Electrolyte, battery and electronic device

Abstract

The application provides an electrolyte, a battery and an electronic device, comprising an amine additive, wherein the amine additive has a cation with a structure shown in the following formula; in the formula, R1, R2, R3, R4 and R5 are each independently selected from at least one of a hydrogen atom, an alkyl group, an alkenyl group, an alkinyl group and a phenyl group; a negative ion of the amine additive comprises a halogen negative ion; and a mass percentage content of the amine additive in the electrolyte is greater than 1 wt%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolyte, and particularly relates to an electrolyte, a battery and an electronic device. BACKGROUND

[0002] In the production process of lithium battery cell raw materials and lithium batteries, metal copper impurities will inevitably be introduced. The distribution of impurity copper is very random. When it is on the positive electrode sheet side, it often dissolves out and deposits on the separator and / or negative electrode in the form of copper dendrites to pierce the separator, causing battery short circuit and increasing production or after-sales maintenance cost.

[0003] Currently, metal copper foreign matter is removed by strengthening raw material incoming inspection and regularly cleaning the production site, but the impurity copper particles that cause battery failure are usually very small, and the above interception method cannot completely eliminate copper foreign matter, especially for micron-sized copper scraps. This way of preventing copper impurities from dissolving out is not ideal.

[0004] Therefore, the problem of copper impurities in the cell piercing the separator to cause battery short circuit cannot be completely eliminated in the prior art. SUMMARY

[0005] The application provides an electrolyte for solving the problem of copper impurities easily piercing the separator to cause battery short circuit in the prior art.

[0006] The application provides a battery comprising the above electrolyte, which has higher safety.

[0007] The application also provides an electronic device comprising the above battery.

[0008] In one aspect, the application provides an electrolyte comprising an amine additive, wherein the amine additive has a cation with a structure as shown in formula (1):

[0009]

[0010] In the formula, R1, R2, R3, R4, R5 and R6 are each independently selected from at least one of a hydrogen atom, an alkyl group, an alkenyl group, an alkyne group and a phenyl group.

[0011] The anion of the amine additive comprises a halide anion.

[0012] The mass percentage content of the amine additive in the electrolyte is greater than 1%wt.

[0013] The electrolyte described above, wherein the mass percentage content of the amine additive in the electrolyte is 1.5% to 3%wt.

[0014] The electrolyte described above, wherein the alkyl group is a C1-C9 alkane.

[0015] The electrolyte as described above, R1, R2, R3, R4, R5, R6 are all hydrogen atoms, alkyl, alkenyl, alkynyl, phenyl.

[0016] The electrolyte as described above, the cation of the amine additive comprises at least one of the structures of formula 2, formula 3:

[0017]

[0018] The electrolyte as described above, the cation of the amine additive comprises at least one of the structures of formula 2, formula 3:

[0019]

[0020] The electrolyte as described above, the anion of the amine additive is chloride.

[0021] The electrolyte as described above, the electrolyte further comprises a lithium salt, the content of the lithium salt in the electrolyte is 0.5-1.2 mol / L, the lithium salt comprises at least one of LiPF6, LiBF4, LiTFSI, LiBOB; and / or,

[0022] The electrolyte further comprises a solvent, the content of the solvent in the electrolyte is 85.00-99.99%wt, the mass fraction of the solvent is relative to the mass fraction of the sum of the mass of the solvent and the additive, the solvent comprises at least one of ethylene carbonate EC, ethyl methyl carbonate EMC, dimethyl carbonate DMC, diethyl carbonate DEC, propylene carbonate PC, fluoroethylene carbonate FEC.

[0023] In still another aspect of the present application, a battery is provided, comprising the electrolyte as described above.

[0024] In still another aspect of the present application, an electronic device is provided, comprising the battery as described above.

