RESUMEN
To develop Co-free LiNiO2-based layered cathode materials is crucial for meeting the demands of the lithium-ion batteries with high energy density, long cycling life, and low cost. Herein, the LiNi1-x-yAlxMgyO2 materials are synthesized by the solid-solid interface elemental interdiffusion strategy. It is elucidated that the Mg2+ and Al3+ ions are mainly doped in the Li slabs and transition metal slabs, respectively, leading to the alteration of the crystal lattice. Furthermore, the incorporation of the Mg2+ ions may induce more Ni2+ ions formed in the transition metal slabs, which would have great impact on the electrochemical performance of the materials. The LiNi1-x-yAlxMgyO2 materials with optimized Mg/Al co-doping exhibit much better electrochemical performance than the pristine LiNiO2 and Al-doped LiNiO2 materials, including cycling stability and rate capability. The in-situ XRD characterization and structural analysis show that stabilization of the crystal structure, preservation of the integrity of the secondary particles, and enlargement of the interlayer spacing by the Mg/Al co-doping are the main factors responsible for the superior performance of the materials. The Mg/Al co-doping strategy might be the promising approach for the design of the cobalt-free nickel-rich materials.
RESUMEN
Infrared nonlinear optical (IR-NLO) materials with wide band gaps are important for generating high-power laser light for modern laser technologies. Herein, a wide band gap IR-NLO material, Rb2CdSi4S10, was rationally designed and fabricated by introducing a NLO-active [Si4S10] T2-supertetrahedron (ST) into the quaternary sulfide system. The Rb2CdSi4S10 shows the largest band gap (4.23 eV) among the quaternary chalcogenide IR-NLO materials reported, which results in a high laser-induced damage threshold (LIDT) of â¼5 × AgGaS2 (AGS) at 1064 nm. At the same time, it has a moderate second-harmonic generation (SHG) response (0.6 × AGS). Based on statistical analyses, the Rb2CdSi4S10 is the first compound to be discovered in the AI2BIICIV4QVI10 family, and also the first Si-rich sulfide IR-NLO material with a [Si4S10] T2-supertetrahedra. The results indicate that Rb2CdSi4S10 is a promising new IR-NLO material, and the NLO-active [Si4S10] T2-ST unit could be used for the exploration of IR-NLO material with excellent performances.
RESUMEN
Stable structure and interface of nickel-rich metal oxides is crucial for practical application of next generation lithium-ion batteries with high energy density. Bulk doping is the promising strategy to improve the structural and interfacial stability of the materials. Herein, we report the impact of vanadium-doping on the structure and electrochemical performance of LiNi0.88Co0.09Al0.03O2 (NCA88). Vanadium doped in high oxidation state (+5) would lead to alteration of the crystal lattice and Li+/Ni2+ cation mixing. Those are the main factors determining the cycling and rate capability of the materials. With optimization of vanadium-doping, the preservation of the integrity of the secondary particles of the materials, the enhancement of the diffusion of Li+ ions, and alleviation of the side reactions of the electrolyte can be efficiently achieved. As a result, NCA88 doped with vanadium of 1.5 mol % can provide superior cycling stability with capacity retention of 84.3% after 250 cycles at 2C, and rate capability with capacity retention of 65.5% at 10C, as compared to the corresponding values of 58.6% and 55% for the pristine counterpart, respectively. The results might be helpful to the selection of dopants in the design of the nickel-rich materials.
RESUMEN
A new heavy metal oxychloride, RbPb8O4Cl9, has been synthesized by a high-temperature solution method. The compound crystallizes in the centrosymmetric space group P4/n (no. 85) and exhibits a three-dimensional (3D) framework constructed from [PbO3Cl3], [PbOCl5] and [RbCl8] polyhedra. RbPb8O4Cl9 is an indirect band gap compound with an experimental band gap of 3.66 eV. The first-principles calculations indicate that the band gap mainly originated from the interaction of Pb 6p, O 2p and Cl 2p states. Meanwhile, the calculated birefringence of RbPb8O4Cl9 is about 0.012 at 1064 nm. The compound is the first alkali metal lead oxyhalide, which enriches the structural diversity of oxyhalides and provides an insight for the exploration of new functional materials.
RESUMEN
Destructive effects of surface lithium residues introduced in synthesis and degradation of the microstructure and electrode/electrolyte interface during cycling of Ni-rich cathode materials are the major problems hindering their wide application. Herein, we demonstrate an exquisite surface modification strategy that can utilize lithium residues on the surface of LiNi0.8Co0.15Al0.05O2 to form a uniform coating layer of lithium boron oxide on the surface of the material. The resulting lithium boron oxide layer can not only efficiently serve as a protective layer to alleviate the side reactions at the electrode/electrolyte interface but also tightly interlink the primary grains of the LiNi0.8Co0.15Al0.05O2 material to prevent the material from degradation of the microstructure. As a result, the optimized lithium boron oxide-coated LiNi0.8Co0.15Al0.05O2 material exhibits a high initial discharge capacity of 202.1 mAh g-1 at 0.1 C with a great capacity retention of 93.59% after 100 cycles at 2 C. Thus, the uniform lithium boron oxide coating endows the NCA material with excellent structural stability and long-term cycling capability.
