Electrode assembly and secondary battery comprising same

Abstract

The present invention relates to an electrode assembly and a secondary battery comprising same and, relates to an electrode assembly having improved performance during high-speed charging, and a secondary battery comprising same. The electrode assembly according to the present invention is an electrode assembly formed by alternately stacking a first electrode, a separator, and a second electrode, wherein the first electrode comprises: a first electrode current collector; and a first electrode active material layer formed on one surface of the first electrode current collector, a plurality of grooves are formed in the first electrode active material layer, and assuming that the thickness of the first electrode active material layer is h and the depth of the grooves is d, the electrode assembly according to the present invention satisfies formula (1): 0.15≤ d / h ≤0.55 ---- (1).

Description

Electrode assembly and secondary battery including the same

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2025-0010704 filed January 23, 2025 and Korean Patent Application No. 10-2026-0008617 filed January 16, 2026, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003] Technology field

[0004] The present invention relates to an electrode assembly and a secondary battery including the same, and more specifically, to an electrode assembly and a secondary battery including the same that improves performance during high-speed charging.

[0005] Recently, with the increasing technological development and demand for mobile devices, the demand for rechargeable secondary batteries as an energy source has been rapidly rising, and consequently, extensive research is being conducted on secondary batteries capable of meeting various requirements. Furthermore, secondary batteries are also attracting attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (Plug-in HEVs), which are being proposed as solutions to address air pollution caused by conventional gasoline and diesel vehicles that use fossil fuels.

[0006] These lithium secondary batteries are classified according to the shape of the battery case into cylindrical and prismatic batteries, in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is embedded in a pouch-type case made of an aluminum laminate sheet.

[0007] In addition, the electrode assembly embedded in the battery case is a power generation element capable of charging and discharging, having a structure comprising a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. It is classified into a jelly-roll type, which is wound with a separator interposed between a long sheet-type positive and negative electrode coated with an active material; a stack type, which is sequentially stacked with a plurality of positive and negative electrodes of a predetermined size interposed in a separator; and a stack-folding type, which is wound after placing unit cells, such as a full cell or a bicell, composed of electrodes of opposite polarities on both sides, on a long sheet-type separator.

[0008] Meanwhile, the above-mentioned positive and negative electrodes are generally manufactured by coating an electrode slurry containing an active material on both sides of each current collector, and various materials are used as the active material. Among these, materials containing graphite are widely used as the negative active material.

[0009] Recently, as battery capacity has increased and the need for various conveniences has led to the necessity of high-speed charging, much research is being conducted on performance improvements for this purpose. In the case of prismatic or cylindrical batteries with volume limitations, the built-in electrode assembly is compressed by the case, and in reality, 100% impregnation of the electrolyte is not achieved in each case. Consequently, when high-speed charging is performed, there are problems such as the occurrence of lithium plating precipitation, which leads to performance degradation. Therefore, research is currently being conducted on the problems that need to be solved due to high-speed charging.

[0010] The present invention has been devised to solve the above problems, and the objective of the present invention is to provide an electrode assembly with improved performance during high-speed charging and a secondary battery including the same.

[0011] The electrode assembly according to the present invention relates to an electrode assembly formed by alternately stacking a first electrode, a separator, and a second electrode, wherein the first electrode comprises a first electrode current collector; and a first electrode active material layer formed on one surface of the first electrode current collector, and a plurality of grooves are formed in the first electrode active material layer, and when the thickness of the first electrode active material layer is h and the depth of the groove is d, the electrode assembly according to the present invention satisfies the following equation (1).

[0012] 0.15≤ d / h ≤0.55 ---- (1).

[0013] The first electrode may be a negative electrode, and the second electrode may be a positive electrode.

[0014] Home can be provided with multiple columns and multiple rows.

[0015] Multiple grooves can be arranged in a grid shape.

[0016] The spacing between the grooves can be 65 µm to 210 µm.

[0017] The diameter of the groove measured on the outer surface of the first electrode active material layer may be 53 µm to 111 µm.

[0018] The diameter of the groove may decrease as it moves in the direction of depth.

