KR20230109901A - Dry discharge method to completely remove electrolyte from secondary battery - Google Patents

Abstract

The present invention proposes a dry discharge method for completely removing an electrolyte of a secondary battery which can completely remove the electrolyte inside the secondary battery at low cost. According to the present invention, a secondary battery is disabled through a two-stage dry discharge, and then is aged for a predetermined period of time in a differential reverse voltage state. Then, during the aging time, remaining lithium coated on a separator of the secondary battery is absorbed into a cathode of the secondary battery and an electrolyte is removed, and all ionized lithium ions are oxidized and become incombustible. Therefore, as there is no need for a disposal facility to dispose of the electrolyte, costs are reduced and the electrolyte can be removed in an environmentally friendly manner.

Description

Dry discharge method to completely remove electrolyte from secondary battery}

The present invention relates to a dry discharge method for removing an electrolyte solution present therein for safe disassembly of a used secondary battery and making it nonflammable.

Secondary batteries, which are easy to apply according to product groups and have electrical characteristics such as high energy density, are commonly applied to electric vehicles (EVs) or hybrid vehicles (HEVs) driven by electric driving sources as well as portable devices. These secondary batteries are currently attracting attention as a new energy source for improving eco-friendliness and energy efficiency in that they do not generate any by-products due to the use of energy, along with the primary advantage of reducing the use of fossil fuels.

While the demand for secondary batteries continues to increase, there is still a lack of research on waste battery disposal methods. That is, management of batteries that are discarded or reprocessed after use is not being conducted.

Secondary batteries such as lithium-ion batteries are vulnerable to heat and easily ignited, and contain organic solvents and metal oxides, making it difficult to extinguish fires with fire extinguishers or water. In addition, it is currently difficult to secure safety in case a battery cell is split by an external impact. In this case, an explosion accident may also occur in smartphones, substations, and ESSs of power plants using secondary batteries.

Therefore, in order to discard or reuse the secondary battery, it is necessary to repair and inspect the battery pack or battery cell, and accordingly, it is necessary to discharge the remaining battery capacity of the secondary battery to an appropriate level. The battery discharge of the secondary battery can be divided into a safe discharge that discharges up to 3.2V to 3.5V per cell for reuse, and a complete discharge that disables up to 0V per cell for recycling. This is because there is a risk of fire and explosion when the remaining battery level of the secondary battery is present beyond an appropriate level. In addition, in some cases, they are transported for disposal or reprocessing, and there is a risk of explosion if the residual voltage in the battery exceeds a certain level. As a safety requirement for transportation, the state of charge (SOC) of the battery should be less than 20%, but for reasons such as working hours, it is not uncommon for the battery to be transported in a state of more than 30%.

Conventionally, as a method of discharging the remaining amount of a battery, there is a method using an electronic load, a method using a salt water discharge method, and the like. However, the above method has problems such as inability to completely disable it because a minimum voltage of a predetermined level or higher remains even after discharging, or to cause environmental pollution.

Accordingly, on October 25, 2021, the present applicant has applied for the 'dry discharge method and device (10-2021-0142633) of a secondary battery for safe transportation, storage, and disassembly' technology. The prior art is a method for efficiently discharging a secondary battery until it reaches a desired energy level (SOC 0% or OV, which is a physically disabled state).

However, the resistance dry discharge of the prior art can discharge the secondary battery in a disabled state, but cannot completely remove the electrolyte therein. Since the electrolyte is classified as a hazardous material, the electrolyte is still removed in a separate disposal facility when the secondary battery is disassembled. Otherwise, when the secondary battery is disassembled, it is exposed to the outside as it is, resulting in a problem facing a dangerous situation.

Korean Patent Application 10-2021-0142633

An object of the present invention has been made to solve the above problems, and to provide a dry discharge method for nonflammability through the electrolyte and chemical stabilization of a secondary battery to completely remove the electrolyte for safe decomposition of a used secondary battery.

In order to achieve the above object, a dry discharge method of a secondary battery according to an embodiment of the present invention includes a first discharge step in which a discharge device of a secondary battery discharges first residual power remaining in the secondary battery after use to a predetermined power by first dry discharge; a second discharge step of completely discharging the second residual power remaining after the first discharge until a desired energy level is reached through a second dry discharge; and removing the electrolyte of the secondary battery by aging the secondary battery that has been discharged for a predetermined time using a differential reverse voltage method.

The aging time is 23 to 25 hours (h).

During the aging time, residual lithium coated on the separator of the secondary battery is absorbed into the positive electrode of the secondary battery, and the electrolyte is completely removed.

