Ngk Insulators, Inc.

The Tokyo Electric Power Company, Incorporated

Kazuhito Furuta

Naoki Hirai

Michitaka Hidaka

Masaki Shimizu

Keita Ikuta

Akiyasu Okuno

Hideki Rachi

An end-of-discharge voltage correction section subtracts, from an end-of-discharge open voltage, the product I&#xd7;RO of a discharge current I of a block and an ohmic resistance RO of the block and the product ITD&#xd7;RP of a discharge current ITD obtained by performing a time delay process on the discharge current and a polarization resistance RP of the block. Then, a resulting value is set as an end-of-discharge voltage VL. The ohmic resistance RO is increased as an equivalent cycle count CY increases, and is increased as a healthy parallel number NPH decreases. An increment &#x394;CY of the equivalent cycle count CY in each charge/discharge cycle becomes greater as a discharge depth DD increases. The healthy parallel number NPH is derived by multiplying a healthy parallel number NPHR of a reference block by the ratio of a capacity CPR of the reference block to a capacity CPS of a target block.

End-of-discharge voltage correction device and end-of-discharge voltage correction method

A current collector positive electrode enabling a NaS battery to be excellent in the charge recovery characteristic and low in internal resistance is provided, which collector has a high resistance layer formed by needle-punching glass fibers with 5 to 15 &#x3bc;m fiber diameter into a felt substrate made of carbon fibers or graphite fibers by needle-punching from one surface of the substrate toward another surface of the substrate. The density of the glass fibers needle-punched into the substrate is gradually decreased in the direction from the above mentioned surface to the other surface of the substrate, and the deepest portions of the needle-punched glass fibers reach the depths of 85 to 100% of the substrate thickness.

Current collector of positive electrode and sodium-sulfur battery using the same

Growing community of inventors

Kasugai, Japan

Kazuhito Furuta