JP2008091328A - Lithium secondary cell and its manufacturing method - Google Patents

Lithium secondary cell and its manufacturing method Download PDF

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JP2008091328A
JP2008091328A JP2007227304A JP2007227304A JP2008091328A JP 2008091328 A JP2008091328 A JP 2008091328A JP 2007227304 A JP2007227304 A JP 2007227304A JP 2007227304 A JP2007227304 A JP 2007227304A JP 2008091328 A JP2008091328 A JP 2008091328A
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solid electrolyte
positive electrode
electrode layer
lithium
lithium secondary
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Katsuji Emura
Taku Kamimura
Mitsuyasu Ogawa
Yukihiro Ota
卓 上村
進啓 太田
光靖 小川
勝治 江村
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Sumitomo Electric Ind Ltd
住友電気工業株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/54Manufacturing of lithium-ion, lead-acid or alkaline secondary batteries

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery having a solid electrolyte and having a high capacity and excellent charge / discharge characteristics.
A lithium secondary battery having a positive electrode layer containing a transition metal element, a solid electrolyte layer, and a negative electrode layer containing lithium, the ratio of the apparent density of the positive electrode layer and the solid electrolyte layer to the theoretical density. Is a lithium secondary battery with 95% or more. In this battery, a positive electrode layer containing a transition metal element is pressure-molded at a pressure of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C., and a solid electrolyte layer is formed on the positive electrode layer. And Step 3 in which a negative electrode layer containing lithium is formed on the solid electrolyte layer.
[Selection figure] None

Description

  The present invention relates to a lithium secondary battery including a solid electrolyte and having a high capacity and excellent charge / discharge characteristics.

  Lithium secondary batteries using a lithium (Li) -based metal for the negative electrode (hereinafter also referred to as negative electrode layer) include those using an organic electrolyte and those using a solid electrolyte. Among them, the one using metal Li has a large discharge capacity per unit volume and is regarded as an ultimate battery. However, when metal Li is used for the negative electrode in the former, while it is repeatedly charged and discharged, it reacts with the electrolyte to form needle-like crystals that break through the separator and reach the positive electrode (hereinafter also referred to as the positive electrode layer), causing a short circuit. there is a possibility. For this reason, contrivances have been made to suppress this, such as composite materials in which carbon and Li metal foil are laminated, and composites with wood metal. Furthermore, since an organic electrolyte is used as the electrolyte, it often cannot withstand the temperature during reflow solder mounting, and there is a problem with heat resistance. On the other hand, the latter has no problem in heat resistance at a temperature comparable to that of reflow soldering. However, for prevention of short circuit by Li, for example, Japanese Patent Application Laid-Open No. 2004-179158 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-127743. As proposed in (Patent Document 2), Li metal or a composite material in which particles thereof are embedded in a carbon-based material has been used as a negative electrode material.

For example, a solid electrolyte layer (hereinafter referred to as battery) between a positive electrode layer (hereinafter also referred to as battery element 1) containing a transition metal element such as lithium cobaltate (LiCoO 2 ) and a negative electrode layer (hereinafter also referred to as battery element 3) containing Li. A lithium secondary battery having a basic structure in which element 2 is also stacked is a means for depositing these elements from the gas phase (hereinafter also referred to as a gas phase synthesis method) and a means for molding from a powder (hereinafter also referred to as a powder method). ). In addition, as a material of a solid electrolyte layer, the said patent document 2 and Journal of Non-Crystalline Solids, 123 (1990) pp.1. As introduced in 328-338 (Non-patent Document 1), Li compounds mainly containing phosphorus (P) and sulfur (S), those further containing oxygen (O), and the above-mentioned patent documents As introduced in 1, a Li compound containing niobium (Nb), tantalum (Ta) and oxygen (O) is known.

  In the case of the powder method, the raw material powder is produced mainly by means of rapid solidification of the melt (hereinafter also referred to as a rapid cooling method) or a mechanical milling method (hereinafter also referred to as an MA method) in which the powder is mixed and reacted with a ball mill or the like. I came. These powders are glassy and / or crystalline and are in the form of discs, lumps or flakes. The former is, for example, Non-Patent Document 1 and Japanese Patent Laid-Open No. 4-231346 (Patent Document 3), and the latter is, for example, Japanese Patent No. 3323345 (Patent Document 4), Japanese Patent Laid-Open No. 2004-265585 ( Patent Document 5) and the like.

