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1. WO2020110074 - MULTICAVITY ELECTRIC POWER ACCUMULATOR

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[ EN ]

MULTICAVITY ELECTRIC POWER ACCUMULATOR

The present patent application for an industrial invention patent relates to an electric power accumulator.

More specifically, the present invention relates to an electrochemical accumulator comprising a plastic case containing a plurality of multicavity regions operating as lead electrodes, alternating with regions operating as separator elements; said system of regions and cavities makes it possible to achieve all characteristics necessary for a continuous operation of the accumulator in one body.

This type of accumulators can be configured for operating in adverse climatic conditions or for having a useful life of the product definitely exceeding ten years, for handling big electric loads as well as for providing a big availability of electric power.

Numerous ways are known in the present state of the art for implementing secondary (or rechargeable) cells wherein the anode, the cathode, and the separator are realized in such a way as to present, internally thereto, holes or connection ducts in which an electrolyte can flow.

An example, amongst many others, is described in WO2017/055984, which discloses an accumulator wherein the anode, the cathode, and the separator are formed on the inner surfaces of a support substrate in which a plurality of cavities is present.

Another example is illustrated in US 8237538 which discloses a battery wherein a conductive material is deposited on a monolithic and porous structure featuring a porosity in a range from 74 to 99%.

Another example is described in US 2008/0176139 which discloses a battery equipped with fibrous electrodes.

The patent document US 3532557 describes a lead battery comprising a polypropylene

plastic case subdivided into a plurality of cell compartments and a plurality of partition walls integrally connected to said case; every compartment is provided with a plurality of electrode and separator regions, forming cell units. Every partition wall is provided with a hole through which the electrolyte can flow between the cell compartments. The battery also comprises exhaust holes for allowing gases to discharge to outside the case.

The patent document US 4735873 describes a lead battery containing a plastic case containing a plurality of hollow cells, each of which comprises a plurality of walls operating as cell separators, provided with a plurality of through holes which allow the electrolyte to freely pass from one cell to the others. The hollow cells are alternatively filled with balls of negative and positive active materials in a strict contact with the surface of the walls of the hollow cell separator.

These examples and many others known in the present state of the art are still affected by a number of technical drawbacks, including the absence of measures aiming at recovering and continuing to use that part of the electrodes (active material) which, in use, tends to precipitate and to accumulate on the case bottom.

Also, in the embodiments known in the present state of the art no measures are known that allow to integrate the separators internally to the structure of an accumulator in a geometrically efficient and structurally effective manner and to optimize the ratio of its volume to the surface of the electrodes.

Also, no technical measures are known in the present state of the art that allow to efficiently cool or heat an accumulator during its operation, because no temperature stabilization systems are known in the present state of the art that are capable of operating in a capillary manner inside the accumulator body and in particular in a vascular manner inside the electrodes, the separators, or the case.

An object of the invention according to the present patent application is therefore to provide an electric power accumulator that overcomes the technical drawbacks of the embodiments known in the present state of the art, and in particular an electric power accumulator that: allows to optimize the ratio of the accumulator volume to the electrode surfaces, thus allowing to provide accumulators featuring a greater capacity, dimensions being equal; allows to integrate the separators and the electrodes in one structure, so that the separators can operate as separation elements between the individual electrodes as well as support elements contributing to support the weight of the accumulator; by virtue of its own inner geometry, allows to recover and to continue to use that part of the electrodes (active material) which, in use, tends to precipitate and accumulate on the case bottom; allows an effective cooling/heating of the accumulator thus obviating the well-known problem of stratification.

The invention achieves the predetermined objects, in that it is an electric power accumulator provided with an outer insulating case configured for accommodating an electrolyte internally to which there is contained, in addition to said electrolyte, a block comprising a structure formed of a plurality of regions provided with cavities communicating with each other to form an alveolar structure; every cavity comprises a wall wherein there is derived at least one hole configured in such a way as to put the volume internal to said wall in communication with the volume external thereto.

Said inner block is formed of an alternation of conductive material regions and insulating material regions, integral with and alternating with each other so as to form electrodes and separators, whereas the region-based geometric structure, formed of a plurality of cavities communicating with each other, is an uninterrupted in correspondence with the surfaces separating the conductive material regions from the insulating material regions. These advantages and others will be apparent from the detailed description of the

invention that is presented below with reference to the attached figures from 1 to 4, which illustrate respectively:

figure 1 - an axonometric outside view of the accumulator according to the invention; figure 2 - a horizontal cross-sectional view of the accumulator of figure 1 showing the intercommunicating cavities;

figure 3 - a horizontal cross-sectional view of the accumulator of the previous figures showing the communication ducts between the inside of the accumulator, in which an electrolyte flows, and the outside of the accumulator;

figure 4 - a horizontal cross-sectional view of the accumulator of figure 1 , showing the ducts that defines a volume, separated from that internally to which an electrolyte can flow, in which a second liquid can flow.

As shown in the figures, an accumulator 1 according to the invention comprises an inner block 10 comprising a plurality of positive electrodes 11 , negative electrodes 12, and separators 13 contained inside an outer case 20.