The first dry discharge and the second dry discharge are discharge methods in which a current is refluxed to an internal circuit, and the energy level is characterized in that the state of charge (SOC) is 0% or OV, which is a physically disabled state.

The first dry discharge and the second dry discharge may be resistance discharges, and the values of resistance elements for discharge are different from each other.

While the first discharging step is in progress, the secondary cell battery discharging device switches to the second discharging step when the power of the secondary cell battery becomes less than a certain level of power.

A dry discharge method of a secondary battery according to another embodiment of the present invention includes, in a secondary battery discharge device, firstly discharging the secondary battery after use using a resistance element having a first resistance value; discharging the secondary battery to a desired energy level, SOC 0%, or a physically disabled state, OV, by using a resistance element having a second resistance value lower than the first resistance value; and aging the secondarily discharged secondary battery in a differential reverse voltage state for 24 hours to remove the electrolyte of the secondary battery.

Reverse voltage is applied to the secondary battery cell to forcibly transfer lithium ions to the anode and oxidize them.

During the aging period of 24 hours, the electrolyte solution is completely removed as residual lithium coated on the separator of the secondary battery is absorbed into the positive electrode of the secondary battery.

According to the present invention, the residual power of the waste secondary battery can be completely discharged to 0V through a two-step resistance discharge, and all of the electrolyte in the secondary battery is completely removed. Therefore, there is an effect of minimizing various risk factors that occurred during reprocessing of the waste secondary cell battery.

According to the present invention, since the electrolyte is removed in a volatilization method, it is environmentally friendly, and since a waste facility for removing the electrolyte is not required, various costs involved in removing the electrolyte can be reduced, thereby securing economic feasibility than before. The effect of securing can also be expected.

According to the present invention, lithium ions contained in the negative electrode material of the secondary battery are completely removed and transferred to the positive electrode to be converted into stable compounds, so that no additional physical/chemical reaction occurs, so even if the secondary battery is cut, ignited, or punched, the possibility of fire or explosion can be completely prevented. In addition, when the secondary battery is recycled again, it is easy to recover the organic metal and there is an effect of reducing the extraction cost.

1 is a configuration diagram of a lithium ion battery for explaining the present invention.
FIG. 2 is a diagram explaining the charging/discharging operating principle of the lithium ion battery of FIG. 1 .
3 is an overall configuration diagram of a dry discharge device for a secondary battery for explaining the dry discharge method of the present invention.
4 is a flowchart illustrating a dry discharge method for completely removing electrolyte from a secondary battery according to a preferred embodiment of the present invention.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, it should be understood that this is not intended to limit the specific embodiments of the present invention, and includes all conversions, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

Terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprise" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but it should be understood that the presence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof is not excluded in advance.

Spatially relative terms such as below, beneath, lower, above, upper, etc. may be used to easily describe a correlation between one element or component and another element or component, as shown in the drawings. Spatially relative terms should be understood as encompassing different orientations of elements in use or operation in addition to the orientations shown in the figures. For example, when an element shown in the drawing is turned over, an element described as below or beneath another element may be placed above or above the other element. Accordingly, the exemplary term below may include both directions of down and above. Elements may also be oriented in other orientations, and thus spatially relative terms may be interpreted according to orientation.

An expression indicating a part such as “part” or “part” used in the present invention means that a corresponding component may indicate a device that may include a specific function, software that may include a specific function, or a combination of a device and software that may include a specific function. However, it cannot be said that it is necessarily limited to the expressed function, and this is only provided to help a more general understanding of the present invention, and various modifications and variations from this description can be made by those skilled in the art in the field to which the present invention belongs.

In addition, it should be noted that all electrical signals used in the present invention, as an example, can be reversed in signs of all electrical signals to be described below when an inverter or the like is additionally provided in the circuit of the present invention. Therefore, the scope of the present invention is not limited to the direction of the signal.

Therefore, the spirit of the present invention should not be limited to the described embodiments and should not be determined, and all things equivalent or equivalent to the claims as well as the following claims belong to the scope of the present invention.

Hereinafter, the present invention will be described in more detail based on the embodiments shown in the drawings.

FIG. 1 is a configuration diagram of a lithium ion battery for explaining the present invention, and FIG. 2 is a diagram explaining the charging and discharging operation principle of the lithium ion battery of FIG. 1 .

As shown in FIG. 1, a lithium ion battery is composed of a positive electrode material (+ electrode) and a negative electrode material (- electrode), a separator between the positive electrode material and the negative electrode material, and an electrolyte solution (or electrolyte).

