Deep cycling Lithium Ion Batteries
Introduction
Due to the combination of power density and high energy, Lithium-ion batteries are building their ways to be utilized for portable devices such as hybrid/electric vehicles, cell phones, laptops, watches, etc. The vehicles running on the energy of fossil fuels emit many hazardous gases. On the other hand, vehicles with Li-ion batteries lower the emission of harmful gases into the atmosphere. The energy obtained from wind, geothermal, solar, and other renewable sources can be stored in Li-ion batteries (LIBs) because of their high energy efficiency. Hence, different industries and government organizations have an interest in using LIBs.
Working
It is considered an achievement for commercial Li-ion batteries to approach the theoretical limit of their practical capacity. But the theoretical limit is not yet crossed, although the demand for high capacity is enhancing. A deeper study is required to evaluate the significant reason for improving the ability of LIBs. In the traditional LIBs, which follow the rocking chair cycling architecture, the charging process shifts the Li+ ions from the cathode to the anode. On the contrary, Li+ ions transfer to the anode from the cathode during discharging of LIBs. For the evaluation of theoretical capacity, the number of Li+ ions, which are shifted during the charging and discharging process, are responsible. Electrodes are the primary source of these Li+ ions, which are utilized to investigate the theoretical capacity.
Conventional LIBs
High-capacity electrode material should be used to improve the rocking chair architecture’s capacity to have more moving Li+ ions in the system. For this purpose, several different intercalation molecules such as Li-metal oxides, Li with silicon, graphene, sulfur, and oxygen have been reported to enhance the production of transferring Li+ ions in the LIBs. However, at least 3.7 percent of commercial LIBs are present in the electrolyte, which is not used in rocking chair architecture for storage purposes. These ions should be moveable to increase the energy capacity. 2 strategies can achieve this. One is bulk intercalation (dual ion batteries), and the second is surface adsorption (supercapacitors). During these strategies, the concentration of electrolytes should remain constant. But in both processes, the electrolyte concentration decreases as the transferring Li+ ions intercalate in the electrode or are adsorbed on the surface of the electrode.
Deep cycling LIBs
Hao and his co-worker reported the hybrid LiFePO4-graphite cathode, which used the Li+ ions and PF-6 transferring ions in electrolyte for intercalation and de-intercalation to get high energy density. However, Hao did not compare the surface adsorption of Li ions and intercalation. Xia and his co-worker investigated deep cycling architecture for LIBs that transfers Li+ ions in the electrolyte to sustain more energy than conventional LIBs — using LiMn2O4-MCMB/Li electrochemical cells in the deep-cycling process of LIBs. Deep cycling Lithium-Ion batteries (LIBs) gave higher capacity, i.e., 57.7% in rocking chair LIB, and the electrolyte concentration remained constant. After 2000 cycles of charging and discharging, 84.4% high capacity is significant compared to conventional LIBs. Hence, deep cycle LIBs sustained current for a more substantial time, making them useful for electronic and vehicle industries.
