JP5311861B2 - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery having high energy density, high discharge-rate characteristics, and excellent charge discharge cycle characteristics. <P>SOLUTION: In the lithium secondary battery having an electrode body 5 formed by spirally winding a laminated body including a negative electrode in which a negative active material layer containing an element having a coefficient of cubic expansion by charge of 1.9 times or more is formed on a negative current collector, a positive electrode in which a positive active material layer containing a lithium transition metal oxide is formed on a positive current collector, and a separator, and housing the electrode body 5 in a cylindrical battery container with a nonaqueous electrolyte impregnated, two positive current collector tabs 7, 7 are arranged at intervals of at least 1/4 or more of the total length of the positive electrode in a position from an inner peripheral side end part in the winding direction of the positive electrode to 2/3 of the total length of the positive electrode, and one negative current collector tab 8 is arranged in an outer peripheral side end part in the winding direction of the negative electrode. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a lithium secondary battery having high energy density and high discharge rate characteristics and excellent charge / discharge cycle characteristics.

  Recently, in lithium secondary batteries, aluminum (Al) having a high volumetric capacity by occlusion of lithium by alloying reaction with lithium instead of graphite material which has been put into practical use for the purpose of increasing energy density. Alloy materials of elements such as tin (Sn) and silicon (Si) have been taken up as candidates for new negative electrode active materials and have been extensively studied.

  However, in an electrode using a material alloyed with lithium as an active material, since the volume change of the active material at the time of occlusion and release of lithium is large, pulverization of the active material and detachment from the current collector are likely to occur. As a result, there is a problem that the current collecting property in the electrode is lowered and the charge / discharge cycle characteristics are deteriorated.

  Therefore, in order to achieve high current collection in the electrode, a negative electrode obtained by sintering and arranging a mixture layer containing an active material made of a silicon-containing material and a binder in a non-oxidizing atmosphere is provided. It has been found that good charge / discharge cycle characteristics are exhibited (see Patent Document 1 below).

Japanese Patent Laid-Open No. 2002-260637

  However, even if the current collection in the electrode can be improved in this way, in the case of a real battery such as a cylindrical type or a flat type, a large volume change of the active material adversely affects other members in the battery. This causes a problem that sufficient charge / discharge characteristics cannot be obtained.

  During charging, that is, when lithium is occluded, stress is generated as the volume of the negative electrode active material containing silicon increases, and is applied to other battery members such as a positive electrode and a resin porous separator. In particular, in the case of a cylindrical battery, since the electrode body has a tight structure that is not easily deformed compared to the case of a flat battery, when stress occurs as the volume of the active material increases, The porous separator made of resin, which is more easily deformed by external force than the positive electrode and the negative electrode, is compressed and clogged. This effect is greatly promoted as the deterioration (expansion) of the negative electrode active material with the progress of the cycle increases. For this reason, the conductivity of lithium ions between the positive and negative electrodes is greatly reduced, and the charge / discharge characteristics are greatly reduced.

  Elements that expand greatly upon charging include silicon (volume expansion coefficient 4.1 times), germanium (volume expansion coefficient 3.7 times), tin (volume expansion coefficient 3.6 times), and aluminum. (Volume expansion coefficient is 1.9 times) and the like, and when these elements are used as the negative electrode active material, the above-described problems are likely to occur.

  Therefore, by forming the current collector tabs of the positive and negative electrodes from the current collectors of the positive and negative electrodes, the deformability of the electrode body is increased, and the compression of the separator during charging in the cylindrical battery is suppressed. It has been found that good charge / discharge characteristics can be obtained (see Patent Document 2 below).

JP 2007-213875 A

  However, even with the configuration disclosed in Patent Document 2, it is still difficult to say that the charge / discharge characteristics have reached a sufficient level.

  Therefore, in view of the above problems, an object of the present invention is to provide a lithium secondary battery having high energy density and high discharge rate characteristics and excellent charge / discharge cycle characteristics.

  In response to such problems, the present inventors have used elements such as silicon (Si), germanium (Ge), aluminum (Al), tin (Sn), etc., which have a large volume expansion coefficient with charging, as the negative electrode active material. In a lithium secondary battery, it is found that it is possible to obtain high energy density, high discharge rate characteristics as well as excellent charge / discharge cycle characteristics by optimizing the arrangement configuration of the current collecting tabs of the positive and negative electrodes, The present invention has been completed.

That is, in the lithium secondary battery according to the present invention (hereinafter also referred to as “first lithium secondary battery”), the negative electrode active material layer containing an element having a volume expansion coefficient of 1.9 times or more upon charging is negative electrode collection. A laminate including a negative electrode formed on a current collector, a positive electrode in which a positive electrode active material layer including a lithium transition metal oxide is formed on a positive electrode current collector, and a separator disposed between the negative electrode and the positive electrode In a lithium secondary battery having an electrode body formed by winding a body in a spiral shape, the electrode body being impregnated with a nonaqueous electrolyte and housed in a cylindrical battery container, the positive electrode spiral Two current collecting tabs are arranged at an interval of at least 1/4 or more of the total length of the positive electrode between the inner peripheral side end in the direction and the position of 2/3 of the total length of the positive electrode, and in the spiral direction of the negative electrode One current collecting tab is disposed only at the outer peripheral side end .

