Battery management system, battery pack including same, and method of establishing charging protocol of lithium secondary battery

Abstract

The present invention relates to a method for establishing a charging protocol of a lithium secondary battery and a battery management system, the system comprising: a measurement unit configured to measure a closed circuit voltage (CCVSOCy) and an open circuit voltage (OCVSOCy) according to a depth of charge (SOCy) at the time of charging with each charging current (I) when a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents; a memory unit configured to collect and store an internal resistance profile obtained by substituting the measured CCVSOCy and OCVSOCy into Equation 1 to calculate an internal correction resistance value (Rrest3-0.1s) according to the depth of charge and plotting the internal correction resistance value (Rrest3-0.1s) according to the depth of charge for each charging current (I); and a control unit configured to determine a limit depth of charge corresponding to each charging current from the internal resistance profile and establish a charging protocol on the basis of the limit depth of charge.

Description

Battery management system, battery pack including same, and method for establishing charging protocol for lithium secondary battery

[0001] This application claims the benefit of Korean Patent Application No. 10-2024-0068449, filed with the Korean Intellectual Property Office on May 27, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for establishing a rapid charging protocol that reflects heat generation and internal resistance resulting from charging and discharging of a large-capacity battery cell, a battery management system capable of establishing such a rapid charging protocol, and a battery pack including the same.

[0003] Recently, the demand for portable electronic devices such as laptops and mobile phones has rapidly increased, as has the demand for electric carts, electric wheelchairs, and electric bicycles. This has led to active research into high-performance batteries capable of repeated charging and discharging. Furthermore, with the gradual depletion of carbon energy and growing environmental concerns, demand for hybrid electric vehicles (HEVs) and electric vehicles (EVs) is steadily increasing worldwide. Consequently, greater interest and research is being focused on vehicle batteries, a core component of HEVs and EVs. Furthermore, the development of rapid charging technology is urgently needed. Rapid charging is particularly crucial for EVs, which lack an additional energy source.

[0004] Charging a battery involves applying current to the battery to accumulate charge and energy, a process that must be carefully controlled. Typically, excessive charge current (C-rate) or charge voltage can permanently degrade battery performance and ultimately lead to complete failure or even catastrophic failure, such as the release of corrosive chemicals or explosion.

[0005] When charging a battery with constant current, if the charging current rate is too low, it takes a very long time to fully charge the battery. Conversely, if the charging current rate is too high, the battery deteriorates rapidly. Therefore, during constant current charging, it is necessary to gradually adjust the charging current rate according to the battery's condition.

[0006] To gradually adjust the current rate during constant current charging, a charge map having a "multi-stage constant current charging protocol" is mainly utilized. The charge map includes at least one data array in which the relationship between multiple current rates and multiple switching conditions is recorded. Whenever each switching condition is satisfied, the next current rate in the sequence can be supplied as the charging current to the battery. The current rate (also referred to as "C-rate") is the value obtained by dividing the charging current by the maximum capacity of the battery, and its unit is "C."

[0007] In the past, in order to derive such a multi-stage constant current charging protocol, a 50 mAh level monocell type three-electrode cell was manufactured, and the depth of charge (SOC; state of charge, hereinafter referred to as 'depth of charge') at which lithium plating occurs on the negative electrode was established as the charging limit for each charging current.

[0008] However, since 3-electrode cells are difficult to manufacture and must be charged and discharged using a dedicated charger / discharger, there were many restrictions such as the completion of manufacturing the 3-electrode cell, the manufacturing time of the 3-electrode cell, and the preparation of a dedicated charger / discharger. In addition, in the process of applying the limiting charge depth confirmed in these 3-electrode cells to large-capacity battery cells with capacities of 40 to 200 Ah, there was no technology that reflected the resistance of the large-capacity battery cell or the heat generation during rapid charging. In addition, in the method of establishing a charging protocol using a 3-electrode cell, as the charging current decreases and the negative electrode composition is advantageous for rapid charging, the lithium plating section is not clearly distinguished, which leads to the subjectivity of the experimenter, and accordingly, when there is a deviation in the battery cell, it is difficult to establish a charging protocol that shows a similar voltage profile.

[0009] Recognizing the above problems, a charging protocol was developed for the production of two-electrode cells. However, recently, with the increasing use of silicon-based active materials (SiC, SiO, etc.) mixed in the negative electrode to enhance rapid charging and capacity characteristics, cell resistance has decreased, and in situations such as high C-rate charging, cases where it is difficult to derive the depth of charge using an analysis method for two-electrode cells are increasing. In addition, cases where analysis becomes difficult are added as the positive electrode material changes depending on the use of the cell, such as from a high-Ni 4.2V cell to a mid-Ni 4.35V cell.

[0010] Therefore, in line with recent cell trends, it is necessary to develop a technology that can derive a charging protocol that can exhibit a similar voltage profile even when there is a deviation in the battery cell while taking into account the resistance of large-capacity battery cells and the heat generation during rapid charging, such as using silicon-based active materials in the negative electrode or Mid Ni active materials in the positive electrode, to enable high current charging.

[0011] <Prior Art Literature>

[0012] Republic of Korea Publication Patent No. 10-2017-0021630

[0013] The present invention has been devised to solve the above problems, and relates to a battery management system and a method for establishing a charging protocol for a lithium secondary battery, which does not require the prior manufacture of a three-electrode cell to derive a limiting charge depth for each charging current, and which can be applied even in situations such as the use of a Mid Ni active material in the positive electrode for rapid charging and capacity enhancement, the mixed use of a silicon-based active material (SiC, SiO, etc.) in the negative electrode, or high C-rate charging during charging.

[0014] According to one embodiment of the present invention, when a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents, the closed circuit voltage (CCV) according to the depth of charge (SOCy) when charging with each charging current (I) SOCy ) and open circuit voltage (OCV) SOCy ) configured to measure the CCV; the measured CCV SOCy Wow OCV SOCy By substituting into Equation 1 below, the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) is configured to collect and store an internal resistance profile plotted by the battery; and a control unit configured to determine a limit charge depth corresponding to each charge current from the internal resistance profile and establish a charge protocol based on the limit charge depth.

[0015] [Formula 1]

[0016]

[0017] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y).

[0018] The above x is 0.1C or more and 8.0C or less,

[0019] The above y is greater than or equal to 0 and less than or equal to 100,

[0020] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y).

[0021] The above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0022] In another embodiment, a battery pack including the battery management system is provided.

[0023] Finally, (a) for a two-electrode battery cell having a positive and negative electrode, when charged with different charging currents, the closed circuit voltage (CCV) according to the depth of charge (SOCy) when charged with each charging current (I) SOCy ) and open circuit voltage (OCV) SOCy ) the process of measuring; (b) in the following equation 1, the measured CCV SOCy Wow OCV SOCy By substituting the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) and (c) a process of collecting an internal resistance profile by plotting the internal resistance profile; and (d) a process of determining a limiting depth of charge corresponding to each charging current from the collected internal resistance profile.

