Patent Description:
The present invention relates to an apparatus and a method for inspecting lithium precipitation in a battery cell, and more particularly, to an apparatus and a method for inspecting lithium precipitation in a battery cell for inspecting whether lithium is deposited inside a secondary battery cell using eddy current.

As prices of energy sources increase due to depletion of fossil fuels and interests in environmental pollution increase, a demand for eco-friendly alternative energy sources becomes an indispensable factor for future life. In particular, as technology development and demand for mobile devices increase, demand for secondary batteries as an energy source is also rapidly increasing.

Typically, in terms of battery shape, there are high demands for prismatic secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones with thin thickness, and, in terms of materials, demands for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries with high energy density, discharge voltage, and output stability, are high.

Among them, a pouch-type lithium secondary battery has a problem in that safety of the battery may be lowered by an internal short circuit caused from local lithium plating occurring within the battery.

<CIT> discloses a determination apparatus which comprises a measuring device that measures the alternating current impedance of a secondary battery. A controller determines the presence or absence of lithium precipitation. A measuring device calculates the negative electrode reaction resistance of the secondary battery based on the characteristic in specific frequency among the characteristics of the alternating current impedance of the secondary battery. The controller determines lithium precipitation, when the negative electrode reaction resistance falls per unit time during the charge of the secondary battery more than a predetermined value.

Accordingly, it is needed to develop a solution for diagnosing whether or not lithium is deposited in a pouch-type lithium secondary battery.

To obviate one or more problems of the related art, embodiments of the present disclosure provide an apparatus for inspecting lithium precipitation with high reliability.

To obviate one or more problems of the related art, embodiments of the present disclosure also provide a method for inspecting lithium precipitation with high reliability.

In order to achieve the objective of the present disclosure, an apparatus for inspecting lithium precipitation on battery cell may comprise: an inspection module including a first sensor for inducing an eddy current in the at least one battery cell and a second sensor for measuring impedance of the at least one battery cell in which the eddy current is induced; and a controller configured to determine whether or not lithium plating has occurred in the at least one battery cell by comparing a measured value of the impedance measured by the second sensor with standard data; wherein the first sensor and the second sensor are provided in a form in which a coil is wound around a magnetizing member, wherein the first sensor induces eddy current in the battery cell by applying an alternating current (AC) of a specific predefined frequency to the coil to form a magnetic field, and wherein the second sensor measures an impedance at the specific predefined frequency for the at least one battery cell.

The Apparatus may further include a delivery module for delivering the at least one battery cell input from the outside to the inspection module.

The first sensor is located on the upper side with respect to the delivery module and the second sensor is located on the lower side with respect to the delivery module, and wherein the first sensor and the second sensor are located on a same vertical line with respect to the delivery module.

The specific frequency has a value corresponding to any one value between <NUM> to <NUM>.

The standard data is pre-verified data obtained by measuring impedance at the specific frequency for a battery cell in which lithium is deposited or for a battery cell in which lithium is not deposited.

The controller is configured to compare a position of an impedance value of the battery cell measured by the second sensor on a complex plane with positions of the first cluster data and the second cluster data based on a dividing line which divides the standard data expressed on the complex plane into first cluster data and second cluster data, so as to determine whether lithium is deposited in the battery cell, wherein the first cluster data is at least one piece of data measured in at least one battery cell in which lithium is deposited, and wherein the second cluster data is at least one data measured in at least one battery cell in which lithium is not deposited.

The battery cell is a pouch-type lithium secondary battery cell.

The battery cell is used in an energy storage system (ESS).

In order to achieve the objective of the present disclosure, a method for inspecting lithium precipitation on battery cell using an inspection module including a first sensor and a second sensor in which a coil is wound around a magnetizing member may comprise: applying an alternating current (AC) of a specific predefined frequency to a coil in the first sensor to form a magnetic field and induce eddy current in the at least one battery cell; measuring impedance of the at least one battery cell at the specific predefined frequency using the second sensor; and determining whether or not lithium plating has occurred in the at least one battery cell by comparing an measured impedance value measured by the second sensor with standard data.

The method may further include delivering the at least one battery cell to the inspection module using a delivery module.

The first sensor is located on the upper side with respect to the delivery module, wherein the second sensor is located on the lower side with respect to the delivery module, and wherein the first sensor and the second sensor are located on a same vertical line with respect to the delivery module.

The determining whether or not lithium plating has occurred in the at least one battery cell includes comparing a position of an impedance value of the battery cell measured by the second sensor on a complex plane with positions of the first cluster data and the second cluster data based on a dividing line which divides the standard data expressed on the complex plane into first cluster data and second cluster data, so as to determine whether lithium is deposited in the battery cell, wherein the first cluster data is at least one piece of data measured in at least one battery cell in which lithium is deposited, and wherein the second cluster data is at least one data measured in at least one battery cell in which lithium is not deposited.

According to embodiments of the present disclosure, an apparatus and a method for inspecting lithium precipitation forms a magnetic field around a battery cell to be inspected to induce an eddy current and compares measured impedance of the battery cell with standard data to detect lithium plating in the battery cell, thereby providing high stability and reliability.

