JP2013062133A - All-solid-state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid-state battery using a high voltage material as a positive electrode active material and reduced in the interface resistance between the positive electrode active material and a solid electrolyte material.SOLUTION: According to the present invention, an all-solid-state battery is provided to solve the problem. The all-solid-state battery includes: a positive electrode active material layer containing a positive electrode active material having an average actuation voltage of 4 V(vs. Li/Li) or more; a negative electrode active material layer containing a negative electrode active material; and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. In the all-solid-state battery, a modifying material having a dielectric constant higher than that of a solid electrolyte material is arranged at an interface between the positive electrode active material and the solid electrolyte material.

Description

  The present invention relates to an all-solid battery that uses a high-voltage material as a positive electrode active material and can reduce the interface resistance between the positive electrode active material and the solid electrolyte material.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. Also in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, all solid-state lithium batteries are attracting attention from the viewpoint of high energy density among various batteries.

  In the field of such all-solid-state lithium batteries, there have been attempts to improve battery performance by paying attention to the interface between the active material and the electrolyte. For example, in Patent Document 1, an all-solid lithium secondary having a Li ion conductor modification layer that is electrochemically stable and has no electron conductivity with respect to the negative electrode layer between the negative electrode layer and the sulfide solid electrolyte layer. A battery is disclosed. This suppresses the formation of the space charge layer at the negative electrode layer side interface of the sulfide-based solid electrolyte layer, thereby reducing the resistance to lithium ion conduction and improving the output. In Patent Document 2, between active material particles and oxide-based inorganic solid electrolyte particles, at least one of sulfolane, which is a solvent having a high dielectric constant and excellent ion conductivity, or a dielectric thereof is impregnated. A lithium battery is disclosed.

Patent Document 3 discloses an all-solid lithium secondary battery laminate including an active material layer and a solid electrolyte layer sintered and joined to the active material layer, and the laminate is analyzed by an X-ray diffraction method. A layered product for an all solid lithium secondary battery in which components other than the component of the active material layer and the component of the solid electrolyte layer are not detected, and the all solid lithium secondary using such a layered product A battery is disclosed. Patent Document 4 discloses a solid electrolyte having a green compact including a sulfide solid electrolyte powder and a BaTiO ₃ powder.

JP 2009-193803 A JP 2002-042862 A JP 2007-005279 A JP 2011-065776 A

The conventional all-solid battery has a problem that the interface resistance between the positive electrode active material and the solid electrolyte material is large. Therefore, for example, when charging / discharging in a room temperature environment, the capacity is significantly reduced. Such an increase in interface resistance is more noticeable when a high-voltage material is used as the positive electrode active material. Specifically, when a high voltage material showing an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more is used as a positive electrode active material, there is a problem that capacity cannot be obtained.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide an all-solid-state battery using a high-voltage material as a positive electrode active material and having reduced interface resistance between the positive electrode active material and the solid electrolyte material. And

In order to achieve the above object, in the present invention, a positive electrode active material layer containing a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more, and a negative electrode active material layer containing a negative electrode active material And a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein the ratio of the solid electrolyte material to the interface between the positive electrode active material and the solid electrolyte material Provided is an all-solid battery characterized in that a modifier having a relative dielectric constant higher than the dielectric constant is disposed.

According to the present invention, the interfacial resistance between the positive electrode active material and the solid electrolyte material is provided by disposing a modifier having a relative dielectric constant higher than that of the solid electrolyte material at the interface between the positive electrode active material and the solid electrolyte material. Can be reduced. Therefore, even when a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or higher is used, the interface resistance can be sufficiently reduced. As a result, charging / discharging in a room temperature environment becomes possible.

  In the said invention, it is preferable that the said modifier is arrange | positioned between the said positive electrode active material layer and the said solid electrolyte layer. This is because the effects of the present invention can be exhibited and manufacturing can be performed more easily.

  In the said invention, it is preferable that the said modifier is an oxide. This is because the modifier can be stable in the atmosphere.

In the above invention, the modified material is preferably a BaTiO _3. This is because the relative dielectric constant is high.

  In the present invention, there is an effect that an all-solid battery can be obtained in which a high voltage material is used as a positive electrode active material and the interface resistance between the positive electrode active material and the solid electrolyte material is reduced.

