JP5618324B2 - Electrochemical cell - Google Patents

Description

  The present invention relates to an electrochemical cell such as a nonaqueous electrolyte secondary battery or an electric double layer capacitor.

  Electrochemical cells are conventionally used as a memory backup power source, a clock function backup power source, and the like in various small electronic devices such as mobile phones, PDAs, and portable game machines. As one of this type of electrochemical cell, a chip-type electrochemical cell is provided that is excellent in airtightness and better in storage stability than a button type (see Patent Document 1).

  The chip-type electrochemical cell includes a concave container and a sealing plate that closes the opening of the concave container. The sealing plate is fixed to the concave container using, for example, a seal ring or a brazing material, and hermetically seals the internal space of the concave container. In this airtight internal space, a positive electrode having a positive electrode active material, a separator, and a negative electrode having a negative electrode active material are stored in order from the bottom side of the concave container.

By the way, as a separator used for this type of electrochemical cell, a porous plate such as a microporous film made of polypropylene, polyethylene or the like, or a nonwoven fabric made of fiber such as polypropylene or polyethylene has been generally used.
However, when the electrochemical cell is mounted on a substrate of an electronic device or the like by reflow, the separator is also required to have heat resistance that can withstand the reflow temperature. In this regard, when the separator is formed of the above material, it cannot withstand the reflow temperature.

  Therefore, in recent years, electrochemical cells using a separator using PTFE (fluororesin), a separator in which glass fibers (whiskers) are bound with a resin binder, or the like are provided so as to be compatible with reflow. .

JP 2001-216852 A

  However, when a separator is formed using PTFE, there is no problem when an electrochemical cell is used as a capacitor. However, when used as a secondary battery, fluorine easily reacts with metal ions. As it was unsuitable. In addition, since the separator may be deformed, for example, at a temperature of about 300 ° C., it is necessary to pay attention to the reflow operation, which is difficult to use.

Further, in the case of a separator in which glass fibers are bound with a resin binder, the melting point of silicon is low, and the binder is particularly vulnerable to heat, and the binding portion may be loosened at the reflow temperature. Therefore, it is necessary to pay attention to the reflow work, which is difficult to use.
In addition, since the glass fiber has a large fiber diameter and the strength of the fiber itself is low, the thickness has to be increased to finish the separator having a certain mechanical strength. Therefore, the volume ratio occupied by the separator in the sealed space in which the positive electrode, the negative electrode, and the separator are accommodated increases, and accordingly, the size of the positive electrode and the negative electrode has to be designed to be small. Therefore, the charge / discharge capacity is likely to decrease.

  Furthermore, the separator made of glass fiber is not only thick but also tends to be a soft sponge having irregularities on the surface. For this reason, the distance between the positive electrode and the negative electrode disposed across the separator is not uniform over the entire surface, and there is a risk that local variations may occur. Therefore, there is a possibility that the electrochemical characteristics accompanying charge / discharge change.

  The present invention has been made in view of such circumstances, and the purpose thereof is to improve the withstand temperature, to perform reflow work without paying attention, to improve the charge / discharge capacity, and It is to provide a high-quality electrochemical cell having stable electrochemical characteristics.

The present invention provides the following means in order to solve the above problems.
(1) An electrochemical cell according to the present invention has a base member on which a first current collector is formed, and a lid member that is fixed to the base member and on which a second current collector is formed, A sealed container in which a storage space is defined between the two members; and an electrochemical element that is stored in the storage space and is chargeable / dischargeable, wherein the electrochemical element is fixed to the first current collector. A first electrode that is in contact with the second current collector in a state where the sheet-shaped isolation member is sandwiched between the first electrode and the first electrode, and metal ions are moved between the first electrode and the first electrode through the electrolyte. And the isolation member has a sintered body obtained by sintering a ceramic fiber body, and the ratio of the fiber body to the material of the isolation member is 80% to 90%. It is characterized by being.

According to the electrochemical cell of the present invention, a voltage is applied between the first electrode and the second electrode via the first current collector and the second current collector, so that the first metal ion is passed through the electrolyte. It can be moved between an electrode and a 2nd electrode, and charging / discharging can be performed.
In particular, the separating member that is disposed between the first electrode and the second electrode and separates both electrodes has a sintered body obtained by sintering a ceramic fiber body at a temperature far exceeding the reflow temperature. Therefore, it has a higher temperature resistance than before and is not easily affected by reflow. Therefore, the reflow operation can be performed without paying attention.

  Further, since the fiber body of ceramic is thinner than glass fiber and stronger than glass fiber, sufficient mechanical strength can be obtained even if the thickness is made thinner than the separator made of conventional glass fiber. it can. Further, since the thickness of the separating member can be reduced, the volume ratio occupied by the separating member in the storage space can be reduced, and the sizes of the first electrode and the second electrode can be increased accordingly. Therefore, the charge / discharge capacity can be improved.

  Furthermore, unlike the case of using a binder such as a binder, it has a sintered body in which a ceramic fiber body is firmly solidified by sintering. It can be. Therefore, it is easy to make the distance between the first electrode and the second electrode disposed across the isolation member uniform over the entire surface. Therefore, the electrochemical characteristics associated with charging / discharging can be stabilized, the capacity during discharging can be stabilized, and the occurrence of abnormal charging, etc. can be suppressed, resulting in a high-quality and reliable electrochemical cell. be able to.

(2) In the electrochemical cell according to the present invention, the fibrous body may be made of alumina or titania.

  In this case, since a fiber body of alumina or titania is used, a sintered body that is sintered at a sintering temperature of about 1000 ° C. to 1700 ° C. that is much higher than the reflow temperature can be obtained. The withstand temperature of the separating member can be further increased. Therefore, it can be set as the electrochemical cell excellent in heat resistance.

