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[Asia Economy Reporter So-yeon Park]

Today, we will learn about the role and composition of the 'electrolyte' according to an explanation from a Samsung SDI battery expert.

Lithium-ion batteries use an electrolyte solution in liquid form.

The electrolyte is a substance that enables the movement of lithium ions (Li+) between the cathode and anode, stabilizes the surfaces of the cathode and anode, and plays a key role among the four main battery materials by enhancing battery life and cell characteristics.

In short, you can think of the electrolyte as the "best driver" for lithium ions traveling between the cathode and anode, acting as a "medium that moves lithium ions quickly and stably," which makes it easier to understand.

The electrolyte mainly consists of lithium salt, organic solvent, and additives. Let's take a look at the roles and characteristics of each.

Pathway for Lithium Ion Movement, Lithium Salt

Lithium salt serves as the pathway through which lithium ions can move.

Therefore, it must easily dissolve in the solvent and dissociate well (the phenomenon where compounds separate into ions), allowing the dissociated ions to move smoothly.

The commonly used lithium salt currently is LiPF6 (composed of lithium, phosphorus, and fluorine), which has superior ion conductivity, solubility, and chemical stability compared to other salts.

Liquid that Dissolves Salt, Organic Solvent

The organic solvent dissolves the lithium salt well, helping lithium ions move smoothly.

There are several required characteristics for organic solvents:

They must have high solubility for lithium salt to effectively separate ionic compounds, and low viscosity to facilitate smooth lithium ion movement.

Depending on the type of solvent, a combination of cyclic carbonates (which have high solubility for salts) and chain carbonates (which have low viscosity) is important to secure high ionic conductivity.

Also, to be used as a solvent, it must have low chemical reactivity because if the solvent reacts with the cathode or anode, safety issues may arise.

As you know, lithium reacts violently with moisture, so the solvent used in the electrolyte does not react with water.

Substance that Determines Electrolyte Characteristics, Additive

Additives are substances added in small amounts for specific purposes, forming protective films on the surfaces of the cathode or anode.

They help lithium ions move smoothly between the cathode and anode and play a key role in preventing battery performance degradation.

Additives can be divided into cathode additives and anode additives. Cathode protective additives stabilize the cathode structure or protect its surface, suppress degradation, improve heat generation, and prevent overcharging.

Anode additives decompose before the solvent, forming a strong film on the anode, improving battery life, reducing heat generation, and maintaining battery capacity.

Both cathode and anode additives share the common traits of dissolving well in the electrolyte solvent and having chemical stability. Different additives are used depending on customer specifications and purposes.

Although additives make up a small portion of the electrolyte, they play a crucial role in the overall electrolyte system by improving lifespan, high-temperature characteristics, and reducing resistance.

What Makes a Good Electrolyte

The electrolyte, composed of lithium salt, organic solvent, and additives, must have important required properties.

Since the electrolyte is a "medium that moves lithium ions quickly and stably," the ability to move lithium ions well is the most important!

The types and content ratios of lithium salt and organic solvent used for this are trade secrets of each company.

Moreover, during battery operation, the electrolyte must be chemically and electrically stable to prevent side reactions that degrade battery performance, and it must have a low freezing point and high boiling point to ensure the battery can always operate.

One of the hottest issues in the battery industry recently is the next-generation battery called the "all-solid-state battery."

This all-solid-state battery uses a solid electrolyte instead of a liquid electrolyte, offering advantages such as no heat generation and no flammability risk, making it relatively safer.

Although commercialization will take some time, many companies including Samsung SDI are actively researching it, so the day we can experience it in our daily lives is not far off.

That concludes our look at electrolytes.

Though it may seem theoretical and difficult, you can think of it like the coffee we commonly enjoy.

Lithium salt is the coffee beans, the organic solvent is the water, and the additive is the syrup, making it easy for non-experts to understand.