Chitin derivative binder and application thereof in all-solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, in particular to a chitin derivative binder and application thereof in an all-solid-state battery. The structural formula of the chitin derivative binder is shown in the specification, in the formula, R is independently selected from any one or more of H, X-C = O-, alkyl,-CH2CH (OH) CH3, Y-NH-C = O-,-CH3 (CH2) and-CH3COONa, and X and Y are alkyl; n is an integer not less than 10. The chitin derivative binder is synthesized for the first time and is applied to composite solid electrolyte film formation, and the composite electrolyte prepared from the chitin derivative has high flexibility and ionic conductivity, is suitable for various electrode materials and an existing lamination process, and has a rapid industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a chitin derivative binder and its application in all-solid-state batteries. BACKGROUND

[0002] Chitin, as a rich biomass resource, widely exists in the shells of shrimps and crabs, has the advantages of environmental degradation, excellent mechanical properties, high thermal stability, and high oxidation decomposition potential, and the polar functional groups such as hydroxyl and amino groups in the molecular chain provide a variety of possibilities for chemical modification and interface control. Studies have shown that chitin has shown the potential to improve the interface stability and electrochemical performance in the separator of traditional liquid batteries and the gel electrolyte matrix. Based on these characteristics, chitin-based materials have broad application prospects in solid-state battery systems, especially in solving the key challenges of poor solid-solid interface contact, interface stress, and sulfide electrolyte brittleness.

[0003] However, the dense hydroxyl groups in the molecular skeleton of chitin make it difficult to dissolve in commonly used battery solvents, limiting the application of chitin in electrolyte membranes. Studies have shown that introducing specific functional groups into the side chain of chitin through chitin derivatization can overcome the solubility problem, but there is no disclosure of using chitin derivatives in solid-state batteries. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, provide a chitin derivative binder and its application in all-solid-state batteries. The present application first uses chitin derivatives for bonding in solid-state batteries. The chitin derivative can be dissolved in commonly used battery solvents, overcoming the solubility problem, and improving the interfacial compatibility with sulfide electrolyte, thereby significantly improving the flexibility and fracture resistance of the electrolyte membrane, and helping to stabilize the interface, reduce the interface impedance, and improve the battery performance.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: According to one aspect of the present application, a chitin derivative binder is provided, which has the following structural formula (I): (I); In formula (I), R is independently selected from any one or several of H, X-C=O-, alkyl, -CH2CH(OH)CH3, Y-NH-C=O-, -CH3(CH2), -CH3COONa, X and Y are alkyl; n is an integer not less than 10.

[0006] Preferably, X and Y are saturated / unsaturated alkanes with ≤16 carbon atoms.

[0007] According to another aspect of the present application, a method for preparing a chitin derivative adhesive is provided, which comprises reacting chitin with a functional group-containing compound.

[0008] Further, the chitin mentioned above can be directly commercially available or extracted by methods well known to those skilled in the art. For example, it can be extracted from shrimp and crab shells, and the extraction method is well known to those skilled in the art and is not particularly limited. For example, the shrimp and crab shells can be first washed with acid and alkali in a circulation manner to remove inorganic minerals and proteins in the shrimp and crab shells; the chitin is deacetylated by heterogeneous deacetylation with hot concentrated alkali, and the deacetylation degree is tested by acid-base titration method, and the chitin is obtained after drying, and the specific method is as follows: S1, 0.1-0.2 parts of shrimp and crab shell powder is put into 1-3 parts of hydrochloric acid solution, stirred for 4h, repeatedly washed with distilled water and suction filtered until the filtrate is neutral, and the solvent is evaporated to obtain; S2, 0.1-0.2 parts of shrimp and crab shell powder obtained in S1 is put into 1-3 parts of sodium hydroxide solution and stirred, repeatedly washed with distilled water and suction filtered until the filtrate is neutral, and the solvent is evaporated; S3, S1 and S2 are sequentially repeated to obtain.