  Of the elements having a volume expansion coefficient of 1.9 times or more due to charging, silicon, which is a representative example, is a material with low electron conductivity, but is formed by a mixture with an insulating resin binder. In the state of the active material layer, the electron conductivity is further inferior. For this reason, at the time of charging / discharging, the polarization due to the IR resistance due to the low electron conductivity in the electrode increases, and the reaction uniformity in the electrode becomes very low. An active material containing silicon tends to be easily deteriorated (or swollen or altered) when the reaction uniformity is low. In this case, the charge / discharge characteristics are greatly deteriorated. In addition, in order to obtain a spirally wound electrode body, particularly when the positive and negative electrodes are rectangular with a long side (side along the spiral direction) / short side (side along the width direction), The tendency of becomes large.

  On the other hand, according to the configuration of the present invention, an interval of at least 1/4 or more of the total length of the positive electrode is provided between the inner peripheral side end in the spiral direction of the positive electrode and the position of 2/3 of the total length of the positive electrode. Two current collecting tabs are arranged, and one current collecting tab is arranged at the outer peripheral side end in the spiral direction of the negative electrode, so that the positive and negative electrodes are elongated in order to form a spirally wound electrode body. Even in the case of a rectangle with a large side (side along the spiral direction) / short side (side along the width direction), the reaction distribution in the electrode body can be made uniform, and the charge / discharge characteristics are degraded. Can be suppressed.

  Further, according to the configuration of the present invention described above, when the electrode body is manufactured, in a state where the positive electrode and the negative electrode are stacked, the positive electrode current collecting tab and the negative electrode current collecting tab overlap at the same position or in the vicinity thereof. Therefore, after winding this laminated body into a take-up electrode body, even if these current collecting tabs are arranged in a straight line with the shortest distance, there are several gaps between the current collecting tabs. Since the surrounding laminated body is interposed, the winding electrode body is easily deformed uniformly, and the winding electrode body can be deformed following the volume expansion of the negative electrode active material during charging. Therefore, the charge / discharge characteristics are hardly deteriorated due to the compression and clogging of the separator.

  Here, for example, in the above configuration, when one negative electrode current collecting tab is also added to the inner peripheral side end in the spiral direction of the negative electrode, the reaction uniformity cannot be improved, and the inner peripheral end Since the positive electrode current collecting tab and the negative electrode current collecting tab overlap each other at a position close to each other, the deformability of the electrode body is lowered, and the charge / discharge characteristics cannot be improved.

  Moreover, according to the structure of the said invention, it has become the structure by which the current collection property in a positive electrode improved and charging / discharging characteristics improved by arranging many positive electrode tabs.

In the positive electrode, the distance between the current collecting tab located on the innermost circumferential side and the current collecting tab located on the outermost circumferential side in the spiral direction is preferably 1/3 to 1/2 of the total length in the spiral direction of the positive electrode. .
In the present invention, “the interval between the current collecting tabs in the spiral direction” means the distance (length) between the centers in the width direction (spiral direction) of each current collecting tab. To do.
If the distance between the positive electrode current collecting tab located on the innermost circumferential side in the spiral direction and the positive electrode current collecting tab located on the outermost circumferential side is 1/3 or more of the total length in the spiral direction of the positive electrode, The positive electrode current collecting tabs are not unevenly distributed with sufficient spacing between the tabs, and as a result, the reaction uniformity within the electrode body and the current collecting property within the positive electrode can be improved. If the distance between the tabs is ½ or less of the total length in the spiral direction of the positive electrode, the distance between the positive electrode current collecting tabs is within an appropriate range, and the reaction uniformity within the electrode body can be improved and charge / discharge characteristics can be improved. Can be improved.

It is desirable that the negative electrode active material layer contains silicon and / or a silicon alloy.
Assuming that the active material contains silicon, as described above, polarization due to IR resistance due to low electron conductivity in the electrode during charging / discharging increases, and reaction uniformity in the electrode becomes very low. The active material is likely to deteriorate (or swell and change), and the charge / discharge characteristics are likely to be greatly reduced. In addition, the positive and negative electrodes are long sides (sides along the spiral direction) in order to form a spirally wound electrode body. / This tendency is particularly great when the rectangle has a short side (side along the width direction).
In addition, a battery using silicon as a negative electrode active material has a lithium occlusion / release potential of silicon that is equivalent to that of graphite even when charging / discharging is performed in the same voltage range as compared to a battery using graphite as a negative electrode active material. Therefore, the potential of the positive electrode is increased accordingly. For this reason, when the electron conductivity in the positive electrode is low and the IR resistance is large, the polarization in the positive electrode at the time of charging / discharging is increased, so that the potential is further increased during charging. At this time, since a large amount of lithium is extracted from the lithium transition metal oxide that is the positive electrode active material layer, the crystal structure is broken and the positive electrode active material is deteriorated. This also tends to cause oxidative decomposition of the electrolyte solution on the positive electrode surface. Therefore, the reduction of the IR resistance in the positive electrode by setting the number of the positive electrode tabs to two or more can suppress such deterioration in the positive electrode and improve the charge / discharge characteristics.

  The above characteristics are also observed in, for example, germanium, but are more remarkable in the case of silicon. In addition, as described above, the volume expansion coefficient of silicon accompanying charging is 4.1 times, for example, 3.7 times for germanium, 3.6 times for tin, and 1.9 times for aluminum. Higher than that. Therefore, when the negative electrode active material layer is configured to contain silicon and / or silicon alloy, the configuration of the present invention, that is, from the inner peripheral side end in the spiral direction of the positive electrode to the position of 2/3 of the total length of the positive electrode. A structure in which two current collecting tabs are disposed at an interval of at least 1/4 of the total length of the positive electrode, and one current collecting tab is disposed at an outer peripheral side end in the spiral direction of the negative electrode; The effect by doing is exhibited further.

