A lithium aluminum titanium phosphate composite polymer, its preparation method and application

Abstract

The present invention discloses a lithium aluminum titanium phosphate composite polymer, a preparation method thereof and an application thereof, belonging to the technical field of lithium ion batteries. The preparation steps of the lithium aluminum titanium phosphate composite polymer include: in an inert atmosphere, dissolving a polymer monomer and a lithium salt in an organic solvent, then adding lithium aluminum titanium phosphate modified by a silane coupling agent, and after the reaction, adding a crosslinking agent to crosslink and polymerize the polymer monomer and the lithium aluminum titanium phosphate modified by the silane coupling agent, and obtaining the lithium aluminum titanium phosphate composite polymer after curing. The present invention utilizes the reactive sites dispersed in the polymer chain to react with the surface groups of the LATP modified by the silane coupling agent, so that the modified LATP particles are uniformly dispersed along the polymer chain. A chemical bond connection is formed between the LATP and the polymer, improving the discontinuous conduction of lithium ions caused by the organic-inorganic interface of the traditional composite electrolyte. The introduction of LATP endows the electrolyte with good mechanical properties and thermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium aluminum titanium phosphate composite polymer, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium aluminum titanium phosphate (LATP) is one of the NASICON ion fast conductors that have been relatively maturely studied at present. It has good room temperature ionic conductivity, low preparation cost, wide raw material sources, and good air stability. It is one of the most promising solid electrolytes for large-scale production. However, its stability to lithium is poor. During the charge and discharge cycle, Ti 4+ will be reduced to Ti 3+ , resulting in unstable electrolyte and short cycle life, which severely limits its application in lithium ion batteries.

[0003] Blending a polymer with LATP to prepare a composite electrolyte helps to weaken the redox reaction on LATP during the charge and discharge process, thus helping to improve the battery life. However, traditional composite solid electrolytes are prepared by blending, and the inorganic nanoparticles and the polymer are connected by physical interactions, with poor reliability. In addition, there is an organic-inorganic interface problem between the polymer and the inorganic nanoparticles, making it difficult for lithium ions to conduct continuously along the polymer-inorganic nanoparticles. Moreover, considering the size effect of the fillers in the composite electrolyte, LATP powder usually requires a smaller particle size. However, a smaller particle size brings a larger surface energy, resulting in easy agglomeration of the powder during the mixing process. The poor dispersibility of LATP powder will lead to uneven interfacial potential, thus easily leading to the growth of lithium dendrites. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a lithium aluminum titanium phosphate composite polymer, a preparation method thereof, and an application thereof. The room temperature conductivity of the provided lithium aluminum titanium phosphate composite polymer is 1.5×10 -5 ~6.6×10 -4 S·cm -1 , and the electrochemical stability window is 4.7~5.6V.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] Technical solution one of the present invention: Provide a preparation method of a lithium aluminum titanium phosphate composite polymer, comprising the following steps:

[0007] Under an inert atmosphere, dissolve a polymer monomer and a lithium salt in an organic solvent, then add lithium aluminum titanium phosphate modified with a silane coupling agent, and after the reaction, add a crosslinking agent to crosslink and polymerize the polymer monomer and the lithium aluminum titanium phosphate modified with the silane coupling agent, and obtain the lithium aluminum titanium phosphate composite polymer after curing;

[0008] The polymer monomer includes at least one of polyethylene glycol diacrylate (PEGDA) and polyethylene glycol diamine;

[0009] In the lithium titanium aluminum phosphate modified by the silane coupling agent, the silane coupling agent includes at least one of amino silane coupling agents and methacryloxy silane coupling agents;

[0010] The crosslinking agent includes at least one of ethylenediamine, polyetheramine, and hexamethylenediamine.

[0011] Optionally, the inert atmosphere includes a nitrogen atmosphere or an argon atmosphere.

[0012] Preferably, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0013] Preferably, the organic solvent includes at least one of tetrahydrofuran, dichloromethane, chloroform, acetonitrile, toluene, dioxane, and N,N-dimethylformamide.

