WO2021017551A1 - 电解液、电池及电池组 - Google Patents

电解液、电池及电池组 Download PDF

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WO2021017551A1
WO2021017551A1 PCT/CN2020/087254 CN2020087254W WO2021017551A1 WO 2021017551 A1 WO2021017551 A1 WO 2021017551A1 CN 2020087254 W CN2020087254 W CN 2020087254W WO 2021017551 A1 WO2021017551 A1 WO 2021017551A1
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electrolyte
battery
zinc
anode
sulfate
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PCT/CN2020/087254
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English (en)
French (fr)
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潘中来
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瑞新材料科技(香港)有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M6/00—Primary cells; Manufacture thereof
    • H01M6/04—Cells with aqueous electrolyte
    • H01M6/06—Dry cells, i.e. cells wherein the electrolyte is rendered non-fluid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/244—Zinc electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0014—Alkaline electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to an electrolyte used in water-based batteries, and batteries and battery packs using the electrolyte, belonging to the technical field of secondary batteries.
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be used to activate active materials by charging after the batteries are discharged.
  • Rechargeable batteries are usually used as power sources and can be adjusted to meet the needs of low-cost and large-scale grid-scale energy storage systems.
  • research in the field of secondary batteries is mainly concentrated on lithium-ion batteries, high-temperature sodium-sulfur batteries, sodium-nickel-chloride batteries, vanadium flow batteries, etc.
  • Lithium-ion batteries have great advantages of rechargeable batteries due to their high energy density and low self-discharge rate.
  • traditional lithium-ion batteries are non-aqueous batteries, which are toxic and may pose environmental risks.
  • additives can be added to rechargeable batteries to increase the charging capacity and suppress the formation of dendrites.
  • Additives provide huge advantages in rechargeable batteries due to their ability to adjust ion transmission, and therefore have a significant impact on battery production, rate performance, and battery life.
  • patents CN201810012406.X and CN201210286489.4 disclose adding polyethylene glycol to the electrolyte
  • patent CN201510474585.5 discloses adding polyethylene glycol octylphenyl ether to the electrolyte
  • CN201410307591.7 discloses adding polyethylene glycol to the electrolyte.
  • Patent CN2017102430154 discloses that magnesium sulfate is added to the electrolyte to suppress the problems of dendrites, corrosion and hydrogen evolution that exist when anode metal ions (such as zinc ions) are charged and discharged in an aqueous solution.
  • the existing water-based zinc battery has a small volume and a small capacity. If the volume is increased, the electrode and the current collector area will be increased correspondingly, which will lead to the following defects: Large-area battery plate The relatively uneven distribution of voltage and current leads to a local over-potential on the surface of the positive electrode, which further produces the side reaction of zinc salt precipitation; the surface of the negative electrode also generates a local over-potential, which promotes dendrite growth and zinc salt precipitation, and a larger current areal density It is also easier to produce more side reactions. Therefore, if a large-volume water-based zinc battery needs to be obtained, it is necessary to solve the problems of dendrites and channel blockage.
  • the technical problem solved by the present invention is to provide an electrolyte, which is used in water-based zinc batteries and can dissolve zinc precipitation and inhibit dendrite growth.
  • the electrolyte of the present invention includes an aqueous electrolyte and an additive, wherein the additive is a neutral alkali metal salt and an oxygen-rich compound, and the aqueous electrolyte includes a metal that can be reduced and deposited at the anode during charge and discharge and the metal can be reversibly oxidized Dissolved anode metal ions.
  • the additive is a neutral alkali metal salt and an oxygen-rich compound
  • the aqueous electrolyte includes a metal that can be reduced and deposited at the anode during charge and discharge and the metal can be reversibly oxidized Dissolved anode metal ions.
  • the neutral alkali metal salt is an alkali metal sulfate; preferably, the neutral alkali metal salt is at least one of sodium sulfate, potassium sulfate, rubidium sulfate, and cesium sulfate.
  • the molar concentration of the neutral alkali metal salt in the electrolyte is 0.1-0.8M.
  • the oxygen-enriched compound is selected from polyethylene glycol, polysorbate, nonylphenol polyethylene glycol ether, polyoxyethylene octyl phenyl ether, polypropylene glycol, polyglycidol, and polyethyleneimine At least one; more preferably, the oxygen-enriched compound is polyethylene glycol; more preferably, the oxygen-enriched compound is polyethylene glycol with a weight average molecular weight of 200-2000 Da.
  • the concentration of the oxygen-enriched compound in the electrolyte is 100 ppm to 200,000 ppm by weight.
  • the pH of the electrolyte is 4-6.
  • the anode metal ion is zinc ion.
  • the aqueous electrolyte is zinc ion salt and lithium ion salt; more preferably, the molar concentration of zinc ions in the electrolyte is 0.1M-3M, and the molar concentration of lithium ions is 0.1M-3M.
  • the electrolyte further includes a solvent, and the solvent is at least one of water and alcohol; more preferably, the solvent is water.
  • the invention also provides a battery.
  • the battery of the present invention includes a cathode, an anode and an electrolyte, and the electrolyte is the above-mentioned electrolyte.
  • the cathode is a lithium-based electrode material.
  • the anode is a zinc-based electrode material.
  • the present invention also provides a battery pack.
  • the battery pack of the present invention includes several batteries, and the battery is the battery of the present invention.
  • the present invention has the following beneficial effects:
  • the present invention dissolves zinc hydroxide precipitation in situ by adding neutral alkali metal salt and PEG and other oxygen-rich compounds in the electrolyte, further rearranges the zinc hydroxide precipitation and dredges ion channels, inhibits the formation of metal dendrites, and finally achieves The purpose of improving battery capacity and cycle life.
  • Figure 1 shows the change in the concentration of soluble salts in a zinc-lithium battery without additives before cycling and after 100 charge-discharge cycles.
  • Figure 2 is a schematic diagram of the additive to relieve the blocked channel.
  • Figure 3 shows the constant current ratio retention rate of the battery of the present invention.
  • Figure 4 shows the 0.2C cycle performance of the four batteries in Example 1.
  • Figure 5 shows the cycle performance of the battery in Example 2 at different rates.
  • Figure 6 shows the cycle performance of the battery in Example 3.
  • Fig. 7 shows the cycle performance of the battery in Example 4.
  • Figure 8 shows the cycle performance of the battery in Example 5.
  • Fig. 9 shows the cycle performance of the battery in Example 6.
  • Fig. 10 shows the cycle performance of the battery in Example 7.
  • Figure 11 shows the cycle performance of the battery in Example 8.
  • Fig. 12 shows the cycle performance of the battery in Example 9.
