Secondary battery and lithium precipitation detection method for the secondary battery

Abstract

The present invention relates to a secondary battery and a lithium precipitation detection method for the secondary battery, and provides a secondary battery, which includes: a positive electrode and a negative electrode; a battery shell that seals the positive electrode and the negative electrode; and a lithium precipitation detection device that is arranged around the positive electrode connector on one side of the battery shell to detect lithium precipitation.

Description

Technical Field

[0001] The present invention relates to a secondary battery and a method for detecting lithium deposition in the secondary battery. Background Art

[0002] Recently, with the popularization of electronic devices such as smartphones, uninterruptible power supplies (UPS), and electric vehicles, as well as the spread of infrastructure for energy storage systems (ESS), research on secondary batteries as power sources has been actively conducted. Such secondary batteries are provided in the form of battery packs including a battery module in which a plurality of battery cells are connected in series and / or in parallel, and a battery management system (BMS) for managing the operation of the battery module.

[0003] In the case of lithium secondary batteries that use lithium ions for redox reactions among various secondary batteries, lithium deposition (lithium dendrite) may occur in the electrodes depending on the use environment of charging and discharging. When lithium deposition occurs, the characteristics of the battery cell may be changed, and therefore, it is necessary to detect early lithium deposition. However, there is no device for detecting lithium deposition in already manufactured battery cells. Summary of the Invention

[0004] Technical issues

[0005] Embodiments of the present invention have been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a secondary battery capable of accurately detecting lithium deposition in the secondary battery and a method for detecting lithium deposition therefor.

[0006] Technical Solution

[0007] In order to solve the above problems, according to one aspect of an embodiment of the present invention, a secondary battery is provided, which includes: a positive electrode and a negative electrode; a battery case configured to seal the positive electrode and the negative electrode; and a lithium precipitation detection device, which is arranged around a joint of the positive electrode at one side of the battery case to detect lithium precipitation.

[0008] According to another feature of this embodiment, the lithium deposition detection device may include a magnetic sensor disposed on a contact region of the positive electrode in the battery housing.

[0009] According to yet another feature of this embodiment, a magnetic sensor may be installed to detect a change in a magnetic field generated between the negative electrode and the positive electrode's joint region and the negative electrode.

[0010] According to still another feature of this embodiment, the magnetic sensor can detect a magnetic field generated by a current flowing from the outer coating portion of the tab region of the positive electrode to the negative electrode.

[0011] According to still another feature of this embodiment, the lithium deposition detection device may include a deformation detection sensor provided on a tab region of the positive electrode in the battery case.

[0012] According to still another feature of this embodiment, the deformation detection sensor may be a strain gauge.

[0013] According to still another feature of this embodiment, the strain gauge may be formed on one side of the surface of the battery case that contacts the positive electrode, or on one side of the surface of the battery case from which the tab extends.

[0014] According to yet another feature of this embodiment, the battery housing may be a flexible pouch.

[0015] In order to solve the above problems, according to another aspect of an embodiment of the present invention, a method for detecting lithium deposition in a secondary battery is provided, in which a positive electrode and a negative electrode are housed in a battery case, the method comprising the following steps: a step of detecting a change in a preset parameter based on a lithium deposition detection device provided around a joint of the positive electrode at one side of the battery case; a step of determining whether the change in the parameter is greater than or equal to a reference value; and a step of determining lithium deposition based on the determined result.

[0016] According to another feature of this embodiment, the lithium deposition detection device may include a magnetic sensor disposed on a tab region of the positive electrode in the battery housing, and in the step of detecting a change in a parameter, a change in a magnetic field measured by the magnetic sensor is detected.

[0017] According to another feature of this embodiment, the lithium precipitation detection device may include a deformation detection sensor arranged on the joint area of the positive electrode in the battery casing, and in the step of detecting the change of the parameter, the deformation of the battery casing as a flexible bag measured by the deformation detection sensor is detected.

[0018] Beneficial effects

[0019] According to the secondary battery having the above-described configuration and the method for detecting lithium deposition of the secondary battery, lithium deposition can be detected in the secondary battery in a sealed state. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram illustrating an electrode assembly of a secondary battery.

[0021] Figure 2 This is an assembly diagram of a pouch-type secondary battery.

