SiO powder for secondary battery and process for producing the same

Abstract

An SiO powder for secondary battery that is used as a negative electrode material of lithium secondary battery and characterized in that the concentration of contained hydrogen is = 80 ppm. The powder would enable striking enhancement of discharge capacity and rate of cycle capacity maintenance and thus would enable realization of a size reduction of lithium secondary battery and cost reduction thereof. There is provided a process for producing such an SiO powder, comprising mixing silicon dioxide powder with a silicon powder of = 30 ppm contained hydrogen concentration, heating the mixture at 1250 DEG to 1350 DEG C so as to achieve gasification of SiO, depositing the SiO on a deposition base, and thereafter carrying out pulverization thereof. Thus, the SiO powder can be produced with high efficiency and can realize substantial reduction of production costs, such as power cost, so that it can find a wide spectrum of application as an SiO powder for secondary battery.

Description

technical field [0001] The present invention relates to SiO powder most suitable for use as a negative electrode material of a lithium secondary battery capable of occluding and releasing lithium by using a lithium ion conductive nonaqueous electrolyte, and a method for producing the same. Background technique [0002] In recent years, along with the remarkable development of portable electronic devices, communication devices, etc., development of secondary batteries with high energy density has been strongly demanded from the viewpoint of economy, size reduction and weight reduction of devices. As such high-energy-density secondary batteries, there are nickel-cadmium batteries, nickel-hydrogen batteries, lithium-ion secondary batteries, and polymer batteries. However, lithium-ion secondary batteries (hereinafter referred to as "lithium secondary batteries") are due to NiCd batteries or NiMH batteries have a longer life and higher capacity than NiCd batteries, so their deman...

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Problems solved by technology

[0015] However, in the negative electrode active materials disclosed in JP-A-2001-118568 and JP-A-2002-260651, when silicon oxide is used as the anode material, although it is desired to set SiO x The value of X in the composition, the specific surface area, or the shape of the powder, etc., to improve the irreversible capacity during the initial charge and discharge or the maintenance of the discharge capacity (cycle), but it cannot alleviate the problem of lithium ion adsorption and desorption. The volume expands, so there is a problem that it cannot ensure sufficient discharge capacity maintenance (cycle performance) as a negative electrode material for lithium secondary batteries

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