  • lithium-based cathodes and zinc-based anodes during charging, lithium ions are deintercalated at the cathode, and zinc ions are reduced and precipitated at the anode; During the discharge, the intercalation reaction of lithium ions occurs at the cathode, and the oxidation and dissolution of zinc ions occur at the zinc anode.
  • the battery performance is usually limited during the cycle of zinc-lithium batteries, and it shows poor cycle performance during constant charging and discharging. This can be attributed to the formation of insoluble zinc hydroxide precipitates. The material will be deposited in the porous electrode, thereby reducing the capacity of the battery.
  • Figure 1 shows the changes in the concentration of soluble salts in the electrolyte before recycling and after 100 cycles of charging and discharging in an ordinary zinc-lithium battery.
  • the concentration uses an energy dispersive X-ray fluorescence analyzer (EDX-LE XRF) Tested.
  • EDX-LE XRF energy dispersive X-ray fluorescence analyzer
  • the anode metal ions will be reduced and precipitated at the anode (ie, the anode), this will inevitably produce metal dendrites.
  • Zinc dendrites are formed on the surface of the anode. Due to repeated charge and discharge cycles, the zinc dendrites can grow from the anode, and furthermore, they will pierce the diaphragm and even approach the cathode.
  • an electrical short circuit can be established between the electrodes via zinc metal including zinc dendrites. This kind of electrical short circuit will cause the battery to malfunction, and the overheating of the battery due to the short circuit will further cause safety hazards, which may further lead to "fire”. Therefore, in zinc-lithium batteries, it is necessary to suppress the growth of dendrites.
  • the research of the present invention found that by adding neutral alkali metal salt and oxygen-rich compound to the electrolyte at the same time, it can not only help to dissolve and rearrange the Zn 2 (OH) 2 SO 4 precipitation, but also smooth the channel in the electrode to keep it more A good capacity can also inhibit and/or prevent the formation of dendrites and maintain good cycle performance of the battery.
  • the electrolyte of the present invention includes an aqueous electrolyte and an additive, wherein the additive is a neutral alkali metal salt and an oxygen-rich compound, and the aqueous electrolyte includes a metal that can be reduced and deposited at the anode during charge and discharge. It can reversibly oxidize dissolved anode metal ions.
  • the additive is a neutral alkali metal salt and an oxygen-rich compound
  • the aqueous electrolyte includes a metal that can be reduced and deposited at the anode during charge and discharge. It can reversibly oxidize dissolved anode metal ions.
  • the aqueous electrolyte plays the role of ion conduction, usually an inorganic salt, and in the electrolyte of the present invention, in addition to the aqueous electrolyte that plays the role of ion conduction, a neutral alkali metal salt and an oxygen-rich compound must be additionally added to achieve Dissolve zinc precipitation, inhibit zinc dendrites, and improve battery cycle performance.
  • the neutral alkali metal salt is an alkali metal sulfate. Adding sulfate will release the alkali metal in the electrolyte solution without introducing other anions to affect the electrochemical performance. Ion, when the hydroxide anion is present, it can dissolve the zinc hydroxide precipitate in situ, further rearrange the zinc hydroxide precipitate and clear the tunnel, as shown in Figure 2.
  • the principle is as follows:
  • M + is an alkali metal ion.
  • the neutral alkali metal salt is at least one of sodium sulfate, potassium sulfate, rubidium sulfate, and cesium sulfate.
  • the increase in metallicity and the increase in alkalinity of the hydroxide corresponding to the neutral alkali metal salt gradually increase from Na, K, Ru to Cs, indicating that the hydroxyzinc precipitate is more easily dissolved in situ.
  • other parameters should be considered comprehensively, such as the solubility of neutral alkali metal salts, the hydrated ion radius of alkaline atoms and the cost.
  • the molar concentration of the neutral alkali metal salt in the electrolyte is 0.1-0.8M.
  • M in the present invention is an abbreviation of the molar concentration unit mol/L.
  • the molar concentration of the neutral alkali metal salt in the electrolyte may be 0.1M, 0.15M, 0.2M, 0.25M, 0.3M, 0.35M, 0.4M, 0.45M, 0.5M, 0.55M , 0.6M, 0.65M, 0.7M, 0.75M, 0.8M, etc.
  • Oxygen-rich compounds are compounds rich in oxygen atoms in the molecule.
  • the addition of oxygen-rich compounds to the battery electrolyte can guide the uniform deposition of zinc ions, prevent zinc accumulation and prevent the growth of dendrites between the electrodes of the battery, thereby preventing battery short circuit and Improve cycle performance.
  • Any oxygen-rich compound can be used.
  • the oxygen-rich compound can be polyethylene glycol and its derivatives, such as polysorbate, nonylphenol polyglycol ether, Polyoxyethylene octyl phenyl ether, etc., can also be other oxygen-rich compounds such as polypropylene glycol, polyglycidol, and heteroatom nitrogen compounds such as polyethyleneimine.
  • the oxygen-enriched compound is polyethylene glycol, and more preferably, the oxygen-enriched compound is polyethylene glycol with a weight average molecular weight Mw of 200 to 2000 Da. Unless otherwise specified, the molecular weights in the present invention are all weight average molecular weights.
  • the concentration of the oxygen-enriched compound in the electrolyte is 100 ppm to 200,000 ppm by weight.
  • the concentration by weight of oxygen-enriched compounds in the electrolyte can be 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 5000 ppm, 10000 ppm, 15000 ppm, 20000 ppm, 50000 ppm, 100000 ppm, 130000 ppm, 150000 ppm, 180,000 ppm, 200000ppm etc.
  • the neutral alkali metal salt and the oxygen-rich compound can be combined arbitrarily without affecting the effect of the present invention.
  • the neutral alkali metal salt and the oxygen-rich compound can be combined arbitrarily without affecting the effect of the present invention.
  • the pH value of the electrolyte is 4-6.
  • a weak acid battery system with a pH of 4 to 6 on the one hand, can prevent the generation of zinc hydroxide precipitation.
  • it can promote the in-situ dissolution of zinc hydroxide precipitation, further rearrange the zinc hydroxide precipitation and clear the channel.
  • the pH range can be adjusted by buffering agents.
  • the pH value of the electrolyte may be pH4, pH4.3, pH4.5, pH4.7, pH5, pH5.3, pH5.5, pH5.8, pH6, etc.
  • the pH of the electrolyte is 4.7.
  • the anode metal ions in the electrolyte can be reduced and deposited to metal at the anode during the charging process, and the metal can be reversibly oxidized to metal ions during the discharge process. That is, when the battery is charged, the anode metal ions in the electrolyte are reduced to metal and deposited on the anode; when the battery is discharged, the metal is oxidized to become metal ions and dissolve from the anode to enter the electrolyte.
  • the anode metal ion is zinc ion.
  • the molar concentration of zinc ions is 0.1M-3M.
