Lithium secondary battery having improved safety against internal short circuit and lithium secondary battery system therefor

Abstract

The invention relates to a lithium secondary battery and a lithium secondary battery system therefor. The lithium secondary battery is provided with a negative electrode having a predetermined volume resistance, thereby allowing the flow of a predetermined current while providing insulation on the surface of the negative electrode in the case of an internal short circuit, and thus it is possible to prevent a meltdown phenomenon and / or rapid heat generation caused by the internal short circuit in the lithium secondary battery. Furthermore, the lithium secondary battery system according to the present invention comprises the lithium secondary battery of the present invention to prevent a meltdown phenomenon and rapid heat generation in the case of an internal short circuit, so that a control operation can be preemptively performed before thermal runaway of the lithium secondary battery occurs. And prevents the occurrence of an additional meltdown phenomenon and / or thermal runaway in an adjacent lithium secondary battery, and thus can improve safety problems due to an internal short circuit.

Description

Technical Field

[0001] The present disclosure relates to a lithium secondary battery having improved safety against internal short circuit and a lithium secondary battery system used therefor.

[0002] This application is based on and claims the benefit of priority from Korean Patent Application No. 10-2023-0026060 filed in the Korean Intellectual Property Office on February 27, 2023, the entire contents of which are incorporated herein by reference in their entirety. Background Art

[0003] Lithium secondary batteries generate electrical energy through redox reactions when lithium ions are intercalated / deintercalated at the positive and negative electrodes. Lithium secondary batteries are manufactured by using materials that allow lithium ions to be reversibly intercalated and deintercalated as active materials for the positive and negative electrodes, and filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes.

[0004] Such lithium secondary batteries are charged / discharged by an electrochemical reaction in which ions are deintercalated / intercalated and moved between active materials of two electrodes. However, when the secondary battery is repeatedly charged / discharged, heat is generated by, for example, electrical misuse (overcharging) or other dangerous factors. When this state continues, the lithium secondary battery will be damaged and exploded, causing damage to the user, so safety measures against heat generation are required.

[0005] [Prior art literature]

[0006] [Patent Document]

[0007] Korean Patent Pending Publication No.10-2011-0067565

[0008] Korean Patent Pending Publication No.10-2021-0054930 Summary of the invention

[0009] Technical issues

[0010] The present disclosure provides a technology related to a lithium secondary battery, which can ensure the safety of the battery when there is an internal short circuit in the lithium secondary battery.

[0011] Technical Solution

[0012] In order to solve the above problems,

[0013] According to one embodiment of the present disclosure,

[0014] A lithium secondary battery comprises: a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode, wherein:

[0015] In the negative electrode, a negative electrode active layer including a carbon-based negative electrode active material and a coating layer including silicon-containing particles are sequentially disposed on a negative electrode current collector, and

[0016] The volume resistance of the negative electrode is about 1.0×10 -4 Ω·cm to 1.0Ω·cm.

[0017] For example, the negative electrode may have a -3 Ω·cm to 9.0×10 -1 Volume resistivity of Ω·cm.

[0018] In addition, the silicon-containing particles may include particles having a ratio of silicon element to oxygen element of about 1:0.5 to 1:1.5.

[0019] In addition, the silicon-containing particles may have an average particle size (D 50 ) and may include a carbon layer on its surface.

[0020] In addition, the coating layer may include about 70 parts by weight or more of the silicon-containing particles and about 30 parts by weight or less of the binder, relative to a total of 100 parts by weight of the coating layer.

[0021] In addition, the coating layer may have an average thickness of about 1.5 μm to 30 μm, and a thickness ratio of the coating layer to the negative electrode active layer may be about 0.01 to 0.3.

[0022] In addition, the positive electrode may include a positive electrode active layer on the positive electrode current collector, the positive electrode active layer including one or more types of positive electrode active materials among compounds represented by the following Formulae 1 and 2:

[0023] [Chemical formula 1]

[0024] LiFe a M 1 1-a XO 4

[0025] [Chemical formula 2]

[0026] Li x [Ni y Co z Mn w M 2 v ]O 2

[0027] In Chemical Formula 1 and Chemical Formula 2,

[0028] M 1 is one or more types of elements selected from the group consisting of W, Cu, Fe, V, Cr, Co, Ni, Mn, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo,

[0029] X is one or more selected from the group consisting of P, Si, S, As and Sb,

[0030] a satisfies 0 <a≤1.0,

[0031] M 2 is one or more types of elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and

[0032] x, y, z, w and v respectively satisfy 1.0≤x≤1.30, 0≤y<1, 0≤z≤1, 0≤w≤1, and 0≤v≤0.1, and y+z+w+v=1.

[0033] Furthermore, according to one embodiment of the present disclosure,

[0034] A lithium secondary battery system comprises: a plurality of battery cell assemblies, each battery cell assembly comprising n (where n is an integer from 3 to 100) lithium secondary batteries according to the present disclosure;

[0035] A charge / discharge unit electrically connected to each battery cell assembly to charge or discharge each battery cell assembly individually;

[0036] a sensing unit electrically coupled to an electrode of each lithium secondary battery included in the battery cell assembly to individually measure at least one of an electric voltage and an electric current of the lithium secondary battery during charge / discharge of each lithium secondary battery; and

[0037] A control unit electrically connected to the charge / discharge unit and the sensing unit to control the charge or discharge of each lithium secondary battery; wherein,

[0038] When the amount of electricity measured by the sensing unit satisfies a predetermined value, the control part stops charging or discharging of the cell assembly including the corresponding lithium secondary battery.

[0039] The control unit may perform the following steps: compare the average power of the battery cell assembly with the power of the individual battery cell assembly, and select the battery cell assembly with an error rate of more than about 5%;

[0040] determining, among the respective lithium secondary batteries disposed in the respective selected cell assemblies, that an internal short circuit has occurred in the respective lithium secondary batteries whose charge measured by the sensing unit is lower than the applied charge of each lithium secondary battery by more than about 0.5%; and

[0041] Charging or discharging of the cell assembly including the corresponding lithium secondary battery determined to be internally short-circuited is stopped.

[0042] In addition, the sensing unit may further include a temperature measurement sensor configured to measure a temperature of each lithium secondary battery provided in the battery cell assembly.

[0043] Furthermore, according to another embodiment of the present disclosure,

[0044] A method for operating a lithium secondary battery system comprises the following steps: comparing an average power of a battery cell assembly with a power of an individual battery cell assembly, and selecting a battery cell assembly having an error rate of more than about 5%;

[0045] determining, among the respective lithium secondary batteries disposed in the respective selected cell assemblies, that an internal short circuit has occurred in the respective lithium secondary batteries whose charge measured by the sensing unit is lower than the applied charge of each lithium secondary battery by more than about 0.5%; and

[0046] Charging or discharging of the cell assembly including the corresponding lithium secondary battery determined to be internally short-circuited is stopped.

[0047] In addition, according to another embodiment of the present disclosure, a non-transitory computer-readable storage medium stores a program for implementing an operating method of a lithium secondary battery system, and the method includes the following steps:

[0048] Compare the average power of the battery cell assembly with the power of the individual battery cell assembly, and select the battery cell assembly with an error rate of more than about 5%;

[0049] determining, among the respective lithium secondary batteries disposed in the respective selected cell assemblies, that an internal short circuit has occurred in the respective lithium secondary batteries whose charge measured by the sensing unit is lower than the applied charge of each lithium secondary battery by more than about 0.5%; and

[0050] Charging or discharging of the cell assembly including the corresponding lithium secondary battery determined to be internally short-circuited is stopped.

[0051] In addition, according to another embodiment of the present disclosure,

[0052] A negative electrode for a lithium secondary battery, comprising: a negative electrode active layer containing a carbon-based negative electrode active material and a coating containing silicon-containing particles on a negative electrode current collector, wherein:

[0053] The silicon-containing particles included in the coating layer include particles in which the ratio of silicon element to oxygen element is about 1:0.5 to 1:1.5, and,

[0054] The volume resistance of the negative electrode is about 1.0×10 -4 Ω·cm to 1.0Ω·cm.

[0055] The silicon-containing particles may include a carbon layer on the surface thereof, and may have an average particle size (D 50 ).

[0056] The coating layer may include about 70 parts by weight or more of the silicon-containing particles and about 30 parts by weight or less of the binder, relative to a total of 100 parts by weight of the coating layer.

[0057] The coating layer may have an average thickness of about 1.5 μm to 30 μm, and a thickness ratio of the coating layer to the negative active layer may be about 0.01 to 0.3.

[0058] Beneficial Effects

[0059] The lithium secondary battery according to the present disclosure includes a negative electrode having a predetermined volume resistance, so that in the case of an internal short circuit, appropriate insulation can be achieved on the negative electrode surface while allowing a predetermined current to leak. Therefore, in the case of an internal short circuit, the lithium secondary battery can be prevented from melting and / or rapidly heating.

[0060] In addition, since the lithium secondary battery system according to the present disclosure includes the above-mentioned lithium secondary battery of the present disclosure, in the case of an internal short circuit, the meltdown phenomenon and rapid heating can be prevented. Therefore, the operation can be pre-controlled before thermal runaway occurs in the corresponding lithium secondary battery, and additional meltdown phenomena and / or thermal runaway can be prevented from occurring in adjacent lithium secondary batteries and / or battery cell assemblies including the secondary batteries. Then, its advantage is that, compared with conventional lithium secondary batteries, the safety problem caused by the internal short circuit is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a structural diagram schematically illustrating a configuration of a lithium secondary battery system according to the present disclosure.

[0062] Figure 2 2 is a diagram schematically illustrating a structure of a control unit in a lithium secondary battery system according to the present disclosure.

