Based on an innovative green recycling route for recycling and re-synthesis of spent lithium-ion batteries, LiCoO₂ was synthesized by a molten salt method with LiCl-KCl as a molten salt medium and LiOH·H₂O and Co₂O₃ as raw materials, and then the button batteries were prepared for resource recycling. The reaction kinetics of lithium cobalt oxide synthesis and the effect of reaction conditions on the structure and morphology of LiCoO₂ were investigated. The battery performance of LiCoO₂ was characterized by electrochemical analysis. The results show that the activation energies of the three endothermic reaction processes in the synthesis calculated by the Kissinger model are 34.212 00, 168.539 25 kJ/mol and 221.261 81 kJ/mol, respectively. The product of LiCoO₂ has a good hexagonal lattice structure when calcined at 750 ℃ for 6 h. The charge-discharge and cycle performance of the battery were tested at 0.2 C rate and 2.4-4.2 V. The experimental battery prepared by LiCoO₂ calcined at 750 ℃ for 6 h has the first charge-discharge specific capacity of 150 mA·h/g and 147 mA·h/g, the Coulombic efficiency is 98%, and the discharge specific capacity after 50 cycles of charge and discharge is still 129 mA·h/g. The battery still has a good charge and discharge performance after rate cycle.

All-solid-state lithium-ion batteries constructed with solid-state electrolytes have extremely high safety and reliability, which are an existing research hotspot in lithium-ion batteries. It is thus a great significance to develop inorganic-polymer composite solid electrolytes. In this paper, Li₇La₃Zr₂O₁₂ (LLZO) nano-powders were prepared by a sol-gel and ball milling method. Also, a solid-state composite polymer electrolyte with LLZO as an active filling material and polyethylene oxide (PEO) blended with polyethylene partial fluoride (PVDF) was prepared by a solution pouring method. The samples were characterized by field emission scanning electron microscopy and X-ray diffraction. The results show that LLZO/PEO/PVDF solid-state composite polymer electrolyte (SCE) membrane with 10% (in mass fraction) LLZO has a high ionic conductivity (8.93×10^-5 S/cm) and a stable electrochemical window (4.9 V). The rate capabilities and cycle performance of LiFePO₄/Li all-solid-state lithium battery with 10%LLZO both are improved. At 60 ℃, the capacity recovery rate is 99.4%, and the capacity retention rate after 100 cycles is 84.1% at 0.2 C.

Adding calcium silicate hydrate seed-polycarboxylate ether (C-S-Hs-PCE) to cement-based materials can effectively improve the early strength. C-S-Hs-PCE can provide nucleation sites for the formation of a hydration product C-S-H gel, effectively promoting the generation of the C-S-H gel, and accelerating the process of cement hydration. The acid-ether ratio is an important structural parameter of comb-type PCE molecules, having an impact on the synthesis and early strength enhancement of C-S-Hs-PCE. This paper investigated the effect of acid-ether ratio on the particle size of C-S-Hs-PCE and the early strength of cement-based materials by using dynamic light scattering (DLS) particle size analysis, total organic carbon analysis, X-ray diffraction, low-field time-domain nuclear magnetic resonance, scanning electronic microscopy, isothermal calorimetry, and compressive strength tests, respectively. The results show that the C-S-Hs-PCE formed at a high acid-ether ratio PCE has a smaller particle size, which is more conducive to promoting the hydration of the silicate phase and the generation of calcium hydroxide and C-S-H gel, thereby accelerating the hydration of the paste, reducing the total porosity of mortar, and improving the early compressive strength of mortar, especially within 24 h.

As electrode materials for supercapacitors, transition metal oxides have some advantages of high theoretical specific capacity, good chemical stability, and abundant sources. However, its inherent poor conductivity, low utilization rate, and poor cycle stability greatly hinder its practical application. Oxygen vacancies in metal oxides can effectively regulate their electronic properties, reduce the band gap, and increase their electrical conductivity, thus significantly improving their electrochemical rate performance. Furthermore, oxygen vacancies can induce a low oxidation state of the metal, provide more active sites for surface redox reactions, and improve its electrochemical storage capacity. The review introduced various preparation methods and characterization techniques of oxygen-vacancy abundant transition metal oxides. This review also represented the latest advances of various metal oxides with oxygen vacancies from single metal oxides, bimetal oxides, and heteroatom doped metal oxides to achieve the superior performance for supercapacitors. In addition, some challenges and opportunities for the further development of metal oxides in electrochemical energy storage were also pointed out.

Supercapacitors have a wide range of potential applications in new energy storage and electric cars due to their high capacity, high power density, and extended cycle life, and the electrode materials are a key to enhancing the supercapacitor performance. NiCoMnSe electrode materials were prepared by a simple low-temperature hydrothermal reaction method and a heat-treatment selenization method using ZIF-67 as a template. The optimum electrochemical performance was obtained via adding carbon nanotube (CNT) or graphene oxide (GO) to the ZIF-67 template. The results show that the optimum NiCoMnSe/CNT electrode has a specific capacitance of 624.0 F/g at 1 A/g and a multiplicative performance of 90.1% at 10 A/g. The capacity retention rate is 88% at 15 A/g for 1 000 cycles. This superior capacitive performance is attributed to the presence of CNT introducing additional mesopores around NiCoMnSe, thus enhancing the contact between the electrolyte and the active material. The NiCoMnSe/CNT/activated carbon device exhibits a high energy density (43.3 W·h/kg) at a power density of 800 W/kg and a good capacity retention (i.e., 91.4% after 1 000 cycles) due to the asymmetric nature of the supercapacitor.

As energy storage materials, transition metal phosphides have attracted recent attention. In this paper, FeP hollow nanorods were fabricated with hydrothermally synthesized MoO₃ nanofibers as a template. The chemical composition, morphological structure and synthetic process of such a product were characterized. Its supercapacitive properties as an electrode material were also investigated. The results show that the developed FeP hollow nanorods have a porous nature with the specific surface area (i.e., 277.4 m²/g) and well-defined interior of about 30 nm thick shell due to the stack, aggregation and adhesion of FeP nanoparticles. The FeP hollow nanorod electrode with a unique morphological structure and a large specific surface area has a superior supercapacitive behavior with the maximum specific capacitance of 243.6 F/g, remarkable rate capability as well as outstanding cycling stability. The capacitance decay of only 13.8% can be achieved after consecutive charge/discharge for 10 000 cycles at a large current density of 5 A/g. The electrochemical performance of FeP hollow nanorods is better than that of some Fe-based supercapacitor electrode materials previously reported.

The massive generation of concrete wastes occupies land resources and causes environmental pollutions. Recycling concrete wastes back to the construction industry can relieve pressures caused by shortages of natural resources, and solve some environmental problems. This review represented the research progress on the key technologies of re-utilizing recycled coarse aggregates (RCAs), recycled concrete fines (RCFs), and recycled concrete powders (RCPs), mainly including the strengthening and modification of RCAs and RCFs through accelerated carbonation, the direct re-activation of RCPs, and its value-added applications. The mechanisms and practical application both were discussed, and the results indicated that the full utilization of concrete wastes could reduce the consumption of river sand, natural gravels, limestone and clay and sequestrate CO₂, thus promoting the carbon neutrality.

To explore the potassium storage potentials of polymetallic selenides, nitrogen-doped carbon coated ZnSe/CoSe/SnSe materials was synthesized by a hydrothermal method. The core of polymetallic selenides exhibits an enhanced electrochemical activity, and a cavity in the structure alleviates the volume effect upon cycle when this compound serves as anode materials of potassium-ion batteries. Meanwhile, the conductive coating shell effectively improves the material conductivity and prevents the active substance from agglomeration during potassium storage. Compared with the uncoated material, ZnSe/CoSe/SnSe@nitrogen-doped carbon material has a better potassium storage performance. The discharge specific capacity still maintains 193 mA·h/g after 800 cycles at a current density of 1 A/g. This work could provide a guide for the design and construction of high-performance potassium ion battery anode materials.

This paper was to clarify the impact of coarse aggregate from printing to aging on 3D printed concrete. The mix design of 3D printed concrete containing coarse aggregate was conducted at a mass ratio of cement paste to aggregate (P/A) based on a continuous and discontinuous grading of coarse aggregate. The buildability, basic mechanical properties, and drying shrinkage properties were tested. The results show that the lower the P/A value is, the higher the maximum buildable height of 3D printed concrete containing coarse aggregate will be, improving the mechanical and drying shrinkage resistance. The excessive proportion of coarse aggregate with large particle sizes affects the constructability and mechanical properties but has a positive effect on reducing the drying shrinkage of concrete when using discontinuous coarse aggregate gradation. Also, the effectiveness of 3D printed concrete containing coarse aggregate in reducing carbon emissions during the production and manufacturing phase was investigated and compared with that of 3D printed mortar and conventional cast methods. Using coarse aggregate in 3D printing concrete technology can effectively reduce carbon emissions during the production stage of concrete raw materials, and it is still necessary to further reduce the use of cement materials. The advantages of 3D printing concrete technology in carbon reduction mainly depend on modeless construction and labor reduction characteristics. Compared to the conventional cast method, 3D printing concrete technology can reduce carbon emissions by 36.5% during production.

Carbon-based materials is considered as the most effective candidate for noble metal oxygen reduction reaction (ORR) catalysts. Among them, graphdiyne as a new type of carbon allotrope is composed by both sp and sp² hybrid carbon atoms and a two-dimensional network structure with a single atomic layer thickness. Therefore, graphdiyne-based materials exhibit a greater intrinsic electrochemical activity due to the inherent conductivity and stability. This review represented the latest progress and achievements on the synthesis of various graphdiyne-based materials and their composites used in the ORR catalysis, and analyzed the advantages of graphdiyne-based carbon materials in the oxygen reduction catalysis from the perspective of electronic structure and catalytic activity. In addition, the prospects and challenges of graphdiyne-based carbon materials in the ORR catalysis were also summarized, thus providing some future research aspects for the design and synthesis of high-quality graphdiyne-based inorganic nonmetal ORR catalysts.