JP5497538B2 - Solid type secondary battery - Google Patents

Description

  The present invention relates to a solid state secondary battery using a solid electrolyte, and particularly to an all solid state lithium secondary battery.

  In recent years, the use of lithium secondary batteries having a high energy density has been rapidly increased in response to increasing demand for portable electronic devices to increase power consumption and reduce size and weight. In these small devices, there is a strong need for miniaturization and weight reduction, so there is a strong demand to reduce the space for mounting the batteries necessary to drive the device, and a slight gap between the electronic components inside the device and the housing. Therefore, thin and flexible secondary batteries with a higher degree of freedom in storage space than conventional cylindrical and button type batteries will be used in the future. It is done.

  As a conventional thin battery, a battery in which the thickness of the battery is suppressed by changing the exterior from a conventional metal can to a laminate pack is known. However, the laminate pack alone has a thickness of about 0.2 to 0.3 mm, and when combined with the internal electrode material and the like, the thickness exceeds 0.3 mm, and the flexibility of the battery cannot be expected so much. Furthermore, an electrolyte containing an organic solvent is enclosed in the laminate pack as in the conventional battery, and the electrolyte solution may evaporate from a slight gap or scratch in the laminate pack, possibly shortening the battery life. In particular, when the battery is downsized, it is necessary to reduce the area of the fused part of the laminate pack, and the electrolyte solution is likely to evaporate.

  In order to solve such a problem, by using a solid electrolyte that does not contain an organic electrolyte, forming a solid electrolyte thin film on the electrode thin film, and further forming another electrode thin film thereon, The development of all-solid-state thin-film batteries that do not use laminate packs or organic electrolytes is underway. For example, Patent Document 1 discloses a technique for forming a positive electrode thin film having good crystallinity at high speed without the need for heat treatment by sputtering using electron cyclotron resonance plasma.

JP 2007-5219 A

  However, lithium metal (Li), which is often used as the negative electrode for all-solid-state lithium secondary batteries, and Li3-xPO4-yNy (LiPON), which is a solid electrolyte, are substances with extremely high reactivity with moisture. Even a slight amount of moisture inside can cause rapid battery deterioration. For this reason, it is general that the surface of the all-solid-state thin film battery is entirely covered with a moisture-resistant protective film to prevent moisture from entering.

  However, even if the moisture-resistant protective film has a sufficiently low water vapor permeability, if any defects such as pinholes are present in the protective film, moisture entering from the lithium metal thin film or LiPON thin film along the thin film. It penetrates widely throughout and degrades the battery. Since the probability that such a defect exists in the moisture-resistant protective film increases as the battery area increases, it has become a major factor that makes it difficult to increase the area of the all-solid-state lithium secondary battery.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to increase the area of a solid-state secondary battery while maintaining battery life and reliability.

A solid state secondary battery according to the present invention includes a first current collector thin film formed in contact with an upper surface of a substrate, and an upper surface of the first current collector thin film, and insertion and release of lithium ions. Alternatively, the first electrode thin film that can be deposited and dissolved, the solid electrolyte thin film that is formed in contact with the upper surface of the first electrode thin film and that conducts lithium ions, and the upper surface of the solid electrolyte thin film are in contact with the first thin film. A second electrode thin film formed of a material different from that of the first electrode thin film and capable of inserting and releasing lithium ions, or precipitation and dissolution; the first electrode thin film; the solid electrolyte thin film; and the second electrode. A first partition that divides the thin film into a plurality of regions and that does not divide the first current collector thin film, and a second partition that is disposed on the outer periphery of the plurality of regions divided by the first partition. And divided by the first partition Is integrally formed in contact a plurality of said second upper surface of the electrode film in the region on the upper surface of the first and second partition wall, and a second current-collecting thin film whose surface is flat A moisture-resistant protective film integrally formed on and in contact with the upper surface of the second current collector thin film excluding only a part of the second partition, and the first and second partitions Is characterized by being formed of a ceramic material that does not transmit water vapor.