[0063] Figure 3 are scanning electron microscope (SEM) images when the cross-sectional structure of the negative electrode provided in the lithium secondary batteries manufactured in Example 2 and Example 3 and the thickness of the coating layer were measured.

[0064] Figure 4 is a cross-sectional view illustrating a structure of an electrode assembly of a lithium secondary battery manufactured in an experimental example for safety testing of a lithium secondary battery according to the present disclosure.

[0065] Figures 5 to 7are graphs illustrating changes in battery temperature and voltage at the negative electrode provided in the lithium secondary batteries of Comparative Example 1, Comparative Example 3, and Comparative Example 4, respectively, in the case of an internal short circuit caused by contact between the positive electrode current collector and the negative electrode surface.

[0066] Figure 8 is a graph illustrating changes in battery temperature and voltage at the negative electrode provided in the lithium secondary battery of Example 2 in the case of an internal short circuit caused by contact between the positive electrode current collector and the negative electrode surface.

[0067] Throughout the several views of the drawings, corresponding reference numerals indicate corresponding parts. The drawings presented are illustrative for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be exaggerated relative to other elements to help improve understanding of the various embodiments. In addition, well-known but well-understood elements that are useful or necessary in commercially feasible embodiments are generally not drawn to facilitate less obstructed viewing of the various embodiments. DETAILED DESCRIPTION

[0068] Various modifications may be made to the present disclosure and may include various embodiments, which are then described in detail in the detailed description.

[0069] However, this is not intended to limit the present disclosure to the embodiments, but should be construed as including all modifications, equivalents, and substitutes included in the spirit and technical scope of the present disclosure.

[0070] In the present disclosure, it should be understood that terms such as "including" or "having" are intended to specify the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and do not preclude the possibility of the presence or addition of one or more other features or numbers, steps, actions, components, parts, or combinations thereof.

[0071] Furthermore, in the present disclosure, when a part such as a layer, a film, a region, or a plate is described as being "on" another part, this includes not only the case where it exists "directly" "on" another part, but also the case where another part exists between them. Conversely, when a part such as a layer, a film, a region, or a plate is described as being "below" another part, this includes not only the case where it exists "directly" "below" another part, but also the case where another part exists between them. Furthermore, in this application, placement "on" may include not only the case where it is placed on the top, but also the case where it is placed on the bottom.

[0072] Furthermore, in the present disclosure, “electricity” refers to the amount of electricity flowing through electrodes during charging or discharging of a lithium secondary battery, which can be quantified as current and / or voltage.

[0073] The terms "about", "approximately" and "substantially" as used in this specification are used to indicate a numerical range or degree or its approximate value taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly using the disclosed contents in which precise or absolute numbers provided to assist in understanding the present disclosure are mentioned.

[0074] In secondary batteries, a porous separator disposed between the positive electrode and the negative electrode is used as an example of a safety measure. When the temperature inside the housing rises above the safe temperature, the porous separator closes the pores in response to the temperature and blocks the movement of ions between the two electrodes, thereby suppressing the electrochemical reaction and achieving safety (shut-down phenomenon).

[0075] However, when the temperature inside the battery rises excessively beyond the temperature release rate of the shell due to uneven diaphragm or other internal short circuit (e.g., short circuit), the diaphragm itself melts and loses its function of insulating the positive electrode from the negative electrode before the shutdown phenomenon of the diaphragm occurs. In addition, when the positive and negative electrodes are short-circuited, chain reactions such as decomposition of the negative electrode active material and the electrolyte, and decomposition of the positive electrode active material (melt-down) are carried out, and then a thermal runaway phenomenon is reached. This thermal runaway phenomenon can cause various problems. That is, not only an explosion is caused in the corresponding secondary battery where the internal short circuit occurs, but also a meltdown phenomenon is caused in the secondary battery adjacent to the corresponding secondary battery, resulting in an additional explosion.

[0076] When an internal short circuit occurs due to contact between electrodes, between electrodes and electrode current collectors, and / or between current collectors included in a secondary battery, a meltdown phenomenon may occur. For example, when an internal short circuit occurs due to contact between a positive electrode current collector (or a positive electrode surface) and a negative electrode, the heat generated increases rapidly due to the resistance value of the short-circuited portion, and a thermal runaway phenomenon is reached in a relatively short time. Therefore, in this case, a device for preventing, suppressing, and / or coping with this is required to achieve the stability of the battery.

[0077] In order to solve this problem, the present disclosure proposes a lithium secondary battery, in which a suitable insulating coating is applied to the surface of the negative electrode active material, and then the resistance of the negative electrode surface is improved. Due to the improvement of the negative electrode surface resistance, the lithium secondary battery according to the present disclosure improves safety in many aspects, such as fundamentally preventing a hard short circuit between the positive electrode current collector and the negative electrode active material.

[0078] Hereinafter, the present disclosure will be described in more detail.

[0079] Lithium secondary battery

[0080] According to one embodiment of the present disclosure,

[0081] A lithium secondary battery comprises a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode, wherein:

[0082] In the negative electrode, a negative electrode active layer including a carbon-based negative electrode active material and a coating layer including silicon-containing particles are sequentially disposed on a negative electrode current collector, and

[0083] The volume resistance of the negative electrode is about 1.0×10 -4 Ω·cm to 1.0Ω·cm.

[0084] The lithium secondary battery according to the present disclosure includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed therebetween, and has a structure in which the electrode assembly is inserted into a battery case and then sealed after injecting an electrolyte composition.

[0085] The negative electrode has a structure in which a negative electrode active layer including a carbon-based negative electrode active material and a coating layer including silicon-containing particles are sequentially stacked on at least one surface of a negative electrode current collector.

[0086] In addition, since the coating layer including silicon-containing particles is provided on the surface of the negative electrode active layer including the carbon-based negative electrode active material, the negative electrode can have a predetermined volume resistance. For example, the coating layer can have a volume resistance of about 1.0×10 -4 The volume resistance may be greater than Ω·cm, or the volume resistance may be about 1.0×10 -4 Ω·cm to 1.0Ω·cm. For example, the coating may have a value of about 8.0×10 -3 Ω·cm to 9.0×10 -1 Ω·cm; 7.0×10 -2 Ω·cm to 9.0×10 -2 Ω·cm; 1.0×10 -1 Ω·cm to 9.0×10 -1 Ω·cm; 1.0×10 -1 Ω·cm to 5.0×10 -1 Ω·cm; 2.0×10 -1 Ω·cm to 8.0×10 -1 Ω·cm; or 5.0×10 -1 Volume resistance of Ω·cm to 1.0Ω·cm.

[0087] In the negative electrode, when the volume resistance exceeds 1.0Ω·cm, in the case of an internal short circuit caused by the contact between the negative electrode surface and the positive electrode current collector (and / or the positive electrode active layer), excessive resistance is generated on the negative electrode surface, and then the flow of current stops completely. Therefore, the short-circuit current of the corresponding lithium secondary battery is blocked, but there is the following problem: in a device including multiple lithium secondary batteries such as a battery module or a battery pack, it is not easy to selectively detect and respond to lithium secondary batteries with internal short circuits in a relatively short time. In this case, in order to cope with the occurrence of internal short circuits, the battery cell assembly including the corresponding lithium secondary battery in which an internal short circuit has occurred must be separated and / or removed from the lithium secondary battery system, so there is a problem of reduced economic feasibility.

[0088] In addition, when the volume resistance of the negative electrode is less than 1.0×10 -4 When the resistance is less than Ω·cm, sufficient insulation cannot be achieved on the negative electrode surface in the event of an internal short circuit. Therefore, there is a problem that a meltdown phenomenon such as decomposition of the negative electrode active material and the electrolyte and decomposition of the positive electrode active material occurs.

[0089] The negative electrode of the present disclosure has a volume resistance that satisfies the above range, so that in the case of an internal short circuit, an appropriate resistance is provided for the negative electrode surface to achieve insulation at the short circuit point. Therefore, in the case of an internal short circuit, the heat generation of the corresponding lithium secondary battery can be significantly reduced, thereby delaying the occurrence of the meltdown phenomenon. In addition, by suppressing the heat generation of the corresponding lithium secondary battery in which an internal short circuit has occurred, additional heat generation and / or meltdown phenomena in adjacent lithium secondary batteries can be prevented. Therefore, it is possible to ensure the time to deal with (handle) problems caused by internal short circuits. In addition, since a very small amount of current (i.e., leakage current) is allowed to flow through the internal short circuit point of the corresponding lithium secondary battery, it is possible to easily determine / diagnose abnormal operations such as internal short circuits. Therefore, the advantage is that it is relatively easy to deal with abnormal operations of the corresponding lithium secondary battery.

[0090] For the negative electrode, in order to satisfy the above range of volume resistance, parameters such as components forming the coating, the content of each component, the mixing form and size of each component, and the thickness ratio of the negative electrode active layer and the coating can be controlled.

[0091] For example, the above-mentioned coating does not act as a resistance layer during normal operation of the lithium secondary battery, so that overvoltage does not occur during charge / discharge. In addition, during abnormal operation such as internal short circuit, the coating acts as a resistance layer, which prevents the current from flowing directly between the negative electrode active layer and the positive electrode active layer and / or the contact between the negative electrode active layer and the positive electrode current collector, and also has the function of leaking a considerable amount of current. For this reason, the coating can have a coating coated on the negative electrode active layer to cover the entire exposed surface of the negative electrode active layer, or in some cases, it can be selectively arranged only on the edge and / or end face of the negative electrode active layer that is easy to contact with the positive electrode current collector (and / or positive electrode active layer, etc.), or it can be selectively arranged only on the center of the negative electrode active layer that may encounter (meet) the positive electrode current collector (and / or positive electrode active layer, etc.) when the diaphragm is damaged by external force.