In addition, the lithium secondary battery according to the present invention (hereinafter also referred to as “second lithium secondary battery”) has a negative electrode active material layer containing an element having a volume expansion coefficient of 1.9 times or more due to charging. A laminate including a negative electrode formed on a current collector, a positive electrode in which a positive electrode active material layer including a lithium transition metal oxide is formed on a positive electrode current collector, and a separator disposed between the negative electrode and the positive electrode In a lithium secondary battery having an electrode body formed by winding a body in a spiral shape, the electrode body being impregnated with a nonaqueous electrolyte and housed in a cylindrical battery container, the positive electrode spiral Two current collecting tabs are arranged at an interval of at least 1/4 of the total length of the positive electrode between the outer peripheral side end in the direction and the position of 2/3 of the total length of the positive electrode . One current collecting tab is disposed only at the peripheral end .

  According to the configuration of the second lithium secondary battery, the arrangement of the positive electrode current collecting tab and the negative electrode current collecting tab is different from the arrangement of the positive electrode current collecting tab and the negative electrode current collecting tab in the first lithium secondary battery. Therefore, the charge / discharge characteristics equivalent to those of the first lithium secondary battery can be obtained.

  However, in the case of the second lithium secondary battery, the positive electrode current collecting tab is positioned on the outer peripheral side of the winding electrode body (especially the outermost periphery or the vicinity thereof), and the positive electrode current collecting tab is used as a sealing lid of the battery. Since it is easy to contact the battery can of the negative electrode when connecting, the positive electrode current collecting tab and the battery can be insulated, for example, by covering the positive electrode current collecting tab with a resin tape and appropriately bending the tab. Measures for avoiding contact with the can are required, and therefore the first lithium secondary battery is more advantageous from the viewpoint of ease of battery production.

In the case of the second lithium secondary battery, for example, when the battery can is made of aluminum and used as a positive electrode can, the sealing lid is used as a negative electrode and the arrangement of the positive and negative electrodes is reversed, the positive electrode current collecting tab is connected to the battery can. Therefore, it can be made equivalent to the first lithium secondary battery in terms of ease of battery production.
However, as the battery can, for example, a battery can made of SUS (stainless steel) has a higher strength and can be a battery can that does not easily expand and contract even when the winding electrode body is deformed. Therefore, the first lithium secondary battery is more advantageous from this viewpoint.

In the second lithium secondary battery, in the positive electrode, the distance between the current collecting tab located on the innermost side in the spiral direction and the current collecting tab located on the outermost side is 1 / of the total length in the spiral direction of the positive electrode. 3 to 1/2 is desirable.
This is for the same reason as in the case of the first lithium secondary battery described above.

In the second lithium secondary battery, it is desirable that the negative electrode active material layer contains silicon and / or a silicon alloy.
This is for the same reason as in the case of the first lithium secondary battery described above.

  According to the present invention, a negative electrode active material layer containing an element having a volume expansion coefficient of 1.9 times or more upon charging formed on a negative electrode current collector, and a positive electrode active material layer containing a lithium transition metal oxide Has an electrode body formed by spirally winding a laminate including a positive electrode formed on a positive electrode current collector and a separator disposed between the negative electrode and the positive electrode. In a lithium secondary battery housed in a cylindrical battery container impregnated with a non-aqueous electrolyte, between the end on the inner peripheral side in the spiral direction of the positive electrode and the position of 2/3 of the total length of the positive electrode, Since two current collecting tabs are arranged at an interval of at least 1/4 of the total length of the positive electrode, and one current collecting tab is arranged at the outer peripheral side end in the spiral direction of the negative electrode, Reaction distribution can be made uniform, and deterioration of charge / discharge characteristics can be suppressed. Rukoto can.

  In addition, when the electrode body is manufactured, in a state where the positive electrode and the negative electrode are laminated, the positive electrode current collecting tab and the negative electrode current collecting tab are not arranged to overlap at the same position or in the vicinity thereof. After turning to a winding electrode body, even if these current collecting tabs are arranged in a straight line at the shortest distance, a stack of several turns is interposed between the current collecting tabs. The winding electrode body is easily deformed uniformly, and even when the negative electrode active material expands during charging, the winding electrode body can be deformed following the volume expansion. Therefore, the separator is compressed and clogged. The charge / discharge characteristics are less likely to deteriorate.

  Moreover, since two or more positive electrode tabs are arrange | positioned, the current collection property in a positive electrode improves, and it can make charge / discharge characteristic favorable.

  Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following best modes, and can be appropriately modified and implemented without departing from the spirit of the present invention.

[Production of negative electrode active material]
First, a polycrystalline silicon lump was produced by a thermal reduction method. Specifically, a silicon core installed in a metal reactor (reduction furnace) is heated by heating to 800 ° C., and purified with high purity monosilane (SiH ₄ ) gas vapor. By flowing a gas mixed with hydrogen, polycrystalline silicon was deposited on the surface of the silicon core, thereby producing a polycrystalline silicon lump produced in a thick rod shape.