The present invention may be modified in various forms and have various embodiments, and specific embodiments thereof are shown by way of example in the drawings and will be described in detail below. It should be understood, however, that there is no intent to limit the present invention to the specific embodiments. Like reference numerals refer to like elements throughout the description of the figures.

It will be understood that, although the terms such as first, second, A, B, and the like may be used herein to describe various elements, these elements should not be limited by these terms. As used herein, the term "and/or" includes combinations of a plurality of associated listed items or any of the plurality of associated listed items.

It will be understood that when an element is referred to as being "coupled" or "connected" to another element, it can be directly coupled or connected to the other element or an intervening element may be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there is no intervening element present.

Terms used in the present application are used only to describe specific embodiments, and are not intended to limit the present invention. A singular form includes a plural form if there is no clearly opposite meaning in the context. In the present application, it should be understood that the term "include" or "have" indicates that a feature, a number, a step, an operation, a component, a part or the combination thereof described in the specification is present, but does not exclude a possibility of presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof, in advance.

Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meanings as commonly understood by one skilled in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having meanings that are consistent with their meanings in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The apparatus for inspecting lithium precipitation according to embodiments of the present invention may detect whether lithium is locally deposited in a region inside a battery cell by using eddy current. Here, the battery cell may be a pouch type lithium secondary battery for an energy storage system (ESS).

In general, lithium secondary batteries may be classified according to a structure of an electrode assembly having a cathode/separator/anode structure. For example, a lithium secondary battery may be classsified as having a jelly-roll (wound type) electrode assembly having a structure in which long sheet-shaped positive electrodes(anode) and negative electrodes(cathode) are wound with a separator interposed therebetween, a stack type (stack type) electrode assembly in which a plurality of anodes and cathodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, or a stack/folding type electrode assembly having a winding structure of bi-cells or full cells in which positive and negative electrodes of a predetermined unit are stacked with a separator interposed therebetween.

Recently, a pouch type battery, having a structure in which a stack type or stack/fold type electrode assembly is embedded in a pouch type battery case of an aluminum laminate sheet has attracted a lot of attention due to low manufacturing cost, low weight, easy shape deformation, etc., and thus, use of the pouch type battery is steadily increasing.

In general, a pouch-type lithium secondary battery is configured to include an electrode assembly, electrode tabs extending from the electrode assembly, electrode leads welded to the electrode tabs, and a battery case accommodating the electrode assembly.

Here, the electrode assembly is a power generating device in which a positive electrode and a negative electrode are sequentially stacked with a separator interposed therebetween, and has a stacked or stacked/folded structure. In addition, the electrode tabs may extend from each electrode plate of the electrode assembly and the electrode lead may be electrically connected to a plurality of electrode tabs extending from each electrode plate by welding.

Meanwhile, a portion of the battery case is exposed to the outside, and an insulating film may be attached to a portion of the upper and lower surfaces of the electrode lead to increase sealing with the battery case and at the same time secure electrical insulation.

In general, a battery case is made of an aluminum laminate sheet, provides a storage space for accommodating an electrode assembly, and has a pouch shape as a whole. Here, in a case of the stacked electrode assembly, the upper end of the battery case is spaced apart from the electrode assembly so that the plurality of positive electrode tabs and the plurality of negative electrode tabs can be coupled to the electrode lead.

Somehow, safety of the lithium secondary battery may deteriorate when lithium is deposited in any one region within the battery cell. Among them, a pouch-type lithium secondary battery has a disadvantage in that it is difficult to confirm whether or not lithium is deposited from the outside because the electrode, the electrode tab, and the welding part are accommodated inside the battery case as described above.

In the following, an apparatus for detecting lithium plating which is capable of easily determining presence or absence of lithium plating in a pouch-type secondary battery using eddy current will be described in more detail with reference to the accompanying drawings.

<FIG> is a plan view of an apparatus for inspecting lithium precipitation according to embodiments of the present invention, <FIG> is a block diagram of an apparatus for inspecting lithium precipitation according to embodiments of the present invention, and <FIG> is a design diagram of an inspection module in an apparatus for inspecting lithium precipitation according to embodiments of the present invention.

Referring to <FIG>, the apparatus for inspecting lithium precipitation <NUM> may include an inspection module <NUM>, a delivery module <NUM> and a controller <NUM>.

The inspection module <NUM> may include a first sensor <NUM> and a second sensor <NUM> to measure impedance of the battery cell <NUM> in which eddy current is induced at a specific frequency.

The delivery module <NUM> may deliver at least one battery cell <NUM> to be tested, which is input from the outside, to the inspection module <NUM> to inspect whether or not lithium is precipitated.

In addition, the controller <NUM> may control operations of the inspection module <NUM> and the delivery module <NUM>, and determine whether or not lithium is deposited in the test target battery cell <NUM> based on a impedance measurement value obtained from the inspection module <NUM>.