  • the molar concentration of zinc ions may be 0.1M, 0.3M, 0.5M, 0.7M, 1M, 1.2M, 1.5M, 1.8M, 2M, 2.1M, 2.4M, 2.5M, 2.8M, 3M, etc.
  • the anode metal ions may be present in the electrolyte in the form of chlorate, sulfate, nitrate, acetate, formate, phosphate, etc., preferably, the anode metal ions are present in the electrolyte in the form of sulfate.
  • the electrolyte also includes cathode ions that participate in the cathode reaction.
  • the cathode ions can be metal ions that are inserted and extracted at the cathode of the battery or ions that participate in the cathode redox reaction during charge and discharge.
  • the cathode ions are metal ions that are inserted and extracted at the cathode of the battery.
  • the cathode ions in the cathode are released into the electrolyte; when the battery is discharged, the ions released during the charging are embedded in the cathode material from the electrolyte.
  • the cathode ions are lithium ions.
  • the molar concentration of lithium ions is 0.1M to 3M.
  • the molar concentration of lithium ions may be 0.1M, 0.3M, 0.5M, 0.7M, 1M, 1.2M, 1.5M, 1.8M, 2M, 2.1M, 2.4M, 2.5M, 2.8M, 3M, etc.
  • the cathodic ions may be present in the electrolyte in the form of chlorate, sulfate, nitrate, acetate, formate, phosphate, etc., preferably, the cathodic ions are present in the electrolyte in the form of sulfate.
  • the electrolyte of the present invention also includes a solvent.
  • the purpose of using the solvent is to dissolve the aqueous electrolyte and additives, and make the electrolyte ionize in the solvent, and finally generate freely movable cations and anions in the electrolyte.
  • the solvent of the present invention is preferably at least one of water and alcohol.
  • the alcohol includes but is not limited to methanol or ethanol. In order to save costs while reducing the risk of environmental pollution, it is more preferred that the solvent is water.
  • the present invention also provides a battery, which includes a cathode, an anode and an electrolyte, and the electrolyte is the above-mentioned electrolyte of the present invention.
  • the cathode may include a cathode current collector and a cathode active material.
  • the present invention has no special restrictions on the cathode current collector, and those skilled in the art can make selections according to needs.
  • the cathode current collector is usually used as a carrier for electron conduction and collection, and does not participate in the electrochemical reaction. That is, within the working voltage range of the battery, the cathode current collector can stably exist in the electrolyte without side reactions, so as to ensure that the battery has a stable Cycle performance.
  • the size of the cathode current collector can be determined according to the use of the battery. For example, if it is used in a large battery that requires high energy density, a cathode current collector with a large area can be used.
  • the thickness of the cathode current collector there is no particular limitation on the thickness of the cathode current collector, and it is usually about 1-100 ⁇ m.
  • the shape of the cathode current collector is also not particularly limited, and may be rectangular or circular, for example.
  • the material constituting the cathode current collector for example, metals, alloys, carbon-based materials, etc. can be used.
  • the cathode current collector has a cathode active material.
  • the cathode active material can be formed on one side of the current collector or on both sides of the cathode current collector.
  • the present invention has no special regulations on the cathode active material, as long as it can reversibly extract and intercalate metal ions, and those skilled in the art can appropriately select.
  • the cathode is a lithium-based electrode material, that is, the metal ions that are reversibly extracted and inserted are lithium ions.
  • the cathode active material may be selected from lithium manganate, lithium nickel cobalt manganate or lithium iron phosphate.
  • the cathode may include a binder.
  • binders are compounds that hold lithium ion battery components together, and are known to increase the life and capacity of these types of batteries.
  • the adhesive can be any existing conventional adhesive and can be obtained from commercial sources known to those skilled in the art.
  • the binder may be selected from one or more of polyvinylidene fluoride, styrene butadiene rubber, carboxymethyl cellulose and the like.
  • the cathode may further include carbon black.
  • carbon black can be used as a conductive additive in a composite cathode of a lithium ion battery. It is known that carbon black helps to enhance the recyclability of the cathode. Carbon black can be obtained from any commercial source known to those skilled in the art.
  • the electrode composite material may include carbon black in an amount of 0.1% by weight to about 30% by weight.
  • the anode may include an anode current collector and an anode active material.
  • the present invention has no special requirements for the anode current collector.
  • the anode current collector only serves as a carrier for electron conduction and collection, and does not participate in electrochemical reactions.
  • the material of the anode current collector can be selected from the metal Ni, Cu, Ag, Pb, Mn, Sn, Fe, Al or at least one of the above-mentioned metals that have undergone passivation treatment, or elemental silicon, or carbon-based materials, or stainless steel or Passivated stainless steel.
  • the anode current collector has an anode active material.
  • the anode active material can be formed on one side of the current collector or on both sides of the anode current collector.
  • the present invention has no special regulations on the anode active material, and those skilled in the art can appropriately select it according to needs.
  • the anode is a zinc-based electrode material. That is, the anode active material is zinc.
  • the anode active material may be zinc powder, which is coated on the anode current collector with a binder.
  • the anode active material may be a zinc plate, which is adhered to the current collector.
  • zinc flakes are directly used as the anode, and the zinc flakes are used as both the anode current collector and the anode active material. At this time, the zinc flake is a carrier for anode charge and discharge.
  • the battery of the present invention uses a lithium-based electrode material as the cathode and a zinc-based electrode material as the anode, thereby forming a zinc-lithium battery.
  • the battery may not contain a separator.
  • a diaphragm between the cathode and the anode in the electrolyte.
  • the diaphragm can avoid short circuit caused by the connection of the positive and negative electrodes caused by other unexpected factors.
  • the diaphragm of the present invention has no special requirements, as long as it is a diaphragm that allows electrolyte and ions to pass through and is electrically insulated.
  • Various separators used in organic lithium ion batteries can be applied to the present invention.
  • the diaphragm allows at least some ions including zinc ions to be transported between the electrodes.
  • the separator can inhibit and/or prevent dendrite formation and battery short circuit.
  • the membrane can be a porous material and can be obtained from any commercial source.
  • the separator can be selected from glass fiber, non-woven fabric, asbestos film, non-woven polyethylene film, nylon, polyethylene, polypropylene, polyvinylidene fluoride, polyacrylonitrile, polyethylene/propylene double-layer separator, polypropylene/ At least one of polypropylene/polypropylene three-layer separators.
  • the cathode material surface density of 0.07g / cm 2 As one embodiment of the present invention using larger than the volume of the battery electrolyte assembly according to the present invention, wherein the size of the battery current collector 7.35cm * 4.45cm, the cathode material surface density of 0.07g / cm 2, 0.2C current surface density of 1.1 mA/cm 2 . According to theoretical calculations and experimental test results, the voltage difference between the upper and lower ends of the positive electrode collector is about 12mV, and the 0.2C charging current of the battery is 36mA.