As shown in figure 2, the inner block 10 comprises a geometrical structure formed of a plurality of cavities 14 communicating with each other.

The block 10 is formed of an alternation of a conductive material, which forms the electrodes 11 , 12, and an insulating material, which forms the separators 13 of the accumulator. For explanatory non-limitative purposes only, lead and polypropylene can be used as a conductive material and an insulating material respectively. Said active and insulating materials alternate with each other to form electrodes and separators featuring appropriate thicknesses. The regions of the block made from an active material and the regions made from an insulating material are integral with each other along a plurality of separation surfaces which, in a preferred but non-limitative embodiment as shown in the figure, might be flat separation surfaces. According to

other embodiments, said separation surfaces between electrodes and separators might assume different shapes (for instance spiral, cylindrical, flat with protrusions) in order to optimize the operation of the accumulator as a function of the shape of the outer case. Also, without prejudice to the object of the invention, the block 10 might be implemented according to additive manufacturing technologies, such as, for example, multi-material 3D molding, in order for the layers to be integral with each other.

It is worth pointing out right away that one of the outstanding features of the accumulator according to the invention is in that the surface that separates the active material and the insulating material not necessarily shall be in correspondence with the boundary between one cavity 14 and the adjacent one, but it might rather be in an arbitrary position with respect to the geometrical structure of the block 10.

As already mentioned, geometrically wise the block 10 comprises a plurality of cavities 14 communicating with each other to form an alveolar structure. Every cavity 14 includes a wall 141 where at least one hole 142 is derived, so as to put the volume internal to said wall 141 in communication with the external volume. Preferably every cavity comprises a plurality of holes on its own wall so that, whenever the block 10 is dipped into an electrolyte, this one can flow internally to the block 10 and also pass through inside the cells. According to a first embodiment, every cell comprises a plurality of pairs of holes arranged on the wall 141 of the cell 14 so as to be opposed to each other.

Conveniently every cell 14 and every space between two adjacent cells also includes a hole on its top, so as to enable air to flow upwards while an electrolyte is being filled, thus preventing air bubbles from getting trapped in the structure.

Geometrically wise, according to a first embodiment illustrated in figure 3, every cell 14 can assume a spherical shape, and the cells 14 can be arranged in layers

superimposed to each other, their centers being arranged vertically. According to another embodiment, the spherical cells might be arranged between each other in layers superimposed to and staggered from each other, the centers of the six cells about each of the neighbor cells forming a hexagon.

Other cell shapes might be used without leaving the scope of the invention, such as, for explanatory non-limitative purposes only, a tetrahedron, a cube, an octahedron, a dodecahedron, or an icosahedron.

The block 10 is thus inserted inside an outer case 20. Conveniently can the outer case be made from the same material as the separators and be integral therewith, so that the weight of the block 10 discharges onto the outer case 20 via the separators 13, and the electrodes do not support other loads but their own weight. For this purpose, the case can be manufactured jointly with the separators and the electrodes, by way of an additive manufacturing.

The case might also comprise, internally thereto, further different systems fostering the operation of the accumulator, such as a temperature variation system and electrical connections between the electrodes. The shape of the case might include holes, recesses, protrusions, or depressions which might be taken advantage of in assembling parts external to the accumulator, as well as inspection holes provided with transparent lids or removable lids.

Because of the geometrical composition of the electrodes and of the accumulator which comprises a plurality of hollow cells communicating with each other, an electrolyte can flow in the entire inner volume of the accumulator, this way operating as a thermal vector. Therefore, in a preferred embodiment, the accumulator according to the invention comprises pumping means and their respective communication ducts 40 between the inside and the outside of the electrolyte, configured in such a way as to make the electrolyte flow within the accumulator and make it possible to extract it, to send it to heat dissipation means, and then to re-insert it inside the case.

The dissipation means are either passive or active dissipation means of a type known in the present state of the art without leaving the object of the invention.

In accordance with a further embodiment, the accumulator according to the invention possibly comprises a set of ducts 50 inside the case, which define a volume, separated from that internally to which the electrolyte can flow, wherein a second liquid can flow to allow for a change of temperature of the component parts of the accumulator without having them mixed with the electrolyte.

Having described the geometry of the accumulator, it is now possible to describe the operation of the thus obtained accumulator.

Whenever an electrolyte is put inside the case 20 containing the block 10, it completely fills the volume left free by the material that forms the block 10, thus filling all cells. At this point, the accumulator operates according to the provisions of the state of the art, but it features the following advantages because of the way how it is implemented.

Because of their geometry, the electrodes are permeable to electrolyte flow and simultaneously they make it possible to recover the precipitate of the active material that forms during the operation, internally to said hollow cells 14. As a matter of fact, the precipitate will tend to settle on the lower surfaces of every cell, and consequently it will be available again for use. This allows to obviate the problem of region pulverization caused by the accumulator being overloaded and the consequent performance falling off. Also, this allows to prevent electrical bridges from being created by a random accumulation of the precipitate material.

Also, the just described geometrical consistency, which allows to optimize the contact surface between electrodes and electrolyte, makes it possible to obtain a greater

electrical density per unit volume as compared to the embodiments known in the

present state of the art.