JP3412473B2 - Non-aqueous electrolyte battery using thin electrodes - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery using thin electrodes.

[0002]

2. Description of the Related Art Currently, lithium primary batteries, lithium secondary batteries and the like are put into practical use as non-aqueous electrolyte batteries. Among these batteries, a lithium secondary battery generally uses a metal thin film as a current collector. The non-aqueous electrolyte has a lower ionic conductivity than that of an aqueous solution. Therefore, it is necessary to increase the contact area with the electrolytic solution by thinning the electrode itself, and a thin metal thin film has been generally used as the collector of the electrode.

[0003]

However, since the cross-sectional area of the metal thin film as the current collector becomes thinner as the current collector becomes thinner, the current collection efficiency of the electrode is lowered and the battery capacity at the time of high rate charge / discharge is reduced. It tended to become smaller. On the other hand, as the thickness of the current collector is increased, the current collection efficiency of the electrode is improved, but the volume of the current collector occupied in the electrode is increased and the battery capacity per unit volume is decreased. Further, since the weight of the battery material other than the active material is increased, the battery capacity in a constant weight is also reduced. The problem to be solved by the present invention is to improve high rate discharge characteristics of a non-aqueous electrolyte battery using a thin electrode made of an active material arranged on the surface of a two-dimensional current collector made of a metal thin film.

[0004]

In order to solve the above-mentioned problems, a thin electrode made of an active material disposed on the surface of the two-dimensional current collector of the present invention and a non-aqueous electrolyte containing an alkali metal ion are used. In the water electrolyte battery, the electrode is a positive electrode and / or a negative electrode, and a portion where an active material is arranged and a portion where an active material is not present are present on the surface of the current collector, and a portion where the active material is not arranged is present. The tab terminal led out or connected from is directly or indirectly connected to the battery external terminal, and the current collector thickness t1 of the portion where the active material is arranged is the current collector thickness of the portion where the active material is not arranged. It is characterized by being thinner than t2. The part where the active material of the current collector is not arranged is generally the part where the tab terminals are connected to the outside of the battery and where power concentration occurs. By lowering the electric resistance (that is, t2> t1), the current collection efficiency of the electrodes can be improved. In addition, a mechanical load is applied to the tab terminal when the tab terminal is handled in the manufacture of a battery, and thus the current collector or the tab terminal may be torn. Further, there is a possibility that the current collecting property of the electrode may be deteriorated due to that. Such a problem is particularly remarkable in the case of an electrode in which a tab terminal member is connected to a portion of the current collector where the active material is not arranged by means such as welding. The reason is that the portion of the current collector where the active material is not arranged becomes the tab terminal connecting portion, and the connecting operation there is essential. The connecting operation has a larger mechanical load on the tab terminal than the other tab terminal handling operations. Further, the contact between the tab terminal and the current collector at the welded portion may be insufficient. Therefore, the thickness of the current collector where the active material is not arranged is made thicker than the current collector where the active material is arranged (that is, t2>
By setting t1), the rigidity of the t2 portion is increased, and such a problem can be overcome.

The above-mentioned two-dimensional current collector is a conductive foil, film, plate or the like made of metal or the like. In addition, the above two-dimensional current collector,
A perforated plate or the like may be used. The thin electrode is a thin electrode using the two-dimensional current collector.

The thin electrode according to the present invention need not necessarily be applied to bipolar electrodes. Even if it is applied to an electrode of one polarity, the effect of improving the high rate discharge characteristics can be sufficiently obtained. That is, if either the positive electrode current collector or the negative electrode current collector uses the two-dimensional current collector according to the present invention, the other polarity current collector is a two-dimensional current collector such as a three-dimensional current collector. It may be other than. Generally, in a non-aqueous electrolyte battery, the positive electrode active material has poorer conductivity than the negative electrode active material. Therefore, if the configuration of the present invention is applied to only one polarity electrode, it is preferably applied to the positive electrode. Needless to say, it is most preferable to apply the configuration of the present invention to bipolar electrodes as in this example. In addition, the part of the current collector where the active material is not arranged is
It is preferable that the electrode exists over the entire end portion in the width direction or the length direction of the electrode from the viewpoint of simplifying the electrode manufacturing process, but is not particularly limited.

