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Tunnel projects in the southwestern mountainous area of China are in full swing. According to the tunnel burial depth, structural characteristics, and chemical erosion environments of the Lixiang railway tunnel, carbonaceous slate specimens obtained in the field were taken to experimentally investigate the physical, mechanical, and creep characteristics of the bedding's slate specimens after chemical erosion. The results of scanning electron microscopy (SEM) indicate that chemical erosion leads to internal damage in the carbonaceous slate specimens, and the internal damages are increasing with the increase of erosion days. Moreover, the specimens' ultrasonic test (UT) results prove that specimens with smaller bedding angles suffer a more serious erosion and induce more internal cracks. Under conventional triaxial compression conditions with 40 MPa of confining pressures, the conventional triaxial compressive strength (σs) decreases with the decrease of the bedding angle and the increase of erosion days, and the failure modes of the specimens are mainly controlled by oblique shear fractures and accompanied by the occurrence of slip dislocation fractures between the bedding inclination. Under creep conditions with 40 MPa of confining pressures, the final deformations of specimens are increasing with the increase of erosion days, which means the longer the erosion days, the greater the deformations. The failure modes of the specimens under creep conditions are controlled by shear fractures, and for the specimen with a 60° bedding angle and long-term erosion, there are block separations and many cavities along the shear planes. Therefore, more attention should be paid to prevent serious failure of the surrounding rock if the surrounding rock has a bedding angle of 60° or suffers long-term erosion. [ABSTRACT FROM AUTHOR]

Poisson's ratios of two-dimensional (2D) all-inorganic perovskites Cs2PbX4 (X = Cl, Br, I) have been calculated by the first-principles calculations. The contribution of each geometric parameter (bond length L , bond angle Φ , rotation angle 𝜃 1 , and tilt angle 𝜃 2 ) to Poisson's ratio is obtained analytically. Through a comprehensive analysis of the geometric deformations of the perovskite under the uniaxial strain, we find that Poisson's ratios of the perovskites are sensitive to the change of the bond length L and the bond angle Φ. In addition, the value of the bond angle Φ 0 in the strain-free structure mainly determines the high in-plane anisotropy of Poisson's ratios in Cs2PbX4. [ABSTRACT FROM AUTHOR]

Traditional approaches for monitoring human gait have severe spatial and temporal restrictions with complex analysis methods and high cost, which are powerless to promote the development of intelligent life involving fitness, sport training, and healthcare. Herein, a portable smart insole system with high spatial resolution and simple manufacturing process to measure plantar pressure distribution anytime, anywhere for gait analysis is proposed. An insole‐shaped array of 104 piezoresistive sensors with highly robust characteristics is assembled, exhibiting a good pressure‐sensing uniformity. The smart insole not only detects the subtle displacement of the center of gravity of the body, but also exhibits a real‐time, high‐resolution thermodynamic diagram of the plantar pressure distribution during human activities. More importantly, the function of motion intelligence identification can be realized by regionalizing and digitizing the whole plantar pressure distribution, achieving an average recognition accuracy of 83.32% among six predefined motions. These results imply that the carbon fiber‐based smart insole can provide an effective approach for convenient gait analysis and motion identification, which has a great potential in the application of future intelligent life. [ABSTRACT FROM AUTHOR]

Oxygen loss is a serious problem of lithium‐rich layered oxide (LLO) cathodes, as the high capacity of LLO relies on reversible oxygen redox. Oxygen release can occur at the surface leading to the formation of spinel or rock salt structures. Also, the lattice oxygen will usually become unstable after long cycling, which remains a major roadblock in the application of LLO. Here, it is shown that Zr doping is an effective strategy to retain lattice oxygen in LLO due to the high affinity between Zr and O. A simple sol‐gel method is used to dope Zr4+ into the LLOs to adjust the local electronic structure and inhibit the diffusion of oxygen anions to the surface during cycling. Compared with untreated LLOs, LLO–Zr cathodes exhibit a higher cycling stability, with 94% capacity retention after 100 cycles at 0.4 C, up to 223 mAh g−1 at 1 C, and 88% capacity retention after 300 cycles. Theoretical calculations show that due to the strong Zr–O covalent bonding, the formation energy of oxygen vacancies has effectively increased and the loss of lattice oxygen under high voltage can be suppressed. This study provides a simple method for developing high‐capacity and cyclability Li‐rich cathode materials for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