In the solid-state secondary battery according to the present invention, the first partition may be formed by dividing the first electrode thin film, the solid electrolyte thin film, and the second electrode thin film into six or more regions. The first electrode thin film, the solid electrolyte thin film, and the second electrode thin film in the region each operate as a solid secondary battery.

  According to the solid state secondary battery disclosed in the present application, there is an effect that the area of the solid state secondary battery can be increased while maintaining the battery life and reliability.

FIG. 1 is an explanatory diagram of the manufacturing process of the all solid-state lithium secondary battery according to the example. FIG. 2 is an external perspective view of the all solid-state lithium secondary battery according to this example. FIG. 3 is an explanatory diagram of the manufacturing process of the all solid-state lithium secondary battery according to the comparative example. FIG. 4 is a diagram illustrating a distribution state of discharge capacity values of the example and the comparative example.

  Embodiments of a solid-state secondary battery according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is an explanatory diagram of the manufacturing process of the all solid-state lithium secondary battery according to the present embodiment. FIG. 2 is an external perspective view of the all solid-state lithium secondary battery according to this example. As shown in FIGS. 1 and 2, the all-solid-state lithium secondary battery according to the present embodiment produces a first electrode thin film 4 capable of inserting and releasing lithium ions or depositing and dissolving on a substrate 1. A solid electrolyte thin film 5 that conducts lithium ions is formed thereon, and a lithium ion can be inserted and released or deposited and dissolved thereon by a material different from that of the first electrode thin film. In the all-solid-state lithium secondary battery formed by forming the electrode thin film 6, a plurality of all-solid-type lithium secondary batteries are divided and formed on one substrate, and the divided all-solid-type lithium A partition wall 3 is formed between the secondary batteries, and all the divided solid state lithium secondary batteries and the partition walls are covered with a moisture-resistant protective film 8 formed integrally.

  Moreover, the all-solid-state lithium secondary battery according to the present embodiment is divided into at least six batteries. The partition walls that divide the all solid-state lithium secondary battery are preferably formed of a ceramic material that does not transmit water vapor.

  In addition, the all solid-state lithium secondary battery according to this example crosses over the partition wall 3 that divides all the individual secondary batteries on the upper surface of each divided all solid-state secondary battery, and all adjacent all A current collector thin film 7 that integrally covers the solid-type lithium secondary battery is formed.

  In the all solid-state lithium secondary battery according to the present embodiment, a plurality of all-solid lithium secondary batteries divided by the partition walls 3 are formed on a single substrate, whereby pinholes existing in the moisture-resistant protective film 8 are formed. Even when water vapor enters the inside of the battery due to a defect such as the above, water vapor does not enter the other part beyond the partition wall 3, and the deterioration of the battery can be suppressed locally.

  Since the probability of occurrence of defects in the moisture-resistant protective film 8 is roughly proportional to the battery area, it is difficult to form the moisture-resistant protective film 8 having no defects as the battery area increases. It has been difficult to ensure the durability and reliability of an all solid lithium secondary battery having an area. On the other hand, partition walls 3 are formed to divide the battery on a single substrate, so that pinholes are generated in the moisture-resistant protective film 8 and water vapor enters the battery and reacts with the LiPON electrolyte and Li negative electrode. However, since the diffusion of moisture in the in-plane direction of the battery is blocked by the partition wall 3, the deterioration of the battery is limited to only one divided battery part surrounded by the partition wall 3. Deterioration due to moisture entering from the hall does not spread. For this reason, it becomes possible to enlarge a battery area, ensuring the reliability of a battery.

