Batteries are ubiquitous in modern life, powering everything from small devices like flashlights and watches to large systems like cars and home solar energy setups. But how exactly do these seemingly magical little devices turn stored chemical energy into usable electricity? Read on to find out.
What’s in a Battery?
Batteries are ubiquitous in modern life, powering everything from small devices like flashlights and watches to large systems like cars and home solar energy setups. But how exactly do these seemingly magical little devices turn stored chemical energy into usable electricity? Read on to find out.
What’s in a Battery?
At its most basic level, a battery consists of three components:
- Anode – The negative electrode from which electrons flow out towards the external circuit. Common anode materials are zinc, lithium, and lead.
- Cathode – The positive electrode that accepts electrons coming in from the external circuit. Common cathodes include manganese dioxide, nickel oxide, and lithium cobalt oxide.
- Electrolyte – The conductive medium that separates the anode and cathode yet allows ion flow between them. Electrolytes can be liquid, gel, or solid.
The anode and cathode electrodes do not touch each other directly. The electrolyte facilitates ion transfer for the electrochemical reactions while preventing the electrodes from short circuiting.
Electrochemical Reactions Release Energy
Within a battery, reduction-oxidation or “redox” chemical reactions release stored chemical energy in the form of electrical energy. At the anode, the metal gives up electrons to the external circuit, becoming oxidized. At the cathode, the positive ions coming through the electrolyte accept the electrons coming in through the circuit, becoming reduced.
The electrolyte allows ions to flow between the anode and cathode to balance the charges while keeping the electrodes separate. The electrons released at the anode cannot re-enter the battery directly but are forced to travel through the external circuit, powering the connected device.
Different Chemicals = Different Voltages
The type of metals or compounds used for the anode and cathode determine the electrical potential energy released by the battery, also known as its voltage. For example, zinc-carbon batteries provide around 1.5V while lithium-ion batteries generate approximately 3.7V.
Connecting batteries in series sums their voltages while connecting in parallel maintains voltage but increases available current. Six 1.5V zinc-carbon batteries combined in series makes a 9V battery. Modern high-capacity lithium-ion batteries use thousands of small battery cells wired in parallel.
Discharge = Chemical to Electrical Energy Conversion
When a battery is powering a device, it is discharging stored chemical energy as electrical energy. The redox reactions drive electron flow from the anode to the cathode through the external circuit, while ions flow internally between electrodes. This flow of electrons is the electric current that powers the device.
The battery will continue providing electricity until one of the reactants becomes depleted and the reactions can no longer sustain electron flow. At this point the battery is discharged and must be replaced or recharged.
Recharge = Electrical to Chemical Energy Conversion
In rechargeable batteries, the chemical reactions are reversible. Applying an external voltage drives the reactions in reverse, re-depositing the reactants onto the electrodes in their original oxidized (anode) and reduced (cathode) forms. This enables the battery to once again provide electricity when discharged.
Examples include lead-acid car batteries and lithium-ion batteries common in consumer electronics. These batteries can discharge and recharge hundreds or thousands of times before reactants are fully depleted.
Batteries Unlocked
In summary, batteries contain electrochemical cells that convert the stored chemical energy of their anode and cathode materials into electrical energy through reduction-oxidation reactions. The electrons released generate current flow through the external circuit while ions flow internally through the electrolyte. Engineer your own battery adventures by mastering these fundamental electrochemical principles!