A pure-phase lithium titanium phosphate electrolyte and a preparation method thereof

Abstract

The application discloses a pure-phase lithium titanium phosphate electrolyte and a preparation method thereof, and the preparation method comprises the following steps: wet ball milling lithium hydroxide monohydrate, titanium oxide, an ammonium phosphate salt, aluminum oxide and a polyhydric alcohol retarder to obtain mixed raw materials; performing drying treatment on the mixed raw materials, screening the mixed raw materials, and performing calcination treatment on the screened mixed raw materials under the condition of 800-1000 DEG C to obtain the pure-phase lithium titanium phosphate electrolyte. By adding the polyhydric alcohol retarder into traditional raw materials for preparing the LATP solid-state electrolyte, the polyhydric alcohol retarder can generate a compound protective film or a complex with the raw materials, hinders the reaction between metal ions and phosphate, delays the hydration reaction, and makes the sintering product very fluffy, so that the operation difficulty is greatly reduced. Therefore, the method can greatly reduce the engineering operation difficulty under the premise of ensuring high purity of the lithium titanium phosphate electrolyte, improves the production efficiency, and is favorable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of solid electrolytes, in particular to a pure-phase lithium titanium phosphate electrolyte and a preparation method thereof. BACKGROUND

[0002] Energy is an important material basis for social development, and traditional fossil energy is increasingly scarce, and developing traditional fossil energy will also cause serious environmental pollution, so developing sustainable new energy has always been a research hotspot. Lithium ion batteries are the development trend of future electrochemical energy storage because they are convenient to use and mature in technology. The growing requirements put forward higher energy function indicators for lithium ion batteries, and high safety, high energy density, high functional rate and long service life are the development needs of lithium ion batteries.

[0003] It is well known that traditional lithium ion batteries have a high safety risk because they contain flammable and explosive organic electrolytes. Secondly, the performance indicators of current lithium ion batteries have basically reached the critical point, but the requirements for high energy density, fast charging and discharging are increasing day by day, and more and more scientists have focused their research on solid-state lithium ion batteries. Solid-state lithium ion batteries not only greatly reduce the safety risks caused by the presence of organic electrolytes, but also have incomparable advantages in improving the overall energy density of the battery, so they are a hot research topic in both academia and industry. As a core component of the full-solid-state battery, the solid-state electrolyte is a key material for realizing high energy density, high cycle stability and high safety of the full-solid-state battery. Generally, an ideal solid-state electrolyte material needs to have high ionic conductivity, high selectivity, good chemical stability, high electronic impedance, good mechanical properties, low cost and simple preparation. Among these properties, the most important and essential one is the ionic conductivity of the material itself.

[0004] NASICON-structured solid-state lithium ion electrolytes have attracted widespread attention due to their high ionic conductivity, good electrochemical and chemical stability, and low raw material cost, and the basic skeleton structure is represented as M2P3O 12 , that is, 2 MO6 octahedrons and 3 PO4 tetrahedrons are connected at the corners to form a structural unit. In the skeleton structure, alkali metals occupy two structural sites M1 and M2, and lithium ions are transported from M1 to M2 through the structural network formed by the MO6 and PO4 skeletons. Among the many derivative structures, the NASICON-type electrolyte prepared by doping Al has a Li 1.3 Al 0.3 Ti 1.7(LATP) has the highest conductivity and is the most widely studied structure. This structure is also considered to be the most likely to be truly commercialized in all-solid-state batteries. Major solid-state battery companies have a demand for industrial production of LATP. The general method for synthesizing LATP can be divided into liquid phase method and solid phase method. The advantage of the liquid phase method is that the particle size is small, but the process is complex and the titanium salt which is easy to hydrolyze needs to be handled carefully, for example, patent CN103825052A needs to use ammonia water to control the pH value. The solid phase method is simple in process and is the mainstream path for small batch synthesis in the laboratory and large batch production in industry. However, there is a big problem in the process engineering of the solid phase method, that is, during the sintering process, no matter what phosphorus source is used, pyrophosphatization reaction will inevitably occur. During the pyrophosphatization reaction process, the material is cross-linked and hardened, and the product is abnormally hard after sintering, which is difficult to carry out the next engineering operation. Because a lot of manpower and material resources are often needed to crush the product in the current production, which greatly wastes production cost and reduces industrial efficiency. Unfortunately, this kind of engineering process optimization is rarely mentioned in the current reports.

