Patent Description:
Electrochemical cells are vital to many electrical systems, in particular portable devices such as mobile phones and laptops and, increasingly, electric vehicles.

The portability of electronic devices/vehicles is dependent on the performance of their cells. In general it is desirable to have a cell that has a large capacity and a short charging time to increase the ratio of time that the devices/vehicles can operate independently of an external power source to time that they must be connected to an external power source for charging.

Various types and configurations of electrochemical cells can be selected based on size, shape, voltage, current and other requirements. Examples of common shapes of cells are pouch cells, cylindrical cells, Swagelok cells and coin cells. The cells may also be connected in a battery to provide the appropriate voltage and/or current for the application.

If a cell is charged too quickly, many undesirable operation conditions can occur; such as: dendrite formation, metallic plating and current hot-spots, each of which can potentially increase the likelihood of a short circuit and damage to the cell.

A common method of quickly charging a cell while avoiding over-charging is to supply a constant current in a first charging phase until a predetermined voltage is reached in the cell and then, in a second charging phase, holding the voltage constant while the current decays to ensure the cell reaches capacity. The first charging phase quickly increases the charge in the cell and the second charging phase is slower.

A C-rate is a measure of the rate of charge or discharge of a cell and is the current divided by the capacity, with units of per hour.

<CIT> proposes a hybrid ionic electronic energy storage device. <CIT> proposes an apparatus and a method for generating and using multi-directional DC and AC electrical currents.

The present invention provides a method of enhancing ion transport in an electrochemical cell according to claim <NUM>.

The changing magnetic field aids ion transport in the electrochemical cell thereby meaning that performance of the battery is enhanced. Optionally, the cell may include a separator between the electrodes. The transport of ions can be improved in the electrolyte and/or in the electrodes and/or in the separator. The changing magnetic field through the cell means that the magnetic flux in the cell varies over time in magnitude and/or direction and/or distribution.

One characteristic of the cell which can be enhanced using the above method is the speed of charging of the cell. Ion transport in cells is often the rate determining process during charging and so aiding the transport of ions speeds up charging of the cell. Another characteristic of the cell which can be enhanced using the above method is the speed of discharging as ion transport is improved in an analogous way during charging. Another characteristic of the cell which can be enhanced using the above method is the capacity of the cell. This may be achieved by performing the method above on the cell during formation of the cell or during operation.

The changing magnetic field is a rotating magnetic field and/or an oscillating magnetic field and/or a pulsing magnetic field.

The changing magnetic field may have a direction with a component perpendicular to the current flow path. The changing magnetic field may have a direction with a component parallel to the current flow path.

Rotation of the magnetic field may be around an axis having a component perpendicular to a direction of the magnetic field. The rotation of the magnetic field may be around an axis having a component parallel to a direction of the magnetic field.

Rotation of the magnetic field may be around an axis having a component perpendicular to a direction of the current flow path. The rotation of the magnetic field may be around an axis having a component parallel to a direction of the current flow path.

The rotating magnetic field is provided by an array of electromagnets which are sequentially activated to effectively rotate the magnetic field.

The electrochemical cell may be a battery. The battery may be a coin cell, a cylindrical cell, a prismatic cell or a pouch cell.

The battery may be a positive ion battery and the current flow path may be the direction of travel of positive ions. The battery may be a lithium-ion battery. Alternatively, the battery may be a negative ion battery and the current flow path may be the direction of travel of negative ions.

The cell may be for powering an electric vehicle, a mobile phone, a laptop computer, a tablet or other portable or stationary device. The cell may be a fuel cell.

The electrochemical cell may be part of an array of two or more cells.

The electrolyte may be a solid, a liquid or a gel. In particular, the electrolyte may be non-aqueous including organic electrolytes.

A magnetic field generator is provided for generating the changing magnetic field. The magnetic field generator is external to the cell.

In some examples, there may be provided a charge accelerator for enhancing performance of an electrochemical cell, the device being configured to carry out a method of enhancing performance of an electrochemical cell described above.

