Functional Materials Letters

Among the electrolytes designed for all solid-state batteries, the phosphosulfide electrolytes stand out with respect to their very high Li-ion conductivities. However, when in contact with metallic lithium anodes, there are remaining challenges to ensure long-term operation stability. Both issues, the Li-ion conductivity and the electrochemical stability vs. metallic lithium, are the subject of this review. After introducing the background for developing all solid-state Li-ion batteries with metallic lithium anode and providing a brief overview on four types of phosphosulfide electrolytes, in Part I of the review a compound treatment on the Li–P–S and the LiSICon type electrolytes had been given. Part II of the review will continue following the same schedule by discussing the chemistry, structure, processing and Li-ion conductivity of the LGPS and the Argyrodite-type phosphosulfides. Emphasis is put on the treatise of the chemistries supported by the consideration of specific phase diagrams and intra-type comparisons of the Li-ion conductivities at ambient temperature. In a summarizing section, inter-type comparisons among selected compositions of the Li–P–S type, the LiSICon-type, the LGPS-type and the Argyrodite-type phosphosulfides are addressed for the two main issues for electrolytes in all solid-state batteries, the Li-ion conductivities and the electrochemical stability vs. metallic lithium. The review is concluded with remarks on the status and the perspectives of the research on Li-ion conducting phosphosulfide electrolytes.

This work describes the synthesis, analysis, and testing of the novel type of La/graphene composites as potential contrasting agents (CAs) for photon-counting computed tomography (PCCT). The impregnation of oxidized graphene nanoflakes (GNFs) with Lanthanum nitrate solution resulted in uniform distribution of La-containing particles on the flake surface with particle size of about 2–3 nm. La was confirmed to be a suitable contrasting element for PCCT that could be visualized in reference phantom media and in the presence of other CAs. Minimum concentration of La in the composites determined by PCCT was in the range of 2.5–5 mg⋅ml${}^{-1}$.

With the large-scale application and development of lithium-ion batteries, the extraction of lithium resources from salt lake brine has gradually become a global focus. Lithium titanium oxides (LTO)-type lithium ion-sieve (LIS) has attracted much attention due to its stable structure, high adsorption capacity, excellent recycling capacity, and environmental protection. In this review, we focused on the structure and adsorption mechanism of titanium-based ion sieves, and the preparation methods of different titanium oxide precursors. Furthermore, three modification methods including ion doping, morphology control, and surface coating were summarized. Finally, the insufficiency problem of current research is proposed, and the improvement and application of titanium-based LIS are prospected.

The self-supported nanoflake-shaped Bi₂Se₂ was synthesized with the convenient method of microwave reaction, and adhered to the flexible carbon fiber felt. A series of electrochemical tests indicate that capacitance of Bi₂Se₂/CF electrode can reach 877.0 C g${}^{-1}$ (1 A g${}^{-1}$). Assembled by ligninbased carbon materials and Bi₂Se₂/CF electrode, the asymmetric capacitor has the energy density of 20.83 W h Kg${}^{-1}$ while the power density can reach 749.9 W kg${}^{-1}$. After circulating for 2000 times under 3 A g${}^{-1}$, the remaining capacitance retention reaches 81% of the initial one.

NASICON-type Li${}_{1+x}$Al${}_x$Ti${}_{2-x}$(PO₄)₃ (LATP) solid electrolyte features low cost of raw materials, high stability against O₂/H₂O, high ionic conductivity and high compatibility with cathode. Despite these merits, the direct contact of Li with LATP would trigger the reduction of Ti${}^{4+}$ into Ti${}^{3+}$, and thereupon decrease ion conductivity and enhance electron conductivity, thus limiting its application. In this work, the garnet Li${}_{6.5}$La₃Zr${}_{1.5}$Ta${}_{0.5}$O${}_{12}$ (LLZTO) particles were chosen to disperse in NASICON-type Li${}_{1.3}$Al${}_{0.3}$Ti${}_{1.7}$(PO₄)₃ matrix in order to strengthen stability against Li metal. During sintering, the matrix/particle reaction occurs, where LLZTO reacts with LATP, inducing the formation of LaPO₄ particles. By optimization of LLZTO content, an enhanced ionic conductivity of 1.03 × 10${}^{-3}$S cm${}^{-1}$ can be harvested. Moreover, introducing LLZTO particles into LATP matrix can slow down the degradation of the electrolyte to a certain extent and provide better interfacial stability of symmetrical battery than pure LATP solid electrolyte.

