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

Abstract

The application relates to the technical field of electrolyte, and discloses an electrolyte additive, a composition for high-voltage electrolyte, a high-voltage electrolyte, a preparation method of the high-voltage electrolyte and a lithium ion battery. 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 at least one selected from triethyl borate, tripropyl borate and tributyl borate; and the component C is at least one selected from 3-aminopropyl triethoxysilane, 1,3-divinyl tetramethyldisiloxane, trimethoxy (3,3,3-trifluoropropyl) silane and triethoxy (pentafluorophenyl) silane. The electrolyte additive has an excellent application prospect in the field of high-voltage electrolyte. The high-voltage electrolyte is stable and resistant to oxidation, and can be applied in a high-voltage range of 3.0-5.0 V.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, specifically to electrolyte additives, compositions for high-voltage electrolytes, high-voltage electrolytes and their preparation methods, and lithium-ion batteries. Background Technology

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

[0003] Currently, the power battery market is dominated by lithium iron phosphate and ternary material technologies. However, the energy density of lithium iron phosphate batteries has been developed to near its limit, and their low-temperature performance is poor. Ternary batteries use expensive metals such as cobalt, which makes them relatively expensive and their high-temperature safety is also poor.

[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 status quo.

[0005] In recent years, layered lithium-rich materials, LiNi x MnyCo 1-x-y O2 and LiNi 0.5 Mn 1.5 A series of industrialized high-voltage cathode materials, such as O4, have come into view. Unfortunately, traditional electrolytes undergo irreversible oxidative decomposition on the cathode surface under high voltage, leading to a series of side reactions such as gas generation, battery swelling, electrode structure damage, transition metal dissolution, and increased polarization voltage, which in turn cause the cycle performance of high-voltage cathode materials to degrade.

[0006] The problem of electrolyte resistance to high-voltage oxidation has become a limiting factor in the development of high-energy-density lithium batteries, making the research of novel high-voltage electrolyte systems urgent.

[0007] CN119009113A discloses a non-aqueous electrolyte for a 4.53V high-voltage lithium-ion battery. This non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte lithium salt, and additives. The additives include conventional additives and isocyanate additives having the structure of formula (I). The non-aqueous organic solvent includes a fluorocarboxylic acid ester solvent having the structure of formula (II). The structures of formula (I) and formula (II) are shown below:

[0008]

[0009] R1 is independently selected from aromatic hydrocarbons, methyl, ethyl, trifluoromethyl, trifluoroethyl, or other halogenated hydrocarbons, wherein the aromatic hydrocarbon ring may be attached to an alkyl, alkenyl, alkynyl, aromatic group, isocyanate group, or halogen; R2 and R3 are independently selected from aromatic hydrocarbons, methyl, ethyl alkyl groups, and any one of alkenyl, alkynyl, and fluoroalkanes, wherein the alkyl and fluoroalkyl groups have less than 4 carbon atoms. The conventional additives are selected from one or more of fluoroethylene carbonate, succinate, adiponitrile, 1,3,6-hexanetrionitrile, 1,2-bis(cyanoethoxy)ethane, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinylene carbonate, vinyl sulfate, tri(trimethyl)silaneborate and tri(trimethyl)silanephosphoborate, tri(triargyl)phosphate, and tri(triallyl)phosphate. However, the electrolyte in this prior art has weak antioxidant capacity and is difficult to adapt to high-voltage material systems above 4.6V. Summary of the Invention

[0010] The purpose of this invention is to overcome the problems of narrow voltage window and easy oxidation of traditional carbonate electrolytes in the prior art.

[0011] To achieve the above objectives, a first aspect of the present invention provides an electrolyte additive containing components A, B, and C in a mass ratio of 1:(0.2-1.5):(0.2-2).

[0012] Component A is propargyl 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, trifluoropropanetrimethoxysilane, and triethoxy(pentafluorophenyl)silane.

[0015] A second aspect of the present invention provides a composition for a high-voltage electrolyte, the composition comprising a lithium salt, an organic solvent, and an electrolyte additive;

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

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

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

[0019] Solvent II is difluoroethylene carbonate, methyl trifluoroethyl carbonate and fluoroethylene carbonate in 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] A third aspect of the present invention provides a method for preparing a high-voltage electrolyte, the method comprising: mixing the high-voltage electrolyte described in the second aspect above with the components in a composition to obtain the high-voltage electrolyte.

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

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

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

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

[0026] (1) The additives 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 when applied to high voltage electrolyte of lithium-ion battery, thereby making the high voltage electrolyte more stable.

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

[0028] (3) The high-voltage electrolyte provided by the present invention can reduce gas production, suppress the dissolution of transition metal ions in the cathode material and the rate of increase in cycle impedance when applied in lithium-ion battery systems (especially lithium nickel manganese oxide systems), and effectively improve the cycle life and storage performance of the battery. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] As previously described, a first aspect of the present invention provides an electrolyte additive containing components A, B, and C in a mass ratio of 1:(0.2-1.5):(0.2-2).

