70
the positive and negative electrodes. The battery reaction occurs when sodium ions
dissolved from the negative electrode combine with sulfur at the positive electrode
to produce sodium polysulfide. At the time of charging, the bonds in the sodium
polysulfide are broken, and sodium ions move to the positive electrode. The charge–
discharge efficiency is about 80%.
The typical characteristic of NAS batteries is that they are high capacity batteries
with high energy density. If capacity is the same, the size of an NAS battery can be
only about one third the size of a lead storage battery. An NAS battery can handle
megawatt-grade electricity storage and it is suitable for large scale solar power systems when arranged in large quantities.
Another potentially appropriate battery is the redox flow battery. This battery
contains a tank containing an electrolytic solution with a potential difference
between the positive electrode and the negative electrode. There is an electrolysis
cell between the two poles, which are connected by a pipe and pump. Historically,
there are various active materials used for electrodes, but currently the most promising type uses vanadium for both the positive and negative electrodes.
While other storage batteries exchange different ions at the electrodes to charge
and discharge, the redox flow battery charges and discharges by the oxidation reduction reaction of the electrolytic solution, so the battery capacity hardly drops. In
other words, long-term use is possible while maintaining the performance. However,
the charge–discharge efficiency is only 75% and the energy density is not high.
Therefore, although it is not suitable for miniaturization, it has the major advantage
that there is no risk of thermal runaway and ignition.
4.1.5 Promising Markets Where Various Uses Can
Be Considered
We introduced three types of storage batteries, but here we will describe the future
prospects for lithium-based storage batteries with the highest charge–discharge efficiency. Table 4.4 shows the current state and future scenario of lithium-ion batteries.
Currently, nickel-based (Ni type) batteries with energy density per kilogram of
250 Wh can be manufactured at ¥13.9/Wh. It is forecast that technology will
advance by 2020, and energy density will be increased to 340 Wh/kg, while manufacturing cost will be reduced to ¥6.6/Wh. In 2030, the active materials will switch
to the Li-S system, the energy density will increase to 530 Wh/kg, but the cost cannot decrease substantially.
Unlike conventional lithium ion batteries, lithium-air batteries do not use metal
compounds, but react with metal lithium and oxygen in the air to generate electricity. Because of the high energy density of these batteries, the automobile industry is
paying attention to this upcoming technology as it can be made smaller and lighter.
Nissan’s EV “Leaf” is equipped with a lithium-ion battery weighing about 300 kg
4 Technology to Support Low-Carbon Society (Utilizing Energy)
the positive and negative electrodes. The battery reaction occurs when sodium ions
dissolved from the negative electrode combine with sulfur at the positive electrode
to produce sodium polysulfide. At the time of charging, the bonds in the sodium
polysulfide are broken, and sodium ions move to the positive electrode. The charge–
discharge efficiency is about 80%.
The typical characteristic of NAS batteries is that they are high capacity batteries
with high energy density. If capacity is the same, the size of an NAS battery can be
only about one third the size of a lead storage battery. An NAS battery can handle
megawatt-grade electricity storage and it is suitable for large scale solar power systems when arranged in large quantities.
Another potentially appropriate battery is the redox flow battery. This battery
contains a tank containing an electrolytic solution with a potential difference
between the positive electrode and the negative electrode. There is an electrolysis
cell between the two poles, which are connected by a pipe and pump. Historically,
there are various active materials used for electrodes, but currently the most promising type uses vanadium for both the positive and negative electrodes.
While other storage batteries exchange different ions at the electrodes to charge
and discharge, the redox flow battery charges and discharges by the oxidation reduction reaction of the electrolytic solution, so the battery capacity hardly drops. In
other words, long-term use is possible while maintaining the performance. However,
the charge–discharge efficiency is only 75% and the energy density is not high.
Therefore, although it is not suitable for miniaturization, it has the major advantage
that there is no risk of thermal runaway and ignition.
4.1.5 Promising Markets Where Various Uses Can
Be Considered
We introduced three types of storage batteries, but here we will describe the future
prospects for lithium-based storage batteries with the highest charge–discharge efficiency. Table 4.4 shows the current state and future scenario of lithium-ion batteries.
Currently, nickel-based (Ni type) batteries with energy density per kilogram of
250 Wh can be manufactured at ¥13.9/Wh. It is forecast that technology will
advance by 2020, and energy density will be increased to 340 Wh/kg, while manufacturing cost will be reduced to ¥6.6/Wh. In 2030, the active materials will switch
to the Li-S system, the energy density will increase to 530 Wh/kg, but the cost cannot decrease substantially.
Unlike conventional lithium ion batteries, lithium-air batteries do not use metal
compounds, but react with metal lithium and oxygen in the air to generate electricity. Because of the high energy density of these batteries, the automobile industry is
paying attention to this upcoming technology as it can be made smaller and lighter.
Nissan’s EV “Leaf” is equipped with a lithium-ion battery weighing about 300 kg
4 Technology to Support Low-Carbon Society (Utilizing Energy)