Sodium-ion battery electrolyte with flame-retardant function, preparation method and application thereof

Abstract

The application discloses a sodium-ion battery electrolyte with a flame-retardant function and a preparation method and application thereof, and comprises the following components in parts by weight: 80-100 parts of a solvent, 18-26 parts of a sodium salt and 1-10 parts of an enhanced flame retardant; the preparation raw materials of the enhanced flame retardant comprise modified nano silicon dioxide; the preparation raw materials of the modified nano silicon dioxide comprise nano silicon dioxide, tannic acid and polyethylene imine. The application provides the sodium-ion battery electrolyte with the flame-retardant function and the preparation method and application thereof; the nano silicon dioxide has good thixotropy, fluidity and thickening property; the organic solvent can improve the dispersibility of the nano silicon dioxide in the electrolyte, makes the electrolyte more stable, and has excellent flame-retardant property.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a sodium-ion battery electrolyte with flame-retardant function, its preparation method, and its application. Background Technology

[0002] Sodium and lithium metal share similar physicochemical properties, and sodium is abundant and inexpensive in the Earth's crust, making sodium batteries a promising trend in future energy storage. However, with the increasing number of battery safety incidents, the safety of sodium-ion batteries has become a primary concern, mainly because sodium's high chemical reactivity makes the electrolyte more reactive and prone to combustion and explosion. Therefore, using flame-retardant or non-flammable electrolytes is an effective way to improve battery safety. While commercially available traditional organic carbonate electrolytes have high dielectric constants and excellent room-temperature performance, their highly flammable nature makes them unsuitable for the safety requirements of sodium-ion batteries.

[0003] Therefore, there is an urgent need for a sodium-ion battery electrolyte with flame-retardant properties and its preparation method to solve the above problems. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a sodium-ion battery electrolyte with flame-retardant properties, its preparation method, and its application. The modified nano-silica is well dispersed, and the all-solid-state sodium-ion battery assembled from this solid electrolyte exhibits high lithium-ion transport number and stable electrochemical properties.

[0005] A sodium-ion battery electrolyte with flame-retardant function according to a first aspect embodiment of the present invention comprises the following components in parts by weight:

[0006] 90-100 parts solvent, 20-26 parts sodium salt, and 1-10 parts flame retardant;

[0007] The raw materials for preparing the enhanced flame retardant include: modified nano-silica;

[0008] The raw materials for preparing the modified nano-silica include: nano-silica, tannic acid, and polyethyleneimine.

[0009] A sodium-ion battery electrolyte with flame-retardant function according to an embodiment of the present invention has at least the following beneficial effects:

[0010] This invention incorporates nano-silica, which exhibits excellent thixotropic, fluid, and thickening properties. Organic solvents enhance the dispersibility of nano-silica in the electrolyte, resulting in a more stable electrolyte and superior flame-retardant properties. Furthermore, this invention modifies the nano-silica by grafting tannic acid and polyethyleneimine onto the surface of the nano-silica particles. The tannic acid is linked to the amino groups of polyethyleneimine via phenolic hydroxyl groups, utilizing steric hindrance to improve the dispersibility of the nano-silica. The resulting electrolyte exhibits excellent high-temperature thermal stability. Polyethyleneimine contains coordinating nitrogen atoms, which promote sodium dissociation and provide channels for sodium ion transport. The nano-silica... The polar groups on the surface of silica can act as crosslinking points to promote the crosslinking of tannic acid and polyethyleneimine, increasing the content of amorphous parts in the system and facilitating the transport of sodium ions. By grafting polyethyleneimine onto the surface of nanoparticles, a steric hindrance effect can be generated between polyethyleneimine segments, inhibiting the crystallization of polyethyleneimine segments. Therefore, the modified nano-silica can play a greater role, and the ionic conductivity is greatly improved. The hydroxyl groups in tannic acid crosslink with sodium ions through coordination bonds to form a stable complex. Through chemical crosslinking, the bonding between molecules is stronger, ensuring the uniform deposition of sodium ions and inhibiting the growth of sodium dendrites and the occurrence of side reactions.

