Method for manufacturing lithium ion secondary battery

Abstract

To properly estimate cell resistance in implementing cell control, and to properly set the upper limit of charging and discharging.SOLUTION: Create samples for each opposed capacity ratio RC and LiBOB addition amount AA[wt%] (S31). Next, perform a storage degradation test to measure initial resistance RI and terminal resistance RE (S32). Calculate the amount of LiBOB added AA that makes the initial resistance RI=terminal resistance RE (S33). Then, observe the correlation between the opposed capacity ratio RC, the LiBOB addition amount AA, and the optimal amount (S34). Approximate the observation results by a linear function and calculate the relation expression F (S35). Calculate the amount of LiBOB added AA[wt%] that sets the appropriate upper limit for charging and discharging by using the relation expression F.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a lithium-ion secondary battery. More specifically, in the manufacturing process of a lithium-ion secondary battery, the present invention relates to a method for manufacturing a lithium-ion secondary battery capable of optimizing the addition amount of an additive added to a non-aqueous electrolyte to improve battery performance.

Background Art

[0002] Lithium-ion secondary batteries have a large capacity per unit mass and can be charged and discharged at high currents, so they are widely used, including as vehicle drive batteries. In lithium-ion secondary batteries, a non-aqueous electrolyte is used, but it decomposes at the potential of the negative electrode during charging. Therefore, according to a predetermined procedure in the conditioning process, a film of SEI (Solid Electrolyte Interphase) with a thickness of several to several tens of nm, composed of organic substances such as lithium alkyl carbonate and inorganic substances such as lithium salts, is formed at the interface between the negative electrode active material and the non-aqueous electrolyte during the first charge. SEI is necessary to suppress the decomposition of the non-aqueous electrolyte during subsequent charge and discharge, but SEI itself has a large resistance and it is not preferable for it to grow to an excessive thickness because it consumes Li and the non-aqueous electrolyte.

[0003] Therefore, it is known to use an additive to the non-aqueous electrolyte to suppress such capacity degradation. For example, as the additive, a lithium bisoxalate borate (LiBOB) - based film-forming agent is often used.

[0004] For example, Patent Document 1 discloses an invention that optimizes the addition amount of lithium bisoxalate borate so that durability and input / output characteristics can be achieved at a high level. According to such an invention, a method for manufacturing a lithium-ion secondary battery has been proposed in which durability and input / output characteristics can be achieved at a high level in a lithium-ion secondary battery.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent Application Laid-Open No. 2014-032777 Summary of the Invention Problems to be Solved by the Invention

[0006] By the way, in the case of a lithium-ion secondary battery, depending on the potential at the negative electrode during charge and discharge, metallic lithium Li may precipitate. Therefore, in order to prevent the precipitation of metallic lithium Li at the negative electrode during charging, control is performed to set an upper limit on the current value during charge and discharge.

[0007] On the other hand, when LiBOB or the like is added to the non-aqueous electrolyte, it takes time to form a film derived from LiBOB at the initial stage of use, so the internal resistance of the cell battery increases. After that, as the formation of the film derived from LiBOB progresses, the internal resistance of the cell battery decreases. Further use causes the reduction decomposition of the film derived from LiBOB to proceed, and a SEI film is formed again, increasing the internal resistance of the cell battery. The charge and discharge control of the lithium-ion secondary battery is carried out assuming the case where the cell resistance is the highest. Therefore, by reducing the maximum value of the cell resistance from the time of shipment to the end stage of capacity deterioration (capacity maintenance rate 78%), the upper limit of the current value can be relaxed.

[0008] Patent Document 1 adjusts and adds the amount of oxalate borate-based additive, but it is a patent for improving cycle performance, gas generation amount, etc., and does not control the cell resistance. Therefore, in conventional lithium-ion secondary batteries, the cell resistance may be overestimated in implementing cell control, and the upper limit values of charge and discharge may be overly suppressed.

[0009] The problem to be solved by the manufacturing method of the lithium-ion secondary battery of the present invention is to appropriately estimate the cell resistance in implementing cell control and appropriately set the upper limit values of charge and discharge. Means for Solving the Problems

[0010] In order to solve the above problems, in the method for manufacturing a lithium ion secondary battery according to the present invention, a battery cell includes a positive electrode plate, a negative electrode plate, and an electrode body in which these are laminated via a separator, and is a method for manufacturing a lithium ion secondary battery in which an oxalate borate-based additive is added to a non-aqueous electrolyte. The opposed capacity ratio R is the capacity ratio of the negative electrode plate to the positive electrode plate on the surface where the positive electrode composite layer of the positive electrode plate and the negative electrode composite layer of the negative electrode plate face each other. C An opposed capacity ratio calculating step of calculating A The initial resistance R I [mΩ] at the initial stage of use of the lithium ion secondary battery according to the amount A E [mΩ] of the additive and the planned end-of-use final resistance R I [mΩ] are obtained in advance, and the initial resistance R E [mΩ] and the final resistance R A [mΩ], and a relational expression F for obtaining the addition amount A C [wt%] of the additive so that they are equal is derived according to the opposed capacity ratio R C An additive addition amount calculation relational expression derivation step of deriving, and from the relational expression F derived in the additive addition amount calculation relational expression derivation step, based on the opposed capacity ratio R I Calculating the addition amount A E [wt%] of the additive so that the initial resistance R A [mΩ] and the final resistance R

[0011] Further, an additive addition step of adding the additive of the oxalate borate-based system having the addition amount A A [wt%] calculated in the additive addition amount calculation step to the non-aqueous electrolyte, a liquid injection step of injecting and sealing the non-aqueous electrolyte added with the additive in the additive addition step into the battery cell, and a conditioning step including a first charge performed under preset conditions after the liquid injection step can be provided.

[0012] The relational expression F derived in the additive addition amount calculation relational expression derivation step is for each opposed capacity ratio R C The addition amount A of the additiveA The initial resistance R of the lithium-ion secondary battery according to [wt%] I [mΩ], and the planned final resistance R E [mΩ], a cell resistance measurement step of measuring, and the opposing capacitance ratio R C For each, the initial resistance R obtained in the cell resistance measurement step I [mΩ] and the final resistance R E [mΩ], the resistance difference ΔR [mΩ] between them, and the addition amount A of the additive A [wt%], a step of deriving the relationship between the addition amount of the additive and the resistance difference, and based on the relationship derived in the step of deriving the relationship between the addition amount of the additive and the resistance difference, the opposing capacitance ratio R C The addition amount A of the additive at which the resistance difference ΔR [mΩ] according to becomes zero A [wt%], a step of deriving a relational expression for calculating the opposing capacitance ratio - additive addition amount relational expression, may be derived as follows.

[0013] When the relational expression F has an optimum addition amount of A A [wt%], an opposing capacitance ratio of R C , a slope of a, and an intercept of b, A A [wt%]=a×R C +b…(Equation 1) can be represented as such.

[0014] In the (Equation 1), 1.0≦a≦2.5, 3.0≦b≦5.0 can be set. The first charge in the conditioning step is the first negative electrode potential V1 [V vs. Li / Li + at which the oxalate borate-based additive is reductively decomposed, and the first hold step in which the first negative electrode potential [V vs. Li / Li + is maintained for a set time, and the second negative electrode potential V2 [V vs. Li / Li + at which the oxalate borate-based additive forms a film on the negative electrode active material, and the second hold step in which the second negative electrode potential [V vs. Li / Li + is maintained for a set time can be included. In this case, the negative electrode potential V1 [V vs. Li / Li of the first hold step+ may satisfy 0.1 ≦ V1 ≦ 1.5. Further, the first holding step can continue for 1 hour or more.

