JP2005259637A - Negative electrode for secondary battery, its manufacturing method, and secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode for a secondary battery having a high capacity, excellent cycle characteristics, and excellent efficiency, by reducing a volume change of the negative electrode when it occludes and discharges a lithium ion, and its manufacturing method. <P>SOLUTION: This negative electrode for the secondary battery is formed of a metal compound nanostruture having a structure in which columnar structures are arranged. A target material and a base material are disposed in a reaction chamber, beam light is irradiated on the target material to excite it while introducing helium into the reaction chamber, a substance contained in the desorbed target material is condensed by helium to grow it, and thereby the electrode for the secondary battery is deposited on the base material as the metal compound nanostructure having the structure in which the columnar structures are arranged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a negative electrode for a secondary battery having high capacity, cycle life, and efficiency, a method for producing the same, and a secondary battery using the same.

  In recent years, with the miniaturization of electronic devices, there has been a demand for higher energy density of batteries. For this reason, high-performance lithium (Li) ion secondary batteries have been developed. Initially, Li secondary batteries used metal Li for the negative electrode, but a negative electrode having a high energy density was obtained, but on the other hand, Li was deposited during charging, resulting in a decrease in charge / discharge efficiency and contact with the positive electrode, resulting in an internal short circuit. Caused a problem. Therefore, at present, Li ion secondary batteries using a graphite-based carbon material that can reversibly store and release Li and have excellent cycle life characteristics and safety as a negative electrode have been put into practical use.

  However, when a graphite-based carbon material is used for the negative electrode, its theoretical capacity is 372 mAh / g, which is smaller than that of metal Li, and its theoretical density is 2.2 g / cc, which is a characteristic characteristic of Li secondary batteries. A sufficient energy density cannot be obtained.

  Thus, metal materials capable of higher capacity per volume have been studied. However, the use of metal materials for negative electrodes has a problem in cycle performance. As the charge and discharge are repeated, the negative electrode repeatedly expands and contracts, causing cracks and the like, and sufficient current collection cannot be maintained. For example, tin (Sn) is known as a substance that can be doped and dedoped with Li, and has a high theoretical capacity of 790 mAh / g. However, it has been difficult to produce a battery with good cycleability because the plate-like Sn is doped with Li because of a large volume expansion. This is considered to be because Sn, which has repeatedly changed in volume by repeated cycles, is released from the plate-like Sn serving as the substrate while containing Li, and does not participate in charge / discharge.

  Furthermore, recently, a metal oxide conductor material has attracted attention as a material having a high charge / discharge capacity. For example, Patent Document 1 discloses that a high discharge capacity was obtained when tin oxide was used for a negative electrode for a Li secondary battery. Patent Document 2 discloses that the charge / discharge capacity per unit weight is increased by increasing the specific surface area of tin oxide. Furthermore, attempts have been made to add a second component element or to make the metal oxide amorphous.

On the other hand, a new configuration of a Li-ion secondary battery using a solid electrolyte has been proposed in response to the demand for miniaturization of a secondary battery and integration with a circuit board. For example, a battery having a configuration in which an electrode and an electrolyte, which are basic constituent materials of a battery, are laminated in a thin film by a vacuum process is disclosed (see Patent Document 3). The above problem is common to the batteries having such a configuration.
Japanese Patent Laid-Open No. 07-122274 Japanese Patent Laid-Open No. 10-23321 JP 2001-76710 A Japanese Patent Laid-Open No. 10-004220 JP-A-10-003904 JP 2003-147514 A JP 2003-306764 A JP 2003-268536 A Laser Research (The Laser Society of Japan) Vol. 28, No. 6, Sasaki, et al., “Preparation of metal oxide nanoparticles by laser ablation”, June 2000

  As described above, the conventional secondary battery has a problem that the cycle life is shortened due to the volume change of the negative electrode during the insertion and release of Li ions. Also, in order to solve this problem, if pores are formed in the negative electrode to increase the specific surface area, the weight of the active material that can be filled in a battery with a constant volume is reduced, and the charge / discharge capacity of the battery is reduced. There was a problem of a decrease.

