Lithium-ion conductor

Abstract

To provide a lithium ion conductor having high ionic conductivity in a high temperature range (80°C or higher).SOLUTION: A lithium ion conductor containing Li-B-I causes a phase transition at 60-80°C, showing high ionic conductivity. It also shows higher ionic conductivity than those of iodide- or bromide-based one of the same group, as well as iodinated sulfide-based one.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to lithium ion conductors. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become increasingly important. In addition, the automotive industry is also working to develop high-output, high-capacity batteries for electric vehicles and hybrid vehicles.

[0003] Non-Patent Document 1 discloses a lithium ion conductor containing a Li7P2S8I phase. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J.Am.Chem.Soc.2015,137,1384-1387 Summary of the Invention [Problem to be solved by the invention]

[0005] The lithium ion conductor described in Non-Patent Document 1 does not have high ion conductivity in the high temperature range (80° C. or higher).

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a lithium ion conductor having high ion conductivity in the high temperature range (80° C. or higher). [Means for solving the problem]

[0007] The lithium ion conductor of the present disclosure includes LiBI4. [Effects of the Invention]

[0008] The present disclosure can provide a lithium ion conductor having high ion conductivity in a high temperature range (80° C. or higher). DETAILED DESCRIPTION OF THE INVENTION

[0009] The lithium ion conductor of the present disclosure includes LiBI4.

[0010] Lithium ion conductors containing the Li7P2S8I phase have low ionic conductivity when used as solid electrolytes in batteries at high temperatures. The researchers found that lithium ion conductors containing Li-BI undergo a phase transition at temperatures between 60 and 80°C, exhibiting high ionic conductivity. The researchers also demonstrated that lithium ion conductors containing Li-BI exhibit higher ionic conductivity than their homologous iodides and bromides, as well as iodine-containing sulfides.

[0011] The lithium ion conductor of the present disclosure may be any material containing LiBI4, may consist of LiBI4, or may contain LiI and BI3 in a molar ratio of 1:1.

[0012] The lithium ion conductor of the present disclosure may be used as a solid electrolyte in various batteries. The battery may be a primary battery or a secondary battery, but particularly a secondary battery. Secondary batteries can be repeatedly charged and discharged. Secondary batteries are useful, for example, as automotive batteries. The battery may be an aqueous battery, a non-aqueous battery, an all-solid-state battery, or the like. The battery may also be a lithium battery, a lithium ion battery, or the like. Furthermore, the all-solid-state battery may be an all-solid-state lithium secondary battery, an all-solid-state lithium ion secondary battery, or the like. The use of the battery is not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the battery may be used as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles. The battery of the present disclosure may also be used as a power source for mobile objects other than vehicles (e.g., trains, ships, and aircraft), or as a power source for electrical appliances such as information processing devices. [Example]

[0013] Example 1 [Synthesis of LiBI4] LiI (manufactured by Kojundo Chemical) and BI3 (manufactured by Kojundo Chemical) were placed in a 500ml ZrO2 pot in a molar ratio of 1:1, and after adding a 5mmφ ZrO2 ball, 100g of heptane was added and stirred at 300 rpm for 1 hour for 20 sets. This was dried in a glove box and the contents were recovered to obtain LiBI4.

[0014] (Comparative Example 1) [Synthesis of LiAlI4] LiAlI4 was obtained in the same manner as in Example 1, except that AlI3 (manufactured by Aldrich) was used as the starting material.

[0015] (Comparative Example 2) [Synthesis of LiGaI4] LiGaI4 was obtained in the same manner as in Example 1, except that GaI3 (manufactured by Aldrich) was used as the starting material.

[0016] (Comparative Example 3) [Synthesis of LiBBr4] LiBBr4 was obtained in the same manner as in Example 1, except that the starting materials were LiBr (manufactured by Kojundo Chemical Co., Ltd.) and BBr3 (manufactured by Nacalai Tesque).

[0017] Comparative Example 4 [Synthesis of Li7P2S8I] Li2S (Alpha) and P2S5 (Aldrich) were mixed in a 2:1 molar ratio in acetonitrile (Aldrich), and the resulting powder was dried at 80 °C to obtain Li3PS4-2ACN, which was then dispersed in LiI dissolved in acetonitrile for 15 minutes, and the resulting slurry was dried in vacuum at 200 °C for 12 hours to synthesize a solid solution of Li7P2S8I.

[0018] [Ionic conductivity measurement] The solid electrolytes (lithium ion conductors) of Example 1 and Comparative Examples 1 to 4 were evaluated for ionic conductivity under the following conditions. A powder cell was fabricated by filling a cylinder with 100-150 mg of solid electrolyte and pressing it at 6 t. This was placed in a desiccator and impedance measurements were performed in a thermostatic chamber at temperatures of 25°C and 80°C. The ionic conductivity at each temperature was calculated from the obtained resistance value and sample thickness. The results are shown in Table 1.

[0019] [Table 1]

[0020] [Evaluation results] As shown in Table 1, LiBI4 does not have a particularly high conductivity at room temperature of 25°C, but a phase transition behavior is observed between 60°C and 80°C, and it was confirmed that the ionic conductivity improves significantly (by four orders of magnitude) at 80°C. This is a phenomenon unique to the BI-based solid electrolyte of Example 1, and is not observed in the iodide-based solid electrolytes of the same group, such as LiAlI4 of Comparative Example 1 and LiGaI4 of Comparative Example 2, or the B-Br-based solid electrolyte of Comparative Example 3. Furthermore, compared to the iodine-containing sulfide-based solid electrolyte of Comparative Example 4, LiBI4 of Example 1 exhibits high ionic conductivity in the high-temperature range of 80°C, making LiBI4 a promising material for increasing the output of batteries in the high-temperature range of 80°C or higher.

Claims

[Claim 1] A solid electrolyte comprising LiBi ４ An all-solid-state battery comprising a lithium ion conductor, comprising:

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