[0014] Preferably, the amino silane coupling agent includes at least one of γ-aminopropyltriethoxysilane (KH550), γ-aminopropyltrimethoxysilane, and γ-aminopropylmethyldiethoxysilane; the methacryloxy silane coupling agent includes γ-methacryloxypropyltrimethoxysilane (KH570) and / or γ-methacryloxypropyltris(trimethylsiloxy)silane.

[0015] In the method for modifying lithium titanium aluminum phosphate with a silane coupling agent in the present invention, the general method for modifying inorganic materials with a silane coupling agent can be used.

[0016] Preferably, the polymer monomer and the lithium salt are added in a ratio of EO:Li = 8:1 to 16:1 in terms of lithium-to-oxygen ratio; the addition amount of the lithium titanium aluminum phosphate modified by the silane coupling agent is 5 to 40 wt.% of the lithium titanium aluminum phosphate composite polymer.

[0017] Preferably, the temperature of the reaction is 25 to 80 °C, and the time is 0.5 to 6 h.

[0018] More preferably, when the polymer monomer is PEGDA and the silane coupling agent used for modification is a methacryloxy silane coupling agent, an initiator is added, and the initiator includes azobisisobutyronitrile (AIBN).

[0019] The second technical solution of the present invention: Provide a lithium titanium aluminum phosphate composite polymer prepared by the preparation method of the above-mentioned lithium titanium aluminum phosphate composite polymer.

[0020] The third technical solution of the present invention: Provide an application of the above-mentioned lithium aluminum titanium phosphate composite polymer in a solid electrolyte.

[0021] The fourth technical solution of the present invention: Provide an application of the above-mentioned lithium aluminum titanium phosphate composite polymer in a lithium-ion battery.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] The present invention utilizes the reactive sites dispersed in the polymer chain to react with the surface groups of the silane-coupled LATP, making the modified LATP particles uniformly dispersed along the polymer chain. A chemical bond is formed between LATP and the polymer, improving the discontinuous lithium-ion conduction caused by the organic-inorganic interface of the traditional composite electrolyte. The introduction of LATP endows the electrolyte with good mechanical properties and thermal stability. This lithium aluminum titanium phosphate composite polymer has good interfacial stability, a wide electrochemical window (>4.5V), and a high room-temperature ionic conductivity (>10 -5 S·cm -1 )

[0024] The preparation process of the lithium aluminum titanium phosphate composite polymer of the present invention is simple and can be produced quantitatively. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the synthesis of the lithium aluminum titanium phosphate composite polymer in Example 1 of the present invention. Detailed Embodiments

[0026] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only for describing specific implementation modes and are not used to limit the present invention.

[0027] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0028] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0029] As used herein, terms such as "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0030] Example 1

[0031] Preparation of lithium aluminum titanium phosphate composite polymer:

[0032] (1) Pre-mix anhydrous ethanol (15 mL) and LATP (1 g) to form a uniform white dispersion system. Separately, mix silane coupling agent KH550 (1 mL) with anhydrous ethanol (10 mL), add deionized water (1 mL), and stir at room temperature for about 2 hours to hydrolyze the silane coupling agent. Subsequently, add the silane coupling agent solution to the LATP dispersion, and stir at 60 °C for 6 hours. Then, centrifuge the dispersion, wash with anhydrous ethanol, repeat three times, and dry at 60 °C under vacuum to obtain a white powder, which is silane coupling agent-modified LATP (KH550@LATP).

[0033] (2) In a glove box filled with argon, mix PEGDA 400 (1 mL), lithium bis(trifluoromethanesulfonyl)imide (312 mg), and acetonitrile (1 mL) until the lithium salt is completely dissolved (the lithium-to-oxygen ratio EO:Li of PEGDA 400 and lithium bis(trifluoromethanesulfonyl)imide is 8:1). Subsequently, add KH550@LATP powder (146 mg), and ultrasonicate for 30 minutes to completely disperse it in the solution. Stir at 60 °C for 2 hours to allow the polymer monomer to fully react with the surface groups of the modified LATP. Then, stop heating and add crosslinking agent ethylenediamine (EDA, 80 μL). After stirring evenly, pour it into a polytetrafluoroethylene mold and heat at 60 °C for 4 hours to completely cure it. Subsequently, dry under vacuum at 60 °C to remove excess solvent. Obtain a white and smooth lithium aluminum titanium phosphate composite polymer (PEGDA-EDA-KH550@LATP), where the proportion of KH550@LATP powder is 10 wt.%.

