Solid electrolyte and solid battery

Abstract

To achieve a solid electrolyte having high lithium ion conductivity.SOLUTION: Provided is a solid electrolyte LAMPP / LMPP having a compositional formula expressed by Li9-xAl3-xMx(PO4)2(P2O7)3, where the element M is one or more selected from Sn, Zr, Ti, Hf, and Ge, and the compositional ratio x of the element M falls within the range of 0<x≤3. The solid electrolyte LAMPP / LMPP can be employed as the solid electrolyte in a solid battery 1 comprising a positive electrode layer 10, a negative electrode layer 20, and an electrolyte layer 30 disposed between them, for example, as the solid electrolyte of the electrolyte layer 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte and a solid-state battery. [Background technology]

[0002] One type of battery known is a solid-state battery that uses a solid electrolyte. For example, solid electrolytes such as LAPP, which has the composition formula LiAl(P0)(PO), and LAPP in which part of the PO is replaced with GeO or SiO are known (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 041669 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] A solid-state battery is composed of a solid electrolyte, a positive electrode, and a negative electrode. In a solid-state battery, the solid electrolyte is responsible for transferring lithium ions between the positive and negative electrodes, and the lithium-ion conductivity of the solid electrolyte can be one of the factors that determine the characteristics of the solid-state battery. Therefore, it is effective to use a solid electrolyte with high lithium-ion conductivity for solid-state batteries. However, conventional solid electrolytes such as LAPP sometimes fail to achieve sufficient lithium-ion conductivity.

[0005] In one aspect, an object of the present invention is to provide a solid electrolyte having high lithium ion conductivity. [Means for solving the problem]

[0006] In one embodiment, the formula is Li 9-x Al 3-x M xThere is provided a solid electrolyte represented by (PO4)2(P2O7)3, where M is one or more elements selected from Sn, Zr, Ti, Hf, and Ge, and the range of x is 0 < x ≦ 3.

[0007] In another aspect, there is provided a solid battery using the solid electrolyte as described above.

Effects of the Invention

[0008] On one side, it becomes possible to realize a solid electrolyte having high lithium ion conductivity.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram for explaining a configuration example of a solid battery. [Figure 2] It is a diagram showing the crystal structure of LAPP. [Figure 3] It is a diagram showing the diffusion path of lithium ions in LAPP. [Figure 4] It is a diagram showing an example of the relationship between temperature and ion conductivity.

Modes for Carrying Out the Invention

[0010] First, a configuration example of a solid battery will be described. FIG. 1 is a diagram for explaining a configuration example of a solid battery. FIG. 1 schematically shows a cross-sectional view of the main part of an example of a solid battery.

[0011] The solid battery 1 shown in FIG. 1 includes a positive electrode layer 10, a negative electrode layer 20, and an electrolyte layer 30 provided therebetween. For example, the solid battery 1 is a rechargeable lithium ion battery (also referred to as a "lithium ion secondary battery" or the like). FIG. 1 shows the basic structural parts of such a lithium ion battery.

[0012] The electrolyte layer 30 contains a predetermined solid electrolyte. Details of the solid electrolyte contained in the electrolyte layer 30 will be described later. The positive electrode layer 10 includes a positive electrode active material. The positive electrode active material of the positive electrode layer 10 may be Li2CoP2O7 (also referred to as "LCPO") or the like. The positive electrode layer 10 may further include a solid electrolyte. The solid electrolyte of the positive electrode layer 10 may be, for example, the same type of material as the solid electrolyte used in the electrolyte layer 30. The positive electrode layer 10 may further include a conductive additive such as a carbon material.

[0013] The anode layer 20 includes an anode active material. Examples of the anode active material for the anode layer 20 include TiO2 and Nb2O5. Examples of the anode active material for the anode layer 20 include lithium and lithium-containing alloys. The anode layer 20 may further include a solid electrolyte. Examples of the solid electrolyte for the anode layer 20 include the same type of material as the solid electrolyte used for the electrolyte layer 30. The anode layer 20 may further include a conductive additive such as a carbon material.

[0014] The solid-state battery 1 has a configuration in which a positive electrode layer 10 is provided on one side of an electrolyte layer 30 and an negative electrode layer 20 is provided on the other side. The solid-state battery 1 is manufactured by firing a laminate formed so that the electrolyte layer 30 is interposed between the positive electrode layer 10 and the negative electrode layer 20 at a predetermined temperature in a predetermined atmosphere. For example, pastes for forming the electrolyte layer 30, the positive electrode layer 10, and the negative electrode layer 20 are prepared, and these pastes are applied and dried in a predetermined stacking order to form the laminate. The formed laminate is then fired at a predetermined temperature in a predetermined atmosphere to remove organic components contained therein and sinter the solid electrolyte, etc., thereby manufacturing the solid-state battery 1.