Next, the polycrystalline silicon lump was pulverized and classified to produce polycrystalline silicon particles (negative electrode active material) having a purity of 99%. The polycrystalline silicon particles had a crystallite size of 32 nm and an average particle size of 10 μm.
The crystallite size was calculated by the Scherrer equation using the half width of the (111) peak of silicon in powder X-ray diffraction, and the average particle size was determined by a laser diffraction method.

(Preparation of negative electrode mixture)
NMP (N-methyl-2-pyrrolidone) as a dispersion medium, the above prepared negative electrode active material, graphite powder having an average particle size of 3.5 μm as a negative electrode conductive agent, and the following chemical formula 1 as a negative electrode binder Varnish of a precursor of a thermoplastic polyimide resin having a glass transition temperature of 300 ° C. and a weight average molecular weight of 50000 (solvent: NMP, concentration: polymerized by heat treatment + 47% by weight of the polyimide resin after imidization) ) Was mixed so that the mass ratio of the negative electrode active material powder, the negative electrode conductive agent powder, and the polyimide resin after imidization was 100: 3: 8.6 to obtain a negative electrode mixture slurry. The precursor varnish of the polyimide resin here can be prepared from 3,3 ′, 4,4′-benzophenonetetracarboxylic acid diethyl ester shown in the following chemical formula 2 and m-phenylenediamine shown in the chemical formula 3 below. 3,3 ′, 4,4′-benzophenonetetracarboxylic acid diethyl ester is obtained by adding 2 equivalents of ethanol in the presence of NMP to 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride shown in the following chemical formula 4. Can be produced by reacting.

(Production of negative electrode)
The negative electrode mixture slurry prepared above was coated on both sides of a 18 μm thick copper alloy foil (C7025 alloy foil, composition: Cu 96.2 wt%, Ni 3 wt%, Si 0.65 wt%, Mg 0.15 wt%) with a surface roughness Ra. (JIS B 0601-1994) is 0.25 μm, and average crest spacing S (JIS B 0601-1994) is applied to both surfaces of a negative electrode current collector roughened by electrolytic copper in air at 25 ° C. After drying in air at 120 ° C., rolling in air at 25 ° C. The obtained product was cut out into a rectangle having a length of 510 mm and a width of 35.7 mm, and then heat-treated at 400 ° C. for 10 hours in an argon atmosphere to obtain a negative electrode having a negative electrode active material layer formed on the surface of the negative electrode current collector. Produced. The amount of the negative electrode mixture layer on the negative electrode current collector was 5.6 mg / cm 2 and the thickness was 56 μm.

  As shown in FIG. 2A, a nickel plate having a length of 46 mm, a width of 3 mm, and a thickness of 70 μm was connected to one end of the negative electrode 3 in the longitudinal direction as the negative electrode current collecting tab 8.

[Preparation of positive electrode active material]
Li ₂ CO ₃ and CoCO ₃ were mixed as a positive electrode active material in a mortar so that the molar ratio of Li and Co was 1: 1, and then pulverized after heat treatment at 800 ° C. for 24 hours in an air atmosphere. A powder of lithium cobalt composite oxide represented by LiCoO ₂ having an average particle diameter of 11 μm was obtained. The positive electrode active material powder obtained had a BET specific surface area of 0.37 m ² / g.

[Production of positive electrode]
To the N-methyl-2-pyrrolidone as a dispersion medium, the produced positive electrode active material powder, the carbon powder having an average particle diameter of 2 μm as the positive electrode conductive agent, and the polyvinylidene fluoride as the positive electrode binder, The conductive agent and the binder were added so that the weight ratio was 95: 2.5: 2.5, and then kneaded to obtain a positive electrode mixture slurry.

As shown in FIG. 1 (a), the positive electrode mixture slurry is formed on both surfaces of an aluminum foil having a thickness of 15 μm, a length of 495 mm, and a width of 33.7 mm as a positive electrode current collector. An uncoated portion N1 having a width of 30 mm and a width W1 of 33.7 mm is further separated from the uncoated portion N1 at the end by a distance of D1 = 215 mm. N2 is further formed on the back surface of the uncoated portions N1 and N2 by forming uncoated portions (not shown) of the same size at positions corresponding to the uncoated portions N1 and N2, respectively. It applied to the area | region of space | interval D1 = 215mm, and the area | region of space | interval D2 = 240mm between the uncoated part N2 of a center part, and the other end of a positive electrode electrical power collector, respectively, dried, and rolled. The amount of the active material layer on the current collector and the thickness of the positive electrode were 45 mg / cm ² and 143 μm at the portion where the active material layer was formed on both sides.

  As shown in FIG. 1A, uncoated portions N1 and N2 of the positive electrode 2 were connected with aluminum plates having a length of 46 mm, a width of 3 mm, and a thickness of 70 μm as the positive electrode current collecting tabs 7 and 7, respectively. Specifically, the uncoated portion N1 at the positive electrode end portion is disposed 5 mm away from the end portion, and the uncoated portion N2 at the positive electrode central portion is disposed at the center in the spiral direction of the uncoated portion N2. In addition, the space | interval of the two positive electrode current collection tabs 7 and 7 is 243.5 mm.

[Preparation of non-aqueous electrolyte]
After dissolving 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate (FEC) and methyl propionate (MP) are mixed at a volume ratio of 2: 8, Then, 0.4 wt% carbon dioxide gas was added to obtain a non-aqueous electrolyte.

