Anode and Cathode in Lithium-ion Battery – Working, Chemical Reactions, and Materials

In this fast-growing age of technology, surrounded by electronic appliances and equipment, batteries have become very important. These batteries control almost all aspects of our daily lives and there are different types of them playing their part. Batteries are electrochemical devices that make use of chemistry to generate electrical energy. Batteries consist of two parts namely: Cathode and Anode. The cathode is a metal oxide and the anode is made up of carbon or graphite. Cathode and anode play a major part in the chemical reactions that produce an electrical output.

How do Anode and Cathode Work In Lithium-ion Batteries

Just like any other electrolytic reaction, the reaction inside the Lithium-ion battery is the same. An exchange of ions occurs between the anode and the cathode with the help of material in between, the electrolyte.

During the discharging state of the battery, lithium ions travel from the anode (negative electrode) to the cathode (positive electrode) via an electrolyte. Whereas, during the charging process of the Lithium-ion battery ions travel from the cathode (positive electrode) to the anode (negative electrode).

The cathode of Lithium-ion batteries is made up of an interpolated Lithium compound, Lithium Manganese Dioxide. The anode, stereotypically, is made up of carbon. During the discharge phase of the battery, an oxidation reaction occurs at the anode which produces Lithium ions (positive), electrons (negative), and some by-products at the anode. Lithium-ions and the electrons are transmitted through the electrolytes which then reunite at the cathode in a reduction reaction.

3.2V 20A Low Temp LiFePO4 Battery Cell -40℃ 3C discharge capacity≥70% Charging temperature：-20~45℃ Discharging temperature: -40~+55℃ pass acupuncture test -40℃ maximum discharge rate：3C

READ MORE

The electrolyte of the Lithium-ion battery is a combination of Lithium salts. The external circuit provides a conductivity path for Lithium ions and electrons produced during the reaction. The electrolyte does not itself get involved in the battery reactions. The reactions that occur during the discharge process lowers the chemical power of the cell which in turn offers electrical energy to whatever load is connected to it through the external circuitry. During the charging process, all of these steps are reversed. At this stage, the external circuitry provides electrical energy for the charging process to start and this electrical energy is saved in the form of chemical energy (obtained through reactions) inside the cell.

What is the Chemical Reaction in Lithium-ion Batteries

1.Half-Cell Reactions

a.Anode Reaction (During Battery Discharge):

At the anode, lithium is oxidized from Li to Li +. Means the oxidation state changes from 0 to +1. The ongoing chemical reaction at the lithium-graphite anode is represented symbolically as:

LiC6  C6 + Li+ + e–

b.Cathode Reaction (During Battery Discharge):

These lithium ions from the anode migrate medium to the cathode via an electrolyte. Here they incorporate into lithium cobalt oxide. And here it reduces cobalt from +4 to +3 oxidation state. All this reaction occurring at the cathode is represented symbolically as:

CoO2 + Li+ + e-  LiCoO2 (s)

2.Overall Reaction (At Battery Discharge)

These chemical reactions occur when the battery is discharging. The overall chemical reaction is represented symbolically as:

LiC6 + CoO2  C6 + LiCoO2

3.Chemical Reaction (At Battery Recharge):

At the recharging of the battery or a cell, all these reactions occur in reverse. This means the lithium ions leave, and the bond at lithium cobalt oxide cathode is broken. These lithium ions again go back to the anode. Here they again get reduced and integrate into the graphite system.

Low Temperature High Energy Density Rugged Laptop Polymer Battery Battery specification: 11.1V 7800mAh -40℃ 0.2C discharge capacity ≥80% Dustproof, resistance to dropping, anti - corrosion, anti - electromagnetic interference

READ MORE

What Anode and Cathode Materials Are Good for Lithium-ion Batteries

Anode and Cathode form up the main parts of the cell which produce reactions that help the batteries perform their main function, providing electrical energy. To keep the battery performances optimum and efficient without any chemical or electrical hazards the following materials have been used in commercially available cells up till now.

Cathode Materials

Cathode materials are generally constructed from LiCoO2 or LiMn2O4.

Cobalt-Based Materials

The cobalt-based material develops a pseudo tetrahedral structure that allows for two-dimensional lithium-ion diffusion. The cobalt-based cathodes are ideal due to their high theoretical specific heat capacity, high volumetric capacity, low self-discharge, high discharge voltage, and good cycling performance.

Manganese-Based Materials

The manganese-based materials adopt a cubic crystal lattice system, which allows for three-dimensional lithium-ion diffusion. Manganese cathodes are attractive because manganese is cheaper and because it could theoretically be used to make a more efficient, longer-lasting battery if its limitations could be overcome. LiFePO4 is also a candidate for large-scale production of lithium-ion batteries such as electric vehicle applications due to its low cost, excellent safety, and high cycle durability.

Anode Materials

Currently, there are three most common materials used in the construction of anodes:

Carbon-Based Anodes

Graphite is the most common form of carbon used in the construction of carbon-based anodes. These anodes consist of hexagonal and rhombohedral shaped sheets. When Lithium-ion comes in contact with the anode, the graphite sheets go through re-arrangements. Carbon-based anodes are cost-effective and easily available. They also possess the most suitable electrochemical properties required in Lithium-ion batteries.

Non-Graphitic Anodes

Since Lithium-ion batteries are subjected to research and consistent developments, advances are being made for the use of modern-graphite carbon. Scientists reported that the use of altered graphitic forms helps to improve electrochemical characteristics. These impure forms of graphite lack the property of graphite to re-arrange itself into layers. The non-graphitic anodes work efficiently in combination with solid electrolytes and can be paired with Lithium-Manganese Oxide.

Lithium-Alloy Anodes

Lithium-Alloy anodes are one of the many recent additions applied to the Lithium-ion battery technology. The Lithium-Aluminum, Li-Al, anode is the first Lithium-Alloy anode developed under this category. These alloy anodes offer great advancements in the recycling of Lithium batteries. Lithium titanium oxide is another alloy anode developed to replace the traditional carbon anodes. These anodes offer additional advantages as they offer improved cycles due to the absence of volumetric changes that occur during the Lithium supplement and removal process. The problem with these anodes is that they can not produce high-density energy outputs due to its high operating voltage levels.