It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. It is a schematic sectional drawing which shows the other example of the all-solid-state battery of this invention. It is a SEM image of the all-solid-state battery obtained in Example 1- Example 6. It is a graph which shows the result of the cyclic voltammetry measurement of the all-solid-state battery obtained in Example 1- Example 6 and the comparative example. It is a graph which shows the result of the constant current charging / discharging measurement of the all-solid-state battery obtained by Example 4 and the comparative example.

  Hereinafter, the all solid state battery of the present invention will be described in detail.

The all solid state battery of the present invention includes a positive electrode active material layer containing a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more, a negative electrode active material layer containing a negative electrode active material, and the positive electrode active material. An all-solid battery having a material layer and a solid electrolyte layer formed between the negative electrode active material layer, and having a higher dielectric constant than the solid electrolyte material at the interface between the positive electrode active material and the solid electrolyte material A modifying material having a relative dielectric constant is arranged.

  FIG. 1 is a schematic cross-sectional view showing an example of the all solid state battery of the present invention. As shown in FIG. 1, the all-solid battery 10 includes a positive electrode active material layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3 formed between the positive electrode active material layer 1 and the negative electrode active material layer 2, A positive electrode current collector 4 that collects current from the positive electrode active material layer 1 and a negative electrode current collector 5 that collects current from the negative electrode active material layer 2 are included. Further, in FIG. 1, a modifier 6 is disposed at the interface between the positive electrode active material layer 1 and the solid electrolyte layer 3. Here, the modifier 6 has a dielectric constant higher than that of the solid electrolyte material contained in the solid electrolyte layer 3.

As another example of the all solid state battery of the present invention, as shown in FIG. 2, the positive electrode active material layer 1 has a positive electrode active material 7 and a solid electrolyte material 8, and the positive electrode active material 7 and The thing by which the modifier 6 is arrange | positioned at the interface of the solid electrolyte material 8 is mentioned. Here, the positive electrode active material 7 has an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more. 2 that are not described in FIG. 2 are the same as those in FIG.

  The all solid state battery of the present invention includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid formed between the positive electrode active material layer and the negative electrode active material layer. It is not particularly limited as long as it has a structure in which a modifier is disposed at the interface between the positive electrode active material and the solid electrolyte material. For example, a thin film type, a powder type, a sintered type Examples include molds.

According to the present invention, the interfacial resistance between the positive electrode active material and the solid electrolyte material is provided by disposing a modifier having a relative dielectric constant higher than that of the solid electrolyte material at the interface between the positive electrode active material and the solid electrolyte material. Can be reduced. Therefore, even when a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or higher is used, the interface resistance can be sufficiently reduced. As a result, charging / discharging in a room temperature environment becomes possible. Moreover, by using a solid electrolyte layer, it becomes difficult to receive oxidative decomposition at the time of charging / discharging, and it can improve cycling characteristics compared with the battery using electrolyte solution.

Here, the mechanism by which the modifier having a relative dielectric constant higher than that of the solid electrolyte material lowers the interface resistance between the positive electrode active material and the solid electrolyte material is not yet clear, but is estimated as follows. The That is, by arranging a material having a high relative dielectric constant at the interface between the positive electrode active material and the solid electrolyte material, an extremely large local electric field applied to the interface during charge / discharge can be relaxed. It is considered that one of the causes is to suppress the formation of the lithium deficient layer. Generally, at the interface between the positive electrode active material and the solid electrolyte material, a large local electric field is caused by the potential difference between the two, and a lithium-deficient layer (thickness: several nm to several μm) is formed on the solid electrolyte material side. It has been. In such a lithium-deficient layer, the lithium concentration in the material is deviated from the optimum composition, so that the Li ion conductivity is lowered, and as a result, the interface resistance is considered to increase. Such a lithium-deficient layer is more prominent as the potential difference between the positive electrode active material and the solid electrolyte material is larger, so that the average operating voltage of the positive electrode active material is higher than 4 V (vs. Li ^/ Li ⁺ ). This is likely to be more noticeable when using voltage materials.