(3) In the electrochemical cell according to the present invention, the electrolyte may be a solid electrolyte, and the isolation member may include the solid electrolyte.

In this case, since the isolation member contains the solid electrolyte, not only the first electrode and the second electrode are isolated, but also between the first electrode and the second electrode using the isolation member. Thus, the metal ions can be moved to ensure charging / discharging.
In particular, since it is not necessary to use a liquid electrolyte, the assemblability is excellent and the productivity can be increased. In addition, since there is no concern that the liquid electrolyte evaporates during reflow, the reflow operation can be performed more efficiently.

(4) Moreover, in the electrochemical cell according to the present invention, the isolation member, the positive electrode, and the negative electrode may be integrally combined in a stacked state.

  In this case, since the isolation member including the solid electrolyte, the positive electrode, and the negative electrode are integrally combined with each other in a stacked state, the assembling work can be easily performed, and the productivity is further increased. be able to.

  According to the electrochemical cell according to the present invention, since the first electrode and the second electrode are isolated by the separating member having a sintered body obtained by sintering the ceramic fiber body, the use temperature is improved, A reflow operation can be performed without paying attention, and a high-quality electrochemical cell with improved charge / discharge capacity and stable electrochemical characteristics can be obtained.

1 is a longitudinal sectional view of a chip-type lithium ion secondary battery showing a first embodiment according to the present invention. It is a longitudinal cross-sectional view which shows the modification of the lithium ion secondary battery shown in FIG. It is a longitudinal cross-sectional view which shows another modification of the lithium ion secondary battery shown in FIG. It is a longitudinal cross-sectional view which shows another modification of the lithium ion secondary battery shown in FIG. It is a longitudinal cross-sectional view of the button-type lithium ion secondary battery which shows 2nd Embodiment concerning this invention.

(First embodiment)
Hereinafter, a first embodiment of an electrochemical cell according to the present invention will be described with reference to FIGS. 1 to 4. In the present embodiment, as an example of an electrochemical cell, a surface-implemented lithium ion secondary battery having a substantially rectangular parallelepiped chip shape will be described as an example.

  As shown in FIG. 1, this lithium ion secondary battery 1 is one of non-aqueous electrolyte secondary batteries, and is stored in a sealed container 2 having a storage space S therein, and in the storage space S. And a rechargeable battery that can be surface-mounted on a substrate (not shown) by, for example, reflow.

The sealed container 2 is formed of a material such as ceramics, glass or resin, and includes a container body (base member) 10 and a sealing plate (lid member) 11 fixed to the container body 10. I have.
The container body 10 is a bottomed cylindrical concave container having a flat bottom wall portion 10a and a frame-shaped peripheral wall portion 10b, and the bottom wall portion 10a and the peripheral wall portion 10b define a recess. . And the said sealing board 11 is being fixed so that this recessed part may be plugged up.
This point will be described in detail. A metal layer 12 is formed on the upper surface of the peripheral wall portion 10b of the container body 10 so as to surround the recess from the radially outer side, and a conductive bonding material is further formed on the metal layer 12. 13 is formed. The sealing plate 11 is stacked on the container body 10 with the bonding material 13 interposed therebetween, and is hermetically fixed to the container body 10 by the dissolution of the bonding material 13. A space defined by the concave portion of the container body 10 and the sealing plate 11 is the above-described storage space S that is hermetically sealed.

Note that the bonding material 13 is, for example, a brazing material such as gold brazing or silver brazing, or a solder material. At this time, the material of the bonding material 13 may be determined in consideration of the familiarity with the sealing plate 11 and the reflow temperature. For example, when the substrate is reflowed at a temperature of about 260 ° C., the bonding material 13 that melts at a temperature higher than 260 ° C. may be used, and the bonding material 13 of about 300 ° C. can be used.
Furthermore, a seal ring made of a metal such as nickel, tin, or kovar plated with gold may be used as the bonding material 13.
In addition, it is preferable to plate the surfaces of the metal layer 12 and the bonding material 13 with nickel, gold, or the like from the viewpoint of improving rust prevention characteristics.

  The metal layer 12 is preferably formed of, for example, nickel or gold that is well-matched with the bonding material 13. As a method for forming the metal layer 12, in addition to electrolytic plating and electroless plating, a vapor phase method such as vacuum deposition may be employed.

On the upper surface of the bottom wall portion 10a of the container body 10 facing the storage space S, a first current collector 15 is formed over substantially the entire surface. Further, a pair of external connection terminals 16 and 17 are formed on the lower surface of the bottom wall portion 10a of the container body 10 in a state where they are electrically separated.
One of the external connection terminals 16 and 17 is electrically connected to the first current collector 15 via a first through electrode 18 that vertically penetrates the bottom wall portion 10a of the container body 10. On the other hand, the other external connection terminal 17 is electrically connected to the metal layer 12 through a second through electrode 19 that vertically penetrates the bottom wall portion 10 a and the peripheral wall portion 10 b of the container body 10.

  The pair of external connection terminals 16 and 17 are, for example, a single-layer film made of a single metal formed by a plating method, a sputtering method, or the like, or a stacked film in which different metals are stacked. The laminated film may be two layers or three layers. For example, in order to perform good reflow with the substrate, it is preferable that the base layer is nickel, the intermediate layer is gold, and the surface layer is solder.

  The sealing plate 11 is a conductive substrate (for example, a substrate formed of a nickel-iron alloy containing about 5% of nickel), and is fixed by welding using the bonding material 13 as described above. In addition, as welding at this time, seam welding by making a roller electrode contact, laser welding, ultrasonic welding, etc. are mentioned.

