Portable Lithium-Ion Battery Power

Lithium batteries are used in various portable electronic devices. They are known for their sleek body and high energy storage capacity.

The primary factors in battery safety are the active materials and electrolytes. Extensive testing is done to determine if these chemicals can withstand electrical and thermal abuse. Current standards include a variety of tests for individual lithium cells and battery packs.

Fast Charging

With advanced functionalities and shrinking form-factors powering these devices has become a bottleneck where improvements in circuit topologies cannot keep pace with the demand. Battery power density is now a primary target for increasing device runtimes and cycle-life.

A well-designed ultra-fast charger assesses the condition of each individual Portable lithium-ion battery cell in a multiple-cell pack and adjusts the charge current to the appropriate level for each cell. The charger controls the pre-charge current, constant current charging (CC phase) and cyclical discharge of each cell in the battery pack.

The temperature of the cell must also be regulated to prevent lithium plating and limit the growth of the solid electrolyte interphase (SEI). This requires an extensive thermal management system that is expensive but essential. It is also critical to avoid overcharging the battery because this can cause damage or even fire.

Specialty chargers have been developed that lower the charging C-rate when a battery reaches a certain state of charge (SoC). This is done by tapering off the current until the battery reaches about 50% SoC and then returning to the normal CCCV charging regime. This can significantly reduce charge time and improve energy-density. This technique is also being applied in some EV batteries. Despite these advances, the lag between voltage and SoC remains an issue that limits the speed at which batteries can be charged.

High Energy Density

If you have ever used a smartphone, tablet or laptop computer you probably know how much energy is stored in the batteries that power them. This high energy density is thanks to lithium.

Energy density is a key battery characteristic and is commonly measured in watt-hours per kilogram. It is sometimes confused with power density, but the two are distinct. Power density measures the output of a battery in terms of watts per kilogram, while energy density measures how much electrical energy is produced for the weight and volume of a battery.

The energy density of lithium batteries depends on the positive and negative electrode materials used. Today’s lithium-ion batteries primarily use intercalation-type cathodes such as LiFePO4, LiCoO2 and graphite. The high energy density of these batteries makes them ideal for portable electronics and electric vehicles.

Lithium batteries are also able to operate in a wider temperature range than other battery types. This is important for electric cars, submarines and drones. However, the low temperature performance of lithium batteries is limited by the chemical limits of the positive and negative electrodes.

This limitation is being addressed by researching Portable lithium-ion battery new electrode materials for lithium batteries. One such material is ternary lithium iron phosphate, which offers an exciting potential for higher energy density in future batteries. Another possibility is a Lithium Ion Polymer (LAB) cell, which uses a dry polymer electrolyte to replace the traditional porous separator. This could lead to a slimmer cell geometry and lower cost.

Long Lifespan

Portable lithium-ion batteries are used in a wide variety of consumer and business applications such as laptops, tablets and mobile phones. They are also found in electric vehicles, hybrid electric vehicles, advanced electric bicycles and scooters, electric golf carts, personal mobility devices and radio-controlled models. They use lithium ions to store energy, a process that is reversible, and their voltages are fairly stable over time.

Li-ion battery lifespan is often measured based on the number of charging cycles, but that measurement can be misleading since a cycle can vary in depth and there are no standards for what constitutes a cycle (see BU-501: Basics About Discharging). More importantly, the longevity of the battery is determined by environmental conditions, not cycling alone. High temperature, dwelling in full state-of-charge and excessive load stress all accelerate capacity fade.

Li-ion batteries can last a long time when properly cared for. They perform best with balanced cycles of charge and discharge, avoiding full or partial discharging. When storing a battery for extended periods, it is important to store it at a mid-state-of-charge. It is recommended to recharge a battery at least once every two months. A battery’s peak charge voltage is another factor that affects lifespan. Each reduction in peak charge voltage reduces the total amount of energy a battery stores by 10 percent.

Low Self-Discharge

Cylindrical lithium batteries are used in a wide range of electronic devices including cell phones, laptops and portable audio-visual equipment. They are also often used to power electric vehicles.

Lithium-ion batteries have several advantages over other electrical energy storage systems. They have a high energy density, good operating temperature range, long lifespan and low self-discharge. They also do not contain toxic cadmium, making them environmentally friendly. In addition, they do not generate hazardous byproducts such as cyanide and lead when they are recharged.

However, these batteries can experience internal short-circuiting due to the formation of dendrites on the anode, which can pierce the separator and cause a fire or explosion. This can be prevented by proper assembling and handling of the battery. It is also important to maintain the correct charge and discharge rates.

The cells in lithium-ion batteries are surrounded by a non-aqueous electrolyte, which prevents water from reaching the cathode and anode. The electrolyte typically contains a lithium salt in an organic solvent, such as ethylene carbonate or propylene carbonate. The electrodes are separated by a current collector and prevented from shorting by a piece of copper with a spot-welded nickel tab.

As a result of their performance and safety, lithium-ion batteries are the preferred electrochemical energy storage system in electric vehicles. However, their capacity fades with aging due to various mechanisms, such as solid electrolyte interphase (SEI) formation and dissolution, thermal runaway and lithium plating. This can be minimized by using an optimum charge-discharge cycle and by selecting the best electrode materials.