[0009] Alternatively, the mass concentration of the hydrochloric acid solution is 10-20%, and the concentration of the sodium hydroxide solution is 1-2.5 mol / L.

[0010] The raw material of the chitin derivative of the present application is derived from shrimp and crab shells and the like, which is a renewable resource and has good biodegradability, conforming to the concept of sustainable development.

[0011] Further, in the preparation process of the chitin derivative, the functional group-containing compound is selected from a compound containing a functional group capable of undergoing alkylation, quaternary ammonium saltation, acylation with amino group, and carboxymethylation, acylation, esterification with hydroxyl group. The compound can be well known to those skilled in the art.

[0012] Further, the functional group-containing compound is selected from a compound containing any one of halogen, acyl chloride group, epoxy group, isocyanate, glycidyl ether.

[0013] Preferably, the functional group-containing compound is selected from any one or a combination of several of fatty acid acyl chloride, halogenated alkyl, epoxy alkyl, alkyl isocyanate, alkyl glycidyl ether, sodium chloroacetate, wherein the alkyl is preferably a saturated / unsaturated alkyl with ≤16 carbon atoms.

[0014] Optionally, the halogenated alkane can exemplarily be exemplified by n-octyl bromide, the alkyl isocyanate can exemplarily be exemplified by octadecyl isocyanate, and the like, the alkyl glycidyl ether can exemplarily be exemplified by butyl glycidyl ether, and the like, and the epoxy compound can exemplarily be exemplified by propylene oxide, butylene oxide, and the like.

[0015] Further, in the preparation of the chitin derivative, an aqueous solution of hydroxide / urea is used as the solvent, wherein the mass ratio of the hydroxide is 5-30%, the mass ratio of the urea is 5-30%, and the rest is water, and the reaction temperature is lower than -10℃.

[0016] Further, in the preparation of the chitin derivative, the molar ratio of chitin to the functional group-containing compound is (1-99):(99-1), for example, it can be 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 20:80, 30:70, 60:40, 50:50, 65:35, 78:22, 85:15, 88:12, 90:10, 95:5, 99:1, or any range between them.

[0017] According to still another aspect of the present application, there is provided a use of the above-mentioned chitin derivative binder in a solid-state battery electrolyte.

[0018] According to still another aspect of the present application, there is provided a full solid-state composite electrolyte film, comprising the following raw materials by weight: 0.2-10 parts of the chitin derivative binder, 0-40 parts of a lithium salt, and 50-99.6 parts of a solid-state electrolyte.

[0019] Further, the particle size of the solid-state electrolyte is not greater than 60μm, and preferably not greater than 30μm.

[0020] Further, the solid-state electrolyte is any one of an oxide, a sulfide, a halide, and an oxyhalide solid-state electrolyte, all of which are well known in the art.

[0021] Optionally, the sulfide solid-state electrolyte is one or more of a glass-ceramic type, a thio-LISICON type, and an argyrodite type, including but not limited to Li2S-P2S5, Li2S-P2S5-MS x , Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li7P3S 11 , Li9P3S9O3, Li 10.35Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 GeP2S 12 , Li6PS5X, Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 , Li 10 SiP2S 12 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , wherein M is selected from any one or a combination of at least two of Si, Ge or Sn, X is selected from any one or a combination of at least two of Cl, Br or I, and 0≤x≤2.

[0022] Further, the lithium salt is a lithium salt known to those skilled in the art, which can be an organic lithium salt or an inorganic lithium salt, and is not particularly limited.

[0023] Further, the solvent comprises any one or more of toluene, xylene, hexane, cyclohexane, isobutyl alcohol, halogenated alkane, ethyl acetate, isobutyl isobutyrate, ethylene carbonate, dimethyl carbonate, acetonitrile. The amount of the solvent is ≥10 mL for 1 g of the chitin derivative binder.

