JP2012038539A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery which is capable of relaxing a stress due to expansion/contraction of an active material.SOLUTION: A battery includes an electrolyte layer and a pair of electrode layers which holds the electrolyte layer therebetween. At least one of the pair of electrode layers comprises a first portion containing a first active material and a second portion containing a second active material having an expansion/contraction characteristic different from that of the first active material. The first portion and the second portion are alternately provided.

Description

  The present invention relates to a battery having an active material.

  A lithium ion secondary battery has the characteristics that it has a higher energy density than other secondary batteries and can operate at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large motive power such as for electric vehicles and hybrid vehicles.

  A lithium ion secondary battery includes a positive electrode layer and a negative electrode layer (a pair of electrode layers) and an electrolyte disposed therebetween, and the electrolyte is composed of, for example, a non-aqueous liquid or solid. When a liquid (hereinafter referred to as “electrolytic solution”) is used as the electrolyte, the electrolytic solution easily penetrates into the positive electrode layer and the negative electrode layer. Therefore, an interface between the active material contained in the positive electrode layer or the negative electrode layer and the electrolytic solution is easily formed, and the performance is easily improved. However, since the widely used electrolyte is flammable, it is necessary to mount a system for ensuring safety. On the other hand, since the solid electrolyte (hereinafter referred to as “solid electrolyte”) is nonflammable, the above system can be simplified. Therefore, a lithium ion secondary battery (hereinafter referred to as “all-solid battery”) in a form provided with a layer containing a solid electrolyte that is nonflammable has been proposed.

  As a technology related to such a battery, for example, Patent Document 1 discloses an all-solid battery including a positive and negative electrode part containing an electrode active material, an electrolyte part made of a solid electrolyte, and a positive and negative electrode current collector. The positive or negative electrode part, or both positive and negative electrode parts, is formed by heating and firing a mixture of an electrode active material and a solid electrolyte in a pressurized state. An all solid state battery is disclosed.

JP 2009-224318 A

  The all-solid-state battery disclosed in Patent Document 1 has a mixture of an electrode active material and a solid electrolyte that are configured by heating and firing in a pressurized state. It is considered possible to reduce the resistance when moving at the interface between the electrode active material and the solid electrolyte. Here, in the battery including the active material capable of occluding and releasing ions, such as the all solid state battery disclosed in Patent Document 1, the active material expands and contracts as the ions are stored and released. When it expands and contracts, the structure of the electrode layer changes. If the structure of the electrode layer changes greatly, the performance of the battery tends to deteriorate. Therefore, in order to suppress the deterioration of the performance of the battery due to the structural change of the electrode layer, it is necessary to take measures against the expansion and contraction of the active material. However, in the all solid state battery disclosed in Patent Document 1, no measures are taken against the expansion and contraction of the active material. Therefore, when the expansion and contraction of the active material is repeated by repeating charge and discharge, there is a problem that the performance of the battery is likely to be deteriorated.

  Then, this invention makes it a subject to provide the battery which can suppress the performance fall resulting from the expansion / contraction of an active material.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention includes an electrolyte layer and a pair of electrode layers sandwiching the electrolyte layer, and at least one of the electrode layers has a first part containing a first active material and an expansion / contraction different from the first active material. A battery comprising: a second part containing a second active material having characteristics, wherein the first part and the second part are provided alternately.

  Here, “a pair of electrode layers” refers to a positive electrode layer and a negative electrode layer. The “first active material” and the “second active material” are materials that can be occluded and released as an active material in the electrode layer of the secondary battery. It refers to the characteristics of expansion and contraction associated with occlusion and release of ions moving between electrode layers.

  Moreover, in the said invention, it is preferable that the 1st part and the 2nd part are alternately provided in the electrode surface.

  Here, the “electrode surface” refers to a surface of the electrode layer whose normal direction is a direction in which the electrolyte layer and the electrode layer are stacked (hereinafter referred to as “stacking direction”). Further, “the first part and the second part are alternately provided on the electrode surface” means that, for example, when a surface obtained by cutting the electrode layer at the electrode surface is confirmed, the adjacent first part (or second part) The first part and the second part are alternately arranged so that the second part (or the first part) is disposed between the first part and the second part. When the positive electrode layer has the first part and the second part, the first part and the second part are alternately provided on the electrode surface of the positive electrode layer, and when the negative electrode layer has the first part and the second part. The first part and the second part are alternately provided on the electrode surface of the negative electrode layer.

  Moreover, in the said invention, it is preferable that the shape of a 1st part or a 2nd part is a column shape.