On the other hand, when a material having a high relative dielectric constant such as BaTiO ₃ is modified at the interface between the positive electrode active material and the solid electrolyte material, a large local electric field generated by the potential difference between the positive electrode active material and the solid electrolyte material is relaxed. Therefore, it is considered that the interfacial resistance is reduced as a result of suppressing the decrease in Li ion mobility in the lithium-deficient layer. Further, it is considered that the higher the relative permittivity of the dielectric, the smoother the movement of Li ions at the interface. Therefore, by arranging a modifying material having a relative dielectric constant higher than that of the solid electrolyte material at the interface between the positive electrode active material and the solid electrolyte material, the average operating voltage is 4 V (vs. Li / Li) as the positive electrode active material. Even in the case of using a high voltage material having a value of ⁺ ) or more, it is considered that the interface resistance between the positive electrode active material and the solid electrolyte material can be sufficiently reduced. As a result, an all-solid battery that can be charged and discharged in a room temperature environment can be obtained.

In Patent Document 2, sulfolane and sulfolane derivatives are solvents having a high dielectric constant and excellent ion conductivity, and are present in the vicinity of the contact point between the active material and the oxide-based inorganic solid electrolyte particles. There is a description that resistance to Li ion conduction is reduced. However, the relative dielectric constant of sulfolane and the oxide-based inorganic solid electrolyte (Li _{1 + x + y} Al _x Ti _2-x Si _y P _3-y O ₁₂ (0 ≦ x ≦ 0.4, 0 ≦ y ≦ 0) used therein (6)) was not described in relation to the relative dielectric constant. According to the study by the present inventors, the relative dielectric constant of sulfolane was lower than that of the oxide-based inorganic solid electrolyte. Therefore, it is considered that the interface resistance between the active material and the oxide-based inorganic solid electrolyte cannot be sufficiently reduced.
Hereinafter, the all solid state battery of the present invention will be described for each configuration.

1. First, the positive electrode active material layer in the present invention will be described. The positive electrode active material layer of the present invention contains at least a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more, and if necessary, a solid electrolyte material, a conductive agent, and a binder. It may contain at least one of.

(1) Positive electrode active material The positive electrode active material used in the present invention is not particularly limited as long as the average operating voltage is 4 V (vs. Li ^/ Li ⁺ ) or more. The average operating voltage of the positive electrode active material is usually 4 V (vs. Li ^/ Li ⁺ ) or more, preferably 4.0 V to 6.0 V, and more preferably 4.5 V to 5 V. More preferably within the range of 5V. The average operating voltage in the present invention can be evaluated using, for example, cyclic voltammetry. That is, when cyclic voltammetry is measured at a small potential pulling speed such as 0.1 mV / sec, the average value of the voltage that gives the peak current on the oxidation side and the voltage that gives the peak current on the reduction side is the average operating voltage. Can be considered.

The positive electrode active material is not particularly limited as long as the average operating voltage can be 4 V (vs. Li ^/ Li ⁺ ) or higher, but is preferably an oxide positive electrode active material. This is because a positive electrode active material layer having a high energy density can be obtained.

As an example of the positive electrode active material, for example, a compound having a spinel structure represented by a general formula LiM ₂ O ₄ (M is at least one of transition metal elements) can be given. The M in the general formula LiM ₂ O ₄ is not particularly limited as long as it is a transition metal element, but is preferably at least one selected from the group consisting of Ni, Mn, Cr, Co, V, and Ti, for example. Among these, at least one selected from the group consisting of Ni, Mn, and Cr is more preferable. Specific examples include LiCr _0.05 Ni _0.50 Mn _1.45 O ₄ , LiCrMnO ₄ , LiNi _0.5 Mn _1.5 O _{4 and the} like. As another example of the positive electrode active material, a compound having an olivine structure represented by a general formula LiMPO ₄ (M is at least one kind of transition metal element) can be given. M in the above general formula is not particularly limited as long as it is a transition metal element, but is preferably at least one selected from the group consisting of Mn, Co, Ni, and V, for example, Mn, Co, Ni More preferably, it is at least one selected from the group consisting of: Specifically, LiMnPO ₄ , LiCoPO ₄ , LiNiPO _{4 and the} like can be mentioned. As another example of the positive electrode active material, a compound having a layered structure represented by a general formula LiMO ₂ (M is at least one kind of transition metal element) can be given. Specific examples include LiNi _0.5 Mn _0.5 O ₂ and LiNi _0.33 Co _0.33 Mn _0.33 O ₂ . Further, examples other than the above-mentioned cathode active _{material, Li 2 MnO 3 -LiNi 1/3 Co} 1/3 Mn 1/3 O 2 solid _{solution, Li 2 MnO 3 -LiNi 0.5 Mn} 1.5 O 2 solid solution , Li ₂ MnO ₃ —LiFeO ₂ solid solution, and the like.

