Lithium Ion Battery

Lithium ion batteries power our laptops, cell phones, hybrid and electric cars, and energy storage for solar and wind.

A battery’s performance depends on its cathode, anode, electrolyte, and separator. Electrolytes must physically keep the anode and cathode apart while allowing lithium ions to move between them.

The cathode is crafted from a precise mix of precious minerals that achieves the battery’s specific voltage. Changes in the crystal’s structure or composition can lead to failure.

Why Lithium Ion Batteries?

Compared to lead-acid batteries, lithium batteries hold more energy in less space. That’s thanks to the technology’s superior “energy density.” It takes 6 kg of lead-acid battery cells to handle the same amount of energy that one kilogram of lithium batteries can manage. This superiority makes lithium batteries a good choice for cordless products that require higher power and longer run times.

Batteries have an anode, a cathode, a separator, and two current collectors (positive and negative). When the battery is charged, the electrolyte carries positively-charged lithium ions from the cathode to the anode through the separator. This process creates free electrons that can be drawn from the positive current collector to power devices.

As a bonus, lithium batteries don’t suffer from the same problem that plagues many lead-acid batteries: sulfation. Sulfation causes sulfate crystals to form on the electrodes and reduces the battery’s performance, eventually forcing you to replace it. Lithium-ion batteries avoid this problem entirely because their chemistry doesn’t produce sulfate crystals.

Another benefit is that lithium batteries are much lighter than other battery types. This can make a big difference in handheld devices and other high-drain items. They can also be mounted in more configurations, including unvented areas, which is not possible with a lead-acid battery. The light weight of lithium batteries is a great advantage for consumers and manufacturers alike.

Lithium Ion Cells

The lithium ion battery, or LIB, is a stack of cells (usually cylindrical or prismatic). Its performance and safety are substantially superior to that of lead-acid batteries and nickel-metal hydride batteries.

The main function of a LIB is to Lithium Ion Battery store energy for later use. For this purpose, it has a high power density: a kilogram of a lithium battery stores 150 watt-hours of energy, while a nickel-metal hydride battery only holds 25 watt-hours per kg.

A Li-ion battery is made of two electrodes, a separator and an electrolyte. During charging, an external electrical power source applies an over-voltage to the cell, forcing electrons from the positive (anode) to migrate toward the negative (cathode). The migration of the lithium ions in the cathode also releases chemical energy that is stored as electrical energy in the anode.

Because of the flammable organic solvent in the electrolyte, lithium ion cells must be hermetically sealed and are generally designed with multiple safety features. This includes shutdown separators that become highly resistive if the cell becomes overheated, internal fuses and current interrupt devices that disconnect the terminals internally in response to excessive current flow or elevated temperatures.

Research on lithium ion cells focuses on improving their performance, safety and durability. For example, materials science & engineering professor Jun Liu has studied the fundamental linkages between the thickness of Li metal in the cell, the depletion of electrolyte and structural evolution of the solid-electrolyte interphase (SEI) layer. He is now part of the Battery500 Consortium, led by PNNL and including CEI director Dan Schwartz, developing next-generation EV batteries that will have energy densities up to 500 watt-hours per kilogram, twice the industry standard.

Lithium Ion Capacity

The capacity of Lithium Ion batteries is measured in ampere-hours (Ah) or milliampere-hours (mAh). An Ah rating represents the amount of current a battery can deliver for one hour. Lithium-ion batteries have high energy density compared to other battery technologies.

The key to lithium ion’s superior performance lies in the cathode material. Common cathode materials include Lithium Cobalt Oxide (or LCO), Lithium Manganese Oxide (or spinel) and Lithium Nickel Manganese Cobalt Aluminum Oxide (or NMC).

During discharge, lithium ions are released from the anode and pass through the electrolyte to the cathode. Then they recombine with their electrons in the cathode, creating a flow of electricity that powers the device. During recharge, the flow is reversed, and lithium ions return to the anode.

In addition to a higher cell voltage, lithium ion cells also have good load characteristics. They deliver a consistent 3.6 volts per cell, which means fewer cells are needed in many applications. This makes lithium ion cells and batteries a great choice for powering smartphones, laptops and other mobile devices.

However, we must consider the environmental impact of using this technology. The production of Lithium-Ion Batteries requires a lot of heavy metals such as Manganese, Cobalt and Nickel. These metals, when improperly disposed of, can pollute the environment. This is why it is essential that we ensure the safe and proper disposal of these batteries.

Lithium Ion Safety

While lithium ion batteries are a safe, reliable, and efficient source of power Solar energy storage system for many e-devices, they can pose risks when damaged or improperly used, charged, or stored. NFPA has many resources to help people avoid these hazards.

Battery safety is especially important as cells get denser. The increased energy density makes it easier for metallic dust particles to enter the separators and cause a fire, so manufacturing methods must become more rigorous. For example, nail penetration was tolerable in older 18650 cells but is not acceptable in the high-density 2.4Ah cell that’s being developed today.

The chemical reactions in a lithium battery produce oxygen gas that can sustain a fire, so it’s critical that the cell is not exposed to excessive heat or to water. If a lithium battery is hot to the touch, has a strange odor or emits white or gray wispy smoke, it’s best to follow your home fire escape plan and remove the device from service until it cools.

Failing cells inside a battery pack can spread the heat into the adjacent ones and cause them to thermally decompose. This is called a thermal runaway and can destroy the entire pack in a matter of seconds. A battery management system, also known as a protection circuit, helps prevent thermal runaway by monitoring a number of aspects of a lithium ion battery. For example, it limits the peak voltage of each cell during charge to ensure that no one cell reaches an unsafe level.