[0019] The second electrode includes a second electrode current collector and a second electrode active material layer formed on one side of the second electrode current collector, and assuming that a groove formed in the first electrode active material layer is filled with the first electrode active material, the ratio of the electrical capacitance of the second electrode active material layer to the first electrode active material layer may be 100:105 to 110.

[0020] The groove can be formed using a laser or a mold.

[0021] A secondary battery according to the present invention comprises an electrode assembly according to the present invention as described above, and a battery case in which the electrode assembly is housed.

[0022] The electrode assembly according to the present invention and the secondary battery including the same have the effect of improving performance during high-speed charging.

[0023] FIG. 1 is a cross-sectional view illustrating an electrode assembly according to Example 1 of the present invention.

[0024] Figure 2 is a plan view illustrating only the first electrode as seen from the F direction.

[0025] Figure 3 is a diagram showing information about the experimental groups targeted in the experimental example of the present invention.

[0026] Figure 4 is a table summarizing the results of Experimental Example 1 of the present invention.

[0027] Figure 5 is a diagram showing the chart data of Figure 4 as a line graph.

[0028] Figure 6 is a table summarizing the results of Experimental Example 2 of the present invention.

[0029] Figure 7 is a diagram showing the chart data of Figure 6 as a line graph.

[0030] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited or restricted by the following embodiments.

[0031] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0032] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0033]

[0034] Example 1

[0035] FIG. 1 is a cross-sectional view illustrating an electrode assembly according to Example 1 of the present invention. FIG. 2 is a plan view illustrating only the first electrode as viewed from direction D. FIG. 3 is a graph showing information regarding the experimental groups targeted in the experimental example of the present invention. FIG. 4 is a graph summarizing the results for Experimental Example 1 of the present invention. FIG. 5 is a graph showing the graph data of FIG. 4 as a line graph. FIG. 6 is a graph summarizing the results for Experimental Example 2 of the present invention. FIG. 7 is a graph showing the graph data of FIG. 6 as a line graph.

[0036] Referring to FIG. 1, the electrode assembly (100) according to Embodiment 1 of the present invention is formed by alternately stacking a first electrode (110), a separator (130), and a second electrode (120). For example, the first electrode (110) may be a negative electrode. The second electrode (120) may be a positive electrode. The first electrode (110) included in the electrode assembly (100) according to Embodiment 1 of the present invention may be one or multiple. Likewise, the second electrode (120) may also be one or multiple. The separator (130) may also be one or multiple. When there are multiple electrodes and separators (130), they may have a form in which they are alternately stacked in the order of the first electrode (110), separator (130), second electrode (120), separator (130)...

[0037] FIG. 1 is a drawing showing an enlarged view of a stacked portion, typically comprising a first electrode (110), a separator (130), and a second electrode (120).

[0038] Referring to FIG. 1, the first electrode (110) may include a first electrode current collector (111) and a first electrode active material layer (112). The first electrode current collector (111) may be made of metal. When the first electrode (110) is a negative electrode, the first electrode current collector (111) may be made of copper, for example. The second electrode (120) may include a second electrode current collector (121) and a second electrode active material layer (122). The second electrode current collector (121) may also be made of metal. When the second electrode (120) is a positive electrode, the second electrode current collector (121) may be made of aluminum, for example.

[0039] The first electrode active material layer (112) can be formed by applying and drying a slurry in which an active material, a conductive material, and a binder are mixed. The first electrode active material layer (112) can be formed on one side of the first electrode current collector (111). Of course, the first electrode active material layer (112) may be formed only on one side of the first electrode current collector (111), or it may be formed on both sides of the first electrode current collector (111).

[0040] The second electrode active material layer (122) can also be formed by applying and drying a slurry in which an active material, a conductive material, and a binder are mixed. Here, specific example materials of the active material may differ from those of the first electrode (110). Since example materials of the active material are widely known in the art, detailed descriptions are omitted here. The second electrode active material layer (122) can be formed on one side of the second electrode current collector (121). Of course, the second electrode active material layer (122) may also be formed only on one side of the second electrode current collector (121), or it may be formed on both sides of the second electrode current collector (121).