[0024] [Formula 1]

[0025]

[0026] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y).

[0027] The above x is 0.1C or more and 8.0C or less,

[0028] The above y is greater than or equal to 0 and less than or equal to 100,

[0029] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y).

[0030] The above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0031]

[0032] The battery management system and charging protocol setting method according to the present invention have the effect of providing a charging protocol that reflects resistance and heat generation directly from a large-capacity battery cell without having to manufacture a three-electrode cell that is cumbersome to manufacture.

[0033] In addition, the battery management system and charging protocol setting method according to the present invention have the effect of non-destructively determining the degree of deterioration of a battery cell even while the battery cell is being operated, and updating the charging protocol by reflecting the deterioration of the battery cell.

[0034] In addition, the battery management system and charging protocol setting method according to the present invention can derive a limiting charge depth even at a low charging current of 1.0C, thereby providing a charging protocol advantageous for rapid charging.

[0035] Additionally, this device has the feature of being able to derive the limiting depth of charge even in situations such as high C-rate charging, without having to manufacture a 3-electrode cell in advance to derive the limiting depth of charge for each charging current, using Mid Ni in the positive electrode to ensure safety such as TP (Thermal propagation), or using a mixture of silicon-based active materials (SiC, SiO, etc.) in the negative electrode to enhance rapid charging and capacity characteristics.

[0036]

[0037] FIG. 1 is a drawing exemplarily showing the configuration of a battery pack including a battery management system according to one embodiment of the present invention.

[0038] FIG. 2 is a schematic diagram illustrating a battery pack including a battery management system according to one embodiment of the present invention.

[0039] Figure 3 is a flowchart of a method for establishing a charging protocol for a lithium secondary battery according to one embodiment of the present invention.

[0040] Figure 4 is a diagram showing a graph modification in the internal resistance profile according to the charging depth of Comparative Example 1.

[0041] Figure 5 is a diagram showing a graph modification in the internal resistance profile according to the charging depth of Example 1.

[0042] Figure 6 is a diagram showing a graph modification in the internal resistance profile according to the charging depth of Reference Example 2.

[0043] Figure 7 is a diagram showing a graph modification in the internal resistance profile according to the charging depth of Example 2.

[0044] Figure 8 is a diagram briefly showing how to proceed with the QC cycle.

[0045] Figure 9 is a diagram showing the QC cycle for the batteries of Manufacturing Examples 1 and 2.

[0046] Figure 10 is a diagram showing the graph modification in the internal resistance profile according to the depth of charge for the degenerated cell and fresh cell of Manufacturing Example 1.

[0047] Figure 11 is a diagram showing the voltage behavior at 2C to explain the IR Drop.

[0048] <Explanation of symbols>

[0049] 1: Battery pack

[0050] 10: Battery cell

[0051] 100: Battery Management System

[0052] 110: Measurement section

[0053] 120: Memory section

[0054] 130: Control unit

[0055] 200: Charging device

[0056]

[0057] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0058] Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0059] In addition, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0060] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0061] Additionally, terms such as control unit described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

[0062] Additionally, throughout the specification, when we say that a part is "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "indirectly connected" with other elements in between.

[0063] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0064] FIG. 1 is a diagram exemplarily illustrating the configuration of a battery pack including a battery management system according to one embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a battery pack including a battery management system according to one embodiment of the present invention.

[0065] Referring to FIG. 1, a battery pack (1) may include a battery cell (10) and a battery management system (100). The battery management system (100) is a battery management system that monitors the voltage, current, temperature, etc. of the battery cell (10) and controls and manages it to prevent overcharging, overdischarging, etc.

[0066] Here, the battery cell (10) is a two-electrode battery cell having a cathode and anode, and refers to a physically separable, independent cell. For example, a pouch-type lithium polymer cell may be considered as the battery cell (10). In addition, the battery cell (10) may be a large-capacity battery cell having a capacity of 40 to 200 Ah.

[0067] Additionally, the battery pack (1) may include a battery module in which one or more battery cells (10) are connected in series and / or in parallel.

[0068] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and including the positive electrode active material.

[0069] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0070] The above positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0071] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0072] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0073] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0074] In one embodiment of the present application, the negative electrode may include a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode composition or a cured product thereof formed on one or both sides of the negative electrode current collector layer.

[0075] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. The negative electrode current collector layer is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0076] In one embodiment of the present application, the thickness of the negative electrode current collector layer may be 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer may be 5 μm or more and 500 μm or less.

[0077] However, the thickness can be varied depending on the type and purpose of the cathode used and is not limited thereto.

[0078] In the present application, the negative electrode composition may include at least one selected from the group consisting of a negative electrode active material, a negative electrode conductive material, and a negative electrode binder.

[0079] In the present application, the negative electrode active material may include at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride.

[0080] In the present application, the carbon-based active material may include a carbon-based material such as graphite or activated carbon.

[0081] In one embodiment of the present application, the carbon-based active material is, as a representative example, natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, or activated carbon, and can be used without limitation as long as it is commonly used in carbon materials for lithium secondary batteries, and specifically, can be used by processing it into a spherical or dot-shaped shape.

[0082] In one embodiment of the present application, the carbon-based active material includes graphite, and the graphite includes artificial graphite and natural graphite, and the weight ratio of the artificial graphite and natural graphite may be 5:5 to 9.5:0.5.

[0083] The artificial graphite according to one embodiment of the present invention may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of the primary particles are aggregated.

[0084] The term "initial particle" used in the present invention means an original particle from which another type of particle is formed, and a plurality of primary particles can be assembled, combined, or assembled to form a secondary particle.

[0085] The term "secondary particles" as used in the present invention means physically distinguishable large particles formed by aggregation, combination or assembly of individual primary particles.

[0086] The artificial graphite of the above primary particles may be manufactured by heat treating at least one selected from the group consisting of needle cokes, mosaic cokes, and coaltar pitch.

[0087] The above artificial graphite is generally manufactured by carbonizing raw materials such as coal tar, coal tar pitch, and petroleum heavy oils at temperatures above 2,500°C. After graphitization, the particle size can be adjusted through grinding and secondary particle formation to enable use as a negative electrode active material. In the case of artificial graphite, crystals are randomly distributed within the particles, and compared to natural graphite, the sphericity is lower and the shape is somewhat pointed.

[0088] The artificial graphite used in one embodiment of the present invention may include MCMB (mesophase carbon microbeads), MPCF (mesophase pitch-based carbon fiber), artificial graphite graphitized in block form, artificial graphite graphitized in powder form, etc., which are widely used commercially. The sphericity of the artificial graphite may be 0.91 or less, or 0.6 to 0.91, or 0.7 to 0.9.

