A MXene composite-based electrode for electrochemical devices is disclosed. Specifically, an electrochemical composite material comprising Ti.sub.3C.sub.2T.sub.x-Nb.sub.2Mo.sub.3O.sub.14 (MXene niobium molybdenum oxide, MXNMO) and a method of synthesizing the MXNMO composite is disclosed. An electrochemical energy storage device including the MXNMO composite as an electrode is also disclosed.

The present invention features a new way of doping layered cathode materials in sodium-ion batteries. Using a high entropy doping strategy, more than four impurity elements can be introduced to the host materials. The present invention applies this high entropy doping strategy to a sodium cathode material. This new high entropy doping strategy allows the layered oxide materials used in the positive electrode of sodium ion battery to achieve higher charge/discharge rate (i.e. capacity retention is better at high discharge rate), long life cycle and reduced reliance on the expensive and toxic cobalt, all of which are desired attributes for improving the performance of sodium ion batteries and reducing their cost.

A particulate crystalline nanocomposite including: a monoclinic bismuth oxide (Bi.sub.2O.sub.3) crystalline phase; a calcium silicate (CaSiO.sub.3) crystalline phase; and, a graphitic carbon nitride (g-C.sub.3N.sub.4) crystalline phase, wherein at least a fraction of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.

A polycrystalline silicon crushed lump has a surface metal concentration of 15.0 pptw or less, in which a copper concentration is 0.30 pptw or less in the surface metal concentration, and a total concentration of iron and zinc is 2.00 pptw or less in the surface metal concentration, and preferably an iron concentration is 1.25 pptw or less, and a zinc concentration is 0.75 pptw or less.

A method for synthesizing a Cu.sub.2(OH).sub.3NO.sub.3/CaSiO.sub.3@g-C.sub.3N.sub.4 nanostructure includes mixing a calcium silicate (CaSiO.sub.3), a graphite-phase carbon nitride (g-C.sub.3N.sub.4) and a copper salt in a glycol solvent to form a mixture. The method also includes microwaving the mixture to form the nanostructure having a multi-phase crystalline structure with controlled morphology.

A metal-supported material including a transition metal excluding Group 4 elements supported on a binary composite oxide. The composite oxide includes a metal element expressed by A.sub.nX.sub.y, where A represents a lanthanoid that is in a partially or entirely trivalent state, X represents an element that is a Group-2 element in a periodic table selected from the group consisting of Ca, Sr, and Ba, or a lanthanoid, and that is different from A, n satisfies 0<n<1, y satisfies 0<y<1, m satisfies 0m<1, and n+y=1. The composite oxide includes a solid solution that is a tetragonal crystal or a cubic crystal, and a ratio of a value (D.sub.ads) of a dispersion degree of the transition metal obtained by an H.sub.2 pulse chemical adsorption method to a value (D.sub.TEM) of the dispersion degree predicted from an average particle diameter of particles of the transition metal obtained from a TEM image satisfies 0<D.sub.ads/D.sub.TEM<1.

A method of synthesizing gallium nitride includes mixing a rare-earth element into melted gallium to create a solution, bubbling earth abundant nitrogen (N.sub.2) into the solution to produce gallium nitride (GaN). A method of dissociating earth abundant nitrogen (N.sub.2) includes providing a solution that contains a rare-earth element, and bubbling earth abundant nitrogen through the solution to produce atomic nitrogen (N).

A positive electrode active material comprises tertiary particles. Each of the tertiary particles includes secondary particles. Each of the secondary particles includes primary particles. Each of the primary particles includes an olivine-type phosphate compound. In at least part of the tertiary particle, a vacant space is formed between the secondary particles.

A SnS dispersion liquid has SnS particles dispersed in a water-based or alcohol-based dispersion liquid, in which the average major axis of the dispersed SnS particles is 100-2000 nm, the average minor axis of the SnS particles is 50-1000 nm, and the average aspect ratio (major axis/minor axis) is 1.2-1.6. A method for producing an SnS dispersion liquid comprises: a vapor deposition step for heating an SnS raw material housed in an evaporation source container and capturing SnS in a capturing container; an isolation step for separating an obtained vapor deposition product from the capturing container to obtain SnS particles; and a dispersion step for dispersing the vapor deposition product obtained in the isolation step in a water-based dispersion liquid. In the vapor deposition step, the heating temperature of the evaporation source container is 700-900 C., and the maximum capturing container temperature of the capturing container is 80-130 C.

A lithium battery with a cathode fabricated using an improved method for slurry formulation and electrode production. The cathode comprises the epsilon polymorph of vanadyl phosphate, -VOPO.sub.4, made from solvothermally synthesized H.sub.2VOPO.sub.4, and optimized to reversibly intercalate two Li-ions to reach full theoretical capacity with a coulombic efficiency of 98%. This material adopts a stable 3D tunnel structure and can extract two Li-ions per vanadium ion, giving a theoretical capacity of 305 mAh/g, with an upper charge/discharge plateau at around 4.0 V, and one lower at around 2.5 V. The -VOPO4 particles may be modified with niobium (Nb) to improve the cycling stability.