DE102018200870A1 - Electrochemical energy storage, method for its maintenance and vehicle - Google Patents

Abstract

The present invention relates to an electrochemical energy store, in particular a lithium-ion cell, a method for the maintenance of such an electrochemical energy store, and a vehicle having such an electrochemical energy store. The electrochemical energy store has a housing with a first valve device which is designed to reversibly produce a gas-conducting connection between an inner space of the housing and an outer area of the housing and to allow a gas volume to escape from the housing via the gas-conducting connection when the first valve device the interior is pressurized with a gas pressure. A second valve device of the housing is configured to reversibly establish a liquid-conducting connection between the outer region of the housing and the interior of the housing and to allow a volume of liquid to enter the housing via the liquid-conducting connection when the second valve device is subjected to a fluid pressure from the outer region ,

Description

The present invention relates to an electrochemical energy store, in particular a lithium-ion cell, a method for the maintenance of such an electrochemical energy store, and a vehicle having such an electrochemical energy store.

Energy storage cells, such as lithium-ion cell, as they are used as energy storage, especially in the field of electromobility, contain components that are involved in the operation of the energy storage cells to chemical reactions for storage or delivery of electrical energy. Within the scope of these reactions, it is possible for individual components of the cells, in particular an electrolyte, to degrade and, if appropriate, unwanted chemical by-products or decomposition products, in particular gases, to form. With increasing age or increasing operating life of the cells, this usually leads to swelling or swelling (referred to in the English-technical language as "swelling") and / or drying of the same, whereby the mechanical stability of the cells is impaired or the performance and capacity as well as the reliability of the cells decreases.

It is known to prevent puffing mechanically, such as by one or more cells are held by tension bands to size. In addition, so-called burst valves (also referred to as burst valves) are usually provided, which trigger before reaching a critical overpressure and thus prevent physical destruction of the cell, in particular the escape of chemically aggressive components.

It is an object of the present invention to provide an electrochemical energy store having a prolonged life.

This object is achieved by an electrochemical energy store according to claim 1 and a method for its maintenance according to claim 9.

A first aspect of the invention relates to an electrochemical energy store, in particular a lithium-ion cell, with a housing, wherein the housing has a first valve device and a second valve device. The first valve device is designed to reversibly produce a gas-conducting connection between an inner space of the housing and an outer area of the housing and to allow a gas volume to escape from the housing via the gas-conducting connection when the first valve device is acted upon from the inner space with a gas pressure. The second valve device is configured to reversibly establish a liquid-conducting connection between the outer region of the housing and the interior of the housing and to allow a liquid volume to enter the housing via the liquid-conducting connection when the second valve device is subjected to a fluid pressure from the outer region.

The resulting in decomposition reactions of components of the electrochemical energy storage gas can thus escape during or shortly after the reaction takes place from the housing. This allows the avoidance of a gradual pressure build-up inside the housing. Accordingly, the inflation of the housing, such as a so-called prismatic hardcase housing or a flexible, so-called. Pouch housing can be reliably avoided or at least significantly reduced. Thus, the life can be extended and the reliability can be increased.

In particular, gaseous reaction products whose accumulation is unavoidable in chemical reactions on a positive electrode, a negative electrode and / or an electrolyte of the energy store repeatedly occur via the gas-conducting compound from the interior of the housing in the outer region of the housing. Accordingly, the chemical components of the energy storage, in particular its electrolyte, must not be designed to prevent gas formation. Similarly, the housing design does not have to be designed to withstand high gas pressure and consequent clamping force. Accordingly, the chemical components and / or the housing design can be chosen flexibly.

The second valve device also makes it possible to compensate for the chemical decomposition of a liquid electrolyte in order to at least substantially maintain the capacity and the capacity of the energy store as the energy storage device ages. In particular, an amount of electrolyte can be repeatedly supplied to the energy store by the second valve device, which corresponds to the amount of gas or at least a part thereof which has already leaked out of the housing via the first valve device. Thus, an efficient operation of the energy storage is possible even after many charging and discharging cycles.

The combination of the first valve device and the second valve device is particularly advantageous because it allows a (gas) volume discharged from the housing via the gas-conducting connection to be replaced by a (liquid) volume introduced into the housing via the liquid-conducting connection. This allows a permanent chemically and mechanically stable as well as powerful and high-capacity energy storage.