For a method for producing a composite in which battery elements of a lithium secondary battery using a powder raw material are laminated (hereinafter also referred to as a battery element composite), see, for example, Journal of Japan Soc. Powder Metallurgy, Vol. 51, no. 2, pp91-97 (Non-patent Document 2), page 92, right column, means for pressure-molding a 10 mm diameter member at a pressure of 300 MPa, for example, Japanese Patent No. 3453099 (Patent Document 6) is a powder. Means for press-molding and integrating the negative electrode active material, the positive electrode active material, and the solid electrolyte at 3700 kg / cm 2 (36 kPa) have been introduced. Further, US Pat. No. 4,477,545 (Patent Document 7) discloses that a sulfide-based solid electrolyte and a lithium metal negative electrode are heated at a pressure of 10,000 to 100,000 psi (about 69 to 690 MPa) at 90 to 100 ° C. Introduces the means of inter-molding. Further, Japanese Patent Publication No. 5-48582 (Patent Document 8), Japanese Patent Application Laid-Open No. 2004-206942 (Patent Document 9) and Japanese Patent Application Laid-Open No. 59-151770 (Patent Document 10) use a sulfide-based solid electrolyte. A battery element composite molding means has been disclosed. Its molding are all carried out at room temperature, of the disclosed molded pressure is sequentially 80,000 psi (about 550MPa), 4ton / cm 2 (about 392 MPa) and 5 ton / cm 2 (about 490 MPa).

Although the molding density of the battery element obtained by the conventional powder method is not clear, the current density when the battery is driven is about several tens μA / cm 2 to several hundreds μA / cm 2 , and is 1 mA / cm 2. It is described as being 2 or less, and is considerably lower than 3 to 10 mA / cm 2 in a normal lithium ion secondary battery using an organic electrolyte.

In addition, in a lithium ion secondary battery using an organic electrolyte, a technique for forming a solid electrolyte film such as Li 4 Ti 5 O 12 on the surface of a positive electrode active material has been developed to improve current density (non-patent literature). 3). Further, in the all-solid-state battery system, in order to improve the current density on the surface of the positive electrode active material, a technique for forming a solid electrolyte film such as Li 4 Ti 5 O 12 on the surface of the positive electrode active material has been developed (non-patent) Reference 4).
JP 2004-179158 A JP 2004-127743 A JP-A-4-231346 Japanese Patent No. 3233345 Japanese Patent Application Laid-Open No. 2004-265685 Japanese Patent No. 3453099 U.S. Pat. No. 4,477,545 Japanese Patent Publication No. 5-48582 JP 2004-206942 A JP 59-151770 A Journal of Non-Crystalline Solids, 123 (1990) pp. 328-338 Journal of Japan Soc. Powder Metallurgy, Vol. 51, no. 2, pp91-97 International Meeting of Lithium Batteries, 2006, Abstract # 85 Proceedings of the 47th Battery Conference, pp. 542-543

  In the battery element composite made by the conventional powder method introduced above, the electrical contact resistance (hereinafter also simply referred to as contact resistance) at the interface of the molded battery element is large, so a high current density cannot be obtained. . The cause is that the constituent particles in the battery molded body are in a point contact state, and a contact area sufficient for the flow of Li ions is not ensured. For this reason, for example, the battery characteristic evaluation of the battery element composite according to Non-Patent Document 2 is performed under charge and discharge under pressure. However, this means requires a large-scale pressurizing means and is not practical.

On the other hand, in a secondary battery of a battery element composite in which thin films are laminated by a vapor phase synthesis method, each battery element is dense and the contact degree of the element interface is high, so that the contact resistance is greatly improved. However, since the positive electrode layer is as thin as 10 to several tens of μm, the capacity density per unit area is about several μAh / cm 2 at most. Therefore, in order to make the capacity density at least 1 mAh / cm 2 , it is necessary to greatly increase the thickness of the positive electrode active material.

