Investigation of cobalt-free lithium-rich layered oxide cathodes for high-performance lithium-ion batteries

Li-rich layered oxides (LLOs) are considered as one of the most promising cathode candidates for next-generation lithium-ion batteries. Unfortunately, their development is challenging, due to the detrimental structure changes and voltage decay that resulted from irreversible oxygen redox and transition metal (TM) migration. This thesis focuses on studying the structural evolution of Co-free LLO cathodes and improving their electrochemical performance. The mechanistic behaviour of Li1.2Ni0.2Mn0.6O2 (LNMO) was comprehensively studied using a series of synchrotron-based characterizations. An intrinsic mechanistic behaviour transition from the monoclinic (C2/c) to the hexagonal (R3̅m) was demonstrated for the first time. Based on this understanding, electrochemically active 4d metal Ruthenium (Ru) was introduced into both R3̅m and C2/c components in LNMO to improve the stability of LNMO. With 3 w.t. % Ru doping, the oxygen lattice is strengthened and the best voltage retention (\u3c 0.45 mV per cycle) is achieved for Co-free LNMO with a high reversible capacity (215 mAh g-1 at 1C). To improve the cycling stability of LLOs, the inhibition of the irreversible TM migration needs also to be considered. A two-phase reaction was revealed in the heavily cycled LNMO, resulting from the accumulative irreversible transition-metal migration and loss. Chromium (Cr) doping was proposed to inhibit the formation of undesirable structural changes, by achieving reversible tetrahedral-octahedral TM migration. It was demonstrated that the oxidated Cr occupies the tetrahedral sites in the Li layer at the high delithiated state, which prevents TM ions from being trapped in the Li layers at the highly delithiated state and stabilizes the structure against cycling. It migrates back to the octahedral sites after lithiation due to energetical benefits. Compared with pristine LNMO, Cr-doped LNMO shows significantly enhanced structural stability with capacity retention up to 99% after 200 cycles at 1C and 71% after 500 long cycles, far surpassing pristine LNMO

Graphene Aerogel-Supported Silicon@Carbon Hybrids with Double Buffering Structure as Anode for Lithium-Ion Battery

Graphene aerogel-supported silicon@carbon (SCG) hybrids with a double buffering structure were prepared via self-assembly and a solvothermal method. Nano-silicon (Si) particles coated with amorphous carbon were uniformly distributed on the surface of graphene. The amorphous carbon transformed from chitosan acted as a bridge to connect Si particles with graphene. The hierarchical structure of the resulting hybrids with multipores not only provided secondary cushions for the expansion of active Si during the charge/discharge process but also created fast access channels for the transmission of Li+. The SCG hybrid exhibited an excellent initial charge capacity of 1298.6 mAh g(-1) and remained at 899.6 mAh g(-1) after 100 cycles at 200 mA g(-1). It also showed a remaining capacity of 737.6 mAh g(-1) at 500 mA g(-1) after 200 cycles. The capacity could reach up to 551.1 mAh g(-1) at a high current density of 2000 mA g(-1). These results suggest that the double buffer and porous structure can solve the problem of volume expansion of Si in Si-based hybrids, thus rendering them suitable for various applications

Synthesis of SiOx/C composite with dual interface as Li-ion battery anode material

A dual interface SiOx/C composite is prepared through a novel, facial, one-step route by redox reaction of organic carbon with silica precursor, using tetraethyl orthosilicate (TEOS) and sucrose as raw material, in which sucrose acts as both a reductant and coated carbon. HRTEM indicates that the composite has a dual interface structure with carbon coating layer and intermediate layer. Crystalline Si approximately 3 nm-20 nm in size is dispersed in amorphous silicon oxide matrix. The SiOx/C is utilized in LIB as anode material and exhibits a high reversible specific capacity of 755 mA h ga(-1) after 300 cycles at 100 mA ga(-1) with capacity retention about 91%. Such outstanding cycling stability can be ascribed to the intermediate layer and carbon scaffold, which serve as a buffering to relieve volume change of produced Si upon cycles. (C) 2019 Published by Elsevier B.V

Interpenetrated 3D porous silicon as high stable anode material for Li-Ion battery

