A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. In comparison with other commercial rechargeable batteries, Li-ion batteries are characterized by higher specific energy, higher energy density, higher energy efficiency, a longer cycle life, and a longer calendar life.
Also noteworthy is a dramatic improvement in lithium-ion battery properties after their market introduction in 1991; over the following 30 years, their volumetric energy density increased threefold while their cost dropped tenfold. In late 2024 global demand passed 1 terawatt-hour per year, while production capacity was more than twice that.
The invention and commercialization of Li-ion batteries may have had one of the greatest impacts of all technologies in human history,as recognized by the 2019 Nobel Prize in Chemistry. More specifically, Li-ion batteries enabled portable consumer electronics, laptop computers, cellular phones, and electric cars. Li-ion batteries also see significant use for grid-scale energy storage as well as military and aerospace applications.
Research on rechargeable Li-ion batteries dates to the 1960s; one of the earliest examples is a CuF2/Li battery developed by NASA in 1965. The breakthrough that produced the earliest form of the modern Li-ion battery was made by British chemist M. Stanley Whittingham in 1974, who first used titanium disulfide (TiS2) as a cathode material, which has a layered structure that can take in lithium ions without significant changes to its crystal structure. Exxon tried to commercialize this battery in the late 1970s, but found the synthesis expensive and complex, as TiS2 is sensitive to moisture and releases toxic hydrogen sulfide (H2S) gas on contact with water. More prohibitively, the batteries were also prone to spontaneously catch fire due to the presence of metallic lithium in the cells. For this, and other reasons, Exxon discontinued the development of Whittingham’s lithium-titanium disulfide battery.
Design
Generally, the negative electrode of a conventional lithium-ion cell is graphite made from carbon. The positive electrode is typically a metal oxide or phosphate. The electrolyte is a lithium salt in an organic solvent. 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.
Electrochemistry
The reactants in the electrochemical reactions in a lithium-ion cell are the materials of the electrodes, both of which are compounds containing lithium atoms. Although many thousands of different materials have been investigated for use in lithium-ion batteries, only a very small number are commercially usable. All commercial Li-ion cells use intercalation compounds as active materials.[49] The negative electrode is usually graphite, although silicon is often mixed in to increase the capacity. The electrolyte is usually lithium hexafluorophosphate, dissolved in a mixture of organic carbonates. A number of different materials are used for the positive electrode, such as LiCoO2, LiFePO4, and lithium nickel manganese cobalt oxides.
During cell discharge the negative electrode is the anode and the positive electrode the cathode: electrons flow from the anode to the cathode through the external circuit. An oxidation half-reaction at the anode produces positively charged lithium ions and negatively charged electrons. The oxidation half-reaction may also produce uncharged material that remains at the anode. Lithium ions move through the electrolyte; electrons move through the external circuit toward the cathode where they recombine with the cathode material in a reduction half-reaction. The electrolyte provides a conductive medium for lithium ions but does not partake in the electrochemical reaction. The reactions during discharge lower the chemical potential of the cell, so discharging transfers energy from the cell to wherever the electric current dissipates its energy, mostly in the external circuit.
During charging these reactions and transports go in the opposite direction: electrons move from the positive electrode to the negative electrode through the external circuit. To charge the cell the external circuit has to provide electrical energy. This energy is then stored as chemical energy in the cell (with some loss, e. g., due to coulombic efficiency lower than 1).
Both electrodes allow lithium ions to move in and out of their structures with a process called insertion (intercalation) or extraction (deintercalation), respectively.
As the lithium ions “rock” back and forth between the two electrodes, these batteries are also known as “rocking-chair batteries” or “swing batteries” (a term given by some European industries).
The following equations exemplify the chemistry (left to right: discharging, right to left: charging).
The negative electrode half-reaction for the graphite is
The positive electrode half-reaction in the lithium-doped cobalt oxide substrate is
The full reaction being
The overall reaction has its limits. Overdischarging supersaturates lithium cobalt oxide, leading to the production of lithium oxide, possibly by the following irreversible reaction:
Overcharging up to 5.2 volts leads to the synthesis of cobalt (IV) oxide, as evidenced by x-ray diffraction:
The transition metal in the positive electrode, cobalt (Co), is reduced from Co4+ to Co3+ during discharge, and oxidized from Co3+ to Co4+ during charge.
The cell’s energy is equal to the voltage times the charge. Each gram of lithium represents Faraday’s constant/6.941, or 13,901 coulombs. At 3 V, this gives 41.7 kJ per gram of lithium, or 11.6 kWh per kilogram of lithium. This is slightly more than the heat of combustion of gasoline; however, lithium-ion batteries as a whole are still significantly heavier per unit of energy due to the additional materials used in production.
Note that the cell voltages involved in these reactions are larger than the potential at which an aqueous solutions would electrolyze.
Indian Mineral Reserve (LITHIUM)
India’s mining ministry informed the villagers that they were sitting on a fortune: 5.9 million metric tons of lithium, a silver-white metal that is a core component of the batteries necessary for India’s transition to clean energy.
The discovery — a first in India — would make the country the holder of the fifth-largest lithium reserve in the world, mining officials announced. Indian media outlets jubilantly reported that companies including Mitsubishi, Tesla, and Ola Electric were eyeing the reserve.
Two years later, nothing has happened. The government tried to auction the lithium block twice in March, and failed both times, due to a lack of bidders. The extraction plans have been halted indefinitely.
There were several red flags surrounding the auction, according to PV Rao, a senior geologist in the mineral industry who represents India at the Committee for Mineral Reserves International Reporting Standards, a forum that sets standards for exploration results.
For one, the amount of lithium in the Salal reserve is much less significant than initially reported, Rao and other industry experts told Rest of World. They said that only about 0.02 million tonnes of lithium carbonate is present in the ore body, a small fraction of the levels seen in other major reserves. Secondly, the reserve holds minerals in clay-deposit form, which is difficult to mine commercially.
According to Rao, the geological report commissioned by the government didn’t contain enough information about the reserve to meet international standards. “That report is [a] very, very skeleton type of report with limited information, based on which the bids are being made,” he said, adding that genealogical reports produced by the Indian government often contain “misleading and quite inadequate” information.
Even if the reserve were truly stocked with “white gold,” as lithium is now sometimes called, mining in Salal village is fraught with challenges. For companies looking to invest in minerals, Jammu and Kashmir is a region full of uncertainties, Puneet Gupta, an electric mobility expert and director at rating agency S&P, told Rest of World. “The state suffers from political instability, violence, and lack of peace — any company coming in will see all those things in the picture,” he said.