  • NAMS helps dissolve the insoluble zinc salt precipitation produced by the side reaction on the positive electrode surface, slows the rise of the battery's internal resistance (increases the constant current ratio retention rate), keeps the electrode stable, and improves the cycle life.
  • the constant current ratio retention rate is shown in Figure 3.
  • D1-1 uses electrolyte without any additives
  • D1-2 uses electrolyte with neutral alkali metal salt
  • D1-3 uses electrolyte with polyethylene glycol
  • S1 uses both neutral Electrolyte of alkali metal salt and polyethylene glycol.
  • the surface of the negative electrode will also generate local over-potential, which promotes side reactions such as dendrite growth and zinc salt precipitation.
  • side reactions due to the synergistic effect of NAMS and oxygen-rich compounds (such as PEG), side reactions are slowed down, and zinc salt consumption is reduced.
  • the electrolyte and additives are kept effective so that the negative electrode remains stable.
  • a larger current areal density is likely to produce more side reactions, so due to the larger battery size in the present invention, it is more difficult to stabilize the cycle. It is necessary to add additives to the electrolyte to improve the cycle stability.
  • the present invention also provides a battery pack, which includes several batteries according to the present invention.
  • the battery pack may include a battery module composed of multiple batteries.
  • the batteries can be connected in series or in parallel. In particular, connect them in series.
  • a certain amount of lithium sulfate and zinc sulfate are weighed, and all are added to deionized water to make the zinc ion concentration 2.1M and the lithium ion concentration 2.6M to obtain electrolyte D1-1.
  • the battery was prepared by referring to the method of Example 1 and its cycle performance was measured.
  • the S2 electrolyte was subjected to a 0.5C charge and discharge test. The results are shown in Figure 5.
  • Example 1 According to the method of Example 1, the above-mentioned electrolytes were used to respectively assemble batteries, and their cycle performance was measured. The results are shown in Figs. It can be seen that, compared with the control group of electrolyte without additives, the cycle performance of the battery is improved after adding the additives of the present invention with different concentrations. It should be pointed out that here S4 and S5 and their corresponding control groups D4 and D5 are matched with an improved positive electrode formula.
  • the positive electrodes of D1-1 and S1, S2, S3 in Examples 1 to 3 all use titanium platinum current collector + 1% styrene butadiene rubber (SBR); the positive electrodes of S4 and the control group D4 use titanium platinum current collector +2% styrene butadiene rubber (SBR) + 0.3% succinonitrile (SN) and the outer surface of the positive electrode sheet is coated with graphene; the positive electrode of S5 and the control group D5 adopts stainless steel current collector + 2% styrene butadiene rubber (SBR) +0.3% Succinonitrile (SN).