[0092] In addition, the coating may contain silicon-containing particles as a main component, and may also contain a binder for forming the silicon-containing particles into a coating. For example, relative to a total of 100 parts by weight of the coating, the content of the silicon-containing particles may be about 70 parts by weight or more, and the content of the binder may be about 30 parts by weight or less. In one embodiment, the content of the silicon-containing particles may be about 85 parts by weight or more; 90 parts by weight or more; 95 parts by weight or more; 80 to 99 parts by weight; 90 to 99 parts by weight; 85 to 95 parts by weight; or 90 to 95 parts by weight, and the content of the binder may be 15 parts by weight or less; 10 parts by weight or less; 5 parts by weight or less; 1 to 20 parts by weight; 1 to 10 parts by weight; 5 to 15 parts by weight; or 5 to 10 parts by weight.

[0093] In the coating disclosed herein, the contents of silicon-containing particles and binder are controlled within the above range, so that the amount of leakage current in the coating can be prevented from being reduced due to excessive binder content, and the phenomenon of reduced shape stability of the coating and damage to the coating due to excessive silicon-containing particles can be prevented.

[0094] The binder can be applied without particular limitation, as long as it is a polymer compound capable of fixing the silicon-containing particles without deteriorating the electrical properties of the coating. For example, the binder may include any one or more selected from the group consisting of: vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylamide, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber and fluororubber.

[0095] The binder can not only firmly fix the silicon-containing particles contained in the coating layer but also has bonding strength with the negative electrode active layer on which the coating layer is formed, thereby improving the durability of the negative electrode.

[0096] In addition, the silicon-containing particles contained in the coating layer may be silicon particles in an oxidized form. For example, the silicon-containing particles may include silicon elements and oxygen elements, wherein their ratio may be about 1:0.5 to 1.5; 1:0.8 to 1.2; or 1:0.9 to 1.1.

[0097] The form of the silicon-containing particles is not particularly limited as long as the element ratio of silicon element to oxygen element in the particles satisfies the above range. For example, the silicon-containing particles may be silicon monoxide (SiO q , where 0.8≤q≤1.2).

[0098] In the present disclosure, the element ratio of silicon element to oxygen element (e.g., the molar ratio of the elements) is controlled as described above, so that the volume resistance of the coating layer composed of silicon-containing particles can be controlled to meet the above predetermined range. Therefore, in the event of an internal short circuit, insulation can be provided for the coating surface, and at the same time, a small amount of current can be leaked into the battery.

[0099] For example, when the ratio of silicon elements is higher than that of oxygen elements, the insulation deteriorates and excessive leakage current is applied at the internal short circuit point. This causes the resistance of the internal short circuit point to increase, and the temperature of the lithium secondary battery to rise rapidly. In addition, when the ratio of silicon elements is lower than that of oxygen elements, the band gap of silicon-containing particles increases, thereby completely blocking leakage current in the event of an internal short circuit. This makes it difficult to selectively determine / diagnose the corresponding lithium secondary battery in which an internal short circuit has occurred.

[0100] In addition, silicon-containing particles have a chemical structure in which lithium ions can be inserted during charging of a lithium secondary battery, and have traditionally been applied as silicon-based negative electrode active materials for application to the negative electrode active layer. However, when silicon-containing particles are applied to the coating of the present invention, the surface area for lithium ion insertion can be significantly reduced due to the low content ratio compared to when applied to the negative electrode active layer. This means that the resistance of silicon-containing particles to lithium insertion occurring in the coating is increased. Therefore, unlike ordinary silicon-based negative electrode active materials, in silicon-containing particles applied to the coating of the present invention, it may be difficult to insert lithium ions during charging of a lithium secondary battery.

[0101] In addition, the silicon-containing particles may have an average particle size (D 50 For example, the silicon-containing particles may have an average particle size (D 50): about 1μm to 10μm; 1μm to 5μm; 1μm to 3μm; 3μm to 9μm; 3μm to 7μm; 10μm to 20μm; 15μm to 20μm; 14μm to 19μm; 5μm to 15μm; 5μm to 10μm; 5μm to 8μm; 7.5μm to 10μm; 5μm to 7.5μm; 6μm to 8μm; or 6μm to 7μm.

[0102] When the average particle size of silicon-containing particles (D 50 ) is less than the above range, the silicon-containing particles tend to penetrate into the negative electrode active layer arranged below the coating layer. Therefore, the resistance at the interface between the negative electrode active layer and the coating layer increases, and then the electrical performance may deteriorate during normal operation of the lithium secondary battery. In addition, when the average particle size (D 50 ) When the above range is exceeded, it is difficult to form a uniform coating. In order to uniformly form the coating, the average thickness of the coating is excessively increased, which leads to a problem of reduced energy density of the negative electrode.

[0103] Here, the average thickness of the coating layer containing silicon-containing particles can be about 1.5 μm to 30 μm, and the average thickness can be greater than the average particle size of the silicon-containing particles. For example, the coating layer can have the following average thickness: about 1.5 μm to 20 μm; 1.5 μm to 10 μm; 1.5 μm to 5 μm; 1.5 μm to 3 μm; 3 μm to 9 μm; 3 μm to 7 μm; 5 μm to 25 μm; 5 μm to 20 μm; 5 μm to 18 μm; 5 μm to 15 μm; 5 μm to 10 μm; 5 μm to 8 μm; 10 μm to 20 μm; 11 μm to 19 μm; 8 μm to 13 μm; 10 μm to 15 μm; 14 μm to 19 μm; 15 μm to 18 μm; 12 μm to 16 μm; or 11 μm to 14 μm. Here, the average thickness of the coating can be measured by a method commonly used in the art for measuring film thickness. The average thickness may refer to the average of any three or more measured values, or may refer to the median between the maximum and minimum values ​​among the measured values.

[0104] In addition, the thickness ratio of the coating layer to the negative electrode active layer may be about 0.05 to 0.3, and for example may be about 0.05 to 0.2; 0.05 to 0.1; 0.05 to 0.09; 0.07 to 0.12; 0.1 to 0.2; 0.15 to 0.25; or 0.15 to 0.2.

[0105] The volume resistance of the negative electrode according to the present disclosure may be affected by: i) the volume resistance of the coating; and ii) the thickness ratio of the negative electrode active layer and the coating. Here, as described above, the volume resistance of the coating can be controlled by, for example, the components forming the coating, the content of each component, and the mixed form and size of each component. However, even if the volume resistance of the coating is controlled, when the thickness of the negative electrode active layer is too thicker than the thickness of the coating and the thickness ratio of the coating to the negative electrode active layer is less than the above lower limit, the electrical performance of the negative electrode can be further improved, but the volume resistance of the negative electrode can be reduced, and then the insulation can be significantly reduced in the case of an internal short circuit. In addition, when the thickness of the negative electrode active layer is equal to or less than the thickness of the coating, and the thickness ratio of the coating to the negative electrode active layer is greater than the above upper limit, the volume resistance of the negative electrode increases significantly. Therefore, in the case of an internal short circuit, the short-circuit current of the lithium secondary battery is blocked, but in a device including multiple lithium secondary batteries such as a battery module or a battery pack, it is not easy to selectively detect and deal with lithium secondary batteries with internal short circuits in a relatively short time. Then, there is a limitation of low economic feasibility.

[0106] Therefore, in the present disclosure, by adjusting the thickness ratio of the coating layer to the negative electrode active layer within the above range, the energy density of the negative electrode can be achieved at a relatively high level, and the volume expansion rate of the negative electrode can be minimized during normal operation of the lithium secondary battery. In addition, the negative electrode has the advantages of preventing the resistance from being significantly increased due to excessive thickness and physically protecting the negative electrode surface in the event of an internal short circuit.

[0107] In addition, the silicon-containing particles may include a carbon layer on their surface to improve the energy density and energy efficiency of the negative electrode during normal operation of the lithium secondary battery. The carbon layer may have the following form: the silicon-containing particles and the carbon particles are evenly mixed, and then the carbon particles are physically and chemically adsorbed on the surface of the silicon-containing particles. In some cases, the carbon layer may also have the form of carbon atoms deposited on the surface of the silicon-containing particles. The carbon layer can improve the conductivity of the particle surface while suppressing the volume expansion of the silicon-containing particles. Therefore, in the coating, in the case of an internal short circuit in the lithium secondary battery, the insulation of the coating is reduced, but during the normal operation of the lithium secondary battery, the volume change of the negative electrode can be minimized and the charge / discharge capacity and efficiency can be improved.

[0108] In addition, the average thickness of the carbon layer can be about 1nm to 1000nm, and can be, for example, about 100nm to 1000nm; 200nm to 1000nm; 500nm to 1000nm; 800nm ​​to 1000nm; 10nm to 200nm; 10nm to 90nm; 10nm to 70nm; 10nm to 50nm; or 10nm to 30nm.

[0109] In addition, the negative electrode active layer included in the negative electrode includes a carbon-based negative electrode active material, and the carbon-based negative electrode active material may include a carbon-based negative electrode active material commonly used in the art. For example, a carbon-based negative electrode active material represents a material containing carbon atoms as a main component. This carbon-based negative electrode active material may include one or more types selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitized carbon, carbon black, acetylene black and Ketjen black. For example, the carbon-based negative electrode active material may include one or more of natural graphite and artificial graphite, but according to an embodiment, it may include natural graphite, or a mixture of natural graphite and artificial graphite.

