An alternating polymer, its synthesis method and applications
By designing a rigid-flexible structure of alternating polymers, the problem of slow electron and ion transport in organic cathode materials for lithium batteries was solved, resulting in a high-performance lithium battery cathode material with high capacity and good cycle stability, while reducing production costs.
Patent Information
- Application Number
- CN202411622604.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2044-11-14
AI Technical Summary
Existing organic cathode materials for lithium batteries struggle to simultaneously achieve both electron transport and rapid ion transport without compromising electrode energy density.
An alternating polymer is used, whose molecular backbone is composed of alternating rigid and flexible segments. It is synthesized through Schiff base reaction and contains a flexible ethyl structure with a rigid benzene ring structure and a ferrocene structure. The ferrocene group and C=N bond group are provided as electroactive sites to realize electrochemical redox reaction.
It achieves both rapid electron and ion transport performance without compromising electrode energy density, providing high theoretical specific capacity, excellent rate performance and good cycling stability, reducing capacity degradation caused by solubility, and lowering commercial production costs.
Smart Images
Figure CN119463081B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium battery material technology, specifically relating to an alternating polymer with both rigid and flexible segments, its synthesis method, and its application in lithium battery cathode materials. Background Technology
[0002] Rechargeable lithium-ion batteries are a mainstay of portable electronics and the rapidly growing electric vehicle sector. The performance of lithium-ion batteries is heavily influenced by the performance of the cathode material. In recent years, with the increasing demand for large-scale energy storage systems and electric vehicles, efforts have focused on developing high-performance lithium-ion battery cathode materials. In particular, organic electrode materials, with their tunable molecular structures, achieve rapid energy storage through redox reactions of active groups. Therefore, organic materials, due to their high capacity and rate performance, hold promise as candidate cathodes for next-generation renewable lithium-ion batteries.
[0003] Ion transport and electron transport determine the performance of organic electrodes. To improve the electronic conductivity of organic electrodes, large and rigid conjugated structures are often designed to accelerate electron transport. However, the strong π-π interactions between rigid conjugated structures lead to tight packing between chains of linear polymers or between layers of two-dimensional layered polymers. This buries active groups and makes it difficult for ions to be rapidly transported to their vicinity. Slow electron or ion transport results in unsatisfactory specific capacity and rate performance of organic electrodes.
[0004] To achieve high-performance organic electrodes for lithium-ion batteries, it is essential to accelerate and synergistically enhance the transport of ions and electrons within the electrode. Currently, during electrode material preparation, conductive materials such as composite carbon nanotubes or graphene are used to improve the electronic conductivity of the electrode and enhance its packing morphology to accelerate ion transport. For example, Professor Yongsheng Chen's research group at Nankai University prepared a composite active material (…) through in-situ polymerization of monomers with graphene. Adv. Mater. 2023, 35, 2211152. When combined with conductive carbon materials, the electronic conductivity is improved and the stacking morphology of the original polymer is enhanced, enabling rapid electron and ion transport within the electrode, thus yielding a high-performance polymer-organic cathode. However, as these conductive carbon materials are inactive components, they increase the overall electrode mass, leading to a decrease in the electrode's energy density and power density. Therefore, there is a strong need to develop new methods to address the slow ion and electron transport in organic electrodes without compromising their energy density. Summary of the Invention
[0005] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides an alternating polymer, its synthesis method and its application in lithium battery cathode materials, which solves the problem that organic cathodes of lithium batteries are difficult to achieve both electron transport and rapid ion transport without compromising electrode energy density.
[0006] To achieve the above objectives, according to a first aspect of the present invention, an alternating polymer is provided, the main molecular chain of which is composed of alternating rigid and flexible segments, wherein the rigid segments contain a rigid benzene ring structure and a ferrocene structure, and the flexible segments are ethyl structures; the structural formula of the alternating copolymer is shown in Formula (I).
[0007]
[0008] Formula (1)
[0009] Wherein, the degree of aggregation n is an integer from 5 to 25.
[0010] As a further improvement of the present invention, the alternating copolymer is synthesized by Schiff base reaction using 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl as reactive monomers.
[0011] As a further improvement of the present invention, the alternating copolymer has ferrocene groups and C=N bond groups, which serve as electroactive sites capable of undergoing electrochemical redox reactions.
[0012] According to a second aspect of the present invention, a method for synthesizing alternating copolymers is provided, comprising the following steps:
[0013] The alternating copolymer was synthesized by heating with 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl as reactants in the presence of a solvent to induce a Schiff base reaction.
