Groups such as CO 3 2– from adsorbed CO 2. The surfaces of all metal oxides are terminated by hydroxyl groups,Īnd the adsorption of species in air may lead to additional surface Interactions between the cathode, metal oxide, and the electrolyte. 17 Depositing a thin layer of metal oxide atopĪ thin film cathode provides a well-defined environment for studying The fully dense film removes the need forīinders, conductive carbon, and slurry processing variations, as wellĪs enables the planar geometry for simplified electrochemical impedanceĪnalysis and direct control of the interfacial environment. Interest (the electrolyte/metal oxide/cathode interface), thin filmĮlectrodes solely comprising the cathode active material can be usedĪs a model environment. To reduce the complexity of the system of In composite electrodes is challenging because of potential interactionsīetween the metal oxide coatings and the binder, conductive carbon,Īnd conductive graphite. Surface coatings are often amorphous, it is worth noting that crystallinity,Ĭation valence, and the chemical stability of oxide coatings all contribute 8 Similarly, metal dissolution from LiNi 0.8Co 0.15Al 0.05O 2 was reduced whenĬoated with 20 nm sputtered films of ZnO which minimized impedance On NMC111 to improve the rate capability at 3 C and structural integrityĪt high temperatures 7 and suppress Mn 2+ dissolution from spinel LiMn 2O 4. Over additional cycles to 4.4 V versus Li/Li +. 4 Surface doping of Ti 4+ in NMC622 with a nanosizedĬoating of TiO 2 was also found to reduce film impedance Mixing in the bulk structure of the pristine material. To improve the rate capability of NMC622 cycled to 4.5 V versus Li/Li + and was attributed to reduced impedance growthīecause of suppression of interfacial reactions and reduced cation Might stabilize the cathode electrolyte interphase (CEI) would informĬell designs for increased energy density of these promising materials.Ī rough 25–35 nm layer of anatase TiO 2 was shown Of these materials at high voltages, so understanding how coatings layered R 3 ̅ m to rock salt) 16 prevents commercial operation Ni-rich NMC (LiNi xMn 圜o zO 2, where x + y + z = 1 and x > 0.5) cycled to high upper cutoff voltages ( e.g., 4.5 V vs Li +/Li) for additionalĮlectrolyte decomposition coupled with structural rearrangement ( i.e. 15īetween these metal oxide coatings to electrolyteĭecomposition is not well understood for cathode materials such as Interface and the beneficial additive LiPO 2F 2 in the electrolyte. Synergies between surface coatings and electrolyte decomposition haveīeen observed, such as Al 2O 3 reacting with LiPF 6 salt to form a passivating layer of AlF 3 at the 4, 10, 13, 14 The mechanisms involved remain a subject of ongoing study, although HF, suppressing transition metal dissolution, and preventing contactīetween the electrolyte and the active material surface. 10, 12− 14 The cause of this stabilization is often attributed to scavenging Impedance rise during cycling and extend cell cycle life by suppressingĮlectrolyte decomposition. The surface of the cathode active materials before electrode preparation.ĭeposition methods include atomic layer deposition, 3 sol–gel synthesis, 2 hydrolyzation, 4 and physical vapor deposition, 11 and the coatings are reported to reduce charge-transfer Thin layers (up to tens of nm) of Al 2O 3, 1− 3 TiO 2, 4− 6 Cr 2O 3, 7, 8 and ZnO 9, 10 have been coated on Of metal oxides are a common mitigation strategyįor stabilizing lithium-ion battery cathode interfaces which degradeĭuring operation at high voltages (≥4.5 V vs Li/Li +). Suggest that the Brønsted acidity of cathodes directly influencesĮlectrolyte degradation, ion transport, and thus, cell lifetime. The basic surface, resulting in better capacity retention. (CEI) thickness as the more acidic surfaces formed a thicker CEI than ThisĬhemistry was more significant than the cathode electrolyte interphase With more neutral surfaces having a LiF/Li xPO yF z ratioĬlose to unity, but basic surfaces had substantially more LiF. These differences appeared to depend on the degree of LiPF 6 salt decomposition at the interface, which was related to acidity, Had higher initial impedance and greater impedance growth with cycling. Cathodes with more acidic surfaces provided higher initial specificĬapacity and capacity retention with cycling. Under high-voltage cycling (4.5 V vs Li/Li +). Role in the cathode/electrolyte interphase composition and impedance Were used to modify the surface chemistry of LiNi 0.6Mn 0.2Co 0.2O 2 and study the acidity’s In this work, thin films of TiO 2, ZnO, and Cr 2O 3, which have different surface acidities/basicities, Oxide coatings have been reported to be an effective approachįor stabilizing cathode interfaces, but the associated chemistry is
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |