RESUMEN
The suboptimal ionic conductivity of commercial polyolefin separators exacerbates uncontrolled lithium dendrite formation, deteriorating lithium metal battery performance and posing safety hazards. To address this challenge, a novel organic-inorganic composite separator designed is prepared to enhance ion transport and effectively suppress dendrite growth. This separator features a thermally stable, highly porous poly(m-phenylene isophthalamide) (PMIA) electrospun membrane, coated with ultralong hydroxyapatite (HAP) nanowires that promote "ion flow redistribution." The synergistic effects of the nitrogen atoms in PMIA and the hydroxyl groups in HAP hinder anion transport while facilitating efficient Li+ conduction. Meanwhile, the optimized unilateral pore structure ensures uniform ion transport. These results show that the 19 µm-thick HAP/PMIA composite separator achieves remarkable ionic conductivity (0.68 mS cm-1) and a high lithium-ion transference number (0.51). Lithium symmetric cells using HAP/PMIA separators exhibit a lifespan exceeding 1000 h with low polarization, significantly outperforming commercial polypropylene separators. Furthermore, this separator enables LiFePO4||Li cells to achieve an enhanced retention of 97.3% after 200 cycles at 1 C and demonstrates impressive rate capability with a discharge capacity of 72.7 mAh g-1 at 15 C.
RESUMEN
High-energy-density lithium-ion batteries (LIBs) with high safety have long been pursued for extending the cruise range of electric vehicles. Owing to the high gravimetric capacity, silicon is a promising alternative to the convention graphite anode for high-energy LIBs. However, it suffers from intrinsic poor interfacial stability with liquid electrolytes, inevitably increasing the risk of thermal runaway and posing serious safety challenges. In this review, we will focus on mitigating thermal runaway of silicon anodes-based LIBs from the perspective of electrolyte design. First, the thermal runaway mechanism of LIBs is briefly introduced, while the specific thermal failure reactions associated with silicon anodes and electrolytes are discussed in detail. We then summarize the safety countermeasures (e. g., thermally stable solid electrolyte interphase, nonflammable electrolytes, highly stable lithium salts, mitigating electrode crosstalk, and solid-state electrolytes) enabled by customized electrolyte design to address these triggers of thermal runaway. Finally, the remaining unanswered questions regarding the thermal runaway mechanism are presented, and future directions to achieve intrinsically safe electrolytes for silicon-based anodes are prospected. This review is expected to provide insightful knowledge for improving the safety of LIBs with silicon-based anodes.
RESUMEN
Maintaining the mechanical strength and hermetic reliability of metal-to-glass-ceramics electrical penetration assembly (MTGC-EPA) is a key concern for ensuring the pressure boundaries of nuclear power plants. The transient temperature change caused by power adjusting or accidents in High Temperature Reactor Pebble-bed Modules may affect the structural health of sealing glass-ceramics, even leading to radiation leakage. To evaluate whether the function could survive temperature variations during the service life, thermal cycling aging experiments were imposed to MTGC-EPA. A grating length-mismatched sensing method to monitor the residual strain, an important factor of glass-ceramics structural health, was demonstrated in real-time by femto-laser inscribed fiber Bragg grating (FBG) sensor during the curing process and thermal cycling aging. Scanning electron microscope (SEM) and leakage rate tests were carried out to obtain the comparisons of microstructure and hermeticity before and after the thermal cycling. The residual strain showed a slight growth trend with thermal cycles repetition and it persisted a high value (~ 4,000 µÎµ) reflected by both Bragg wavelength shift and spectrum shape. The grating length mismatched single FBG embedded in glass-ceramics was feasible to demodulate the temperature and strain simultaneously, and the embedded FBG method achieved the structural health monitoring of MTGC-EPA during thermal cycling aging with good accuracy and reliability. Combining with the results of SEM and leakage rate detecting, the structural health of MTGC-EPA was demonstrated to be capable to endure the severe thermal conditions in nuclear reactors.
RESUMEN
Residual stress is an essential factor to keeping the hermeticity and robustness of a glass-to-metal seal structure. The purpose of this report is to demonstrate a novel protocol to characterize and measure residual stress in a glass-to-metal seal structure without destroying the insulation and hermeticity of sealing materials. In this research, a femto-laser inscribed fiber Bragg grating sensor is used. The glass-to-metal seal structure that is measured consists of a metal shell, sealing glass, and Kovar conductor. To make the measurements worthwhile, the specific heat treatment of metal-to-glass seal (MTGS) structure is explored to obtain the model with best hermeticity. Then, the FBG sensor is embedded into the path of sealing glass and becomes well-fused with the glass as the temperature cools to RT. The Bragg wavelength of FBG shifts with the residual stress generated in sealing the glass. To calculate the residual stress, the relationship between Bragg wavelength shift and strain is applied, and the finite element method is also used to make the results reliable. The online monitoring experiments of residual stress in sealing glass are carried out at different loads, such as high temperature and high pressure, to broaden functions of this protocol in harsh environments.