Battery pack and vehicle including the battery pack

Abstract

A battery pack according to an embodiment of the present disclosure includes at least one battery cell including a positive electrode, a separator, and a negative electrode including a negative electrode active material having at least a portion of silicon oxide; a module housing configured to accommodate the at least one battery cell therein; and a pressurizing unit configured to elastically pressurize the battery cell to prevent a volumetric change of the battery cell when the battery cell is charged or discharged, the pressurizing unit having a pressure for pressing the battery cell set according to a content of the silicon oxide relative to a total weight of the negative electrode active material.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0146721, filed on October 29, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present disclosure relates to a battery pack and a vehicle including the battery pack, and more particularly to a battery pack and a vehicle including the battery pack that effectively suppresses the swelling phenomenon of battery cells provided in the battery pack and improves the cycle life characteristics of the battery cells. [Background technology]

[0003] Currently, commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Lithium secondary batteries have almost no memory effect compared to nickel-based secondary batteries and can be charged and discharged freely. Lithium secondary batteries are also attracting attention due to their extremely low self-discharge rate and high energy density.

[0004] Lithium secondary batteries mainly use lithium-based oxides and carbon materials as the positive and negative electrode active materials, respectively, and include an electrode assembly in which a separator is sandwiched between positive and negative electrode plates coated with the positive and negative electrode active materials, and an exterior material that hermetically houses the electrode assembly together with an electrolyte.

[0005] Generally, lithium secondary batteries are divided into can-type secondary batteries and pouch-type secondary batteries depending on the type of exterior material. Can-type secondary batteries have an electrode assembly built into a metal can. Pouch-type secondary batteries have an electrode assembly built into a pouch made of an aluminum laminate sheet.

[0006] Recently, secondary batteries have been widely used not only in small devices such as portable electronic devices but also in medium-sized and large devices such as automobiles and power storage devices. At least one battery pack is typically installed in such medium-sized and large devices. To increase the capacity and output of such battery packs, multiple battery cells may be housed inside a pack housing. For example, pouch-type secondary battery cells, which are easy to stack, are often used in such medium-sized and large devices. Here, a pouch-type battery cell refers to a secondary battery in which an electrode assembly is housed in a pouch made of a flexible polymer material with an irregular shape.

[0007] Meanwhile, in the case of battery cells in a battery pack, a swelling phenomenon occurs in which the battery cells swell during repeated charging and discharging. In consideration of this swelling phenomenon that occurs during charging and discharging, when stacking battery cells in a conventional battery pack, the battery cells are spaced apart at a certain distance. In addition, in the conventional technology, a method of pressurizing the battery cells to suppress gas generation has been used to suppress the swelling phenomenon of the battery cells.

[0008] However, if the swelling of the battery cell becomes severe, the internal pressure of the battery cell may increase, causing the cell casing of the battery cell to burst, resulting in the internal components of the battery cell leaking out, or the battery cell exploding. Therefore, it is very important to suppress the swelling of the battery cell included in the battery pack in order to increase the life and stability of the battery pack.

[0009] However, conventional methods for controlling the swelling phenomenon of battery cells have only involved applying a uniform pressure to the battery cells using a pressure member without considering the characteristics of the battery cells, which has resulted in significant limitations in controlling the swelling phenomenon in accordance with the characteristics of the battery cells. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Korean Patent Application Publication No. 10-2020-0040975 [Patent Document 2] Japanese Patent Application Publication No. 2019-091630 [Patent Document 3] Korean Patent Application Publication No. 10-2018-0026210 [Patent Document 4] Korean Patent Application Publication No. 10-2020-0058248 Summary of the Invention [Problem to be solved by the invention]

[0011] The present disclosure provides a battery pack and a vehicle including the battery pack in which the cycle life characteristics of the battery cells are improved by effectively suppressing the swelling phenomenon of the battery cells provided in the battery pack. [Means for solving the problem]

[0012] According to one aspect of the present disclosure, there is provided a module housing configured to accommodate the at least one battery cell including a positive electrode, a separator, and a negative electrode including a negative electrode active material having at least a portion of silicon oxide; and a pressurizing unit configured to elastically pressurize the battery cell to prevent a volumetric change of the battery cell during charging and discharging of the battery cell, the pressurizing unit having a pressure that pressurizes the battery cell according to a content of the silicon oxide relative to a total weight of the negative electrode active material.

[0013] In an embodiment, the pressure unit may include an elastic member configured to apply pressure in a direction opposite to a direction in which the battery cell expands in volume.

[0014] In another embodiment, the battery cell may include two or more battery cells, and may further include a buffer pad interposed between the two or more battery cells and configured to buffer volume expansion of the battery cells.

[0015] In yet another embodiment, the battery management system includes: at least one battery cell including a positive electrode, a separator, and a negative electrode including a negative electrode active material having at least a portion of silicon oxide; a module housing configured to accommodate the at least one battery cell; a pressurizing unit configured to elastically pressurize the battery cell to prevent a volume change of the battery cell when the battery cell is charged or discharged; a sensor unit configured to acquire information about the battery cell; and a battery management system that controls the pressurizing unit to increase or decrease the pressurizing force of the pressurizing unit based on the information about the battery cell acquired by the sensor unit.

[0016] In yet another embodiment, the information about the battery cell acquired by the sensor unit may include at least one of state information of the battery cell's SoH (state of health), charge / discharge cycles, and volume expansion coefficient.

[0017] In yet another embodiment, the acquired status information of the battery cell is a charge / discharge cycle, and the battery management system may be configured to increase the pressure of the pressure unit as the charge / discharge cycle increases.

[0018] In yet another embodiment, the pressure applying unit further includes an electric cylinder having a cylinder shaft and an elastic member, and the cylinder shaft can be configured to move forward toward the battery cell to apply pressure to the elastic member or move backward in the opposite direction to the direction toward the battery cell to release the pressure on the elastic member, depending on the battery management system.

[0019] In yet another embodiment, the battery management system may further include a pressure sensor configured to sense a pressure applied to the battery cell by the elastic member, and may be configured to increase or decrease the pressure of the pressure unit according to the pressure measured by the pressure sensor.

[0020] According to yet another aspect, the module housing includes a movable outer wall that supports the pressure unit and is configured to be movable in a direction toward the battery cell or in a direction opposite to the direction toward the battery cell, and the pressure unit further includes an electric cylinder having a cylinder shaft connected to the movable outer wall, and an elastic member interposed between the battery cell and the movable outer wall, the electric cylinder being located outside the module housing, and the cylinder shaft of the electric cylinder being configured to press the movable outer wall so that the movable outer wall moves toward the battery cell or in a direction opposite to the direction toward the battery cell.