[0031] Component A is propargyl 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, trifluoropropanetrimethoxysilane, 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 this invention have discovered that, in this preferred embodiment, the resulting additive enables the constructed interfacial film to be more compact, and can more effectively reduce the dissolution of cathode material ions during application in high-voltage electrolytes for lithium-ion batteries.

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

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

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

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

[0039] Solvent II is difluoroethylene carbonate, methyl trifluoroethyl 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 embodiment, solvent II is a mixture of difluoroethylene carbonate, methyl trifluoroethyl carbonate, and fluoroethylene carbonate in a mass ratio of 1:(1.4-2.0):(0.7-1.5). The inventors of this invention have discovered that, under this preferred embodiment, the high-voltage electrolyte exhibits better oxidative stability.

[0043] Preferably, the content of the electrolyte additive is 5.0-8.0 wt%, based on the total mass of the electrolyte. The inventors of this invention have discovered that, under this preferred condition, the high-voltage electrolyte prepared exhibits better oxidative stability.

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

[0045] According to another preferred embodiment, the lithium salt is LiN(SO2F)2 and LiPF6 in a mass ratio of 1:(8-12).

[0046] In this invention, LiN(SO2F)2 refers to lithium bis(fluorosulfonyl)imide (abbreviated as LiFSI).

[0047] As previously described, a third aspect of the present invention provides a method for preparing a high-voltage electrolyte, the method comprising: mixing the high-voltage electrolyte described in the second aspect with the components in the composition to obtain the high-voltage electrolyte.

[0048] To obtain a more uniform and stable high-voltage electrolyte, the present invention provides a preferred embodiment in which the method for preparing the high-voltage electrolyte includes:

[0049] S1: First, the lithium salt is mixed with the organic solvent in 3-5 portions to obtain mixture I;

[0050] S2: The additive and the mixture I are mixed by a second stirring to obtain the high-voltage electrolyte.

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

[0052] In a preferred embodiment, the conditions for the second stirring and mixing include: a temperature of 10-25°C and a rotation speed of 500-1000 rpm.

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

[0054] As previously described, a fifth aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte.

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

[0056] To obtain a lithium-ion battery with superior electrochemical performance, preferably, the positive electrode active material of the positive electrode is selected from layered lithium-rich materials, LiNi... x MnyCo 1-x-y O2 and LiNi 0.5 Mn 1.5 At least one of O4.

[0057] In a preferred embodiment, the negative electrode 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 does not have any special requirements for the selection of the diaphragm, and those skilled in the art can select it as needed. For example, the diaphragm is a PE diaphragm.

[0059] In the following examples, unless otherwise specified, all instruments, reagents, and materials used are conventional and can be obtained through legitimate commercial channels. Unless otherwise stated, all reagents used are commercially available analytical grade products.

[0060] Component A:

[0061] Component A-1: ​​Triargyl 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 salts: LiN(SO2F)2 and LiPF6 in a mass ratio of 1:10.

[0069] Table 1

[0070] Electrolyte additive formulation Formula 1 Formula 2 Formula 3 Component A type Component A-1 Same as formula 1 Same as formula 1 mass / g 3 Same as formula 1 2.8 Component B type Component B-1 Component B-2 Same as formula 1 mass / g 2 Same as formula 1 1.2 Component C type Component C-1 Component C-2 Same as formula 1 mass / g 2 Same as formula 1 3 Naming of electrolyte additives TJ-1 TJ-2 TJ-3

[0071] Continued from Table 1

[0072]

[0073] Example 1

[0074] This embodiment illustrates the preparation of a high-voltage electrolyte according to the formulation in Table 2 and the method described below:

[0075] S1: First, the lithium salt is mixed with the organic solvent in 5 equal portions to obtain mixture I;

[0076] S2: The additive and the mixture I are mixed by a second stirring to obtain the high-voltage electrolyte.

[0077] The conditions for the first stirring and mixing are: temperature -10℃ and speed 800 rpm.

[0078] The second mixing conditions include: temperature 23℃ and speed 600rpm.

[0079] Example 2

[0080] This embodiment uses a similar method to Example 1, except that the formulation is different; see Table 2 for details, and a high-voltage electrolyte is prepared.

[0081] Example 3

[0082] This embodiment uses a method similar to that of Example 1, except that: in this embodiment, an equal mass of electrolyte additive TJ-3 is used to replace electrolyte additive TJ-1 in Example 1;

[0083] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0084] Example 4

[0085] This embodiment uses a method similar to that of Example 1, except that, while keeping the contents of solvent I and solvent II constant, the mass ratio of difluoroethylene carbonate, methyl trifluoroethyl carbonate and fluoroethylene carbonate in solvent II is adjusted to 1:2.5:0.5.