<FIG> is a cross-sectional view of a first sensor and a second sensor in an inspection module according to embodiments of the present invention.

Referring to <FIG>, the inspection module <NUM> may include a first sensor <NUM> and a second sensor <NUM>. According to the embodiment, the first sensor <NUM> and the second sensor <NUM> may be formed in a structure in which a coil is wound around a magnetizing member (not shown) having magnetism. Here, the diameter of the coil may be <NUM> to <NUM>. For example, when the diameter of the coil is less than <NUM>, an impedance measurement value measured by the second sensor <NUM> to be described later may be low. On the contrary, when the diameter of the coil exceeds <NUM> mm, noise may be generated in the impedance measurement value measured by the second sensor <NUM>, and thus reliability may deteriorate. Accordingly, in order to determine whether or not lithium is deposited inside the battery cell <NUM>, a user may select an optimal coil diameter by appropriately adjusting the diameter of the coil within the numerical range described above.

In addition, the inspection module <NUM> may further include a case C to protect the first sensor <NUM> and the second sensor <NUM>. For example, the case C may be provided in a cylindrical shape with one end closed and the other open. Here, one end may be an end positioned close to an object to be inspected.

<FIG> is a conceptual diagram for explaining eddy current induction principle of a battery cell according to embodiments of the present invention.

Referring to <FIG>, the first sensor <NUM> may be a sensor for inducing eddy current in the battery cell <NUM> to be inspected.

More specifically, according to the embodiments, when an alternating current at a specific frequency is applied to the coil by the controller <NUM> to be described later, magnetic field may be formed around the coil of the first sensor <NUM>. For example, the specific frequency may be any one value from <NUM> to <NUM>, or any one value from <NUM> to <NUM>.

Subsequently, when the battery cell <NUM> to be inspected is located within a magnetic field area by the delivery module <NUM> to be described later, induced electromotive force may be generated in the battery cell <NUM> due to electromagnetic induction. Accordingly, an eddy current that disturbs the magnetic field may flow through the battery cell <NUM>.

Referring back to <FIG> and <FIG>, the second sensor <NUM> may be positioned on a vertical line corresponding to the first sensor <NUM> with respect to the delivery module <NUM>. In other words, the first sensor <NUM> and the second sensor <NUM> are located on the same vertical line with respect to the delivery module <NUM>, the first sensor <NUM> is is located in the upper side with respect to the delivery module <NUM> and the second sensor <NUM> may be located in the lower side with respect to the delivery module <NUM>. Accordingly, the second sensor <NUM> may measure impedance in the battery cell <NUM> in which eddy current is induced by the first sensor <NUM>. Here, the eddy currents may show difference in measured values according to resistance in the measurement area.

Meanwhile, the inspection module <NUM> may further include first to fourth position adjusting members <NUM>, <NUM>, <NUM>, and <NUM>. Here, the first to fourth position adjusting members <NUM>, <NUM>, <NUM>, and <NUM> may be configured to move the positions of the first sensor <NUM> and the second sensor <NUM>.

More specifically, one side of the first position adjusting member <NUM> may be coupled to the first sensor <NUM>, and the other side of the first position adjusting member <NUM> may be coupled to the third position adjusting member <NUM> by a position fixing bolt <NUM>.

In addition, one side of the second position adjusting member <NUM> may be coupled to the second sensor <NUM> and the other side of the second position adjusting member <NUM> may be coupled to the third position adjusting member <NUM> by a position fixing bolt <NUM>.

Meanwhile, one side of the third position adjusting member <NUM> may be coupled to the first position adjusting member <NUM> and the second position adjusting member <NUM>, and the other side may be combined with the fourth positioning adjusting member <NUM> by a position fixing bolt <NUM>.

Here, the first position adjusting member <NUM> and the second position adjusting member <NUM> may be spaced apart from one side of the third position adjusting member <NUM> by a predetermined distance and coupled thereto.

The third position adjusting member <NUM> may include a sliding groove (not shown) of a predetermined length on one side for adjusting a position of the first position adjusting member <NUM> and a position of the second position adjusting member <NUM>.

In other words, the third position adjusting member <NUM> may include a first sliding groove (not shown) at a part coupled to the first position adjusting member <NUM>. Accordingly, the first position adjusting member may move in a vertical direction along the first sliding groove within a length range of the first sliding groove.

In addition, the third position adjusting member <NUM> may include a second sliding groove (not shown) at a part coupled to the second position adjusting member <NUM>. Accordingly, the second position adjusting member <NUM> may move in a vertical direction along the second sliding groove within a length range of the second sliding groove.

Thus, the first position adjusting member <NUM> and the second position adjusting member <NUM> may move in a vertical direction, respectively, along the first and second sliding grooves of the third position adjusting member <NUM> under control of the controller <NUM>. In other words, the controller <NUM> moves the first position adjusting member <NUM> and the second position adjusting member <NUM> in a vertical direction, respectively, so that the first sensor <NUM> and the second sensor <NUM> may be adjusted to be closer or farther to a battery cell to be inspected on a cell-by-cell basis.