[0021] Meanwhile, according to another aspect of the present disclosure, a vehicle includes at least one battery pack. [Effects of the Invention]

[0022] The battery pack of the present disclosure includes a pressurizing unit configured to elastically pressurize the battery cell to prevent volumetric changes of the battery cell during charging and discharging, and the pressurizing unit has a pressure setting that applies pressure to the battery cell depending on the silicon oxide content relative to the total weight of the negative electrode active material of the negative electrode, thereby controlling swelling in accordance with the swelling characteristics of the battery cell. That is, the inventors of the present disclosure discovered that volumetric changes during charging and discharging of a battery cell vary depending on the silicon oxide content of the negative electrode active material of the battery cell. Therefore, the inventors of the present disclosure invented a battery pack including a pressurizing unit that applies pressure to the battery cell depending on the silicon oxide content of the negative electrode active material of the battery cell to control swelling of the battery cell mounted in a module housing. Therefore, the battery pack of the present disclosure can effectively control swelling of the battery cell and improve the life and stability of the battery pack.

[0023] That is, the battery pack of the present disclosure includes a pressure unit in which the pressure is set in consideration of the swelling phenomenon of the battery cell due to the content of the negative electrode active material in the negative electrode, so that the battery cell is not pressurized with unnecessary excessive force. Conversely, when the swelling phenomenon is large, the amount of gas generated inside the battery cell can be effectively reduced by using the pressure unit set to a larger pressure. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view schematically illustrating a battery pack according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a side view schematically illustrating a battery cell of the battery pack according to the embodiment of the present disclosure. [Figure 3] 1 is an exploded perspective view schematically illustrating a configuration of a battery cell of a battery pack according to an embodiment of the present disclosure. FIG. [Figure 4]FIG. 2 is an exploded perspective view schematically illustrating a positive electrode, a separator, and a negative electrode of a battery cell of a battery pack according to an embodiment of the present disclosure. [Figure 5] 2 is a vertical cross-sectional view schematically showing the battery pack of FIG. 1 taken along line AA'. FIG. [Figure 6] FIG. 10 is a vertical cross-sectional view schematically illustrating a battery pack according to another embodiment of the present disclosure. [Figure 7] FIG. 1 is a conceptual diagram illustrating a battery pack according to an embodiment of the present disclosure. [Figure 8] FIG. 10 is a vertical cross-sectional view schematically illustrating a battery pack according to still another embodiment of the present disclosure. [Figure 9] FIG. 10 is a vertical cross-sectional view schematically illustrating a battery pack according to still another embodiment of the present disclosure. [Figure 10] 1 is a schematic diagram illustrating an automobile according to an embodiment of the present disclosure; [Figure 11] 1 is a graph showing the change in capacity retention rate and thickness due to charge / discharge cycles of a battery cell according to Example 1 of the present disclosure. [Figure 12] 1 is a graph showing the capacity retention rate and expansion force of a battery cell according to Example 1 of the present disclosure over charge and discharge cycles. [Figure 13] 10 is a graph showing the change in capacity retention rate and thickness due to charge / discharge cycles of a battery cell according to Example 2 of the present disclosure. [Figure 14] 10 is a graph showing the capacity retention rate and expansion force of a battery cell according to Example 2 of the present disclosure over charge and discharge cycles. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present disclosure will be described in detail below with reference to the drawings. When describing the present disclosure, if it is determined that a detailed description of related known functions or configurations may obscure the gist of the present disclosure, the detailed description thereof will be omitted. Furthermore, the following embodiments may be modified into various other forms, and the scope of the technical idea of ​​the present disclosure is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more complete and complete, and to fully convey the technical idea of ​​the present disclosure to those skilled in the art.

[0026] It should be understood that the technology described in this disclosure is not limited to a particular embodiment, but includes various modifications, equivalents, and / or alternatives of the embodiments of the present disclosure.

[0027] In connection with the description of the drawings, like reference numerals may be used for like components.

[0028] In this disclosure, the terms "have," "can have," "include," or "can include" indicate the presence of a given feature (e.g., a value, a function, an operation, or a component such as a part) and do not exclude the presence of additional features.

[0029] In this disclosure, phrases such as "A or B," "at least one of A and / or B," or "one or more of A and / or B" include all possible combinations of the items listed together. For example, "A or B," "at least one of A and B," or "at least one of A or B" can refer to (1) at least one A, (2) at least one B, or (3) both at least one A and at least one B.

[0030] FIG. 1 is a perspective view that schematically illustrates a battery pack 100 according to an embodiment of the present disclosure. FIG. 2 is a side view that schematically illustrates a battery cell 110 of the battery pack 100 according to an embodiment of the present disclosure. FIG. 3 is an exploded perspective view that schematically illustrates the configuration of the battery cell 110 of the battery pack 100 according to an embodiment of the present disclosure. FIG. 4 is an exploded perspective view that schematically illustrates a positive electrode 114, a separator 115, and a negative electrode 116 of the battery cell 110 of the battery pack 100 according to an embodiment of the present disclosure. FIG. 5 is a vertical cross-sectional view that schematically illustrates the battery pack 100 of FIG. 1 cut along line A-A'.

[0031] 1 to 5, a battery pack 100 according to an embodiment of the present disclosure includes at least one battery cell 110, a module housing 120, and a pressurizing portion .

[0032] Specifically, the battery cell 110 includes a cell case 111, an electrode assembly 112 having an electrode tab 113, an electrode lead 117, an insulating film 118, and an electrolyte (not shown).

[0033] The cell casing 111 may be a pouch-type cell casing made of a flexible material. However, the shape of the lithium secondary battery of the present disclosure is not particularly limited, and may be a cylindrical shape using a can, a prismatic shape, a pouch shape, a coin shape, or the like. For example, the cell casing 111 may include a first cell sheet 111a covering the upper part of the electrode assembly 112 and a second cell sheet 111b coupled to a portion of the lower surface of the first cell sheet 111a to cover the lower part of the electrode assembly 112. Each of the first cell sheet 111a and the second cell sheet 111b may be a laminate sheet. Specifically, the laminate sheet may have a structure in which a thin metal film (e.g., an Al film) is laminated between a water-resistant polymer film (e.g., nylon) and a thermally adhesive polymer film (e.g., cast polypropylene). The structure of the laminate sheet and the materials constituting each layer are widely known in the technical field to which the present disclosure pertains, and therefore, detailed description thereof will be omitted.

[0034] To seal the cell casing 111, the peripheries of the first cell sheet 111a and the second cell sheet 111b may be heat-sealed to each other. The heat-sealing method may include a process of pressing at least a portion of the peripheries of the first cell sheet 111a and the second cell sheet 111b, which face each other, in a stacked state, using a high-temperature device (e.g., a hot press). Here, the heat-sealing temperature may be 110°C to 150°C. For example, the cell casing 111 may include a sealing portion formed by heat-sealing the peripheries of the first cell sheet 111a and the second cell sheet 111b to each other.

[0035] The cell casing 111 may include an accommodating space S that accommodates the electrode assembly 112, the electrode lead 117, and the electrolyte. For example, the accommodating space S may be a cup-shaped portion formed by compressing a portion of at least one of the two cell sheets 111a and 111b using a high-temperature hot press. The accommodating space S may be a portion P that protrudes outward from each of the cell sheets 111a and 111b. The accommodating space S of the cell casing 111 may be large enough to accommodate all of the electrodes 114, 116, the separator 115, and the electrolyte. For example, as shown in FIG. 3, the accommodating space S of the cell casing 111 may be formed by combining an upwardly protruding portion P of the first cell sheet 111a and a downwardly recessed portion R of the second cell sheet 111b.

