Sulfonate-based additive-containing electrolyte for sodium-ion battery, and use thereof

Abstract

A sulfonate-based additive-containing electrolyte for a sodium-ion battery, and the use thereof in the technical field of sodium-ion batteries. The sulfonate-containing metal organic film-forming additive can form a compact and uniform SEI film on the surface of an electrode, so as to stabilize interfaces of a positive electrode and a negative electrode. In addition, an electrostatic shielding layer is formed under the action of manganese ions, such that the generation of sodium dendritic crystals can be effectively inhibited.

Description

A sodium ion battery electrolyte containing a sulfonate-based additive and its application Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to an electrolyte for sodium ion batteries containing a sulfonate-based additive and applications thereof. Background Art

[0002] In recent years, sodium-ion batteries, as a new type of secondary battery, have abundant sodium resources and excellent high and low temperature performance. Against the backdrop of the "dual carbon" goal, emerging industries that use electrochemical energy storage as renewable energy have been rapidly developing. Among them, lithium-ion batteries (LIBs) have been widely used in power vehicles, 3C digital products, energy storage and other fields due to their advantages such as high energy density, good cycle performance, high operating voltage and long service life. With the rapid growth of market demand, the scale of lithium battery manufacturing has reached an unprecedented level. The problem that followed was that the price of lithium carbonate, the core raw material of the battery, once soared, and the cost of the entire battery manufacturing industry soared. Compared with lithium-ion batteries, sodium-ion batteries have the potential to adapt to high energy density and relatively low cost, so the research and development of sodium-ion batteries has gained momentum.

[0003] Sodium-ion batteries (SIBs) have become one of the most attractive and feasible battery technologies because sodium reserves are abundant and widely distributed compared to the lithium used in lithium-ion batteries (LIBs). In addition, the current collector of SIBs can use widely available and lighter aluminum instead of copper. As important components of the battery, the positive electrode material and the negative electrode material determine the overall performance indicators of the battery, but as the connection between the two, the electrolyte is also an extremely important link in the transport of sodium ions. However, the current exploration of sodium-ion batteries is mostly focused on the development of electrode materials and the improvement of performance, and there are relatively few reports on electrolytes. As an intermediate bridge connecting the positive and negative electrode material systems, the electrolyte plays a vital role, and the addition of a small amount of functional molecules can significantly improve the overall performance of the battery.

[0004] For example, the patent application with publication number CN107851847A provides a non-aqueous electrolyte and a non-aqueous electrolyte battery that can exhibit high output characteristics at low temperatures even when the battery has been used to a certain extent, and exhibits good high-rate characteristics at room temperature, and further can also exhibit sufficient performance at low temperatures even after storage at high temperatures. The present invention is characterized in that the following non-aqueous electrolyte is used, the non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent, and comprising a difluoroionic complex (1-Cis) with a cis stereo configuration represented by the general formula (1-Cis), and at least one compound selected from the group consisting of a cyclic sulfonate, a cyclic sulfonate having an unsaturated bond, a cyclic sulfate, a cyclic disulfonate, a chain disulfonate, a cyclic disulfonic anhydride, a nitrile-containing compound, a silyl phosphate derivative, and a silyl borate derivative. For another example, patent application publication number CN104508896A provides a non-aqueous electrolyte and a storage device using the non-aqueous electrolyte. The non-aqueous electrolyte is a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent. The non-aqueous electrolyte contains 0.001 to 5% of 1,3-dioxane and further contains 0.001 to 5% of at least one selected from a specific phosphate compound, a specific cyclic sulfonate compound, and a cyclic acid anhydride containing a side chain having an allylic hydrogen. The non-aqueous electrolyte can improve the electrochemical properties at high temperatures, thereby reducing not only the capacity retention rate after a high-temperature cycle test, but also the rate of increase in electrode thickness.

[0005] However, commercial sodium-ion batteries still have problems such as low cycle performance, low cycle retention rate and poor high-temperature storage performance. Therefore, there is an urgent need to explore an effective electrolyte to solve the above problems.

[0006] Summary of the Invention

[0007] Based on the problems of low cycle performance, low cycle retention rate and poor high-temperature storage performance of commercial sodium ion batteries in the prior art, the present invention provides an electrolyte for sodium ion batteries containing a sulfonate-based additive and its application.