[0015] Conductors such as electrodes or current collectors (not shown) may be connected to the positive electrode layer 10 and the negative electrode layer 20 of the solid-state battery 1. For example, the solid-state battery 1 is in the form of a chip-type battery that can be mounted on another electronic component such as a circuit board using electrodes connected to the positive electrode layer 10 and the negative electrode layer 20, respectively. Alternatively, the solid-state battery 1 may be housed in a pouch-shaped laminate film (exterior body) to be in the form of a thin battery, or may be housed in a coin-shaped, cylindrical, prismatic, or other battery can (exterior body) to be in the form of a coin-shaped battery, cylindrical battery, prismatic battery, or the like.

[0016] When the solid-state battery 1 is charged, lithium ions are conducted from the positive electrode layer 10 through the electrolyte layer 30 to the negative electrode layer 20 and are taken up therein, and when the solid-state battery 1 is discharged, lithium ions are conducted from the negative electrode layer 20 through the electrolyte layer 30 to the positive electrode layer 10 and are taken up therein. In the solid-state battery 1, charge and discharge operations are realized by such lithium ion conduction that occurs when a predetermined current is passed through the positive electrode layer 10 and the negative electrode layer 20.

[0017] 1 illustrates a solid-state battery 1 (basic structure) including one each of the electrolyte layer 30, the positive electrode layer 10, and the negative electrode layer 20, but the number of each layer is not limited to one. The solid-state battery 1 may be configured to include one or more of each layer, as long as the electrolyte layer 30 is provided between the pair of the positive electrode layer 10 and the negative electrode layer 20.

[0018] As described above, the solid-state battery 1 uses a solid electrolyte in its electrolyte layer 30, or further in one or both of the positive electrode layer 10 and the negative electrode layer 20. The solid electrolyte is responsible for transferring lithium ions between the positive electrode layer 10 (its positive electrode active material) and the negative electrode layer 20 (its negative electrode active material) during charging and discharging of the solid-state battery 1. Therefore, the lithium ion conductivity of the solid electrolyte can be a factor that determines the characteristics of the solid-state battery 1. In order to improve the characteristics of the solid-state battery 1 and expand its applications, the solid electrolyte of the solid-state battery 1 is required to have high lithium ion conductivity.

[0019] In addition, the solid electrolyte of the solid-state battery 1 preferably exhibits two-dimensional or three-dimensional lithium ion conductivity. Different from liquid electrolytes, the solid electrolyte has a relatively small degree of freedom in the diffusion direction of lithium ions. Therefore, in the solid-state battery 1, in order to secure a sufficient diffusion path for lithium ions and achieve high lithium ion conductivity, it is preferable to use a solid electrolyte in which the diffusion direction of lithium ions is two-dimensional or three-dimensional rather than one-dimensional.

[0020] In view of such a point, here, a solid electrolyte having the following configuration is used to realize a solid electrolyte having high lithium ion conductivity and the solid-state battery 1 using the same.

[0021] That is, here, as the solid electrolyte, the composition formula is Li 9-x Al 3-x M x (PO4)2(P2O7)3, where the element M is one or more elements selected from Sn, Zr, Ti, Hf, and Ge, and the range of the composition ratio x of the element M is 0 < x ≤ 3. Hereinafter, the solid electrolyte having such a configuration is also referred to as "LAMPP / LMPP" for convenience.

[0022] The solid electrolyte LAMPP / LMPP has a structure in which part or all of the Al in LAPP (Li9Al3(PO4)2(P2O7)3) mainly composed of Li, Al, P, and O is substituted with a predetermined element M. The element M is one or more elements selected from Sn, Zr, Ti, Hf, and Ge. The solid electrolyte LAMPP / LMPP is obtained by substituting part or all of the trivalent element Al in LAPP with a tetravalent element M such as Sn, Zr, Ti, Hf, and Ge.

[0023] Here, the crystal structure of LAPP is shown in FIG. 2. FIG. 2 shows a superlattice in which four unit cells 100 of LAPP are arranged in a 2×2×1 array. In addition, the diffusion path of lithium ions in LAPP is shown in FIG. 3.

