JP2017152243A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery superior in battery characteristics, which enables the effective conduction of a pre-doping process without reducing the mechanical strength of an electrode.SOLUTION: A lithium ion secondary battery comprises at least, one or more positive electrodes 1, and one or more negative electrodes 3. The positive electrode 1 has a plate-like positive electrode current collector 11, and a positive electrode active material layer 12 provided on each or one of faces of the positive electrode current collector. The negative electrode 3 has a plate-like negative electrode current collector 31, and a negative electrode active material layer 32 provided on each or one of faces of the negative electrode current collector. The positive electrode current collector 11 and the negative electrode current collector 31 are each composed of a porous plate having through-holes 11a, 31a. The positive electrode current collector 11 and the negative electrode current collector 31 are arranged so that when the rate of a total area of the through-holes 11a, 31a to a one-side total area of each electrode current collector in plan view is defined as an open porosity K(K1, K2), the open porosity K1 of the positive electrode current collector 11 is lower than the open porosity K2 of the negative electrode current collector 31.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lithium ion secondary battery.

  Generally, a lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte. As the positive electrode and the negative electrode, electrodes each having an electrode active material layer are used. This electrode active material layer is usually formed by applying a composition containing an electrode active material, a conductive additive and a binder to a current collector. In the lithium ion secondary battery, the electrode active material is an important factor related to the battery capacity, and as the negative electrode active material, for example, graphite (graphite), silicon, silicon oxide or the like is used.

  The negative electrode active material has a function of occluding or releasing lithium ions during charge / discharge, but lithium ions react irreversibly with the negative electrode active material during initial charging, resulting in a decrease in battery capacity (discharge capacity). There is a problem of end. In order to avoid such a decrease and realize high capacity, conventionally, a treatment (pre-doping treatment) of previously doping lithium ions into the negative electrode active material layer constituting the negative electrode has been performed before the initial charge. If the irreversible reaction as described above is caused in advance by performing the pre-doping treatment, the generation of the irreversible reaction and by-products can be suppressed during the subsequent initial charging.

  In addition, in a lithium ion secondary battery in which the negative electrode active material layer is subjected to the above pre-doping treatment, in order to increase the diffusion efficiency of lithium ions during the pre-doping treatment, conventionally, a positive electrode current collector and a negative electrode current collector that constitute the positive electrode and the negative electrode A punching metal or the like in which a plurality of through holes are formed is used for both bodies (see, for example, Patent Document 1). By using a punching metal for each current collector as in the battery described in Patent Document 1, lithium diffuses and moves in the battery through a plurality of through holes, so that the pre-doping treatment can be performed effectively.

JP 2009-188141 A

  However, when a plurality of through-holes are formed in the current collector, the mechanical strength, particularly the tensile strength, of the current collector is reduced. For example, when each electrode expands or contracts due to charge / discharge In addition, there is a problem that any of the electrodes is physically damaged to deteriorate the battery characteristics. Such physical damage of the electrode was particularly remarkable on the positive electrode side using a punching metal made of aluminum foil as each current collector.

  The present invention has been made in view of the above problems, and can provide a lithium ion secondary battery that can be effectively pre-doped without lowering the mechanical strength of the electrode and has excellent battery characteristics. Objective.

  The inventors of the present invention have made extensive studies in order to realize a lithium ion secondary battery capable of performing an effective pre-doping process without reducing the mechanical strength of the electrode. As a result, it is possible to increase the electrode strength while maintaining the diffusion effect of lithium ions by the pre-doping process by optimizing the relationship between the opening ratios of the through holes formed in each current collector. The headline and the present invention were completed.

  That is, the invention described in claim 1 includes at least one or more positive electrodes and one or more negative electrodes, and the positive electrode is a plate-shaped positive electrode current collector and a positive electrode provided on both surfaces or one surface thereof. An active material layer, and the negative electrode includes a plate-shaped negative electrode current collector and a negative electrode active material layer provided on both sides or one side of the negative electrode current collector, and the positive electrode current collector and the negative electrode current collector The body comprises a perforated plate having a plurality of through holes, and each of the positive electrode current collector and the negative electrode current collector has a total area in plan view of the plurality of through holes with respect to the entire area of one side. It is a lithium ion secondary battery in which the opening ratio of the positive electrode current collector is lower than the opening ratio of the negative electrode current collector when the ratio is the respective open area ratio.

  According to the present invention, the mechanical strength and elongation of the positive electrode current collector are reduced by lowering the open hole ratio of the through hole in the positive electrode current collector than the open hole ratio of the through hole in the negative electrode current collector. Both can be improved. At this time, it is preferable that the maximum tensile strength of the positive electrode is larger than the maximum stress due to expansion of the negative electrode, and the elongation of the positive electrode is larger than the maximum elongation of the negative electrode. This suppresses physical damage to the positive electrode including the positive electrode current collector having a low strength when each electrode expands and contracts with charge and discharge, thereby reducing the battery characteristics. Can be prevented. In addition, since the positive electrode current collector and the negative electrode current collector are provided with a plurality of through holes with an optimized open area ratio, lithium ions can be effectively diffused into the negative electrode active material layer by pre-doping treatment. And a sufficient discharge capacity can be secured. Therefore, it is possible to realize a lithium ion secondary battery that is excellent in battery characteristics because the discharge capacity is suppressed from being reduced when the battery is repeatedly used for charging and discharging.

  A second aspect of the present invention is the lithium ion secondary battery according to the first aspect, wherein an opening ratio of the plurality of through holes in the negative electrode current collector is more than 15% and 50% or less, and the positive electrode collector The opening ratio of the plurality of through holes in the electric body is more than 0% and 30% or less.

  According to the present invention, the mechanical strength of each electrode is ensured by optimizing both the aperture ratio of the plurality of through holes in the negative electrode current collector and the aperture ratio of the plurality of through holes in the positive electrode current collector. It is possible to carry out an effective pre-doping process while further ensuring the elongation and further improving the elongation rate. Therefore, when the charging / discharging is used repeatedly as described above, the reduction of the discharge capacity is suppressed, and the effect of improving the battery characteristics is remarkably obtained.

  The invention of claim 3 comprises one or more positive electrodes and one or more negative electrodes, wherein the positive electrode comprises a plate-shaped positive electrode current collector and a positive electrode active material layer provided on both sides or one side thereof. The negative electrode has a plate-like negative electrode current collector and a negative electrode active material layer provided on both sides or one side thereof, and the positive electrode current collector has no through hole. The negative electrode current collector is a lithium ion secondary battery comprising a perforated plate having a plurality of through holes.

  According to the present invention, since the positive electrode current collector is composed of a non-perforated plate and the negative electrode current collector is composed of a perforated plate having a plurality of through holes, as described above, the through holes of the negative electrode current collector are opened. As in the case where the opening ratio of the through holes in the positive electrode current collector is lower than the porosity, the mechanical strength of the positive electrode current collector, in particular, the tensile strength can be ensured and the elongation rate can be improved. Thereby, the mechanical strength and elongation rate of the positive electrode in which the positive electrode current collector is used are improved. Therefore, in the same manner as described above, it is possible to suppress physical damage of the positive electrode including the positive current collector having a low strength, and to prevent deterioration of battery characteristics, particularly during charging and discharging. On the other hand, since the negative electrode current collector is provided with a plurality of through holes, lithium ions can be effectively diffused into the negative electrode active material layer by the pre-doping treatment, and a sufficient discharge capacity can be ensured. Therefore, it is possible to realize a lithium ion secondary battery that is excellent in battery characteristics because the discharge capacity is suppressed from being reduced when the battery is repeatedly used for charging and discharging.

