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The safety issue caused by thermal runaway poses a huge threat toward the lifespan and application of high-density electrochemical energy storage devices, especially in the field of micro-energy, such as microsupercapacitors (MSCs). The heat accumulation is difficult to be eliminated, considering the narrow space inside integrated electronic devices attached to the MSC group. Active thermal management is of paramount importance to ensure the normal operation of electronic devices. However, existing one-time thermal protection strategies cannot fully meet current requirements. Herein, we report a promising thermoreversible temperature-responsive electrolyte system, which can shut down the current flow before thermal runaway occurs, thanks to the sol-gel transition of Pluronic [poly(ethylene oxide)

A tetraphenyl porphyrin tetrasulfonic acid (TPPS)-modified three-dimensional porous Mn3O4/PANi composites electrode was prepared, which has excellent electrical conductivity and rate performance. The conductivity and stability of polyaniline (PANi) gels have been improved due to the doping of TPPS and its conjugated molecular structure. Furthermore, the Mn3O4/PANi composites gel similar to reinforced concrete structure were prepared by coating PANi cross-linked by TPPS on one-dimensional Mn3O4 nanorods. On the one hand, modified PANi gel act as a functional coating of Mn3O4 nanorods, providing structural protection and providing more active sites. On the other hand, the overlapping Mn3O4 nanorods and PANi gel form a three-dimensional porous network structure, which has a high specific surface area, provides more channels for the transfer of electrons and electrolyte ions, and effectively improves the conductivity of Mn3O4. The specific capacitance of the composite electrode can reach 422 F g−1 at a current density of 0.5 A g−1, and the specific capacitance can reach 265 F g−1 at a high current density of 10 A g−1. After 2000 cycles, the capacity loss was only 11%. And the charge transfer resistance is only 1.2 Ω. These excellent electrochemical performances, as a result of the stable structure formed by TPPS modification and three-dimensional porous morphology, suggesting that these composites have an enormous potential in energy application.

Thermal runaway has always been a significant safety issue that high-performance electronic devices urgently need to solve. These existing strategies are limited by the lack of reversibility and low conductivity. Here, we propose a novel thermoreversible self-protection microsupercapacitor (TS-MSC) based on a thermoresponsive polymer electrolyte to prevent thermal runaway. When heating above the low critical solution temperature (LCST), a gelation process occurs in the smart electrolyte and effectively inhibits the migration of ions, leading to a decreased specific capacitance and an increased internal resistance of the MSC. However, the electrolyte transforms to a solution state at room temperature in which ions can freely migrate. Benefiting by sol-gel transition of the smart electrolyte, the TS-MSCs can exhibit different electrochemical performances at elevated temperatures, demonstrating an active method of achieving thermoreversible and dynamic self-protection. In addition, 3D printing technology and substrate versatility provide an attractive method in the design of integrated micropower devices. Therefore, such functional TS-MSCs offer a promising strategy to solve the safety issues of the nowadays portable microelectronic devices.

Self-healable and stretchable electrolytes are extremely desirable for next-generation flexible energy storage devices. Nevertheless, most of previously reported autonomous self-healing electrolytes possess only moderate mechanical strength and recoverability, as well as poor ionic conductivity and low operating voltage window. In this work, a type of ionogel electrolytes is reported on the basis of a dual-dynamic network composed of metal-ligand (Li+-PEO) coordination and hydrogen bonding. Impressively, the ionogel electrolytes exhibit high tensile fracture strength (0.96 MPa), stretchability (≈1847%) and electrochemical stability up to about −4 to 4 V. A novel all-in-one self-healable micro-supercapacitor prototype is proposed by adopting direct ink writing technique, whereas the electrode material is directly printed onto the ionogel film which acts as a flexible substrate and gel-electrolyte simultaneously. The maximum energy density of the all-in-one micro-supercapacitor reaches 81.88 μWh cm−2 at a power density of 0.75 mW cm−2. In the absence of external stimulus, the damaged micro-supercapacitor can achieve up to 98% self-healing efficiency after 2 min at room temperature. Our research provides new fundamental insights into the construction of stretchable and self-healable ionogels and offers guidelines for the design of integrated micro-supercapacitors to deliver better electrochemical performance.

This study accounts the controllable design over the structure and morphology of Ni-P nanomaterials directly growing on cellulose paper, and its excellent non-enzymatic electrocatalytic performance to urea. The Ni-P papers were prepared by simple solution soaking and electroless bathing. And the simple experimental steps and mild experimental conditions make it possible for large-scale industrial production, and potential for practical applications. In addition, tuning the pH and concentration of the electroless bath, the Ni-P nanomaterials with different morphologies of nanoflower, nanosheet, nanowire microsphere and microsphere were obtained. The Ni-P nanomaterials impart conductivity to cellulose paper while being potently sensitive to urea owing to its high catalytic activity. Cellulose paper has a large specific area and open macroporous framework which hadn't been damaged during the process of electroless bathing, providing much more activated sites for Ni-P deposition. And the prepared Ni-P papers, as composite materials of cellulose papers loading Ni-P nanomaterials, have high electrocatalytic properties to urea. Comparing the electrochemical behaviors of the four Ni-P paper electrodes with different morphologies, the Ni-P nanoflower paper electrode showed the best electrochemical performance with highest sensitivity of 683.46 μA mM−1 cm−2 in the low concentration range (0–1 mM) and 1140 μA mM−1 cm−2 in the high concentration range (1–11 mM), lowest detection limit of 12 μM, shortest response time of 3 s, which may owes to the highest surface area of the Ni-P nanoflower structure. It also has a good stability in room environment remaining 97% after 35 days of storage. Moreover, the electrocatalytic activities of the four Ni-P paper electrodes are ranked as follows: nanoflower > nanosheet > nanowire microsphere > microsphere. What's more, the long-term stability and repeatability, good selectivity of the flexible Ni-P paper make it successfully applied to swimming pool water quality monitoring.