The cathode the "positive" end" absorbs the electrons from that electrolyte, completing the circuit. The common batteries we use to power remote controls, flashlights, and toys--usually named by letters like AA, AAA, C, D--are all alkaline batteries: the cathode is made of manganese dioxide, the anode is made of zinc and the electrolyte is a potassium hydroxide.
When a battery is correctly placed in a device, electrons stream from the anode to the cathode, and this is what powers the device.
A regular battery battery dies when the anode eventually corrodes and the chemical reaction can no longer happen. Once a regular battery is dead, there's not much you can do with it except recycle it. But when you plug a rechargeable battery, also known as a secondary cell, into the wall, the charger forces electrons to stream the opposite direction, and the battery gets refilled with electrons i.
More important, recharging an old-fashioned alkaline battery is not safe. During or after a recharge, the battery might generate enough hydrogen gas to cause an explosion.
In their rechargeable form, alkaline cells have undergone several changes. They have been redesigned to allow for a more efficient reverse reaction, they contain a catalyst to minimize hydrogen formation and they have safety vents that prevent the buildup of excess pressure during recharging. He clarifies why some reactions are irreversible: "All batteries, both rechargeable and nonrechargeable, undergo electrochemical reactions.
When a battery is discharged, an electrochemical oxidation reaction proceeds at the negative electrode, and an electrochemical reduction reaction occurs at the positive electrode. When one attempts to recharge a battery by reversing the direction of electric current flow, the opposite takes place: a reduction reaction proceeds at the negative electrode, and an oxidation reaction takes place at the positive electrode.
For example, when the battery is recharged, the overall electrochemical reduction reaction at the negative electrode is identical to the electrochemical oxidation reaction that proceeded at the negative electrode when the battery was discharged, only written in reverse. When the battery is charged, the overall reduction reaction that proceeds at the negative electrode may not be the true reverse of the oxidation reaction that proceeded when the battery was discharged.
For example, metal oxidation might be the sole oxidation reaction during battery discharge, whereas the formation of hydrogen a highly inflammable and therefore dangerous gas might be a significant reduction reaction during battery recharging. For example, rough or filamentary structures may form in the battery after repeated charge- discharge cycles.
These structures can result in unwanted growth of the electrode and subsequent electronic contact between the battery electrodes- -a short circuit. In the case of the nickel-cadmium battery, the cadmium electrode has two important features.
With a lead anode, a lead dioxide cathode and a sulfuric acid electrolyte, the Plante battery was a precursor to the modern-day car battery. Non-rechargeable batteries, or primary cells , and rechargeable batteries, or secondary cells , produce current exactly the same way: through an electrochemical reaction involving an anode, cathode and electrolyte.
In a rechargeable battery, however, the reaction is reversible. When electrical energy from an outside source is applied to a secondary cell, the negative-to-positive electron flow that occurs during discharge is reversed, and the cell's charge is restored. The most common rechargeable batteries on the market today are lithium-ion LiOn , though nickel-metal hydride NiMH and nickel-cadmium NiCd batteries were also once very prevalent.
When it comes to rechargeable batteries, not all batteries are created equal. NiCd batteries were among the first widely available secondary cells, but they suffered from an inconvenient problem known as the memory effect. Basically, if these batteries weren't fully discharged every time they were used, they would quickly lose capacity.
NiCd batteries were largely phased out in favor of NiMH batteries. These secondary cells boast a higher capacity and are only minimally affected by the memory effect, but they don't have a very good shelf life.
Like NiMH batteries, LiOn batteries have a long life, but they hold a charge better, operate at higher voltages, and come in a much smaller and lighter package.
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