[0036] The electrodes 114, 116 may be at least one positive electrode 114 and at least one negative electrode 116, depending on their electrical polarity. For example, the positive electrode 114 may be manufactured by forming a positive electrode mixture layer M1, which is a mixture of a positive electrode active material, a conductive material, and a binder, on a current collector made of an aluminum alloy material. The negative electrode 116 may be manufactured by forming a negative electrode mixture layer M2, which is a mixture of a negative electrode active material, a conductive material, and a binder, on a current collector made of a copper alloy material. A separator 115 may be interposed between the positive electrode 114 and the negative electrode 116. The separator 115 may serve to interrupt an internal short circuit between the positive electrode 114 and the negative electrode 116 and to impregnate the electrode with an electrolyte. The separator 115 of the present disclosure may be made of any separator material commonly used in secondary batteries. For example, the separator 115 may include at least one of polyethylene and polypropylene. In addition, the electrode assembly 112 may be formed by stacking the positive electrode 114, the separator 115, and the negative electrode 116 in order.

[0037] The positive electrode 114 can be manufactured by forming a positive electrode mixture layer M1 on a positive electrode current collector. The positive electrode mixture layer M1 can be formed by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, a solvent, etc., followed by drying and rolling.

[0038] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used.

[0039] The positive electrode active material may contain a lithium composite transition metal oxide in which the content of nickel among the transition metals is 50 atm % or more, preferably 70 atm % or more, in order to improve the capacity characteristics and stability of the battery.

[0040] A representative example of the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 or LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode active material may include a lithium nickel cobalt manganese-based oxide such as O2, or may include a lithium nickel cobalt manganese aluminum-based oxide.

[0041] In addition, the positive electrode active material may be a compound capable of reversibly intercalating and deintercalating lithium, such as a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-O Ni O O4 (where 0 < o < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < ...... p2 [[ID=2...... Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements respectively, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1)) or a compound containing a sulfur substance capable of charge and discharge by a phase transition change can also be used.

[0042] The positive electrode active material can be contained in the positive electrode slurry at 80 wt% to 99.5 wt% based on the total weight of the solid content, specifically, it can be contained at 85 wt% to 95 wt%. Here, when the content of the positive electrode active material is 80 wt% or less, the energy density may be low and the capacity may decrease.

[0043] The binder is a component that facilitates bonding of the active material and conductive material, etc., and bonding to the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of the solid content of the positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terephthalate (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0044] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and examples thereof include at least one of carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystal structures; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0045] The conductive material is typically added in an amount of 1 to 30 wt % based on the total weight of the solids in the positive electrode slurry. The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when the positive electrode active material and, optionally, the binder and conductive material are included. For example, the solvent may be added so that the solids concentration in the slurry containing the positive electrode active material and, optionally, the binder and conductive material, is 10 to 70 wt %, preferably 20 to 60 wt %.

[0046] The negative electrode 116 may be manufactured by forming a negative electrode mixture layer M2 on a negative electrode current collector. The negative electrode mixture layer M2 may be formed by coating a negative electrode current collector with a slurry containing the negative electrode active material, a binder, a conductive material, and a solvent, followed by drying and rolling.

[0047] The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, etc., can be used. Furthermore, like the positive electrode current collector, the surface can be formed with fine irregularities to strengthen the binding force of the negative electrode active material, and the negative electrode current collector can be used in various forms such as a film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0048] The negative electrode active material may further include at least one selected from the group consisting of a material capable of being doped and dedoped with lithium, lithium metal, nickel metal, copper metal, SUS metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals with lithium, a metal composite oxide, and a transition metal oxide.

[0049] The material capable of doping and dedoping lithium includes Si, SiO x(0 < x ≤ 2), Si - Y alloy (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn - Y (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. may be mentioned, and at least one of these can also be used in combination with SiO2. As the element Y, it can be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof. In one embodiment, the negative electrode active material contains at least a part of silicon oxide (SiO x (0 < x ≤ 2)).

[0050] As the carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon - based negative electrode active material generally used in lithium - ion secondary batteries can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or both can be used. Examples of the crystalline carbon include graphite such as plate - shaped, flaky, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low - temperature fired carbon), hard carbon, mesophase pitch carbide, fired coke, etc.

[0051] As the metal or an alloy of these metals with lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn or an alloy of these metals with lithium can be used.

[0052] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) can be selected from the group consisting of those used.

[0053] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0054] The negative electrode active material can be contained in the negative electrode slurry at 80% to 99% by weight based on the total weight of the solid content.

[0055] As a component that facilitates the bonding between the conductive material, the active material, and the current collector, the binder is usually added to the negative electrode 116 slurry at 1% to 30% by weight based on the total weight of the solid content. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, and the like.

[0056] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 1 to 20 wt % based on the total weight of the solid content of the negative electrode slurry. Such a conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0057] The solvent may include at least one of water, N-Methyl-2-pyrrolidone (NMP), and an organic solvent such as alcohol, and may be used in an amount that provides a desired viscosity when the negative electrode active material and, optionally, the binder and the conductive material are included. For example, the solvent may be included so that the solid content of the slurry containing the negative electrode active material and, optionally, the binder and the conductive material as solid contents, is 50 wt % to 75 wt %, preferably 50 wt % to 65 wt %.

[0058] The separator 115 may serve to prevent internal short circuits between the electrodes and to impregnate the electrolyte. The separator 115 may be a commonly used porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminate thereof, or a commonly used porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, polyethylene terephthalate fiber, or the like, but is not limited thereto.

[0059] Here, the pore diameter of the porous separator is generally 0.01 μm to 50 μm, and the porosity may be 5% to 95%.

[0060] The thickness of the porous separator can generally be in the range of 5 μm to 300 μm.

[0061] The electrode tab 113 may not be coated with a mixture of the electrode active material, conductive material, and binder. The electrode tab 113 may be a path through which electrons can move. The electrode tab 113 may be formed by cutting a plain portion that is not coated with the positive electrode active material, or may be formed separately by connecting a separate conductive member to the plain portion of the electrode using ultrasonic welding or the like. For example, as shown in FIG. 3, the positive electrode 114 and the negative electrode 116 may each have an electrode tab 113 protruding from one side. For example, the positive electrode 114 has a positive electrode tab 113a protruding in the negative direction of the X axis. The negative electrode 116 has a negative electrode tab 113b protruding in the positive direction of the X axis. However, the present invention is not limited to this configuration. For example, the electrode tab 113 may be formed on at least one of the first, second, third, and fourth sides in the front, back, left, and right directions of the electrode.