  Furthermore, the shape of the negative electrode used in the prior art is powdery. When a powdered material is used as the negative electrode, a binder is required, and therefore the unit weight and charge / discharge capacity per unit volume are reduced.

  Therefore, as the negative electrode of the secondary battery, the active material is arranged with regularity in a uniform shape with no wasted space, and the thickness of the active material layer is also made uniform, so that more Li can be occluded and released. This leads to an improvement in energy density per weight and per volume of the battery.

  The present invention has been made in view of the above points, and provides a negative electrode for a secondary battery that reduces the volume change of the negative electrode during insertion and extraction of Li ions and has high capacity, cycle life, and efficiency. Objective. And in the manufacturing method, it aims at providing the manufacturing process for obtaining the negative electrode for secondary batteries which can acquire those favorable characteristics.

  In order to solve the above problems, the negative electrode for a secondary battery of the present invention is a negative electrode for a secondary battery composed of a metal compound nanostructure having a structure in which columnar structures are arranged.

  With the above configuration, the active material can be arranged with regularity in a uniform shape with no wasted space, and the thickness of the active material layer can be made uniform, further smoothing the insertion and release of Li. Further, it is possible to provide a negative electrode for a secondary battery having improved energy density per weight and volume of the battery, and a method for producing the same.

  More specifically, the invention described in claim 1 of the present invention is a negative electrode for a secondary battery characterized in that it is composed of a metal compound nanostructure having a structure in which columnar structures are arranged.

  Furthermore, as described in claim 2, it is desirable that the columnar structure has a fine dendritic structure having a nanometer size as a constituent unit.

  With the above configuration, the active material can be arranged with regularity in a uniform shape with no wasted space, and the thickness of the active material layer can be made uniform, and the negative electrode at the time of occlusion and release of Li ions The volume change of can be reduced.

  Here, as described in claim 3, the metal compound nanostructure has at least one selected from Sn, In, Si, Ge, Al, Ga, Sb, Bi, and Ti as a component. It is preferable that it is composed of an oxide conductor. With this configuration, it is not necessary to mix conductive materials for maintaining conductivity, and the negative electrode can be filled with higher density.

  The invention described in claim 4 is a secondary battery using the secondary battery negative electrode according to any one of claims 1 to 3.

  The invention according to claim 5 is a thin film solid lithium secondary battery comprising a negative electrode using the negative electrode according to any one of claims 1 to 3, a solid electrolyte, and a positive electrode.

  With the above configuration, a secondary battery with high capacity, cycle life, and efficiency can be provided.

  The invention according to claim 6 controls the size of the high temperature and high pressure region formed in the vicinity of the target material by arranging the target material and the base material in the reaction chamber and irradiating the target material with beam light. Therefore, adjusting the pressure of the atmospheric gas introduced into the reaction chamber and the distance between the target material and the substrate, and introducing the atmospheric gas at the pressure into the reaction chamber, the target material The base material is formed of a metal compound nanostructure having a structure in which columnar structures are arranged by condensing and growing a substance contained in the target material that has been excited and desorbed by irradiating the target with a beam of light in the atmospheric gas. And a step of depositing on the negative electrode for a secondary battery.

  Here, as described in claim 7, it is desirable that the columnar structure has a fine dendritic structure having a nanometer size as a constituent unit.

  With the above configuration, it is possible to provide a manufacturing method that facilitates thinning and fixing of the negative electrode for a secondary battery.

  The invention described in claim 8 is a secondary battery using the negative electrode for a secondary battery manufactured by the method described in claim 6 or 7.

  According to the present invention, by forming a negative electrode for a secondary battery composed of a metal compound nanostructure having a structure in which columnar structures are arranged, the active material has regularity in a uniform shape without wasted space. It is possible to provide a negative electrode for a secondary battery having a high charge / discharge capacity and a high energy density that is less likely to be deteriorated due to repeated charge / discharge, and can be made uniform in thickness. it can.