(Production of electrode body)
Using one positive electrode and one negative electrode, and two polyethylene microporous membrane separators having a piercing strength of 340 g and a porosity of 39%, each having a thickness of 20 μm, a length of 560 mm, and a width of 37.7 mm, And the negative electrode are opposed to each other with a separator interposed therebetween, and the positive electrode current collecting tab 7 on the positive electrode end side is the innermost periphery and the negative electrode current collecting tab 8 is the outermost outer periphery. After winding in a spiral shape, the winding core was pulled out to produce a cylindrical electrode body 5 having a diameter of 12.8 mm and a height of 37.7 mm as schematically shown in FIG.
As apparent from the above configuration, in FIGS. 1 and 2, the left side of the positive electrode and the negative electrode is the inner peripheral side (winding side) in the spiral direction (winding direction), and the right side is the outer periphery in the spiral direction. This is the side (winding end side).

[Production of battery]
As shown in a cross-sectional structure in FIG. 4, the cylindrical electrode body 5 and the non-aqueous electrolyte are inserted into a SUS cylindrical outer can 1 in a CO ₂ atmosphere at 25 ° C. and 1 atm. A battery having a height of 43 mm was produced.
Here, the outline of the battery will be shown based on the schematic cross-sectional view of FIG. This battery includes a cylindrical metal outer can 1 having an opening at the top, an electrode body 5 in which a positive electrode 2 and a negative electrode 3 are opposed to each other with a separator 4 interposed between them, and an inside of the electrode body 5. The nonaqueous electrolytic solution impregnated in and the sealing lid 6 that seals the opening of the metal outer can 1 described above. The sealing lid 6 is a positive electrode terminal, the metal outer can 1 is a negative electrode terminal, and the positive electrode current collecting tabs 7 and 7 attached to the upper surface side of the electrode body 5 are attached to the sealing lid 6 and the lower surface side. A negative electrode current collecting tab 8 is connected to the metal outer can 1. The upper and lower surfaces of the electrode body 5 are covered with an upper insulating plate 9 and a lower insulating plate 10 for insulating the electrode body 5 from the metal outer can 1. The sealing lid 6 is caulked and fixed to the opening of the metal outer can 1 via an insulating packing 11.
Thus, the battery has a structure capable of being charged and discharged as a secondary battery.

[First embodiment]
In the following first example (Example 1 and Comparative Examples 1 to 4), the installation positions of the positive electrode current collecting tab and the negative electrode current collecting tab (the inner peripheral side portion, the central portion and the outer peripheral side portion in the winding direction) The effect of the difference on the charge / discharge characteristics was investigated.

Example 1
As the battery of Example 1, a battery manufactured in the same manner as the battery described in the best mode for carrying out the invention was used.
The battery thus produced is hereinafter referred to as the present invention battery A1.

(Comparative Example 1)
As shown in FIG. 2B, the negative electrode current collector tabs 8b and 8b were connected to both ends of the negative electrode 3 with nickel plates having a length of 46 mm, a width of 3 mm, and a thickness of 70 mm, respectively. A battery was produced in the same manner as described above. Both the negative electrode current collecting tabs 8b and 8b were connected to the bottom of the cylindrical metal outer can in the same manner as the negative electrode current collecting tab 8 of Example 1.
The battery thus produced is hereinafter referred to as comparative battery Z1.

(Comparative Example 2)
As shown in FIG. 1B, an uncoated portion in the vicinity of the center in the longitudinal direction of the positive electrode 2b is used as a coated portion, and a distance D3 = 465 mm between an uncoated portion N1 at one end of the positive electrode current collector and the other end. A battery was fabricated in the same manner as in Example 1 except that the positive electrode active material layer was formed in the region and the positive electrode current collecting tab was not provided in this region.
The battery thus produced is hereinafter referred to as comparative battery Z2.

(Comparative Example 3)
As shown in FIG. 1 (c), the length L3 = 10 mm and the width W1 = 33.7 mm at the end opposite to the uncoated portion N1 having the length L1 = 30 mm and W1 = width 33.7 mm. The coated portion N3 was formed, and the positive current collecting tab 7c was installed at the center of the spiral direction. The positive current collecting tab was not installed in the uncoated portion N1 having a length L1 = 30 mm and W1 = width 33.7 mm. A battery was fabricated in the same manner as in Comparative Example 1 above. The distance between the two positive electrode current collecting tabs 7 and 7c is 240 mm, and the distance between the uncoated portions N2 and N3 where the positive electrode current collecting tabs 7 and 7c are installed is D4 = 230 mm. Further, the two positive electrode current collecting tabs 7 and 7c are connected to the sealing lid in the same manner as the positive electrode current collecting tabs 7 and 7 of the first embodiment.
The battery thus produced is hereinafter referred to as comparative battery Z3.

(Comparative Example 4)
As shown in FIG. 1 (d), a battery was obtained in the same manner as in Comparative Example 1 except that no positive electrode current collecting tab was installed in the uncoated portion N1 having a length L1 = 30 mm and W1 = width 33.7 mm. Was made.
The battery thus produced is hereinafter referred to as comparative battery Z4.

[Evaluation of charge / discharge cycle characteristics]
About the said this invention battery A1 and comparative battery Z1-Z4, the charge / discharge cycle characteristic was evaluated on the following charge / discharge cycle conditions.

