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Different chemistry of lithium-ion batteries (2022) | Simple Explanation

Introduction -

A battery comes with various chemistry that directly determine the cell's performance.

When discussing "battery chemistry," we refer to the cathode component. With a few exceptions, carbon anodes are typically used in lithium-ion batteries.

It is essential to remember that the anode and cathode materials and other elements in both electrodes significantly impact how the battery performs.

Lithium Cobalt Oxide (LCO) -

These cells, also known as LCOs, have a very high energy density. LCO cells with a 18650 form factor are used to make the majority of laptop battery packs. Most of the highest energy density cells now on the market employ LCO. LCO is a hazardous substance, and LCO-based cells can release a lot of energy if they are overcharged or reach the temperature at which LCO degrades.

With extra safety features to reduce the dangers of this highly reactive chemical, LCO has been employed effectively in large-format applications involving many tiny cells. Additionally, LCO is less stable than other electrode materials and does not perform exceptionally well in terms of cycle life.

LCO has the highest cost per kilogram as raw material compared to other typical cathode materials. Still, due to its high energy density, it may have a lower cost per watt-hour when used in cells.

Typical applications include - Laptops, mobile phones, tablets etc.

Lithium Nickel Oxide (LNO) -

For lithium-ion battery cathodes, lithium nickel oxide is a relatively recent material. Although it has a lower level of safety, it has an energy density of around 15% higher than LCO.

Blends of nickel and cobalt have been devised to benefit from nickel's higher energy and lower cost while also enhancing the thermal stability of the cell.

However, this has come at the expense of the cell's capabilities because of the slower rate of lithium diffusion.

Typical applications include - Electric Bicycles/Scooters, Electric Forklifts etc.

Lithium nickel/manganese/cobalt oxide (NMC) -

Nickel, manganese, and cobalt oxides make up the NMC cathode. Because of its high energy and power density, respectable cycle and calendar life, higher safety than pure cobalt cathodes, and effective performance at high and low temperatures, NMC has been employed successfully in hybrid and electric vehicles.

The reduced cobalt percentage decreases the material cost because cobalt is so expensive. The ratios of nickel, manganese, and cobalt can also be adjusted in different NMC formulations. The most widely used variant, 1-1-1 NMC, uses equal amounts of the three elements.

Typical applications include - EVs, HEVs, Electric Bicycles/Scooters, Electric Forklifts etc.

Nickel cobalt aluminium (NCA) -

Image source - Sumitomo Metal Mining

Due to their relative specialization, NCA cathodes are only used in a limited number of applications. A trace amount of aluminium oxide is added to a nickel-cobalt alloy that is principally used. NCA is less expensive than LCO material, has a larger energy capacity, and has better cycle life characteristics.

All other common cathode materials have a worse safety margin, with the exception of LCO, which has a slightly better safety margin than NCA. NCA cathodes have a lower voltage than LCO cathodes.

Typical applications include - Electric Bicycles/Scooters, Electric Bikes etc.

Lithium manganese oxide (LMO)/carbon -

Because lithium manganese oxide has the highest cathode voltage among the most widely used cathode materials, the cell voltage for manganese cathodes is relatively high, approaching 4.2V at the fully charged state. Because of the material's exceptionally low impedance, LMO-based cells have extensive power capabilities.

This occurs due to the three-dimensional structure of the lithium insertion and reinsertion pathways as opposed to the two-dimensional channels employed by LCO and LNO. Manganese-based cathodes have a low calendar and cycle life due to capacity loss, particularly at high temperatures. Capacity is lost as manganese dissolves in the electrolyte.

Typical applications include - Power tools, electric bikes, medical devices etc.

Lithium iron phosphate (LFP)/carbon -

Lithium iron phosphate, which is far more stable than other cathode materials, offers the best level of safety among the common cathode materials. LFP material has a higher thermal runaway temperature and a more minor cathode breakdown energy release than cathodes made of transition metal oxides.

Compared to other cathode materials, LFP has a lower energy density, which implies that an LFP-based system will be larger and heavier. Energy density for LFP cells ranges from 90 to 140 Wh/kg. These cells would have a 3.3V nominal voltage and a 2.5V to 3.75V operational voltage range.

Typical applications include - EVs, bicycles, solar devices etc.

Lithium titanate (LTO) -

The energy density and specific energy of lithium titanate cells are poor (typically less than 90 Wh/kg), and they also have a very low cell voltage (less than half that of the cells with the highest energy density) (as low as 1.8V at full discharge).

Due to the anode material's much smaller volume change during charge and discharge than carbon, lithium titanate-based batteries are significantly more expensive than most other cell types despite having extremely extended cycle life capabilities. At 80% depth of discharge, many LTO cells have a 10,000+ cycle capacity (could be four to six times greater than other cells).

Because LTO cells usually have permissible recharge rates above 10C or ten times the rate at which the battery can be charged in an hour, they are desirable for many applications. This enables recharge times of no more than ten minutes. The operational temperature range of LTO is greater than most other cells. The SEI (solid-electrolyte interphase) is avoided, better conductivity electrolytes can be used, and rapid recharging is possible without the risk of lithium plating because LTO anodes operate at voltages that are significantly greater than those required for lithium plating. These elements allow LTO cells to generate extraordinarily high power densities.

Typical applications include – Street lights, forklifts, electric power trains etc.

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