The degradation of Li‐ and Mn‐rich (LMR) cathodes primarily results from the thermodynamic instability of lattice oxygen and the resulting oxygen release. This is promoted by localized lattice strain, which develops dynamically during electrochemical reactions involving repeated Li‐ion intercalation and extraction. However, the role of chemomechanical strain in degrading lattice oxygen's stability is not yet well‐understood. Here, the research indicates that uneven strain distribution causes bending, resulting in lower activation energy for oxygen vacancy creation and injection into particle interiors at bending points. Combining in situ transmission electron microscopy and theoretical simulations, it is shown that the largest O─O interaction occurs at the maximum curvature point, reducing Mn─O bonding strength, promoting oxygen dimer formation, and eventually initiating oxygen release from LMR. As a result, a process is designed to adjust the Li‐content and the distribution of the two‐phase structure, achieving better cycling stability in LMR cathodes with a more balanced distribution of strain. These results provide insights into enhancing LMR cycling stability while utilizing their high capacity. [ABSTRACT FROM AUTHOR]

To decrease the contaminant leaching and radon exhalation from uranium tailings, a phosphoric acid-based geopolymer (PAG) precursor was selected as a solidifying agent to bind coarse sands to achieve compact structures. Machine learning was applied to explore the optimal ratio of geopolymer preparation, aimed at achieving a higher compressive strength of solidified bodies. Results showed that the maximum compressive strength of 18.964 MPa appeared at the mass ratio of 2.8 for phosphoric acid/kaolin. The uranium leaching rate of 0.70 × 10−6 cm/d on the 42nd day was three orders of magnitude less than the clay mixture-based geopolymer solidified bodies. The successful synthesis of geopolymer was evidenced by the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), the homogeneous and dense structure of solidified bodies was characterized by the scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides are promising cathode materials for lithium-ion batteries due to their high reversible capacities (more than 250 mAh g−1). Nevertheless, in operation, the oxygen lattice would be transformed into O 2 gas with phase transformation. Thus, to suppress O 2 gas, it is necessary to pre-generate the oxygen vacancies in the surface of materials. Herein, for facile and scalable pre-generation of oxygen vacancies, pristine Li 2 MnO 3 ·LiNi 1/3 Co 1/3 Mn 1/3 O 2 oxide (PLR-NCM) is treated directly by CO 2 gas just at the room temperature. The modified material (MLR-NCM), with rich oxygen vacancies in the surface and no obvious structural change inside, shows a discharge capacity of 321 mAh g−1 based on half-cells at 55 °C and 0.1 C (1.0 C = 250 mA g−1), and 240 mAh g−1 as full cells at the room temperature. In addition, it also exhibits high cycling and rate performance owing to the significantly improved lithium ion and electron diffusion efficiencies. Importantly, by real-time monitoring of structural evolution using in situ XRD technique, we find that the O 2 gas release of the modified material is successfully suppressed. This facile method proposed in our work provides a new strategy for greatly improving the performance of lithium-ion batteries. Image 1 • Modified Li-rich layered materials (MLR-NCM) with rich oxygen vacancies are prepared. • Oxygen vacancies in MLR-NCM are formed by facile and scalable direct CO 2 treatments. • MLR-NCM show high Li-storage capacity, cycling and rate performances. • In situ XRD technique is used to confirm that oxygen vacancies suppress O 2 release. • Full cells with MLR-NCM perform excellent Li-storage performance at room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D Janus face graphene (JFG) substrate is prepared in large scale by facile process. • Distinct Janus face comes from different aperture size and N-doping on both sides. • Dendrite growth is suppressed when lithiophilic layer is as Li deposition interface. • Li@JFG composite anode achieves efficient Li electro-plating/stripping. • Li@JFG anode has high coulomb efficiency, small polarization and stable cycle. The dendrite growth and irreversibility of lithium (Li) metal anode seriously hinders the wide-scale application of high-energy–density rechargeable batteries. Here, we report a thin Janus-faced graphene substrate, consisting of lithiophilic-lithiophobic faces separately, for Li plating/stripping. The visualized analysis demonstrates that the unique Janus-faced graphene structure provides different lithiophilic sites and pore channels to steer the Li electrodeposition and suppress the dendrite growth. As expected, the Janus-faced graphene anode achieves long-term Li plating/stripping with high Coulombic efficiency, small polarization and stable cycling throughout the symmetry, asymmetry and LiFePO 4 full cells. Such an encouraging strategy for reversible Li plating/stripping provides a promising way to design long-life carbon-base anode materials for Li metal batteries. [ABSTRACT FROM AUTHOR]

