Preparation method and energy storage application of small organic molecule negative electrode material

Abstract

The invention discloses a lithium biphenyl dicarboxylate-based organic negative electrode material for a sodium-ion battery as well as a preparation method and application of the lithium biphenyl dicarboxylate-based organic negative electrode material. Aiming at the key problems of low conductivity, serious electrolyte dissolution, poor interface stability and the like of the existing small organic molecule negative electrode material, the high-performance lithium biphenyl dicarboxylate negative electrode material is developed through molecular structure design and process innovation. The material is prepared by a three-step method comprising the following steps: deprotonating to obtain a precursor, precipitating and purifying, separating a product, and activating in an inert atmosphere. The lithium biphenyl dicarboxylate prepared by the method is small in particle size, high in uniformity and high in tap density. And under the high current of 500mA / g, the capacity retention ratio can still reach more than 90% after 450 cycles. Therefore, the prepared biphenyl lithium dicarboxylate is applied to green organic sodium ion batteries and shows large-scale application potential in the fields of industrial peak-load shifting energy storage batteries, photovoltaic wind-photovoltaic matched energy storage and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of organic small molecule negative electrode materials of sodium ion batteries, and particularly relates to a preparation method for synthesizing lithium diphenyldicarboxylate negative electrode material based on deprotonation of diphenyldicarboxylic acid, and application in sodium ion batteries. BACKGROUND

[0002] Energy is the material basis for human survival and development. Accelerating the development of renewable energy has become an important task for the development of China's energy industry. In this regard, the Chinese government has taken many measures, including establishing a carbon exchange, developing wind power generation, solar power generation, and geothermal power generation. In 2024, the proportion of new energy power generation in China was 18.5%. As the cheapest and most deployed power generation technology in the world, solar and wind power, like most renewable and clean energy, have the problems of intermittency and instability, so there is an urgent need to develop a new type of battery energy storage system with high energy density, low cost, and high safety to solve the seasonal changes in power supply and demand and fill the long-term power supply gap. It can build an intelligent power grid that can shave peak load, regulate peak and frequency, and meet people's growing demand for electricity.

[0003] Unfortunately, due to cost and safety issues, the further development of current commercial lithium-ion battery systems has been severely hampered. Moreover, as the global demand for renewable and environmentally friendly resources continues to grow, there is an increasing demand for non-toxic and economically biodegradable materials. Organic sodium-ion batteries, with their high safety of 0V discharge and low-cost, green material selection, have become a powerful complementary battery to the lithium-ion battery-dominated energy storage system. Therefore, as an ideal green battery system, organic sodium-ion batteries have great potential for large-scale application in the field of high-power density demand such as industrial peak shaving and valley filling energy storage batteries, photovoltaic and wind power matching energy storage, and power grid frequency regulation.

[0004] As a new electrode material system for sodium-ion batteries, organic small molecule negative electrode materials have attracted widespread attention from academia and industry in recent years due to their unique molecular structure and designability. This type of material mainly achieves energy storage through reversible redox reactions between active functional groups in the molecules (such as carbonyl, imine, etc.) and sodium ions, showing significant technical advantages. First, in terms of theoretical specific capacity, organic small molecule materials generally have a high capacity characteristic of 300-600mAh / g, far exceeding traditional hard carbon negative electrode materials (about 300mAh / g). This high capacity characteristic is due to the rich redox active sites in its molecular structure, which can realize multi-electron transfer reactions. Secondly, organic materials have excellent molecular designability. By introducing different functional groups or constructing specific conjugated structures, the sodium storage potential, electronic conductivity and structural stability of the material can be precisely controlled. For example, the introduction of electron-withdrawing groups in the diphenylcarboxylic acid molecule can effectively reduce the working potential, thereby reducing the risk of electrolyte decomposition and sodium dendrite formation. Third, organic materials are primarily composed of lightweight elements such as carbon, hydrogen, and oxygen. These materials are widely available and environmentally friendly, being obtained through biomass conversion or chemical byproducts. Their synthesis process is typically simple, not requiring energy-intensive processing steps such as high-temperature sintering. This offers significant advantages in cost control and sustainable development. Furthermore, the unique structural flexibility of organic materials can effectively buffer volume changes during sodium ion insertion and extraction, thereby improving the structural stability and cycle life of the electrode.