Overall, the invention allows the operation of an electrochemical energy storage with extended life.

In a preferred embodiment, the first valve device, the second valve device, or both are designed as a check valve. Thus, the gas pressure and / or the level of the housing with respect to an electrolyte can be repeatedly regulated, while at the same time the penetration of moisture from the outer region of the housing can be avoided in the interior of the housing.

In this case, the check valve preferably has a valve seat, in which a closure element, such as a ball, a cone, a flap or a membrane, in particular by a Verspannelement is pressed, wherein the Verspannelement acts against the gas pressure or the liquid pressure. The bracing element may be formed as a spring with a predetermined spring constant, so that an automatic opening of the check valve is possible. The first and / or second valve device can be carried out reliably and space-saving.

Alternatively, the bracing element can be designed to be actively controllable, for example as a controllable actuator. As a result, the first valve device can be actively opened or closed based on a monitoring of the gas pressure and / or the second valve device as a function of the time of provision of the fluid.

In a further preferred embodiment, the first valve device is set up to establish the gas-conducting connection when the gas pressure reaches or exceeds a predetermined first pressure threshold value. The first predetermined pressure threshold value is preferably below a critical gas pressure, for example below 7 to 10 bar, at which physical destruction or at least damage to the energy store or its housing may occur. In particular, the first predetermined pressure threshold is less than 50%, preferably less than 35%, more preferably less than 25% of the critical gas pressure. This allows a timely, in particular substantially continuous, degassing of the energy store.

Alternatively or additionally, the second valve device is designed to establish the liquid-conducting connection when the fluid pressure reaches or exceeds a predetermined second pressure threshold value. Preferably, the predetermined second pressure threshold value corresponds to a pressure that can be generated by a pump device for filling the housing with an electrolyte. This allows the reliable refilling of electrolyte, without inadvertently other liquids or gases can pass from the outside into the interior of the housing.

Preferably, the predetermined second pressure threshold value is a dynamic pressure threshold, which is or is determined as a function of an internal pressure of the housing. The second valve device may in particular be arranged to establish the liquid-conducting connection when the liquid pressure is higher by a predetermined pressure difference than the internal pressure in the interior of the housing. As a result, the electrolyte can also be reliably replenished independently of the prevailing pressure inside the housing.
In a further preferred embodiment, the predetermined first pressure threshold value corresponds to a gas pressure at which a deformation of the housing occurs due to the gas pressure. The predetermined first pressure threshold value may correspond approximately to a gas pressure at which a pouch housing develops substantial bulges, in particular in which the volume enclosed by the pouch housing increases by more than 1%, preferably more than 2.5%, preferably more than 5% , Thus, a permanent destruction or at least a permanent damage to the housing can be avoided.

In a further preferred embodiment, the predetermined first pressure threshold is between 0.5 and 4 bar, preferably between 1 and 2 bar, in particular between 1.25 and 1.5 bar, above one or the ambient pressure in the outer region of the housing. As a result, the first valve device can be repeatedly actuated without a critical gas pressure in the housing, for example between 7 and 10 bar, which would lead to the reversible destruction or damage of the housing, being reached or exceeded.

In a further preferred embodiment, the housing further comprises a third valve device, which is configured to irreversibly produce an additional gas-conducting connection between the interior of the housing and the outer region of the housing when the first valve device acts on the gas pressure from inside and the gas pressure in the interior decreases with a gradient that is less than or equal to a predetermined pressure gradient. In other words, the third valve device is set up to reduce the gas pressure in the interior of the housing, if an already prevailing gas pressure, in particular above the predefined first pressure threshold value, by the first valve means not reduced or a further increase in the gas pressure can not be limited by the first valve means. The predetermined pressure gradient preferably corresponds to a rate at which the first valve device can conduct gas from the housing interior to the outer region of the housing, and depends, for example, on a cross section of a valve opening, in particular a valve seat, of the first valve device. The operation of the energy storage can be made even safer.

Preferably, the third valve device is designed as a burst valve, which can produce the additional gas-conducting connection between the interior and the outer region of the housing once. The burst valve may be, for example, a membrane which is preferably loadable up to a critical gas pressure, for example between 7 and 10 bar, above which a permanent destruction or at least damage to the housing may occur. This allows the third valve device reliably and automatically trigger.

