1, 3, 5-isopropyl trimesic acid composite material and application thereof

Abstract

The invention discloses a 1, 3, 5-isopropyl trimellitate composite material and an application of the 1, 3, 5-isopropyl trimellitate composite material, and the 1, 3, 5-isopropyl trimellitate composite material is in a composite material form of 1, 3, 5-isopropyl trimellitate (SYZ) and metatitanic acid (TiO2.H2O). The obtained composite material shows relatively high specific capacity and certain cycle and rate performance, and can be used as a lithium ion battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery materials, and particularly relates to a 1,3,5-trimethylbenzene isopropyl ester composite material and application thereof. BACKGROUND

[0002] Lithium ion batteries (LIBs) are widely used as energy storage devices due to their high energy density and long cycle life. However, traditional anode materials face limitations. Graphite, as the most commonly used anode material, has a limited theoretical capacity (372 mAh / g). Silicon-based materials can provide higher capacity, but they undergo significant volume changes during charge and discharge cycles, leading to structural instability and rapid performance degradation. Titanium-based oxides, such as spinel-structured Li4Ti5O 12 , have excellent cycle stability and safety (due to their high operating voltage of about 1.55 V vs. Li / Li + , avoiding lithium dendrite and SEI film problems), but their theoretical capacity is low (about 175 mAh / g) and energy density is not high.

[0003] To meet the growing demand for higher energy density, longer life, and more environmentally friendly energy storage devices, organic electrode materials have become a promising research direction. Organic materials are mainly composed of lightweight, high-abundance elements such as carbon, hydrogen, oxygen, and nitrogen, with advantages such as wide availability, environmental friendliness, strong structural designability, and potential high capacity. Among many organic materials, compounds containing carbonyl groups (C=O), such as quinones, anhydrides, carboxylates, and esters, are of great interest because the carbonyl group can undergo reversible redox reactions (enolization) to store lithium ions. This type of material usually has a lower redox potential, making it suitable for use as an anode material.

[0004] However, one major drawback of many small-molecule organic electrode materials is their tendency to dissolve in the organic carbonate-based electrolytes commonly used in lithium ion batteries, leading to active material loss and rapid capacity decay. To address this issue, researchers have proposed various strategies, such as polymerizing small molecules into insoluble polymers, lithium salt formation, or compounding with conductive carbon materials.

[0005] In ester compounds, some polymer esters such as polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET) have been used as negative electrode materials and shown certain lithium storage capacity. However, the research on organic small molecule esters with clear structure and specific functional group arrangement as lithium ion battery negative electrode active materials is still relatively less. In particular, the research on how to synthesize such small molecule esters by simple method and optimize the structure to obtain high capacity and good stability still needs to be further deepened. 1,3,5-benzenetricarboxylic acid has three carboxyl groups, which can be derived into small molecules with multiple ester active sites, but the performance of its esterification product as a lithium ion battery negative electrode material has not been fully explored. In addition, the traditional esterification reaction is usually reversible and has low yield, and an efficient synthesis method needs to be developed.

[0006] Therefore, there is a need in the art to develop new organic small molecule ester negative electrode materials with excellent electrochemical performance, as well as simple, efficient and suitable for large-scale production preparation methods. SUMMARY

[0007] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification of the present application to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0008] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0009] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a 1,3,5-benzenetricarboxylic acid isopropyl ester composite material.

[0010] To solve the above technical problems, the present application provides the following technical solutions: the composite material is a mixture consisting of 40% to 50% by mass of 1,3,5-benzenetricarboxylic acid ethyl ester and 50% to 60% by mass of titanium dioxide hydrate TiO2·H2O.

[0011] As a preferred scheme of the 1,3,5-benzenetricarboxylic acid isopropyl ester composite material of the present application, the preparation method of the composite material comprises, mixing 1,3,5-benzenetricarboxylic acid, tetrabutyl titanate and isopropyl alcohol to obtain a reaction mixture; heating and incubating the reaction mixture to perform a solvothermal reaction; after the reaction is completed, naturally cooling to room temperature, filtering to collect the solid product, washing with isopropyl alcohol for several times, vacuum drying to obtain the 1,3,5-benzenetricarboxylic acid isopropyl ester composite material.

[0012] In a preferred embodiment of the 1,3,5-pyromellitic isopropyl ester composite material of the present invention, the molar ratio of 1,3,5-pyromellitic acid to tetrabutyl titanate is 2 to 1:1.