In addition, vertical direction movements of the first sensor <NUM> and the second sensor <NUM> may be fixed by the position fixing bolts <NUM> and <NUM> of the first position adjusting member <NUM> and the second position adjusting member <NUM>. According to an embodiment, a user may adjust the position of the first position adjusting member <NUM> and the second position adjusting member <NUM>, and then tighten the position fixing bolts <NUM> and <NUM> that are coupled with the third position adjusting member <NUM>, thereby fixing the movements of the first sensor <NUM> and the second sensor <NUM>.

Meanwhile, the fourth position adjusting member <NUM> may be coupled to the third position adjusting member <NUM> by a position fixing bolt <NUM>.

More specifically, the fourth position adjusting member <NUM> may include a third sliding groove having a predetermined length for adjusting a position of the third position adjusting member <NUM>. Accordingly, the third position adjusting member <NUM> may move in a horizontal direction along the third sliding groove within a length range of the third sliding groove.

In addition, the fourth position adjusting member <NUM> may further include a position fixing bolt <NUM>. Accordingly, a user may move the third position adjusting member <NUM> to a desired position through the third sliding groove, and fix the third position adjusting member <NUM> to the fourth position adjusting member <NUM> by manipulating the position fixing bolt <NUM>. Accordingly, the third position adjusting member <NUM> may fix horizontal movement of the first sensor <NUM> and the second sensor <NUM> coupled to the third position adjusting member <NUM>.

<FIG> is a plan view of a delivery module in an apparatus for inspecting lithium precipitation according to embodiments of the present invention and <FIG> is an image of a delivery module in an apparatus for inspecting lithium precipitation according to embodiments of the present invention.

Referring to <FIG> and <FIG>, the delivery module <NUM> may transfer the battery cell <NUM> which is put into the lithium precipitation inspection apparatus <NUM> according to embodiments of the present invention toward the inspection module <NUM>. In addition, the delivery module <NUM> may transfer the inspected battery cell <NUM> to a carrying-out port.

While the inspection module <NUM> measures impedance of the battery cell being inspected, the delivery module <NUM> may transfer a following battery cell to a position where the battery cell being inspected was stayed immediately before. Accordingly, the following battery cell may have a certain waiting time for inspection. Thereafter, when the inspection of the battery cell ends and the battery cell moves out of the inspection area, the delivery module <NUM> may transfer the following battery cell into the inspection area. Accordingly, the inspection module <NUM> may measure impedance according to a specific frequency of the battery cell.

In addition, the delivery module <NUM> may control a traveling speed of a specific battery cell within the inspection area and a traveling speed of a battery cell outside the inspection area differently, by the controller <NUM> to be described later. For example, the traveling speed of a battery cell to be tested within the inspection area may be slower than the traveling speed of battery cells located out of the inspection area.

The delivery module <NUM> may include a transfer die <NUM> extending from an input point of the battery cell to a carrying-out point, and transfer means <NUM>, <NUM>, and <NUM> for transferring the battery cell.

Here, the transfer die <NUM> may include a plurality of nests <NUM> in which the battery cells <NUM> are seated between one unit movement section and an adjacent unit movement section.

The nest <NUM> may be a receiving groove recessed into the transfer die <NUM> to correspond to a shape of the battery cell, and thus, the battery cell <NUM> can be seated therein. Accordingly, when the delivery module <NUM> is moving, the battery cells may be aligned by being seated in the nest and transported from the input point to the inspection area.

Meanwhile, the transfer means <NUM>, <NUM>, and <NUM> include a lifting unit <NUM> that lifts the battery cell from the transfer die <NUM> and a driving unit <NUM> that transfers the lifting unit <NUM> in a traveling direction of the battery cell <NUM>. Here, the driving unit <NUM> may be implemented in various forms for moving the lifting unit <NUM>.

The lifting unit <NUM> may be a cylinder reciprocating up and down by hydraulic pressure or pneumatic pressure.

The lifting unit <NUM> may be provided in a form of two narrow rods extending in a direction parallel to the traveling direction of the battery cell <NUM> and having a predetermined length. According to the embodiment, the lifting unit <NUM> may be spaced apart from each other above and below a central line parallel to a longitudinal direction of the transfer die <NUM> (the traveling direction of the battery cell).

The lifting unit <NUM> may support the battery cell <NUM> and transfer the battery cell <NUM> while moving in the traveling direction of the battery cell <NUM> as the driving unit <NUM> moves.

The lifting unit <NUM> according to embodiments of the present invention may include one or more adsorption holes <NUM> for adsorbing the battery cell <NUM>. Here, the number of adsorption holes <NUM> may be properly adjusted as needed.

The lifting unit <NUM> may be extended and elevated by the driving unit <NUM> to adsorb the battery cell <NUM> in order to pick up the battery cell <NUM>.