Here, as the separator, a porous thin film of polyethylene (PE) and polypropylene (PP) having a thickness of about 10 to 35 μm may be used.

And the electrolyte may be an aportic solution that does not contain water. It can be seen that this electrolyte serves as a medium for lithium ions to move between the + and - electrodes inside the battery.

Referring to FIG. 2, when the lithium ion battery is charged, 'LiXXO ₂ 'is separated into 'Li' and 'XXO ₂ '(XX; N, CO, Al, Mn), and at this time, the electrolyte is coated on the separator when first charged. SEI (Solid Electrolyte Interface, passivation film) phenomenon occurs. Discharging is the reverse reaction to charging.

2, when the charging operation of the lithium ion battery proceeds, when electrons in the negative electrode material are forcibly sent to the positive electrode, the lithium ions in the negative electrode material move to the positive electrode material through the electrolyte and react with the positive electrode active material to be converted into a stable state. Therefore, additional physical and chemical reactions do not occur thereafter, so there is no possibility of fire or explosion. That is, a fire or explosion of a lithium ion battery causes a fire or explosion by causing a chemical reaction that oxidizes lithium ions or absorbs electrons as the protective film of lithium ions absorbed in the negative electrode material is destroyed.

3 is an overall configuration diagram of a dry discharge device for a secondary battery for explaining the dry discharge method of the present invention.

As shown in FIG. 3, a secondary battery 100 to be discharged is provided, and the secondary battery 100 may be the rechargeable lithium ion battery described in FIG. 1, or may include one or a plurality of lithium ion batteries. In the case of a plurality of lithium ion batteries, a loading device (not shown) for loading the batteries may be provided.

In the present invention, the remaining power of the secondary battery 100 is firstly discharged, and the remaining power after the first discharge is secondarily discharged to disable it, and then a differential reverse voltage is applied to the secondary battery 100 for a predetermined time (eg, about 24 hours) to completely volatilize the electrolyte and completely remove Li+ ions. In FIG. 3 , it can be said that only the configuration for discharging the secondary battery 100 is shown. Here, the differential reverse voltage means that when a reverse voltage is differentially applied according to the electrolytic state of the battery and electrons are forcibly transferred to the anode, lithium ions (Li+) ionized at the anode move from the anode to the anode through the electrolyte and are oxidized.

Both the first discharge and the second discharge use a resistive discharge method. That is, the 1st discharge is to discharge from the remaining power to a certain power range, and the 2nd discharge is to completely discharge the remaining power remaining after the 1st discharge to the desired energy level, SOC 0%, or OV, which is a physically disabled state. The reason for this complete discharge is to safely transport, store, and disassemble the secondary battery.

A first resistance element 110 and a second resistance element 120 are provided for the first discharge and the second discharge. Here, the resistance value of the first resistance element 110 is greater than that of the second resistance element 120 .

Switching units (SW1 to SW4) for selecting the first resistance element 110 and second resistance element 120 and a control unit 130 for turning on/off the switching units (SW1 to SW4) are included. The controller 130 automatically performs the secondary discharge when the secondary battery 100 is discharged to a certain power range according to the primary discharge. For example, when the remaining power before the start of discharge is considered to be 100%, the first discharge may be about 90%, and the second discharge may be regarded as discharging the remaining 10%. Therefore, 100% of the remaining power can be completely discharged through the first and second discharge. Here, the controller 130 may continuously monitor the secondary battery 100, check the start time of the secondary discharge, and operate the switching units SW1 to SW4 to control the secondary discharge to continue.

4 is a flowchart illustrating a dry discharge method of a secondary battery according to a preferred embodiment of the present invention.

In order to dispose of or recycle used secondary batteries, a discharging or disabling process is required. In general, even if the secondary battery is discharged, the cell voltage of the lithium ion battery can be discharged up to 3.2V in the conventional method, and discharge below that voltage is impossible.

Referring to FIG. 4 , first, at least one secondary battery is loaded on a loading device or the like for complete discharge. Thereafter, a discharge start command is transmitted (S100).

Then, the controller 130 turns on the switching units SW1 and SW2 so that the secondary battery 100 is connected to the first resistance element 110 . At this time, the switching units SW3 and SW4 are turned off. Accordingly, a primary discharging process in which the residual power remaining in the secondary batteries 100 is converted into resistance and lost as heat is performed (S110). At this time, heat is generated during the first discharge process, and the heat can be cooled by driving a fan (not shown) provided in a loading device or the like.

