Electrolyte additive, composition for high-voltage electrolyte, high-voltage electrolyte and preparation method thereof, and lithium ion battery

Abstract

The invention relates to the technical field of electrolytes, and discloses an electrolyte additive, a composition for a high-voltage electrolyte, the high-voltage electrolyte, a preparation method of the high-voltage electrolyte and a lithium ion battery. The additive comprises a component A, a component B and a component C in a mass ratio of 1: (0.2-1.5): (0.2-2), the component A is tripropargyl phosphate; the component B is selected from at least one of triethyl borate, tripropyl borate and tributyl borate; the component C is selected from at least one of 3-aminopropyltriethoxysilane, 1, 3-divinyltetramethyldisiloxane, trimethoxy (3, 3, 3-trifluoropropyl) silane and triethoxy (pentafluorophenyl) silane, and the component C is selected from at least one of 3-aminopropyltriethoxysilane, 1, 3-divinyltetramethyldisiloxane, trimethoxy (3, 3, 3-trifluoropropyl) silane and triethoxy (pentafluorophenyl) silane. The electrolyte additive provided by the invention has an excellent application prospect in the field of high-voltage electrolyte. The high-voltage electrolyte provided by the invention has good stability and oxidation resistance, and can be applied in a high-voltage range of 3.0-5.0 V.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, and particularly to electrolyte additives, compositions for high-voltage electrolytes, high-voltage electrolytes and their preparation methods, and lithium-ion batteries. Background Art

[0002] With the iterative update of new energy battery technology, how to further improve the energy density of batteries has become a hot topic of current research.

[0003] Currently, the power battery market is dominated by the technical routes of lithium iron phosphate and ternary materials. However, the energy density of lithium iron phosphate batteries has been developed close to the limit, and their low-temperature performance is poor; ternary batteries use expensive metals such as cobalt, resulting in relatively high costs and poor high-temperature safety.

[0004] Therefore, in order to further seek batteries with high energy density, low cost, good low-temperature performance, and safety and stability, the market urgently needs new high-voltage material systems to change this situation.

[0005] In recent years, a series of industrialized high-voltage cathode materials such as layered lithium-rich materials, LiNi x MnyCo 1-x-y O 2 and LiNi 0.5 Mn 1.5 O 4 have come into people's view. Unfortunately, traditional electrolytes will undergo irreversible oxidative decomposition on the surface of the positive electrode at high voltages, resulting in a series of side reactions such as gas generation, battery swelling, electrode structure damage, transition metal dissolution, and increased polarization voltage, thereby leading to the attenuation of the cycle performance of high-voltage cathode materials.

[0006] The problem of high-voltage oxidation resistance of electrolytes has become a limiting factor in the development of high-energy-density lithium batteries, and it is urgent to study new high-voltage electrolyte systems.

[0007] CN119009113A discloses a non-aqueous electrolyte for a 4.53V high-voltage lithium-ion battery with lithium cobaltate. The non-aqueous electrolyte contains a non-aqueous organic solvent, an electrolyte lithium salt, and an additive. The additive contains a conventional additive and an isocyanate additive having the structure of formula (Ⅰ). The non-aqueous organic solvent contains a fluorinated carboxylic acid ester solvent having the structure of formula (Ⅱ). The structures of formula (Ⅰ) and formula (Ⅱ) are as follows:

[0008]

[0009] Among them, R 1 is independently selected from aromatic hydrocarbons, methyl, ethyl, trifluoromethyl, trifluoroethyl, or other halogenated hydrocarbons. The aromatic hydrocarbon ring may be connected with alkyl, alkenyl, alkynyl, aromatic group, isocyanate group, or halogen; the R2 and R 3 are each independently selected from any one of aromatic hydrocarbons, methyl, ethyl-based alkyl groups, and alkenyl, alkynyl, and fluoroalkyl groups, and the number of carbon atoms in the alkyl and fluoroalkyl groups is less than 4. The conventional additives are selected from one or more of fluoroethylene carbonate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, 1,2-bis(cyanoethoxy)ethane, 1,3-propane sultone, 1,3-propene sultone, vinylene carbonate, ethylene sulfate, tris(trimethyl)silyl borate, and tris(trimethyl)silyl phosphonate borate, tris(tripropargyl) phosphate, and tris(triallyl) phosphate. However, the electrolyte in this prior art has weak antioxidant ability and is difficult to adapt to high-voltage material systems above 4.6V. SUMMARY OF THE INVENTION

[0010] The object of the present invention is to overcome the problems in the prior art that the voltage window of the traditional carbonate electrolyte is relatively narrow and it is easily oxidized.