The driving unit <NUM> may be located on a lower surface with respect to the transfer die <NUM>. The driving unit <NUM> may pass through an opening <NUM> formed in the transfer die <NUM> and ascend to the top of the transfer die <NUM> according to a control signal from the controller <NUM> to be described later. Then, the controller <NUM> to be described later may fix the battery cell <NUM> to the lifting unit <NUM> by applying a vacuum to the adsorption holes <NUM>.

The apparatus for inspecting lithium precipitation according to embodiments of the present invention provides the lifting unit <NUM> including adsorption holes <NUM>, so that vibration of the battery cell <NUM> being transported through the lifting unit <NUM> may be suppressed, thereby prevening the battery cell <NUM> from being disturbed in alignment or from being detached from the lifting unit <NUM>. Therefore, the apparatus for inspecting lithium precipitation according to the embodiments of the present invention may be able to measure an impedance value with high reliability even during transfer of the battery cell. However, the apparatus for inspecting lithium precipitation according to embodiments of the present invention is not limited to an embodiment in which the battery cell <NUM> is adsorbed to the lifting unit <NUM> by applying vacuum through the adsorption holes <NUM>, but may have various forms in which the battery cell <NUM> can be fixed to the lifting unit <NUM>.

Meanwhile, the delivery module <NUM> of the apparatus for inspecting lithium precipitation according to embodiments of the present invention may include a plurality of unit movement sections, and the transfer means <NUM>, <NUM>, and <NUM> may travel back and forth one unit movement section or two or more unit movement sections.

For example, the transfer means <NUM>, <NUM>, and <NUM> may pick up a battery cell placed at a starting point of a unit movement section and transport it to a starting point of an adjacent unit movement section. Thereafter, the transfer means <NUM>, <NUM>, and <NUM> that have completed transfer of the battery cell <NUM> in the unit movement section may return to the starting point of the unit movement section. In other words, the delivery module <NUM> may sequentially transfer a plurality of battery cells <NUM> by repeatedly performing the above process.

Explaining a process in which a battery cell <NUM> to be inspected is put into and taken out of the apparatus for inspecting lithium precipitation according to embodiments of the present invention in detail, when a battery cell is put in a nest <NUM> located at a battery cell input point, the driving unit <NUM> may operate the lifting unit <NUM>. Accordingly, the lifting unit <NUM> may pass through the opening <NUM> of the transfer die <NUM> and moved upward to the top of the transfer die <NUM>.

Thereafter, the lifting unit <NUM> raised to the upper part of the transfer die <NUM> may adsorb the battery cell <NUM> seated on the nest <NUM>. Accordingly, the battery cell <NUM> can be prevented from being detached from the lifting unit <NUM> or out of alignment during transfer and movement due to vibration during inspection can be minimized. A method of adsorbing the battery cell <NUM> by the lifting unit <NUM> is not limited to the above-described embodiment as long as movement of the battery cell <NUM> during transfer can be minimized.

The lifting unit <NUM> is coupled to the driving unit <NUM> and can be reciprocally moved by the driving unit <NUM>.

Accordingly, the lifting unit <NUM> adsorbing the battery cell <NUM> may move, by the driving unit <NUM>, horizontally in a direction in which the inspection module <NUM> is installed while maintaining a raised state. Thus, the battery cell <NUM> supported or adsorbed by the lifting unit <NUM> may be transferred together.

The lifting unit <NUM> may release the vacuum after transferring the battery cell <NUM> to an adjacent nest <NUM>. Thereafter, the lifting unit <NUM> may descend to a lower part of the transfer die <NUM> together with the driving unit <NUM> and return to its original position. Accordingly, one battery cell <NUM> may be transferred from one unit movement section to an adjacent unit movement section.

Thereafter, the delivery module <NUM> according to embodiments of the present invention may sequentially repeat the above process to transfer a battery cell <NUM> from an inlet to a nest <NUM> closest to the inspection module <NUM>.

Meanwhile, the apparatus for inspecting lithium precipitation according to embodiments of the present invention may further include an alignment module (not shown) for aligning the battery cell <NUM> seated in the nest <NUM> closest to the inspection module <NUM>.

The aligning module may align the battery cell <NUM> immediately before performing an eddy current inspection, thereby improving reliability of the inspection.

The battery cell <NUM> aligned by the aligning module may be adsorbed to the lifting unit <NUM> again. Accordingly, impedance of the battery cell <NUM> may be measured by the inspection module <NUM> including a first sensor <NUM> and a second sensor <NUM> in a state in which eddy current is induced at a specific frequency.

It is preferable that a traveling speed of the battery cell <NUM> within the inspection area by the inspection module <NUM> is constant to increase accuracy of the inspection. In addition, the traveling speed of the battery cell <NUM> during passing through the inspection area may be controlled differently from a transfer speed of the battery cell <NUM> located on the transfer die outside the inspection area.

Thereafter, the battery cell <NUM> for which impedance measurement has been completed by the inspection module <NUM> may be transported to an outlet by means of transfer means <NUM>, <NUM>, and <NUM>.