Due to this first discharge process, about 90% of the remaining power before the discharge process can be discharged.

The controller 130 continuously checks the amount of remaining power of the secondary battery 100 (S120). And when the check result is less than a certain power (ie, less than active power) (S130), that is, when discharged to about 90%, the control unit 130 turns off the switching units (SW1, S2W), and turns on the switching units (SW3, SW4). Then, the secondary battery 100 and the second resistance element 120 are connected, and a second discharge operation using the second resistance element 120 is performed (S140). And, the second discharging operation is performed until the secondary battery becomes 0V in a desired level (SOC 0%) or a physically disabled (OV) state (S150).

When the second discharging operation is performed, the voltage remaining in the secondary battery 100 will be discharged to 0V, and the secondary battery 100 can be disabled.

Next, a reverse voltage is applied to the disabled secondary battery 100 (S160). The differential reverse voltage method can be said to be for oxidizing lithium ions inside the secondary battery 100 by artificially generating a current passage of the secondary battery 100 .

According to the present invention, after applying a reverse voltage to the secondary pre-battery 100, the reverse voltage state is differentially maintained for about 24 hours (S170). During the reverse voltage condition, the current carrying path must not be lost. Then, Li+ ions move to the positive electrode following the electrons that were forcibly transferred to the positive electrode (anode) of the residual lithium coated on the separator during the first charge. Therefore, the electrolyte solution disappears while being absorbed by the + electrode for 24 hours. According to this process, all of the electrolyte in the disabled secondary battery can be removed.

According to the experiment, it was found that all of the electrolyte was removed and nonflammable after about 24 hours. That is, as a result of checking the secondary battery by using a cutter after 24 hours in the differential reverse voltage state, it was found that the electrolyte was all volatilized and disappeared.

As described above, the present invention removes all of the electrolyte inside the secondary battery by aging the secondary battery disabled by the primary and secondary discharge in a differential reverse voltage state for 24 hours.

Although described with reference to the illustrated embodiments of the present invention as described above, these are merely examples, and those skilled in the art to which the present invention pertains will clearly appreciate that various modifications, changes, and equivalent other embodiments are possible without departing from the gist and scope of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

100: secondary cell battery
110: first resistance element
120: second resistance element
130: control unit
SW1 ~ SW4: switch

Claims (9)

A secondary battery battery discharge device,
a first discharge step of discharging first residual power remaining in secondary cells to be recycled after use to a certain power by first dry discharge;
a second discharge step of completely discharging the second residual power remaining after the first discharge until a desired energy level is reached through a second dry discharge; and
A dry discharge method of a secondary battery, characterized in that it comprises the step of removing the electrolyte solution of the secondary battery by aging the secondary battery for a predetermined time in a differential reverse voltage state. According to claim 1,
The aging time is 23 to 25 hours (h), a dry discharge method of a secondary battery. According to claim 1,
During the aging time, the electrolyte solution is completely removed while the residual lithium coated on the separator of the secondary battery is absorbed by the positive electrode of the secondary battery. According to claim 1,
The first dry discharge and the second dry discharge are discharge methods in which a current is refluxed to an internal circuit, and the energy level is a state of charge (SOC) of 0% or a physically disabled state of OV. Dry discharge method of a secondary battery, characterized in that. According to claim 1,
The first dry discharge and the second dry discharge may be resistive discharge,
A dry discharge method of a secondary cell battery in which the values of resistance elements for discharging are different. According to claim 1,
During the first discharge step,
The dry discharge method of the secondary cell battery, wherein the discharge device of the secondary cell battery switches to the secondary discharge step when the power of the secondary cell battery becomes less than a certain power and continues to discharge. A secondary battery battery discharge device,
firstly discharging the secondary battery after use using a resistance element having a first resistance value;
discharging the secondary battery to a desired energy level, SOC 0%, or a physically disabled state, OV, by using a resistance element having a second resistance value lower than the first resistance value; and
The dry discharge method of a secondary battery, characterized in that it comprises the step of removing the electrolyte solution of the secondary battery by aging the secondary battery for 24 hours in a differential reverse voltage state. According to claim 7,
A dry discharge method of a secondary pre-battery, wherein a reverse voltage is applied to the secondary battery cell to forcibly transfer lithium ions to an anode and oxidize them. According to claim 7,
During the aging time of 24 hours, the electrolyte solution is completely removed while the residual lithium coated on the separator of the secondary battery is absorbed by the positive electrode of the secondary battery.

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