  Examples of the shape of the positive electrode active material include a particle shape such as a true sphere and an oval sphere, and a thin film shape. Moreover, when a positive electrode active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. Further, the content of the positive electrode active material in the positive electrode active material layer is preferably in the range of 10 wt% to 99 wt%, for example, and more preferably in the range of 20 wt% to 90 wt%.

(2) Positive electrode active material layer The positive electrode active material layer in the present invention may contain other materials as necessary in addition to the above-described positive electrode active material, and examples thereof include solid electrolyte materials. . The solid electrolyte material is not particularly limited as long as it is used in a general all solid state battery, but is lower than the relative dielectric constant of the modifying material described in the section “2. Modifying material” described later. Those having a relative dielectric constant are preferable. For example, the solid electrolyte material described in the section of “3. Solid electrolyte layer” described later can be suitably used. The content of the solid electrolyte material in the positive electrode active material layer is, for example, preferably in the range of 1% by weight to 90% by weight, and more preferably in the range of 10% by weight to 80% by weight.

  Furthermore, the positive electrode active material layer may contain a conductive agent from the viewpoint of improving the conductivity of the positive electrode active material layer in addition to the solid electrolyte material described above. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Moreover, the positive electrode active material may contain a binder. Examples of such a binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

  The thickness of the positive electrode active material layer varies depending on the type of the all-solid battery intended, but is preferably in the range of 0.1 μm to 1000 μm, for example. Further, the method for forming the positive electrode active material layer is not particularly limited as long as it can form the target positive electrode active material layer.

2. Modified material The modified material in this invention is arrange | positioned in the interface of a positive electrode active material and a solid electrolyte material, and has a dielectric constant higher than the dielectric constant of a solid electrolyte material. Since the modifier in the present invention has a relative dielectric constant higher than that of the solid electrolyte material, when the battery is used, the extremely large local electric field applied to the interface between the positive electrode active material and the solid electrolyte material is relaxed. Formation of a lithium-deficient layer on the solid electrolyte material side can be suppressed. For this reason, the decrease in the movement of the Li ions is suppressed, and the interface resistance can be lowered.

  The modifying material in the present invention has a dielectric constant higher than that of the solid electrolyte material. As a method for measuring the relative dielectric constant, for example, a method described in JIS C 2565 (such as a cavity resonator method) or a method in which the method described in JIS C 2565 is improved as a sample insertion hole closed type (sample insertion hole closure). Perturbation type cavity resonator method). Specifically, the dielectric constant can be calculated by inserting a sample into the cavity resonator and measuring the change in the resonance frequency before and after inserting the sample. Further, the ratio (B / A) of the relative dielectric constant (B) of the solid electrolyte material to the relative dielectric constant (A) of the modifier is not particularly limited as long as the effect of the present invention can be obtained. , Preferably in the range of 0.001-1, more preferably in the range of 0.005-0.5, and particularly preferably in the range of 0.01-0.1.

  The modifier in the present invention is not particularly limited as long as it has a relative dielectric constant higher than that of the solid electrolyte material, but is preferably a ferroelectric. This is because the relative permittivity of the modifying material can be increased, so that the effect of smoothing the movement of Li ions can be obtained by suppressing deposition and unevenness due to Li ions at the interface between the positive electrode active material and the solid electrolyte material. . Therefore, the extremely large local electric field applied to the interface described above can be relaxed, and the interface resistance can be reduced. Moreover, such an effect can be obtained not only in the vicinity of the modifying material but also in a place away from the modifying material, and by arranging a small amount of the modifying material at the interface between the positive electrode active material and the solid electrolyte material, the interface resistance can be efficiently reduced. be able to.