  The technology according to the present embodiment demonstrates the effect of improving the durability and reliability of the battery regardless of the number of divisions of the battery. For example, in the state where the battery is divided into two, one of the divided batteries is completely When the battery deteriorates, the capacity of the battery as a whole is reduced by half. As a power source in an actual apparatus, a battery whose capacity is reduced to about 60 to 70% is usually treated as a deteriorated battery, and it is difficult to say that the durability of the battery is sufficiently improved in the battery divided into two. On the other hand, in the case of a 6-divided battery, even if one divided battery deteriorates due to pinholes, etc., the decrease in capacity is about 17%, and even if the remaining divided batteries generally decrease in capacity by about 20% due to normal deterioration, 66% This is a calculation in which a certain amount of capacity remains. Therefore, although the effects of the present invention are exhibited regardless of the number of divisions of the battery, from the viewpoint of improving the durability of the battery, it is desirable that it is divided into at least six divisions.

  In addition, as a material of the partition wall that divides the battery, it is necessary to have characteristics such as being an insulator, low reactivity with the electrode and the electrolyte thin film constituting the battery, and low affinity with moisture, Hydrophobic polymers and ceramics such as oxides and nitrides can be used. In particular, ceramic materials have low water vapor permeability compared to polymer materials, so that sufficient water vapor blocking properties can be obtained even if the partition wall thickness is reduced, and an increase in battery area due to partition wall formation can be suppressed, Because the heat resistance is high, there is no deformation or alteration due to substrate heating during battery fabrication or thermal radiation during film formation, and the degree of freedom in selecting a film formation method is high. Particularly preferred.

  Furthermore, as an all-solid battery dividing method, each divided battery may be manufactured in an independent state including the current collector, but with respect to the moisture-resistant protective film, moisture can enter from the side surface of the outer peripheral portion. Therefore, a shape in which all divided batteries are covered with a single continuous protective film is preferable to a shape in which each divided battery is covered with an independent moisture-resistant protective film.

  When forming such a continuous sheet of moisture-resistant protective film, if there is a step on the surface on which the film is formed, the moisture-resistant protective film has uneven film thickness, partial concentration of stress, etc. This is likely to occur, and there is a high possibility that defects such as cracks will occur in the protective film in that portion, which may reduce the yield in manufacturing the battery and the reliability of the battery.

  For this reason, the current collector formed inside the moisture-resistant protective film also has an individual solid-state secondary battery on the top surface of each individual solid-state secondary battery, rather than forming a separate current collector thin film on each divided battery. Forming a current collector thin film that crosses over the partition walls dividing the secondary battery and covers all adjacent all-solid-state lithium secondary batteries makes the current collector independent for each battery. In this case, there is no step in the outer peripheral portion of the current collector, and the surface on which the moisture-resistant protective film is formed becomes flat, which is preferable from the viewpoint of improving the reliability of the battery. Furthermore, since the metal thin film has a relatively low water vapor permeability, it is preferable to form a continuous current collector thin film from the viewpoint of improving the moisture resistance of the battery.

  Next, with reference to FIG. 1, a manufacturing process of the all solid-state lithium secondary battery will be described. FIG. 1A to FIG. 1G are diagrams for explaining the configuration of an all-solid-state lithium secondary battery according to the present embodiment based on the manufacturing method, and show cross-sectional views of the battery in each step. Yes.

  First, as shown in FIG. 1A, a positive electrode current collector metal mask is mounted on a predetermined position of an RF sputtering apparatus on a polyimide substrate (substrate 1) having a length of 25 mm, a width of 50 mm, and a thickness of 50 μm. Sputtering power was 100W, argon gas pressure was 1Pa, Ti was sputtered, Pt sputtering was performed without breaking the vacuum, and Ti-Pt cathode current collector thin film 2 with length 24mm, width 40mm, film thickness 0.5μm Formed.

  Next, sputtering is performed on the positive electrode current collector thin film 2 using an RF sputtering apparatus under the conditions of a sputtering power of 100 W and an oxygen gas pressure of 1 Pa, and the thickness of the positive electrode current collector is 24 mm long, 35 mm wide, and 35 mm thick. A 6 μm thick SiO 2 film was formed. Next, with the metal mask for the partition placed on the SiO2 film, it is attached to a predetermined position of the reactive ion etching apparatus, and the SiO2 film is etched using CF4 gas to form the positive and negative electrodes and the electrolyte thin film of the battery. Etching was performed on the SiO2 film at 8 portions of a rectangular portion of 10 mm in length and 6 mm in width to form an SiO2 partition wall (partition wall 3) for dividing the all-solid-state secondary battery into 8 sections as shown in FIG. In addition, the thickness of the partition between batteries was 0.5 mm.

