Transformation of Polyoxometalate into 3D Porous Li-Containing Oxide: A Case Study of gamma-LiV2O5 for High-Performance Cathodes of Li-Ion Batteries

The development of cathode materials with high Li storage capacity and fast Li-ion diffusion kinetics is considered to be a promising way to extend the energy and power densities of Li-ion batteries (LIBs). As potential high-capacity cathode materials for LIBs, polyoxometalates (POMs) suffer greatly from inherent drawbacks. Therefore, another possibility for the application of POMs in LIBs is shown, which is to transform POMs into relevant 3D porous Li-containing oxides. Here, a unique 3D porous gamma-LiV2O5 film is successfully prepared by combining the electrostatic spray deposition technique and the POM as a precursor. Outstanding high capacity with stable cycling performance and excellent rate capability is realized based on 3D porous nanostructure and thin-film morphology, which effectively facilitate the transport of both lithium ion and electron. Moreover, this work demonstrates the feasibility of achieving high-performance metal oxide cathode by the transformation of POMs and also shows the superiority of gamma-phase over alpha-phase as a starting cathode material in LIBs as well

Toward High Power-High Energy Sodium Cathodes: A Case Study of Bicontinuous Ordered Network of 3D Porous Na-3(VO)(2)(PO4)(2)F/rGO with Pseudocapacitance Effect

Developing high power-high energy electrochemical energy storage systems is an ultimate goal in the energy storage field, which is even more difficult but significant for low-cost sodium ion batteries. Here, fluoride is successfully prepared by the electrostatic spray deposition (ESD) technique, which greatly expands the application scope of ESD. A two-step strategy (solvothermal plus ESD method) is proposed to construct a bicontinuous ordered network of 3D porous Na-3(VO)(2)(PO4)(2)F/reduced graphene oxide (NVOPF/rGO). This two-step strategy makes sure that NVOPF can be prepared by ESD, since it avoids the loss of F element during synthesis. The obtained NVOPF particles are as small as 15 nm, and the carbon content is only 3.5% in the final nanocomposite. Such a bicontinuous ordered network and small size of electroactive particles lead to the significant contribution of the pseudocapacitance effect to sodium storage, resulting in real high power-high energy sodium cathodes. The cathode exhibits excellent rate capability and cycling stability, whose rate performance is one of the best ever reported in both half cells and full cells. Moreover, this work provides a general and promising strategy for developing high power-high energy electrode materials for various electrochemical energy storage systems

A Series of Weakley-type Polyoxomolybdates: Synthesis, Characterization, and Magnetic Properties by a Combined Experimental and Theoretical Approach

Using DCC as the dehydrating agent, a series of Weakley-type polyoxomolybdates [Bu₄N]₃{Ln­[Mo₅O₁₃(OMe)₄(NO)]₂} (Ln = Tb, Dy, Ho, Er) were synthesized in a one-pot reaction and structurally characterized by elemental, IR, UV–vis analysis, PXRD, and single-crystal X-ray diffraction. Furthermore, the static and dynamic measurements were utilized to investigate their magnetic performances. Typically, slow relaxation of magnetization was observed for Dy analogues with an energy barrier for the reversal of the magnetization of 50 K, which is the highest barrier height observed on the polyoxomolybdates-based single-molecule magnets (SMMs). For a deep understanding of the appearance of the SMM behavior on Weakley-type polyoxomolybdates series, <i>ab initio</i> calculations on {Dy­[Mo₅O₁₃(OMe)₄(NO)]₂}^3– have been conducted