[0025] The present application provides an electrolyte, comprising an amine additive with a content greater than 1wt%, the amine additive has a special structure of a cation with multiple benzene ring structures combined with amine groups, which can prevent local aggregation and deposition of metal foreign matter, make the deposition morphology of dissolved copper on the negative electrode more flat, avoid the formation of long and thin copper dendrites to pierce the separator and cause short circuit of the battery, and improve the performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A schematic diagram of the formation of copper dendrites without the amine additive of the present application;

[0027] Figure 2 A schematic diagram of uniform deposition of copper metal in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be combined with embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] In a first aspect, the present application provides an electrolyte comprising an amine additive, the amine additive having a cation with a structure as shown in formula (1):

[0030]

[0031] In the formula, R1, R2, R3, R4, R5, R6 are each independently selected from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a phenyl group;

[0032] The anion of the amine additive comprises a halide anion.

[0033] The mass percentage content of the amine additive in the electrolyte is greater than 1%wt.

[0034] In the formula, R1, R2, R3, R4, R5, R6 are each independently selected from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a phenyl group;

[0035] The alkenyl group refers to a straight-chain or branched-chain alkenyl group having 1-9 carbon atoms and containing at least one carbon-carbon double bond, for example, the alkenyl group can be a vinyl group, a propenyl group, a 1-butene group, a 2-butene group, an isobutenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, etc.

[0036] The alkynyl group refers to a straight-chain or branched-chain alkynyl group having 1-9 carbon atoms and containing at least one carbon-carbon triple bond, for example, the alkynyl group can be an ethynyl group, a propynyl group, a 1-butynyl group, a 2-butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, etc.

[0037] Due to the inevitable introduction of metal copper impurities in the production process of lithium battery cell raw materials and lithium batteries, the distribution of impurity copper is very random. When it is on the positive electrode sheet side, it often dissolves and deposits on the separator and / or negative electrode, as shown in Figure 1 These dissolved copper often preferentially aggregates and deposits at one or more points, forming elongated sharp dendrites, i.e., copper dendrites, and such elongated copper dendrites are very easy to pierce the separator, leading to the connection of positive and negative electrodes and short circuit, increasing the production or after-sales maintenance cost.

[0038] Therefore the present application provides an electrolyte, which can change the deposition form of the dissolved copper, such as Figure 2 As shown in the figure, since the negative active material is composed of particles of different sizes, the size difference of the particles leads to the rough surface of the negative electrode sheet, and the charge density difference between the protruding and recessed areas. The electrolyte in the present application can make the cations preferentially adsorb on the protruding areas of the negative electrode by adding more than 1% wt of amine additives with the special structure of multiple benzene ring structures combined with amine groups, so as to increase the overpotential of the protruding areas and make the copper ions not easily deposit on the position, but preferentially deposit on the recessed areas of the negative electrode. Thus, the flattening effect of affecting the deposition position by changing the local overpotential is achieved, and the generation of local metal dendrites is effectively avoided. In the case of the same deposition amount, the morphology of the copper deposition is more flat, which avoids the battery short circuit caused by the penetration of the separator by the long and thin copper dendrites, and improves the performance of the battery.

[0039] The present application provides an electrolyte, which includes more than 1% wt of amine additives with the special structure of cations with multiple benzene ring structures combined with amine groups, which can prevent the local aggregation and deposition of metal impurities, make the deposition morphology of the dissolved copper on the negative electrode more flat, avoid the battery short circuit caused by the penetration of the separator by the long and thin copper dendrites, and improve the performance of the battery.

[0040] Further, the mass percentage content of the amine additive in the electrolyte is 1.5-3%.

[0041] The inventors found that when the mass percentage content of the amine additive in the electrolyte is 1.5-3%, the cations in it can further preferentially adsorb on the protruding areas of the negative electrode, increase the overpotential of the protruding areas, and further strengthen the flattening effect of the amine additive on the deposition position of copper impurities, which more effectively avoids the generation of local metal dendrites.

[0042] The present application does not limit the source of the amine additive, which can be obtained from the market or synthesized by the preparation method known in the prior art.

[0043] In a specific embodiment, the alkyl group is a C1-C9 alkane.

[0044] The inventors found that when the alkyl group is a C1-C9 alkane, the cations in it can further preferentially adsorb on the protruding areas of the negative electrode, increase the overpotential of the protruding areas, and further strengthen the flattening effect of the amine additive on the deposition position of copper impurities, which more effectively avoids the generation of local metal dendrites.