[0062] The battery cell 110 according to an embodiment of the present disclosure may further include an electrode lead 117 coupled to a portion of the electrode tab 113. The electrode lead 117 may be made of an electrically conductive metal. As shown in FIG. 3 , the electrode lead 117 may include a positive electrode lead connected to the positive electrode tab 113a and a negative electrode lead connected to the negative electrode tab 113b. The electrode lead 117 may be connected to one or more electrode tabs 113 in various ways, such as by welding. A portion of the electrode lead 117 may be exposed to the outside of the cell casing 111. That is, the electrode lead 117 serves as an electrode terminal of the battery cell 110. For example, when the electrode lead 117 is electrically connected to the positive electrode 114, it may serve as a positive electrode terminal of the battery cell 110. When the electrode lead 117 is electrically connected to the negative electrode 116, it may serve as a negative electrode terminal of the battery cell 110. The battery cell 110 may include an insulating film 118 configured to wrap a portion of the outer surface of the electrode lead 117. The insulating film 118 electrically insulates the cell casing 111 from the electrode lead 117 and may be configured to be heat-sealed to the cell casing 111.

[0063] In one embodiment, the term "electrolyte" refers to a solid-state or liquid-state electrolyte. The battery cell 110 according to one embodiment of the present disclosure can be charged and discharged by ion exchange between the positive electrode 114 and the negative electrode 116 via the electrolyte. The electrolyte can be located between the positive electrode 114 and the negative electrode 116 to allow ions to move between the positive electrode 114 and the negative electrode 116. The electrolyte can also be located on the surface and in the pores of the separator 115. For example, when the battery cell 110 is a lithium secondary battery, a non-aqueous electrolyte solution can typically be used.

[0064] Meanwhile, the module housing 120 may be configured to accommodate at least one battery cell 110 therein. The module housing 120 may have an appearance of a rectangular parallelepiped with an open interior. A portion of the module housing 120 facing the battery cell 110 may be covered or coated with a non-conductive material that does not conduct electricity. The module housing 120 may be made of, for example, metal or plastic. The module housing 120 may be made of, for example, aluminum alloy or stainless steel, which have excellent thermal conductivity. For example, the module housing 120 may have a front wall, a rear wall, a left wall, a right wall, a top wall, and a bottom wall. The battery pack 100 may include two or more battery cells 110. For example, as shown in FIG. 5, 15 battery cells 110 stacked in the front-to-back direction (Y-axis direction) may be mounted on the bottom wall of the module housing 120.

[0065] In addition, the pressurizing unit 130 may be configured to elastically pressurize the battery cell 110 to prevent a volume change of the battery cell 110 when the battery cell 110 is charged or discharged. For example, if the battery pack 100 includes a plurality of battery cells 110 stacked in the front-to-rear direction (Y-axis direction), each of the plurality of pressurizing units 130 may elastically pressurize the front and rear sides of the plurality of battery cells 110. Here, "elastically" pressurizing means that the battery cell 110 is pressed using the elastic force of the pressurizing unit 130. For example, the pressurizing unit 130 may elastically increase the pressure applied to the battery cell 110 as the volume of the battery cell 110 increases. Conversely, the pressurizing unit 130 may elastically decrease the pressure applied to the battery cell 110 as the volume of the battery cell 110 decreases.

[0066] The pressurizing unit 130 may be set (configured) to have an appropriate pressure to pressurize the battery cell 110 depending on the content of silicon oxide relative to the total weight of the negative electrode active material. For example, if the content of silicon oxide relative to the total weight of the negative electrode active material is relatively higher than a predetermined content, the battery pack 100 may include the pressurizing unit 130 set to a high pressure to pressurize the battery cell 110. Conversely, if the content of silicon oxide relative to the total weight of the negative electrode active material is relatively lower than a predetermined content, the battery pack 100 may include the pressurizing unit 130 set to a low pressure to pressurize the battery cell 110.

[0067] For example, when the silicon oxide content relative to the total weight of the negative electrode active material is 5 wt %, the pressure applied by the pressurizing unit 130 during contraction and expansion of the battery cell 110 may be 250 kgf to 350 kgf. When the silicon oxide content relative to the total weight of the negative electrode active material is 20 wt %, the pressure applied by the pressurizing unit 130 during contraction and expansion of the battery cell 110 may be 900 kgf to 1000 kgf. That is, as the silicon oxide content relative to the total weight of the negative electrode active material increases, the pressurizing unit 130 may be set to a higher pressure. Conversely, as the silicon oxide content relative to the total weight of the negative electrode active material decreases, the pressurizing unit 130 may be set to a lower pressure. This is because when the silicon oxide content of the negative electrode active material of the battery cell 110 is relatively high, the volume change due to expansion of the battery cell 110 during charging becomes larger.

[0068] In addition, in one embodiment, as the number of charge / discharge cycles increases, the pressure applied by the pressure unit 130 may increase. For example, when the content of silicon oxide relative to the total weight of the negative electrode active material is 5 wt %, the pressure of the pressure unit 130 pressing the battery cell 110 may be set to 0 kgf to 250 kgf when the number of charge / discharge cycles is 0 to 15 (a state where the SoH is high), the pressure of the pressure unit 130 may be set to 100 kgf to 400 kgf when the number of charge / discharge cycles is 70 to 110, and the pressure of the pressure unit 130 may be set to 200 kgf to 500 kgf when the number of charge / discharge cycles is 170 to 200.

[0069] According to this configuration of the present disclosure, the battery pack 100 of the present disclosure includes a pressurizing unit 130 configured to elastically pressurize the battery cell 110 to prevent a volumetric change of the battery cell 110 during charging and discharging of the battery cell 110, and the pressurizing force for pressing the battery cell 110 is set according to the content of silicon oxide relative to the total weight of the negative electrode active material, thereby making it possible to control the swelling phenomenon in accordance with the swelling characteristics of the battery cell 110. That is, the battery pack 100 of the present disclosure sets the pressurizing force according to the type and / or content of the negative electrode active material of the battery cell 110, taking into consideration that the degree of volumetric change varies depending on the charging and discharging of the battery cell 110.

[0070] Accordingly, the battery pack 100 of the present disclosure includes a pressurizing unit 130 that is set to apply a pressure to the battery cell 110 in consideration of the content of silicon oxide in the negative electrode active material of the battery cell 110, in order to effectively control swelling of the battery cell 110 mounted in the module housing 120. That is, the battery pack 100 of the present disclosure can avoid applying excessive pressure to the battery cell 110, and conversely, when swelling is significant, the amount of gas generated inside the battery cell 110 can be effectively reduced by using the pressurizing unit 130 that is set to apply a larger pressure.

[0071] 1 to 3, in one embodiment, a battery pack 100 includes a battery cell 110 including a positive electrode 114, a negative electrode 116, and a separator 115 disposed between the positive electrode 114 and the negative electrode 116. The negative electrode 116 may be configured to include silicon oxide. For example, the negative electrode may be configured to include a negative electrode active material including silicon oxide. The battery pack 100 further includes a module housing 120 that accommodates the battery cell 110 and a pressurizing unit 130. The pressurizing unit 130 is configured to prevent swelling of the battery cell 110. The swelling of the battery cell 110 may vary depending on the content of silicon oxide. For example, a first battery cell (not shown) may include a negative electrode including a first negative electrode active material having a first content of silicon oxide. In this case, a first battery pack (not shown) including the first battery cell may experience a first swelling phenomenon having a first expansion rate. The second battery cell (not shown) may include a negative electrode including a second negative electrode active material having a second content of silicon oxide. In this case, a second swelling phenomenon having a second expansion rate may occur in a second battery pack (not shown) including the second battery cell. Here, the first content and the second content are different, and the first expansion rate and the second expansion rate are different. Because different swelling phenomena occur in the first battery pack and the second battery pack, the first battery pack and the second battery pack may include different pressurizing units (not shown). That is, the first battery pack and the second battery pack may include a first pressurizing unit and a second pressurizing unit, respectively. The first pressurizing unit is configured to apply a first pressure to the first battery cell. The second pressurizing unit is configured to apply a second pressure to the second battery cell.