  In order to increase the capacity density of a lithium secondary battery using a solid electrolyte, it is necessary to significantly increase the amount of the positive electrode active material per unit area, regardless of whether the powder method or the vapor phase synthesis method is used. In addition to the positive electrode active material and the positive electrode current collector, it is necessary to ensure sufficient electrical contact between the battery elements of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer.

  The present invention relates to a lithium secondary battery having a positive electrode layer containing a transition metal element, a solid electrolyte layer, and a negative electrode layer containing lithium, and the ratio of the apparent density of the positive electrode layer and the solid electrolyte layer to the theoretical density is 95%. This is the lithium secondary battery. Further, as an example, the present invention includes one in which the solid electrolyte is a lithium ion conductive solid electrolyte containing lithium (Li), phosphorus (P), and sulfur (S) as main components.

  In the secondary battery of the present invention described above, for example, the positive electrode layer containing a transition metal element is pressure-molded at a pressure of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C., and the solid electrolyte layer is Step 2 formed on the positive electrode layer, and Step 3 of forming a negative electrode layer containing lithium on the solid electrolyte layer. In this case, in Step 2, the solid electrolyte layer may be pressure-molded on the positive electrode layer under the same temperature and pressure conditions as in Step 1. Of course, both the positive electrode layer and the solid electrolyte layer may be simultaneously molded and integrated in step 1. In step 2, the solid electrolyte layer may be formed on the positive electrode by a gas phase synthesis method.

  According to the present invention, it is possible to provide a lithium secondary battery including a solid electrolyte layer excellent in charge / discharge characteristics at a practical current density comparable to that of a lithium ion secondary battery containing an organic electrolyte.

The positive electrode layer of the battery of the present invention is made of a material containing a transition metal element in the periodic table. Preferable examples of the material of the positive electrode layer include lithium cobalt oxide (chemical formula LiCoO 2 ), lithium manganate (chemical formula LiMn 2 O 4 ), and lithium iron phosphate (chemical formula LiFePO 4 ). Examples of the negative electrode layer include carbon (C) and lithium (Li), as well as aluminum (Al), silicon (Si), tin (Sn), and alloys of these with lithium.

  The material of the positive electrode layer and the solid electrolyte layer of the secondary battery according to the present invention is configured such that the ratio of the apparent density to the theoretical density (hereinafter also referred to as the theoretical density ratio) is 95% or more, preferably 98% or more. Yes. As a result, each particle of the positive electrode layer and the negative electrode layer is in direct contact with the particles of the same layer at the interface with the solid electrolyte layer, and the unit of the positive electrode active material that effectively contacts the solid electrolyte layer at the interface. The amount per area can be greatly increased. As a result, a lithium secondary battery including a solid electrolyte layer excellent in practical current density and charge / discharge characteristics comparable to a lithium secondary battery using an organic electrolyte can be provided.

The theoretical density ratio in the present invention is defined by the ratio (%) of the apparent density to the theoretical density of each battery element material. The theoretical density ρ t of the composite material constituting the battery element of the present invention is a value ρ n obtained by multiplying the theoretical density ρ n of the constituent chemical component n by the volume ratio v n (%) of the component in the battery element. v is the total sum Σρ n v n of n, apparent density [rho a composite material, a value w / v defined by the volume v calculated mass w of the same material from the outer dimensions. Therefore, the theoretical density ratio is represented by w / (v · Σρ n v n ) [%].

The reason why both the theoretical density ratios of the positive electrode layer and the solid electrolyte layer of the battery of the present invention are 95% or more is that the lithium ion conductivity in and between these battery elements is as described above when the ratio is less than 95%. This is because a battery having a practical density (1 mAh / cm 2 ) or more cannot be obtained at a practical level of current density (1 mA / cm 2 or more). In addition, it is natural to ensure sufficient electrical contact at the interface between the positive electrode active material and the positive electrode current collector.