[0045] In a specific embodiment, R1, R2, R3, R4, R5, and R6 are one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a phenyl group.

[0046] In detail, the groups of R1, R2, R3, R4, R5 and R6 are the same, and each of R1, R2, R3, R4, R5 and R6 is one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group and a phenyl group.

[0047] In a specific embodiment, each of R1, R2, R3, R4, R5 and R6 is a methyl group, and the amine additive is methyl violet, such as M19432 reagent from Merick Reagent Factory; this can further enable copper impurities to be preferentially adsorbed in the recessed area of the negative electrode, more effectively avoid the generation of local metal dendrites, and further improve the battery performance.

[0048] Further, in a specific embodiment of the present application, the cation of the amine additive includes at least one of the structures of formula 2 and formula 3.

[0049]

[0050] Further, in a specific embodiment of the present application, the cation of the amine additive includes at least one of the structures of formula 4 and formula 5.

[0051]

[0052] When the structure formula of the cation of the amine additive conforms to at least one of the above formula 2 to formula 5, the special group combination can synergize with the amine substance, further enabling copper impurities to be preferentially adsorbed in the recessed area of the negative electrode, more effectively avoiding the generation of local metal dendrites, and further improving the battery performance.

[0053] The present application does not limit the anion of the amine additive, and any anion that can be paired with the cation in the present application is acceptable.

[0054] Alternatively, the anion of the amine additive is chloride. The combination of chloride and the cation in the present application to form the amine additive can further enable copper impurities to be preferentially adsorbed in the recessed area of the negative electrode, more effectively avoid the generation of local metal dendrites, and further improve the battery performance.

[0055] The present application does not specifically limit the specific composition of the electrolyte. Generally, the electrolyte further includes a lithium salt and a solvent.

[0056] In a specific embodiment, the electrolyte further includes a lithium salt, the content of the lithium salt in the electrolyte is 0.5-1.2 mol / L, and the lithium salt includes at least one of LiPF6, LiBF4, LiTFSI and LiBOB; and / or,

[0057] The electrolyte further comprises a solvent, the content of the solvent in the electrolyte is 85.00-99.99%wt, the mass fraction of the solvent is relative to the mass of the sum of the mass of the solvent and the additive, and the solvent comprises at least one of ethylene carbonate EC, ethyl methyl carbonate EMC, dimethyl carbonate DMC, diethyl carbonate DEC, propylene carbonate PC, and fluoroethylene carbonate FEC.

[0058] In the present application, the mass fraction of the solvent refers to the mass proportion of the solvent based on the sum of the mass of the solvent and the additive.

[0059] By further limiting the lithium salt, the type of the solvent, and the content of the solvent in the electrolyte, the copper impurities can be preferentially adsorbed in the recessed area of the negative electrode, the generation of local metal dendrites can be more effectively avoided, and the battery performance can be further improved.

[0060] In a second aspect, the present application provides a battery comprising the electrolyte of the first aspect.

[0061] The present application provides a battery comprising the electrolyte of the first aspect, and the electrolyte comprises an amine additive with a content greater than 1wt%, the amine additive has a special structure of a cation with multiple benzene ring structures combined with an amine group, can prevent local deposition of metal foreign matter, makes the deposition morphology of dissolved copper on the negative electrode more flat, avoids the formation of long and thin copper dendrites to pierce the separator and cause short circuit of the battery, and improves the performance of the battery.

[0062] The present application does not limit the specific type and structure of the positive electrode, the negative electrode, and the separator in the battery.