[0015] The negative electrode potential V2 [V vs. Li / Li + of the second holding step may satisfy 0.5 ≦ V2 ≦ 2.0. Further, the second holding step can continue for 1 hour or more. In the initial charging, the starting charging rate R ON [C] may satisfy 4 ≦ R ON ≦ 8.5, and the ending charging rate R OFF [C] may be set to 0.01 ≦ R OFF ≦ 0.1.

[0016] The opposed capacity ratio R C may satisfy 1.48 ≦ R C ≦ 1.82. The additive of the oxalate borate system can be lithium bis(oxalato)borate.

Advantages of the Invention

[0017] According to the method for manufacturing a lithium-ion secondary battery of the present invention, the cell resistance can be appropriately estimated and the upper and lower limits of charge and discharge can be appropriately set in carrying out cell control.

Brief Description of the Drawings

[0018]

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[0019] Hereinafter, the manufacturing method of the lithium-ion secondary battery of the present invention will be described with reference to FIGS. 1 to 14 according to an embodiment of the manufacturing method of the lithium-ion secondary battery 1. This embodiment is an example and does not limit the present invention.

[0020] (Outline of this embodiment) [Regarding the SEI and the film derived from LiBOB] The SEI film is formed by the first charge immediately after the manufacture of the lithium-ion secondary battery 1. The SEI exists between the negative electrode active material and the non-aqueous electrolyte 13, and lithium ions Li+ It smooths the absorption and release of lithium into the negative electrode and suppresses the decomposition of the non-aqueous electrolyte 13. Therefore, the SEI film is essential for maintaining good battery characteristics.

[0021] However, the SEI film is formed by decomposition products of the non-aqueous electrolyte 13 and additives, and lithium ions Li + are incorporated during its formation process. By repeatedly charging and discharging or storing the battery for a long time, the SEI film becomes thicker. This not only increases the resistance inside the cell but also may lead to a decrease in battery capacity due to the consumption of lithium ions Li + and the decomposition of the non-aqueous electrolyte 13.

[0022] To address this problem, it has been proposed to pre-add a film-forming material to the non-aqueous electrolyte 13. The film-forming material is a compound having a lithium salt, for example, lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2, hereinafter referred to as "LiBOB"). Adding LiBOB can suppress the formation of the SEI film and thus suppress the internal resistance [mΩ] of the cell.

[0023] Figure 1 is a table showing the change in the internal resistance [mΩ] of the cell with the number of storage days of the lithium-ion secondary battery 1 and the amount of LiBOB added. Figure 2 is a graph showing the relationship in Figure 1. As shown in Figures 1 and 2, at the start of use, both have a relatively high internal resistance [mΩ], and the internal resistance [mΩ] decreases significantly after approximately 10 days of storage. After that, the internal resistance [mΩ] gradually increases, and in this experiment, it is high after 150 days. This is thought to be because the SEI film formed in the initial conditioning process is replaced by the LiBOB-derived film, resulting in a decrease in the internal resistance [mΩ]. Subsequently, the LiBOB-derived film is also reductively decomposed and replaced by the SEI film again.

[0024] When comparing these in detail, when the storage days are 0 days, the one with a LiBOB addition amount of 0.5 [wt%] has the highest resistance of 0.04524 [mΩ]. In comparison, the one with a LiBOB addition amount of 0.3 [wt%] has a cell resistance of 0.04017 [mΩ], and the one with a LiBOB addition amount of 0.4 [wt%] has a cell resistance of 0.04010 [mΩ], with the cell resistance [mΩ] becoming smaller.

[0025] Also, the resistance with LiBOB addition amounts of 0.3 [wt%] and 0.4 [wt%] is the smallest when the storage days are 10 days. On the other hand, the cell resistance [mΩ] with a LiBOB addition amount of 0.5 [wt%] is the smallest when the storage days are 30 days.

[0026] After that, the cell resistance [mΩ] increases in all cases. However, when the storage days are 60 days, the cell resistance [mΩ] with a LiBOB addition amount of 0.5 [wt%] is smaller compared to the cell resistance [mΩ] with LiBOB addition amounts of 0.3 [wt%] and 0.4 [wt%].

[0027] And then, until the storage days reach 150 days, the cell resistance [mΩ] with a LiBOB addition amount of 0.5 [wt%] is smaller compared to the cell resistance [mΩ] with LiBOB addition amounts of 0.3 [wt%] and 0.4 [wt%].

[0028] From the above, initially, the cell resistance [mΩ] with a LiBOB addition amount of 0.5 [wt%] is larger compared to the cell resistance [mΩ] with LiBOB addition amounts of 0.3 [wt%] and 0.4 [wt%]. However, afterwards, the cell resistance [mΩ] with a LiBOB addition amount of 0.5 [wt%] becomes the smallest.

[0029] From this experiment, the relationship between the SEI and the film derived from LiBOB as described above can be verified. <Formation of the Film Derived from LiBOB> Here, the formation of the film derived from LiBOB will be explained. Figure 3 is a diagram showing the chemical changes in which the film derived from LiBOB is formed from LiBOB. As shown in Figure 3, lithium bisoxalate borate (LiBOB, LiB(C2O4)2) added to the non-aqueous electrolyte 13 shows the following reaction during the first charge in the conditioning process.

[0030] First stage: LiBOB decomposes into two compounds, Li2C2O4 and a composite of EC (ethylene carbonate) and PEO (polyethylene oxide, -(CH2CH2O)n-), LiOCO2R).

[0031] Second stage: Li2C2O4 reacts with PEO and LiOCO2R to form a stable film consisting of Li2CO3, PEO, and LiOCO2R on the surface of the negative electrode active material particles. Since the reaction in the second stage does not occur unless the reaction in the first stage occurs, it is presumed that the reaction proceeds in two stages. For this reason, LiBOB is considered to have two reduction peaks. And it is considered necessary to ensure the reaction in the first stage in order to form a film derived from LiBOB on the surface of the negative electrode active material.

[0032] That is, it can be seen that LiBOB added to the non-aqueous electrolyte 13 forms a film derived from LiBOB through two-step chemical changes. Figure 4 shows the change in the value of dQ / dV [Wh / V] in the change of the negative electrode potential [V vs. Li / Li + . The horizontal axis represents the negative electrode potential [V vs. Li / Li + based on Li, and the vertical axis represents dQ / dV [Wh / V] at that time. The change in the case of the lithium-ion secondary battery 1 without adding LiBOB to the non-aqueous electrolyte 13 is shown by the graph G0. Also, the change in the case of the lithium-ion secondary battery 1 with LiBOB added to the non-aqueous electrolyte 13 is shown by the graph G1.

[0033] As shown in Figure 4, in the graph G0 showing the change in the case of the lithium-ion secondary battery 1 without adding LiBOB to the non-aqueous electrolyte 13, a horizontal portion is formed approximately in the vicinity of 0.7 to 0.9 [V vs. Li / Li + . Furthermore, a flat graph is also formed at approximately 1.2 [V vs. Li / Li + or more.