[0022] Figure 3 This is a conceptual diagram of a secondary battery for explaining the shape of lithium deposition.

[0023] Figure 4This is a conceptual cross-sectional view of a secondary battery for explaining the effect of lithium deposition.

[0024] Figure 5 is a diagram illustrating a configuration of a secondary battery according to an embodiment of the present inventive concept.

[0025] Figure 6 is a conceptual cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0026] Figure 7 is a diagram illustrating a battery pack to which a secondary battery is applied according to an embodiment of the present invention.

[0027] Figure 8 This is an example for detecting Figure 7 Flowchart of a method for lithium deposition in a secondary battery.

[0028] Figure 9 is a diagram illustrating a configuration of a secondary battery according to another embodiment of the present inventive concept.

[0029] Figure 10 This is an example for detecting Figure 9 Flowchart of a method for lithium deposition in a secondary battery.

[0030] Figure 11 is a diagram illustrating a configuration of a secondary battery according to still another embodiment of the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, various embodiments will be described in detail with reference to the accompanying drawings. In this document, the same reference numerals are used for the same components in the drawings, and repeated description of the same components will be omitted.

[0032] For the various embodiments of the present invention disclosed in this document, specific structural or functional descriptions have been illustrated only for the purpose of describing the embodiments of the present invention, and the various embodiments of the present invention may be implemented in various forms and should not be construed as limited to the embodiments described in this document.

[0033] Expressions such as "first," "second," "firstly," or "secondly" used in various embodiments may modify various elements regardless of their order and / or importance, and may not limit the corresponding elements. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component, without departing from the scope of the present invention.

[0034] The terms used in this document are for describing particular embodiments only and may not be intended to limit the scope of other embodiments.Unless mentioned otherwise, terms in the singular may include plural forms.

[0035] Figure 1 1 is a schematic diagram illustrating an electrode assembly 10 of a secondary battery. In an embodiment of the present invention, a case where a lithium secondary battery is used as the secondary battery will be described.

[0036] In the electrode assembly 10 according to the embodiment of the present invention, first, a slurry in which a positive electrode active material 1012, a binder, and a conductive agent are mixed is applied to the positive electrode current collector 1011, and a slurry in which a negative electrode active material 1022, a binder, and a conductive agent are mixed is applied to the negative electrode current collector 1021 to manufacture a positive electrode (cathode cathode) 101 and a negative electrode (anode) 102. In addition, a unit cell is formed by stacking the manufactured positive electrode 101 and negative electrode 102 (with a separator 103 between the positive electrode 101 and the negative electrode 102). Again, as Figure 1 As shown, unit cells are stacked on each other to form an electrode assembly 10 having a predetermined shape.

[0037] The positive electrode 101 and the negative electrode 102 used in the present invention are not particularly limited to both electrodes 101 and 102, and therefore can be manufactured in a shape in which electrode active materials 1012 and 1022 are joined to electrode current collectors 1011 and 1021 according to conventional methods known in the art. Here, for example, the positive electrode 101 can be manufactured by applying a slurry in which the positive electrode active material 1012, a conductive agent, and a binder are mixed to the positive electrode current collector 1011 and then drying and pressing the slurry. At this time, if necessary, the slurry may further include a filler. The positive electrode 101 can be manufactured in a sheet shape and then mounted on a roll.

[0038] The positive electrode current collector 1011 typically has a thickness of 3 μm to 500 μm. The positive electrode current collector 1011 is typically made of a material having high electrical conductivity without causing chemical changes. This material may be surface-treated with, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel having carbon, nickel, titanium, silver, or the like surface-treated on its surface, but is not limited thereto. In addition, the positive electrode current collector 1011 may have fine concave and convex portions formed on the surface of the positive electrode current collector 1011 to increase the adhesion of the positive electrode active material 1012. In addition, the positive electrode current collector 1011 may have various shapes such as a film, a sheet, a foil, a mesh, a porous body, a foam, or a non-woven fabric.

[0039] The positive electrode active material 1012 may include a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a substituted compound having one or more transition metals; such as Li1+ x Mn 2-xLithium manganese oxides such as LiMnO4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, etc.; 1-x M x Ni-type lithium nickel oxide represented by the chemical formula of LiMn O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); 2-x M x A lithium manganese composite oxide represented by LiMnO2 (M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3Mo8 (M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li is substituted with alkaline earth ions; a disulfide compound; Fe2(MoO4)3, etc. However, this embodiment is not limited thereto.