(Charge / discharge cycle conditions)
-Charging condition in the first cycle After performing constant current charging for 4 hours at a current of 45 mA, constant current charging is performed until the battery voltage reaches 4.2 V at a current of 180 mA, and further a current value at a voltage of 4.2 V The battery was charged at a constant voltage until the current became 45 mA.
-First cycle discharge conditions Constant current discharge was performed at a current of 180 mA until the battery voltage reached 2.75V.
-Charging conditions after the second cycle Constant current charging was performed at a current of 900 mA until the battery voltage reached 4.2 V, and further constant voltage charging was performed at a voltage of 4.2 V until the current value reached 45 mA.
-Discharge conditions after the second cycle Constant current discharge was performed at a current of 900 mA until the battery voltage reached 2.75V.

(Calculation of discharge rate characteristics and cycle life)
The discharge rate characteristics and cycle life were determined by the following calculation method.
Discharge rate characteristics Discharge capacity at the second cycle / discharge capacity at the first cycle × 100
Cycle life The number of cycles when the capacity retention ratio (the value obtained by dividing the discharge capacity at the nth cycle by the discharge capacity at the second cycle) reaches 50%.

(Measurement of resistance)
At the end of the first cycle discharge, the AC resistance of the battery at 1 kHz was also measured.

(Characteristic value calculation / measurement results)
Table 1 shows the 1 kHz AC resistance, discharge rate characteristics, and cycle life of the present invention battery A1 and comparative batteries Z1 to Z4.
In Table 1, each characteristic value is expressed as an index with each value of 1 kHz AC resistance, discharge rate characteristic, and cycle life of the battery A1 of the present invention as 100, and “inside” indicates the winding direction (vortex Direction), “middle” represents the central part in the winding direction, and “outer” represents the outermost part in the winding direction.

(Discussion)
As apparent from Table 1, in the positive electrode 2, two current collectors are spaced from the inner peripheral side end in the spiral direction to a position that is 2/3 of the total length of the positive electrode with an interval of approximately ½ of the total length of the positive electrode. The battery A1 of the present invention having the tabs 7 and 7 and the negative electrode 3 having one current collecting tab 8 at the outer peripheral end in the spiral direction has the arrangement configuration of the current collecting tabs of the positive and negative electrodes. It can be seen that both the discharge rate characteristics and the cycle life can be achieved at high values as compared with different comparative batteries Z1 to Z4.

  In the battery A1 of the present invention, the arrangement of the current collecting tabs of the positive and negative electrodes is optimized as described above, so that the length of the positive and negative electrodes is increased in order to form the electrode body 5 in a spiral shape. However, the reaction distribution in the electrode body 5 can be made uniform, and the positive electrode current collecting tabs 7 and 7 and the negative electrode current collector are stacked in a state in which the positive electrode 2 and the negative electrode 3 are laminated when the electrode body 5 is manufactured. Since the tabs 8 are not arranged to overlap at the same position or in the vicinity thereof, the current collecting tabs 7, 7, 8 are the shortest distances after the laminated body is wound to form the winding electrode body 5. Even if it is arranged in a straight line, the electrode body 5 can be easily deformed by charging a plurality of laminated bodies between the current collecting tabs 7, 7, 8. The occurrence of clogging of the separator at the time is suppressed, and the positive electrode The arrangement of tabs 7,7 are made it possible to improve the current collection performance in the positive electrode 2, presumably because it was possible to suppress the acceleration of the deterioration due to increase in polarization at the positive electrode 2.

  On the other hand, in the comparative battery Z1, compared with the battery A1 of the present invention, the negative electrode current collecting tab 8b is additionally installed, and the current collecting property is improved because the battery internal resistance is reduced. The charge / discharge characteristics are not improved. This is because, in the comparative battery Z1, the positive electrode current collecting tab 7 and the negative electrode current collecting tab 8b overlap each other in the vicinity of the innermost periphery, so that the deformability of the electrode body is reduced, and the negative electrode current collecting tab 8b. This is probably because the reaction uniformity in the electrode body decreased due to the addition of.

  In addition, no improvement in charge / discharge characteristics is observed in the comparative batteries Z2 to Z4. This is because the comparison batteries Z2 and Z4 have only one positive electrode current collecting tab 7 so that the reaction uniformity and current collection performance at the positive electrode are not improved. This is probably because the electric tab 7c and the negative electrode current collecting tab 8b overlap each other at a close position, so that the deformability of the electrode body is lowered.

[Second Embodiment]
In the following second examples (Examples 1 and 2 and Comparative Example 5), the difference in the distance between the positive electrode current collecting tab on the inner peripheral side and the positive electrode current collector tab on the outer peripheral side in the winding direction is the charge / discharge characteristic. We examined the effect of this.

(Example 2)
In the first embodiment, as shown in FIG. 1A, the length L1 of one end of the positive electrode 2 is 30 mm, the uncoated portion N1 having a width W1 of 33.7 mm, and the length L2 of the central portion is 10 mm. The interval D1 with the uncoated portion N2 having the width W1 = 33.7 mm was set to 215 mm. However, by changing the position of the uncoated portion at the center, the uncoated portion at the end and the uncoated portion at the center Four types of batteries were produced in the same manner as in Example 1 except that the interval was changed to 130 mm, 180 mm, 235 mm, and 280 mm. The intervals between the two positive electrode current collecting tabs in each battery are 158.5 mm, 208.5 mm, 263.5 mm, and 308.5 mm, respectively, and the ratio of these intervals to the total positive electrode length is 32.0%. 42.1%, 53.2% and 62.3%.
The four types of batteries thus produced are hereinafter referred to as present invention batteries A2 to A5.

