Batteries have become an integral part of our daily lives powering a wide variety of portable devices like smartphones, laptops, tablets, cameras etc. Secondary batteries also known as rechargeable batteries provide a reliable source of power that can be recharged multiple times by passing current in the opposite direction of its discharge. Some common types of secondary batteries include lead-acid batteries, lithium-ion batteries, nickel-cadmium batteries etc.

Chemistry Behind Secondary Batteries

All batteries work on the basic principle of electrochemistry where a spontaneous redox reaction is set up between the anode and cathode through an electrolyte when an external load is connected. In a secondary battery, this spontaneous redox reaction is reversible allowing the battery to be recharged. The specific chemistry however differs between battery types.

Lead-acid batteries which are commonly used in automobiles have lead dioxide as the positive electrode and lead as the negative electrode. During discharge, lead reacts with sulfuric acid to form lead sulfate and release electrons which flow through the external circuit to the lead dioxide electrode. Upon recharge, the redox reaction is reversed with current flowing in the opposite direction.

Lithium-ion batteries have emerged as the dominant chemistry in portable electronics due to their high energy density. They use lithium ions as charge carriers shuttling between the negative graphite anode and positive lithium metal oxide cathode. During discharge, lithium ions are extracted from the layered crystal structure of the cathode and inserted into the graphite anode. Recharge restores the lithium ions to the cathode.

Nickel-cadmium batteries were popular earlier but have reduced usage now due to environmental concerns over cadmium. They utilize a nickel oxyhydroxide positive plate and a cadmium negative plate. The transfer of electrons and ions during charge-discharge involves chemical changes in both electrodes.

Mechanism of Charge-Discharge

The exact charge-discharge mechanism varies between battery chemistries but broadly follows the same steps. During discharge, a spontaneous redox reaction occurs between the two electrodes generating electron flow through the external circuit. Lithium ions travel internally from the cathode to the anode phase.

For recharging, an external power source forces current in the opposite direction. At the anode, the electroactive material accepts electrons from the external circuit and converts to its charged form. Simultaneously at the cathode, electrons are removed and the electroactive material is reconverted to its discharged state. Lithium ions also move in the reverse direction – from the anode back to the cathode phase.

This charge-discharge cycling can occur hundreds to thousands of times in Secondary Battery depending on chemistry, materials used, depth of discharge and environmental factors like temperature. Rechargeable batteries are designed so the internal components can withstand repeated structural changes without degradation.

Applications of Secondary Batteries

The widespread adoption of portable electronics has majorly driven advancements in secondary batteries over the past few decades. Some key areas where rechargeable batteries are utilized:

– Consumer Electronics: Smartphones, laptops, tablets, power banks etc. rely heavily on lithium-ion batteries for their compact, high-capacity power needs.

– Electric Vehicles: With the push for electrification of transportation, substantial R&D is focused on developing advanced lithium-ion battery packs for electric cars, buses and two-wheelers.

– Energy Storage: Lithium-ion and lead-acid batteries are increasingly used for stationary energy storage applications like renewable energy integration, backup power and microgrids.

– Industrial Equipment: Industrial processes, machinery, robots, warehouses utilize SLA or lithium-ion battery packs for mobility and backup requirements.

– Medical Devices: Portable medical equipment like surgical tools, patient monitors, wearables require reliable rechargeable batteries.

Advantages and Limitations

Secondary batteries hold numerous advantages like the ability to be re-energized hundreds of times, environmental friendliness over primary batteries, better performance than older NiCad technology. However, limitations remain around factors like:

– Limited Cycle Life: Batteries can degrade over hundreds of charge cycles losing capacity. Heat, depth of discharge impact this.

– Cost: Lithium-ion cell costs while declining are still higher than lead-acid equivalents limiting some applications.

– Safety: Cell damage risks, overheating during fast charging are challenges, especially for large battery packs in EVs. Strict protocols are required.

– Environmental Impact: Proper e-waste disposal is needed to minimize pollution from discarded batteries containing heavy metals like cadmium, lead.

– Charge Time: Replenishing large battery capacities can take hours even with fast charging, unlike refueling vehicles.

Future Outlook

The steady rise of battery-dependent technologies and surge in electric vehicles is driving intensive R&D to develop advanced secondary battery materials, designs and manufacturing techniques that can address current limitations. Some key focus areas include new lithium-ion chemistries with higher energy density like lithium-sulfur and solid-state batteries; low-cost alternatives to cobalt for cathodes; improved thermal management and safety; recycling processes. With continuous innovation, batteries are projected to power a growing share of the global energy needs over the coming decades.

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1.  Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it