As an example of the battery of the present invention when the above conditions are satisfied, the discharge capacity retention rate when the voltage during charging is 4.2 V, the voltage during discharging is 3 V, and the current value is 3 mA / cm 2. However, there are 95% or more. Note that the above condition setting levels for the voltage during charging and the voltage and current during discharging are normal for lithium secondary batteries. In conventional lithium secondary batteries, including those described in the above-mentioned documents, the discharge capacity maintenance rate under the same conditions is at most 25%.

  Hereinafter, representative examples of the method for producing the secondary battery of the present invention will be described. In this example, at least the starting material of the positive electrode layer is a powder. As described above, the secondary battery of the present invention includes, for example, step 1 in which a positive electrode layer containing a transition metal element is pressure-molded at a pressure of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C. The electrolyte layer is obtained by a method including Step 2 in which the positive electrode layer is formed on the positive electrode and Step 3 in which a negative electrode layer containing lithium is formed on the solid electrolyte layer. In this case, in step 2, the solid electrolyte layer may be pressure-molded on the positive electrode layer under the same temperature and pressure conditions as in step 1, and both the positive electrode layer and the solid electrolyte layer are molded integrally at the same time. It may be made. The solid electrolyte layer may be formed on the positive electrode by a vapor phase synthesis method. Further, in step 3, the negative electrode layer may be formed on the solid electrolyte layer by pressure bonding or vapor phase synthesis, or the negative electrode layer raw material may be laminated simultaneously or stepwise together with the positive electrode layer and the solid electrolyte layer to increase the pressure. It may be formed by adjusted powder molding.

The raw material powder for the positive electrode layer used in step 1 may be any material that contains a transition metal element in the periodic table of elements, but is usually a mixture of a solid electrolyte, a conductive additive, and an active material. For example, as described above, lithium cobalt oxide (chemical formula LiCoO 2 ) -based or spinel-type lithium manganate (chemical formula LiMn 2 O 4 ) -based lithium complex oxide may be used. Examples of the solid electrolyte powder in this case include (1) glassy powder that has been melted at high temperature and then rapidly cooled to near room temperature (melt-quench, melt quench or quenching method), and (2) mechanical milling. ) Glass-like powders, (3) powders obtained by heat-treating these glass-like powders in whole or in part (hereinafter referred to as re-crystallized powders), and (4) powders of the above form Examples thereof include a mixture and a composite of (5) the above-mentioned powder. The lithium ion conductivity of these solid electrolyte powders is preferably 1 × 10 −4 S / cm or more, and more preferably 1 × 10 −3 S / cm or more. Examples of conductive additives to be added include ketjen black, acetylene black, carbon fibers made by vapor deposition, carbon materials such as graphite, nickel (Ni), copper (Cu), stainless steel (SUS), etc. There are metal powders.

An oxide layer may be coated on the surface of the active material particles of the positive electrode layer. The oxide layer needs to have lithium ion conductivity. The solid electrolyte containing sulfur (S) easily reacts with an oxide-based positive electrode active material such as LiCoO 2 , and depending on the way of mixing, a reaction layer having poor Li ion conductivity may be formed at the interface. In particular, when heated, the reaction between the S-containing solid electrolyte and the oxide-based positive electrode active material is further promoted. By forming the lithium ion conductive oxide layer on a part of the positive electrode active material particles, generation of a reaction layer formed at the interface with the S-containing solid electrolyte can be suppressed.

  The thickness of the lithium ion conductive oxide layer may be 1 nm (nanometer) or more. Moreover, although the upper limit of thickness is influenced by the ionic conductivity of the lithium ion conductive oxide layer, it needs to be 100 nm or less. When the thickness exceeds 100 nm, the resistance value increases and the resistance is increased under the influence of the ion conduction characteristics of the lithium ion conductive oxide layer.

  The coverage on the positive electrode active material particles is desirably 10% or more and 90% or less of the total surface area. If it is less than 10%, the covering effect is limited, and if it exceeds 90%, current cannot be collected and the battery characteristics deteriorate.