  Invention of Claim 4 is a lithium ion secondary battery of Claim 3, Comprising: The said negative electrode collector is a ratio of the total area which planarly viewed the said several through-hole with respect to the whole area of one side. The open area ratio is more than 15% and not more than 50%.

  According to the present invention, the positive electrode current collector is made a non-porous plate, and the aperture ratio of the plurality of through holes in the negative electrode current collector is optimized to ensure the mechanical strength of each electrode. Further, it is possible to perform an effective pre-doping process while further improving the elongation rate. Therefore, similarly to the above, when the charge and discharge are repeatedly used, the discharge capacity is prevented from decreasing, and the effect of improving the battery characteristics is remarkably obtained.

  The invention of claim 5 is the lithium ion secondary battery according to any one of claims 1 to 4, wherein the negative electrode active material layer is pre-doped with lithium before initial charging. It is characterized by.

  According to the present invention, first of all, since the configuration adopts a positive electrode current collector and a negative electrode current collector that are optimized for the presence or absence of a plurality of through holes and an open area ratio, lithium of the lithium ion secondary battery before the initial charge can be obtained. By pre-doping, lithium ions can be effectively diffused. Therefore, a sufficient discharge capacity can be secured and a lithium ion secondary battery excellent in battery characteristics can be realized.

According to the lithium ion secondary battery of the present invention, the following effects can be obtained by the above-described solving means.
That is, according to the present invention, the mechanical strength of the positive electrode current collector is obtained by adopting a configuration in which the open area ratio of the through holes in the positive electrode current collector is lower than the open area ratio of the through holes in the negative electrode current collector. In particular, since the tensile strength can be secured and the elongation rate can be increased, the mechanical strength and the elongation rate of the positive electrode using the positive electrode current collector are also improved. Thereby, when expansion and contraction occur in each electrode with charge / discharge, it is possible to suppress physical damage of the positive electrode including the positive electrode current collector having a particularly low strength, and to prevent deterioration of battery characteristics. . In addition, the positive electrode current collector and the negative electrode current collector are provided with a plurality of through holes with an optimized opening ratio, so that lithium ions can be effectively diffused into the negative electrode active material layer by pre-doping treatment. And a sufficient discharge capacity can be secured.
Therefore, it is possible to realize a lithium ion secondary battery that is excellent in battery characteristics because the discharge capacity is suppressed from being reduced when the battery is repeatedly used for charging and discharging.

It is sectional drawing which illustrates typically an example of the lithium ion secondary battery which concerns on this invention. FIG. 2 is a cross-sectional view schematically illustrating an example of a lithium ion secondary battery according to the present invention, and is an enlarged view of a main part of FIG. 1. It is sectional drawing which illustrates typically the other example of the lithium ion secondary battery which concerns on this invention, and is a figure which expands and shows the principal part of FIG.

  Hereinafter, the configuration of an embodiment of a lithium ion secondary battery according to the present invention will be described in detail with reference to FIGS. 1 to 3 as appropriate. Note that the drawings used in the following description may show the characteristic parts in an enlarged manner for the sake of convenience in order to make the characteristics easy to understand. There is. In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.

[Lithium ion secondary battery]
FIG. 1 is a cross-sectional view showing a stacked lithium ion secondary battery 10 according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of the lithium ion secondary battery 10 shown in FIG. It is sectional drawing shown.

  As shown in FIG. 1, the lithium ion secondary battery 10 of this embodiment includes a plurality of positive electrodes 1, separators 2 that form an electrolyte layer, and negative electrodes 3. The illustrated lithium ion secondary battery 10 includes an electrode laminate 9 having a plurality of electrode units in which a negative electrode 3 having a rectangular shape in plan view, a separator 2 and a positive electrode 1 are sequentially laminated. The illustrated electrode laminate 9 includes four electrode units in which the negative electrode 3 / the separator 2 / the positive electrode 1 are sequentially laminated, that is, the first electrode unit U1 to the fourth electrode unit U4. A separator 2 is disposed between the electrode units stacked in the electrode stack 9. Furthermore, on the outer side of the first electrode unit U1, a negative electrode 3 in which a lithium metal foil 4 is arranged on one side is laminated via a separator 2 so that the negative electrode 3 is the outermost layer.

  Furthermore, as shown in FIG. 2, in the lithium ion secondary battery 10 of the present embodiment, the positive electrode 1 includes a plate-like positive electrode current collector 11 and a positive electrode active material layer 12 provided on both sides or one side thereof. The negative electrode 3 includes a plate-shaped negative electrode current collector 31 and a negative electrode active material layer 32 provided on both sides or one side thereof. In the illustrated example, the positive electrode current collector 11 and the negative electrode current collector 31 are formed of a perforated plate having a plurality of through holes 11a and 31a.

  Each positive electrode 1 provided in the lithium ion secondary battery 10 of the present embodiment includes a positive electrode current collector 11 formed of a perforated plate in which a plurality of through holes are formed (punched). Positive electrode active material layers 12 and 12 made of a positive electrode material are formed on both surfaces of the body. The thickness of the positive electrode active material layers 12, 12 is preferably 5 μm to 80 μm, for example.

  As the positive electrode current collector 11 used for each positive electrode 1, for example, an aluminum foil is used. In the example shown in FIG. 2, a plurality of such aluminum foils are penetrated from one surface to the opposite surface. The through-hole 11a is formed.

  Each separator 2 forms an electrolyte layer in which a porous resin sheet is impregnated with an electrolyte solution containing lithium ions. The thickness of the separator 2 is preferably 5 μm to 30 μm, for example.

  Each negative electrode 3 has a negative electrode current collector made of a copper foil having a plurality of through-holes, and a negative electrode active material made of a negative electrode material containing a silicon compound such as silicon oxide on both surfaces of the negative electrode current collector. Material layers 32 are formed. The thickness of the negative electrode active material layers 32, 32 is preferably, for example, 5 μm to 50 μm.

  As the negative electrode current collector 31 used for each negative electrode 3, for example, a copper foil is used, and a plurality of through holes 31a are formed in the copper foil so as to penetrate from one surface to the opposite surface. Being done.

Moreover, the lithium metal foil 4 is provided in the electrode laminated body 9 of the lithium ion secondary battery 10 so that it may contact the single side | surface side of each negative electrode 3, respectively. These lithium metal foils 4 serve as a lithium ion supply source in the pre-doping process. As for the thickness of each lithium metal foil 4, 10 micrometers-500 micrometers are preferable, for example.
In the present embodiment, the lithium metal foil 4 is provided adjacent to all the negative electrodes 3, but the lithium metal foil 4 is not an essential configuration, and may be provided adjacent to or in the vicinity of any negative electrode 3. it can.