[0110] In addition, the carbon-based negative electrode active material can be a spherical graphite particle formed by aggregating a plurality of scaly graphites. Examples of scaly graphite can include natural graphite and artificial graphite, and those obtained by graphitization, such as mesophase calcined carbon (blocky mesophase) and coke (coarse coke, green coke, pitch coke, needle coke, petroleum coke, etc.) where the raw materials are tar and asphalt. For example, the carbon-based negative electrode active material can be a particle obtained by using a plurality of natural graphites with high crystallinity. In addition, a graphite particle can be formed by aggregating about 2 to 100 scaly graphites (e.g., 3 to 20 scaly graphites).

[0111] In addition, the carbon-based negative active material may have an average particle size (D 50 ), and may have, for example, an average particle size (D 50 ): about 0.5μm to 15μm; 0.5μm to 10μm; 5μm to 20μm; 10μm to 20μm; 12μm to 18μm; 2μm to 7μm; 0.5μm to 5μm; or 1μm to 3μm.

[0112] Furthermore, along with the carbon-based negative electrode active material as a main component, the negative electrode active layer may optionally further include, for example, a conductive material, a binder, and other additives as required.

[0113] The conductive material may include one or more types of carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, and the like.

[0114] As an example, as the conductive material contained in the negative electrode active layer, carbon black, carbon nanotube, carbon fiber, etc. can be used alone or in combination.

[0115] Relative to a total of 100 parts by weight of the negative electrode active layer, the content of the conductive material may be about 0.1 to 10 parts by weight, or may be, for example, about 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight. In the present disclosure, by controlling the content of the conductive material within the above range, the increase in negative electrode resistance and the decrease in charging capacity due to low content of the conductive material can be prevented. In addition, problems caused by excessive conductive material, such as a decrease in charging capacity due to a decrease in the content of the negative electrode active material, or a decrease in fast charging characteristics due to an increase in the amount of negative electrode active layer loading, can be prevented.

[0116] In addition, the binder can be appropriately applied within the range that the electrical properties of the electrode are not reduced, as a component for the bonding of auxiliary negative electrode active materials, conductive materials, etc. and the bonding with the current collector. For example, the binder may include any one or more selected from the group consisting of: vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber and fluororubber.

[0117] The content of the binder may be about 0.1 to 10 parts by weight relative to a total of 100 parts by weight of the negative electrode active layer, or may be, for example, about 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. In the present disclosure, by controlling the content of the binder contained in the negative electrode active layer within the above range, the viscosity of the active layer due to low binder content can be prevented from being reduced, or the electrical performance of the electrode due to excessive binder can be prevented from being reduced.

[0118] In addition, there is no particular limitation on the negative electrode current collector as long as it has relatively high conductivity without causing chemical changes in the corresponding battery. For example, copper, stainless steel, nickel, titanium, calcined carbon, etc. can be used, and in the case of copper or stainless steel, materials whose surfaces are treated with carbon, nickel, titanium, silver, etc. can also be used. In addition, considering the conductivity and total thickness of the negative electrode to be manufactured, the average thickness of the negative electrode current collector can be appropriately applied in the range of about 1 μm to 500 μm.

[0119] In addition, the positive electrode includes a positive electrode composite layer prepared by coating, drying and pressing a positive electrode slurry containing a positive electrode active material on a positive electrode current collector. The positive electrode slurry may optionally further include a conductive material, a binder, other additives, etc. as needed.

[0120] The positive electrode active material is a material capable of electrochemically causing a reaction on the positive electrode current collector, and may include one or more of lithium metal oxides that allow lithium ions to be reversibly intercalated and deintercalated and are represented by the following Chemical Formula 1 and Chemical Formula 2:

[0121] [Chemical formula 1]

[0122] LiFe a M 1 1-a XO 4

[0123] [Chemical formula 2]

[0124] Li x [Ni y Co z Mn w M 2 v ]O 2

[0125] In Chemical Formula 1 and Chemical Formula 2,

[0126] M 1 is one or more types of W, Cu, Fe, V, Cr, Co, Ni, Mn, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B or Mo,

[0127] X is one or more of P, Si, S, As or Sb,

[0128] a satisfies 0 <a≤1.0,

[0129] M 2 is one or more of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, or Mo, and

[0130] x, y, z, w and v respectively satisfy 1.0≤x≤1.30, 0≤y<1, 0≤z≤1, 0≤w≤1, and 0≤v≤0.1, and y+z+w+v=1.

[0131] The compounds represented by Chemical Formula 1 and Chemical Formula 2 are lithium metal oxides used as positive electrode active materials of lithium secondary batteries in the art. Among them, the lithium composite metal oxide represented by Chemical Formula 2 is a ternary lithium oxide containing nickel (Ni), cobalt (Co) and manganese (Mn) as main components. The lithium composite metal oxide has a high energy density, so it has the advantages of being suitable for medium or large secondary batteries in transportation fields such as electric vehicles (EV) or power storage such as energy storage systems (ESS) in terms of performance such as output.

[0132] Examples of the compound represented by Chemical Formula 1 may include LiFePO 4 、LiFe 0.8 Mn 0.2 PO 4 、LiFe 0.7 Mn 0.3 PO 4 and LiFe 0.5 Mn 0.5 PO 4 . In addition, as the nickel (Ni) content increases, the charge / discharge capacity of the lithium composite metal oxide increases, but exhibits low chemical / structural stability. Therefore, an exothermic reaction is likely to occur. This leads to a problem of a high probability of fire. For example, when a short-circuit current flows inside the battery, an exothermic reaction may occur. Therefore, in a lithium secondary battery according to the present disclosure, a coating that satisfies a predetermined volume resistance is introduced into the negative electrode. Then, in the event of an internal short circuit caused by contact between the negative electrode surface and the positive electrode current collector (and / or the positive electrode active layer), the exothermic reaction is suppressed while leaking a very small amount of current, thereby preventing problems that occur continuously after an internal short circuit. Therefore, it has the advantage of improving safety.

[0133] Examples of these lithium metal oxides represented by Chemical Formula 2 may include LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.9 Co 0.05 Mn 0.05 O 2 、LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O2 , and LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O 2 .

[0134] In addition, the content of the positive electrode active material may be about 85 parts by weight or more, or may be, for example, about 90 parts by weight or more, 93 parts by weight or more, or 95 parts by weight or more, relative to the weight of the positive electrode active layer.

[0135] In addition, the positive electrode active layer may further include a conductive material, a binder, other additives, and the like, together with the positive electrode active material.

[0136] Here, the conductive material is used to improve the electrical properties of the positive electrode, and those commonly used in the art can be applied. Its example can include one or more types selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, denka black, ketjen black, super-P, channel black, furnace black, lamp black, thermal black, graphene and carbon nanotubes.

[0137] In addition, the content of the conductive material can be about 0.1 parts by weight to 5 parts by weight, or can be, for example, about 0.1 parts by weight to 4 parts by weight; 2 parts by weight to 4 parts by weight; 1.5 parts by weight to 5 parts by weight; 1 part by weight to 3 parts by weight; 0.1 parts by weight to 2 parts by weight; or 0.1 parts by weight to 1 part by weight, relative to the weight of each positive electrode active layer.

[0138] In addition, the binder plays the role of bonding the positive electrode active material, the positive electrode additive and the conductive material to each other, and as long as it has this function, it can be used without particular limitation. For example, the binder may include one or more types of resins selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethyl methacrylate and copolymers thereof. As an example, the binder may include polyvinylidene fluoride.

[0139] In addition, the content of the binder may be about 1 to 10 parts by weight, and for example, about 2 to 8 parts by weight; or 1 to 5 parts by weight, relative to the weight of each positive active layer.

[0140] For example, the total thickness of the positive active layer may be about 50 μm to 300 μm, or may be 100 μm to 200 μm; 80 μm to 150 μm; 120 μm to 170 μm; 150 μm to 300 μm; 200 μm to 300 μm; or 150 μm to 190 μm.

[0141] In addition, in the positive electrode, for the positive electrode current collector, those having high conductivity and not causing chemical changes in the corresponding battery can be used. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, materials whose surfaces are treated with carbon, nickel, titanium, silver, etc. can also be used. In addition, considering the conductivity and total thickness of the positive electrode to be manufactured, the average thickness of the current collector can be appropriately applied in the range of about 3 μm to 500 μm.

[0142] In addition, the separator inserted between the positive electrode and the negative electrode of each unit cell is an insulating film with high ion permeability and mechanical strength, and as long as it is commonly used in the art, there is no particular limitation. For example, polypropylene; polyethylene; and polyethylene-propylene copolymers containing one or more types of chemically resistant and hydrophobic polymers can be used. The separator may have the form of a porous polymer substrate, such as a sheet or nonwoven fabric containing the above polymer, or in some cases, may have the form of a composite separator in which organic or inorganic particles are coated with an organic binder on a porous polymer substrate. In addition, the separator may have an average pore size of about 0.01 μm to 10 μm and an average thickness of about 5 μm to 300 μm.

[0143] Meanwhile, the lithium secondary battery according to the present disclosure may be a secondary battery having the following form: it may include a stacked, zigzag, or zigzag stacked electrode assembly in which the possibility of contact between the positive electrode current collector (and / or the positive electrode active layer) and the negative electrode active layer is relatively high. As an example, the lithium secondary battery according to the present disclosure may be a pouch-type secondary battery or a square secondary battery.