[0024] According to still another aspect of the present application, a preparation method of a full-solid composite electrolyte film is provided, comprising the following steps: According to a formula, the chitin derivative binder, the solid electrolyte and the lithium salt are uniformly mixed, and then wet-cast into a film, thereby obtaining the full-solid composite electrolyte film.

[0025] Further, the mixing method includes, but is not limited to, screw extrusion, stirring, gas stirring, ball milling, internal mixing, mixing, etc.

[0026] According to still another aspect of the present application, the full-solid composite electrolyte film is applied in a full-solid battery.

[0027] According to still another aspect of the present application, a monolithic full-solid battery is provided, which is obtained by directly laminating the composite electrolyte film and a lithium ion battery electrode sheet.

[0028] According to another aspect of the present application, a bipolar all-solid-state battery is provided, which is obtained by directly laminating the composite electrolyte film and a lithium ion battery electrode sheet.

[0029] Compared with the prior art, the present application has the following beneficial effects: 1. The present application is the first time. The present application is the first time to synthesize a chitin derivative binder, a new method and a new strategy for a composite solid electrolyte; 2. Chitin can be extracted from discarded shrimp and crab shells to obtain high-value raw materials, which is environmentally friendly and has high economic benefits. The prepared chitin derivative binder has good environmental degradability and is more environmentally friendly than traditional polymer binders; 3. The chitin contains a large number of functional groups, which are further derivatized to construct a high-performance composite solid electrolyte membrane system, which is of great significance to the industrialization of all-solid-state batteries.

[0030] 4. The derivatization method involved in the present application is simple and easy to operate. The induction conditions required for chitin derivatization are mild, the binding and film forming are convenient and fast, and it is beneficial to large-scale thin layering (<20 μm), which is beneficial to improving the energy density and safety, and improving the stability of the electrolyte; 5. The chitin derivative binder composite electrolyte provided by the present application has high flexibility and ionic conductivity, high voltage resistance, a wide electrochemical window, and is suitable for various electrode materials and existing lamination processes, and has a fast industrialization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 XRD test curve of the composite electrolyte and pure electrolyte prepared in Example 1.

[0032] Figure 2 Raman test curve of the composite electrolyte and pure electrolyte prepared in Example 1.

[0033] Figure 3 Mechanical test curve of the solid-state lithium battery electrolyte assembled in Example 1.

[0034] Figure 4 Ionic conductivity curve of the composite electrolyte prepared in Example 1.

[0035] Figure 5 Scanning electron microscope picture of the composite electrolyte prepared in Example 1.

[0036] Figure 6 Long cycle performance of the solid-state lithium battery assembled in Example 1 at room temperature at 0.5C.

[0037] Figure 7Charge-discharge curves of the solid-state lithium battery assembled for Example 1 at room temperature 0.5C for the first 100 cycles.

[0038] Figure 8 Long cycle performance of the solid-state lithium battery assembled for Example 2 at room temperature 0.5C.

[0039] Figure 9 Long cycle performance of the solid-state lithium battery assembled for Example 3 at room temperature 0.5C.

[0040] Figure 10 Long cycle performance of the solid-state lithium battery assembled for Example 4 at room temperature 0.5C. DETAILED DESCRIPTION

[0041] The following non-limiting examples can make the person skilled in the art more fully understand the present application, but in no way limit the present application. The following content is only an exemplary description of the scope claimed by the present application, and the person skilled in the art can make various changes and modifications to the application disclosed in the present application, and it should also belong to the scope claimed by the present application.

[0042] In the following specific examples, the sulfide electrolyte is Li7P3S 11 , the lithium salt is LiCl, it should be noted that the following examples are only examples of the sulfide electrolyte and lithium salt, and any lithium salt and sulfide electrolyte known to those skilled in the art can be replaced to achieve the effect of the present application, and does not limit the present application.

[0043] The present application will be further described in the following specific examples. The various chemical reagents used in the examples of the present application are obtained by conventional commercial routes unless otherwise specified.