[0011] To achieve the above object, in the first aspect of the present invention, an electrolyte additive is provided. The additive contains components A, B, and C in a mass ratio of 1:(0.2 - 1.5):(0.2 - 2);

[0012] Component A is tripropargyl phosphate;

[0013] Component B is selected from at least one of triethyl borate, tripropyl borate, and tributyl borate;

[0014] Component C is selected from at least one of 3-aminopropyltriethoxysilane, 1,3-divinyltetramethyldisiloxane, trifluoropropyltrimethoxysilane, and triethoxy(pentafluorophenyl)silane.

[0015] In the second aspect of the present invention, a composition for a high-voltage electrolyte is provided. The composition contains a lithium salt, an organic solvent, and an electrolyte additive;

[0016] Based on the total mass of the composition, the content of the lithium salt is 10wt% - 16wt%, the content of the organic solvent is 75wt% - 85wt%, and the content of the electrolyte additive is 0.1wt% - 10wt%;

[0017] Based on the total mass of the organic solvent, the organic solvent is a combination of 10wt% - 40wt% of solvent I and 60wt% - 90wt% of solvent II;

[0018] Solvent I is selected from at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0019] The solvent II is difluoroethylene carbonate, methyltrifluoroethyl carbonate and fluoroethylene carbonate with a mass ratio of 1:(1 - 2.5):(0.5 - 1.5);

[0020] The electrolyte additive is the electrolyte additive described in the first aspect above.

[0021] The third aspect of the present invention provides a method for preparing a high-voltage electrolyte, which includes: mixing the components in the composition of the high-voltage electrolyte described in the second aspect above to obtain the high-voltage electrolyte.

[0022] The fourth aspect of the present invention provides a high-voltage electrolyte prepared by the method described in the third aspect above.

[0023] The fifth aspect of the present invention provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte;

[0024] The electrolyte is the high-voltage electrolyte described in the fourth aspect above.

[0025] Through the above technical solutions, the present invention has at least the following advantages:

[0026] (1) The additive provided by the present invention can make the constructed interface film more compact, and can more effectively reduce the dissolution of positive electrode material ions during the application in the high-voltage electrolyte of lithium-ion batteries, thereby making the high-voltage electrolyte more stable.

[0027] (2) The high-voltage electrolyte prepared by using the composition for high-voltage electrolyte provided by the present invention has good oxidation resistance and can be applied in a high-voltage system of 5V.

[0028] (3) The high-voltage electrolyte provided by the present invention can reduce gas generation, inhibit the dissolution of transition metal ions in the positive electrode material and the growth rate of cycle impedance when applied in a lithium-ion battery system (especially the lithium nickel manganese oxide system), and effectively improve the cycle life and storage performance of the battery. Detailed Embodiments

[0029] The endpoints and any values disclosed in this article for a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0030] As described above, the first aspect of the present invention provides an electrolyte additive, which contains components A, B and C with a mass ratio of 1:(0.2 - 1.5):(0.2 - 2);

[0031] Component A is triallyl phosphate;

[0032] Component B is selected from at least one of triethyl borate, tripropyl borate, and tributyl borate;

[0033] Component C is selected from at least one of 3-aminopropyltriethoxysilane, 1,3-divinyltetramethyldisiloxane, trifluoropropyltrimethoxysilane, and triethoxy(pentafluorophenyl)silane.

[0034] Preferably, the additive contains Component A, Component B, and Component C in a mass ratio of 1:(0.5 - 1):(0.5 - 1). The inventors of the present invention have found that in this preferred case, the obtained additive can make the constructed interfacial film more compact and can more effectively reduce the dissolution of cathode material ions during the application to high-voltage electrolytes for lithium-ion batteries.

