Lithium Ion Battery Lifespan
Lithium batteries power our modern world from cordless appliances to electric cars. They are available in different shapes, sizes and capacities depending on the application.
Conventional lithium ion batteries have a liquid electrolyte but newer designs use a dry solid polymer that resembles a plastic film and allows ions to exchange. This enables the battery to have a longer lifespan and avoids the problem of metallic lithium plating during discharge.
The energy density of a Lithium Ion Battery battery measures the amount of electrical power it can hold per unit of its weight. It is usually expressed in watt-hours per kilogram (Wh/kg). The higher the energy density, the more powerful and portable the battery.
In battery chemistry, the energy density is determined by the lithium ions and how they are moved between the positive and negative electrodes. The anode consists of a metal oxide while the cathode is porous carbon. In the cell, ions shuttle back and forth between these two via an electrolyte solution and separator. This process is accompanied by a formation of the solid electrolyte interface, or SEI. Lithium salts in the electrolyte solution aid the movement of ions, as well as provide conductivity and help to form the SEI. The electrolyte can be made with different mixtures depending on the cell’s temperature. For example, an electrolyte for low temperatures will contain less viscous liquids than one made for room temperature applications.
The ternary materials that make up the anodes of Li-ion batteries are typically composed of lithium nickel-cobalt-manganese oxides. These compounds are used because they have good performance and a low intercalation voltage. This is important, as a high intercalation voltage may cause dendrites to grow and eventually pierce the separator during charging. This is a dangerous event and can lead to thermal runaway.
Unlike nickel-cadmium or lead batteries, lithium-ion batteries do not need to be exercised (deep-cycled) to restore their capacity. Lithium ion battery cell designs are also less complex than those of other chemistries, which helps reduce costs. These characteristics make the lithium-ion chemistry the fastest growing battery technology on the market. Lithium-ion batteries are available in several small cylindrical sizes, making them ideal for handheld devices like digital cameras and mobile phones. They are also used to power electric vehicles and other forms of transport, such as scooters and bicycles, as well as radio-controlled models and the Mars Curiosity rover.
The lithium-ion battery has a negative electrode made of graphite, and a positive electrode made from a metal oxide or other non-flammable material that acts as a current collector. The two electrodes are separated by an electrolyte, typically a lithium salt in an organic solvent. During discharge, lithium ions move from the negative electrode to the positive electrode, depositing themselves between the materials in an intercalation process. During recharge, this process is reversed.
During the initial stage of charging, the charger applies a constant current to the battery at a steadily increasing voltage until the top-of-charge limit per cell is reached. If the voltage rises too quickly, a buildup of a solid layer called the SEI film can develop on the positive electrode, which can lead to internal short circuits and battery failure.
The lifespan of lithium ion batteries has not been the primary concern for most consumers. This is partly because of the rapid innovation cycles in portable electronic devices which tend to be replaced every two years or so. However as battery technology enters the market for more durable consumer and investment goods such as (hybrid) electrical vehicles and temporary storage systems for renewable energy sources a better evaluation of lifespan becomes necessary. With a few simple precautions it is possible to extend the useful life of lithium batteries significantly.
The longevity of a battery pack depends on the amount of cycles it can undergo before the maximum charge capacity drops Lithium Ion Battery to 80% of new condition. Cycle counts are influenced by various factors including calendar time, temperature and cycling regimes. For example, extreme deep discharges can irreparably harm a battery, leading to metal plating on the inside which will render it useless or even hazardous.
In order to get the most out of your lithium ion battery, avoid extreme discharges and try to keep it in an optimal charge band. This is easy enough for most users as their battery management systems will prevent batteries from reaching full and low charge limits. Alternatively, some manufacturers offer a smart charger which communicates with the battery and regulates its charge and discharging currents to maximize its lifespan.
While lithium ion batteries have a great track record, these power sources are not without risks. As with any battery, they can overheat, catch fire, or even explode. This is because they pack so much energy in a small space. The good news is that most of these incidents are caused by user error or misuse. It is important to follow the proper usage and storage guidelines.
Battery safety is a hot topic due to recent news reports of devices like laptops, smartphones, and E-bikes catching fire. These battery fires are often the result of improper charging, unattended charges, incompatible chargers or cheap knock-off batteries. Some batteries also have internal issues that can cause a short circuit. For example, on rare occasions microscopic metal particles can enter the battery cell during manufacturing and cause a thermal runaway that can lead to fires or explosions.
If you notice that a battery in your device has become swollen or is emitting an unusual smell, don’t continue using it. Instead, remove the battery and place it on a nonconductive surface such as concrete or sand and keep it away from combustible materials until you can get rid of it properly. You should also contact the manufacturer of your product or local household hazardous waste program for directions on proper disposal.