[0089] Additionally, the artificial graphite may have a particle size of 5 to 30 μm, preferably 10 to 25 μm.

[0090] Specifically, the D50 of the artificial graphite primary particles may be 6 µm to 15 µm, or 6 µm to 10 µm, or 6 µm to 9 µm. When the D50 of the primary particles satisfies this range, the primary particles can be formed to have high graphitization, and the orientation index of the negative electrode active material particles can be appropriately secured, thereby improving the rapid charging performance.

[0091] The above artificial graphite secondary particles may be formed by assembling primary particles. That is, the secondary particles may be a structure formed by agglomerating the primary particles through an assembling process. The secondary particles may include a carbonaceous matrix that allows the primary particles to agglomerate. The carbonaceous matrix may include at least one of soft carbon and graphite. The soft carbon may be formed by heat-treating pitch.

[0092] The above carbonaceous matrix may be included in the secondary particles in an amount of 8 wt% to 16 wt%, specifically 9 wt% to 12 wt%. The above range is lower than the content of the carbonaceous matrix used in conventional artificial graphite secondary particles. This means that the particle size of the primary particles in the secondary particles is controlled, so that even if the content of the carbonaceous matrix required for assembly is small, structurally stable secondary particles can be manufactured, and the amount of primary particles constituting the secondary particles can also be uniform.

[0093] The artificial graphite secondary particle includes a carbon coating layer on the surface, and the carbon coating layer may include at least one of amorphous carbon and crystalline carbon.

[0094] The above crystalline carbon can further improve the conductivity of the negative electrode active material. The above crystalline carbon can include at least one selected from the group consisting of fluorene and graphene.

[0095] The amorphous carbon can appropriately maintain the strength of the covering layer and suppress the expansion of the natural graphite. The amorphous carbon can be a carbonaceous material formed using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic substances as a source of a chemical vapor deposition method.

[0096] The above-mentioned other organic carbide may be a carbide of an organic carbide selected from sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or kedohexose and combinations thereof.

[0097] The D50 of the above artificial graphite secondary particles may be 10 ㎛ to 25 ㎛, specifically 12 ㎛ to 22 ㎛, and more specifically 13 ㎛ to 20 ㎛. When the above range is satisfied, the artificial graphite secondary particles can be evenly dispersed within the slurry, and the charging performance of the battery can also be improved.

[0098] The tap density of the above artificial graphite secondary particles may be 0.85 g / cc to 1.30 g / cc, specifically 0.90 g / cc to 1.10 g / cc, and more specifically 0.90 g / cc to 1.07 g / cc. When the above range is satisfied, the packing of the artificial graphite secondary particles within the negative electrode can be smoothly performed, which means that the negative electrode adhesive strength can be improved.

[0099] The above natural graphite may generally be in the form of plate-shaped aggregates before being processed, and the plate-shaped particles may be manufactured into a spherical shape with a smooth surface through post-processing such as particle crushing and reassembly processes in order to be used as an active material for manufacturing electrodes.

[0100] The natural graphite used in one embodiment of the present invention may have a sphericity of greater than 0.91 and less than or equal to 0.97, or from 0.93 to 0.97, or from 0.94 to 0.96.

[0101] The above natural graphite may have a particle size of 5 to 30 μm, or 10 to 25 μm.

[0102] According to one embodiment of the present invention, the weight ratio of the artificial graphite and natural graphite may be 5:5 to 9.5:0.5, or 5:5 to 9.3:0.7, or 5:5 to 9:1, or 6:4 to 9:1. When the weight ratio of the artificial graphite and natural graphite satisfies this range, a better output may be exhibited, and lifespan and rapid charging performance may be advantageous.

[0103] In the present application, the silicon-based active material is SiOx (x=0), SiOx (0 <x<2), SiC, 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함할 수 있다.

[0104] In the present application, the silicon-based active material may include SiC.

[0105] In the present application, the negative active material may include a carbon-based active material and a silicon-based active material.

[0106] In the present application, the silicon-based active material may be 50 parts by weight or less, preferably 40 parts by weight or less, based on 100 parts by weight of the negative active material, and may specifically include 30 parts by weight or less, and may include 1 part by weight or more and 3 parts by weight or more.

[0107] In one embodiment of the present application, the negative electrode conductive material may include at least one selected from the group consisting of a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0108] In one embodiment of the present application, the dot-shaped conductive material may be used to improve conductivity of the negative electrode, and refers to a dot-shaped or spherical conductive material having conductivity without causing chemical change. Specifically, the dot-shaped conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of implementing high conductivity and excellent dispersibility.

[0109] In one embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-shaped graphite.

[0110] In the present application, the negative conductive material may be a linear conductive material such as a carbon nanotube. The carbon nanotube may be a bundle-type carbon nanotube. The bundle-type carbon nanotube may include a plurality of carbon nanotube units. Specifically, the term "bundle type" herein, unless otherwise stated, refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged in parallel or entangled with their longitudinal axes in substantially the same orientation. The carbon nanotube unit has a graphite sheet in the form of a cylinder with a nano-sized diameter and has an sp2 bonding structure. At this time, the graphite sheet may exhibit characteristics of a conductor or a semiconductor depending on the angle and structure at which it is rolled. The above bundled carbon nanotubes can be uniformly dispersed during the manufacture of a cathode compared to entangled type carbon nanotubes, and can smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0111] In one embodiment of the present application, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0112] The negative electrode binder according to one embodiment of the present application serves to hold the active material and conductive material in order to prevent distortion and structural deformation of the negative electrode structure when the volume of the silicon-based active material expands and relaxes. If the above-mentioned role is satisfied, all general binders can be applied, and specifically, an aqueous binder can be used, and more specifically, a PAM-based binder can be used.

[0113] Accurately determining the point at which lithium plating occurs (the deposition point) is essential for ensuring cell cycle durability. Deriving depth of charge using conventional three-electrode methods has the drawback of failing to reflect the ohmic resistance caused by actual cell field-effect ratio (f / p) changes. Furthermore, changes in cell ohmic resistance due to field-effect ratio (f / p) also significantly impact charging performance. Therefore, deriving depth of charge from the cell itself is a crucial technology.

[0114] For anode active materials utilizing carbon-based materials, as lithium is inserted into the anode, the potential decreases to a level similar to that of lithium. Furthermore, as resistance or current increases, lithium may accumulate on the surface rather than being inserted into the graphite layer, resulting in plating. Therefore, a safe charging protocol is established by determining the depth of charge at which lithium plating occurs in the anode as the critical depth of charge.