  As shown in FIG. 2, the metal plate (metal foil) constituting the positive electrode current collector 11 and the negative electrode current collector 31 is provided with a large number of through holes 11 a and 31 a. In the present embodiment, the through holes 11 a and 31 a are provided in the current collectors of the positive electrode 1 and the negative electrode 3, so that lithium ions can easily pass between the electrodes in a state where the positive electrode 1 and the negative electrode 3 are stacked. To diffuse and move. Thus, the pre-doping treatment of lithium is performed uniformly on each electrode, the charge transfer resistance during battery use is reduced, and the battery capacity retention rate is improved.

The aperture ratio (K1) of the positive electrode current collector 11 refers to the ratio of the total area in plan view of the plurality of through holes 11a to the total area on one side. Similarly, the aperture ratio (K2) of the negative electrode current collector 31 refers to the ratio of the total area in plan view of the plurality of through holes 31a to the total area on one side. In the present embodiment, the aperture ratio K1 of the positive electrode current collector 31 is lower than the aperture ratio K2 of the negative electrode current collector 31 (K2> K1).
In FIG. 2, in order to make the through holes 11a easily visible, each through hole 11a is drawn large for convenience, and K2> K1 is not drawn accurately.

  As in the above-described configuration, first, the opening ratio K1 of the through-hole 11a in the positive electrode current collector 11 is made lower than the opening ratio K2 of the through-hole 31a in the negative electrode current collector 31. It is possible to ensure the mechanical strength, in particular, the tensile strength, of the positive electrode current collector 11 which is made of the above soft metal material and has a lower strength than the negative electrode current collector 31. Further, the elongation rate can be improved. Thereby, the mechanical strength and elongation rate of the positive electrode 1 in which the positive electrode current collector 11 is used are improved, and when the respective electrodes expand and contract with charge / discharge, the positive electrode 1 including the positive electrode current collector 11 Since physical damage can be suppressed, battery characteristics can be prevented from deteriorating. In addition, since the positive electrode current collector 11 and the negative electrode current collector 31 are provided with a plurality of through holes 11a and 31a with the optimized open area ratios K1 and K2, the negative electrode active is performed by pre-doping treatment during battery manufacture. Lithium ions can be effectively diffused into the material layer 32, and a sufficient discharge capacity can be secured. Therefore, when the charge / discharge is used repeatedly, the discharge capacity is suppressed from decreasing, and the lithium ion secondary battery 10 having a high capacity expression rate and excellent charge / discharge characteristics and excellent battery characteristics can be realized.

In the lithium ion secondary battery 10 of the present embodiment, the aperture ratio K2 of the plurality of through holes 31a in the negative electrode current collector 31 is more than 15% and 50% or less, and the plurality of through holes in the positive electrode current collector 11 is used. It is preferable that the opening ratio K1 of the holes 11a is more than 0% and not more than 30%.
In the lithium ion secondary battery 10, first, when the open area ratio K <b> 2 of the plurality of through holes 31 a in the negative electrode current collector 31 is in the above range, the lithium pre-doping treatment can be more effectively performed. On the other hand, when the aperture ratio K1 of the plurality of through holes 11a in the positive electrode current collector 11 is in the above range, the mechanical strength of the positive electrode current collector 11 can be ensured more reliably. Further, the elongation rate can be improved. That is, by optimizing the aperture ratios K1 and K2 of the through holes 11a and 31a in each current collector, there is no physical damage of the electrodes, and the discharge capacity is reduced when charging and discharging are repeatedly used. Therefore, the battery characteristics of the lithium ion secondary battery 10 are remarkably improved.

  When lithium doping treatment or initial charging is performed in the presence of an electrolyte solution containing a lithium ion fluoride salt, lithium fluoride is formed on the surface of the negative electrode active material layer constituting the negative electrode active material layer containing a silicon compound. A SEI (Solid Electrolyte Interface) containing (LiF) is formed. In general, this SEI prevents the entry of solvent molecules solvated with lithium ions into the negative electrode when charging and discharging are repeated during use, and suppresses damage of the negative electrode structure, thereby preventing secondary recharge of lithium ions. This is considered to contribute to the improvement of the cycle characteristics of the battery.

In the example shown in FIG. 1, each positive electrode 1 has a lead wire, and each lead wire is connected and bundled to form a lead tab 1z.
Each negative electrode 3 has a lead wire, and each lead wire is connected and bundled to form a lead tab 3z.
The electrode laminate 9 is housed in an exterior body made of aluminum laminate (not shown) together with the electrolytic solution. The lead tab 1z and the lead tab 3z are extended to the outside of the exterior body, and the exterior body is sealed so that the electrolyte solution inside does not leak.

  The electrode laminate 9 of the lithium ion secondary battery 10 illustrated in FIG. 1 includes five negative electrodes 3. Further, as shown in the enlarged view of the main part of FIG. 2, each of the negative electrodes 3 is provided with a lithium metal foil 4 at a position in contact with one side opposite to the separator 2 or at a distance close to each other. Has been.

  In the example shown in FIG. 1, the electrode laminate 9 of the lithium ion secondary battery 10 includes five negative electrodes 3, but the number of stacked negative electrodes 3 is not particularly limited, and for example, 1 to 20 negative electrodes 3 may be laminated. In the illustrated example, the outermost layer at both ends of the electrode laminate 9 of the lithium ion secondary battery 10 is such that one outermost layer is the negative electrode 3 and the other outermost layer is a lithium metal foil provided on one side of the negative electrode 3. Although it is set to 4, it is not limited to this, The positive electrode 1 may be sufficient.

  In addition, the lithium metal foil 4 provided in contact with one side of each negative electrode 3 shown in FIG. 1 is obtained by, for example, lithium pre-doping treatment at the time of battery manufacture (before initial charging). A part or all of the above may be dissolved.

  In addition, in the lithium ion secondary battery 10 of the example shown in FIG. 1, although the structure which provided the lithium metal foil 4 in the single side | surface side of each negative electrode 3 is shown, it is not limited to this. As in the example shown in FIGS. 1 and 2, if both the positive electrode current collector 11 and the negative electrode current collector 31 are provided with through holes 11 a and 31 a, for example, By providing the lithium metal foil 4 on only one side of the negative electrode 3 in the vicinity of the outer layer, all the negative electrode active material layers 32 provided in each negative electrode 3 can be pre-doped.

In FIG. 2, the lithium ion secondary battery 10 having a configuration in which both of the positive electrode current collector 11 of the positive electrode 1 and the negative electrode current collector 31 of the negative electrode 3 are provided with a plurality of through holes 11 a and 31 a will be described. However, the present invention is not limited to such a configuration.
For example, in the lithium ion secondary battery having an electrode laminate including a plurality of positive electrodes 1, separators 2, and negative electrodes 3 shown in FIG. 1, the configuration shown in the enlarged cross-sectional view of the main part in FIG. It is also possible to constitute a lithium ion secondary battery 10A having an electrode laminate 9A provided with (positive electrode current collector 11A) and negative electrode 3 (negative electrode current collector 31). In the example of the electrode laminate 9A shown in FIG. 3, the positive electrode current collector 11A of the positive electrode 1A is made of a non-perforated plate having no through holes, while the negative electrode current collector 31 of the negative electrode 3 is composed of a plurality of It is the structure which consists of a perforated board which has the through-hole 31a.