[0034] The schematic diagram of the synthesis of the lithium aluminum titanium phosphate composite polymer in Example 1 of the present invention is shown in Figure 1 .

[0035] Example 2

[0036] Preparation of lithium aluminum titanium phosphate composite polymer:

[0037] The difference from Example 1 is that the crosslinking agent used is polyetheramine 400 (PPGBAE, 0.5 mL), and the lithium aluminum titanium phosphate composite polymer PEGDA-PPGBAE-KH550@LATP is prepared. Other implementation conditions are the same as those in Example 1.

[0038] Example 3

[0039] Preparation of lithium aluminum titanium phosphate composite polymer:

[0040] Different from Example 1: The crosslinking agent used was hexamethylenediamine (HDA, 80 μL), and the obtained lithium aluminum titanium phosphate composite polymer was PEGDA-HDA-KH550@LATP. Other implementation conditions were the same as those in Example 1.

[0041] The performance of the lithium aluminum titanium phosphate composite polymers obtained in Examples 1-3 was characterized, and the test results are shown in Table 1.

[0042] Table 1 Performance of the lithium aluminum titanium phosphate composite polymers obtained in Examples 1-3

[0043] Example Average thickness (mm) <![CDATA[Ionic conductivity (S·cm -1 , 25 °C)]]> Electrochemical stability window (V) 1 0.036 <![CDATA[0.662×10 -4 > 5.04 2 0.033 <![CDATA[1.33×10 -4 > 5.19 3 0.034 <![CDATA[0.878×10 -4 > 5.14

[0044] It can be seen from Table 1 that as the length of the diamine chain segment increases, the ionic conductivity increases. This may be because when the length of the diamine chain segment is short, the crosslinking density of the polymer is large, and the flexibility of the lithium aluminum titanium phosphate composite polymer decreases, resulting in a decrease in ionic conductivity. When there are a large number of ether oxygen structures in the diamine chain segment, the lithium conduction ability of the polymer chain is enhanced, so the ionic conductivity increases.

[0045] Example 4

[0046] Preparation of lithium aluminum titanium phosphate composite polymer:

[0047] Different from Example 1: The silane coupling agent used was KH570 (1 mL), and the modified LATP obtained was KH570@LATP. AIBN was used as an initiator to initiate the free radical polymerization of KH570@LATP and PEGDA, and the obtained lithium aluminum titanium phosphate composite polymer was PEGDA-EDA-KH570@LATP. Other implementation conditions were the same as those in Example 1.

[0048] Example 5

[0049] Preparation of lithium aluminum titanium phosphate composite polymer:

[0050] Different from Example 4: The crosslinking agent used was hexamethylenediamine (HDA, 80 μL), and the obtained lithium aluminum titanium phosphate composite polymer was PEGDA-HDA-KH570@LATP. Other implementation conditions were the same as those in Example 4.

[0051] Example 6

[0052] Preparation of lithium aluminum titanium phosphate composite polymer:

[0053] Different from Example 4: The crosslinking agent used was polyetheramine 400(PPGBAE, 0.5 mL) was used to prepare lithium aluminum titanium phosphate composite polymer PEGDA - PPGBAE - KH570@LATP, and other implementation conditions were the same as those in Example 4.

[0054] The performance of the lithium aluminum titanium phosphate composite polymers obtained in Examples 4 - 6 was characterized, and the test results are shown in Table 2.