[0034] For the graph G1 showing the changes in the case of the lithium-ion secondary battery 1 with LiBOB added to the non-aqueous electrolyte 13, the negative electrode potential [V vs. Li / Li + is approximately around 0.7 [V vs. Li / Li + , an inflection point is observed and a bottom is formed. Also, around approximately 1.7 [V vs. Li / Li + , an inflection point is observed and a bottom is formed.

[0035] Such a reaction is presumably because reduction decomposition occurs around when the negative electrode potential is approximately 0.7 [V vs. Li / Li + , and a film is formed around 1.7 [V vs. Li / Li + , so energy is consumed in the chemical change.

[0036] From this, it is presumed that such a reduction reaction is occurring. By maintaining the negative electrode potential [V vs. Li / Li + at the negative electrode potential of 0.65 [V vs. Li / Li + and the negative electrode potential of 1.5 [V vs. Li / Li + , it can be seen that the above reduction reaction can be promoted.

[0037] From the graph shown in FIG. 4, it can be presumed that the above first stage of forming a film derived from LiBOB occurs around when the negative electrode potential is approximately 0.7 [V vs. Li / Li + , and the second stage occurs around 1.7 [V vs. Li / Li + .

[0038] Therefore, in this embodiment, at 0.65 [V vs. Li / Li + where the reaction of the first stage starts and 1.5 [V vs. Li / Li + where the reaction of the second stage starts, the negative electrode potential [V vs. Li / Li + is maintained for a certain period of time (1 hour in this embodiment). For this reason, it is possible to effectively form a film derived from LiBOB.

[0039] FIG. 5 is a graph showing an example of the relationship between the elapsed time at the first charge and the cell voltage [V] in a general conditioning process. The horizontal axis represents the elapsed time from the start of the first charge. The vertical axis represents the cell voltage [V], which is the open circuit voltage OCV of the cell battery at that time. When LiBOB is added to the non-aqueous electrolyte 13, during the first charge in the conditioning process, at a certain negative electrode potential [V vs. Li / Li + , the cell voltage [V] is maintained. This state of maintenance is called "hold", and such a process is called a "hold process". Also, the negative electrode potential [V vs. Li / Li + is called the "hold potential".

[0040] As shown in FIG. 5, it can be seen that charging starts from 0 [V] and is held for a certain period of time at the timings when it reaches approximately 1.3 [V], 2.2 [V], 2.92 [V], and 3.18 [V]. Note that in the graph shown in FIG. 5, it is held not only for the purpose of holding LiBOB but also for other purposes, so it is multi-stage.

[0041] <Opposite capacity ratio R C and the negative electrode potential V N [V vs. Li / Li + > FIG. 6 is a graph showing the relationship between the capacity [mAh] of the cell battery and the voltage or potential. The horizontal axis represents the capacity [mAh] of the cell battery. The vertical axis represents the cell voltage [V], the positive electrode potential [V vs. Li / Li + , and the negative electrode potential [V vs. Li / Li + . Graph V S shows the cell voltage V S [V], graph V N shows the negative electrode potential V N [V vs. Li / Li + , and graph V P shows the positive electrode potential V P [V vs. Li / Li + .

[0042] On the graph, the cell voltage V S [V] is the negative electrode potential V N [V vs. Li / Li+ and the positive electrode potential V P [V vs. Li / Li + is shown as the difference. When the counter capacitance ratio R C is decreased, the graph of the negative electrode potential V N shifts to the right, so even at the same cell voltage V S the negative electrode potential V N [V vs. Li / Li + becomes higher. For this reason, if the conditions for the first charge in the conditioning process are defined by the cell voltage V S [V], an error will occur in the negative electrode potential V N [V vs. Li / Li + , and the film formation state on the negative electrode active material will be different. For the above reasons, the conditions for the conditioning process are defined by the negative electrode potential V N [V vs. Li / Li + .

[0043] Figure 7 shows the conditions for the conditioning process regarding LiBOB in the lithium ion secondary battery 1 of this embodiment. The method of the first charge will be described in detail with reference to Figure 7. In this embodiment, first, charging is started from the cell voltage V S 0 [V]. Then, the negative electrode potential [V vs. Li / Li + based on Li is monitored, and charging is performed at a charging rate of 4.5 [C] until the negative electrode potential reaches 0.65 [V vs. Li / Li + . When the negative electrode potential reaches 0.65 [V vs. Li / Li + , charging is paused and held for a certain period of time (1 hour in this embodiment). The reason for setting it to 0.65 [V vs. Li / Li + is that, as shown in Figure 4, in this embodiment, there is a peak in the reductive decomposition of LiBOB at approximately 0.7 [V vs. Li / Li + , in order to promote this reductive decomposition reaction.

[0044] After a certain period of time has elapsed, charging is again performed at a charging rate of 4.5 [C] until the negative electrode potential reaches 1.5 [V vs. Li / Li + . After that, when the negative electrode potential reaches 1.5 [V vs. Li / Li +Once it reaches that level, charging is paused and held for a certain period of time (1 hour in this embodiment). 1.5 [V vs. Li / Li + is set because, as shown in Fig. 4, in this embodiment, there is a peak in the formation of the film derived from LiBOB at approximately 1.7 [V vs. Li / Li + , and this is to promote the reaction of forming this film.

[0045] After a certain period of time has passed, charging is continued until full charge is reached. Then, when the current reaches the cut-off current of 0.014 [C], charging is terminated. Here, the "cut-off current" indicates the minimum value of the current passed during CV (Constant Voltage) charging. To fix the LiBOB film, it is necessary to hold the negative electrode potential near the reduction potential of LiBOB for a certain period of time. Therefore, at the first charge, after charging to the hold potential by CC (Constant Current) charging, the negative electrode potential is made approximately constant by CV charging to fix the LiBOB film. Here, a large current is passed by CC charging immediately after the start of the first charge, but the current value decreases as time passes. From here, a current is passed to hold the potential by CV charging. And the minimum value of the current value during this CV charging is defined as the cut-off current.

[0046] Note that this procedure is for fixing the film derived from LiBOB. Therefore, as shown in Fig. 5, it does not prevent holding at a certain hold potential [V vs. Li / Li + for other purposes or performing current management [W] and voltage management [V] as control during charging.

[0047] <Principle of this embodiment> In the manufacturing method of the lithium-ion secondary battery 1 of this embodiment, based on such background art, in the following manner, when implementing cell control, the cell resistance is appropriately estimated and the upper and lower limits of charge and discharge are appropriately suppressed.

[0048] First, in the opposing capacity ratio calculation step, the opposing capacity ratio R, which is the capacity ratio of the negative electrode plate 2 to the positive electrode plate 3 on the surface where the positive electrode plate 3 and the negative electrode plate 2 face each other C is calculated. Next, in the additive amount calculation relational equation derivation process, the additive amount A A The initial resistance R of the lithium-ion secondary battery 1 at the beginning of use according to I and the end-stage resistance R at the end of the planned use E Then, the initial resistance R I and terminal resistance R E The amount of additive A that is equal to A The relation F for finding the capacitance ratio R C Derive according to:

[0049] From this relation F, the opposing capacitance ratio R C Based on the initial resistance R I and terminal resistance R E The amount of additive A that is equal to A Calculate. In the additive addition process, the additive amount A calculated in the additive amount calculation process is A The oxalate-borate based additive is added to the non-aqueous electrolyte 13, which is then injected into the battery cell in the electrolyte injection step and sealed.

