Lithium-ion batteriesLithium-ion batteries are constructed of several key components, including an anode, cathode, separator, casing, electrolyte, and a pair of current collectors.

Typically, the negative electrode of a conventional lithium-ion cell is made from graphite. The positive electrode is typically a metal oxide or phosphate. The electrolyte is a lithium salt in an organic solvent.Silberberg, M. (2006). Chemistry: The Molecular Nature of Matter and Change, 4th Ed. New York (NY): McGraw-Hill Education. p. 935, . The negative electrode (which is the anode when the cell is discharging) and the positive electrode (which is the cathode when discharging) are prevented from shorting by a separator. The electrodes are connected to the powered circuit through two pieces of metal called current collectors.

The negative and positive electrodes swap their electrochemical roles (anode and cathode) when the cell is charged. Despite this, in discussions of battery design the negative electrode of a rechargeable cell is often just called "the anode" and the positive electrode "the cathode".

In its fully lithiated state of LiC6, graphite correlates to a theoretical capacity of 1339 coulombs per gram (372 mAh/g). The positive electrode is generally one of three materials: a layered oxide (such as lithium cobalt oxide), a polyanion (such as lithium iron phosphate) or a spinel (such as lithium manganese oxide). More experimental materials include graphene-containing electrodes, although these remain far from commercially viable due to their high cost.

Lithium reacts vigorously with water to form lithium hydroxide (LiOH) and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes moisture from the battery pack. The non-aqueous electrolyte is typically a mixture of organic carbonates such as ethylene carbonate and propylene carbonate containing complexes of lithium ions.MSDS: National Power Corp Lithium Ion Batteries (PDF). tek.com; Tektronix Inc., 7 May 2004. Retrieved 11 June 2010. Ethylene carbonate is essential for making solid electrolyte interphase on the carbon anode, but since it is solid at room temperature, a liquid solvent (such as propylene carbonate or diethyl carbonate) is added.

The electrolyte salt is almost always lithium hexafluorophosphate (), which combines good ionic conductivity with chemical and electrochemical stability. The hexafluorophosphate anion is essential for passivating the aluminium current collector used for the positive electrode. A titanium tab is ultrasonically welded to the aluminium current collector. Other salts like lithium perchlorate (), lithium tetrafluoroborate (), and lithium bis(trifluoromethanesulfonyl)imide () are frequently used in research in tab-less coin cells, but are not usable in larger format cells, often because they are not compatible with the aluminium current collector. Copper (with a spot-welded nickel tab) is used as the current collector at the negative electrode.

Current collector design and surface treatments may take various forms: foil, mesh, foam (dealloyed), etched (wholly or selectively), and coated (with various materials) to improve electrical characteristics.

Depending on materials choices, the voltage, energy density, life, and safety of a lithium-ion cell can change dramatically. Current effort has been exploring the use of novel architectures using nanotechnology to improve performance. Areas of interest include nano-scale electrode materials and alternative electrode structures.

The manufacturing of lithium-ion batteries and their components requires the use of cleanrooms. The electrolyte filling and subsequent sealing steps are carried out autonomously inside dry rooms, which are cleanrooms with an extremely low dew point, often below -50 degrees Celsius. This is because electrolytes such as Lithium hexafluorophosphate are highly sensitive to moisture which can reduce lifespan measured in charge cycles or battery capacity. The concentration of H2O in air must be kept below 100 parts per million. Cathode coating, and cell assembly (not battery pack assembly) can also be carried out inside these rooms. The room can be divided into zones with several humidity levels, with the most dry reserved for the electrolyte filling and cell sealing areas, and the others reserved for cathode coating and cell assembly. Dedicated dehumidification units (DHUs) are used to dry the air, which use an absorption process with silica desiccant on a wheel which absorbs humidity from an airstream as it passes through the wheel and then the wheel rotates into another airstream to regenerate the desiccant by drying it with heated air. The rooms have airlocks. These are also known as desiccant dehumidifiers. Personal protective equipment is required to enter the rooms during operation due to the adverse health effects of dry air.https://volta.foundation/the-not-so-dry-topic-of-battery-dry-rooms/

Cathode

Transition metal oxides (TMOs) are widely used as cathode materials as the variable oxidation state of transition metal cations allows these oxides to reversibly host lithium ions (Li⁺) and undergo efficient redox (reduction-oxidation) reactions. While oxygen ions are commonly assumed to remain in a 2- oxidation state, the role of oxygen redox in facilitating lithium insertion is instrumental in these cathodes. The layered or framework structures of TMOs allow Li⁺ insertion/extraction during charging/discharging, while their transition metals and oxygen anions participate in electron transfer, enabling high energy density and stability. Three classes have been commercialized: (1) layered oxides, (2) spinel oxides and (3) oxoanion complexes. All were discovered by Goodenough and his collaborators.

