JP2008305608A - Electrode for lithium secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a secondary battery excellent in charge/discharge characteristic. <P>SOLUTION: In the electrode for the secondary battery in which an electrode active material layer is laminated on a substrate by an aerosol deposition method, (1) the substrate contains at least one kind selected from a group comprising Cu, Ni and Fe, (2) an average thickness of the substrate is 5-40 μm, (3) the electrode active material is composite powder comprising an A component which is at least one kind selected from a group comprising Si and Sn and a B component which is at least one kind selected from a group comprising V, Fe, Co, Ni, Cu, Ag and Sb, (4) the laminated amount of the electrode active material is 5-15 mg/cm<SP>2</SP>, and (5) the porosity of the electrode active material is 20-50%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel electrode for a lithium secondary battery and a method for producing the same.

  Lithium secondary batteries such as lithium ion batteries and lithium polymer batteries have a high energy density, and in recent years, their use is expanding as main power sources for mobile communication devices, portable electronic devices and the like.

  Conventionally, various carbon materials such as graphite and carbon having a low crystallinity have been widely used as negative electrode materials for lithium secondary batteries. However, when only a carbon material is used, the usable current density is low and the theoretical capacity (discharge capacity) is also insufficient. For example, when only the graphite, which is one of the carbon materials, is used as the negative electrode material, the theoretical capacity is as low as 372 mAh / g, and thus further increase in capacity is desired.

  On the other hand, it is known that a high theoretical capacity can be obtained when lithium metal is used as the negative electrode material. However, when lithium metal is used, dendrites are deposited on the negative electrode during charging, and therefore, there is a problem that dendrites reach the positive electrode side by repeating charge and discharge, causing an internal short circuit. In addition, dendrites have a high reaction activity due to their large specific surface area, and a non-electron-conducting interface film consisting of decomposition products of the solvent is formed on the surface of the dendrite before the internal short circuit occurs. The resistance increases and the charge / discharge efficiency decreases. For these reasons, a lithium secondary battery using lithium metal as a negative electrode material has a problem of short cycle life, and has not yet reached a stage where it is widely put into practical use.

  Therefore, development of a negative electrode material for a lithium secondary battery, which is a substance having a discharge capacity larger than that of a general-purpose carbon material and made of a material other than lithium metal, is desired. For example, elements such as Si and Sn, nitrides and oxides thereof can form an alloy with lithium and occlude lithium, and the occlusion amount is much larger than that of carbon materials. The development of negative electrode materials is progressing.

  However, it has been pointed out that the negative electrode material containing these substances may cause large expansion / contraction of the electrode as lithium is absorbed and released during repeated charge / discharge cycles, and the electrode itself may be broken down. ing.

  Furthermore, since it has a large initial irreversible capacity as compared with the carbon material of the conventional electrode, the charge / discharge efficiency does not become close to 100%, resulting in a problem that the cycle deterioration becomes large.

  In order to solve the above problems, a metal element or a metalloid element capable of forming an alloy with lithium or a single metal element, an alloy or a compound is formed in recent years, and includes a porous body having pores in a continuous solid. A negative electrode has been proposed. Since this negative electrode is difficult to collapse when inserting and extracting lithium, it is said that excellent charge / discharge cycle characteristics can be obtained (Patent Document 1).

Further, the negative electrode particles having the surface of the particles of the negative electrode active material coated with the conductive material film are conveyed by a carrier gas and sprayed onto the negative electrode substrate at a high speed, and then subjected to heat treatment or reduction treatment to thereby obtain a negative electrode substrate. A negative electrode manufactured by forming a negative electrode active material film having a gap thereon has been proposed. This negative electrode has excellent charge / discharge cycle characteristics, and it is said that a negative electrode for a lithium battery having excellent durability and output characteristics can be obtained (Patent Document 2).
JP 2004-022512 A JP 2007-005201 A

  However, since the negative electrode of the cited document 1 requires steps such as catalytic conversion / removal of foamed urethane, there is a problem that the production is complicated and the production cost is increased.

  Also in the manufacturing method of the cited document 2, it is complicated to coat the conductive material film on the particle surface of the negative electrode active material, and there is a problem that the manufacturing cost increases. Moreover, since the negative electrode particles are sprayed onto the negative electrode substrate at high speed by the carrier gas, there is a problem that the substrate is damaged. Furthermore, since it heat-processes at the heating temperature of 400-550 degree | times, there also exists a problem which reduces the intensity | strength of a base material.