The modifier in the present invention is usually a solid. Therefore, the fluidity is extremely low, and the modifier can be more reliably disposed at the interface between the positive electrode active material and the solid electrolyte material without moving. Examples of such modifiers include oxides, sulfides, nitrides, etc. Among them, oxides are preferable. This is because it is stable in the atmosphere. Specific examples of the oxide modifier include BaTiO ₃ , LiNbO ₃ , LiTaO ₃ , Li ₂ B ₄ O ₇ , Rochelle salt, TiO ₂ , SiO ₂ , MgO, PZT (lead zirconate titanate), AlPO ₄ , Al ₂ O ₃ , Li ₃ PO ₄ , LiAlSiO ₄ , Li—P—Si—O, Li—B—Si—O and the like can be mentioned, and among these, BaTiO ₃ is preferable. This is because the relative dielectric constant is high. Specific examples of the sulfide modifier include vanadium sulfide, magnesium sulfate, and the like, and specific examples of the nitride modifier include Si ₃ N ₄ , SiAlON, and the like.

Examples of the shape of the modifier include particle shapes such as a true sphere and an elliptic sphere. The average particle diameter of such a modifier is, for example, preferably 1 nm or more, more preferably 3 nm or more, and particularly preferably 5 nm or more. This is because if the average particle size is smaller than the above range, it may be difficult to achieve the intended effect. Further, when the modifying material used in the present invention is BaTiO ₃ , there is an effect that the relative dielectric constant increases as the average particle size increases. Moreover, as an average particle diameter of the said modifier, it is preferable that it is 100 nm or less, for example, it is more preferable that it is 50 nm or less, and it is especially preferable that it is 30 nm or less. This is because if the average particle size is larger than the above range, the ion conductivity at the interface may be lowered. In this connection, the measurement method of the average particle diameter, and a method for measuring the D ₅₀ using a particle size distribution meter and the like.

  The modifier in the present invention is disposed at the interface between the positive electrode active material and the solid electrolyte material. As an example of the position where the modifier is disposed, an interface between the positive electrode active material layer and the solid electrolyte layer can be cited. By disposing the modifier at the above position, the intended all solid state battery can be manufactured more easily. Another example of the position where the modifier is disposed is the interface between the positive electrode active material and the solid electrolyte material in the positive electrode active material layer. In this case, the modifier may be supported on at least one of the positive electrode active material and the solid electrolyte material.

The content of the modifier is not particularly limited as long as the effect of the present invention can be exhibited, and is preferably adjusted as appropriate depending on the type of the solid electrolyte material and modifier used. For example, when the modifier is disposed between the positive electrode active material layer and the solid electrolyte layer, the surface coverage of the positive electrode active material layer by the modifier in plan view is within a range of 1% to 95%. It is preferably within a range of 5% to 70%, more preferably within a range of 10% to 50%. When the surface coverage is less than the above range, the effects of the present invention may not be sufficiently obtained. On the other hand, when the surface coverage exceeds the above range, an insulator such as BaTiO ₃ is used. If the modifier is used, the movement of Li ions may be difficult, and the effect of the present invention may be diminished. The surface coverage is a value that can be calculated from an image obtained by a scanning electron microscope (SEM).

3. Next, the solid electrolyte layer in the present invention will be described. The solid electrolyte layer in the present invention is formed between the positive electrode active material layer and the negative electrode active material layer and contains at least a solid electrolyte material. The relative dielectric constant of the solid electrolyte material used in the present invention is preferably lower than the relative dielectric constant of the modifying material described above. Examples of such a solid electrolyte material include a sulfide solid electrolyte material and an oxide solid electrolyte material.

Examples of the oxide solid electrolyte material used in the present invention include LiPON (for example, Li _2.9 PO _3.3 N _0.46 ), LiLaTiO (for example, Li _0.34 La _0.51 TiO ₃ ), and LiLaZrO. _{(e.g., Li 7 La 3 Zr 2 O} 12) can be exemplified. Among these, LiPON is particularly preferable because it can be formed at room temperature. Other examples of the oxide solid electrolyte material include a compound having a NASICON type structure. As an example of a compound having a NASICON type structure, a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2) can be given. In the above general formula, the range of x may be 0 or more, more preferably greater than 0, and more preferably 0.3 or more. On the other hand, the range of x may be 2 or less, and is preferably 1.7 or less, and more preferably 1 or less. Above all, in the present invention, the oxide solid electrolyte _{material, Li 1.5 Al 0.5 Ge 1.5 (} PO 4) is preferably _3. Another example of the compound having a NASICON structure is a compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2). In the above general formula, the range of x may be 0 or more, more preferably greater than 0, and more preferably 0.3 or more. On the other hand, the range of x may be 2 or less, and is preferably 1.7 or less, and more preferably 1 or less. Above all, in the present invention, the oxide solid electrolyte _{material, Li 1.3 Al 0.3 Ti 1.7 (} PO 4) is preferably _3.