[0008] In order to solve the above problems, the following technical solutions are adopted:

[0009] The present invention provides an electrolyte for sodium ion batteries containing a sulfonate-based additive, comprising a sodium salt, an ester organic solvent and an additive, and further comprising a sulfonate-based organic metal film-forming additive.

[0010] The general formula of the sulfonate-containing organic metal film-forming additive is [Mn(bipy)(H2O)4][3-OH-2,7-NDS];

[0011] Here, Mn represents manganese ion, bipy represents 4,4'-bipyridine, and 3-OH-2,7-NDS represents disodium 3-hydroxy-2,7-naphthalene disulfonate.

[0012] The present invention aims to develop a long-cycle sodium-ion battery by adding a metal organic film-forming special additive containing sulfonic acid esters to form a stable and dense solid electrolyte interface (SEI and CEI) film on the positive and negative electrode surfaces. Currently, there are three main methods to improve the chemical stability and thermal stability of carbonate-based electrolytes: (1) designing a high-concentration electrolyte; (2) introducing a diluent to design a local high-concentration electrolyte; and (3) introducing functional additives. The first two methods often increase the viscosity due to the increase in salt concentration, resulting in lower ion mobility. However, the introduction of sulfonic acid ester additives into ester-based electrolytes has good film-forming properties and low cost. The present invention explores the use of sulfonic acid ester-containing metal organic film-forming special additives. The sulfonic acid ester group has the function of forming positive and negative electrode films, thereby improving the cycle stability and high-temperature storage performance of sodium ions compared to traditional unsaturated carbonate additives. At the same time, under the action of metal ions, an electrostatic shielding layer is formed, which can effectively inhibit the formation of sodium dendrites.

[0013] Preferably, the sulfonic acid ester-containing organic metal film-forming additive is obtained by a substitution reaction between disodium 3-hydroxy-2,7-naphthalene disulfonate and manganese sulfate, and a coordination reaction between the obtained reactant and 4,4'-bipyridine.

[0014] Furthermore, 10-28 parts by weight of disodium 3-hydroxy-2,7-naphthalene disulfonate, 15-25 parts of manganese sulfate, 5-10 parts of 4,4'-bipyridine and 800-1200 parts of methanol solution are mixed and stirred for reaction for 30 minutes to obtain a sulfonic acid ester-containing organic metal film-forming additive.

[0015] Sodium salt and one or more solvents and additives are mixed to form a basic electrolyte, and then an organic metal film-forming additive is mixed with the basic electrolyte to form a sodium ion battery electrolyte suitable for room temperature.

[0016] The mass of the sulfonate-containing organic metal film-forming additive accounts for 0.5%-2% of the total mass of the sodium ion battery electrolyte.

[0017] In some embodiments of the present invention, the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium bis(oxalatoborate) (NaBOB), sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI);

[0018] The sodium salt is preferably sodium hexafluorophosphate;

[0019] The concentration of the sodium salt is 0.8-1.2 mol / L.

[0020] In some embodiments of the present invention, the ester organic solvent is selected from at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0021] Preferably, the ester organic solvent is diethyl carbonate, propylene carbonate, and ethylene carbonate; the mass percentage is (50-65%): (15-25%): (5-10%).

[0022] In some embodiments of the present invention, the additive is selected from conventional additives of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) and at least one of 1,3-propylene glycol cyclic sulfate (PCS), 1,3-propane sultone (PS), methylene methanedisulfonate (MMDS) and propenyl-1,3-propane sultone (PES);

[0023] The additive is preferably a common film-forming additive fluoroethylene carbonate (FEC).

[0024] The mass of the additive accounts for 0.8%-5% of the total mass of the sodium ion battery electrolyte. In the embodiment of the present invention, 1% of the total mass of the electrolyte is added as an example, but the invention is not limited thereto.

[0025] In some of the embodiments, the mass fraction of the sodium salt in the electrolyte containing the metal organic film-forming additive containing sulfonate is: in some of the embodiments, the mass percentage of the sodium salt is 10% to 20%, the mass percentage of the organic solvent is 70% to 90%, and the mass percentage of the additive is 1% to 10%.

