Enamel-like Layer of Nanohydroxyapatite Stabilizes Zn Metal Anodes by Ion Exchange Adsorption and Electrolyte pH Regulation

The instability of Zn anode caused by severe dendrite growth and side reactions has restricted the practical applications of aqueous zinc-ion batteries (AZIBs). Herein, an enamel-like layer of nanohydroxyapatite (Ca5(PO4)3(OH), nano-HAP) is constructed on Zn anode to enhance its stability. Benefiting from the ion exchange between Zn2+ and Ca2+, the adsorption for Zn2+ in enamel-like nano-HAP (E-nHAP) layer can effectively guide Zn deposition, ensuring homogeneous Zn2+ flux and even nucleation sites to suppress Zn dendrites. Meanwhile, the low pH of acidic electrolyte can be regulated by slightly soluble nano-HAP, restraining electrolyte corrosion and hydrogen evolution. Moreover, the E-nHAP layer features high mechanical flexibility due to its enamel-like organic–inorganic composite nanostructure. Hence, symmetric cells assembled by E-nHAP@Zn show superior stability of long-term cycling at different current densities (0.1, 0.5, 1, 5, and 10 mA cm–2). The E-nHAP@Zn∥E-nHAP@Cu cell exhibits an outstanding cycling life with high Coulombic efficiency of 99.8% over 1000 cycles. Notably, the reversibility of full cell based on CNT/MnO2 cathode can be effectively enhanced. This work shows the potential of drawing inspiration from biological nanostructure in nature to develop stable metal electrodes

Acetylacetone-Directed Controllable Synthesis of Bi₂S₃ Nanostructures with Tunable Morphology

Uniform 5 μm Bi2S3 microspheres and 8 μm microflowers were solvothermally synthesized in acetylacetone solution through thermolysis of the Bi3+-dithizone complex without any templates or surfactants. Bi2S3 microspheres composed of nanorods with a diameter of 20−40 nm were synthesized at 180 °C for 12 h. In similar conditions at 240 °C for 3 days, microflowers composed of nanowires with lengths up to several micrometers and diameter of 20−40 nm were obtained. Field-emission scanning electron microscopy (FESEM) showed in the initial stage in the formation process that smooth spherical cores were observed, then on the surface of the cores nanoparticles appeared, and finally nanorods or nanowires grew out and microspheres and microflowers formed. Electrochemical experiments using Bi2S3 in a lithium ion battery indicated that the first discharge capacity of Bi2S3 microflowers could reach about 148 mA h g−1

Microscale Mn₂O₃ Hollow Structures: Sphere, Cube, Ellipsoid, Dumbbell, and Their Phenol Adsorption Properties

Various Mn2O3 hollow structures, such as spheres, cubes, ellipsoids, and dumbbells have been synthesized through the following process: The surfaces of the prepared MnCO3 microspheres, microcubes, and microellipsoids were oxidized by KMnO4 to form a core/shell structure. Similarly, the surface of a dumbbell-like MnCO3 intermediate can also be oxidized by KMnO4. As the MnCO3 or MnCO3 intermediate cores were dissolved by acid, the MnO2 shells were formed. Calcining these MnO2 shells at 500 °C, polycrystalline Mn2O3 hollow structures were obtained. The morphologies of these hollow structures were similar to their precursors. The as-prepared hollow Mn2O3 materials were used as adsorbents in water treatment, and the hollow Mn2O3 spheres, cubes, ellipsoids, and dumbbells could respectively remove about 77%, 83%, 81%, and 78% of phenol

Enamel-like Layer of Nanohydroxyapatite Stabilizes Zn Metal Anodes by Ion Exchange Adsorption and Electrolyte pH Regulation