  • SBR styrene butadiene rubber
  • SN succinonitrile
  • the above-mentioned electrolyte solutions S6 to S9 were used to assemble batteries respectively, and the cycle performance was measured.
  • the results are shown in Figs. It can be seen that, compared with the control group D6 of the electrolyte without additives, the cycle performance of the battery is improved after adding the additives of the present invention with different concentrations.
  • S6 to S9 and the corresponding control group D6 are matched with the positive electrode formula after mass production.
  • the positive electrode uses a stainless steel current collector + 2% styrene butadiene rubber (SBR) + 0.3% succinonitrile (SN).

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Abstract

一种用于水系电池的电解液，以及利用该电解液的电池和电池组，属于二次电池技术领域。解决的技术问题是提供一种电解液，该电解液，包括水性电解质和添加剂，其中，所述添加剂为中性碱金属盐和富氧化合物，所述水性电解质包括在充放电过程中能够在阳极还原沉积为金属且该金属能可逆氧化溶解的阳极金属离子。通过在电解液中加入中性碱金属盐以及PEG等富氧化合物，从而原位溶解氢氧化锌沉淀，进一步重排氢氧化锌沉淀并疏通离子通道，抑制金属枝晶的形成，最终达到提高电池容量和循环寿命的目的。

Description

电解液、电池及电池组
相关申请的交叉引用
本申请要求在2019年7月26日提交的美国专利申请No.62879168的权益和优先权，该申请No.62879168的全部内容通过引用并入本文。
技术领域
本发明涉及一种用于水系电池的电解液，以及利用该电解液的电池和电池组，属于二次电池技术领域。
背景技术
随着对小型便携式设备的要求不断提高，对电源的要求也越来越高，需要寻求合适的，高效，紧凑，轻便和安全的可持续电源。
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性物质激活而继续使用的电池。充电电池通常用作电源，可以进行调整以满足低成本和大型电网规模的储能系统的需求。目前，二次电池领域的研究主要集中在锂离子电池、高温钠硫电池、钠镍氯电池、钒液流电池等，但是，无论哪种电池，均无法同时满足廉价、安全、寿命长的要求。而锂离子电池由于其具有高能量密度和低自放电率而具有可充电电池的巨大优势。但传统的锂离子电池为非水电池，有毒且可能造成环境风险。
近来，具有安全、高功率、大容量的基于水性电解质的可充电电池被广泛研究。尤其是具有锌金属阳极的水性电解质电池(锌离子电池)，由于其具有丰度、高稳定性、低成本和无毒的特性，应用前景广泛。但是，这类型的碱性电池依旧存在缺点。
通常，在含水碱性电池中，由于使用碱性电解质，这些电池会表现出低循环性，碱性电解质会具有很强的腐蚀性，并导致阴极和阳极中的电极插层性能下降。此外，如果发生泄漏，碱性电解质的存在可能对环境和人体都具有危险。
另外，水系锌电池在反复的充电和放电过程期间，由于锌的溶解和锌金属沉淀物的不均匀累积而沉积在阳极表面上，有可能会堵塞离子通道，从而限制了电池的性能。此外，在电池中不可避免的会形成锌枝晶，锌枝晶的存在会导致腐蚀，自放电以及潜在的短路，可能带来安全风险并缩短电池循环寿命。
为了克服缺陷，目前，可以将添加剂加入到可再充电电池中以增加充电容量并抑 制枝晶的形成。添加剂由于可调节离子传输的能力而在可充电电池中提供了巨大的优势，因此对电池的生产，速率性能和电池寿命产生了重大影响。比如专利CN201810012406.X、CN201210286489.4公开了在电解液中加入聚乙二醇，专利CN201510474585.5公开了在电解液中加入聚乙二醇辛基苯基醚，CN201410307591.7公开了在电解液中加入聚乙烯醇，这些有机富氧化合物的加入，能够抑制腐蚀和枝晶，但是，这种提高是有限的，所应用的电池也是小体积电池。专利CN2017102430154公开了在电解液中加入硫酸镁，从而抑制阳极金属离子(例如锌离子)在水溶液中充放电时存在的枝晶、腐蚀以及析氢等问题。
此外，现有的水系锌电池，体积较小，容量较小，而如果将体积增大，则会相应的增大电极，增加集流体面积，将会导致以下缺陷：大面积的电池极板上电压和电流分布相对不均匀，导致正极表面局部产生过电势，进而进一步产生锌盐沉淀副反应；负极表面也会产生局部过电势，促进枝晶生长及锌盐沉淀，而较大的电流面密度也更容易产生更多的副反应。因此，如果需要得到大体积的水系锌电池，需要解决枝晶和通道堵塞两方面的问题。
发明内容
针对以上缺陷，本发明解决的技术问题是提供一种电解液，该电解液应用在水系锌电池中，能够溶解锌沉淀，抑制枝晶生长。
本发明电解液，包括水性电解质和添加剂，其中，所述添加剂为中性碱金属盐和富氧化合物，所述水性电解质包括在充放电过程中能够在阳极还原沉积为金属且该金属能可逆氧化溶解的阳极金属离子。
优选的，所述中性碱金属盐为碱金属硫酸盐；优选所述中性碱金属盐为硫酸钠、硫酸钾、硫酸铷、硫酸铯中的至少一种。
进一步优选的，中性碱金属盐在电解液中的摩尔浓度为0.1～0.8M。
优选的，所述富氧化合物为聚乙二醇、聚山梨酸酯、壬基酚聚乙二醇醚、聚氧乙烯辛基苯基醚、聚丙二醇、聚缩水甘油、聚乙烯亚胺中的至少一种；更优选所述富氧化合物为聚乙二醇；更优选所述富氧化合物为重均分子量为200～2000Da的聚乙二醇。
进一步优选的，富氧化合物在电解液中按重量计浓度为100ppm～200000ppm。
优选的，所述电解液的pH值为4～6。
优选的，所述阳极金属离子为锌离子。
优选的，所述水性电解质为锌离子盐和锂离子盐；更优选在电解液中，锌离子的摩尔浓度为0.1M～3M，锂离子的摩尔浓度为0.1M～3M。
优选的，所述电解液中还包括溶剂，所述溶剂为水、醇中的至少一种；更优选所述溶剂为水。
本发明还提供一种电池。
本发明电池，包括阴极、阳极和电解液，所述电解液为上述电解液。