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] In view of the deficiencies of the prior art described above, the purpose of the present application is to provide a pure phase lithium titanium phosphate electrolyte and a preparation method thereof, which aims to solve the problem that the solid phase method for preparing LATP will cause pyrophosphatization reaction, making the sintered product abnormally hard, resulting in low production efficiency and high cost of LATP.

[0007] The technical scheme of the present application is as follows:

[0008] A preparation method of a pure phase lithium titanium phosphate electrolyte, comprising the following steps:

[0009] wet ball milling lithium hydroxide monohydrate, titanium oxide, ammonium phosphate salt, aluminum oxide and polyol retarder to obtain mixed raw materials;

[0010] After drying treatment, the mixed raw materials are sieved, and the sieved mixed raw materials are calcined at 800-1000 DEG C to obtain the pure phase lithium titanium phosphate electrolyte.

[0011] The preparation method of the pure phase lithium titanium phosphate electrolyte, wherein the ammonium phosphate salt is diammonium hydrogen phosphate or dihydrogen ammonium phosphate.

[0012] The preparation method of the pure phase lithium titanium phosphate electrolyte, wherein the polyol retarder is one or more of polyvinyl alcohol, polypropylene alcohol and sugar alcohol.

[0013] The preparation method of the pure-phase lithium titanium phosphate electrolyte, wherein the content of the polyol type retarder in the mixed raw material is 0.01wt%-30wt%.

[0014] The preparation method of the pure-phase lithium titanium phosphate electrolyte, wherein the rotation speed of the wet ball milling treatment is 80-300rpm, and the time is 30-720min.

[0015] The preparation method of the pure-phase lithium titanium phosphate electrolyte, wherein the ball-to-material ratio is 3:1-5:1 during the step of wet ball milling treatment.

[0016] The preparation method of the pure-phase lithium titanium phosphate electrolyte, wherein the drying temperature is 55-100℃, and the drying time is 0.5-48h during the step of drying treatment of the mixed raw material.

[0017] The preparation method of the pure-phase lithium titanium phosphate electrolyte, wherein the calcination time is 1-6h, and the heating rate is 1-10℃ / min during the step of calcination treatment of the sieved mixed raw material.

[0018] A pure-phase lithium titanium phosphate electrolyte prepared by the preparation method of the pure-phase lithium titanium phosphate electrolyte.

[0019] Beneficial effects: The present application provides a preparation method of a pure-phase lithium titanium phosphate electrolyte, which adds a polyol type retarder to the traditional raw material for preparing a LATP solid-state electrolyte. The polyol type retarder can form a compound protective film or a complex with the raw material, hinder the reaction between metal ions and phosphate, delay the progress of the hydration reaction, and make the sintering product very fluffy, thereby greatly reducing the operation difficulty. Therefore, the method of the present application can greatly reduce the engineering operation difficulty and improve the production efficiency under the premise of ensuring the high purity of the lithium titanium phosphate electrolyte, which is conducive to large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flow chart of the preparation method of the pure-phase lithium titanium phosphate electrolyte.

[0021] Figure 2 The schematic diagram of the traditional solid-phase method for synthesizing a LATP solid-state electrolyte.

[0022] Figure 3 The schematic diagram of the pure-phase lithium titanium phosphate electrolyte prepared by the method of Example 1

[0023] Figure 4 The XRD diagram of the pure-phase lithium titanium phosphate electrolyte prepared by the method of Example 1 DETAILED DESCRIPTION

[0024] The present application provides a pure phase lithium titanium phosphate electrolyte and a preparation method thereof. To make the purpose, technical scheme and effects of the present application clearer and more explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0025] Referring to Figure 1 , Figure 1 A preparation method flow chart of a pure phase lithium titanium phosphate electrolyte provided by the present application is shown in the figure, which includes the following steps:

[0026] S10, wet ball milling lithium hydroxide monohydrate, titanium oxide, ammonium phosphate salt, aluminum oxide and polyol retarder to obtain mixed raw materials;

[0027] S20, after drying treatment of the mixed raw materials, sieving, calcining the sieved mixed raw materials at 800-1000℃ to obtain a pure phase lithium titanium phosphate electrolyte.