[0005] However, organic small molecule negative electrode materials still face many key scientific problems and technical challenges in practical applications. The first and foremost problem is their low intrinsic conductivity. Most organic small molecule materials are insulators with poor electronic conductivity, which seriously restricts the performance of their rate performance. At present, the conductivity is mainly improved through strategies such as carbon composites, conductive polymer coating or chemical doping, but these methods often lead to a decrease in the content of active substances, thereby sacrificing the specific capacity advantage of the material. Secondly, the solubility problem of organic materials in organic electrolytes is particularly prominent, especially in ester or ether electrolyte systems. Small molecule organic materials are prone to dissolution and loss, resulting in electrode structure destruction and rapid capacity decay. Although dissolution can be suppressed to a certain extent by polymerization or cross-linking, these strategies usually increase the complexity and cost of the synthesis process. Third, the interface stability between organic electrode materials and electrolytes is poor, and irreversible side reactions are prone to occur, which leads to generally low first-cycle efficiency (usually less than 80%), seriously affecting the energy density output of the entire battery. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present application is to overcome the problems of low stability and low initial efficiency caused by low conductivity and easy solubility in organic solvents of organic small molecules, and to prepare an organic small molecule negative electrode material with high energy density and high stability through molecular structure design and process innovation and apply it in a sodium ion battery.

[0007] To this end, the present application provides the following technical solutions:

[0008] (1) Solution preparation and deprotonation reaction: under constant temperature water bath conditions, lithium hydroxide is dissolved in deionized water, and a uniform solution is formed by constant stirring. Diphenic acid is added to the above solution in batches, and deionized water is slowly added until the mixture is completely dissolved to form a clear solution. Under continuous stirring, anhydrous ethanol is slowly added, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is in progress. (2) Precipitation purification and product separation: after the above reaction solution is continuously stirred for a period of time, it is quickly transferred to anhydrous ethanol, and immediate precipitation is observed. The mixed system is aged for a period of time, then the precipitate is separated using a suction filtration device, and washed with anhydrous ethanol to remove residual reactants. The obtained product is dried in a vacuum drying oven to ensure complete removal of moisture.

[0009] (3) Material activation treatment: the dried precursor is evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, constant temperature is maintained for a period of time. After the activation process is completed, it is cooled to room temperature, and finally the lithium diphenic acid negative electrode material is obtained.

[0010] The mol ratio of diphenic acid to hydroxide in step (1) is (1:4-1:2)

[0011] The temperature of the water bath heating in step (1) is (40-80)℃, and the dropwise addition amount of ethanol is (20-70)ml.

[0012] The stirring time in step (2) is (6-12)h, and the stirring rate is 600rpm;

[0013] The amount of ethanol used in step (2) is (100-300)ml; the standing time is (6-12)h; and the separation method of the product is centrifugation or suction filtration.

[0014] The activation temperature of the tube furnace in step (3) is (200-300)℃, the heating rate is 2-5℃ / min, and the holding time is (3-6)h.

[0015] On the other hand, the present application provides a simple and environmentally friendly lithium diphenic acid electrode active material prepared by the above preparation method, and further provides a sodium ion battery, wherein the active material in the negative electrode material of the sodium ion battery is the lithium diphenic acid material prepared by the above application method.

[0016] The technical solution of the present invention has the following advantages:

[0017] 1. Addressing key drawbacks of organic small molecule materials: A high-temperature, inert atmosphere activation step prevents oxidation while allowing lithium biphenyl dicarboxylate to form a partially carbonized microstructure, significantly improving the material's electronic conductivity and overcoming the strong insulating properties of traditional organic small molecules. Furthermore, the rigid conjugated structure and crystallinity of lithium biphenyl dicarboxylate effectively reduce its solubility in organic electrolytes, thereby improving cycling stability.

[0018] 2. The preparation process is simple and efficient: Water bath heating, ethanol precipitation, and mild reaction conditions avoid the need for high temperatures, high pressures, or complex equipment, resulting in simple operation and low cost. The concentration of the lithium hydroxide aqueous solution precisely controls the degree of deprotonation of biphenyldicarboxylic acid, ensuring consistent product chemical properties.

[0019] 3. Excellent electrochemical performance: The aromatic ring structure and multi-carbonyl active sites of lithium biphenyl dicarboxylate can realize multi-electron reactions. At a high current of 500mA / g, after a period of activation of the active sites, its discharge specific capacity is as high as 302mAh / g. The activated material has extremely low dissolution loss in the electrolyte. Combined with the enhanced conductivity of carbonization, the capacity retention rate can still reach more than 90% after 450 cycles at a high current of 500mA / g.

