RESUMO
As the power core of an electric vehicle, the performance of lithium-ion batteries (LIBs) is directly related to the vehicle quality and driving range. However, the charge-discharge performance and cycling performance are affected by the temperature. Excessive temperature can cause internal short circuits and even lead to safety issues, such as thermal runaway. The separator plays a crucial role in protecting the battery from regular operation, preventing direct touch between the cathode and the anode while allowing the transport of lithium ions. In this study, we have designed a thermoregulating separator in the shape of calabash, which uses melamine-encapsulated paraffin phase change material (PCM) with a wide enthalpy (0-168.52 J g-1) to dissipate the heat generated inside the battery promptly. Under extra-long-use conditions, the heat emitted by the battery is absorbed by the PCM without causing a significant temperature rise that triggers thermal runaway. The PCM separator can effectively suppress the temperature increase caused by battery penetration. Due to the unique structure of the PCM, the battery is short-circuited; it can significantly delay the internal temperature rise of the battery and quickly dissipate the heat, which is consistent with the characteristics of natural calabash in nutrient absorption and water diffusion, improving the melting and heat storage efficiency of the PCM. The design of the phase change separator provides an effective reference for overheat protection and improved safety in lithium-ion batteries.
RESUMO
The severe dependence of traditional phase change materials (PCMs) on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios. Here, we introduced metal ions to induce the self-assembly of MXene nanosheets and achieve their ordered arrangement by combining suction filtration and rapid freezing. Subsequently, a series of MXene/ K+/paraffin wax (PW) phase change composites (PCCs) were obtained via vacuum impregnation in molten PW. The prepared MXene-based PCCs showed versatile applications from macroscale technologies, successfully transforming solar, electric, and magnetic energy into thermal energy stored as latent heat in the PCCs. Moreover, due to the absence of binder in the MXene-based aerogel, MK3@PW exhibits a prime solar-thermal conversion efficiency (98.4%). Notably, MK3@PW can further convert the collected heat energy into electric energy through thermoelectric equipment and realize favorable solar-thermal-electric conversion (producing 206 mV of voltage with light radiation intensity of 200 mw cm-2). An excellent Joule heat performance (reaching 105 °C with an input voltage of 2.5 V) and responsive magnetic-thermal conversion behavior (a charging time of 11.8 s can achieve a thermal insulation effect of 285 s) for contactless thermotherapy were also demonstrated by the MK3@PW. Specifically, as a result of the ordered arrangement of MXene nanosheet self-assembly induced by potassium ions, MK3@PW PCC exhibits a higher electromagnetic shielding efficiency value (57.7 dB) than pure MXene aerogel/PW PCC (29.8 dB) with the same MXene mass. This work presents an opportunity for the multi-scene response and practical application of PCMs that satisfy demand of next-generation multifunctional PCCs.