  Next, the substrate is mounted at a predetermined position of the ECR sputtering apparatus with the metal mask for the partition wall mounted thereon, and the RF output is 500 W, the microwave output is 800 W, and the gas content in an oxygen-argon mixed gas (oxygen: argon = 1: 40). Sputtering was performed under a pressure of 0.3 Pa, and a 4 μm-thick LiCoO 2 positive electrode thin film (first electrode thin film 4) was removed from the SiO 2 film by etching as shown in FIG. It was formed on the current collector thin film 2. Further, a substrate on which a LiCoO2 positive electrode thin film (first electrode thin film 4) is formed is attached to a predetermined position of an RF sputtering apparatus with a metal mask for a partition placed thereon, and sputtering power is 100 W and nitrogen gas pressure is 1 Pa using Li3PO4 as a sputtering source. By performing reactive sputtering using nitrogen gas under the conditions described above, a LiPON electrolyte thin film (solid electrolyte thin film 5) having a thickness of 1 μm is formed into a LiCoO2 thin film (first electrode thin film 4) as shown in FIG. Formed on top.

  Next, as shown in FIG. 1 (e), a substrate is mounted at a predetermined position of a vacuum vapor deposition apparatus with a metal mask for partition walls placed thereon, and a 1 μm thick Li negative electrode thin film (second electrode thin film) is formed by resistance heating vapor deposition. 6) was formed on the LiPON electrolyte thin film (solid electrolyte thin film 5).

  Next, with the metal mask for the barrier ribs removed and the metal mask for the negative electrode current collector attached, the substrate is attached to a predetermined position of the vacuum deposition apparatus, and as shown in FIG. A 0.3 μm thick Cu negative electrode current collector thin film 7 is continuously covered with the SiO 2 barrier 3 and the Li negative electrode thin film (second electrode thin film 6), and the negative electrodes of adjacent all-solid-state secondary batteries are electrically connected to each other. As shown, it was formed by resistance heating vapor deposition.

Next, after removing the metal mask for the negative electrode current collector, the substrate is placed at a predetermined position of the RF sputtering apparatus, and the 2 μm thick SiO2 moisture resistant material is exposed on the upper surface of the battery so that the tab of the negative electrode current collector 7 is exposed. The protective film 8 was formed by sputtering using an RF sputtering apparatus under the conditions of a sputtering power of 100 W and an oxygen gas pressure of 1 Pa, and an all-solid lithium secondary battery having a total area of 4.8 cm ² divided into eight by partition walls was produced.

  FIG. 2 is a perspective view of the fabricated battery, and the same components as those in FIG. 1 are given the same reference numerals. Although it cannot be directly observed because it is covered with the moisture-resistant protective film 8 and the negative electrode current collector 7, an all-solid-state lithium secondary battery divided into square portions indicated by broken lines in the figure is formed. ing. The cross-sectional views shown in FIG. 1A to FIG. 1G correspond to the cross-section of the portion indicated by x-x ′ in FIG.

  The fabricated battery was connected to a charge / discharge test apparatus, charged to 4.3 V with a current of 1 mA, and then discharged to 2.0 V. As a result, a discharge capacity of 0.95 mAh was obtained, and it was confirmed that the battery operated as a secondary battery. After preparing 20 similar batteries, charging to 4.3V with 1mA current and discharging to 2.0V, confirm the initial discharge capacity of each battery, then constant temperature and humidity at 60 ° C and 90% relative humidity After storing in the bath for one month, an accelerated deterioration test was performed in which the battery was charged and discharged again under the same conditions and the discharge capacity was measured. When calculating the discharge capacity ratio obtained by dividing the discharge capacity after the degradation test by the initial discharge capacity, only one of the 20 batteries has a discharge capacity ratio of 70% or less, and 13 have a value of 80% or more. showed that.