[0013] As a preferred embodiment of the 1,3,5-pyromellitic triacrylate composite material of the present invention, wherein the molar ratio of 1,3,5-pyromellitic triacrylate to isopropanol is 1:80 to 1:90.

[0014] As a preferred embodiment of the 1,3,5-pyromellitic isopropyl ester composite material of the present invention, wherein the reaction mixture is heated and kept at a temperature of 180~200℃ for 12~36 h.

[0015] As a preferred embodiment of the 1,3,5-trimethylammonium acrylate composite material of the present invention, the vacuum drying is carried out at a temperature of 50-60°C for 10-14 hours.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of 1,3,5-pyromellitic isopropyl ester composite material in the preparation of lithium-ion batteries.

[0017] In a preferred embodiment of the application described in this invention, the 1,3,5-pyromellitic isopropyl ester composite material is used to prepare a negative electrode material for lithium-ion batteries. The negative electrode material is prepared by mixing the 1,3,5-pyromellitic isopropyl ester composite material with a conductive agent and a binder. The theoretical capacity of the negative electrode material is 717 mAh / g.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide a lithium-ion battery, characterized in that: the negative electrode material is prepared using a 1,3,5-pyromellitic isopropyl ester composite material.

[0019] Beneficial effects of this invention: This invention discloses a one-step solvothermal method for preparing the material, in which 1,3,5-pyromellitic tricarboxylic acid (BTC) and isopropanol react in the presence of tetrabutyl titanate (TBT) as a promoter. TBT promotes the esterification reaction by consuming water as a byproduct through hydrolysis. Optimized preparation conditions include a holding temperature of 190°C, a holding time of 24 hours, and a BTC to TBT molar ratio of 2:1. The resulting SYBZ composite material exhibits high specific capacity, good cycle stability with capacity recovery, and good rate performance, demonstrating great potential as a negative electrode for lithium-ion batteries. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 (A) XRD patterns and (B) yields of SYBZ samples prepared at different holding temperatures (180-200℃).

[0021] Figure 2 (A) Cyclic performance and (B) Rate performance of SYBZ samples prepared at different insulation temperatures.

[0022] Figure 3 (A) XRD patterns and (B) yields of SYBZ samples prepared at 190 °C for different holding times (0–36 h).

[0023] Figure 4 (A) Cyclic performance and (B) Rate performance of SYBZ samples prepared at different holding times.

[0024] Figure 5 (A) XRD patterns and (B) yields of SYBZ samples prepared at 190℃ for 24 h using different amounts of TBT (0.5~3 ml).

[0025] Figure 6 (A) Cycling performance and (B) Rate performance of SYBZ samples prepared with different amounts of TBT.

[0026] Figure 7 (A) XRD pattern, (B) long-cycle performance, and (C) rate performance of SYBZ composite material prepared under optimized conditions.

[0027] Figure 8 (A) Electrochemical impedance spectroscopy (EIS) Nyquist plot and (B) Z' vs. ω⁻¹ / ² plot of SYBZ composite material prepared under optimized conditions.

[0028] Figure 9 Cyclic voltammetry (CV) curves of SYBZ composite materials prepared under optimized conditions.

[0029] Figure 10 Fourier transform infrared (FT-IR) spectra of BTC raw material and SYBZ composite material.

[0030] Figure 11X-ray photoelectron spectroscopy (XPS) of SYBZ composite material prepared under optimized conditions: (A) Full spectrum, (B) C 1s, (C) O 1s, (D) Ti 2p.

[0031] Figure 12 Thermogravimetric analysis (TGA / DTG) curves of SYBZ composites prepared under optimized conditions.

[0032] Figure 13 This is a schematic diagram of the synthesis mechanism of the proposed ester materials.

[0033] Figure 14 The dQ / dV curves are for the first two cycles of the SYBZ composite material.

[0034] Figure 15 The discharge capacity contribution diagram of SYBZ composite material. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Raw materials used in the embodiments of this invention: 1,3,5-Pyromellitic tricarboxylic acid (BTC): 98% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Tetrabutyl titanate (TBT): Analytical grade (AR), purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Isopropanol: ≥99.5% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Conductive carbon black (Super P, KS-6), polyvinylidene fluoride (PVDF), N-methylpyrrolidone (NMP), copper foil, lithium metal sheet, electrolyte, and separator: battery grade, all purchased from Guangdong Candlelight New Energy Technology Co., Ltd.

