The fundamental battery chemistry or more correctly the Electrochemistry. This is the cathode, anode and electrolyte. What are they, who makes them, where next on the roadmap, what is the latest research and what are the pros and cons of each.
Typically we plot Power Density versus Energy Density. In this plot the dots represent data from real cell datasheets.
The main chemistries are:
Lithium Ion
In a rechargeable lithium ion battery lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Current production cells have an energy density ~280Wh/kg.
The cathode is a lithium transition metal oxide, eg manganese or cobalt or a combination of transitional metals: LCO, LMO, NCA, NMC, LFP, LMFP. The anode is normally a graphite-based material, which can intercalate or release lithium, this can have a percentage of Silicon to increase the capacity. Alternatively the anode can be Lithium Titanate (LTO).
Sodium Ion
Analogous to the lithium-ion battery but using sodium ions (Na+) as the charge carriers. The working of the sodium based chemistry and cell construction are almost identical with those of the commercially widespread lithium-ion battery types, but sodium compounds are used instead of lithium compounds.
Lead Acid
The Lead Acid Battery is a battery with electrodes of lead oxide and metallic lead that are separated by an electrolyte of sulfuric acid. Energy density 40-60 Wh/kg.
Nickel Metal Hydride
The Nickel Metal Hydride battery has a nickel-hydroxide cathode, a metal hydride (a variety of metal alloys are used) anode, and aqueous potassium hydroxide electrolyte. This is a rechargeable battery chemistry that has been superseded by lithium ion, but has seen a lot of use in Toyota hybrids. Energy density 40-110 Wh/kg at cell level.
Solid State is still very much in the technical development stage and although has significant hurdles to overcome before we see large scale industrialisation it is very significant.
Solid-State
Any battery technology that uses solid electrodes and solid electrolyte. This offers potential improvements in energy density and safety, but has very significant challenges with cycling, manufacturing and durability of the solid sandwich.
There are many other types of battery cell and we have listed these below.
Aluminium Air
High energy density and low cost. The aluminium anode and air cathode along with an aqueous electrolyte, generate power through the oxidation of aluminium by oxygen from the air. However, a major issue is the corrosion of the aluminium anode thus reducing capacity and compromising calendar life.
Aluminium Ion
The aluminium metal anode can exchange three electrons during the electrochemical process, hence can deliver a high theoretically high volumetric and gravimetric capacity. However, anode, cathode and electrolyte development is required before this type of cell can exploit the high energy density with a stability over a lifetime of cycles.
Dual-Ion
A battery technology that offers a low cost solution for grid based storage. Cations and anions both participate in the intercalation and deintercalation processes using graphite as both cathode and anode material.
Fluoride-Ion
Seen as a replacement for lithium and possibly the post-lithium technology with “up to 7x the Wh/kg” of current Lithium technology.
Lithium Air
Promised as the beyond lithium ion technology with unrivaled energy density. However, even though a huge amount of scientific effort has gone into understanding the chemistry and reactions it is not mature enough to develop into a workable battery at this stage. If anything the focus has moved to solid state lithium ion batteries.
Lithium Sulfur
Perhaps the most mature of the beyond Li-ion’ battery chemistries with a potential energy density of >600Wh/kg. Also with the potential for substantially reduced costs and improved safety. However, a number of challenges mean that cycle life has been poor. Hence the potential attracts attention and much needed research at the fundamental chemistry stage.
Magnesium-Ion
Function very similar to lithium-ion batteries, comparable energy density to lithium-ion along with potential for improvement as there are double the electrons for every individual magnesium ion. Magnesium is more abundant than lithium. However, there are a lot more possible side reactions with magnesium-ion.
Nickel Cadmium
Rechargeable battery that uses nickel oxide hydroxide and metallic cadmium as electrodes.
Nickel Hydrogen
This has the positive electrode of nickel oxide from the nickel-cadmium cell, and a hydrogen negative electrode from the hydrogen-oxygen fuel cell. The energy density is low at ~60Wh/kg, cost high, but cycle life can be ~200,000 and hence find a niche application in space craft.
Nickel Iron
The NiFe battery, nickel(III) oxide-hydroxide positive plates and iron negative plates, with an electrolyte of potassium hydroxide. A very low gravimetric energy density of 19 to 25Wh/kg.
Potassium Ion
Potential to be a low cost storage based chemistry, but large large change of ~60% of graphite with the insertion of K ions puts high strain on lattice and so limits cycling. Technology development is behind that of Lithium and Sodium Ion based batteries.
Sodium-Nickel-Chloride Molten Salt Battery
Also known as the Zebra Battery.
Zinc Air
Perhaps the most promising metal-air battery technology. Typically it has a zinc anode, an oxygen permeable cathode, a separator, and a caustic alkaline electrolyte. Promising low cost, high stability and high energy density.
Zinc Bromine
Promising flow battery technology.
Zinc Carbon
A primary battery chemistry, commonly used in batteries for radios, toys and household goods.
References
- Jianmin Ma et al, “The 2021 battery technology roadmap”, 2021 J. Phys. D: Appl. Phys. 54 183001
- P Butler, P Eidler, P Grimes, S Klassen and R Miles, Zinc/Bromine Batteries, Sandia Labs