[0020] 4. Significant environmental and cost advantages: Using water and ethanol as the primary solvents avoids the use of toxic organic reagents (such as DMF and THF). The reaction byproducts are water or volatile ethanol, which can be easily processed and recycled, offering significant environmental advantages. Furthermore, biphenyl dicarboxylic acid is an industrialized product, and its hydroxide is inexpensive and readily available. The reagent costs involved in this experimental process are low, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 1 is an XRD pattern of lithium biphenyldicarboxylate in Example 1 of the present invention, biphenyldicarboxylic acid in Comparative Example 1, and potassium biphenyldicarboxylate in Comparative Example 2;

[0023] Figure 2 is a scanning electron microscope (SEM) image of lithium biphenyl dicarboxylate in Example 1 of the present invention;

[0024] Figure 3 is a transmission electron microscope (TEM) image of lithium diphenyldicarboxylate in Example 1 of the present application;

[0025] Figure 4 is an infrared spectrum of lithium diphenyldicarboxylate in Example 1 of the present application;

[0026] Figure 5 is a CV curve of lithium diphenyldicarboxylate in Example 1 of the present application at a scan rate of 0.2 mV / s;

[0027] Figure 6 is a specific capacity-voltage curve of lithium diphenyldicarboxylate material in Example 1 of the present application as a negative electrode material for sodium ion batteries at a current density of 500 mA / g;

[0028] Figure 7 is a cycle stability diagram of lithium diphenyldicarboxylate in Example 1 of the present application and lithium diphenyldicarboxylate in Comparative Example 1, potassium diphenyldicarboxylate in Comparative Example 2 as a negative electrode material for sodium ion batteries at a current density of 500 mA / g; DETAILED DESCRIPTION

[0029] The following examples are provided to better enable those skilled in the art to further understand the application and are not intended to limit the scope of the application. The content and scope of the present application are not limited by the content of the examples, and any product that is the same or similar to the present application obtained by the inspiration of the present application or by combining the present application with other prior art features falls within the scope of the present application.

[0030] Unless otherwise indicated, the experimental procedures or conditions in the examples can be carried out according to the conventional experimental procedures described in the literature. The reagents or instruments used are not specified by the manufacturer, and are conventional reagents that can be obtained commercially.

[0031] Example 1

[0032] Example 1 provides a preparation method of lithium diphenyldicarboxylate negative electrode material, which realizes efficient deprotonation and material activation of diphenyldicarboxylic acid by precise control of reaction conditions. The specific steps are as follows: (4) Solution preparation and deprotonation reaction: Dissolve 40 mmol of lithium hydroxide in 5 ml of deionized water under the condition of a 60 °C constant temperature water bath, and form a uniform solution at a stirring rate of 600 rpm. Add 10 mmol of diphenyldicarboxylic acid weighed in advance to the above solution in batches, and slowly add 20 mL of deionized water to the mixture until it is completely dissolved, forming a clear light yellow solution. Slowly add 30 mL of anhydrous ethanol under continuous stirring, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is in progress.

[0033] Dissolve 40 mmol of lithium hydroxide in 5 ml of deionized water under the condition of a 60 °C constant temperature water bath, and form a uniform solution at a stirring rate of 600 rpm. Add 10 mmol of diphenyldicarboxylic acid weighed in advance to the above solution in batches, and slowly add 20 mL of deionized water to the mixture until it is completely dissolved, forming a clear light yellow solution. Slowly add 30 mL of anhydrous ethanol under continuous stirring, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is in progress.

[0034] (5) Precipitation purification and product separation: After the reaction solution is continuously stirred for 10 h, it is quickly transferred to a 250 mL

[0035] Immediately after the mixture is placed in anhydrous ethanol, a white precipitate is observed. The mixture is aged for 6 h,

[0036] The precipitate is then separated using a suction filtration device and washed three times with anhydrous ethanol to remove residual reactants.

[0037] The obtained product is placed in a 60°C vacuum drying oven for 12 h to ensure complete removal of water.

[0038] (6) Material activation treatment: The dried precursor is uniformly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature is programmed to increase to 250°C at a rate of 5°C / min and held for 3 h.

[0039] After the activation process is complete, the temperature is naturally cooled to room temperature, and the lithium biphenyl dicarboxylate negative electrode material is finally obtained.

[0040] Figure 1 is the XRD pattern of lithium biphenyl dicarboxylate in Example 1 of the present application, lithium biphenyl dicarboxylate in Comparative Example 1, and potassium biphenyl dicarboxylate in Comparative Example 2;

[0041] Figure 2 is the scanning electron microscope (SEM) image of lithium biphenyl dicarboxylate in Example 1 of the present application;

[0042] Figure 3 is the transmission electron microscope (TEM) image of lithium biphenyl dicarboxylate in Example 1 of the present application;

[0043] Figure 4 is the infrared spectrum of lithium biphenyl dicarboxylate in Example 1 of the present application;

[0044] The electrochemical performance test method of the organic small molecule negative electrode material prepared in Example 1 of the present application is as follows:

[0045] (1) Preparation of the electrode sheet: The negative electrode sheet is cut into a 11 mm diameter electrode sheet using a 11 mm cutter, and the mass is weighed using a precision balance. The mass of the active material lithium biphenyl dicarboxylate is calculated according to the solid raw material ratio of active material: super P: PVDF of 6:3:1. The above electrode sheet is taken into an argon atmosphere glove box to assemble a half battery, and the negative electrode shell, a 14 mm diameter sodium sheet, a glass fiber separator, 170 ml of electrolyte, an electrode, a 1 mm gasket, and a spring are sequentially placed to complete the battery assembly. The battery is compressed by a button cell sealing machine, and the battery model is CR2032 button cell. The electrolyte is NaPF6 / DIGLYME, wherein DIGLYME is diethylene glycol dimethyl ether. The battery is taken out of the glove box and left to stand for 24 h before measuring the electrochemical performance.