  Therefore, there is a demand for a method for producing a negative electrode for a lithium secondary battery that exhibits good battery performance such as an excellent charge / discharge cycle by a simple method.

  As a result of intensive studies in view of the problems of the prior art, the present inventor has found that the above object can be achieved by obtaining a specific process, and has completed the present invention. That is, this invention relates to the electrode for lithium secondary batteries manufactured by the manufacturing method of the following lithium secondary battery electrode, and the manufacturing method.

Item 1. An electrode for a secondary battery in which an electrode active material layer is laminated on a substrate by an aerosol deposition method,
(1) The base material includes at least one selected from the group consisting of Cu, Ni and Fe,
(2) The average thickness of the substrate is 5 μm to 40 μm,
(3) The electrode active material layer is at least one selected from the group consisting of A, which is at least one selected from the group consisting of Si and Sn, and V, Fe, Co, Ni, Cu, Ag and Sb. Consisting of a composite powder composed of B component,
(4) The lamination amount of the electrode active material layer is 5 to 15 mg / cm ² .
(5) The porosity of the electrode active material layer is 20 to 50%.
An electrode characterized by that.

  Item 2. Item 2. The electrode according to Item 1, wherein the composite powder has a primary particle size of 10 nm to 300 nm and an average secondary particle size of 1 μm to 10 μm.

  Item 3. Item 3. The electrode according to Item 1 or 2, further comprising a lithium layer on the electrode active material layer.

  Item 4. Item 4. The electrode according to Item 3, wherein the stacking amount of the lithium layer corresponds to 80 to 120% of the initial irreversible capacity of the electrode active material layer.

Item 5. A method for producing an electrode for a lithium secondary battery by laminating an electrode active material layer on a substrate,
(1) From an A component which is at least one selected from the group consisting of Si and Sn and (2) a B component which is at least one selected from the group consisting of V, Fe, Co, Ni, Cu, Ag and Sb A step of laminating the composed composite powder on a substrate containing at least one selected from the group consisting of Cu, Ni and Fe and having an average thickness of 5 μm to 40 μm by an aerosol deposition method; Manufacturing method provided.

  Item 6. Item 6. The production method according to Item 5, wherein the composite powder has a primary particle size of 10 nm to 300 nm and an average secondary particle size of 1 µm to 10 µm.

  Item 7. The manufacturing method of Claim 5 or 6 which performs the aerosol deposition method on the conditions whose pressure difference of a film-forming chamber and an aerosol chamber is 20 kPa-70 kPa.

Item 8. The gas for transporting the composite powder is at least one selected from the group consisting of Ar and N _2, the manufacturing method according to any one of Items 5-7.

  Item 9. Item 9. The method according to any one of Items 5 to 8, further comprising a step of laminating a lithium layer on the surface of the electrode active material layer.

  Item 10. Item 10. The manufacturing method according to Item 9, wherein the laminating step is a step of heat-treating at 90 to 180 ° C after the lithium layer is pressure-bonded to the electrode material surface.

The present invention is an electrode for a secondary battery in which an electrode active material layer is laminated on a base material by an aerosol deposition method. (1) The base material is selected from the group consisting of Cu, Ni and Fe. (2) The thickness of the substrate is 5 μm to 40 μm, and (3) the electrode active material layer is at least one element selected from the group consisting of Si and Sn. A composite powder comprising a component and a B component which is at least one element selected from the group consisting of V, Fe, Co, Ni, Cu, Ag and Sb, and (4) Lamination of the electrode active material layer The amount is 5 to 15 mg / cm ² , and (5) the porosity of the electrode active material layer is 20 to 50%.

  The present invention is characterized in that an electrode active material layer is laminated on a substrate by an aerosol deposition method. Thereby, the adhesiveness of an electrode active material layer and a base material is excellent, and it can function as an electrode for alkaline secondary batteries with favorable cycling characteristics. This is because the electrode active material layer is laminated by the aerosol deposition method, so that the electrode active material layer becomes (1) the composite powders constituting the electrode active material layer, and the composite powder and the base material are binders. (2) the composite powder is randomly arranged and a predetermined void is formed in the electrode active material layer (porous structure), etc. It is presumed to be caused.