[0063] Optionally, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material. The positive electrode current collector used includes an aluminum foil; the positive electrode active material includes at least one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide, or lithium nickel manganese oxide; other positive electrode active materials used include a binder, a conductive agent, or other optional additives, the binder can be selected from at least one of styrene butadiene rubber (SBR), polyvinylidene fluoride, water-based acrylic resin, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methyl cellulose, polytetrafluoroethylene (PTFE), polyvinyl alcohol, ethylene-vinyl acetate copolymer (EVA), polyvinyl ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB); the positive electrode conductive agent can be selected from at least one of super conductive carbon, graphene, acetylene black, conductive carbon black, ketjen black, carbon dots, conductive graphite, carbon nanotubes, Super P (SP), and carbon nanofibers. In a specific embodiment, the positive electrode material includes at least one of lithium iron phosphate, lithium cobaltate, lithium titanate, and lithium nickel cobalt manganese ternary material.

[0064] Optionally, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, the negative electrode current collector including at least one of a copper foil, a nickel foil, or a carbon-based current collector; the negative electrode active material layer includes at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composite material, silicon-oxygen-carbon material, Li-Sn alloy, Li-Sn-O alloy, silicon-oxygen material, Sn, SnO, SnO 2 and lithium-aluminum alloy; the negative electrode binder can be selected from at least one of styrene butadiene rubber (SBR), polyvinylidene fluoride, water-based acrylic resin, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methyl cellulose, polytetrafluoroethylene (PTFE), polyvinyl alcohol, ethylene-vinyl acetate copolymer (EVA), polyvinyl ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB); the negative electrode conductive agent can be selected from at least one of super conductive carbon, graphene, acetylene black, conductive carbon black, ketjen black, carbon dots, conductive graphite, carbon nanotubes, Super P (SP), and carbon nanofibers.

[0065] Optionally, the diaphragm material can be selected from a porous material diaphragm film known for good chemical stability and mechanical stability, and the diaphragm film can be made of at least one of non-woven fabric, glass fiber, polytetrafluoroethylene, polyether sulfone, polypropylene, polyolefin, aromatic polyamide, polyethylene, and the like; the diaphragm film can be a single layer or a multi-layer composite film.

[0066] In a third aspect, the present application provides an electronic device comprising the battery of the second aspect.

[0067] The present application is not limited to a specific type of electronic device, and can include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, sound boxes, and any device that requires a battery to power it.

[0068] Hereinafter, an electrolyte provided by the present application will be described in detail through specific examples.

[0069] Example 1

[0070] The composition of the electrolyte in this example includes 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7), and 1.5 wt% of an amine additive; wherein the amine additive has a cation with a structure as shown in formula (1), R1, R2, R3, R4 are methyl groups, R5, R6 are hydrogen atoms, and the anion is chloride.

[0071] Example 2

[0072] The composition of the electrolyte in this example includes 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7), and 2 wt% of an amine additive.

[0073] Example 3

[0074] The difference between this example and Example 1 is that it includes 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7), and 3 wt% of an amine additive.

[0075] Example 4

[0076] The difference between this example and Example 1 is that it includes 1.0 mol / L of LiTFSI, EC / EMC (weight ratio 3:7), and 3 wt% of an amine additive.

[0077] Example 5

[0078] The embodiment is different from example 1 in that 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7) and 1.5 wt% of the amine additive are included, wherein the amine additive has a cation with a structure as shown in formula (1), R1, R2, R3, R4, R5 and R6 are methyl groups, and the anion is chloride.

[0079] Example 6

[0080] The embodiment is different from example 1 in that 1.0 mol / L of LiPF6, EC / EMC (weight ratio 5:5) and 1.5 wt% of the amine additive are included; wherein the amine additive has a cation with a structure as shown in formula (1), R1, R2, R3 and R4 are methyl groups, R5 and R6 are hydrogen atoms, and the anion is chloride.

[0081] Comparative Example 1

[0082] The comparative example is different from example 1 in that 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7) and 1 wt% of the amine additive are included. Wherein the amine additive has a cation with a structure as shown in formula (1), R1, R2, R3 and R4 are methyl groups, R5 and R6 are hydrogen atoms, and the anion is chloride.

[0083] Comparative Example 2

[0084] The comparative example is different from example 1 in that 1.0 mol / L of LiPF6, EC / EMC (weight ratio 3:7) and 0.5 wt% of the amine additive are included.

[0085] Comparative Example 3

[0086] The comparative example is different from example 1 in that no amine additive is added.