[0014] As a further improvement of the present invention, the molar ratio of 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl is 1~1.5:1;
[0015] The concentrations of 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl in the reaction system were 0.05~0.1 mol / L, respectively.
[0016] As a further improvement of the present invention, the Schiff base reaction system also contains a catalyst, the concentration of which is 0~2 mol / L.
[0017] As a further improvement of the present invention, the solvent is one or more of n-butanol, 1,4-dioxane, o-dichlorobenzene, and mesitylene.
[0018] As a further improvement of the present invention, the catalyst is acetic acid.
[0019] As a further improvement of the present invention, the Schiff base reaction is carried out at a temperature of 100-120 °C for a reaction time of 48-72 h.
[0020] According to a third aspect of the present invention, an application of an alternating copolymer in a lithium battery cathode material is provided, wherein the alternating copolymer is used, or the alternating copolymer is obtained by the synthesis method described above; the lithium battery includes a lithium-ion battery and a lithium metal battery.
[0021] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:
[0022] (1) The alternating copolymer of the present invention contains both rigid conjugated segments that are beneficial to electron transport and flexible twisted segments that are beneficial to ion transport. Through the structural design that combines rigidity and flexibility, it effectively avoids the shortcomings of either entirely rigid or entirely flexible segments, while possessing the advantages of both. The present invention can solve the problem of organic cathodes having both rapid ion transport and electron transport without in-situ compounding with inactive conductive carbon materials. Therefore, the present invention can achieve both rapid electron and ion transport performance without compromising the energy density of the electrode.
[0023] (2) The alternating copolymer of the present invention uses ferrocene groups and C=N bond groups as active sites, and achieves charge storage through the redox reaction of the two. When it is used as an organic cathode material for lithium batteries, multiple active sites provide 192 mAh g. -1 The theoretical specific capacity is high, and the ferrocene group uses anions as charge carriers, which improves the working voltage and has fast electrode reaction kinetics, ensuring the high energy density and power density of the polymer electrode.
[0024] (3) The alternating copolymer of the present invention contains a rigid conjugated structure, and the conjugated part has Π-Π interaction, which effectively reduces its solubility in organic electrolyte. When the alternating copolymer is used as an organic cathode material for lithium batteries, it effectively avoids the capacity reduction problem caused by dissolution, which is beneficial to improving the cycle stability of the battery.
[0025] (4) The synthesis method of the alternating copolymer of the present invention is simple, has a high yield, and uses readily available raw materials, which helps to reduce the cost of commercial production. When used as a cathode material for lithium batteries, it exhibits excellent rate performance (60% of the capacity at 10C and 40% of the capacity at 0.5C at 50C), high utilization of active sites (78% utilization of active sites at 0.5C), and good cycle stability (60% capacity retention after 3500 cycles at 10C). The present invention provides a new approach for constructing organic electrodes with excellent rate performance and high utilization of active sites, and is expected to serve as a cathode material for next-generation lithium batteries. Attached Figure Description
[0026] Figure 1 The infrared spectrum of the alternating copolymer synthesized in Example 1 of this invention;
[0027] Figure 2 The cyclic voltammetry curves of the alternating copolymer synthesized in Example 1 of this invention when used as a cathode material for lithium batteries are shown.
[0028] Figure 3 The charge-discharge curves of the alternating copolymer synthesized in Example 1 of this invention when used as a positive electrode material for lithium batteries are shown.
[0029] Figure 4 The rate performance of the alternating copolymer synthesized in Example 1 of this invention as a positive electrode material for lithium batteries;
[0030] Figure 5 This describes the long-cycle performance of the alternating copolymer synthesized in Example 1 of this invention when used as a positive electrode material for lithium batteries. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by known methods.
[0032] This invention provides an alternating copolymer with both rigid and flexible segments, the main molecular chain of which is composed of alternating rigid and flexible segments. The rigid segments contain rigid benzene ring structures and ferrocene structures, and the flexible segments are ethyl structures. The structural formula of the alternating copolymer is shown in Formula (I).
[0033]
[0034] Formula (1).
[0035] Wherein, the degree of aggregation n is an integer from 5 to 25.
[0036] The alternating copolymers of this invention contain both rigid conjugated segments that facilitate electron transport and flexible twisted segments that facilitate ion transport. Through a structural design that combines rigidity and flexibility, the shortcomings of either entirely rigid or entirely flexible segments are effectively avoided, while also possessing the advantages of both. This allows for both rapid electron and ion transport without compromising the electrode energy density.
[0037] The alternating copolymer is synthesized via a Schiff base reaction using 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl as reactive monomers. The alternating copolymer possesses ferrocene groups and C=N bonds, which serve as electroactive sites capable of undergoing electrochemical redox reactions, thereby achieving charge storage.
