Lithium cobalt oxide, sometimes called lithium cobaltate[2] or lithium cobaltite,[3] is a chemical compound with formula LiCoO
2. The cobalt atoms are formally in the +3 oxidation state, hence the IUPAC name lithium cobalt(III) oxide.
Lithium cobalt oxide is a dark blue or bluish-gray crystalline solid,[4] and is commonly used in the positive electrodes of lithium-ion batteries.
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The structure of LiCoO
2 has been studied with numerous techniques including x-ray diffraction, electron microscopy, neutron powder diffraction, and EXAFS.[5]
The solid consists of layers of monovalent lithium cations (Li+
) that lie between extended anionic sheets of cobalt and oxygen atoms, arranged as edge-sharing octahedra, with two faces parallel to the sheet plane.[6] The cobalt atoms are formally in the trivalent oxidation state (Co3+
) and are sandwiched between two layers of oxygen atoms (O2&#;
).
In each layer (cobalt, oxygen, or lithium), the atoms are arranged in a regular triangular lattice. The lattices are offset so that the lithium atoms are farthest from the cobalt atoms, and the structure repeats in the direction perpendicular to the planes every three cobalt (or lithium) layers. The point group symmetry is R 3 ¯ m {\displaystyle R{\bar {3}}m} in Hermann-Mauguin notation, signifying a unit cell with threefold improper rotational symmetry and a mirror plane. The threefold rotational axis (which is normal to the layers) is termed improper because the triangles of oxygen (being on opposite sides of each octahedron) are anti-aligned.[7]
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Fully reduced lithium cobalt oxide can be prepared by heating a stoichiometric mixture of lithium carbonate Li
2CO
3 and cobalt(II,III) oxide Co
3O
4 or metallic cobalt at 600&#;800 °C, then annealing the product at 900 °C for many hours, all under an oxygen atmosphere.[6][3][7]
Nanometer-size particles more suitable for cathode use can also be obtained by calcination of hydrated cobalt oxalate β-CoC
2O
4·2H
2O, in the form of rod-like crystals about 8 μm long and 0.4 μm wide, with lithium hydroxide LiOH, up to 750&#;900 °C.[9]
A third method uses lithium acetate, cobalt acetate, and citric acid in equal molar amounts, in water solution. Heating at 80 °C turns the mixture into a viscous transparent gel. The dried gel is then ground and heated gradually to 550 °C.[10]
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The usefulness of lithium cobalt oxide as an intercalation electrode was discovered in by an Oxford University research group led by John B. Goodenough and Tokyo University's Koichi Mizushima.[11]
The compound is now used as the cathode in some rechargeable lithium-ion batteries, with particle sizes ranging from nanometers to micrometers.[10][9] During charging, the cobalt is partially oxidized to the +4 state, with some lithium ions moving to the electrolyte, resulting in a range of compounds Li
xCoO
2 with 0 < x < 1.[3]
Batteries produced with LiCoO
2 cathodes have very stable capacities, but have lower capacities and power than those with cathodes based on (especially nickel-rich) nickel-cobalt-aluminum (NCA) or nickel-cobalt-manganese (NCM) oxides.[12] Issues with thermal stability are better for LiCoO
2 cathodes than other nickel-rich chemistries although not significantly. This makes LiCoO
2 batteries susceptible to thermal runaway in cases of abuse such as high temperature operation (>130 °C) or overcharging. At elevated temperatures, LiCoO
2 decomposition generates oxygen, which then reacts with the organic electrolyte of the cell, this reaction is often seen in Lithium-Ion batteries where the battery becomes highly volatile and must be recycled in a safe manner. The decomposition of LiCoO2 is a safety concern due to the magnitude of this highly exothermic reaction, which can spread to adjacent cells or ignite nearby combustible material.[13] In general, this is seen for many lithium-ion battery cathodes.
The delithiation process is usually by chemical means,[14] although a novel physical process has been developed based on ion sputtering and annealing cycles,[15] leaving the material properties intact.
