Mystery of car battery's current solved

Chemists have solved the 150 year-old mystery of what gives the lead-acid battery, found under the hood of most cars, its unique ability to deliver a surge of current.

Lead-acid batteries are able to deliver the very large currents needed to start a car engine because of the exceptionally high electrical conductivity of the battery anode material, lead dioxide.

However, even though this type of battery was invented in 1859, up until now the fundamental reason for the high conductivity of lead dioxide has eluded scientists.

A team of researchers from Oxford University, the University of Bath, Trinity College Dublin, and the ISIS neutron spallation source, have explained for the first time the fundamental reason for the high conductivity of lead dioxide.

A report of the research appeared in a recent issue of Physical Review Letters
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'The unique ability of lead acid batteries to deliver surge currents in excess of 100 amps to turn over a starter motor in an automobile depends critically on the fact that the lead dioxide which stores the chemical energy in the battery anode has a very high electrical conductivity, thus allowing large current to be drawn on demand,' said Professor Russ Egdell of Oxford University's Department of Chemistry, an author of the paper.

'However the origin of conductivity in lead oxide has remained a matter of controversy. Other oxides with the same structure, such as titanium dioxide, are electrical insulators.'

Through a combination of computational chemistry and neutron diffraction, the team has demonstrated that lead dioxide is intrinsically an insulator with a small electronic band gap, but invariably becomes electron rich due to the loss of oxygen from the lattice, causing the material to be transformed from an insulator into a metallic conductor.

The researchers believe these insights could open up new avenues for the selection of improved materials for modern battery technologies.

Professor Egdell said: 'The work demonstrates the power of combining predictive materials modelling with state-of-the-art experimental measurements.'



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The electric current

In Erenovable continue marking some of the key concepts necessary to understand how electricity..In this case we will make sure to clarify a concept which, while use you on a daily basis, we do not always understand completely: the current electric.

At the beginning of the 19th century, was one of the great advances on the way to the electric power generation. It was invented by Alessandro Volta: the stack. This revolutionary object was the first electrochemical device that could be used as a source of electricity, able to deliver energy in a continuous and stable.

From there, the electrical phenomena research advanced rapidly. Some of the most important postulates that could establish were:

the electric charge is in more or less linked nature in the structure of materials, i.e. with greater or lesser ability to move in response to its interaction with electric fields..the negative charge residing on the electrons is, more often, is free, for example in metals. in them, some of the electrons have a degree of freedom like the molecules in a gaseous state. Their movement is erratic, and in gas, not a net sense of movement can be recognized.

Following this series of laws, you could discover that when you install a field within a metallic conductor, particles tend to follow preferably the signal from the field and can then be a sense of movement in their movements. This is what we call electric current.

Like most of the drivers of electric circuits are metallic, it is necessary to be in them the sense real or physical movement of the electrons against the electric field.

In the electrolyte or gaseous conductors, the charge carriers can also be positive, so that their displacement is contrary to the previous.

For simplicity, establishing a conventional sense of the current movement and is the positive charge carriers, i.e. in favour of the electric field.

Do do is defined as the electrical current to the ratio between the NET burden ? q that crosses a certain section of the driver per unit time? t. In symbols:

The unit of electric current is the ampere (A) that corresponds to a constant current which a load of a coulomb is going through any normal section of the driver by every second.

Its name was chosen in homage to the contributions of the French André Marie Ampère (1775-1836), who at the beginning of the 19th century established the principles of electrodynamics, relating the concepts of electricity and electrical potential, and also made other important contributions in the theory of electricity and magnetism.

Still learning more about the theory of electricity in these special items: