阅读说明：本技术 一种亲水性隔膜及含有该亲水性隔膜的电池 (Hydrophilic diaphragm and battery containing same ) 是由 黄杜斌 王春源 李爱军 何鑫 田波 刘兴坤 陈锦华 于 2021-01-05 设计创作，主要内容包括：本发明公开了亲水性隔膜及含有该亲水性隔膜的电池,所述亲水性隔膜为含亲水性高分子材料的微孔膜；所述亲水性隔膜的孔径为0.1-5um,厚度为20-500um,孔隙率为30％-90％。本发明的有益效果为：本发明所述亲水性隔膜在水性电解液中的浸润性明显优于商业的PP、PE微孔膜以及亲水性处理的聚烯烃隔膜,吸收水性电解液的能力更强,隔膜的电导率更高；本发明所述亲水性隔膜具有均匀的微孔结构,其阻隔能力高于无纺布、纤维纸和玻璃纤维膜,可以降低电池发生内部短路的风险；由本发明所述的亲水性隔膜与电解液共同作用诱导锌枝晶规则生长,提高金属锌电极的循环寿命；优化Zn溶解/沉积的极化过电势,提高锌电极的电化学性能。(The invention discloses a hydrophilic diaphragm and a battery containing the same, wherein the hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.1-5um, the thickness is 20-500um, and the porosity is 30% -90%. The invention has the beneficial effects that: the wettability of the hydrophilic diaphragm in the aqueous electrolyte is obviously superior to that of commercial PP and PE microporous membranes and hydrophilic polyolefin diaphragms, the capacity of absorbing the aqueous electrolyte is stronger, and the conductivity of the diaphragm is higher; the hydrophilic diaphragm has a uniform microporous structure, has higher barrier capability than non-woven fabrics, fiber paper and glass fiber membranes, and can reduce the risk of internal short circuit of the battery; the hydrophilic diaphragm and the electrolyte act together to induce the zinc dendrite to grow regularly, so that the cycle life of the metal zinc electrode is prolonged; the polarization overpotential of Zn dissolution/deposition is optimized, and the electrochemical performance of the zinc electrode is improved.)

1. A hydrophilic diaphragm is characterized in that the hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.1-5um, the thickness is 20-500um, and the porosity is 30% -90%.

2. The hydrophilic membrane of claim 1, wherein the hydrophilic polymeric material is at least one of nylon 6, nylon 66, polyethersulfone, cellulose acetate, or cellulose nitrate.

3. The hydrophilic membrane according to claim 1, wherein the hydrophilic membrane further comprises a non-woven fabric or a fiber paper, and the non-woven fabric or the fiber paper and the hydrophilic polymer microporous membrane are mutually covered and bonded to form a hydrophilic membrane; the thickness of the hydrophilic membrane is 40-500 um.

4. The hydrophilic separator according to claim 1, wherein the hydrophilic separator is used in a neutral or slightly acidic secondary aqueous battery.

5. The hydrophilic separator according to claim 1, wherein the hydrophilic separator is applied to an aqueous sodium ion battery, an aqueous lithium ion battery, an aqueous zinc-based battery, or an aqueous mixed ion battery.

6. A battery comprising the hydrophilic separator according to any one of claims 1 to 5, wherein the battery comprises the hydrophilic separator, an electrolyte, a positive electrode and a negative electrode:

the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises a metal oxide capable of reversibly extracting-embedding ions; the metal oxide is manganese oxide MnxOy, x is more than 0 and less than or equal to 3, and y is more than 0 and less than or equal to 4;

the negative electrode is at least one of metal zinc or zinc alloy.

7. The battery according to claim 6, wherein the hydrophilic separator is a microporous membrane containing a hydrophilic polymer material, and the hydrophilic polymer material is cellulose acetate and/or cellulose nitrate.

8. The battery according to claim 7, wherein the hydrophilic separator has a pore size of 0.1 to 5um, a thickness of 40 to 300um, and a porosity of 30 to 90%.

9. The hydrophilic separator-containing battery according to claim 8, wherein the pore size of the hydrophilic separator is 0.1-0.8 um.

10. The hydrophilic separator-containing battery according to claim 7, wherein the pore size of the hydrophilic separator is 0.1-0.45 um; the thickness of the hydrophilic membrane is 40-150 um; the porosity of the hydrophilic membrane is 60% -90%.

11. The hydrophilic separator-containing battery according to claim 6, wherein the electrolyte contains a solvent, a solute:

the solvent is water or a mixture of water and an organic solvent; the organic solvent is at least one of formamide, dimethyl sulfoxide, N-N dimethylformamide, sulfolane and methanol, and the mass ratio of the organic solvent to water is (0.01-0.6) to 1;

the solute is an electrolyte or a compound containing an organic functional group R-R', and an electrolyte salt capable of providing zinc ions;

the organic functional group R is a hydrophilic group, and is at least one of a sulfonic group, a nitro group, a quaternary ammonium group, an amino group, a carboxyl group, an ester group or an ether group;

the organic functional group R 'is a hydrophobic group, and the organic functional group R' is at least one of alkyl, cycloalkyl, perhaloalkyl or phenyl with the C atom number more than 1.

12. The battery of claim 11, wherein the electrolyte is at least one of sodium dodecylbenzene sulfonate, cetyltrimethylammonium bromide, sodium carboxymethylcellulose, sodium benzoate, zinc benzene sulfonate, zinc trifluoromethanesulfonate, zinc methanesulfonate, or zinc acetate; the compound is at least one of urea, thiourea, acetamide, polyvinyl alcohol, polyacrylamide, polyoxyethylene or polyvinylpyrrolidone.

13. The battery according to claim 11, wherein the electrolyte salt capable of providing zinc ions is at least one of zinc sulfate, zinc sulfamate, zinc chloride, zinc methanesulfonate, zinc trifluoromethanesulfonate, or zinc acetate.

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to a hydrophilic diaphragm and a battery containing the same.

Background

Energy and environmental problems have become key problems related to sustainable development all over the world, and the development of novel green renewable energy sources and chargeable and dischargeable energy storage devices has become an urgent task for human beings. In recent years, lithium ion batteries have the advantages of high energy density, long cycle life, no memory effect and the like, and are widely applied to the fields of portable electronic products, vehicle power batteries, large-scale energy storage, communication base stations and the like. However, the lithium ion battery is limited in specific application scenarios due to high cost, limited lithium storage capacity, poor safety and environmental pollution. In addition, the energy density of the lead-acid battery which is the mainstream in the market is only 25-45Wh/kg, the used concentrated sulfuric acid electrolyte has strong corrosivity, and the leakage can cause a great safety problem. In addition, lead acid battery electrode materials are lead and lead dioxide, and heavy metal pollution caused by the large-scale use of lead acid battery electrode materials causes great harm to human health and environment, such as 'blood lead' events, and pollution of heavy metal lead to soil, water sources and the like. The traditional nickel-cadmium battery contains a large amount of harmful heavy metal elements, can cause serious environmental pollution in the production and waste stages when being applied in a large scale, has strict requirements on environmental temperature, and is only suitable for indoor operation environments. The nickel-metal hydride battery has the problems of high cost and scarce alloy raw materials of the negative electrode, and is not suitable for large-scale use. The traditional primary zinc-manganese battery can not be charged and discharged, and has the problems of recovery treatment and the like after use, thereby causing great resource waste and environmental pollution. The traditional alkaline rechargeable zinc/manganese dioxide battery has the defects of short cycle life, low performance stability, incapability of large-current charging and discharging and the like.

Secondary aqueous batteries are new rechargeable batteries that have been developed in recent years, such as aqueous sodium ion batteries, aqueous potassium ion batteries, aqueous lithium ion batteries, aqueous zinc ion batteries, and aqueous hybrid ion batteries. Compared with an organic electrolyte system battery, the secondary water system battery has the advantages of environmental friendliness and high safety. Meanwhile, as the neutral or slightly acidic electrolyte is used, compared with the traditional aqueous alkaline and acidic battery, the electrolyte has the advantages of low corrosivity, long cycle life and the like, and has wide application prospect.