[0115] That is, since a cathode using only carbon-based materials has a specific inflection point where the resistance drops, it is relatively easy to set the depth of charge.

[0116] Recently, the use of silicon-based active materials as negative active materials is essential to secure high capacity, high energy density, and rapid charging. However, as the content of silicon-based active materials increases, it becomes more difficult to identify the inflection section of the resistance. In addition, due to the need for rapid charging, the C-rate is increasing during charging, and as the C-rate increases, it also becomes more difficult to identify the inflection section of the resistance. For example, as the content of silicon-based active materials increases, it becomes difficult to distinguish the inflection when the R(diff) value is small.

[0117] Specifically, Fig. 4 illustrates an analysis method for finding a resistance inflection point according to an increase in SOC by varying the C-rate for an anode using a silicon-based active material (SiC 15%) using a conventional method. As can be seen in Fig. 4, for an anode using a silicon-based active material, the inflection point is not derived from the resistance measurement results for each C-rate, making it difficult to derive the depth of charge.

[0118] This is expected to be a problem that occurs in silicon-based (SiO, SiC, etc.) active materials compared to carbon-based active materials because the phase change mechanism during charging is different and the resulting resistance change is different. For example, carbon-based active materials undergo an insertion reaction during charging, which results in little structural change and is reversible, resulting in low charge transfer resistance. In contrast, silicon-based active materials undergo an alloying reaction and also undergo structural change due to volume expansion, resulting in high charge transfer resistance and diffusion resistance even under normal operation. Therefore, carbon-based active materials exhibit less resistance change under normal operation, making it easier to detect resistance changes when lithium plating occurs than silicon-based active materials.

[0119] Similarly, as the C-rate increases, the charge transfer resistance and diffusion resistance increase, making it difficult to detect changes in charge transfer and diffusion resistance due to precipitation at the relaxation time.

[0120] Accordingly, the present application introduced a method of determining the depth of charge at which lithium plating occurs in the negative electrode as the limiting depth of charge, as the resistance value increases while Li+ is intercalated or an alloy is formed in the negative electrode active material (i.e., as the SOC increases), and a parallel resistance is generated when Li+ is plated, and at this time, the R value decreases, leading to the present application. That is, as in Equation 1 according to the present application, R rest 3s R in value rest 0.1sExcluding (IR drop), the inflection section of the resistance can be easily identified, and specifically, it is normal behavior for the R value to increase as charging progresses, and as Li plating progresses as the SOC increases, a parallel resistance is formed in addition to the Li insertion, and the R value decreases. At this time, the resistance value is plotted, and the section where the resistance increases and then decreases can be introduced as the limiting depth of charge.

[0121] In general, when comparing the behavior when lithium plating occurs and the behavior when lithium plating does not occur, when lithium plating does not occur, the voltage drops immediately, whereas when lithium plating occurs, the voltage drops slowly as additional plated lithium is inserted.

[0122] Here, 3s means the section in which the voltage change over time is the greatest, and the definition may be somewhat different because the resistance component is different for each cell, but theoretically, when the relaxation time behavior is plotted in a situation in which lithium plating occurs, the case in which the dV / dt value drops sharply can be generalized to 3s. In other words, this application defines 3s as the time in the vicinity of the sharp drop in the dV / dt value that derived a pattern that well represents the QC Cycle durability in the evaluation results.

[0123] Also, R in this application rest 0.1s(IR drop) 0.1 second is defined as the time to subtract only the ohmic resistance with the largest IR drop, and specifically, if the IR drop occurred within a shorter time, that time can be used, and it was used to define the largest IR drop ratio of 0.1 second within 3 seconds. Fig. 11 is data to explain this, and specifically shows the voltage behavior at 2C. When looking at the voltage behavior of the resting point of SOC 67, which is the deposition point, and SOC 20, which is not, both cases show a form in which the IR drop is severe, and it can be seen that the ratio of 0.1 second within 3 seconds is quite large.

[0124] Specifically, Fig. 5 illustrates an analysis method for finding a resistance inflection point according to an increase in SOC by introducing a charging protocol according to the present application and varying the C-rate for a battery having the same negative electrode as Fig. 4. As can be seen in Fig. 5, R(diff) increases (as SOC increases) while Li+ is intercalated into graphite or alloyed with SiO or SiC, etc., and when Li+ is plated, a parallel resistance is generated, causing R(diff) to decrease, so this point can be determined as the precipitation point.

[0125] That is, as can be seen in Fig. 4, when R(diff) is small, such as when there is an excess of silicon-based active materials such as SiC, the ratio of R(0.1s) to the entire R(3s) is large, making it difficult to distinguish the inflection. At this time, as shown in Fig. 5, R excluding IR drop (R 0.1s) from the change in the entire resistance (R 3s) rest3-0.1s If you look at only (Rdiff), the inflection section becomes clearly visible. As mentioned above, this is because R increases while Li+ is intercalated into graphite or alloyed with SiO or SiC (as SOC increases). rest3-0.1s(Rdiff) increases, and when Li+ is plated, a parallel resistance is created, causing R rest3-0.1s (Rdiff) decreases, so this is the result that can be determined as the precipitation point. That is, by plotting R(diff) and R(rest 3-0.1s) in Fig. 5, it can be seen that the section where the resistance increases and then decreases can be identified as the precipitation point.

[0126] The present invention derives a lithium-plating point, which serves as a reference for setting a limit depth of charge in establishing a rapid charging protocol, from an internal resistance profile plotting an internal resistance value according to the depth of charge of a battery cell.

[0127] Referring to FIG. 1, a battery management system (100) according to the present invention may include a measurement unit (110), a memory unit (120), and a control unit (130).

[0128] In the embodiment of FIG. 2, the battery management system (100) according to the present invention may further include a connection unit (140) configured to be connected to a charging device (200) capable of supplying a charging current to the battery cell according to a charging protocol established by the control unit (130).

[0129] The charging device (200) can be connected to a battery pack (1). In addition, the charging device (200) connected to the battery pack (1) can supply a charging current to the battery cell (10) according to a charging protocol established by the control unit (130).

[0130] And, the battery management system (100) can control the operation of the switching unit (SW) to control charging and discharging of the battery cell (10) or / and the battery module.

[0131] The measuring unit (110) is configured to measure the state information of the battery cell, which includes at least one of voltage and depth of charge for the battery cell (10). The measuring unit (110) according to the embodiment of the present invention measures the closed circuit voltage (CCV) according to the depth of charge (SOCy) in order to calculate the internal resistance value of the battery cell (10). SOCy ) and open circuit voltage (OCV) depending on depth of charge (SOCy) SOCy ) is configured to measure the closed circuit voltage (CCV) measured by the measuring unit (110). SOCy ) and open circuit voltage (OCV) SOCy ) is the basic data for calculating the internal resistance value at the corresponding charge depth (SOCy).

