The reason why dry batteries can provide power for electronic devices is that they use chemical reactions to realize the conversion of "chemical energy to electrical energy". Their internal structure is simple but contains an exquisite scientific logic. Different from wet batteries, the electrolyte of dry batteries is not liquid but paste or solid, which is the origin of their "dryness", and also gives them the advantages of portability and no leakage.
Taking the most common alkaline dry battery as an example, its interior is mainly composed of four parts: positive electrode, negative electrode, electrolyte and isolation layer. The positive electrode is usually composed of manganese dioxide (MnO₂) and graphite, and the function of graphite is to enhance conductivity; the negative electrode is a zinc cylinder (Zn), which is both an electrode and the shell of the battery; the electrolyte is a paste solution of potassium hydroxide (KOH), which is responsible for transferring ions; the isolation layer is used to separate the positive and negative electrodes to prevent short circuit, and allow ions to pass through.
The working process of a dry battery is essentially a redox reaction between the positive and negative electrodes. When the battery is connected to a circuit, the zinc atoms at the negative electrode lose electrons and are oxidized into zinc ions (Zn²⁺). The electrons flow to the positive electrode through the external circuit, forming an electric current to supply power to external devices; at the same time, the manganese dioxide at the positive electrode gains electrons and is reduced under the action of the electrolyte, combining with water to form manganese hydroxide (Mn(OH)₂).
In this process, the potassium hydroxide in the electrolyte plays the role of transferring ions, ensuring that the reactions at the positive and negative electrodes can proceed continuously until one of the reactants is exhausted, and the battery's power is also exhausted. This is why disposable dry batteries cannot be recharged repeatedly—the chemical reactions inside them are irreversible, and after the reactants are consumed, they cannot be restored by charging.
Different types of dry batteries have different electrode materials and electrolytes, and their reaction principles are slightly different. For example, the electrolyte of carbon-zinc dry batteries is ammonium chloride paste solution, with low reaction efficiency and small capacity; while lithium batteries use lithium as the negative electrode and solid or gel electrolyte, with high reaction efficiency, large capacity, and reversible reactions, so they can be recharged repeatedly. But no matter which type of dry battery, its core energy conversion logic is "chemical energy converted into electrical energy", which is the fundamental scientific principle of dry battery operation.
