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. [1] [2] 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.
In general, a battery is made of one or several galvanic cells, where each cell consists of cathode, anode, separator, and in many cases current collectors. In flexible batteries all these components need to be flexible. These batteries can be fabricated into different shapes and sizes and by different methods. [3] One approach is to use polymer binders to fabricate composite electrodes where conductive additives are used to enhance their conductivity. The electrode materials can be printed or coated onto flexible substrates. The cells are assembled into flexible packaging materials to maintain bendability. Others approaches include the filtering of electrode suspension through filters to form free-standing films, or use flexible matrix to hold electrode materials. There are also other designs like cable batteries. [4]
There have been many efforts in adapting conventional batteries such as zinc-carbon and lithium ion, and at the same time new materials such as those based on nanoparticle complexes are being developed for flexible battery and supercapacitor electrodes. [5] For example, there are efforts at developing flexible lithium-ion batteries. Some studies have introduced nanocarbons into flexible lithium-ion batteries, and there are batteries with Li4Ti5O12 and LiFePO4 as anode and cathode, with graphene-based current collector. [6] Carbon nanotube electrodes have been reported too: pristine, [7] and combined with Li4Ti5O12, LiCoO2, [8] or SnO2. [9] Another development is the paper-thin flexible self-rechargeable battery that combines a thin-film organic solar cell with an extremely thin and highly flexible lithium-polymer battery. This recharges itself when exposed to light. [10]
Disposable, primary flexible primary batteries which are the equivalent of AA and AAA batteries are also of great interest with applicability in smart cards, medical patches, greeting cards, toys, and disposable devices. [11] Advantages of primary batteries with aqueous electrolyte over lithium-ion batteries include their eco-friendliness and the ease of fabrication. A flexible zinc-carbon battery using single-walled carbon nanotubes was reported in 2010. [12]
Alkaline batteries are more durable than conventional zinc-carbon batteries under heavy load. An alkaline battery uses MnO2 as the active material along with zinc anode, and KOH is used as an electrolyte here. A flexible alkaline cell offers several challenges because compared to zinc-carbon cells using weak acidic or neutral electrolytes, KOH is more basic and corrosive. Gaikwad has proposed an alkaline battery using nylon mesh in 2011. [13]
Commercialization efforts for flexible lithium-ion and zinc-carbon systems are ongoing. LG is proposing to mass-produce a flexible cable battery. [14] The global market for thin film batteries increased from $33.5 million in 2011 to $51.8 million in 2012, and is estimated to be valued at $87.3 million by the end of 2013. [15]
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.
A lithium polymer battery, or more correctly, lithium-ion polymer battery, is a rechargeable battery of lithium-ion technology using a polymer electrolyte instead of a liquid electrolyte. Highly conductive semisolid (gel) polymers form this electrolyte. These batteries provide higher specific energy than other lithium battery types. They are used in applications where weight is critical, such as mobile devices, radio-controlled aircraft, and some electric vehicles.
An alkaline battery is a type of primary battery where the electrolyte has a pH value above 7. Typically these batteries derive energy from the reaction between zinc metal and manganese dioxide.
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.
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.
Batteries provided the main source of electricity before the development of electric generators and electrical grids around the end of the 19th century. Successive improvements in battery technology facilitated major electrical advances, from early scientific studies to the rise of telegraphs and telephones, eventually leading to portable computers, mobile phones, electric cars, and many other electrical 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.
Nanoarchitectures for lithium-ion batteries are attempts to employ nanotechnology to improve the design of lithium-ion batteries. Research in lithium-ion batteries focuses on improving energy density, power density, safety, durability and cost.
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.
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.
Lithium–silicon batteries are lithium-ion batteries that employ a silicon-based anode, and lithium ions as the charge carriers. Silicon based materials, generally, have a much larger specific capacity, for example, 3600 mAh/g for pristine silicon. The standard anode material graphite is limited to a maximum theoretical capacity of 372 mAh/g for the fully lithiated state LiC6.
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.
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.
This is a history of the lithium-ion battery.