[0046] (2) Half-cell performance test: On a Xinwei battery charge and discharge tester, under constant current charge and discharge conditions of 0-3V and 500mA / g, the charge capacity, cycle efficiency, and cycle stability of the button cell were tested and analyzed after 450 cycles. After 450 cycles, the capacity retention rate was still above 90%, and the coulombic efficiency of the cycle was close to 100%.

[0047] Figure 5 1 is a CV curve of lithium biphenyldicarboxylate at a scan rate of 0.2 mV / s in Example 1 of the present invention;

[0048] Figure 6 1 is a specific capacity-voltage curve at a current density of 500 mA / g when the lithium biphenyl dicarboxylate material is used as the negative electrode material for a sodium ion battery in Example 1 of the present invention;

[0049] Figure 7 1 is a graph showing the cycling stability of the lithium biphenyldicarboxylate in Example 1 of the present invention, the biphenyldicarboxylic acid in Comparative Example 1, and the potassium biphenyldicarboxylate in Comparative Example 2 as negative electrode materials for sodium ion batteries at a current density of 500 mA / g;

[0050] Example 2

[0051] Example 2 provides a method for preparing a lithium biphenyl dicarboxylate negative electrode material. The method achieves efficient deprotonation of biphenyl dicarboxylic acid and material activation by precisely controlling the reaction conditions. The specific steps are as follows: (1) Solution preparation and deprotonation reaction: Under a constant temperature water bath at 60°C, 20 mmol of lithium hydroxide is dissolved in 5 ml of deionized water and stirred at 600 rpm to form a uniform solution. 10 mmol of biphenyl dicarboxylic acid weighed in advance is added to the above solution in batches, and 20 mL of the solution is slowly added dropwise.

[0052] Deionized water was added until the mixture was completely dissolved to form a clear light yellow solution. Under continuous stirring, 30 mL of anhydrous ethanol was slowly added dropwise. At this time, trace suspended particles appeared in the system, indicating that the deprotonation reaction was in progress.

[0053] (2) Precipitation purification and product separation: After the above reaction solution was stirred for 10 h, it was quickly transferred to 250 mL

[0054] In anhydrous ethanol, a white precipitate was immediately observed. The mixed system was allowed to stand for 6 hours for aging.

[0055] The precipitate was then separated using a suction filtration device and washed three times with anhydrous ethanol to remove residual reactants.

[0056] The obtained product was placed in a vacuum drying oven at 60°C and dried for 12 h to ensure that the moisture was completely removed.

[0057] (3) Material activation treatment: The dried precursor was evenly spread on a magnetic boat and placed in a tube furnace. Under an argon atmosphere, the temperature was raised to 250°C at a rate of 5°C / min and kept constant for 3 h.

[0058] After the activation process is completed, it is naturally cooled to room temperature to finally obtain the lithium biphenyl dicarboxylate negative electrode material.

[0059] Example 3

[0060] Example 3 provides a method for preparing a lithium biphenyl dicarboxylate negative electrode material. The method achieves efficient deprotonation of biphenyl dicarboxylic acid and material activation by precisely controlling the reaction conditions. The specific steps are as follows: (1) Solution preparation and deprotonation reaction: In a constant temperature water bath at 40°C, 40 mmol of lithium hydroxide is dissolved in 5 ml of deionized water and stirred at 600 rpm to form a uniform solution. 10 mmol of biphenyl dicarboxylic acid weighed in advance is added to the above solution in batches, and 20 mL of the solution is slowly added dropwise.

[0061] Deionized water was added until the mixture was completely dissolved to form a clear light yellow solution. Under continuous stirring, 30 mL of anhydrous ethanol was slowly added dropwise. At this time, trace suspended particles appeared in the system, indicating that the deprotonation reaction was in progress.

[0062] (2) Precipitation purification and product separation: After the above reaction solution was stirred for 10 h, it was quickly transferred to 250 mL

[0063] In anhydrous ethanol, a white precipitate was immediately observed. The mixed system was allowed to stand for 6 hours for aging.