优选的，所述阴极为锂基电极材料。
进一步优选的，所述阳极为锌基电极材料。
本发明还提供一种电池组。
本发明电池组，包括若干个电池，所述电池本发明所述的电池。
与现有技术相比，本发明具有如下有益效果：
本发明通过在电解液中加入中性碱金属盐以及PEG等富氧化合物，从而原位溶解氢氧化锌沉淀，进一步重排氢氧化锌沉淀并疏通离子通道，抑制金属枝晶的形成，最终达到提高电池容量和循环寿命的目的。
附图说明
图1为没有添加剂的锌锂电池中，循环前以及100次充放电循环后电池中可溶盐浓度的变化。
图2为添加剂疏导堵塞通道示意图。
图3为本发明电池的恒流比保持率。
图4为实施例1中四组电池0.2C循环性能。
图5为实施例2中电池不同倍率的循环性能。
图6为实施例3中电池的循环性能。
图7为实施例4中电池的循环性能。
图8为实施例5中电池的循环性能。
图9为实施例6中电池的循环性能。
图10为实施例7中电池的循环性能。
图11为实施例8中电池的循环性能。
图12为实施例9中电池的循环性能。
具体实施方式
在下面给出的描述中，可以参考水性锌离子电池。然而，所描述的电解液可适用于非基于锌的其他电池单元和电池组。
一般的，在包括但不限定于锌锂电池(即锂基阴极锌基阳极)的水系电池中，充电时，在阴极发生锂离子的脱嵌，在阳极发生锌离子的还原和沉淀；而在放电期间，在阴极发生锂离子的嵌入反应，锌离子的氧化和溶解则在锌阳极处发生。受充放电原理影响，锌锂电池在循环使用过程中，电池性能通常受到限制，在恒定充电和放电过程中表现出较差的循环性能，这可归因于形成不溶性氢氧化锌沉淀，该不溶物将会沉积在多孔电极中，从而降低电池的容量。
图1示出了在普通锌锂电池中，循环使用前以及充放电循环100次后，电解液中可溶盐的浓度变化，该浓度采用能量色散型X射线荧光分析仪(EDX-LE XRF)测试得到。从图1可明显看出，循环100次后，电解液中Zn 2+和SO 4 2-离子明显减少，表明该电池经过多次循环后，形成了不溶性Zn 2(OH) 2SO 4沉淀。这种沉淀将会进入多孔电极中，堵塞电极中的离子通道，影响离子的传输，并且增加电极内阻，降低容量。
此外，由于阳极金属离子将会在阳极(即负极)发生离子的还原和沉淀，这将会不可避免的产生金属枝晶，具体到锌锂电池中，在充电和放电的过程中，可导致在阳极表面上形成锌枝晶，由于重复的充放电循环，锌枝晶可以从阳极向外生长，进一步的，将会刺穿隔膜，甚至接近阴极。当锌枝晶到达阴极时，可以经由包括锌枝晶的锌金属在电极之间建立电短路。这种电短路会导致电池故障，并且由于短路引起的电池过热会进一步导致安全隐患，这可能进一步导致“起火”。因此，在锌锂电池中，需要抑制枝晶的生长。
而本发明研究发现，通过同时向电解液中添加中性碱金属盐和富氧化合物，不仅可以有助于溶解和重新排列Zn 2(OH) 2SO 4沉淀，疏导电极内通道使其保持更好的容量，还能抑制和/或防止枝晶形成，保持电池良好的循环性能。
因此，本发明的电解液，包括水性电解质和添加剂，其中，所述添加剂为中性碱金属盐和富氧化合物，所述水性电解质包括在充放电过程中能够在阳极还原沉积为金属且该金属能可逆氧化溶解的阳极金属离子。
其中，水性电解质起着离子传导的作用，通常为无机盐，而本发明的电解液中，除了起离子传导作用的水性电解质，还需额外加入中性碱金属盐和富氧化合物，才能起到溶解锌沉淀，抑制锌枝晶，提高电池循环性能的作用。
作为本发明的一个优选的实施方法，所述中性碱金属盐为碱金属硫酸盐，加入硫酸盐，将会在不引入其他阴离子来影响电化学性能的前提下，在电解质溶液中释放碱金属离子，当存在氢氧根阴离子时，它可以原位溶解氢氧化锌沉淀，进一步重排氢氧化锌沉淀并疏通隧道，详见图2。其原理如下：
Figure PCTCN2020087254-appb-000001
其中，M +为碱金属离子。
优选的，所述中性碱金属盐为硫酸钠、硫酸钾、硫酸铷、硫酸铯中的至少一种。金属性增加和中性碱金属盐相应的氢氧化物的碱度增加的趋势从Na，K，Ru到Cs逐渐增加，表明羟基锌沉淀物更容易就地溶解。在实际使用中，应综合考虑其他参数，如中性碱金属盐的溶解度，碱性原子的水合离子半径和成本。优选地，中性碱金属盐在电解液中的摩尔浓度为0.1～0.8M。本发明的M为摩尔浓度单位mol/L的简写。
作为一些具体的实施方式，中性碱金属盐在电解液中的摩尔浓度可以为0.1M、0.15M、0.2M、0.25M、0.3M、0.35M、0.4M、0.45M、0.5M、0.55M、0.6M、0.65M、0.7M、0.75M、0.8M等。
富氧化合物为分子中富含氧原子的化合物，在电池电解液中添加富氧化合物，可以引导锌离子均匀沉积，防止锌聚集并阻止电池的电极之间枝晶的生长，从而防止电池短路并改善循环性能。可以使用任意富含氧原子的化合物，作为优选的实施方式，富氧化合物为可以为聚乙二醇以及聚乙二醇的衍生物，比如聚山梨酸酯、壬基酚聚乙二醇醚、聚氧乙烯辛基苯基醚等，也可以为其他富氧化合物比如聚丙二醇、聚缩水甘油，还可以为聚乙烯亚胺等杂原子氮化合物中。
优选的，所述富氧化合物为聚乙二醇，更优选的，所述富氧化合物为重均分子量M w为200～2000Da的聚乙二醇。如无特殊说明，本发明中的分子量均为重均分子量。
作为优选方案，富氧化合物在电解液中按重量计浓度为100ppm～200000ppm。在本发明的一些实施方式中，富氧化合物在电解液中按重量计浓度可以为100ppm、500ppm、1000ppm、1500ppm、2000ppm、5000ppm、10000ppm、15000ppm、20000ppm、50000ppm、100000ppm、130000ppm、150000ppm、180000ppm、200000ppm等。
中性碱金属盐和富氧化合物可以任意组合，均不影响本发明的效果。比如，包括 但不限于硫酸钠和聚乙二醇的组合、硫酸钠和聚山梨酸酯的组合、硫酸钠和壬基酚聚乙二醇醚的组合、硫酸钠和聚氧乙烯辛基苯基醚的组合、硫酸钠和聚丙二醇的组合、硫酸钠和聚缩水甘油、硫酸钠和聚乙烯亚胺的组合、硫酸钾和聚乙二醇的组合、硫酸钾和聚山梨酸酯的组合、硫酸钾和壬基酚聚乙二醇醚的组合、硫酸钾和聚氧乙烯辛基苯基醚的组合、硫酸钾和聚丙二醇的组合、硫酸钾和聚缩水甘油、硫酸钾和聚乙烯亚胺的组合、硫酸铷和聚乙二醇的组合、硫酸铷和聚山梨酸酯的组合、硫酸铷和壬基酚聚乙二醇醚的组合、硫酸铷和聚氧乙烯辛基苯基醚的组合、硫酸铷和聚丙二醇的组合、硫酸铷和聚缩水甘油、硫酸铷和聚乙烯亚胺的组合、硫酸铯和聚乙二醇的组合、硫酸铯和聚山梨酸酯的组合、硫酸铯和壬基酚聚乙二醇醚的组合、硫酸铯和聚氧乙烯辛基苯基醚的组合、硫酸铯和聚丙二醇的组合、硫酸铯和聚缩水甘油、硫酸铯和聚乙烯亚胺的组合。
为了使电池性能更加的优化，所述电解液的pH值为4～6。pH值为4～6的弱酸电池系统，一方面可以防止氢氧化锌沉淀的产生。另一方面在加入添加剂后，可以促进原位溶解氢氧化锌沉淀，进一步重排氢氧化锌沉淀并疏通通道。pH的范围可以通过缓冲剂来调节。
在本发明的一些实施方式中，电解液的pH值可以为pH4、pH4.3、pH4.5、pH4.7、pH5、pH5.3、pH5.5、pH5.8、pH6等。作为优选方案，电解液的pH为4.7。