  As shown in FIG. 3, the negative electrode current collector 11A is made of a non-porous plate, and the negative electrode current collector 31 is made of a perforated plate having a plurality of through holes 31a. Similarly to the case where the opening ratio of the through hole in the positive electrode current collector is lower than the opening ratio of the through hole in the electric current collector, the mechanical strength of the positive electrode current collector 11A, particularly the securing of the tensile strength and the elongation rate Can be improved. This improves the mechanical strength and elongation of the positive electrode 1A in which the positive electrode current collector 11A is used, so that when each electrode expands and contracts due to charge / discharge, the positive electrode 1A including the positive electrode current collector 11A The occurrence of physical damage can be suppressed, and the battery characteristics can be prevented from deteriorating. On the other hand, since the negative electrode current collector 31 is provided with a plurality of through holes 31a, lithium ions can be effectively diffused into the negative electrode active material layer 32 by the pre-doping process, and a sufficient discharge capacity can be secured. Therefore, when the charge / discharge is used repeatedly, the discharge capacity is prevented from decreasing, and the lithium ion secondary battery 10A having excellent battery characteristics can be obtained.

  In the configuration illustrated in FIG. 3, the open area ratio K2 of the plurality of through holes 31a in the negative electrode current collector 31 obtained in the same manner as described above is preferably in the range of more than 15% and 50% or less, and 30% More preferably, it is 50% or less. Thus, by optimizing the aperture ratio K2 of the plurality of through holes 31a in the negative electrode current collector 31 within the above range, it is possible to effectively perform the lithium pre-doping treatment. Therefore, as described above, the electrode is not physically damaged, and the discharge capacity is suppressed from being lowered when repeated charging and discharging are used. Therefore, the battery characteristics of the lithium ion secondary battery 10A are remarkable. To improve.

  In addition, when the electrode laminate 9A including the positive electrode 1A using the positive electrode current collector 11A made of a non-porous plate as illustrated in FIG. 3 is employed, when the lithium pre-doping treatment is performed, the lithium ion Is difficult to pass through the positive electrode current collector 11A, it is preferable to provide a lithium metal foil 4 on each of the negative electrodes 3 as shown in FIGS.

  The lithium ion secondary battery according to the present invention has both the positive electrode provided with the positive electrode current collector composed of the perforated plate and the positive electrode equipped with the positive electrode current collector composed of the non-porous plate as described above. It may be.

<Method for producing lithium ion secondary battery>
Hereinafter, an example of the manufacturing method of the lithium ion secondary battery 10 will be described.
As a manufacturing method of the lithium ion secondary battery 10, for example, the negative electrode 3, the separator 2, and the positive electrode 1 are sequentially laminated by a known method, and the lithium metal foil 4 is further provided on one side of the negative electrode 3 opposite to the separator 2 side. Are in contact or in proximity to each other to form an electrode unit. Then, a plurality of these electrode units, in the example shown in FIG. 1, four electrode units are laminated by a known method to form an electrode laminate 9.
Next, lithium is pre-doped on the negative electrode active material layer 32 constituting the negative electrode 3 in a state where the entire electrode laminate 9 is impregnated with the electrolytic solution.

Although it does not specifically limit as a preparation method of the negative electrode 3, For example, the following methods are mentioned.
First, as described above, a plate-shaped negative electrode current collector 31 punched by appropriately setting the opening ratio K2 of the through hole 31a is prepared. Then, a negative electrode material containing a silicon compound is applied to one surface of the negative electrode current collector 31 to provide a negative electrode active material layer 32, and a negative electrode active material layer 32 is also provided to the other surface as necessary. .

Similarly, the manufacturing method of the positive electrode 1 is not particularly limited, and for example, a manufacturing method similar to that of the negative electrode 3 can be used.
That is, first, as described above, the plate-like positive electrode current collector 11 punched by setting the aperture ratio K1 of the through hole 11a appropriately is prepared. Then, a positive electrode material is applied to one surface and / or the other surface of the positive electrode current collector 11 to provide the positive electrode active material layer 12.

  The electrode laminate 9 shown in FIG. 1 is produced by laminating a separator 2 between a positive electrode 1 and a negative electrode 3 to produce an electrode unit as shown in FIG. 2, and further laminating a plurality of this electrode unit. Obtained by. At this time, if the negative electrode active material layer 32 is provided on the surface facing the outside of the negative electrode current collector 31 constituting the negative electrode 3 disposed in the outermost layer of the electrode laminate 9, the electrode is difficult to bend, An effect is obtained in which peeling of the active material layer hardly occurs. In addition, as described above, in the example illustrated in FIGS. 1 and 2, the lithium metal foil 4 that is a lithium supply body is in contact with or separated from one surface on the opposite side of the separator 2 in each negative electrode 3. Is provided.

  In the lithium pre-doping treatment, the entire electrode laminate 9 is preferably immersed in the electrolytic solution. Lithium ions eluted from each lithium metal foil 4 diffuse and move to each negative electrode 3, and are doped into the negative electrode active material layer 32. The type of the electrolytic solution may be any as long as it contains a solvent capable of eluting lithium ions. For example, an electrolytic solution containing a known electrolyte such as a lithium salt is preferable.

  The lithium pre-doping treatment is completed when the lithium ions eluted from the lithium metal foil 4 fill the irreversible capacity of the negative electrode active material. The standard of completion of such lithium pre-doping treatment is set empirically. That is, by appropriately changing the time and temperature of the dope treatment and measuring the capacity retention rate of the experimentally manufactured battery, conditions for obtaining the best capacity retention rate are set. Usually, at the completion of the lithium pre-doping treatment, a part or all of each lithium metal foil 4 is dissolved and disappears.

  The temperature of the pre-doping treatment of lithium, that is, the temperature of the electrolytic solution in which the electrode laminate 9 is immersed is preferably 20 ° C. or less, more preferably 15 ° C. or less, and further preferably 10 ° C. or less. Moreover, the lower limit of the pre-doping temperature of lithium is a temperature at which the electrolytic solution does not freeze, and is usually preferably 0 ° C. or higher. By performing the pre-doping treatment of lithium in the above temperature range, the doping rate can be moderated, so that the negative electrode active material layer 32 provided in each negative electrode 3 provided in the electrode laminate 9 is uniformly doped with lithium. Is done. Thus, lithium is uniformly doped with respect to the negative electrode active material 32, whereby the lithium ion secondary battery 10 having an excellent capacity retention rate when the battery is used is obtained.

  As a lithium ion secondary battery that can be manufactured by the manufacturing method described above, for example, it has a negative electrode active material layer formed using a negative electrode material in which silicon oxide, a conductive additive, and a binder are blended, In addition, a battery including a negative electrode pre-doped with lithium can be given.