[0064] The precipitate was then separated using a suction filtration device and washed three times with anhydrous ethanol to remove residual reactants.

[0065] The obtained product was placed in a vacuum drying oven at 60°C and dried for 12 h to ensure that the moisture was completely removed.

[0066] (3) Material activation treatment: The dried precursor was evenly spread on a magnetic boat and placed in a tube furnace. Under an argon atmosphere, the temperature was raised to 250°C at a rate of 5°C / min and kept constant for 3 h.

[0067] After the activation process is completed, it is naturally cooled to room temperature to finally obtain the lithium biphenyl dicarboxylate negative electrode material.

[0068] Example 4

[0069] Example 4 provides a preparation method of lithium biphenyldicarboxylate negative electrode material, which realizes efficient deprotonation of biphenyldicarboxylic acid and material activation by accurately controlling reaction conditions. The specific steps are as follows: (1) solution preparation and deprotonation reaction: under the condition of 80°C constant temperature water bath, 40mmol of lithium hydroxide is dissolved in 5ml of deionized water to form a uniform solution at a stirring rate of 600rpm. 10mmol of biphenyldicarboxylic acid weighed in advance is added to the above solution in batches, and 20mL

[0070] of deionized water is slowly added dropwise until the mixture is completely dissolved to form a clear light yellow solution. Under continuous stirring, 30mL of anhydrous ethanol is slowly added dropwise, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is proceeding.

[0071] (2) precipitation purification and product separation: after the above reaction solution is continuously stirred for 10h, it is quickly transferred to 250mL

[0072] of anhydrous ethanol, and white precipitate is immediately observed. The mixed system is allowed to stand for 6h for aging,

[0073] and then the precipitate is separated by suction filtration device and washed with anhydrous ethanol three times to remove residual reactants.

[0074] The obtained product is placed in a 60°C vacuum drying oven for drying for 12h to ensure complete removal of water.

[0075] (3) material activation treatment: the dried precursor is evenly spread in a magnetic boat and placed in a tube furnace. Under the protection of argon atmosphere, the temperature is programmed to rise to 250°C at a rate of 5°C / min, and kept constant for 3h.

[0076] After the activation process is completed, it is naturally cooled to room temperature, and finally the lithium biphenyldicarboxylate negative electrode material is obtained.

[0077] Example 5

[0078] Example 5 provides a preparation method of lithium biphenyldicarboxylate negative electrode material, which realizes efficient deprotonation of biphenyldicarboxylic acid and material activation by accurately controlling reaction conditions. The specific steps are as follows: (1) solution preparation and deprotonation reaction: under the condition of 60°C constant temperature water bath, 40mmol of lithium hydroxide is dissolved in 5ml of deionized water to form a uniform solution at a stirring rate of 600rpm. 10mmol of biphenyldicarboxylic acid weighed in advance is added to the above solution in batches, and 20mL

[0079] of deionized water is slowly added dropwise until the mixture is completely dissolved to form a clear light yellow solution. Under continuous stirring, 30mL of anhydrous ethanol is slowly added dropwise, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is proceeding.

[0080] (2) Precipitation purification and product isolation: After 12 h of continuous stirring, the reaction solution was quickly transferred to a 250 mL

[0081] White precipitate was observed immediately in anhydrous ethanol. The mixture was left to stand for 6 h for aging,

[0082] The precipitate was then separated using a suction filtration apparatus and washed with anhydrous ethanol three times to remove residual reactants.

[0083] The resulting product was placed in a 60 °C vacuum drying oven for 12 h to ensure complete removal of moisture.

[0084] (3) Material activation treatment: The dried precursor was evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature was programmed to rise to 250 °C at a rate of 5 °C / min and held for 3 h.

[0085] After the activation process was complete, it was naturally cooled to room temperature, and finally the lithium biphenyl dicarboxylate negative electrode material was obtained.

[0086] Example 6

[0087] Example 6 provides a method for preparing a lithium biphenyl dicarboxylate negative electrode material, which achieves efficient deprotonation of biphenyl dicarboxylic acid and material activation by precisely controlling the reaction conditions. The specific steps are as follows: (1) Solution preparation and deprotonation reaction: Under the condition of a 60 °C constant temperature water bath, 40 mmol of lithium hydroxide was dissolved in 5 mL of deionized water to form a uniform solution at a stirring speed of 600 rpm. 10 mmol of biphenyl dicarboxylic acid was added to the above solution in batches, and 20 mL

[0088] of deionized water was slowly added to the mixture until it was completely dissolved, forming a clear light yellow solution. Under continuous stirring, 30 mL of anhydrous ethanol was slowly added, at which time a small amount of suspended particles appeared in the system, indicating that the deprotonation reaction was in progress.