[0041] FIG. 1 is a cross-sectional view illustrating an electrode assembly (100) according to Embodiment 1 of the present invention. FIG. 2 is a plan view illustrating only the first electrode (110) as viewed from the F direction. Referring to FIG. 1 and FIG. 2, a plurality of grooves (113) are formed in the first electrode active material layer (112). Although grooves (113) are formed in the first electrode active material layer (112), grooves (113) may not be formed in the second electrode active material layer (122). The grooves (113) may be formed in a plurality and may be formed in a plurality of columns and rows.

[0042] And, the electrode assembly (100) according to Example 1 of the present invention is an electrode assembly (100) that satisfies the following equation (1), where the thickness of the first electrode active material layer (112) is h and the depth of the groove (113) is d.

[0043]

[0044] 0.15≤ d / h ≤0.55 ---- (1).

[0045]

[0046] The above equation (1) represents the ratio of the depth (d) of the groove (113) to the thickness (h) of the first electrode active material layer (112). Since the thickness (h) of the first electrode active material layer (112) can be considered to be a somewhat constant value, the value of d / h increases as the groove (113) is dug deeper.

[0047] The electrode assembly (100) according to Embodiment 1 of the present invention has such a configuration that it can have the effect of improving performance during high-speed charging. First, the deeper the groove (113) is dug, the larger the surface area exposed to the outside from the first electrode active material layer (112). In this case, it may mean that the area reacting with the electrolyte increases as the groove (113) is dug deeper. An increase in the area reacting with the electrolyte means that lithium ions from the positive electrode can be smoothly inserted into the negative electrode over a larger area during reactions such as charging and discharging. The smooth insertion of lithium ions over a larger area means that the reaction is active and the battery performance improves. Considering this principle, it can be thought that the deeper the groove (113) is dug, the better the battery performance can be.

[0048] However, while the present invention is based on this basic idea, the distinguishing feature of the present invention is that as the groove (113) becomes deeper, a significantly improved battery performance enhancement effect is exhibited within a certain ratio numerical range.

[0049] Experimental Examples 1 and 2 described below explain how the electrode assembly (100) according to Example 1 of the present invention exhibits an enhanced effect within a specific ratio numerical range during high-speed charging.

[0050]

[0051] (Experimental Example 1)

[0052] Experimental Example 1 is an experiment showing the effect of further improving the rate retention rate according to the charging speed during high-speed charging in the present invention.

[0053] First, FIG. 3 is a diagram showing information about the experimental groups that are the subject of the experimental example of the present invention. Referring to FIG. 3, the experimental subject labeled Ref. refers to an electrode assembly (100) in which a groove (113) is not formed in the first electrode active material layer (112). Ref. is an abbreviation for Reference.

[0054] And each experimental subject from SET 1 to SET 10 represents an electrode assembly (100) in which a groove (113) is formed in the first electrode active material layer (112). For experimental subjects from SET 1 to SET 10, the groove (113) is formed deeper as the number following SET increases. In Experimental Example 1, the groove (113) was formed using a laser. That is, the groove (113) was formed by irradiating the first electrode active material layer (112) with a laser. The depth (d) of the groove (113) was adjusted and formed using the principle that increasing the intensity of the laser results in the formation of a deeper groove (113). That is, the values ​​labeled "Power (%)" in the left column represent the laser intensity. For example, SET 1 means that the laser power is 10% of the reference laser intensity, and SET 2 means that the laser power is 20% of the reference laser intensity. In this case, it means that the laser intensity in SET 2 is twice the laser intensity in SET 1. Here, the reference laser intensity can be 320 kW. In this case, for example, the laser intensity of 10% can be 32 kW.

[0055] In this way, a groove (113) was formed in the first electrode active material layer (112) by gradually increasing the laser intensity by 10%. Accordingly, as SET 1 to SET 10, a groove (113) with a deeper depth (d) was formed. In this way, the depth (d) of the groove (113) was formed to 4 µm in SET 1, 11 µm in SET 2, 16 µm in SET 3, 45 µm in SET 9, and 51 µm in SET 10. The remaining values ​​are listed in the table, so a detailed description is omitted here.

[0056] In addition, as an experimental condition, the spacing (b) between the grooves (113) and the grooves (113) was formed to be 200 μm, and the grooves (113) were arranged in multiple columns and multiple rows, and in particular, formed in a regular grid shape as shown in FIG. 2. That is, the distance between the grooves (113) in the horizontal direction and the distance between the grooves (113) in the vertical direction were made equal.

