Lithium Ion Battery

Lithium ion batteries are the dominant rechargeable battery technology used in mobile electronics, laptops and electric vehicles. They combine good energy and power density with low cost and safety.

During discharge the electric current from the anode dissolves lithium ions in the cathode, generating chemical energy. To charge, the anode absorbs electrons from the external circuit.

Energy Density

The energy density of a battery measures how much power the battery can deliver in proportion to its weight. It is typically measured in Watt-hours per kilogram (Wh/kg), but can also be expressed as a percentage of its capacity.

Energy density is important in batteries because it relates to how much power the battery can supply over time. Power is a function of voltage times current, so the higher the battery’s energy density, the more power it can provide over time.

Lithium-ion batteries have high energy density compared to other rechargeable batteries. They are used in portable electronics, electric vehicles, and large-scale storage systems. Lithium-ion batteries have made a significant contribution to portable electronics and have provided a foundation for the rapid expansion of information technology devices in our daily lives.

However, there are challenges with storing lithium-ion energy at extreme temperatures. When lithium-ion batteries are charged at very low temperatures, metallic lithium can form dendrites that pierce the anode separator and lead to internal short circuiting.

This type of degradation can be reduced by increasing the temperature of the cell during charging and discharging, but this requires more expensive and bulky components. Another way to increase the energy density of a lithium-ion battery is to use a lower-voltage cathode material. Currently, most lithium batteries use a graphite anode and ternary nickel-cobalt-manganese cathodes.

Weight

Lithium battery packs have a low Lithium Ion Battery weight compared to lead-acid batteries of the same capacity. This is due to the smaller and lighter cell design. In addition, lithium batteries can be installed upside down, in any orientation, and still leak-free due to the cells being individually sealed.

Moreover, lithium batteries have a much lower self-discharge than nickel-metal hydride (NiMH) batteries. This means that they will keep their charge in storage for a longer period of time. This is an important feature for cordless tools such as drills and irons, as well as electric vehicles and energy storage applications.

Another advantage of lithium ion batteries is that they can be charged at a faster rate than lead-acid batteries. This is especially helpful for industrial applications such as terminal tractors, where every minute spent on breaks is costly.

The low weight and high energy density of Lithium Ion Battery lithium ion batteries make them suitable for many applications, from cordless tools to electric cars. They are also environmentally friendly and do not produce any harmful gases during operation.

However, there are some disadvantages to this type of battery. One is that they can be expensive to manufacture. Additionally, they can be a little dangerous to handle due to their high specific energy. In addition, they require a special charging circuit to prevent overheating and shortening the life of the battery.

Voltage

The voltage of a lithium battery is a function of the chemistry and the external circuit. During discharge the electrochemical reactions of the battery produce negative lithium ions and positive electrons that move through the external circuit. The ions and electrons recombine on the cathode in a reduction half-reaction. The anode and the cathode are made of different materials, but they share some characteristics: They must be able to conduct current and provide a safe operating voltage.

The anode of a Li-ion cell is often made of graphite powder that has been combined with a copper film to allow for the flow of electrons. Depending on the overall battery chemistry and the electrode design, the anode can have other material combinations as well. The cathode is also a complex material, but the chemistry is generally less critical than that of the anode.

Like other batteries, the cathode of a Li-ion battery suffers from aging effects, especially at low cell voltages. These effects manifest as structural degradation of the cathode, such as Li+/Ni2+ cation mixing in nickel-rich materials. In addition, the anode surface can become contaminated with impurities, and the conductive additive can dissipate, reducing capacity.

Charging the battery reverses these reactions and transports electric energy from the external circuit to the negative electrode (anode). The energy is stored as chemical potential energy in the cell, with some loss due to coulombic efficiency. Extended storage can lead to the formation of a layer of solid-electrolyte interface (SEI) on the carbon anode, which increases cell resistance and reduces cycling capacity.

Safety

Despite the widespread use of lithium-ion batteries in mobile phones, laptops and electric vehicles and residential solar battery systems, there are concerns about their safety. In the event of a battery failure, they can become unstable and disintegrate, potentially causing fires.

These batteries contain a flammable liquid electrolyte and can catch fire when overheated, damaged or mishandled. A faulty charger that creates excessive heat can cause the internal safety circuit to fail, which can trigger an uncontrolled chemical reaction in the battery cell. This process is known as thermal runaway and it cannot be stopped once it is triggered.

Although most lithium-ion batteries are manufactured safely, physical damage or incorrect usage can lead to a failure. Always use the manufacturer’s cord and power adapter, which are designed specifically for the device, and do not overcharge or store batteries in direct sunlight. Keep them away from combustible materials, such as clothes and bedding. If you see a battery or device with a strange odor, changing shape, or leaking or smoking, discontinue its use immediately and assess the situation. If safe to do so, move it away from combustible items and call 9-1-1.

As lithium-ion battery technology advances, manufacturers will continue to increase energy density and improve manufacturing methods. These improvements are vital to ensuring their safety. As the cells become denser, they require a more stringent separation between cathode and anode. An intrusion of even a microscopic amount of metallic dust into the separator will trigger an SEI, which will degrade capacity and cycling stability.