[0089] (2) Precipitation purification and product isolation: After 10 h of continuous stirring, the reaction solution was quickly transferred to a 250 mL

[0090] of anhydrous ethanol, where white precipitate was observed immediately. The mixture was left to stand for 6 h for aging,

[0091] The precipitate was then separated using a suction filtration apparatus and washed with anhydrous ethanol three times to remove residual reactants.

[0092] The resulting product was placed in a 60 °C vacuum drying oven for 12 h to ensure complete removal of moisture.

[0093] (3) Material activation treatment: The dried precursor was evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature was programmed to rise to 200°C at a rate of 5°C / min, and held for 3 h.

[0094] After the activation process, natural cooling to room temperature was performed, and finally a lithium biphenyl dicarboxylate negative electrode material was obtained.

[0095] Example 7

[0096] Example 7 provides a method for preparing a lithium biphenyl dicarboxylate negative electrode material, which realizes efficient deprotonation of biphenyl dicarboxylic acid and material activation by precisely controlling the reaction conditions. The specific steps are as follows: (1) Solution preparation and deprotonation reaction: Under the condition of a 60°C constant temperature water bath, 40 mmol of lithium hydroxide was dissolved in 5 ml of deionized water to form a uniform solution at a stirring speed of 600 rpm. 10 mmol of biphenyl dicarboxylic acid was added to the above solution in batches, and 20 mL of deionized water was slowly added to the mixture until it was completely dissolved, forming a clear light yellow solution. Under continuous stirring, 30 mL of anhydrous ethanol was slowly added, at which time a small amount of suspended particles appeared in the system, indicating that the deprotonation reaction was proceeding.

[0097] (2) Precipitation purification and product separation: After the above reaction solution was continuously stirred for 10 h, it was quickly transferred to a 250 mL

[0098]

[0099] After the activation process, natural cooling to room temperature was performed, and finally a lithium biphenyl dicarboxylate negative electrode material was obtained.

[0100] Subsequently, the precipitate was separated using a suction filtration device and washed three times with anhydrous ethanol to remove residual reactants.

[0101] The obtained product was placed in a 60°C vacuum drying oven for 12 h to ensure complete removal of water.

[0102] (3) Material activation treatment: The dried precursor was evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature was programmed to rise to 300°C at a rate of 5°C / min, and held for 3 h.

[0103] After the activation process, natural cooling to room temperature was performed, and finally a lithium biphenyl dicarboxylate negative electrode material was obtained.

[0104] Example 8

[0105] ​Example 8 provides a preparation method of lithium diphenyl dicarboxylate negative electrode material, which realizes efficient deprotonation of diphenyl dicarboxylic acid and material activation by precisely controlling reaction conditions. The specific steps are as follows: (4) Solution preparation and deprotonation reaction: under the condition of a 60°C constant temperature water bath, 40 mmol of lithium hydroxide is dissolved in 5 ml of deionized water to form a uniform solution at a stirring speed of 600 rpm. 10 mmol of diphenyl dicarboxylic acid weighed in advance is added to the above solution in batches, and 20 mL of deionized water is slowly added to the mixture to completely dissolve the mixture and form a clear light yellow solution. Under continuous stirring, 30 mL of anhydrous ethanol is slowly added, at which time a small amount of suspended particles appear in the system, indicating that the deprotonation reaction is in progress.

[0106]

[0107] (5) Precipitation purification and product separation: after the above reaction solution is continuously stirred for 10 h, it is quickly transferred to 250 mL of anhydrous ethanol, and white precipitate is immediately observed. The mixed system is allowed to stand for 6 h for aging,

[0108]

[0109] Subsequently, the precipitate is separated using a suction filtration device and washed three times with anhydrous ethanol to remove residual reactants.

[0110] The obtained product is placed in a 60°C vacuum drying oven for 12 h to ensure complete removal of water.

[0111] (6) Material activation treatment: the dried precursor is evenly spread in a magnetic boat and placed in a tube furnace. Under an argon protective atmosphere, the temperature is programmed to rise to 250°C at a rate of 5°C / min and held for 6 h.

[0112] After the activation process is completed, it is naturally cooled to room temperature, and finally the lithium diphenyl dicarboxylate negative electrode material is obtained.

[0113] Example explanation:

[0114] By changing the amount of lithium hydroxide used in step (1) of Example 2, it is found that the change of solution pH value has limited effect on the synthesis process when the reactant ratio is changed within a reasonable range, which is mainly due to the buffering effect of the subsequent anhydrous ethanol dilution and long-term aging (6 h) process on the acidity and alkalinity of the system. Finally, the residual reactants are washed away by three times of alcohol washing, and the excess lithium hydroxide mainly serves to increase the yield of the finally generated lithium diphenyl dicarboxylate, without affecting its electrochemical performance.