[0044] Example 1 A method for preparing a chitin derivative, comprising the following steps: The extracted chitin raw material is added to a sufficient amount of a mixed solvent of 20% KOH / 15% urea / 65% water, stirred and dissolved at a low temperature of -15°C to obtain a viscous and transparent chitin aqueous solution. At -15°C, propylene oxide is slowly added to the above solution at a molar ratio of chitin: propylene oxide = 3:1, stirred for 24 hours, washed and dried to obtain 2-hydroxypropyl chitin, denoted as chitin derivative A1.

[0045] The embodiment also provides a solid-state electrolyte prepared from the above chitin derivative A1, and the specific method is as follows: the whole electrolyte preparation process is carried out in an argon atmosphere glove box (H2O <0.5 ppm, O2 <0.5 ppm). 1 g of chitin derivative A1 is dissolved in 10 mL of toluene, stirred at room temperature until completely dissolved, then 15 g of sulfide electrolyte and 4 g of lithium salt are added, and the reaction is continued to stir at room temperature for 2 h, then the post-reaction solution is formed into a film by casting, and the chitin derivative adhesive sulfide composite electrolyte film is obtained after drying on a glove box hot plate. The film is cut into a circular piece with a diameter of 10 mm to obtain the chitin derivative adhesive sulfide composite electrolyte. The composite electrolyte is tested by XRD, infrared, mechanical property, ion conductivity and scanning electron microscopy, and compared with the pure electrolyte, and the results are shown in Figures 1-5

[0046] The XRD results show that, compared with the pure electrolyte, the composite electrolyte does not appear an extra impurity peak, and presents good crystallinity, which indicates the accurate preparation of the chitin derivative. The infrared test results show that the composite electrolyte appears an extra absorption peak in the characteristic functional group region of the chitin derivative, which indicates that the chitin is successfully introduced as an adhesive. Compared with the mechanical property of the solid-state electrolyte film with butyl rubber as an adhesive (comparative example 1), the chitin derivative adhesive sulfide composite electrolyte film shows better mechanical property, and this excellent mechanical property can effectively inhibit the generation of dendrites in the battery operation. Figure 4 The results show that this composite electrolyte film shows smaller impedance, and excellent ion conductivity can effectively improve the transmission speed of lithium ions. Through the SEM test, the chitin derivative adhesive solid-state electrolyte shows excellent material compatibility and adhesion.

[0047] To verify the performance of the above solid-state electrolyte, an eight-system ternary nickel-cobalt-manganese (NCM811) is used as a positive electrode, and a lithium silicon is used as a negative electrode to obtain a solid-state NCM811 / lithium silicon battery with a chitin derivative adhesive sulfide composite electrolyte. The obtained solid-state battery is placed in a 30°C constant temperature box for 6 h, and then an electrochemical charge-discharge test is carried out by using a Wuhan Lan electric test system. The long cycle performance of the solid-state NCM811 / lithium silicon battery at room temperature at 0.5C and the charge-discharge curve of the first 100 cycles at room temperature at 0.5C are respectively shown in Figure 6 7

[0048] ​​​The results show that the solid-state NCM811 / lithium-silicon battery is tested at 0.5C in the voltage range of 2-4.3V (vs. Li+ / Li), and after 120 cycles, the capacity still remains at 144 mA / g, showing good electrochemical stability. The chitin derivative-bonded sulfide composite solid electrolyte of the application exhibits excellent ionic conductivity, providing a key basis for the battery to achieve excellent high-rate discharge performance and power density.

[0049] Example 2 A preparation method of a chitin derivative includes the following steps: The extracted chitin raw material is added to a mixed solvent of 20% KOH / 15% urea / 65% water, and is dissolved by stirring at a low temperature of-20°C to obtain a viscous and transparent chitin aqueous solution. At-20°C, chlorobutanol is slowly added to the above solution at a molar ratio of chitin: chlorobutanol = 2.5:1, and is stirred for 20 hours to obtain chlorobutyl chitin ether, which is denoted as chitin derivative A2.

