The method includes mixing and heat-treating carbon nanotubes, a water-soluble polymer dispersant, and an iron (Fe) precursor to form an iron oxide-carbon precursor; mixing and calcining a lithium precursor and the iron oxide-carbon precursor at a temperature of 500? C. or higher to form lithium-iron oxide particles; and heat-treating a mixture containing the lithium-iron oxide particles and a lithium difluoro(oxalato)borate under an oxygen-containing gas atmosphere at a temperature of less than 300? C. to form a lithium-iron oxide coated with a lithium difluoro(oxalato)borate-containing layer.

Described herein is a battery cell having an anode or cathode comprising an acidified metal oxide (AMO) material, preferably in monodisperse nanoparticulate form 20 nm or less in size, having a pH<7 when suspended in a 5 wt % aqueous solution and a Hammett function H.sub.0>?12, at least on its surface.

A method for efficiently preparing ferrate based on nascent state interfacial activity. The method is as follows: (a) preparing nascent iron solution; (b) adding an oxidizing agent to the iron solution of step (a); (c) adding alkali solution or alkali particles to the mixed solution of step (b), mixing by stirring, and carrying out solid-liquid separation; (d) adding a stabilizing agent to the liquid separated out in step (c), and thus obtaining ferrate solution. The yield is 78-98%. The prepared ferrate solution is stable and can be stored for 3-15 days.

The invention relates to novel materials of the formula: A.sub.uM.sup.1.sub.vM.sup.2.sub.wM.sup.3x02.sub. wherein A is one or more alkali metals; M.sup.1 comprises one or more redox active metals with an oxidation state in the range +2 to +4; M.sup.2 comprises tin, optionally in combination with one or more transition metals; M.sup.3 comprises one or more transition metals either alone or in combination with one or more non-transition elements selected from alkali metals, alkaline earth metals, other metals, metalloids and non-metals, with an oxidation state in the range +1 to +5; wherein the oxidation state of M1, M2, and M3 are chosen to maintain charge neutrality and further wherein is in the range 00.4; U is in the range 0.3<U<2; V is in the range 0.1V<0.75; W is in the range 0<W<0.75; X is in the range 0X<0.5; and (U+V+W+X)<4.0. Such materials are useful, for example as electrode materials, in rechargeable battery applications.

According to one embodiment, an active material including a composite oxide is provided. The composite oxide has a monoclinic crystal structure and is represented by the general formula Li.sub.wM1.sub.2xTi.sub.8yM2.sub.zO.sub.17+, wherein: M1 is at least one selected from the group consisting of Cs, K, and Na; M2 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn, and Al; 0w10; 0<x<2; 0<y<8; 0<z<8; and 0.50.5.

The present application discloses a lithium-rich iron-based composite material and a preparation method and application thereof. The lithium-rich iron-based composite material includes a lithium-rich iron-based material having a molecular formular of aLiFeO.sub.2.Math.bLi.sub.2O.Math.cM.sub.xO.sub.y, where a, b, and c are numbers of moles, and 0?c/(a+b+c)?0.02, 1.8?b/a?2.1, M is a doping element, and 1?y/x?2.5. The lithium-rich iron-based composite material can provide abundant lithium, and the lithium-rich iron-based material has a high purity and low residual alkali on the surface, which lead to high capacity and good lithium supplementing effect, as well as good stability for storage and processing. The application of the lithium-rich iron-based composite material in a lithium-supplementing additive for cathodes, a cathode material, a cathode and a lithium-ion battery.

Provided is a material that can be used as a potassium secondary battery positive electrode active material (particularly a potassium ion secondary battery positive electrode active material), other than Prussian blue, by using a potassium compound and a potassium ion secondary battery positive electrode active material comprising the potassium compound, the potassium compound being represented by general formula (1):

K.sub.nA.sub.kBO.sub.m,

wherein A is a positive divalent element in groups 7 to 11 of the periodic table; B is positive tetravalent silicon, germanium, titanium or manganese, excluding a case in which A is manganese and B is titanium, and a case in which A is cobalt and B is silicon; n is 1.5 to 2.5; and m is 3.5 to 4.5.

By using a potassium ion secondary battery positive electrode active material comprising a potassium compound represented by general formula (1): K.sub.nM.sub.m, wherein M is copper or iron, n is 0.5 to 3.5, and m is 1.5 to 2.5, provided is a potassium ion secondary battery positive electrode active material having higher theoretical discharge capacity and higher effective capacity than a potassium secondary battery using Prussian blue as a positive electrode active material.

A method for efficiently preparing ferrate based on nascent state interfacial activity. The method is as follows: (a) preparing nascent iron solution; (b) adding an oxidizing agent to the iron solution of step (a); (c) adding alkali solution or alkali particles to the mixed solution of step (b), mixing by stirring, and carrying out solid-liquid separation; (d) adding a stabilizing agent to the liquid separated out in step (c), and thus obtaining ferrate solution. The yield is 78-98%. The prepared ferrate solution is stable and can be stored for 3-15 days.

A battery comprising an acidified metal oxide (AMO) material, preferably in monodispersed nanoparticulate form 20 nm or less in size, having a pH<7 when suspended in a 5 wt % aqueous solution and a Hammett function H.sub.0>?12, at least on its surface.