[0115] ​​Changing the temperature of water bath heating in step (1) of Example 3 and Example 4 in the range of 40-80℃, it is found that the temperature change has multiple effects on the reaction system: on the one hand, the increase of temperature significantly improves the solubility of reactants in the solvent, which makes the amount of deionized water and ethanol required in the subsequent process correspondingly reduced. On the other hand, the increase of temperature effectively accelerates the reaction kinetics, which significantly shortens the reaction time. It is worth noting that the increase of temperature will lead to the tendency of agglomeration of the trace amount of suspended particles formed in the solution, but under the action of continuous mechanical stirring (600 rpm), the internal convection of the solution effectively inhibits the further growth of the particles, so it has no significant effect on the electrochemical performance of the final product.

[0116] Changing the duration of stirring in step (2) of Example 5, it can be found that the extension of stirring time helps to increase the convection and reduce the occurrence of particle agglomeration, making the solution more clear and transparent, although the improvement of electrochemical performance is limited, but it helps to improve the consistency of the product.

[0117] Changing the constant temperature temperature and extending the constant temperature time in step (3) of Example 6, Example 7, Example 8 in a certain range can achieve the purpose of material activation, of course, the activation temperature should not be lower than 200℃, otherwise it is not possible to completely remove the bound water inside the organic small molecule material, and it is not possible to achieve full activation. If the activation temperature is higher than 300℃, the organic material may be over-carbonized due to its small molecular weight, or even completely converted into an inorganic phase, losing the characteristics of organic electrode materials. Otherwise, the material may be over-carbonized or even completely carbonized into an inorganic material due to its small molecular weight. Experimental results show that the best activation condition is to heat at 250℃ for 3h, which not only saves electricity, but also ensures full activation of the material on the basis of maintaining its organic molecular structure characteristics.

[0118] Comparative Example 1

[0119] Comparative Example 1 provides a preparation method of a biphenyl dicarboxylic acid negative electrode material, the specific steps are as follows:

[0120] (1) Dry the biphenyl dicarboxylic acid in a 60℃ vacuum drying oven for 12h to ensure that the material is dry.

[0121] (2) Material activation treatment: evenly spread the dried biphenyl dicarboxylic acid in a magnetic boat, and place it in a tube furnace. Under the protection of argon atmosphere, program the temperature to rise to 250℃ at a rate of 5℃ / min, and keep the temperature constant for 3h.

[0122] After the activation process is completed, naturally cool to room temperature to obtain a biphenyl dicarboxylic acid negative electrode material.

[0123] Figure 11 and 2 are XRD patterns of lithium biphenyldicarboxylate in Example 1 of the present invention, biphenyldicarboxylic acid in Comparative Example 1, and potassium biphenyldicarboxylate in Comparative Example 2.

[0124] Figure 7 1 is a graph showing the cycling stability of the lithium biphenyldicarboxylate in Example 1 of the present invention, the biphenyldicarboxylic acid in Comparative Example 1, and the potassium biphenyldicarboxylate in Comparative Example 2 as negative electrode materials for sodium ion batteries at a current density of 500 mA / g;

[0125] Comparative Example 2

[0126] Comparative Example 2 provides a method for preparing a potassium biphenyl dicarboxylate negative electrode material, the specific steps are as follows: (1) Solution preparation and deprotonation reaction: In a constant temperature water bath at 60°C, 40 mmol of potassium hydroxide was dissolved in 5 ml of deionized water, and a stirring rate of 600 rpm was used to form a uniform solution. 10 mmol of biphenyl dicarboxylic acid weighed in advance was added to the above solution in batches, and 35 mL of the solution was slowly added dropwise.

[0127] Deionized water was added until the mixture was completely dissolved to form a clear light yellow solution. Under continuous stirring, 50 mL of anhydrous ethanol was slowly added dropwise. At this time, trace suspended particles appeared in the system, indicating that the deprotonation reaction was in progress.

[0128] (2) Precipitation purification and product separation: After the above reaction solution was stirred for 10 h, it was quickly transferred to 250 mL

[0129] A white precipitate was immediately observed in anhydrous ethanol. The mixture was allowed to stand for 6 hours for aging, then the precipitate was separated by centrifugation and washed three times with anhydrous ethanol to remove residual reactants. The resulting product was dried in a vacuum oven at 60°C for 12 hours to ensure complete removal of moisture.

[0130] (3) Material activation treatment: The dried precursor was evenly spread on a magnetic boat and placed in a tube furnace. Under an argon atmosphere, the temperature was raised to 250°C at a rate of 5°C / min and kept constant for 3 h.

[0131] After the activation process is completed, it is naturally cooled to room temperature to finally obtain the potassium biphenyldicarboxylate negative electrode material.