In addition, as a material of the sealing board 11, the thing with the same thermal expansion coefficient as the container main body 10 is desirable. By aligning the thermal expansion coefficient, when heating for sealing the sealing plate 11 or when the lithium ion secondary battery 1 is heated by reflow or the like, cracks, strains, etc. due to differences in the thermal expansion coefficient are generated. Since it can suppress that it generate | occur | produces between the container main body 10 and the sealing board 11, the sealing performance of the storage space S can be improved.
Furthermore, when the container body 10 and the sealing plate 11 are fixed by parallel seam welding, it is desirable that the material of the sealing plate 11 is a material that is compatible with the bonding material 13. Specifically, when a seal ring made of a metal such as Kovar coated with electrolytic nickel or electroless nickel is used as the bonding material 13, the sealing plate 11 is also coated with electrolytic nickel or electroless nickel on the material such as Kovar. It is preferable. This eliminates the need to increase the welding power more than necessary during parallel seam welding.

  A second current collector 20 is formed on the entire bottom surface of the sealing plate 11. However, since the sealing plate 11 of this embodiment is a conductive substrate, the sealing plate 11 itself also serves as the second current collector.

The first current collector 15 and the second current collector 20 are preferably tungsten, silver, or gold that has excellent corrosion resistance and can be formed by a film thickness method.
In addition, in order to prevent dissolution in the liquid electrolyte W, which will be described later, when a noble potential is applied, it is composed of valve metal (valve metal: a metal that forms a corrosion-resistant passive film on the surface) or carbon. May be. Examples of the valve metal include aluminum, titanium, tantalum, niobium, hafnium, zirconium, and the like, and it is particularly desirable to use aluminum or titanium.

  Furthermore, it is preferable that the first current collector 15 and the second current collector 20 are formed on the underlayer using a chromium layer as the underlayer. By forming the base layer, it is possible to improve the adhesion of the current collectors 15 and 20 to the container body 10. In addition to the chromium layer, a titanium layer is also suitable as the base layer. This titanium layer can be used not as a base layer but as a current collector itself.

  The electrochemical element 3 is stacked on the positive electrode (first electrode) 25 fixed to the first current collector 15 and the positive electrode 25 with a separator (separating member) 26 interposed therebetween, and filled in the storage space S. And a negative electrode (second electrode) 27 that moves lithium ions (metal ions) to and from the positive electrode 25 through a liquid electrolyte (electrolyte) W.

  Each of the positive electrode 25 and the negative electrode 27 has an electrode active material (positive electrode active material, negative electrode active material) (not shown) that is involved in the electrochemical reaction. The positive electrode 25 and the negative electrode 27 may be metal oxides or the like that can move lithium ions between the two through the liquid electrolyte W and can occlude and release the lithium ions. Further, the positive electrode 25 and the negative electrode 27 may be configured by adding a conductive additive for the purpose of increasing the electron conductivity between the electrode active materials and further adding a binder to maintain the shape of the electrode. Absent.

The positive electrode 25 of both the electrodes 25 and 27 is fixed on the first current collector 15 using a conductive adhesive or the like (not shown) and is electrically connected to the first current collector 15. Thereby, the positive electrode 25 is electrically connected to one external connection terminal 16 via the first current collector 15 and the first through electrode 18. A sheet-like separator 26 and a negative electrode 27 are stacked on the positive electrode 25 in this order.
The negative electrode 27 is electrically connected in contact with the second current collector 20 formed on the lower surface of the sealing plate 11 on the upper surface. Accordingly, the negative electrode 27 is electrically connected to the other external connection terminal 17 through the second current collector 20 and the second through electrode 19.
The interelectrode distance H between the positive electrode 25 and the negative electrode 27 is the thickness of the separator 26.

The separator 26 is a member that separates the positive electrode 25 and the negative electrode 27 and restricts the direct contact between the electrodes 25 and 27. Even if an impact or the like is received, the electrodes 25 and 27 come into contact with each other and are electrically It is designed not to short-circuit.
The separator 26 of the present embodiment has a sintered body obtained by sintering a fiber body of alumina (Al ₂ O ₃ ) or titania (TiO ₂ ), which is a ceramic, at a sintering temperature of 1000 ° C. to 1700 ° C. . The ratio of the alumina or titania fiber body in the material of the separator 26 is 80 % to 90%.
As the crystal structure of alumina (Al ₂ O ₃ ), α type and β type can be used, and as the crystal structure of titania (TiO ₂ ), anatase type, rutile type and brookite type can be used. .

  The liquid electrolyte W is a non-aqueous electrolyte (liquid) in which, for example, a lithium salt from which moisture has been similarly removed is dissolved in an organic solvent from which moisture has been previously removed to 100 ppm or less. The negative electrode 27 and the separator 26 are immersed.

According to the lithium ion secondary battery 1 configured as described above, when a voltage is applied between the positive electrode 25 and the negative electrode 27 via the pair of external connection terminals 16 and 17, the lithium ions are passed through the liquid electrolyte W. While moving between the positive electrode 25 and the negative electrode 27, it is occluded and released by the positive electrode active material and the negative electrode active material. Thereby, charge is exchanged by electrochemical reaction, and charging / discharging is performed.
Note that lithium ions are released from the positive electrode 25 during charging and stored in the negative electrode 27, and released from the negative electrode 27 during discharge and stored in the positive electrode 25.

  In particular, according to the lithium ion secondary battery 1 of the present embodiment, the separator 26 separating the positive electrode 25 and the negative electrode 27 has alumina or titania at a sintering temperature of about 1000 ° C. to 1700 ° C. far exceeding the reflow temperature. Since the sintered body is obtained by sintering the fiber body, the use temperature is higher than the conventional one, and it is hardly affected by reflow. Therefore, the reflow operation can be performed without paying attention.