  The base material is not limited as long as it contains at least one selected from the group consisting of Cu, Ni and Fe. For example, it may be composed of a single element of Cu, Ni, or Fe, an alloy composed of at least two of these, or an alloy of at least one of these and another element. Among these, Cu is particularly preferable. Thereby, when it uses as a negative electrode base material, it is hard to melt | dissolve at the time of charging / discharging reaction, and can demonstrate the outstanding electroconductivity.

  The surface roughness of the substrate is not particularly limited, and any of known smooth rolled copper foil, electrolytic copper foil having a rough surface and a smooth surface, and the like can be used. In particular, in the present invention, the substrate surface is preferably smooth. For example, it may be smoothed by a known rolling process, electrolytic smoothing process, or the like.

  The average thickness of the base material is 5 μm to 40 μm, preferably about 10 μm to 35 μm. If the average thickness is less than 5 μm, the deformation and wrinkle of the substrate may be increased. When the average thickness exceeds 40 μm, the rigidity of the base material increases when the electrode is bent, so that the electrode active material layer falls off or the entire electrode thickness increases, and the capacity of the battery itself decreases due to battery design. As a result, it becomes impossible to achieve a compact battery, which is an advantage of the alloy-based electrode. The average thickness in the present invention is measured by a digitalmatic micrometer.

  The electrode active material layer is selected from (1) an A component which is at least one element selected from the group consisting of Si and Sn, and (2) a group consisting of V, Fe, Co, Ni, Cu, Ag and Sb. It is composed of a composite powder composed of a B component which is at least one element.

  Although the ratio of the A component and the B component is not limited, it is preferable that the total amount of both is 100 atomic%, and the A component is about 30 to 70 atomic% and the B component is about 70 to 30 atomic%, more preferably. The A component is about 40 to 60 atomic% and the B component is about 60 to 40 atomic%.

  Preferable combinations of the A component and the B component include, for example, Sn—Cu, Sn—V, Sn—Fe, Sn—Co, Sn—Ag, Sn—Sb and the like.

  The composite powder constituting the electrode active material layer preferably has a primary particle size of 10 nm to 300 nm, and an average particle size (average secondary particle size) of secondary aggregates of 1 μm to 10 μm, more preferably. 2 μm to 8 μm.

  In particular, the primary particle size of the composite powder is preferably substantially in the range of 10 nm to 300 nm. Specifically, 90% or more of the primary particles are preferably in the range of 10 nm to 300 nm among all the primary particles.

  As such a composite powder, for example, it is preferable to use a powder produced by a mechanical alloying method described later.

  In the present invention, the primary particle diameter is a value measured by visual observation with a transmission electron microscope. The average secondary particle diameter is, for example, a value obtained by a laser diffraction method using a laser diffraction apparatus (manufactured by Shimadzu Corporation, “SALD-3000”).

The lamination amount (mass) of the electrode active material layer laminated on the substrate is usually about 5 to 15 mg / cm ² , preferably about 6 to 12 mg / cm ² . If it is less than 5 mg / cm ² , the capacity required for the battery cannot be obtained. On the other hand, when it exceeds 15 mg / cm ² , delamination between the electrode active material layer and the substrate tends to occur.

  The average thickness of the electrode active material layer is not limited, but is usually about 10 μm to 40 μm, preferably about 13 μm to 30 μm.

  The porosity of the electrode active material layer is about 20 to 50%. Preferably it is 30 to 50%. If it is less than 20%, the volume change of the electrode at the time of charge / discharge increases, and the deterioration of the cycle characteristics increases. On the other hand, if it exceeds 50%, the thickness of the entire electrode increases, and the capacity of the battery itself decreases due to the battery design, and it becomes impossible to achieve the compactness of the battery, which is an advantage of the alloy electrode.

  The porosity in the present invention refers to the ratio between the true density of the composite powder (the state before constituting the electrode active material layer) and the density of the electrode active material layer laminated by the aerosol deposition method. That is, it is obtained by the following formula (1).

  Porosity (%) = [(Density of electrode active material layer) / (True density of composite powder)] × 100 (1)

  The true density of the composite powder can be measured, for example, by dry density measurement by a constant volume expansion method using a dry automatic densimeter (“Acupic 1330” manufactured by Shimadzu Corporation). The density of the electrode active material layer can be determined by a value obtained by dividing the mass of the electrode active material layer by the volume occupied by the active material layer.