[0144] Lithium secondary battery system

[0145] Furthermore, according to one embodiment of the present disclosure,

[0146] A lithium secondary battery system includes: battery cell assemblies, each including n (where n is an integer from 3 to 100) lithium secondary batteries according to the present disclosure;

[0147] a charge / discharge unit electrically coupled to each battery cell assembly to charge or discharge each battery cell assembly individually;

[0148] a sensing unit electrically coupled to an electrode of each lithium secondary battery included in the battery cell assembly to individually measure at least one amount of electricity among a voltage and a current of the secondary battery during charge / discharge of each lithium secondary battery; and

[0149] A control unit is electrically connected to the charge / discharge unit and the sensing unit to control the charge or discharge of each battery cell assembly, wherein

[0150] When the amount of electricity measured by the sensing unit satisfies a predetermined value, the control part stops charging or discharging of the cell assembly including the corresponding lithium secondary battery.

[0151] Figure 1 Schematic diagram of the configuration of a lithium secondary battery system according to the present disclosure. Figure 1 According to the present disclosure, the lithium secondary battery system 10 includes: a battery cell assembly 110, each battery cell assembly 110 includes n lithium secondary batteries 111 (where n is an integer from 3 to 100) of the present disclosure; a charge / discharge unit 120, which is electrically connected to each battery cell assembly 110 to charge or discharge each battery cell assembly individually; a sensing unit 130, which is electrically connected to the electrodes of each lithium secondary battery 111 included in the battery cell assembly 110 to measure the voltage and / or current of each secondary battery 111 individually during the charge / discharge of the lithium secondary battery; a control unit 140, which is electrically connected to the charge / discharge unit 120 and the sensing unit 130 to control the charge or discharge of each battery cell assembly 110; and a secondary battery pack 150. Meanwhile, the lithium secondary battery 111 includes a positive electrode 111a and a negative electrode 111b, and the secondary battery pack 150 includes a positive terminal 112a and a negative terminal 112b.

[0152] Figure 2 is a block diagram illustrating a hardware configuration for realizing the control section 140 included in the lithium secondary battery system according to the present disclosure.

[0153] The control section 140 according to one embodiment disclosed in this document may include an MCU 142, a memory 144, a communication I / F 146, and an input / output I / F 148. The MCU 142 is a micro control unit, and is a processor that executes various programs stored in the memory 144, processes various data used in the programs, and performs the functions of the control section 140.

[0154] The memory 144 can store operation data of various programs related to the operation of the lithium secondary battery system in order to operate the control unit 140. A plurality of such memories 144 can be provided as needed. The memory 144 can be a volatile memory or a non-volatile memory. For a volatile memory as the memory 144, RAM, DRAM, SRAM, etc. can be used. For a non-volatile memory as the memory 144, ROM, PROM, EAROM, EPROM, EEPROM, flash memory, etc. can be used. The examples of the memory 144 listed above are merely examples, and the present disclosure is not limited thereto.

[0155] The communication I / F 146 is configured to send various data to / receive various data from the server, and may be various devices capable of supporting wired or wireless communication. For example, through the communication I / F 146, a program or various data for operating the control unit 140 may be sent to or received from a separately prepared external server by wire or wirelessly. The input / output I / F 148 may provide an interface for connecting an input device (not shown) such as a keyboard, a mouse, or a touch panel and an output device such as a display (not shown) to the MCU 142 to allow data to be sent and received.

[0156] The lithium secondary battery system 10 is configured to individually measure and monitor the voltage and / or current of each of the n lithium secondary batteries 111 constituting the battery cell assembly 110 during charging or discharging of the secondary battery to detect an internal short circuit of the secondary battery 111. Then, when an internal short circuit is detected, charging or discharging of only the battery cell assembly 110 including the corresponding lithium secondary battery 111 is immediately stopped.

[0157] For example, for conventional secondary battery systems, a technology has been developed for diagnosing internal short circuits in secondary batteries by measuring temperature changes of batteries being charged and / or discharged or by using changes in the state of charge (SOC) caused by self-discharge in the case of an internal short circuit. However, when an internal short circuit of a secondary battery actually occurs, it progresses to thermal runaway in a relatively short time due to a meltdown phenomenon. Therefore, in the case of the above-mentioned technology, there are limitations: because the diagnostic accuracy is not high or the diagnostic process is complicated, and then it takes a relatively long time to identify an internal short circuit, it is difficult to cope with thermal runaway.

[0158] However, the lithium secondary battery system 10 according to the present disclosure includes the above-mentioned lithium secondary battery 111 of the present disclosure, and the above-mentioned lithium secondary battery includes a negative electrode in which a coating having a predetermined volume resistance is provided on the surface of the negative electrode active layer. Therefore, in the case where the positive electrode current collector (or positive electrode active layer) contacts the surface of the negative electrode and causes an internal short circuit, it is possible to achieve appropriate insulation on the surface of the negative electrode while allowing a very low amount of leakage current to flow through the negative electrode. Here, in the case of an internal short circuit, in a conventional lithium secondary battery, the voltage and current are close to 0V and 0A, respectively, due to the leakage current. However, the remaining predetermined current flows through the lithium secondary battery 111 according to the present disclosure after the loss of a trace leakage current, so the remaining current can be used to detect and / or determine the internal short circuit of the lithium secondary battery 111 with relatively high accuracy in a very short time. In addition, in the lithium secondary battery 111, the heat generated by the internal short circuit (such as short circuit heat) can be significantly reduced, thereby delaying the occurrence of the melting phenomenon. In addition, the heat of the corresponding lithium secondary battery with internal short circuit can be prevented from causing additional heat generation and / or melting phenomenon in the adjacent lithium secondary battery. Therefore, the coping (or processing) time for preventing the corresponding lithium secondary battery that has internal short circuit from thermal runaway can be ensured.

[0159] In order to realize the above-mentioned features, the sensing unit 130 is electrically connected to the lithium secondary battery 111 separately from the charging / discharging unit 120, and can measure the electrical characteristics of the secondary battery electrodes (especially the negative electrode) flowing through each lithium secondary battery in real time during the charging or discharging of the lithium secondary battery 111. Here, the electrical characteristics are characteristics related to the electricity flowing through the electrodes (especially the negative electrode) of the lithium secondary battery, and can include current, voltage, etc. The electrical characteristics measured in this way can be sent to the control unit 140.

[0160] As an example, the sensing unit 130 can measure one or more types of voltage and current of each lithium secondary battery 111 individually. In the lithium secondary battery system 10 according to the present disclosure, the above-mentioned lithium secondary battery 111 of the present disclosure is included in the battery cell assembly, so that even if an internal short circuit occurs, insulation is achieved on the negative electrode surface, and a predetermined current remaining after a very small amount of leakage current is lost is applied. Therefore, by the change of at least one of the current and voltage, it is possible to quickly diagnose whether an internal short circuit has occurred in the lithium secondary battery 111 individually.

[0161] The sensing unit 130 may include measures commonly used in the art to measure electrical characteristics of current flowing through each lithium secondary battery 111. For example, the sensing unit 130 may include a current measuring sensor for measuring current or a voltage measuring sensor for measuring voltage.

[0162] In addition, the sensing unit 130 may further include a temperature measurement sensor (not shown) inside the battery cell assembly 110. The temperature measurement sensor is used to measure the temperature of each lithium secondary battery 111 disposed in the battery cell assembly 110. When the temperature of the secondary battery increases, the current of the lithium secondary battery may increase. When the current is too large due to an overload caused by a load fluctuation connected to the system, the input or disconnection of a transformer or capacitor, or the operation of a motor or motor, the temperature of the secondary battery may increase. The sensing unit 130 may also include a temperature measurement sensor that measures the temperature of each lithium secondary battery 111 to reflect the current change caused by such a temperature increase of the secondary battery in addition to the internal short circuit of the lithium secondary battery. Therefore, when determining an internal short circuit, the error rate can be further reduced.

[0163] In addition, the control part 140 is electrically coupled to each of the charging / discharging unit 120 and the sensing unit 130. The control part 140 monitors the electrical properties of each lithium secondary battery 111 in real time during the charging and / or discharging of each battery cell assembly 110, and at the same time, individually detects and / or determines the internal short circuit of the lithium secondary battery 111 through the change of the electrical properties. Then, the control part 140 controls the charging or discharging of the battery cell assembly 110 including the corresponding lithium secondary battery 111 in which the internal short circuit has occurred.

[0164] As an example, the control section 140 monitors in real time the electrical characteristics of each lithium secondary battery 111 transmitted from the sensing unit 130. Then, when there is a change in the transmitted electrical characteristics, the control section 140 determines whether the amount of change satisfies a predetermined value; then, when the predetermined value is satisfied, the charging or discharging of the cell assembly 110 including the corresponding lithium secondary battery 111 is individually controlled through the charging / discharging unit 120.

[0165] Specifically, the control unit 140 receives the individual charges of all lithium secondary batteries 111 included in the lithium secondary battery system 10 from the sensing unit 130. Then, the charge of each battery cell assembly 110 including these batteries and the average value of the charges of multiple battery cell assemblies 110 (i.e., the average charge (A) of the battery cell assembly 110) can be calculated based on the individual charges sent by the lithium secondary batteries 111. The charge may represent a voltage and / or current that may reflect a correction value based on the temperature of each lithium secondary battery. The correction value is measured by the temperature measurement sensor of the sensing unit 130. In addition, the average charge (A) of the battery cell assembly 110 may be the average charge of all battery cell assemblies included in the lithium secondary battery system, and in some cases, may also be the average charge of some battery cell assemblies among all the battery cell assemblies.

[0166] By comparing the average power (A) of the cell assembly 110 calculated in this way with the power of each cell assembly 110 individually, a cell assembly 110 with an error rate of about 5% or more, for example, about 7% or more; 10% or more; 5% to 20%; or 5% to 15% can be preliminarily selected. The preliminary selection is the process of selecting cell assemblies of lithium secondary batteries including lithium secondary batteries that are considered to have problems among all lithium secondary batteries. The time required to monitor the applied power preset for charging / discharging of all lithium secondary batteries and the power of individual lithium secondary batteries can be shortened, thereby providing rapidity in determining internal short circuits of lithium secondary battery systems.