[0026] The present invention also provides a sodium ion battery, comprising a positive electrode material, an electrolyte and a negative electrode material, wherein the electrolyte is the electrolyte for the sodium ion battery.

[0027] Preferably, the positive electrode material is a layered nickel-manganese positive electrode Na x Ni 0.5+y Mn 0.5-y O2, wherein x=0.9-1.1, y=0-0.2. The negative electrode material is hard carbon.

[0028] The present invention also provides a method for preparing an electrolyte containing the sulfonate-containing metal organic film-forming additive, comprising the following steps:

[0029] (1) Under an argon atmosphere, one or more organic solvents are mixed and stirred to obtain a uniform mixed solution, and the mixed solution is treated with molecular sieves for more than 48 hours to ensure that the water content is below 1 ppm;

[0030] (2) dissolving the sodium salt in the mixed solution of step (1);

[0031] (3) dissolving the metal organic film-forming additive in the mixed solution of step (2), stirring uniformly at room temperature to obtain the carbonate-based electrolyte containing sulfonic acid ester.

[0032] The present invention has the following beneficial effects:

[0033] The sulfonate-containing metal organic film-forming additive provided by the present invention can form a dense and uniform SEI film on the electrode surface, stabilize the positive and negative electrode interfaces, and at the same time, under the action of manganese ions, form an electrostatic shielding layer, which can effectively inhibit the generation of sodium dendrites. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a diagram showing the electrochemical test results of the electrolyte of Example 1 in the first week;

[0035] FIG2 is a diagram showing the electrochemical test results of the electrolyte of Example 2 in the first week;

[0036] FIG3 is a diagram showing the electrochemical test results of the electrolyte of Example 3 in the first week;

[0037] FIG4 is a diagram showing the electrochemical test results of the electrolyte of Example 4 in the first week;

[0038] FIG5 is a graph showing the electrical performance test results of batteries assembled with the electrolytes prepared in the examples and comparative examples. DETAILED DESCRIPTION

[0039] Example 1

[0040] A method for preparing a carbonate-based electrolyte containing a sulfonic acid ester compound, the preparation method comprising the following steps:

[0041] 17.4 g of disodium 3-hydroxy-2,7-naphthalene disulfonate, 24.1 g of manganese sulfate, 6.8 g of 4,4'-bipyridine and 900 ml of methanol solution were added to a stirring kettle and stirred at room temperature for 30 min to obtain the sulfonate-containing organic metal film-forming additive, recorded as D1.

[0042] Under an argon atmosphere, diethyl carbonate, propylene carbonate, and ethylene carbonate were mixed in a mass ratio of 53:20:9. To 100g of the mixed electrolyte, 17.5g of sodium hexafluorophosphate was added to give a concentration of 1.0mol / L. Fluorinated ethylene carbonate was then added at a concentration of 1% of the total mass of the electrolyte to form the base electrolyte. This electrolyte was designated E0. 1.5% D1 was then added, i.e., 1.5g of D1 was added to the base electrolyte. This electrolyte was designated E1.

[0043] Example 2

[0044] In this embodiment, the difference from Example 1 is that the content of the electrolyte additive is 2% by mass of the electrolyte solvent, that is, 2g of D1 is added to the basic electrolyte. This electrolyte is recorded as E2.

[0045] Example 3

[0046] In this embodiment, the difference from Example 1 is that the content of the electrolyte additive is 1% by mass of the electrolyte solvent, that is, 1g of D1 is added to the basic electrolyte. This electrolyte is recorded as E3.

[0047] Example 4

[0048] In this embodiment, the difference from Example 1 is that the electrolyte additive content is 0.5% by mass of the electrolyte solvent, that is, 0.5 g of D1 is added to the basic electrolyte. This electrolyte is recorded as E4.

[0049] Example 5

[0050] A method for preparing a carbonate-based electrolyte containing a sulfonic acid ester compound, the preparation method comprising the following steps:

[0051] 10 g of disodium 3-hydroxy-2,7-naphthalene disulfonate, 15 g of manganese sulfate, 5 g of 4,4'-bipyridine and 800 ml of methanol solution were added to a stirring kettle and stirred at room temperature for 30 min to obtain the sulfonate-containing organic metal film-forming additive, recorded as D2.