[0024] As shown in Figure 2, LAPP, i.e., Li9Al3(PO4)2(P2O7)3, contains Li, Al, P, and O as constituent elements, and has a structure in which Li, AlO6, PO4, and P2O7 are assembled in a predetermined arrangement. LAPP has the space group P-3c1 and has two-dimensional lithium ion diffusion paths as shown in Figure 3.

[0025] Since LAPP has two-dimensional lithium ion diffusion paths, it can be a candidate for the solid electrolyte used in the solid-state battery 1. However, it cannot necessarily be said that LAPP provides sufficient lithium ion conductivity (Comparative Example 1 below).

[0026] In contrast to LAPP, the solid electrolyte LAMPP / LMPP has a structure in which some or all of the Al in LAPP is replaced with a specific element M, such as Sn, Zr, Ti, Hf, or Ge. The solid electrolyte LAMPP / LMPP, like the LAPP shown in Figures 2 and 3, has a space group P-3c1 and two-dimensional lithium ion diffusion paths. Meanwhile, in the solid electrolyte LAMPP / LMPP, the trivalent Al in LAPP is replaced with the tetravalent element M, resulting in the formation of lithium vacancies. This reduces the energy required for lithium ion conduction in the solid electrolyte LAMPP / LMPP. As a result, the solid electrolyte LAMPP / LMPP can achieve higher lithium ion conductivity than LAPP.

[0027] The solid electrolyte LAMPP / LMPP having the above configuration is used for the electrolyte layer 30 of the solid battery 1 (FIG. 1), or further for one or both of the positive electrode layer 10 and the negative electrode layer 20. The use of the solid electrolyte LAMPP / LMPP increases the lithium ion conductivity during charging and discharging of the solid battery 1, thereby improving the charge and discharge characteristics of the solid battery 1. The use of the solid electrolyte LAMPP / LMPP with high lithium ion conductivity realizes a solid battery 1 that exhibits excellent charge and discharge characteristics.

[0028] When the above-described LCPO is used as the positive electrode active material of the positive electrode layer 10 of the solid state battery 1, since LCPO is a phosphate, taking into consideration the affinity with LCPO, the suppression of side reactions during firing, and the like, it is preferable to use a phosphate as the solid electrolyte used in the solid state battery 1, just like the positive electrode active material. This is because if a solid electrolyte that has low affinity with LCPO or that is likely to undergo side reactions with LCPO during firing, which is performed in the manufacturing process of the solid state battery 1, is used, the charge / discharge characteristics of the solid state battery 1 may be degraded.

[0029] In contrast, the solid electrolyte LAMPP / LMPP is a phosphate in which part or all of the Al in LAPP is replaced with a specific element M. Therefore, even when the solid electrolyte LAMPP / LMPP is used as a solid electrolyte in a solid battery 1 using LCPO, a phosphate, as the positive electrode active material, it has good affinity with LCPO, and side reactions with LCPO are suppressed during firing in the manufacturing process of the solid battery 1. Therefore, the solid electrolyte LAMPP / LMPP is useful as a solid electrolyte in a solid battery 1 using LCPO as the positive electrode active material. Note that the solid electrolyte LAMPP / LMPP is also useful as a solid electrolyte in a solid battery 1 using other phosphates, not just LCPO, as the positive electrode active material.

[0030] In addition, from the viewpoint of reducing the cost of the solid electrolyte and the solid battery 1 using the same, it is preferable that the solid electrolyte is inexpensive, in other words, that the elements constituting the solid electrolyte are inexpensive. Here, as one type of solid electrolyte, NASICON (Na super ionic conductor) type LAGP (Li 1.5 Al 0.5 Ge 1.5 Oxide-based solid electrolytes such as (PO4)3 are known. LAGP exhibits excellent lithium ion conductivity in three dimensions, making it useful as a solid electrolyte for use in solid-state batteries. However, LAGP contains Ge, a relatively expensive element. In addition to NASICON-type oxide solid electrolytes, perovskite-type and garnet-type oxide solid electrolytes also exist, but these also contain rare metals such as La, Ta, and Nb, which are highly scarce and relatively expensive.

[0031] In contrast, LAPP, which is composed primarily of Li, Al, P, and O, is a material composed of relatively inexpensive elements. The solid electrolyte LAMPP / LMPP is obtained by substituting a portion or all of the Al in such LAPP with a specific element M. By selecting at least one of relatively inexpensive Sn, Zr, and Ti as the element M substituting for Al in LAPP, the cost of the resulting solid electrolyte LAMPP / LMPP can be reduced compared to a case in which none of these elements is selected as the element M. As a result, the cost of the solid battery 1 using the solid electrolyte LAMPP / LMPP can be reduced.

