An object of the present invention is to provide a composite material usable as a negative electrode material of a lithium-ion secondary battery.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer coating a surface of the carbonaceous material, in which the metal oxide layer coats the surface of the carbonaceous material, forming a sea-island structure in which the metal oxide layer is scattered in islands, and a coating rate of the carbonaceous material with the metal oxide layer is 20% or more and 80% or less.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer and amorphous carbon layer coating the surface of the carbonaceous material, in which the metal oxide layer is scattered in islands on the surface of the carbonaceous material.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer coating the surface of the carbonaceous material, in which the metal oxide layer has at least a portion having a thickness of more than 10 nm, and in a coated area with the metal oxide, an area percentage of a portion having a thickness of 10 nm or less is 70% or more and 99% or less, and an area percentage of the portion having a thickness of more than 10 nm is 1% or more and 30% or less. A composite material of the present invention also includes: a carbonaceous material; and a metal oxide layer and amorphous carbon layer coating the surface of the carbonaceous material, in which the metal oxide layer has at least a portion having a thickness of more than 10 nm, and in a coated area with the metal oxide layer, an area percentage of a portion having a thickness of 10 nm or less is 30% or more and 70% or less, and an area percentage of the portion having a thickness of more than 10 nm is 30% or more and 70% or less.

An object of the present invention is to provide a composite material usable as a negative electrode material of a lithium-ion secondary battery.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer coating a surface of the carbonaceous material, in which the metal oxide layer coats the surface of the carbonaceous material, forming a sea-island structure in which the metal oxide layer is scattered in islands, and a coating rate of the carbonaceous material with the metal oxide layer is 20% or more and 80% or less.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer and amorphous carbon layer coating the surface of the carbonaceous material, in which the metal oxide layer is scattered in islands on the surface of the carbonaceous material.

A composite material of the present invention includes: a carbonaceous material; and a metal oxide layer coating the surface of the carbonaceous material, in which the metal oxide layer has at least a portion having a thickness of more than 10 nm, and in a coated area with the metal oxide, an area percentage of a portion having a thickness of 10 nm or less is 70% or more and 99% or less, and an area percentage of the portion having a thickness of more than 10 nm is 1% or more and 30% or less. A composite material of the present invention also includes: a carbonaceous material; and a metal oxide layer and amorphous carbon layer coating the surface of the carbonaceous material, in which the metal oxide layer has at least a portion having a thickness of more than 10 nm, and in a coated area with the metal oxide layer, an area percentage of a portion having a thickness of 10 nm or less is 30% or more and 70% or less, and an area percentage of the portion having a thickness of more than 10 nm is 30% or more and 70% or less.

A method of diagnosing degradation of an electrode active material for a secondary battery including obtaining a first differential curve (dQ/dV) by differentiating an initial charge/discharge curve obtained by performing first charging and first discharging of the lithium secondary battery in a voltage range of 2.5 V to 4.2 V, and obtaining a second differential curve (dQ/dV) by differentiating a charge/discharge curve obtained by performing second charging and second discharging of the lithium secondary battery in a voltage range of 2.5 V to 4.2 V, and diagnosing whether a beta phase of the positive electrode active material has been formed by comparing maximum discharge peak values of the first differential curve and the second differential curve.

A method of diagnosing degradation of an electrode active material for a secondary battery including obtaining a first differential curve (dQ/dV) by differentiating an initial charge/discharge curve obtained by performing first charging and first discharging of the lithium secondary battery in a voltage range of 2.5 V to 4.2 V, and obtaining a second differential curve (dQ/dV) by differentiating a charge/discharge curve obtained by performing second charging and second discharging of the lithium secondary battery in a voltage range of 2.5 V to 4.2 V, and diagnosing whether a beta phase of the positive electrode active material has been formed by comparing maximum discharge peak values of the first differential curve and the second differential curve.