[0132] The measuring unit (110) varies the charging current (I) for the battery cell (10) and measures the closed circuit voltage (CCV) according to the depth of charge. SOCy ) and open circuit voltage (OCV) SOCy ) is configured to measure each. In exemplary embodiments, the charging current (I) may be selected in multiple ranges from 0.1C to 8.0C, specifically from 0.33C to 7.0C, and more specifically from 0.5C to 5.0C. In addition, the interval of the charging current (I) may be set at an interval of 0.1C to 1.0C. For example, for the battery cell (10), charging is performed up to SOC 100% with various values ​​of charging current (I) set at an interval of 0.25C, such as 0.25C - 0.5C - 0.75C - 2.75C - 3.0C, and the measuring unit (110) measures the closed circuit voltage (CCV) according to the depth of charge (SOCy) each time charging with each charging current (I). SOCy ) and open circuit voltage (OCV) SOCy ) is configured to measure closed circuit voltage (CCV). SOCy ) and open circuit voltage (OCV) SOCy) can be set at intervals of 2.5% of SOC, 5% of SOC, or 10% of SOC.

[0133] The above memory unit (120) measures the CCV measured by the measuring unit (110). SOCy Wow OCV SOCy By substituting into Equation 1 below, the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) can be collected and stored by plotting the internal resistance profile.

[0134] [Formula 1]

[0135]

[0136] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y).

[0137] The above x is 0.1C or more and 8.0C or less,

[0138] The above y is greater than or equal to 0 and less than or equal to 100,

[0139] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y).

[0140] The above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0141] Since the difference between the closed circuit voltage and the open circuit voltage is caused by the voltage drop in the internal resistance, the actual internal resistance value of the battery cell can be calculated by dividing the difference between the closed circuit voltage and the open circuit voltage by the (rapid) charging current.

[0142] At this time, the open circuit voltage (OCV) SOCy ) is the closed circuit voltage (CCV) SOCy ) may be measured within 1 to 30 seconds, or within 1 to 15 seconds, or within 1 to 10 seconds, or within 2 to 9 seconds from the time of measurement.

[0143] In the present application, the memory unit has an internal correction resistance value (R) according to the depth of charge at intervals of 1 to 2.5 for the y value. rest3-0.1s ) and collects and stores the internal resistance profile.

[0144] That is, the memory section continuously adjusts the internal compensation resistance value (R) according to the depth of charge at intervals of 1 to 2.5 for SOC-based y values ​​of 0 to 100. rest3-0.1s ) is a system that creates, collects, and stores profiles that are plotted.

[0145] The above control unit (130) is configured to determine a limit charging depth corresponding to each charging current from the internal resistance profile for each charging current (I) stored in the memory unit, and establish a charging protocol based on this.

[0146] The control unit (130) of the present invention determines the depth of charge (SOC) at the point where the shape of the graph in the internal resistance profile changes from flat to a downward trend. y ) can be configured to determine the value as the above limit filling depth.

[0147] That is, the control unit of the present invention can be configured to calculate the Rdiff(y) value represented by the above equation 1, and determine the y value that satisfies │Rdiff(y)-Rdiff(y+2.5)│ value of 0.1 or more and the y value of 5 or more as the limit filling depth.

[0148] Specifically, the measurement starts from SOC 0 (y=0) in a completely discharged state, charges by SOC 2.5, measures the resistance, forms a graph, and repeats SOC 2.5, 5, 7.5, etc. until the end voltage is reached, and the measurement ends. At this time, the control unit derives a y value in which │Rdiff(y)-Rdiff(y+2.5)│ is 0.1 or more when the y value is 5 or more, and this can be derived as the depth of charge.

[0149] Figure 5 shows the closed circuit voltage (CCV) according to the depth of charge (SOCy) by the charging current (I) according to one embodiment of the present invention. SOCy ) and open circuit voltage (OCV) depending on depth of charge (SOCy) SOCy ) is measured, and the internal resistance value (R SOCy ) and calculate the internal resistance value (R) according to the depth of charge (SOCy). SOCy ) is plotted to show the internal resistance profile according to the depth of charge.

[0150] Referring to FIG. 5, internal resistance profiles according to the depth of charge are shown for various values ​​of charging current set at intervals of 0.25 C in the charging current (I) range of 0.5 C to 4.0 C.

[0151] Examining these profiles, we can see that the internal resistance profile changes with depth of charge, initially flat and then dropping sharply. That is, across nearly the entire range of charge currents (0.5C to 4C), a constant resistance value of approximately 0.3 to 0.4 is observed, followed by a decreasing trend. The point at which this rapid decline in resistance begins can be considered the point at which lithium plating occurs.

[0152] When lithium plating occurs, lithium ions are inserted into the graphite layer of the negative electrode during the charging pause and simultaneously bind to the lithium plating portion. That is, in the charge depth section before lithium plating occurs, lithium ions are inserted into the negative electrode and exist as a series resistance, but in the charge depth section after lithium plating occurs, the lithium ions are inserted into the negative electrode and the lithium plating occurs, forming a parallel resistance, causing the overall resistance to drop. Therefore, in the internal resistance profile according to the charge depth, a decrease in the internal resistance value is an indicator that lithium plating has occurred.

[0153] Accordingly, the control unit (130) of the present invention determines the depth of charge (SOC) at which the shape of the internal resistance profile according to the depth of charge changes from flat to a downward trend. y ) is determined as the limit charging depth. Then, the control unit (130) can establish a charging protocol based on the limit charging depth corresponding to each charging current (I) as described above.

[0154] The battery management system (100) according to the present invention has the effect of enabling the measuring unit (110), memory unit (120), and control unit (130) to charge the battery cell according to a charging protocol that reflects the resistance of the large-capacity battery cell (10) and the heat generated by rapid charging.

[0155] In the present application, the control unit provides a battery management system configured to periodically derive a new limit charge depth corresponding to each charge current according to repeated charge and discharge of a battery cell and re-establish a charge protocol.

[0156] The above control unit (130) may be configured to periodically derive a new limit charge depth corresponding to each charge current according to the repeated charge and discharge of the battery cell, thereby reestablishing the charge protocol. This is to reflect the deterioration of the battery cell according to the repeated charge and discharge.

[0157] For example, the control unit (130) causes the measurement unit (110) to measure the closed circuit voltage (CCV) according to the depth of charge (SOCy) when charging with each charging current (I) for the battery cell every 100 cycles. SOCy ) and open circuit voltage (OCV) depending on depth of charge (SOCy) SOCy ) to measure each CCV, and cause the memory unit (120) to store the measured CCV in the following equation 1. SOCy Wow OCV SOCy By substituting the internal resistance value (R) according to the depth of charge SOCy ) and, for each charging current (I), collects an internal resistance profile that plots the internal resistance value according to the charging depth, controls the same to be stored, and derives a new limit charging depth corresponding to each charging current from the internal resistance profile stored in the memory, and establishes a new charging protocol that reflects the degradation based on this.