[0011] According to some embodiments of the present invention, the particle size of the nano-silica is 100-500 nm.

[0012] According to some embodiments of the present invention, the solvent is one of ethylene glycol dimethyl ether and triethylene glycol dimethyl ether, and the sodium salt is at least one of sodium hexafluorophosphate and sodium trifluoromethanesulfonate.

[0013] According to some embodiments of the present invention, the method for preparing the modified nano-silica includes mixing the nano-silica and the tannic acid and then adding polyethyleneimine for reaction.

[0014] According to some embodiments of the present invention, in the preparation of the modified nano-silica, the mixing temperature is 50-80°C.

[0015] According to some embodiments of the present invention, in the preparation of the modified nano-silica, the mixing time is 13-18 hours.

[0016] According to some embodiments of the present invention, the sodium salt includes at least one of sodium hexafluorophosphate and sodium trifluoromethanesulfonate.

[0017] According to some embodiments of the present invention, the enhanced flame retardant further includes an ammonium acid mixture.

[0018] According to some embodiments of the present invention, the ammonium acid mixture includes at least one of ammonium butyloctanoate, ammonium pentaborate, ammonium dodecanoate, and ammonium phosphate.

[0019] According to some embodiments of the present invention, the ammonium acid mixture includes ammonium butyl octanoate, ammonium pentaborate, ammonium dodecanoate, and ammonium phosphate; the weight ratio of the ammonium butyl octanoate, the ammonium pentaborate, the ammonium dodecanoate, and the ammonium phosphate is 1-2:3-4:1:0.5-1.

[0020] A method for preparing a sodium-ion battery electrolyte according to an embodiment of a second aspect of the present invention includes adding the sodium salt to the solvent and mixing, followed by adding an enhanced flame retardant and continuing mixing.

[0021] According to an embodiment of a third aspect of the present invention, an all-solid-state sodium-ion battery is provided, wherein the raw materials for preparing the all-solid-state sodium-ion battery include the sodium-ion battery electrolyte.

[0022] According to some embodiments of the present invention, the all-solid-state sodium-ion battery includes a positive electrode and a negative electrode.

[0023] According to some embodiments of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on the positive current collector.

[0024] According to some embodiments of the present invention, the positive current collector is aluminum foil.

[0025] According to some embodiments of the present invention, the positive electrode active material layer includes a positive electrode active material, a first conductive agent, and a first binder.

[0026] According to some embodiments of the present invention, the positive electrode active material includes at least one of Prussian blue, sodium vanadium phosphate, and sodium iron phosphate.

[0027] According to some embodiments of the present invention, the first conductive agent includes at least one of conductive graphite, carbon nanotubes and graphene.

[0028] According to some embodiments of the present invention, the first adhesive comprises polyvinylidene fluoride or styrene-butadiene rubber.

[0029] According to some embodiments of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector.

[0030] According to some embodiments of the present invention, the negative current collector comprises aluminum foil or copper foil.

[0031] According to some embodiments of the present invention, the negative electrode active material layer includes a negative electrode active material, a second conductive agent, and a second binder.

[0032] According to some embodiments of the present invention, the negative electrode active material comprises hard carbon and / or soft carbon.

[0033] According to some embodiments of the present invention, the second conductive agent includes at least one of conductive graphite, carbon nanotubes, and graphene.

[0034] According to some embodiments of the present invention, the second adhesive comprises any one of polyvinylidene fluoride, styrene-butadiene rubber, and sodium alginate. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below, with examples of the embodiments shown below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The following examples are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all conventional products that can be purchased commercially.

