Non-aqueous electrolyte secondary battery

Abstract

To provide a means for achieving adequate charge / discharge cycle characteristics in a non-aqueous electrolyte secondary battery having large capacity and a large area even when a mixture of a high-capacity Si material and a carbon material that swells little is used as a negative electrode active material. A non-aqueous electrolyte secondary battery in which the value of the ratio of the battery volume with respect to the rated capacity is 10 cm3 / Ah or less and the rated capacity is 3 Ah or more, the non-aqueous electrolyte secondary battery comprising a power generation element that includes:a positive electrode in which a positive electrode active material layer including a positive electrode active material is formed on the surface of a positive electrode current collector; a negativeelectrode in which a negative electrode active material layer including a negative electrode active material is formed on the surface of a negative electrode current collector; and a separator. The non-aqueous electrolyte secondary battery is characterized in that: the negative electrode active material layer contains a negative electrode active material represented by formula (1), namely, [alpha](Si material) + [beta](carbon material) (in the formula, the Si material is one or more substances selected from the group consisting of Si-containing alloys and SiOx (x represents the number of oxygen atoms satisfying the valence of Si) that is a mixture of amorphous SiO2 particles and Si particles, the carbon material is one or more substances selected from the group consisting of graphite, hardly graphitizable carbon, and amorphous carbon, [alpha] and [beta] represent the mass% of the individual components in the negative electrode active material layer, 80 <= [alpha] + [beta] <= 98, 0.1 <=[alpha] <= 40, and 58 <= [beta] <= 97.9); and when a plurality of discretionary locations within the plane of the negative electrode active material layer are selected, the difference between the maximum value and the minimum value of the area ratio (%) occupied by a binder in the field of view of each of images of a cross section of the negative electrode active material layer is within 10%.

Description

technical field [0001] The present invention relates to a nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery of the present invention can be used, for example, as a driving power source and an auxiliary power source for engines of vehicles such as electric vehicles, fuel cell vehicles, and hybrid electric vehicles. Background technique [0002] In recent years, reductions in the amount of carbon dioxide have been required in response to global warming. Therefore, non-aqueous electrolyte secondary batteries with less environmental burden are being used not only in portable devices, but also in power supply devices for electric vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), and fuel cell vehicles. . Lithium-ion secondary batteries for application to electric vehicles are required to have a large capacity and a large area. [0003] Conventionally, carbon materials such as graphite, which are advantageous in terms...

AI Technical Summary

Problems solved by technology

[0005] However, a lithium-ion secondary battery using a material that alloys with Li, especially Si, as the negative electrode has a large expansion and contraction in the negative electrode during charge and discharge.

For example, the volume expansion when absorbing Li ions is about 1.2 times in the graphite material, while in the Si material, when Si and Li are alloyed, the transition from the amorphous state to the crystalline state causes about 4 times. Large volume change, so there is a problem of reducing the cycle life of the electrode

In addition, in the case of Si negative electrode active materials, capacity and cycle durability are in a trade-off relationship, and there is a problem that it is difficult to improve cycle durability while exhibiting high capacity.

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