Structure and composition changes of ZFO-C ( carbon covered ZnFe2O4) nanoparticles [1] used in anodes during Li+ batteries charge and discharge cycles was monitored at the atomic level as a function of time by using XAS [2], a chemical sensitive and short range probe, and by selectively tuning the detection depth by collecting electrons, total and partial yield, and photon fluorescence yield. ZFO (ZnFe2O4) spinel partially inverts [1] after Li insertion in octahedral sites and concomitant migration of Zn from tetrahedral sites. This mechanism is competitive with the conversion alloying mechanism of LiO2, LiZn and separation of metallic Fe. The reversibility of the present transformation is difficult to be tracked by conventional techniques as the disorder dominates and the diffraction techniques fail in following the microscopic phases during the charging and discharging cycle. X-ray absorption experiments have been conceived and realized to study the modification of the signals related to the structure during the lithiation process. To this aim a full multiple scattering calculation was employed, with assistance of full potential to best treat the open structures by using a virtual bcc network of empty spheres. This method will be used for k-shells while L2,3 edges will be studied by means of the empirical program (CTM4XAS) [3]. The nanostructrues of the anode material, consisting of 30-50 nm size covered ZFO particles covered by C, interact with battery environment made by binder ( carboxymethylcellulose) , solid electrolyte (LiPF6) and solvent (mixture of ethylene and dimethyl carbonate). XAS allows to grasp the inner mechanisms of the interface formation and cycling mechanism at the basis of the high capacitance material. In particular the role of the surface and of a partially reversible interface increasing the Li storage limit is under study by the present methods. References 1.Bresser D., Adv. Energy Mater. 2013, 3, 513–523 2. Di Cicco et al., Adv. Enegy Mater. 1500642 (2015)
Structure and chemical composition reversibility during Li-ion rocking chair battery operation based on ZFO anodes
MIJITI, YIMIN;GUNNELLA, Roberto;NOBILI, Francesco;PASQUALINI, MARTA;REZVANI, SEYED JAVAD;CIAMBEZI, MATTEO;DI CICCO, Andrea
2016-01-01
Abstract
Structure and composition changes of ZFO-C ( carbon covered ZnFe2O4) nanoparticles [1] used in anodes during Li+ batteries charge and discharge cycles was monitored at the atomic level as a function of time by using XAS [2], a chemical sensitive and short range probe, and by selectively tuning the detection depth by collecting electrons, total and partial yield, and photon fluorescence yield. ZFO (ZnFe2O4) spinel partially inverts [1] after Li insertion in octahedral sites and concomitant migration of Zn from tetrahedral sites. This mechanism is competitive with the conversion alloying mechanism of LiO2, LiZn and separation of metallic Fe. The reversibility of the present transformation is difficult to be tracked by conventional techniques as the disorder dominates and the diffraction techniques fail in following the microscopic phases during the charging and discharging cycle. X-ray absorption experiments have been conceived and realized to study the modification of the signals related to the structure during the lithiation process. To this aim a full multiple scattering calculation was employed, with assistance of full potential to best treat the open structures by using a virtual bcc network of empty spheres. This method will be used for k-shells while L2,3 edges will be studied by means of the empirical program (CTM4XAS) [3]. The nanostructrues of the anode material, consisting of 30-50 nm size covered ZFO particles covered by C, interact with battery environment made by binder ( carboxymethylcellulose) , solid electrolyte (LiPF6) and solvent (mixture of ethylene and dimethyl carbonate). XAS allows to grasp the inner mechanisms of the interface formation and cycling mechanism at the basis of the high capacitance material. In particular the role of the surface and of a partially reversible interface increasing the Li storage limit is under study by the present methods. References 1.Bresser D., Adv. Energy Mater. 2013, 3, 513–523 2. Di Cicco et al., Adv. Enegy Mater. 1500642 (2015)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