[0039] The instruments used in the embodiments of this invention are as follows: Vacuum drying oven: DZF-6050, Shanghai Jinghong Experimental Equipment Co., Ltd.; Glove box: Universal series, Shanghai Micron Electromechanical Technology Co., Ltd.; Electrochemical workstation: CHI650, Wuhan Koster Instrument Co., Ltd. (for CV and EIS testing); Battery testing system: CT2001A, Wuhan Landian Electronics Co., Ltd. (for charge and discharge testing); X-ray diffractometer (XRD): Ultima IV, Rigaku Corporation, Japan; Scanning electron microscope (SEM): GeminiSEM 300, Zeiss AG, Germany; X-ray photoelectron spectroscopy (XPS): K-Alpha+, Thermo Fisher Scientific, USA; Fourier transform infrared spectroscopy (FT-IR): Nicolet iS20, Thermo Fisher Scientific, USA; Thermogravimetric analyzer (TGA): STA449F3, Netzsch Instruments GmbH, Germany.

[0040] Performance testing method in this embodiment of the invention: (1) Electrochemical performance (battery assembly): The prepared 1,3,5-trimethylammonium acrylate composite material (active material), conductive agent KS-6, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 6:2:1:1. Using N-methylpyrrolidone (NMP) as a solvent, the mixture was ground and mixed evenly in a mortar to form a slurry. The slurry was uniformly coated onto a copper foil current collector and dried in a vacuum drying oven at 100℃ for 12 hours. After drying, the electrode sheets were cut into 12 mm diameter discs. CR2032 coin cells were assembled in an argon-filled glove box with water and oxygen contents both below 1 ppm. A lithium metal sheet (15 mm diameter) was used as the counter electrode, and a Celgard 2500 polypropylene membrane (16 mm diameter) was used as the separator. The electrolyte was prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a mass ratio of 1:1:1. The assembled battery was allowed to stand for 5 hours before testing.

[0041] (2) Capacity and cycle test: Constant current charge and discharge test was performed using the LAND CT2001A battery test system.

[0042] Test voltage range: 0.01 ~ 3.0 V.

[0043] Test current density: Long-cycle charge-discharge test was performed at a current density of 100 mA / g.

[0044] (3) Rate performance test: The test was conducted using the LAND CT2001A battery test system.

[0045] Test voltage range: 0.01 ~ 3.0 V.

[0046] Test procedure: Charge-discharge tests were performed sequentially at different current densities of 0.1 A / g, 0.5 A / g, 1.0 A / g, 2.0 A / g, and 5.0 A / g. Finally, the current density was restored to 0.1 A / g and the cycle was continued to evaluate the capacity performance and recovery ability of the material at high current densities.

[0047] Example 1 This embodiment provides a method for preparing 1,3,5-trimethylbenzene isopropyl ester composite material, including the following steps: (1) Dissolve 1.2608 g (about 6 mmol) of 1,3,5-trimethylammonium phosphate (BTC) in 40 mL of isopropanol and stir. Add 1 mL (about 3 mmol) of tetrabutyl titanate (TBT) to the solution quickly. A white precipitate is formed immediately. Stir the mixture at room temperature for an additional 30 minutes. (2) The resulting suspension was transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene, sealed, and heated. The reaction mixture was heated to 190 °C and kept at that temperature for 24 hours. (3) After the reaction is completed, the reactor is allowed to cool naturally to room temperature. The solid product is collected by filtration, washed several times with isopropanol, and dried under vacuum at 60°C for 12 hours to obtain white powdery 1,3,5-pyromellitic tricarboxylate SYBZ composite material.

[0048] The obtained product exhibits good crystallinity, and its XRD pattern shows characteristic diffraction peaks at 2θ values ​​of approximately 9.05°, 10.11°, 10.67°, 16.03°, 16.97°, 18.73°, 21.38° (strongest peak), 24.27°, 25.24°, 27.97°, and 32.27°.

[0049] Example 2 This embodiment provides a method for preparing a lithium-ion battery, including the following steps: (1) Preparation of negative electrode sheet: The active material SYBZ composite material, conductive agent KS-6, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) prepared in Example 1 were mixed in a mass ratio of 6:2:1:1. An appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent. The mixture was ground and mixed evenly in a mortar to form a slurry. The slurry was evenly coated on a copper foil current collector and dried in a vacuum drying oven at 100°C for 12 hours to remove the solvent. After drying, it was cut into circular electrode sheets with a diameter of 12 mm.