(Comparative Example 5)
The battery was fabricated in the same manner as in Example 1 except that the distance between the uncoated part at the end and the uncoated part at the central part was changed to 320 mm by changing the position of the uncoated part at the center in the positive electrode. Produced. The interval between the two positive electrode tabs is 348.5 mm, and the ratio of these intervals to the total positive electrode length is 70.4%.
The battery thus produced is hereinafter referred to as comparative battery Z5.

[Evaluation of charge / discharge cycle characteristics]
Regarding the inventive batteries A2 to A5 and the comparative battery Z5, the 1 kHz AC resistance, the discharge rate characteristics, and the cycle life were obtained in the same manner as in the case of the inventive battery A1 and the comparative batteries Z1 to Z4 shown in the first embodiment. . The characteristic values obtained are shown in Table 2.
In Table 2, each characteristic value is expressed as an index with each value of 1 kHz AC resistance, discharge rate characteristic, and cycle life of the battery A1 of the present invention as 100, and “inside” indicates the winding direction (vortex Direction), “middle” represents the central part in the winding direction, and “outer” represents the outermost part in the winding direction.

(Discussion)
As is clear from Table 2, the distance between the positive electrode current collecting tab located at the innermost peripheral portion and the positive electrode current collecting tab located at the outermost peripheral portion in the spiral direction is 1/3 or more of the total length of the positive electrode in the spiral direction. Inventive batteries A1 and A3 that are less than / 2 have higher discharge rate characteristics and cycle life than Inventive batteries A2, A4, A5 and comparative battery Z5, in which the positive electrode current collecting tab interval is outside the above range. It turns out that it is possible to achieve both.

  This is presumably because the inventive batteries A1 and A3 have higher reaction uniformity within the electrode body than the inventive batteries A2, A4, A5 and the comparative battery Z5.

  Further, the comparative battery Z5 is greatly deteriorated in all characteristic values as compared with the batteries A1 to A5 of the present invention. This is because the distance between the positive electrode current collecting tab located at the innermost peripheral portion and the positive electrode current collecting tab located at the outermost peripheral portion in the spiral direction exceeds 2/3 of the total positive electrode length and is excessive. This is probably because the uniformity is greatly reduced.

[Other matters]
(1) Of the negative electrode current collecting tabs 8b and 8b (see FIG. 2B) at both ends of the negative electrode 3 in Comparative Example 3 of the first embodiment, the negative electrode current collecting tabs 8b located at the outer peripheral side end portions are installed. According to this, the arrangement of the positive electrode current collecting tabs 7 and 7c (see FIG. 1 (c)) and the negative electrode current collecting tab 8b is the positive electrode current collecting tab in the battery A1 of the present invention of Example 1. 7, 7 (see FIG. 1 (a)) and the negative electrode current collecting tab 8 (see FIG. 2 (a)) are substantially reversed inward and outward (substantially left-right symmetrical). It becomes the structure which can acquire the favorable charge / discharge characteristic equivalent to the case.

  However, in this case, the positive electrode current collecting tab 7c is positioned at the outer peripheral side end portion of the winding electrode body, and when the positive electrode current collecting tab 7c is connected to the sealing lid of the battery, it is easy to come into contact with the negative electrode outer can. Therefore, in order to avoid contact between the positive electrode current collecting tab 7c and the outer can, for example, the positive electrode current collecting tab 7c is covered with a resin tape to be insulated, or the positive electrode current collecting tab 7c is appropriately bent. You can take measures such as

  In this case, for example, the outer can may be made of aluminum to form a positive electrode can, the sealing lid may be a negative electrode, and the arrangement of the positive and negative electrodes may be reversed. According to this, the positive electrode current collecting tab 7c is connected to the outer can. Therefore, the above measures for avoiding contact can be made unnecessary.

(2) In addition to the two positive electrode current collecting tabs 7 and 7 of the positive electrode 2 in Example 1 of the first example (see FIG. 1A), for example, between the both positive electrode current collecting tabs 7 and 7 It is also possible to provide a total of three or more positive electrode current collecting tabs, such as further installing a third positive electrode current collecting tab at an appropriate position such as a central position.

  However, if, for example, the total length of the positive electrode is long and a sufficient interval is secured between the current collecting tabs even if the number of current collecting tabs is increased, the more the number of current collecting tabs installed, the better the reaction uniformity and current collection of the positive electrode. It is considered desirable because it can improve the electrical properties, but when the total length of the positive electrode is about the same as the above embodiment, the current collecting tabs are densely arranged when the number of current collecting tabs is increased. Therefore, there is a possibility that the deformability of the electrode body is lowered, and therefore it is desirable to use two positive electrode current collecting tabs.

(3) Of the two positive electrode current collecting tabs 7 and 7 of the positive electrode 2 in Example 1 of the first example, the current collecting tab 7 located on the innermost peripheral side in the spiral direction is shown in FIG. Strictly speaking, the positive electrode 2 is disposed at a position slightly closer to the center side than the inner peripheral side end in the spiral direction of the positive electrode 2, but the positive electrode active material layer is formed at a position closer to the center side. Since the position on the uncoated portion N1 is functionally equivalent to the inner peripheral side end of the positive electrode 2 in the spiral direction, the position closer to the center is also “the inner periphery in the positive electrode spiral direction”. It shall be included in the “side end”.