[0038] The present invention also provides a method for synthesizing the above-mentioned alternating copolymer, comprising the following steps:
[0039] Using 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl as reactive monomers, a Schiff base reaction was carried out upon heating in the presence of a solvent to synthesize the alternating copolymer shown in formula (I).
[0040] The above synthetic reaction formula is shown in formula (II).
[0041]
[0042] Formula (II).
[0043] In some embodiments, the molar ratio of 1,1'-ferrocenediformaldehyde and 4,4'-diaminobibenzyl is 1 to 1.5:1. The concentrations of 1,1'-ferrocenediformaldehyde and 4,4'-diaminobibenzyl in the reaction system are 0.05 to 0.1 mol / L, respectively.
[0044] In some embodiments, the Schiff base reaction system also includes a catalyst, the concentration of which is 0-2 mol / L.
[0045] In some embodiments, the solvent is one or more of n-butanol, 1,4-dioxane, o-dichlorobenzene, and mesitylene; the catalyst is acetic acid.
[0046] In some embodiments, the Schiff base reaction is carried out at a temperature of 100-120 °C for a time of 48-72 h.
[0047] In some specific embodiments of the present invention, the method for synthesizing the above-mentioned alternating copolymer includes the following steps:
[0048] 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl were mixed, and solvent and catalyst were added. The mixture was heated to 100-120 °C and reacted for 48-72 h.
[0049] After the reaction was completed, the product was filtered and washed with an organic solvent capable of dissolving the reactants (such as N,N-dimethylformamide or anhydrous methanol), and then vacuum dried to obtain the alternating copolymer.
[0050] The present invention also provides an application of the above-mentioned alternating copolymer in lithium battery cathode materials, wherein the lithium battery includes lithium-ion batteries and lithium metal batteries.
[0051] When the alternating copolymer is used as the positive electrode material of a lithium battery, the C=N bond groups and ferrocene groups of the alternating copolymer serve as active sites, achieving charge storage through their redox reactions. Its charge-discharge mechanism is shown in equation (III).
[0052]
[0053] Formula (3).
[0054] The assembled half-cells are in the range of 1.2–4.0 (vs. Li / Li). + Charge-discharge tests were conducted within the potential range of [missing information]. First, a charging step was performed. When charging reached 3.2–3.6 V, ferrocene was oxidized to ferrocene ions. After fully charging (to 4.0 V), a discharge was performed. Discharging to 3.6–3.2 V, ferrocene ions were reduced back to ferrocene; further discharging to 2.4–2.0 V, C=N was reduced to CN-Li bonds. After complete discharge (to 1.2 V), the charging process continued. Within the 2.0–2.4 V range, CN-Li bonds were oxidized back to C=N bonds; further charging to 3.2–3.6 V, ferrocene was oxidized back to ferrocene ions, and this process was repeated in subsequent discharge-charge cycles. During the charge-discharge process, a total of three electron redox reactions occurred in each repeating unit, providing 192 mAh g [missing information]. -1 The high theoretical specific capacity. The ferrocene group uses anions as charge carriers, which increases the operating voltage and has fast electrode reaction kinetics, ensuring high energy density and power density of the polymer electrode.
[0055] The following is an example:
[0056] It should be noted that the alternating copolymers of the present invention are synthesized via a Schiff base reaction using 1,1'-ferrocenediformaldehyde and 4,4'-diaminobibenzyl as reactive monomers. This synthesis process is based on a reversible linear polycondensation mechanism. For reversible linear polycondensation, the relative molecular mass of the polymer can be expressed by the average degree of polymerization n, n = (1 + r) / (1 + r - 2rP), where r is the molar ratio of the functional groups of the two monomers, and P is the degree of group reactivity. In the alternating copolymers synthesized in this invention, the degree of polymerization n is an integer from 5 to 25. The degree of polymerization n of the alternating copolymers in the following examples was estimated using the above method.
[0057] Example 1
[0058] The alternating copolymer of this embodiment is synthesized according to the following steps:
[0059] 1,1'-ferrocene dicarboxaldehyde (48.4 mg, 0.2 mmol) and 4,4'-diaminobibenzyl (42.4 mg, 0.2 mmol) were added to a pressure-resistant reaction flask, followed by the addition of 2 mL of mesitylene and 2 mL of 1,4-dioxane as reaction solvents, and 200 μL of acetic acid as a catalyst. The system was heated to 120 °C and reacted for 72 hours. After the reaction was completed, the product was filtered out and washed successively with organic solvents such as N,N-dimethylformamide and anhydrous methanol to dissolve the monomers. After vacuum drying at 80 °C overnight, the alternating copolymer shown in formula (I) was obtained, where n=5, and the final yield was 92%.