[0035] As described above, the second aspect of the present invention provides a composition for high-voltage electrolytes, which contains a lithium salt, an organic solvent, and an electrolyte additive;

[0036] Based on the total mass of the composition, the content of the lithium salt is 10 wt% - 16 wt%, the content of the organic solvent is 75 wt% - 85 wt%, and the content of the electrolyte additive is 0.1 wt% - 10 wt%;

[0037] Based on the total mass of the organic solvent, the organic solvent is a combination of 10 wt% - 40 wt% of Solvent I and 60 wt% - 90 wt% of Solvent II;

[0038] Solvent I is selected from at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0039] Solvent II is difluoroethylene carbonate, methyltrifluoroethyl carbonate, and fluoroethylene carbonate in a mass ratio of 1:(1 - 2.5):(0.5 - 1.5);

[0040] The electrolyte additive is the electrolyte additive described in the first aspect above.

[0041] Preferably, Solvent I is propylene carbonate and / or ethylene carbonate.

[0042] In a preferred case, Solvent II is difluoroethylene carbonate, methyltrifluoroethyl carbonate, and fluoroethylene carbonate in a mass ratio of 1:(1.4 - 2.0):(0.7 - 1.5). The inventors of the present invention have found that in this preferred case, the prepared high-voltage electrolyte has better oxidation stability.

[0043] Preferably, based on the total mass of the electrolyte, the content of the electrolyte additive is 5.0 - 8.0 wt%. The inventors of the present invention have found that in this preferred case, the oxidation stability of the prepared high-voltage electrolyte is better.

[0044] According to a preferred specific embodiment, based on the total mass of the organic solvent, the organic solvent is a combination of 10 - 30 wt% of solvent I and 70 - 90 wt% of solvent II.

[0045] According to another preferred specific embodiment, the lithium salt is LiN(SO 2 F) 2 and LiPF 6 .

[0046] In the present invention, LiN(SO 2 F) 2 refers to lithium bis(fluorosulfonyl)imide salt (abbreviated as LiFSI).

[0047] As described above, the third aspect of the present invention provides a method for preparing a high-voltage electrolyte, which includes: mixing each component in the composition of the high-voltage electrolyte described in the second aspect above to obtain the high-voltage electrolyte.

[0048] In order to obtain a more uniform and stable high-voltage electrolyte, the present invention provides a preferred specific embodiment. The method for preparing the high-voltage electrolyte includes:

[0049] S1: First, mix the lithium salt with the organic solvent in 3 - 5 times by first stirring to obtain a mixed solution I;

[0050] S2: Second, stir and mix the additive with the mixed solution I to obtain the high-voltage electrolyte.

[0051] Preferably, the conditions for the first stirring and mixing include: the temperature is -12°C to -8°C, and the rotation speed is 500 - 1000 rpm.

[0052] Preferably, the conditions for the second stirring and mixing include: the temperature is 10 - 25°C, and the rotation speed is 500 - 1000 rpm.

[0053] As described above, the fourth aspect of the present invention provides a high-voltage electrolyte prepared by the method described in the third aspect above.

[0054] As described above, the fifth aspect of the present invention provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte;

[0055] The electrolyte is the high-voltage electrolyte described in the fourth aspect above.

[0056] In order to obtain a lithium-ion battery with more excellent electrochemical performance, preferably, the positive active material of the positive electrode sheet is selected from at least one of layered lithium-rich materials, LiNi x MnyCo 1-x-y O 2 and LiNi 0.5 Mn 1.5 O 4 .

[0057] Preferably, the negative active material of the negative electrode sheet is selected from at least one of carbon materials (natural graphite, artificial graphite) and silicon materials (silicon-carbon materials, silicon-oxygen materials).

[0058] It should be noted that the present invention has no special requirements for the selection of the separator, and those skilled in the art can select it according to needs. Exemplarily, the separator is a PE separator.

[0059] In the following examples, unless otherwise specified, the instruments, reagents, materials, etc. involved are all conventional instruments, reagents, materials, etc., and can be obtained through regular commercial channels. Among them, unless otherwise stated, the reagents used are commercially available analytical pure products.

[0060] Component A:

[0061] Component A-1: Tripropargyl phosphate.

[0062] Component B:

[0063] Component B-1: Tributyl borate.

[0064] Component B-2: Tripropyl borate.

[0065] Component C:

[0066] Component C-1: 1,3-Divinyltetramethyldisiloxane.

[0067] Component C-2: Triethoxy(pentafluorophenyl)silane.

[0068] Lithium salt: LiN(SO 2 F) 2 and LiPF 6 .