In some examples, there may be provided a method of charging an electrochemical cell comprising the steps of providing a current or voltage to the cell from a power source whilst performing a method of enhancing performance of an electrochemical cell described above. In this disclosure, charging a cell includes moving ions in a cell whether imposed by a current or voltage or by spontaneous movement of the ions.

In some examples, there may be provided a method of discharging an electrochemical cell comprising the steps of extracting a current or voltage from the cell whilst performing a method of enhancing performance of an electrochemical cell described above.

The arrangement of equipment shown in <FIG> can be used to enhance and monitor the performance of a cell <NUM> while charging or discharging. The cell <NUM> is located on top of a rotating magnetic field generator <NUM>. The cell <NUM> is connected to the potentiostat and computer <NUM> via terminals <NUM>. The potentiostat controls the potential across the cell <NUM> and may charge or discharge the cell <NUM>. The computer monitors the current, and/or capacity and/or voltage of the cell <NUM>. The rotating magnetic field generator <NUM> provides a rotating magnetic field through the cell <NUM>.

This arrangement can be used for testing the cell, but when monitoring of the cell <NUM> is not required, the potentiostat, computer <NUM> and terminals <NUM> can be removed and optionally replaced by a power source or drain for charging or discharging the cell.

In the arrangement of <FIG>, the cell <NUM> is located on top of the rotating magnetic field generator <NUM>, but in other embodiments of the invention, the cell <NUM> and rotating magnetic field generator <NUM> may be oriented differently as long as the rotating magnetic field generator <NUM> can produce a magnetic field through the cell <NUM>.

The rotation of the magnetic field may be around an axis substantially parallel to the direction of the magnetic field produced. For example, the direction of the magnetic field produced in the cell <NUM> may be substantially parallel to a direction between the magnetic field generator <NUM> and the cell <NUM> and the rotation of the field may be around an axis parallel to a direction between the magnetic field generator <NUM> and the cell <NUM> as shown in <FIG>.

Alternatively, the rotation of the magnetic field may be around an axis substantially perpendicular to the direction of the magnetic field produced. For example, the direction of the magnetic field produced in the cell <NUM> may be substantially perpendicular to a direction between the magnetic field generator <NUM> and the cell <NUM> and the rotation of the field may be around an axis parallel to a direction between the magnetic field generator <NUM> and the cell <NUM>.

The rotating magnetic field generator <NUM> in the arrangement of <FIG>, may be replaced with a changing magnetic field generator that produces a changing magnetic field that varies in another way. For example, a changing magnetic field generator may be used to produce a magnetic field that rotates and/or oscillates and/or pulses.

The following examples of apparatuses and methods show the effect of changing magnetic fields on the charging of several commercially available batteries. All of the examples show reduced time to charge the cells in the presence of a changing magnetic field. The cells are of various geometries and chemical make ups and are described in more detail below.

In this disclosure, the term "under field conditions" refers to the presence of a changing magnetic field. In the examples explained below, results for charging the cells in the presence of a changing magnetic field are shown along with comparative examples of the cells in the absence of a changing magnetic field. The arrangements used in the examples and in the comparative examples differ only in that the magnetic field provided in the comparative examples is constant in direction and magnitude, whereas the magnetic field provided in the examples is changing.

<FIG> shows an arrangement used to enhance performance of a pouch cell <NUM>. The magnetic field generator <NUM> produces a magnetic field having a direction parallel to the direction shown by the arrow in <FIG>. The magnetic field produced rotates in the direction shown by the arrow in <FIG>. The magnetic field passes through pouch cell <NUM>.

The magnetic field may be offset from the axis of rotation to ensure that the magnetic flux in the cell changes over time.

The magnetic field generator <NUM> is an electromagnet powered by power supply <NUM>. Potentiostat <NUM> is connected to the pouch cell <NUM> and controls the potential over the cell and can be used to charge or discharge the cell.