In the lithium ion secondary battery 10 obtained by the above manufacturing method, the relationship between the aperture ratio K2 of the through hole 31a in the negative electrode current collector 31 and the aperture ratio K1 of the through hole 11a in the positive electrode current collector 11 is optimal. It becomes a thing.
As a result, the mechanical strength of the positive electrode current collector 11 can be ensured and the elongation rate can be improved, and the mechanical strength and the elongation rate of the positive electrode 1 can also be improved. In this case, it is possible to prevent physical damage of the positive electrode 1 from occurring, and thus it is possible to prevent deterioration of battery characteristics. In addition, since the positive electrode current collector 11 and the negative electrode current collector 31 are provided with a plurality of through holes 11a and 31a with optimized aperture ratios K1 and K2, the negative electrode active material is obtained by pre-doping at the time of battery manufacture. Lithium ions can be effectively diffused into the layer 32, and a sufficient discharge capacity can be secured.
Therefore, when the charge / discharge is repeatedly used, the discharge capacity is prevented from decreasing, and the lithium ion secondary battery 10 having a high capacity expression rate and excellent charge / discharge characteristics and excellent battery characteristics is obtained.
Furthermore, since the lithium ion secondary battery 10 manufactured by the above method is provided with a plurality of through holes 11a and 31a in the positive electrode current collector 11 and the negative electrode current collector 31, not only at the time of manufacturing the battery, Even when the battery is used, the electrolyte (electrolytic solution) diffuses efficiently. Thereby, it becomes possible to further improve the battery characteristics of the lithium ion secondary battery 10.

  In the manufacturing method described in the present embodiment, for example, even when a lithium ion secondary battery 10A as shown in FIG. 3 is manufactured, a non-porous plate is used for the positive electrode current collector 11A included in the positive electrode 1A. Except for this point, it can be produced by the same method as described above.

  Although the material which can be used in the lithium ion secondary battery which concerns on this invention is illustrated below, this invention is not limited to these.

[Negative electrode material]
Examples of the negative electrode material used for each negative electrode 3 include a material in which a silicon compound as a negative electrode active material, a particulate conductive auxiliary, a fibrous conductive auxiliary, and a binder are blended.
The silicon compound as the negative electrode active material is preferably silicon oxide.

(Silicon oxide)
_{Examples of the} silicon oxide include those represented by the general formula “SiO _z (wherein z is any number from 0.5 to 1.5)”. Here, when the silicon oxide is viewed in “SiO” units, this SiO is amorphous SiO, or around the Si of the nanocluster so that the molar ratio of Si: SiO ₂ is about 1: 1. This is a composite of Si and SiO _{2 in} which SiO ₂ exists. SiO ₂ is presumed to have a buffering action against the expansion and contraction of Si during charging and discharging.

  The shape of the silicon oxide is not particularly limited, and for example, silicon oxide such as powder or particles can be used.

  In the negative electrode material, the ratio of the amount of silicon oxide to the total amount of silicon oxide, particulate conductive auxiliary, fibrous conductive auxiliary and binder can be, for example, 40 to 85% by mass. By the proportion of the silicon oxide blending amount being not less than the lower limit of the above range, the discharge capacity of the lithium ion secondary battery is further improved, and the proportion of the silicon oxide blending amount is not more than the upper limit of the above range. Thus, stable maintenance of the negative electrode structure is facilitated.

(Particulate conductive aid)
The particulate conductive aid is in the form of particles functioning as a conductive aid, and preferred examples include carbon black such as acetylene black and ketjen black; graphite (graphite); fullerene and the like.
A particulate conductive support agent may be used individually by 1 type, and may use 2 or more types together.

  In the negative electrode material, the ratio of the amount of the particulate conductive additive to the total amount of silicon oxide, the particulate conductive additive, the fibrous conductive additive and the binder can be, for example, 3 to 30% by mass. . When the proportion of the particulate conductive additive is equal to or more than the lower limit of the above range, the effect of using the particulate conductive assistant is more significantly obtained, and the proportion of the particulate conductive assistant is blended. Is less than or equal to the upper limit of the above range, the effect of the combined use with the fibrous conductive additive can be more remarkably obtained.

(Fibrous conductive aid)
The fibrous conductive auxiliary agent is a fibrous one that functions as a conductive auxiliary agent, and preferable examples include carbon nanotubes and carbon nanohorns.

In the negative electrode active material layer, which will be described later, the fibrous conductive auxiliary agent preferably contributes to structural stabilization of the negative electrode active material layer by forming a network structure throughout the negative electrode active material layer, and in the negative electrode active material layer. It is presumed that a conductive network is formed on the surface to contribute to improvement of conductivity.
A fibrous conductive support agent may be used individually by 1 type, and may use 2 or more types together.

  In the negative electrode material, the ratio of the amount of the fibrous conductive additive to the total amount of silicon oxide, particulate conductive additive, fibrous conductive assistant and binder can be, for example, 1 to 25% by mass. . The effect of using the fibrous conductive additive is more prominent because the proportion of the fibrous conductive additive is equal to or more than the lower limit of the above range, and the proportion of the fibrous conductive assistant is blended. Is less than or equal to the upper limit of the above range, the effect of improving the conductivity by the combined use with the particulate conductive additive can be obtained more remarkably.

  In the negative electrode material, the mass ratio (blending mass ratio) of the blending amount of “particulate conduction aid: fibrous conduction aid” can be, for example, 90:10 to 30:70. When the blending mass ratio of the particulate conductive additive and the fibrous conductive additive is in such a range, the effect of improving the conductivity by the combined use of the particulate conductive additive and the fibrous conductive additive can be obtained more remarkably. .

(binder)
The binder contained in the negative electrode material may be a known one, and preferable ones are polyacrylic acid (PAA), lithium polyacrylate (PAALi), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-propylene hexafluoride. Copolymer (PVDF-HFP), styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene glycol (PEG), carboxymethylcellulose (CMC), polyacrylonitrile (PAN), polyimide (PI) ) Etc. can be illustrated.
A binder may be used individually by 1 type, may use 2 or more types together, and when using 2 or more types together, the combination and ratio may be suitably selected according to the objective.

  In the negative electrode material, the ratio of the blending amount of the binder to the total blending amount of silicon oxide, particulate conductive additive, fibrous conductive additive, and binder can be, for example, 3 to 30% by mass. The negative electrode structure is more stably maintained when the proportion of the binder is equal to or higher than the lower limit of the above range, and the discharge capacity is more when the proportion of the binder is equal to or lower than the upper limit of the above range. improves.

(Other ingredients)
The negative electrode material may further contain other components not corresponding to these, in addition to silicon oxide, particulate conductive auxiliary, fibrous conductive auxiliary and binder.
The other components can be arbitrarily selected according to the purpose, and as a preferable one, a solvent for dissolving or dispersing the above-described compounding components (silicon oxide, particulate conductive assistant, fibrous conductive assistant, binder) Can be illustrated.
Thus, it is preferable that the negative electrode material further blended with a solvent is a liquid composition having fluidity at the time of use.