[0069] Table 1

[0070] Electrolyte Additive Formulation Formulation 1 Formulation 2 Formulation 3 Component A Type Component A-1 Same as Formulation 1 Same as Formulation 1 Mass / g 3 Same as Formulation 1 2.8 Component B Type Component B-1 Component B-2 Same as Formulation 1 Mass / g 2 Same as Formulation 1 1.2 Component C Type Component C-1 Component C-2 Same as Formulation 1 Mass / g 2 Same as Formulation 1 3 Naming of Electrolyte Additive TJ-1 TJ-2 TJ-3

[0071] Continued Table 1

[0072]

[0073] Example 1

[0074] This example is used to illustrate the preparation of a high-voltage electrolyte according to the formulation in Table 2 and the method described as follows:

[0075] S1: First, divide the lithium salt into 5 equal parts and stir and mix it with the organic solvent for the first time to obtain a mixed solution I;

[0076] S2: Stir and mix the additive with the mixed solution I for the second time to obtain the high-voltage electrolyte.

[0077] The conditions for the first stirring and mixing include: the temperature is -10°C and the rotation speed is 800 rpm.

[0078] The conditions for the second stirring and mixing include: the temperature is 23°C and the rotation speed is 600 rpm.

[0079] Example 2

[0080] This example is carried out by a method similar to that of Example 1, the difference being: the formulation is different; specifically, refer to Table 2, and a high-voltage electrolyte is prepared.

[0081] Example 3

[0082] This example is carried out by a method similar to that of Example 1, the difference being: in this example, an equal mass of electrolyte additive TJ-3 is used to replace electrolyte additive TJ-1 in Example 1;

[0083] The unlisted parts are the same as those in Example 1, and a high-voltage electrolyte is prepared.

[0084] Example 4

[0085] This example is carried out by a method similar to that of Example 1, the difference being: on the basis of keeping the contents of solvent I and solvent II unchanged, the mass ratio of vinylene carbonate difluoride, methyl trifluoroethyl carbonate and fluoroethylene carbonate in solvent II is adjusted to 1:2.5:0.5;

[0086] The unlisted parts are the same as those in Example 1, and a high-voltage electrolyte is prepared.

[0087] Example 5

[0088] This example is carried out by a method similar to that of Example 1, the difference being: the dosage of the electrolyte additive is adjusted to 4.5 g;

[0089] The unlisted parts are the same as those in Example 1, and a high-voltage electrolyte is prepared.

[0090] Comparative Example 1

[0091] This comparative example was carried out in a similar manner to Example 1, except that in this comparative example, an equal mass of electrolyte additive TJ-D1 was used to replace electrolyte additive TJ-1 in Example 1;

[0092] Parts not listed were the same as those in Example 1, and a high-voltage electrolyte was prepared.

[0093] Comparative Example 2

[0094] This comparative example was carried out in a similar manner to Example 1, except that in this comparative example, an equal mass of electrolyte additive TJ-D2 was used to replace electrolyte additive TJ-1 in Example 1;

[0095] Parts not listed were the same as those in Example 1, and a high-voltage electrolyte was prepared.

[0096] Comparative Example 3

[0097] This comparative example was carried out in a similar manner to Example 1, except that in this comparative example, an equal mass of electrolyte additive TJ-D3 was used to replace electrolyte additive TJ-1 in Example 1;

[0098] Parts not listed were the same as those in Example 1, and a high-voltage electrolyte was prepared.

[0099] Comparative Example 4

[0100] This comparative example was carried out in a similar manner to Example 1, except that in this comparative example, an equal mass of electrolyte additive TJ-D4 was used to replace electrolyte additive TJ-1 in Example 1;

[0101] Parts not listed were the same as those in Example 1, and a high-voltage electrolyte was prepared.

[0102] Comparative Example 5

[0103] This comparative example was carried out in a similar manner to Example 1, except that in this comparative example, an equal mass of electrolyte additive TJ-D5 was used to replace electrolyte additive TJ-1 in Example 1;

[0104] Parts not listed were the same as those in Example 1, and a high-voltage electrolyte was prepared.