+ Common cathode materials Technology Major producers (2023) Target application NotesLithium nickel manganese cobalt oxideNMC, LiNiMnCoO Ronbay Technology, Easpring, EcoPro, Umicore, L&F, PoscoElectric vehicles, power tools, grid energy storageGood specific energy and specific power densityLithium nickel cobalt aluminium oxideNCA, LiNiCoAlORonbay Technology, EcoProElectric vehicles, power tools, grid energy storageHigh energy density, good life spanLithium nickel cobalt manganese aluminium oxideNCMA, LG Chem, Hanyang UniversityElectric vehicles, grid energy storageGood specific energy, improved long-term cycling stability, faster chargingLithium manganese oxideLMO, LiMnO and lithium manganese rich (LMR)Posco, L&FPower tools, electric vehiclesFast charging speed, cheap, low cycle life Lithium iron phosphateLFP, LiFePO Shenzhen Dynanonic, Hunan Yuneng, LOPAL, Ronbay Technology Electric vehicles, grid energy storage Better safety, long cycle life, cheap, good thermal stability >Lithium cobalt oxideLCO, LiCoOEaspring, UmicoreHandheld electronicsHigh energy density

Layered oxides LiCoO2 was used in the first commercial lithium-ion battery made by Sony in 1991. The layered oxides have a pseudo-tetrahedral structure comprising layers made of MO6 octahedra separated by interlayer spaces that allow for two-dimensional lithium-ion diffusion. The band structure of LixCoO2 allows for true electronic (rather than polaronic) conductivity. However, due to an overlap between the Co4+ t2g d-band with the O2- 2p-band, the x must be >0.5, otherwise O2 evolution occurs. This limits the charge capacity of this material to ~140 mA h g−1.

Several other first-row (3d) transition metals also form layered LiMO2 salts. Some can be directly prepared from lithium oxide and M2O3 (e.g. for M=Ti, V, Cr, Co, Ni), while others (M= Mn or Fe) can be prepared by ion exchange from NaMO2. LiVO2, LiMnO2 and LiFeO2 suffer from structural instabilities (including mixing between M and Li sites) due to a low energy difference between octahedral and tetrahedral environments for the metal ion M. For this reason, they are not used. However, Na+ and Fe3+ have sufficiently different sizes that NaFeO2 can be used in sodium-ion batteries.

Similarly, LiCrO2 shows reversible lithium (de)intercalation around 3.2 V with 170–270 mAh/g. However, its cycle life is short, because of disproportionation of Cr4+ followed by translocation of Cr6+ into tetrahedral sites. On the other hand, NaCrO2 shows a much better cycling stability. LiTiO2 shows Li+ (de)intercalation at a voltage of ~1.5 V, which is too low for a cathode material.

These problems leave and as the only practical layered oxide materials for lithium-ion battery cathodes. The cobalt-based cathodes show high theoretical specific (per-mass) charge capacity, high volumetric capacity, low self-discharge, high discharge voltage, and good cycling performance. Unfortunately, they suffer from a high cost of the material.

In addition to a lower (than cobalt) cost, nickel-oxide based materials benefit from the two-electron redox chemistry of Ni: in layered oxides comprising nickel (such as nickel-cobalt-manganese NCM and nickel-cobalt-aluminium oxides NCA), Ni cycles between the oxidation states +2 and +4 (in one step between +3.5 and +4.3 V),Ohzuku, T., Ueda, A. & Nagayama, M. Electrochemistry and structural chemistry of (R3m) for 4 volt secondary lithium cells. J. Electrochem. Soc. 140, 1862–1870 (1993). cobalt- between +2 and +3, while Mn (usually >20%) and Al (typically, only 5% is needed) remain in +4 and 3+, respectively. Thus increasing the Ni content increases the cyclable charge. For example, NCM111 shows 160 mAh/g, while (NCM811) and (NCA) deliver a higher capacity of ~200 mAh/g. NCM and NCA batteries are collectively called ternary lithium batteries.

It is worth mentioning so-called "lithium-rich" cathodes that can be produced from traditional NCM (, where M=Ni, Co, Mn) layered cathode materials upon cycling them to voltages/charges corresponding to Li:M<0.5. Under such conditions a new semi-reversible redox transition at a higher voltage with ca. 0.4-0.8 electrons/metal site charge appears. This transition involves non-binding electron orbitals centered mostly on O atoms. Despite significant initial interest, this phenomenon did not result in marketable products because of the fast structural degradation (O2 evolution and lattice rearrangements) of such "lithium-rich" phases.

Cubic oxides (spinels) LiMn2O4 adopts a cubic lattice, which allows for three-dimensional lithium-ion diffusion. Manganese cathodes are attractive because manganese is less expensive than cobalt or nickel. The operating voltage of Li-LiMn2O4 battery is 4 V, and ca. one lithium per two Mn ions can be reversibly extracted from the tetrahedral sites, resulting in a practical capacity of <130 mA h g–1. However, Mn3+ is not a stable oxidation state, as it tends to disproportionate into insoluble Mn4+ and soluble Mn2+. LiMn2O4 can also intercalate more than 0.5 Li per Mn at a lower voltage around +3.0 V. However, this results in an irreversible phase transition due to Jahn-Teller distortion in Mn3+:t2g3eg1, as well as disproportionation and dissolution of Mn3+.

An important improvement of Mn spinel are related cubic structures of the LiMn1.5Ni0.5O4 type, where Mn exists as Mn4+ and Ni cycles reversibly between the oxidation states +2 and +4. This materials show a reversible Li-ion capacity of ca. 135 mAh/g around 4.7 V. Although such high voltage is beneficial for increasing the specific energy of batteries, the adoption of such materials is currently hindered by the lack of suitable high-voltage electrolytes. In general, materials with a high nickel content are favored in 2023, because of the possibility of a 2-electron cycling of Ni between the oxidation states +2 and +4.

LiV2O4 (lithium vanadium oxide) operates as a lower (ca. +3.0 V) voltage than LiMn2O4, suffers from similar durability issues, is more expensive, and thus is not considered of practical interest.

Oxoanionic