  Moreover, since the manufacturing method of the negative electrode for secondary batteries of this invention is a highly purified vapor-phase thin film process, since a highly purified metal compound nanostructure can be directly deposited on a base material, It is possible to provide a manufacturing method that facilitates thinning and fixing of the negative electrode for a battery.

  Furthermore, a secondary battery having a high cycle life, a high charge / discharge capacity, and a high energy density can be provided by producing a secondary battery using the negative electrode for a secondary battery of the present invention. In particular, the thin-film solid Li secondary battery using the negative electrode for a secondary battery of the present invention has high compatibility with a semiconductor process, and therefore, the battery can be incorporated on a semiconductor integrated circuit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In this embodiment, a negative electrode for a secondary battery will be described.

  The negative electrode for a secondary battery in the present embodiment is composed of a metal compound nanostructure having a structure in which columnar structures having a size of about several tens of nm to several hundreds of nm are arranged with gaps. Furthermore, each columnar structure is composed of a fine dendritic structure having a size of about several nm to 100 nm. As a material of this metal compound nanostructure, a metal compound having any one or more selected from Sn, In, Si, Ge, Al, Ga, Sb, Bi, and Ti as a component, which can occlude and release Li Is used. That is, in the present application, non-transition metals represented by these are used.

  Further, the main component of the metal compound nanostructure is an oxide conductor having as a component at least one selected from Sn, In, Si, Ge, Al, Ga, Sb, Bi, and Ti. Is preferred. With this configuration, it is not necessary to mix conductive materials for maintaining conductivity, and the negative electrode can be filled with higher density.

  As a negative electrode for a secondary battery having the above structure, FIG. 1 shows an electron micrograph of a negative electrode for a secondary battery comprising a tin oxide nanostructure. (A) is the cross-sectional observation photograph by a scanning electron microscope (SEM), and has the structure where the columnar structure was arranged, and the thickness is substantially uniform. (B) is a photograph of the tip of the columnar structure of (a) observed with a transmission electron microscope (TEM) having high resolution, and the columnar structure is formed with a fine dendritic structure of nanometer size. I understand.

  In the above configuration, by forming a nanometer-sized fine dendritic structure, it is possible to increase the specific surface area of the active material and enable high-density packing, and smoothly and efficiently absorb and release Li ions. it can. In addition, by arranging the columnar structure having this dendritic structure as a regular unit with regularity, the thickness of the active material layer can be controlled to be constant, and a binder is not required during the production of the negative electrode. The diffusion of Li ions in the battery can be made uniform, and the energy density per weight and per volume of the secondary battery can be improved. Furthermore, the void formed by the dendritic structure and the columnar structure relaxes the volume change of the negative electrode during the insertion and extraction of Li ions, so that the cycle characteristics of the secondary battery can be improved.

(Embodiment 2)
In the present embodiment, the method for manufacturing the negative electrode for a secondary battery described in Embodiment 1 will be described in detail by taking the case of tin oxide as an example.

In this embodiment, a tin oxide nanostructure is deposited on a substrate by laser ablation in an atmospheric gas. The laser ablation method is a method of irradiating a target material with laser light having a high energy density (pulse energy: about 1.0 J / cm ² or more) and melting and desorbing the surface of the target material to be irradiated. .

  This method is characterized by a non-thermal equilibrium and massless process. A specific effect on non-thermal equilibrium is that spatial and temporal selective excitation is possible. In particular, because it has spatial selective excitation properties, in a conventional thermal process or plasma process, a considerably large area or the entire reaction vessel is exposed to heat or ions, whereas in the laser ablation method, only a necessary material source is present. Therefore, a clean process in which contamination with impurities is suppressed can be obtained. Further, the massless property means that the damage property is remarkably low as compared with the same non-thermal equilibrium ion process. Desorbed materials in laser ablation are mainly atoms, molecules, and clusters (consisting of several to several tens of atoms) that are ions and neutral particles, and their kinetic energy is several tens eV for ions. In the case of neutral particles, the level reaches several eV. This is a much higher energy region than the heated evaporation atoms, but a much lower energy region than the ion beam.

