Hitachi, Ltd.

Seogchul Shin

Naoki Kimura

Eiji Seki

Kohei Honkura

Yuuji Nagashima

Takashi Kamijoh

An electricity storage system includes: a plurality of rechargeable batteries connected in parallel; and a control unit that controls the rechargeable batteries. The control unit detects a deactivation target rechargeable battery of which charge or discharge need to be deactivated, of the rechargeable batteries, electrically separates and deactivates the deactivation target rechargeable battery from a load in a case where a charging rate of the deactivation target rechargeable battery is lower than a predetermined charging rate, and performs control such that a temperature of the deactivated rechargeable battery is within a predetermined temperature range. In this manner, it is possible to disperse ions inside a battery such that it is possible to recover performance of the battery.

Electricity storage system and method for controlling electricity storage system

A lithium ion secondary battery having a negative electrode includes a negative electrode active material containing at least one of two material of silicon and a silicon compound and carbon, a weight mixing ratio of at least one of two material of the silicon and the silicon compound and the carbon is 20:80 to 50:50, when Dof particles of at least one of two material of the silicon and the silicon compound is x, Dof particles of the carbon is y, and the weight mixing ratio of the carbon is z, y&#x2264;&#x2212;1.17x+0.45z is satisfied, the x is between 2 &#x3bc;m and 10 &#x3bc;m, the y is between 10 &#x3bc;m and 23 &#x3bc;m, and the z is between 50% and 80% by weight, and a coefficient of expansion when the negative electrode is fully charged is 110% or more and 140% or less.

Lithium ion secondary battery and manufacturing method of the lithium ion secondary battery

A lithium ion secondary battery includes: a positive electrode including a positive electrode active material; a negative electrode formed by coating a negative electrode active material mixture onto a surface of a negative electrode collector, the negative electrode active material mixture including a negative electrode active material, a conductive additive, and a binder; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, in which the negative electrode active material includes graphite and an Si alloy, inequities of 0.43&#x2266;x&#x2266;9.0 and 8&#x2266;y&#x3c;18 are satisfied when a mass ratio of the graphite and the Si alloy is defined as x and a coating amount of the negative electrode active material mixture is defined as y (mg/cm). Thus, an initial capacity thereof can be increased and a capacity retention rate thereof can be improved in the lithium ion secondary battery which includes the Si alloy in the negative electrode.

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Tokyo, Japan

Seogchul Shin