[0040] The conductive agent can be added in an amount of 1 wt% to about 50 wt% based on the total weight of the mixture including the positive electrode active material 1012. The conductive agent is generally made of a material that has electrical conductivity without causing chemical changes. The conductive agent may include, for example, conductive materials such as: graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, Ketjen black, furnace black, channel black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; or polyphenylene derivatives.

[0041] The binder may be a component that facilitates bonding of the active material to the conductive agent and to the current collector, and may be generally added at 1 wt % to 50 wt % based on the total weight of the mixture including the positive electrode active material 1012. Examples of the binder may include polyvinyl fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0042] A filler may optionally be used as a component to suppress expansion of the positive electrode 101. Furthermore, a general filler may be used if the filler is a fibrous material that does not cause chemical changes. Examples of fillers include olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fiber and carbon fiber.

[0043] For example, the negative electrode 102 can be manufactured by coating the negative electrode current collector 1021 with the negative electrode active material 1022 and then drying and pressing the negative electrode active material 1022. If necessary, the negative electrode active material 1022 can optionally include a conductive agent, a binder, a filler, etc. The negative electrode 102 can be manufactured in a sheet form and mounted on a roll.

[0044] The negative electrode current collector 1021 generally has a thickness of 3 μm to 500 μm. The negative electrode current collector 1021 is generally made of a material having conductivity without causing a chemical change. Examples of the material include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel having a surface treatment of carbon, nickel, titanium, silver, etc. on its surface, or an aluminum-cadmium alloy. In addition, the negative electrode current collector 1021 can form fine irregularities on the surface of the negative electrode current collector 1021 to increase the bonding force of the negative electrode active material 1022. Further, the negative electrode current collector 1021 can have various shapes such as a film, a sheet, a foil, a net, a porous body, a foam, or a non-woven fabric.

[0045] The negative electrode active material 1022 can include, for example: carbon such as non-graphitized carbon, graphite-based carbon, etc.; metal composite oxides such as LixFe2O3 (0 ≤ x ≤ 1), LixWO2 (0 ≤ x ≤ 1), SnxMe1-xMe’yOz (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, elements in the first group, second group and third group found in the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc.; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, etc.; conductive polymers such as polyacetylene, etc.; Li-Co-Ni-based materials, etc.

[0046] Generally, a known polyolefin-based separator or a composite separator in which an organic composite layer or an inorganic composite layer is formed on an olefin-based material can be used as the separator for insulating the electrodes 101 and 102 between the positive electrode 101 and the negative electrode 102, but it is not limited thereto.

[0047] According to an embodiment of the present invention, the electrode assembly 10 having the above structure is accommodated in the battery case 13, and then, an electrolyte is injected to manufacture the secondary battery 1.

[0048] Figure 2 It is an assembly drawing of a pouch-type secondary battery.

[0049] In the process of manufacturing the pouch-type secondary battery 1, as described above, after the electrode assembly 10 is formed, the electrode assembly 10 is inserted into the battery case 13 and sealed after the electrolyte is injected.

[0050] like Figure 2 As shown, the electrode assembly 10 includes an electrode tab 11. The electrode tabs 11 are respectively connected to the positive electrode 101 and the negative electrode 102 of the electrode assembly 10 to protrude to the outside of the electrode assembly 10, thereby providing a path for electrons to move between the inside and the outside of the electrode assembly 10. The electrode current collectors 1011 and 1021 of the electrode assembly 10 may include active material coated portions coated with electrode active materials 1012 and 1022, respectively, and active material uncoated portions not coated with electrode active materials 1012 and 1022. In addition, each electrode tab 11 may be formed by cutting the active material uncoated portion or by connecting a separate conductive member to the active material uncoated portion via ultrasonic welding. As shown Figure 2 As shown, the electrode tabs 11 may protrude in the same direction from one side of the electrode assembly 10, but the present invention is not limited thereto. For example, the electrode tabs 11 may protrude in different directions from each other.