  Such a clean and less damaged laser ablation process is suitable for the fabrication of nanostructures with controlled impurity mixing, composition, crystallinity, and the like. Moreover, since such a nanostructure can be directly deposited on a base material, it is easy to make the negative electrode thin and fixed. In order to fabricate the nanostructure using the laser ablation method, it is desirable that the target material has absorption in the wavelength region of the laser beam that is a light source.

FIG. 2 is a diagram showing a configuration of a nanostructure manufacturing apparatus used for manufacturing the tin oxide nanostructure of the present invention. Here, the case where a tin oxide nanostructure as shown in FIG. 1 is produced by performing laser ablation using a tin oxide (SnO ₂ ) sintered target will be described.

  In FIG. 2, reference numeral 201 indicates a metal reaction chamber in which a target is disposed. At the bottom of the reaction chamber 201 is provided an ultra-vacuum exhaust system 202 that exhausts the air in the reaction chamber 201 to make the reaction chamber 201 ultra-vacuum. A gas introduction line 204 that supplies atmospheric gas to the reaction chamber 201 is attached to the reaction chamber 201. A mass flow controller 203 that controls the flow rate of the atmospheric gas supplied to the reaction chamber 201 is attached to the gas introduction line 204. A gas exhaust system 205 that differentially exhausts the atmospheric gas in the reaction chamber 201 is provided at the bottom of the reaction chamber 201. A valve is provided in the gas introduction line 204 between the reaction chamber 201 and the mass flow controller 203. Valves are also provided between the ultra-vacuum exhaust system 202 and the reaction chamber 201 and between the gas exhaust system 205 and the reaction chamber 201, respectively.

A target holder 206 that holds the target 207 is disposed in the reaction chamber 201. A rotation shaft 206a is attached to the target holder 206, and the target 207 is rotated (8 rotations / minute) by rotating the rotation shaft under the control of a rotation control unit (not shown). A base material 209 is disposed so as to face the surface of the target 207. A substance desorbed and ejected from the target 207 excited by laser light irradiation is deposited on the base material 209. Here, a tin dioxide (SnO ₂ ) polycrystalline sintered body target (purity 99.9%) is used as the target.

  A pulsed laser light source 208 that irradiates the target 207 with laser light as an energy beam is disposed outside the reaction chamber 201. A laser introduction window 210 for introducing laser light into the reaction chamber 201 is attached to the upper part of the reaction chamber 201. On the optical path of the laser light emitted from the pulse laser light source 208, a slit 211, a lens 212, and a reflecting mirror 213 are arranged in order from the laser light source 208, and the laser light emitted from the pulse laser light source 208 is transmitted through the slit 211. It is shaped, collected by the lens 212, reflected by the reflecting mirror 213, and irradiated to the target 207 installed in the reaction chamber 201 through the laser introduction window 210.

The operation of the nanostructure manufacturing apparatus having the above configuration will be described. The inside of the reaction chamber 201 is evacuated to an ultimate vacuum of about 1.0 × 10 ⁻⁶ Pa by an ultra-high vacuum exhaust system 202 mainly composed of a turbo molecular pump, and then from a gas introduction line 204 via a mass flow controller 203. , He gas is introduced. Here, the atmospheric rare gas pressure in the reaction chamber 201 is set to one pressure value in the range of about 10 to 1000 Pa by interlocking with the operation of the gas exhaust system 205 mainly composed of a scroll pump or a helical groove pump.

