Identifying the components of a Li-ion Battery

Battery- the energy solutions that propel Electric Vehicles are at the core of India's mobility transformation goal. Their importance has again come to the fore with the budget announcement of a forthcoming battery swapping policy. While the current market share of EVs in India is around 1%, India has committed to achieving EV 30@30, which means that 30% of total private vehicle ownership in the country would be of EVs by 2030. Accomplishing this target would lead to the addition of 24 million EV two-wheelers, 2.9 million EV three-wheelers and 5.4 million four wheelers.1 With the battery swapping policy in place, at least twice the number of batteries would be required to propel these vehicles.

Moreover, any battery cannot be used in EVs. They need Lithium-ion batteries for efficient functioning. Lithium-ion batteries are highly capable when compared to other battery types. Advancements in Lithium-ion battery technology have propelled the growth of the EV segment. While several components lead to the formation of a Li-ion battery, some prominent components form the core of these energy storage devices.

Components of a Li-ion battery

Lithium-ion Batteries have four major components- Cathode, Anode, Electrolyte and Separator. Each of these parts is crucial to the functioning of the battery. The absence of any of these can render it useless.

Cathode: Chemical reactions of the Lithium, generates electricity in a Li-ion battery, and hence it occupies the space categorized as the cathode. However, controlling an unstable Lithium is not possible in the pure element form, so a combination of Lithium and Oxygen- lithium oxide is used in the cathode. Lithium Oxide is the active material of a Li-ion battery. A thin aluminum foil holds the cathode frame coated with a compound constituted of active material, conductive additive and binder. The addition of the conductive additive boosts conductivity, and the binder serves as an adhesive that facilitates the active material and the conductive additive to fix sufficiently on the aluminum substrate. The battery's capacity and voltage are dependent on the type of active material used for the cathode. A higher quantity of lithium results in a bigger and better battery capacity. Also, a greater potential difference between cathode and anode leads to a higher voltage. While the potential difference for the anode is generally low, it is relatively high for the cathode. And hence, it plays a substantial role in deciding the battery voltage.

Anode: Anode is the next important thing in a Li-ion battery. The anode substrate is also coated with an active material which enables electric current to flow through the external circuit while permitting reversible absorption/emission of lithium ions released from the cathode. During the charging of the battery, the lithium ions storage happens in the anode. A conducting wire connects the cathode to the anode (discharged state), facilitating the natural flow back of lithium ions to the cathode through the electrolyte. The electron (e-) split from the lithium ions move along the wire to generate electricity. The anode is made with graphite as it has a stable structure.

The cathode substrate also has active material, conductive additive and a binder. Graphite's intrinsic qualities- structural stability, low electrochemical reactivity, lithium-ion storing capabilities and price make it the most suitable anode material.

Electrolyte: Electrolytes facilitate the movement of lithium ions while the electrons separated from them move through the wire. This ability of electrolytes is crucial to the use of electricity in the battery; it plays a significant role by serving as a channel that fosters the movement of lithium ions between the anode and the cathode while preventing the movement of electrons. Materials with high ionic conductivity are primarily used to make electrolytes so that the unabated movement of ions continues. Salts, solvents and additives constitute the electrolyte. While salt allows the movement of lithium ions, solvents are organic liquids that help dissolve the salts. Small amounts of additives are induced for certain specific functions. Electrolyte created in this manner prohibits the movement of electrons while allowing the movement of ions to the electrodes. The electrolyte type decides the movement speed of ions, and hence only those electrolytes which meet rigid requirements can be used.

Separator: The separator acts as an absolute barrier between the cathode and anode. The separator and the electrolyte play a crucial role in determining the safety of the battery. It prevents the direct flow of electrons and cautiously allows the ions to pass through microscopic holes. Since they have a crucial function, they must meet all the requisite physical and electrochemical conditions. Commercially synthetic resins such as polyethylene (PE) and polypropylene (PP) are used as separators.

These four components play a decisive role in the performance, efficiency, durability, and safety of Li-ion batteries. If India needs to achieve the sustainable mobility targets, it needs to strengthen its abilities to manufacture each of these parts. While the country's manufacturing capabilities may face a roadblock due to the unavailability of resources and lack of refining technologies, it may opt for alternative practices like recycling to extract minerals necessary for manufacturing these battery components.