  In the electrode of the present invention, a lithium layer may be further provided on the electrode active material layer. As a result, an electrode having even more excellent reversibility, charge / discharge characteristics, and cycle characteristics can be obtained.

  The lithium layer only needs to contain a lithium element, and is selected from the group consisting of Li alone, Li and Al, In, Pb, Ag, Zn, Mg, Bi, Ga, Sn, Cu, Au, and the like. An alloy with at least one metal or a metal compound can be used. More specifically, Li, 99.9-80 mass% Li-0.1-20 mass% Al, 99.9-80 mass% Li-0.1-20 mass% In, 99.9-80 mass% Li-0. 1-20 mass% Pb, 99.9-80 mass% Li-0.1-20 mass% Ag, 99.9-80 mass% Li-0.1-20 mass% Zn, 99.9-80 mass% Li-0.1 20 mass% Mg, Li-0.1-20 mass% Bi, 99.9-80 mass% Li-0.1-20 mass% Ga, 99.9-80 mass% Li-0.1-20 mass% Sn, 99.9- Examples thereof include 80 mass% Li-0.1 to 20 mass% Cu, 99.9 to 80 mass% Li-0.1 to 20 mass% Au, and the like.

  The stacking amount of the lithium layer is not particularly limited and may be appropriately determined according to the stacking amount of the electrode active material layer. For example, the lithium layer may be adjusted to 80 to 120% of the initial irreversible capacity of the electrode active material layer. do it. If it is less than 80%, the reduction amount of the irreversible capacity may be reduced. On the other hand, if it exceeds 120%, lithium may deposit in a dendritic shape on the electrode surface during rechargeable battery, which may cause a short circuit.

  The electrode for a lithium secondary battery of the present invention is particularly suitable for use as a negative electrode.

  The lithium secondary battery of the present invention only needs to include the electrode for the lithium secondary battery of the present invention, and is produced by combining the electrode with a known or commercially available electrolytic solution, a container, or the like. Further, any type of battery such as a coin-type battery, a cylindrical battery, and a square battery may be used.

Method for Producing Lithium Secondary Battery Electrode The method for producing an electrode for lithium secondary battery of the present invention comprises (1) an A component that is at least one selected from the group consisting of Si and Sn, and (2) V, Fe. A composite powder composed of at least one B component selected from the group consisting of Co, Ni, Cu, Ag and Sb, containing at least one selected from the group consisting of Cu, Ni and Fe; It is characterized by comprising a step of laminating a substrate having an average thickness of 5 μm to 40 μm by an aerosol deposition method. That is, the production method of the present invention is characterized in that a composite powder composed of an A component and a B component is laminated on a specific substrate by an aero deposition method.

  In general, the aerosol position method is a method of forming a desired film on the surface of a substrate by dispersing a powder raw material such as fine particles in a gas and spraying an aerosol to the surface of a substrate. In the present invention, in particular, the composite powder is used as a powder raw material, and an electrode active material layer is laminated on a substrate using a desired film forming apparatus.

  An aerosol deposition method film forming apparatus used in the present invention is illustrated in FIG. This film forming apparatus conveys an aerosol generator 1 and an aerosol 5 in which a material powder (in the present invention, a composite powder in a state before being converted into an aerosol) 4 is dispersed in a carrier gas to generate an aerosol (composite powder) 5. A transport pipe 8, an injection nozzle 10 for injecting the aerosol 5, a film forming chamber 9 in which a substrate 11 is built, and a gas exhaust processing mechanism 13 for evacuating the film forming chamber 9 are provided. The aerosol generator 1 is provided with an aerosol chamber 3 in which the material powder 4 can be accommodated, and a vibration device 7 attached to the aerosol chamber and vibrating the aerosol chamber. An inlet pipe 6 from a gas cylinder for introducing a carrier gas is connected to the aerosol chamber. The leading end of the introduction tube 6 may be disposed, for example, about 10 mm to 30 mm above the bottom surface of the aerosol chamber and buried in the material powder 4.