In this state, a laser beam is irradiated from the pulse laser light source 208 to the surface of the SnO ₂ polycrystalline sintered body target 207 having a purity of 99.9%, which is disposed on the target holder 206 having a rotation mechanism. Here, an argon fluorine (ArF) excimer laser (wavelength: 193 nm, pulse width: 12 ns, pulse energy: 50 mJ, energy density: 1 J / cm ² , repetition frequency: 10 Hz) was used. At this time, a laser ablation phenomenon occurs on the surface of the SnO ₂ target 207, and Sn and O ions or neutral particles (atoms, molecules, and clusters) are desorbed. It is ejected while maintaining the size of molecules and clusters mainly in the target normal direction (that is, the normal direction to the surface of the target 207). This desorbed material collides with atmospheric gas atoms (here, He), thereby making the flight direction messed up and dissipating kinetic energy into the atmosphere (ie, He). Aggregation is promoted. As a result, it is deposited as a nanostructure on the substrate 209 facing away by about 35 mm. Therefore, the average particle diameter of tin oxide deposited on the substrate increases as the number of collisions with the atmospheric gas atoms increases, that is, as the atmospheric gas pressure increases. In addition, neither the temperature of the base material 209 nor the temperature of the target 207 is positively controlled.

  By the above method, the fine structure was evaluated by observation with a scanning electron microscope for the tin oxide deposited by changing the pressure of the He gas as the atmospheric gas in the range of 10 to 1000 Pa. As a result, a thin-film-like deposit composed of fine particles having a minimum constitutional unit of several nm or less is obtained at 10 Pa, and the formation of a columnar structure is observed at 100 Pa while the fine particles of the smallest constitutional unit grow and increase with increasing pressure. It came to be able to. When the pressure was further increased, the columnar structures became clearly visible, and it was observed that voids were formed in each columnar structure.

As an example, an electron microscope observation photograph of tin oxide deposited at a He gas pressure of 266 Pa is shown in FIGS. (A) is a cross-sectional SEM observation photograph, which is a structure in which columnar structures with a width of about 80 nm are arranged with gaps, and the thickness is approximately uniform at about 560 nm. (B) is a high-resolution TEM observation photograph of the tip of the columnar structure of (a), and it can be seen that the columnar structure is formed from a fine dendritic structure having a length of about 50 nm. Furthermore, as a result of the composition analysis of the obtained nanostructure, it was found that SnO ₂ having the same composition as the target was obtained in any case.

  When the pressure was further increased, a columnar structure was not seen from about 500 Pa, and a polycrystalline body having a size of about 100 to 200 nm was aggregated.

  The above results are summarized and shown in the (1) column of Table 1. When the target-substrate distance (D) is 35 mm and He is used as the atmospheric gas, the nanostructure has a structure in which columnar structures are arranged with gaps in the range of the gas pressure (P) of about 100 to 500 Pa. It was found that a body was formed.

以上においては、雰囲気ガスとして、Ｈｅガスを用いたが、Ａｒ，Ｋｒ，Ｘｅ，Ｎ₂等の他の不活性ガスを用いてもよい。この場合、気体密度がＨｅガスの場合と同等になるように圧力を設定すればよい。例えば、雰囲気ガスとしてＡｒ（気体密度：１．７８ｇ／ｌ）を用いる場合には、Ｈｅ（気体密度：０．１８ｇ／ｌ）を基準とすると０．１倍程度の圧力に設定すればよい。

In the above, He gas is used as the atmospheric gas, but other inert gases such as Ar, Kr, Xe, and N ₂ may be used. In this case, what is necessary is just to set a pressure so that a gas density may become equivalent to the case of He gas. For example, when Ar (gas density: 1.78 g / l) is used as the atmospheric gas, the pressure may be set to about 0.1 times based on He (gas density: 0.18 g / l).

  The results of fine structure evaluation by scanning electron microscope observation on the tin oxide deposited using Ar as the atmospheric gas and changing the gas pressure are summarized in the column (2) of Table 1. It was found that a columnar structure can be obtained at a pressure lower by an order of magnitude than that of He gas.

Further, in laser ablation, there is a correlation between the atmospheric gas pressure (P) and the target-substrate distance (D). A substance emitted from the target by laser irradiation forms a plasma state called a plume. Since this plume is affected by the collision with the atmospheric gas, the size of the plume is dependent on the gas pressure. The higher the gas pressure, the smaller the plume. Furthermore, the characteristics of the deposit are highly dependent on the speed at which the injected material from the target reaches the substrate. For this reason, in order to obtain the same characteristics, there is a correlation that PD ⁿ = constant as a process condition in which the speed is constant, and the value of n is about 2 to 3. Therefore, for example, when D is doubled, the corresponding gas pressure may be about 1/4 to 1/8.