[0050] (2) Battery assembly: CR2032 button cells were assembled in an argon-filled glove box with both water and oxygen content below 1 ppm.

[0051] The battery assembly sequence is as follows: negative electrode shell, negative electrode sheet prepared above, separator (Celgard 2500, diameter 16mm), lithium metal sheet (diameter 15mm, used as counter electrode and reference electrode), stainless steel gasket, spring sheet and positive electrode shell.

[0052] During the assembly process, an appropriate amount of electrolyte is added. The electrolyte is 1 M LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a mass ratio of 1:1:1.

[0053] (3) Let it stand: After assembly, the battery was left to stand at room temperature for 5 hours to ensure that the electrolyte fully wetted the electrode materials before electrochemical performance testing was conducted.

[0054] Comparative Example 1 This comparative example provides a SYBZ composite material prepared under non-optimized temperature conditions, comprising the following steps: (1) Dissolve 1.2608 g (about 6 mmol) of 1,3,5-trimethylammonium phosphate (BTC) in 40 mL of isopropanol and stir. Quickly add 1 mL (about 3 mmol) of tetrabutyl titanate (TBT) to the solution, and a white precipitate is produced. Stir the mixture at room temperature for 30 minutes. (2) The resulting suspension was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel reactor, sealed, and heated. The reaction mixture was heated to 180 °C and kept at that temperature for 24 hours. (3) After the reaction is complete, the mixture is naturally cooled to room temperature, filtered, washed with isopropanol, and dried under vacuum to obtain the comparative sample.

[0055] Comparative Example 2 The difference between this comparative example and Comparative Example 1 is that the heat preservation temperature in step (2) is adjusted to 200℃, while the other steps are the same as those in Comparative Example 1, and 1,3,5-trimethylbenzene isopropyl ester composite material is obtained.

[0056] The performance test results of Example 1 and Comparative Examples 1 and 2 are as follows: Figure 1 , 2 As shown, when the holding temperature is 180℃, XRD testing indicates that the sample is non-crystallized and exists in an amorphous state, with the XRD pattern showing broad peaks. Figure 1A), with a low yield (approximately 37%), electrochemical testing showed that its discharge specific capacity at a current density of 100 mA / g was only about 200 mAh / g, and its cycle stability was poor, resulting in low electrochemical capacity. Figure 2 A).

[0057] When the holding temperature is 190℃, the product crystallizes to obtain the target SYBZ phase, which exhibits the best electrochemical performance with a yield of about 56%.

[0058] When the holding temperature is 200℃, the diffraction peak of SYBZ disappears, and the diffraction peak of poorly crystallized metatitanic acid appears. Figure 1 A) The yield increased slightly (approximately 56%), but the product was no longer the target ester material, and the electrochemical capacity (especially the cycling capacity) decreased significantly. Figure 2 A).

[0059] In summary, the synthesis temperature window for SYBZ is very narrow and must be strictly controlled at around 190℃. If the temperature is too low, crystallization will not occur, and if the temperature is too high, decomposition or failure to form the target product will occur.

[0060] Example 3 The difference between this embodiment and embodiment 1 is that the heat preservation time in step (2) is adjusted to 0, 12h and 36h respectively, while the other steps are the same as in embodiment 1, and 1,3,5-trimethylbenzene isopropyl ester composite material is obtained.

[0061] The results are as follows Figure 3 , 4 As shown in Figure 3A, when the holding temperature is 0h and 12h, the product does not crystallize, the yield is low (38-40%), and the electrochemical capacity is poor. Figure 4 A).

[0062] When the holding temperature is 24 h, the product crystallizes to obtain the target SYBZ phase, which exhibits the best electrochemical performance with a yield of about 56%.

[0063] When the holding temperature is 36 hours, an impurity phase (poorly crystallizable metatitanic acid) appears. Figure 3 A) Although the yield increased slightly (about 59%), the crystallinity of the target phase decreased, and the electrochemical capacity also decreased accordingly (Figure 4A).

[0064] In summary, the holding time for SYBZ also needs to be precisely controlled. If the time is too short, crystallization will not occur, and if the time is too long, impurities will be generated. 24 hours is the preferred time to obtain a pure crystalline phase and the best performance.