[0057] And based on the state before forming the groove (113), the ratio of the electrical capacitance of the second electrode active material layer (122) to the first electrode active material layer (112) was formed to be 100:108. This means that the active material layer was formed first with this amount, and then the groove (113) was formed in the first electrode active material layer (112). Here, the first electrode (110) is the negative electrode, and the second electrode (120) is the positive electrode.

[0058] Generally, when manufacturing electrodes, regarding the amounts of positive and negative active materials (which are proportional to electrical capacitance), the negative active material is formed to be more abundant, but the difference between the two is not significant; instead, they are formed in somewhat corresponding amounts. The reason for making the negative active material more abundant is that if the negative active material is smaller, there is insufficient space for lithium released from the positive electrode to enter, leading to lithium precipitation. If lithium precipitation occurs, battery performance drops significantly. Furthermore, the reason the negative active material is not formed with a large difference compared to the positive active material is that if there is an excessive amount of only the negative active material, it cannot all be utilized in the reaction, which could result in waste of the negative active material. Therefore, when manufacturing batteries, the amount of negative active material is generally formed to be corresponding to the amount of positive active material, but slightly greater.

[0059] Referring to the table in FIG. 3, the thickness (h) of the first electrode active material layer (112) was applied as a constant value of 85 μm. In this case, when the d / h value is calculated for each SET, it is 0.047 for SET 1, 0.13 for SET 2, and 0.19 for SET 3, and in the same way, it is 0.53 for SET 9 and 0.6 for SET 10. Since the remaining values ​​are listed in the table, detailed descriptions will be omitted here.

[0060] Referring to Fig. 4, Experimental Example 1 measured the electric capacity retention rate according to the charging speed during high-speed charging using these experimental subjects. Referring to the table shown in Fig. 4, the unit C in the values ​​listed in the left column, such as 0.1C and 0.33C, represents the C-rate, which indicates the charging speed. For example, 1C is the standard speed, which means the speed at which a predetermined standard electric capacity is charged within one hour (e.g., the speed at which a battery is fully charged within one hour). 0.5C means the speed at which a predetermined standard electric capacity is charged within two hours (e.g., the speed at which a battery is fully charged within two hours). Additionally, 2C means the speed at which the standard electric capacity is charged within 30 minutes (e.g., the speed at which a battery is fully charged within 30 minutes).

[0061] Calculated in this way, 0.1C represents the rate of charging the standard electrical capacity over 10 hours. Looking at the table in Figure 4, at 0.1C, each experimental subject shows a value of 100%. This implies that since 0.1C is a sufficiently slow charging rate, the electrical capacity is charged to 100% of the standard capacity without any leakage from the standard electrical capacity, and is maintained (retained).

[0062] For example, to explain SET 1 specifically, it means that if charged sufficiently slowly at 0.1C, the electrical capacity is charged and maintained to 100% of the standard capacity. However, if this charging speed is increased to 0.33C, it means that only 73% of the electrical capacity charged at 0.1C is charged and maintained. Furthermore, if this is increased to 1C, the charged and retained electrical capacity decreases further to 17.1%, and if increased to 2C, it decreases even more to 3.9%. As such, as charging becomes faster, the charged and retained electrical capacity decreases.

[0063] This is similar to the principle that when you have 100g of water in cup A and you try to transfer it to cup B with a narrow opening, if you pour it very slowly, you can transfer all 100g of water from cup A to cup B, whereas if you pour it very quickly, some of the 100g of water from cup A leaks out and some is transferred to cup B.

[0064] However, looking at the results of conducting these experiments on Ref. and SET 1 to SET 10, it can be seen that there is a significantly improved performance effect for the subjects of SET 3 to SET 9.

[0065] For example, looking at the experiment charged at 0.5C, the values ​​were 56.6% in SET 1 and 51.6% in SET 2, while a significant increase was observed in SET 3 to 63.3%. Additionally, looking at the experiment charged at 1C, the values ​​were 17.1% in SET 1 and 15.1% in SET 2, while a significant increase was observed in SET 3 to 23.0%. This means that the electrical capacity retention rate is improved to a higher level in SET 3. Being able to have a higher electrical capacity retention rate under the same charging speed condition of 1C implies that the battery performance has been improved.