  Here, the “cylindrical shape” refers to a cylindrical shape whose axial direction is the stacking direction. When the first part is cylindrical, the electrode layer having the first part and the second part is configured by filling the space around the plurality of first parts (columnar shape) with the second part. . Similarly, when the second part is cylindrical, the electrode layer having the first part and the second part is configured by filling the space around the plurality of second parts (columnar) with the first part. The

In the present invention, the first active material is preferably Li ₄ Ti ₅ O ₁₂ .

In the present invention in which the first active material is Li ₄ Ti ₅ O ₁₂ , the second active material is preferably LiCoO ₂ .

  In the battery of the present invention, the electrode layer contains the first active material and the second active material that have different expansion and contraction characteristics due to occlusion and release of ions. The second parts having substances are alternately provided. By adopting such a configuration, the change in the electrode layer due to the expansion or contraction of one of the first active material and the second active material can be suppressed by the portion containing the other active material having different expansion / contraction characteristics. Therefore, the structural change of the electrode layer due to the expansion and contraction of the active material can be suppressed. Therefore, according to this invention, the battery which can suppress the performance fall resulting from the expansion / contraction of an active material can be provided.

  Moreover, in this invention, it becomes easy to suppress the performance fall resulting from the expansion / contraction of an active material because the 1st part and the 2nd part are alternately provided in the electrode surface.

  Moreover, in this invention, when the shape of a 1st part or a 2nd part is a column shape, it becomes easy to suppress the structural change of the electrode layer resulting from the expansion / contraction of an active material.

In the present invention, by first active material is _Li 4 _Ti 5 _{O 12,} at a low SOC (low state of _charge), by Li ₄ Ti _{5 O 12,} it is possible to cause occlusion of lithium ions . Among Li ₄ Ti ₅ O ₁₂ , especially Li ₄ Ti ₅ O _{12 that} has been introduced with oxygen deficiency and nitrogen substitution has good conductivity. By adopting such a configuration, in addition to the above effects, at the time of low SOC A battery capable of exhibiting high input / output characteristics can be provided.

Further, in the present invention in which the first active material is Li ₄ Ti ₅ O ₁₂ , when the second active material is LiCoO _2, it is possible to cause occlusion and release of lithium ions with LiCoO ₂ at high SOC. . Therefore, by adopting such a configuration, it is possible to provide a battery that can suppress performance degradation due to expansion and contraction of the active material not only at low SOC but also at high SOC.

It is sectional drawing explaining the battery 10 of this invention. It is another sectional view explaining battery 10 of the present invention. It is a figure explaining the charge condition (SOC) of the battery of this invention.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below. In the drawings, some reference numerals may be omitted.

  FIG. 1 is a cross-sectional view illustrating a battery 10 of the present invention. 2A is a cross-sectional view taken along the line IIA-IIA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. 1 is the stacking direction, and the back / front direction of FIGS. 2A and 2B is the stacking direction. As shown in FIG. 1, the battery 10 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 sandwiched between the positive electrode layer 1 and the negative electrode layer 2, and a positive electrode current collector 4 connected to the positive electrode layer 1. And a negative electrode current collector 5 connected to the negative electrode layer 2. A positive electrode lead (not shown) is connected to the positive electrode current collector 4, a negative electrode lead (not shown) is connected to the negative electrode current collector 5, and each component shown in FIG. Used in a state of being accommodated in (not shown).

As shown in FIGS. 1 and 2A, the positive electrode layer 1 has a first part 1a and second parts 1b, 1b,..., And the first part 1a and second parts 1b, 1b,. Are alternately provided on the electrode surface of the positive electrode layer 1. The shape of the second parts 1b, 1b,... Is a cylindrical shape whose axial direction is the stacking direction, and the first part 1a is filled around the second parts 1b, 1b,. The active material (LiCoO ₂ ) contained in the first part 1a and the active material contained in the second parts 1b, 1b,... (Li ₄ Ti ₅ O ₁₂ subjected to oxygen defect and nitrogen substitution introduction. in simply and may be referred to as "Li ₄ Ti ₅ O _12.") is different from the characteristics of expansion and contraction caused by the occlusion and release of ions, storage and release the row of lithium ions at lower potential side than LiCoO ₂ Li ₄ Ti ₅ O _{12 which} is easily broken has good electronic conductivity.