  FIG. 4 is a diagram showing a distribution state of the discharge capacity value of the present embodiment. FIG. 4 also shows the distribution of discharge capacity values in the comparative example.

  A battery of a comparative example will be described. As a comparative example, an all solid-state lithium secondary battery having substantially the same dimensions as in Example 1 and not divided by the partition walls was produced. FIG. 3A to FIG. 3G are cross-sectional views of steps for explaining the configuration according to the comparative example based on the manufacturing method. In addition, the same code | symbol is provided to the component same as FIG.

  First, as shown in FIG. 3 (a), in the same manner as in the embodiment, a positive electrode current collector metal mask is placed on a polyimide substrate 1 having a length of 25 mm, a width of 50 mm, and a thickness of 50 μm. Mounting, Sputtering power 100W, Argon gas pressure is 1Pa Ti sputtering, Pt sputtering without breaking vacuum, 24mm vertical, 40mm horizontal, 0.5μm thick Ti-Pt positive current collector A thin film 2 was formed.

  Next, sputtering is performed on the positive electrode current collector 1 using an RF sputtering apparatus under the conditions of a sputtering power of 100 W and an oxygen gas pressure of 1 Pa, and the thickness of the positive electrode current collector is 24 mm long, 35 mm wide, and 35 mm thick. A 6 μm SiO 2 film was formed. Next, with the metal mask for the outer peripheral part placed on the SiO2 film, it is attached to a predetermined position of the reactive ion etching apparatus, and the SiO2 film is etched using CF4 gas to form the positive and negative electrodes of the battery and the electrolyte thin film. The rectangular SiO2 film having a length of 20 mm and a width of 24 mm was etched to form a SiO2 film 9 that would be the outer periphery of the all-solid-state secondary battery as shown in FIG.

  Next, the substrate is attached to a predetermined position of the ECR sputtering apparatus with the metal mask for the outer peripheral portion placed thereon, and in the same manner as in the example, the RF output is 500 W in the oxygen-argon mixed gas (oxygen: argon = 1: 40), micro Sputtering was performed under the conditions of a wave output of 800 W and a gas partial pressure of 0.3 Pa, and the 4 μm thick LiCoO 2 positive electrode thin film (first electrode thin film 4) was removed by etching as shown in FIG. A part of the Ti—Pt positive electrode current collector thin film 2 was formed.

  Further, a substrate on which a LiCoO2 positive electrode thin film (first electrode thin film 4) is formed is attached to a predetermined position of an RF sputtering apparatus with a metal mask for the outer periphery placed thereon, and sputtering is performed using Li3PO4 as a sputtering source in the same manner as in Example 1. By performing reactive sputtering using nitrogen gas under the conditions of electric power of 100 W and nitrogen gas pressure of 1 Pa, as shown in FIG. 3D, a LiPON electrolyte thin film (electrolyte thin film 5) having a thickness of 1 μm is formed as a LiCoO2 thin film (first film). 1 on the electrode thin film 4).

  Next, as shown in FIG. 3 (e), the substrate is attached to a predetermined position of the vacuum vapor deposition apparatus with the metal mask for the outer peripheral portion placed thereon, and a Li negative electrode having a thickness of 1 μm is formed by resistance heating vapor deposition in the same manner as in Example 1. A thin film (second electrode thin film 6) was formed on the LiPON electrolyte thin film (electrolyte thin film 5). Next, with the metal mask for the outer peripheral part removed and the metal mask for the negative electrode current collector attached, the substrate is attached to a predetermined position of the vacuum deposition apparatus, and as shown in FIG. A Cu negative electrode current collector thin film 7 having a thickness of 0.3 μm was formed by resistance heating vapor deposition so as to continuously cover the outer peripheral SiO 2 thin film 9 and the Li negative electrode thin film (second electrode thin film 6).