[0072] Therefore, the battery pack 100 of the present disclosure can effectively control the swelling phenomenon of the battery cells 110 provided therein by taking into consideration the content of silicon oxide, thereby improving the life and stability of the battery pack 100.

[0073] The content of the silicon oxide may be 5 wt% to 20 wt% based on the total weight of the negative electrode active material. If the content of the silicon oxide is less than 5 wt%, the content of the silicon oxide is excessively low compared to the remaining negative electrode active material, which may result in a reduced charge capacity per unit amount of the negative electrode active material mixture. Furthermore, if the content of the silicon oxide is more than 20 wt%, the content of the silicon oxide is excessively high compared to the remaining negative electrode active material, which may result in a large volume change during charge and discharge. As the content of the silicon oxide increases, the expansion and contraction of the negative electrode increases. As a result, the electrical contact between the silicon oxide-based negative electrode active material and the graphite-based negative electrode active material may be insufficient, which may result in a reduced cycle performance.

[0074] Therefore, in the battery pack 100 according to an embodiment of the present disclosure, the content of the silicon oxide is 5 wt% to 20 wt% based on the total weight of the negative electrode active material, so that the battery cell 110 mounted in the battery pack 100 has an appropriate level of energy density, and the battery cell 110 can expand and contract at an appropriate and controllable level, thereby easily controlling the swelling phenomenon of the battery cell 110.

[0075] Meanwhile, referring to FIG. 5 , the pressing unit 130 of the battery pack 100 according to an embodiment of the present disclosure may include an elastic member 131. The elastic member 131 may be configured to press the battery cell 110 in a direction F opposite to a direction B of volumetric expansion. For example, the elastic member 131 may be a spring having a predetermined elasticity. One end of the elastic member 131 in the direction in which the elastic force is exerted may be configured to support the inner surface of the module housing 120. The other end of the elastic member 131 in the direction in which the elastic force is exerted may be configured to support one side of the battery cell 110. For example, as shown in FIG. 5 , the battery pack 100 may include a plurality of elastic members 131 inside the module housing 120. The plurality of elastic members 131 may be provided on the left and right sides of the battery cell 110. Each of the plurality of elastic members 131 may be configured to expand and contract in length in response to expansion and contraction due to charging and discharging of the battery cell 110. For example, the elastic member 131 may be configured to increase the pressure applied to the battery cell 110 when the battery cell 110 expands. Conversely, the elastic member 131 may be configured to decrease the pressure applied to the battery cell 110 when the battery cell 110 contracts.

[0076] FIG. 6 is a vertical cross-sectional view schematically illustrating a battery pack 100 according to another embodiment of the present disclosure.

[0077] 6, a battery pack 100 according to another embodiment of the present disclosure may further include a buffer pad 140, compared to the battery pack 100 of FIG. 5. The buffer pad 140 may be, for example, a silicone pad or a sponge. However, the buffer pad 140 is not limited to this form and may be any material that can expand and contract in response to the expansion and contraction caused by the charging and discharging of the battery cells 110.

[0078] The buffer pad 140 may be interposed between two or more battery cells 110. For example, as shown in FIG. 6, the buffer pad 140 may be interposed between 15 battery cells 110.

[0079] Therefore, according to this configuration of the present disclosure, the battery pack 100 of the present disclosure further includes a buffer pad 140 interposed between two or more battery cells 110 and configured to buffer the volumetric expansion of the battery cells 110. This makes it easy to space the two or more battery cells 110 apart from each other in consideration of the volumetric expansion that occurs when each of the two or more battery cells 110 is charged or discharged, and to space the two or more battery cells 110 apart at a predetermined interval within the module housing 120. This spacing prevents the arrangement of the two or more battery cells 110 from being distorted during use of the battery pack 100, and the buffer pad 140 can play a role in dispersing the expansion force of the battery cells 110 and preventing pressure from concentrating on one part of the battery cells 110.

[0080] Fig. 7 is a conceptual diagram schematically illustrating the appearance of a battery pack 100 according to one embodiment of the present disclosure, and Fig. 8 is a vertical cross-sectional view schematically illustrating the appearance of a battery pack 100 according to still another embodiment of the present disclosure.

[0081] 7 and 8 in addition to FIGS. 1 and 5 , the battery pack 100 according to an embodiment of the present disclosure may further include a battery management system (BMS) 150. The battery management system 150 may control the pressure applied to the battery cell 110 by the pressure unit 130 to increase or decrease. For example, the battery management system 150 may include a sensor unit 151 configured to sense the state of the battery cell 110. Here, the sensor unit 151 may include one or more of a voltage sensor 151v, a current sensor 151a, and a temperature sensor 151t. The voltage sensor 151v and the current sensor 151a may be electrically connected to the battery cell 110. The temperature sensor 151t may be located inside the module housing 120. For example, the voltage sensor 151v and the current sensor 151a may be incorporated into the battery management system 150. For example, the battery management system 150 can measure the temperature, voltage, and current of the battery cells 110 using a current sensor 151a, a voltage sensor 151v, and a temperature sensor 151t.

[0082] The battery management system 150 may be configured to acquire information about the battery cell 110. For example, the battery management system 150 may be configured to acquire at least one of the state of health (SoH), charge / discharge cycles, and volume expansion coefficient of the battery cell 110. However, the information about the battery cell 110 is not limited thereto. Here, the "SoH" may be the health state of the battery cell 110 indicating a deterioration state. In other words, the SoH can be considered as the battery capacity retention. Here, the "charge / discharge cycle" means that the battery cell 110 is charged to a predetermined capacity and discharged to a predetermined capacity. Here, the "volume expansion coefficient" means the rate of change in volume between the charged state and the discharged state of the battery cell 110.

[0083] For example, the battery management system 150 can use known techniques to calculate the State of Charge (SoC) from the measured temperature, voltage, and current of the battery cell 110. In one embodiment, the battery management system 150 can calculate the SoH using the following formula:

[0084] Formula: Measured capacity = Measured cumulative current / SoC change

[0085] To explain an example of a process of calculating the measured capacity using a formula and then calculating the SoH value using the calculated measured capacity, for example, if the initial capacity of a battery is 50 Ah, the SoC during standby before charging is 20%, the SoC during standby after charging is 70%, and the cumulative current measured over a predetermined period is 20 Ah, the measured capacity can be calculated by dividing the cumulative current by the SoC change. That is, the measured capacity is 20 Ah × 100 ÷ (70% - 20%) = 40 Ah, and the measured SoH is calculated as (40 Ah ÷ 50 Ah) × 100 = 80%. Therefore, in this case, the SoH value is calculated as 80%.