[0055] Table 2 Performance of the lithium aluminum titanium phosphate composite polymers obtained in Examples 4 - 6

[0056] Example Average thickness (mm) <![CDATA[Ionic conductivity (S·cm -1 , 25 °C)]]> Electrochemical stability window (V) 4 0.034 <![CDATA[1.232×10 -4 > 5.09 5 0.034 <![CDATA[1.709×10 -4 > 5.15 6 0.037 <![CDATA[5.332×10 -4 > 5.19

[0057] It can be seen from Table 2 that when the silane coupling agent for surface modification of LATP was changed to KH570, the performance of the composite electrolytes prepared with each cross - linker was improved. This is mainly because the surface of KH570 - modified LATP has acrylate bonds, which have better hydrophobicity. It is more evenly dispersed in organic solvents, further reducing aggregation and improving ionic conductivity.

[0058] Example 7

[0059] Preparation of lithium aluminum titanium phosphate composite polymer:

[0060] The difference from Example 1 is that the solvent used in step (2) is N,N - dimethylformamide (1 mL), and other implementation conditions are the same as those in Example 1.

[0061] Example 8

[0062] Preparation of lithium aluminum titanium phosphate composite polymer:

[0063] The difference from Example 1 is that the solvent used in step (2) is dichloromethane (1 mL), and other implementation conditions are the same as those in Example 1.

[0064] Example 9

[0065] Preparation of lithium aluminum titanium phosphate composite polymer:

[0066] The difference from Example 1 is that the solvent used in step (2) is tetrahydrofuran (1 mL), and other implementation conditions are the same as those in Example 1.

[0067] The performance of the lithium aluminum titanium phosphate composite polymers obtained in Examples 7 - 9 was characterized, and their room - temperature ionic conductivities were 5.34×10 -5 S·cm -1 、7.96×10 -5 S·cm -1 、6.30×10 -5 S·cm -1; The electrochemical stability windows are 5.03 V, 5.18 V, and 5.12 V in sequence.

[0068] Example 10

[0069] Preparation of lithium aluminum titanium phosphate composite polymer:

[0070] Different from Example 1: The lithium salt used in step (2) is lithium tetrafluoroborate (LiBF4), EO:Li = 8:1, and other implementation conditions are the same as those in Example 1.

[0071] Example 11

[0072] Preparation of lithium aluminum titanium phosphate composite polymer:

[0073] Different from Example 1: The lithium salt used in step (2) is lithium hexafluoroborate (LiBF6), EO:Li = 8:1, and other implementation conditions are the same as those in Example 1.

[0074] Perform performance characterization on the lithium aluminum titanium phosphate composite polymers obtained in Examples 10 - 11. Their room-temperature ionic conductivities are 6.64×10 -5 S·cm -1 、7.13×10 -5 S·cm -1 ; The electrochemical stability windows are 5.15 V and 5.21 V in sequence.

[0075] Example 12

[0076] Preparation of lithium aluminum titanium phosphate composite polymer:

[0077] Different from Example 1: EO:Li = 16:1, and other implementation conditions are the same as those in Example 1.

[0078] Example 13

[0079] Preparation of lithium aluminum titanium phosphate composite polymer:

[0080] Different from Example 1: EO:Li = 12:1, and other implementation conditions are the same as those in Example 1.

[0081] Perform performance characterization on the lithium aluminum titanium phosphate composite polymers obtained in Examples 12 - 13. Their room-temperature ionic conductivities are 2.24×10 -5 S·cm -1 、3.27×10 -5 S·cm -1 , and the decrease in conductivity is due to the increase in crystallinity caused by the increase in EO:Li. At the same time, the decrease in the concentration of Li ions contained in the electrolyte also leads to the decrease in ionic conductivity.

[0082] Example 14

[0083] Preparation of lithium aluminum titanium phosphate composite polymer:

[0084] The difference from Example 1 is that the addition amount of KH550@LATP is 5 wt.% of the lithium aluminum titanium phosphate composite polymer, and other implementation conditions are the same as those in Example 1.

[0085] Example 15

[0086] Preparation of lithium aluminum titanium phosphate composite polymer:

[0087] The difference from Example 1 is that the addition amount of KH550@LATP is 20 wt.% of the lithium aluminum titanium phosphate composite polymer, and other implementation conditions are the same as those in Example 1.