Referring back to <FIG>, the controller <NUM> is electrically connected to the inspection module <NUM>. Accordingly, the controller <NUM> may receive an impedance measurement value of the battery cell <NUM> to be inspected, in which eddy current is induced at a specific frequency, from the inspection module <NUM> to determine whether or not lithium is deposited in the battery cell <NUM>. More specifically, the controller <NUM> may compare the eddy current impedance measurement value of the battery cell <NUM> being inspected received from the inspection module <NUM> with standard data to determine whether or not lithium is deposited in the battery cell. Here, the standard data may be pre-verified data obtained by measuring impedance at a specific frequency of a battery cell in which lithium is precipitated or a battery cell in which lithium is not precipitated. A method of determining whether lithium is deposited in a battery cell being inspected using standard data will be described in detail below.

Targeting a pouch-type lithium-ion battery cell with a battery capacity of <NUM> Ah in a form of a bidirectional tab, <NUM> newly manufactured battery cells in which are confirmed by CT measurement that lithium plating has not occured and <NUM> battery cells in which are confirmed by CT measurement that lithium plating has occured were prepared.

Thereafter, impedances of the battery cells for each frequency were individually measured using an eddy current sensor for the battery cells.

Here, the battery cells were arranged so that a boundary between a positive electrode tab and an electrode plate was positioned at the center of the eddy current sensor, and the battery cells were fixed to maintain a <NUM> gap from the eddy current sensor, and then individual impedances of the battery cells were measured.

<FIG> is an impedance measurement graph of standard data when the frequency is <NUM> according to a first experimental example of the present invention, <FIG> is an impedance measurement graph of standard data when the frequency is <NUM> according to a second experimental example of the present invention, and <FIG> is an impedance measurement graph of standard data when the frequency is <NUM> according to a comparative example of the present invention.

Referring to <FIG>, when the frequency is <NUM>, the measured impedance values of battery cells in which lithium is precipitated are clustered in quadrants <NUM> and <NUM> on a complex plane graph, and the measured impedance values of battery cells in which lithium is not precipitated are clustered in quadrants <NUM> and <NUM>. In other words, when the frequency is <NUM>, the measured impedance values of the battery cells in which lithium is deposited may be clustered in the upper side with respect to a first linear dividing line L1, and the measured impedance values of the battery cells in which lithium is not deposited may be clustered and positioned in the lower side of the first linear dividing line L1.

In addition, referring to <FIG>, when the frequency is <NUM>, the measured impedance values of battery cells in which lithium is precipitated are clustered in quadrant <NUM> on a complex plane graph, and the measured impedance values of battery cells in which lithium is not precipitated are clustered in quadrant <NUM>. In other words, when the frequency is <NUM>, the measured impedance values of the battery cells in which lithium is deposited may be clustered in the left side with respect to a second linear dividing line L2, and the measured impedance values of the battery cells in which lithium is not deposited may be clustered and positioned in the right side of the second linear dividing line L2.

On the other hand, referring to <FIG>, when the frequency is <NUM>, it can be seen that the impedance measurement values of lithium-precipitated battery cells and the impedance measurement values of non-lithium-precipitated battery cells are scattered rather than clustered with each other. Accordingly, when the frequency is <NUM>, it is not possible to obtain a linear dividing line dividing impedance measurement values of lithium-precipitated battery cells and impedance measurement values of non-lithium-precipitated battery cells.

In addition, although not shown in the figures, in addition to <NUM>, at frequencies outside a range from <NUM> to <NUM> and outside a range from <NUM> to <NUM>, the impedance measurement values of lithium-precipitated battery cells and the impedance measurement values of non-lithium-precipitated battery cells are scattered rather than clustered, so it is difficult to distinguish them from each other using a dividing line.

Accordingly, the apparatus for inspecting lithium precipitation according to embodiments of the present invention may determine whether or not lithium is deposited in the battery cell by checking a position of the impedance measurement value of the battery cell being inspected at specific frequenies range based on a dividing line obtained from standard data of impedances of the battery cells measured in advance at the specific frequencies. According to an embodiment, the specific frequency may be any one value within a range of <NUM> to <NUM> or a range of <NUM> to <NUM>.

Meanwhile, the controller <NUM> may control the inspection module <NUM> and the transfer means <NUM>, <NUM>, and <NUM>. The controller <NUM> may be implemented as a conventional programmable electronic computer combined with a memory for controlling transfer and transfer speed of the plurality of battery cells <NUM>. According to an embodiment, the controller <NUM> may be provided as a processor that executes at least one program command stored in a memory. Here, the processor may mean a central processing module (CPU), a graphics processing module (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed.

The apparatus for inspecting lithium precipitation according to embodiments of the present invention has been described above. Hereinafter, a method for inspecting lithium precipitation according to embodiments of the present invention with regard to operations of the controller in the apparatus for inspecting lithium precipitation will be described.

<FIG> is a flow chart of a method for inspecting lithium precipitation according to embodiments of the present invention.