The instability of Zn anode caused by severe dendrite growth and side reactions has restricted the practical applications of aqueous zinc-ion batteries (AZIBs). Herein, an enamel-like layer of nanohydroxyapatite (Ca5(PO4)3(OH), nano-HAP) is constructed on Zn anode to enhance its stability. Benefiting from the ion exchange between Zn2+ and Ca2+, the adsorption for Zn2+ in enamel-like nano-HAP (E-nHAP) layer can effectively guide Zn deposition, ensuring homogeneous Zn2+ flux and even nucleation sites to suppress Zn dendrites. Meanwhile, the low pH of acidic electrolyte can be regulated by slightly soluble nano-HAP, restraining electrolyte corrosion and hydrogen evolution. Moreover, the E-nHAP layer features high mechanical flexibility due to its enamel-like organic–inorganic composite nanostructure. Hence, symmetric cells assembled by E-nHAP@Zn show superior stability of long-term cycling at different current densities (0.1, 0.5, 1, 5, and 10 mA cm–2). The E-nHAP@Zn∥E-nHAP@Cu cell exhibits an outstanding cycling life with high Coulombic efficiency of 99.8% over 1000 cycles. Notably, the reversibility of full cell based on CNT/MnO2 cathode can be effectively enhanced. This work shows the potential of drawing inspiration from biological nanostructure in nature to develop stable metal electrodes

Polyaniline-Assisted Synthesis of Si@C/RGO as Anode Material for Rechargeable Lithium-Ion Batteries

A novel approach to fabricate Si@carbon/reduced graphene oxides composite (Si@C/RGO) assisted by polyaniline (PANI) is developed. Here, PANI not only serves as “glue” to combine Si nanoparticles with graphene oxides through electrostatic attraction but also can be pyrolyzed as carbon layer coated on Si particles during subsequent annealing treatment. The assembled composite delivers high reversible capacity of 1121 mAh g^–1 at a current density of 0.9 A g^–1 over 230 cycles with improved initial Coulombic efficiency of 81.1%, while the bare Si and Si@carbon only retain specific capacity of 50 and 495 mAh g^–1 at 0.3 A g^–1 after 50 cycles, respectively. The enhanced electrochemical performance of Si@C/RGO can be attributed to the dual protection of carbon layer and graphene sheets, which are synergistically capable of overcoming the drawbacks of inner Si particles such as huge volume change and low conductivity and providing protective and conductive matrix to buffer the volume variation, prevent the Si particles from aggregating, enhance the conductivity, and stabilize the solid–electrolyte interface membrane during cycling. Importantly, this method opens a novel, universal graphene coating strategy, which can be extended to other fascinating anode and cathode materials

A Deep Reduction and Partial Oxidation Strategy for Fabrication of Mesoporous Si Anode for Lithium Ion Batteries

A deep reduction and partial oxidation strategy to convert low-cost SiO₂ into mesoporous Si anode with the yield higher than 90% is provided. This strategy has advantage in efficient mesoporous silicon production and <i>in situ</i> formation of several nanometers SiO₂ layer on the surface of silicon particles. Thus, the resulted silicon anode provides extremely high reversible capacity of 1772 mAh g^–1, superior cycling stability with more than 873 mAh g^–1 at 1.8 A g^–1 after 1400 cycles (corresponding to the capacity decay rate of 0.035% per cycle), and good rate capability (∼710 mAh g^–1 at 18A g^–1). These promising results suggest that such strategy for mesoporous Si anode can be potentially commercialized for high energy Li-ion batteries

Stable Plating and Stripping of Lithium Metal Anodes through Space Confinement and Stress Regulation

Lithium metal anodes suffer from enormous mechanical stress derived from volume changes during electrochemical plating and stripping. The utilization of derived stress has the potential for the dendrite-free deposition and electrochemical reversibility of lithium metal. Here, we investigated the plating and stripping process of lithium metal held within a cellular three-dimensional graphene skeleton decorated with homogeneous Ag nanoparticles. Owing to appropriate reduction-splitting and electrostatic interaction of nitrogen dopants, the cellular skeletons show micron-level pores and superior elastic property. As lithium hosts, the cellular skeletons can physically confine the metal deposition and provide continuous volume-derived stress between Li and collectors, thus meliorating the stress-regulated Li morphology and improving the reversibility of Li metal anodes. Consequently, the symmetrical batteries exhibit a stable cycling performance with a span life of more than 1900 h. Full batteries (NCM811 as cathodes) achieve a reversible capacity of 181 mA h g–1 at 0.5 C and a stable cycling performance of 300 cycles with a capacity retention of 83.5%. The meliorative behavior of lithium metal within the cellular skeletons suggests the advantage of a stress-regulating strategy, which could also be meaningful for other conversion electrodes with volume fluctuation