The pouch cell <NUM> is formed of a first electrode and a second electrode separated from one another by an electrolyte. The electrodes are substantially parallel and extend across a length and width of the cell. The pouch cell <NUM> has contacts for each of the electrodes which may be connected to a potentiostat as shown in <FIG>.

The pouch cell <NUM> is oriented so that the direction of the magnetic field passes through the first electrode of the cell, through the electrolyte and through the second electrode. The direction of the magnetic field is parallel to the direction of a current path between the electrodes. The rotation plane of the magnetic field is parallel to the planes of the electrodes.

<FIG> shows the capacity of pouch cell <NUM> when charged in the presence of a magnetic field produced by the magnetic field generator <NUM> when the field is (i) rotating (shown by the dashed line) and (ii) not rotating (shown by the solid line). The pouch cell <NUM> was charged in two phases. In the first phase, the cell was charged from <NUM>. 4V to <NUM>. 2V at <NUM>. 841A until <NUM>. 2V was reached and then in the second phase, the cell was held at constant voltage while the current decayed and capacity was reached.

The first phase where a constant current is applied to the cell can be seen by the horizontal line portions of the current graph in <FIG>. The second phase where voltage is held constant and current decays while full capacity is reached can be seen where the current changes. The straight horizontal lines to t = <NUM> and <NUM> seconds for no changing field and changing field respectively, represent the constant current portion of the charging and t onwards representing the constant voltage portion of the charging.

A magnetic field was produced by an electromagnet in the magnetic field generator <NUM>. During the cycle shown by the dashed line, the electromagnet was spun at <NUM> rpm. The results show that the time taken to charge the cell was reduced by <NUM>% by the presence of the rotating magnetic field.

<FIG> shows the current and voltage during the charging of the pouch cell <NUM> in the conditions described in relation to <FIG>. Again, the dashed line shows the charge when the magnetic field is rotating and the solid line shows charging when the magnetic field is not rotating (it is constant). The graphs show that, in the presence of a rotating magnetic field, the time taken to reach the voltage of <NUM>. 2V is increased so that the first phase of charging where current is applied is maintained for a longer period.

As the first phase of charging increases the charge held by the cell more quickly than the second phase, this means that charging overall is quicker when the rotating magnetic field is present through the cell.

<FIG> shows the capacity of the pouch cell <NUM> when charged in the presence of a magnetic field produced by magnetic field generator <NUM> when the field is (i) rotating (shown by the dashed line) and (ii) not rotating (shown by the solid line). The pouch cell <NUM> was charged in two phases. In the first phase, the cell was charged from <NUM>. 4V to <NUM>. 2V at <NUM>. 841A until <NUM>. 2V was reached and then in the second phase, the cell was held at constant voltage while the current decayed and capacity was reached.

As can be seen in <FIG>, in both cycles the cells were charged to <NUM>. 2V, but in the cycle where the magnetic field was rotating, the capacity of the cell was increased by <NUM>%. The speed of charge was also increased by the rotation of the magnetic field.

<FIG> shows results of testing a pouch cell <NUM>. The pouch cell <NUM> has a 400mAh capacity and has dimensions of <NUM> by <NUM> by <NUM>. The pouch cell <NUM> is commercially available via the part information: +PL-<NUM>-2C, <NUM>. 7V 400mAh -PO <NUM><NUM>.

The rate of charge of the pouch cell <NUM> is shown in <FIG> for nine charge cycles. Cycles <NUM> to <NUM>, <NUM> and <NUM> were in the presence of a magnetic field rotating at <NUM> rpm and cycle <NUM> was in the presence of the magnetic field rotating at <NUM> rpm. Cycles <NUM> to <NUM> were in the presence of a static magnetic field.

As can be seen in <FIG>, the rate of charging was consistently increased by the rotation of the magnetic field by around <NUM>%.