[0028] Specifically, the traditional solid phase method for synthesizing LATP solid electrolyte does not add retarder, and the raw materials will produce hydration reaction to form chemical hardening cement-like substances, which are relatively hard on the outside and inside. At the same time, since the raw materials generally contain volatile substances, serious swelling phenomenon occurs, as shown in Figure 2 The present application adds polyol retarder to the traditional raw materials for preparing LATP solid electrolyte, which will form a compound protective film or complex with the raw materials, hindering the reaction of metal ions and phosphate, thus delaying the hydration reaction, making the sintering product very fluffy, and greatly reducing the operation difficulty. Further, the ammonium phosphate salt will decompose into phosphoric acid under high temperature, and the phosphoric acid will undergo crosslinking reaction under high temperature. There are various metal oxide particles in the raw materials, the surface of which will slowly dissolve to form hydrosol, which gradually increases with the reaction, and the sols connect with each other to form gel, which will harden after saturation. After adding polyol retarder to the raw materials, the polyol retarder contains multiple hydroxyl groups, which can preferentially undergo acid-alcohol condensation reaction with phosphoric acid, thus effectively preventing the crosslinking of phosphate, thereby preventing gel hardening. Therefore, the method of the present application can greatly reduce the engineering operation difficulty and improve the production efficiency under the premise of ensuring the high purity of lithium titanium phosphate electrolyte, which is conducive to large-scale industrial production.

[0029] In some embodiments, the ammonium phosphate salt is diammonium hydrogen phosphate or ammonium dihydrogen phosphate, but is not limited thereto.

[0030] In some embodiments, the polyol retarder is one or more of polyvinyl alcohol, polypropylene alcohol and sugar alcohol, but is not limited thereto.

[0031] In some embodiments, the polyol-based retarder is present in the mixture in an amount of 0.01wt%-30wt%.

[0032] In some embodiments, the wet ball milling is performed at a speed of 80-300rpm for 30-720min, and the ball-to-material ratio is 3:1-5:1.

[0033] In some embodiments, the drying is performed at a temperature of 55-100℃ for 0.5-48h.

[0034] In some embodiments, the calcination is performed for 1-6h at a heating rate of 1-10℃ / min.

[0035] The application also provides a pure-phase lithium titanium phosphate electrolyte prepared by the method.

[0036] The method for preparing a pure-phase lithium titanium phosphate electrolyte is further explained below by means of specific examples:

[0037] Example 1

[0038] A method for preparing a pure-phase lithium titanium phosphate electrolyte:

[0039] 1. Lithium hydroxide monohydrate is used as the lithium source, titanium oxide is used as the titanium source, diammonium hydrogen phosphate is used as the phosphorus source, and aluminum oxide is used as the doping element. Polyvinyl alcohol is used as the retarder. The raw materials are uniformly ground by wet ball milling according to the ratio, wherein the content of the retarder is 15wt%, the ball milling speed is 150rpm / min, the ball milling time is 120min, and the ball-to-material ratio is 4:1.

[0040] 2. The mixed raw materials obtained in step 1 are transferred to a drying oven for drying, the drying temperature is 70℃, and the drying time is 24h. After drying, the materials are sieved, 100g of the mixed raw materials are weighed, and the white product is obtained by calcination at 900℃. A sintering dish made of 99% pure corundum is used for sintering, the powder filling thickness is 5cm, the calcination time is 3h, and the heating and cooling rate is 8℃ / min.

[0041] The product (lithium titanium phosphate electrolyte) after sintering in this example is shown in FIG. 1, and it can be seen from FIG. 1 that the lithium titanium phosphate electrolyte prepared in this example is very fluffy, which effectively reduces the operation difficulty of the subsequent operation process. Figure 3 Figure 3 The product after sintering in this example is subjected to XRD testing, and the results are shown in FIG. 2, and it can be seen from FIG. 2 that the lithium titanium phosphate electrolyte prepared in this example is a pure phase.

[0042] The product after sintering in this example is subjected to XRD testing, and the results are shown in FIG. 2, and it can be seen from FIG. 2 that the lithium titanium phosphate electrolyte prepared in this example is a pure phase. Figure 4 Figure 4 ​​It can be seen that the lithium titanium phosphate electrolyte prepared in the embodiment is a pure cubic phase and does not contain other impurity phases.

[0043] Embodiment 2

[0044] A method for preparing a pure-phase lithium titanium phosphate electrolyte comprises the following steps:

[0045] 1. Lithium hydroxide monohydrate is used as a lithium source, titanium oxide is used as a titanium source, ammonium dihydrogen phosphate is used as a phosphorus source, aluminum oxide is used as a doping element, and polyvinyl alcohol is used as a retarder. The raw materials are uniformly ground according to the ratio and by using a wet ball mill, wherein the content of the retarder is 0.01 wt%, the ball mill rotation speed is 300 rpm / min, the ball mill time is 30 min, and the ball-to-material ratio is 3:1.