[0051] In the electrode assembly 10, the electrode lead 12 is connected to the electrode tab 11 by spot welding. In addition, a portion of the electrode lead 12 is surrounded by an insulating portion 14. The insulating portion 14 can be configured to be confined within a sealing portion 134, where the upper shell 131 and the lower shell 132 of the battery case 13 are heat-fused so that the electrode lead 12 is joined to the battery case 13. In addition, the electricity generated from the electrode assembly 10 can be prevented from flowing to the battery case 13 through the electrode lead 12, and the sealing of the battery case 13 can be maintained. Therefore, the insulating portion 14 can be made of a non-conductive non-conductor having non-conductivity. Generally, although an insulating tape that is easily attached to the electrode lead 12 and has a relatively thin thickness is mainly used as the insulating portion 14, the present invention is not limited thereto. For example, various components can be used as the insulating portion 14 as long as the component can insulate the electrode lead 12.

[0052] Depending on the formation position of the positive electrode tab 111 and the negative electrode tab 112, the electrode lead 12 may extend in the same direction or in directions different from each other. The positive lead 121 and the negative electrode lead 122 may be made of materials different from each other. That is, the positive electrode lead 121 may be made of the same material as the positive current collector 1011 (i.e., aluminum (Al) material), and the negative electrode lead 122 may be made of the same material as the negative current collector 1021 (i.e., copper (Cu) material or copper material coated with nickel (Ni)). In addition, the portion of the electrode lead 12 protruding to the outside of the battery case 13 may be provided as a terminal portion and electrically connected to an external terminal.

[0053] In the pouch-type secondary battery 1 according to an embodiment of the present invention, the battery case 13 may be a bag made of a flexible material. Hereinafter, a case where the battery case 13 is a pouch-type will be described. The battery case 13 accommodates the electrode assembly 10 in a manner that exposes a portion of the electrode lead 12 (i.e., the terminal portion) and is then sealed. Figure 2 As shown, the battery case 13 includes an upper case 131 and a lower case 132. A cup portion 133 having an accommodation space 1331 for accommodating the electrode assembly 10 is formed in the lower case 132, and the upper case 131 covers the upper portion of the accommodation space 1331 to prevent the electrode assembly 10 from being separated to the outside of the battery case 13. Figure 2 As shown, one side of the upper housing 131 and one side of the lower housing 132 may be connected to each other. However, the present invention is not limited thereto. For example, the upper housing 131 and the lower housing 132 may be manufactured separately in a manner of being separated from each other.

[0054] When the electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 and the insulating portion 14 is provided on a portion of the electrode lead 12, the electrode assembly 10 can be accommodated in the accommodation space 1331 provided in the lower case 132, and the upper case 131 can cover the upper side of the accommodation space 1331. In addition, when the electrolyte is injected and the sealing portion formed on the edge of each of the upper case 131 and the lower case 132 is sealed, the secondary battery 1 is manufactured.

[0055] Figure 3 This is a conceptual diagram of the secondary battery 1 for explaining the shape of lithium deposition. Figure 3 The shape when viewed in the direction in which the positive electrode 101 and the negative electrode 102 are stacked is illustrated.

[0056] Figure 3 (a) illustrates the shape of the secondary battery 1 in a normal state. The positive electrode tab 111 extends from the positive electrode 101 to expose the positive electrode lead 121 to the outside of the battery case 13. In addition, the negative electrode tab 112 extends from the negative electrode 102 on the opposite side through the separator 103 to expose the negative electrode lead 122 to the outside of the battery case 13. Here, under normal circumstances, the coating material is not applied to the connection portion connecting the positive electrode active material 1012 to the positive electrode tab 111 (i.e., the neck portion of the positive electrode tab 111).

[0057] However, due to manufacturing process reasons, there is a case where the area where the coating material is applied extends beyond the neck portion of the positive electrode tab 111 . Figure 3 (b) illustrates a shape in which the coating material is externally applied to the positive electrode tab 111 .

[0058] As described above, when the coating material is externally applied to the neck portion of the positive electrode tab 111 , the following phenomenon occurs.

[0059] Figure 4 This is a conceptual cross-sectional view of a secondary battery for explaining the effect of lithium deposition. Figure 4 The case of charging a secondary battery is illustrated.