[0052] Under an argon atmosphere, diethyl carbonate, propylene carbonate, and ethylene carbonate were mixed in a mass ratio of 53:20:9. To 100g of the mixed electrolyte, 17.5g of sodium hexafluorophosphate was added to achieve a concentration of 1.0 mol / L. Fluorinated ethylene carbonate was then added at 1% of the total mass of the electrolyte to form the base electrolyte. This electrolyte, designated E0, was then added with 1.5% D2, i.e., 1.5g of D2 was added to the base electrolyte.

[0053] Example 6

[0054] A method for preparing a carbonate-based electrolyte containing a sulfonic acid ester compound, the preparation method comprising the following steps:

[0055] 28 g of disodium 3-hydroxy-2,7-naphthalene disulfonate, 25 g of manganese sulfate, 10 g of 4,4'-bipyridine and 1200 ml of methanol solution were added to a stirring kettle and stirred at room temperature for 30 min to obtain the sulfonate-containing organic metal film-forming additive, recorded as D3.

[0056] Under an argon atmosphere, diethyl carbonate, propylene carbonate, and ethylene carbonate were uniformly mixed in a mass ratio of 53:20:9. To 100g of the mixed electrolyte, 17.5g of sodium hexafluorophosphate was added to achieve a concentration of 1.0 mol / L. Fluorinated ethylene carbonate was then added at 1% of the total mass of the electrolyte to form the base electrolyte. This electrolyte, designated E0, was then added with 1.5% D3 (i.e., 1.5g of D3 was added to the base electrolyte).

[0057] Comparative Example 1

[0058] In this embodiment, the difference from Example 1 is that D1 is replaced with a film-forming additive PES, and the content of the electrolyte additive accounts for 1.5% by mass of the electrolyte solvent, that is, 1.5 g of PES is added to the basic electrolyte.

[0059] Comparative Example 2

[0060] In this embodiment, the difference from Example 1 is that D1 is replaced with a film-forming additive PS. The content of the electrolyte additive accounts for 1.5% of the electrolyte solvent by mass, that is, 1.5 g of PS is added to the basic electrolyte.

[0061] Comparative Example 3

[0062] In this embodiment, the difference from Example 1 is that D1 is replaced with a film-forming additive PCS electrolyte additive content of 1.5% by mass ratio of the electrolyte solvent, that is, 1.5g PCS is added to the basic electrolyte.

[0063] Test Example 1

[0064] (1) Preparation of positive electrode

[0065] The positive electrode materials (NaNi 0.5 Mn 0.5 O2), ultrafine carbon powder (Super-P), polyvinylidene fluoride (PVDF), and then disperse them in NMP (N-methylpyrrolidone). Stir and disperse them until they are stable and uniform under the action of a vacuum disperser to obtain a positive electrode slurry; after filtering the positive electrode slurry, evenly coat it on both sides of aluminum foil; after rolling to a thickness of 120μm, die-cut to obtain a positive electrode sheet.

[0066] (2) Preparation of negative electrode sheet

[0067] The negative electrode material (hard carbon), ultrafine carbon powder (Super-P), styrene-butadiene rubber (SBR) and LA glue are mixed in a mass ratio of 96:1.5:3 (wt%), and then an appropriate amount of deionized water is added. The mixture is stirred and dispersed in a vacuum disperser until it is stable and uniform to obtain a negative electrode slurry; the negative electrode slurry is filtered and evenly coated on both sides of aluminum foil; the negative electrode sheet is obtained by rolling to a thickness of 167 μm and die-cutting.

[0068] (3) Preparation of sodium ion batteries

[0069] The positive electrode sheet, the negative electrode sheet and the separator were stacked and welded to the tabs to obtain a bare cell. The bare cell was placed in an aluminum-plastic film package and pre-sealed. Then, 190 g of the electrolyte prepared in the embodiment and the comparative example was injected on both sides of the separator, and then the sodium ion battery was obtained after the secondary sealing, formation and capacity separation processes.

