An immobilized selenium body, made from carbon and selenium and optionally sulfur, makes selenium more stable, requiring a higher temperature or an increase in kinetic energy for selenium to escape from the immobilized selenium body and enter a gas system, as compared to selenium alone. Immobilized selenium localized in a carbon skeleton can be utilized in a rechargeable battery. Immobilization of the selenium can impart compression stress on both the carbon skeleton and the selenium. Such compression stress enhances the electrical conductivity in the carbon skeleton and among the selenium particles and creates an interface for electrons to be delivered and or harvested in use of the battery. A rechargeable battery made from immobilized selenium can be charged or discharged at a faster rate over conventional batteries and can demonstrate excellent cycling stability.

An immobilized selenium body, made from carbon and selenium and optionally sulfur, makes selenium more stable, requiring a higher temperature or an increase in kinetic energy for selenium to escape from the immobilized selenium body and enter a gas system, as compared to selenium alone. Immobilized selenium localized in a carbon skeleton can be utilized in a rechargeable battery. Immobilization of the selenium can impart compression stress on both the carbon skeleton and the selenium. Such compression stress enhances the electrical conductivity in the carbon skeleton and among the selenium particles and creates an interface for electrons to be delivered and or harvested in use of the battery. A rechargeable battery made from immobilized selenium can be charged or discharged at a faster rate over conventional batteries and can demonstrate excellent cycling stability.

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.

A secondary battery and a preparation method thereof, and a battery module, battery pack, and apparatus containing a secondary battery are provided. In some embodiments, the secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, where the positive electrode plate includes a positive electrode current collector and a positive electrode film layer that is disposed on at least one surface of the positive electrode current collector and that includes a positive electrode active material, and the negative electrode plate includes a negative electrode current collector and a negative electrode film layer that is disposed on at least one surface of the negative electrode current collector and that includes a negative electrode active material; and the positive electrode active material includes a first material and a second material.

A secondary battery and a preparation method thereof, and a battery module, battery pack, and apparatus containing a secondary battery are provided. In some embodiments, the secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, where the positive electrode plate includes a positive electrode current collector and a positive electrode film layer that is disposed on at least one surface of the positive electrode current collector and that includes a positive electrode active material, and the negative electrode plate includes a negative electrode current collector and a negative electrode film layer that is disposed on at least one surface of the negative electrode current collector and that includes a negative electrode active material; and the positive electrode active material includes a first material and a second material.

A nanoparticle cluster reduction method yields a new composition of matter including a large percentage (e.g., 75% or higher percentage) of primary nanoparticles in the new composition of matter. The particle reduction method reduces the size of nanoparticle clusters in material of the new composition of matter, allows particle reduction of specific nanoparticle cluster sizes, and allows particle reduction to primary nanoparticles. This new composition of matter can include a high permittivity and high resistivity dielectric compound. This new composition of matter, according to certain examples, has high permittivity, high resistivity, and low leakage current. In certain examples, the new composition of matter constitutes a dielectric energy storage device that is a battery with very high energy density, high operating voltage per cell, and an extended battery life cycle. An example method can include a controlled gas evolution reaction to reduce the size of nanoparticle clusters.

A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 μm. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 μm. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

Various methods and techniques for enhancing a silicon-containing anode for a battery cell are presented. The methods may include providing a silicon-containing anode having reversible electrochemical capabilities including a silicon-containing material and an anode material compatible with a lithium-ion battery chemistry having porous and conductive mechanical properties. The methods may also include enriching a surface layer of the silicon-containing anode with sodium ions to intersperse the sodium ions between silicon atoms of the silicon-containing material. The methods may also include displacing the sodium ions with potassium ions to form a compression layer in the silicon-containing anode. The potassium ions may place the silicon atoms of the silicon-containing material in a pre-compressive state to counteract internal stress exerted on the silicon-containing material.