[0060] Figure 4 (a) is a conceptual diagram showing the case where lithium precipitation occurs in the thickness direction of the positive electrode 101. Even when lithium precipitation occurs in the thickness direction, a height reversal of approximately 0.1 mm or less occurs between the positive electrode 101 and the negative electrode 102. In addition, lithium ions generated in the positive electrode 101 at a higher position than the negative electrode 102 move to the area closest to the negative electrode 102 (the portion illustrated as a rectangular shape on the surface of the negative electrode active material 1022). In other words, the current density in the corresponding area increases.

[0061] Figure 4 (b) conceptually illustrates the case where lithium precipitation occurs in the surface direction of the positive electrode 101. Even when lithium precipitation occurs in the surface direction, a reversal of a height of about 0.2 mm or more occurs between the positive electrode 101 and the negative electrode 102. Moreover, the lithium ions generated in the positive electrode 101 at a higher position than the negative electrode 102 move to the area closest to the negative electrode 102 (the portion illustrated in a rectangular shape on the surface of the negative electrode active material 1022). That is, the current density in the corresponding area increases. Here, Figure 4 The situation described in (a) is different. Figure 4 When lithium deposition occurs in the plane direction as shown in (b), lithium ions during charge move to the side surfaces of the negative electrode active material 1022 and the surface of the negative electrode active material 1022 .

[0062] That is to say, if Figure 4 As shown in (a) and (b), when lithium deposition occurs due to the use of the secondary battery 1, it can be seen that the current density in a local area inside the secondary battery 1 changes abnormally compared to the normal state. Therefore, in the embodiment of the present invention, the change in current density can be detected by a very simple configuration as described above to detect the occurrence of lithium deposition.

[0063] Figure 5 is a diagram illustrating a configuration of a secondary battery 1 according to an embodiment of the present inventive concept. Figure 5 (a) illustrates the shape when viewed in the direction in which the positive electrode 101 and the negative electrode 102 are stacked, and Figure 5 (b) illustrates the shape when viewed in a direction perpendicular to the direction in which the positive electrode 101 and the negative electrode 102 are stacked (side surface of the secondary battery 1 ).

[0064] Reference Figure 5(a) and (b), the magnetic sensor 20 as a lithium precipitation device for detecting lithium precipitation is installed on one side of the battery case 13 that accommodates the positive electrode 101 and the negative electrode 102, and then sealed. The magnetic sensor 20 is arranged around the positive electrode connector 111 on the side of the battery case 13 where lithium precipitation occurs. Preferably, when viewed in the direction of stacking the positive electrode 101 and the negative electrode 102, the magnetic sensor 20 is arranged on the upper end of the positive electrode connector 111. That is, the magnetic sensor 20 is set to be arranged in the upper end area of the positive electrode connector 111 which is the surface of the battery case 13. Although not shown, the magnetic sensor 20 can be connected to the outside by wire or wirelessly to send the measured magnetic field value to the outside.

[0065] As described above, the magnetic sensor 20 is installed to detect the magnetic field and changes in the magnetic field generated by the current between the positive electrode 101 and the negative electrode 102. Specifically, the magnetic sensor 20 can detect the magnetic field generated by the current flowing from the over-coated portion to the negative electrode 102 at the joint area of the positive electrode 101.

[0066] Figure 6 is a conceptual cross-sectional view of a secondary battery 1 according to an embodiment of the present invention. Figure 6 Conceptually illustrates the Figure 4 The cross-sectional view of FIG. 1 shows a case where a magnetic sensor 20 is provided as a lithium deposition device.

[0067] If you can Figure 6 As shown in (a) and (b), the magnetic sensor 20 can be configured to be arranged in the upper end area of the positive terminal 111 as the surface of the battery case 13 to detect changes in the magnetic field caused by the current density changing due to lithium deposition. That is, in addition to the current between the positive electrode 101 and the negative electrode 102 when the magnetic sensor 20 is charged, the magnetic field generated by the current generated between the lithium deposition and the negative electrode 102 is measured. In addition, by comparing the magnetic field measured when lithium deposition occurs with the magnetic field measured when lithium deposition does not occur, the magnetic sensor 20 can detect the occurrence of lithium deposition.

[0068] Figure 7 is a diagram illustrating a battery pack 2 to which a secondary battery is applied according to an embodiment of the present invention.