[0050] In the conditioning process, an initial charge is performed under preset conditions to form a coating derived from LiBOB. As a result, the initial resistance R of the lithium-ion secondary battery 1 I and terminal resistance R E and are equal to each other, controlling the upper limit voltage based on these resistance values ​​enables the safest and most efficient use of the lithium ion secondary battery 1. Hereinafter, a method for manufacturing the lithium ion secondary battery 1 of this embodiment will be described in detail.

[0051] (Configuration of this embodiment) <Configuration of lithium-ion secondary battery 1> First, an example of a lithium ion secondary battery 1 that is the premise of this embodiment will be described in detail. Note that there is no limitation on the type of battery to which the present invention is applied.

[0052] FIG. 8 is a perspective view showing an outline of the external configuration of the lithium ion secondary battery 1 of the present embodiment. First, the configuration of the lithium ion secondary battery 1 of the present embodiment, which is an example of the present invention, will be described.

[0053] As shown in FIG. 8, the lithium ion secondary battery 1 is configured as a cell battery. The lithium ion secondary battery 1 includes a plate-shaped rectangular parallelepiped battery case 11 having an opening on the upper side. An electrode body 12 is accommodated inside the battery case 11. The battery case 11 is filled with a non-aqueous electrolyte 13 from a liquid injection hole. The battery case 11 is made of a metal such as an aluminum alloy, and forms an electrolytic cell sealed by a lid. The lithium ion secondary battery 1 also includes a positive electrode external terminal 14 and a negative electrode external terminal 15 used for charging and discharging electric power. The positive electrode external terminal 14 is electrically connected to a positive electrode current collector terminal 16 inside the battery case 11 through the lid. Further, the negative electrode external terminal 15 is electrically connected to a negative electrode current collector terminal 17 inside the battery case 11 through the lid. The positive electrode current collector terminal 16 is electrically connected to the positive electrode current collecting portion 33 (see FIG. 9) of the electrode body 12. Also, the negative electrode current collector terminal 17 is electrically connected to the negative electrode current collecting portion 23 (see FIG. 9) of the electrode body 12.

[0054] <Electrode body 12> FIG. 9 is a schematic diagram showing the configuration of the wound electrode body 12. The electrode body 12 is formed by laminating a large number of negative electrode plates 2, positive electrode plates 3, and separators 4 disposed therebetween. The laminated negative electrode plates 2, positive electrode plates 3, and separators 4 are wound to form a flat shape. The negative electrode plate 2 has a negative electrode composite material layer 22 formed on a negative electrode current collector 21 made of a copper foil serving as a base material. A negative electrode current collecting portion 23 is provided on one end side in the width direction W (winding axis direction) orthogonal to the winding direction L. The negative electrode current collecting portion 23 has a configuration in which the negative electrode composite material layer 22 is not formed and the negative electrode current collector 21 is exposed.

[0055] The positive electrode plate 3 has a positive electrode mixture layer 32 formed on a positive electrode current collector 31 made of an aluminum foil serving as a base material. As shown in FIG. 9, a positive electrode current collector portion 33 is provided on the other end side (the side opposite to the negative electrode current collector portion 23) in the width direction W (the winding axis direction) orthogonal to the direction (winding direction L) in which the positive electrode current collector 31 is wound. In the positive electrode current collector portion 33, the positive electrode mixture layer 32 is not formed and the metal of the positive electrode current collector 31 is exposed.

[0056] <Laminated structure of the electrode body 12> As shown in FIG. 9, the basic configuration of the electrode body 12 of the lithium-ion secondary battery 1 includes a negative electrode plate 2, a positive electrode plate 3, and a separator 4.

[0057] The negative electrode plate 2 includes negative electrode mixture layers 22 on both surfaces of a negative electrode current collector 21 serving as a negative electrode base material. One end portion of the negative electrode current collector 21 is a negative electrode current collector portion 23 where the metal is exposed. The positive electrode plate 3 includes positive electrode mixture layers 32 on both surfaces of a positive electrode current collector 31 serving as a positive electrode base material. The other end portion of the positive electrode current collector 31 is a positive electrode current collector portion 33 where the metal is exposed.

[0058] The negative electrode plate 2 and the positive electrode plate 3 are stacked via a separator 4 to form a laminate. As shown in FIG. 9, this laminate is wound in the longitudinal direction around a winding axis to form a wound-type electrode body 12 that is flattened as shown in FIG. 6.

[0059] <Non-aqueous electrolyte 13> The non-aqueous electrolyte 13 of the lithium-ion secondary battery 1 according to the present embodiment shown in FIG. 8 is a composition in which a lithium salt is dissolved in an organic solvent. As the lithium salt, LiClO4, LiPF6, LiAsF6, LiBF4, LiSO3CF3, etc. can be used. As the organic solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, sulfur compounds such as ethyl methyl sulfone, butane sultone, or phosphorus compounds such as triethyl phosphate, trioctyl phosphate, etc. can be mentioned. As the non-aqueous electrolyte 13, these can be used by mixing one or more types thereof. Note that the composition of the non-aqueous electrolyte 13 is not limited to this.

[0060] In the present embodiment, EC (ethylene carbonate) is used as the organic solvent. Also, in the present embodiment, as described above, a compound containing a lithium salt is added as an additive as the film-forming material. For example, lithium bisoxalate borate (LiBOB, LiB(C2O4)2, hereinafter referred to as "LiBOB") is added.

[0061] <Constituent elements of the electrode body 12> Next, the negative electrode plate 2, the positive electrode plate 3, and the separator 4, which are the constituent elements constituting the electrode body 12, will be described.

[0062] <Negative electrode plate 2> As shown in FIG. 2, a negative electrode mixture layer 22 is formed on both surfaces of a negative electrode current collector 21, which is a negative electrode base material, to form a negative electrode plate 2. In the source process (FIG. 5: S2), a negative electrode mixture paste is applied to the negative electrode current collector 21 for the negative electrode mixture layer 22. Then, through a drying process, a pressing process, and a cutting process, the negative electrode plate 2 is completed.

[0063] In this embodiment, the negative electrode current collector 21 is made of a Cu foil. The negative electrode current collector 21 serves as a base as an aggregate of the negative electrode composite layer 22 and has a function of a current collecting member that collects electricity from the negative electrode composite layer 22. One end portion of the negative electrode current collector 21 is a negative electrode current collecting portion 23 where the metal surface is exposed without the formation of the negative electrode composite layer 22. That is, the negative electrode active material particles are electrically connected to the negative electrode external terminal 15 via the negative electrode current collector 21, the negative electrode current collecting portion 23, and the negative electrode current collecting terminal 17.

[0064] The negative electrode composite layer 22 is composed of a negative electrode active material as a raw material, a binder (binding material) as a sub-material here, an additive, and the like. The raw material and the sub-material are mixed with an organic solvent or the like and kneaded to produce a negative electrode composite paste. This negative electrode composite paste is applied to the negative electrode current collector 21. The applied negative electrode composite paste is dried and shaped by pressing to complete the negative electrode plate 2.