[0158] Accordingly, the battery management system according to the present invention has the effect of being able to non-destructively determine the degree of deterioration of a battery cell even while the battery cell is being operated, and update the charging protocol by reflecting the deterioration of the battery cell.

[0159] Figure 3 is a flowchart of a method for establishing a charging protocol for a lithium secondary battery according to one embodiment of the present invention.

[0160] Referring to FIG. 3, a method for establishing a charging protocol according to an embodiment of the present invention comprises: (a) when a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents, a closed circuit voltage (CCV) according to a depth of charge (SOCy) when charging with each charging current (I) SOCy ) and open circuit voltage (OCV) SOCy ) the process of measuring;

[0161] (b) In the following equation 1, the measured CCV SOCy Wow OCV SOCy By substituting the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) is a process of collecting internal resistance profiles by plotting them; and

[0162] (c) a process of determining a limiting charge depth corresponding to each charge current from the internal resistance profile collected above.

[0163] [Formula 1]

[0164]

[0165] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y).

[0166] The above x is 0.1C or more and 8.0C or less,

[0167] The above y is greater than or equal to 0 and less than or equal to 100,

[0168] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y).

[0169] The above R rest 0.1sis the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0170] In establishing a charging protocol according to the present invention, the limiting charge depth is the charge depth (SOC) at which the shape of the internal resistance profile according to the charge depth changes from a flat to a descending trend. y ) can be a value.

[0171] In the conventional charging protocol establishment method, a three-electrode cell with a capacity of 50 mAh was manufactured in advance to derive the limiting depth of charge, and the lithium-plating point according to the cathode potential was derived as the limiting depth of charge. However, the present invention does not require the manufacture of a three-electrode cell, and can directly derive the limiting depth of charge by calculating the internal resistance value for a large-capacity two-electrode battery cell with a capacity of 40 to 200 Ah.

[0172] A method for establishing a charging protocol according to exemplary embodiments further includes a process of mapping a charging protocol based on a limit charging depth for each charging current, and the mapping process may be such that charging is performed with the corresponding charging current up to a limit charging depth for each charging current, but the charging current decreases as the charging depth increases.

[0173] The above mapping process may be such that charging is performed with the corresponding charging current up to a limit depth of charge for each charging current, but the charging current decreases as the charging depth increases. For example, if the limit depth of charge corresponding to a charging current of 3.0C is 40% of SOC, the limit depth of charge corresponding to a charging current of 2.5C is 45% of SOC, the limit depth of charge corresponding to a charging current of 2.0C is 55% of SOC, and the limit depth of charge corresponding to a charging current of 1.5C is 65%, then the mapping may be such that charging is performed with a charging current of 3.0C up to 40% SOC, with a charging current of 2.5C up to 45% SOC, with a charging current of 2.0C up to 55% SOC, and with a charging current of 1.5C up to 65% SOC.

[0174]

[0175] Hereinafter, a battery management system and a charging protocol establishment method of the present invention, which derive a limit charging depth corresponding to a charging current and establish a charging protocol according to the present invention, will be described in detail with specific examples.

[0176] Manufacturing Example 1

[0177] (1) Manufacturing of anode

[0178] A cathode slurry was prepared by adding a cathode active material (Li(NiaCobMnc)O2, where NCM excluding lithium (Li) and oxygen (O2) has a ratio of Ni:Co:Mn=60 / 10 / 30, satisfying the ratio (a:b:c=0.60:0.10:0.30)), a cathode conductive agent (LB.CNT), and a binder (PVdF, KF9700) in a weight ratio of 97.0:1.56:1.44 to a solvent (N-methylpyrrolidone, NMP). The cathode slurry was applied to an aluminum (Al) thin film, which is a cathode current collector, and dried, and then rolled using a roll press to prepare a cathode.

[0179] (2) Manufacturing of cathode

[0180] The negative active material was prepared in a ratio of 68:17:15 of artificial graphite:natural graphite:Si / C (average particle diameter (D50): 9.5㎛).

[0181] Afterwards, the negative active material, SWCNT (single wall-CNT, specific surface area 1160 m 2 / g, ) and polyacrylamide as a binder were prepared in a weight ratio of 96:0.05:3.95 to prepare a negative electrode active material layer composition. A negative electrode slurry was prepared by adding distilled water as a solvent for forming a negative electrode slurry (solid content concentration 46 wt%).

[0182] As a mixing method, water and dispersant were dispersed using a homo mixer at 1500 rpm for 10 min, then the negative electrode active material was added and planetary dispersed at 45 rpm for 30 min, then SWCNT was added and dispersed using a homo mixer at 500 rpm for 45 min, and then viscosity was adjusted and a binder was added and mixed to prepare a negative electrode slurry.

[0183] The negative electrode slurry was coated on both sides of a copper current collector (thickness: 6 μm) as a negative electrode collector at a loading amount of 7.00 mg / cm2, rolled, and dried for 10 hours to form a negative electrode active material layer (thickness: 80 μm).

[0184] (3) Manufacturing of secondary batteries

[0185] An electrode assembly was manufactured by interposing a compressible thin film separator (PE 9um) ceramic coating 3um / 3um between the positive and negative electrodes. After positioning the electrode assembly inside a case, an electrolyte was injected into the case to manufacture a lithium secondary battery.

[0186] Manufacturing Example 2

[0187] In the above Manufacturing Example 1, a secondary battery was manufactured in the same manner as in Manufacturing Example 1, except that artificial graphite:natural graphite were prepared in a ratio of 80:20 as the negative electrode active material during the manufacturing of the negative electrode, and a dot-shaped conductive material (D50:40㎛, specific surface area: 65m2 / g) was used instead of SWCNT.

[0188] Comparative Example 1

[0189] For a battery cell of Manufacturing Example 1 with an SOC of 2.5%, while charging with a charging current of 0.5 C, the measuring unit measured the closed circuit voltage (CCVSOCy) and open circuit voltage (OCVSOCy) of the battery cell at intervals of a depth of charge of 2.5% of SOC, and by substituting the measured values ​​into the following equation, the internal resistance value at the corresponding depth of charge was calculated.

[0190] [ceremony]

[0191] Internal resistance value according to charge depth (RSOCy) = (CCVSOCy - OCVSOCy) / I

[0192] Then, by plotting the depth of charge on the x-axis and the corresponding relationship of the internal resistance value on the y-axis, the internal resistance profile according to the depth of charge as shown in Fig. 4 was stored in the memory unit.