<FIG> shows the time taken to charge pouch cell <NUM> in eight charge cycles with a rotating field at <NUM> rpm, a rotating field at <NUM> rpm, and a static magnetic field (labelled 'no field' in the figure). As can be seen in <FIG>, the time taken to charge the cell is consistently decreased by around <NUM>% in the presence of a rotating magnetic field.

<FIG> shows results of testing a pouch cell <NUM>. The pouch cell <NUM> has a 200mAh capacity and has dimensions of <NUM> by <NUM> by <NUM>. The pouch cell <NUM> is commercially available via the part information: -PL-<NUM>-2C, <NUM>. 7V 210mAh +PO <NUM>.

The rate of charge of the pouch cell <NUM> is shown in <FIG> for two charge cycles. The first cycle was in the presence of a magnetic field rotating at <NUM> rpm and the second cycle was in the presence of a static magnetic field.

As can be seen in <FIG>, the rate of charging was dramatically increased by the rotation of the magnetic field.

<FIG> shows the time taken to charge pouch cell <NUM> in a charge cycle with a rotating field at <NUM> rpm, and a static magnetic field (labelled 'no field' in the figure). As can be seen in <FIG>, the time taken to charge the cell at 4C is decreased by <NUM>% in the presence of a rotating magnetic field.

<FIG> shows an arrangement used to enhance performance of a Swagelok-type cell <NUM>. The magnetic field generator <NUM> produces a magnetic field having the direction parallel to the direction shown by the arrow in <FIG>. The magnetic field produced rotates in the direction shown by the arrow in <FIG>. The magnetic field passes through Swagelok cell <NUM>.

The magnetic field generator <NUM> is an electromagnet powered by power supply <NUM>. Potentiostat <NUM> is connected to the Swagelok cell <NUM> and controls the potential over the cell and can be used to charge the cell.

The Swagelok cell <NUM> is formed of a first electrode and a second electrode separated from one another by an electrolyte and separator material. The electrodes are substantially parallel and extend across a length and width of the cell. The Swagelok cell <NUM> has contacts for each of the electrodes which may be connected to a potentiostat as shown in <FIG>.

The Swagelok cell <NUM> is oriented so that the direction of the magnetic field passes through the cell, perpendicularly to the direction of a current path between the electrodes. The rotation plane of the magnetic field is perpendicular to the planes of the electrodes.

<FIG> shows results of testing Swagelok cell <NUM>. The Swagelok cell <NUM> has dimensions of <NUM> by <NUM>. The Swagelok cell <NUM> is commercially available as a LMO/Graphite Swagelok cell.

The rate of charge of the Swagelok cell <NUM> is shown in <FIG> for charge cycles at 1C, 2C and 3C, each in the presence of a rotating magnetic field and in the presence of a static magnetic field (labelled as no field in the figure). The rotating magnetic field had a speed of <NUM> rpm.

As can be seen in <FIG>, the rate of charging was consistently increased by the rotation of the magnetic field.

<FIG> shows the time taken to charge Swagelok cell <NUM> in charge cycles at 1C, 2C and 3C, each in the presence of a rotating magnetic field and in the presence of a static magnetic field (labelled as no field in the figure). As can be seen in <FIG>, the time taken to charge the cell <NUM> is consistently decreased in the presence of a rotating magnetic field.

<FIG> shows an arrangement used to enhance performance of a cylindrical cell <NUM>. The magnetic field generator <NUM> produces a magnetic field having the direction parallel to the direction shown by the arrow in <FIG>. The magnetic field produced rotates in the direction shown by the arrow in <FIG>. The magnetic field passes through cylindrical cell <NUM>.

The cylindrical cell <NUM> is formed of a first electrode and a second electrode separated from one another by an electrolyte. The electrodes are rolled into a spiral configuration and extend across a length of the cell. The cylindrical cell <NUM> has contacts for each of the electrodes which may be connected to a potentiostat as shown in <FIG>.

The cylindrical cell <NUM> is oriented in <FIG> so that the direction of the magnetic field passes through the cross-section of the cylindrical shape, perpendicularly to a direction between the flat ends of the cylindrical shape. The rotation plane of the magnetic field is perpendicular to the planes of the end faces of the cylindrical cell.

