Electrolyte, battery and electronic equipment

Abstract

The present invention provides an electrolyte, a battery and an electronic device, the electrolyte comprises an amine additive, the amine additive has cations with a structure represented by the following formula; in the formula, R1, R2, R3, R4 and R5 are respectively and independently selected from at least one of hydrogen atoms, alkyl, alkenyl, alkynyl and phenyl; anions of the amine additive comprise halogen anions; the mass percentage content of the amine additive in the electrolyte is not less than 1% wt. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytes, and in particular relates to an electrolyte, a battery and an electronic device. Background Art

[0002] During the production process of lithium battery cell raw materials and lithium batteries, metallic copper impurities are inevitably introduced. The distribution of impure copper is very random. When it is on the positive electrode side, it tends to dissolve and deposit on the diaphragm and / or negative electrode in the form of copper dendrites, which grow through the diaphragm and cause battery short circuit, increasing production or after-sales maintenance costs.

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

[0004] Therefore, the existing technology still cannot eliminate the problem of copper impurities in the battery cell piercing the diaphragm and causing battery short circuit. Summary of the invention

[0005] The invention provides an electrolyte for solving the problem in the prior art that copper impurities easily pierce a diaphragm and cause a battery short circuit.

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

[0007] The present invention also provides an electronic device, comprising the battery.

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

[0009]

[0010] In the formula, R1, R2, R3, R 4、 R5 and R6 are each independently selected from at least one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a phenyl group;

[0011] The anion of the amine additive includes a halogen anion;

[0012] The mass percentage of the amine additive in the electrolyte is not less than 1%wt.

[0013] In the electrolyte as described above, the mass percentage of the amine additive in the electrolyte is 1% to 3%wt.

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

[0015] The electrolyte as described above, R1, R2, R3, R 4、 R5 and R6 are each one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group and a phenyl group.

[0016] In the electrolyte as described above, the cation of the amine additive includes at least one of the structures of Formula 2 and Formula 3:

[0017]

[0018] In the electrolyte as described above, the cation of the amine additive includes at least one of the structures of Formula 2 and Formula 3:

[0019]

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

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

[0022] The electrolyte also includes a solvent, the content of the solvent in the electrolyte is 85.00-99.99%wt, the mass fraction of the solvent is the mass fraction relative to the sum of the masses of the solvent and the additive, 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.

[0023] Another aspect of the present invention provides a battery, comprising the electrolyte as described above.

[0024] Another aspect of the present invention provides an electronic device, comprising the battery as described above.

[0025] The invention provides an electrolyte, comprising an amine additive with a content of not less than 1wt%, wherein the amine additive has a cation with a special structure of 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 smoother, avoid the formation of slender copper dendrites and piercing a diaphragm to cause a battery short circuit, and improve the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the formation of copper dendrites in the present invention without additives;

[0027] Figure 2FIG. 4 is a schematic diagram of uniform deposition of copper metal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0030]

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

[0032] The anion of the amine additive includes a halogen anion;

[0033] The mass percentage of the amine additive in the electrolyte is not less than 1%wt.

[0034] Wherein, alkyl refers to a straight chain or branched chain alkyl having 1 to 11 carbon atoms, for example, alkyl can be methyl, ethyl, propyl, etc.;

[0035] Alkenyl refers to a straight or branched alkenyl group having 1 to 9 carbon atoms and containing at least one carbon-carbon double bond, for example, alkenyl can be ethenyl, propenyl, 1-butenyl, 2-butenyl, isobutenyl, pentenyl, hexenyl, heptenyl, octenyl, etc.;

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

[0037] Since metallic copper impurities are inevitably introduced in the raw materials of lithium battery cells and the production process of lithium batteries, the distribution of impurity copper is very random. When it is on the positive electrode side, it often dissolves and deposits on the diaphragm and / or the negative electrode, such as Figure 1 As shown, the dissolved copper tends to preferentially accumulate and deposit at one or several points to form slender and sharp branches, namely copper dendrites. Such slender copper dendrites can easily pierce the separator, causing a short circuit between the positive and negative electrodes, and increasing production or after-sales maintenance costs.