Next, after removing the metal mask for the negative electrode current collector, the substrate is placed at a predetermined position of the RF sputtering apparatus, and the 2 μm thick SiO2 moisture resistant material is exposed on the upper surface of the battery so that the tab of the negative electrode current collector 7 is exposed. The protective film 8 was formed by sputtering using an RF sputtering apparatus under the conditions of a sputtering power of 100 W and an oxygen gas pressure of 1 Pa to produce an integrated all-solid lithium secondary battery having a total area of 4.8 cm ² .

  The manufactured battery was connected to a charge / discharge test apparatus, charged to 4.3 V with a current of 1 mA, and then discharged to 2.0 V. As a result, a discharge capacity of 0.97 mAh was obtained, and it was confirmed to operate as a secondary battery. Twenty similar batteries were produced and subjected to an accelerated deterioration test under the same conditions as in the examples. When the discharge capacity ratio was calculated, of the 20 batteries, only 4 batteries had a discharge capacity ratio of 90% or more, and the remaining 16 batteries showed values of 50% or less.

  In the embodiment, platinum is used for the positive electrode as the current collector material and copper is used for the negative electrode. However, other metal materials may be gold, iridium, aluminum, titanium, tantalum and the like. In addition, lithium cobaltate was used as the positive electrode material, but other positive electrode materials used in ordinary lithium secondary batteries may be used, such as lithium iron phosphate, manganese spinel, and lithium nickelate, as long as thin film formation is possible. Absent.

  Further, although lithium metal is used as the negative electrode material, other metal oxides such as lithium alloy, tungsten oxide, niobium oxide, vanadium oxide, and tin oxide may be used. In the above-described embodiments, ECR sputtering was used for the positive electrode, RF sputtering was used for the electrolyte, and vacuum deposition was used for the negative electrode. However, a film forming technique suitable for the material to be used may be used. The film forming technique is not limited.

  As described above, according to the solid-type secondary battery of the present invention, it is possible to greatly improve the battery life and reliability. In addition, it is possible to suppress a decrease in battery life and reliability expected when the area of the solid secondary battery is increased.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Positive electrode current collector thin film 3 Partition wall 4 First electrode thin film 5 Solid electrolyte thin film 6 Second electrode thin film 7 Negative electrode current collector thin film 8 Moisture resistant protective film 9 SiO 2 film

Claims (2)

A first current collector thin film formed in contact with the upper surface of the substrate ;
A first electrode thin film formed in contact with the upper surface of the first current collector thin film and capable of inserting and releasing lithium ions, or depositing and dissolving;
A solid electrolyte thin film formed in contact with the upper surface of the first electrode thin film and through which lithium ions are conducted;
A second electrode thin film formed of a material different from that of the first electrode thin film in contact with the upper surface of the solid electrolyte thin film and capable of inserting and releasing lithium ions, or precipitation and dissolution;
A first partition that divides the first electrode thin film, the solid electrolyte thin film, and the second electrode thin film into a plurality of regions and does not divide the first current collector thin film ;
A second partition disposed on the outer periphery of the entire plurality of regions divided by the first partition;
A plurality of regions divided by the first barrier ribs are integrally formed in contact with the upper surface of the second electrode thin film and the upper surfaces of the first and second barrier ribs , and the surface is flat. 2 current collector thin films;
A moisture-resistant protective film integrally formed in contact with the upper surface of the second current collector thin film excluding only a part of the second partition;
With
The first and second partition walls are made of a ceramic material that does not transmit water vapor.   The first partition wall divides the first electrode thin film, the solid electrolyte thin film, and the second electrode thin film into six or more regions, and the first electrode thin film and the solid in each of the divided regions 2. The solid type secondary battery according to claim 1, wherein the electrolyte thin film and the second electrode thin film each operate as a solid type secondary battery.

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