[0066] In addition, if you look at the region where the SET number is large and the groove (113) is deep, you can see that the performance (retention rate) decreases as it passes a certain value. For example, if you look at the experiment charged at 0.5C, the values ​​are 65.8% at SET 8 and 67.7% at SET 9, while there is a significant drop to 53.8% at SET 10. Also, if you look at the experiment charged at 1C, the values ​​are 25.0% at SET 8 and 28.4% at SET 9, while there is a significant drop to 15.3% at SET 10. The fact that it can have a lower electrical capacity retention rate under the same 1C condition means that the battery performance has deteriorated.

[0067] Looking at these results, it can be seen that there is a significantly improved performance effect for the experimental subjects from SET 3 to SET 9. The d / h value in SET 3 is 0.19, and the d / h value in SET 9 is 0.53. Also, SET 4 to SET 8 have values ​​between those in SET 3 and SET 9. That is, for SET 3 to SET 9, the d / h value is 0.19 ≤ d / h ≤ 0.53, which satisfies the range of 0.15 ≤ d / h ≤ 0.55 in Equation (1) above, so it can be seen that there is a significant performance improvement effect. In addition, since SET 1 has a d / h value of 0.047, SET 2 has a d / h value of 0.13, and SET 10 has a d / h value of 0.6, it can be seen that the performance improvement effect is non-existent or negligible because the d / h values ​​fall outside the range of 0.15 ≤ d / h ≤ 0.55 in Equation (1) above.

[0068] This can be visually represented by the graph in Fig. 5. The graph in Fig. 5 is a line graph of the data in Fig. 4. Looking at the graph, it can be seen that it is largely divided into Group A (refer to the dotted circle at the top) and Group B (refer to the dotted circle at the bottom). Group A corresponds to the graph for SET 3 to SET 9, and Group B corresponds to the graph for Ref. SET 1, SET 2, and SET 10. Looking at this graph, it can be seen that there is a significant performance improvement effect in SET 3 to SET 9.

[0069]

[0070] (Experimental Example 2)

[0071] Experimental Example 2 is an experiment demonstrating the performance improvement effect in terms of 3C Li plating SoC% (charge amount at the time of 3C lithium precipitation). In Experimental Example 2, the same experimental subjects as in Experimental Example 1 were used in the experiment.

[0072] Specifically, the experiment of Experimental Example 2 is an experiment to measure the charged electrical capacity at the point when lithium is first deposited when the electrode assembly is charged at 3C (where C represents the C-rate, and a speed of 3C refers to a situation of very high-speed charging). In this experiment, the point at which lithium is first deposited was determined by measuring the voltage. That is, the change in voltage during the charging process was measured and a graph was plotted, and the point at which the derivative value first becomes zero on the graph was set as the point at which lithium is first deposited. At the moment lithium is deposited, the deposited lithium blocks the flow of charge, so the change in voltage can become zero at that point.

[0073] First, taking SET 1 as an example, it can be seen that when the experimental subject of SET 1 is charged at a rate of 3C, lithium is first deposited when it is charged to 21.19%. Also, it can be seen that when the experimental subject of SET 2 is charged at a rate of 3C, lithium is first deposited when it is charged to 23.62%. However, when the experimental subject of SET 3 is charged at a rate of 3C, lithium is first deposited when it is charged to 26.09%.

[0074] Interpreting this, it means that for SET 1, there is no problem even if charging is carried out at a very high speed of 3C until 21.19% is charged, but after 21.19%, the charging speed must be lowered to prevent problems from occurring.

[0075] In the case of SET 2, there is no problem with charging at very high speed 3C until it reaches 23.62%, but it means that the charging speed must be lowered from 23.62% onwards to prevent problems.

[0076] In comparison, SET 3 can be charged at a very high speed of 3C without any problems until it reaches 26.09%, but it means that the charging speed must be lowered after 26.09% to prevent problems from occurring.

[0077] Therefore, since SET 3 is capable of 3C high-speed charging until it reaches a higher charge amount than SET 1 and 2, it can be interpreted that it has significantly improved battery performance compared to SET 1 and SET 2.