In a further preferred embodiment, the first and / or the second and / or the third valve device is arranged spatially between a positive electrical connection and a negative electrical connection on an outer side of the housing. As a result, the first and / or the second and / or the third valve device remain easily accessible, even if a plurality of energy stores, for example a plurality of energy storage cells, are connected or stacked in series to form a module.

A second aspect of the invention relates to a vehicle, in particular a motor vehicle, with an electrochemical energy store according to the first aspect of the invention.

A third aspect of the invention relates to a method of maintaining an electrochemical energy store according to the first aspect of the invention, comprising the steps of: (i) sensory detection of a level of a liquid in the interior of the housing; (ii) applying the fluid pressure to the second valve device from the exterior of the housing when the detected level reaches or falls below a predetermined level threshold. For example, it can be checked in a workshop, how large the remaining volume of an electrolyte in the housing. If it is determined that part of the electrolyte has already been decomposed by the operation of the energy store, i. the liquid volume has dropped below a liquid volume threshold required for optimum operation of the energy store, the electrolyte can be refilled via the second valve device or the housing can be replenished. As a result, an original life of the energy store, which is determined by the amount of electrolyte filled in the housing during the production of the energy store, can be extended.

In particular, the level of the liquid can be determined by weighing the energy store. Thus, the second valve device can be acted upon from the outside of the housing with the fluid pressure when the weight of the energy storage reaches or falls below a predetermined weight threshold. This allows a simplification of the maintenance process.

The features and advantages described in relation to the first aspect of the invention and its advantageous embodiment apply, at least where technically feasible, for the second and third aspects of the invention and its advantageous embodiment and vice versa.

• 1 ein Ausführungsbeispiel eines erfindungsgemäßen elektrochemischen Energiespeichers; und
• 2 ein weiteres Ausführungsbeispiel eines Energiespeichers mit zu einem Modul gestapelten Energiespeicherzellen.

Further features, advantages and possible applications of the invention will become apparent from the following description in conjunction with the figures, in which the same reference numerals for the same or corresponding elements of the invention are used throughout. At least partially schematically show:

• 1 an embodiment of an inventive electrochemical energy storage device; and
• 2 a further embodiment of an energy storage with stacked to a module energy storage cells.

1 shows an embodiment of an electrochemical energy storage device according to the invention 1 with a housing 2 which is an interior area 10 from an outdoor area 20 of the housing 2 separates.

The energy storage is in the example shown as an energy storage cell, such as lithium-ion cell, and the housing 2 as a prismatic hardcase housing with solid housing walls 2a educated. Due to the substantially cuboid shape, the housing 2 several energy storage cells easily to an energy storage module (see 2 ) are stacked.

The housing walls 2a which the interior area 10 delimiting, enclose an electrode assembly, in particular consisting of a negative electrode 11 , a positive electrode 12 and a liquid electrolyte 13 , Unlike in the example shown, the interior 10 , in particular at the first start of the energy storage 1 . completely filled by the electrode assembly, in particular with the electrolyte 13 be filled.

The while operating the energy storage 1 As a rule, occurring chemical reactions lead to the degeneration of the electrode arrangements. In particular, with increasing age of the energy store 1 an increasing part of the electrolyte 13 gaseous. Due to the increased space requirement of the gas thus increases the gas pressure in the interior 10 ,

To an uncontrolled increase in gas pressure, ultimately destroying or at least damaging the energy storage 1 would lead to avoid is a first valve device 3 intended. The first valve device is set up, the interior 10 with the outside area 20 connect reversibly gas-conducting and thereby lowering the gas pressure in the interior 10 allow when the gas pressure on the first valve device 3 becomes sufficiently large, in particular reaches or exceeds a predetermined first pressure threshold.

The first valve device 3 is advantageously designed as a check valve, in the example shown, a bracing 3a with the predetermined first threshold pressure on a closure element 3b acts and thereby on a valve seat 3c suppressed. This closes the first valve device 3 gas-tight. Increases the gas pressure in the interior 10 however, above the predetermined first threshold pressure, the closure element becomes 3b by the gas pressure from the valve seat 3c lifted, leaving the gas from the interior 10 over the first valve device 3 in the outdoor area 20 can escape. The gas-conducting connection between the interior 10 and outdoor area 20 can be prepared in this way essentially as often without the gas and / or liquid, such as moisture, from the outside 20 over the first valve device 3 in the interior 10 can get.