[0088] Example 16

[0089] Preparation of lithium aluminum titanium phosphate composite polymer:

[0090] The difference from Example 1 is that the addition amount of KH550@LATP is 30 wt.% of the lithium aluminum titanium phosphate composite polymer, and other implementation conditions are the same as those in Example 1.

[0091] Example 17

[0092] Preparation of lithium aluminum titanium phosphate composite polymer:

[0093] The difference from Example 1 is that the addition amount of KH550@LATP is 40 wt.% of the lithium aluminum titanium phosphate composite polymer, and other implementation conditions are the same as those in Example 1.

[0094] Perform performance characterization on the lithium aluminum titanium phosphate composite polymers obtained in Examples 14 - 17. Their room-temperature ionic conductivities are 3.18×10 -5 S·cm -1 、6.22×10 -5 S·cm -1 、5.28×10 -5 S·cm -1 、3.98×10 -5 S·cm -1 . The change in conductivity first increases and then decreases with the change in concentration. This is mainly because when the filler concentration is 5 wt.%, the contribution of the inorganic filler to the ionic conductivity is less and the improvement is small; as the concentration of inorganic particles increases, new lithium-ion transport channels are formed and the ionic conductivity is improved; when it exceeds a certain threshold, due to a certain degree of agglomeration, the surface area decreases, which hinders the transport of lithium ions, so the ionic conductivity shows a downward trend.

[0095] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of lithium titanium aluminum phosphate composite polymer, characterized in that, It includes the following steps: Under an inert atmosphere, dissolve a polymer monomer and a lithium salt in an organic solvent, then add lithium titanium aluminum phosphate modified with a silane coupling agent. After the reaction, add a crosslinking agent to crosslink and polymerize the polymer monomer and the lithium titanium aluminum phosphate modified with the silane coupling agent, and obtain the lithium titanium aluminum phosphate composite polymer after curing; The polymer monomer includes at least one of polyethylene glycol diacrylate and polyethylene glycol diamine; In the lithium titanium aluminum phosphate modified with the silane coupling agent, the silane coupling agent includes at least one of an amino silane coupling agent and a methacryloxy silane coupling agent; The crosslinking agent includes at least one of ethylenediamine, polyetheramine and hexamethylenediamine.

2. The preparation method of the lithium aluminum titanium phosphate composite polymer according to claim 1, characterized in that, The lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium tetrafluoroborate and lithium bis(trifluoromethanesulfonyl)imide; 3. The preparation method of the lithium aluminum titanium phosphate composite polymer according to claim 1, characterized in that, The organic solvent includes at least one of tetrahydrofuran, dichloromethane, chloroform, acetonitrile, toluene, dioxane and N,N-dimethylformamide; 4. The preparation method of the lithium titanium aluminum phosphate composite polymer according to claim 1, characterized in that, The amino silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and γ-aminopropylmethyldiethoxysilane; the methacryloxy silane coupling agent includes γ-methacryloxypropyltrimethoxysilane and / or γ-methacryloxypropyltris(trimethylsiloxy)silane.

5. The preparation method of the lithium titanium aluminum phosphate composite polymer according to claim 1, wherein The polymer monomer and the lithium salt are added in a ratio of EO:Li = 8:1 to 16:1; the addition amount of the lithium titanium aluminum phosphate modified with the silane coupling agent is 5 to 40 wt.% of the lithium titanium aluminum phosphate composite polymer.

6. The preparation method of the lithium aluminum titanium phosphate composite polymer according to claim 1, characterized in that, The temperature of the reaction is 25 to 80 °C, and the time is 0.5 to 6 h.

7. A lithium titanium aluminum phosphate composite polymer prepared by the preparation method of the lithium titanium aluminum phosphate composite polymer according to any one of claims 1 to 6.

8. Application of the lithium titanium aluminum phosphate composite polymer according to claim 7 in a solid electrolyte.

9. Application of the lithium titanium aluminum phosphate composite polymer according to claim 7 in a lithium ion battery.

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