Experimental study on relationship between SOC and OCV of lithium-ion batteries

Abstract

Electric Vehicles (EVs) are developed rapidly due to the energy and the environment problem. Lithium-ion batteries play an important role in energy storage system of EVs or other devices. The characteristics of power lithium-ion batteries are closely connected to ambient temperature. A battery testing system, including the charge/discharge device, the thermal chamber, DAQ card and etc, was constructed. With which, the experiments of 18650 cells and packs are carried out for the laws between SOC and OCV, also for the discharge capacity with different rates and ambient temperatures. These results can be used in battery management system (BMS) design for electric vehicles..

Physical Interpretations of Electrochemical Impedance Spectroscopy of Redox Active Electrodes for Electrical Energy Storage

“…Most parameters were taken from the literature. For electrodes consisting of transition metal oxides, the equilibrium potential difference Δψ eq can be modeled as a linear function of the state-of-charge (SOC) defined ad c 1,P / c 1,P,max , where c 1,P,max is the maximum intercalated lithium concentration in the pseudocapacitive electrode. − Note that for 100 μm thick MnO 2 dense films, Δψ eq ( t ) (in V) was measured as Here, c 1,P,max was taken as c 1,P,max ≈ 31.9 mol/L, corresponding to fully lithiated manganese dioxide LiMnO 2 . , The initial concentration of Li + in the electrode c 1,P,0 was chosen as the equilibrium concentration solution for electrode potential equal to ψ dc . The transfer coefficient α was assumed to be 0.5.…”

“…Here, c 1,P,max was taken as c 1,P,max ≈ 31.9 mol/L, corresponding to fully lithiated manganese dioxide LiMnO 2 . 65,66 The initial concentration of Li + in the electrode c 1,P,0 was chosen as the equilibrium concentration solution for electrode potential equal to ψ dc . The transfer coefficient α was assumed to be 0.5.…”

Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

“…These parameters include (i) the electrolyte properties r , a, z, D, and c ∞ , (ii) the pseudocapacitive layer properties ψ eq , c 1,P,max , c 1,P,0 , D 1,P , k 0 , α, and σ P , (iii) the electrical conductivity of the conducting nanorod and current collector σ C , (iv) the electrode and electrolyte dimensions r i , r t , L, L c , L s , and L r , and (v) the operating conditions T , ψ max , ψ min , and v. Typical values of these parameters were collected from the literature. 47,65,73,[75][76][77][78][79][80][81][82][83][84][85][86] The binary and symmetric electrolyte simulated corresponded to 1 M LiClO 4 in propylene carbonate (PC) solvent, i.e., c ∞ = 1 M. 62 The dielectric constant of the electrolyte was taken as constant and equal to r = 66.1 corresponding to that of PC at zero electric field. 75 The effective solvated ion diameters a and diffusion coefficient D were taken as those of Li + ion (z = 1) in PC and equal to a = 0.67 nm and D = 2.6 × 10 −10 m 2 /s.…”

“…For LiMnO 2 , ρ and M were reported as ρ ≈ 3.0 g/cm 3 and M = 93.9 g/mol 80 yielding c 1,P,max ≈ 31.9 mol/L. Finally, the initial concentration of Li + in the electrode was chosen as c 1,P,0 ≈ 6.38 mol/L such that the initial equilibrium potential difference ψ eq (t = 0) was zero.…”

“…This expression was used in the present study with the maximum intercalated lithium concentration in the pseudocapacitive layer Li m M p O q estimated as c 1,P,max = mρ/M where ρ and M are the density and molar mass of the fully intercalated metal oxide. For LiMnO 2 , ρ and M were reported as ρ ≈ 3.0 g/cm 3 and M = 93.9 g/mol 80 yielding c 1,P,max ≈ 31.9 mol/L. Finally, the initial concentration of Li + in the electrode was chosen as c 1,P,0 ≈ 6.38 mol/L such that the initial equilibrium potential difference ψ eq (t = 0) was zero.…”