Elucidating the cathode chemical process of lithium ion batteries using in-situ XASF electrochemical cell

JORI, KHALIL; THOMAS, JORGE E.; GIOVANETTI, LISANDRO J.; SANSERVINO, MIGUEL A.; AZEVEDO, GUSTAVO; FELIX REQUEJO; ARNALDO VISINTIN

Campinas

Encuentro; 28th RAU Annual Users Meeting LNLS/CNPEM; 2018

CNPEM

To improve the performance and efficiency of Libased batteries is indispensable to have a clear comprehension of the processesthat occurs during the use of these systems. But sometimes, thesephysicochemical processes cannot be detected by electrochemical measurements,and in the case of lithium ion batteries, the possibility to makeelectrochemical experiments in a classical tree electrodes open cell joined toother chemical or physical techniques is very hard. Typical impediments to thistype of experiment are, for example, the nature of the electrodes, electrolytesand working conditions of these types of batteries. For this reason we developan in-situ lithium ion battery cell system capable to work in typicalcurrent/potentials experiments for these kinds of batteries and at the sametime allow performing X-Ray absorption experiments over the active materials.Mn spinels (used as cathode) were synthetized bythe traditional method of solid phase calcination, starting from thestoichiometric mixture of Li and Mn carbonates and Ni oxide in atmosphere of O2at 820 ºC for 12 hours. The samples were grounded and conditioned for carryforward the electrochemical experiments.In the recent literature In situ x-ray absorptiondemonstrate to be a very useful elucidating the structural and electronicchanges that follows lithiation/delithiation process1. In this workwe highlight some of our recent results using in situ x-ray absorptionspectroscopy obtained at the DAXS beamline. XAS measurements were done in situat Ni-K edge and at Mn-K edge for comparative purposes in order to intent todetermine the role of the Ni inclusion in the lithiation/delithiation process. Inboth experiments, at Ni and Mn K edges, XANES demonstrate to be sensitive tothe Li intercalation. The comparison of spectra obtained for samples with andwithout Ni shows a higher variation on the Mn K edge in the samples withoutNi.  The biggest change during thedischarge is observed on the Ni K edge and is associated to the variation onthe oxidation state and coordination number of the Ni atoms during Liintercalation.