[0065] In this embodiment, the negative electrode active material is powdery graphite particles GP made of graphite (graphite) having a layered structure, and is a material capable of occluding and releasing lithium ions Li + ions. <Positive electrode plate 3> As shown in FIG. 6, the positive electrode plate 3 is composed of a positive electrode current collector 31 which is a positive electrode base material, and a positive electrode composite layer 32 applied thereto. In the source process (FIG. 5: S1), a positive electrode composite paste is applied to the positive electrode current collector 31 for the positive electrode composite layer 32. Thereafter, the positive electrode plate 3 is completed through a drying process, a pressing process, and a cutting process. The manufacturing method of the positive electrode plate 3 of this embodiment is performed in the process of manufacturing this positive electrode plate 3, which will be described in detail later.

[0066] The positive electrode composite layer 32 is formed on both sides of the positive electrode current collector 31 which is a positive electrode base material to constitute the positive electrode plate 3. The positive electrode current collector 31 is made of an Al foil in the embodiment. The positive electrode current collector 31 serves as a base as an aggregate of the positive electrode composite layer 32 and has a function of a current collecting member that collects electricity from the positive electrode composite layer 32.

[0067] First, although the positive electrode substrate constituting the positive electrode current collector 31 was exemplified as an Al foil, for example, it may be composed of a conductive material made of a metal having good conductivity. As a material having good conductivity, for example, in addition to the Al foil, a material containing an Al alloy can be used. The configuration of the positive electrode current collector 31 is not limited to this.

[0068] The positive electrode composite layer 32 is formed by coating and drying a positive electrode composite paste on the positive electrode current collector 31. The positive electrode composite layer 32 contains, in addition to positive electrode active material particles, additives such as a conductive auxiliary material, a binder, and a dispersant.

[0069] The positive electrode active material particles contain a lithium transition metal oxide having a layered crystal structure. The lithium transition metal oxide contains one or more predetermined transition metal elements in addition to Li. The transition metal element contained in the lithium transition metal oxide is preferably at least one of Ni, Co, and Mn. The positive electrode active material of the present embodiment exemplifies a ternary system so-called NCM having a lithium transition metal oxide containing all of Ni, Co, and Mn.

[0070] Note that the positive electrode active material of the present embodiment is not limited to those having a lithium transition metal oxide containing all of Ni, Co, and Mn. Further, in addition to these, a composition containing, for example, Al may be used.

[0071] <Separator 4> The separator 4 is a highly insulating non-woven fabric made of polypropylene or the like, which is a porous resin for holding the non-aqueous electrolyte 13 between the negative electrode plate 2 and the positive electrode plate 3. Further, as the separator 4, a porous polymer film such as a porous polyethylene film, a porous polyolefin film, and a porous polyvinyl chloride film, or a lithium ion or ion conductive polymer electrolyte film can be used alone or in combination.

[0072] <Manufacturing method of the lithium ion secondary battery 1 of the present embodiment> FIG. 10 is a flowchart showing the manufacturing process of the lithium-ion secondary battery 1 of the present embodiment. Next, an example of the manufacturing method of the lithium-ion secondary battery 1 of the present embodiment will be described with reference to the flowchart of FIG. 10.

[0073] <Source process (S1)> In the manufacturing process of the lithium-ion secondary battery 1, first, the source process (S1) is performed. In the source process (S1), raw materials are received, and components such as the negative electrode plate 2, the positive electrode plate 3, and the separator 4 are manufactured. In the present embodiment, the negative electrode plate 2 is manufactured by coating the negative electrode current collector 21 with the negative electrode composite layer 22. Also, the positive electrode plate 3 is manufactured by coating the positive electrode current collector 31 with the positive electrode composite layer 32. Then, the negative electrode plate 2 and the positive electrode plate 3 are laminated via the separator 4. This laminate is wound to form the electrode body 12.

[0074] In the electrode body 12 configured in this way, the negative electrode composite layer 22 and the positive electrode composite layer 32 are opposed to each other. Here, in the present embodiment, the ratio of the capacity of the negative electrode composite layer 22 to the positive electrode composite layer 32 that are opposed to each other is defined as the opposed capacity ratio R C . This opposed capacity ratio R C is calculated from the basis weight [g / m 2 of the negative electrode active material and the positive electrode active material to be coated, the opposed electrode length, and the coating width, respectively. The opposed capacity ratios R C of the examples of the present embodiment are 1.48, 1.65, and 1.82. Note that this process is the opposed capacity ratio calculation process of the present invention.

[0075] <Assembly process (S2)> After the source process, when the components of the lithium-ion secondary battery 1 are manufactured, these components are assembled in the assembly process (S2).

[0076] As shown in FIG. 9, the positive electrode current collecting terminal 16 and the negative electrode current collecting terminal 17 are welded to the wound electrode body 12, and the positive electrode external terminal 14 and the negative electrode external terminal 15 are attached via the lid of the battery case 11. The lid configured in this way is attached so as to cover the opening of the main body of the battery case 11 and is welded and sealed.

[0077] <Liquid injection process (S3)> When the assembly process (S2) is completed, the liquid injection port 18 is open. Here, the lithium-ion secondary battery 1 is heated to volatilize the internal moisture. After the interior is dried, the non-aqueous electrolyte 13 is injected.

[0078] Here, the non-aqueous electrolyte 13 to be injected will be described. Prior to the liquid injection process (S3), the addition amount of the additive composed of LiBOB to be added to the non-aqueous electrolyte 13 is calculated. <Additive addition amount calculation process> Here, let the addition amount of the additive to the non-aqueous electrolyte 13 be A A [wt%]. In this example, the addition amount A A [wt%] is set to 0.3 [wt%] and 0.5 [wt%]. For each of these addition amounts A A [wt%], the initial resistance R I [mΩ] of the cell battery at the initial stage of use is measured. Similarly, the end resistance R E [mΩ] at the planned end of use is obtained in advance. In this example, "end of use" refers to the time when the capacity retention rate of the cell battery reaches 78 [%]. Next, the initial resistance R I [mΩ] and the end resistance R E [mΩ] such that the addition amount A A of the additive is obtained, and the relational expression F is derived according to the opposed capacity ratio R C . This process corresponds to the additive addition amount calculation relational expression derivation process of the present invention.

[0079] Also, from the relational expression F derived in the additive addition amount calculation relational expression derivation process, based on the opposed capacity ratio R C calculated in the opposed capacity ratio calculation process, the addition amount A I [mΩ] of the additive such that the initial resistance R E [mΩ] and the end resistance R A [mΩ] are equal is calculated. This process corresponds to the additive addition amount calculation process of the present invention.

[0080] <Derivation of relational expression F> FIG. 11 is a flowchart showing the process of deriving the relational expression F. Here, the process of deriving the relational expression F will be described.

[0081] <Sample preparation> First, samples for each counter capacitance ratio R C and LiBOB addition amount A A [wt%] are prepared (S31).

[0082] FIG. 12 is a table showing the counter capacitance ratio R C and LiBOB addition amount A A [wt%] of the samples of this example. The counter capacitance ratio R C is such that at level A, the counter capacitance ratio R C = 1.82, at level B, the counter capacitance ratio R C = 1.65, and at level C, the counter capacitance ratio R C = 1.48. Also, in levels A to C, in the non-aqueous electrolyte 13, LiBOB addition amounts A A = 0.3 [wt%] and LiBOB addition amounts A A = 0.5 [wt%] are added respectively.