Examples of the sulfide solid electrolyte material used in the present invention include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S ₅ —Li ₂ O, _{Li 2 S-P 2 S 5} -Li 2 O-LiI, Li 2 S-SiS 2, Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li _{2 S-SiS 2 -B 2 S} 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n ( However, m and n are positive numbers. Z is any one of Ge, Zn, and Ga.), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —. Li _x MO _y (where, x, y is the number of positive .M is, P, Si, e, B, Al, Ga, either an In.) and the like. The description of “Li ₂ S—P ₂ S ₅ ” means a sulfide solid electrolyte material using a raw material composition containing Li ₂ S and P ₂ S _5, and the same applies to other descriptions. is there. More specifically, for example, Li ₇ P ₃ S ₁₁ , Li _3.25 P _0.95 S ₄ , Li _3.25 Ge _0.25 P _0.75 S _{4 and the} like can be mentioned.

  Examples of the shape of the solid electrolyte material include particle shapes such as true spheres and ellipsoids, and thin film shapes. Moreover, when a solid electrolyte material is a particle shape, it is preferable that the average particle diameter exists in the range of 50 nm-5 micrometers, for example, and it is more preferable that it exists in the range of 100 nm-3 micrometers.

  The solid electrolyte layer is preferably composed only of the above-described solid electrolyte material, but may contain a modifier as necessary. The content of the modifying material in the solid electrolyte layer is preferably in the range of 0.01 wt% to 10 wt%, for example, and more preferably in the range of 0.1 wt% to 5 wt%. . The modifier used for the solid electrolyte layer is the same as that described in the section “2. Modifier” above, and is not described here. Moreover, the solid electrolyte layer may further contain a binder as necessary. The binder used for the solid electrolyte layer is the same as in the positive electrode active material layer described above.

  The thickness of the solid electrolyte layer varies greatly depending on the type of the solid electrolyte material and the configuration of the all-solid battery, but is preferably in the range of 0.1 μm to 1000 μm, for example, 0.1 μm to 300 μm. More preferably within the range. The method for forming the solid electrolyte layer is not particularly limited as long as it is a method capable of forming the target solid electrolyte layer.

4). Next, the negative electrode active material layer in the present invention will be described. The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte material and a conductive agent as required. When the all-solid battery of the present invention is an all-solid lithium battery, the negative electrode active material is not particularly limited as long as it can occlude and release Li ions, which are conductive ions. For example, a carbon active material And a metal active material. Examples of the carbon active material include graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. On the other hand, examples of the metal active material include alloy materials such as Li alloy and Sn—Co—C, In, Al, Si, and Sn. In addition, examples of other negative electrode active materials include oxide materials such as Li ₄ TiO ₅ .

  Note that the solid electrolyte material and the conductive agent used in the negative electrode active material layer are the same as those in the solid electrolyte layer and the positive electrode active material layer described above, respectively. The thickness of the negative electrode active material layer is, for example, in the range of 0.1 μm to 1000 μm. The method for forming the negative electrode active material layer is not particularly limited as long as it can form the target negative electrode active material layer.

5. Other Configurations The all solid state battery of the present invention has at least the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Among them, SUS is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Among them, SUS is preferable. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the all solid state battery. Moreover, the battery case used for a general all-solid-state battery can be used for the battery case used for this invention, For example, the battery case made from SUS etc. can be mentioned. Further, the all solid state battery of the present invention may be one in which the power generating element is formed inside the insulating ring.

6). All-solid-state battery In this invention, the interface resistance of a positive electrode active material and a solid electrolyte material can be reduced by arrange | positioning the modifier mentioned above in the interface of a positive electrode active material layer and a solid electrolyte layer. Therefore, even when a high-voltage material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or more is used as the positive electrode active material, the interface resistance can be reduced, and an all-solid battery that can be charged and discharged in a room temperature environment is obtained. be able to. The all solid state battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Examples of the shape of the all solid state battery include a coin type, a laminate type, a cylindrical type, and a square type.