  The results of fine structure evaluation by scanning electron microscope observation on the tin oxide deposited with the target-substrate distance (D) of 50 mm and changing the He gas pressure are summarized in the column (3) in Table 1. . It was found that a columnar structure can be obtained at a pressure of about ½ compared to the case of D = 35 mm.

Note that in the production of metal oxide nanostructures, particularly when the atmospheric gas pressure is low, oxygen injected from the target is exhausted as gas molecules, and deposited on the substrate. Oxygen loss may occur in the structure. In such a case, a mixed gas of an inert gas and an oxidizing gas may be used as the atmospheric gas. In this case, the substance (mainly atoms, ions, and clusters) ejected from the target by laser irradiation is in contact with the oxidizing gas in addition to the physical interaction (impact, scattering, confinement effect) with the inert gas. Since it reaches the substrate through chemical interaction (oxidation reaction), oxidation of the metal oxide nanostructure deposited on the substrate can be promoted. As the oxidizing gas, if O ₂ , O ₃ , N ₂ O, NO ₂ or the like is used and the ratio is 0.1 to 50% in mass flow rate ratio, compared with the case where only the oxidizing gas is used. This is preferable because it can be consistent with other processes. Also in this case, the pressure may be set so that the average gas density of the atmosphere mixed gas is equivalent to that in the case of the He gas.

Furthermore, it is effective to activate the oxidizing gas by applying energy. For example, when an ArF excimer laser is used as the laser light source, the O ₂ molecules are also easily decomposed by laser irradiation to become active O atoms or ions, which promotes the oxidation of the injection material from the target. Become.

As an example, as a result of depositing tin oxide at a gas pressure of 266 Pa using He-diluted 1% O ₂ gas as the atmospheric gas, a nanostructure similar to that shown in FIG. 1 was obtained.

Moreover, it may be necessary to further adjust the composition and crystallinity of the tin oxide nanostructure obtained by the above method. In such a case, it is effective to add a step of heating the substrate after deposition and maintaining it at a constant temperature. For example, when an X-ray diffraction measurement was performed on a sample obtained by heat-treating an SnO ₂ nanostructure deposited at He gas pressure: 667 Pa in oxygen gas at 200 to 350 ° C. for 10 minutes, the nanostructure crystals It was found that the performance was improved. Alternatively, a SnO ₂ nanostructure deposited at a He gas pressure of 667 Pa can be reduced by performing a heat treatment at 300 to 400 ° C. for 10 minutes in nitrogen gas to obtain a SnO nanostructure.

  As described above, according to the manufacturing method of the tin oxide nanostructure of the present embodiment, it is not necessary to heat the substrate, and even if an inert gas not containing oxygen is used, the target is controlled by controlling the atmospheric gas pressure. Nanostructures reflecting the composition could be fabricated. As a result, the composition of the target 307 was maintained by optimizing the interaction (collision, scattering, confinement effect) of the substance (mainly atoms, ions, and clusters) emitted from the target by laser irradiation and the atmospheric gas. This indicates that it is possible to produce a metal compound nanostructure having a structure in which columnar structures having nanometer-sized fine dendritic structures as constituent units are arranged.

  Further, as apparent from the above results, the size of the dendritic structure of the structural unit can be controlled by the pressure of the atmospheric gas. Therefore, in the above method for producing a metal oxide nanostructure, the structure control in the deposition direction of the nanostructure becomes possible by changing the introduction pressure of the atmospheric gas during laser ablation. Physical properties can be controlled.

(Embodiment 3)
In the present embodiment, a secondary battery using the negative electrode for a secondary battery of the present invention will be described by taking a thin-film solid Li battery using a solid electrolyte as an example.