[0083] <A storage degradation test is performed to measure the initial resistance RI and the final resistance RE (S32)> Under the conditions of the counter capacitance ratio R C shown in FIG. 12, samples of levels A, B, and C are prepared, and for LiBOB addition amounts A A = 0.3 [wt%] and LiBOB addition amounts A A = 0.5 [wt%], the initial resistance R I [mΩ] and the final resistance R E [mΩ] are measured.

[0084] The initial resistance RI [mΩ] is the cell resistance R S [mΩ] measured when the conditioning process is completed. The measurement is to apply a constant current [A] and calculate the cell resistance R S [mΩ] from the cell voltage [V] at that time, and set it as the initial resistance R I [mΩ].[[]END]

[0085] Also, in this example, charge and discharge are repeated, and when the battery capacity [Ah] reaches 78[%] of the initial capacity, it is defined as the end of use, and the cell resistance RS be the end resistance R E [mΩ]. And the end resistance R E [mΩ] - initial resistance R I [mΩ] = resistance difference ΔR [mΩ].

[0086] <Initial resistance R I = end resistance R E The LiBOB addition amount A A is calculated (S33)> Next, the LiBOB addition amount A I = end resistance R E The LiBOB addition amount A A is calculated (S33). Figure 13 shows the LiBOB addition amount A A [wt%] and the relationship between the resistance difference ΔR [mΩ] for each of the samples at levels A, B, and C shown in Figure 12.

[0087] The horizontal axis represents the LiBOB addition amount A A [wt%] for the non-aqueous electrolyte 13, and the vertical axis represents the initial resistance R I [mΩ] and the difference between the end resistance R E [mΩ], which is the resistance difference ΔR [mΩ]. Graph G A represents the measurement results at level A, G B represents the measurement results at level B, G C represents the measurement results at level C.

[0088] At level A, as shown by the plotted point P A in graph G A / 0.3 when the LiBOB addition amount A A = 0.3 [wt%], the resistance difference ΔR [mΩ] is approximately 0.028 [mΩ]. Also, as shown by the plotted point P A / 0.5 when the LiBOB addition amount A A = 0.5 [wt%], the resistance difference ΔR [mΩ] is approximately 0.020 [mΩ]. Connect these plotted points with a straight line, and the intersection point X A which is the intersection with the vertical axis where the resistance difference ΔR = 0, is approximately A the LiBOB addition amount A AIf it is set to 1.00 [wt%], the resistance difference ΔR [mΩ] becomes approximately zero.

[0089] At level B, in graph G B the plotted point P B / 0.3 as shown, when the amount A of LiBOB added A = 0.3 [wt%], the resistance difference ΔR [mΩ] shows approximately 0.025 [mΩ]. Also, as shown at plotted point P B / 0.5 when the amount A of LiBOB added A = 0.5 [wt%], the resistance difference ΔR [mΩ] shows approximately 0.015 [mΩ]. Connecting these plotted points with a straight line, the intersection point X B which is the intersection with the resistance difference ΔR = 0 on the vertical axis A is approximately the amount A of LiBOB added A = 0.83 [wt%]. In other words, if the amount A of LiBOB added

[0090] At level C, in graph G C the plotted point P C / 0.3 as shown, when the amount A of LiBOB added A = 0.3 [wt%], the resistance difference ΔR [mΩ] shows approximately 0.002 [mΩ]. Also, as shown at plotted point P C / 0.5 when the amount A of LiBOB added A = 0.5 [wt%], the resistance difference ΔR [mΩ] shows approximately -0.007 [mΩ]. Connecting these plotted points with a straight line, the intersection point X C which is the intersection with the resistance difference ΔR = 0 on the vertical axis A is approximately the amount A of LiBOB added A = 0.35 [wt%]. In other words, if the amount A of LiBOB added

[0091] <Opposite capacitance ratio R C and the amount A of LiBOB added A and observe the correlation with the optimal amount (S34) Next, the opposite capacitance ratio R C and the amount A of LiBOB added AObserve the correlation with the optimal amount (S34). FIG. 14 shows the counter capacity ratio R C and the optimal amount A of LiBOB added A is a graph showing the relationship. The horizontal axis represents the counter capacity ratio RC, and the vertical axis represents the amount A of LiBOB added A [wt%]. As shown in FIG. 13, for the sample at level A with a counter capacity ratio RC = 1.82, the optimal amount A of LiBOB added A [wt%] was 0.31 [wt%]. Also, for the sample at level B with a counter capacity ratio RC = 1.65, the optimal amount A of LiBOB added A [wt%] was 0.81 [wt%]. For the sample at level C with a counter capacity ratio RC = 1.48, the optimal amount A of LiBOB added A [wt%] was 0.97 [wt%].

[0092] <Approximate the observation results by a linear function and calculate the relational expression F (S35)> When these data are plotted on FIG. 14, level A becomes plot point P1, level B becomes plot point P2, and level C becomes plot point P3. The relationship between the counter capacity ratio RC and the amount A of LiBOB added A [wt%] is A A [wt%]=a×R C +b in the form of a linear function. And in this embodiment, based on these three points, by regression analysis, A A [wt%]=a×R C +b to obtain a straight line in the form of a linear function, a = -1.93 and b = 3.89. In this embodiment, the relational expression F is obtained as A A [wt%]=-1.93×R C +3.89. The relational expression F is derived through the above procedure.

[0093] Then, based on the amount A of LiBOB added A [wt%] for which the relational expression F was derived, LiBOB is added to the non-aqueous electrolyte 13, the battery cell is filled with the liquid, and sealed. In this process, the lithium ion secondary battery 1 is completed.

[0094] <Conditioning process (S4)> The completed lithium-ion secondary battery 1 is subjected to a conditioning process (S4). The conditioning process (S4) is mainly aimed at activating the battery by the first charge and forming a SEI film in parallel therewith.

[0095] The specific content of the conditioning process is as described in the explanation of the formation of the film derived from LiBOB. By this predetermined conditioning process, a film derived from LiBOB is appropriately formed.

[0096] Also, in the conditioning process, an aging process is also performed. In the aging process, it is left standing at a predetermined temperature for a long time to eliminate the stabilization of the SEI film, micro short circuits due to the mixing of fine metal powder in the cell battery, and chemical micro short circuits derived from the non-aqueous electrolyte 13.

[0097] <Inspection process (S5)> After the conditioning process (S4) is completed, inspection before shipment is performed. The inspections include, for example, OCV (open circuit voltage), DC-IR (internal resistance), self-discharge, battery capacity [Wh], etc. If these inspections are passed, it will be shipped.

[0098] (Operation of this embodiment) The manufacturing method of the lithium-ion secondary battery 1 of this embodiment is to experimentally obtain the relationship between the counter capacity ratio R C of the lithium-ion secondary battery 1 to be manufactured in advance, the LiBOB addition amount A A and the cell resistance R S . Then, the initial resistance R A which is the internal resistance at the initial stage of use with respect to the LiBOB addition amount A I [mΩ] and the end resistance R E [mΩ] which is the internal resistance at the end of use are calculated. Then, the LiBOB addition amount A I for which the initial resistance R E [mΩ] and the end resistance R A [mΩ] are equal is added to the non-aqueous electrolyte 13. And a film derived from LiBOB is formed by performing the first charge under predetermined conditions.

