*1.2.2.1 Thin film batteries*

Thin film based LIBs ought to be established loads of wellbeing in consequence of their potential applications as overbearing power sources for micro-electronic devices such as smart cards, sensors and implantable medical devices since many thin film micro-batteries adopt flimsy metal lithium as an anode, development of the cathodes with high energy density becomes significant [35]. All Lithium ion batteries have certain limitations such as spreading out fire, explosive nature of hazards chemicals and overheating at the positive as well as negative electrodes take place while the charge–discharge process in a liquid electrolyte sealed in a metal container [36]. Consequently, all-solid state battery with a solid electrolyte should be very safe and reliable. The schematic stack diagram of solid state thin film battery is shown in **Figure 4** [17]. The thin film SSB consisting anode, cathode and solid state electrolyte in the form of thin film to avoids explosive hazards chemicals, leakage free devices and flexible nature. The electrodes used in thinfilm batteries are limited to those that exhibit little volume change during Li ion insertion /deinsertion, since expansion-contraction is restricted in solid-state films [37]. For thin film SSB device fabrication PVD techniques play vital role especially PLD is unique tool for solid state electrolyte deposition in thin film SSB device production. Accordingly, Gil Yoon et al. stated LiCoO2 thin film cathodes fabricated by PLD and the thin film cathode delivered maximum areal capacity 25 μAh cm−2 [38]. Kuwata et al. demonstrated solid state electrolyte based LiCoO2 thin film cathodes by PLD and the solid state battery delivered maximum capacity 9.5 μAh cm−2 [39]. Park et al. reported Si thin film prepared by PLD for micro battery application, Si thin film electrode delivered maximum areal capacity about 96.7 μAh cm−2 [40]. Previously reported literatures reveals that the thin film electrodes used as a coin cell type battery devices. Thus, Author reveals that the thin film based coin cell fabrication by using schematic diagram of thin film battery as displayed in **Figure 5**.

**Figure 4.** *Schematic stack diagram of solid state thin film battery.*

**Figure 5.** *Schematic representation of structure of thin film battery.*

#### *1.2.2.2 From supercapacitor to supercapbatteries*

SCs still have restricted ordinary -life practical application for that their energy density is not comparable to with that of other EESs such as batteries, which the criteria of upcoming energy necessity is far away from adequate to extent. This status spurs ground breaking consequence in the design and preparation of novel hybrid EES that could combining two mechanism is the more advantages than batteries and SCs, which is denoted as supercapbatteries (=supercapacitor + battery) [41]. Therefore, hybrid energy storage devices known as supercapbatteries are rising as a replacement to overwhelm the disadvantage of conventional supercapacitors and batteries, by combining the benefits of each of them, which are superior power and energy density, respectively. A hybrid device is combined by two electrodes with different energy storage mechanism, such as Electric Double Layer Capacitor (EDLC) and faradaic processes; this hybridization of two electrodes could form use of their compatible potential window to increase the voltage window of the device, hence attempt has been made to attain high energy density without yielding constitutional power delivery and very long cycle life of SCs. It deserves that the electrochemical performance of Supercapbattery is nearly attendant to the reasonable design of electrode materials, particularly battery-type materials which deliver large capacity developed from dynamical Faradaic redox reactions. Consequently, the consideration of novel battery-type materials based on various Nanostructures has become a research focal point to encourage the electrochemical performance of Supercapbatteries [42, 43]. Recently Author group designed thin film based supercapbatteries by using PLD. In this work, the fabricated supercapbattery device [28] made by two Transition Metal Oxides (TMOs) such as WO3 and V2O5, here WO3 exhibited pseudo-capacitive behavior and V2O5 revealed the battery type behavior. Further, cyclic voltammograms of thin film supercapbattery consisting of WO3 as negative electrode and V2O5 as positive electrode and their three electrode configuration is presented in **Figure 6a**. The thin film supercapbattery device can reached voltage window 1.8 V (**Figure 6b**) in an aqueous 2 M KOH electrolyte and the thin film device reached 1.6 V in a solid state PVA-KOH gel electrolyte.

*Physicochemical Approaches for Thin Film Energy Storage Devices through PVD Techniques DOI: http://dx.doi.org/10.5772/intechopen.99473*

#### **Figure 6.**

*(a) CV curve combination V2O5 and WO3 thin films in a three electrode configuration; (b) CV curve comparison of Supercapbattery both aqueous and solid state electrolytes.*

**Figure 7.**

*(a) Charge discharge profile of V2O5 thin film in a three electrode configuration; (b) charge discharge profile of V2O5 symmetric supercapacitor.*

#### *1.2.2.3 Supercapbatteries in an electrochemical approach*

Supercapbattery devices having high effective battery type electrode materials, which is determined slow kinetics, rate performances quit low and less number of cycling stability. Supercapbattery devices construct the larger potential of battery materials such they are fashionable redox active nature permitting faradaic reaction processes with high energy density materials are appropriate for positive electrodes and pseudo-behavior materials are highly suitable for negative electrodes [41, 43]. In this similarity, author reported the electrochemical investigation of V2O5 thin film electrode in a three electrode configuration delivered maximum capacity of 3.25 mAh g−1 at a current density of 0.6 A g−1 as displayed in **Figure 7a**. Even though V2O5 thin film symmetric device exhibited maximum capacity 160 mAh g−1 at a current density of 1.3 Ag−1 as shown in **Figure 7b**.

Furthermore, a thin film supercapbattery device was assembled by using PLD process, in this work V2O5 as a cathode because of it is perform battery nature and WO3 as an anode as it deliver pseudo capacitive behavior. The supercapbattery device shows the better redox behavior in a semi solid state electrolyte was used for fabrication, the thin film device exhibit the maximum voltage of 1.6 V clearly which

**Figure 8.**

*(a) CV curve of thin film supercapbattery device in different sweep rates; (b) discharge profile for the thin film supercapbattery device.*

indicates CV and discharge profile curves shown in **Figure 8a** and **b**. The supercapbattery device showed excellent rate performance as displayed in **Figure 8b**; the device delivered maximum volumetric discharge capacity of 32 mAh cm−3 at a current density of 1.3 A cm−3. This is the first thin film supercapbattery energy storage was reported by using PLD system [28]. The agreeing thin film supercapbattery device fabrication cost is very low due to author used alkaline based PVA-KOH electrolyte and the total mass of 0.2 to 0.5 mg of active materials used for thin film supercapbattery fabrication. Therefore, thin film supercapbattery device is economical and eco friendly in nature.