Confronting issues of silicon-based anode for its huge volume change (similar to 320%), porous silicon attracts note-worthy attention. Most previous studies are concentrated on designing various sacrificial templates to endow silicon with marvelous shapes or structures. Herein, without the assistance of sacrificial template, a template-free method is developed to fabricate interpenetrated three-dimensional porous silicon. A silica composite gel, which possesses numerous nano-pores, is primarily constructed, and the silicon can be inherently equipped with these nano-pores via modified magnesiothermic reduction. Scanning electron microscope and transmission electron microscope images illustrate that the as-prepared porous silicon possesses bi-continuous structure. It also exhibits high initial reversible capacity (similar to 1.41 mAh cm(-2) at 0.16 mA cm(-2)), superior cycling stability (similar to 0.98 mAh cm(-2) after 200 cycles), and good rate performance. In addition, analysis of cyclic voltammetry curves and electrochemical impedance spectroscopy demonstrate that this porous silicon possesses appropriate channels for rapid Li(+ )transport and low electrochemical reaction polarization resistance

Impact of Forest City Selection on Green Total Factor Productivity in China under the Background of Sustainable Development

In the critical period of strengthening the construction of ecological civilization, the construction of forest cities has become an important measure to promote urban ecosystem restoration and achieve sustainable development. Based on the mechanism of forest city promoting green development, the construction of a national forest city is regarded as a “quasi-natural experiment”. Using China’s urban panel data from 2005 to 2019, the impact of national forest city construction on urban green total factor productivity was evaluated using Multistage asymptotic double difference. The results show that National Forest Cities with environmental regulation can significantly promote regional green total factor productivity, which is still valid after a series of Robustness tests. Mechanism analysis shows that forest city construction not only affects territorial spatial planning but also forms a linkage with green technology innovation, mutual promotion and mutual promotion to jointly promote the sustainable development goals. This paper argues that building a national forest city is an important measure to achieve China’s sustainable development goals in the new era, but in the process of policy implementation, it is necessary to implement the national forest city selection system according to local conditions

Experimental and Theoretical Study on the Fatigue Crack Propagation in Stud Shear Connectors

Steel-concrete composite girder bridges are subjected to reciprocal cyclic loading from vehicles, and the stud shear connectors are the key components for transmitting shear forces. Thus, it is necessary to study the fatigue performance of the stud shear connectors. At present, there are few studies on the fatigue crack propagation process of studs, and the variation curve of the crack depth of studs with the number of fatigue loading cycles is not clear. In this study, the degradation law of fatigue properties and the fatigue crack propagation law of stud shear connectors in steel-concrete composite structures are examined under fatigue loading. The fatigue properties, i.e., failure mode, the dynamic slip-fatigue number curve, cross-sectional characteristics, and the residual bearing capacity of the stud specimens, are first systematically studied through ten standard push-out specimen tests. The test results show that the relative value of the fatigue crack extension area increases, while the relative value of the residual bearing capacity of the studs decreases approximately linearly. Then, the expression of the relationship between the fatigue crack depth and the residual load-bearing capacity of the stud is proposed, based on the fatigue crack theory of fracture mechanics. Finally, combined with the ABAQUS and FRANC3D software, a fatigue crack propagation finite element analysis (FEA) model of the stud is established. The FEA results showed that the trends in the number of cyclic loads and the fatigue crack depth of studs are basically the same for the simulation curve, test curve and theoretical calculation curve

An all-in-one sodium-ion thin-film battery with stretchable and self-chargeable functions for wearable electronics

Stretchable batteries suggest promising potential for the energy supply of wearable electronics. However, they always need to be replaced or wired for charging, interfering the continuous work of wearable electronics. Besides, deviation or delamination between the inner components under repeated deformations are also bottlenecks need to be addressed. Herein, a novel all-in-one thin-film sodium-ion battery (AFSIB) with stretchable and self-chargeable functions was designed by a simple electrospinning route. In the AFSIB, two stretchable symmetric electrode films are attached on each surface of a stretchable piezo-electrolyte film, and there is a strong interaction between the films via the close connection of fibers at the interface. When suffered from an external force, the stretchable piezo-electrolyte film can act as a nanogenerator and provide an internal potential to drive the migration of Na+ ions for electrochemical reaction and energy storage, enabling the formation of self-charging capability of AFSIB. Besides, the strong interaction between the films enables the achievement of stable “All-in-One” structure of AFSIB, which can accommodate the damages comes from repeated deformations. This work paves a new approach for developing stretchable and self-chargeable energy devices for the continuous and stable energy supply of wearable electronics