Co₂FeGa Heusler alloy nanowires with diameters of about 30, 60 and 110 nm were prepared using a template-assisted electrochemical deposition method. We observe the different angular dependences of coercivity and remanence ratio for these samples. Magneto-transport measurements show that the 30 nm diameter Co₂FeGa nanowires has a large magnetoresistance up to −56%, which is much higher than 60 and 110 nm diameter Co₂FeGa nanowires. This is the first time that the magnetoresistance properties of Co₂FeGa nanowires were presented.

Lignin-based carbon nanomaterials (LCN) were prepared from alkaline lignin (AL) by hydrolysis, spray drying and high temperature treatment. Then, the physical and chemical structures of LCN were analyzed by SEM, BET, organic element analyzer, FTIR, Raman, UV–vis and XPS. The results showed that the yield of LCN was 26.34% of the mass of AL. The particle size of LCN was 120–350 nm, and three to seven particles with diameter of 40–100 nm are accumulated. Its specific surface area was 374.74 m²/g with the average pore size of 4.79 nm. The ratio of sp² to sp³ was 1.39 and the band gap was 3.42 eV. The simplified apparent formula of LCN was C${}_{21}$H₄O with an unsaturation of 20, containing C–C, C=C, C–O, O=C–O and C–H groups. The chemical structure model of LCN was constructed by Chem 3D software. Therefore, this study successfully prepared a special material and analyzed its physical and chemical structure, which was conducive to the structural analysis of carbon nano-materials.

In this paper, the oxidation mechanism of carbon monoxide (CO) on two-dimensional porphyrin sheet within a single cobalt atom (Co-TDPs) was studied by density functional theory with dispersion (DFT-D). The stability of Co-TDPs at different temperatures was verified by first-principle molecular dynamics simulations. Absorption energies of reactant and product to anchor to the Co–N₄ site showed CO and O₂ adsorption to be stronger than the CO₂ adsorption. In addition, the Langmuir–Hinshelwood, Eley–Rideal (ER), and ter-molecular Eley–Rideal (TER) mechanisms were used to investigate the reaction mechanisms of CO oxidation on Co-TDPs. The Langmuir–Hinshelwood (LH) and ER mechanisms were feasible reaction profiles of CO oxidation because of their smaller energy barrier. The results suggested that the Co-TDPS was acting as a catalyst for CO oxidation in the mild condition.

In this work, first-principles calculations of Sr₃MgSi₂O₈ with Eu${}^{2+}$, Ca${}^{2+}$ and Ba${}^{2+}$ dopants have been performed. These results reveal that the Eu${}^{2+}$ ions prefer to substitute the Sr${}^{2+}$ in 8f site. In addition, Ca${}^{2+}$ and Ba${}^{2+}$ have been introduced into the crystal structure to generate complex cation environments in Sr₃MgSi₂O₈. Through the analysis of the crystal structure and electronic band structure, it can be found that the lattice size, band gap value along with the density of states of Sr₃MgSi₂O₈ could be changed and the coordination environments around the Eu${}^{2+}$ could be modulated through the Ca${}^{2+}$ or Ba${}^{2+}$ substituting for Sr${}^{2+}$. The Ca${}^{2+}$ doping would induce decreased crystal structure and band gap value between the VB and CB. Meanwhile, the Ba${}^{2+}$ doping would induce enlarged crystal structure and band gap value between the VB and CB. Especially, the bond length range of Eu${}^{2+}$ and O${}^{2-}$ could be expanded through the doping of Ca${}^{2+}$ or Ba${}^{2+}$. In summary, it can be concluded that the doped Ca${}^{2+}$ and Ba${}^{2+}$ in Sr₃MgSi₂O₈ could successfully modulate the coordination environment around the Eu${}^{2+}$ and thus lead to multiple light emissions of Eu${}^{2+}$.

Shape memory polymer (SMP) has drawn much attention in the fields of aerospace, microsystems and biomedicine as a typical smart material with unique shape memory properties. The porous SMPs (P-SMPs) have been manufactured for the applications of reduce noise and insulate thermal. A constitutive model of P-SMPs that proposed based on phase transition theory has been investigated in this work. First, combining Mori–Tanaka method and phase transition theory, a modified micromechanics constitutive model of P-SMPs has been presented to describe the thermal-mechanical behavior of P-SMPs. Then, a series of experiments including uniaxial tension, stress relaxation and thermal cycling test have been conducted to determine the parameters of the modified constitutive model. Finally, the correctness of the proposed constitutive model has been verified by comparing the results of the thermodynamic cycle process including heating recovery and cooling loading stages obtained by the numerical simulation results and thermodynamic cycle experiment. The results show that with a porosity f = 0.1, the strain and stress mean square errors of the constitutive model based on the phase transition theory are 0.22 and 0.0102, respectively, which means that the constitutive model proposed based on phase transition theory can reflect the shape memory properties of P-SMP materials.