[0078] Looking at the deep area of ​​the groove (113) (d), it means that in the case of SET 9, there is no problem even if charging is carried out at a very high speed of 3C until 29.6% is charged, but after 29.6%, the charging speed must be lowered so that no problem occurs.

[0079] In the case of SET 10, there is no problem even if charging is carried out at a very high speed of 3C until it reaches 21.94%, but this means that the charging speed must be lowered from 21.94% onwards to prevent problems. Therefore, it can be seen that the battery performance in SET 10 is significantly lower than in SET 9.

[0080] Figure 10 visually illustrates these experimental results. Figure 7 shows the chart data of Figure 6 as a line graph.

[0081] It is shown that the 3C Li plating SoC(%) value increases rapidly as it progresses from SET 1 through SET 2 to SET 3, increases with a somewhat linear change from SET 3 to SET 9, and then drops sharply when moving from SET 9 to SET 10. Looking at this graph, it can be visually seen that there is a significant improvement in battery performance from SET 3 to SET 9.

[0082] The d / h value in SET 3 is 0.19, and the d / h value in SET 9 is 0.53. Also, SET 4 to SET 8 have values ​​between those in SET 3 and those in SET 9. That is, for SET 3 to SET 9, the d / h value is 0.19 ≤ d / h ≤ 0.53, which falls within the range of 0.15 ≤ d / h ≤ 0.55 in Equation (1) above, indicating a significant performance improvement effect. Furthermore, since the d / h value in SET 1 is 0.047, in SET 2 is 0.13, and in SET 10 is 0.6, the d / h values ​​in these are outside the range of 0.15 ≤ d / h ≤ 0.55 in Equation (1) above, indicating that there is no or minimal performance improvement effect.

[0083]

[0084] Based on the experimental results examined above, it can be seen that a significant performance improvement effect occurs in SET 3 through SET 9. The interpretation of this may be based on the following principle.

[0085] First, regarding the significant increase in performance that occurs with SET 3, this can be explained in relation to the impregnation of the electrolyte. For example, since no groove (113) is formed in the Ref. electrode, the electrolyte can only seep in vertically from the outer surface when attempting to impregnate. Therefore, impregnation may not be relatively smooth. Consequently, 100% impregnation may not occur in all the very deep parts of the first electrode active material layer (112). However, once the depth (d) of the groove (113) is formed to a certain depth, the electrolyte can also be impregnated in the horizontal direction within the groove (113). This may mean that horizontal impregnation occurs simultaneously in a certain deep area in addition to vertical impregnation from the outer surface. Therefore, at the moment the groove (113) passes a certain depth, a moment may occur in which 100% impregnation occurs in all the very deep parts of the first electrode active material layer (112). It can be interpreted that a rapid increase in performance may occur if one passes through the depth of such moments.

[0086] Additionally, matters related to the fluidity of the electrolyte can be considered. Since swelling may occur in the electrode during the charging process, the electrolyte may exhibit some degree of fluidity. However, if a groove (113) is formed, the fluidity of the electrolyte within the groove (113) with a certain depth may become zero (or a value close to zero). Of course, if the depth (d) of the groove (113) is minimal, the fluidity of the electrolyte inside the groove (113) will not be zero as it is affected by the fluidity of the electrolyte; however, beyond a certain depth, the fluidity inside the groove (113) may become zero (or a value close to zero) as it is not affected by the fluidity of the electrolyte.

[0087] Therefore, it can be interpreted that a rapid increase in performance may occur when passing through the depth (d) of the groove (113) where the fluidity can become zero. The better the process of lithium ions from the positive electrode being inserted into the negative electrode, the better the performance may be, and if the fluidity of the electrolyte is zero and in a static state, it may be more advantageous for smooth lithium ion insertion.

[0088] Meanwhile, regarding the rapid decline in performance that occurs as SET 10 is reached, the first factor to consider is the negative electrode side reaction. The reaction between the electrolyte and the negative electrode active material during the charging process, which forms a byproduct SEI (Solid Electrolyte Interphase) film layer, is called a negative electrode side reaction. Since the SEI film layer hinders the flow of lithium ions and charges, it can be a factor that reduces battery performance. As the depth (d) of the groove (113) increases, the reaction area becomes larger, which can mean that the area where the SEI film layer is formed also becomes larger. Therefore, beyond a certain depth, the formation of the SEI film inside the groove (113) can cause the battery performance to drop rapidly.