[0193] Afterwards, the same process as above was repeated for each charging current of 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C, 2.75C, 3.0C, 3.5C, 3.75C, and 4.00C, and the internal resistance profile according to each charge depth (SOCy) for each charging current was stored in the memory.

[0194] Thereafter, the control unit determines the charging degree at the point where the graph shape changes from a flat to a descending trend in the internal resistance profile according to the charging depth of FIG. 4 stored in the storage unit as the limit charging depth for each charging current, and it can be confirmed that the point where the flat to descending trend changes is not clearly derived.

[0195] Example 1

[0196] For a battery cell of Manufacturing Example 1 with an SOC of 2.5%, the measurement unit was charged based on the SOC of 2.5% of the capacity while charging at a C-rate of 0.5C at 25°C, and the resistance values ​​when charging was performed in a pattern of charging to SOC 2.5% (CCVSOC y), resting for 3 seconds (OCVSOC y), and resting for 0.1 seconds (OCVSOC y) were calculated, and the measured values ​​were substituted into the equation below to calculate the internal resistance value at the corresponding charge depth.

[0197] [ceremony]

[0198]

[0199] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y), and the above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0200] By plotting the depth of charge on the x-axis and the corresponding relationship of the internal resistance value on the y-axis, the internal resistance profile according to the depth of charge, as shown in Fig. 5, was stored in the memory unit.

[0201] Afterwards, the same process as above was repeated for each charging current of 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C, 2.75C, 3.0C, 3.5C, 3.75C, and 4.00C, and the internal resistance profile according to each charge depth (SOCy) for each charging current was stored in the memory.

[0202] Thereafter, the control unit determined the charging degree at the point where the graph shape changes from flat to descending in the internal resistance profile according to the charging depth of FIG. 5 stored in the storage unit as the limit charging depth for each charging current, and established a charging protocol as shown in Table 1 below as a result.

[0203] Charge current (C-rate) 4.00 3.75 3.5 3.25 3.02 75 2.5 2.25 2.01 75 1.5 1.25 1.00 75 0.5 Depth of charge (SOC) 5 25 3 5 4.5 5 6 5 9 6 2 6 5 6 8 7 1 7 4.5 7 7 5 8 1 8 5 8 9 5 9 4

[0204] Reference Example 2

[0205] For a battery cell of Manufacturing Example 2 with an SOC of 2.5%, while charging with a charging current of 0.5 C, the measuring unit measured the closed circuit voltage (CCVSOCy) and open circuit voltage (OCVSOCy) of the battery cell at intervals of a depth of charge of 2.5% of SOC, and by substituting the measured values ​​into the following equation, the internal resistance value at the corresponding depth of charge was calculated.

[0206] [ceremony]

[0207] Internal resistance value according to charge depth (RSOCy) = (CCVSOCy - OCVSOCy) / I

[0208] Then, by plotting the depth of charge on the x-axis and the corresponding relationship of the internal resistance value on the y-axis, the internal resistance profile according to the depth of charge as shown in Fig. 6 was stored in the memory unit.

[0209] Afterwards, the same process as above was repeated for each charging current of 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C, 2.75C, 3.0C, 3.5C, 3.75C, and 4.00C, and the internal resistance profile according to each charge depth (SOCy) for each charging current was stored in the memory.

[0210] Thereafter, the control unit determines the charging degree at the point where the graph shape changes from a flat to a descending trend in the internal resistance profile according to the charging depth of FIG. 6 stored in the storage unit as the limit charging depth for each charging current, and it can be confirmed that the point where the flat to descending trend changes is not clearly derived.

[0211] Example 2.

[0212] For a battery cell of Manufacturing Example 2 with SOC 2.5%, the measurement unit was charged based on SOC 2.5% of the capacity while charging at a C-rate of 0.5C at 25℃, and the resistance values ​​when charging was performed in a pattern of charging to SOC 2.5% (CCVSOC y), resting for 3 seconds (OCVSOC y), and resting for 0.1 second (OCVSOC y) were calculated, and the measured values ​​were substituted into the following equation to calculate the internal resistance value at the corresponding charge depth.

[0213] [ceremony]

[0214]

[0215] The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y), and the above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

[0216] By plotting the depth of charge on the x-axis and the corresponding relationship of the internal resistance value on the y-axis, the internal resistance profile according to the depth of charge, as shown in Fig. 7, was stored in the memory unit.

[0217] Afterwards, the same process as above was repeated for each charging current of 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C, 2.75C, 3.0C, 3.5C, 3.75C, and 4.00C, and the internal resistance profile according to each charge depth (SOCy) for each charging current was stored in the memory.

[0218] Thereafter, the control unit determined the charging degree at the point where the graph shape changes from flat to descending in the internal resistance profile according to the charging depth of FIG. 7 stored in the storage unit as the limit charging depth for each charging current, and established a charging protocol as shown in Table 2 below as a result.

[0219] Charge Current (C-rate) 4.00 3.75 3.5 3.25 3.02 75 2.5 2.25 2.01 75 1.5 1.25 1.00 75 0.5 Depth of Charge (SOC) Fresh 3 1 32 5 35 37 5 40 42 5 45 47 5 5 0.5 5 5 9 5 6 47 0 8 0 9 2 5 Depth of Charge (SOC) aged 1 9 7 22 22 4.6 27 129 6 32 34 5 37 40 44 5 5 0.5 5 6 67 48 3.8

[0220] Reference Example 1 is for a cathode with Gr 100%, and although the resistance inflection section is relatively well visible even with R3s, as can be seen in Fig. 7, a depth of charge of 24.9 minutes was derived by referring to R diff (R3-0.1s), which shows the change better. Comparative Example 1 is for a SiC 15% cell, and as can be seen in Fig. 4, the inflection section where the resistance drops is not clearly visible with R rest 3s, and a depth of charge of 13.9 minutes was derived by utilizing R diff (R3-0.1s), as shown in Fig. 5.

[0221] That is, in the case of Comparative Example 1 and Reference Example 2, it was confirmed that it was difficult to derive the depth of charge using the existing method, and it was confirmed from Example 1 and Example 2 that the depth of charge could be derived according to the method of the present application.

[0222] Experimental Example 1: Capacity Retention Rate Evaluation

[0223] The QC cycle was performed in the same manner as in Figure 8, and measurements were made in the following manner.

[0224] 1) Normal cycle (blue charge / discharge): 1 / 3C to SOC0-100, 4.35V, 0.05C cut-off CC-CV charge / rest 30min / 1 / 3C to SOC100-8, SOC8 voltage CC cut-off / rest 30min,

[0225] 2) QC cycle (red charge / green charge / blue discharge): Charge to the depth of charge derived up to SOC8-80 / charge to SOC80-100 at 1 / 3C, 4.35V, 0.05C cut-off CC-CV / rest 30min / charge to SOC100-8 at 1 / 3C, SOC8 voltage CC cut-off / rest 30min

[0226] After repeating the two cycles of 1) and 2) above, the left Y-axis in Fig. 8 indicates the retention of the charge amount in ① of the diagram, and the right Y-axis indicates the voltage at the end of the last step of the Quick charge in ② of the diagram.

