Development of a cathode material based on
the Li_xLa_yMn_1–yO₂ electrode system for lithium ion batteries

• E.S. Guseva, R.K. Frantsev and S.S. Popova

Yu.A. Gagarin Saratov State Technical University, ul. Polytechnicheskaya, 77, Saratov, 410054 Russian Federation

Abstract: The cathode material is the main factor determining the capacity, power and cost of lithium-ion cells (LIC). The particle size and surface area of the cathode material determine the resistance of solid-phase diffusion and the charge transfer reactions on the positive electrode in a lithium-ion cell. Thus, to create a battery capable of operating at high currents, it is necessary to reduce the size of crystals of the active material. Studies were aimed at improving the electrochemical characteristics of LIC of the Li/MnO₂ system by modifying the MnO₂ electrode with lanthanum, which favors the formation of additional vacancies for moving lithium ions in the structure of the cathode material and provides an increase in the discharge current density and discharge time, as well as improves the electrode cycleability. To solve the problem on the way to successful commercialization of spinel cathodes, the problem of dissolution of a small amount of manganese ions from the spinel surface followed by their transfer to the anode, which in turn deactivated the anode surface (the anode underwent corrosion damage), was solved. The proposed mechanism for the dissolution of manganese ions includes disproportionation by the scheme: 2Mn³⁺→Mn²⁺+Mn⁴⁺. Choosing an anode that is corrosion resistant to the electrolyte during cycling was another important task. To inhibit the corrosion of the anode, lanthanum ions were incorporated into the anode because a LiAl anode by itself actively interacts with the electrolyte, which results in electrode embrittlement and hence shortens the battery life time. The intermetallic compounds chosen by us based on the LaLiAl anode favored the inhibition of corrosion in the aprotic electrolyte solution during the cycling process and stability of the electrode morphology. The effect of cathodic polarization and temperature of lanthanum salicylate solution on the kinetics of formation of a thin-film La_yMn_1-yO₂ electrode is also considered in this study. Using the degree of recovery method, the compositions of the Li_xMnO₂, La_yMn_1–yO₂, and Li_xLa_yMn_1–yO₂ electrode phases formed were determined. The currentless chronopotentiometry method was used to determine the stability of the resulting chemical compounds of lanthanum in the MnO₂ electrode structure. Based on the cyclic chronovoltammetry results, good reversibility of the Li_xLa_yMn_1–yO_2–σ(C₆₀)_n electrode was established. The results of galvanostatic cycling indicate that the discharge capacity of the electrodes increases in the series: Li_xMnO₂ > Li_xLa_yMn_1–yO₂ > Li_xLa_yMn_1–yO_2–σ(C₆₀)_n.

Int. J. Corros. Scale Inhib., 2019, 8, no. 2, 282-290 PDF (777 K)
doi: 10.17675/2305-6894-2019-8-2-10

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