[0089] Secondly, regarding the rapid decline in performance that occurs as SET 10 is reached, the destruction of particles due to laser irradiation may be the cause (of course, particle destruction may also occur when physical impact is applied to form a hole). To explain specifically, the electrode active material layer is composed of an active material, a conductive material, and a binder bonded together. A laser can destroy these bonds. Digging the groove (113) deep may mean that there are more particles whose bonds are destroyed in this way. The destroyed particles refer to active material particles whose bonds with the conductive material and binder have been severed. Since these destroyed active material particles are particles that cannot react, an increase in such particles means that the resistance hindering the flow of lithium ions and charges increases. Therefore, beyond this predetermined depth, these destroyed active material particles may cover the ion pathways, causing a rapid decline in performance.

[0090]

[0091] Referring to FIG. 2, in the electrode assembly (100) according to Embodiment 1 of the present invention, the grooves (113) formed in the first electrode active material layer (112) can be formed using a laser or a mold. The grooves (113) can be arranged in a plurality of columns and a plurality of rows. In particular, referring to FIG. 2, the plurality of grooves (113) may be arranged in a regular grid shape. The spacing (b) between the grooves (113) formed in the first electrode active material layer (112) may be 65 μm to 210 μm. Preferably, it may be 200 μm. When the plurality of grooves (113) are arranged in a regular grid shape, the spacing (b) between the grooves (113) may have the same value when measured in the horizontal direction and when measured in the vertical direction.

[0092] Also, the diameter (w) of the groove (113) measured on the outer surface of the first electrode active material layer (112) may be 53 μm to 111 μm. More preferably, the diameter (w) of the groove (113) may be 55 μm to 109 μm. For reference, when forming the groove (113) with a laser, the laser power may be increased to form the groove (113) in order to make the depth (d) of the groove (113) deeper. However, since increasing the power irradiates more energy, the diameter (w) of the groove (113) may become larger. Based on this principle, when actually forming the groove (113) in the electrode active material layer, if the depth (d) of the groove (113) is made deeper, the diameter (w) of the groove (113) may be increased.

[0093] Referring to FIG. 1, the groove (113) may have a shape in which the diameter decreases as it goes in the depth direction. In this case, the diameter of the groove (113) may decrease as it goes in the depth direction (the same direction as the F direction). Conversely, the groove (113) may have a shape in which the diameter increases as it goes in the depth direction. In this case, the diameter of the groove (113) may increase as it goes in the F direction.

[0094] Also, the ratio of the electrical capacitance of the second electrode active material layer (122) and the first electrode active material layer (112) may be 100:105 to 110. For example, if the electrical capacitance of the second electrode active material layer (122) is 1000 mAh, the electrical capacitance of the first electrode active material layer (112) may be 1050 to 1100 mAh. This ratio of electrical capacitance may be a value assumed when assuming that the groove (113) formed in the first electrode active material layer (112) is filled with the first electrode (110) active material.

[0095] Generally, when making electrodes, the electrical capacitance of the positive active material and the electrical capacitance of the negative active material are formed such that the electrical capacitance of the negative active material is greater, but without creating a significant difference, they are formed in a somewhat corresponding amount. This is to prevent lithium from precipitating when the amount of the negative electrode is small. Also, the electrical capacitance of the negative active material is not formed to be significantly greater than that of the positive active material. The reason for this is to prevent waste of the negative active material, as a large amount of negative active material alone cannot be used in the reaction. In this regard, when the first electrode (110) is the negative electrode and the second electrode (120) is the positive electrode, the ratio of the electrical capacitance of the second electrode active material layer (122) and the first electrode active material layer (112) can be 100:105 to 110.

[0096] And, assuming that the ratio of electrical capacitance is a value when the groove (113) formed in the first electrode active material layer (112) is filled with the first electrode (110) active material, it may mean the electrical capacitance of the first electrode active material layer before forming the groove (113) in the first electrode active material layer (112). That is, when the first electrode (110) and the second electrode (120) are initially manufactured, the ratio of electrical capacitance of the second electrode active material layer (122) and the first electrode active material layer (112) is manufactured to be 100:105 to 110, and then, the process of forming the groove (113) in the first electrode active material layer (112) is carried out. In the case of an electrode assembly manufactured in this way, it may partially affect the decrease in battery performance when moving from SET 9 to SET 10 in the previous experiment.

