Guangyu Li

Lithium-sulfur batteries show great potential for next-generation energy storage but suffer from the shuttle effect, low conductivity, and sluggish kinetics, resulting in poor cycling and power performance. In this work, Mo atoms were uniformly incorporated into amorphous carbon nanosheets via a metal-coordinated polymerization of dopamine, followed by the uniform anchoring of Ni quantum dots on their surfaces. The oxygen anions coordinated with Mo atoms act as strong binding sites, effectively adsorbing lithium atoms of lithium polysulfide species. As a benefit from the height matching, the sulfur species are able to fully contact the quantum dot ledges and undergo rapid catalytic cleavage. As a result, the optimized sulfur cathode delivers a high initial specific capacity of 1340.2 mAh g^-1 at 0.2 C and 821.7 mAh g^-1 at 1 C and retains 495.8 mAh g^-1 after 500 cycles at 1 C, with a low capacity decay rate of only 0.079% per cycle.

The development of lithium-sulfur batteries (LSBs) is hindered by the solubility of polysulfide intermediates. Herein, we synthesized oxygen-doped MoS₂ on a highly conductive CNT as a cathode material for LSBs. The spaced oxygen dopants on the catalyst surface enable Li polysulfide chains to adsorb parallel to the catalyst surface. This configuration restricts solubility and accelerates the conversion of soluble Li polysulfides to insoluble Li₂S. Therefore, the Mo(S-O)₂/CNT cathode demonstrates an impressive discharge capacity (1410.4 mAh g^-1 at 0.2 C and 880.3 mAh g^-1 at 2 C) along with exceptional cycle stability, retaining 62.7% capacity after 100 cycles at 0.2 C and showing a low decay rate of 0.094% per cycle over 400 cycles at 2 C in LSBs. This work will inspire further research on the deanchoring design of Li₂S from negatively charged polar dopants in catalysts as well as studies on the synchronization of catalysis with the anchoring-deanchoring process.

As potential degradable biomaterials, magnesium (Mg) alloys have development prospects in the field of orthopedic load-bearing, whereas the clinical application has encountered a bottleneck due to a series of problems caused by its rapid corrosion. In this study, strontium-substituted calcium phosphate (CaP) coatings with different structures were prepared on the surface of the Mg matrix by a simple one-step electrodeposition method at different temperatures, which enhanced the poor corrosion resistance of the Mg matrix. The coated sample prepared at 65 °C reduced the corrosion current density by 3 orders of magnitude and increased the impedance by nearly 2 orders of magnitude compared with bare Mg alloy, thanks to its dense fibrous structure similar to that of natural bones. Although the coating composition varies with different preparation temperatures, CaP, as an inorganic component similar to natural bone, has good cytocompatibility. Doping the right amount of strontium, which is a trace element in human bones, is beneficial to stimulate osteoblast differentiation, inhibit the activity of osteoclasts, and induce the formation of bone tissues. This provides a new option for modifying the Mg alloy with CaP coatings as a base.

Magnesium (Mg) alloys, a degradable material, have been studied for medical applications due to their excellent mechanical and chemical properties. However, their applications are limited by rapid corrosion. In this work, stearic acid and sodium stearate were used to treat the silane-induced calcium phosphate dihydrate coating to improve its protection for the Mg alloy further without changing the bone-like structure of calcium phosphate. The different effects of stearic acid treatment and sodium stearate treatment were compared. Electrochemical test and immersion test results confirmed that the corrosion resistance of the stearic acid-treated composite coating was greatly enhanced with a reduced corrosion current density by 3 orders of magnitude and hydrogen evolution reduced to 1/25 after 14 days. The stearic acid-treated coating also exhibited improved in vitro biocompatibility corroborated by promoted cell viability and better cell morphology.

Magnesium (Mg) and its alloys have exhibited great potential for orthopedic applications; however, their poor corrosion resistance and potential cytotoxicity have hindered their further clinical applications. In this study, we prepared a calcium phosphate (Ca–P) coating with a micro–nanofibrous porous structure on the Mg alloy surface by a chemical conversion method. The morphology, composition, and corrosion performance of the coatings were investigated by scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), immersion tests, and electrochemical measurements. The effects of the preparation temperature of the Ca–P coatings were analyzed, and the results confirmed that the coating obtained at 60 °C had the densest structure and the best corrosion resistance. In addition, a systematic investigation into cell viability, ALP activity, and cell morphology confirmed that the Ca–P coating had excellent biocompatibility, which could effectively promote the proliferation, differentiation, and adhesion of osteoblasts. Hence, the Ca–P coating demonstrates great potential in the field of biodegradable Mg-based orthopedic implant materials.

In order to solve the problem caused by rapid corrosion of magnesium (Mg) and its alloys in clinical application, dicalcium phosphate dihydrate (DCPD) coatings with different current densities (0.1 mA cm ⁻² , 0.4 mA cm ⁻² , 1.0 mA cm ⁻² ) and deposition time (10 min, 30 min, 60 min) were prepared by galvanostatic deposition method with the Mg alloys as the cathode. The effects of current density and deposition time on the structure and composition of coatings were analyzed by scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction. Electrochemical corrosion results showed that the polarization resistance of the 0.4 mA cm ⁻² −30 min sample was 68 times that of Mg alloy. And 7 d of long-term corrosion also confirmed its predominant corrosion resistance (hydrogen evolution was only 1/7 of that of Mg alloy), and better biomineralization ability. This was undoubtedly helpful to improve the mechanical integrity and biocompatibility of Mg alloy, thus enhancing the possibility of their clinical application.