Structural batteries are multifunctional materials or structures, capable of acting as an electrochemical energy storage system (i.e. batteries) while possessing mechanical integrity. [1] [2] [3]
They help save weight and are useful in transport applications [4] [5] such as electric vehicles and drones, [6] because of their potential to improve system efficiencies. Two main types of structural batteries can be distinguished: embedded batteries and laminated structural electrodes. [7]
Embedded batteries represent multifunctional structures where lithium-ion battery cells are efficiently embedded into a composite structure, and more often sandwich structures. In a sandwich design, state-of-the-art lithium-ion batteries are embedded forming a core material and bonded in between two thin and strong face sheets (e.g. aluminium). In-plane and bending loads are carried by face sheets while the battery core takes up transverse shear and compression loads as well as storing the electrical energy. The multifunctional structure can then be used as a load-bearing as well as an energy storage material. [8]
In laminated structural electrodes the electrode material possesses an intrinsic load-bearing and energy storage function. Such batteries are also called massless batteries, since in theory vehicle body parts could also store energy thus not adding any additional weight to the vehicle as additional batteries would not be needed. [9] An example for such batteries are those based on a zinc anode, manganeseoxide cathode and a fiber/ polymer composite electrolyte. [10] The structural electrolyte enables stable charge and discharge performance. This assembly has been demonstrated in an unmanned aerial vehicle. A commonly proposed structural battery is based on a carbon fiber reinforced polymer (CFRP) concept. Here, carbon fibers serve simultaneously as electrodes and structural reinforcement. The lamina is composed of carbon fibers that are embedded in a matrix material (e.g. a polymer). Multiple layers of carbon fibers are impregnated with a matrix that enables load transfer between the fibers but also lithium-ion transport, unlike commonly used vinylester or epoxy matrices. This type of energy storage system can be based on a nickel [11] or on lithium-ion chemistry. [12] The laminate is made of the combination of a negative electrode, a separator and a positive electrode, embedded in an ionically conductive and structural electrolyte. In the laminated structural electrodes concept, carbon fibers can be used to intercalate e.g. lithium-ions (structural anode); similarly, to commercially available graphite anodes. The structural cathode consists of carbon fibers coated with electrochemically active species, e.g. lithium oxide particles. An example of a structural battery exploiting a carbon fiber negative electrode and lithium iron phosphate positive electrode was demonstrated to be capable of lighting an LED. [13] Some separator material is used in between the two structural electrodes to prevent short-circuits. [14] [15] However, the CFRC concept described above is still being researched. [16]
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.
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.
Nanodot can refer to several technologies which use nanometer-scale localized structures. Nanodots generally exploit properties of quantum dots to localize magnetic or electrical fields at very small scales. Applications for nanodots could include high-density information storage, energy storage, and light-emitting devices.
A paper battery is engineered to use a spacer formed largely of cellulose. It incorporates nanoscopic scale structures to act as high surface-area electrodes to improve conductivity.
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.
The thin-film lithium-ion battery is a form of solid-state battery. Its development is motivated by the prospect of combining the advantages of solid-state batteries with the advantages of thin-film manufacturing processes.
A solid-state battery 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 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.
A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor, with a capacitance value much higher than solid-state capacitors but with lower voltage limits. It bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charge and discharge cycles than rechargeable batteries.
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.
NASICON is an acronym for sodium (Na) super ionic conductor, which usually refers to a family of solids with the chemical formula Na1+xZr2SixP3−xO12, 0 < x < 3. In a broader sense, it is also used for similar compounds where Na, Zr and/or Si are replaced by isovalent elements. NASICON compounds have high ionic conductivities, on the order of 10−3 S/cm, which rival those of liquid electrolytes. They are caused by hopping of Na ions among interstitial sites of the NASICON crystal lattice.
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.
A dual carbon battery is a type of battery that uses graphite as both its cathode and anode material. Compared to lithium-ion batteries, dual-ion batteries (DIBs) require less energy and emit less CO2 during production, have a reduced reliance on critical materials such as Ni or Co, and are more easily recyclable.
A zinc-ion battery or Zn-ion battery (abbreviated as ZIB) uses zinc ions (Zn2+) as the charge carriers. 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). Thus, ZIBs are different than non-rechargeable (primary) batteries which use zinc, such as alkaline or zinc–carbon batteries.
The piezoelectrochemical transducer effect (PECT) is a coupling between the electrochemical potential and the mechanical strain in ion-insertion-based electrode materials. It is similar to the piezoelectric effect – with both exhibiting a voltage-strain coupling - although the PECT effect relies on movement of ions within a material microstructure, rather than charge accumulation from the polarization of electric dipole moments.
A solid-state silicon battery or silicon-anode all-solid-state battery is a type of rechargeable lithium-ion battery consisting of a solid electrolyte, solid cathode, and silicon-based solid anode.
Structural composite supercapacitors are multifunctional materials that can both bear mechanical load and store electrical energy. That when combined with structural batteries, could potentially enable an overall weight reduction of electric vehicles.