[0167] In addition, among the n lithium secondary batteries included in each battery cell assembly, a voltage difference may occur between the batteries during charging / discharging. This voltage difference between the batteries may be caused by the manufacturing process of each lithium secondary battery or external factors, which may then affect the capacity and life of the lithium secondary battery and may cause each lithium secondary battery to be overcharged and / or over-discharged. Therefore, battery cell balancing can be performed to prevent this situation. Battery cell balancing can be performed by applying a microcurrent to a circuit structure applied to a lithium secondary battery system. In this case, a charge deviation may occur between the lithium secondary batteries. Therefore, by setting the error rate between the average charge (A) and the charge of each lithium secondary battery to about 5% or more, the accuracy of determining an internal short circuit can be further improved.

[0168] Next, when the power of the individual lithium secondary battery is lower than the preset applied power for charging or discharging of the lithium secondary battery 111 included in the preliminarily selected cell assembly 110 by more than about 0.5%, the control unit 140 may determine that the corresponding lithium secondary battery is internally short-circuited.

[0169] Generally speaking, when an internal short circuit occurs in a lithium secondary battery, the measured current and voltage may be close to 0A and 0V, respectively, due to the leakage current generated at the short circuit point. However, in the lithium secondary battery system according to the present disclosure, since a coating of a negative electrode is provided in the secondary battery, not only a predetermined insulation can be achieved on the surface of the negative electrode, but also a predetermined amount of current can flow in the case of an internal short circuit. This current is the applied current remaining after the loss of a very small amount of current leaked at the internal short circuit point, and therefore may be lower than the applied current preset for charging or discharging the lithium secondary battery. This deviation between the preset applied current amount and the current amount can be about 0.5% or more of the preset applied current amount, and can be, for example, about 0.5% or more; 1% or more; 2% or more; 3% or more; 5% or more; 10% or more; 15% or more; 20% or more; 30% or more; 50% or more; 70% or more; 5% to 90%; 5% to 50%; 10% to 30%; 50% to 90%; 0.5% to 20%; 0.5% to 10%; 0.5% to 5%; 0.5% to 3%; or 5% to 10%.

[0170] The control unit 140 may send a charge or discharge stop signal to the charge / discharge unit 120 to stop the charging or discharging of the cell assembly 110 including the corresponding lithium secondary battery 111 determined to be internally short-circuited, and then stop the charging or discharging of the corresponding lithium secondary battery 111. When receiving the charge or discharge stop signal from the control unit 140, the charge / discharge unit 120 may selectively stop the charging or discharging of the cell assembly 110 including the corresponding lithium secondary battery 111. In the present disclosure, when an internal short circuit occurs in a lithium secondary battery, charging or discharging is controlled based on the cell assembly. Therefore, compared with when the response to the internal short circuit is performed based on the lithium secondary battery, not only the response time can be further reduced, but also the maintenance efficiency can be improved during the normal use of the lithium secondary battery system.

[0171] Meanwhile, the battery cell assembly 110 may include two or more lithium secondary batteries 111 of the present disclosure, or may include, for example, 2 to 100; 2 to 50; 2 to 30; 5 to 20; 3 to 5; 5 to 20; or 10 to 20 lithium secondary batteries 111 .

[0172] The lithium secondary batteries 111 may be electrically connected in series, in parallel, or in a series-parallel hybrid form.

[0173] As an example, n lithium secondary batteries can be connected in parallel and installed inside the battery cell assembly. According to the lithium secondary battery system of the present disclosure, in the event of an internal short circuit, charging / discharging is controlled based on the battery cell assembly. However, as described above, when n lithium secondary batteries arranged inside the battery cell assembly are electrically connected in parallel, the advantage is that among the n lithium secondary batteries, the charging / discharging of the corresponding lithium secondary batteries in which an internal short circuit has occurred can be additionally controlled separately. In addition, the advantage is that when an internal short circuit occurs in any lithium secondary battery, the charging or discharging of each lithium secondary battery can be controlled.

[0174] In addition, the battery cell assembly 110 may be a battery module or a battery pack, depending on the number of lithium secondary batteries contained in the battery cell assembly 110, or the shape and / or type of the housing containing these secondary batteries. In addition, when a plurality of such battery cell assemblies 110 (150) are included, the plurality of battery cell assemblies may refer to a battery pack or an energy storage system.

[0175] In addition, the charging / discharging unit 120 is electrically connected to the battery cell assembly 110 individually, and has a function of charging or discharging each battery cell assembly 110. To this end, the charging / discharging unit 120 can be electrically connected to an external power source PS for charging the battery cell assembly 110 and an electric load EL for using the power stored in the battery cell assembly 110 individually.

[0176] The types of the external power source PS and the electric load EL are not particularly limited as long as they correspond to methods generally applied to products to which the lithium secondary battery system 10 is applied.

[0177] As an example, the external power source PS is a device that can provide constant current or constant voltage charging power to each battery cell assembly 110. When the lithium secondary battery system 10 is applied to an electric vehicle (EV), the external power source PS may include a charging station for the electric vehicle (EV), and in some cases, may include a separate power source or an auxiliary battery contained in the electric vehicle (EV).

[0178] In addition, the electric load EL is a device that uses the power stored in the battery cell assembly 110 and discharges the lithium secondary battery 111 provided in the battery cell assembly 110. When the lithium secondary battery system 10 is applied to an electric vehicle (EV), the electric load EL may be, for example, an inverter or a motor applied to the electric vehicle (EV). The inverter may perform a function of converting a direct current provided from the battery cell assembly 110 included in the lithium secondary battery system 10 into an alternating current. The motor may be driven using the alternating current provided from the inverter.

[0179] In addition, the lithium secondary battery system 10 according to the present disclosure may further include an input / output unit (not shown) through which charging / discharging conditions may be input to the control part 140 and a user may check a result determined by the control part 140 .

[0180] The lithium secondary battery system 10 can change the conditions of applying voltage or applying current during charging and / or discharging according to the type of the electric load EL electrically connected to the charging / discharging unit 120 or the use environment. In order to input the charging / discharging conditions thus changed to the control section 140, the input / output unit may include a user input device commonly used in the art, such as a keyboard, a mouse, a barcode recognizer, a voice recognizer, and a touch screen.

[0181] In addition, when the control unit 140 determines that an internal short circuit has occurred in the battery cell assembly 110, in order to notify the user of, for example, whether an internal short circuit has occurred; the time of occurrence; and the location of the corresponding lithium secondary battery 111 and / or the corresponding battery cell assembly 110 determined to have an internal short circuit, the input / output unit may include output devices commonly used in the art, such as a display device (e.g., a monitor or a touch screen), and an audio output device.

[0182] In addition, the lithium secondary battery system 10 according to the present disclosure has the above-mentioned configuration, and then has excellent safety against internal short circuits, so it can be used as a power source for medium and large devices that require, for example, high energy density and high safety against internal short circuits. Examples of these medium and large devices can include: electric tools powered and driven by electric motors; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters (Escooters); electric golf carts; and energy storage systems (ESSs), and hybrid electric vehicles (HEVs) can be exemplified.

[0183] In addition, the electronic or electrical device described in this specification and / or any other related device or component can be implemented using any suitable hardware, firmware (e.g., application specific integrated circuit), software, or a combination of software, firmware and hardware. For example, the various components of these devices can be formed on an integrated circuit (IC) chip or a single IC chip. In addition, the various components of these devices can be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB) or a substrate. The electrical connection or interconnection described in this specification can be implemented by wiring or conductive elements on a circuit carrier such as a PCB or other types. For example, the conductive element can include metallization such as surface metallization, and / or pins, and can include conductive polymers or ceramics. In addition, electrical energy can be transmitted via a wireless connection such as using electromagnetic radiation or light.

[0184] In addition, the various components of these devices can be processes or threads executed on one or more processors within one or more computing devices, executing computer program instructions and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in a memory, which can be implemented in a computing device using standard memory devices (such as, for example, random access memory (RAM)). The computer program instructions can also be stored in other non-transitory computer readable media (such as, for example, CD-ROMs and flash drives).

[0185] Furthermore, those skilled in the art will recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or that the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the exemplary embodiments of the present disclosure.

[0186] Since the lithium secondary battery system according to the present disclosure has the above configuration, a predetermined current can be applied in the event of an internal short circuit. Therefore, before thermal runaway occurs in the corresponding lithium secondary battery that has already short-circuited, charging and / or discharging can be controlled in advance. In addition, since additional meltdown phenomena and / or thermal runaway can be prevented from occurring in adjacent lithium secondary batteries, the lithium secondary battery system can be effectively applied to, for example, a battery module or battery pack that uses multiple lithium secondary batteries.

[0187] Hereinafter, the present disclosure will be described in more detail with reference to Examples and Experimental Examples.

[0188] Meanwhile, the following examples and experimental examples are merely illustrative of the present disclosure, and the contents of the present disclosure are not limited to the following examples and experimental examples.

[0189] Examples 1 to 5 and Comparative Examples 1 to 5. Fabrication of Lithium Secondary Batteries

[0190] Cathode Manufacturing

[0191] Preparation of LiNi with a particle size of 5 μm 0.8 Co 0.1 Mn 0.1 O 2 As the positive electrode active material, it was then mixed with a carbon-based conductive agent and polyvinylidene fluoride as a binder in N-methylpyrrolidone (NMP) at a weight ratio of 94:3:3 to form a slurry. The slurry was cast on a thin aluminum plate, dried in a vacuum oven at 120°C, and rolled to prepare a positive electrode.