In addition, since the fiber body of alumina or titania is thinner than the glass fiber and stronger than the glass fiber, sufficient mechanical strength can be obtained even if the separator is made thinner than the conventional glass fiber separator. be able to. For example, the thickness may be about 20 μm, which is about 1/10 of the thickness of a separator made of a conventional glass fiber.
And since the thickness of the separator 26 can be made thin, the volume ratio which the separator 26 occupies in the storage space S can be made small, and the size of the positive electrode 25 and the negative electrode 27 can be enlarged correspondingly. Therefore, the charge / discharge capacity can be improved.

Furthermore, unlike the case of using a binder such as a binder, it has a sintered body in which alumina and titania fiber bodies are firmly solidified by sintering, so that a hard sheet shape in which irregularities do not easily appear on the surface. Separator 26.
Therefore, it is easy to make the distance between the positive electrode 25 and the negative electrode 27 disposed with the separator 26 between them uniform over the entire surface. Therefore, the electrochemical characteristics associated with charging / discharging can be stabilized, the capacity during discharging can be stabilized, and the occurrence of abnormal charging, etc. can be suppressed, resulting in a high quality and reliable secondary battery. be able to.

  The lithium ion secondary battery 1 of this embodiment includes, for example, a notebook computer, a mobile phone, a cordless phone, a headphone stereo, a video camera, a digital camera, a portable electronic dictionary, a calculator, a memory card, a PDA, and a portable game device. It can be suitably used as a power source backup for a memory and a clock function.

In the first embodiment, since the sealing plate 11 itself is a conductive substrate, it can be easily and reliably fixed to the container body 10 and the sealing plate 11 can be used as an external connection terminal. Is possible. That is, it is possible to apply a voltage between the positive electrode 25 and the negative electrode 27 via the one external connection terminal 16 and the sealing plate 11.
The sealing plate 11 is not limited to the conductive substrate, and may be formed of a material such as ceramics, glass, or resin. Even in this case, it is possible to reliably connect the negative electrode 27 and the other external connection terminal 17 using the second current collector 20. In this case, it is preferable to form the sealing plate 11 with the same material as the container body 10. By carrying out like this, the thermal expansion coefficient of the container main body 10 and the sealing board 11 can be made the same.

In the first embodiment, ceramics, glass, resin, and the like are given as examples of the material of the container body 10. More specifically, for example, the ceramic material is HTCC (High Temperature Co-fired Ceramic) made of alumina. ), LTCC (Low Temperature Co-fired Ceramic) made of glass ceramics, or the like can be used.
As the glass material, soda lime glass, lead glass, borosilicate glass, or the like can be used, but borosilicate glass is desirable in consideration of workability.
The resin material is preferably a thermoplastic resin. For example, PPS (polyphenylene sulfide), PEEK (polyether ether ketone), LCP (liquid crystal polymer), PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene perfluoro). Alkyl vinyl ether copolymer), ETFE (tetrafluoroethylene / ethylene copolymer), and the like can be used.

  In addition, when forming the container main body 10 using the PPS, for example, a plurality of PPS films can be laminated and formed. In this PPS film, an opening (hole) can be formed with a press or the like in order to provide a concave portion that becomes a cavity in advance. Moreover, it is also possible to give an opening part and printing as a marking for the positioning. When printing is performed as the marking, a marking method by heating using a laser (for example, a carbon dioxide laser or a YAG laser) or ink jet printing can be performed. Moreover, when wiring is provided in the intermediate part between films, metals, such as a lead frame, can be used. As the metal used for the lead frame, for example, stainless steel or aluminum can be used in addition to the copper alloy.

  Further, when the container body 10 is formed using the above alumina, for example, the through electrode portion is punched into a green sheet, screen-printed with an ink containing a high melting point metal material such as tungsten, and fired. It is possible to obtain a container body 10 having 18, 19. Then, what is necessary is just to form the metal layer 12 by plating nickel, gold | metal | money, etc. on the upper surface of the surrounding wall part 10b of the container main body 10. FIG.

Further, when the container body 10 is formed using low-melting glass ceramics, for example, conductor printing is performed on the peripheral wall portion 10b and the bottom wall portion 10a to form portions that become wiring, and then the peripheral wall portion 10b and the bottom It is also possible to form the container body 10 by laminating the wall 10a and firing them at a low temperature.
Specifically, the first current collector 15 is formed on the upper surface of the bottom wall portion 10a, the pair of external connection terminals 16 and 17 are formed on the lower surface, and the first through electrode 18 and a part of the second through electrode 19 are formed. It is formed in advance. And the remaining part of the 2nd penetration electrode 19 is previously formed in the surrounding wall part 10b. Thereafter, the bottom wall portion 10a and the peripheral wall portion 10b are laminated and fired to integrate them, and the second through electrode 19 on the bottom wall portion 10a side and the second on the peripheral wall portion 10b side. The through electrode 19 can be integrated. Thereby, the container main body 10 can be obtained.

Moreover, in the said 1st Embodiment, although the 1st penetration electrode 18 and the 2nd penetration electrode 19 were both formed in straight shape, you may form so that it may become a cross-sectional taper shape.
For example, the first through electrode 18 is formed such that the diameter gradually decreases from the first current collector 15 toward the external connection terminal 16, and the second through electrode 19 is similarly connected from the metal layer 12 to the external connection. You may form so that a diameter may reduce gradually as it goes to the terminal 17. FIG.
By so doing, when the bonding material 13 is dissolved and the sealing plate 11 is fixed, the internal pressure in the sealed container 2 rises due to an increase in the vapor pressure of the liquid electrolyte W, and the first through electrode 18 and the first through electrode 18 Even if an external force acts on the two through electrodes 19, it is possible to prevent the through electrodes 18 and 19 from falling off due to the external force.

