RESUMO
Enhancing the energy density of layered oxide cathode materials is of great significance for realizing high-performance sodium-ion batteries and promoting their commercial application. Lattice oxygen redox at high voltage usually enables a high capacity and energy density. But the structural degradation, severe voltage decay, and the resultant poor cycling performance caused by irreversible oxygen release seriously restrict the practical application. Herein we introduce a novel fence-type superstructure (2a × 3a type supercell) into O3-type layered cathode material Na0.9Li0.1Ni0.3Mn0.3Ti0.3O2 and achieve a stable cycling performance at a high voltage of 4.4 V. The fence-type superstructure effectively inhibits the formation of the vacancy clusters resulting from out-of-plane Li migration and in-plane transition metal migration at high voltage due to the wide d-spacing, thereby significantly reducing the irreversible release of lattice oxygen and greatly stabilizing the crystal structure. The cathode exhibits a high energy density of 545 Wh kg-1, a high rate capability (112.8 mAh g-1 at 5C) and a high cycling stability (85.8%@200 cycles with a high initial capacity of 148.6 mAh g-1 at 1C) accompanied by negligible voltage attenuation (98.5%@200 cycles). This strategy provides a distinct spacing effect of superstructure to design stable high-voltage layered cathode materials for Na-ion batteries.
RESUMO
Sulfide electrolytes with high ionic conductivity hold great promise for all-solid-state lithium batteries. However, the parasitic redox reactions between sulfide electrolyte and Li metal result in interfacial instability and rapid decline of the battery performance. Herein, a redox-resistible Li6 PS5 Cl (LPSC) electrolyte is created by regulating the electron distribution in LPSC with Mg and F incorporation. The introduction of Mg triggers the electron agglomeration around S atom, inhibiting the electron acceptance from Li, and F generates the self-limiting interface, which hinders the redox reactions between LPSC and Li metal. This redox-resistible Li6 PS5 Cl-MgF2 electrolyte therefore presents a high critical current density (2.3 times that of pristine electrolyte). The LiCoO2 /Li6 PS5 Cl-MgF2 /Li cell shows an outstanding cycling stability (93.3 %@100â cycles at 0.2â C). This study highlights the electronic structure modulation to address redox issues on sulfide-based lithium batteries.
RESUMO
Dendrite-free Zn metal anodes with high depth-of-discharge (DoD) and robust cycle performances are highly desired for the practical application of aqueous Zn-ion batteries. Herein, the zincophobic/hydrophilic nature of Metal-N-C through manipulating the electronic interactions between metal and coordination atoms is successfully reversed, thereby fabricating a zincophilic/hydrophobic asymmetric Zn-N3Py+1Pr-C (consisting of a Zn center coordinated with 3 pyridinic N atoms and 1 pyrrolic N atom) host, which realizes uniformed Zn deposition and a long lifespan with high DoD. The experimental and theoretical investigations demonstrate weakened interaction between pyrrolic N and metal center in the asymmetric Zn-N3Py+1Pr-C triggers downshift of the Zn 3d-band-center and a new localization nonbonding state in the N and C 2p-band, resulting in preferred Zn adsorption to water adsorption. Consequently, the asymmetric Zn-N3Py+1Pr-C host delivers small Zn nucleation overpotential and high Coulombic efficiency of 98.3% over 500 cycles. The symmetric cells with Zn-N3Py+1Pr-C@Zn anode demonstrate 500 h dendrite-free cycles at DoD up to 50%. The Zn-N3Py+1Pr-C@Zn/S-PANI full cell also shows a robust long-term cycle performance of 1000 cycles at 10 A g-1. This strategy of constructing zincophilic/hydrophobic Metal-N-C may open up their application for the dendrite-free metal anode.