CN1091306C - Solid electrolyte and preparation and uses thereof - Google Patents

Abstract

The solid electrolyte of the present invention is a composite system composed of an inorganic electrolyte and an organic polymer electrolyte. The interaction between the organic electrolyte and the inorganic electrolyte is used to make the ion conductivity as high as 10 ^-3 S/cm; the addition of organic matter greatly improves the The machinability of the system is improved. The invention can be used in the fields of lithium-ion secondary batteries, electrochromic devices, sensors and the like.

Description

A kind of solid electrolyte and its preparation method and application

Technical field:

The invention relates to a novel solid electrolyte and its preparation method and application. The electrolyte has the advantages of high ion conductivity, good machining performance, safety and no leakage. It is expected to replace traditional liquid electrolytes in lithium-ion secondary batteries, electrochromic devices and sensors, and has broad application prospects.

Background technique:

Solid electrolyte is a general term for ionically conductive solids, which have the advantages of safe use, no leakage, no pollution, less self-discharge and long life. In today's increasingly serious energy problem, it has aroused people's interest more and more. Studies have found that composite inorganic electrolytes have high ion conductivity, for example, the room temperature ion conductivity of the AlCl ₃ -LiClO ₄ composite system reaches 10 ^-2.3 S/cm. Studies have also shown that the compounding of inorganic salts can destroy the crystal structure of a single inorganic salt, lower the melting point of the inorganic salt electrolyte, and make it easier for inorganic cations to move freely from the bondage of anions [see CAAngell, nature, 362, 137-139 (1993)]. However, its poor machinability and poor film-forming properties greatly limit its practical application.

Organic polymer solid electrolyte is a new type of solid electrolyte developed in the past ten years. This kind of polymer is based on polyether polymer material, and alkali metal ions are used as carrier ions. In addition to the performance of general solid electrolytes, it also has a remarkable feature: strong plasticity. This feature brings two advantages: easy to process into a film, reduce the internal resistance of the battery; good contact with the electrode to increase the charge and discharge current. However, polymer solid electrolytes also have fatal shortcomings: the ionic conductivity is lower than the level of practical application, the main reason is that as the content of inorganic salts in the polymer electrolyte increases, the dissociated inorganic ions accumulate, making effective The number of carriers decreases, and the ion conductivity is greatly reduced [see US Patent 4882243]. The highest room temperature ionic conductivity reported so far is only 10 ^-4 S/cm, which greatly limits its practical application.

Invention content:

The object of the present invention is to overcome the disadvantages of poor machining performance of inorganic molten salt electrolyte and low ion conductivity in polymer electrolyte, and provide high ion conductivity and good machining performance.

The present invention proposes a novel solid electrolyte, a composite system consisting of "organic electrolyte (organic salt)-inorganic electrolyte (inorganic salt)": several organic salts with polar groups of different structures are synthesized, and then the organic salt Combining with inorganic salts, combining the advantages of inorganic salts and organic polymer electrolytes, on the one hand, using the interaction between organic salts and inorganic salts to further destroy the crystal phase structure of inorganic salts, promote the dissociation of inorganic salts, and make their ion conduction The rate is as high as 10 ^-3 S/cm; on the other hand, due to the use of organic salts, the skeleton of organic molecules can also play a role in improving the mechanical processing properties of the system.

The solid electrolyte of the present invention is composed of the following components (percentage by weight): component 1: inorganic salt; content: 20-90% component 2: organic salt; content: 10-80%

The above component 1 includes: LiClO ₄ , LiClO ₃ , LiNO ₃ , LiOAC, LiI, Li ₂ CO ₃ , Li ₂ SO ₄ , LiCl, LiBr, LiCF ₃ SO ₃