[0192] Negative electrode manufacturing

[0193] A mixed graphite obtained by mixing natural graphite (average particle size: 10±1 μm) and artificial graphite (average particle size: 8±1 μm) at a weight ratio of 2:8 was prepared as a negative electrode active material, and carbon black as a conductive material and carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as a binder were prepared. Then, 95 parts by weight of the mixed graphite, about 1 part by weight of carbon black, 1.5 parts by weight of carboxymethyl cellulose (CMC) and 2.5 parts by weight of styrene butadiene rubber (SBR) were mixed with water to have a solid content of 50%, thereby preparing a negative electrode slurry.

[0194] Separately, silicon-containing particles and styrene-butadiene rubber (SBR) and carbon black as a conductive material were added to water and mixed for 20 to 30 minutes to prepare a coating slurry. Here, i) the content of each component contained in the coating slurry; ii) the type of silicon-containing particles; and iii) the particle size (D 50 ) are adjusted as described in Table 1 below.

[0195] When the negative electrode slurry and the coating slurry are prepared separately, the slurry is simultaneously cast on a copper sheet (thickness: 10 μm) conveyed in a roll-to-roll manner (conveying speed: 5 m / min) by using a double-die coater. Here, the negative electrode slurry and the coating slurry are cast so that the average thickness becomes 100 μm to 200 μm and 5 μm to 20 μm respectively along the conveying direction of the copper sheet. The copper sheet on which the slurry is simultaneously cast is dried in a vacuum oven at 120°C and rolled to prepare a negative electrode (the thickness ratio of the coating layer to the negative electrode active layer is about 0.17).

[0196] Scanning electron microscope analysis was performed on the cross sections of the negative electrodes prepared in Examples 2 and 3, and the results are shown in Figure 3 (A) and Figure 3 In addition, the volume resistance of each prepared negative electrode was measured. The measurement results are presented in Table 1.

[0197] Manufacturing of lithium secondary batteries

[0198] A separator made of 18 μm polypropylene was placed between the previously prepared positive electrode and negative electrode, and inserted into a pouch-type case, and then the electrolyte composition was injected. Thus, a 1 Ah-class lithium secondary battery was assembled.

[0199] [Table 1]

[0200]

[0201] Comparative Example 7. Manufacture of lithium secondary battery

[0202] A lithium secondary battery was manufactured by performing the same method as in Example 2 except that the negative electrode active layer and the coating layer were formed when the negative electrode was manufactured so that the thickness ratio of the coating layer (average thickness: 1.5 μm) to the negative electrode active layer became 0.02. Here, the volume resistance of the negative electrode was about 4.375×10 -3 .

[0203] Examples 6 to 10 and Comparative Examples 8 to 14. Fabrication of Lithium Secondary Battery System

[0204] By using each of the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7, a Figure 2 A lithium secondary battery system of the configuration shown.

[0205] For example, 10 lithium secondary batteries manufactured in each of Examples 1 to 5 and Comparative Examples 1 to 7 were prepared, and the five prepared lithium secondary batteries were placed in the battery thickness direction and then fixed, thereby manufacturing two battery cell assemblies 110. The charging / discharging unit 120 and the sensing unit 130 are each electrically connected in parallel to the positive electrode 111a and the negative electrode 111b of each lithium secondary battery provided in the battery cell assembly. The charging / discharging unit 120 used here is provided with a separate port to which an external power supply PS and an electric load EL can be electrically connected. The sensing unit 130 used here is provided with a current measuring sensor for measuring the current of the negative electrode 111b and a temperature measuring sensor for measuring the surface temperature of each lithium secondary battery.

[0206] In addition, the charging / discharging unit 120 and the sensing unit 130 are each electrically connected to the control unit 140, and the control unit 140 used here is provided with a touch screen. Through the touch screen, during the charging and / or discharging of each lithium secondary battery provided in the battery cell assembly 110, voltage and current conditions are input, and then, for example, whether an internal short circuit has occurred during the charging / discharging period; the time when the internal short circuit occurs; and the position of the corresponding lithium secondary battery 111 determined to be internally short-circuited among the lithium secondary batteries of the battery cell assembly is output.

[0207] The external power source PS and the electric load EL are connected to each port of the charging / discharging unit 120, and the charging / discharging of the battery cell assembly is performed. During the charging / discharging process of the battery cell assembly, it is confirmed that the sensing unit 130 measures the current flowing through the negative electrode of each lithium secondary battery and the surface temperature of the lithium secondary battery in real time, and transmits the current and the surface temperature to the control unit 140. Then, the surface of any lithium secondary battery 111 among the lithium secondary batteries 111 arranged in the battery cell assembly 110 is pressed, thereby causing an internal short circuit in the corresponding lithium secondary battery 111.

[0208] When an internal short circuit occurs in the lithium secondary battery 111, the sensing unit 130 measures the current and the surface temperature of each lithium secondary battery provided in the battery cell assembly 110, and transmits the measured current value and the surface temperature of the lithium secondary battery to the control unit 140. The control unit 140 calculates an average value of the transmitted current, and reflects a measured temperature correction value based on the lithium secondary battery on the calculated average value to obtain a current average value (A).

[0209] The control unit 140 compares the current average value (A) calculated in this way with the transmission current value of the lithium secondary battery and the preliminarily selected lithium secondary battery with an error rate of 5% to 10%. Then, the control unit 140 diagnoses that an internal short circuit has occurred in a lithium secondary battery whose current amount is 0.5% to 5% lower than the applied current preset for charging or discharging of the selected lithium secondary battery. In addition, the control unit 140 sends an electrical signal to the charging / discharging unit 120 to stop charging / discharging the battery cell assembly 110 including the lithium secondary battery diagnosed as having an internal short circuit, thereby stopping charging / discharging the corresponding battery cell assembly 110. In this regard, in the example lithium secondary battery system, the charging / discharging of the battery cell assembly was stopped before the corresponding lithium secondary battery caught fire, while in the lithium secondary battery system of the control example, the corresponding lithium secondary battery caught fire before the charging / discharging of the battery cell assembly was stopped.

[0210] Next, the control unit 140 sends to the input / output unit (e.g., a touch screen) whether an internal short circuit has occurred during charging / discharging; the time when the internal short circuit occurred; and the position of the corresponding lithium secondary battery 111 determined to be internally short-circuited among the lithium secondary batteries in the battery cell assembly, and the input / output unit outputs the sent items to the touch screen.

[0211] Experimental example.

[0212] The following experiment was conducted to evaluate the performance of the lithium secondary battery system according to the present disclosure under an internal short circuit condition.

[0213] Figure 4The structure of the battery cell assembly 211 (i.e., the lithium secondary battery used in the experiment) is shown, which includes a positive electrode 211a, a negative electrode 211b, and a separator 211c. The positive electrode 211a includes a positive electrode current collector 211a-1 and a positive electrode active layer 211a-2, while the negative electrode 211b includes a negative electrode current collector 211b-1, a negative electrode active layer 211b-2, and a negative electrode coating 211b-3. According to one embodiment, as Figure 4 As shown, a 1Ah-class pouch-type lithium secondary battery (N / P ratio = about 1.07) for experiment was manufactured by performing the same method as Examples 1 to 5 and Comparative Examples 1 to 7, except that a separator 211c having a hollow central portion 211c-1 was used, and a positive electrode 211a on which a central portion of a positive electrode active layer 211a-2 was not formed was used, so that the positive electrode current collector 211a-1 met the negative electrode active layer 211b-2 in the hollow portion of the separator 211c.

[0214] Each manufactured lithium secondary battery was fully charged, and the center portion of the pouch-type lithium secondary battery was pressed to 1 MPa to cause an internal short circuit. Then, the voltage of the lithium secondary battery and the surface temperature of the lithium secondary battery were measured for 100 seconds. This internal short circuit causing experiment was repeated three times in total.

[0215] At 100 seconds after the internal short circuit, the voltage of the lithium secondary battery and the surface temperature of the lithium secondary battery were measured, and their average values ​​were calculated. Then, after the internal short circuit was caused, it was checked whether a fire occurred in the lithium secondary battery, and the time taken for the battery temperature to reach the maximum value was checked. The results are presented in Table 2 below. In addition, Figures 5 to 8 2 shows the voltage and temperature changes according to the elapsed time.

[0216] Figure 5 1 is a graph illustrating changes in voltage at the negative electrode and battery temperature in the lithium secondary battery of Comparative Example 1 in the case of an internal short circuit caused by contact between the positive electrode current collector and the negative electrode surface. In the corresponding case of the comparative example, it can be seen that the voltage changes rapidly, thus generating a relatively high current, causing the temperature to rise rapidly, and can cause fire in, for example, about 5 seconds.

[0217] also, Figure 6 is a graph illustrating changes in battery temperature and voltage at the negative electrode provided in the lithium secondary battery of Comparative Example 3 in the case where an internal short circuit is caused by contact between the positive electrode current collector and the negative electrode surface. Figure 6 The case of the control example corresponds to the case where the ceramic on the negative electrode surface is slightly coated with a conductive material, and it can be seen that the voltage hardly changes over time, and as a result, for example, no current flows even under a compression of 1 MPa, and the temperature hardly changes. In addition, in this case, no fire occurs, but since the temperature does not change, abnormalities in the battery cell cannot be detected.

[0218] also, Figure 7 : is a graph illustrating changes in battery temperature and voltage at the negative electrode provided in the lithium secondary battery of Comparative Example 4 in the case of an internal short circuit caused by contact between the positive electrode current collector and the negative electrode surface. That is, in this case, there is also a problem that in the case of an internal short circuit, the voltage drops rapidly in a fully charged state, and a fire occurs.

