A zinc-ion battery or Zn-ion battery (abbreviated as ZIB) uses zinc ions (Zn2+) as the charge carriers. [1] Specifically, ZIBs utilize Zn metal as the anode, Zn-intercalating materials as the cathode, and a Zn-containing electrolyte. Generally, the term zinc-ion battery is reserved for rechargeable (secondary) batteries, which are sometimes also referred to as rechargeable zinc metal batteries (RZMB). [2] Thus, ZIBs are different than non-rechargeable (primary) batteries which use zinc, such as alkaline or zinc–carbon batteries.
In 2011, Feiyu Kang's group showcased for the first time the reversible Zn-ion insertion into the tunnel structure of alpha-type manganese dioxide (MnO2) host used as the cathode in a ZIB. [3] [4]
The University of Waterloo in Canada owns patent rights to zinc-ion battery technology developed in its laboratories. [5] [6] The Canadian company Salient Energy is commercialising the zinc-ion battery technology. [7]
Other forms of rechargeable zinc batteries are also being developed for stationary energy storage, although these are not explicitly zinc-ion. For example, Eos Energy Storage is developing a zinc-halide battery in which the cathode reaction involves the oxidation and reduction of halides. [8] Eos Energy Storage is producing 1.5GWh of ‘Made in America’ zinc batteries to be used in the Texas and California electric grids. [9] [10]
ZIBs are an alternative to lithium-ion batteries for grid-scale energy storage because of their affordability, safety, and compatibility with aqueous electrolytes. Research challenges at the anode, electrolyte, and cathode currently prevent its further commercialization. [11]
A zinc metal negative electrode holds a high theoretical volumetric capacity (5854 Ah L−1), gravimetric capacity (820 Ah kg−1), and natural abundance. [2] Zinc production and proven reserves exist at a higher scale than lithium metal due to zinc’s use in galvanization and its broad geographic availability. [12] Other benefits of zinc metal as an anode material include its compatibility with both aqueous and non-aqueous electrolytes and its higher safety and lower environmental toxicity compared to lithium. [13]
Challenges to the Zn metal anode in the typical near-neutral aqueous electrolyte include the hydrogen evolution reaction and anode corrosion, which can cause capacity loss. Dendrite growth also occurs on Zn metal, like on Li metal, due to uneven plating. [14] While these dendrites can cause capacity loss and cell short-circuit, they do not cause the explosion and fire risk of lithium metal batteries due to the aqueous electrolytes. Current research strategies to address these challenges include anode capping layers and structural and chemical changes to the Zn metal. [14]
Aqueous electrolytes are the dominant form in ZIBs due to their high conductivity, low price, non-flammability, and environmental safety. Typical Zn salts are ZnSO4, Zn(OTf)2, and Zn(TFSI)2. [13] Zinc sulfate is widely used today because of its lower cost and electrode stability, but the larger triflate and TFSI anions can lead to higher conductivities. Despite the advantages of aqueous electrolytes, the hydrogen evolution reaction and facile dendrite growth limit their use. Electrolyte additives such as buffering agents or other zinc salts can improve the performance of the aqueous electrolyte, as can the use of superconcentrated electrolytes, by altering the zinc solvation structure. [15]
Non-aqueous electrolytes are another area of current research that uses organic liquid or ionic liquid electrolytes to prevent the hydrogen evolution reaction. Despite the lower conductivities and higher costs of these electrolytes, they can have higher voltage stability windows than water (1.7V) as well as higher coulombic efficiencies and cycle lifetimes due to an absence of the hydrogen evolution reaction. Current research includes methods to increase the conductivity and lower the charge transfer resistance of these electrolytes. [16]
Manganese and Vanadium oxides are the most popular cathode materials for ZIBs due to their stability and theoretical capacity. [13] MnO2 cathodes come in multiple phases with different intercalation geometries and specific capacities, the most studied of which are the alpha-, gamma-, and delta-types. In addition to these two materials, Prussian blue analogues, spinel-structured oxides, hexacyanoferrates, and organic materials are also being explored as cathode materials. [17] [18] Additional research is needed to confirm the exact reaction mechanisms and electrolyte-cathode relationship in ZIBs.