In the first embodiment, the average particle size of the positive electrode active material is preferably 500 μm or less, more preferably 100 μm or less, particularly 50 to 0.1 μm. The active material is preferably composed of primary particle aggregates having an average particle size of 1 μm or more and 20 μm or less formed by aggregating primary particles having an average particle size of 0.1 μm or more and 2.5 μm or less. It is preferably composed of primary particle aggregates having an average particle size of 3.5 μm or more and 9.5 μm or less formed by collecting primary particles having a diameter of 0.1 μm or more and 2.5 μm or less.
Further, in the primary particle aggregate, 80% or more of the total volume is preferably 1 μm or more and 15 μm or less, more preferably 85% or more of the total volume, and further preferably 90% or more of the total volume.
The specific surface area is preferably 0.05~100m ² / g, more preferably 0.1 to 50 m ² / g, especially 0.1~30m ² / g is good.

  Moreover, a positive electrode active material can also be used in mixture of 2 or more types. This can be applied when changing the voltage range to be used or detecting the remaining capacity by voltage.

The negative electrode active material is preferably B in the periodic table capable of occluding and releasing lithium ions, or an alloy or oxide of one or more elements selected from B and a transition metal, and particularly preferably an oxide of silicon.
The silicon oxide is represented by the composition formula LixSiOy, and lithium ion can be occluded and released from a lithium-containing silicon oxide in which the lithium content x and the oxygen content y are 1.5 ≦ x ≦ 4 and 0 <y <2, respectively. Substances can be used. That is, an oxide of silicon containing lithium in its crystal structure or amorphous structure and capable of inserting and extracting lithium ions by electrochemical reaction in a non-aqueous electrolyte, wherein the number of lithium atoms relative to the number of silicon atoms X is 1.5 or more and 4.0 or less, and a composite oxide having a composition in which y, which is a ratio of the number of oxygen atoms to the number of silicon atoms, is larger than 0 and smaller than 2.
The lithium state in the composite oxide is preferably mainly ions, but is not necessarily limited.

  Moreover, as a preferable production method of the lithium-containing silicon oxide LixSiOy (where 1.5 ≦ x ≦ 4, 0 <y <2) used as the negative electrode active material, the following two types of methods can be mentioned, These are not limited.

  In the first method, each simple substance of silicon and lithium or a compound thereof is mixed or mixed at a predetermined molar ratio, while in a non-oxidizing atmosphere such as in an inert atmosphere or vacuum, or when silicon and lithium are mixed. In this method, heat treatment is performed in an atmosphere in which the amount of oxygen is controlled so as to obtain a predetermined oxidation number, thereby forming a composite oxide of silicon and lithium.

  Each compound of silicon and lithium as the starting material is heat-treated in a non-oxidizing atmosphere, such as each oxide, hydroxide, salt such as carbonate, nitrate, or organic compound. Are preferred to produce the respective oxides. As a method for mixing these starting materials, in addition to a method of directly dry-mixing each raw material powder, these raw materials were dissolved or dispersed in water, alcohol or other solvent, and were uniformly mixed or reacted in the solution. Thereafter, various methods such as a drying method, a method in which these raw materials are atomized or ionized by heating, electromagnetic waves, light, or the like and simultaneously or alternately deposited or deposited are possible.

  The temperature of the heat treatment performed after mixing the raw materials in this manner or while mixing varies depending on the starting raw materials and the heat treatment atmosphere, but the synthesis is possible at 400 ° C. or higher, preferably 600 ° C. or higher. On the other hand, since a disproportionation reaction may occur between silicon and tetravalent silicon oxide at a temperature of 800 ° C. or higher in an inert atmosphere or in a vacuum, a temperature of 600 to 800 ° C. is preferable in such a case.

Among these starting material combinations, as a lithium feedstock, lithium oxide by heat treatment such as a salt of lithium oxide Li ₂ O, lithium hydroxide LiOH, Li ₂ CO ₃ or LiNO ₃ or a hydrate thereof, etc. In the case where a silicon compound or a silicon lower oxide SiOy ′ (where 0 <y ′ <2) is used as a silicon source, the mixture thereof is used in an inert atmosphere or in a vacuum. It can be synthesized by heat treatment in an atmosphere in which oxygen is cut off, and the amount of oxygen or oxygen partial pressure in the heat treatment atmosphere can be easily controlled and production is easy, which is particularly preferable.

  In addition, when various silicic acids having hydrogen as a silicon compound are used as a starting material, or when lithium hydroxide or the like is used as a lithium compound, hydrogen is not completely desorbed by heat treatment. A part of the product remains, and lithium and hydrogen can coexist and are included in the present invention.

  Furthermore, together with lithium or its compound and silicon or its compound, other alkali metals such as sodium, potassium and rubidium, alkaline earth metals such as magnesium and calcium, and / or iron, nickel, cobalt, manganese, vanadium, titanium, niobium In addition, other metals such as tungsten, molybdenum, copper, zinc, tin, lead, aluminum, indium, bismuth, gallium, germanium, carbon, boron, nitrogen, phosphorus, etc. By mixing and heat-treating, metals or non-metals other than lithium can coexist with lithium and silicon, and these cases are also included in the present invention.

  The lithium-containing silicon oxide thus obtained can be used as a negative electrode active material as it is or after being subjected to processing such as pulverization and granulation as necessary. Similarly to the second method described below, the lithium-containing silicon oxide further occludes lithium ions by an electrochemical reaction between the lithium-containing silicon oxide and lithium or a lithium-containing substance, or Conversely, lithium ions may be increased or decreased by releasing lithium ions from the composite oxide, and the negative electrode active material may be used.