A solvent can be arbitrarily selected according to the kind of compounding component, and water and an organic solvent can be illustrated as a preferable thing.
Preferred organic solvents include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; linear or cyclic amides such as N-methylpyrrolidone (NMP) and N, N-dimethylformamide (DMF); acetone and the like Can be exemplified.
A solvent may be used individually by 1 type, may use 2 or more types together, and when using 2 or more types together, the combination and ratio may be suitably selected according to the objective.

  The amount of the solvent in the negative electrode material is not particularly limited, and may be adjusted as appropriate according to the purpose. For example, when a negative electrode material that is a liquid composition containing a solvent is applied and dried to form a negative electrode active material layer, the solvent composition is adjusted so that the liquid composition has a viscosity suitable for coating. What is necessary is just to adjust a compounding quantity. Specifically, in the negative electrode material, the blending of the solvent so that the ratio of the total amount of the blending components other than the solvent to the total amount of the blending components is preferably 5 to 60% by mass, more preferably 10 to 35% by mass. Adjust the amount.

  When a component other than the solvent (other solid component) is blended as the other component, the proportion of the blended amount of the other solid component with respect to the total amount of the blended component other than the solvent in the negative electrode material is 10 mass. % Or less, and more preferably 5% by mass or less.

  A negative electrode material can be manufactured by mix | blending a silicon oxide, a particulate-form conductive support agent, a fibrous conductive support agent, a binder, and another component as needed.

Examples of the material of the negative electrode current collector on which the negative electrode active material layer is formed include copper (Cu), titanium (Ti), nickel (Ni), and stainless steel.
The negative electrode current collector is preferably in the form of a sheet (plate), and the thickness is preferably 5 μm to 20 μm.

  The diameter (hole diameter) of the plurality of through holes in the negative electrode current collector is, for example, preferably 0.01 mm to 5 mm, more preferably 0.1 mm to 1 mm, and still more preferably 0.2 mm to 0.5 mm. When it is at least the lower limit of the above range, an electrolyte such as lithium ion can easily pass through the current collector, and when it is at most the upper limit of the above range, the negative electrode active material layer can be sufficiently retained. . The size of the plurality of through holes may be the same or different. The plurality of through holes are preferably distributed evenly throughout the current collector.

[Positive electrode material]
Examples of the positive electrode material include a positive electrode material in which a positive electrode active material, a binder, a solvent, and a conductive auxiliary agent are blended as necessary.

As the positive electrode active material, a lithium metal acid compound represented by the general formula “LiM _x O _y (wherein M is a metal; x and y are composition ratios of metal M and oxygen O)” Can be illustrated.
Examples of such a metal acid lithium compound include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and the like, and olivine iron phosphate having a similar composition. Lithium (LiFePO ₄ ) can also be used.
In the above general formula, M may be a plurality of metal acid lithium compounds. As such a metal acid lithium compound, the general formula “LiM ¹ _p M ² _q M ³ _r O _y (formula Where M ¹ , M ² and M ³ are different types of metals; p, q, r and y are the composition ratios of the metals M ¹ , M ² and M ³ and oxygen O). What is represented can be exemplified. Here, p + q + r = x. Examples of such a metal acid lithium compound include LiNi _0.33 Mn _0.33 Co _0.33 O ₂ .
A positive electrode active material may be used individually by 1 type, and may use 2 or more types together.

Examples of the conductive aid in the positive electrode material include graphite (graphite); carbon black such as ketjen black and acetylene black; carbon nanotube; carbon nanohorn; graphene; fullerene.
The conductive auxiliary in a positive electrode may be used individually by 1 type, and may use 2 or more types together.

The binder, the solvent and the current collector in the positive electrode material may all be the same as the binder, the solvent and the current collector in the negative electrode.
Examples of the material of the positive electrode current collector on which the positive electrode active material layer is formed include aluminum (Al), titanium (Ti), nickel (Ni), and stainless steel.
The positive electrode current collector is preferably in the form of a sheet (plate), and the thickness is preferably 2 μm to 50 μm, and more preferably 5 μm to 20 μm. While the thinner is advantageous for reducing the weight and thickness of the battery, if it is too thin, the tensile strength is inferior, and the positive electrode active material layer is easily damaged due to expansion / contraction due to charge / discharge. Within the preferred range, the balance between the weight reduction and thickness reduction of the battery and the strength retention and elongation rate of the current collector are good.

  For example, the diameter (hole diameter) of the plurality of through holes in the positive electrode current collector is preferably 0.01 mm to 5 mm, more preferably 0.1 mm to 1 mm, and still more preferably 0.2 mm to 0.5 mm. When it is at least the lower limit of the above range, an electrolyte such as lithium ion can easily pass through the current collector, and when it is below the upper limit of the above range, the positive electrode active material layer can be sufficiently retained and It can prevent that the tensile strength of an electric body falls extremely. The size of the plurality of through holes may be the same or different. The plurality of through holes are preferably distributed evenly throughout the current collector.

  The ratio of the amount of each of the positive electrode active material, the binder, the solvent, and the conductive additive to the total amount of the blending components in the positive electrode material is the ratio of the negative electrode active material, the binder, the solvent, and the total amount of the blending components in the negative electrode material. The ratio can be the same as the ratio of the respective amounts of the conductive assistant.

[Electrolyte]
As the electrolytic solution, those used in known lithium ion secondary batteries can be applied. For example, lithium hexafluorophosphate (LiPF ₆ ), lithium boron tetrafluoride (LiBF ₄ ), lithium bisfluorosulfonyl Examples include those prepared by dissolving a known lithium salt such as imide (LiFSI), bis (trifluoromethanesulfonyl) imide lithium (LiN (SO ₂ CF ₃ ) ₂ , LiTFSI) in an organic solvent.
The electrolyte in the electrolytic solution may be used alone or in combination of two or more.

Examples of the organic solvent in the electrolytic solution include carbonate compounds such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and vinylene carbonate; lactone compounds such as γ-butyrolactone; methyl formate, methyl acetate And carboxylic acid ester compounds such as methyl propionate; ether compounds such as tetrahydrofuran and dimethoxyethane; nitrile compounds such as acetonitrile; and sulfone compounds such as sulfolane.
An organic solvent may be used individually by 1 type, and may use 2 or more types together.
The lithium concentration in the electrolytic solution may be the same as that of a known lithium ion secondary battery.
In the electrolytic solution, an optional component used for the electrolytic solution of a known lithium ion secondary battery may be blended within a range not impairing the effects of the present invention.

[Separator]
Examples of the material of the separator 2 include a porous resin film, a nonwoven fabric, and glass fiber.
Further, as the separator 2, a porous insulating layer formed on the surface of the positive electrode active material layer or the surface of the negative electrode active material layer, which can insulate the positive electrode 1 and the negative electrode 3 and can hold and permeate the electrolytic solution is also applicable. It is. The porous insulating layer is formed by, for example, a known method in which a composition containing insulating inorganic particles and a binder resin is applied to the surface of the negative electrode 3 or the positive electrode 1 and dried. The thickness of the porous insulating layer is preferably about 0.5 μm to 50 μm, for example.

