4. Challenges and Opportunities4.1. Technical ChallengesThe idea of using battery systems in power grids first emerged in the 1980s. Notable examplessince the 1980s are the BESS in Berlin, Lausanne, South Korea, Jeju Island, and other small islandsystems [133-138]. The integration of BESS in the power grid helps to solve many problems of thepower grid [139-143]. However, the effect of BESS on the power grid depends directly on the efficiencyof the system's connection to the main grid. Different power electronic topologies address theseproblems. According to the characteristics of the network, the most suitable of these topologies isselected. In addition, the battery systems should respond to issues in the grid on a millisecond timescale.This task is critical because of the stochastic na ture of renewable energy resources in modern powergrids. If the BESS fail in response time and opera tional control, large-scale technical and economiclosses result for both consumers and utilities. Thus, the control of BESS is the most critical task ingrid-scale applications [108,144-148].Battery systems have started to change the transportation sector in recent years, and the roleof electric vehicles (EV) in modern grids will be one of the factors that determine the future. Thebattery systems of electric vehicles provide a variety of ancillary services to support the networkwhen the power grid is insufficient. However, the complex distribution of EV across the network cancause control problems, and this may lead to frequency and voltage instabilities and overloads on thenetwork during the energy transfer from the vehicle-to-grid (V2G). However, at present, the numberof vehicles and battery sizes is not enough to implement this concept in practice [149-153].Aging is an inevitable process that occurs in all electrochemical devices, including batteries. Thisprocess changes the capacity of a device over time. A long-lasting and demanding application results inboth performance and capacity reduction of the BESS and affects the economic parameters of businessvia increased operational and replacement cost [145].It is notable that there are no significant differences in the lifetime of the most popular batterytypes used in the grid. According to Table 1, lithium-ion and lead-acid batteries, which are among thetwo most popular types, have a lifetime of up to 15 years, considering average usage characteristics.Of course, this period is likely to change depending on the circumstances. For example, batterymanagement systems can make progress in extending the battery life by controlling the chargingand discharging cycles of the batteries with the help of optimization methods, and new generationapproaches such as AI and machine learning.One of the critical issues for batteries is safety levels. Fortunately, significant improvements havebeen observed in the safety levels of batteries with recent developments. If a safety comparison is madebetween the two leading batteries, such as lead-acid and lithium-ion, both lead-acid and lithium-ionbatteries have a thermal runaway risk due to their structure. Since lithium-ion batteries have a higherenergy density than lead-acid batteries, they may create a riskier situation in terms of safety.