[0038] Therefore, the present invention provides an electrolyte that can change the deposition form of dissolved copper, such as Figure 2 As shown, since the negative electrode active material is composed of particles of different sizes, the difference in particle sizes leads to a rough and uneven surface of the negative electrode plate, and there are differences in charge density in the raised and recessed areas. The electrolyte in the present invention adds an amine additive with a content of not less than 1%wt, and utilizes the special structure of multiple benzene ring structures combined with amine groups in its cations, so that the cations can be preferentially adsorbed on the raised areas of the negative electrode, so that the overpotential of the raised areas is increased, so that copper ions are not easily deposited at this position, but will be preferentially deposited in the recessed areas of the negative electrode. In this way, the leveling effect of affecting the deposition position by changing the local overpotential is achieved, and the formation of local metal dendrites can be effectively avoided. Under the condition of the same deposition amount, the morphology of the copper deposition is flatter, which avoids the battery short circuit caused by the copper ion piercing the diaphragm, thereby improving the performance of the battery.

[0039] The invention provides an electrolyte, comprising an amine additive with a content of not less than 1%wt, wherein the amine additive has a cation with a special structure of multiple benzene ring structures combined with amine groups, can prevent local aggregation and deposition of metal foreign matter, make the deposition morphology of dissolved copper on the negative electrode smoother, avoid the formation of slender copper dendrites and piercing a diaphragm to cause a battery short circuit, and improve the performance of the battery.

[0040] Furthermore, the mass percentage of the amine additive in the electrolyte is 1-3%.

[0041] The inventors have found that when the mass percentage of amine additives in the electrolyte is 1-3%, the cations therein can be further preferentially adsorbed on the raised area of ​​the negative electrode, thereby increasing the overpotential of the raised area, further enhancing the leveling effect of the amine additives on the deposition position of copper impurities, and more effectively avoiding the formation of local metal dendrites.

[0042] The present invention does not limit the source of the amine additives, which may be obtained from the market or synthesized by a 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 therein can be further preferentially adsorbed on the raised area of ​​the negative electrode, thereby increasing the overpotential of the raised area, further strengthening the leveling effect of the amine additive on the deposition position of copper impurities, and more effectively avoiding the formation of local metal dendrites.

[0045] In one embodiment, R1, R2, R3, R 4、 R5 and R6 are each one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group and a phenyl group.

[0046] Specifically, R1, R2, R3, R 4、 The groups of R5 and R6 are the same, and R1, R2, R3, R4, R5, and R6 are all one of hydrogen atom, alkyl group, alkenyl group, alkynyl group, and phenyl group.

[0047] In one embodiment, R1, R2, R3, R 4、 R5 and R6 are both methyl groups, and the amine additive is methyl violet, such as the M19432 reagent produced by the Myrel reagent manufacturer; this can further enable copper impurities to be preferentially adsorbed in the recessed area of ​​the negative electrode, more effectively avoiding the formation of local metal dendrites, and further improving battery performance.

[0048] Further, in one embodiment of the present invention, the cation of the amine additive includes

[0049] At least one of the structures of Formula 2 and Formula 3:

[0050]

[0051] Further, in one embodiment of the present invention, the cation of the amine additive includes

[0052] At least one of the structures of Formula 4 and Formula 5:

[0053]

[0054] When the structural formula of the cation of the amine additive conforms to at least one of the above formulas 2 to 5, its special group combination can work synergistically with the amine substance to further make the copper impurities preferentially adsorbed in the recessed area of ​​the negative electrode, more effectively avoid the formation of local metal dendrites, and further improve the battery performance.

[0055] The present invention does not limit the anion of the amine additive, and any anion that can be paired with the cation in the present invention can be used.

[0056] Optionally, the anion of the amine additive is a chloride ion. Selecting the chloride ion to combine with the cation in the present invention to form an amine additive can further make the copper impurities preferentially adsorbed in the recessed area of ​​the negative electrode, more effectively avoiding the formation of local metal dendrites, and further improving battery performance.

[0057] The present invention does not specifically limit the specific composition of the electrolyte. Generally, the electrolyte further includes a lithium salt and a solvent.