[0060] The infrared spectrum of the alternating copolymer synthesized in this embodiment is shown below. Figure 1 As shown, the infrared characteristic peaks of amino and aldehyde monomers have basically disappeared, indicating that the polymerization reaction is complete.
[0061] The alternating copolymer synthesized in this embodiment was used as the positive electrode material for lithium batteries. It was ground with a commercial conductive agent and binder at a mass ratio of 6:3:1. After the powder was ground uniformly, N,N-dimethylpyrrolidone was added dropwise as a solvent while grinding and mixing continued until a uniform slurry with a certain degree of fluidity was obtained. The slurry was then coated onto aluminum foil using a doctor blade. Finally, the aluminum foil coated with the active slurry was dried and pressed into an electrode sheet. The prepared electrode sheet was then assembled with a commercial separator and lithium foil to form a lithium battery for performance testing.
[0062] The cyclic voltammetry curve of the lithium battery assembled using the alternating copolymer synthesized in this embodiment as the positive electrode material at a scan rate of 0.1 mV / s is shown below. Figure 2 As shown. Voltage was observed at 3.2–3.6 V and 2.0–2.4 V (vs. Li). + Two pairs of redox peaks ( / Li). The first is attributed to Fe. 2+ and Fe 3+ The conversion between them, Fe 3+ This is the p-type redox active moiety, which is related to the imine group of the n-type redox active moiety (Adv. Mater. 2023, 35, 2211152.). This indicates that the alternating copolymer material has multiple electrochemical active sites, enabling multi-electron transfer and thus improving its theoretical capacity.
[0063] The lithium battery assembled using the alternating copolymer synthesized in this embodiment as the positive electrode material operates at 0.5C (1C = 192 mAg). -1 The charge / discharge curves under these conditions are as follows: Figure 3 As shown. The results indicate that it can provide approximately 150 mAh g at 0.5 C. -1The specific capacity is 78%, and the corresponding active site utilization rate is 78%, which exceeds the corresponding value of polymer organic cathodes for lithium-ion batteries in many existing technologies, indicating that the electrode has a good electron transport path.
[0064] The rate performance of the lithium battery assembled using the alternating copolymer synthesized in this embodiment as the positive electrode material is as follows: Figure 4 As shown in the figure. The results indicate that its capacity decays slowly at high rates, with the capacity at 10C being 60% of that at 0.5C, and the capacity at 50C being 40% of that at 0.5C, indicating that the electrode has a fast electron and ion transport rate. The excellent rate performance is attributed to the rigid-flexible structural design of the alternating copolymer.
[0065] The lithium battery assembled using the alternating copolymer synthesized in this embodiment as the positive electrode material exhibits the following long-cycle performance: Figure 5 As shown. The results indicate that the initial capacity at 10C is 90 mAh g. -1 After 3500 cycles, the capacity retention rate is 60%, and the excellent cycling stability is due to the stable structure of the polymer.
[0066] Example 2
[0067] The difference between the synthesis of the alternating copolymer in this embodiment and that in Example 1 is that the amount of reactant monomer, solvent and catalyst are all increased by 10 times, while other reaction conditions and steps are the same, to obtain the alternating copolymer shown in Formula (I), where n is 15 and the yield is 90%.
[0068] The alternating copolymer obtained in this embodiment was used as the positive electrode material for lithium batteries. Electrode preparation, battery assembly, and performance testing were performed under the same conditions and steps as in Example 1. The performance of the polymer obtained in this embodiment as a positive electrode material for lithium batteries is basically similar to that in Example 1.
[0069] Example 3
[0070] The difference between the synthesis of the alternating copolymer in this embodiment and that in Example 1 is only in the proportion of reactant monomers added. In this embodiment, 1,1'-ferrocenedicarboxaldehyde (72.6 mg, 0.3 mmol) and 4,4'-diaminobibenzyl (42.4 mg, 0.2 mmol) are used as reactant monomers, and the other reaction conditions and steps are the same, to obtain the alternating copolymer shown in Formula (I), where n is 18 and the yield is 85%.
[0071] The alternating copolymer obtained in this embodiment was used as the positive electrode material for lithium batteries. Electrode preparation, battery assembly, and performance testing were performed under the same conditions and steps as in Example 1. The performance of the polymer obtained in this embodiment as a positive electrode material for lithium batteries is basically similar to that in Example 1.