The in continuous operation of the energy storage 1 occurring degeneration of the electrolyte 3 also has a drop in the electrolyte level 13a result. This reduces the capacity and performance of the energy storage 1 ,

To counteract this, the housing points 2 a second valve device 4 on, for establishing a liquid-conducting connection between the outside area 20 and the interior 10 is set when the second valve device 4 from the outside area 20 out with a fluid pressure, which in particular is greater than a predetermined second pressure threshold, is applied.

Analogous to the first valve device 3 is the second valve device 4 preferably as a check valve with a clamping element 4a , a closure element 4b and a valve seat 4c formed, wherein the clamping element 4a the closure element 4b , preferably substantially at the second predetermined pressure threshold, on the valve seat 4c suppressed.

About the second valve device 4 can thus electrolyte 13 in the interior 10 be filled without gas and / or electrolyte 13 from the interior 10 via the second valve device 4 in the outdoor area 20 can escape. For this purpose, for example, a pumping device which is set up to generate a pressure which corresponds to or exceeds the predetermined second pressure threshold value, from the outside to the second valve device 4 be connected. The energy storage 1 with the electrolyte refilled in this way 13 Therefore, it can be operated without sacrificing capacity and performance over a long period of time.

Preferably, the refilling with the electrolyte 13 executed when the level 13a of the electrolyte 13 has fallen to or below a predetermined level threshold. This can be checked, for example, during maintenance, for example in a workshop. Alternatively or additionally, the energy store 1 , in particular the housing 2 , A sensor device which is set up the level 13a of the electrolyte 3 in the interior 10 of the housing 2 , preferably substantially continuously, to be detected or measured. On the basis of this, for example by means of a control device connected to the pump device, the refilling of the missing electrolyte 13 be performed by the second valve device 4 is subjected to a fluid pressure which is above the predetermined second pressure threshold.

It may be provided, the pressure in the interior 10 of the housing 2 by deliberate discharge of gas, in particular via the first valve device 3 to reduce, so that by means of the pumping device the electrolyte 13 via the second valve device 4 in the case 2 can be filled. For this purpose, the first valve device 3 preferably arranged, the gas-conducting connection with appropriate actuation from outside the housing 2 produce, especially if the pressure in the interior 10 of the housing 2 is still smaller than the predetermined first pressure threshold.

To the safety of the energy storage 1 To further increase, the housing has 2 also a third valve device 5 on which is set up another gas-conducting connection between the interior 10 and the outside area 20 make irreversible when the of the first valve device 3 illustrated gas-conducting connection is insufficient to the gas pressure in the interior 10 to lower or at least keep constant. In other words, the production of the further gas-conducting connection depends on the course of the gas pressure in the interior 10 after establishing the gas-conducting connection through the first valve device 3 from. If the pressure curve lies above a predetermined pressure gradient, ie if the gas pressure drops more than predetermined by the pressure gradient, there is no need for further regulation of the gas pressure. On the other hand, if the pressure curve lies above the predetermined pressure gradient, ie if the gas pressure drops less than predetermined by the pressure gradient, the gas is generated in the interior 10 possibly no longer controllable, leaving the third valve device 5 triggers and once the further gas-conducting compound produces.

The predetermined pressure gradient can be in particular zero, so that the third valve device 5 the further gas-conducting connection only produces, if the gas pressure despite the opened first valve means 3 continues to increase, ie in particular when the gas pressure is above the predetermined first pressure threshold.

The third valve device 5 is preferably designed as a so-called. Burst valve and in particular adapted to trigger when the gas pressure in the interior 10 reaches or exceeds a critical gas pressure, for example between 7 and 10 bar. The third valve device 5 can be designed as a membrane that can not withstand a pressure above the critical gas pressure.

2 shows a further embodiment of an energy storage 1 with multiple energy storage cells stacked into a module, as associated with 1 have been described. For reasons of clarity, the same elements are provided therein only once with reference times.