As a material of the lithium ion conductive oxide, Li 2 O—SiO 2 , Li 2 O—B 2 O 3 , Li 2 O—P 2 O 5 , Li 2 O—TiO 2 , Li 2 O—Nb 2 O 5 , an amorphous compound of Li 2 O—Al 2 O 3 , Li 2 O—Ga 2 O 3 , Li 2 O—Bi 2 O 3 , Li 2 O—La 2 O 3 , and a composite compound thereof It is done. As a forming method, there are a wet method such as a sol-gel method and an aqueous solution method, and a vapor phase method such as a sputtering method and an MOCVD method.

  The positive electrode layer is produced, for example, by mixing each raw material powder obtained by the above means with a ball mill or the like and then performing pressure molding. In addition, in order to make the powder after mixing easy to handle until molding, and further to improve the compressibility at the time of molding, it is desirable to reduce the volume (filling volume per unit mass). For this reason, granulation etc. may be performed after mixing. However, in that case, it is desirable to take appropriate measures within a range that does not impair the function of the battery element, such as ensuring purity.

  The pressure molding in step 1 is performed at a pressure in the range of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C. The heating and pressurizing means may be any means as long as the theoretical density ratio of 95% or more can be secured and the practical function of the positive electrode layer is not adversely affected. For example, if the pressurizing means is a normal in-mold powder molding method, various embodiments can be applied, such as by interposing a heat source such as a sheet heater suitable for the mold or in a heated area. Is possible. The reason why the temperature at the time of pressurization is room temperature or higher and 250 ° C. or lower is that the plastic deformation of the solid electrolyte is insufficient if it is lower than room temperature (20 ° C.), and if it exceeds 250 ° C., the solid electrolyte is altered or the crystallinity is changed. This is because the ion conduction characteristics may be deteriorated. Since the powder particles of each constituent component in the raw material, particularly the solid electrolyte powder particles, are sufficiently plastically deformed by molding, the state in which the particles are in close contact with each other is maintained even after the pressure is released. The pressure is in the range of 750 to 2000 MPa. Desirably, it is 900 MPa or more. When the pressure is less than 750 MPa, the adhesion state between the particles is not maintained after the pressure is released, and a particle having a theoretical density ratio of 95% or more cannot be stably obtained. On the other hand, depending on the material, there may be no upper limit to the pressure from the viewpoint of increasing the contact interface between the battery elements. However, when the pressure exceeds 2000 MPa, the effect of increasing the bulk density due to the pressure increase is reduced, and the material of the molded container Is not practical because it is expensive and has a short useful life.

As the raw material powder for the solid electrolyte layer used in Step 2, for example, various chemical compositions prepared by the means (1) to (5) as mentioned in the description of Step 1 above are used. The lithium ion conductivity of the solid electrolyte layer after molding needs to be at least 1 × 10 −4 S / cm. The electronic conductivity is preferably 1 × 10 −9 S / cm or less. This is because if the electron conductivity exceeds this value, a leakage current is generated between the positive and negative electrodes, and the electrodes are easily short-circuited. While taking the above into consideration, it is necessary to select the type of raw material powder, its preparation means, etc. according to the specifications of the battery to be manufactured. In view of such a viewpoint and the above-described problem of the present invention, for example, those containing lithium (Li), phosphorus (P), and sulfur (S) are desirable. Furthermore, in order to ensure chemical stability with respect to the negative electrode layer mainly composed of Li metal, it is more desirable to include, for example, oxygen (O) in addition to these components. In addition, when using the mixture (composite material) of a several raw material component, it mixes by the means as mentioned in the description of the powder used for the above-mentioned positive electrode layer. If necessary, adjustment of the shape, size and distribution of the particles, granulation to improve the flow of the powder during molding, and adjustment of the bulk are performed.

  The solid electrolyte raw material powder is filled on the positive electrode layer pressure-molded using the raw material powder prepared as described above, and pressure-molded. The selection of the molding temperature and the pressurizing condition conforms to the contents already described in the description of the step 1. The solid electrolyte layer may be formed on the molded positive electrode layer by a gas phase synthesis method. Examples of the vapor phase synthesis method include a vapor deposition method, an ion plating method, a sputtering method, and a laser ablation method.