[0087] Test Example 1

[0088] A capacity of 12 mAh lithium iron phosphate / graphite battery is selected, and a copper foil with a size of 1 mm 2 is placed on the surface of the positive electrode sheet to simulate foreign matter. If the particle size is too small to cause battery short circuit, it loses the meaning of research, therefore the copper scrap with a size of about 1 mm2is selected; the electrolyte in the above examples and comparative examples is injected into the battery, and the battery is charged at 0.02C, and the upper limit protection voltage is 3.8V. The dissolution process of the metal foreign matter is mostly completed in the first charging, and the copper foil with a size of 1 mm 2The copper foil will cause short circuit of the capacity battery, and the copper dissolution ratio is taken as the basis for improving the effect of copper dissolution, the copper dissolution ratio = (copper in negative electrode + separator) / (copper in positive electrode + negative electrode + separator) * 100%, wherein the copper in the positive electrode, negative electrode and separator is accurately measured by ICP test, the higher the copper dissolution ratio, the more the amount of deposited copper that the negative electrode and the separator can accommodate under the condition of containing the same amount of copper foreign matter in the positive electrode, the wider the safety margin of the battery; therefore, the termination condition of the experiment is selected as the voltage drop or 0V in the charging process, at this time the copper dissolved in the negative electrode forms dendritic crystals to pierce the separator and cause internal short circuit of the battery; the specific test results are shown in Table 1.

[0089] Table 1 copper dissolution ratio in different electrolyte formulations

[0090]

[0091]

[0092] As can be seen from Table 1, when excessive copper impurities are added to the positive electrode sheet, copper will be dissolved and deposited in the negative electrode to form copper dendrites, when the copper dendrites grow to a certain extent, they will pierce the separator and cause battery short circuit, in the examples, the electrolyte provided by the application can accommodate more copper in the negative electrode and the separator, which shows that the copper in the examples with the electrolyte provided by the application is deposited on the surface of the negative electrode in a more flat manner, rather than in the form of long and sharp dendrites, which improves the performance of the battery.

[0093] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent replacement for part or all of the technical features thereof; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrolyte, characterized in that, Including amine additives, said amine additives having cations with the structure shown in formula (1): In the formula, R1, R2, R3, R4, R5, and R6 are each independently selected from at least one of hydrogen atom, alkyl, alkenyl, alkynyl, and phenyl; The anions of the amine additives include halogen anions; The amine additive has a mass percentage content greater than 1% wt in the electrolyte.

2. The electrolyte according to claim 1, characterized in that, The amine additive has a mass percentage of 1.5% to 3% wt in the electrolyte.

3. The electrolyte according to claim 1 or 2, characterized in that, The alkyl group is a C1-C9 alkane.

4. The electrolyte according to any one of claims 1-3, characterized in that, R1, R2, R3, R4, R5, and R6 are all one of the following: hydrogen atom, alkyl, alkenyl, alkynyl, or phenyl.

5. The electrolyte according to claim 4, characterized in that, The cations of the amine additives include at least one of the structures of Formula 2 and Formula 3; 6. The electrolyte according to any one of claims 1-3, characterized in that, The cations of the amine additives include at least one of the structures of formula 4 and formula 5:

7. The electrolyte according to any one of claims 1-6, characterized in that, The anion of the amine additive is chloride ion.

8. The electrolyte according to any one of claims 1-7, characterized in that, The electrolyte further includes a lithium salt, the content of which is 0.5–1.2 mol / L, and the lithium salt includes at least one selected from LiPF6, LiBF4, LiTFSI, and LiBOB; and / or, The electrolyte further includes a solvent, the content of which in the electrolyte is 85.00 to 99.99% wt, and the solvent includes at least one of ethylene carbonate EC, ethyl methyl carbonate EMC, dimethyl carbonate DMC, diethyl carbonate DEC, propylene carbonate PC, and fluoroethylene carbonate FEC.

9. A battery, characterized in that, Includes the electrolyte according to any one of claims 1-8.

10. An electronic device, characterized in that, Includes the battery as described in claim 9.

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