As discussed further below, in other embodiments, the cylindrical cell may alternatively be oriented so that the direction of the magnetic field passes through the ends of the cylindrical cell.

The magnetic field generator <NUM> is an electromagnet powered by power supply <NUM>. Potentiostat <NUM> is connected to the cylindrical cell <NUM> and controls the potential over the cell and can be used to charge the cell.

<FIG> shows results of testing cylindrical cell <NUM>. The cylindrical cell <NUM> has dimensions of <NUM> by <NUM>. The cylindrical cell <NUM> is commercially available as a cylindrical <NUM> mAh LG <NUM> cell.

The rate of charge of the cylindrical cell <NUM> is shown in <FIG> for six charge cycles. Cycles <NUM> and <NUM> were in the presence of a magnetic field rotating at <NUM> rpm, cycle <NUM> was in the presence of the magnetic field rotating at <NUM> rpm and cycle <NUM> was in the presence of a magnetic field rotating at <NUM> rpm. Cycles <NUM> and <NUM> were in the presence of a static magnetic field. In cycles <NUM> and <NUM>, the cylindrical cell was positioned so at an orientation <NUM> degrees from the position shown in <FIG> so that a flat end of the cell faces the magnetic field generator <NUM>.

As can be seen in <FIG>, the rate of charging was generally higher in the presence of a rotating magnetic field.

<FIG> shows the time taken to charge cylindrical cell <NUM> in the charge cycles of <FIG>. As can be seen in <FIG>, the time taken to charge the cell <NUM> was generally lower in the presence of a rotating magnetic field.

The principle of improved transport of ions resulting in improved charging speed and/or increased capacity within an electrochemical cell exhibited by the examples above may be explained by a reduction in activation energy as explained below for an example of a positive ion cell.

The ion velocity, v, within a liquid electrolyte will increase until overcome by drag forces, FD. The electric field force, FE, which drives the motion of the ion can be described by: <MAT>.

The drag force can be approximated from Stoke's law as: <MAT>.

Equating the electric and drag forces determines the terminal velocity of the ion, thus mobility, ui: <MAT> <MAT>.

The mobility influences the conductivity through the equation: <MAT> ci molar concertation.

In a polymer electrolyte the Ohmic resistance, σ, can be described by: <MAT>.

The Maxwell-Faraday equation predicts that a time varying magnetic field, δB/δt, will always accompany a spatially-varying, non-conservative electric field, E(r, t), described by: <MAT>.

And the electric field, E, at a given point is defined as the vector electric field force, FE, for a given charge, q: <MAT>.

Therefore, the magnetic field influences the activation energy as: <MAT>.

Finally conductivity is related to cell resistivity, ρi, thus Ohmic potential losses, ηohmic, via: <MAT>.

So, in the presence of a magnetic field, a polymer membrane conducting positive ions will experience a reduced Ohmic potential losses through a net reduction in the activation energy related to the ionic mobility associated with proton transport.

The magnetic field can be produced using a permanent magnet or an electromagnet.

Using a permanent magnet, in the presence of a magnetic field, a polymer membrane conducting positive ions will experience a reduced Ohmic potential losses through a net reduction in the activation energy <MAT>.

Using an electromagnet, in the presence of a magnetic field, a polymer membrane conducting positive ions will experience a reduced Ohmic potential losses through a net reduction in the activation energy: <MAT>.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention as defined in the appended claims.

Claim 1:
A method of enhancing ion transport in an electrochemical cell having a first electrode and a second electrode and electrolyte between the first and second electrodes, the first and second electrodes defining a current flow path, the method comprising, in addition to the electrochemical cell, providing a magnetic field generator for providing a changing magnetic field through the electrochemical cell during formation of the electrochemical cell, wherein the changing magnetic field is a rotating magnetic field and/or an oscillating magnetic field and/or a pulsing magnetic field.