[0032] As described above, the solid electrolyte LAMPP / LMPP is used for the electrolyte layer 30 of the solid battery 1. The cathode layer 10, which is in contact with the electrolyte layer 30 of the solid battery 1, may also be made of the same solid electrolyte LAMPP / LMPP as the electrolyte layer 30. This allows for high lithium ion conductivity between the electrolyte layer 30 and the cathode layer 10. Furthermore, as described above, when a phosphate oxide such as LCPO is used as the cathode active material, it is effective to use the solid electrolyte LAMPP / LMPP, which is a phosphate oxide, for the cathode layer 10. However, a different solid electrolyte from the solid electrolyte LAMPP / LMPP, such as LAGP, may also be used for the cathode layer 10. The anode layer 20, which is in contact with the electrolyte layer 30 of the solid battery 1, may also be made of the same solid electrolyte LAMPP / LMPP as the electrolyte layer 30. This allows for high lithium ion conductivity between the electrolyte layer 30 and the anode layer 20. However, the negative electrode layer 20 may also be made of a solid electrolyte different from the solid electrolyte LAMPP / LMPP, such as LAGP.

[0033] As described above, as the solid electrolyte used in the solid-state battery 1, a material having a two-dimensional or three-dimensional lithium ion diffusion path is preferable in order to obtain high lithium ion conductivity. Further, when a phosphate-based positive electrode active material is used, it is preferable that a phosphate-based material is also used for the solid electrolyte. LAPP (Li9Al3(PO4)2(P2O7)3) is one of the materials that satisfy these conditions, has a space group P-3c1, is a material having a two-dimensional lithium ion diffusion path, and is a phosphate-based material. In order to improve the lithium ion conductivity of this LAPP, a part or all of the trivalent Al is replaced with a tetravalent element M, and the solid electrolyte LAMPP / LMPP (Li 9-x Al 3-x M x (PO4)2(P2O7)3, 0 < x ≤ 3) is obtained. The element M that replaces Al is one or more elements selected from Sn, Zr, Ti, Hf, and Ge.

[0034] Similar to LAPP, the solid electrolyte LAMPP / LMPP has a space group P-3c1 and has a two-dimensional lithium ion diffusion path. On the other hand, in the solid electrolyte LAMPP / LMPP, a structure in which a part or all of the trivalent Al in LAPP is replaced with a tetravalent element M is adopted, so that lithium deficiency is formed. As a result, in the solid electrolyte LAMPP / LMPP, the energy required for lithium ion conduction is reduced, and the lithium ion conductivity can be increased compared to LAPP.

[0035] The improvement of the lithium ion conductivity in the solid electrolyte LAMPP / LMPP is an effect due to the occurrence of lithium deficiency, and the dependence on the type of element M is small. Therefore, even if any one or two or more of Sn, Zr, Ti, Hf, and Ge are used as the element M, the effect of improving the lithium ion conductivity can be obtained. Incidentally, when two or more of Sn, Zr, Ti, Hf, and Ge are used as the element M, their combination is not particularly limited, and any two or more elements M may be combined and used.

[0036] When one or more of Sn, Zr, and Ti are used as the element M of the solid electrolyte LAMPP / LMPP, or when a combination of one or both of Hf and Ge with one or more of Sn, Zr, and Ti is used, the costs of the solid electrolyte LAMPP / LMPP and the solid battery 1 using it can be reduced compared to when only Hf or Ge is used as the element M.

[0037] Molecular dynamics calculations confirmed that in the solid electrolyte LAMPP / LMPP, the more the content of element M (composition ratio x) is increased, the more lithium deficiency occurs, and that when the content of element M is at its maximum value of x = 3, i.e., when the solid electrolyte LMPP is formed by replacing all of the Al in LAPP with element M, the lithium ion conductivity tends to be greatest.