[0072] Example 4
[0073] The synthesis of the alternating copolymer in this embodiment differs from that in Example 1 only in the amounts of reactants, solvent, and catalyst. Specifically, in this embodiment, 1,1'-ferrocenedicarboxaldehyde (0.242 g, 1 mmol) and 4,4'-diaminobibenzyl (0.242 mg, 1 mmol) were used as reactants, 10 mL of n-butanol was used as the solvent, 1 mL of acetic acid was used as the catalyst, the reaction time was 48 hours, and the reaction temperature was 100 °C, yielding the alternating copolymer shown in formula (I), where n is 25 and the yield is 87%.
[0074] The alternating copolymer obtained in this embodiment was used as the positive electrode material for lithium batteries. Electrode preparation, battery assembly, and performance testing were performed under the same conditions and steps as in Example 1. The performance of the polymer obtained in this embodiment as a positive electrode material for lithium batteries is basically similar to that in Example 1.
[0075] Example 5
[0076] The difference between the synthesis of the alternating copolymer in this embodiment and that in Example 1 is that the solvent is changed to 4 mL of o-dichlorobenzene and the amount of acetic acid catalyst is changed to 450 μL, so as to obtain the alternating copolymer shown in Formula (I), where n is 12 and the yield is 80%.
[0077] The alternating copolymer obtained in this embodiment was used as the positive electrode material for a lithium-ion battery. Electrode preparation, battery assembly, and performance testing were performed under the same conditions and steps as in Example 1. The performance of the polymer obtained in this embodiment as a lithium-ion battery positive electrode material was basically similar to that of Example 1.
[0078] Example 6
[0079] The difference between the synthesis of the alternating copolymer in this embodiment and that in Example 1 is that no acetic acid catalyst is used, resulting in the alternating copolymer shown in Formula (I), where n is 5 and the yield is 78%.
[0080] The alternating copolymer obtained in this embodiment was used as the positive electrode material for a lithium-ion battery. Electrode preparation, battery assembly, and performance testing were performed under the same conditions and steps as in Example 1. The performance of the polymer obtained in this embodiment as a lithium-ion battery positive electrode material was basically similar to that of Example 1.
[0081] The alternating copolymers of this invention have a simple synthesis process, high yield, and can be mass-produced. When used as positive electrode materials for lithium batteries, the assembled lithium batteries exhibit excellent rate performance, high specific capacity, and good long cycle performance, showing potential for constructing novel, environmentally friendly, and sustainable organic lithium batteries.
[0082] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. An alternating copolymer, characterized in that, Its molecular backbone consists of alternating rigid and flexible segments. The rigid segments contain rigid benzene ring structures and ferrocene structures, while the flexible segments are ethyl structures. The structural formula of the alternating copolymer is shown in Formula (I). Formula (1) Wherein, the degree of aggregation n is an integer from 5 to 25.
2. The alternating copolymer as claimed in claim 1, characterized in that, The alternating copolymer is synthesized via a Schiff base reaction using 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl as reactive monomers.
3. The alternating copolymer as described in claim 1 or 2, characterized in that, The alternating copolymer has ferrocene groups and C=N bond groups, which serve as electroactive sites and can undergo electrochemical redox reactions.
4. A method for synthesizing an alternating copolymer, used to prepare the alternating copolymer according to any one of claims 1-3, characterized in that, Includes the following steps: The alternating copolymer was synthesized by heating with 1,1'-ferrocenediformaldehyde and 4,4'-diaminobibenzyl as reactants in the presence of a solvent to induce a Schiff base reaction.
5. The synthesis method as described in claim 4, characterized in that, The molar ratio of 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl is 1~1.5:1; The concentrations of 1,1'-ferrocene dicarboxaldehyde and 4,4'-diaminobibenzyl in the reaction system are 0.05~0.1 mol / L, respectively.
6. The synthesis method as described in claim 4 or 5, characterized in that, The Schiff base reaction system also contains a catalyst, and the concentration of the catalyst in the reaction system is 0~2 mol / L.
7. The synthesis method as described in claim 4 or 5, characterized in that, The solvent is one or more of n-butanol, 1,4-dioxane, o-dichlorobenzene, and mesitylene.
8. The synthesis method as described in claim 6, characterized in that, The catalyst is acetic acid.
9. The synthesis method as described in claim 4 or 5, characterized in that, The Schiff base reaction is carried out at a temperature of 100-120°C for a time of 48-72 h.
10. The application of an alternating copolymer in lithium battery cathode materials, characterized in that, The alternating copolymer according to any one of claims 1-3 is used, or the alternating copolymer is obtained by the synthesis method according to any one of claims 4-9; the lithium battery includes lithium-ion batteries and lithium metal batteries.