Zinc-ion battery chemistries have the potential to penetrate into the flexible electronic markets, where demand for flexible energy storage devices has been increasing. Flexible batteries must be safe and ultra-thin, and zinc-ion chemistries provide much safer alternatives to similarly energy-dense batteries like lithium-ion batteries. Current research has shown that flexible zinc-ion batteries (FZIBs) with hydrogel electrolytes show outstanding performance and stretching and bending characteristics. For one cell, discharge curves for different bending radii of the cell align with the curve for the original flat state with only a minor loss in capacity, showing that the cell works well even when deformed. [19] It has even been found that a FZIB could be run-over with a car and still retain discharge capacities similar to the initial state. [20]
However, future work must be done to bring FZIB technology from the lab to real-world applications, especially in terms of finding appropriate electrolytes and suitable compatible electrodes. Promising flexible electrolytes are hydrogels, which have high ionic conductivity and good flexibility, but are sensitive to the environment because of their fragile nature. [19]
One significant benefit of aqueous zinc-ion batteries (AZIBs) is their lower environmental impacts compared to other battery chemistries like lithium-ion (LIB) or sodium-ion (NIB) batteries. The chemistry of AZIBs means they can be assembled under ambient conditions without a controlled inert, oxygen and moisture-free environment like LIBs or NIBs, which has less of an environmental impact. In addition, the aqueous electrolytes used in AZIBs are better for human health and the environment compared to the organic, often toxic, electrolytes used in LIBs. In a life cycle assessment study done on six different AZIB battery chemistries, the global warming indicator ranged from 22.1 to 95.2 kg CO2 equivalent. Compared to the median of 120 kg CO2 equivalent for LIBs, AZIBs are equal to or better than LIBs in terms of their emissions.
Currently, the AZIB’s cathode, separator and anode are the main drivers of its global warming potential. The cathode is often produced in a multistage fabrication process and requires energy-demanding materials like nickel or tetrahydrofuran. The separator contributes a significant amount to the global warming potential because it must be mechanically robust to protect against dendrite formation, meaning a significant amount of glass microfiber must be used, which carries a relatively large embedded energy.
There are many avenues of research being pursued that can further improve the environmental impact of the AZIBs. Currently, the lower volumetric energy density of AZIBs compared to lithium-oxygen or lithium-sulfur batteries requires the use of larger AZIB cells to store the same amount of energy. Creating cathodes that can operate at higher voltages with higher mass loadings will shrink the required cell size, reducing material use and improving the environmental footprint. In addition, fixing the capacity fade encountered by these batteries over time will lengthen the lifespan of the batteries and reduce their cradle-to-grave impacts. Lastly, research is being conducted on the use of renewable materials as electrolytes and separators, particularly polysaccharides and its derivatives which can create hydrogels with adequate mechanical properties and good electrochemical performance. [21]
The recycling process for ZIBs is currently in its infant stages. Some studies have shown that metallic zinc can be recovered from the batteries with over 99% efficiency through evaporation and separation, and this material can be recycled indefinitely without changes in its physical properties. While the separator will pose a larger challenge for recycling, the use of biopolymer electrolytes allows for environmentally friendly recycling approaches. If organic electroactive materials (OEMs) are used, they demonstrate high solubility in inexpensive organic solvents and are stable in both their charged and discharged states. This allows for OEM AZIBs to be recycled at any state of charge with a high recovery potential. [22]
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit. Electrodes are essential parts of batteries that can consist of a variety of materials (chemicals) depending on the type of battery.
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.
A zinc–air battery is a metal–air electrochemical cell powered by the oxidation of zinc with oxygen from the air. During discharge, a mass of zinc particles forms a porous anode, which is saturated with an electrolyte. Oxygen from the air reacts at the cathode and forms hydroxyl ions which migrate into the zinc paste and form zincate, releasing electrons to travel to the cathode. The zincate decays into zinc oxide and water returns to the electrolyte. The water and hydroxyl from the anode are recycled at the cathode, so the water is not consumed. The reactions produce a theoretical voltage of 1.65 Volts, but is reduced to 1.35–1.4 V in available cells.
A flow battery, or redox flow battery, is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system on separate sides of a membrane. Ion transfer inside the cell occurs across the membrane while the liquids circulate in their respective spaces.
Nanobatteries are fabricated batteries employing technology at the nanoscale, particles that measure less than 100 nanometers or 10−7 meters. These batteries may be nano in size or may use nanotechnology in a macro scale battery. Nanoscale batteries can be combined to function as a macrobattery such as within a nanopore battery.