[0050] The example also provides a solid electrolyte prepared from the above chitin derivative A2, and the specific method is as follows: the whole electrolyte preparation process is carried out in an argon atmosphere glove box (H2O<0.5 ppm, O2<0.5 ppm). 1g of chitin derivative A2 is dissolved in 20mL of toluene, and is stirred at room temperature until completely dissolved. Then, 15g of sulfide electrolyte and 4g of lithium salt are added, and the reaction is continued to stir at room temperature for 2h. Then, the reaction solution is formed into a film by casting, and is dried on a glove box hot plate to obtain a chitin derivative-bonded sulfide composite electrolyte film. The film is cut into a circular piece with a diameter of 10mm to obtain a chitin derivative-bonded sulfide composite electrolyte.

[0051] A solid-state NCM811 / lithium-silicon battery is assembled according to the method provided in Example 1 and using the composite electrolyte provided in the example. The obtained solid-state battery is placed in a 30°C constant temperature box for 6h, and then electrochemical charge-discharge test is carried out using a Wuhan Lan electric test system. The long cycle performance of the solid-state NCM811 / lithium-silicon battery at room temperature at 0.5C is measured as shown in Figure 8 .

[0052] Example 3 A preparation method of a chitin derivative includes the following steps: The extracted chitin raw material is added to a mixed solvent of 20% KOH / 15% urea / 65% water, and is dissolved by stirring at a low temperature of-20°C to obtain a viscous and transparent chitin aqueous solution. At-20°C, chlorobutanol is slowly added to the above solution at a molar ratio of chitin: chlorobutanol = 2.5:1, and is stirred for 20 hours to obtain chlorobutyl chitin ether, which is denoted as chitin derivative A2.

[0053] The present embodiment also provides a solid-state electrolyte prepared from the above chitin derivative A3, and the specific method is as follows: the whole electrolyte preparation process is carried out in an argon atmosphere glove box (H2O <0.5 ppm, O2 <0.5 ppm). 1 g of chitin derivative A3 is dissolved in 10 mL of toluene, stirred at room temperature until completely dissolved, then 15 g of sulfide electrolyte and 4 g of lithium salt are added, and the reaction is continued to stir at room temperature for 2 h, then the reaction solution is cast into a film, and after drying on the glove box hot plate, a chitin derivative bonded sulfide composite electrolyte film is obtained. The film is cut into a circular piece with a diameter of 10 mm to obtain a chitin derivative bonded sulfide composite electrolyte.

[0054] According to the method provided in embodiment 1, a solid-state NCM811 / lithium-silicon battery is assembled using the composite electrolyte provided in the present embodiment. The obtained solid-state battery is placed in a 30°C constant temperature box for 6 h, and then electrochemical charge-discharge test is carried out using a Wuhan Blue Electric Test System. The long cycle performance of the solid-state NCM811 / lithium-silicon battery at room temperature at 0.5C is as shown in Figure 9

[0055] Embodiment 4 A preparation method of a chitin derivative, comprising the following steps: The extracted chitin raw material is added to a mixed solvent of 15% KOH / 15% urea / 70% water, and stirred and dissolved at a low temperature of -25°C to obtain a viscous and transparent chitin aqueous solution. At -25°C, sodium chloroacetate is slowly added to the above solution at a molar ratio of chitin:sodium chloroacetate = 1.5:1, and stirred for 24 h, washed and dried to obtain carboxymethyl chitin, denoted as chitin derivative A4.

