The safety of power batteries in the automotive industry is of paramount importance and cannot be emphasized enough. As lithium-ion battery technology continues to evolve, the energy density of these batteries increases, thereby amplifying the potential risks linked to battery failures. This study explores pivotal safety challenges within the electric vehicle sector, with a particular focus on thermal runaway and gas emissions originating from lithium-ion batteries. We offer a non-dispersive infrared (NDIR) gas sensor designed to efficiently monitor battery emissions. Notably, carbon dioxide (CO₂) gas sensors are emphasized for their ability to enhance early-warning systems, facilitating the timely detection of potential issues and, in turn, improving the overall safety standards of electric vehicles. In this study, we introduce a novel CO₂ gas sensor based on the advanced pyroelectric single-crystal lead niobium magnesium titanate (PMNT), which exhibits exceptionally high pyroelectric properties compared to commercially available materials, such as lithium tantalate single crystals and lead zirconate titanate ceramics. The specific detection rate of PMNT single-crystal pyroelectric infrared detectors is more than four times higher than lithium tantalate single-crystal infrared detectors. The PMNT single-crystal NDIR gas detector is used to monitor thermal runaway in lithium-ion batteries, enabling the rapid and highly accurate detection of gases released by the battery. This research offers an in-depth exploration of real-time monitoring for power battery safety, utilizing the cutting-edge pyroelectric single-crystal gas sensor. Beyond providing valuable insights, the study also presents practical recommendations for mitigating the risks of thermal runaway in lithium-ion batteries, with a particular emphasis on the development of effective warning systems.

(Na_0.5Bi_0.5)TiO₃ (NBT)-based materials have been widely studied for their large electric-field-induced strains. However, a high coercive field (E_c) has long hindered the applications of NBT-based materials. Here, we propose a simple method to significantly reduce the E_c of rhombohedral NBT-based crystals through domain engineering. By applying an alternating current (AC) electric field along the [001] direction, the E_c of Mn-doped (Na_0.485K_0.015Bi_0.5)TiO₃ single crystal can be reduced from 70 to 20 kV/cm after about 25 cycles without sacrificing the ferroelectric polarization. Meanwhile, the piezoelectric coefficient d₃₃ and the optical transparency of the crystals are also enhanced compared with those after direct-current electric field poling. The domain structure characterization shows that the AC cycles can form a laminar domain configuration, in which the 109° domain walls are parallel to (001) planes. It is demonstrated that in the laminar domain configuration, almost only 71° polarization switching occurs when the external electric field is reversed. The required energy for polarization reversal is significantly lower than that of the “4R” domain configuration; thus, the E_c is reduced greatly. The low E_c is maintained after depolarization at 250 °C, evidencing good thermal stability of the laminar domain configuration. Furthermore, this method is also applicable to other rhombohedral single crystals and may be applied to [001]-textured polycrystalline ceramics in the future; thus, it may indeed benefit the practical applications of NBT-based piezoelectric devices.

The pyroelectric effect plays a critical role in thermal imaging and energy harvesting. Despite extensive efforts to enhance performance through doping and composite engineering, the mechanisms underlying defect dipole coupling with phase structures remain poorly understood, impeding the advancement of defect-engineered symmetry modulation. Here, we report an abnormal pyroelectric phenomenon where the pyroelectric coefficient ( p ) increases notably when poling temperature exceeds the orthorhombic-to-tetragonal phase transition temperature ( T _O-T ) in potassium sodium niobate ceramics. The p at 200°C ( p = 45.4 × 10 ⁻⁴ C m ⁻² K ⁻¹ ) rises more than sevenfold compared to poling within the orthorhombic phase ( p = 6.5 × 10 ⁻⁴ C m ⁻² K ⁻¹ ), representing the highest value reported to date and offering benefit for high-temperature thermal sensing. A dual mechanism is proposed, involving rigid-ion displacement and defect dipole alignment, which respectively contribute to increased displacement charge and space charge. Our findings establish a paradigm for optimizing high-temperature pyroelectrics through a simple, symmetry-confined thermal poling.

Tire pressure monitoring systems (TPMSs) are essential for maintaining driving safety by continuously monitoring critical tire parameters, such as pressure and temperature, in real time during vehicle operation. Among these parameters, tire pressure is the most significant, necessitating the use of highly precise, cost-effective, and energy-efficient sensing technologies. With the rapid advancements in micro-electro-mechanical system (MEMS) technology, modern automotive sensing and monitoring systems increasingly rely on MEMS sensors due to their compact size, low cost, and low power consumption. This study presents a novel high-precision capacitive pressure sensor based on a capacitive micromachined ultrasonic transducer (CMUT) structure and a silicon–silicon direct bonding process. The proposed design offers exceptional performance with high accuracy, ultra-low power consumption, and reduced production costs, making it an optimal solution for enhancing the precision and efficiency of TPMS. Leveraging its low power requirements, capacitive sensing technology emerges as a superior choice for energy-efficient systems in the automotive industry.