*3.3. Batteries with Embedded Sensors*

Over time, battery performance changes substantially. This may be the result of a multitude of undesirable material side reactions that eventually lead to capacity fading and impedance growth, which may raise safety concerns about dendritic short circuits. It is essential to properly manage and monitor batteries when they are in use. To perform this, a battery management system (BMS) is typically used. Each cell's voltage, current, and temperature are kept within its ideal safety parameters by the BMS. There are states of a battery, such as the state of charge (SoC) that shares the energy storage information one battery has [96] and the state of health (Soh) that describes the capability of a battery to hold on to a charge as compared to a new battery [97]. These parameters can never be examined directly, but can be analyzed with the help of voltage, current, and temperature measurements. Currently, they are accurately measured and optimized using intelligent algorithms [97]. These all-measurement techniques involve sensors to track all such parameters that share all information related to battery life. Implantable sensors that are integrated into battery cells are thus receiving more and more attention.

This approach will enable us to measure previously unmeasured quantities, learn more about the physical parameters, and comprehend the parasitic chemical activities that happen inside of the cells. This results in the improvement of dependability and advancing the security of batteries. The factors such as pressure, strain, expansion, temperature, and composition of the proposed electrolyte enable the numerous possibilities when computed using next-generation state estimation techniques [98].

Another recent area of study is batteries that can heal themselves. Unwanted chemical alterations within the cell are the cause of battery breakdown. Reversing these modifications to return the battery to its initial configuration and operation is the idea behind selfhealing in batteries. Batteries with self-healing capabilities will focus on repairing damaged electrodes on their own to restore their conductivity, controlling ion movement inside the cell, and reducing the impact of parasitic side effects. Due to the difficult chemical environment that self-healing mechanisms must operate in, the field of battery technology has been sluggish to adopt them, but the subject is presently gaining ground quickly. There are some polymer-based substrates that heal themselves and are commonly known as self-healing polymer substrates (SHPS). Their primary goal is to repair all damages on electrodes and try to restore the conductivity [99]. Self-healing polymer binders, such as those used in silicon anodes, are designed to keep fractured active material particles from losing electrical contact with one another [100]. Functionalized membranes, which can trap undesirable molecules and stop them from reacting with other components in the cell, are another potential idea.

On the other hand, self-healing electrolytes have healing agents that can dissolve undesirable depositions [90]. The enclosed self-healing molecules are a promising concept for the future. These are made up of therapeutic substances housed in microcapsules. By supplying the proper stimulus, the healing chemicals can be released when necessary. The functions of sensing and self-healing should be emphasized as being closely related. Smart batteries combine both of these features so that in the first place a BMS will receive signals from the integrated sensors and analyze them. In the event that a fault is found, the BMS will signal the actuator, stimulating the proper self-healing procedure. The reliability, lifetime, user confidence, and safety of future batteries will all be maximized by this ground-breaking strategy.

One may be thinking about integrating the sensors with the battery, so for this purpose as described in [91], where an integrated conductivity and temperature (CT) micro-sensor for the conductivity high-precision measurement of electric car battery coolant was inserted, one may embed the sensor with the battery in the same manner. An inter-digital microelectrode is made for conductivity sensing, and the temperature sensor cell is a thin-film platinum resistor. With a resolution of 0.1 S/cm, the integrated CT sensor has a respectable limit of detection. Moreover, sensors have a high-precision signal collection and processing circuit constructed for them, and a desirable full-scale measuring error is seen. Moreover, once this sensor is deployed the data can later be easily transported to a static IP using the Internet of Things and can perform several AI algorithms for further monitoring and predictive maintenance.