[0056] The present embodiment also provides a solid-state electrolyte prepared from the above chitin derivative A4, and the specific method is as follows: the whole electrolyte preparation process is carried out in an argon atmosphere glove box (H2O <0.5 ppm, O2 <0.5 ppm). 1 g of chitin derivative A4 is dissolved in 25 mL of toluene, stirred at room temperature until completely dissolved, then 15 g of sulfide electrolyte and 4 g of lithium salt are added, and the reaction is continued to stir at room temperature for 2 h, then the reaction solution is cast into a film, and after drying on the glove box hot plate, a chitin derivative bonded sulfide composite electrolyte film is obtained. The film is cut into a circular piece with a diameter of 10 mm to obtain a chitin derivative bonded sulfide composite electrolyte.

[0057] ​The solid-state NCM811 / lithium-silicon battery was assembled according to the method provided in Example 1 using the composite electrolyte provided in this example. The obtained solid-state battery was placed in a 30 °C thermostat for 6 h, and then electrochemical charge-discharge test was performed using a Wuhan Blue Electric Test System. The long cycle performance of the solid-state NCM811 / lithium-silicon battery at room temperature at 0.5 C was measured as shown in Figure 10

[0058] Comparative Example 1 This comparative example provides a solid-state electrolyte prepared from butyl nitrile rubber, according to the following method: the entire electrolyte preparation process was carried out in an argon atmosphere glove box (H2O < 0.5 ppm, O2 < 0.5 ppm). 1 g of butyl nitrile rubber was dissolved in 25 mL of toluene, stirred at room temperature until completely dissolved, then 15 g of sulfide electrolyte and 4 g of lithium salt were added, and the reaction was continued to stir at room temperature for 2 h. The reaction solution was then cast into a film, which was dried on a glove box hot plate to obtain a butyl nitrile rubber bonded sulfide composite electrolyte film. The film was cut into a 10 mm diameter disc to obtain a butyl nitrile rubber bonded sulfide composite electrolyte, and the mechanical properties of the composite electrolyte were tested.

[0059] The above description of the examples is to facilitate the understanding and use of the invention by those of ordinary skill in the art. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without having to go through creative labor. Therefore, the present application is not limited to the above examples, and improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.​

Claims

1. A chitin derivative adhesive, characterized in that, Its structural formula is shown in equation (I) or equation (II) below: （I）； In formula (I), R is independently selected from any one or more of H, XC=O-, alkyl, -CH2CH(OH)CH3, Y-NH-C=O-, -CH3(CH2), and -CH3COONa, where X and Y are alkyl groups; and n is an integer not less than 10.

2. The application of the chitin derivative binder according to claim 1 in all-solid-state batteries.

3. An all-solid-state composite electrolyte membrane, characterized in that, It comprises the following raw materials in parts by weight: 0.2-10 parts of the chitin derivative binder as described in claim 1, 0-40 parts of lithium salt, and 50-99.8 parts of solid electrolyte.

4. The all-solid-state composite electrolyte membrane according to claim 3, characterized in that, The particle size of the solid electrolyte is no greater than 60 μm.

5. The all-solid-state composite electrolyte membrane according to claim 4, characterized in that, The solid electrolyte is any one of oxide, sulfide, halide, or oxyhalide solid electrolytes.

6. The all-solid-state composite electrolyte membrane according to claim 5, characterized in that, The solid electrolyte is one or more of the following types: glass-ceramic, thio-LISICON, and argyrodite.

7. The method for preparing the all-solid-state composite electrolyte membrane according to any one of claims 3-6, characterized in that, The process includes the following steps: according to the formula, chitin derivatives, lithium salts, and solid electrolytes are mixed evenly, and then wet-cast into a film to obtain the final product.

8. The application of the all-solid-state composite electrolyte membrane according to any one of claims 3-6 in all-solid-state batteries.

9. A single-cell all-solid-state battery, characterized in that, It is obtained by directly stacking and assembling the composite electrolyte membrane as described in any one of claims 3-6 with lithium-ion battery electrodes.

10. A bipolar all-solid-state battery, characterized in that, It is obtained by directly stacking and assembling the composite electrolyte membrane as described in any one of claims 3-6 with lithium-ion battery electrodes.

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