Referring to <FIG>, the controller <NUM> in the apparatus for inspecting lithium precipitation may transfer the battery cell for inspection, which is input from the outside by the delivery module <NUM>, to the inspection module <NUM> (S100). A detailed method of transferring the battery cell for inspection to the inspection module <NUM> by using the delivery module <NUM> is same with the description stated above with regard to the apparatus for inspecting lithium precipitation, and thus, it will be omitted.

Thereafter, the controller <NUM> may operate the first sensor <NUM> of the inspection module <NUM> to induce eddy current in the battery cell <NUM> (S200).

In more detail according to the embodiments, the controller <NUM> may apply an alternating current at a specific frequency to a coil in the first sensor <NUM>. Accordingly, a magnetic field may be formed around the battery cell <NUM>. Here, the specific frequency may be any one of values from <NUM> to <NUM>, or any one of values from <NUM> to <NUM>.

Then, the controller <NUM> may locate the first sensor <NUM> close to the battery cell <NUM>. Accordingly, induced electromotive force may be generated around the battery cell <NUM> due to electromagnetic induction, and eddy current may flow in the battery cell <NUM> in a direction obstructing the magnetic field.

The controller <NUM> may measure impedance of the battery cell <NUM> to which the eddy current is induced using a second sensor <NUM> located close to the battery cell <NUM> together with the first sensor <NUM> (S300).

Thereafter, when measurement of the impedance of the battery cell <NUM> by the second sensor <NUM> is completed, the controller <NUM> may move the first sensor <NUM> and the second sensor <NUM> which are located close to the battery cell to an initial position to maintain a certain distance from to the battery cell <NUM>.

In addition, the controller <NUM> may compare the measured impedance value of the battery cell obtained by the second sensor <NUM> to standard data (S400). Here, the standard data may be pre-verified data obtained by measuring impedance at the specific frequency for a battery cell in which lithium is precipitated or a battery cell in which lithium is not precipitated. Here, the specific frequency may be the same value as the specific frequency applied to the coil in the first sensor.

Accordingly, the controller <NUM> may determine whether or not lithium in the battery cell is precipitated (S500).

According to an embodiment, the controller <NUM> may compare the impedance measurement value of the battery cell obtained from the second sensor <NUM> with the standard data in real time to determine whether lithium is deposited in the battery cell in real time.

According to another embodiment, the controller <NUM> may collect impedance measurement values of the battery cell obtained from the second sensor <NUM> according to a predetermined criteria set by a user. Thereafter, the controller <NUM> may compare the collected impedance measurement values of the plurality of battery cells with the standard data to determine whether lithium is deposited in each battery cell. For example, the predetermined criteria may be time or a number of battery cells whose impedances are measured by the second sensor.

Describing a method for determining whether lithium is precipitated in a battery cell in more detail, the apparatus for inspecting lithium precipitation according to embodiments of the present invention may pre-acquire a dividing line at a corresponding frequency, obtained from pre-measured standard data for each frequency. For example, the dividing line may be a linear reference line that divides first cluster data of lithium-precipitated battery cells and second cluster data of non-lithium-precipitated battery cells among standard data at a specific frequency.

Thereafter, the apparatus for inspecting lithium precipitation may determine whether lithium is deposited in the battery cell by using the impedance measurement value of the battery cell measured at a specific frequency and the pre-obtained dividing line at the specific frequency.

According to an embodiment, the apparatus for inspecting lithium precipitation may display impedance measurement values according to eddy currents at a specific frequency on a complex plane in real time. In addition, the apparatus for inspecting lithium precipitation may display a dividing line obtained from standard data corresponding to the specific frequency on the complex plane.

Thereafter, the apparatus for inspecting lithium precipitation may compare positions of real-time impedance measurement values of battery cells located on the complex plane with positions of the first cluster data and the second cluster data with reference to the dividing line.

Here, when the impedance measurement value of the battery cell on the complex plane is present at a point where the first cluster data is located with reference to the dividing line, the apparatus for inspecting lithium precipitation may determine that lithium is precipitated in the battery cell.

On the other hand, if the impedance measurement value of the battery cell on the complex plane based on the dividing line is present at the point where the second cluster data is located with reference to the dividing line, the apparatus for inspecting lithium precipitation may determine that lithium is not precipitated in the battery cell.

According to another embodiment, the apparatus for inspecting lithium precipitation may display a plurality of impedance measurement values according to eddy currents at a specific frequency, collected according to predetermined critera, on a complex plane. In addition, the apparatus for inspecting lithium precipitation may display a dividing line obtained from standard data corresponding to a corresponding frequency on the complex plane.

Thereafter, the apparatus for inspecting lithium precipitation may analyze positions of impedance measurement data of a plurality of battery cells located on the complex plane. For example, the apparatus for inspecting lithium precipitation may determine whether the measurement data form a cluster. Thereafter, the apparatus for inspecting lithium precipitation may check if the clustered measurement data on the complex plane is located in a similar position to the first cluster data and the second cluster data of the standard data based on the dividing line or an arbitrary reference line having a same slope as that of the dividing line. Here, based on the dividing line, when the impedance measurement value of the battery cell on the complex plane is present at a point where the first cluster data is located, the apparatus for inspecting lithium precipitation may determine that lithium is precipitated in the battery cell.

