02: The Lithium-Ion Battery

Hi everyone! In this post, I will explain everything you need to know about the lithium-ion battery for my project.

Battery Basics

Let’s first go over some basic background on batteries.

A battery is a device that stores chemical energy and converts it into electrical energy. It typically consists of one or more electrochemical cells, which are composed of two electrodes, an anode and a cathode, separated by an electrolyte and a separator. When a battery is connected to an electrical circuit, chemical reactions occur at the anode (oxidation) and cathode (reduction), causing electrons to flow from the negative terminal (anode) to the positive terminal (cathode), generating an electric current. Ions then move through the electrolyte to complete the circuit. The separator prevents short-circuiting from direct contact between the two electrodes.

There are many different types of batteries, categorized into primary (single-use) and secondary (rechargeable) batteries. Primary batteries are commonly used in applications where recharging is not necessary. They often provide a convenient, portable power source for devices such as remote controls, flashlights, clocks, and various other consumer electronics. Examples of primary batteries include alkaline (the most common household battery) and lithium metal. Secondary batteries, on the other hand, can be recharged and reused multiple times. These batteries are commonly used in applications where frequent battery replacement is inconvenient or costly, such as in portable electronics, electric vehicles, and renewable energy storage systems. Examples of primary batteries include lead-acid (found in non-electric cars) and lithium-ion.

In my project, I will be focusing on lithium-ion batteries, which is the most widely used battery in consumer electronics.

Lithium-ion Batteries (LIBs)

Lithium-ion batteries (LIBs) use lithium ions (hence the name) as the charge carriers. The cathode typically contains lithium transition metal oxides such as lithium cobalt oxide (LiCoO2) (LCO), lithium iron phosphate (LiFePO4) (LFP) and lithium manganese oxide (LiMn2O4) (LMO). LCO is most commonly used as the cathode because of its durability and high energy density. The anode typically contains graphite, which allows the lithium ions to intercalate during charging and de-intercalate during discharging.

LIBs are one of the most advanced secondary batteries, in terms of gravimetric and volumetric energy. Some advantages of lithium-ion batteries include a high energy density, a higher energy efficiency, and a lower self-discharge rate. They are found everywhere, most notably in portable consumer electronics, electric vehicles, and energy storage.

LIB Configurations

Lithium-Ion Batteries (LIBs) comes in a variety of form factors (configurations), which can be categorized into: cylindrical, coin, prismatic, and pouch.

Coin Cells

Starting with the simplest one, coin cells, also called button cells, are compact and have a flat, disc-like shape, similar to a coin or button (hence the name). They consist of electrodes (anode and cathode), electrolytes, separators, housing, insulators, springs, and spacers. I have already explained electrodes, electrolytes, and separators above. Coin cell housing is typically a stainless steel metal can and acts as the negative terminal of the battery. An insulating ring prevents electrical contact between the positive and negative terminals. Finally, springs and spacers help with structural integrity when in inserted into a device. Due to their size, they are used in small electronic devices such as watches, calculators, and key fobs.

Cylindrical Cells

Cylindrical cells are cells enclosed in a rigid cylinder can and are the most common. These cells are easy to manufacture and have good mechanical stability. Its components include electrodes, separators, electrolytes, cylindrical cans, and terminal collectors. The electrode materials and electrolytes are enclosed within a cylindrical metal can and have metal tabs attached to the can, which serve as the positive and negative terminals for external electrical connections. They are widely used due to their reliability, availability, and compatibility with a range of electronic devices and systems. In electric vehicles, cylindrical cells are grouped together into modules and combined into larger battery packs.

Prismatic Cells

Prismatic cells are packaged in a hard, welded aluminum or steel casing and feature a rectangular or square shape. It consists of electrodes, separators, electrolytes, and prismatic enclosures. The electrode materials and electrolytes are enclosed within a rectangular casing, which provides protection and insulation for the cell’s internal components. Similar to cylindrical cells, prismatic cells have metal tabs or leads attached to the casing, serving as the positive and negative terminals for external electrical connections. Prismatic cells offer advantages in terms of space utilization, packing efficiency, and mechanical stability. Their flat shape allows for efficient space utilization, making them suitable for applications that require compact and high-capacity battery packs, such as electric vehicles and energy storage systems.

Pouch Cells

Finally, we have pouch cells. Rather than using a metallic cylinder and glass-to-metal electrical feed-through, conductive foil-tabs were welded to the electrodes and brought to the outside in a fully sealed way. It consists of electrodes, separators, electrolytes, pouch packaging, and current collectors. The electrode materials and electrolyte are contained within a flexible, laminated pouch made of polymer materials, which is designed to be lightweight, thin, and durable. Current collectors, usually made of aluminum or copper, are attached to the electrodes to facilitate the flow of electrical current. Pouch cells have the highest packaging efficiency and great energy density, but tend to swell and therefore are more vulnerable to penetration. Unlike other cell formats, no universal sizes exist and each manufacturer designs its own (which is be a good thing, as they can be resized to fit each application’s needs). They are found in thin profile handheld devices like mobile phones and modern tablets.

Sources

Deng, D. Li‐ion batteries: basics, progress, and challenges. Energy Science & Engineering 2015, 3 (5), 385–418. https://doi.org/10.1002/ese3.95.

Kumar, R. Lithium-Ion battery for electric transportation. In CRC Press eBooks; 2024; pp 156–172. https://doi.org/10.1201/9781003464556-8.