The inactivation ability of SARS-CoV-2 (COVID-19) was examined using two types of transparent Cu₂O thin films with different crystallinities on a Na-free glass substrate. The low-crystallinity Cu₂O thin film, which was fabricated by irradiating 254 nm ultraviolet (UV)-light with an intensity of 6.72 mW cm${}^{-2}$ onto a spin-coated precursor film involving Cu${}^{2+}$ complexes at room temperature, exhibited an outstanding COVID-19 inactivation ability to reduce 99.999% of the virus after 1 h of incubation. The X-ray diffraction results of the UV-irradiated thin film indicated a cubic Cu₂O lattice with a small crystallite size of 2 ± 1 nm. Conversely, the high-crystallinity Cu₂O thin film with a crystallite size of 16 ± 3 nm, obtained by heating a spin-coated precursor film containing another Cu${}^{2+}$ complex, showed a negligibly low inactivation activity at the same level as the Na-free glass substrate. The eluted concentrations of Cu ions from both Cu₂O thin films were analyzed after immersion in Dulbecco’s modified Eagle’s medium (DMEM) for 0.25–2 h. The eluted Cu–ion concentration of 1.16 ppm was observed for the UV-irradiated thin film by DMEM immersion after 1 h, but that of 0.04 ppm was observed for the heat-treated thin film. This indicated that an important factor of virus inactivation on Cu₂O thin films is highly related to the elution of Cu ions that occurred from the surface in the medium.

SrTiO₃ is a high temperature thermoelectric material with calcium titanite structure that is environmentally friendly and affordable, but the high thermal conductivity at high temperatures limits its development, so how to maintain high electrical properties while reducing thermal conductivity is the most important problem facing SrTiO₃. SiGe and SrTiO₃ are both thermoelectric materials in the intermediate and high temperature region and have a lot of commonalities, and it is likely to obtain high thermoelectric properties through the interfacial effect of both, however, there is not any study on the compound regulation of the two. Therefore, in this study, phosphorus (P)-doped SiGe was compounded with Zr, La and Nb co-doped SrTiO₃. 3 mol.%SiGe(C)/97 mol.% Sr${}_{0.9}$La${}_{0.1}$Ti${}_{0.89}$Zr${}_{0.01}$Nb${}_{0.1}$O₃(Zr₁Si₃(C)) obtained by sintering under carbon reducing atmosphere shows a relatively large power factor of and low thermal conductivity of 2.88 Wm${}^{-1}$K${}^{-1}$ at 1000 K, achieve a ZT value to 0.42 at 1000 K. This is at a high level in this study of SrTiO₃ composite thermoelectric materials and provides a new idea for the subsequent study of composite modulation.

Lithium-rich oxide cathode material focuses the attention of many researchers due to its excellent electrochemical performance for lithium–ion batteries. Further improvement on the performance with a strong operability approach can be beneficial to its industrialization and commercialization. In this work, the effect of powder compaction pressure in sintering process on the electrochemical performance of Li${}_{1.2}$Mn${}_{0.54}$Ni${}_{0.13}$Co${}_{0.13}$O₂ cathode material is investigated. Four cathode materials under different powder compaction pressure are synthesized by sol–gel method. The XRD analysis results reveal their consistency on the crystal structure. But there is a slight difference on particle size and microstructure found by SEM analysis. Electrochemical tests show that a cathode material under medium compaction pressure exhibits the best performance with a discharge capacity of 170.3 mAh⋅g${}^{-1}$ at the rate of 200 mA⋅g${}^{-1}$ with 89.35% retention after 100 cycles. This work reveals that the powder compaction pressure does have influence on the cycle and rate performance and this relation is not proportional and linear.

In this paper, the nonmetallic Si${}^{4+}$-doped modified lanthanum aluminate (LaAlO₃) solid electrolyte for the first time, which has particular scientific significance, and LaAl${}_{1-}$${}_x$Si${}_x$O${}_{3-}$${}_{\delta }$ material was successfully prepared by the sol–gel method. LaAl${{}_{1-}}_x$Si${}_x$O${{}_{3-}}_{\delta }$ is a ceramic material sintered at 1100${}^{\circ }$C for 2 h in an air atmosphere. The surface microstructure and electrochemical properties of the samples were tested by multiple characterization methods. The results show that the LaAl${{}_{1-}}_x$Si${}_x$O${{}_{3-}}_{\delta }$ has good sintering activity, high crystallinity, and a grain radius of approximately 25 nm. At 800${}^{\circ }$C, the ionic conductivity is above 1.05E− 04 S⋅cm${}^{-1}$ and the activation energy is lower than 1.19 eV.