  A pressure difference P is generated between the film forming chamber 9 and the aerosol chamber 3 by adjusting the amount of gas generated by the gas generator 2 and the amount of exhaust of the gas exhaust processing mechanism 13. The pressure difference P is preferably 20 kPa to 70 kPa. More preferably, it is 35 kPa to 65 kPa. By laminating the electrode active material layer with this pressure difference, the adhesion between the electrode active material layer and the substrate in the obtained electrode and the interparticle bond between the composite powders can be strengthened. Moreover, the burden (deformation, generation | occurrence | production of a wrinkle etc.) to a base material can also be suppressed. If the pressure is less than 20 kPa, the adhesion between the composite powders is lowered and the porosity is likely to exceed 50%, and the adhesion between the electrode active material layer and the substrate is also lowered, resulting in cycle deterioration of the electrode. May be easier. When it exceeds 70 kPa, the porosity becomes less than 20% by volume, and the volume change of the electrode during charging / discharging becomes large as in the case of an electrode using a conventional binder, and the cycle characteristics may be deteriorated.

  The substrate-jet nozzle distance 12 is preferably 2 mm to 30 mm. If it is less than 2 mm, the straightness of the powder contained in the carrier gas is strong and the substrate may be damaged. If it exceeds 30 mm, the straightness of the powder contained in the carrier gas is weak and the film formation rate may be lowered.

The gas (carrier gas) for conveying the material powder used in the aerosol deposition method may be appropriately determined according to the type of substrate and its thickness, but is selected from the group consisting of Ar and N _{2 in the} present invention. At least one gas is preferred. By using this gas, the gas flow rate can be delayed and the burden on the substrate can be suppressed. In addition, the composite powders and the composite powder and the substrate can be more closely adhered to each other, and the decrease in the porosity of the obtained electrode active material layer can be suppressed.

  The temperature at the time of performing the aerosol deposition method (temperature in the film formation chamber) may be about room temperature, specifically about 15 to 50 ° C., preferably about 20 to 40 ° C. Thereby, the strength reduction of a base material can be suppressed.

  Examples of the substrate 11 are the same as those described above. That is, it contains at least one of Cu, Ni and Fe and has an average thickness of 5 μm to 40 μm (preferably 10 μm to 35 μm). By selecting such a base material, it is possible to suppress the deformation of the base material and the formation of wrinkles during the aerosol deposition process, and it is possible to obtain an electrode that exhibits an excellent electrical conductivity because the active material is unlikely to fall off. .

  The composite powder composed of the A component and the B component used in the aerosol deposition method of the present invention is preferably processed in advance by a mechanical alloying method, a mechanical milling method, or the like. The mechanical alloying method and the mechanical milling method can be performed based on known conditions. For example, the A component and the B component prepared so as to be a composite powder having a desired mixing ratio may be charged into a ball mill and pulverized. By adopting this method, miniaturization and alloying can be promoted, and the primary particle diameter can be refined to a powder having a particle diameter of 10 nm to 300 nm to adjust to secondary particles having an average particle diameter of 1 μm to 10 μm. By producing a composite powder obtained by such a mechanical alloying method by an aero deposition method, an electrode having a desired structure can be suitably produced.

  As an apparatus used in the mechanical alloying method and the mechanical milling method, a mixer, a disperser, a pulverizer and the like generally used in the powder field can be used as they are. Specific examples include a reiki machine, a ball mill, a vibration mill, an agitator mill, and the like. Moreover, although either a dry type or wet type may be sufficient, it is preferable that it is a dry type which is not complicated on a process. Milling conditions can be set as appropriate according to the properties of the desired composite powder, etc. Generally, the centrifugal acceleration (input energy) in processing at room temperature (especially 10 to 40 ° C.) is 5 to 20 G. Is preferably about 7 to 15G.

  In the present invention, a lithium layer may be further laminated on the surface of the electrode active material layer of the electrode for a lithium secondary battery produced as described above. Although the lamination method is not limited, for example, it may be provided by transferring the lithium layer to the surface of the electrode active material layer using a transfer film in which a lithium layer is laminated on a film such as a plastic sheet. This transfer method will be described with reference to FIG. 2. After the lithium layer 16 formed on the plastic sheet and the electrode active material layer surface of the electrode 15 produced by the aerosol deposition method are overlaid, a roll press machine 14 is used. Then, only the plastic sheet 18 is peeled off from the pressure-bonded material 17 (the electrode 17 for the lithium secondary battery made of aerosol deposition covered with the lithium layer).

  After the transfer, heating may be performed as necessary. Thereby, lithium can be doped in the lithium irreversible site in the crystal lattice of the electrode active material layer of the electrode covered with the lithium layer manufactured as described above, and as a result, the reversibility of the electrode can be improved. .

