Provided are a positive electrode active material for a lithium secondary battery, a method of preparing the same, and a lithium secondary battery including the same.

According to an exemplary embodiment, a positive electrode active material for a lithium secondary battery which includes lithium metal oxide particles and a coating layer placed on at least a part of a surface of the lithium metal oxide particles may be provided, wherein the coating layer includes B, LiOH, Li.sub.2CO.sub.3, and Li.sub.2SO.sub.4.

A secondary battery with favorable cycle performance is provided. Alternatively, a secondary battery with higher capacity is provided. A positive electrode active material layer including a first graphene layer, a second graphene layer, and a positive electrode active material. The first graphene layer includes a first region covering the positive electrode active material. The second graphene layer includes a second region covering the positive electrode active material and a third region overlapping with the first region. The first region includes a plane positioned between the positive electrode active material and the third region and formed of arranged six-membered carbon rings. The positive electrode active material includes a fourth region with a layered rock-salt structure. A lithium layer with a layered rock-salt structure included in the fourth region is substantially perpendicular to the plane formed of six-membered carbon rings and included in the second region.

The present exemplary embodiments relate to a positive electrode active material, a manufacturing method thereof, and a lithium secondary battery including the same. A positive active material for a lithium secondary battery according to an exemplary embodiment is a lithium metal oxide particle in the form of secondary particles including a plurality of primary particles: a first coating layer positioned on at least a part of the surface of the primary particle, and a second coating layer positioned over at least a portion of the secondary particle surface, the first coating layer comprising a first niobium compound, the second coating layer comprising the first niobium compound and a second niobium compound having a composition different from the first niobium compound.

A positive electrode active material for an all-solid-state lithium ion secondary battery, containing: a lithium-metal composite oxide particle having a niobium solid solution layer and a center other than the niobium solid solution layer; and a coating layer coating at least a part of a surface of the lithium-metal composite oxide particle and formed of a compound containing lithium and niobium, an average thickness of the coating layer is 2 nm or more and 1 μm or less, and an average thickness of the niobium solid solution layer is 0.5 nm or more and 20 nm or less.

An electrochemical device, including a positive electrode. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer includes particles A and particles B. A circularity of a particle A is R.sub.A, a cross-sectional area of the particle A is S.sub.A, a circularity of a particle B is R.sub.B, a cross-sectional area of the particle B is S.sub.B, where R.sub.B<0.4≤R.sub.A and S.sub.B<20 μm.sup.2≤S.sub.A. Based on a total area of a cross section of the positive electrode in a direction perpendicular to the positive current collector, a ratio of a total area percent of the particles A to a total area percent of the particles B is 1:9 to 8:2. The electrochemical device exhibits excellent electrochemical performance, especially reduces the amount of generated gas and improves cycle stability of the electrochemical device.

An electrode plate includes a current collector, a first active substance layer, a second active substance layer, and an insulation layer. The current collector includes a first surface, the first active substance layer includes a first active substance, and the second active substance layer includes a second active substance. The first active substance layer is sandwiched between the current collector and the second active substance layer and covers a first portion of the first surface, the insulation layer covers a second portion of the first surface, and the first active substance layer and the insulation layer are stacked to form an overlapped portion in a length direction of the electrode plate. The current collector can be covered by a high-resistance layer, thereby improving safety performance of the electrochemical apparatus and the electronic apparatus.

A negative electrode plate includes: a current collector; and a negative electrode framework located on the current collector, where the negative electrode framework includes at least a first negative electrode framework layer and a second negative electrode framework layer, the first negative electrode framework layer is located between the current collector and the second negative electrode framework layer, and a porosity of the first negative electrode framework layer is higher than a porosity of the second negative electrode framework layer. With this design, side reactions between lithium metal and an electrolyte can be reduced, formation of lithium dendrites can be inhibited, and drastic swelling and contraction of the negative electrode plate in volume due to intercalation and deintercalation of lithium ions can be greatly alleviated or even eliminated, thereby improving safety and stability of the electrochemical apparatus.

Provided is a positive electrode for a secondary battery, which has a multi-layer structure including a first positive electrode active material layer and a second positive electrode active material layer, wherein the first positive electrode active material layer includes a first lithium composite transition metal oxide containing nickel, cobalt, and manganese, the second positive electrode active material layer includes a second lithium composite transition metal oxide containing nickel, cobalt, and manganese, the first lithium composite transition metal oxide and the second lithium composite transition metal oxide have mutually different nickel contents, wherein the positive electrode active material layer including a lithium composite transition metal oxide having a relatively high nickel content includes an electrolyte additive, and the positive electrode active material layer including a lithium composite transition metal oxide having a relatively low nickel content does not include an electrolyte additive.

An electrochemical device includes a negative electrode plate including a negative current collector provided with a negative active material layer and a positive electrode plate including a positive current collector provided with a positive active material layer. The positive active material layer includes a first region. The first region includes a second region and a third region that does not overlap the second region by any area. A first insulation layer is disposed on a surface of the second region. The negative active material layer includes a fourth region facing towards the third region. An area S2 mm.sup.2 of the second region and an area S1 mm.sup.2 of the first region satisfy: S2<S1≤1.5S2, and a ratio CB of a unit-area capacity of the fourth region to a unit-area capacity of the third region is greater than or equal to 1.1.

A method of producing a positive electrode for a non-aqueous electrolyte secondary battery, includes: providing a lithium transition metal composite oxide having a layered structure, having a ratio D.sub.50/D.sub.SEM of 1 or more and 4 or less, and having a certain content of nickel and a certain content of cobalt; bringing the lithium transition metal composite oxide into contact with a cobalt compound to obtain an adhered material; heat-treating the adhered material at a temperature higher than 700° C. and lower than 1100° C. to obtain a heat-treated product; obtaining a positive electrode composition containing the heat-treated product, a conductive auxiliary agent, and a binder; and applying and pressurizing the positive electrode composition onto a collector to form an active material layer having a density of 2.7 g/cm.sup.3 or more and 3.9 g/cm.sup.3 or less on the collector.