[0097] That is, the NP reversal phenomenon may not occur until the groove (113) is formed to a certain depth. Here, the NP reversal phenomenon means that the amount of the negative electrode active material layer becomes smaller than the amount of the positive electrode active material layer. However, the moment the groove (113) in the negative electrode is dug to a depth greater than a certain depth, the NP reversal phenomenon may occur. When the NP reversal phenomenon occurs, lithium precipitation may occur because there is insufficient negative electrode active material for the lithium ions from the positive electrode active material to be inserted. As a result, the battery performance may decrease from the point at which the NP reversal phenomenon occurs.

[0098]

[0099] Example 2

[0100] Embodiment 2 of the present invention differs from Embodiment 1 in that it is a secondary battery comprising an electrode assembly (100) according to Embodiment 1 of the present invention.

[0101] Content common to Example 1 will be omitted as much as possible, and Example 2 will be described. That is, it is obvious that if content not explained in Example 2 is necessary, it can be considered as content of Example 1.

[0102] Referring to FIG. 1, a secondary battery according to Example 2 of the present invention may include an electrode assembly (100) described in Example 1 and a battery case (not shown) that accommodates the electrode assembly (100) inside. Since the electrode assembly (100) has been described previously, further description thereof will be omitted here.

[0103] The battery case can be provided in various shapes. In the case of a battery case accommodating a jelly-roll type electrode assembly, it can be provided in the form of a cylindrical metal can or a prismatic metal can. Additionally, if the electrode assembly is formed in a stack type or a stack-and-fold type, the battery case can be provided in a pouch type. The pouch-type case can be formed by laminating resin layers on both sides of an aluminum layer.

[0104]

[0105] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

[0106] [Explanation of the symbol]

[0107] 100: Electrode assembly

[0108] 110: First electrode

[0109] 111: First electrode current collector

[0110] 112: First electrode active material layer

[0111] 113: Home

[0112] 120: Second electrode

[0113] 121: Second electrode current collector

[0114] 122: Second electrode active material layer

[0115] 130: Separator

[0116] w: Diameter of the groove

[0117] b: Spacing between grooves

[0118] d: depth of the groove

[0119] h: Thickness of the electrode active material layer

Claims

1. An electrode assembly formed by alternately stacking a first electrode, a separator, and a second electrode, wherein The first electrode above is, First electrode current collector; and It includes a first electrode active material layer formed on one surface of the first electrode current collector, and A plurality of grooves are formed in the first electrode active material layer, and When the thickness of the first electrode active material layer is h and the depth of the groove is d, Electrode assembly satisfying the following equation (1). 0.15≤ d / h ≤0.55 ---- (1) 2. In Claim 1, An electrode assembly characterized in that the first electrode is a negative electrode and the second electrode is a positive electrode.

3. In Claim 1, The electrode assembly is characterized in that the above-mentioned groove is provided in a plurality of columns and a plurality of rows.

4. In Claim 1, An electrode assembly characterized in that the plurality of grooves are arranged in a grid shape.

5. In Claim 1, An electrode assembly characterized in that the spacing (b) between the grooves is 65 µm to 210 µm.

6. In Claim 1, An electrode assembly characterized in that the diameter (w) of the groove measured on the outer surface of the first electrode active material layer is 53 μm to 111 μm.

7. In Claim 1, The above-mentioned groove is an electrode assembly characterized by a diameter that decreases as it goes deeper.

8. In Claim 1, The second electrode above is, Second electrode current collector; and It includes a second electrode active material layer formed on one surface of the second electrode current collector, and Assuming that the groove formed in the first electrode active material layer is filled with the first electrode active material, An electrode assembly characterized in that the ratio of the electrical capacitance of the second electrode active material layer and the first electrode active material layer is 100:105 to 110.

9. In Claim 1, The above groove is an electrode assembly formed through a laser or mold.

10. Electrode assembly according to claim 1; and A secondary battery comprising a battery case in which the above electrode assembly is housed.

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