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Lithium-ion batteries find extensive applications, ranging from powering smartphones to serving in renewable energy storage systems and electric vehicles. Therefore, researchers are working to develop their performance and overcome challenges related to them, such as storage capacity, safety, and problems related to the environment.
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Image Credit: RHJPhtotos/Shutterstock.com
Researchers have given significant attention to the development of cathode materials, as they have a pivotal role in achieving high-performance lithium-ion batteries (LIBs). Among the materials integrated into cathodes, manganese stands out due to its numerous advantages over alternative cathode materials within the realm of lithium-ion batteries, as it offers high energy density, enhancing safety features, and cost-effectiveness.
In this article, we will explore the role of manganese in lithium-ion batteries, its advantages, limitations, and new research.
Lithium manganese oxide (LMO) batteries are a type of battery that uses MNO2 as a cathode material and show diverse crystallographic structures such as tunnel, layered, and 3D framework, commonly used in power tools, medical devices, and powertrains.
LMO batteries are known for their fast charging and discharging capabilities, providing a high operating voltage and energy output. Moreover, they have good thermal stability, reducing the risk of overheating and enhancing safety features.
Furthermore, manganese, the main component, is relatively inexpensive, making LMO batteries cost-effective.
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LMO batteries exhibit certain drawbacks, notably rapid capacity fading resulting from the loss of electrical connections between nanoparticles and the current collector.
Additionally, they may have a limited energy density compared to certain lithium-ion chemistries, affecting their ability to store large amounts of energy.
Despite their good thermal stability, LMO batteries can be sensitive to extreme temperatures.
Nickel Manganese Cobalt Oxide (NMC) Batteries NMC is one of the lithium batteries in which manganese is used as one of the components of the cathode, which also consists of nickel and cobalt oxide typically denoted as LiNiMnCoO2. This formula signifies an equal ratio of metals but this ratio may change based on the required performance characteristics.
NMC batteries are widely used in electric vehicles as they provide a balance between energy density, cost-effectiveness, and long drive range; moreover, they provide a high current required during acceleration.
NMC batteries offer a relatively high energy density, allowing them to store a substantial amount of energy in a compact space.
The incorporation of manganese contributes to the thermal stability of NMC batteries, reducing the risk of overheating during charging and discharging.
NMC chemistry allows for variations in the nickel, manganese, and cobalt ratios, providing flexibility to tailor battery characteristics based on specific application requirements.
NMC batteries exhibit good cycling performance, allowing for a high number of charge and discharge cycles with minimal degradation in capacity. This is crucial for long-lasting and reliable energy storage.
Although NMC batteries are less expensive than other cathode materials, they are still relatively expensive due to the presence of cobalt as one of their components. For this reason, researchers are working to reduce or replace cobalt.
NMC batteries are generally considered safer than some alternatives, but there is still a risk of thermal runaway and overheating, especially in situations of overcharging or physical damage. Thermal management systems are essential to mitigate this risk such as air cooling, liquid cooling, and phase change materials.
Over time, NMC batteries might undergo voltage fade, resulting in a reduction in their voltage levels during cycling. This occurrence has the potential to influence the overall performance and efficiency of the battery.
The cathode known as lithium manganese spinel, denoted as LiMn2O4, adopts a spinel crystal structure that consists of a cubic close-packed arrangement of oxygen ions. Within this structure, lithium ions are situated in tetrahedral sites, whereas manganese ions occupy octahedral sites.
Lithium Manganese Spinel is used in various applications such as electric vehicles, portable electronics, and grid-level energy storage.
Lithium Manganese Spinel has a good cycling performance due to several factors such as structure stability, manganese ion fast diffusion, and balanced electrochemical performance.
Manganese is the key component of these batteries, which contributes to lowering their overall cost.
LMS batteries have good thermal stability, which is a crucial factor for ensuring safety and reliability.
Overcharging lithium manganese spinel cathodes can result in the formation of manganese ions in higher oxidation states, leading to increased susceptibility to dissolution. This can compromise the structural integrity of the cathode.
