Panasonic Corp developed a nickel-cadmium (Ni-Cd) rechargeable battery capable of charging/discharging even at a temperature as low as -40°C.
The company will start to ship samples of the battery, “Cadnica GT Series,” in August 2013. It plans to start volume production at its Sumoto Plant in fiscal 2014 at a rate of one million units per month.
The lowest temperature at which most of the existing rechargeable batteries can be used is -20°C. At a temperature lower than that, it is not possible to ensure enough capacity. The new battery was realized by (1) reducing the sizes of negative-electrode active materials, (2) improving electrolyte and (3) employing a strong sintered carrier for the positive electrode.
First, Panasonic increased the surface area of the negative plate by 100% by reducing the sizes of the negative-electrode active materials near the surface of the plate because the response of the active materials deteriorates at a low temperature. As a result, it improved low-temperature properties by 50%.
Second, the electrolyte of Panasonic’s previous product is frozen at a temperature of -30°C or lower. Therefore, the company improved the electrolyte so that the low-temperature properties do not deteriorate while increasing the density of the electrolyte to lower the freezing point.
Third, there is a problem that, when an overcharge occurs at a low temperature, γ-NiOOH tends to be generated instead of β-NiOOH, which is normally generated, at the positive electrode. The volume density of γ-NiOOH is about 20% higher than that of β-NiOOH. As a result, when γ-NiOOH inflates, the life of the battery is shortened.
To solve this problem, Panasonic employed a positive plate having a Ni frame structure strengthened by sintering technology. With such technologies, the company ensured that, even at a temperature of -40%deg;C, the capacity of the battery is higher than 60% that of the capacity at a normal temperature.
Panasonic plans to apply the Cadnica GT to traffic lights, base stations, backup power sources for servers, etc, emergency lighting systems in refrigerated warehouses, street lamps using photovoltaic (PV) batteries and stand-alone power supply systems such as power storage systems.
Especially, it is considering expanding sales of the battery for use in the Hokkaido region of Japan, northern areas of the US, Canada, Russia, Northern Europe and other cold regions where it is difficult to stably use rechargeable batteries in winter as well as in refrigerated warehouses.
Panasonic will release SC, C and D sizes of the Cadnica GT Series. The SC size has a diameter of 22.9mm, length of 43.0mm, mass of about 47g and capacity of 1,500mAh. The C size has a diameter of 26.0mm, length of 50.0mm, mass of about 73g and capacity of 2,500mAh. The D size has a diameter of 33.2mm, length of 59.5mm, mass of about 150g and capacity of 4,000mAh.
The operating temperature range of the three sizes is -40 to +60°C.