion-Substituted Li₇TaO₆

One approach to enhance the conductivity of a lithium-containing material is to widen the diffusion channel, such as the case of the superionic material Li10GeP2S6. This work unravels the enhanced diffusivity of Li+ in Li7TaS6 and Li7TaSe6, which are based on the known Li7TaO6 superionic conductor. Using density functional theory, we calculate the electronic and structural properties of the three materials and utilize ab initio molecular dynamics simulations to model the diffusion dynamics. Both Li7TaS6 and Li7TaSe6 are shown to exhibit an order of magnitude improvement in the diffusion coefficient relative to the parent material and a slight drop in their corresponding activation barriers. These materials are potential candidates for application in lithium solid-state electrolytes, with performance that is competitive with Li10GeP2S6

Blocking Directional Lithium Diffusion in Solid-State Electrolytes at the Interface: First-Principles Insights into the Impact of the Space Charge Layer

Understanding the degradation mechanisms in solid-state lithium-ion batteries at interfaces is fundamental for improving battery performance and for designing recycling methodologies for batteries. A key source of battery degradation is the presence of the space charge layer at the solid-state electrolyte–electrode interface and the impact that this layer has on the thermodynamics of the electrolyte structure. Currently, Li10GeP2S12 in its pristine form has one of the highest lithium conductivities and has been used as a template for designing even higher conductivity derived structures. However, being an ionic material with mostly linear diffusion, it is prone to path-blocker defects, which we show here to be especially prevalent in the space charge layer. We analyze the thermodynamic properties of a number of path-blocker defects using density functional theory and their potential crystal decomposition and find that the presence of an electrostatic potential in the space charge layer elevates the likelihood of existence of these defects, which otherwise would not be likely to form in the bulk of the electrolyte away from electrodes. We use ab initio molecular dynamics to assess the impact of these defects on the diffusivity of the crystal and find that they all reduce the lithium diffusivity. While our work focuses on Li10GeP2S12, it is relevant to any solid-state electrolyte with mainly linear diffusion

Systematic Investigation of Functional Ligands for Colloidal Stable Upconversion Nanoparticles

<div> <p>Despite intense efforts on surface functionalization to generate hydrophilic upconversion nanoparticles (UCNPs), long-term colloidal stability in physiological buffers remains a major concern. Here we quantitatively investigate the competitive adsorption of phosphate, carboxylic acid and sulphonic acid onto the surface of UCNPs and study their binding strength to identify the best conjugation strategy. To achieve this, we designed and synthesized three di-block copolymers composed of poly(ethylene glycol) methyl ether acrylate and a polymer block bearing phosphate, carboxylic or sulphonic acid anchoring groups prepared by an advanced polymerization technique, Reversible Addition Fragmentation Chain Transfer (RAFT). Analytical tools provide the evidence that phosphate ligands completely replaced all the oleic acid capping molecules on the surface of the UCNPs compared with incomplete ligand exchange by carboxylic and sulphonic acid groups. In the meanwhile, simulated quantitative adsorption energy measurements confirmed that among three functional groups, calculated adsorption strength for phosphate anchoring ligands is higher which is in good agreement with experimental results regarding the best colloidal stability especially in phosphate buffer solution. The finding suggests that polymers with multiple anchoring negatively charged phosphate moieties provide excellent colloidal stability for lanthanide ion-doped luminescent nanoparticles for various potential applications.</p> </div> <br