Non-aqueous electrolyte secondary battery

Abstract

[Problem] To provide a non-aqueous electrolyte secondary battery having a large capacity and a large area, which can realize sufficient charge-discharge cycle characteristics even if a mixture of a high-capacity Si material and a low-expansion carbon material is used as the active material of the negative electrode means. [Solution] A non-aqueous electrolyte secondary battery, characterized in that the ratio of the battery volume to the rated capacity is 10cm 3 / Ah or less and a rated capacity of 3Ah or more, which has a power generating element comprising: a positive electrode formed by forming a positive electrode active material layer containing a positive electrode active material on the surface of a positive electrode current collector; a negative electrode comprising It is formed by forming a negative electrode active material layer comprising a negative electrode active material on the surface of the negative electrode collector; and a separator, the aforementioned negative electrode active material layer contains formula (1)=α (Si material)+β (carbon material) ( , the Si material is selected from as amorphous SiO 2 SiO with a mixture of particles and Si particles x (x represents the number of oxygen used to satisfy the atomic valence of Si) and one or more of the group consisting of Si-containing alloys, and the carbon material is selected from the group consisting of graphite, non-graphitizable carbon, and amorphous carbon One or more, α and β represent the mass % of each component in the negative electrode active material layer, 80≤α+β≤98, 0.1≤α≤40, 58≤β≤97.9. ) shown in the negative electrode active material, when selecting a plurality of arbitrary positions in the layer of the negative electrode active material, the maximum value and the minimum value of the area ratio (%) that the binder occupies in the field of view area of ​​each image of the negative electrode active material layer cross section The difference between the values ​​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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