A lithium-ion capacitor is a hybrid type of capacitor classified as a type of supercapacitor. It is called a hybrid because the anode is the same as those used in lithium-ion batteries and the cathode is the same as those used in supercapacitors. Activated carbon is typically used as the cathode. The anode of the LIC consists of carbon material which is often pre-doped with lithium ions. This pre-doping process lowers the potential of the anode and allows a relatively high output voltage compared to other supercapacitors.
A solid-state battery (SSB) is an electrical battery that uses a solid electrolyte for ionic conductions between the electrodes, instead of the liquid or gel polymer electrolytes found in conventional batteries. Solid-state batteries theoretically offer much higher energy density than the typical lithium-ion or lithium polymer batteries.
The lithium–air battery (Li–air) is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow.
A metal–air electrochemical cell is an electrochemical cell that uses an anode made from pure metal and an external cathode of ambient air, typically with an aqueous or aprotic electrolyte.
A potassium-ion battery or K-ion battery is a type of battery and analogue to lithium-ion batteries, using potassium ions for charge transfer instead of lithium ions.
Sodium-ion batteries (NIBs, SIBs, or Na-ion batteries) are several types of rechargeable batteries, which use sodium ions (Na+) as their charge carriers. In some cases, its working principle and cell construction are similar to those of lithium-ion battery (LIB) types, but it replaces lithium with sodium as the intercalating ion. Sodium belongs to the same group in the periodic table as lithium and thus has similar chemical properties. However, in some cases, such as aqueous batteries, SIBs can be quite different from LIBs.
Sir Peter George Bruce, is a British chemist, and Wolfson Professor of Materials in the Department of Materials at the University of Oxford. Between 2018 and 2023, he served as Physical Secretary and Vice President of the Royal Society. Bruce is a founder and Chief Scientist of the Faraday Institution.
Aluminium-ion batteries (AIB) are a class of rechargeable battery in which aluminium ions serve as charge carriers. Aluminium can exchange three electrons per ion. This means that insertion of one Al3+ is equivalent to three Li+ ions. Thus, since the ionic radii of Al3+ (0.54 Å) and Li+ (0.76 Å) are similar, significantly higher numbers of electrons and Al3+ ions can be accepted by cathodes with little damage. Al has 50 times (23.5 megawatt-hours m-3) the energy density of Li-ion batteries and is even higher than coal.
Research in lithium-ion batteries has produced many proposed refinements of lithium-ion batteries. Areas of research interest have focused on improving energy density, safety, rate capability, cycle durability, flexibility, and reducing cost.
Flexible batteries are batteries, both primary and secondary, that are designed to be conformal and flexible, unlike traditional rigid ones. They can maintain their characteristic shape even against continual bending or twisting. The increasing interest in portable and flexible electronics has led to the development of flexible batteries which can be implemented in products such as smart cards, wearable electronics, novelty packaging, flexible displays and transdermal drug delivery patches. The advantages of flexible batteries are their conformability, light weight, and portability, which makes them easy to be implemented in products such as flexible and wearable electronics. Hence efforts are underway to make different flexible power sources including primary and rechargeable batteries with high energy density and good flexibility.
Magnesium batteries are batteries that utilize magnesium cations as charge carriers and possibly in the anode in electrochemical cells. Both non-rechargeable primary cell and rechargeable secondary cell chemistries have been investigated. Magnesium primary cell batteries have been commercialised and have found use as reserve and general use batteries.
The glass battery is a type of solid-state battery. It uses a glass electrolyte and lithium or sodium metal electrodes.
Calcium (ion) batteries are energy storage and delivery technologies (i.e., electro–chemical energy storage) that employ calcium ions (cations), Ca2+, as the active charge carrier. Calcium (ion) batteries remain an active area of research, with studies and work persisting in the discovery and development of electrodes and electrolytes that enable stable, long-term battery operation. Calcium batteries are rapidly emerging as a recognized alternative to Li-ion technology due to their similar performance, significantly greater abundance, and lower cost.
Multivalent batteries are energy storage and delivery technologies (i.e., electro-chemical energy storage) that employ multivalent ions, e.g., Mg2+, Ca2+, Zn2+, Al3+ as the active charge carrier in the electrolytes as well as in the electrodes (anode and cathode). Multivalent batteries are generally pursued for the potentially greater capacity, owing to greater ion valency, as well as natural mineral abundance.
This is a history of the lithium-ion battery.