A negative electrode active material for a secondary battery comprising silicate composite particles including silicon particles and a lithium silicate phase. The silicon particles are dispersed in the lithium silicate phase, the silicate composite particles have a porosity of 2% or less. In a diffraction pattern by X-ray diffraction (XRD), a ratio I.sub.2/I.sub.1 is 0.3 or less, the ratio I.sub.2/I.sub.1 being a ratio of an integrated intensity I.sub.2 of a peak derived from the lithium silicate phase that appears in a range of 2θ of 23° to 25° relative to an integrated intensity I.sub.1 of a peak derived from Si(111) plane of the silicon particles that appears in a range of 2θ of 27° to 30°.

A negative electrode active material for a secondary battery includes silicate composite particles including silicon particles and a silicate phase. The silicon particles are dispersed in the silicate phase, and the silicon particles contain a first element of at least one selected from the group consisting of germanium and aluminum.

An electrochemical element includes a current collector, and an active material layer on the current collector, wherein the active material layer includes active material particles each having a lithium silicate composite particle including a lithium silicate phase and silicon particles dispersed therein, and a first coating that covers at least a portion of a surface of the lithium silicate composite particle, the first coating includes an oxide of a first element other than a non-metal element, and the active material layer has a thickness TA, and T1b<T1t, where T1b is a thickness of the first coating covering the lithium silicate composite particle at a position of 0.25 TA from the current collector surface in the active material layer, and T1t is a thickness of the first coating covering the lithium silicate composite particle at a position of 0.75 TA from the current collector surface in the active material layer.

An electrochemical element includes a current collector, and an active material layer supported on the current collector, wherein the active material layer contains lithium silicate composite particles each including a. lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material, a first coating covers at least a portion of a surface of the lithium silicate composite particles and at least a portion of a surface of the electrically conductive carbon material, the first coating includes an oxide of a first element other than a non-metal element, and T1.sub.A>T1.sub.c is satisfied, where T1.sub.A is an average thickness of the first coating that covers at least a portion of the surface of the lithium silicate composite particles, and T1.sub.c is an average thickness of the first coating that covers at least a portion of the surface of the electrically conductive carbon material.

An electrochemical cell for a lithium accumulator comprising: a negative electrode comprising metallic lithium as active material; a positive electrode associated with an aluminium current collector; and an electrolyte placed between the negative electrode and the positive electrode, wherein the negative electrode is provided with a layer comprising a compound containing aluminium at its face in contact with the electrolyte, and in that the electrolyte comprises at least one lithium salt chosen from among lithium imide, lithium triflate, lithium perchlorate salts and mixtures thereof.

The present disclosure relates to the technical field of lithium ion battery cathode materials, and particularly discloses a method for preparing a carbon-coated lithium iron phosphate material from ferrous phosphate. The method comprises: mixing self-made ferrous phosphate with a carbon source, and sintering at a low temperature under nitrogen to remove a part of crystal water to obtain carbon-coated ferrous phosphate with a small amount of crystal water; evenly mixing ferrous phosphate with a lithium source, a phosphorus source and multiple carbon sources, and adjusting until a proper iron-to-phosphorus ratio is 0.960-0.975 and a carbon content is 1.5%-1.8%; subsequently drying slurry to obtain material powder; and sintering the material powder through a two-stage temperature rising curve, naturally cooling and then pulverizing to obtain the carbon-coated lithium iron phosphate material. The nano lithium iron phosphate material prepared by the method has high compaction, high capacity and long cycle performance.

A negative active material for a rechargeable lithium battery and a rechargeable lithium battery, the negative active material includes a porous silicon-carbon composite that includes silicon, carbon, and magnesium silicate (MgSiO.sub.3), wherein the negative active material has a diffraction peak intensity ratio I.sub.MgSiO3(610)/I.sub.Si(111) of 0.001<I.sub.MgSiO3(610)/I.sub.Si(111)<0.01, which is a ratio of a diffraction peak intensity I.sub.MgSiO3(610) by MgSiO.sub.3 at 2θ=30° to 32° to a diffraction peak intensity I.sub.Si(111) by Si(111) detected at 2θ=27.5° to 29.5° in a X-ray diffraction analysis.

An active material for a lithium ion secondary battery includes core particles containing SiO or M-SiO materials where M is selected from Al, Cu, Fe, K, Li, Mg, Na, Ni, Sn, Ti, Zn, Zr, or any combination thereof, and an amorphous Group 13 or Group 15 material (“G13/G15 material”) comprising at least one element selected from boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), or bismuth (Bi), coated on the core particles.

Disclosed are a coating composition for a composite positive electrode active material and a method of preparing a composite positive electrode active material using the same.

A preparation method of a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder includes steps of: (Step 1) simultaneously adding NaVO.sub.3 and Na.sub.2S.9H.sub.2O into deionized water, and then magnetically stirring, and obtaining a black turbid solution; (Step 2) sealing after putting the black turbid solution into an inner lining of a reaction kettle, fixing the sealed inner lining in an outer lining of the reaction kettle, placing the reaction kettle into a homogeneous reactor, and then performing a hydrothermal reaction; and (Step 3) after completing the hydrothermal reaction, naturally cooling the reaction kettle to the room temperature, and then alternately cleaning through water and alcohol, and then collecting a product, drying the product, and finally obtaining the tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder with a thickness in a range of 30-60 nm and a single crystal structure grown along a (002) crystal orientation.