Stable Plating and Stripping of Lithium Metal Anodes through Space Confinement and Stress Regulation

Lithium metal anodes suffer from enormous mechanical stress derived from volume changes during electrochemical plating and stripping. The utilization of derived stress has the potential for the dendrite-free deposition and electrochemical reversibility of lithium metal. Here, we investigated the plating and stripping process of lithium metal held within a cellular three-dimensional graphene skeleton decorated with homogeneous Ag nanoparticles. Owing to appropriate reduction-splitting and electrostatic interaction of nitrogen dopants, the cellular skeletons show micron-level pores and superior elastic property. As lithium hosts, the cellular skeletons can physically confine the metal deposition and provide continuous volume-derived stress between Li and collectors, thus meliorating the stress-regulated Li morphology and improving the reversibility of Li metal anodes. Consequently, the symmetrical batteries exhibit a stable cycling performance with a span life of more than 1900 h. Full batteries (NCM811 as cathodes) achieve a reversible capacity of 181 mA h g–1 at 0.5 C and a stable cycling performance of 300 cycles with a capacity retention of 83.5%. The meliorative behavior of lithium metal within the cellular skeletons suggests the advantage of a stress-regulating strategy, which could also be meaningful for other conversion electrodes with volume fluctuation

Enamel-like Layer of Nanohydroxyapatite Stabilizes Zn Metal Anodes by Ion Exchange Adsorption and Electrolyte pH Regulation

The instability of Zn anode caused by severe dendrite growth and side reactions has restricted the practical applications of aqueous zinc-ion batteries (AZIBs). Herein, an enamel-like layer of nanohydroxyapatite (Ca5(PO4)3(OH), nano-HAP) is constructed on Zn anode to enhance its stability. Benefiting from the ion exchange between Zn2+ and Ca2+, the adsorption for Zn2+ in enamel-like nano-HAP (E-nHAP) layer can effectively guide Zn deposition, ensuring homogeneous Zn2+ flux and even nucleation sites to suppress Zn dendrites. Meanwhile, the low pH of acidic electrolyte can be regulated by slightly soluble nano-HAP, restraining electrolyte corrosion and hydrogen evolution. Moreover, the E-nHAP layer features high mechanical flexibility due to its enamel-like organic–inorganic composite nanostructure. Hence, symmetric cells assembled by E-nHAP@Zn show superior stability of long-term cycling at different current densities (0.1, 0.5, 1, 5, and 10 mA cm–2). The E-nHAP@Zn∥E-nHAP@Cu cell exhibits an outstanding cycling life with high Coulombic efficiency of 99.8% over 1000 cycles. Notably, the reversibility of full cell based on CNT/MnO2 cathode can be effectively enhanced. This work shows the potential of drawing inspiration from biological nanostructure in nature to develop stable metal electrodes

Stable Plating and Stripping of Lithium Metal Anodes through Space Confinement and Stress Regulation

Lithium metal anodes suffer from enormous mechanical stress derived from volume changes during electrochemical plating and stripping. The utilization of derived stress has the potential for the dendrite-free deposition and electrochemical reversibility of lithium metal. Here, we investigated the plating and stripping process of lithium metal held within a cellular three-dimensional graphene skeleton decorated with homogeneous Ag nanoparticles. Owing to appropriate reduction-splitting and electrostatic interaction of nitrogen dopants, the cellular skeletons show micron-level pores and superior elastic property. As lithium hosts, the cellular skeletons can physically confine the metal deposition and provide continuous volume-derived stress between Li and collectors, thus meliorating the stress-regulated Li morphology and improving the reversibility of Li metal anodes. Consequently, the symmetrical batteries exhibit a stable cycling performance with a span life of more than 1900 h. Full batteries (NCM811 as cathodes) achieve a reversible capacity of 181 mA h g–1 at 0.5 C and a stable cycling performance of 300 cycles with a capacity retention of 83.5%. The meliorative behavior of lithium metal within the cellular skeletons suggests the advantage of a stress-regulating strategy, which could also be meaningful for other conversion electrodes with volume fluctuation