[0227] - Capacity retention rate evaluation: The cycle was performed until the voltage of ② reached 4.35 V and then terminated (600 cycles in this experiment), and the results are shown in Table 3 below.

[0228] Equation 1: Charging capacity in each cycle ① / Initial charging capacity * 100

[0229] Example 1 Example 2 Capa. Reten. (%) @ 600 cycle 94.192.6

[0230] As can be seen in Fig. 9, the patterns of 24.9 minutes and 13.9 minutes derived from different chemistries, such as the negative electrodes of Gr 100% (Example 2, Manufacturing Example 2, set 1) and SiC 15% (Example 1, Manufacturing Example 1, set 2), show similar QC cycle life. Both cells reached 4.35 V at the 500th cycle and showed comparable cycle performance until then, which shows that the depth-of-charge analysis method according to the present application is very effective. The capacity decrease after reaching the end voltage is judged to be due to the difference in degradation due to the difference in chemistry, and ideally, it is used until the end voltage is reached, and the difference in retention of 1.5% at 600 cycles corresponds to a value that can be viewed as a level of variation between cells.

[0231] For reference, as can be seen in Fig. 10 and Table 2, the range (R) of the present invention formula 1 for the aged cell of Manufacturing Example 2 (Example 2) diff (R 3-0.1s )) When we derive the absolute resistance compared to the fresh cell, the resistance increased from 0.30mOhm to 0.35mOhm, and the rate of increase also shows different values ​​depending on the charge rate. In addition, the plating zone where the resistance increases and then drops also shows a result of stretching toward the lower SOC, so it is judged that the degree of degradation is different depending on the charge rate. Therefore, it was confirmed that it is possible to identify the degree of degradation through non-destructive testing during cycle operation and to modify the rapid charging protocol according to the change in charge depth.

Claims

1. For a two-electrode battery cell with a positive and negative electrode, when charged with different charging currents, the closed circuit voltage (CCV) according to the depth of charge (SOCy) when charged with each charging current (I) SOCy ) and open circuit voltage (OCV) SOCy ) measuring unit configured to measure; The above measured CCV SOCy Wow OCV SOCy By substituting into Equation 1 below, the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) and a memory unit configured to collect and store the internal resistance profile plotted; and A battery management system including a control unit configured to determine a limit charge depth corresponding to each charge current from the above internal resistance profile and establish a charge protocol based on the determined limit charge depth. [Formula 1] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y). The above x is 0.1C or more and 8.0C or less, The above y is greater than or equal to 0 and less than or equal to 100, The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y). The above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

2. In the first paragraph, the memory unit has an internal correction resistance value (R) according to the depth of charge at intervals of 1 to 2.5 for the y value. rest3-0.1s ) to collect and store the internal resistance profile.

3. In the first paragraph, the control unit determines the depth of charge (SOC) at the point where the graph shape of the internal resistance profile changes from flat to a downward trend. y ) A battery management system configured to determine a value as a limit depth of charge.

4. In the first paragraph, the control unit calculates the Rdiff(y) value represented by the above formula 1, and determines the y value that satisfies │Rdiff(y)-Rdiff(y+2.5)│ value of 0.1 or more and the y value of 5 or more as the limit charge depth, a battery management system.

5. A battery management system according to claim 1, wherein the control unit is configured to periodically derive a new limit charge depth corresponding to each charge current according to repeated charge and discharge of the battery cell, and to re-establish a charge protocol.

6. A battery management system comprising a connection unit configured to be connected to a charging device to supply charging current to the battery cell according to a charging protocol established by the control unit in the first paragraph.

7. A battery management system according to claim 1, wherein the measuring unit is configured to measure status information of a battery cell including at least one of a voltage and a depth of charge of the battery cell.

8. A battery pack comprising a battery management system according to any one of claims 1 to 7.

9. In the 8th paragraph, the battery pack comprises a plurality of battery cells having a capacity of 1 Ah to 200 Ah. 10.(a) For a two-electrode battery cell having a positive and negative electrode, when charged with different charging currents, the closed circuit voltage (CCV) according to the depth of charge (SOCy) when charged with each charging current (I) SOCy ) and open circuit voltage (OCV) SOCy ) the process of measuring; (b) In the following equation 1, the measured CCV SOCy Wow OCV SOCy By substituting the internal compensation resistance value (R) according to the depth of charge rest3-0.1s ) is calculated, and for each charging current (I), the internal correction resistance value (R) according to the charging depth is calculated. rest3-0.1s ) is a process of collecting internal resistance profiles by plotting them; and (c) A method for establishing a charging protocol for a lithium secondary battery, including a process of determining a limiting charge depth corresponding to each charging current from the internal resistance profile collected above: [Formula 1] The above equation 1 is a value calculated by charging the battery cell at 25℃ with a C-Rate of x based on SOC y% of the capacity, and charging in a pattern of charging SOC y% (CCVSOC y) and then resting for 3 seconds (OCVSOC y). The above x is 0.1C or more and 8.0C or less, The above y is greater than or equal to 0 and less than or equal to 100, The above R rest 3s is the resistance value after charging SOC y% (CCVSOC y) and resting for 3 seconds (OCVSOC y). The above R rest 0.1s is the resistance value after charging SOC y% (CCVSOC y) and resting for 0.1 seconds (OCVSOC y).

11. In the 10th paragraph, in the process (c), the limit charge depth is the charge depth (SOC) at the point where the graph shape of the internal resistance profile changes from flat to a downward trend. y ) A method for establishing a charging protocol for a lithium secondary battery, characterized in that the charging protocol is determined by a value.

12. In the 10th paragraph, in the process (c), the limit charging depth is calculated by the process of calculating the Rdiff(y) value represented by the formula 1; and │Rdiff(y)-Rdiff(y+2.5)│The process of deriving the y value that satisfies the value of 0.1 or more and the y value of 5 or more as the limit filling depth; A method for establishing a charging protocol for a lithium secondary battery including:

13. A method for establishing a charging protocol for a lithium secondary battery, wherein the capacity of the two-electrode cell in the 10th paragraph is 1 Ah to 200 Ah.

14. In the 10th paragraph, a process of mapping a charging protocol based on a limit charging depth for each charging current is further included. The above mapping process is a method for establishing a charging protocol for a lithium secondary battery, characterized in that the charging current is mapped so that the charging current is charged up to a limit charging depth for each charging current, but the charging current decreases as the charging depth increases.

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