  FIG. 3 is a cross-sectional view showing the configuration of a thin-film solid Li secondary battery using the secondary battery negative electrode of the present invention. In FIG. 3, reference numeral 31 denotes a substrate, which has a structure in which a positive electrode 32, a solid electrolyte 33, and a negative electrode 34 are sequentially laminated, and an extraction electrode 35 is formed on the negative electrode 34.

  As the substrate 31, a metal material plate, foil, or the like can be used. Or what vapor-deposited the electrically conductive film on various transparent materials, such as glass, or an opaque material may be used.

As a material constituting the positive electrode 32, materials normally used for a positive electrode of a Li ion secondary battery can be used. For example, Li _x CoO ₂ , Li _x MnO ₂ , Li _x Mn ₂ O ₄ , Li _x NiO ₂ , Compounds such as Li _x TiS ₂ , Li _x MoS ₂ , and Li _x Mo ₆ S ₈ (where x ≧ 0) can be used.

The solid electrolyte 33 is at least selected from the group consisting of SiS ₂ , Al ₂ S ₃ , P ₂ S ₅ , B ₂ S ₃ , Li ₂ O, Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₂ CO _3. An inorganic electrolyte containing one kind may be used. More preferably, as the electrolyte, it may be used Li ₂ S-X, or a glass solid electrolyte composed of Li ₂ S-X-Y. Here, X represents at least one selected from the group consisting of SiS ₂ , Al ₂ S ₃ , P ₂ S ₅ , and B ₂ S ₃ , and Y represents Li ₂ O, Li ₃ PO ₄ , Li ₂ SO _4. And at least one selected from the group consisting of Li ₂ CO ₃ . Alternatively, an organic solid electrolyte may be used. For example, a tetracyanoquinodimethane (TCNQ) compound or the like can be used.

  As a method of forming the positive electrode 32 or the solid electrolyte 33, a method such as vacuum deposition, sputtering, CVD, or coating by a sol-gel method of materials constituting each of them may be used.

  The negative electrode 34 is manufactured by depositing the negative electrode made of the metal oxide nanostructure described in the first embodiment. In the negative electrode produced in this way, volume change in the storage and release of Li ions by tin oxide is alleviated.

  Since the thin-film solid secondary battery having the above configuration has high compatibility with a semiconductor process, the battery can be incorporated on a semiconductor integrated circuit.

(Example 1)
First, a Cu thin film having a thickness of 100 nm was formed as a substrate 31 on a glass plate by sputtering. A LiCoO ₂ film serving as the positive electrode 32 was formed thereon by sputtering so as to have a thickness of about 500 nm, and then a LiTCNQ compound as the solid electrolyte 33 was deposited by about 1 μm. On the solid electrolyte 33, the columnar tin oxide nanostructure shown in FIG. 1 with a He gas pressure of 266 Pa is formed to a thickness of about 500 nm using the metal compound nanostructure manufacturing method described in the first embodiment. A negative electrode was formed by direct deposition. Further, after depositing an Al thin film as the take-out electrode 35, SiO ₂ was deposited as a protective film to obtain a thin film solid Li secondary battery.

About the produced thin film solid Li secondary battery, the charge / discharge test was done in 0.2-1.3V in the low current density of 0.2 mA / cm < ² >. As a result, it had battery performance, and the discharge capacity at the first charge was about 70 mAh / g in terms of the weight of the negative electrode. In addition, 10 charge / discharge cycle tests are repeated, and the 10th discharge capacity retention ratio ((10th discharge capacity / first discharge capacity) × 100 (%)) with respect to the first discharge capacity is measured. Thus, the cycle performance was evaluated. As a result, the maintenance rate of the discharge capacity was about 85%.

(Comparative Example 1)
The substrate 31, the positive electrode 32, and the solid electrolyte 33 were produced in the same manner as in Example 1. Next, 10 wt% of acetylene black as a conductive additive and 10 wt% of polyvinylidene fluoride as a binder were mixed with 80 wt% of commercially available tin oxide powder to prepare a negative electrode mixture. This negative electrode mixture was dissolved in an appropriate amount of N-methylpyrrolidone, applied and molded on the solid electrolyte 33, and dried under reduced pressure at 110 ° C. to form the negative electrode. Furthermore, the extraction electrode 35 and the protective film were produced in the same manner as in Example 1 to obtain a thin film solid Li secondary battery.