Moreover, as shown in FIG.1 and FIG.2 (b), the negative electrode layer 2 has 1st part 2a and 2nd part 2b, 2b, ..., 1st part 2a and 2nd part 2b, 2b. ,... Are alternately provided on the electrode surface of the negative electrode layer 2. The shape of the second parts 2b, 2b,... Is a cylindrical shape whose axial direction is the stacking direction, and the first part 2a is filled around the second parts 2b, 2b,. The active material (Nb ₂ O ₅ ) contained in the first part 2a and the active material contained in the second parts 2b, 2b,... (Li ₄ Ti ₅ O ₁₂ subjected to oxygen defect and nitrogen substitution introduction) ) And the characteristics of expansion and contraction associated with the occlusion and release of ions, and Nb ₂ O _{5, which} is more likely to occlude and release lithium ions on the higher potential side than Li ₄ Ti ₅ O ₁₂ , has good electron conduction. It has sex.

FIG. 3 is a diagram for explaining the state of charge (SOC) of the battery 10 of the present invention. The vertical axis of FIG. 3 is voltage [V], and the horizontal axis is SOC. The higher the SOC is on the left side of FIG. 3, the lower the SOC is on the right side of FIG. A region surrounded by an alternate long and short dash line in FIG. 3 is an example of a high SOC, and a region surrounded by a dotted line in FIG. 3 is an example of a low SOC. As shown in FIG. 3, the voltage of the battery 10 is high when the SOC is high, and the voltage of the battery 10 is low when the SOC is low. Here, in the positive electrode layer 1, lithium ions are easily occluded and released by LiCoO ₂ when the SOC is high, and lithium ions are easily occluded and released by Li ₄ Ti ₅ O ₁₂ when the SOC is low. When in LiCoO ₂ is occlusion and release of lithium ions are easy to high SOC carried _out, since the Li ₄ Ti _{5 O 12} in occlusion and release of lithium ions is not easily performed due to the expansion and contraction of the first part 1a containing LiCoO ₂ the deformation of the positive electrode layer 1, second part 1b containing a high SOC during expansion and shrinkage hardly _{Li 4 Ti 5 O 12, 1b} , by ..., can be suppressed. _Further, when the Li ₄ Ti _{5 O 12} occlusion and release of lithium ions is carried out in an easy low SOC, because storage and release of lithium in the LiCoO ₂ ions is not easily _performed, Part 2 1b containing of Li ₄ Ti _{5 O 12} The deformation of the positive electrode layer 1 due to the expansion and contraction of 1b,... Can be suppressed by the first part 1a containing LiCoO ₂ that is difficult to expand and contract at low SOC. As described above, according to the positive electrode layer 1, since deformation due to expansion and contraction of the active material can be suppressed even at low SOC and high SOC, it is possible to suppress deterioration due to expansion and contraction of the active material. it can.

Further, in the negative electrode layer 2, lithium ions are easily occluded and released by Nb ₂ O ₅ when the SOC is high, and lithium ions are easily occluded and released by Li ₄ Ti ₅ O ₁₂ when the SOC is low. When the high SOC to occlusion and release of lithium ions is easily performed by Nb ₂ O _5, since Li ₄ Ti ₅ hardly _{O 12} in occlusion and release of lithium ions is performed, the expansion of the first part 2a containing _Nb 2 _{O 5} The deformation of the negative electrode layer 2 due to the shrinkage can be suppressed by the second parts 2b, 2b,... Containing Li ₄ Ti ₅ O ₁₂ that are difficult to expand and shrink at high SOC. In addition, when the SOC is low, in which Li ₄ Ti ₅ O ₁₂ is liable to occlude and release lithium ions, in Nb ₂ O ₅ , it is difficult to occlude and release lithium ions. Therefore, the second containing Li ₄ Ti ₅ O ₁₂ The deformation of the negative electrode layer 2 due to the expansion and contraction of the parts 2b, 2b,... Can be suppressed by the first part 2a containing Nb ₂ O ₅ that is difficult to expand and contract at low SOC. As described above, according to the negative electrode layer 2, it is possible to suppress deformation accompanying expansion and contraction of the active material even at low SOC and high SOC. it can. Therefore, according to the battery 10 having the positive electrode layer 1 and the negative electrode layer 2, it is possible to suppress deterioration associated with expansion and contraction of the active material both at low SOC and at high SOC.

