Lithium-Ion Batteries | ChemTalk

Core Concepts

In this article, you will explore the lithium-ion battery, its compartments, and redox reactions that occur within it. You will also gain an overview of its work functions, applications, and advantages and disadvantages.

Introduction

A lithium-ion battery (LIB) is a rechargeable battery that stores and releases energy through the reversible flow of lithium (Li⁺) ions between the anode and the cathode. The anode is made of graphite, which consists of layers of graphene. These graphene layers can efficiently store Li⁺ ions between them, which is the very reason why the device is called a lithium-ion battery. When we charge the device, Li⁺ ions migrate to the anode from the cathode, and while discharging, the process reverses: Li⁺ ions then move from the anode to the cathode.

Composition of Lithium-Ion Batteries

There are several components of a LIB, each with a crucial role to play. In this section, we’ll provide a tour of the major parts of a LIB that impart its function.

Anode

As discussed earlier, the anode is typically made of graphite, which is composed of stacked graphene layers. This makes it efficient in accommodating lithium ions. Graphite’s layered structure makes it suitable for storing lithium ions through a process known as intercalation. In addition, graphite is a good electrical conductor due to its delocalized pi electrons, which enable the smooth flow of electrons during charging and discharging.

Cathode

A LIB’s cathode is usually made of lithium metal oxides. Most commonly used metal oxides are lithium cobalt oxide (LiCoO₂), lithium manganese oxide (LiMnO₂), and lithium iron phosphate (LiFePO₄). These lithium metal oxides serve as the primary source of Li⁺ ions in the LIB. The reason we use these transition metal oxides because they can either accept or donate electrons during the charging and discharging processes, enabling the redox reactions that drive the battery. We’ll discuss these redox reactions in more detail shortly.

Electrolyte

In lithium-ion batteries, the electrolyte is usually a mixture of organic carbonates such as ethylene carbonate, dimethyl carbonate, or diethyl carbonate. Within this solvent mixture, lithium salts are dissolved. Commonly used salts include lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate (LiClO₄), and, in some cases, lithium hexafluoroarsenate (LiAsF₆). The solvents must be non-aqueous because lithium is highly reactive with water, which makes the use of aqueous solutions unsuitable. This strong reactivity arises from lithium’s tendency to lose its single valence electron and form a stable Li⁺ ion. The reaction with water is also highly exothermic, driven by lithium’s strong electropositivity and the large hydration energy released when Li⁺ ions are stabilized in water.

Redox Reactions in Lithium-Ion Batteries

LIBs undergo a series of oxidation-reduction (redox) reactions which drive their charging and discharging processes.

Overall Cell Reaction (Charge – Reverse)

During discharge of a LIB, Li⁺ ions move from the anode to the cathode. Conversely, during charging, Li⁺ ions migrate from the cathode to the anode, where they are stored between the graphene layers of graphite. As described above, this insertion of Li⁺ into the graphite structure is called intercalation. The reversibility of this process is the basis of the rechargeability of lithium-ion batteries.

In a lithium-ion battery, the LiCoO₂ cathode contains cobalt in its oxidation state of Co³⁺. When charging, Co³⁺ is oxidized to Co⁴⁺, which represents an increase in its oxidation number. Conversely, during discharge, Co⁴⁺ is reduced back to Co³⁺, decreasing the oxidation number and restoring the material to its original state. Each lithium-ion cell operates at a voltage of about 4.6 – 4.7 V.

Applications of Lithium-Ion Batteries

Lithium-ion batteries are widely used in a variety of real-world applications. Some familiar uses include cell phones, laptops, computers, digital cameras, pacemakers, and power tools.

Advantages of Lithium-Ion Batteries

1. Since lithium is the lightest metal in the periodic table, lithium-ion batteries are remarkably lightweight. This low weight is one of their major advantages, as it makes them highly suitable for portable devices such as smartphones, laptops, and other everyday gadgets that require both mobility and long-lasting power.

2. LIB is less toxic than lead or cadmium batteries. Lead and cadmium would function in a battery format, but their use would pose a bigger risk to people’s health. Lead poisoning can contribute to neurological and cardiovascular problems, and cadmium exposure can damage organs and potentially cause cancer. Although lithium exposure can also present some health risks, the risks are considered less significant than those associated with lead or cadmium. Using lithium, as opposed to certain other metals, in an LIB is a compromise between the battery’s desired functionality and ensuring the battery is safe for consumers to use.

3. Nanoparticles have a much larger surface area compared to bulk materials. When electrodes are designed and engineered on the nanoscale, their surface area increases drastically, providing more active sites for lithium-ion intercalation. This enhanced surface area improves ion transport, resulting in faster charge-discharge rates and overall better battery performance.

4. Most lithium-ion batteries are equipped with a battery management system (BMS), which enhances both safety and efficiency. The BMS includes heat sensors to monitor temperature and voltage converters to regulate power flow. It also contains protective circuits to prevent over-charging, over-discharging, and short circuiting. These advanced features not only extend the battery’s lifespan, but also make it more reliable compared to other battery technologies.

Disadvantages of Lithium-Ion Batteries

1. Lithium-ion batteries contain lithium and transition metal oxides, which are highly reactive. At high temperatures, these materials can undergo rapid exothermic reactions, sometimes resulting in fire or explosion. Although BMSs are designed to minimize these risks, thermal instability remains a significant challenge for lithium-ion battery technology.

2. Highly reactive lithium can react violently with water, producing LiOH and hydrogen gas, which can be dangerous.

3. Compared to nickel-cadmium (Ni-Cd) rechargeable batteries, lithium-ion batteries are more expensive. This higher cost is mainly due to the use of costly raw materials, complex manufacturing processes, and the need for advanced safety systems.

Conclusion

To sum up, a lithium-ion battery consists of a graphite anode, a lithium metal oxide cathode, and a non-aqueous electrolyte containing lithium salts. The anode stores lithium ions through intercalation, and lithium ions travel back and forth between the electrodes during redox reactions. During discharge, lithium ions move from the anode to the cathode, while during charging, the process reverses — demonstrating the redox reactions that power the lithium-ion battery. Although lithium-ion batteries face challenges such as high production costs and safety concerns, their high energy density, long cycle life, and lightweight design make them indispensable for modern technology.