[0099] In order to suppress the precipitation of Li metal, an upper limit of the charge and discharge rate is provided, but the initial resistance R I [mΩ] and the final resistance R E [mΩ] can be set to be equal in the case of the lithium ion secondary battery 1 configured in this way, which can have the highest upper limit. According to the manufacturing method of the lithium ion secondary battery 1 of the present embodiment, the cell resistance can be appropriately estimated and the upper limit value of charge and discharge can be appropriately set in carrying out cell control. Therefore, the performance of the lithium ion secondary battery 1 can be fully exerted.

[0100] (Effect of this embodiment) (1) According to the manufacturing method of the lithium ion secondary battery 1 of the present embodiment, there is an effect that the cell resistance can be appropriately estimated and the upper limit value of charge and discharge can be appropriately set in carrying out cell control.

[0101] (2) In this embodiment, there is a counter capacity ratio calculation step of calculating the counter capacity ratio R which is the capacity ratio of the negative electrode plate 2 to the positive electrode plate 3 on the surface where the positive electrode composite material layer 32 of the positive electrode plate 3 and the negative electrode composite material layer 22 of the negative electrode plate 2 face each other. For this reason, there is an effect that the counter capacity ratio R which affects the cell resistance can be accurately calculated. C C

[0102] (3) The initial resistance R A [mΩ] at the initial stage of use of the lithium ion secondary battery 1 according to the LiBOB addition amount A I [wt%] and the final resistance R E [mΩ] at the planned final stage of use are obtained in advance. The LiBOB addition amount A I such that the initial resistance R E [mΩ] and the final resistance R A [mΩ] are equal is obtained. In this case, the additive addition amount calculation relational expression derivation step of deriving the relational expression F according to the counter capacity ratio R C is provided. Based on the counter capacity ratio R C calculated in the counter capacity ratio calculation step from the relational expression F derived in the additive addition amount calculation relational expression derivation step, the initial resistance R I [mΩ] and the final resistance R​​E The addition amount A of LiBOB at which [mΩ] becomes equal A It includes an additive addition amount calculation step of calculating [wt%]. Therefore, according to the relational expression F, the addition amount A of LiBOB can be easily A There is an effect that an appropriate amount of [wt%] can be obtained.

[0103] (4) The addition amount A of LiBOB calculated in the additive addition amount calculation step A It includes an additive addition step of adding an oxalate borate-based additive of [wt%] to the non-aqueous electrolyte 13. Further, it includes a liquid injection step of injecting and sealing the non-aqueous electrolyte 13 to which the additive has been added in the additive addition step into the battery cell. Further, after the liquid injection step, it includes a conditioning step including a first charge performed under preset conditions. Therefore, in performing cell control, the cell resistance R S [mΩ] can be appropriately estimated, and the lithium-ion secondary battery 1 capable of appropriately setting the upper limit values of charge and discharge can be manufactured.

[0104] (5) The relational expression F derived in the additive addition amount calculation relational expression derivation step is obtained by the following procedure. For each opposing capacity ratio R C , the initial resistance R of the lithium-ion secondary battery 1 corresponding to the addition amount A of LiBOB A [wt%], and the planned final resistance R I [mΩ], a cell resistance measurement step of measuring is performed. For each opposing capacity ratio R E , the initial resistance R obtained in the cell resistance measurement step C [mΩ], the final resistance R I [mΩ], and the resistance difference ΔR [mΩ] between them and the addition amount A of LiBOB E [wt%], a step of deriving the relationship between the additive addition amount and the resistance difference is performed. Then, based on the relationship derived in the step of deriving the relationship between the additive addition amount and the resistance difference, the addition amount A of LiBOB at which the resistance difference ΔR [mΩ] corresponding to the opposing capacity ratio R A becomes zero is calculated, and the relational expression F is derived. With the relational expression F derived in this way, there is an effect that an appropriate amount of the addition amount A of LiBOB C [wt%] can be easily obtained. A [wt%] can be easily obtained. A There is an effect that an appropriate amount of [wt%] can be obtained.

[0105] (6) When the relational expression F has the optimal LiBOB addition amount as A A [wt%], the counter capacity ratio as R C , and when the slope is a and the intercept is b, A A [wt%]=a×R C +b…(Equation 1). Therefore, there is an effect that the appropriate amount of the LiBOB addition amount A A [wt%] of the additive can be easily obtained.

[0106] (7) In (Equation 1), if 1.0≦a≦2.5 and 3.0≦b≦5.0, there is an effect that the appropriate amount of the LiBOB addition amount A A [wt%] suitable for the lithium ion secondary battery 1 can be obtained.

[0107] (8) The first charge in the conditioning process is carried out at the first negative electrode potential V1 [V vs. Li / Li + at which the oxalate borate-based additive is reductively decomposed for a set time, and includes a first hold process in which the first negative electrode potential V1 [V vs. Li / Li + is maintained. Also, at the second negative electrode potential V2 [V vs. Li / Li + at which the oxalate borate-based additive forms a film on the negative electrode active material for a set time, and includes a second hold process in which the second negative electrode potential V2 [V vs. Li / Li + is maintained. Therefore, a film derived from the oxalate borate-based additive can be surely and stably formed.

[0108] (9) The negative electrode potential V1 [V vs. Li / Li + of the first hold process can be set to 0.1≦V1≦1.5. The first hold process continues for 1 hour or more. The negative electrode potential V2 [V vs. Li / Li + of the second hold process can be set to 0.5≦V2≦2.0. The second hold process continues for 1 hour or more. In the first charge, the starting charge rate R ON [C] is set to 4≦R ON ≦8.5, and the ending charge rate ROFF [C] was set such that 0.01 ≤ R OFF ≤ 0.1. Therefore, a film derived from an oxalate borate-based additive can be easily and surely formed stably.

[0109] (10) Opposing capacitance ratio R C was set such that 1.48 ≤ R C ≤ 1.82. Therefore, there is an effect that the initial resistance R I [mΩ] and the final resistance R E [mΩ] can be made equal. (11) The oxalate borate-based additive is lithium bisoxalate borate. Therefore, the invention of the present embodiment can be preferably implemented.

[0110] (Alternative example) 〇Although the lithium ion secondary battery 1 of the present embodiment exemplifies a battery cell that constitutes a battery pack for driving a hybrid vehicle, the lithium ion secondary battery 1 may be one used as a single cell. Further, its application may be for stationary use or for use as a power source for a portable device.

[0111] 〇Although the lithium ion secondary battery 1 of the present embodiment exemplifies one provided with a flat thin plate-shaped rectangular parallelepiped battery case 11, its shape is not limited, such as a cylindrical shape. ○The numerical values and numerical ranges of the present embodiment are optimized for the lithium ion secondary battery 1 in the present embodiment, and can be appropriately optimized by those skilled in the art according to the characteristics of the target battery.

[0112] ○The flowcharts shown in FIGS. 10 and 11 are an example of a manufacturing method of the lithium ion secondary battery 1 of the present embodiment, and those skilled in the art can add, delete, change the order, or change the procedure.

[0113] ○In addition, the configuration can be added, deleted, or changed by those skilled in the art without departing from the scope of the claims.