[0070] Normal temperature cycle test:

[0071] At 25°C, the sodium-ion battery after capacity separation was charged at a constant current and constant voltage of 1C to 3.90V, with a cut-off current of 0.05C, and then discharged at a constant current of 1C to 1.5V. This constituted a charging cycle. The battery was then cycled 200 times under the above conditions.

[0072] The first-cycle coulombic efficiency is the discharge capacity of the corresponding capacity at 1C / the discharge capacity of the capacity, and its calculation formula is:

[0073] Discharge capacity of the divided capacity / discharge capacity of the divided capacity×100%;

[0074] After 200 cycles of charge and discharge, the 200th cycle retention rate is calculated using the following formula:

[0075] 200th cycle discharge capacity / first cycle discharge capacity × 100%.

[0076] High temperature storage performance test:

[0077] The battery was charged at room temperature at 1C constant current and constant voltage to 3.9V, with a cut-off of 0.05C. The battery was then discharged at 1C constant current with a cut-off of 1.5V. The average capacity was calculated after three cycles as the initial capacity C0, and the volume of the tested sodium-ion battery was V0. The battery was charged at room temperature at 1C constant current and constant voltage to 3.9V, with a cut-off of 0.05C. The battery was then placed in a high-temperature test cabinet and stored at 55°C for 7 days.

[0078] Table 1 shows the battery electrical performance test results of Examples 1-4 and Comparative Examples 1-3.

[0079] According to the results in Table 1 and Figures 1-5: Compared with Comparative Examples 1-3, the sodium ion batteries of Examples 1-4 have been greatly improved in terms of room temperature cycling and high temperature storage.

Claims

1. An electrolyte for a sodium ion battery containing a sulfonate-based additive, comprising a sodium salt, an ester organic solvent, and an additive, characterized in that: Also included is a sulfonate-containing organic metal film-forming additive, wherein the general formula of the sulfonate-containing organic metal film-forming additive is: [Mn(bipy)(H2O)4][3-OH-2,7-NDS]; Here, Mn represents manganese ion, bipy represents 4,4'-bipyridine, and 3-OH-2,7-NDS represents disodium 3-hydroxy-2,7-naphthalene disulfonate.

2. The sodium ion battery electrolyte according to claim 1, wherein The sulfonic acid lipid-containing organic metal film-forming additive is obtained by a substitution reaction between disodium 3-hydroxy-2,7-naphthalene disulfonate and manganese sulfate, and a coordination reaction between the obtained reactant and 4,4'-bipyridine.

3. The sodium ion battery electrolyte according to claim 2, characterized in that By weight, 10-28 parts of 3-hydroxy-2,7-naphthalene disulfonic acid disodium, 15-25 parts of manganese sulfate, 5-10 parts of 4,4'-bipyridine and 800-1200 parts of methanol solution are mixed and stirred for reaction for 30 minutes to obtain a sulfonic acid ester-containing organic metal film-forming additive.

4. The sodium ion battery electrolyte according to claim 1, wherein The mass of the sulfonate-containing organic metal film-forming additive accounts for 0.5%-2% of the total mass of the sodium ion battery electrolyte.

5. The sodium ion battery electrolyte according to claim 1, wherein The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(oxalatoborate), sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide; The concentration of the sodium salt is 0.8-1.2 mol / L.

6. The electrolyte for sodium ion batteries according to claim 1, characterized in that The ester organic solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate.

7. The electrolyte for sodium ion batteries according to claim 1, characterized in that The additive is selected from at least one of vinylene carbonate, fluoroethylene carbonate, 1,3-propylene glycol cyclic sulfate, 1,3-propane sultone, methylene methanedisulfonate and propenyl-1,3-propane sultone; The mass of the additive accounts for 0.8%-5% of the total mass of the electrolyte for the sodium ion battery.

8. A sodium ion battery comprising a positive electrode material, an electrolyte and a negative electrode material, characterized in that: The electrolyte is the electrolyte for sodium ion batteries according to any one of claims 1 to 7.

9. The sodium ion battery according to claim 8, characterized in that The positive electrode material is a layered nickel-manganese positive electrode Na x Ni 0.5+y Mn 0.5-y O2, where x = 0.9 ~ 1.1, y = 0 ~ 0.

2.

10. The sodium ion battery according to claim 8, characterized in that The negative electrode material is hard carbon.

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