[0058] In a specific embodiment, the electrolyte further includes a lithium salt, the content of the lithium salt in the electrolyte is 0.5 to 1.2 mol / L, and the lithium salt includes at least one of LiPF6, LiBF4, LiTFSI, and LiBOB; and / or,

[0059] The electrolyte also includes a solvent, the content of the solvent in the electrolyte is 85.00-99.99%wt, the mass fraction of the solvent is the mass fraction relative to the sum of the masses of the solvent and the additive, 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.

[0060] The mass fraction of the solvent in the present invention refers to the mass proportion of the solvent based on the sum of the masses of the solvent and the additives.

[0061] By further limiting the types of lithium salts and solvents and their contents in the electrolyte, copper impurities can be preferentially adsorbed in the recessed areas of the negative electrode, more effectively avoiding the formation of local metal dendrites and further improving battery performance.

[0062] In a second aspect, the present invention provides a battery comprising the electrolyte of the first aspect.

[0063] The present invention provides a battery, comprising the electrolyte of the first aspect, wherein the electrolyte comprises an amine additive in an amount of not less than 1wt%, wherein the amine additive has a cation having a special structure of multiple benzene ring structures combined with amine groups, and can prevent local aggregation and deposition of metal foreign matter, so that the deposition morphology of dissolved copper at the negative electrode is smoother, and the formation of slender copper dendrites that pierce the diaphragm and cause battery short circuit is avoided, thereby improving the performance of the battery.

[0064] The present invention does not limit the specific types and structures of the positive electrode, negative electrode and separator in the battery.

[0065] Optionally, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on one side or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. The positive electrode current collector used includes aluminum foil; the positive electrode active material includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide or lithium nickel manganese oxide; the other positive electrode active materials used include a binder, a conductive agent or other optional additives, and the binder can be selected from styrene-butadiene rubber (SBR), polyvinylidene fluoride, water-based acrylic resin, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinyl pyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polypropylene 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 polymethylcellulose and polyvinyl butyral (PVB); the positive electrode conductive agent can be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, Ketjen black, carbon dots, conductive graphite, carbon nanotubes, SuperP (SP) and carbon nanofibers. In a specific embodiment, the positive electrode material includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium titanate, and nickel-cobalt-manganese ternary materials.

[0066] Optionally, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode current collector includes at least one of copper foil, nickel foil or a carbon-based current collector; the negative electrode active material layer includes natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite materials, silicon-oxygen-carbon materials, Li-Sn alloys, Li-Sn-O alloys, silicon-oxygen materials, 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), polyvinyl pyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polypropylene 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 polymethylcellulose and polyvinyl butyral (PVB); the negative electrode conductor can be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, Ketjen black, carbon dots, conductive graphite, carbon nanotubes, SuperP (SP) and carbon nanofibers.

[0067] Optionally, the diaphragm material can be selected from a well-known porous material isolation membrane with good chemical stability and mechanical stability. The material of the isolation membrane can be selected from at least one of non-woven fabric, glass fiber, polytetrafluoroethylene, polyethersulfone, polypropylene, polyolefin, aromatic polyamide, polyethylene, etc.; the isolation membrane can be a single-layer or multi-layer composite film.

[0068] In a third aspect, the present invention provides an electronic device comprising the battery of the second aspect.

[0069] The present invention is not limited to the specific types of electronic devices, and may include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, speakers, and any other devices that require batteries to power them.

[0070] Hereinafter, an electrolyte provided by the present invention is described in detail through specific embodiments.

[0071] Example 1

[0072] The electrolyte in this embodiment is composed of: 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 1.5 wt% amine additives; 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 a chloride ion.

[0073] Example 2

[0074] The composition of the electrolyte in this embodiment includes: the difference between this embodiment and embodiment 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 2 wt% amine additives.

[0075] Example 3

[0076] The difference between this embodiment and embodiment 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 3 wt % of amine additives.

