Lithium Ion Battery Drivers
Lithium Ion Battery Drivers
Lithium ion batteries have become ubiquitous in portable electronics and increasingly in electric vehicles and large-scale energy storage. They are a significant driver of ongoing fundamental and applied research into battery materials, chemistry and manufacturing.
A conventional lithium ion battery is composed of an anode made from graphite and a cathode that is a metal oxide. These are separated from each other by an electrolyte and protected from short circuiting by a piece of metal called the current collector.
Chargers
The battery chargers that you use with your lithium batteries have a big effect on their performance and longevity. Lithium ions move inside the electrodes and change their positions during charging, affecting capacity. If a lithium-ion battery isn’t charged at the right rate, it can lose a large portion of its lifetime.
Consumer and industrial chargers typically charge to a specific end-of-charge voltage. This prevents overcharging the battery, which damages it and reduces run time. However, some applications, such as electric vehicles and solar energy storage, prefer a lower end-of-charge voltage for longer battery life.
Battery chargers regulate the current, voltage and temperature of a battery during the charging process. They also check for reverse polarity and disconnect the battery when the voltage reaches a dangerous level.
Batteries
Lithium batteries are electrochemical energy storage devices. They contain negative (anode) and positive (cathode) electrodes, a porous separator to conduct lithium ions during charging/discharging and an electrolyte solution.
The Department of Energy’s Vehicle Technologies Office works Lithium Ion Battery on increasing the power density of lithium-ion batteries. This means increasing the voltage and capacity, while lowering the cost.
Most consumer products charge Li-ion at 4.20V/cell to maximize capacity and runtime. Industrial applications may choose lower thresholds for safety reasons.
Battery chemistries are identified by their chemical symbols, or short form names such as lithium cobalt oxide. They are also characterized by their cell structure: cylindrical, prismatic or pouch cells. The performance of a battery is measured by its cycle count and other metrics such as internal resistance and self-discharge. Cycle counts are useful for predicting battery life, but they do not account for usage and environmental factors.
Anodes
A lithium-ion battery consists of a negative anode, a positive cathode and an electrolyte conducting between them. During discharge, ions flow from the anode to the cathode through the electrolyte. During charging, the ions flow the other way.
In the anode, lithium ions are inserted and extracted in a process called intercalation or deintercalation. The anode material must be able to accommodate these movements and allow the ions to pass through the cell separator.
If anode materials fail to do so, the cells will suffer from internal short circuiting. This causes a chain reaction that can lead to heat, fire or explosion.
To address these issues, researchers are developing silicon-based and Si-derivative anodes that are characterized by high cycling stability and energy density. These anodes have a porous structure that accelerates the transport of Li ions. The pore network also resists volume changes that would degrade the SEI layer and reduce the anode capacity.
Cathodes
A battery consists of two electrodes (anode and cathode) separated by an electrolyte and a separator. During discharge the negative metal oxide anode conducts electric current to the positive carbon cathode, which stores lithium ions. This reaction lowers the chemical potential of the cell and transfers energy to the external circuit.
The main degradation pathway of nickel-cobalt-aluminum and lithium iron phosphate batteries occurs in the anode. Its most important mechanism involves the formation of an electrolyte interphase on the anode surface, which decreases the capacity by irreversibly trapping Li+ ions and leads to high ohmic impedance.
Single crystals with a smooth surface and a small boundary size have the best performance in this regard. Using LNMO cathodes with elevated conductivity and short electron-ion movement length leads to very low dislocation density and superior cycling. The performance of these cathodes increases at higher voltages. This is due to reversible de-lithiation of the LNMO composite channel up to 5 V versus Li+/Li, which does not occur in NMC-type cathodes.
Electrolytes
The electrolyte in Lithium batteries has a significant impact on battery performance. It determines the wetting rate of the electrode and separator as well as the capacity and lifetime of the cell. Too little electrolyte reduces the energy density of the cell, whereas too much electrolyte is dead weight and increases production costs.
Room temperature ionic liquid electrolytes with specific cations and anions provide good electrical conductivity between the positive and negative electrodes. They also have the advantage of avoiding safety hazards caused by unwanted reactions and electrolyte depletion.
However, the characterization of the interface film based on NMR is complicated by the co-embedding of the solvents in the electrode material and the complex chemical composition of the electrode-electrolyte interfacial films. This requires advanced characterization techniques such as in situ and ex situ NMR that can investigate the dynamics of the film formation process and identify the factors that influence its properties.
Recycling
Sustainable consumption requires that we recycle and reuse the materials in our products rather than extracting new raw materials. This reduces the demand for new sources of metal and can help alleviate pressure on natural resources in developing countries.
It is important that lithium batteries are not disposed Lithium Ion Battery of in general waste or standard mixed recycling bins, where they can come into contact with water and catch fire. This can be particularly dangerous during transport or at waste management facilities and poses a risk to employees and the surrounding environment.
In addition, the extraction of the raw materials used in lithium ion batteries can create a lot of environmental and social problems. For example, the cobalt that is used in many batteries comes from countries with conflict and instability. Recycling these batteries can help to decrease the need for new cobalt and other minerals, and can also reduce the risk of human exposure to toxic chemicals.