  The method for producing an all-solid battery of the present invention is not particularly limited as long as it is a method capable of obtaining the above-described all-solid battery, and a method similar to a general method for producing an all-solid battery may be used. it can. For example, when the all-solid-state battery is in the form of a thin film, the positive electrode active material layer is formed on the substrate, the above-described modifier layer is formed on the positive electrode active material layer, and then the solid electrolyte layer and the negative electrode active material layer are sequentially formed. And a method of laminating.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The present invention will be described more specifically with reference to the following examples and comparative examples.

[Example 1]
(Preparation of positive electrode active material layer)
As a substrate, glassy carbon having a thickness of 0.2 mm was prepared. Next, a layer made of LiCr _0.05 Ni _0.50 Mn _1.45 O ₄ having a thickness of 60 nm was formed on the substrate by a PLD method to obtain a positive electrode active material layer.
Each condition of the PLD method is as follows.
Target composition: Li _1.2 Cr _0.05 Ni _0.50 Mn _1.45 O ₄
-Chamber pressure: 200 mTorr
-Target-substrate distance: 8.5 cm
-Substrate temperature: 700 ° C
・ Deposition time: 120 min

(Arrangement of modifiers)
A slurry (solid content concentration: 8% by weight, manufactured by JGC Catalysts & Chemicals Co., Ltd.) in which BaTiO ₃ having an average particle diameter of 10 nm is dispersed in 2-methoxyethanol is prepared and diluted 10 times to obtain a dispersion (solid content concentration). : 0.8 wt%). Next, the dispersion was applied onto the positive electrode active material layer described above by spin coating. Then, it hold | maintained for 60 minutes on a hotplate (180 degreeC), the solvent was volatilized, the modifier layer was formed, and the laminated body of the positive electrode active material layer / modifier layer was obtained.
The conditions for the spin coating method are as follows.
・ Rotation speed: 5000rpm
・ Processing time: 2 min

(Preparation of solid electrolyte layer)
A solid electrolyte layer made of LiPON having a thickness of 5 μm is formed on the above positive electrode active material layer / modifier layer laminate by RF magnetron sputtering in an Ar—N mixed atmosphere, and the positive electrode active material layer / modification A laminate of material layer / solid electrolyte layer was obtained.
The conditions of the RF magnetron sputtering method are as follows.
Target composition: Li ₃ PO ₄
-Chamber pressure: 4Pa
-Target-substrate distance: 13 cm
・ Vapor deposition time: 50hour

(Preparation of negative electrode active material layer)
Lithium metal was deposited on the positive electrode active material layer / modifier layer / solid electrolyte layer laminate by the resistance heating vapor deposition method to form a negative electrode active material layer having a thickness of 5 μm, and an all-solid battery was fabricated.

[Example 2]
The same as in Example 1 except that the dispersion (solid content concentration: 0.16 wt%) obtained by diluting the slurry (solid content concentration: 8 wt%, manufactured by JGC Catalysts & Chemicals Co., Ltd.) 50 times was used. An all-solid battery was produced by this method.

[Example 3]
The same as in Example 1 except that the dispersion (solid content concentration: 0.08 wt%) obtained by diluting the slurry (solid content concentration: 8 wt%, manufactured by JGC Catalysts & Chemicals Co., Ltd.) 100 times was used. An all-solid battery was produced by this method.

[Example 4]
Example 1 except that a slurry (solid content concentration: 0.008% by weight) obtained by diluting a slurry (solid content concentration: 8% by weight, manufactured by JGC Catalysts & Chemicals) 1000 times was used. An all-solid battery was produced by this method.

[Example 5]
Example 1 except that a dispersion (solid content concentration: 0.004% by weight) obtained by diluting a slurry (solid content concentration: 8% by weight, manufactured by JGC Catalysts & Chemicals Co., Ltd.) 2000 times was used. An all-solid battery was produced by this method.

[Example 6]
The same as Example 1 except that the dispersion (solid content concentration: 0.0008% by weight) obtained by diluting the slurry (solid content concentration: 8% by weight, manufactured by JGC Catalysts & Chemicals Co., Ltd.) 10,000 times was used. An all-solid battery was produced by this method.

[Evaluation 1]
(SEM observation)
The dispersion containing BaTiO ₃ used in Examples 1 to 6 was dispersed on a quartz substrate by spin coating, and the distribution of BaTiO ₃ was observed with a scanning electron microscope (SEM). The obtained SEM images are shown in FIGS. In addition, Table 1 shows the surface coverage with BaTiO ₃ calculated from the SEM image.