Further, Li ₄ Ti ₅ O _{12 which} is contained in the second parts 1b, 1b,... Of the positive electrode layer 1 and is liable to occlude / release lithium ions at low SOC has good electronic conductivity. Yes. Therefore, the battery 10 can exhibit high input / output characteristics even at low SOC. Further, Nb ₂ O _{5 which} is contained in the first part 2a of the negative electrode layer 2 and is liable to occlude and release lithium ions at high SOC has a good electron conductivity. Therefore, the battery 10 can exhibit high input / output characteristics even at high SOC. Therefore, according to the present invention, it is possible to provide the battery 10 that exhibits high input / output characteristics at low SOC and high SOC. In the past, in order to improve the input / output characteristics, a technique for mixing a conductive aid into the electrode layer has been developed. However, if a large amount of a conductive aid that does not contribute to the occlusion and release of ions is mixed into the electrode layer. The energy density of the battery tends to decrease. On the other hand, in the battery 10, input / output characteristics are improved by mixing an active material having good electronic conductivity with the electrode layer. Therefore, according to the present invention, the energy density of the battery 10 can be increased.

The 1st part 1a was produced by putting the mixture mix | blended so that it might become active material: solid electrolyte: binder = 50-75: 45-20: 5 by mass ratio in a solvent, for example. The composition is prepared by applying the composition to the surface of the positive electrode current collector 4 where the first part 1a is to be formed by a known method and drying the composition. As the solid electrolyte contained in the first part 1a, for example, Li ₂ S and P ₂ S ₅ are mixed so that the mass ratio is Li ₂ S: P ₂ S ₅ = 50: 50 to 100: 0. The sulfide solid electrolyte produced by the above (for example, the sulfide solid electrolyte produced by mixing Li ₂ S and P ₂ S ₅ so that the mass ratio is Li ₂ S: P ₂ S ₅ = 70: 30), etc. Can be used. As the binder, for example, polyvinylidene fluoride (PVDF) can be used. The width of the first part 1a (the length in the horizontal direction in FIG. 2A) and the depth (the length in the vertical direction in FIG. 2A) can be set to 50 mm, for example. The thickness of the portion 1a (the length in the vertical direction in FIG. 1) can be set to 30 μm, for example.

  The second parts 1b, 1b,... Are, for example, mixed in a solvent by mixing a mixture in which mass ratio is active material: solid electrolyte: binder = 50 to 75:45 to 20: 5 The composition prepared in this manner is applied by a known method on the surface of the positive electrode current collector 4 on which the second parts 1b, 1b,... Are to be formed, and dried. The second parts 1b, 1b,... Can contain the same solid electrolyte as that of the first part 1a, and the same binder as that of the first part 1a can be used. The thickness (the length in the vertical direction of FIG. 1) of the second parts 1b, 1b,... Can be set to 30 μm, for example.

The first part 2a can be produced by the same method as the first part 1a except that Nb ₂ O ₅ is used as the active material and is produced on the surface of the negative electrode current collector 5, and the first part 2a is larger than the first part 2a. The sheath thickness can be the same as that of the first part 1a. The second part 2b, 2b, ... uses the _Li 4 _Ti 5 _{O 12} as the active material, except for making the surface of the negative electrode current collector 5, Part 2 1b, 1b, ... in the same manner as The diameter and thickness of the 2nd part 2b can be made the same as that of the 2nd part 1b.

  The electrolyte layer 3 includes, for example, the positive electrode layer 1 including the first part 1a and the second parts 1b, 1b,... Produced by the above method, or the first part 2a and the second part 2b produced by the above method. A composition prepared by blending the surface of the negative electrode layer 2 with 2b,... In a mass ratio such that solid electrolyte: binder = 99: 1 and mixing the mixture in a solvent is known. It is produced by applying and drying by a method. As the solid electrolyte contained in the electrolyte layer 3, for example, the same solid electrolyte as that contained in the positive electrode layer 1 or the negative electrode layer 2 can be used, and as the binder, for example, the positive electrode layer 1 or the negative electrode layer can be used. The same binder as used for 2 can be used. The thickness of the electrolyte layer 3 can be set to 20 μm, for example.

  The positive electrode current collector 4 can be made of, for example, nickel, copper, aluminum, platinum, platinum-palladium, gold, silver, ITO (indium-tin oxide), or the like. Similarly to the positive electrode current collector 4, the negative electrode current collector 5 can be made of, for example, nickel, copper, aluminum, platinum, platinum-palladium, gold, silver, ITO (indium-tin oxide), or the like. it can.

  In the above description of the present invention, the case where a sulfide solid electrolyte is used as the solid electrolyte is exemplified, but the present invention is not limited to the embodiment. In the present invention, a known solid electrolyte that can be used in a battery can be appropriately used.