[0086] The battery management system 150 can also be configured to increase or decrease the pressure applied by the pressurizing unit 130 based on the acquired SoH of the battery cell 110. For example, the smaller the acquired SoH, the more the battery management system 150 can increase the pressure applied by the pressurizing unit 130. Conversely, the larger the acquired SoH, the more the battery management system 150 can decrease the pressure applied by the pressurizing unit 130.

[0087] However, the factors that the battery management system 150 should consider to change the pressure of the pressure unit 130 are not limited to the SoH. For example, the battery management system 150 may further consider at least one of the number of charge / discharge cycles of the battery cell 110 and the volume expansion coefficient of the battery cell 110.

[0088] For example, if the content of silicon oxide relative to the total weight of the negative electrode active material is 5 wt%, the battery management system 150 may set the pressure of the pressure unit 130 that pressurizes the battery cell 110 to 0 kgf to 250 kgf for 0 to 15 charge / discharge cycles (high SoH), may set the pressure of the pressure unit 130 to 100 kgf to 400 kgf for 70 to 110 charge / discharge cycles, and may set the pressure of the pressure unit 130 to 200 kgf to 500 kgf for 170 to 200 charge / discharge cycles. For example, if the content of silicon oxide relative to the total weight of the negative electrode active material is 20 wt%, the battery management system 150 may set the pressure of the pressure unit 130 that pressurizes the battery cell 110 to a range of 0 to 1000 kgf, taking into account the SoH or the number of charge / discharge cycles.

[0089] Therefore, in the battery pack 100 of the present disclosure, the battery management system 150 is configured to increase or decrease the pressure of the pressurizing unit 130 in consideration of at least one of the acquired state information of the battery cell 110, the charge / discharge cycle, and the volumetric expansion coefficient, thereby effectively controlling the swelling phenomenon of the battery cell 110 due to the SoH of the battery cell 110. That is, in the battery pack 100 of the present disclosure, the volumetric expansion of the battery cell 110 tends to increase as the SoH of the battery cell 110 decreases, so the battery management system 150 can increase the pressure of the pressurizing unit 130 in accordance with the degree of volumetric expansion of the battery cell 110, thereby effectively suppressing the swelling phenomenon of the battery cell 110. As a result, the battery pack 100 of the present disclosure can effectively extend the life of the battery cell 110.

[0090] 7 and 8, the pressurizing unit 130 of the battery pack 100 according to another embodiment of the present disclosure may further include an electric cylinder 132 having a cylinder shaft 132a, as compared with the battery pack 100 of FIG. 5. Here, the elastic member 131 may be connected to an end of the cylinder shaft 132a. The elastic member 131 may be, for example, a spring. Here, the electric cylinder 132 may include an electric motor (not shown).

[0091] The cylinder shaft 132a can be advanced toward the battery cell 110 by the battery management system 150 so as to apply pressure to the elastic member 131. Conversely, the cylinder shaft 132a can be configured to be moved backward by the battery management system 150 in the direction opposite to the direction toward the battery cell 110 so as to release the pressure on the elastic member 131. That is, when the cylinder shaft 132a advances toward the battery cell 110 by control of the battery management system 150, the pressure with which the elastic member 131 applies pressure to the battery cell 110 can be increased. Conversely, when the cylinder shaft 132a moves backward in the direction opposite to the direction toward the battery cell 110 (direction away from the battery cell) by control of the battery management system 150, the pressure with which the elastic member 131 applies pressure to the battery cell 110 can be decreased.

[0092] Therefore, the battery pack 100 according to yet another embodiment of the present disclosure includes an electric cylinder 132 controlled by a battery management system 150 and an elastic member 131 connected to an end of a cylinder shaft 132a of the electric cylinder 132, and thereby the pressing force of the elastic member 131 can be controlled by the battery management system 150. As a result, the battery pack 100 of the present disclosure can appropriately control the pressing force of the pressing unit 130 in consideration of the degree of swelling (expansion) of the battery cell 110 and the SoH of the battery cell 110.

[0093] 7 and 8, in another embodiment, the sensor unit 151 may further include, for example, a pressure sensor 151p. For example, as shown in FIG. 8, the battery management system 150 may detect the degree of expansion of the battery cells 110 using the pressure sensor 151p installed inside the module housing 120. For example, as shown in FIG. 8, the pressure sensor 151p may be located inside the module housing 120 so as to come into contact with the battery cell 110 arranged outermost in the stacking direction of the plurality of battery cells 110 when the volume of two or more battery cells 110 expands. Here, the pressure sensor 151p may transmit a signal indicating whether or not the battery cells 110 are contacted to the battery management system 150 via wired or wireless communication.

[0094] Meanwhile, referring again to Fig. 8, a battery pack 100 according to yet another embodiment of the present disclosure may further include a film-type pressure sensor 151p compared to the battery pack 100 of Fig. 5. The remaining configuration of the battery pack 100 of Fig. 8 other than the temperature sensor 151t, the pressure sensor 151p, and the electric cylinder 132 may be the same as that of the battery pack 100 of Fig. 5.

[0095] For example, the pressure sensor 151p may have a film shape. Such a film-shaped pressure sensor 151p may be interposed between the battery cell 110 and the elastic member 131. The pressure sensor 151p may be configured to sense a pressure applied to the battery cell 110 by the elastic member 131. For example, the pressure sensor 151p may include a piezoelectric element that generates electricity according to the pressure applied to the sensor. The pressure sensor 151p may be connected to the battery management system 150 by an electric wire so as to transmit an electric signal corresponding to the sensed pressure to the battery management system 150.

[0096] The battery management system 150 may be configured to increase or decrease the pressure of the pressurizing unit 130 in accordance with the pressure measured by the pressure sensor 151p. For example, the battery management system 150 may adjust an appropriate pressure with which the pressurizing unit 130 pressurizes the battery cell 110 based on the pressure value measured by the pressure sensor 151p. For example, the battery management system 150 may measure the pressure with which the electric cylinder 132 presses the battery cell 110 using the pressure sensor 151p, and when the measured pressure is lower than a predetermined pressure that can suppress the swelling phenomenon of the battery cell 110, may move the cylinder shaft 132a of the electric cylinder 132 forward toward the battery cell 110. Conversely, when the measured pressure is higher than the predetermined pressure that can suppress the swelling phenomenon of the battery cell 110, the battery management system 150 may move the cylinder shaft 132a of the electric cylinder 132 backward in a direction away from the battery cell 110.

[0097] Therefore, according to such a configuration of the present disclosure, the battery pack 100 of the present disclosure further includes a pressure sensor 151p configured to sense the pressure applied to the battery cell 110 by the elastic member 131, and thereby, under the control of the battery management system 150, the elastic member 131 can exert a pressure within an appropriate range that can effectively suppress the swelling phenomenon of the battery cell 110. As a result, the battery pack 100 of the present disclosure can prevent failures or accidents caused by the swelling phenomenon of the battery cell 110 in advance and effectively increase the service life of the battery pack 100.

[0098] FIG. 9 is a vertical cross-sectional view schematically illustrating a battery pack 100 according to still another embodiment of the present disclosure.