In FIGS. 3A to 3F, the portion that appears white is BaTiO _{3. When the} observation results of Examples 1 to 6 are compared, by using a dispersion having a high solid content concentration, It was confirmed that a modifier layer containing many BaTiO ₃ was formed. Therefore, when a modifier layer is formed on the positive electrode active material layer by spin coating, similarly, a modifier layer containing more BaTiO ₃ can be obtained by using a dispersion having a high solid content concentration. It is thought that it is formed.

(Specific permittivity measurement)
The relative dielectric constant at 1 GHz of the BaTiO ₃ powder and LiPON thin film used in Examples 1 to 6 was measured. Specifically, measurement was performed based on a measurement method obtained by improving the method described in JIS C 2565 into a closed hole type using 0.3638 g of BaTiO ₃ powder having a particle size of 10 nm. Further, a 5 μm thick LiPON thin film deposited on a quartz substrate was formed and measured based on the same method. As a result, the relative dielectric constant of the LiPON thin film was 11.2, and the relative dielectric constant of the BaTiO ₃ powder was 359.4. From this, it was confirmed that the relative dielectric constant of BaTiO ₃ used as the modifier is higher than that of the LiPON thin film used as the solid electrolyte layer.

[Comparative example]
An all-solid battery was produced in the same manner as in Example 1 except that the modifier layer was not formed.

[Evaluation 2]
(Cyclic voltammetry (CV) measurement)
Using the all-solid-state batteries prepared in Examples 1 to 6 and the comparative example, cyclic voltammetry measurement was performed with an insertion speed of 0.1 mV / sec and a voltage scanning range of 2.5 V to 5.3 V. It was. The measurement results of Examples 1 to 6 and the comparative example are shown in FIGS. Table 2 shows the peak current values obtained in Examples 1 to 6 and the comparative example.

  As shown in FIG. 4 and Table 2, the all solid state battery obtained in Example 4 exhibited the highest peak current value.

(Constant current charge / discharge measurement)
Using the all solid state battery obtained in Example 4 that showed the highest peak current value in the CV measurement and the comparative example, the current was set to 1 μA, and the cut-off current was set to 3.5 V to 4.8 V. Current charge / discharge measurement was performed. The results are shown in FIGS. 5 (a) and 5 (b), respectively.

As shown to Fig.5 (a), in the all-solid-state battery obtained in Example 4, charging / discharging was possible at room temperature, and the capacity | capacitance of 80 mAh / g was able to be obtained. This is presumably because the interface resistance can be drastically reduced because a layer containing BaTiO ₃ as a modifier is formed at the interface between the positive electrode active material layer and the solid electrolyte layer. Moreover, in the all-solid-state battery obtained in Example 4, it was possible to charge and discharge stably at room temperature for 100 cycles or more. This is because the solid electrolyte layer makes it difficult to undergo oxidative decomposition even when used in combination with a positive electrode active material that is a high-voltage material, and it is thought that the cycle characteristics are improved as compared with a battery using a conventional electrolytic solution. . On the other hand, as shown in FIG.5 (b), in the all-solid-state battery obtained by the comparative example, charging / discharging could not be performed at room temperature. This is presumably because the resistance at the interface between the positive electrode active material layer and the solid electrolyte layer is extremely large.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 6 ... Modifier 7 ... Positive electrode active material 8 ... Solid electrolyte material 10 ... All-solid-state battery

Claims (4)

A positive electrode active material layer containing a positive electrode active material having an average operating voltage of 4 V (vs. Li ^/ Li ⁺ ) or higher, a negative electrode active material layer containing a negative electrode active material, the positive electrode active material layer, and the negative electrode active material layer An all-solid battery having a solid electrolyte layer formed between
An all-solid battery, wherein a modifying material having a relative dielectric constant higher than that of the solid electrolyte material is disposed at an interface between the positive electrode active material and the solid electrolyte material.   The all-solid-state battery according to claim 1, wherein the modifier is disposed between the positive electrode active material layer and the solid electrolyte layer.   The all-solid-state battery according to claim 1, wherein the modifying material is an oxide. The all-solid-state battery according to any one of claims 1 to ₃ , wherein the modifying material is BaTiO ₃ .