[0132] Figure 1 1 and 2 are XRD patterns of lithium biphenyldicarboxylate in Example 1 of the present invention, biphenyldicarboxylic acid in Comparative Example 1, and potassium biphenyldicarboxylate in Comparative Example 2.

[0133] Comparative Example Description:

[0134] Comparative Example 1 used activated biphenyl dicarboxylic acid as the negative material and found that the initial capacity was less than 150 mAh / g. This is because the strong electronegativity of the carboxyl group in biphenyl dicarboxylic acid leads to electron localization, resulting in extremely low electronic conductivity, and the rigid biphenyl skeleton limits the diffusion kinetics of Na + In addition, biphenyl dicarboxylic acid is easily soluble in organic solvents, so its capacity retention rate is less than 80% after 450 cycles at a large current of 500 mA / g.

[0135] In Comparative Example 2, by changing lithium hydroxide for protonation to potassium, which is in the same main group as lithium, i.e. potassium hydroxide, as the radius of the metal ion in the biphenyl dicarboxylate salt increases The solubility of the material in anhydrous ethanol shows a regular change: the solubility of lithium biphenyl dicarboxylate in anhydrous ethanol is larger, and the solubility of potassium biphenyl dicarboxylate is the smallest, so the amount of deionized water and ethanol added in the subsequent process is increased accordingly. In the final product, the lithium biphenyl dicarboxylate particles have the smallest particle size, uniform distribution, and the highest tap density, while the potassium biphenyl dicarboxylate powder is fluffy and partially agglomerated, with the lowest tap density. The smaller ionic radius of lithium ions forms a tighter coordination structure with the biphenyl dicarboxylate skeleton, thereby stabilizing the carboxylate group and inhibiting the dissolution of the active material in the electrolyte, and thus having a stable electrode / electrolyte interface, which helps to achieve capacity and cycle stability. The potassium biphenyl dicarboxylate, on the other hand, due to the large ionic radius of the potassium ion, leads to a loose coordination structure, which not only fails to improve the dissolution problem, but also further deteriorates the electrochemical performance due to severe agglomeration.

[0136] Obviously, the above examples are only examples for clearly illustrating the present application, and are not limitations on the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. Provided is a method for preparing a lithium biphenyl dicarboxylate negative electrode material. The method achieves efficient deprotonation of biphenyl dicarboxylic acid and material activation by precisely controlling the reaction conditions. The specific steps are as follows: (1) Solution Preparation and Deprotonation Reaction: Lithium hydroxide was dissolved in deionized water in a constant temperature water bath and stirred continuously to form a homogeneous solution. Biphenyldicarboxylic acid was added to the solution in batches and deionized water was slowly added dropwise until the mixture was completely dissolved to form a clear solution. Anhydrous ethanol was slowly added dropwise under continuous stirring. At this point, trace suspended particles appeared in the system, indicating that the deprotonation reaction was ongoing. (2) Precipitation purification and product isolation: After the reaction solution is stirred for a period of time, it is quickly transferred to anhydrous ethanol, and precipitation is immediately observed. The mixed system is allowed to stand for a period of time for aging, and then the precipitate is separated by filtration and washed with anhydrous ethanol to remove residual reactants. The resulting product is dried in a vacuum drying oven to ensure complete removal of moisture. (3) Material activation: The dried precursor is evenly spread on a magnetic boat and placed in a tube furnace. The temperature is maintained constant for a period of time under an argon atmosphere. After the activation process is completed, the material is cooled to room temperature to obtain the lithium biphenyl dicarboxylate negative electrode material.

2. The preparation method according to claim 1, characterized in that The molar ratio of biphenyldicarboxylic acid to hydroxide in step (1) is (1:6-1:2); the water bath heating temperature in step (1) is (40-80)°C, and the amount of ethanol added is (20-70) ml.

3. The preparation method according to claim 1 or 2, characterized in that The water bath stirring time in step (2) is (6-12) h; the stirring rate is 600 rpm; the amount of ethanol used in step (2) is (100-300) ml; the standing time is (6-12) h; and the product is separated by centrifugation or filtration.

4. The preparation method according to claim 1-3, characterized in that In the step (3), the activation temperature of the tubular furnace is (200-300)°C, the heating rate is 2-5°C / min, and the holding time is (3-6)h.

5. A lithium biphenyl dicarboxylate negative electrode active material based on efficient deprotonation of biphenyl dicarboxylic acid and material activation, prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the lithium biphenyldicarboxylate negative electrode active material prepared by the preparation method according to any one of claims 1 to 4 or the lithium biphenyldicarboxylate active material according to claim 5 in the negative electrode of an organic sodium ion battery.

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