The above component 2 includes several synthetic sulfates, sulfonates, carbonates and quaternary ammonium salts with polar groups, such as: (low) polyoxyethylene lithium sulfate (PEGSO ₄ Li), (low ) Lithium Polyoxyethylene Sulfonate (PEGSO ₃ Li), Lithium Propionate, Lithium Lauryl Sulfate, Lithium Nonylphenol (Low) Polyoxyethylene Sulfate, Lithium Nonylphenol (Low) Polyoxyethylene Sulfate , Lithium polystyrene sulfonate, Lithium polyvinyl alcohol sulfate, Polymethylsiloxane Propoxypolyoxyethylene Lithium Sulfate (PMSPSLi), Polymethacrylic Acid Lithium Polyoxyethylene Sulfonate, Polymethacrylic Acid Oligomerized Ethylene Oxide Tetramethylammonium Chloride.

The preparation process of the "organic salt-inorganic salt" composite system electrolyte of the present invention is carried out in the following sequence steps:

1 Drying and dehydration: Reagent-grade inorganic salts such as LiClO ₃ and Li ₂ SO ₄ are dried and dehydrated in a vacuum oven at successively increasing temperature from 40°C, 60°C, 80°C, 100°C, and 120°C until the sample no longer loses weight.

2 Compounding of organic salt-inorganic salt system: heating and melting 20%-90% of inorganic salt such as LiClO ₃ and 10-80% of dried organic salt such as PEGSO ₄ Li, PEGSO ₃ Li or PMSPSLi, and drying After fully mixing in the oven, transfer to a vacuum oven to dry at 120°C until the sample no longer loses weight, and finally place the sample in a desiccator to cool.

The solid electrolyte prepared by the present invention has achieved the following inventive effects: (1) fully utilizing the interaction of organic salts and inorganic salts to improve the room temperature ionic conductivity of the solid electrolyte, reaching the highest value reported in the current non-aqueous system, see Table 1 ; (2) The organic molecular skeleton improves its mechanical processing performance. The invention can be used in lithium ion secondary batteries, electrochromic devices, sensors and other fields.

The relationship between the room temperature ionic conductivity (conductivity) and composition of different systems in Table 1 LiClO ₃ content 0% 10% 20% 40% 60% 80% 100

%Electricity of Example 1 1.6 × 3.1 × 1.4 × 1.2 × 1.5 × 8.6 × 1.7 × Conductivity (S/cm) 10 ^-5 10 ^-5 10 ^{-7 10 -6 10 -5} 10 ^-4 10 ^-4Example The electrical conductivity of the second embodiment 2.4 × 3.2 × 2.1 × 1.5 × 2.2 × 5.9 × 1.7 × conductivity (S/cm) 10 ^-5 10 ^-5 10 ^-7 10 ^-6 10 ^-5 10 ^-4 10 ^-4 The electrical conductivity of the third embodiment 1.6 × 2.5 × 3.9 × 2.5 × 3.5 × 1.05 × 1.7 × Conductivity (S/cm) 10 ^-5 10 ^-5 10 ^-7 10 ^-6 10 ^-5 10 ^-3 10 ^-4 Electrical conductivity of Comparative Example 1 1.7 × - 4.8 × 8.5 × 1.9 × 7.9 × 1.7 ×Conductivity (S/cm) 10 ^-7 10 ^-6 10 ^-5 10 ^-4 10 ^-4 10 ^{-4Comparative} example 2: 5.01 × 3.16 × 1.25 × 1.61 × 6.3 × 1.58 × 1.7 × Conductivity (S/cm) 10 ^-6 10 ^-5 10 ^-5 10 ^-7 10 ^-6 10 ^-5 10 ^-4

Detailed ways:

Embodiment one

LiClO ₃ -PEGSO ₄ Li: The organic salt PEGSO ₄ Li with a highly polar group and the inorganic salt LiClO ₃ were chosen to be combined. It was found that the room temperature ionic conductivity of the system increased first and then decreased with the increase of LiClO ₃ content, and in When the content of LiClO ₃ is 80%, the maximum value is 8.6×10 ^-4 S/cm, which has reached the practical level.