The present application relates to a battery module including a first-type battery cell and a second-type battery cell at least connected in series, where the first-type battery cell and the second-type battery cell are battery cells of different chemical systems, the first-type battery cell includes N first battery cell(s), and the second-type battery cell includes M second battery cell(s), where N and M are positive integers; and when a battery state of health (SOH) of a first battery cell is the same as an SOH of a second battery cell, and a state of charge (SOC) of the first battery cell is the same as an SOC of the second battery cell, a ratio of a total charge capacity of a first negative electrode sheet of the first battery cell to a total charge capacity of a second negative electrode sheet of the second battery cell is 0.8 to 1.2.

The present application relates to a battery module including a first-type battery cell and a second-type battery cell at least connected in series, where the first-type battery cell and the second-type battery cell are battery cells of different chemical systems, the first-type battery cell includes N first battery cell(s), and the second-type battery cell includes M second battery cell(s), where N and M are positive integers; and when a battery state of health (SOH) of a first battery cell is the same as an SOH of a second battery cell, and a state of charge (SOC) of the first battery cell is the same as an SOC of the second battery cell, a ratio of a total charge capacity of a first negative electrode sheet of the first battery cell to a total charge capacity of a second negative electrode sheet of the second battery cell is 0.8 to 1.2.

The negative electrode disclosed herein includes: a negative electrode current collector; and a negative electrode active material layer formed on the surface of the negative electrode current collector. The negative electrode active material layer contains silicon oxide containing at least one alkali earth metal. The negative electrode active material layer includes at least a first layer and a second layer. The first layer is disposed between the second layer and the negative electrode current collector. The second layer contains 2 mass % or less of the silicon oxide containing the alkali earth metal, relative to 100 mass % of the negative electrode active material in the second layer. The amount of the alkali earth metal in the first layer calculated based on energy dispersive X-ray spectroscopy using a scanning electron microscope image is higher than the amount of the alkali earth metal in the second layer.

According to one embodiment, provided is a nonaqueous electrolyte battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode includes lithium manganese composite oxide particles having a spinel crystal structure and lithium cobalt composite oxide particles. The negative electrode includes a titanium-containing oxide. The nonaqueous electrolyte contains a propionate ester. The battery satisfies 0.8≤p/n≤1.2 and 1≤w/s≤60. p denotes a capacity per unit area of the positive electrode. n denotes a capacity per unit area of the negative electrode. w denotes a content of the propionate ester in the nonaqueous electrolyte and is in a range of 10% by weight to 60% by weight. s denotes an average particle size of the lithium manganese composite oxide particles.

This application provides a positive active material and a preparation method thereof, an electrochemical battery, a battery module, a battery pack, and an apparatus. The positive active material includes an inner core and a coating layer, where the coating layer coats a surface of the inner core. The inner core is selected from a ternary material with a molecular formula of Li.sub.1+a[Ni.sub.xCo.sub.yMn.sub.zM.sub.bM′.sub.c]O.sub.2−dY.sub.d, where distribution of each of the doping elements M, M′, and Y in the inner core meets the following condition: there is a reduced mass concentration gradient from an outer side of the inner core to a center of the inner core. The positive active material herein features high gram capacity, high structural stability, and high thermal stability, so that the electrochemical battery has excellent cycle performance and storage performance and high initial discharge gram capacity.

A cell for use in an electrochemical cell, such as a lithium-ion secondary battery that includes a positive electrode with an active material that acts as a cathode and a current collector; a negative electrode with an active material that acts as an anode and a current collector; a non-aqueous electrolyte; and a separator placed between the positive and negative electrodes. At least one of the cathode, the anode, the electrolyte, and the separator includes an inorganic additive in the form of a metal aluminate or a mixture of metal aluminates that absorbs one or more of moisture, free transition metal ions, or hydrogen fluoride (HF) that become present in the cell. One or more of the cells may be combined in a housing to form a lithium-ion secondary battery. The inorganic additive may also be incorporated as a coating applied to the internal wall of the housing.