However, many separators commonly used in secondary aqueous batteries at present are selected from lithium ion batteries, lead acid batteries, and alkaline batteries, such as nonwoven fabrics, glass fiber films, fiber papers, and microporous films. The non-woven fabric, the glass fiber membrane and the fiber paper have large aperture and high porosity, have good liquid absorption performance and low internal resistance, however, fine particles on the surface of the electrode easily penetrate through the diaphragm to cause internal short circuit, particularly, metal dendrites are generated on the surface of the electrode in the charging and discharging process and penetrate through the diaphragm to cause battery short circuit, so that the non-woven fabric, the glass fiber membrane and the fiber paper with large aperture cannot meet the use requirements of most secondary batteries.

In order to reduce the risk of short circuit of the battery, the commercial secondary battery mostly adopts a microporous membrane with the characteristics of small aperture and uniform pore distribution as a battery diaphragm. Microporous membranes made of polyolefin materials PP and PE are widely applied to lithium ion batteries, but the polyolefin materials have poor hydrophilicity and cannot be directly used in water-based secondary batteries. In order to improve the hydrophilicity of the polyolefin microporous membrane, the membrane needs to be subjected to a hydrophilic treatment. Patent CN100452485C discloses a polyolefin microporous membrane with a polymer monomer grafted on the surface, which enhances the hydrophilicity of PP microporous membrane. Patent CN110676416A discloses an alkaline battery separator, which is made by hydrophilizing polyolefin microporous membrane and then bonding an auxiliary liquid absorption separator to improve the liquid absorption capacity of the composite separator. However, the polyolefin microporous membrane subjected to hydrophilic treatment has a problem that the liquid-absorbing capacity of the surface is improved, and the polyolefin material itself has insufficient liquid-absorbing capacity.

In addition, the liquid absorption performance can be improved by adopting a hydrophilic material to manufacture the diaphragm. Patent CN104072794B discloses a polyarylether/hydrophilic resin composite membrane, which is added with a proper amount of hydrophilic resin during the manufacturing process to improve the performance of the diaphragm in absorbing alkaline electrolyte. Patent CN110165308A discloses a negatively charged porous ion conducting membrane composed of strongly hydrophilic sulfonated resin, which has the function of blocking the migration of zincate ions and preventing the growth of zinc dendrites in alkaline batteries.

Battery separators used in strong acid, strong base or organic solvent environments need to have good stability, and therefore, the choice of separator materials is limited. And the secondary water system battery diaphragm with lower corrosivity can get rid of the limitation of materials, and the selectivity is higher. Hydrophilic polymer materials such as polyamide, polyethersulfone, polyurethane, nitrocellulose, etc. are used as membranes having a microporous structure, and are now commercially used as hydrophilic filtration membranes in the fields of biology and medicine. The microporous membrane has strong hydrophilicity, small aperture, high porosity and uniform pore distribution, and the thickness and the structural strength of the microporous membrane can meet the use requirements of batteries, thereby being very suitable for being used as a secondary water system battery diaphragm.

In view of the above, the present invention is based on a hydrophilic filtration membrane in the biological and medical fields, develops a battery separator that can satisfy both high barrier properties and good hydrophilicity, and is applied to a secondary aqueous battery. Furthermore, based on the unique structure and material properties of the hydrophilic polymer microporous membrane, the problems of poor cycle stability and high polarization potential of a zinc electrode in the secondary water-based zinc-based battery and battery short circuit caused by dendritic crystal growth are solved, and an unexpected effect is achieved. The invention also provides the application of the hydrophilic microporous membrane in a secondary water-based zinc-based battery, and the cycling stability of the battery under high current density is improved.

Disclosure of Invention

The application mainly aims to provide a hydrophilic diaphragm with a microporous structure and strong hydrophilicity, and solves the problem that electrode particles penetrate through the diaphragm in the battery circulation process to cause battery short circuit; also, the use of the hydrophilic separator in a battery method is provided.

In order to achieve the above purpose, the invention provides the following technical scheme:

in a first aspect of the present invention, a hydrophilic membrane is provided, wherein the hydrophilic membrane is a microporous membrane containing a hydrophilic polymer material; the aperture of the hydrophilic diaphragm is 0.1-5um, the thickness is 20-500um, and the porosity is 30% -90%.

In the above hydrophilic separator, as a preferred embodiment, the hydrophilic polymer material is at least one of nylon 6, nylon 66, polyethersulfone, cellulose acetate or cellulose nitrate.

As a preferred embodiment, the hydrophilic membrane further comprises a non-woven fabric or a fiber paper, and the non-woven fabric or the fiber paper and the microporous membrane of the hydrophilic polymer material are mutually covered and bonded to form the hydrophilic membrane; preferably, the hydrophilic membrane has a thickness of 40-500 um.

The hydrophilic separator is preferably used in a neutral or acidic secondary aqueous battery; the hydrophilic diaphragm is applied to a water system sodium ion battery, a water system lithium ion battery, a water system zinc-based battery or a water system mixed ion battery.

In a second aspect of the present invention, there is provided a battery comprising the above hydrophilic separator, the battery comprising the hydrophilic separator, an electrolyte, a positive electrode and a negative electrode;

the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises a metal oxide capable of reversibly extracting-embedding ions; preferably, the metal oxide is manganese oxide MnxOy, 0< x ≦ 3, 0< y ≦ 4;

the negative electrode is at least one of metal zinc or zinc alloy.

The above battery comprising a hydrophilic separator, as a preferred embodiment, the hydrophilic separator is a microporous membrane comprising a hydrophilic polymer material, preferably, the hydrophilic polymer material is cellulose acetate and/or cellulose nitrate.

Preferably, the pore diameter of the hydrophilic membrane is 0.1-5um, the thickness of the hydrophilic membrane is 40-300um, and the porosity of the hydrophilic membrane is 30% -90%.

Preferably, the pore size of the hydrophilic membrane is 0.1-0.8 um.

Preferably, the pore size of the hydrophilic membrane is 0.1-0.45 um; the thickness of the hydrophilic membrane is 40-150 um; the porosity of the hydrophilic membrane is 60% -90%. (ii) a

The above battery comprising a hydrophilic separator, as a preferred embodiment, the electrolyte comprises a solvent, a solute:

the solvent is water or a mixture of water and an organic solvent; preferably, the organic solvent is at least one of formamide, dimethyl sulfoxide, N-N dimethylformamide, sulfolane and methanol, and more preferably, the mass ratio of the organic solvent to water is (0.01-0.6) to 1;

the solute is an electrolyte or a compound containing an organic functional group R-R', and an electrolyte salt capable of providing zinc ions;

preferably, the organic functional group R is a hydrophilic group, more preferably, the organic functional group R is at least one of a sulfonic acid group, a nitro group, a quaternary ammonium group, an amino group, a carboxyl group, an ester group, or an ether group;

preferably, the organic functional group R 'is a hydrophobic group, and more preferably, the organic functional group R' is at least one of an alkyl group having a number of C atoms greater than 1, a cycloalkyl group, a perhaloalkyl group, or a phenyl group.

The above-mentioned battery comprising a hydrophilic separator, as a preferred embodiment, the electrolyte is at least one of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, sodium carboxymethylcellulose, sodium benzoate, zinc benzenesulfonate, zinc trifluoromethanesulfonate, zinc methanesulfonate or zinc acetate;

the above battery comprising a hydrophilic separator, as a preferred embodiment, the compound is at least one of urea, thiourea, acetamide, polyvinyl alcohol, polyacrylamide, polyoxyethylene, or polyvinylpyrrolidone.

In the above battery including the hydrophilic separator, as a preferred embodiment, the electrolyte salt capable of providing zinc ions is at least one of zinc sulfate, zinc sulfamate, zinc chloride, zinc methanesulfonate, zinc trifluoromethanesulfonate, or zinc acetate.