[0036] Example 1

[0037] This embodiment discloses a method for preparing a sodium-ion battery electrolyte with flame-retardant function, including the following steps:

[0038] The method for preparing modified nano-silica in this embodiment is as follows:

[0039] A1: Weigh a certain amount of nano-silica (particle size 100nm) to be coated, add Tris buffer and sonicate for 20min. Then weigh tannic acid, dissolve it in Tris buffer, pour it into the previously dispersed nano-silica solution, and rinse the beaker with a small amount of Tris buffer to remove any remaining solution. Cover the beaker with plastic wrap, make holes to allow oxygen to enter, and ensure that the concentration of tannic acid is 2g / L and the concentration of nano-silica is 1g / L. Sonicate the mixture for 15min, then place it in a 25℃ water bath and stir magnetically at 180r / min for 1h. After the reaction is complete, use deionized water as the washing solution, centrifuge twice at 8000r / min for 15min, freeze-dry in a freeze dryer, and then grind to obtain tannic acid-coated silica particles.

[0040] A2: First, dissolve polyethyleneimine in Tris solution, weigh tannic acid-coated silica particles, stir evenly, and react in a 50℃ water bath for 13 hours at a speed of 200 r / min. After the reaction is completed, dry at 50℃ to obtain modified nano silica with a polyimide concentration of 1.5 g / L.

[0041] A3: Mix ethylene glycol, ammonium acid, and modified nano-silica in a mixer, heat and stir for 25 minutes at a temperature of 65°C and a speed of 600 r / min to obtain an enhanced flame retardant.

[0042] Preparation of a flame-retardant sodium-ion battery electrolyte:

[0043] B1: Weigh out 80 parts by weight of ethylene glycol dimethyl ether, 18 parts by weight of sodium hexafluorophosphate and 1 part by weight of the enhanced flame retardant from Example 1, and set aside.

[0044] B1: Add sodium hexafluorophosphate to the solvent and mix evenly. Then add the flame retardant and continue mixing evenly to obtain the sodium-ion battery electrolyte with flame retardant function.

[0045] Example 2

[0046] This embodiment discloses a method for preparing an all-solid-state sodium-ion battery. The difference between this embodiment and Embodiment 1 is that in step A3, no ammonium acid mixture is added, while the other conditions are the same.

[0047] Example 3

[0048] This embodiment discloses a method for preparing an all-solid-state sodium-ion battery. The difference between this embodiment and Embodiment 1 is that in step A3, the ammonium acid mixture only includes ammonium butyloctanoate and ammonium pentaborate, while the other conditions are the same.

[0049] Comparative Example 1:

[0050] The difference between Comparative Example 1 and Example 1 is that no flame retardant is added.

[0051] Comparative Example 2:

[0052] The difference between Comparative Example 2 and Example 1 is that DOPO is used instead of the reinforcing flame retardant.

[0053] Comparative Example 3:

[0054] The difference between Comparative Example 3 and Example 1 is that unmodified nano-silica was used.

[0055] Comparative Example 4:

[0056] The difference between Comparative Example 4 and Example 1 is that no polyethyleneimine was added to the unmodified nano-silica.

[0057] Test Example 1

[0058] The electrolytes prepared in the above examples and comparative examples were subjected to performance tests, and the results are shown in Table 1:

[0059] The conductivity test method is as follows:

[0060] The electrochemical window was obtained using linear sweep voltammetry (LSV) with a Li / SPE / SS cell. A potential (relative to the Li electrode) was applied to the cell and scanned against the working electrode SS at a constant rate. The horizontal and vertical axes of the scan curve represent voltage and current, respectively. If the cell is in a steady state, the current does not change with increasing voltage and remains essentially zero. The potential corresponding to the inflection point or peak of the current sharp increase is the electrochemical window of the polymer solid electrolyte. During the test, the scan rate was 0.01 V / s, and the scan voltage range was 2.5 V-8 V vs Li+ / Li.