Explanation of reference signs

[0114] R C …Opposite capacity ratio A A [wt%]…Addition amount of LiBOB (with respect to non-aqueous electrolyte 13) R S [mΩ]…Cell resistance R I [mΩ]…Cell resistance at the initial stage of use R E [mΩ]…Cell resistance at the end stage of use ΔR [mΩ]…Resistance difference F…Relational expression a…Slope b…Intercept V1 [V vs. Li / Li + …First negative electrode potential V2 [V vs. Li / Li + …Second negative electrode potential R ON [C]…Initial charging rate R OFF [C]…Final charging rate V S [V]…Cell voltage V P [V vs. Li / Li + …Positive electrode potential V N [V vs. Li / Li + …Negative electrode potential 1…Lithium-ion secondary battery (cell battery) 11…Battery case 12…Electrode body 13…Non-aqueous electrolyte 14…Positive electrode external terminal 15…Negative electrode external terminal 16…Positive electrode current collector terminal 17…Negative electrode current collector terminal 18…Liquid injection port 2…Negative electrode plate 21…Negative electrode current collector 22…Negative electrode composite layer 23…Negative electrode current collecting part 3…Positive electrode plate 31…Positive electrode current collector 32…Positive electrode composite layer 33…Positive electrode current collecting part 4...Separator

Claims

1. A method for manufacturing a lithium-ion secondary battery, comprising a positive electrode plate, a negative electrode plate, and an electrode body in which these are laminated via a separator in a battery cell, and adding an oxalate borate-based additive to a non-aqueous electrolyte, The facing capacitance ratio R, which is the capacitance ratio of the negative electrode plate to the positive electrode plate on the surface where the positive electrode composite material layer of the positive electrode plate and the negative electrode composite material layer of the negative electrode plate face each other Ｃ A facing capacitance ratio calculation step for calculating The addition amount A of the additive Ａ The initial resistance R at the initial stage of use of the lithium-ion secondary battery corresponding to [wt%], Ｉ [mΩ], and the end resistance R at the planned end of use Ｅ [mΩ] are obtained in advance, and the initial resistance R Ｉ [mΩ] and the end resistance R Ｅ [mΩ] such that the addition amount A of the additive becomes equal, Ａ [wt%] is obtained, and the relational expression F is the opposing capacitance ratio R Ｃ According to the above, a step of deriving an additive addition amount calculation relational expression for derivation, From the relational expression F derived in the step of deriving the relational expression for the additive addition amount, based on the facing capacitance ratio R calculated in the step of calculating the facing capacitance ratio Ｃ calculate the addition amount A Ｉ [mΩ] of the initial resistance R and the final resistance R Ｅ [mΩ] of the additive such that they are equal, which is an additive addition amount calculation step for calculating the addition amount A Ａ [wt%]; characterized by comprising the above.

2. The addition amount A calculated in the additive addition amount calculation step Ａ An additive addition step of adding the oxalate borate-based additive in [wt%] to the non-aqueous electrolyte A liquid injection step of injecting and sealing the non-aqueous electrolyte to which the additive has been added in the additive addition step into the battery cell, and a conditioning step including a first charge performed under preset conditions after the liquid injection step The method for manufacturing a lithium-ion secondary battery according to claim 1, characterized by comprising the above.

3. The relational expression F derived in the relational expression derivation step for calculating the additive addition amount is The facing capacitance ratio R Ｃ For each, the addition amount A Ａ Of the additive [wt%], the initial resistance R Ｉ Of the lithium ion secondary battery [mΩ], and the planned final resistance R Ｅ A cell resistance measurement step of measuring [mΩ], and The above-mentioned opposing capacitance ratio R Ｃ Each time, the initial resistance R Ｉ [mΩ] obtained in the cell resistance measurement step and the final resistance R Ｅ [mΩ], the resistance difference ΔR [mΩ] therebetween, and the addition amount A Ａ [wt%] to obtain the relationship between the addition amount of the additive and the resistance difference, and a step of deriving the relationship between the addition amount of the additive and the resistance difference The capacitance ratio R according to the relationship derived by the step of deriving the relationship between the additive addition amount and the resistance difference, and the additive addition amount A [wt%] at which the resistance difference ΔR [mΩ] becomes zero are calculated. A step of deriving a capacitance ratio - additive addition amount relational expression for deriving the relational expression; Ｃ The capacitance ratio R according to the relationship derived by the step of deriving the relationship between the additive addition amount and the resistance difference, and the additive addition amount A [wt%] at which the resistance difference ΔR [mΩ] becomes zero are calculated. A step of deriving a capacitance ratio - additive addition amount relational expression for deriving the relational expression; Ａ A step of deriving a capacitance ratio - additive addition amount relational expression for deriving the relational expression; The method for manufacturing a lithium-ion secondary battery according to claim 1, characterized by being derived by

4. The relational expression F has an optimal addition amount of A Ａ [wt%], an opposing capacitance ratio of R Ｃ , when the slope is a and the intercept is b A Ａ [wt%] = a × R Ｃ + b…(Equation 1) The method for manufacturing a lithium-ion secondary battery according to claim 3, characterized by being represented by

5. In the above (Formula 1), 1.0 ≤ a ≤ 2.5 and 3.0 ≤ b ≤ 5.

0. The method for manufacturing a lithium-ion secondary battery according to claim 4, characterized by this.

6. The first charge in the conditioning step is The first negative electrode potential V at which the oxalate borate-based additive is reductively decomposed １ [V vs. Li / Li + , for a set time, the first hold step of maintaining the first negative electrode potential [V vs. Li / Li + , and the second negative electrode potential V at which the oxalate borate-based additive forms a film on the negative electrode active material ２ [V vs. Li / Li + , for a set time, the second hold step of maintaining the second negative electrode potential [V vs. Li / Li + , the method for manufacturing a lithium ion secondary battery according to claim 2, characterized by including these steps.

7. The negative electrode potential V of the first holding step １ [V vs. Li / Li + satisfies 0.1 ≤ V １ ≤ 1.5, and the method for manufacturing a lithium ion secondary battery according to claim 6 is characterized by this.

8. The first hold step of the lithium-ion secondary battery manufacturing method according to claim 7, characterized by continuing for 1 hour or more.

9. The negative electrode potential V of the second holding step ２ [V vs. Li / Li + satisfies 0.5 ≤ V ２ ≤ 2.0, and the method for manufacturing a lithium ion secondary battery according to claim 6 is characterized by this.

10. The second hold step of the lithium-ion secondary battery manufacturing method according to claim 9, characterized by continuing for 1 hour or more.

11. In the initial charging, the starting charging rate R ＯＮ [C] is set such that 4 ≤ R ＯＮ ≤ 8.5, and the ending charging rate R ＯＦＦ [C] is set such that 0.01 ≤ R ＯＦＦ ≤ 0.

1. The method for manufacturing a lithium ion secondary battery according to claim 6, characterized in that the above is set.

12. The facing capacitance ratio R Ｃ satisfies 1.48 ≤ R Ｃ ≤ 1.82, and the method for manufacturing a lithium ion secondary battery according to claim 1 is characterized by this.

13. The method for manufacturing a lithium-ion secondary battery according to any one of claims 1 to 12, characterized in that the oxalate borate-based additive is lithium bisoxalate borate.

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