[0069] The battery pack 2 may be used in the form of a battery pack for an electric vehicle or a battery rack for an energy storage device.

[0070] Reference Figure 7 The battery pack 2 may include a battery module 200 , a battery management system 210 (hereinafter referred to as “BMS”), a switch unit 220 , and the like.

[0071] The battery module 200 includes one or more chargeable and dischargeable battery cells 201. The battery module 200 may include a combination of multiple battery cells 201 connected in series and / or in parallel. According to an embodiment of the present invention, the battery cell 201 may be the secondary battery 1 described above. The battery cell 201 may be a lithium-ion (Li-ion) battery, a lithium-ion polymer (Li-ion polymer) battery, or the like.

[0072] BMS210 can control the operation of the switch unit 220 to control the charging and discharging of the battery module 200. In addition, BMS210 can monitor the voltage, current, temperature, etc. of the battery module 200 and / or each battery cell 201 included in the battery module 200. In addition, in order to monitor by BMS210, sensors or various measurement modules (not shown) can be additionally installed at any location such as the battery module 200, the charging / discharging path or the battery pack 2. BMS210 can calculate parameters representing the state of the battery module 200 (e.g., SOC or SOH) based on the monitored measurement values (such as voltage, current and temperature). In addition, BMS210 can send the calculated various data to an external device (e.g., a host controller) through a communication device.

[0073] The BMS 210 controls and manages the overall operation of the battery pack 2. To this end, the BMS 210 may include various components, for example, a MICOM as a controller that executes programs and controls the overall operation of the BMS 210, a memory that stores computer programs required for the operation of the BMS 210, input / output devices such as sensors or measuring devices, a communication device for communicating with external devices, and other peripheral circuits.

[0074] In the battery pack 2 according to an embodiment of the present invention, the battery cell 201 includes a magnetic sensor 20 as a means for detecting lithium precipitation. Therefore, the BMS 210 can receive the magnetic field value measured by the magnetic sensor 20 by wire and / or wirelessly to determine whether the magnetic field has changed due to lithium precipitation, and if there is a change, determine whether the change is equal to or greater than a reference value.

[0075] If the magnetic field received from the magnetic sensor 20 is determined to have changed, and the change in the magnetic field is equal to or greater than the reference value, the BMS 210 determines that the use of the battery cell 201 is unsuitable due to lithium deposition. In this case, the BMS 210 may stop the operation of the battery pack 2 or notify the host controller of the fact that lithium deposition has occurred in the corresponding battery cell 201.

[0076] Figure 8 This is an example for detecting Figure 7 Flowchart of a method for lithium deposition in a secondary battery 1.

[0077] Reference Figure 8 When the battery pack 2 is driven (S1), charging and discharging are performed in the individual battery cells 201. Here, as described above, if lithium deposition occurs during charging and discharging, the current density changes compared to a case where lithium deposition does not occur, and as a result, the magnetic field generated around it also changes. Therefore, the magnetic field is measured based on the magnetic sensor installed on the battery cell 201 to monitor lithium deposition (S2). In other words, the change in the magnetic field is detected as a parameter for detecting lithium deposition.

[0078] Based on the monitoring result, it is determined whether the magnetic field between the positive and negative electrodes has changed (S3). If it is determined that the magnetic field has not changed ("No" in step S3), the process proceeds to step S6, and if the magnetic field has changed ("Yes" in step S3), it is determined whether the change is equal to or greater than the reference value (S4).

[0079] When the magnetic field change is greater than or equal to the reference value, it is determined that lithium deposition has occurred ("Yes" in step S4), and the fact that lithium deposition has occurred is notified to the outside (S5). Of course, the driving of the battery pack 2 or only the operation of the battery cell 201 can be stopped without notifying the outside of the fact that lithium deposition has occurred.

[0080] Thereafter, it is determined whether the driving of the battery pack 2 is ended (S6), and when the driving of the battery pack 2 is stopped due to lithium deposition, or when the use of the battery pack 2 itself is ended, the process for monitoring lithium deposition is ended, and if not, the process returns to step S2 to repeat the above process.

[0081] As described above, based on the secondary battery 1 and the battery pack 2 including the secondary battery 1 according to the embodiment of the present invention, lithium deposition can be accurately detected even in a secondary battery sealed by a battery case.