[0061] The lithium-ion transference number (LTN) of a solid electrolyte is the proportion of lithium ions that occupy all the ions transported between the positive and negative electrodes. It largely represents the electrochemical performance of a lithium battery, and its proportion directly reflects the battery's performance. The LTN is obtained using the steady-state constant voltage-current method (CA), employing a Li / SPE / Li battery. A small constant potential is applied to the battery, and the change in response current over time is recorded. The current is maximum at initial polarization; the initial current l0 is recorded. After reaching steady state, the steady-state current Iss is recorded. The LTN can be calculated using the formula t... + =I ss / I0 calculates to:

[0062] Where t represents the lithium ion transference number of the solid electrolyte, I0 represents the current at the beginning of polarization, and I ss This represents the current after reaching steady state. A constant voltage of 50mV was applied during the test. The results are shown in Table 1.

[0063] Table 1 Electrolyte Performance Tests

[0064]

[0065] The difference between Comparative Example 1 and Example 1 is that no flame retardant is added, and under these conditions, the service life is significantly shortened.

[0066] The difference between Comparative Example 2 and Example 1 is that DOPO was used instead of the reinforcing flame retardant, and the service life under this condition was shorter than that of Example 1.

[0067] The difference between Comparative Example 3 and Example 1 is that unmodified silica is added. Under this condition, nano-silica can play a certain flame retardant role, but it will agglomerate, resulting in a decrease in the conductivity of the system.

[0068] The difference between Comparative Example 4 and Example 1 is that: no polyethyleneimine was added for modification. Polyethyleneimine contains coordinating atoms N, which can promote the dissociation of sodium and provide a channel for the transport of sodium ions. Under the conditions of Comparative Example 4, the conductivity decreased.

[0069] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0070] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A sodium-ion battery electrolyte with flame-retardant function, characterized in that, Includes the following components by weight: 90-100 parts solvent, 20-26 parts sodium salt, and 1-10 parts flame retardant; The raw materials for preparing the enhanced flame retardant include: modified nano-silica; The raw materials for preparing the modified nano-silica include: nano-silica, tannic acid, and polyethyleneimine; The nano-silica particles are grafted with tannic acid and polyethyleneimine, with the tannic acid linked by phenolic hydroxyl groups and the amino groups of polyethyleneimine.

2. The sodium-ion battery electrolyte according to claim 1, characterized in that, The solvent is one of ethylene glycol dimethyl ether and triethylene glycol dimethyl ether, and the sodium salt is at least one of sodium hexafluorophosphate and sodium trifluoromethanesulfonate.

3. The sodium-ion battery electrolyte according to claim 1, characterized in that, The method for preparing the modified nano-silica includes mixing the nano-silica and the tannic acid, and then adding polyethyleneimine for reaction.

4. The sodium-ion battery electrolyte according to claim 3, characterized in that, The mixing temperature is 50~80℃.

5. The sodium-ion battery electrolyte according to claim 3, characterized in that, The mixing time is 13-18 hours.

6. The sodium-ion battery electrolyte according to claim 3, characterized in that, The sodium salt includes at least one of sodium hexafluorophosphate and sodium trifluoromethanesulfonate.

7. The sodium-ion battery electrolyte according to claim 1, characterized in that, The enhanced flame retardant also includes a mixture of ammonium acids.

8. The sodium-ion battery electrolyte according to claim 7, characterized in that, The ammonium acid mixture includes at least one of ammonium butyloctanoate, ammonium pentaborate, ammonium dodecanoate, and ammonium phosphate.

9. The sodium-ion battery electrolyte according to claim 8, characterized in that, The ammonium acid mixture includes ammonium butyl octanoate, ammonium pentaborate, ammonium dodecanoate, and ammonium phosphate; the weight ratio of the ammonium butyl octanoate, the ammonium pentaborate, the ammonium dodecanoate, and the ammonium phosphate is 1~2:3~4:1:0.5~1.

10. A method for preparing a sodium-ion battery electrolyte as described in any one of claims 1 to 9, characterized in that, include: After the sodium salt is added to the solvent and mixed, an enhanced flame retardant is added and the mixture is continued.

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