  In the second method, a silicon-containing lower oxide SiOy (where 2> y> 0) that does not contain lithium is synthesized in advance, and the obtained silicon lower oxide SiOy and a substance containing lithium or lithium are used. In this method, lithium ions are occluded in the lower oxide SiOy of silicon by electrochemical reaction to obtain a lower oxide LixSiOy of silicon containing lithium.

Such silicon lower oxide SiOy has a stoichiometric composition such as SiO _1.5 (Si ₂ O ₃ ), SiO _1.33 (Si ₃ O ₄ ), SiO and SiO _0.5 (Si ₂ O), and y May be of any composition greater than 0 and less than 2.
These silicon lower oxides SiOy can be produced by various known methods as described below. That is,
(1) A method in which silicon dioxide SiO ₂ and silicon Si are mixed at a predetermined molar ratio and heated in a non-oxidizing atmosphere or in a vacuum.
(2) A method in which silicon dioxide SiO ₂ is heated in a reducing gas such as hydrogen H ₂ to reduce a predetermined amount. (3) A method in which silicon dioxide SiO ₂ is mixed with a predetermined amount of carbon C, metal, or the like and heated to reduce the predetermined amount.
(4) A method in which silicon Si is heated with oxygen gas or oxide to oxidize a predetermined amount.
(5) A CVD method or a plasma CVD method in which a mixed gas of a silicon compound gas such as silane SiH ₄ and oxygen O ₂ is heated or plasma decomposed.
And so on.

  The lower oxide SiOy of silicon includes silicon, alkali metals such as hydrogen, sodium, potassium and rubidium, alkaline earth metals such as magnesium and calcium, and / or iron, nickel, cobalt, manganese, vanadium, titanium and niobium. , Tungsten, molybdenum, copper, zinc, tin, lead, aluminum, indium, bismuth, gallium, germanium, carbon, boron, nitrogen, phosphorus, etc. It is included in the present invention.

The occlusion of lithium ions by electrochemical reaction of silicon with the lower oxide SiOy can be performed in the battery after the battery is assembled or in the battery manufacturing process or inside the battery or outside the battery. It can be done like this. That is,
(1) One electrode (working electrode, positive electrode 25) formed by molding a lower oxide of silicon or a mixed mixture of them with a conductive agent and a binder into a predetermined shape and containing metallic lithium or lithium The material is in contact with a lithium ion conductive non-aqueous electrolyte as the other electrode (counter electrode, negative electrode 27) and the electrodes 25 and 27 are opposed to each other to form an electrochemical cell, and the working electrode is suitable for the direction in which the cathode reaction occurs. The lithium ions are electrochemically occluded in the lower oxide of silicon. The obtained working electrode is used as it is as the negative electrode 27 or as the negative electrode active material constituting the negative electrode 27 to constitute a non-aqueous electrolyte secondary battery.

(2) A lower electrode of silicon or a mixture of these with a conductive agent and a binder is formed into a predetermined shape, and lithium or an alloy of lithium is pressure-bonded or brought into contact therewith to form a laminated electrode. This is incorporated into the non-aqueous electrolyte secondary battery as the negative electrode 27. A method in which the laminated electrode is in contact with an electrolyte in a battery to form a kind of local battery, which is self-discharged and lithium is occluded electrochemically by the lower oxide of silicon.
(3) A nonaqueous electrolyte secondary battery using a lower oxide of silicon as a negative electrode active material and a material containing lithium and capable of occluding and releasing lithium ions as a positive electrode active material is configured. A method in which lithium ions released from the positive electrode 25 by being charged when used as a battery are occluded in the lower oxide of silicon.

The compounding ratio of the electrode components in the present invention is 30 to 95% by weight as the electrode active material and 1 to 70% by weight of the carbonaceous material used as the conductive auxiliary agent with respect to the total weight of each electrode. The mixing ratio varies depending on the volume change of the occlusion / release of lithium ions of the active material, electrical conductivity, electrode shape, and the like. When the composition of the electrode active material is a composite oxide represented by Li _{a Tb} L _c O _d or a transition metal oxide such as manganese dioxide, the electrode active material is 75 to 95% by weight, the carbonaceous material is 2 to 2%. More preferably, it is used in the range of 15% by weight.
Moreover, when various oxides, such as a silicon, tin, and a transition metal, are used as an electrode active material, 30 to 70 weight% of an electrode active material and 70 to 30 weight% of a carbonaceous material are more preferable. The binder is preferably insoluble in the electrolytic solution, but is not particularly limited. One kind of a polysaccharide, a thermoplastic resin, a thermosetting resin, a polymer having rubber elasticity, or a mixture or It can be used as a coalescence.

In the first embodiment, the first current collector 15 is electrically connected to the one external connection terminal 16 through the first through electrode 18 and the second current collector 20 is connected through the second through electrode 19. However, the present invention is not limited to this case.
For example, as shown in FIG. 2, the first current collector 15 and one external connection terminal 16 are electrically connected to each other via side electrodes 41 and 42 formed on the side surface of the container body 10, and the second current collector 20 and the other external connection terminal 17 may be electrically connected. This point will be described in detail.

The first current collector 15 extends to the side surface of the container body 10 on the side where the one external connection terminal 16 is formed. One side electrode 41 is formed on the side surface of the container body 10 so as to connect the first current collector 15 extending to the side surface and the external connection terminal 16.
On the other hand, the other side electrode 42 is formed on the side surface of the container body 10 so as to connect the metal layer 12 formed on the upper surface of the peripheral wall portion 10 b of the container body 10 and the other external connection terminal 17.
Even in the lithium ion secondary battery 40 configured as described above, the same operation and effect can be obtained only by the connection route between the external connection terminals 16 and 17 and the first current collector 15 and the second current collector 20 being different. It is effective and can be used as a surface mount type secondary battery.