  Moreover, in the said description regarding this invention, although the form in which the electrolyte layer 3 containing a solid electrolyte was arrange | positioned between the positive electrode layer 1 and the negative electrode layer 2, this invention is limited to the said form. is not. In the present invention, an electrolyte layer constituted by holding a known electrolyte solution in a known separator as necessary may be sandwiched between a positive electrode layer and a negative electrode layer.

In the above description regarding the present invention, the active material contained in the first part 2a is Nb ₂ O ₅ , and the active material contained in the second parts 2b, 2b,. It was exemplified by the Li ₄ Ti ₅ O ₁₂ in which the form, the present invention is not limited to this embodiment. In the battery of the present invention, Li ₄ Ti ₅ O ₁₂ that has no oxygen defects and no introduction of nitrogen substitution is used as the active material contained in the first part 2a, and contained in the second parts 2b, 2b,. As the active material, Li ₄ Ti ₅ O ₁₂ into which oxygen defects and nitrogen substitution are introduced may be used.

  Moreover, in the said description regarding this invention, the positive electrode layer 1 provided with 1st part 1a and 2nd part 1b, 1b, ... and the negative electrode layer 2 provided with 1st part 2a and 2nd part 2b, 2b, ... are provided. However, the present invention is not limited to the embodiment. The battery of the present invention may include a positive electrode layer having a first part and a second part, and a negative electrode layer that is not provided with a countermeasure against deformation due to expansion and contraction of the active material. It is. As an example of such a form, when the active material contained in a negative electrode layer is made into one type (for example, when a negative electrode layer is comprised with carbon materials, such as graphite), etc. can be mentioned. In addition, the battery of the present invention is provided with a negative electrode layer having a first part and a second part, while being provided with a positive electrode layer in which measures against deformation caused by expansion and contraction of the active material are not provided. It is also possible. However, from the viewpoint of making the battery easy to suppress the deterioration of the battery, it is preferable that the positive electrode layer having the first part and the second part and the negative electrode layer are provided. Furthermore, from the standpoint of providing a battery in a form in which the deformation due to expansion and contraction of the active material is suppressed and deterioration is easily suppressed, either one of the first part and the second part may be amorphous or polymer. It is preferable that the active material is contained.

  Further, in the above description regarding the present invention, the mode in which the second parts 1b, 1b,... Including the active material that easily absorbs and releases lithium ions at low SOC and has good electron conductivity is illustrated. The present invention is not limited to this form. However, from the viewpoint of providing a battery exhibiting high input / output characteristics at low SOC, etc., when the positive electrode layer having the first part and the second part is provided, occlusion / release of lithium ions at low SOC is performed. It is preferable that the positive electrode layer contains an active material that is easily formed and has good electron conductivity. Further, in the above description of the present invention, an example in which the first part 2a is provided, which includes an active material that easily absorbs and releases lithium ions at high SOC and has good electronic conductivity, is provided. It is not limited to the said form. However, from the viewpoint of providing a battery exhibiting high input / output characteristics at high SOC, etc., when the negative electrode layer having the first part and the second part is provided, occlusion / release of lithium ions at high SOC is performed. It is preferable that the negative electrode layer contains an active material that is easily formed and has good electronic conductivity.

  In the above description regarding the present invention, a battery in which two types of active materials are contained in the positive electrode layer and the negative electrode layer has been mentioned, but the present invention is not limited to this form. The battery of the present invention can also have a form in which three or more types of active materials having different expansion and contraction characteristics are contained in the positive electrode layer and the negative electrode layer.

  Moreover, in the said description regarding this invention, although the battery of the form from which lithium ion moves between a pair of electrode layers was illustrated, this invention is not limited to the said form. The battery of the present invention can be a battery in which other ions such as sodium ions move between a pair of electrode layers.

  The battery of the present invention can be used for electric vehicles and hybrid vehicles.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode layer 1a ... 1st part 1b ... 2nd part 2 ... Negative electrode layer 2a ... 1st part 2b ... 2nd part 3 ... Electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 10 ... Battery

Claims (5)

An electrolyte layer, and a pair of electrode layers sandwiching the electrolyte layer,
At least one of the electrode layers has a first part containing a first active material, and a second part containing a second active material having an expansion / contraction characteristic different from that of the first active material, 1 part and said 2nd part are provided alternately, The battery characterized by the above-mentioned. The battery according to claim 1, wherein the first part and the second part are alternately provided on the electrode surface. The battery according to claim 1 or 2, wherein a shape of the first part or the second part is a columnar shape. The battery according to claim 1, wherein the first active material is Li ₄ Ti ₅ O ₁₂ . The battery according to claim 4, wherein the second active material is LiCoO ₂ .