[0046] 2. The mixed raw materials obtained in step 1 are transferred to a drying oven for drying, the drying temperature is 55℃, and the drying time is 48 h. After drying, the materials are sieved, 200 g of the mixed raw materials are weighed, and the white product is obtained by calcining at 1000℃. A 99% pure corundum sintering dish is used for sintering, the powder filling thickness is 10 cm, the calcining time is 6 h, and the temperature rising and falling rate is 2℃ / min. The lithium titanium phosphate electrolyte prepared in the embodiment is fluffy, which effectively reduces the operation difficulty of the subsequent operation process.

[0047] Embodiment 3

[0048] A method for preparing a pure-phase lithium titanium phosphate electrolyte comprises the following steps:

[0049] 1. Lithium hydroxide monohydrate is used as a lithium source, titanium oxide is used as a titanium source, ammonium dihydrogen phosphate is used as a phosphorus source, aluminum oxide is used as a doping element, and polyvinyl alcohol is used as a retarder. The raw materials are uniformly ground according to the ratio and by using a wet ball mill, wherein the content of the retarder is 0.01 wt%, the ball mill rotation speed is 300 rpm / min, the ball mill time is 30 min, and the ball-to-material ratio is 3:1.

[0050] 2. The mixed raw materials obtained in step 1 are transferred to a drying oven for drying, the drying temperature is 55℃, and the drying time is 48 h. After drying, the materials are sieved, 200 g of the mixed raw materials are weighed, and the white product is obtained by calcining at 1000℃. A 99% pure corundum sintering dish is used for sintering, the powder filling thickness is 10 cm, the calcining time is 6 h, and the temperature rising and falling rate is 2℃ / min. The lithium titanium phosphate electrolyte prepared in the embodiment is fluffy, which effectively reduces the operation difficulty of the subsequent operation process.

[0051] Embodiment 4

[0052] A method for preparing a pure-phase lithium titanium phosphate electrolyte comprises the following steps:

[0053] 1. Lithium hydroxide monohydrate as lithium source, titanium oxide as titanium source, diammonium hydrogen phosphate as phosphorus source, aluminum oxide as doping element, polyvinyl alcohol as retarder, the raw materials are ground uniformly according to the ratio and by wet ball milling, the content of the retarder is 20wt%, the ball milling speed is 200rpm / min, the ball milling time is 360min, and the ball to material ratio is 5:1.

[0054] 2. The mixed raw materials of step 1 are transferred to a drying oven for drying, the drying temperature is 90℃, the drying time is 32h. After drying, the product is sieved, 150g of the mixed raw materials are weighed, and the white product is obtained by calcining at 900℃; corundum sintering dish with 99% purity is used during sintering, the powder filling thickness is 8cm, the calcining time is 4h, and the heating and cooling rate is 18℃ / min. The lithium titanium phosphate electrolyte prepared in this example is fluffy, which effectively reduces the operation difficulty of the subsequent operation process. It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for producing a pure-phase lithium titanium phosphate electrolyte, characterized by, The method comprises the steps of: wet ball milling lithium hydroxide monohydrate, titanium oxide, ammonium phosphate salt, aluminum oxide and a polyhydric alcohol-based retarder to obtain a mixed raw material; the polyhydric alcohol-based retarder is one or more of polyvinyl alcohol, polypropylene alcohol and sugar alcohol; the content of the polyhydric alcohol-based retarder in the mixed raw material is 0.01wt%-30wt%; sifting the mixed raw material after drying treatment, and calcining the sifted mixed raw material at 800-1000℃ to obtain a pure-phase lithium titanium phosphate electrolyte; acid-ester condensation reaction occurs between the polyhydric alcohol-based retarder and phosphoric acid produced by decomposition of the ammonium phosphate salt, preventing cross-linking of the ammonium phosphate salt and preventing gel hardening; the ammonium phosphate salt is di-ammonium hydrogen phosphate or ammonium dihydrogen phosphate; the wet ball milling is performed at a speed of 80-300rpm for 30-720min; in the step of wet ball milling, the ball-to-material ratio is 3:1-5:1; in the step of drying the mixed raw material, the drying temperature is 55-100℃ and the drying time is 0.5-48h; in the step of calcining the sifted mixed raw material, the calcining time is 1-6h and the temperature rising rate is 1-10℃ / min.

2. A pure phase lithium titanium phosphate electrolyte, characterized in that, The pure-phase lithium titanium phosphate electrolyte is prepared by the method of claim 1.

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