[0086] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0087] Example 5

[0088] This embodiment uses a method similar to that of Example 1, except that the amount of electrolyte additive is adjusted to 4.5g.

[0089] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0090] Comparative Example 1

[0091] This comparative example was conducted using a method similar to that of Example 1. The difference is that this comparative example used an equal mass of electrolyte additive TJ-D1 to replace the electrolyte additive TJ-1 in Example 1.

[0092] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0093] Comparative Example 2

[0094] This comparative example was conducted using a method similar to that of Example 1. The difference is that this comparative example used an equal mass of electrolyte additive TJ-D2 to replace electrolyte additive TJ-1 in Example 1.

[0095] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0096] Comparative Example 3

[0097] This comparative example was conducted using a method similar to that of Example 1. The difference is that this comparative example used an equal mass of electrolyte additive TJ-D3 to replace electrolyte additive TJ-1 in Example 1.

[0098] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0099] Comparative Example 4

[0100] This comparative example was conducted using a method similar to that of Example 1. The difference is that this comparative example used an equal mass of electrolyte additive TJ-D4 to replace electrolyte additive TJ-1 in Example 1.

[0101] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0102] Comparative Example 5

[0103] This comparative example was conducted using a method similar to that of Example 1. The difference is that this comparative example used an equal mass of electrolyte additive TJ-D5 to replace electrolyte additive TJ-1 in Example 1.

[0104] For any parts not listed, the same high-voltage electrolyte was prepared as in Example 1.

[0105] Table 2

[0106]

[0107] Test case

[0108] 1. Preparation of a 1.5Ah lithium-ion pouch cell

[0109] Under an environment of 23±5℃ and relative humidity ≤20%, the positive electrode (spinel LiNi) is stacked using a lamination process. 0.5 Mn 1.5 The raw cell is assembled sequentially from O4 material, negative electrode sheet (artificial graphite + CVD silicon-carbon material, with a mass ratio of artificial graphite to CVD silicon-carbon material of 95:5), and separator (PE separator); then, a 1.5Ah finished lithium-ion soft-pack battery (LNMO / / Gr.@Si / C soft-pack battery) is produced through processes such as baking, electrolyte injection, formation, aging, and capacity testing. The electrolyte injection coefficient is 4.5g / Ah (i.e., 4.5g of electrolyte is injected per Ah capacity cell), and the electrolyte type is the high-voltage electrolyte obtained in the above examples.

[0110] The electrochemical performance of the prepared lithium-ion pouch cells was tested using a battery testing system, as detailed below:

[0111] Cyclic performance testing method: At 25℃, the 1.5Ah lithium-ion soft-pack battery after capacity testing is charged to 4.85V at a constant current and constant voltage of 1.0C (1.0C = 1500mA), with a cutoff current of 0.05C. Then, it is discharged to 3.4V at a constant current of 1.0C. This cycle is repeated 200 times. The cycle capacity retention rate is calculated using the following formula:

[0112] Capacity retention rate after 200 cycles (%) = (Discharge capacity after 200 cycles / Discharge capacity after the first cycle) × 100%;

[0113] Capacity retention rate (%) after 7 days of storage at 45℃ = (Discharge capacity of 100% SOC cell after 7 days of storage at 45℃ / Initial discharge capacity) × 100%; the results are shown in Table 3:

[0114] Table 3

[0115]

[0116] The above results demonstrate that the additive provided by this invention has excellent application potential in high-voltage electrolytes for lithium-ion batteries. Applying the high-voltage electrolyte provided by this invention to lithium-ion battery systems results in lithium-ion batteries exhibiting superior 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 scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electrolyte additive, characterized in that, The additive contains components A, B, and C in a mass ratio of 1:(0.2-1.5):(0.2-2); Component A is propargyl phosphate; Component B is selected from at least one of triethyl borate, tripropyl borate, and tributyl borate. 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 component A, component B, and 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 lithium salt content is 10wt%-16wt%, the organic solvent content is 75wt%-85wt%, and the electrolyte additive content is 0.1wt%-10wt%. Based on the total mass of the organic solvent, the organic solvent is a combination of 10wt%-40wt% solvent I and 60wt%-90wt% solvent II; Solvent I is selected from at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; 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 as described in claim 1 or 2.

4. The composition according to claim 3, characterized in that, 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 5.0-8.0 wt%.

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% solvent I and 70-90 wt% 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 includes: mixing the high-voltage electrolyte according to any one of claims 3-7 with the components in the composition to obtain the high-voltage electrolyte.

9. The high-voltage electrolyte prepared by the method of claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; The electrolyte is the high-voltage electrolyte as described in claim 9.

Images