[0038] Comparative Examples and Examples will be described below. (Comparative Example 1) Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [x=0], i.e., a LAPP model of Li9Al3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0039] Example 1 Li 9-x Al 3-x M xA model of (PO4)2(P2O7)3 [M=Sn, x=1], ​​i.e., Li8Al2Sn(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0040] Example 2 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with M=Sn, x=2, i.e., Li7AlSn2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0041] Example 3 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with M=Sn, x=3, i.e., Li6Sn3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0042] Example 4 Li 9-x Al 3-x M xA (PO4)2(P2O7)3 model with [M=Zr, x=1], ​​i.e., Li8Al2Zr(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0043] Example 5 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Zr, x=2], i.e., Li7AlZr2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0044] Example 6 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Zr, x=3], i.e., Li6Zr3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0045] Example 7 Li 9-x Al 3-x M xA (PO4)2(P2O7)3 model with [M=Ti, x=1], ​​i.e., Li8Al2Ti(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0046] Example 8 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Ti, x=2], i.e., Li7AlTi2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0047] Example 9 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Ti, x=3], i.e., Li6Ti3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0048] Example 10 Li 9-x Al 3-x M xA (PO4)2(P2O7)3 model with [M=Hf, x=1], ​​i.e., Li8Al2Hf(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0049] Example 11 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Hf, x=2], i.e., Li7AlHf2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0050] Example 12 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Hf, x=3], i.e., Li6Hf3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0051] Example 13 Li 9-x Al 3-x M xA (PO4)2(P2O7)3 model with [M=Ge, x=1], ​​i.e., Li8Al2Ge(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0052] Example 14 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Ge, x=2], i.e., Li7AlGe2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean square displacement of Li obtained by the calculation.

[0053] Example 15 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with [M=Ge, x=3], i.e., Li6Ge3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0054] Example 16 Li 9-x Al 3-x M xA (PO4)2(P2O7)3 model with M = Sn, Zr, x = 1, i.e., Li8Al2(SnZr)(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics simulations were performed for 100 picoseconds at 1 femtosecond intervals at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K). The ionic conductivity was calculated from the calculated mean-square displacement of Li.

[0055] Example 17 Li 9-x Al 3-x M x A (PO4)2(P2O7)3 model with M = Sn, Zr, x = 2, i.e., Li7Al(SnZr)2(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics simulations were performed for 100 picoseconds at 1 femtosecond intervals at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K). The ionic conductivity was calculated from the calculated mean-square displacement of Li.

[0056] Example 18 Li 9-x Al 3-x M x A model of (PO4)2(P2O7)3 [M = Sn, Zr, x = 3], i.e., Li6(SnZr)3(PO4)2(P2O7)3, was prepared and a 2x2x1 superlattice was created. Using this model, molecular dynamics calculations were performed for 100 picoseconds at temperatures T = 127°C (400K), 327°C (600K), 527°C (800K), and 727°C (1000K) with 1 femtosecond intervals. The ionic conductivity was calculated from the mean-square displacement of Li obtained by the calculation.

[0057] Table 1 shows the ionic conductivities at each temperature obtained in Comparative Example 1 and Examples 1-18.

[0058] [Table 1]

[0059] An example of the relationship between temperature and ionic conductivity is shown in Figure 4. Figure 4 shows, as an example, the relationship between temperature and ionic conductivity obtained in Comparative Example 1 and Examples 1-3 (M = Sn). Figure 4 shows the ionic conductivity [S / cm] of Comparative Example 1 and Examples 1-3 shown in Table 1 as a function of the reciprocal of temperature T, 1 / T [×10 -3 1 / K].

[0060] As can be seen from Table 1, in Examples 4-6 (M=Zr), Examples 7-9 (M=Ti), Examples 10-12 (M=Hf), Examples 13-15 (M=Ge), and Examples 16-18 (M=Sn, Zr), the relationship between temperature and ionic conductivity shows roughly the same tendency as in Figure 4, but for convenience, the plots are not shown here.

[0061] First, focusing on the LAPP of Comparative Example 1 and Examples 1-3 in which the Al substitution element M was Sn, as shown in Table 1 and FIG. 4, in both Comparative Example 1 and Examples 1-3, a tendency was observed in which the ionic conductivity increased as the temperature T increased. In Examples 1-3, a tendency was observed in which the ionic conductivity was higher than that of Comparative Example 1 at any temperature T. In Examples 1-3, a tendency was observed in which the ionic conductivity increased as the Sn composition ratio x increased at any temperature T, and the ionic conductivity was highest when the composition ratio x was 3, which was the maximum value.

[0062] Similarly, for Examples 4-6 in which Zr was used as the substitution element M for Al in LAPP (Comparative Example 1), a tendency for the ionic conductivity to increase as the temperature T increased was observed in all of Examples 4-6, as shown in Table 1. Examples 4-6 tended to exhibit higher ionic conductivity than Comparative Example 1 at all temperatures T. In Examples 4-6, a tendency for the ionic conductivity to increase as the Zr composition ratio x increased was generally observed, and in the temperature range below temperature T=527°C (800K), the ionic conductivity was highest when the composition ratio x was at its maximum value of 3.