[0099] 9, a battery pack 100 according to yet another embodiment of the present disclosure may differ from the battery pack 100 of FIG. 8 in that it includes a movable outer wall W configured to be movable within the module housing 120 and the position of the elastic member 131 is different. The remaining configuration of the battery pack 100 of FIG. 9 may be the same as that of the battery pack 100 of FIG. 8.

[0100] The movable outer wall W may be configured to support the elastic member 131 of the pressing unit 130. For example, referring to FIG. 9 , the movable outer wall W may be configured to support one side (right side) of the elastic member 131 of the pressing unit 130. The movable outer wall W may be configured to be movable in a direction toward the battery cell 110 (the direction in which the battery cell is located) or in a direction opposite to the direction toward the battery cell 110. For example, as shown in FIG. 9 , the movable outer wall W may be a part of a side wall (right side wall) of the module housing 120. The movable outer wall W may be configured to be movable in the internal space of the module housing 120 that accommodates the battery cell 110. For example, as shown in FIG. 9 , the movable outer wall W may be configured to be movable toward the battery cell 110 within the internal space of the module housing 120. The movable outer wall W may be configured to be movable in a direction away from the battery cell 110 within the internal space of the module housing 120.

[0101] The pressure applying unit 130 may further include an electric cylinder 132A configured to move the movable outer wall W. A cylinder shaft 132a of the electric cylinder 132A may be connected to the movable outer wall W. The electric cylinder 132A can move the cylinder shaft 132a forward or backward under the control of the battery management system 150.

[0102] The electric cylinder 132A may be located outside the module housing 120. For example, the electric cylinder 132A may be located on the left or right side of the module housing 120. For example, as shown in FIG. 9, one side of the electric cylinder 132A opposite to the cylinder shaft 132a may be fixed to a wall. Here, the cylinder shaft 132a of the electric cylinder 132A may be connected to the movable outer wall W of the module housing 120.

[0103] The cylinder shaft 132a of the electric cylinder 132A may be configured to pressurize the moving outer wall W so that the moving outer wall W moves toward the battery cell 110. Alternatively, the cylinder shaft 132a of the electric cylinder 132A may be configured to move backward so that the moving outer wall W moves in the direction opposite to the direction toward the battery cell 110.

[0104] The pressing unit 130 may further include an elastic member 131 interposed between the battery cell 110 and the moving outer wall W. The elastic member 131 may be pressed by the moving outer wall W. For example, when the cylinder shaft 132a of the electric cylinder 132A advances toward the battery cell 110 under the control of the battery management system 150, the moving outer wall W moves toward the battery cell 110, and the elastic member 131 may be compressed by the movement of the moving outer wall W. As a result, the pressing force of the elastic member 131 pressing the battery cell 110 may increase.

[0105] Conversely, when the cylinder shaft 132a of the electric cylinder 132A moves backward in a direction away from the battery cell 110 under the control of the battery management system 150, the movable outer wall W moves in a direction away from the battery cell 110, and the amount of compression of the elastic member 131 by the movable outer wall W can be reduced. As a result, the pressure of the elastic member 131 pressing against the battery cell 110 can be reduced.

[0106] Therefore, according to such a configuration of the present disclosure, the battery pack 100 of the present disclosure has the electric cylinder 132A of the pressurizing unit 130 located outside the module housing 120, thereby making it possible to secure a larger internal space for accommodating the battery cells 110 of the battery pack 100 compared to the case where the electric cylinder 132 is located inside the module housing 120 as in the battery pack 100 of Fig. 8. This allows the battery pack 100 of the present disclosure to effectively increase the energy density.

[0107] FIG. 10 is a schematic diagram illustrating an automobile 300 according to an embodiment of the present disclosure.

[0108] 10 , an automobile 300 according to an embodiment of the present disclosure includes at least one battery pack 100. The automobile 300 of the present disclosure may have a body configured to mount the battery pack 100 thereon. The automobile 300 may be, for example, a hybrid automobile or an electric automobile. While FIG. 10 illustrates the automobile 300 as an example, it can be understood that any device using such a battery pack 100 is included in the embodiments of the present disclosure.

[0109] Meanwhile, referring again to FIGS. 1 to 5, a method for manufacturing a battery pack according to one embodiment of the present disclosure is a method for manufacturing a battery pack 100, and includes the steps of preparing at least one battery cell 110 including a positive electrode 114, a separator 115, and a negative electrode 116 including the negative electrode active material having at least a portion of the silicon oxide.

[0110] The method of manufacturing a battery pack of the present disclosure includes a step of housing at least one battery cell 110 in an interior space formed inside a module housing 120 .

[0111] In addition, the manufacturing method of the battery pack of the present disclosure includes a step of installing a pressurizing unit 130 configured to elastically pressurize the battery cell 110 to prevent a volume change of the battery cell 110 during charging and discharging of the battery cell 110, and the pressurizing force for pressing the battery cell 110 is set taking into account the content of the silicon oxide with respect to the total weight of the negative electrode active material.

[0112] Therefore, according to this configuration of the present disclosure, the manufacturing method of the battery pack of the present disclosure includes a pressurizing unit 130 in which a pressure that pressurizes the battery cell 110 is set according to the content of the silicon oxide relative to the total weight of the negative electrode active material of the negative electrode 116. This makes it possible to suppress volume expansion in accordance with the swelling characteristics that occur during charging and discharging of the battery cell 110, and more effectively improve the lifespan and stability of the battery pack 100 compared to a battery pack that does not take the content of silicon oxide into consideration.

[0113] Hereinafter, the change in thickness and expansion force of a battery cell depending on the content of silicon oxide in the negative electrode active material will be described using test examples.

[0114] [Example 1: Manufacturing of battery cell] (SiO X The content of the negative electrode active material is 5 wt% of the total weight of the negative electrode active material. A positive electrode active material slurry was prepared by adding a positive electrode active material (NCMA (Li[Ni, Co, Mn, Al]O2)), a conductive material (carbon black), and a binder (polyvinylidene fluoride: PVDF) to a solvent, N-methyl-2-pyrrolidone (NMP). The positive electrode active material slurry was applied to a positive electrode current collector (aluminum thin film) with a thickness of 15 μm, dried, and then roll-pressed to prepare a positive electrode.

[0115] Graphite, amorphous SiO with a content of 5 wt% of the total weight of the negative electrode active material X(0 < x ≤ 2), conductive material (carbon black), and binder (polyvinylidene fluoride, PVDF) were added to NMP as a solvent, and then mixed to produce a negative electrode active material slurry. After the negative electrode active material slurry was applied and dried on a negative electrode current collector (copper thin film) with a thickness of 10 μm, roll pressing was performed to produce a negative electrode.

[0116] The positive electrode, a separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP), and the negative electrode were laminated to produce an electrode assembly. The prepared electrode assembly was stored in a pouch, and after injecting electrolyte into the storage space of the pouch so as to be impregnated into the electrode assembly, the pouch was sealed to produce a battery cell. Here, the electrolytic solution was produced by dissolving lithium hexafluorophosphate (LiPF6) with a concentration of 1.15 M in an organic solvent composed of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixed volume ratio of EC / EMC / DEC 3 / 4 / 3).