  In step 3, a negative electrode layer is formed on the solid electrolyte layer obtained by the above means. For the material of the negative electrode layer, an alloy mainly containing Li metal is usually used. Since these alloys are soft, high adhesion to the solid electrolyte layer is ensured, and further, there is almost no expansion or contraction in the surface direction of the negative electrode layer at the boundary with the solid electrolyte layer during charge / discharge. For this reason, a stable interface is formed. There are several options for the form of the negative electrode layer, such as a rolled foil and a deposited layer. The forming means is selected according to the desired form. For example, if it is foil-like, it may be pressure-bonded on the solid electrolyte layer. Also, for example, if a pressure-bonded layer or a vapor-deposited layer of metal foil containing Al, Sr, Mg, Ca is formed in advance on the solid electrolyte layer, when Li is supplied during battery charging, A means for automatically alloying with these components can also be adopted. The thickness of the negative electrode layer is not limited as long as it can be prevented that current can no longer be collected due to expansion or contraction in the thickness direction during charge / discharge.

  In addition, when three layers of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are formed by lamination, in Step 1, the raw material powder of the positive electrode layer and the solid electrolyte layer is stacked and filled, or a material that is a raw material of the negative electrode layer is further formed thereon It is also possible to adopt a means for simultaneously pressing and integrating in the mounted state.

  In the above, an example of the manufacturing method of the secondary battery of this invention has been demonstrated. This example is a case where at least the positive electrode layer is formed by powder molding, but if the thickness of the positive electrode layer is sufficient and the theoretical density ratio between the positive electrode layer and the solid electrolyte layer is 95% or more, Any means can be used without sticking to the means described. For example, the raw material may be a lump or a composite material of this and a powder. For example, the molding means may be any means that can satisfy a desired practical function such as isostatic pressing or rolling. Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

Both battery elements were laminated under various conditions described in the table using materials of various combinations of A to G made of materials of the positive electrode (battery element 1) and the solid electrolyte (battery element 2) described in Table 1. The composite was molded, and an Li alloy film containing 5 atomic% of Al and having a thickness of 1 μm was formed on the solid electrolyte layer of each obtained molded body sample by vapor deposition. Next, the battery element composite sample was assembled into a coin-type battery container and caulked into a battery sample. After charging these battery samples at 4.2 V, the discharge by the voltage 3V current value 0.38mA in to 1 mA (current density no (equivalent to approximately 3mA / cm 2 in current density) approximately 7.9mA / cm 2 The discharge characteristics of the battery were evaluated by shaking the power supply capacity, and the capacity retention ratio (theoretical calculated discharge) at a typical current value of 0.76 mA (corresponding to a current density of approximately 6 mA / cm 2 ). The ratio of the measured value to the capacity) was confirmed. The results are shown in Table 1.

* Indicates comparative example

  The horizontal axis of Table 1 will be described below. The material in the column of “positive electrode layer” indicates three combinations of A to C in which the prepared positive electrode active material and solid electrolyte are changed. The contents of each combination are as shown in Table 2. The molding conditions are the temperature and pressure when these mixtures are filled in a mold and pressed. The theoretical density ratio is a value calculated by the above formula from the mass and volume of the obtained molded positive electrode. The material in the column of “Solid electrolyte layer” is a prepared solid electrolyte, and the symbol indicates the type. Table 3 shows the composition and form of D to G. The average particle size of the F and G powders in Table 3 is the average value of the maximum diameters of the flaky particles. The display rules in the columns of molding conditions and theoretical density ratio are the same as in the case of the positive electrode described above. The “Battery Discharge Characteristics” column shows the evaluation results of the discharge characteristics after charging at 4.2 V in the battery evaluation described above, and the capacity maintenance rate when the discharge voltage is 3 V and the set current value is 0.76 mA. Show.

