Ion Lithium Battery Technology

Lithium batteries are a revolution in energy storage and power generation. They are safer, last longer and provide more power than any previous battery chemistry.

A lithium battery has a positive and negative electrode, an electrolyte and a separator. When charged, lithium ions migrate through the electrolyte from the cathode to the anode.

Types

Lithium batteries have made great strides since their commercial introduction in the early 1990s. They power many small electronic appliances such as cell phones, tablets and laptops and have also gotten a foothold in the electric vehicle market. Lithium battery technology offers higher energy density than nickel cadmium or alkaline alternatives.

There are six main lithium ion chemistries: Li-cobalt, Li-manganese, Li-iron, Li-phosphate, Li-titanate and NMC. Each has unique properties that have led to different applications and use cases. The chemistries are named for the main active materials and their abbreviations often appear in full or in short form on product packaging or labels.

The basic structure of a lithium battery includes a cathode immersed in an electrolyte solution separated by a separator. Lithium ions flow freely between the anode and cathode through the separator during discharge, while reversing this process during charge causes a current to flow in the opposite direction. Other elements are also sometimes included, such as a PTC (positive temperature coefficient) or CID (circuit interrupt device), which prevent fire or explosion due to manufacturing defects or abuse.

Lithium batteries come in different shapes and sizes. They can be prismatic, cylindrical or pouch cells. Some of them can be very thin and flat for easy integration into limited space. Other types are able to bend and fit into complex spaces for electrification of special vehicles or industrial equipment.

Materials

The materials used to make ion lithium batteries must enable lithium ions to move between the cathode and anode. The most critical component is the electrolyte, which is a liquid or ion lithium battery gel that contains salts and solvents. It must have high ionic conductivity to ensure that only lithium ions pass between the electrodes.

The chemistry that allows this movement depends on the type of cathode and anode material. The first rechargeable Li-ion battery was conceived in the 1970s by M. Stanley Whittingham and John Goodenough using a titanium disulfide cathode and a lithium-aluminum anode. Their invention paved the way for today’s batteries that are used in power tools, phones and laptop computers.

Modern lithium-ion batteries use various chemistries and cathode materials to optimize specific energy and power handling. The most common are LiCoO2, LiFePO4, NiMH, and NMC* (Nickel Manganese Cobalt Aluminum Oxide).

Each battery chemistry has its own set of strengths and weaknesses. The chemistry also determines the maximum safe operating voltage. Below this limit, the copper anode current collector decomposes and releases flammable gases that cause internal short circuiting during charging. The cell must be kept in a sealed container to prevent the release of these gases. Extended cycling below 2.5 V causes metallic lithium plating on the anode, which depletes cyclable lithium inventory and decreases cycle capacity.

Voltage

Lithium-ion batteries are one of the most important technologies in human history, having enabled mobile consumer electronics, laptop computers and cellular phones, as well as electric cars, or what has been called the e-mobility revolution. They also have significant utility for grid-scale energy storage and other applications requiring large amounts of electrical power for long periods.

The basic battery consists of an anode and cathode, separated by a separator and electrolyte. During discharge, lithium ions flow from the anode to the cathode through the electrolyte and separator; during charging they reverse direction. In this process the negative terminal of the battery has an excess of electrons compared to the positive, resulting in electric potential energy differences (or voltage) that can be converted into other forms of energy like light or heat.

Voltage varies depending on many factors like the battery chemistry, age and condition, the charging stage and the environment. For example, cycling and discharging at high rates reduces lifespans while prolonged storage and cold temperatures increase degradation. Moreover, internal resistance increases with cycling and Portable lithium-ion battery age and can trigger degradation processes such as plating of metallic lithium on the anode, which leads to irreversible capacity loss.

Discharge

When you plug your battery in to charge, the charger applies a higher voltage than the cell, forcing lithium ions into the electrodes. This creates an electric current from the positive current collector (via the separator) to the negative one, powering your device. This process is called intercalation. It’s an important part of what makes lithium-ion batteries so useful — they produce a much higher voltage than the 1.5 volts in an alkaline AA battery, allowing them to pack more energy into a smaller space and making laptops, for example, lighter and more portable.

Lithium-ion chemistry prefers partial discharge over deep discharge. Taking it all the way down can lead to acid stratification, with higher concentrations at the bottom of the battery and lower ones at the top. It also hastens capacity loss.

In addition, frequent overcharging and over-discharging can hasten degradation of the active material in the electrodes, which leads to material shedding or grid corrosion. This can also cause the battery to produce a less efficient electric current. Over the course of a battery’s life cycle, this can greatly affect how far it can travel on one charge or how many years it lasts in an electric car. The temperature in which a battery operates is also important: extreme temperatures can damage the cells, causing them to lose their optimal shape for ion exchanges. This can make the ions more difficult to extract, which reduces a battery’s capacity.