[0117] [Example 2: Manufacture of Battery Cell] (SiO X The content of which is 10 wt% of the total weight of the negative electrode active material) The positive electrode active material (NCMA (Li[Ni, Co, Mn, Al]O2)), conductive material (carbon black), and binder (polyvinylidene fluoride: PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent to produce a positive electrode active material slurry. After the positive electrode active material slurry was applied and dried on a positive electrode current collector (aluminum thin film) with a thickness of 15 μm, roll press was performed to produce a positive electrode.

[0118] Graphite, amorphous SiO with a content of 10 wt% of the total weight of the negative electrode active material X (0 < x ≤ 2), conductive material (carbon black), and binder (polyvinylidene fluoride, PVDF) were added to NMP as a solvent, and then mixed to produce a negative electrode active material slurry. After the negative electrode active material slurry was applied and dried on a negative electrode current collector (copper thin film) with a thickness of 10 μm, roll pressing was performed to produce a negative electrode.

[0119] The fabricated cathode, a 14 μm-thick porous polyethylene separator, and the fabricated anode were stacked to fabricate an electrode assembly. The prepared electrode assembly was placed in a pouch, and the electrolyte was poured into the pouch's storage space so that it impregnated the electrode assembly. The pouch was then sealed to fabricate a battery cell. The electrolyte was prepared by dissolving 1.15 M lithium hexafluorophosphate (LiPF6) in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (EC / EMC / DEC in a volume ratio of 3 / 4 / 3).

[0120] [Test example] The lithium secondary batteries of Examples 1 and 2 were fixed with a torque of 4 Nm using a fixture, and 200 charge / discharge cycles were performed at a charge current (0.33 C) and a discharge current (0.33 C) in an atmosphere at a temperature of 45° C., within a driving voltage range of 2.8 V to 4.2 V. A load cell was installed as a pressure measurement unit to measure the expansion force due to the swelling phenomenon of the secondary batteries during charge / discharge.

[0121] In addition, during 200 charge / discharge cycles of the lithium secondary battery, the cycle capacity retention rate (corresponding to SoH), which is the ratio of the discharge capacity to the initial capacity, the change in thickness of the battery cell due to the swelling phenomenon, and the expansion force were measured, and the measurement results are shown in Figures 11 to 14.

[0122] The test results showed that in Example 1, the thickness change after 200 charge / discharge cycles was changed from 0.31 mm to 0.15 mm, the capacity retention rate was 91.2%, and the range of the expansion force was changed from 498 kgf to 233 kgf. In Example 2, the thickness change after 200 charge / discharge cycles was changed from 0.36 mm to 0.15 mm, the capacity retention rate was 91.3%, and the range of the expansion force was changed from 530 kgf to 210 kgf.

[0123] Compared to Example 1, which has a silicon oxide content of 5 wt%, Example 2, which has a silicon oxide content of 10 wt%, shows that the battery cell thickness change is about 16% greater and the expansion force is about 6.42% greater based on the charge state after 200 cycles. In other words, the test results confirmed that as the silicon oxide content in the negative electrode active material increases, the battery cell thickness change and expansion force during charging become greater.

[0124] In addition, as shown in the test example results, the battery pack of the present disclosure can set the pressure of the pressure unit corresponding to the expansion force in consideration of the change in the expansion force of the battery cell depending on the content of silicon oxide in the negative electrode active material.

[0125] Although the embodiments have been described above with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, the above techniques may be performed in a different order than the above-described method, and / or the components of the above-described systems, structures, devices, circuits, etc. may be combined or combined in a different manner than the above-described method, or may be replaced or replaced by other components or equivalents, and still achieve suitable results.

[0126] Accordingly, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims. [Explanation of symbols]

[0127] 100 Battery Pack 110 battery cells 111 Cell Case 112 Electrode assembly 113, 113a, 113b Electrode tab, positive electrode tab, negative electrode tab 114, 115, 116 Positive electrode, separator, negative electrode 117 Electrode Lead 118 Insulating film 120 module housing 130 Pressure unit 131 Elastic member 132 Electric Cylinder 132a Cylinder shaft 140 buffer pad 150 Battery Management System 151 Sensor unit 151p, 151t, 151a, 151v pressure sensor, temperature sensor, current sensor, voltage sensor W Movable outer wall 300 cars

Claims

1. at least one battery cell including a positive electrode, a separator, and a negative electrode including a negative electrode active material having at least a portion of silicon oxide; a module housing configured to accommodate the at least one battery cell therein; a pressure unit configured to elastically pressurize the battery cell to prevent a volume change of the battery cell when the battery cell is charged or discharged, the pressure of the pressure unit being set according to a content of the silicon oxide with respect to a total weight of the negative electrode active material.

2. The battery pack according to claim 1 , wherein the pressure unit includes an elastic member configured to apply pressure in a direction opposite to a direction of volume expansion of the battery cell.

3. The battery cell includes two or more cells; The battery pack according to claim 1 , further comprising a buffer pad interposed between the two or more battery cells and configured to buffer volume expansion of the battery cells.

4. A sensor unit configured to acquire information about the battery cell; a battery management system that controls the pressure unit to increase or decrease the pressure of the pressure unit based on information about the battery cell acquired by the sensor unit, The pressure applying unit is The battery pack according to claim 1 , further comprising an elastic member disposed inside the module housing and configured to pressurize the battery cells in a direction opposite to a direction of volumetric expansion of the battery cells.

5. 5. The battery pack of claim 4, wherein the information about the battery cell acquired by the sensor unit includes at least one of state of health (SoH), charge / discharge cycles, and volume expansion coefficient of the battery cell.

6. 6. The battery pack according to claim 5, wherein the acquired state information of the battery cell is a charge / discharge cycle, and the battery management system is configured to increase the pressure of the pressure unit as the charge / discharge cycle increases.

7. The pressure applying unit further includes an electric cylinder having a cylinder shaft, 5. The battery pack according to claim 4, wherein the cylinder shaft is configured to move forward toward the battery cell to apply pressure to the elastic member or move backward in a direction opposite to the direction toward the battery cell to release pressure on the elastic member, by the battery management system.

8. a pressure sensor configured to sense a pressure applied to the battery cell by the elastic member; The battery management system includes: The battery pack according to claim 4 , wherein the pressure applied by the pressure unit is increased or decreased in accordance with the pressure measured by the pressure sensor.

9. The module housing includes: a movable outer wall configured to support the pressing unit and to be movable in a direction toward the battery cell or in a direction opposite to the direction toward the battery cell; The pressure applying unit further includes an electric cylinder having a cylinder shaft connected to the moving outer wall, the elastic member is interposed between the battery cell and the movable outer wall, 5. The battery pack according to claim 4, wherein the electric cylinder is located outside the module housing, and a cylinder shaft of the electric cylinder is configured to pressurize the moving outer wall so that the moving outer wall moves toward the battery cell or moves in a direction opposite to a direction toward the battery cell.

10. A motor vehicle comprising at least one battery pack according to any one of claims 1 to 9.

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