Renewable energy such as solar has a basic problem: No sun , no power. In order to make it more usable the Power must be stored for off peak use when the sun does not shine. Batteries though die when repeatedly recharged. Stanford researchers have developed part of better battery, a new electrode that employs crystalline nanoparticles of a copper compound. In laboratory tests, the electrode survived 40,000 cycles of charging and discharging, after which it could still be charged to more than 80 percent of its original charge capacity. For comparison, the average lithium ion battery can handle about 400 charge/discharge cycles before it deteriorates too much to be of practical use.
Rechargeable batteries have their energy content restored by charging, some deterioration occurs on each charge—discharge cycle. Low-capacity NiMH batteries (1700—2000 mA·h) can be charged for about 1000 cycles, whereas high-capacity NiMH batteries (above 2500 mA·h) can be charged for about 500 cycles.
Short-term transients, including those related to wind and solar sources, present challenges to the electrical grid. Stationary energy storage systems that can operate for many cycles, at high power, with high round-trip energy efficiency, and at low cost are required. Existing energy storage technologies cannot satisfy these requirements.
The new electrode was made using crystalline nanoparticles of a copper compound called copper hexacyanoferrate. Most batteries fail because of accumulated damage to an electrode’s crystal structure caused as ions – the electrically charged particles whose movements either charge or discharge a battery – move in and out of the electrode. In comparison, the atomic structure of the crystals found in the new electrode have an open framework that allows ions to easily move in and out without damaging the electrode.
Laboratory tests saw the electrode survive 40,000 charging/discharging cycles, after which it could still be charged to 80 percent of its original capacity. This is a huge improvement over an average lithium-ion battery, which can handle around 400 charge/discharge cycles before it deteriorates too much for practical use. And because the ions can move so freely, the charging and discharging cycles of the new electrode are extremely fast.
There are a few issues still, these batteries are very large so they will not be practical for anything other than a power grid. Also, its chemical properties make it only usable as a high voltage electrode and every battery needs two electrodes – a high voltage electrode for the cathode and a low voltage electrode for the anode – in order to create the voltage difference that produces electricity. This means the researchers will have to find another material to use for the anode before they can build an actual battery.
Article by Andy Soos, appearing courtesy Environmental News Network.