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Electrochemical Reaction Engineering
Published in James J. Carberry, Arvind Varma, Chemical Reaction and Reactor Engineering, 2020
Gary G. Trost, Victoria Edwards, John S. Newman
Three system efficiencies characterize the performance of a battery. Coulombic efficiency is a measure of the reversibility of the electrodes or the presence of side reactions. It is given by the ratio of the number of coulombs released during discharge to the number of coulombs required to charge the system back to its initial state. Energy efficiency is calculated by multiplying the coulombic efficiency by the ratio of average discharge voltage to average charging voltage. Differences in charge and discharge voltages are due to irreversibilities associated with the ohmic potential drop in the solution and matrix, and overpotentials associated with electrode kinetics and mass transfer resistances. Coulombic efficiencies can often approach 100%, while energy efficiencies are typically 50 to 80%. The method of charging and discharging the battery will affect both of these numbers.
Optimised state of charge estimation in lithium-ion batteries by the modified particle filter method
Published in Lin Liu, Automotive, Mechanical and Electrical Engineering, 2017
Renzhuo Wan, Binbiao Pan, Fan Yang, Jun Wang, Quan Chen
Coulombic efficiency is defined as a ratio of the total discharge capacity and charge capacity at a specific condition. Here, the coulombic efficiency is calculated at different temperatures using the above temperature-capacity data. Figure 2(a) shows the relationship between coulombic efficiency and temperature. We find that the coulombic efficiency ⊠c keeps at 1 at intermediate temperature ranging from 5 to 30°C, and about 1.4% maximum fluctuations at very low temperature and above 35°C. It is described by five-order polynomial function as Equation 6: Cc(T)=m0+m1T+m2T2+m3T3+m4T4
Nanomaterials for Lithium(-ion) Batteries
Published in Sam Zhang, Materials for Devices, 2023
Two challenging issues that silicon anode material faces are volume expansion and unstable SEI film [75]. During lithiation, Si anode material has a large volume change as high as 320%, which leads to falling off of the active material from a conductive network, and results in particle cracked, which seriously affects the cycling performance of the Si-base anode. At the same time, due to the ever-changing volume, the SEI layer constantly varies, which in turn leads to the constant consumption of Li+. This process manifests itself as a lower Coulombic efficiency in measured electrochemical performance.
Scale-up single chamber of microbial fuel cell using agitator and sponge biocarriers
Published in Environmental Technology, 2023
Sima Malekmohammadi, Seyed Ahmad Mirbagheri
Coulombic efficiency is the efficiency with which electrons are transferred in a system to carry out an electrochemical reaction. A higher coulombic efficiency indicates that the microorganisms in the microbial fuel cell were in optimal conditions and were provided with proper nutrition. For better comparison, the results are shown simultaneously in Figure 7. As can be seen, an increase in time leads to an increase in efficiency. In larger reactors, this phenomenon is more noticeable since there is more space and substrate available. Consequently, the activity of the microorganism does not decrease dramatically, and the area under the graph increases significantly.
Investigating the ohmic behavior of mediator-less microbial fuel cells using sewerage water as the bio-anode
Published in Cogent Engineering, 2022
Thiong’o Mbarire, Osano Aloys, Bakari Chaka
The energy balance of MFCs illustrates the difference in charge and discharge power at any instant of the MFC. The energy balance of the MFC is a function of its Coulombic and voltage efficiency. Coulombic efficiency denotes the ratio of input charges to the output ones during discharging (Wang et al., 2018). The energy balance of the MFCs was found to increase linearly with magnitude of the impedance of the cell. On the other hand, voltage efficiency denotes the voltage balance during charging and discharging the cell (Nakata, 2019). The cells’ SOC have a direct impact on their voltage efficiency. A battery whose voltage varies linearly with the SOC (such as these MFCs) is likely to have less voltage efficiency. From Table 2, the MFC connected to a larger resistor (16,000 Ω) had less energy balance (28.2 J/s) implying less Coulombic efficiency. The ratio of charge input/output was lower than the rest indicating more stable regimes. The MFC connected to the smallest impedance (1,000 Ω) had the most energy balance (336.1 J/s) implying more deviation in input and output power. The stability of the regime in this MFC was thus affected. This deviation can be attributed to more secondary reactions resulting from a higher power capacity in this MFC. Some of the reactions include electrolysis of water, weak acids and other side-reactions contributing to Faradaic and non-Faradaic current in this MFC. In a research trying to recover energy during wastewater treatment using MFCs, Capodaglio et al. (2013) observed a Coulombic efficiency ranging from 0.8% to 1.9%. This value is by far less than those of conventional battery systems which enjoy Coulombic efficiencies. MFC systems with higher Coulombic efficiencies are affiliated with more unstable regimes. This phenomenon is good for wastewater purification but bad for the cell health.