  In a glove box filled with Ar gas having a dew point of −90 ° C., put each positive electrode active material, solid electrolyte and acetylene black powder in a planetary ball mill made of alumina in the combinations and quantitative ratios shown in Table 2, Each was stirred and mixed for 1 hour. The mixed powder is put into a 4 mm diameter cemented carbide mold in which a heating source is incorporated, and added as shown in Table 1 in combination with each of the solid electrolyte raw materials separately prepared by the component constitution and manufacturing method shown in Table 3. The pressure conditions were changed, and 30 molded bodies each having the thickness shown in Table 1 were produced using a hydraulic press. The filling amount of the powder into the mold of each layer was confirmed in advance according to each molding condition, and adjusted to the thickness described in the table. In addition, about each theoretical density ratio (%), five test pieces were extracted, the mass and volume of each molded object were confirmed, and it calculated using the theoretical density calculated from each raw material structure. The values in Table 1 are the arithmetic average values. Further, a negative electrode layer was vapor-deposited on the solid electrolyte layer as described above to prepare a battery composite sample comprising battery elements 1 to 3. Next, each composite sample was assembled into a battery case and caulked to obtain a coin-type battery sample. In addition, the formation procedure of the layer by vapor deposition is as follows. First, the positive electrode layer of Sample 4 was formed by sputtering, the solid electrolyte layer of the same sample was formed by vapor deposition, and the solid electrolyte layers of Samples 26 to 28 were formed by vapor deposition.

  The produced coin-type battery sample was charged at 4.2 V, and then the capacity retention rate was confirmed when the current value was 0.76 mAh at a discharge voltage of 3 V. Even when a negative electrode layer having the same chemical composition made of a foil-like metal is placed on a molded body made of the same positive electrode layer and solid electrolyte layer as that of Sample 1, the secondary battery having the same characteristic level as Sample 1 is formed. It turns out that it is obtained. Although not shown in Table 1, the battery sample of Sample No. 15 was charged at 4.2 V and then discharged at a discharge voltage of 3 V and a current value of 0.38 mA. The discharge capacity was 0.35 mA, which is theoretical. It was 97% of the discharge capacity (theoretical value) calculated to 0.36 mA.

  In the case of using a material in which a part of boron (B) and sulfur (S) is replaced with oxygen (O) or nitrogen (N) instead of phosphorus (P) in the chemical composition of the solid electrolyte layer, It has been found that a lithium secondary battery having a higher current density and discharge capacity retention rate can be obtained by integrating the positive electrode layer and the solid electrolyte layer more densely and more closely by the means of the present invention.

A lithium ion conductive oxide layer was formed on the surface of the positive electrode active material. LiCoO 2 was used as the positive electrode active material, and Li 2 O—SiO 2 -based amorphous was used as the lithium ion conductive oxide layer. The lithium ion conductive oxide was formed as follows. A coating solution was prepared by mixing a tetraethylorthosilicate solution in a solution in which Li metal was dissolved in ethanol. After immersing and mixing LiCoO 2 powder in this coating solution, the solvent ethanol is removed by evaporation, and heat treatment is performed at 400 ° C. to form a Li 2 O—SiO 2 amorphous film on the surface of LiCoO 2 particles. Formed. The film thickness of the formed amorphous film was 10 nm from the increase in weight.

Using a LiCoO 2 active material in which a Li 2 O—SiO 2 amorphous film is formed, mixing is performed at a mixing ratio of 70% by weight of active material and 30% by weight of sulfide solid electrolyte, and a positive electrode active material layer Formed. Other than that, an all-solid battery was produced in the same manner as in Example 1.

  Regarding the battery performance, even when the current density was further doubled to 1.5 mA, approximately the same charge / discharge capacity was secured.

  The lithium secondary battery including the solid electrolyte layer of the present invention has excellent charge / discharge characteristics and a current density comparable to a lithium ion secondary battery containing an organic electrolyte. For this reason, according to the present invention, it is possible to provide a lithium secondary battery more useful than the conventional one including the solid electrolyte layer.