[0082] Figure 9 is a diagram illustrating a configuration of a secondary battery 1 according to another embodiment of the present inventive concept. Figure 9 (a) illustrates the shape when viewed in the direction in which the positive electrode 101 and the negative electrode 102 are stacked. Figure 9 (b) illustrates the shape when viewed in a direction perpendicular to the direction in which the positive electrode 101 and the negative electrode 102 are stacked (side surface of the secondary battery 1 ).

[0083] Reference Figure 9In (a) and (b), a deformation detection sensor 30 as a lithium deposition device for detecting lithium deposition is installed on one side of the battery case 13 that houses the positive electrode 101 and the negative electrode 102, and then sealed. A strain gauge can be used as the deformation detection sensor 30. The deformation detection sensor 30 is arranged around the positive electrode tab 111 on the side of the battery case 13 where lithium deposition occurs. Preferably, when viewed in the direction of stacking the positive electrode 101 and the negative electrode 102, the magnetic sensor 20 can be arranged on the upper end of the positive electrode tab 111. Alternatively, the deformation detection sensor 30 can be arranged on the upper end of the connection portion between the positive electrode 101 and the positive electrode tab 111 of the battery case 13. With reference to the battery case 13 as a reference, among the several surfaces of the battery case 13, the deformation detection sensor 30 can be installed on at least one of the side surfaces from which the positive electrode tab 111 extends or the side surfaces that are in contact with the positive electrode 101 of the battery case 13 (facing the positive electrode 101 of the battery case 13). Although not shown, the deformation detecting sensor 30 may be connected to the outside by wire or wirelessly to transmit the measured magnetic field value to the outside.

[0084] exist Figure 9 In the embodiment, the first deformation detection sensor 31 is formed on one side of the surface of the battery case 13 from which the positive terminal 111 extends. In addition, the second deformation detection sensor 32 is formed on the side of the battery case 13 facing the positive electrode 101. Figure 9 , the first deformation detection sensor 31 and the second deformation detection sensor 32 are exemplified, but only one sensor may be formed.

[0085] As described above, the deformation detection sensor 30 is disposed around the positive electrode tab 111. When lithium deposition occurs, the hardness of the electrode surface changes, and this change in hardness can be detected in the battery housing 13. Therefore, the deformation detection sensor 30 can be installed in an appropriate location to detect lithium deposition. However, in this embodiment, since deformation of the battery housing 13 caused by lithium deposition is detected, the battery housing 13 is preferably a flexible bag.

[0086] Figure 10 This is an example for detecting Figure 9 Flowchart of a method for lithium deposition in a secondary battery.

[0087] Reference Figure 10When the battery pack 2 is driven (S11), charging and discharging are performed in the individual battery cells 201. Here, as described above, if lithium precipitation occurs during charging and discharging, the hardness of the electrode changes compared to a case where lithium precipitation does not occur, and therefore, the battery case 13 surrounding the electrode may be deformed. Therefore, deformation is measured based on a deformation detection sensor installed on the battery cell 201 to monitor lithium precipitation (S12). That is, the deformation of the battery case 13 is detected as a parameter for detecting lithium precipitation.

[0088] Based on the monitored result, it is determined whether the displacement of the battery case 13 has occurred (S13). If it is determined that the displacement has not occurred (i.e., there is no deformation) ("No" in step S13), the process proceeds to step S16, and if the deformation has occurred ("Yes" in step S13), it is determined whether the displacement is equal to or greater than the reference value (S14).

[0089] When the displacement is greater than or equal to the reference value, it is determined that lithium deposition has occurred ("Yes" in step S14), and the fact that lithium deposition has occurred is notified to the outside (S15). Of course, the driving of the battery pack 2 or only the operation of the battery cell 201 may be stopped without notifying the outside of the fact that lithium deposition has occurred.

[0090] Thereafter, it is determined whether the driving of the battery pack 2 is ended (S16), and when the driving of the battery pack 2 is stopped due to lithium deposition, or when the use of the battery pack 2 itself is ended, the process for monitoring lithium deposition is ended, and if not, the processing returns to step S12 to repeat the above processing.

[0091] As described above, based on the secondary battery 1 and the battery pack 2 including the secondary battery 1 according to the embodiment of the present invention, lithium deposition can be accurately detected even in a secondary battery sealed by a battery case.