Resveratrol Induces Autophagy and Apoptosis in Non-Small-Cell Lung Cancer Cells by Activating the NGFR-AMPK-mTOR Pathway

Resveratrol (RSV) has been reported to induce autophagy and apoptosis in non-small-cell lung cancer A549 cells, and the nerve growth factor receptor (NGFR) regulates autophagy and apoptosis in many other cells. However, the effect of NGFR on autophagy and apoptosis induced by RSV in A549 cells remains unclear. Here, we found that RSV reduced the cell survival rate in time- and concentration-dependent manners, activating autophagy and apoptosis. Lethal autophagy was triggered by RSV higher than 55 μM. The relationship between autophagy and apoptosis depended on the type of autophagy. Specifically, mutual promotion was observed between apoptosis and lethal autophagy. Conversely, cytoprotective autophagy facilitated apoptosis but was unaffected by apoptosis. RSV enhanced NGFR by increasing mRNA expression and prolonging the lifespan of NGFR mRNA and proteins. RSV antagonized the enhanced autophagy and apoptosis caused by NGFR knockdown. As the downstream pathway of NGFR, AMPK-mTOR played a positive role in RSV-induced autophagy and apoptosis. Overall, RSV-induced autophagy and apoptosis in A549 cells are regulated by the NGFR-AMPK-mTOR signaling pathway

O3-Type Cathodes for Sodium-Ion Batteries: Recent Advancements and Future Perspectives

Over recent decades, rapid advancements in energy technology have transformed human life. Lithium-ion batteries (LIBs) have played a pivotal role nevertheless concerns about limited lithium resources and price fluctuations underscore the need for sustainability. Sodium-ion batteries (SIBs), operating on principles akin to LIBs, have emerged as promising candidates for rechargeable batteries in the next generation of energy storage systems, primarily due to their cost-effectiveness and sustainable attributes. Analogous to LIBs, the cathode in SIBs assumes a critical role in dictating the electrochemical performance of the battery. Therefore, the research and development of cathode materials for SIBs take on paramount significance. O3-type SIB cathodes, inspired by the successful O3-type LIB cathodes (e. g., LiCoO2 and NMC variants), hold promise for commercial applications. This comprehensive overview offers an in-depth exploration of various unary-metal oxide cathode materials characterized by an O3-layered structure. Subsequently, nickel (Ni), manganese (Mn), and Ni/Mn-based O3 cathode materials are conducted a comprehensive study, assessing the effects of element substitution and doping on capacity, phase transitions, and cycle life. In light of the current challenges, advancing SIB cathode materials of future directions will propose, addressing key considerations in the pursuit of enhanced performance and sustainable energy storage solutions

Synergistic Effects of Phase Transition and Electron-Spin Regulation on the Electrocatalysis Performance of Ternary Nitride

Transition metal nitrides (TMNs) have great potential use in energy storage and conversion owing to tunable electronic and bonding characteristics. Novel iron rich nitrides nanoparticles anchored on the N-doped porous carbon, named as (CoxFe1–x)3N@NPC (0 ≤ x \u3c 0.5) are designed here. The synergistic effects of phase transition and electron-spin regulation on oxygen electrocatalysis are testified. A core–shell structure of (CoxFe1–x)3N with high dispersibility is induced by an intermediate phase transition process, which significantly suppresses coarsening of the metallic nitrides. The Co incorporation regulates d-band electrons spin polarization. The t2g5eg1 of FeII with the ideal eg electron filling boosts intrinsic activity. (Co0.17Fe0.83)3N@NPC with optimal cobalt content holds electronic configuration with moderate eg electron filling (t2g5eg1), which balances the adsorption of *O2 and the hydrogenation of *OH, improving bifunctional catalytic performances. Both liquid and solid-state zinc–air batteries assembled based (Co0.17Fe0.83)3N@NPC cathodes substantially deliver higher peak power density and remarkable energy density