As a result of conducting a charge / discharge test in the range of 0.2 to 1.3 V at a low current density of 0.2 mA / cm ² for the prepared thin-film solid Li secondary battery, the discharge capacity at the first charge was negative The weight was about 30 mAh / g. In addition, as a result of evaluating the cycle performance by repeating the charging and discharging 10 times, the retention rate of the discharge capacity was about 50%.

  From the results of Example 1 and Comparative Example 1 above, it was confirmed that by using the negative electrode composed of the columnar non-transition metal oxide nanostructure of the present invention, the discharge capacity was large and the charge / discharge cycleability was also good. .

  In the present embodiment, the thin-film solid Li secondary battery has been described. However, the Li ion secondary battery of the present invention may be applied to commonly used configurations of a positive electrode, a negative electrode, an electrolyte, and a separator. Absent. For example, as the electrolyte, an electrolytic solution obtained by dissolving a salt normally used as an electrolytic solution in a Li ion secondary battery in an organic solvent may be used.

  The negative electrode for a secondary battery according to the present invention is useful as a negative electrode for a secondary battery having little deterioration due to repeated charge / discharge and having a high charge / discharge capacity and a high energy density.

  The secondary battery using the secondary battery negative electrode according to the present invention is useful as a secondary battery having a high cycle life, a high charge / discharge capacity, and a high energy density. In particular, since the thin film solid Li secondary battery using the negative electrode for secondary battery of the present invention has high compatibility with the semiconductor process, it is possible to incorporate the battery on a semiconductor integrated circuit. It can be expected to be put into practical use as an ultra-compact and highly reliable power source.

Electron micrograph of tin oxide nanostructure in Embodiment 1 of the present invention The block diagram which shows the nanostructure production apparatus in Embodiment 2 of this invention Sectional drawing which shows the structure of the thin film solid lithium ion secondary battery in Embodiment 3 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 201 Reaction chamber 202 Ultra-high vacuum exhaust system 203 Mass flow controller 204 Gas introduction line 205 Gas exhaust system 206 Target holder 207 Target 208 Pulse laser light source 209 Deposition substrate 210 Laser introduction window 211 Slit 212 Lens 213 Reflector 214 Plume 31 Substrate 32 Positive electrode 33 Solid electrolyte 34 Negative electrode 35 Extraction electrode

Claims (8)

A negative electrode for a secondary battery, comprising a metal compound nanostructure having a structure in which columnar structures are arranged. The negative electrode for a secondary battery according to claim 1, wherein the columnar structure has a fine dendritic structure having a nanometer size as a constituent unit. The metal compound nanostructure is composed of an oxide conductor having at least one selected from Sn, In, Si, Ge, Al, Ga, Sb, Bi, and Ti as a component. The negative electrode for a secondary battery according to claim 1 or 2, characterized in that: A secondary battery using the negative electrode according to claim 1. A thin film solid lithium secondary battery comprising a negative electrode using the negative electrode according to any one of claims 1 to 3, a solid electrolyte, and a positive electrode. Introducing the target material and the substrate into the reaction chamber, and controlling the size of the high temperature and high pressure region formed in the vicinity of the target material by irradiating the target material with beam light. The step of adjusting the pressure of the atmospheric gas and the distance between the target material and the substrate, and excitation by irradiating the target material with beam light while introducing the atmospheric gas at the pressure into the reaction chamber And condensing and growing a substance contained in the detached target material in the atmospheric gas, and depositing a metal compound nanostructure having a structure in which columnar structures are arranged on the substrate. A method for producing a negative electrode for a secondary battery. The method for producing a negative electrode for a secondary battery according to claim 6, wherein the columnar structure has a fine dendritic structure having a nanometer size as a constituent unit. A secondary battery using a negative electrode produced by the method according to claim 6.

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