A critical challenge in the commercialization of layer-structured Ni-rich materials is the fast capacity drop and voltage fading due to the interfacial instability and bulk structural degradation of the cathodes during battery operation. Herein, with the guidance of theoretical calculations of migration energy difference between La and Ti from the surface to the inside of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , for the first time, Ti-doped and La 4 NiLiO 8 -coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes are rationally designed and prepared, via a simple and convenient dual-modification strategy of synchronous synthesis and in situ modification. Impressively, the dual modified materials show remarkably improved electrochemical performance and largely suppressed voltage fading, even under exertive operational conditions at elevated temperature and under extended cutoff voltage. Further studies reveal that the nanoscale structural degradation on material surfaces and the appearance of intergranular cracks associated with the inconsistent evolution of structural degradation at the particle level can be effectively suppressed by the synergetic effect of the conductive La 4 NiLiO 8 coating layer and the strong TiO bond. The present work demonstrates that our strategy can simultaneously address the two issues with respect to interfacial instability and bulk structural degradation, and it represents a significant progress in the development of advanced cathode materials for high-performance lithium-ion batteries.
Aqueous Zn-ion batteries (AZIBs) have been recognized as promising energy storage devices due to their high theoretical energy density and cost-effectiveness. However, side reactions and Zn dendrite generation during cycling limit their practical application. Herein, ammonium acetate (CH 3 COONH 4 ) is selected as a trifunctional electrolyte additive to enhance the electrochemical performance of AZIBs. Research findings show that NH 4 + (oxygen ligand) and CH 3 COO -(hydrogenligand) with preferential adsorption on the Zn electrode surface can not only hinder Zn anode directly contact with active H 2 O, but also regulate the pH value of the electrolyte, thus suppressing the parasitic reactions. Additionally, the formed SEI is mainly consisted of Zn 5 (CO 3 ) 2 (OH) 6 with a high Zn 2+ transference number, which could achieve a dendrite-free Zn anode by homogenizing Zn deposition. Consequently, the Zn||Zn symmetric batteries with CH 3 COONH 4 -based electrolyte can operate steadily at an ultrahigh current density of 40 mA cm -2 with a cumulative capacity of 6880 mAh cm -2 , especially stable cycling at −10 °C. The assembled Zn||MnO 2 full cell and Zn||activated carbon capacitor also deliver prominent electrochemical reversibility. This work provides unique understanding of designing multi-functional electrolyte additive and promotes a long lifespan at ultrahigh current density for AZIBs.
Nickel-rich layered oxide cathode materials for advanced lithium-ion batteries have received much attention recently because of their high specific capacities and significant reduction of cost. However, these cathodes are facing a fundamental challenge of loss in performance as a result of surface lithium residue, side reactions with the electrolyte and structure rearrangement upon long-term cycling. Herein, by capturing the lithium residue on the surface of LiNiCoMnO (NCM) cathode material as Li source, we propose a hybrid coating strategy incorporating lithium ions conductor LiAlO with superconductor LiTiO to overcome those obstinate issues. By taking full advantage of this unique hybrid nanomembrane coating architecture, both the lithium ion diffusion ability and electronic conductivity of LiNiCoMnO cathode material are improved, resulting in remarkably enhanced electrochemical performances during high voltage operation, including good cycle performance, high reversible capacity, and excellent rate capability. A high initial discharge capacity of 227 mAh g at 4.4 V cutoff voltage with Coulombic efficiency of 87.3%, and reversible capacity of 200 mAh g with 98% capacity retention after 100 cycles at a current density of 0.5 C can be attained. The improved electrochemical performance can be attributed to the synergetic contribution from the removal of lithium residues and the unique hybrid nanomembrane coating architecture. Most importantly, this surface modification technique could save some cost, simplify the technical procedure, and show great potential to optimize battery performance, apply in a large scale and extend to all nickel-rich cathode material.
The room-temperature magnetic properties of core–shell
iron–iron
oxide nanoclusters (NCs) synthesized by a cluster deposition system
were investigated, and their dependence on mean cluster size is discussed.
In this study, the surface/boundary spins of clusters were not frozen
and were thermally activated during the measurements. The intercluster
interactions between clusters and intracluster interactions between
the iron core (ferromagnetic) and iron oxide shell (ferrimagnetic)
were investigated by field-dependent isothermal remanent magnetization
and dc demagnetization measurements at room temperature. The Henkel
and ΔM plots support the existence of dipolar
intercluster interactions that become stronger with the growth of
the clusters. The derivative of the initial magnetization curve implies
that smaller clusters require lower fields and less time than larger
ones to overcome various energy barriers before saturating the moments
along the field direction. Coercive field and magnetization were also
correlated with the interaction parameters. To compare the room-temperature
magnetic results, one system was studied at low temperature, where
exchange coupling at the interface between the oxide and metallic
phases was observed through bias effect and anisotropy enhancement.
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