  The heating temperature is preferably 90 to 180 ° C. If the temperature is less than 90 ° C., lithium doping may be insufficient. On the other hand, if the temperature exceeds 180 ° C., the lithium covering the lithium secondary battery electrode made of aerosol deposition dissolves before diffusing and the lithium is separated on the surface of the electrode active material layer, so that the dope may be insufficient. is there.

  Since the electrode for a lithium secondary battery of the present invention has a specific structure in which an electrode active material layer is formed by an aerosol deposition method, the adhesion between the base material and the active material particles (composite particles), and This is an electrode with strong bonding between the active material particles. For this reason, volume change at the time of lithium alloy phase formation at the time of charge can be eased, and exfoliation, pulverization, etc. of an electrode active material layer by repetition of lithium occlusion / release can be controlled. That is, the cycle characteristics are excellent.

  Moreover, when the electrode of this invention has a lithium layer on an electrode active material layer, it can exhibit the further outstanding reversibility, the outstanding charging / discharging characteristic, cycling characteristics, etc.

  According to the manufacturing method of the present invention, since a complicated process is not required, a lithium secondary battery electrode having excellent cycle characteristics and the like can be manufactured easily and at low cost.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

Example 1
<Mechanical alloying method>
Sn and Cu are used as the active material powder (raw material) and mixed so that the blending ratio is 1: 1 by atomic ratio, and 0.5 parts of stearic acid is added as a lubricant to 100 parts by weight of this active material powder (SnCu). Part by weight was mixed. Next, this mixture is put into a pulverizer (“Attritor MA1D” manufactured by Mitsui Mining Co., Ltd., bearing steel balls with a diameter of 2 mm: 16 kg), and a composite powder composed of intermetallic compound Cu ₆ Sn ₅ phase and Sn phase is prepared. As obtained, the centrifugal acceleration (input energy) was set to about 7 to 15 G, and the mechanical alloying treatment for 2 hours was performed.

As a result of measuring the particle size of the primary particles of the obtained composite powder with a transmission electron microscope, it was confirmed that all the particles were in the range of 10 to 300 nm. The average secondary particle size (average secondary particle size) of the composite powder was measured by a laser diffractometer “SALD-3000” manufactured by Shimadzu Corporation and confirmed to be 8.0 μm. It was confirmed that the true density of the composite powder was 7.5 g / cm ³ as a result of measurement using a dry automatic density meter “Accumic 1330” manufactured by Shimadzu Corporation by dry density measurement by a constant volume expansion method.

<Aerosol deposition method (AD method)>
The obtained composite powder was used to produce the electrode of the present invention by an aerosol deposition method using the film forming apparatus shown in FIG. Electrode preparation by the aerosol deposition method was carried out using 30 g of the obtained composite powder with a rolled copper foil having an average thickness of 10 μm as a substrate, (1) substrate-nozzle distance: 10 mm, (2) nozzle diameter: 30 mm in diameter, (3) Film formation chamber-aerosol chamber pressure difference: 50 kPa (4) Carrier gas: N ₂ gas. The produced electrode was 30 mm square and had a film thickness of 22 μm. The mass of the electrode active material layer was 10.1 mg / cm ² , and the porosity was 44.1%. This electrode was extracted with a 1 cm ² circular punch and dried under reduced pressure at 120 ° C. for 3 hours to produce a test electrode (negative electrode) of the present invention.

Using the prepared negative electrode, and using metallic lithium having a capacity of about 20 times or more the calculated test electrode capacity as the counter electrode (positive electrode), 1 mol of LiPF ₆ / ethylene carbonate (EC) + diethyl carbonate (DEC). Using a (EC: DEC = 1: 1 (volume ratio)) solution as an electrolyte, a coin-type test cell (CR2032 type) was produced. Next, the prepared test cells were charged until reaching 0V at a constant current density of about 0.2 mA / cm ^2, after 10 minutes of rest, to 1.0V at a constant current density of about 0.2 mA / cm ² Discharged until reached. This was evaluated by repeatedly charging and discharging as one cycle. The ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 1st cycle was taken as 77.8% as the discharge capacity retention rate. The discharge capacity at the 50th cycle was 2.9 mAh / cm ² . The results are shown in Table 1.

Examples 2-14
Using the same active material powder as in Example 1, an electrode was prepared by the aerosol deposition method in the same manner as in Example 1 under the conditions shown in Table 1. The results are shown in Table 1. The laminated electrode active material layer had a mass of 5.6 to 12.2 mg / cm ² and a porosity of 34.9 to 49.5%. The discharge capacity retention rates were all 65.2% or more. The discharge capacity at the 50th cycle was ² to 2.6 mAh / cm ² .

Examples 15-20
Active material powders of the type shown in Table 1 were mixed at the blending ratio (atomic ratio) shown in Table 1, and composite powders were obtained by the same mechanical alloying method as in Example 1.

The composite powder thus obtained was subjected to the electrode deposition by the aerosol deposition method in the same manner as in Example 1 under the conditions described in Table 1. The results are shown in Table 1. The active material mass was 8.8 to 10.6 mg / cm ² , and the porosity was 38.6 to 46.5%. The discharge capacity retention rate was 70.2% or more in all cases. The discharge capacity at the 50th cycle was ² to 2.4 mAh / cm ² .

Comparative Examples 1-3
Using the same active material powder as in Example 1, an electrode was produced by the aerosol deposition method in the same manner as in Example 1 under the conditions described in Table 1. The results are shown in Table 1. When the differential pressure of the carrier gas in Comparative Example 1 was lowered to 15 kPa, the mass of the laminated electrode active material layer was as small as 4.8 mg / cm ² and the porosity was as large as 64.9%. When the differential pressure of the carrier gas of Comparative Example 2 was increased to 80 kPa, the mass of the laminated electrode active material layer was as large as 16.1 mg / cm ² and the porosity was as small as 10%. When the carrier gas cooling capacity of Comparative Example 3 is greater than that of N ₂ and Ar, the mass of the laminated electrode active material layer is as small as 2.8 mg / cm ² and the porosity is 11.3%. It became low. In either case, the adhesion to the substrate was poor, delamination occurred, and it was difficult to use as an electrode, and the discharge capacity retention rate was as low as 60% or less.

Comparative Example 4
Sn and Cu were used as the active material powder, and an atomized powder was prepared by a water atomization method so that the mixing ratio of Sn and Cu was 1: 4 in atomic ratio. As a result of measuring the particle size of the primary particles of the obtained atomized powder with a transmission electron microscope, all the particles were 500 nm or more. The average diameter of the secondary agglomerated grains was 7.8 μm as a result of measurement by a laser diffraction method. An electrode was produced by the aerosol deposition method under the conditions shown in Table 1 in the same manner as in Example 1 except that this composite powder was used. The results are shown in Table 1. Although the differential pressure was 45 kPa with N ₂ carrier gas, when the atomized powder was used instead of the composite powder, the mass of the laminated electrode active material layer was as small as 2.4 mg / cm ² and the porosity was as small as 15%. The adhesion to the substrate is poor, delamination occurs, and it is difficult to use as an electrode. The discharge capacity retention rate is 38.2%, and the discharge capacity at the 50th cycle is 0. It was as low as 5 mAh / cm ² .

Comparative Example 5
85 parts by weight of the same active material powder as in Example 1, 10 parts by weight of 5 parts by weight of N-methylpyrrolidone (NMP) solution in which 5% by mass of a binder (polyvinylidene fluoride: PVdF) is dissolved, and 5 parts by weight of carbon black Were mixed to prepare a mixture. Subsequently, the said mixture was apply | coated to the electrolytic copper foil with the doctor blade, and the uniform coating film (about 4-5 mg / cm < ² >) was formed. After this was dried at 80 ° C. for about 10 minutes to volatilize and remove NMP, the electrolytic copper foil and the coating film were closely joined with a roll press machine, and the average thickness of the electrode active material layer was about 10 μm. Was made. The sheet was extracted with a 1 cm ² circular punch and dried under reduced pressure at 120 ° C. for 3 hours to obtain a test electrode (negative electrode) of Comparative Example 5.

Test cells were prepared and evaluated in the same manner as in Example 1. The discharge capacity retention rate was 17.6%, and the discharge capacity at the 50th cycle was as low as 0.3 mAh / cm ² . Since the test cell produced by the coating method is greatly deteriorated due to the volume change of the active material layer due to repeated charge / discharge cycles, sufficient charge / discharge cycle characteristics could not be obtained.

