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Hardware Architecture of IoT and Wearable Devices
Published in Mohammad Ayoub Khan, Internet of Things, 2022
Whether for BAN or WBAN, power is one of the major issues specifically to implantable wearable devices. Figure 4.5 depicts a comparative view of the power requirements for different communication protocols and data rates. With the advances in technologies, wireless sensors generate wide range of data bits per second. A pacemaker typically generates in few Kbps and an endoscope may generate few Mbps. The traditional battery (lithium ion) system has certain limitations in the driving capabilities and flexibility. New advances have created bendable, flexible battery which surely benefits the wearable domain. A new proposed laminated outer body with internal battery structure assists in leak proof and prevents from overheat. Panasonic in its first bendable created 0.02 inch thick, bendable with a radius of 25 mm, 25 degrees. In development stage the bendable battery has a 17.5 mAh to 60 mAh as compared to 1960 mAh in traditional batteries [14].
Fabric based printed-distributed battery for wearable e-textiles: a review
Published in Science and Technology of Advanced Materials, 2021
Adnan E. Ali, Varun Jeoti, Goran M. Stojanović
Among several commercially available flexible batteries, aqueous zinc chemistries were effective for the development of low-cost, high throughput products [123,124]. Due to its high theoretical capacity, low cost compared to lithium-ion batteries, and safe battery chemistry, the zinc anode battery has been researched for the light-weight and flexible battery market [125,126]. However, usually these batteries are not rechargeable and also have high impedance, so their practical application is limited to low-power, disposable electronics. To address this problem, different studies have focused towards developing a printed, rechargeable zinc battery with enhanced performance [127,128]. The monovalent silver oxide-zinc, Ag2O-Zn, chemistry is one of the alkaline batteries which have received significant research attention because of their rechargeable chemistry and tolerance to high discharge current [129,130]. These batteries have a high power as well as a high energy density, which is due to the fact that zinc is the most electropositive element suitable for aqueous solutions [131]. The success and widespread acceptance of electronic textiles depends on their ability to be manufactured through existing textile technologies and use the textile area for storing as well as harvesting energy. Integrating an electrochemical energy storage functionality onto textile fabrics using the monovalent silver oxide-zinc based chemistry was researched [132]. The fabricated textile-based battery generates DC voltage and current when moistened by ionically conducting liquids, such as sweat, readily available on our body which serves as an electrolyte. The electrochemical cell consists of the monovalent sliver oxide, Ag2O, cathode and the zinc anode electrodes deposited onto polyester fabrics using a screen-printing technology. The chemistry of these batteries involves an oxidation-reduction reaction of the two electrode materials, where the monovalent silver oxide cathode and the zinc anode electrodes are reduced and oxidized as shown in (11) and (12), respectively.
Bending impact on the performance of a flexible Li4Ti5O12-based all-solid-state thin-film battery
Published in Science and Technology of Advanced Materials, 2018
Alfonso Sepúlveda, Jan Speulmanns, Philippe M. Vereecken
To better characterize the effect of exposure to air of the fully encapsulated flexible battery the CVs measured at different times are compared. Figure 6(a) shows that after one day of exposure to air almost no change in the peak shape is visible, although the delithiation peak is slightly smaller. However, after four days the peaks shift, decrease, and broaden, which indicates increasing overcharging due to higher internal resistances. This trend continues for the remaining days of air exposure. For this reason we compare the (de)-lithiation resistances. The resistance is obtained from the slope of the respective peak in the CVs and is shown in Figure 6(b). For all measuring points the lithiation resistances are higher than the delithiation ones and both resistances show an exponential growth with air exposure time. Directly after exposure to air the resistances are around 38 Ω (delithiation) and 125 Ω (lithiation). After 9 days the resistances increase to around 1375 Ω (delithiation) and 2245 Ω (lithiation). This large increase in cell resistance can indicate extensive oxidation of the Li-metal anode due to the moisture/oxygen diffusion through the encapsulating parts and interfacial resistance between electrodes and electrolyte. Also, this long cycling could lead to the development of ‘dead’ inactive Li regions due to plating and stripping of Li-metal. Figure 5(c)–(e) shows a top view of the fully encapsulated flexible battery showing an obvious oxidation evolution on the Li-metal anode. The flexibility and mechanical integrity of the encapsulated thin-film battery are demonstrated in Figure 5(b). Even after 4 days of air exposure the battery is operational and can easily light up a light-emitting diode (LED) even when bent. The Li metal anode surface is analyzed with ImageJ software to calculate the degree of oxidation from the images taken in days 1, 4, and 9 (Figs. 5(c)–(e)). The area of the Li-metal is only taken into account by fixing the threshold from the 32-bit image. The Li-anode oxidized surfaces obtained are 22, 40, and 86%. There is a similar trend when comparing the oxidation of the Li-metal anode to the increase in cell resistance. This can serve as a confirmation that the cell resistance of the thin-film battery mainly arises from the oxidation of the Li-metal anode.