Further, the tab terminal may be derived from the current collector, that is, a part of the current collector member may be cut out into a tab terminal shape, or the tab terminal member may be provided at a portion where the active material of the current collector is not arranged. It may be connected by means such as welding. The tab terminal and the external current collecting terminal may be directly connected by means such as welding, or the tab terminal and the external current collecting terminal may be indirectly connected via a functional member such as a PTC element. It may be connected. As a method of making t2 thicker than t1, there is a method of ultrasonically bonding a metal foil to a part of the current collector whose entire surface is t1, or depositing the same kind of metal, and making that part t2.

In the present invention, in the case of a current collector in which the tab terminal member is connected to a portion of the current collector where the active material is not arranged by means such as welding, the tab terminal member itself is used for current collection. It is not defined as the part where the active material of the body is not arranged.

Further, it is preferable that t2 does not exceed the sum of t1 and the thickness of the active material, because the volumetric energy density of the battery does not decrease. Thus, when discussing that "t2 does not exceed the sum of t1 and the thickness of the active material", t2 is an electrode using a current collector in which a part of the current collector member is cut out into a tab terminal shape. In the case of, it is expressed as it is as t2. Further, in the case of an electrode using a current collector in which a tab terminal member is connected to a portion (surface) where the active material of the current collector is not disposed by means such as welding, the active material of the current collector is not distributed. The thickness of the portion that is not formed is expressed as t2 ′ below as the sum of t2 and the thickness of the tab terminal member.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below by taking a so-called lithium ion secondary battery as an example of the non-aqueous electrolyte battery of the present invention. FIG. 1 shows a cross section and a plan view of an example of a negative electrode for a non-aqueous electrolyte battery according to the present invention. 1 is t1
= 10 μm of a copper negative electrode current collector, and 30 μm of copper foil 2 is ultrasonically bonded to both surfaces of a portion where the active material is not arranged, thereby forming a negative electrode current collector with a thickness of 90 μm at t2. . Reference numeral 3 denotes an active material mixture, which is a mixture of a carbon material and polyvinylidene fluoride as a binder, and is applied to both surfaces of the negative electrode current collector 1 at 70 μm each. Reference numeral 4 is a copper tab terminal (thickness: 80 μm) ultrasonically bonded to the copper foil 2.

Similarly, FIG. 2 shows a cross section and a plan view of an example of the positive electrode for a non-aqueous electrolyte battery according to the present invention. 5 is the thickness t1
= 20 μm of the positive electrode current collector, and the aluminum foil 6 of 20 μm is ultrasonically bonded to both surfaces of the portion where the active material is not arranged, thereby forming a positive electrode current collector of t2 having a thickness of 60 μm. 7 is an active material mixture which is a mixture of LiMn ₂ O ₄ , a carbon material as a conductive agent, and polyvinylidene fluoride as a binder, and 85 μm each on one side of the positive electrode current collector 5,
It is coated on both sides. 8 is a tab terminal (thickness 100 μm) made of aluminum, which is ultrasonically bonded to the aluminum foil 6.

The positive electrode and the negative electrode were wound around a separator having a thickness of 25 μm to produce a spiral electrode group. After this electrode group was inserted into a metal 18650 type battery container, the negative electrode tab terminal 4 was welded to the battery container, and the positive electrode tab terminal 8 was welded to the positive electrode external terminal which also functions as a battery lid. As the electrolytic solution, LiPF ₆ (solute) was dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate, and the solution was injected into the battery container. After injecting the electrolytic solution, the battery container was sealed with the battery lid.