Example 21
A layer made of Li metal on the surface of a plastic sheet (polypropylene, thickness 50 μm) by a film forming process for about 10 minutes under a pressure difference (injection energy) of 20 to 80 kPa using a gas deposition apparatus (manufactured by ULVAC). (Thickness 3.7 μm, 0.2 mg / cm ² ) was formed. The initial irreversible capacity of the formed Li layer was 0.748 mAh / cm ² .

The Li layer was brought into contact with the electrode active material layer on the surface of the negative electrode (initial irreversible amount: 0.741 mAh / cm ² ) prepared in Example 1, and was crimped by a roll press using the apparatus shown in FIG. After heat treatment at 100 ° C., only the plastic sheet was peeled off to transfer the Li layer to the surface of the electrode active material layer. Using this Li layer laminated negative electrode, a test cell was prepared and evaluated in the same manner as in Example 1.

  The initial charge / discharge capacity curves of the test cells of Examples 1 and 21 are shown in FIG. As apparent from the capacity of the initial charge / discharge curve of FIG. 3, the initial irreversible capacity exists in the test cell of Example 1, whereas the irreversible capacity does not exist in the test cell of Example 21.

FIG. 1 shows an aerosol deposition method film forming apparatus used in the present invention. FIG. 2 shows a transfer apparatus used in the present invention. FIG. 3 is a graph showing the initial charge / discharge characteristics of the electrodes of Examples 1 and 21.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aerosol generating part 2 Gas generating part 3 Aerosol container 4 Material powder 5 Aerosol 6 Gas introduction pipe 7 Vibrator 8 Aerosol conveyance pipe 9 Film formation chamber 10 Injection nozzle 11 Base material 12 Base material-nozzle gap 13 Gas exhaust treatment mechanism 14 Roll Press machine 15 Aerosol deposition electrode 16 Lithium layer 17 Bonded material 18 Plastic sheet P1 Deposition chamber pressure P2 Aerosol chamber pressure P Pressure difference between both chambers

Claims (10)

An electrode for a secondary battery in which an electrode active material layer is laminated on a substrate by an aerosol deposition method,
(1) The base material includes at least one selected from the group consisting of Cu, Ni and Fe,
(2) The average thickness of the substrate is 5 μm to 40 μm,
(3) The electrode active material layer is at least one selected from the group consisting of A, which is at least one selected from the group consisting of Si and Sn, and V, Fe, Co, Ni, Cu, Ag and Sb. Consisting of a composite powder composed of B component,
(4) The lamination amount of the electrode active material layer is 5 to 15 mg / cm ² .
(5) The porosity of the electrode active material layer is 20 to 50%.
An electrode characterized by that.   The electrode according to claim 1, wherein the composite powder has a primary particle size of 10 nm to 300 nm and an average secondary particle size of 1 μm to 10 μm.   The electrode according to claim 1, further comprising a lithium layer on the electrode active material layer.   The electrode according to claim 3, wherein the amount of the lithium layer stacked corresponds to 80 to 120% of the initial irreversible capacity of the electrode active material layer. A method for producing an electrode for a lithium secondary battery by laminating an electrode active material layer on a substrate,
(1) an A component that is at least one selected from the group consisting of Si and Sn, and (2) a B component that is at least one selected from the group consisting of V, Fe, Co, Ni, Cu, Ag, and Sb A step of laminating a composite powder composed of a base material containing at least one selected from the group consisting of Cu, Ni and Fe by an aerosol deposition method on a substrate having an average thickness of 5 μm to 40 μm; A manufacturing method comprising:   The production method according to claim 5, wherein the composite powder has a primary particle diameter of 10 nm to 300 nm and an average secondary particle diameter of 1 μm to 10 μm.   The manufacturing method of Claim 5 or 6 which performs the aerosol deposition method on the conditions whose pressure difference of a film-forming chamber and an aerosol chamber is 20 kPa-70 kPa. The gas for transporting the composite powder is at least one selected from the group consisting of Ar and N _2, The process according to any one of claims 5-7.   The manufacturing method in any one of Claims 5-8 which further includes the process of laminating | stacking a lithium layer on the electrode active material layer surface.   The manufacturing method according to claim 9, wherein the step of laminating is a step of performing heat treatment at 90 to 180 ° C. after the lithium layer is pressure-bonded to the electrode material surface.

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