[0092] Figure 11 is a diagram illustrating a configuration of a secondary battery according to still another embodiment of the present invention.

[0093] In this embodiment, the magnetic sensor 20 and the deformation detection sensor 30 are simultaneously formed into a lithium deposition detection device. As described above, when compared with the method using only the magnetic sensor 20 Figure 5 secondary battery or using only the deformation detection sensor 30 Figure 9 When compared with secondary batteries, lithium deposition can be detected more accurately.

[0094] Unless otherwise specified, the terms "include", "comprising" and "having" described above mean that the corresponding components may exist and should be interpreted as being able to further include other components without excluding other components. Unless otherwise defined, all terms including technical terms or scientific terms may be interpreted as having the same meaning as that generally understood by those of ordinary skill in the art. Terms such as terms that are commonly used and already in dictionaries should be interpreted as having meanings that match the contextual meanings in the art. In this specification, unless clearly defined, terms are not ideally interpreted as formal meanings.

[0095] The subject matter disclosed above should be considered as illustrative rather than restrictive, and the appended claims are intended to cover all such modifications, enhancements and other embodiments that fall within the true spirit and scope of the present disclosure. Therefore, the embodiments of the present disclosure are considered to be illustrative rather than restrictive, and the technical spirit of the present disclosure is not limited to the aforementioned embodiments. Therefore, the scope of the present invention is not limited by the detailed description of the present invention but by the appended claims, and all differences within the scope will be interpreted as included in the present invention.

[0096] CROSS-REFERENCE TO RELATED APPLICATIONS

[0097] This application claims priority from Korean Patent Application No. 10-2020-0030312 filed on March 11, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

Claims

1. A secondary battery, comprising: an electrode assembly, the electrode assembly comprising a positive electrode and a negative electrode; a battery housing configured to seal the positive electrode and the negative electrode; as well as a lithium precipitation detection device, the lithium precipitation detection device being provided around the connector of the positive electrode at one side of the battery housing to detect lithium precipitation, the connector of the positive electrode protruding to the outside of the electrode assembly, The lithium deposition detection device includes a magnetic sensor disposed on a joint region of the positive electrode in the battery housing.

2. The secondary battery according to claim 1, wherein The magnetic sensor is installed to detect a change in a magnetic field generated between the joint regions of the negative electrode and the positive electrode.

3. The secondary battery according to claim 1, wherein The magnetic sensor detects a magnetic field generated by a current flowing from an overcoated portion of the tab region of the positive electrode to the negative electrode.

4. The secondary battery according to claim 1, wherein The lithium deposition detection device includes a deformation detection sensor provided on a tab region of the positive electrode in the battery case.

5. The secondary battery according to claim 4, wherein The deformation detection sensor is a strain gauge.

6. The secondary battery according to claim 5, wherein The strain gauge is formed on one side of a surface of the battery case that contacts the positive electrode, or on one side of a surface of the battery case from which the tab extends.

7. The secondary battery according to claim 4, wherein The battery housing is a flexible bag.

8. A method for detecting lithium deposition in a secondary battery, wherein an electrode assembly including a positive electrode and a negative electrode is housed in a battery case, the method comprising the following steps: a step of detecting a change in a preset parameter based on a lithium deposition detection device provided around a joint of the positive electrode at one side of the battery housing, the joint of the positive electrode protruding outside the electrode assembly; a step of determining whether a change in the preset parameter is greater than or equal to a reference value; as well as determining a step of lithium precipitation based on the determined result, The lithium deposition detection device includes a magnetic sensor disposed on a joint region of the positive electrode in the battery housing.

9. The method according to claim 8, wherein In the step of determining the change of the preset parameter, when the change of the preset parameter is greater than or equal to the reference value, it is determined that the lithium precipitation occurs.

10. The method according to claim 8, wherein In the step of detecting the change of the preset parameter, the change of the magnetic field measured by the magnetic sensor is detected.

11. The method according to claim 8, wherein The lithium precipitation detection device includes a deformation detection sensor provided on the joint area of the positive electrode in the battery housing, and In the step of detecting the change in the preset parameter, deformation of the battery case as a flexible bag measured by the deformation detection sensor is detected.

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