(4) Further, for example, the arrangement of the positive electrode current collecting tabs 7 and 7 and the negative electrode current collecting tab 8 of the battery A1 of the present invention in Example 1 of the first example is such that the winding electrode body after being wound in a spiral shape In the state, it is desirable to disperse the electrodes as much as possible because the distance between the current collecting tabs 7, 7, and 8 is large, so that the deformability of the electrode body is improved. FIG. 5 is a schematic diagram showing an example of an arrangement state of two positive electrode current collecting tabs and one negative electrode current collecting tab in the winding electrode body. In the example shown in FIG. 5A, in the state of the wound electrode body 5a after being wound in a spiral shape, one of the two positive electrode current collecting tabs 70a is positioned at the center, and the other positive electrode current collector is formed. The tab 70a and one negative electrode current collecting tab 80a are concentrated and arranged in a range that forms an angle α of 90 ° or less. In the example shown in FIG. 5B, the wound electrode body 5b after winding. In this state, one of the two positive electrode current collecting tabs 70b is located at the center, and the other positive electrode current collecting tab 70b and one negative electrode current collecting tab 80b form an angle β that exceeds 90 ° with respect to each other. It is considered that the deformability of the electrode body 5b is better when the latter current collecting tabs 70b, 70b, and 80b are dispersed.
In the case where the former current collecting tabs 70a, 70a, and 80a are concentrated, for example, when the angle α between the positive electrode current collecting tab 70a and the negative electrode current collecting tab 80a in the middle portion is about 0 °. Is arranged such that the three current collecting tabs 70a, 70a, 80a are aligned in a straight line at the shortest distance. Even in this case, the electrode body 5a is wound (ie, spirally wound). In the previous), in the state where the positive electrode and the negative electrode are laminated, the positive electrode current collecting tabs 70a, 70a and the negative electrode current collecting tab 80a are not arranged to overlap at the same position or in the vicinity thereof. After the winding electrode body 5a is wound, a laminated body of several turns is interposed between the current collecting tabs 70a, 70a, 80a, so that the winding electrode body 5a has a uniform deformability. Secured.

  The present invention can be suitably applied to a cylindrical lithium secondary battery mounted on a small portable device or the like.

It is an expanded view of four types of positive electrodes used in the best mode of the present invention and having different arrangement configurations of current collecting tabs. It is an expanded view of two types of negative electrodes from which the arrangement structure of the current collection tab used by the best form of this invention differs. It is a perspective view of the winding electrode body used by the best form of this invention. It is a schematic sectional drawing of the lithium secondary battery produced with the best form of this invention. It is a top view which shows typically the example of the arrangement configuration in the winding electrode body of the current collection tab used by the best form of this invention.

Explanation of symbols

5: Electrode body 7: Positive electrode current collection tab 8: Negative electrode current collection tab

Claims (6)

A negative electrode in which a negative electrode active material layer containing an element having a volume expansion coefficient of 1.9 times or more upon charging is formed on the negative electrode current collector, and a positive electrode active material layer containing a lithium transition metal oxide on the positive electrode current collector An electrode body formed by spirally winding a laminate including a positive electrode formed on the electrode and a separator disposed between the negative electrode and the positive electrode, and the electrode body is impregnated with a non-aqueous electrolyte. In a lithium secondary battery housed in a cylindrical battery container
Two current collecting tabs are disposed at an interval of at least 1/4 or more of the total length of the positive electrode between the inner peripheral side end in the spiral direction of the positive electrode and a position of 2/3 of the total length of the positive electrode, The lithium secondary battery in which one current collection tab is arrange | positioned only at the outer peripheral side edge part in the spiral direction.
  The distance between the current collecting tab located on the innermost circumferential side and the current collecting tab located on the outermost circumferential side in the spiral direction in the positive electrode is 1/3 to 1/2 of the total length in the spiral direction of the positive electrode. 2. The lithium secondary battery according to 1.   The lithium secondary battery according to claim 1 or 2, wherein the negative electrode active material layer contains silicon and / or a silicon alloy. A negative electrode in which a negative electrode active material layer containing an element having a volume expansion coefficient of 1.9 times or more upon charging is formed on the negative electrode current collector, and a positive electrode active material layer containing a lithium transition metal oxide on the positive electrode current collector An electrode body formed by spirally winding a laminate including a positive electrode formed on the electrode and a separator disposed between the negative electrode and the positive electrode, and the electrode body is impregnated with a non-aqueous electrolyte. In a lithium secondary battery housed in a cylindrical battery container
Two current collecting tabs are disposed at an interval of at least 1/4 or more of the total length of the positive electrode from the outer peripheral side end in the spiral direction of the positive electrode to a position of 2/3 of the total length of the positive electrode. A lithium secondary battery in which one current collecting tab is arranged only at an inner peripheral side end in a spiral direction.
  The distance between the current collecting tab located on the innermost circumferential side and the current collecting tab located on the outermost circumferential side in the spiral direction in the positive electrode is 1/3 to 1/2 of the total length in the spiral direction of the positive electrode. 4. The lithium secondary battery according to 4.   The lithium secondary battery according to claim 4 or 5, wherein the negative electrode active material layer contains silicon and / or a silicon alloy.

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