Cycling stability can be affected when the battery is operated over its full voltage range. Extended cycling within the upper and lower voltage limits may contribute to capacity fade and reduced overall performance.
Voltage fade is another issue observed in lithium manganese spinel cathodes, where the operating voltage of the battery may decrease over time. This can affect the energy density and efficiency of the battery.
The cathode in these batteries is composed of iron, manganese, lithium, and phosphate ions; these kinds of batteries are used in power tools, electric bikes, and renewable energy storage.
LiFeMnPO4 batteries are known for their enhanced safety characteristics, including resistance to thermal runaway and reduced risk of overheating and fires.
The combination of iron, manganese, and phosphate contributes to the stability of the cathode material, leading to a longer cycle life and improved performance.
The absence of hazardous materials like cobalt in their composition makes them environmentally friendly.
LiFeMnPO4 batteries may have a lower energy density compared to some other lithium-ion batteries; this means that they may not be the best choice for high-energy-demand scenarios, such as electric vehicles.
The cost of manufacturing LiFeMnPO4 batteries can be higher compared to certain lithium-ion batteries, affecting their widespread usage.
Researchers have explored various surface coatings to enhance the stability and reactivity of manganese-rich cathodes. Thin film coatings, chemical grafting, and protein immobilization are commonly used methods.
Achieving uniform and conformal coverage on electrode surfaces is critical for optimal sensor and biomedical applications.
The performance of manganese-based cathodes is significantly influenced by their morphology and crystal structure.
Researchers have explored layered structures with adjustable interlayer spacing, enabling better lithium diffusion and increased capacity. Additionally, tunnel structures offer excellent rate capability and stability.
Manganese is emerging as a promising metal for affordable and sustainable battery production, and manufacturers like Tesla and Volkswagen are exploring manganese-rich cathodes to reduce costs and improve scalability.
Volkswagen&#;s versatile &#;unified cell&#; design aims to use multiple cathode materials, including manganese, to achieve cost-effective and high-performance batteries.
Manganese continues to play a crucial role in advancing lithium-ion battery technology, addressing challenges, and unlocking new possibilities for safer, more cost-effective, and higher-performing energy storage solutions. ongoing research explores innovative surface coatings, morphological enhancements, and manganese integration for next-gen batteries. These developments aim to address challenges such as capacity fading, voltage fade, and manufacturing costs, fostering a sustainable, efficient, and environmentally friendly future.
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Li, H., Zhang, W., Sun, K., Guo, J., Yuan, K., Fu, J., Zhang, T., Zhang, X., Long, H., Zhang, Z., Lai, Y., & Sun, H. (). Manganese-Based Materials for Rechargeable Batteries beyond Lithium-Ion. Advanced Energy Materials. [Online] Available at: https://onlinelibrary.wiley.com/doi/full/10./aenm..
Nunez, C. (, June 4). Researchers eye manganese as key to safer, cheaper lithium-ion batteries. Argonne National Laboratory. [Online] Available at: https://www.anl.gov/article/researchers-eye-manganese-as-key-to-safer-cheaper-lithiumion-batteries.
Kour, S., Tanwar, S., & Sharma, A. L. (). A review on challenges to remedies of MnO2 based transition-metal oxide, hydroxide, and layered double hydroxide composites for supercapacitor applications. Materials Today Communications. [Online] Available at: https://www.sciencedirect.com/science/article/abs/pii/S.
Capasso, C., Iannucci, L., Patalano, S., Veneri, O., & Vitolo, F. Battery Thermal Management Systems: A Case Study on Li-NMC storage systems for electric vehicles. [Online] Available at: https://ieeexplore.ieee.org/abstract/document/.
Heng, Y.-L., Wu, X.-L., et al. (). Research progress on the surface/interface modification of high-voltage lithium oxide cathode materials. Energy Materials. [Online] Available at: https://www.oaepublish.com/articles/energymater..18.
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