Owing to the high theoretical specific capacity, transition metal selenides (TMSs) have emerged as promising anode materials for lithium-ion batteries (LIBs). However, the application of TMSs still confronts fast capacity decay and sluggish reaction kinetics associated to their inherent poor conductivity and huge volume expansion during lithiation-delithiation cycles. Herein, the fine ZnSe nanoparticles are implanted into N-doped porous carbon nanosheets through synchronous pyrolysis/selenization of a leaf-like zeolitic imidazolate framework mixed with selenium powder. The highly dispersed fine ZnSe nanoparticles (NPs) coupled with conductive porous carbon nanosheets (denoted as ZnSe/NC) endow the resultant composite with superior structural merits for facilitating electron/ion transfer, thus alleviating the volume fluctuation. The systematic electrochemical investigation illustrates that the as-prepared ZnSe/NC-700 electrode can obtain a high reversible capacity (426.5 mAh g−1 at 1 A g−1 after 1000 cycles), excellent cycling stability (368.9 mAh g−1 after 1800 cycles at 2 A g−1) and nearly 100％ columbic efficiency. In all, our strategy provides a new idea for synthesis of unique anode materials in LIBs. [Display omitted] • The fine ZnSe nanoparticles/N-doped porous carbon nanosheets (ZnSe/NC-700) are synthesized. • The ZnSe/NC-700 can be obtained through synchronous pyrolysis/selenization. • The ZnSe/NC-700 delivers a high reversible capacity and excellent cycling stability. • Kinetics analysis verifies the pseudocapacitive behavior of the ZnSe/NC-700. [ABSTRACT FROM AUTHOR]

Doping is a very effective way to optimize the electrochemical performance of electrodes by tuning the electron configurations on an atomic scale. Here, to obtain excellent Co 3 O 4 electrodes for lithium ion storage, a meaningful defect-engineering of carbon-doping Co 3 O 4 microrods strongly coupling with nitrogen-doped carbon (C–Co 3 O 4 @N–C) is designed and validated. Compared with unmodified Co 3 O 4 microrods, the defect-rich C–Co 3 O 4 @N–C microrod electrode features a remarkably high initial Coulombic efficiency of 84.5% and specific capacity of 1130 mAh g−1 at 0.2 A g−1, excellent cycling stability (1265 and 1036 mAh g−1 capacity retention after 110 and 500 cycles at 0.2 A g−1 and 1 A g−1, respectively) and superior rate capacity (452 mAh g−1 capacity retention after 3000 cycles at 5 A g−1). These results demonstrate that introducing rich defects by carbon dopants and nitrogen-doping carbon can effectively modulate the electron structure and accelerate the carrier transport of materials. This valid stratagem greatly elevates lithium-ion battery performance and can be further extended to other transition metal oxides and fields. Image 1 • Carbon doping effectively tunes electron configurations of Co 3 O 4 , improving electron conductivity. • Unique microrod structures can self-adapt to volume expansion during cycles. • Ultralow nitrogen-doped carbon accelerates carrier diffusion of Co 3 O 4 electrodes. • Coupling nitrogen-doped carbon with carbon doped Co 3 O 4 features high Li-storage properties. [ABSTRACT FROM AUTHOR]