<Effect>
According to the lithium ion secondary battery 10 according to the present invention, as described above, the opening ratio K1 of the through hole 11a in the positive electrode current collector 11 is higher than the opening ratio K2 of the through hole 31a in the negative electrode current collector 31. Since the mechanical strength of the positive electrode current collector 11, in particular, the tensile strength can be ensured and the elongation rate can be improved, the mechanical strength and elongation of the positive electrode 1 in which the positive electrode current collector 11 is used. The rate is also improved. Thereby, when expansion and contraction occurs in each electrode with charge / discharge, the physical damage of the positive electrode 1 including the positive electrode current collector 11 having particularly low strength is suppressed, and the battery characteristics are reduced. Can be prevented. In addition, since the positive electrode current collector 11 and the negative electrode current collector 31 are provided with a plurality of through holes 11a and 31a with optimized aperture ratios K1 and K2, the negative electrode active material layer 32 is subjected to pre-doping treatment. Lithium ions can be effectively diffused and a sufficient discharge capacity can be secured. Therefore, when the charge and discharge are repeatedly used, the discharge capacity is prevented from being reduced, and the lithium ion secondary battery 10 having excellent battery characteristics can be realized.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

<Example 1>
[Production of negative electrode]
Silicon monoxide (SiO, average particle size 1.0 μm, 69 parts by mass), SBR (3 parts by mass), and polyacrylic acid (12 parts by mass) were placed in a reagent bottle, and distilled water was added to adjust the concentration. Then, it mixed for 2 minutes at 2000 rpm using the self-revolving mixer. Subsequently, acetylene black (10 mass parts) was added to this mixture, and it mixed for 2 minutes at 2000 rpm using the self-revolving mixer. Then, this mixture was subjected to a dispersion treatment with an ultrasonic homogenizer for 10 minutes, and then this dispersion was again mixed at 2000 rpm for 2 minutes using a self-revolving mixer to obtain a slurry of a negative electrode material.

[Preparation of cathode material]
Lithium cobaltate (LiCo ₂ O) (93 parts by mass), polyvinylidene fluoride (PVDF) (4 parts by mass), and carbon black (3 parts by mass) as a conductive additive are mixed to prepare a positive electrode mixture. This was dispersed in N-methylpyrrolidone (NMP) to obtain a positive electrode material slurry.

[Production of negative electrode]
First, as the negative electrode current collector 31, a punched copper foil having a plurality of through holes 31a (vertical × horizontal = 40 mm × 55 mm, thickness 10 μm, hole diameter 0.35 mm, aperture ratio 30%, Fukuda metal foil powder Industrial Co., Ltd.) was prepared.
And after apply | coating said negative electrode material with the coating thickness of 30 micrometers on both surfaces of the negative electrode collector 31 and making it dry, the negative electrode active material layer 32 of the substantially the same area as the negative electrode collector 31 is obtained. The formed negative electrode 3 was obtained.

[Production of positive electrode]
First, as the positive electrode current collector 11, a punched aluminum foil having a plurality of through holes 11a (vertical × horizontal = 40 mm × 55 mm, thickness 15 μm, hole diameter 0.35 mm, open area ratio 15%, Fukuda metal foil powder Industrial Co., Ltd.) was prepared.
Then, the positive electrode material is applied to the both sides of the positive electrode current collector 11 with a coating thickness of 42.5 μm, dried, and then pressed to form a positive electrode active material layer having substantially the same area as the positive electrode current collector 11. The positive electrode 1 in which 12 was formed was obtained.

[Preparation of electrolyte]
To a mixed solvent of EC and PC (EC: PC = 30: 70 (volume ratio)), add a lithium oxalate-boron trifluoride complex to a concentration of 1.0 mol / kg, and mix at 23 ° C. Thus, an electrolytic solution was obtained.

[Production of electrode laminate]
The electrode laminate 9 shown in FIGS. 1 and 2 was manufactured by the following method.
First, a separator 2 (manufactured by Sekisui Chemical Co., Ltd.) having a thickness of 25 μm and a surface area of 42 cm × 57 cm is disposed between the negative electrode 3 and the positive electrode 1 produced above and laminated to form an electrode unit (negative electrode / separator / positive electrode). Got.
Next, four electrode units were prepared, and a lithium metal foil 4 having a thickness of 100 μm and having substantially the same area as that of the negative electrode 3 was placed on one surface of the negative electrode 3 opposite to the separator 2 side.
Then, the first to fourth electrodes are arranged with the separator 2 disposed between the electrode units so that the positive electrode 1 and the negative electrode 3 (lithium metal foil 4) of the adjacent units face each other. Units U1 to U4 were stacked. The outermost layer of this laminate is a lithium metal foil 4 disposed on one side of the positive electrode 1 of the first unit U1 and the negative electrode 3 of the fourth unit U4.
Furthermore, on the surface of the positive electrode 1 of the first unit U1 of the outermost layer, the negative electrode 3 in which the lithium metal foil 4 is arranged on one side via the separator 2 is installed so that the negative electrode 3 becomes the outermost layer, An electrode laminate 9 was obtained (see FIG. 1).

[Battery assembly]
With the lead tab 3z electrically connecting each negative electrode 3 constituting the electrode laminate 9 and the lead tab 1z electrically connecting each positive electrode 1 protruding outward, the electrode laminate 9 is aluminum laminated. The lithium ion secondary battery shown in FIG. 1 and FIG. 2 is housed in an unillustrated exterior body and temporarily sealed, and the electrolyte is injected into the exterior body and then sealed. 10 was obtained.

[Lithium pre-doping process]
The lithium ion secondary battery 10 produced above was fixed in a state where it was pressurized with a pressure jig, and was left in a thermostatic bath at 25 ° C. for 72 hours to perform a lithium pre-doping treatment.

<Example 2>
In Example 2, in the electrode laminate 9 produced in Example 1, punching aluminum foil (length × width = 40 mm × 55 mm, thickness 15 μm, hole diameter 0. 0 mm) used for the positive electrode current collector 11 in each positive electrode 1. 35 mm, manufactured by Fukuda Metal Foil Powder Co., Ltd.), the positive electrode 1 and the electrode laminate 9 were subjected to the same conditions and procedures as in Example 1 except that one having a through-hole ratio of 10% was adopted. A lithium ion secondary battery 10 was produced in the same manner as in Example 1 (see FIG. 1).
Then, a lithium pre-doping treatment was performed under the same conditions and procedures as in Example 1.

<Example 3>
In Example 3, punching aluminum foil (length × width = 40 mm × 55 mm, thickness 15 μm, hole diameter 0. 0 mm) used for the positive electrode current collector 11 in each positive electrode 1 in the electrode laminate 9 produced in Example 1. 35 mm, manufactured by Fukuda Metal Foil Powder Co., Ltd.), the positive electrode 1 and the electrode laminate 9 were produced under the same conditions and procedures as in Example 1, except that a non-perforated plate without through holes was adopted. A lithium ion secondary battery 10 was produced in the same manner as in Example 1.
Then, a lithium pre-doping treatment was performed under the same conditions and procedures as in Example 1.