Although a lithium ion secondary battery is targeted in this example, the battery system is not particularly limited. When a lithium ion secondary battery is targeted as in this example, the positive electrode active material and the negative electrode active material can be changed as appropriate. As the positive electrode active material, it is possible to use an intercalation compound such as lithium cobalt oxide or lithium nickel oxide, or a partial replacement material with other elements of these active material elements. As the negative electrode active material, besides the carbon material (including graphite), a metal chalcogenide capable of electrochemically inserting and removing lithium can be used. However, when the positive electrode active material of the non-aqueous electrolyte battery is lithium manganate (including partially substituted material by other element) which is lower in cost than lithium cobalt oxide as in this example, or when it is included, the present invention is particularly It is thought to exert its effect. The reason is that lithium manganate generally has lower electron conductivity than lithium cobalt oxide, lithium nickel oxide, and the like, and is expected to improve the conductivity of an electrode including the lithium manganate. Further, as the material of the current collector, the material of the current collector tab, and the material of the material to be placed in the portion where the active material of the current collector is not arranged, those other than those used in this example can be appropriately used. Also, t2> t
Other than this example, the means for setting 1 may be etching of the t1 portion, mechanical grinding, electrodeposition of the same metal on the t2 portion, and the like. If t1 etching or mechanical grinding (sandblasting) is used, the t1 surface will be roughened,
It is considered that the adhesion between the current collector / active material is improved and the high rate discharge performance of the battery is further improved. In addition, t of the current collector
A means for directly or indirectly rolling one portion is also conceivable. Further, in this example, the configuration of t2> t1 is applied to the bipolar electrodes, but t2> t1 is applied only to one polar electrode.
The high rate discharge characteristics are improved even if the configuration of (3) is applied. In this example, the tab terminal is a member different from the current collector, but the tab terminal may be derived from the current collector, that is, a part of the current collector member may be cut into a tab terminal shape. Further, in this example, the tab terminal and the external current collecting terminal are directly connected, but the tab terminal and the external current collecting terminal are indirectly connected via a functional member such as a PTC element. Is also good.

As in this example, the sum of t2 and the tab terminal thickness (t2 ') is preferably less than or equal to the thickness of the electrode on which the active material is arranged. The reason is that, when a battery is formed by an electrode group in which electrodes are laminated or wound, a portion corresponding to t2 ′ may change the shape of the electrode group. When the shape of the electrode group changes, the battery fabrication (particularly the step of inserting the electrode group into the battery container) becomes difficult, and the distance between the electrodes in the battery is locally increased to increase the internal resistance of the battery. May reduce the energy density per unit volume and create a detrimental factor. Of course, when the tab terminal is led out from the current collector, that is, when an electrode in which a part of the current collector member is cut out into a tab terminal shape is used, t2
Is preferably not more than the thickness of the electrode on which the active material is arranged.

[0015]

[Examples] Lithium ion secondary batteries of Examples 1 to 3 and a conventional example were prepared under the following conditions and comparatively examined. (Production of Battery of Example 1) The battery was produced under the conditions described in the embodiment of the invention.

Positive electrode: t1 = 20 μm, t2 = 60 μm, t2 ′ = 160 μm Sum of active material thickness and t1 = 190 μm Negative electrode: t1 = 10 μm, t2 = 70 μm, t2 ′ = 150 μm Sum of active material thickness and t = 150 μm ( Preparation of Battery of Example 2) A battery of Example 1 was prepared except that the copper foil 6 had a thickness of 20 μm.

Positive electrode: t1 = 20 μm, t2 = 60 μm, t2 ′ = 160 μm Sum of active material thickness and t1 = 190 μm Negative electrode: t1 = 10 μm, t2 = 50 μm, t2 ′ = 130 μm Sum of active material thickness and t = 150 μm ( Preparation of Battery of Example 3) A battery of Example 1 was prepared except that the copper foil 2 had a thickness of 40 μm.

Positive electrode: t1 = 20 μm, t2 = 60 μm, t2 ′ = 160 μm Sum of active material thickness and t1 = 190 μm Negative electrode: t1 = 10 μm, t2 = 90 μm, t2 ′ = 170 μm Active material thickness and t1 sum = 150 μm ( Preparation of Battery of Conventional Example) A battery was prepared under the same conditions as the battery of Example 1 except that the copper foil 2 and the aluminum foil 6 were not provided.

Positive electrode: t1 = 20 μm, t2 = 20 μm Negative electrode: t1 = 10 μm, t2 = 10 μm The discharge capacities of the batteries of Examples 1 to 3 and the conventional example were measured by changing the discharge rate. The result is shown in FIG.