[0105] Table 2

[0106]

[0107] Test Example

[0108] 1. Prepare a 1.5 Ah lithium-ion soft-pack battery

[0109] At a temperature of 23±5°C and a relative humidity of ≤20%, the positive electrode sheet (spinel LiNi 0.5 Mn 1.5 O 4 material), the negative electrode sheet (artificial graphite + CVD silicon-carbon material, the mass ratio of artificial graphite to CVD silicon-carbon material is 95:5), and the separator (PE separator) are assembled into a bare battery cell in sequence by the lamination process; then a 1.5Ah finished lithium-ion soft-pack battery (LNMO / / Gr.@Si / C soft-pack battery) is obtained through processes such as baking-injection-forming-aging-capacity grading. The injection coefficient is 4.5g / Ah (that is, 4.5g of electrolyte is injected into the battery cell per Ah of capacity), and the electrolyte type is each high-voltage electrolyte prepared in the above examples.

[0110] The electrochemical performance of the prepared lithium-ion soft-pack battery is tested by a battery test system, as follows:

[0111] Cycling performance test method: At 25°C, the 1.5Ah lithium-ion soft-pack battery after capacity grading is charged at a constant current and voltage of 1.0C (1.0C = 1500mA) to 4.85V with a cut-off current of 0.05C, and then discharged at a constant current of 1.0C to 3.4V. This cycle is repeated. After 200 charge-discharge cycles, the cycling capacity retention rate is calculated. The calculation formula is as follows:

[0112] Capacity retention rate at the 200th cycle (%) = (discharge capacity at the 200th cycle / discharge capacity at the first cycle) × 100%;

[0113] Capacity retention rate after storage at 45°C for 7 days (%) = (discharge capacity of the 100% SOC battery cell after storage at 45°C for 7 days / first discharge capacity) × 100%; The results are shown in Table 3:

[0114] Table 3

[0115]

[0116] It can be seen from the above results that the additive provided by the present invention has good application in the high-voltage electrolyte of lithium-ion batteries. Applying the high-voltage electrolyte provided by the present invention to the lithium-ion battery system enables the lithium-ion battery to have excellent cycle life and storage performance.

[0117] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An electrolyte additive, characterized in that: The additive contains component A, component B and component C in a mass ratio of 1:(0.2-1.5):(0.2-2); The component A is tripropargyl phosphate; The component B is selected from at least one of triethyl borate, tripropyl borate and tributyl borate; The component C is selected from at least one of 3-aminopropyltriethoxysilane, 1,3-divinyltetramethyldisiloxane, trifluoropropanetrimethoxysilane and triethoxy(pentafluorophenyl)silane.

2. The electrolyte additive according to claim 1, characterized in that: The additive contains the component A, the component B and the component C in a mass ratio of 1:(0.5-1):(0.5-1).

3. A composition for a high voltage electrolyte, characterized in that: The composition contains lithium salt, organic solvent and electrolyte additive; Based on the total mass of the composition, the content of the lithium salt is 10wt%-16wt%, the content of the organic solvent is 75wt%-85wt%, and the content of the electrolyte additive is 0.1wt%-10wt%; Based on the total mass of the organic solvent, the organic solvent is a combination of 10wt%-40wt% of solvent I and 60wt%-90wt% of solvent II; The solvent I is selected from at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; The solvent II is difluoroethylene carbonate, methyl trifluoroethyl carbonate and fluoroethylene carbonate in a mass ratio of 1: (1-2.5): (0.5-1.5); The electrolyte additive is the electrolyte additive according to claim 1 or 2.

4. The composition according to claim 3, characterized in that The solvent II is difluoroethylene carbonate, methyl trifluoroethyl carbonate and fluoroethylene carbonate in a mass ratio of 1:(1.4-2.0):(0.7-1.5).

5. The composition according to claim 3 or 4, characterized in that Based on the total mass of the electrolyte, the content of the electrolyte additive is 5.0-8.0wt%.

6. The composition according to claim 3 or 4, characterized in that Based on the total mass of the organic solvent, the organic solvent is a combination of 10-30 wt % of solvent I and 70-90 wt % of solvent II.

7. The composition according to claim 3 or 4, characterized in that The lithium salt is LiN(SO2F)2 and LiPF6 in a mass ratio of 1:(8-12).

8. A method for preparing a high voltage electrolyte, characterized in that: The method comprises: mixing the components in the composition for high-voltage electrolyte according to any one of claims 3 to 7 to obtain the high-voltage electrolyte.

9. A high voltage electrolyte prepared by the method according to claim 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; The electrolyte is the high voltage electrolyte according to claim 9.

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