Analysis of Electrodes of Lithium-ion Cells

In this article, Rahul Bollini lists the nuances of different cathode and anode chemistries of Lithium-ion cells.

Cathodes

LCO (Lithium Cobalt Oxide) – Technology commercialised by Sony, Japan, in 1990 and is used till date in cell phone batteries. It delivers a nominal cell voltage of 3.85V and has a full charge voltage of 4.35V. It has a specific capacity of more than 160 mAh/g. LCO is considered the most unsafe type of cell chemistry.

LMO (Lithium Manganese Oxide) – LMO was popularly used in first-generation Nissan Leaf EV. As Manganese is cheaper than Cobalt and Nickel, it is the cheapest commercially available oxide-based electrode. LMO batteries can deliver high power and have a specific capacity of more than 110 mAh/g.

NMC 111 or 333 (Lithium Nickel Manganese Cobalt Oxide) – First generation NMC cathode material (equal parts of Nickel, Manganese and Cobalt) which took the market by storm by providing cells with high energy density (gravimetric and volumetric). It was popularly being used in electric vehicle applications. All variants of NMC have a nominal voltage of 3.6V and a full charge voltage of 4.2V. It has a specific capacity of more than 150 mAh/g.

NMC 532 (Lithium Nickel Manganese Cobalt Oxide) – Second generation of NMC cathode (five parts of Nickel, three parts of Manganese and two parts of Cobalt) after a brief existence of NMC 442. NMC 532 power (EV grade) cathode dominated the market for the most part of 2021. It is cheaper than NMC 111 and has a specific capacity of more than 160 mAh/g.

NMC 622 (Lithium Nickel Manganese Cobalt Oxide) – Third generation of NMC cathode (six parts of Nickel, two parts of Manganese and two parts of Cobalt). NMC 622 power (EV grade) cathode is expected to dominate the market in 2022 before NMC 811 comes into play. It has a specific capacity of more than 170 mAh/g.

NMC 811 (Lithium Nickel Manganese Cobalt Oxide) – The latest generation of NMC cathode in the market and its commercialisation for EVs is being worked on a large scale. It has a specific capacity of more than 180 mAh/g.

NMC 811 (Lithium Nickel Manganese Cobalt Oxide) – The latest generation of NMC cathode in the market and its commercialisation for EVs is being worked on a large scale. It has a specific capacity of more than 180 mAh/g.

NCA (Lithium Nickel Cobalt Aluminium Oxide) – Popularly used by ISRO for space applications, NCA is also used in Tesla electric vehicles. It is less safe than NMC and has a narrow window of operating temperature, but its cells offer the highest energy density (gravimetric and volumetric) in the market. Has a nominal voltage of 3.6V and a full charge voltage of 4.2V. It has a specific capacity of more than 190 mAh/g.

LFP (Lithium Iron Phosphate) – The most popular cathode material in the market known for its cost, safety and high cycle life. Has a lower energy density (gravimetric and volumetric). It has a nominal voltage of 3.2V and a full charge voltage of 3.6V. It has a specific capacity of more than 150mAh/g. LFP batteries are popular in electric three wheelers, electric buses and energy storage systems.

LFMP (Lithium Iron Manganese Phosphate) – An upcoming cathode with characteristics of LFP but with a higher cell voltage. It can replace the traditional 12V LFP battery that uses 4 LFP cells with 3 LFMP cells. Has a specific capacity of more than 150 mAh/g. LFMP has the potential to replace the complete market of LFP.

LNMO (Lithium Nickel Manganese Oxide) – In this cathode, the Cobalt component from NMC is eliminated. It has one part of Nickel and three parts of Manganese. It can charge up to a full charge voltage of 5V, but its commercial production has not yet taken off due to the unavailability of electrolyte that supports up to 5V charging. Has a specific capacity of more than 130 mAh/g.

Anodes

C (Graphite) – The most popular commercially used anode in the market. Artificial graphite is preferred over natural graphite due to its longer cycle life ability, and it delivers a specific capacity of 350 mAh/g.

SiC (Silicon-Graphite) – Silicon can deliver a specific capacity of more than 3000mAh/g. Silicon is mixed with graphite in small quantities to achieve a Silicon-Graphite composite anode that can deliver more than 400 mAh/g.

The percentage composition of Silicon isn’t notched up too much because it tends to expand up to 300% of its original volume during lithiation and can cause an imbalance in the mechanical stability of the cell. Incorporating Silicon allows for faster-charging properties.

LTO (Lithium Titanate or Lithium Titanium Oxide) – LTO is the only electrode powder in the market which is white in colour. It allows for ultra-fast charging (charge 80% in 6 minutes), and it also increases the cycle life of the cell to the next level, generally about 25,000 cycles. Yinlong from China and Toshiba’s SCiB (super charge ion battery) use this anode.

Any battery company that claims to have developed a fast-charging battery with very high cycle life is most likely using LTO cells inside their battery packs. NMC-LTO cells have a nominal voltage of 2.3V and a full charge voltage of 2.8V.

About the Author

Rahul Bollini is an independent R&D consultant in the field of Lithium-ion cells and batteries. The author can be reached at bollinienergy@gmail.com or +91 72049 57389.


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