Embodiment two

LiClO ₃ -PEGSO ₃ Li: Combining the organic salt PEGSO ₃ Li and the inorganic salt LiClO ₃ , it was found that the room temperature ionic conductivity of the system also reached the maximum value of 5.9×10 ^-4 S/cm when the content of LiClO ₃ was 80%, but the low Ionic conductivity in LiClO ₃ -PEGSO ₃ system.

Embodiment Three

PMSPSLi-LiClO ₃ : After compounding methylsiloxane propyl oligopolyoxyethylene lithium sulfate (PMSPSLi) with soft chains and LiClO ₃ , its room temperature ionic conductivity reaches a maximum value of 1.05 when the content of LiClO ₃ is 80% ×10 ^-3 S/cm, the ionic conductivity is also the highest value reported for non-aqueous electrolytes, and contains 20% organic polymers, which has reached a practical level. Comparative example one

As a comparison, LiClO ₃ and Li ₂ SO ₄ were compounded in different proportions. It can be found that with the addition of LiClO ₃ , the room temperature ionic conductivity of the composite system gradually increased, and reached a peak when the content of LiClO ₃ was 80%. big value. The results show that the recombination of inorganic salts promotes the dissociation of inorganic salts and increases the number of effective carriers, so the room temperature ionic conductivity increases with the addition of the second component, and reaches an extreme within a certain range. big value. Comparative example two

PEO600-LiClO ₃ : As a comparison, when PEO600 and LiClO ₃ are combined, it can be seen that the ion conductivity of the PEO600-LiClO ₃ system is much lower than that of the PEGSO ₄ Li-LiClO ₃ composite system. This strongly illustrates that simple organic matter cannot destroy the crystallization of inorganic salts, but organic salts can destroy the crystal structure of inorganic salts and promote the dissociation of inorganic salts.

Claims (3)

1. A solid electrolyte, characterized in that the solid electrolyte is a composite system composed of an inorganic electrolyte and an organic electrolyte, and its components and contents are as follows by weight percentage: Inorganic salt: 20%-90%, organic salt: 10%-80%, The above-mentioned inorganic salts are lithium perchlorate, lithium chlorate, lithium nitrate, lithium acetate, lithium iodide, lithium carbonate, lithium sulfate, lithium chloride, lithium bromide, lithium trifluoromethanesulfonate, and the above-mentioned organic salts are oligomeric oxidation Lithium Vinyl Sulfate, Lithium Oligoethylene Oxide Sulfonate, Lithium Propionate, Lithium Lauryl Sulfate, Lithium Nonylphenol Oligoethylene Oxide Sulfate, Lithium Nonylphenol Oligoethylene Oxide Sulfate, Polystyrene Lithium Sulfonate, Lithium Polyvinyl Alcohol Sulfate, Lithium Polymethylsiloxane Propyl Oligoxyethylene Oxide Sulfate, Lithium Polymethacrylic Oligomerized Ethylene Oxide Hexasulfonate, Polymethacrylic Oligomerized Ethylene Oxide Tetramethyl ammonium chloride. 2. The preparation method of a solid electrolyte according to claim 1, characterized in that the steps are carried out in the following order: (1) Drying and dehydration: Reagent-grade inorganic salt lithium chlorate or lithium sulfate is dried and dehydrated in a vacuum oven at 40°C, 60°C, 80°C, 100°C, and 120°C; (2) Compounding of organic salt-inorganic salt system: 20-90% of inorganic salt lithium chlorate and 10-80% of oligoethylene oxide lithium sulfate, oligooxyethylene sulfonate lithium or polymethylsilane Oxyalkylpropyl oligomerized oxyethylene lithium sulfate is heated and melted, and after being fully mixed in a drying oven, it is transferred to a vacuum oven to dry at 120°C. 3. The use of a solid electrolyte according to claim 1, characterized in that it is applied in the field of lithium-ion secondary batteries, electrochromic devices or sensors.