Claims (8)

  1. A lithium secondary battery having a positive electrode layer containing a transition metal element, a solid electrolyte layer, and a negative electrode layer containing lithium, wherein the ratio of the apparent density of the positive electrode layer and the solid electrolyte layer to the theoretical density is 95% or more Lithium secondary battery.
  2. The lithium secondary battery according to claim 1, wherein the solid electrolyte layer is a lithium ion conductive solid electrolyte mainly composed of lithium (Li), phosphorus (P), and sulfur (S).
  3. Step 1 in which a positive electrode layer containing a transition metal element is pressure-molded at a pressure of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C., and Step 2 in which a solid electrolyte layer is formed on the positive electrode layer. And a step 3 of forming a negative electrode layer containing lithium on the solid electrolyte layer.
  4. 4. The lithium secondary battery according to claim 3, wherein the step 2 is a step in which the solid electrolyte layer is pressure-molded on the positive electrode at a pressure of 750 to 2000 MPa under a temperature condition of room temperature to 250 ° C. 5. Production method.
  5. The method of manufacturing a lithium secondary battery according to claim 3, wherein the step 2 is a step in which the solid electrolyte layer is formed on the positive electrode layer by a vapor phase synthesis method.
  6. 6. The method of manufacturing a lithium secondary battery according to claim 3, wherein the step 3 is a step in which the negative electrode layer is formed on the solid electrolyte layer by a pressure bonding method or a gas phase synthesis method.
  7. 3. The lithium secondary battery according to claim 1, wherein a lithium ion conductive oxide layer is coated on a part of the surface of the positive electrode active material particles in the positive electrode layer containing the transition metal element.
  8. 6. The lithium secondary according to claim 3, wherein a lithium ion conductive oxide layer is coated on a part of the surface of the positive electrode active material particles in the positive electrode layer containing the transition metal element. Battery manufacturing method.
JP2007227304A 2006-09-04 2007-09-03 Lithium secondary cell and its manufacturing method Pending JP2008091328A (en)

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JP2009266728A (en) * 2008-04-28 2009-11-12 Toyota Motor Corp Resistance layer formation suppression coat layer covered positive electrode active material, and all solid lithium secondary battery using it
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JP2009277383A (en) * 2008-05-12 2009-11-26 Sumitomo Electric Ind Ltd Li2s-p2s5 based solid electrolyte, and method of manufacturing the same
JP2009277565A (en) * 2008-05-16 2009-11-26 Sumitomo Electric Ind Ltd Film-forming method and battery
JP2009301959A (en) * 2008-06-16 2009-12-24 Sumitomo Electric Ind Ltd All-solid lithium secondary battery
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CN102024932A (en) * 2009-09-11 2011-04-20 丰田自动车株式会社 Electrode active material layer, all solid state battery, manufacturing method for electrode active material layer, and manufacturing method for all solid state battery
JP2011086610A (en) * 2009-09-17 2011-04-28 Ohara Inc All-solid battery and method of manufacturing the same
WO2012099178A1 (en) * 2011-01-19 2012-07-26 住友電気工業株式会社 Nonaqueous electrolyte battery
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JP2013012416A (en) * 2011-06-29 2013-01-17 Sumitomo Electric Ind Ltd Nonaqueous electrolyte battery and nonaqueous electrolyte battery manufacturing method
US9413034B2 (en) 2011-07-27 2016-08-09 Toyota Jidosha Kabushiki Kaisha Method for manufacturing solid battery
JP2013051033A (en) * 2011-08-30 2013-03-14 Semiconductor Energy Lab Co Ltd Manufacturing method of electrode and power storage device
JP2015506063A (en) * 2011-11-29 2015-02-26 コーニング インコーポレイテッド Reaction sintering of ceramic lithium ion solid electrolyte
CN104221183A (en) * 2011-11-29 2014-12-17 康宁股份有限公司 Reactive sintering of ceramic lithium-ion solid electrolytes
JP2018092936A (en) * 2011-11-29 2018-06-14 コーニング インコーポレイテッド Reaction sintering of ceramic lithium ion solid electrolyte
US10411288B2 (en) 2011-11-29 2019-09-10 Corning Incorporated Reactive sintering of ceramic lithium-ion solid electrolytes
US9843071B2 (en) 2012-07-11 2017-12-12 Toyota Jidosha Kabushiki Kaisha All-solid-state battery and method for manufacturing the same
US10141602B2 (en) 2013-12-26 2018-11-27 Toyota Jidosha Kabushiki Kaisha Lithium solid battery, lithium solid battery module, and producing method for lithium solid battery

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