Temperature measurements of Li-ion batteries are important for assisting Battery Management Systems in controlling highly relevant states, such as State-of-Charge and State-of-Health. In addition, temperature measurements are essential to prevent dangerous situations and to maximize the performance and cycle life of batteries. However, due to thermal gradients, which might quickly develop during operation, fast and accurate temperature measurements can be rather challenging. For a proper selection of the temperature measurement method, aspects such as measurement range, accuracy, resolution, and costs of the method are important. After providing a brief overview of the working principle of Li-ion batteries, including the heat generation principles and possible consequences, this review gives a comprehensive overview of various temperature measurement methods that can be used for temperature indication of Li-ion batteries. At present, traditional temperature measurement methods, such as thermistors and thermocouples, are extensively used. Several recently introduced methods, such as impedance-based temperature indication and fiber Bragg-grating techniques, are under investigation in order to determine if those are suitable for large-scale introduction in sophisticated battery-powered applications.

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This short communication presents a method to measure the integral temperature of organic light-emitting diodes (OLEDs). Based on electrochemical impedance measurements at OLEDs, a non-zero intercept frequency (NZIF) can be determined which is related to the OLED temperature. The NZIF is defined as the frequency at which the imaginary part of the impedance is equal to a predefined (non-zero) constant. The advantage of using an impedance-based temperature indication method through an NZIF is that no hardware temperature sensors are required and that temperature measurements can be performed relatively fast. An experimental analysis reveals that the NZIF is clearly temperature dependent and, moreover, also DC current dependent. Since the NZIF can readily be measured this impedance-based temperature indication method is therefore simple and convenient for many applications using OLEDs and offers an alternative for traditional temperature sensing.

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Li-ion batteries have drawn considerable attention in the last decades due to the fact that these devices have a relative high energy density, long cycle life and low self-discharge rate. However, challenges are met in monitoring and controlling the states of a Li-ion battery, such as State of Charge, State of Health and temperature. In this thesis a new method is proposed in order to measure the (internal) battery temperature of Li-ion batteries through the so-called intercept frequency. The intercept frequency can be determined by measuring the battery impedance. After determining the intercept frequency, it can be related to the (internal) temperature. However, it turns out that some measurement issues arise when this new method is applied in, for example, electric vehicles. Impedance measurements in these typical applications are heavily disturbed by electric components and crosstalk, resulting in inaccurate temperature indications. In this thesis these disturbances are comprehensively described and solved in order to accurately measure the battery temperature. Furthermore, the impedance of both battery electrodes has been measured by the application of reference electrodes. The application of reference electrodes makes it possible to measure the intercept frequency of both electrodes and, subsequently, to determine which electrode is responsible for the intercept frequency behaviour of the total battery.@en

Li₄Ti₅O₁₂ is well known to be a safe and efficient anode material for Li-ion batteries. A metal-organic chemical vapor deposition process has been developed for the synthesis of Li₄Ti₅O₁₂ thin film anodes on planar and 3D substrates. The influences of various deposition parameters, including precursor flow rates and post-annealing temperatures, have been investigated by material and electrochemical analyses. Li₄Ti₅O₁₂ thin films deposited at the optimized process parameters showed a high crystallinity and high electrochemical activity. A reversible storage capacity of 151 mAh/g was achieved at a current of 0.5 C, corresponding to 86.3% of the theoretical specific capacity of Li₄Ti₅O₁₂. Up to almost 600 cycles, the electrodes showed no significant capacity loss. Furthermore, the deposited thin film anodes also showed excellent rate performance. Compared to the storage capacity at 0.5 C, 93% of the capacity was maintained at 10 C. Thin films were also deposited on highly structured substrates to investigate the uniformity and electrochemical performance. With the same footprint area, the 3D Li₄Ti₅O₁₂ film anode showed a 2.5 times higher storage capacity than planar electrode.

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