Further, by combining the through electrode and the side electrode, the first current collector 15 and the one external connection terminal 16 are electrically connected, and the second current collector 20 and the other external connection terminal 17 are electrically connected. I do not care.
For example, as shown in FIG. 3, a first current collector 15 having a cross-sectional area smaller than that of the positive electrode 25 is formed at the approximate center of the positive electrode 25 on the bottom wall portion 10 a of the container body 10. The body 15 and one side electrode 41 are connected to each other using one internal electrode 46 formed in the bottom wall portion 10a. Further, the second through electrode 19 that is electrically connected to the second current collector 20 is formed partway through the bottom wall portion 10a, and the second through electrode is formed using the other internal electrode 47 formed in the bottom wall portion 10a. The electrode 19 and the other side electrode 42 are connected to each other.

With this configuration, the first current collector 15 can be electrically connected to one external connection terminal 16 via one internal electrode 46 and one side electrode 41. Further, the second current collector 20 can be conducted to the other external connection terminal 17 through the second through electrode 19, the other internal electrode 47, and the other side electrode 42.
Even in the lithium ion secondary battery 45 configured as described above, the same operation and effect can be obtained only by the connection route between the external connection terminals 16 and 17 and the first current collector 15 and the second current collector 20 being different. It is effective and can be used as a surface mount type secondary battery.

  As shown in FIG. 1 to FIG. 3, the first current collector 15 and the second current collector 20 may be electrically connected to the one external connection terminal 16 and the other external connection terminal 17. Such a connection route may be used.

  Moreover, in the said 1st Embodiment, although the base member was made into the bottomed cylindrical container main body 10 and the lid member was made into the flat sealing board 11, it is not limited to this case, A base member and a lid member As long as the storage space S can be defined between the base member and the lid member, the base member and the lid member may be formed in any shape.

For example, as shown in FIG. 4, a sealed container 51 in which the base member is a flat base substrate 52 and the lid member is a capped tubular lid 53 may be used.
A first through electrode 18 and a second through electrode 19 are formed on the base substrate 52, respectively.

The lid 53 is connected to the cylindrical peripheral wall 53a, the upper end of the peripheral wall 53a, the top wall 53b that closes the peripheral wall 53a, the lower end of the peripheral wall 53a, and the peripheral wall. A flange portion 53c extending outward in the radial direction of the portion 53a. The flange portion 53c is superimposed on the base substrate 52 with the metal layer 12 and the bonding material 13 interposed therebetween.
The lid 53 is fixed on the base substrate 52 by welding using the bonding material 13. At this time, a space defined by the peripheral wall portion 53 a and the top wall portion 53 b of the lid 53 and the base substrate 52 is defined as a storage space S. Further, the second current collector 20 is formed on the inner surface of the lid 53.

  Even with the lithium ion secondary battery 50 configured in this way, the same operational effects can be obtained only by changing the shape of the sealed container 51, and it can be used as a surface mount type secondary battery. It is.

(Second Embodiment)
Next, a second embodiment according to the present invention will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that a chip-type secondary battery is used in the first embodiment, whereas a button-type secondary battery is used in the second embodiment. It is.

  That is, as shown in FIG. 5, the lithium ion secondary battery 60 of the present embodiment is fixed to the bottomed cylindrical positive electrode can (base member) 62 and the positive electrode can 62 via the gasket 63, A sealed container 61 having a negative electrode can (lid member) 64 that defines a sealed storage space S between the positive electrode can 62 and the electrochemical element 3 stored in the storage space S is provided.

The positive electrode can 62 is formed, for example, by drawing a stainless plate material into a bottomed cylindrical shape, and its opening edge has a circular shape in plan view. The negative electrode can 64 is formed in a cylindrical shape with an opening, and the opening edge thereof enters the inside of the positive electrode can 62 and sandwiches the gasket 63 with the positive electrode can 62. Moreover, the opening edge of the positive electrode can 62 is crimped inward in the radial direction, and the gasket 63 is pressed against the negative electrode can 64 to seal it.
In this way, the positive electrode can 62 and the negative electrode can 64 are connected and fixed to each other via the gasket 63.

  Note that the negative electrode can 64 may have a two-layer structure in which stainless steel and hard aluminum are bonded together by rolling. In this case, the stainless steel layer may be formed outside and the hard aluminum layer formed inside.

  A first current collector 15 made of a conductive resin adhesive containing carbon as a conductive filler is formed on the bottom surface of the positive electrode can 62, and a positive electrode pellet (first electrode) 65 is formed through the first current collector 15. Is fixed. The positive electrode pellet 65 may be bonded to the positive electrode can 62 via the first current collector 15, and then the positive electrode can 62 and the positive electrode pellet 65 may be integrated (unitized) by drying under reduced pressure. . In this case, the drying under reduced pressure may be performed at 280 ° C. for about 8 hours, for example.

The positive electrode pellet 65 is made of, for example, a LiMn-containing oxide mixed with graphite as a conductive agent and polyacrylic acid resin as a binder in a ratio of 90: 7: 3 to form a positive electrode mixture. The agent is pressure-molded into pellets. Specifically, 7.5 mg of the positive electrode mixture is pressure-molded with a force of ² ton / 2 cm ² into a pellet form.

On the positive electrode pellet 65, a lithium foil (second electrode) 66 serving as a negative electrode is disposed via a separator 26 . Li Chiumufoiru 66 are those punched in a diameter of 2 mm, a thickness of 0.22 mm.

The solvent used in the liquid electrolyte W of this embodiment is preferably one or more polyethylene glycol dialkyl ethers selected from diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, and ethylene glycol dimethyl ether. And a mixed solvent selected from ethylene glycol diacyl ether.
In this embodiment, the storage space S is filled with 5 μl of lithium perfluoromethylsulfonylimide dissolved in the mixed solvent at a concentration of 1 mol / l.