[0065] Example 4 The difference between this embodiment and Example 1 is that the amount of TBT used in step (1) is replaced with 0.5 mL, 2 mL and 3 mL respectively. The remaining steps are the same as in Example 1, and 1,3,5-trimethylbenzene isopropyl ester composite material is obtained.

[0066] The results are as follows Figure 5 , 6 As shown, when the amount of TBT added is 0.5 ml, the ratio of BTC:TBT ≈ 4:1, and the product is crystalline SYBZ. Figure 5 A) The yield is about 52%, the cycle performance is the best, and the overall capacity is the highest (Figure 6A). However, at current densities of 0.5 A / g and higher, the rate performance is not as good as that of the 1 ml sample (Figure 6B).

[0067] When the amount of TBT added is 1 ml, the ratio of BTC:TBT is approximately 2:1, and the product is crystalline SYBZ. The XRD peak intensity may change (Figure 5A). The yield is about 56%, and the rate performance is better than that of the 0.5 ml sample, resulting in the best overall performance.

[0068] When the TBT addition amount was 2 ml and 3 ml, the BTC:TBT ratio was approximately 1:1 and 2:3, respectively. The diffraction peaks of the organic material (SYBZ) disappeared, mainly due to the poor crystallinity of metatitanic acid. Figure 5 A) The yield further increased (64-71%), but this was mainly due to the contribution of metatitanic acid, and the electrochemical capacity decreased significantly. Figure 6 A).

[0069] In summary, TBT is essential, but for SYBZ, excessive TBT (≥2 ml) will completely inhibit the formation of the target product. 0.5 ml TBT has the highest cycling capacity, but 1 ml TBT (molar ratio approximately 2:1) offers better rate performance and overall performance, making it the preferred dosage. Specifically: Electrochemical performance: The SYBZ composite material prepared under optimal conditions (190°C, 24h, 1ml TBT) exhibits certain electrochemical activity as a negative electrode for lithium-ion batteries.

[0070] Capacity and Cycling: For lithium metal testing (0.01-3.0V, 100 mA / g), the first discharge capacity was 868.7 mAh / g. The capacity dropped to 448.5 mAh / g in the second cycle, and recovered to 414 mAh / g after 100 cycles.

[0071] Rate performance: The material exhibits good rate performance, retaining approximately 200 mAh / g capacity at 1 A / g. Capacity recovery is good.

[0072] Example 5 This embodiment describes the performance characterization and mechanism analysis of the SYBZ (isopropyl ester) composite material prepared in Example 1. Specifically: (1) Figure 7 The images show the XRD pattern and electrochemical performance of the SYBZ material prepared in Example 1. Compared with Comparative Example 1 (prepared at 180°C), Example 1 (prepared at 190°C) formed a well-crystallized SYBZ phase, thus achieving higher reversible capacity (868.7 mAh / g in the first cycle) and excellent cycling stability.

[0073] (2) EIS test: The test was conducted using a CHI650 electrochemical workstation. The test frequency range was 100 kHz to 0.1 Hz, and the AC signal amplitude was 5 mV. The results are as follows: Figure 8 As shown, the charge transfer resistance (Rct) of the SYBZ sample is 137.062 Ω, and the Warburg coefficient (σ) is 64.74. Compared with methyl ester (SJZ) and ethyl ester (SYZ), SYBZ exhibits a relatively high impedance value due to the large steric hindrance of the isopropyl branch, but still maintains good ion transport capability.

[0074] (3) CV analysis: Tests were performed using a CHI650 electrochemical workstation. The test voltage range was 0.01 ~ 3.0V (relative to Li / Li). + The scan rate was 0.1 mV / s (kinetic analysis covers 0.1–1.0 mV / s). Results are as follows: Figure 9 As shown, the CV curves of the SYBZ sample reveal oxidation peaks at 0.1187 V, 0.1606 V, and 0.2449 V, and reduction peaks at 0.0577 V, 0.0865 V, and 0.1801 V. Kinetic analysis indicates that the b-value of the SYBZ sample is 0.702, suggesting significant pseudocapacitive control characteristics during lithium storage, which is beneficial for rapid charge-discharge at high rates.

