BATTERY TECHNOLOGY Why are some batteries not rechargeable?
Batteries are ubiquitous today, and both rechargeable and non-rechargeable types are used across a broad spectrum of applications. But why aren’t all types of battery rechargeable?
The fundamentals of the battery have remained largely unchanged since their invention by Italian physicist Alessandro Volta in 1800.
All batteries, even Volta's original ones, have an anode, electrolyte, and cathode. The anode, which is the negative end, provides electrons to the electrolyte through a chemical reaction. The cathode, which is the positive end, absorbs these electrons from the electrolyte, which completes a circuit.
Although all batteries follow this fundamental structure and method of operation, they are broadly separated into two types: primary and secondary.
Primary vs secondary batteries
Primary battery cells are single-use, non-rechargeable batteries. Typical battery chemistries for primary batteries are your standard alkaline batteries such as AA, AAA, C, and D.
In these alkaline batteries, the cathode is made of manganese dioxide while the anode is made of zinc and the electrolyte is a potassium hydroxide. When a primary battery is correctly inserted into a device, electrons move from the anode to the cathode, and this provides power to the device.
Secondary battery cells are rechargeable to their original condition. These are the types of batteries found in devices such as smartphones, electronic tablets, and automobiles.
Secondary batteries are recharged by passing current through the circuit in the opposite direction to the current during discharge. Secondary batteries fall into two sub-categories depending on their applications:
- Batteries that are used as energy storage devices to deliver energy on demand, such as standby power sources.
- Cells that are used as primary cells, but are recharged after use. Examples of these include batteries that are used in consumer electronics and electric vehicles.
Why are primary battery cells not rechargeable?
Primary batteries are cells made of materials such as zinc and carbon. Chemically oxidisation occurs on the anode and reduction on the cathode in an irreversible process. Most primary cells also utilize electrolytes that are contained within absorbent material or a separator, where there is no liquid electrolyte. These are known as “dry cells”.
Primary cells essentially die when the anode material corrodes because chemical reactions can no longer take place. In other words, the process of discharging these primary battery cells causes non-reversible changes to the battery system.
In contrast, a current can be put through secondary battery cells backwards to reverse most of the discharge process. This recharges the battery. This can only be done a limited number of times in a typical lithium-ion cell before it begins to degrade and hold less charge.
Primary vs secondary batteries compared
Primary batteries are cheap and are used wherever there is an inaccessible, disposable, or long-time discharge expected whereas secondary batteries are used for more demanding applications.
Here’s a quick comparison of the two:
|Primary (non-rechargeable) batteries||Secondary (rechargeable) batteries|
|Lower initial cost.||Higher initial cost.|
|Lighter and smaller, which means that they are more suited for smaller, portable applications.||Traditionally less suited for portable applications, although Li-ion technology has changed this.|
|Longer service per charge and good charge retention.||Compared to primary batteries, traditional secondary batteries have inferior retention.|
|Not suitable for heavy load or high discharge rate applications.||Suitable for high discharge rate performance at heavy loads.|
|Limited to specific applications.||Incredible versatile and can be used across a variety of applications.|
Summary: Why are some batteries not rechargeable?
- Batteries are broadly split into two categories: rechargeable and non-rechargeable.
- Non-rechargeable batteries are made of materials that degrade after current has been expended, which means that they are single use and “die” after being discharged.
- Rechargeable batteries on the other hand can have current passed through them in reverse to reverse their charge state, but this can only be done a limited number of times.
- Rechargeable batteries can only be done a limited number of times.
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