Incidents in the use of lithium-ion batteries are usually caused by the malfunction of flammable organic liquid electrolytes with poor thermal stability. Therefore, the development of noncombustible electrolytes is regarded as one of the most effective means to prevent the safety hazards of lithium-ion batteries. Ionic liquids have attracted much interest recently, mainly due to their high ionic conductivity, low volatility, and incombustibility. The application of ionic liquids to the preparation of quasi-solid-state gel electrolytes combines the advantages of ionic liquids and avoids the risks of organic liquid electrolytes. Therefore, the solid-state ionogels have been considered as a promising alternative electrolyte system, especially for the much-desired energy storage devices with higher energy density and flexibility. This review focuses on the recent progress of ionogel electrolytes for lithium-ion batteries. The preparation strategies for ionogel electrolytes based on different frameworks, namely inorganic matrix, organic matrix, and organic-inorganic hybrid matrix, are discussed. Subsequently, efforts to improve the properties of the ionogel electrolytes, including the ionic conductivity, mechanical properties, and lithium-ion transfer number, are summarized. Besides, the applications of ionogel electrolytes in high-voltage lithium-ion batteries and lithium metal batteries as well as the batteries under extreme environments are outlined. Finally, the perspectives in studying and improving the performances of ionogel electrolytes for advanced lithium-ion batteries are provided.

Hybrid Ionogel Electrolytes for Advanced Lithium Secondary Batteries: Developments and Challenges.

High-sensitivity temperature sensor based on PDMS-coated photonic crystal fiber interferometer

A compact sensor integrated in a single hollow core Bragg fiber (HCBF) is proposed and demonstrated for simultaneous measurement of strain and temperature. The sensor is manufactured by splicing a 3-mm-long homemade HCBF sandwiched between two segments of single-mode fibers (SMFs) with a lateral offset at one end. Experimental results demonstrate that both Mach–Zehnder interferometer (MZI) and Bragg resonant mechanism are coexisting in the HCBF-based sensor. Two sensing mechanisms have different strain and temperature sensitivities with good linearity. The axial strain sensitivities of −0.4 and 0.33 pm/ $\mu \varepsilon $ and the temperature sensitivities of 40.8 and 26.5 pm/°C are obtained by monitoring the wavelength shifts with axial strain and temperature in temperature range of 60°–80°. Therefore, simultaneous measurement of temperature and strain can be achieved by using a characteristic matrix approach. Due to the large refractive index (RI) difference between the core and cladding of the Bragg fiber, the length of HCBF for forming mode interference in the sensor could be greatly reduced. This makes the sensor more compact than most previous reports for simultaneous measurement of temperature and strain.

A Compact Sensor Integrated in a Single Hollow Core Bragg Fiber for Simultaneous Measurement of Temperature and Strain

CubeSats are small satellites produced usually by off-the-shelf components that are designed to propose space exploration and research to universities reducing expenses and development time. Since most of their components are commercial and temperatures in space range between −100 °C and 120 °C, the thermal profile of the devices must be considered in the design process to optimize the efficiency and to avoid system failures. Among the different kinds of temperature sensors reported in the literature, the use of printed resistance temperature detectors (RTDs) is interesting to embed the sensor in the structure thus reducing the weight of the satellite. In this frame, the use of innovative Industry 4.0 technologies allows both the improvement of the metrological characteristics of the sensors and the reduction of the costs increasing the material use efficiency. In this work, two aluminum alloys and three plastic were tested as substrates for the development of printed silver-based temperature sensors. The sensors were characterized in the [−10; 100] °C temperature range using both an oven and a climatic chamber in order to assess the resistance at 0 °c, the temperature coefficient of resistance (TCR) as well as the hysteresis of the devices. The results showed that the metallic substrates performed better, with TCRs bigger than 2.5 $10-3^{\circ}\mathrm{C}^{-1}$ and low hysteresis. Among the plastic substrates, Kapton produced the most stable TCRs values with values around $2.3\cdot 10-3\circ \mathrm{C}-1$. Even though ABS performed similarly (TCR around $2.0\cdot 10-3^{\circ}\mathrm{C}^{-1}$), it presented linearity and hysteresis issues at high temperatures.

Preliminary Results on Fully-Printed and Silver-Based Temperature Sensors for Aerospace Industry

Sensitivity-Enhanced Temperature Sensor Utilizing Core Offset and Hollow Core Bragg Fiber

The development of high-performance solid-state electrolytes to replace conventional liquid organic electrolytes has received intensive attention because of the improvements in the safety, flexibility, reliability, and cycling stability of lithium-ion batteries (LIBs). In this work, we present a double-network ionogel electrolyte (DNIE) through the preparation of interpenetrating polymer networks (IPNs). This DNIE exhibits good mechanical properties, excellent flexibility, nonflammability, high ionic conductivity (4.13×10−4 S cm−1 at room temperature), electrochemical stability (>4.8 V), and the ability to suppress Li dendrite formation. The Li/LiFePO4 cell assembled with the DNIE exhibits superior cycling performance while also delivering a steady high discharge capacity of 133.7 mAh g−1 and a Coulombic efficiency of 99.8 % after 220 cycles at a charge/discharge rate of 0.2 C. Importantly, the DNIE(200 %)-20 % electrolytes can be prepared on the surface of graphite anodes through in situ gelling, which can improve the stability of the active layer and the adhesion between the active layer and current collector in mechanical bending at different angles. After assembling into soft-packed batteries in the configuration of LiCoO2|DNIE(200 %)-20 %|graphite via the in situ gelling of DNIE(200 %)-20 % on the surface of the graphite electrode, the flexible batteries showed excellent cycling stability (capacity retention >98 %) even when folded more than 100 times. 

Weiping Chen

Papers

Sensitivity-Enhanced Temperature Sensor Utilizing Core Offset and Hollow Core Bragg Fiber

Double‐Network Ionogel Electrolyte with Superior Mechanical Performance and High Safety for Flexible Lithium‐Ion Batteries

An Improved Strategy of Passive Micro Direct Methanol Fuel Cell: Global Mass Transport Mechanism Optimization Dominated by a Single Hydrophilic Layer