From FIG. 3, the batteries of Examples 1 to 3 and the battery of the conventional example showed no difference in discharge capacity under the condition of small discharge rate, but the batteries of Examples 1 to 3 at discharge rates of 1 CmA or more. However, the capacity was obviously higher than that of the conventional battery. The larger the discharge rate of the batteries of Examples 1 to 3, the larger the difference in discharge capacity from the batteries of the conventional example. Therefore, the thickness t2 of the positive electrode current collector or the negative electrode current collector where the active material mixture is not applied is made thicker than the current collector thickness t1 where the active material mixture is applied. From this, it is understood that the high-rate discharge characteristics could be improved by reducing the electric resistance. Further, comparing the battery of Example 3 with the battery of the conventional example in FIG. 3, it can be seen that the battery of the conventional example has a larger discharge capacity than the battery of Example 3 at a discharge rate of less than 0.5 CmA. This is because the negative electrode t2 of the battery of Example 3 was
It is considered that, since the sum of t1 and the thickness of the active material was exceeded, the shape of the wound electrode group was slightly deformed, the distance between the electrodes in the battery was locally widened, and the internal resistance of the battery was slightly large. However, at a discharge rate of 1 CmA or more, the battery of Example 3 had a higher capacity than the battery of the conventional example. This is considered to be because under such a high discharge rate condition, the difference in discharge capacity due to the current collection efficiency of the current collector is larger than the difference in discharge capacity due to the slight difference in battery internal resistance.

The batteries of Examples 1 to 3 are t2 of the negative electrode current collector.
However, even when only t2 of the positive electrode current collector was similarly changed, the same tendency as the difference in discharge capacity of the batteries of Examples 1 to 3 shown in FIG. 3 was observed.

[0022]

According to the present invention, in a non-aqueous electrolyte battery having a thin electrode made of an active material disposed on the surface of a two-dimensional current collector and a non-aqueous electrolyte containing alkali metal ions, a collector made of a metal thin film is used. The high rate discharge characteristics of the non-aqueous electrolyte battery using the electric body could be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view and a schematic plan view of a thin electrode (negative electrode) according to the present invention.

FIG. 2 is a schematic cross-sectional view and a schematic plan view of a thin electrode (positive electrode) according to the present invention.

FIG. 3 is a diagram showing changes in discharge capacity when the discharge rate of a non-aqueous electrolyte battery is changed.

[Explanation of symbols]

1. Negative electrode current collector 2. Copper foil 3. Negative electrode active material mixture 4. Copper tab terminal 5. Positive electrode collector 6. Aluminum foil 7. Positive electrode active material mixture 8. Aluminum tab terminal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01M 10/40 H01M 10/40 Z (56) Reference JP-A-1-265449 (JP, A) JP-A-10-3900 ( JP, A) JP 2001-176489 (JP, A) JP 59-98571 (JP, A) JP 9-161840 (JP, A) JP 7-254416 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/64 H01M 2/22 H01M 4/02 H01M 6/16 H01M 10/40

Claims (3)

(57) [Claims] 1. A non-aqueous electrolyte battery comprising a thin electrode made of an active material arranged on the surface of a two-dimensional current collector and a non-aqueous electrolyte containing an alkali metal ion, wherein the electrode is a positive electrode and / or a negative electrode. There is a portion where the active material is arranged and a portion where the active material is not arranged on the surface of the current collector, and the tab terminal derived or connected from the portion where the active material is not arranged is directly or indirectly. A thin electrode that is connected to an external terminal of a battery and has a current collector thickness t1 in a portion where the active material is arranged is thinner than a current collector thickness t2 in a portion where the active material is not arranged. Water electrolyte battery. 2. A non-aqueous electrolyte battery using a thin electrode according to claim 1, wherein t2 does not exceed the sum of t1 and the thickness of the active material. 3. A non-aqueous electrolyte battery using a thin electrode according to claim 1, wherein the electrode is a positive electrode and the positive electrode active material contains lithium manganate.