  Even with the button-type lithium ion secondary battery 60 configured as described above, only the chip type and the button type are different, and the same operational effects can be obtained, and the operating temperature is improved. A reflow operation can be performed without paying attention, and a high-quality secondary battery with improved charge / discharge capacity and stable electrochemical characteristics can be obtained.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in each of the above embodiments, for each material of the positive electrode, the negative electrode, and the liquid electrolyte, lithium ions can be moved between the positive electrode and the negative electrode, and charge and discharge can be performed by receiving and transferring charges by occlusion and release of the lithium ions. If so, it may be freely selected as appropriate.
For example, FeS may be used as the positive electrode active material, and SiO may be used as the negative electrode active material. Moreover, you may use the intermetallic compound which makes metal lithium and alloys, such as Li-Al alloy, as a positive electrode active material and lithium-containing manganese oxide as a negative electrode active material.
In addition, as an intermetallic compound of lithium, Li-In alloy, Li-Sn alloy, Li-Si alloy, etc. can be illustrated besides Li-Al. These intermetallic compounds may be added with a third additive in addition to the above-described elements for the purpose of improving the strength and the like of the material. Examples thereof include elements such as Ca, Mg, Si, Mn, and V. .

  In each of the above embodiments, a lithium ion secondary battery has been described as an example of an electrochemical cell. However, the present invention is not limited to this case. For example, a lithium secondary battery using metal lithium or an alloy of metal lithium and another metal such as aluminum or tin as the negative electrode active material may be used, or a carbon-based material capable of occluding lithium ions in the negative electrode active material is used. An electric double layer capacitor such as a lithium ion capacitor in which lithium ions are doped in advance can also be applied.

  In each of the above embodiments, the storage space is filled with the liquid electrolyte, and the negative electrode, the positive electrode, and the separator are immersed. Even in this case, the electrochemical reaction can be performed by reliably allowing the liquid electrolyte to be present at the interface between the separator and the positive electrode and the interface between the separator and the negative electrode.

Moreover, as an electrolyte, it is not limited to a liquid electrolyte, You may utilize a solid electrolyte.
In this case, an inorganic solid electrolyte (Li ₂ S, SiS ₂ , Li ₄ SiO ₄ ) is kneaded into a ceramic paper that is a sintered body obtained by sintering a fiber body of alumina or titania, or an electrode is formed by hot pressing. And a solid electrolyte can be used as a separating member instead of a separator.
In addition, as a method of integrating the electrode and the solid electrolyte, using a physical method such as the SPS method (electric current sintering = plasma sintering) in a state in which the solid electrolyte is arranged and stacked between the positive electrode and the negative electrode, The electrode and the solid electrolyte may be integrated. In addition, after depositing the solid electrolyte on the surface of the positive electrode or the negative electrode by using a physical method such as laser ablation deposition method, RF sputtering method, vacuum deposition, etc., sandwiched between the positive electrode and the negative electrode, and after overlapping, It may be used after being integrated by pressure bonding or the like.
Even in this case, for example, lithium ions can be moved between the positive electrode and the negative electrode through the solid electrolyte, so that a reliable electrochemical reaction can be performed and it can be used as an electrochemical cell. .

  In particular, in this case, since it is not necessary to use a liquid electrolyte, the assemblability is excellent and the productivity can be increased. In addition, since there is no concern that the liquid electrolyte evaporates during reflow, the reflow operation can be performed more efficiently.

  Further, when the solid electrolyte sheet is used as a separating member, the solid electrolyte sheet, the positive electrode, and the negative electrode may be combined together in advance in a state where they are laminated with each other. By doing so, since the positive electrode, the negative electrode, and the solid electrolyte sheet can be handled as one unit, the assembling work can be further facilitated, and the productivity can be further increased.

S ... Storage space W ... Liquid electrolyte (electrolyte)
1, 40, 45, 50, 60 ... lithium ion secondary battery (electrochemical cell)
2, 51, 61 ... Sealed container 3 ... Electrochemical element 10 ... Container body (base member)
11. Sealing plate (lid member)
DESCRIPTION OF SYMBOLS 15 ... 1st electrical power collector 20 ... 2nd electrical power collector 25 ... Positive electrode (1st electrode)
26. Separator (isolation member)
27 ... Negative electrode (second electrode)
52. Base substrate (base member)
53. Lid (lid member)
62 ... Positive electrode can (base member)
64 .. Negative electrode can (lid member)
65 ... Positive electrode pellet (first electrode)
66 ... Lithium foil (second electrode)

Claims (4)

A base member in which the first current collector is formed, and a lid member in which the second current collector is formed while being fixed to the base member, and a storage space is defined between the two members. A sealed container;
An electrochemical element housed in the housing space and chargeable / dischargeable,
The electrochemical element is
A first electrode fixed to the first current collector;
A second electrode that is in contact with the second current collector in a state of being stacked on the first electrode with a sheet-like isolation member interposed therebetween, and moves metal ions to and from the first electrode through the electrolyte. ,
The isolation member has a sintered body obtained by sintering a ceramic fiber body ,
The electrochemical cell according to claim 1 , wherein a ratio of the fibrous body to the material of the isolation member is 80% to 90% . The electrochemical cell according to claim 1.
The electrochemical cell is made of alumina or titania. The electrochemical cell according to claim 1 or 2,
The electrolyte is a solid electrolyte;
The electrochemical cell, wherein the isolation member includes the solid electrolyte. The electrochemical cell according to claim 3,
The electrochemical cell, wherein the isolation member, the positive electrode, and the negative electrode are integrally combined in a stacked state.

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