WhatIsABattery
From Simreal
What is a battery? A battery is a convenient, portable, chemically driven electricity pump. A chemical redox (reduction/oxidation) reaction occurs at two electrodes which are separated by an ionically conductive electrolyte. The reduction reaction occurs at the cathode, which is the positive electrode. The oxidation reaction occurs at the anode, which is the negative electrode.
Now, the terms ìanodeî and ìcathodeî have always been confusing to me. Isn't the cathode the negative side of a component? But itís listed as the positive terminal of the battery! Both definitions are correct. The anode is, formally, the terminal or electrode where electrons leave a system. In a source of current flow like a battery or generator, the anode is the negative terminal. But in a passive energy-consuming component, it is the positive terminal. Conversely, the cathode is positive on a battery yet negative on a passive component. Of course, where electrons leave a battery, they are entering a component -- so the anode (electrons source) of the battery is connected to the cathode (electron sink) of a component.
This, of course, begs the question ñ what is electricity? And what is it doing when it is "flowing?"
When the battery discharges, powering your circuit, the anode oxidizes and creates a surplus of electrons. These electrons then flow through your circuit (the load) and re-enter the battery at the cathode. They can get back in through the cathode because that terminal is performing the chemical process called reduction, which combines the electrons with the cathode. The electrolyte that bathes both the anode and cathode finishes this electron loop, allowing the electrons to hitch a ride to the anode for a further trip through the oxidation reaction.
Of course, like all good things, itís far more complicated than the previous paragraph lets on. First off batteries donít create electrons ñ they just provide a means of moving them around, like a pump. Second itís not just electrons, the negatively charged particles, that move. Protons also flow in a battery circuit. Finally, electricity is not made out of electrons; it just sounds like it is from most discussions on the subject. Electricity comes in two flavors, positive particles (protons, in the world of electronics) and negative particles (electrons). Protons and electrons carry an equal charge "strength."
In the metal wires of an electrical circuit you get a flow of electrons from the anode to the cathode. However, in the ionic solution that is the electrolyte of a battery, there is a flow in opposite direction of both positively and negatively charged atoms (but not electrons). The electrical current flow inside the electrolyte must exactly match the electron flow outside the battery through the load. Because of this internal flow the internal resistance of the battery to the ionic flow is an important factor in how much energy it can provide over a given time.
One set of Anode, Cathode, and Electrolyte make up a single battery cell. A single cell will typically produce 1.2 to 1.5 volts of electricity at a current level that is dependent on the cellís physical size and chemistry. Due to internal resistance, a high current draw may result in a lower voltage level (such as 1.1 or even 1.0 volts).
To get a higher voltage, multiple cells are strung together end-to-end (Anode to Cathode to Anode to Cathode, etc). To get more current, the cells are attached side-by-side (Anode to Anode, and Cathode to Cathode).
