Lithium-ion batteries (LiBs) have been widely used in a variety of applications, however they still suffer from low capacity retention, large capacity fade ratio or inability to charge efficiently at low temperatures, especially below −20 °C. The reasons behind these drawbacks originate from the nature of active materials such as the anode and the cathode, along with the composition of electrolyte solutions. In particular, from the perspective of active materials, it has been reported that the most common problems arise from the dramatic increase in the resistances, especially charge transfer resistance, and the decrease of lithium-ion diffusivity, by more than one order of magnitude. In this report, we review the most recent strategies in the development of anode and cathode materials and composites, focusing on enhanced electronic and ionic conductivities for improved low-temperature electrochemical performance. Our overview aims to provide a comprehensive comparative study of the proposed methods to overcome the low-temperature challenges in order to develop high energy-density LiBs with enhanced capacity retention, cycling stability and high-rate capability under extreme conditions.

During the past decade, microelectronics incorporated inkjet-printing technology as a versatile tool for industrial applications, as it combines high printing quality and resolution along with low cost compared to conventional microelectronics techniques that require high cost and complex equipment. In addition, inherently, inkjet printing requires no photolithography steps. In this review paper we present temperature sensors that have been manufactured by inkjet printing. Based on the main active sensing material, the research studies are classified into four different types, i.e. metal and metal oxide-based, carbon-based, polymer-based and composite that combine properties of multiple active materials. It is demonstrated that silver ink has been, by far, the most popular material for metal based temperature sensors with a temperature coefficient of resistance (TCR) of around 2 × 10 ^-3 ◦C ^-1 . Silver sensors as well as almost all metal, carbon and polymer based sensors were either resistance temperature detectors (RTDs) or thermistors. Regarding polymer and carbon-based sensors, it was found that, in some cases, they outperformed metal-based sensors in terms of TCR, although fabrication using such materials had a less predictable result with a TCR ranging from -16 × 10 ^-3 ◦C ^-1 to 2 × 10 ^-3 ◦C ^-1 . Finally, in the case of composite materials as temperature sensors, several combinations of active materials exhibited interesting results and yielded a variety of sensing technologies such as thermocouples and radio frequency based.

Graphene oxide (GO) is a promising material for H2O vapour sensing. However, H2O sensing mechanisms are still under investigation especially in the case of thermally reduced GO. To this purpose, planar devices were fabricated by spin-coating graphene oxide on glass substrates. Ultra high response to H2O was recorded but poor repeatability and stability over time were also noted. Three different degrees of thermal reduction were applied to improve material stability. An inverse change of resistance was observed for reduced graphene oxide compared to pure graphene oxide upon interaction with H2O. The sensing mechanisms that govern GO and reduced GO behaviour were studied based on DC measurements. In the case of GO, strong ionic conductivity was proposed whereas in the case of reduced GO mixed electronic/ionic with the leading mechanism affected by H2O percentage in air, degree of material reduction and sensor working temperature. Finally, it was found that by promoting one sensing mechanism over the other, improved operating humidity range of the sensor can be achieved.