[0219] Figure 8 2 is a graph illustrating changes in battery temperature and voltage at the negative electrode in the lithium secondary battery of Example 2 in multiple experiments when an internal short circuit is caused by contact between the positive electrode current collector and the negative electrode surface. That is, it can be seen that according to the present disclosure, when SiO or carbon-coated SiO is coated on the negative electrode surface, the current (voltage) gradually and relatively slowly decreases at an SOC state of 100. In this case, even during an internal short circuit, a fire does not occur.

[0220] Separately, as in the manufacture of Example 6, a lithium secondary battery system is manufactured by using a battery cell assembly. The battery cell assembly includes a 1Ah-class pouch-type lithium secondary battery manufactured in advance for the experiment, and 9 pouch-type lithium secondary batteries manufactured in each of Examples 1 to 5 and Comparative Examples 1 to 7. While the manufactured lithium secondary battery system is charged / discharged, an internal short circuit is induced in the lithium secondary battery used for the experiment. Here, the voltage applied during the system charge / discharge is adjusted to 4.2V.

[0221] Then, the lithium secondary battery system was checked to see whether the lithium secondary battery used for the experiment was diagnosed as internally short-circuited, and the location of the internally short-circuited lithium secondary battery was determined. The results are presented in Table 2 below.

[0222] [Table 2]

[0223]

[0224]

[0225] As shown in Table 2 and Figures 5 to 8 As shown, since the lithium secondary battery according to the present disclosure includes a coating having a predetermined volume resistance on the surface of the negative electrode, it is found that insulation is achieved in the case of an internal short circuit in the lithium secondary battery while a small amount of current is applied. Then, while maintaining a relatively high voltage, the temperature of the lithium secondary battery is maintained below 90°C. In addition, it is found that the lithium secondary battery system including the above lithium secondary battery can diagnose whether the lithium secondary battery is internally short-circuited by using a small amount of current applied after the internal short circuit, and the corresponding position can also be accurately determined.

[0226] In addition, it was found that in the lithium secondary batteries of Comparative Examples 1, 2, 4, and 7, in which no coating was provided or the volume resistance of the coating was significantly reduced, the temperature rapidly increased within a few seconds and a fire occurred in the case of an internal short circuit. Due to this rapid thermal runaway, it has been found that the lithium secondary battery system cannot determine whether the battery is internally short-circuited.

[0227] In addition, in the lithium secondary batteries of Comparative Examples 3, 5, and 6 in which the volume resistance of the middle coating layer exceeded about 1 Ω·cm, it was found that no leakage or temperature increase occurred in the case of an internal short circuit. However, in the lithium secondary battery system, it was found that in the case of an internal short circuit in the above-mentioned lithium secondary battery, it was impossible to determine: i) whether the battery was internally short-circuited; and ii) the location of the internally short-circuited lithium secondary battery.

[0228] From these results, it can be found that since the lithium secondary battery according to the present disclosure includes a negative electrode that satisfies a predetermined volume resistance, in the case of an internal short circuit, not only can insulation be achieved on the surface of the negative electrode, but also a predetermined current can flow. Therefore, the melting phenomenon and / or rapid heating of the lithium secondary battery can be prevented, and the time to deal with the internal short circuit can be ensured. In addition, it can be found that the lithium secondary battery system including the lithium secondary battery of the present disclosure uses an applied current in the case of an internal short circuit, thereby quickly determining whether the lithium secondary battery is internally short-circuited and the location of the lithium secondary battery with an internal short circuit with relatively high accuracy and speed.

[0229] From the foregoing it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration and that various modifications may be made without departing from the scope and spirit of the present disclosure.

[0230] Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

[0231] [reference numerals]

[0232] 10: Lithium-ion secondary battery system

[0233] 110: Battery cell assembly 111: Lithium-ion secondary battery

[0234] 111a: positive electrode of lithium secondary battery 111b: negative electrode of lithium secondary battery

[0235] 112a: Positive terminal 112b: Negative terminal

[0236] 120: Charging / discharging unit 130: Sensing unit

[0237] 140: Control unit 142: MCU

[0238] 144: Memory 146: Communication I / F

[0239] 148: Input / output interface

[0240] 150: Secondary battery pack

[0241] PS: External power supply EL: Electrical load

[0242] 211: Lithium secondary battery for experiment

[0243] 211a-1: positive electrode current collector 211a-2: positive electrode active layer

[0244] 211b-1: negative electrode current collector 211b-2: negative electrode active layer

[0245] 211b-3: Negative electrode coating

[0246] 211c: Diaphragm 211c-1: Hollow center portion of the diaphragm

Claims

1. A lithium secondary battery, comprising: A positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein, in the negative electrode, a negative electrode active layer comprising a carbon-based negative electrode active material and a coating layer comprising silicon-containing particles are sequentially disposed on a negative electrode current collector, and The volume resistance of the negative electrode is about 1.0×10 -4 Ω·cm to 1.0Ω·cm.

2. The lithium secondary battery according to claim 1, wherein The negative electrode has a diameter of about 8.0×10 -3 Ω·cm to 9.0×10 -1 Volume resistivity of Ω·cm.

3. The lithium secondary battery according to claim 1, wherein The silicon-containing particles include particles having a ratio of silicon element to oxygen element of about 1:0.5 to 1:1.

5.

4. The lithium secondary battery according to claim 1, wherein The silicon-containing particles have an average particle size (D) of about 1 μm to 20 μm. 50 ).

5. The lithium secondary battery according to claim 1, wherein The silicon-containing particles include a carbon layer on a surface thereof.

6. The lithium secondary battery according to claim 1, wherein The coating layer includes about 70 parts by weight or more of silicon-containing particles and about 30 parts by weight or less of a binder, relative to a total of 100 parts by weight of the coating layer.

7. The lithium secondary battery according to claim 1, wherein: The coating has an average thickness of about 1.5 μm to 30 μm, and A thickness ratio of the coating layer to the negative electrode active layer is about 0.01 to 0.

3.

8. The lithium secondary battery according to claim 1, wherein The positive electrode includes a positive electrode active layer on a positive electrode current collector, the positive electrode active layer including one or more types of positive electrode active materials among compounds represented by the following Chemical Formula 1 and Chemical Formula 2: [Chemical formula 1] LiFe a M 1 1-a XO4 [Chemical formula 2] Li x [Ni y Co z Mr w M 2 v ]O2 In the chemical formula 1 and the chemical formula 2, M 1 is one or more types of W, Cu, Fe, V, Cr, Co, Ni, Mn, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B or Mo, X is one or more of P, Si, S, As or Sb, a satisfies 0 <a≤1.0, M 2 is one or more of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, or Mo, and x, y, z, w and v respectively satisfy 1.0≤x≤1.30, 0≤y<1, 0≤z≤1, 0≤w≤1 and 0≤v≤0.1, and y+z+w+v=1.

9. A lithium secondary battery system, comprising: A plurality of battery cell assemblies, each battery cell assembly comprising n lithium secondary batteries according to claim 1 (wherein n is an integer from 3 to 100); a charge / discharge unit electrically coupled to each of the battery cell assemblies to individually charge or discharge each of the battery cell assemblies; a sensing unit electrically coupled to an electrode of each lithium secondary battery included in the battery cell assembly to individually measure at least one amount of electricity among a voltage and a current of each lithium secondary battery during charge / discharge of each lithium secondary battery; as well as a control unit electrically coupled to the charging / discharging unit and the sensing unit to control charging or discharging of each of the battery cell assemblies; When the power level of the corresponding lithium secondary battery measured by the sensing unit meets a predetermined value, the control unit stops charging or discharging the battery cell assembly including the corresponding lithium secondary battery.

10. The lithium secondary battery system according to claim 9, wherein: The control unit performs a series of processes including the following: Comparing the average power of the battery cell assembly with the power of a single battery cell assembly, and selecting a battery cell assembly with an error rate of more than about 5%; Among the respective lithium secondary batteries disposed in the respective selected cell assemblies selected in the selection process, determining that an internal short circuit has occurred in the respective lithium secondary batteries whose charge measured by the sensing unit is lower than the applied charge of each lithium secondary battery by more than about 0.5%; as well as Charging or discharging of the cell assembly including the corresponding lithium secondary battery determined to be internally short-circuited is stopped.

11. The lithium secondary battery system according to claim 9, wherein: The sensing unit further includes a temperature measurement sensor configured to measure a temperature of each lithium secondary battery disposed in the battery cell assembly.

12. A negative electrode for a lithium secondary battery, the negative electrode for a lithium secondary battery comprising: A negative electrode active layer and a coating layer located on the negative electrode current collector, wherein the negative electrode active layer comprises a carbon-based negative electrode active material, and the coating layer comprises silicon-containing particles, The silicon-containing particles included in the coating include particles having a silicon element and an oxygen element ratio of about 1:0.5 to 1:1.5, and The volume resistance of the negative electrode is about 1.0×10 -4 Ω·cm to 1.0Ω·cm.

13. The negative electrode for a lithium secondary battery according to claim 12, wherein: The silicon-containing particles include a carbon layer on the surface thereof and have an average particle size (D 50 ).

14. The negative electrode for a lithium secondary battery according to claim 12, wherein: The coating layer includes about 70 parts by weight or more of silicon-containing particles and about 30 parts by weight or less of a binder, relative to a total of 100 parts by weight of the coating layer.

15. The negative electrode for a lithium secondary battery according to claim 12, wherein: The coating has an average thickness of about 1.5 μm to 30 μm, and A thickness ratio of the coating layer to the negative electrode active layer is about 0.01 to 0.3.

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