[0075] (4) The material was characterized and analyzed using a Fourier transform infrared spectrometer (model: Nicolet iS20) and an X-ray photoelectron spectrometer (model: K-Alpha+). Figure 10 and Figure 11 The images are FT-IR and XPS spectra, respectively. It can be seen that the characteristic carboxyl peak of the starting material BTC disappears in the FT-IR spectrum, while the peak at 1720.49 cm⁻¹ disappears. -1 (C=O) and 1247.06 cm -1The presence of a characteristic ester group peak at (CO) and the binding energies of 288.65 eV (C=O) and 286.49 eV (CO) in the C 1s spectrum of XPS further confirm the occurrence of the esterification reaction. Simultaneously, the Ti 2p spectrum shows the presence of titanium dioxide hydrate (metitanic acid) on the material surface, accounting for approximately 50%–60%, which is related to the hydrolysis of tetrabutyl titanate during the synthesis of SYBZ.

[0076] (5) TGA test: A thermogravimetric analyzer (model: STA449F3) was used under a nitrogen (N2) atmosphere. The heating rate was set to 10℃ / min, and the test temperature range was from room temperature to 500℃. The results are as follows: Figure 12 As shown, the peak weight loss rate of the SYBZ sample occurred at 241.4℃, demonstrating good thermal stability.

[0077] (6) Mechanism analysis: Assuming that each molecule stores 9 lithium ions (6 on the benzene ring and 1 on each ester carbonyl group), based on the molecular weight of SYBZ (approximately 336.36 g / mol), its theoretical capacity is 717 mAh / g. Figure 13 This is a schematic diagram of the reaction mechanism.

[0078] Figure 14 The dQ / dV curves are for the first two cycles of the SYBZ composite material.

[0079] Figure 15 The discharge capacity contribution diagram of SYBZ composite material.

[0080] This invention utilizes the reaction of 1,3,5-pyromellitic tricarboxylic acid (BTC) and isopropanol in the presence of tetrabutyl titanate (TBT) as a promoter. TBT promotes the esterification reaction by consuming water as a byproduct through hydrolysis, thus yielding an isopropyl 1,3,5-pyromellitic tricarboxylic acid (SYBZ) composite material. Optimized preparation conditions include a holding temperature of 190°C, a holding time of 24 hours, and a BTC to TBT molar ratio of 2:1. The resulting SYBZ composite material exhibits high specific capacity, good cycle stability with capacity recovery, and excellent rate performance, demonstrating great potential as a negative electrode for lithium-ion batteries.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A 1,3,5-pyromellitic isopropyl ester composite material, characterized in that: The composite material is a mixture consisting of 40% to 50% ethyl 1,3,5-trisimilar phenyltricarboxylate and 50% to 60% titanium dioxide hydrate TiO2·H2O by mass.

2. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 1, characterized in that: The method for preparing the composite material includes, 1,3,5-pyromellitic acid, tetrabutyl titanate and isopropanol were mixed to obtain a reaction mixture; The reaction mixture is heated and kept at a constant temperature to carry out a solvothermal reaction; After the reaction was completed, the product was naturally cooled to room temperature, filtered and collected, washed several times with isopropanol, and dried under vacuum to obtain the 1,3,5-trimethylammonium phosphate isopropyl composite material.

3. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 2, characterized in that: The molar ratio of 1,3,5-pyromellitic acid to tetrabutyl titanate is 2 to 1:

1.

4. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 2, characterized in that: The molar ratio of 1,3,5-tristyric acid to isopropanol is 1:80 to 1:

90.

5. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 2, characterized in that: The reaction mixture is heated and kept at a temperature of 180~200℃ for 12~36 h.

6. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 5, characterized in that: The insulation temperature is 190℃, and the insulation time is 24 hours.

7. The 1,3,5-pyromellitic isopropyl ester composite material as described in claim 2, characterized in that: The vacuum drying process involves a drying temperature of 50-60°C and a drying time of 10-14 hours.

8. The application of the 1,3,5-pyromellitic isopropyl ester composite material as described in any one of claims 1 to 7 in the preparation of lithium-ion batteries.

9. The application as described in claim 8, characterized in that: The 1,3,5-pyromellitic isopropyl ester composite material is used to prepare the negative electrode material for lithium-ion batteries. The negative electrode material is prepared by mixing the 1,3,5-pyromellitic isopropyl ester composite material according to any one of claims 1 to 7 with a conductive agent and a binder. The theoretical capacity of the negative electrode material is 717 mAh / g.

10. A lithium-ion battery, characterized in that: The negative electrode material was prepared by using the 1,3,5-pyromellitic isopropyl ester composite material according to any one of claims 1 to 7.

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