The hydrophilic diaphragm and the electrolyte are compounded, so that the problem of battery short circuit caused by the fact that the diaphragm is pierced by the growth of zinc dendrite in the secondary water-based zinc-based battery is solved, and the service life of the secondary zinc-based battery is prolonged.

Compared with the prior art, the invention has the beneficial effects that:

the wettability of the hydrophilic diaphragm in the aqueous electrolyte is obviously superior to that of commercial PP and PE microporous membranes and hydrophilic polyolefin diaphragms, the capacity of absorbing the aqueous electrolyte is stronger, and the conductivity of the diaphragm is higher; the hydrophilic diaphragm provided by the invention has a uniform microporous structure, the barrier capability of the hydrophilic diaphragm is higher than that of non-woven fabrics, fiber paper and glass fiber membranes, and the risk of internal short circuit of the battery can be reduced.

The hydrophilic diaphragm and the electrolyte act together to induce the zinc dendrite to grow regularly, so that the cycle life of the metal zinc electrode is prolonged; the polarization overpotential of Zn dissolution/deposition is optimized, the electrochemical performance of a zinc electrode is improved, a battery manufactured by adopting the hydrophilic diaphragm does not need to carry out additional processing treatment on a zinc cathode, the process is simple and feasible, and the hydrophilic diaphragm is suitable for large-scale application.

Drawings

FIG. 1 is a scanning electron micrograph of hydrophilic membranes of examples a1-a3 and ac1 and ac3 of the present invention;

FIG. 2 shows the surface topography of the zinc electrode in the cells of examples b1, bc1-bc3 of the present invention;

FIG. 3 is a comparison of polarization curves for cells of examples b1, bc1 and bc3 of the present invention;

FIG. 4 is a time-voltage curve of a battery of example b1 of the present invention;

FIG. 5 is a graph comparing the cycling performance of cells of examples c1-c3 and cc1, cc2 of the present invention.

Detailed Description

In order to make the technical solutions in the embodiments of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to examples, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Example a1

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.2um, the thickness is 0.12mm, and the porosity is 68%; the hydrophilic polymer material is nylon 6; the hydrophilic membrane of example a1 is designated a 1.

Example a2

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.2um, the thickness is 0.12mm, and the porosity is 71%; the hydrophilic polymer material is polyether sulfone; the hydrophilic membrane of example a2 is designated a 2.

Example a3

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.2um, the thickness is 0.12mm, and the porosity is 75%; the hydrophilic polymer material is nitrocellulose; the hydrophilic membrane of example A3 is designated A3.

Example a4

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.2um, the thickness is 0.12mm, and the porosity is 74%; the hydrophilic polymer material is cellulose acetate; the hydrophilic membrane of example a4 is designated a 4.

Example a5

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.2um, the thickness is 0.12mm, and the porosity is 75%; the hydrophilic polymer material is a mixture of cellulose acetate and nitrocellulose; the hydrophilic membrane of example a5 is designated a 5.

Example a6

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.45um, the thickness is 0.12mm, and the porosity is 79%; the hydrophilic polymer material is a mixture of cellulose acetate and nitrocellulose; the hydrophilic membrane of example a6 is designated a 6.

Example a7

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 0.8um, the thickness is 0.12mm, and the porosity is 81%; the hydrophilic polymer material is a mixture of cellulose acetate and nitrocellulose; the hydrophilic membrane of example a7 is designated a 7.

Example a8

The hydrophilic diaphragm is a microporous membrane containing a hydrophilic high polymer material; the aperture of the hydrophilic diaphragm is 1.2um, the thickness is 0.12mm, and the porosity is 82%; the hydrophilic polymer material is a mixture of cellulose acetate and nitrocellulose; the hydrophilic membrane of example a8 is designated a 8.