电解液中的阳极金属离子，在充电过程中在阳极能够还原沉积为金属，放电过程中该金属可逆氧化为金属离子。即在电池充电时，电解液中的阳极金属离子还原成金属，沉积在阳极上；在电池放电时，该金属氧化成为金属离子并从阳极上溶出，进入电解液。优选地，阳极金属离子为锌离子。作为优选方案，锌离子的摩尔浓度为0.1M～3M。在本发明的一些实施方式中，锌离子的摩尔浓度可以为0.1M、0.3M、0.5M、0.7M、1M、1.2M、1.5M、1.8M、2M、2.1M、2.4M、2.5M、2.8M、3M等。
阳极金属离子可以以氯酸盐、硫酸盐、硝酸盐、醋酸盐、甲酸盐、磷酸盐等形式存在于电解液中，优选的，阳极金属离子以硫酸盐形式存在于电解液中。
电解液还包括参与阴极反应的阴极离子。该阴极离子可以是在电池阴极发生嵌入和脱出的金属离子或在充放电过程中参与阴极氧化还原反应的离子。
在本发明的实施方式中，该阴极离子是在电池阴极发生嵌入和脱出的金属离子。在电池充电时，阴极中的该阴极离子脱出到电解液中；电池放电时，充电时脱出的该 离子又从电解液中嵌入到阴极材料中。优选地，阴极离子为锂离子。作为优选方案，锂离子的摩尔浓度为0.1M～3M。在本发明的一些实施方式中，锂离子的摩尔浓度可以为0.1M、0.3M、0.5M、0.7M、1M、1.2M、1.5M、1.8M、2M、2.1M、2.4M、2.5M、2.8M、3M等。
阴极离子可以以氯酸盐、硫酸盐、硝酸盐、醋酸盐、甲酸盐、磷酸盐等形式存在于电解液中，优选的，阴极离子以硫酸盐形式存在于电解液中。
本发明的电解液中还包括溶剂。采用溶剂的目的是用来溶解水性电解质以及添加剂，并使得电解质在溶剂中电离，最终在电解液中生成可自由移动的阳离子和阴离子。
作为优选的实施方式，本发明的溶剂优选为水、醇中的至少一种。其中醇包括但不限于甲醇或乙醇。为了节约成本同时减小环境污染风险，更优选所述溶剂为水。
本发明还提供一种电池，该电池单元包括阴极、阳极和电解液，所述电解液为本发明上述的电解液。
本发明实施方式中，阴极可以包括阴极集流体和阴极活性物质。
本发明对于阴极集流体没有特殊限制，本领域技术人员可以根据需要进行选择。阴极集流体通常作为电子传导和收集的载体，不参与电化学反应，即在电池工作电压范围内，阴极集流体能够稳定的存在于电解液中而基本不发生副反应，从而保证电池具有稳定的循环性能。阴极集流体的大小可根据电池的使用用途来确定。例如，如果在要求高能量密度的大型电池中使用，则可以使用面积大的阴极集流体。对阴极集流体的厚度没有特殊限制，通常为1～100μm左右。对于阴极集流体的形状也没有特别地限定，例如可以为长方形或圆形。对构成阴极集流体的材料没有特殊限制，例如，可以采用金属、合金、碳基材料等。
阴极集流体上具有阴极活性物质。阴极活性物质可以形成于集流体的一面，也可以形成于阴极集流体的两面，本发明对阴极活性物质没有特殊规定，只要能可逆脱出-嵌入金属离子即可，本领域技术人员可以根据需要适当选择。
优选的，所述阴极为锂基电极材料，即可逆脱出-嵌入的金属离子为锂离子。在该情况下，优选的，阴极活性物质可以选自锰酸锂、镍钴锰酸锂或磷酸铁锂。
根据本发明的一个实施方式，阴极可包含粘合剂。典型地，粘合剂是将锂离子电池组件保持在一起的化合物，并且已知可提高这些类型的电池的寿命和容量。粘合剂可以是任何现有的常规粘合剂，并且可以从本领域技术人员已知的商业来源获得。粘 合剂可以选自聚偏二氟乙烯，丁苯橡胶，羧甲基纤维素等中的一种或多种。
根据本发明的一个实施方式，阴极还可包含炭黑。在本发明的一个具体实施方案中，炭黑可用作锂离子电池复合阴极中的导电添加剂。已知炭黑有助于增强阴极的可循环性。炭黑可以从本领域技术人员已知的任何商业来源获得。在本发明的特定实施方案中，电极复合材料可包含0.1重量％至约30重量％的量的炭黑。
本发明实施方式中，阳极可以包括阳极集流体和阳极活性物质。
本发明对于阳极集流体没有特殊要求。阳极集流体仅作为电子传导和收集的载体，不参与电化学反应。阳极集流体的材料可选自金属Ni、Cu、Ag、Pb、Mn、Sn、Fe、Al或经过钝化处理的上述金属中的至少一种，或者单质硅，或者碳基材料，或者不锈钢或者经钝化处理的不锈钢。
阳极集流体上具有阳极活性物质。阳极活性物质可以形成于集流体的一面，也可以形成于阳极集流体的两面，本发明对阳极活性物质没有特殊规定，本领域技术人员可以根据需要适当选择。
在一个优选实施方式中，所述阳极为锌基电极材料。即阳极活性物质为锌。
在一个实施方式中，阳极活性物质可以为锌粉，采用粘结剂涂覆在阳极集流体上。在另一个实施方式中，阳极活性物质可以采用锌板，粘在集流体上。
在一个优选实施方式中，直接采用锌片作为阳极，锌片既作为阳极集流体，同时也为阳极活性物质。此时，锌片为用于阳极充放电的载体。
在优选的实施方式中，本发明的电池采用锂基电极材料为阴极，锌基电极材料为阳极，由此组成锌锂电池。
在本发明中，电池可以不含隔膜。当然，为了提供更好的安全性能，优选在电解液中位于阴极与阳极之间还设有隔膜。隔膜可以避免其他意外因素造成的正负极相连而造成的短路。
本发明的隔膜没有特殊要求，只要是允许电解液以及离子通过且电子绝缘的隔膜即可。有机锂离子电池采用的各种隔膜，均可以适用于本发明。通常，隔膜允许在电极之间输送至少一些包括锌离子在内的离子。优选地，隔膜可抑制和/或防止枝晶形成以及电池短路。隔膜可以是多孔材料，并且可以从任何商业来源获得。隔膜可以选自玻璃纤维，无纺布，石棉膜，无纺聚乙烯膜，尼龙，聚乙烯，聚丙烯，聚偏二氟乙烯，聚丙烯腈，聚乙烯/丙烯双层隔板，聚丙烯/聚丙烯/聚丙烯三层隔板中的至少一种。
作为本发明一个实施方式，采用本发明的电解液组装成大体积电池，其中，电池集流体尺寸为7.35cm*4.45cm，阴极材料面密度为0.07g/cm 2，0.2C电流面密度为1.1mA/cm 2。由理论计算和实验测试结果可知，正极集流体上下端电压差约为12mV，该电池的0.2C充电电流为36mA。
大面积的电池极板上电压和电流分布相对不均匀，导致正极表面局部产生过电势，进而产生锌盐沉淀副反应，因此维持循环保持率难度更高。NAMS帮助溶解正极表面副反应所产生的难溶锌盐沉淀，减缓电池内阻上升(恒流比保持率提高)，使电极得以保持稳定，提升循环寿命，恒流比保持率详见图3。图3中，D1-1采用未添加任何添加剂的电解液，D1-2采用添加中性碱金属盐的电解液，D1-3为采用添加聚乙二醇的电解液，S1采用同时添加中性碱金属盐和聚乙二醇的电解液。
此外，负极表面亦会产生局部过电势，促进枝晶生长及锌盐沉淀等副反应，本发明中由于NAMS和富氧化合物(如PEG)的协同作用，减缓副反应、降低锌盐消耗，使电解液和添加剂得以保持有效，从而使负极保持稳定。
较大的电流面密度容易产生更多的副反应，因此由于本发明中较大的电池尺寸，稳定循环的难度更高。需要在电解液中加入添加剂，才能提高循环稳定性。
本发明还提供一种电池组，包括若干个本发明所述的电池。电池组可包含由多个电池组成的电池模块。电池可以串联或并联连接。特别地，将它们串联连接。
下面结合实施例对本发明的具体实施方式做进一步的描述，并不因此将本发明限制在所述的实施例范围之中。
实施例1