In this case, each of the energy storage cells has a housing 2 with a first valve device 3 , a second valve device 4 and a third valve device 5 on. The first valve device 3 is adapted to a gas-conducting connection between an interior of the respective housing 2 and an outdoor area 20 the housing 2 when the first valve device 3 from the interior of a gas pressure is applied, which is in particular above a predetermined first pressure threshold. The second valve device 4 is designed to provide a fluid-conducting connection between the outside area 20 and the interior of the respective housing 2 when the second valve device 3 from the outside area 20 out with a liquid pressure is applied, which is in particular above a predetermined second pressure threshold. The third valve device 5 is adapted to a further gas-conducting connection between the interior of the respective housing 2 and the outside area 20 when the gas pressure in the interior decreases with a gradient equal to or less than a predetermined pressure gradient.

The first, second and third valve means 2 . 3 . 4 are each spatially between a negative electrical connection 11 a and a positive electrical connection 12a the energy storage cells arranged. As a result, the energy storage cells can both be electrically contacted on the same side and connected to a line system (not shown) via which the first valve devices 3 leaked gases dissipated or the second valve devices 4 be subjected to a fluid pressure, for example by connection to a corresponding pumping device. This minimizes design problems when installing such a module in a vehicle.

While at least one exemplary embodiment has been described above, it should be understood that a large number of variations exist. It should also be understood that the described exemplary embodiments are nonlimiting examples only and are not intended to thereby limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide those skilled in the art with guidance for implementing at least one example embodiment, it being understood that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the scope of the appended claims deviated from, and its legal equivalents.

LIST OF REFERENCE NUMBERS

1

electrochemical energy storage

2

casing

3

first valve device

4

second valve device

3a, 4a

bracing

3b, 4b

closure element

3c, 4c

valve seat

5

third valve device

10

interior

11

negative electrode

11 a

negative electrical connection

12

positive electrode

12a

positive electrical connection

13

electrolyte

13a

level

20

outdoors

Claims (9)

Electrochemical energy store (1), in particular lithium-ion cell, with a housing (2), wherein the housing (2) comprises: a first valve device (3) which is arranged to reversibly produce a gas-conducting connection between an interior space (10) of the housing (2) and an exterior area (20) of the housing (2) and a gas volume from the housing (2) via the gas-conducting Let escape connection when the first valve means (3) from the interior (10) out with a gas pressure is applied; and a second valve means (4) adapted to reversibly establish a liquid-conducting connection between the outer region (20) of the housing (2) and the inner space (10) of the housing (2) and a liquid volume in the housing (2) via the liquid-conducting Connection to enter, when the second valve device (4) from the outer region (20) out with a liquid pressure is applied. Electrochemical energy storage (1) after Claim 1 wherein the first valve means (3), the second valve means (4), or both are formed as a check valve. Electrochemical energy storage (1) after Claim 1 or 2 wherein the first valve means (3) is arranged to establish the gas-conducting connection when the gas pressure reaches or exceeds a predetermined first pressure threshold and / or the second valve means (4) is adapted to establish the liquid-conducting connection when the fluid pressure exceeds a predetermined second pressure threshold reached or over riding. Electrochemical energy storage (1) after Claim 3 wherein the predetermined first pressure threshold corresponds to a gas pressure at which deformation of the housing (2) by the gas pressure occurs. Electrochemical energy storage (1) after Claim 3 or 4 , wherein the predetermined first pressure threshold value between 0.5 and 4 bar, preferably between 1 and 2 bar, in particular between 1.25 and 1.5 bar above one or the ambient pressure in the outer region (20) of the housing (2). Electrochemical energy store (1) according to one of the preceding claims, wherein the housing (2) further comprises a third valve means (5) which is arranged, in an irreversible manner an additional gas-conducting connection between the interior (10) of the housing (2) and the outer region (20) of the housing (2), when the first valve means (1) from the interior of the gas pressure is applied and the gas pressure in the interior (10) decreases with a gradient which is less than or equal to a predetermined pressure gradient. Electrochemical energy store (1) according to one of the preceding claims, wherein the first and / or the second and / or the third valve means (3, 4, 5) spatially between a positive electrical connection (11a) and a negative electrical connection (12a) an outer side of the housing (2) is arranged. Vehicle, in particular motor vehicle, with an electrochemical energy store (1) according to one of the preceding claims. Method for maintaining an electrochemical energy store (1) according to one of Claims 1 to 7 sensor, comprising: sensory detection of a level (13a) of a liquid in the interior (10) of the housing (2); Acting on the second valve device (4) from the outer region (20) of the housing (2) out with the fluid pressure when the detected level (13a) reaches or falls below a predetermined level threshold.

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