[0063] Similarly, for Examples 7-9 in which Ti was used as the Al substitution element M in LAPP (Comparative Example 1), a tendency for the ionic conductivity to increase as the temperature T increased was observed in all of Examples 7-9, as shown in Table 1. Examples 7-9 tended to exhibit higher ionic conductivity than Comparative Example 1 at all temperatures T. In Examples 7-9, a tendency for the ionic conductivity to increase as the Ti composition ratio x increased was generally observed, and in the temperature range of temperature T=327°C (600K) or higher, the ionic conductivity was highest when the composition ratio x was at its maximum value of 3.

[0064] Similarly, for Examples 10-12 in which Hf was used as the substitution element M for Al in LAPP (Comparative Example 1), a tendency for the ionic conductivity to increase as the temperature T increased was observed in all of Examples 10-12, as shown in Table 1. Examples 10-12 tended to exhibit higher ionic conductivity than Comparative Example 1 at all temperatures T. Examples 10-12 tended to exhibit higher ionic conductivity as the Hf composition ratio x increased at all temperatures T, and the ionic conductivity was highest when the composition ratio x was 3, which was the maximum value.

[0065] Similarly, for Examples 13-15 in which Ge was substituted for the Al substitution element M in LAPP (Comparative Example 1), a tendency for the ionic conductivity to increase as the temperature T increased was observed in all of Examples 13-15, as shown in Table 1. Examples 13-15 tended to exhibit higher ionic conductivity than Comparative Example 1 at all temperatures T. Examples 13-15 also tended to exhibit higher ionic conductivity as the Ge composition ratio x increased at all temperatures T, with the highest ionic conductivity being achieved when the composition ratio x was 3.

[0066] Similarly, for Examples 16-18 in which Sn and Zr were used as the Al-substituting element M in LAPP (Comparative Example 1), a tendency for the ionic conductivity to increase as the temperature T increased was observed in all of Examples 16-18, as shown in Table 1. Examples 16-18 tended to exhibit higher ionic conductivity than Comparative Example 1, except when the temperature T was 727°C (1000K) and the Sn and Zr composition ratio x was relatively low, x = 1 or 2. In Examples 16-18, a tendency for the ionic conductivity to increase as the Sn and Zr composition ratio x increased was generally observed, and in the temperature range of T = 327°C (600K) or higher, the ionic conductivity was highest when the composition ratio x was the maximum value, x = 3.

[0067] As described above, the solid electrolyte applicable to the solid battery 1 is a solid electrolyte having a composition formula of Li 9-x Al 3-x M xA solid electrolyte LAMPP / LMPP is provided, which is represented by (PO4)2(P2O7)3, wherein the element M is at least one element selected from Sn, Zr, Ti, Hf, and Ge, and the range of the composition ratio x of the element M is 0 < x ≤ 3. That is, a solid electrolyte LAMPP / LMPP is provided in which part or all of the trivalent Al in LAPP (Li9Al3(PO4)2(P2O7)3) is replaced with a tetravalent predetermined element M. According to such a solid electrolyte LAMPP / LMPP, it is possible to obtain one having higher ionic conductivity than LAPP, that is, higher lithium ion conductivity than LAPP. By using the solid electrolyte LAMPP / LMPP having high lithium ion conductivity, it is possible to realize a solid battery 1 having excellent charge and discharge characteristics.

Explanation of Symbols

[0068] 1 Solid battery 10 Positive electrode layer 20 Negative electrode layer 30 Electrolyte layer 100 Unit cell

Claims

1. The composition formula is Li ９－ｘ Al ３－ｘ M ｘ (P.O. ４ ) ２ (P ２ O ７ ) ３ wherein M is one or more elements selected from Sn, Zr, Ti, Hf, and Ge, and x is in the range of 0<x≦3.

2. 2. The solid electrolyte according to claim 1, having a crystal structure in space group P-3c1.

3. An electrolyte layer comprising the solid electrolyte according to claim 1 or 2; a positive electrode layer provided on one side of the electrolyte layer; a negative electrode layer provided on the other side of the electrolyte layer; [0010] A solid-state battery, including:

4. The positive electrode layer is Li ２ CoP ２ O ７ The solid-state battery of claim 3 , comprising:

5. The solid-state battery according to claim 4 , wherein the positive electrode layer further comprises the solid electrolyte.

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