A battery is a storage device that stores chemical energy for later conversion to electrical energy. Every battery contains one or more electrochemical cells. Within those cells, chemical reactions take place, creating a flow of electrons in a circuit. This flow of electrons provides the electric current required to do the work!
Every battery has a positive side called a cathode , a negative side called an anode , and a type of electrolyte that chemically reacts with them. The most common types of rechargeable batteries available for our use today are lithium-ion and lead-acid batteries. Lead-acid batteries have been around for over years. They are the oldest rechargeable batteries in existence. Scientists developed lead-acid batteries in the mids. These batteries use old technology to store energy for conversion to electricity.
Each volt lead-acid battery contains six 6 cells, and each cell contains a mixture of sulfuric acid and water. Each cell has a positive terminal and a negative terminal. When the battery is generating power, it is discharging as it does so. The chemical reaction causes the sulfuric acid to break down into the water stored inside each cell for the purpose of diluting the acid. So the use of power depletes the acid. This is the chemical equation for the negative plate that releases electrons.
The HSO-4 is the acid that gets consumed when releasing electrons and hydrogen ions. That process is the storing of energy. Later, we convert the energy stored in the acid to electricity for use. While there are many different types of lead-acid batteries, they all use the same chemical energy storage process. You may recall an earlier mention of the cathode positive side and the anode negative side of a battery.
As it turns out, cathodes and anodes are capable of storing lithium ions. Energy is stored and released when lithium ions move from the cathode to the anode through the electrolyte. Unlike all lead-acid batteries that use the same chemical reaction, lithium-ion batteries come in many different chemistries. When we connect an almost flat battery to an external electricity source, and send energy back in to the battery, it reverses the chemical reaction that occurred during discharge.
This sends the positive ions released from the anode into the electrolyte back to the anode, and the electrons that the cathode took in also back to the anode.
Over the course of several charge and discharge cycles, the shape of the battery's crystals becomes less ordered. High-rate cycling leads to the crystal structure becoming more disordered, with a less efficient battery as a result.
In some cells, it is caused by the way the metal and the electrolyte react to form a salt and the way that salt then dissolves again and metal is replaced on the electrodes when you recharge it. The way some crystals form is very complex, and the way some metals deposit during recharge is also surprisingly complex, which is why some battery types have a bigger memory effect than others.
The imperfections mainly depend on the charge state of the battery to start with, the temperature, charge voltage and charging current. Over time, the imperfections in one charge cycle can cause the same in the next charge cycle, and so on, and our battery picks up some bad memories. The memory effect is strong for some types of cells, such as nickel-based batteries.
Another aspect of rechargeable batteries is that the chemistry that makes them rechargeable also means they have a higher tendency towards self-discharge. This is when internal reactions occur within the battery cell even when the electrodes are not connected via the external circuit. This results in the cell losing some of its chemical energy over time.
A high self-discharge rate seriously limits the life of the battery—and makes them die during storage. The lithium-ion batteries in our mobile phones have a pretty good self-discharge rate of around 2—3 per cent per month, and our lead-acid car batteries are also pretty reasonable—they tend to lose 4—6 per cent per month.
A non-rechargeable alkaline battery only loses around 2—3 per cent of its charge per year. All these words basically describe the strength of a battery, right? Well, sort of. This is also known as electrical potential, and depends on the difference in potential between the reactions that occur at each of the electrodes, that is, how strongly the cathode will pull the electrons through the circuit from the anode. The higher the voltage, the more work the same number of electrons can do.
The higher the current, the more work it can do at the same voltage. Within the cell, you can also think of current as the number of ions moving through the electrolyte, times the charge of those ions.
The higher the power, the quicker the rate at which a battery can do work—this relationship shows how voltage and current are both important for working out what a battery is suitable for. So, we always have to be careful when we talk about battery capacity and remember what the battery is going to be used for. This is the amount of energy a device can hold per unit volume, in other words, how much bang you get for your buck in terms of power vs.
With a battery, generally the higher the energy density the better, as it means the battery can be smaller and more compact, which is always a plus when you need it to power something you want to keep in your pocket. The main goal for this use would be to simply store as much electricity as possible, as safely and cheaply as possible. Video: How do batteries work? View details and transcript.
A range of materials it used to be just metals can be used as the electrodes in a battery. Over the years, many, many different combinations have been tried out, but there are only a few that have really gone the distance. But why use different combinations of metals anyway? Different materials have different electrochemical properties, and so they produce different results when you put them together in a battery cell. For example, some combinations will produce a high voltage, very quickly, but then drop off rapidly, unable to sustain that voltage for long.
This is good if you need to produce, say, a sudden flash of light like a camera flash. Another reason to use different combinations of metals is that often two or more battery cells need to be stacked to obtain the required voltage, and it turns out that some electrode combinations stack together much more happily than other combinations. Our different needs over time have led to the development of a huge array of battery types. To read more about them, and what the future holds for battery power, check out our other Nova topics.
How a battery works Expert reviewers. Luigi Galvani found that the legs of frogs suspended on brass hooks would twitch when prodded with a probe made of another type of metal. Scientists study processes in rechargeable batteries because they do not completely reverse as the battery is charged and discharged. Over time, the lack of a complete reversal can change the chemistry and structure of battery materials, which can reduce battery performance and safety.
But we are still far from comprehensive solutions for next-generation energy storage using brand-new materials that can dramatically improve how much energy a battery can store. This storage is critical to integrating renewable energy sources into our electricity supply. Because improving battery technology is essential to the widespread use of plug-in electric vehicles, storage is also key to reducing our dependency on petroleum for transportation.
BES supports research by individual scientists and at multi-disciplinary centers. This center studies electrochemical materials and phenomena at the atomic and molecular scale and uses computers to help design new materials. This new knowledge will enable scientists to design energy storage that is safer, lasts longer, charges faster, and has greater capacity. As scientists supported by the BES program achieve new advances in battery science, these advances are used by applied researchers and industry to advance applications in transportation, the electricity grid, communication, and security.
0コメント