[0077] Example 4

[0078] The difference between this embodiment and embodiment 1 is that it includes 1.0 mol / L of LiTFSI, EC / EMC (weight ratio 3:7) and 3 wt % of amine additives.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 1.5 wt% of amine additives, wherein the cation of the amine additive has a structure as shown in formula (1), R1, R2, R3, R 4、 R5 and R6 are methyl groups, and the anion is a chloride ion.

[0081] Example 6

[0082] The difference between this embodiment and embodiment 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 5:5) and 1.5 wt% of amine additives; 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 a chloride ion.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 1 wt% of an amine additive. The amine additive has a cation having 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 a chloride ion.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that it includes 1.0 mol / L LiPF6, EC / EMC (weight ratio 3:7) and 0.5 wt% of amine additives.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 1 is that no amine additive is added.

[0089] Test Example 1

[0090] Select a 12mAh lithium iron phosphate / graphite battery and place a 1mm thick electrode on the surface of the positive electrode. 2 Copper foil is used to simulate foreign matter. If the particle size is too small to cause a short circuit in the battery, the research loses its significance. Therefore, the copper scraps are selected to be about 1mm2 in size. The electrolytes in the above embodiments and comparative examples are injected into the battery, and the battery is charged at 0.02C with an upper limit protection voltage of 3.8V. Most of the dissolution process of the metal foreign matter is completed in the first charge, and 1mm 2The copper foil will definitely cause a short circuit in a battery of this capacity. The copper dissolution ratio is used as the basis for improving the copper dissolution effect. Copper dissolution ratio = (negative electrode + copper in diaphragm) / (positive electrode + negative electrode + copper in diaphragm) * 100%, wherein the copper in the positive and negative electrode sides and the diaphragm is accurately measured by ICP test. The higher the copper dissolution ratio, the more the negative electrode and diaphragm can accommodate deposited copper when the positive electrode contains the same amount of copper foreign matter, and the wider the safety margin of the battery. Therefore, the termination condition of the experiment is selected when the voltage drops suddenly or becomes 0V during charging. At this time, the copper dissolved in the negative electrode forms dendrites that pierce the diaphragm, causing an internal short circuit in the battery. The specific test results are shown in Table 1.

[0091] Table 1 Copper dissolution ratio in different electrolyte formulations

[0092]

[0093] It can be seen from Table 1 that when excessive copper impurities are added to the positive electrode sheet, copper will be dissolved and deposited at the negative electrode to form copper dendrites. When the copper dendrites grow to a certain extent, they will pierce the diaphragm and cause the battery to short circuit. The electrolyte provided by the present invention is used in the embodiment. Compared with the comparative example, the embodiment can accommodate more copper dissolved in the negative electrode and the diaphragm, indicating that in the embodiment with the addition of the electrolyte provided by the present invention, copper is deposited on the negative electrode surface in a flatter manner, rather than in the form of slender and sharp dendrites, thereby improving the performance of the battery.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that: The invention comprises an amine additive, wherein the amine additive has a cation having a structure as shown in formula (1): In the formula, R1, R2, R3, R 4、 R5 and R6 are each independently selected from at least one of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a phenyl group; The anion of the amine additive includes a halogen anion; The mass percentage of the amine additive in the electrolyte is not less than 1%wt.

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

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 to 3, characterized in that R1, R2, R3, R4, R5, and R6 are each a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, or a phenyl group.

5. The electrolyte according to claim 4, characterized in that The cation of the amine additive includes at least one of the structures of Formula 2 and Formula 3; 6. The electrolyte according to any one of claims 1 to 3, characterized in that: The cation of the amine additive includes at least one of the structures of Formula 4 and Formula 5:

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

8. The electrolyte according to any one of claims 1 to 7, characterized in that: The electrolyte further comprises a lithium salt, the content of the lithium salt in the electrolyte is 0.5 to 1.2 mol / L, and the lithium salt comprises at least one of LiPF6, LiBF4, LiTFSI, and LiBOB; and / or, The electrolyte also includes a solvent, the content of the solvent in the electrolyte is 85.00-99.99%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: The electrolyte comprising the electrolyte according to any one of claims 1 to 8.

10. An electronic device, characterized in that: A battery comprising the battery of claim 9.

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