Coulombic efficiency battery

The performance of a battery is often designed to be limited by one electrode ia order to achieve special performance characteristics, such as overcharge protection and safety. The coulombic efficiency of the active mass is of particular iaterest ia battery design and performance. 

The addition of some metal ions, such as Mg2+,Zn2+, In3+,orGa3+, and some organic additives, such as 2-thiophene, 2-methylfuran, or benzene, to propylene carbonate-LiC104 improved the coulombic efficiency for lithium cycling [112]. Lithium deposition on a lithium surface covered with a chemically stable, thin and tight layer which was formed by the addition of HF to electrolyte can suppress the lithium dendrite formation in secondary lithium batteries [113]. 

Zinc is electrodeposited from the sodium zincate electrolyte during charge. As in the zinc/bromine battery, two separate electrolytes loops ("posilyte" and "nega-lyte") are required. The only difference is the quality of the separator The zinc/ bromine system works with a microporous foil made from sintered polymer powder, but the zinc/ferricyanide battery needs a cation exchange membrane in order to obtain acceptable coulombic efficiencies. The occasional transfer of solid sodium ferrocya-nide from the negative to the positive tank, to correct for the slow transport of complex cyanide through the membrane, is proposed [54],... 

However, under these conditions, the energy density is lower than with the (CH> ), electrode, whereas, on the other hand, the coulombic efficiencies attain values of 98 %. In some cases PA in its n-doped form has also been used as battery anode (cell type 3) 190,191,241) -j-jjg discharging reaction in a cell with a TiS2 cathode is as follows ... 

The first cell has the maximum capacity of 108 A h kg" and the energy density of 111 W h kg" The coulombic efficiency was close to 100% over at least 2000 complete cycles when cycled between 1.35 V and 0.5 V at a constant current density of 1 mA cm". The second cell also showed excellent recyclability (4000 cycles with 95% coulombic efficiency), on the other hand the discharge capacity decreased steadily from 40 to 25 A h kg" after 4000 cycles. In PANI batteries with aprotic... 

The coulombic efficiency of a cell is defined as Qp/Qj. It is often more useful to determine the capacity of each half-cell separately, since for operational reasons, most practical batteries do not have an equal number of equivalents of anodic and cathodic reactants. 

Figure 5 Dependence of coulombic efficiency ( ) and discharge capacity (O) of (a) Li/PMMA gel/PPy battery, (b) Li/PAN gel/PPy battery on number of cycles. Charging and discharging current densities are 0.1 mA cm-2.

Battery performance is rated on the basis of the charge capacity, available energy, delivered power, and charge retention during OCV conditions for rechargeable systems, the coulombic efficiency and stability to repeated charge-discharge cycles are also important parameters. 

A rechargeable battery also requires highly reversible half-reactions at the two electrodes to maintain its capacity performance for hundreds of charge-discharge cycles. Coulombic efficiency values fi) of the charge-discharge cycles (Eq. (20))... 

This phenomenon degrades the Coulombic efficiency of the anode, then it has to be minimized for practical applications where high capacity is required. This could be overcome by particular aluminum alloys more resistant to corrosion, but the competing requirement of fast anodic dissolution makes very difficult the research of the suitable material [36, 37]. Another possibility to improve the anode performance is to modify the electrolyte composition by adding corrosion inhibitors [38]. The difficulties met up today in this field leave the possibility to use the aluminum-air batteries only as mechanically rechargeable systems, with practical performance (300-500 Wh/kg) very far from the theoretical values (Table 1.8 Fig. 5.14). 

Recently Osaka et al [260] studied a lithium/ polypyrrole secondary battery system using PEO-LiC104 as a solid polymer electrolyte. The battery showed fairly high coulombic efficiency of about 95% with an output voltage of 3.0 V and performed very well for 1400 charge-discharge cycles after initial 100 scans required to reach optimum value. However, efficiency... 

The driving force for an electrochemical reaction to proceed is polarization of the electrode, i.e. the potential difference between the equilibrium potential of the reaction and the electrode potential. The rate of the electrochemical reaction depends on the hindrances that have to be overcome by the reacting particles for the reaction to proceed. The hydrogen reaction on lead proceeds with great hindrances, i.e. at high overpotential. Hence, the competing reaction of lead sulfate reduction to lead proceeds with high coulombic efficiency and kinetic stability. This, in turn, ensures stable performance of the lead—acid battery. 

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