<Comparative example>
In the comparative example, in the electrode laminate produced in Example 1, punching aluminum foil (vertical × horizontal = 40 mm × 55 mm, thickness 15 μm, hole diameter 0.35 mm, Fukuda Metal, used for the positive electrode current collector in each positive electrode Example 1 except that the aperture ratio of the through-holes is 30%, and the aperture ratios of the positive electrode current collector and the negative electrode current collector are set to be the same. The positive electrode 1 and the electrode laminate 9 were produced under the same conditions and procedures as in Example 1, and a lithium ion secondary battery was produced in the same manner as in Example 1.
Then, a lithium pre-doping treatment was performed under the same conditions and procedures as in Example 1.

<Evaluation method>
[Evaluation of charge / discharge characteristics of lithium ion secondary battery]
About the lithium ion secondary battery produced by said Examples 1-3 and the comparative example, until the electric current value converges to 0.05C by making constant current constant voltage charge of 0.1C in 25 degreeC into the upper limit voltage 4.35V Then, a constant current discharge of 0.1 C was performed up to 2.5V.
Subsequently, the charge / discharge current was set to 0.5 C, and the charge / discharge cycle was repeated three times in the same manner as described above to stabilize the state of the lithium ion secondary battery.

Subsequently, charging / discharging was performed by the method similar to the above by setting charging / discharging electric current as 0.2C.
And based on this result, the capacity expression rate (%): {[discharge capacity (mAh) at the first cycle] / [rated capacity (mAh)]} × 100) and the charge / discharge current as 1 C are the same. The capacity retention rate at 100 cycles (%): ({[discharge capacity at the 100th cycle (mAh)] / [discharge capacity at the 1st cycle (mAh)]} × 100) Was calculated.

[Presence or absence of electrode collapse after charge / discharge characteristics test of lithium ion secondary battery]
Disassembling the lithium ion secondary batteries of Examples 1 to 3 and the comparative example evaluated for charge / discharge characteristics according to the above procedure, visually confirming the positive electrode and the negative electrode where expansion and contraction occur with charge / discharge, and whether there is physical damage confirmed.

<Evaluation results>
As a result of the above-described evaluation test, first, Example 2 in which the aperture ratio of the through holes provided in the positive electrode current collector was 10% and the non-perforated plate (the aperture ratio 0%) were changed to the positive electrode current collector. In Example 3 used for the above, no physical damage such as cracking in the positive electrode occurred. On the other hand, in Example 1 in which the aperture ratio of the through holes provided in the positive electrode current collector was 15%, it was confirmed that cracks occurred in a part of the positive electrode, but the performance as a battery was improved. Was insignificant. This is because the positive electrode current collector has no through-holes or has a low open-hole ratio, improving the mechanical strength and elongation of the positive electrode current collector made of aluminum metal foil. For this reason, it is considered that physical damage such as cracking is suppressed when expansion or contraction of the positive electrode and the negative electrode accompanying charging / discharging occurs.

  On the other hand, in the comparative example in which the aperture ratio of the through holes provided in the positive electrode current collector was 30% and the same aperture ratio as that of the negative electrode current collector, the charge and discharge characteristics (cycle characteristics) after the test In the confirmation of decomposition, it was confirmed that the entire positive electrode was cracked. This is because the opening ratio of the through holes provided in the positive electrode current collector is large, and the mechanical strength of the positive electrode current collector made of aluminum metal foil is reduced. It is considered that when the positive electrode and the negative electrode expanded or contracted due to repeated discharge, the entire positive electrode with low strength was cracked.

  In addition, the relationship between the aperture ratio (including 0%) of the through holes provided in the positive electrode current collector and the aperture ratio of the through holes provided in the negative electrode current collector is within the range specified in the present invention. In Examples 1-3, the capacity retention ratio after repeating 100 cycles of charge / discharge was 80 (%) (Example 1), 85 (%) (Example 2), 90 (%) In Example 3) and in all examples, it was 80 (%) or more, and it was confirmed that the cycle characteristics were excellent. This is probably because the negative electrode current collector is provided with a through-hole, and lithium ions are effectively diffused and moved in the lithium pre-doping process during battery production, which increases the discharge capacity. . Further, as described above, in Examples 1 to 3, it was considered that excellent cycle characteristics were obtained because no large physical damage occurred in the electrodes.

  On the other hand, in the comparative example in which the aperture ratio of the through holes in the positive electrode current collector and the negative electrode current collector was set to be the same (30%), the capacity retention rate after repeating 100 cycles of charge / discharge was 55 ( %) And remarkably inferior to Examples 1-3. As described above, in the comparative example, cracking occurred in the entire positive electrode, so that the battery characteristics were remarkably deteriorated and the cycle characteristics were inferior. The results are shown in Table 1.

  From the results of the examples described above, the lithium ion secondary battery having the configuration according to the present invention can be effectively pre-doped without reducing the mechanical strength of the electrode, and has excellent battery characteristics. It is clear.

DESCRIPTION OF SYMBOLS 10,10A ... Lithium ion secondary battery, 1, 1A ... Positive electrode, 11, 11A ... Positive electrode collector, 11a ... Through-hole (several through-holes), 12 ... Positive electrode active material layer, 1z ... Lead tab, 2 ... Separator DESCRIPTION OF SYMBOLS 3 ... Negative electrode, 31 ... Negative electrode collector, 31a ... Through-hole (several through-holes), 32 ... Negative electrode active material layer, 3z ... Lead tab, 4 ... Lithium metal foil, 9 ... Electrode laminated body, U1, U2, U3, U4 ... Electrode unit

Claims (5)

At least one or more positive electrodes and one or more negative electrodes,
The positive electrode has a plate-shaped positive electrode current collector and a positive electrode active material layer provided on both sides or one side thereof,
The negative electrode has a plate-shaped negative electrode current collector and a negative electrode active material layer provided on both sides or one side thereof,
The positive electrode current collector and the negative electrode current collector are composed of a perforated plate having a plurality of through holes,
Further, each of the positive electrode current collector and the negative electrode current collector has a ratio of a total area in a plan view of the plurality of through-holes with respect to the total area of one surface, and the negative electrode current collector A lithium ion secondary battery, wherein the positive electrode current collector has a lower porosity than a body.   The opening ratio of the plurality of through holes in the negative electrode current collector is more than 15% and 50% or less, and the opening ratio of the plurality of through holes in the positive electrode current collector is more than 0% and 30% or less. The lithium ion secondary battery according to claim 1. One or more positive electrodes and one or more negative electrodes,
The positive electrode has a plate-shaped positive electrode current collector and a positive electrode active material layer provided on both sides or one side thereof,
The negative electrode has a plate-shaped negative electrode current collector and a negative electrode active material layer provided on both sides or one side thereof,
The positive electrode current collector is a non-porous plate having no through holes,
The negative electrode current collector is formed of a perforated plate having a plurality of through holes.   4. The negative electrode current collector has a hole area ratio, which is a ratio of a total area of the plurality of through holes in a plan view with respect to the entire area of one side, in a range of more than 15% and 50% or less. 5. The lithium ion secondary battery described in 1.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the negative electrode active material layer is pre-doped with lithium before initial charging.

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