Battery strategy goes flat: Net-zero target at risk Contents

Appendix 4: Abbreviations, acronyms and technical terms


The positive electrode. Electrons flow into the anode from the external circuit, and recombine with positive ions

Balancing services

A set of interventions that are used to keep the electricity grid operating within normal parameters. For example, the output of electricity sources (and the demand from some large customers) can be increased or decreased to help balance supply and demand, and to maintain the correct voltage and frequency. In the UK, there interventions are secured via contracts between the National Grid as the System Operator and the owners of electricity sources and customers with high demand


A device that stores chemical energy and supplies an electrical current. A battery is also called a battery pack, and is composed of multiple cell


Department for Business, Energy and Industrial Strategy


Battery electric vehicle. A vehicle that is propelled by an electric motor powered by a battery that is charged from an external power source


A device that stores chemical energy and supplies an electrical current. A cell consists of two electrodes, an electrolyte, a membrane and a casing. Multiple cells are combined to form a battery (also called a battery pack)


A material that assists a chemical reaction but is not itself changed by the reaction, and hence remains in place to assist the reaction again


The negative electrode. Electrons separate from atoms (which become positively charged ions) at the cathode, and then flow out into the external circuit

Charging time

How long it takes to recharge the battery after its charge has been depleted


Combined heat and power. A CHP unit uses an energy source (e.g. natural gas or hydrogen) to produce electricity and to use the ‘waste’ heat (e.g. for heating buildings or water)

Critical raw materials

Materials that are essential for national objectives, including minerals used in the manufacture of batteries and fuel cells

Cycle life

The number of times the battery can be charged and discharged before its performance falls below an acceptable level


Department for Transport


Energy Futures Laboratory

Electric trains

Locomotives propelled by electric motors that are powered by an external source of electricity that is provided via overhead cables or live rails. This is distinct from a battery train that uses an electric motor that is powered by an onboard battery


A component within a battery or fuel cell where electrons and ions separate or recombine


A material in a battery that contains particles that react at the anode and cathode to form electrical charge carriers. The electrolyte can conduct ions between the electrodes


A device that uses electricity to break down water into oxygen and hydrogen; it is essentially the opposite of a fuel cell. The process is called electrolysis


A negatively charged particle that composes the electrical current in most circuits.


The total amount of work that can be done, such as lighting a light or turning a motor. The greater the energy available, the longer the work can be maintained. The basic unit of energy in electrical engineering is the watt-hour (Wh)

Energy density

The amount of energy a battery contains in proportion to its mass, typically measured in watt-hours per gram (Wh/g)

Energy stored

The product of a battery’s energy density and mass, giving the total amount of energy that it can contain, measured in Wh

Energy vector

The media that transport energy. Energy vectors include primary energy sources such as gas that can be transported easily, and ‘intermediaries’ such as electricity and hydrogen


Engineering and Physical Sciences Research Council


Electric vehicle, a generic term, referring to any of the other types noted in this glossary, such as BEVs, PHEVs and FCEVs


Fuel cell electric vehicle. A vehicle that uses a fuel cell to power an electric motor

Fuel cell

A device in which a fuel (containing hydrogen) reacts with another chemical (such as oxygen) without combustion, to produce an electrical current, heat and water (as well as other chemicals in the case of fuels other than pure hydrogen)

Heat pump

A device that uses a power source (e.g. electricity) to pump a fluid around a system of pipes in order to move heat from a cooler region to a warmer region. It operates in essentially the opposite manner to a refrigerator, and is an option for heating buildings

High temperature fuel cell

A fuel cell that operates at up to 1,000°C. Also called solid oxide fuel cells (SOFC)


A charged particle, formed when an atom gains or loses one or more electron

Intermediate temperature fuel cell

A fuel cell that operates at 200–300°C

On-road charging

Charging an electric vehicle either using via a pantograph to make contact with overhead cables or using electromagnetic induction to access energy from cables buried within the road

Life cycle

The sequence of manufacture, use and disposal or recycling of a product


A next-generation battery technology that is being developed


The standard battery for most applications at present, in which lithium-ions are the ions that conduct the electrical charge through the electrolyte


A next-generation battery technology that is being developed

Low temperature fuel cell

A fuel cell that operates at 60–100°C. Also known as ‘polymer electrolyte membrane’ or ‘proton-exchange membrane’ (PEM) fuel cells


A thin sheet that separates two regions. In a battery, the membrane sits between the anode and the cathode to prevent them from touching each other, but the membrane is ‘semi-permeable’ to allow ions to flow through it. The membrane in a battery is also called a separator


Natural History Museum


Plug-in hybrid electric vehicle. A vehicle that can use either internal combustion engine fuelled by a liquid fuel or an electric motor powered by battery that is charged from an external power source


How quickly work can be done—that is, power is the ‘energy per unit time’. The greater the power, the more rapidly work is done. The basic unit of power is the watt (W)

Redox flow battery

A battery in which liquid electrolytes are pumped through the cell from external tanks, allowing larger volumes of electrolyte to interact with the electrodes. Also called simply a ‘flow battery’


Society of Motor Manufacturers and Traders


A next-generation battery technology that operates in much the same way as lithium-ion technology, but with different materials, including sodium in place of lithium

Solid-state battery

A next-generation battery technology in which all components are solid, including the electrolyte (which is liquid is current batteries)


A term used to describe applications other than transport, for example batteries or fuel cells used in electricity grids or in buildings are said to be ‘stationary applications’


A device that stores energy for release in electrical form. Compared to a battery, it stores less energy and releases it more rapidly


UK Energy Research Centre


Warwick Manufacturing Group

© Parliamentary copyright 2021