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What Is the Electrolyte in Lithium-Ion Batteries? 

 September 19, 2021

By  Phil Borges

Lithium-ion batteries are efficient and rechargeable batteries that have a range of applications. These usually comprise positive and negative electrodes (cathode and anode), an electrolyte and separators.

The electrolyte in lithium-ion batteries can either be liquid or solid in its form. Most commonly, liquid electrolytes tend to be used, although several advancements are being made to use others like polymer and ceramic electrolytes to improve the functions of these electrolytes. Some electrolytes may also be hybrid in their form.

It is also important to be aware of the importance and safety levels of electrolytes, along with the additives that make electrolytes more efficient. If you want to find out more about these along with the details of each kind of electrolyte, you can continue reading the following sections.

What Electrolyte Is Used in Lithium-Ion Batteries?

Let’s take a look at some electrolytes that are or can be used in lithium-ion batteries.

Aqueous

Aqueous or liquid electrolytes are most widely and commonly used in lithium-ion batteries. Aqueous electrolytes are generally a combination of salts that are mixed with an organic solvent. These salts can include oxides or phosphates while the solvents tend to be carbonates of some form or the other.

Aqueous electrolytes can offer a good rate of conductivity. When the battery is being utilized or discharged, these electrolytes can easily facilitate the transfer of ions from the anode to the cathode. Similarly, during the process of charging, the salts from the electrodes are brought back to the electrolyte.

The solvents further assist this process to create an efficient system.

Polymer

Polymer electrolytes could either be in solid or gel form. These polymers can be a good way to get rid of the issues with liquid electrolytes, such as flammability and strength.

Solid polymers can be strong, stable and safe to use. Polyethylene oxide is a common form of electrolyte that is used. However, these electrolytes can have lower levels of conductivity, but this can be solved by mixing in lithium salts.

Gel polymers are much safer to use while still being firm and stable enough. They are less prone to exploding or catching fire. They can also be good in terms of conduction but fall short when it comes to their strength.

Ceramic

Ceramic electrolytes can also be good electrolytes for lithium-ion batteries since they are in the solid form—mainly composed of metal oxides that offer a good amount of conductivity of ions to enable the electrochemical reaction in the battery.

Since these are in solid form, they can prevent leakages that are more common with aqueous electrolytes. As a result, the safety level can be maintained without leaking out toxic elements into the atmosphere.

Sulfides can also be used here to improve conductivity. Several salts can further add to the efficiency of this electrolyte.

Ionic Liquids

Room-temperature ionic liquids (RTILs) are liquid in form but can help solve the issues of leakages, fires and explosions that commonly characterize aqueous electrolytes.

Along with this safety factor, these ionic liquids have high rates of conductivity of ions as well while also being stable and soluble for various kinds of compounds.

However, since these liquids tend to be much thicker than other liquid electrolytes, they tend to be a bit more restricted in terms of conduction. This issue can be solved by adding some compounds or additives.

They are also a lot more expensive as compared to regular liquids.

Hybrid

Due to multiple issues that can exist with any of the above individual electrolyte solutions, several suggestions have been made to combine two of the options to create a stronger, highly conductive and safer solution.

These could either be two solid materials such as polymer and another oxide or sulfide or one liquid and one solid material such as polymer and ionic liquids.

This kind of combination can help strengthen the conductive properties of the materials while also making the electrolyte solve the problems these materials can otherwise face on their own.

Overall, this can be a good way to improve the efficiency of lithium-ion batteries.

Importance of the Electrolyte in Lithium-Ion Batteries

Electrolytes in lithium-ion batteries are mainly meant to help transport ions between the positive and negative electrodes. This can take place in a particular direction depending on the process being carried out, whether that includes charging or discharging.

During the discharging process, the chemical energy is converted into electrical energy. This makes use of the electrolyte to form compounds at the electrodes that help to power the battery.

During the charging process, the electrical energy gets reconverted into chemical energy, allowing the compounds to go back to their original forms such that the electrolyte gets back to its original state, although some losses are bound to take place.

Safety Levels of the Electrolyte

The electrolyte that is generally used in lithium-ion batteries is present in an aqueous form. It is highly volatile and flammable and can lead to short circuits, fires or explosions in extreme situations.

This can not only release toxic pollutants into the atmosphere but can also have several health hazards on the people nearby.

Overcharging and overheating can also cause the electrolyte to leak out, which can be equally hazardous.

Moreover, since lithium-ion batteries tend to have a high voltage output, they can lead to a lot of charge drainage if they are stored for an extended period.

In fact, several safety hazards have led to recalls of phones containing these batteries along with restrictions on their transport in airplanes.

How Can Electrolytes Be Made More Efficient?

Electrolytes can be made more efficient by adding certain additives or chemicals to them in order to enhance their function even more.

Even though lithium salts are already added to improve the conductivity of electrolytes, additives can be a way to improve their strength and resistance against external conditions such as temperature fluctuations and more.

While these may not be sufficient by themselves to provide a solution, they are important to improve the overall quality and stability of the electrolyte so that its lifespan can be maintained.

Frequently Asked Questions

What other materials are used in lithium-ion batteries?

Apart from the electrolyte, lithium-ion batteries also have the cathode and the anode that form the positive and negative electrodes respectively.

At the positive electrode, a suitable lithium compound is used while graphite is generally the preferred choice for the negative electrode.

Depending on the specific kind of lithium-ion battery, the materials can also change. For example, lithium polymer, lithium cobalt oxide and other kinds of compounds such as oxides and phosphates can be used.

Depending on the kind of material used, the self-discharge rate, efficiency, capacity, lifespan, voltage and more can be determined accurately.

Do electrolytes need to be maintained or replaced?

General and regular maintenance of lithium-ion batteries are necessary to maintain efficiency. When it comes to electrolytes, they tend to lose some of their efficiency over time due to frequent losses that take place during the electrochemical processes of the battery.

These losses are normal and lead to a steady rate of self-discharge as the battery begins to age. It is not necessary to replace the salts or acids in the electrolyte, but some older batteries require you to keep topping up the solvent.

However, in most cases, you might not even need to do that since the electrolyte can suffice on its own. In case of certain issues like leaks or explosions, you might need to get the electrolyte replaced.

If this happens, you should take your battery or device to a professional.

In the case of regular cleaning of the battery, you can do this on your own while wearing suitable safety equipment.

Which is the best kind of electrolyte for lithium-ion batteries?

Currently, liquid electrolytes are most common in lithium-ion batteries. However, due to the hazards that they can cause, improvements are being made in figuring out better substances to be used as electrolytes, as discussed previously in this article.

These could either be polymer, ceramic, ionic liquids or a combination of some of these. With improved research, these better options can be brought into practice.

About the author

Hi, I'm Phil Borges.. thanks for reading.. My wife says I can't shut up about batteries so to save my marriage I've started this blog .. where I'd be ranting about batteries! Please leave a comment if you have any questions, I'm happy to help!

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