电解液1(S1)的制备：
称取一定量的硫酸锂、硫酸锌、硫酸钠和聚乙二醇，全部加入去离子水中，使锌离子浓度为2M，锂离子浓度为2M，钠离子浓度为0.8M，聚乙二醇的浓度为400ppm、分子量为400，得到电解液S1。
对比电解液1(D1-1)的制备：
称取一定量的硫酸锂和硫酸锌，全部加入去离子水中，使锌离子浓度为2.1M，锂离子浓度为2.6M，得到电解液D1-1。
对比电解液2(D1-2)的制备：
称取一定量的硫酸锂、硫酸锌和硫酸钠，全部加入去离子水中，使锌离子浓度为 2M，锂离子浓度为2M，钠离子浓度为0.8M，得到电解液D1-2。
对比电解液3(D1-3)的制备：
称取一定量的硫酸锂、硫酸锌和聚乙二醇，全部加入去离子水中，使锌离子浓度为2.1M，锂离子浓度为2.6M，聚乙二醇的浓度为400ppm，得到电解液D1-3。
电池的制备：
以锂基电极材料为阴极，以锌基电极材料为阳极，分别采用上述电解液S1、D1-1、D1-2、D1-3，组装得到的四组大体积电池。四组电池中，阴极、阳极隔膜均相同，仅有电解液不同，电池集流体尺寸为7.35cm*4.45cm，阴极材料面密度为0.07g/cm 2。
电池循环性能测试：
将上述四组电池进行0.2C充放电测试，测定其循环性能，其结果见图4。图中，D1-1采用未添加任何添加剂的电解液，D1-2采用添加中性碱金属盐的电解液，D1-3为采用添加聚乙二醇的电解液，S1采用同时添加中性碱金属盐和聚乙二醇的电解液。
从图4可以明显看出，在电解液中，单独添加硫酸钠，并不能改性循环性能，单独添加PEG，可在一定程度上改善循环性能，而同时添加硫酸钠和PEG，将会极大程度的提高循环性能，电池的循环寿命明显延长。
实施例2
电解液2(S2)的制备：
称取一定量的硫酸锂、硫酸锌、硫酸钠和聚乙二醇，全部加入去离子水中，使锌离子浓度为2M，锂离子浓度为2.4M，钠离子浓度为0.4M，聚乙二醇的浓度为400ppm、分子量为400，得到电解液S2。
参照实施例1的方法制备得到电池并测定其循环性能，其中S2电解液进行0.5C充放电测试，其结果见图5。
从图5中可以看出，同时添加硫酸钠和PEG，可同时提高0.2C和0.5C的倍率性能。
实施例3
电解液3(S3)的制备：
称取一定量的硫酸锂、硫酸锌、硫酸钾和聚乙二醇，全部加入去离子水中，使锌离子浓度为2M，锂离子浓度为2.4M，钾离子浓度为0.4M，聚乙二醇的浓度为400ppm，得到电解液S3。
参照实施例1的方法制备得到电池并测定其循环性能，其结果见图6。
从图6可以看出，在本发明的电解液中，中性碱金属盐采用钠盐和钾盐均可以提高电池的循环寿命。
实施例4、5
按照实施例1的方法，制备得到不同离子浓度的电解液，具体的浓度见表1。
表1
Figure PCTCN2020087254-appb-000002
按照实施例1的方法，用上述电解液分别组装成电池，测定其循环性能，结果见图7和图8。可见，与未添加添加剂的电解液的对照组相比，加入本发明不同浓度的添加剂后，电池的循环性能均有所提高。需要指出的是，这里S4和S5及其对应的对照组D4和D5搭配了改进后的正极配方。具体的，实施例1～3中的D1-1和S1、S2、S3的正极均采用钛铂集流体+1％丁苯橡胶(SBR)；S4及其对照组D4的正极采用钛铂集流体+2％丁苯橡胶(SBR)+0.3％丁二腈(SN)并且正极片外表面有石墨烯涂敷；S5及其对照组D5的正极采用不锈钢集流体+2％丁苯橡胶(SBR)+0.3％丁二腈(SN)。
实施例6～9
按照实施例1的方法，制备得到不同离子浓度的电解液，具体的浓度见表2。
表2
Figure PCTCN2020087254-appb-000003
按照实施例1的方法，用上述电解液S6～S9分别组装成电池，测定其循环性能， 结果见图9～12。可见，与未添加添加剂的电解液的对照组D6相比，加入本发明不同浓度的添加剂后，电池的循环性能均有所提高。需要指出的是，这里S6～S9及其对应的对照组D6搭配了量产后的正极配方。具体的，正极采用不锈钢集流体+2％丁苯橡胶(SBR)+0.3％丁二腈(SN)。

Claims (18)

  1. 一种电解液，其特征在于：包括水性电解质和添加剂，其中，所述添加剂为中性碱金属盐和富氧化合物，所述水性电解质包括在充放电过程中能够在阳极还原沉积为金属且该金属能可逆氧化溶解的阳极金属离子。
  2. 根据权利要求1所述的电解液，其特征在于：所述中性碱金属盐为碱金属硫酸盐。
  3. 根据权利要求1所述的电解液，其特征在于：所述中性碱金属盐为硫酸钠、硫酸钾、硫酸铷、硫酸铯中的至少一种。
  4. 根据权利要求1所述的电解液，其特征在于：中性碱金属盐在电解液中的摩尔浓度为0.1～0.8M。
  5. 根据权利要求1所述的电解液，其特征在于：所述富氧化合物为聚乙二醇、聚山梨酸酯、壬基酚聚乙二醇醚、聚氧乙烯辛基苯基醚、聚丙二醇、聚缩水甘油、聚乙烯亚胺中的至少一种。
  6. 根据权利要求1所述的电解液，其特征在于：所述富氧化合物为聚乙二醇。
  7. 根据权利要求1所述的电解液，其特征在于：所述富氧化合物为重均分子量为200～2000Da的聚乙二醇。
  8. 根据权利要求1所述的电解液，其特征在于：富氧化合物在电解液中按重量计浓度为100ppm～200000ppm。
  9. 根据权利要求1所述的电解液，其特征在于：所述电解液的pH值为4～6。
  10. 根据权利要求1所述的电解液，其特征在于：所述阳极金属离子为锌离子。
  11. 根据权利要求1所述的电解液，其特征在于：所述水性电解质为锌离子盐和锂离子盐。
  12. 根据权利要求11所述的电解液，其特征在于：在电解液中，锌离子的摩尔浓度为0.1M～3M，锂离子的摩尔浓度为0.1M～3M。
  13. 根据权利要求1所述的电解液，其特征在于：所述电解液中还包括溶剂，所述溶剂为水、醇中的至少一种。
  14. 根据权利要求12所述的电解液，其特征在于：所述溶剂为水。
  15. 一种电池，包括阴极、阳极和电解液，其特征在于，所述电解液为权利要求1～14任一项所述的电解液。
  16. 根据权利要求14所述的电池，其特征在于：所述阴极为锂基电极材料。
  17. 根据权利要求15或16所述的电池，其特征在于：所述阳极为锌基电极材料。
  18. 一种电池组，包括若干个电池，所述电池为权利要求15～17任一项所述的电池。
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US20180316064A1 (en) * 2015-10-21 2018-11-01 Research Foundation Of The City University Of New New York Additive for Increasing Lifespan of Rechargeable Zinc-Anode Batteries
CN105762406A (zh) * 2016-05-10 2016-07-13 北京石油化工学院 一种有机型锌离子二次电池

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