A method for inspecting lithium precipitation according to embodiments of the present invention has been described above. Hereinafter, a lithium precipitation inspecting experiment of a battery cell, which is performed using the apparatus for inspecting lithium precipitation according to embodiments of the present invention, will be described in detail.

Using the apparatus for inspecting lithium precipitation according to embodiments of the present invention including a coil-type magnetic sensor as a first sensor and an eddy current sensor as a second sensor, lithium precipitation was inspected for a pouch-type lithium-ion battery cell in a form of a bi-directional tab having a battery capacity of <NUM> Ah.

Here, while a boundary between a positive electrode tab of the battery cell and an electrode plate is placed at the center of the eddy current sensor, and a distance between the boundary of the battery cell and the eddy current sensor is fixed to maintain a <NUM> interval, and the frequency of the first sensor is adjusted to <NUM>, <NUM>, and <NUM>, the impedances of the battery cells for each frequency were individually measured.

Subsequently, as a result of the inspection, experimental data obtained for four battery cells that are determined to have no lithium precipitated and four battery cells that are determined to have lithium precipitated and the standard data at the corresponding frequency were displayed on a single complex plane and compared.

<FIG> is an impedance measurement graph of standard data and experimental data when the frequency is <NUM> according to a third experimental example of the present invention, <FIG> is an impedance measurement graph of standard data and experimental data when the frequency is <NUM> according to a fourth experimental example of the present invention, and <FIG> is an impedance measurement graph of standard data and experimental data when the frequency is <NUM> according to a fifth experimental example of the present invention.

Referring to <FIG>, when the frequency is <NUM>, the experimental data measured by the second sensor on the complex plane are classified and located in a cluster form of the first experimental data and the second experimental data, based on a pre-obtained first dividing line L1.

Here, the first experimental data is impedance measurement data of four battery cells in which it was determined that lithium was precipitated and the second experimental data is impedance measurement data of four battery cells in which it was determined that lithium was not precipitated.

In other words, it was confirmed that the impedance measurement data of the battery cell had a cluster form depending on whether or not lithium was precipitated.

Thereafter, pre-acquired standard data at a frequency of <NUM> was plotted on the complex plane, and cluster positions of the first experimental data and the second experimental data were compared.

As a result of the comparison, it was confirmed that the first experimental data and the first standard data were clustered in the first quadrant and the second quadrant located on the upper side with respect to the first dividing line L1, and the second experimental data and the second standard data were clustered in the third and fourth quadrants located on the lower side of the first dividing line L1.

Furthermore, referring to <FIG>, pre-acquired standard data at a frequency of <NUM> was plotted on the same complex plane and the first experimental data and the second experimental data were compared.

As a result of the comparison, it was confirmed that the first experimental data and the first standard data were clustered in the third quadrant located on the left side of the second dividing line L2, and the second experimental data and the second standard data were clustered in the first quadrant located on the right side of the second dividing line L2.

Meanwhile, referring to <FIG>, it was confirmed that the first experimental data and the second experimental data on the complex plane at a frequency of <NUM> did not show any clustering.

Accordingly, it can be confirmed that apparatus for inspecting lithium precipitation according to the embodiments and the experimental examples of the present invention is capable of non-destructive inspection of a battery cell for lithium precipitation (lithium plating) within a specific frequency range.

In the above, the apparatus and the method for inspecting lithium precipitation in the battery cell according to embodiments of the present invention have been described.

An apparatus and method for inspecting lithium precipitation according to embodiments of the present invention forms a magnetic field around a battery cell to be inspected to induce an eddy current and compares measured impedance of the battery cell with standard data to detect lithium plating in the battery cell, thereby providing high stability and reliability.

The operations of the method according to the embodiments of the present invention may be implemented as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored. In addition, the computer-readable recording medium may be distributed in a network-connected computer system to store and execute computer-readable programs or codes in a distributed manner.

In addition, the computer-readable recording medium may include a hardware device, such as a ROM, a RAM, and a flash memory, specially configured to store and execute program instructions. The program instructions may include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer by using an interpreter or the like.

Claim 1:
An apparatus for inspecting lithium plating (<NUM>) in at least one battery cell (<NUM>) using eddy current, the apparatus comprising:
an inspection module (<NUM>) including a first sensor (<NUM>) for inducing an eddy current in the at least one battery cell and a second sensor (<NUM>) for measuring impedance of the at least one battery cell in which the eddy current is induced; and
a controller (<NUM>) configured to determine whether or not lithium plating has occurred in the at least one battery cell by comparing a measured value of the impedance measured by the second sensor with standard data;
wherein the first sensor and the second sensor are provided in a form in which a coil is wound around a magnetizing member,
wherein the first sensor induces eddy current in the battery cell by applying an alternating current (AC) of a specific predefined frequency to the coil to form a magnetic field, and
wherein the second sensor measures an impedance at the specific predefined frequency for the at least one battery cell.