Example a9

A hydrophilic diaphragm is prepared by mutually covering and bonding a microporous membrane containing a hydrophilic high polymer material and a non-woven fabric; the non-woven fabric is a PET non-woven fabric with the thickness of 0.1mm, and the microporous membrane of the hydrophilic polymer material is a microporous membrane which is 0.12mm in thickness, 0.2um in pore diameter and 68% in porosity and takes nylon 6 as a material; the hydrophilic membrane of example a9 is designated a 9.

Example a10

A hydrophilic diaphragm is prepared by mutually covering and bonding a microporous membrane containing a hydrophilic high polymer material and a non-woven fabric; the non-woven fabric is a PET non-woven fabric with the thickness of 0.1mm, and the microporous membrane of the hydrophilic high polymer material is a microporous membrane which is 0.12mm in thickness, 0.2um in pore size and 79% in porosity and takes a mixture of cellulose acetate and cellulose nitrate as a material; the hydrophilic membrane of example a10 is designated a 10.

Comparative example ac1

Comparative example AC1 the hydrophilic membrane was a PET nonwoven film and comparative example AC1 the hydrophilic membrane was designated AC 1.

Comparative example ac2

Comparative example AC2 the hydrophilic separator was an AGM glass fiber film and comparative example AC2 the hydrophilic separator was designated AC 2.

Comparative example ac3

Comparative example ac3 the hydrophilic membrane was a hydrophilic PP microporous membrane with a thickness of 40um, a pore size of 0.2um, and a porosity of 43%; comparative example AC3 the hydrophilic membrane is designated AC 3.

Comparative example ac4

Comparative example AC4 the hydrophilic separator was made by bonding a hydrophilic PP microporous membrane with a thickness of 40um, a pore size of 0.2um, and a porosity of 43% to a PET nonwoven membrane with a thickness of 0.1mm, and the hydrophilic separator was designated as AC4 in comparative example AC 4.

1. Liquid absorption Performance test of the hydrophilic separator of the present invention

Cutting a hydrophilic diaphragm with the diameter of 19mm, weighing the mass of the hydrophilic diaphragm as m1, then immersing the hydrophilic diaphragm in 2mol/L aqueous solution of zinc methanesulfonate, taking the hydrophilic diaphragm out and removing redundant electrolyte on the surface after the hydrophilic diaphragm is fully wetted, and weighing the mass m2 of the wetted hydrophilic diaphragm, wherein the liquid absorption rate of the diaphragm is (m2-m1)/m1 multiplied by 100%.

2. Porosity testing of the hydrophilic separator of the present invention

Cutting a hydrophilic diaphragm with the diameter of 19mm, weighing the mass of the hydrophilic diaphragm as m1, then immersing the hydrophilic diaphragm in pure water for 2h, taking the hydrophilic diaphragm after the hydrophilic diaphragm is fully wetted, lightly wiping off water on the surface by using filter paper, and weighing the mass m2 of the wetted diaphragm, wherein the porosity of the diaphragm is (m2-m1) rho 1/(m2 rho 1+ m1 rho 1-m1 rho 2) × 100%, wherein rho 1 and rho 2 are the densities of the diaphragm material and the pure water respectively.

3. Conductivity testing of the hydrophilic membranes of the invention

Cutting a hydrophilic diaphragm wafer with the diameter of 19mm and a stainless steel sheet with the diameter of 15mm, soaking the hydrophilic diaphragm in 2mol/L zinc methanesulfonate aqueous solution, assembling a symmetrical battery of the stainless steel sheet after the hydrophilic diaphragm is fully wetted, and carrying out an alternating current impedance test. And performing fitting analysis on the test result to obtain the resistance Rs of the hydrophilic diaphragm, and calculating the resistance value of the hydrophilic diaphragm per unit area according to a formula sigma L/(A.Rs), wherein sigma is the conductivity of the hydrophilic diaphragm, L is the thickness of the hydrophilic diaphragm, and A is the area of the stainless sheet.

The results of the measurements of the liquid absorption, porosity and conductivity of the hydrophilic membranes of examples a1-a10 and comparative examples ac1-ac4 are shown in table 1.

Table 1 hydrophilic membrane imbibition performance, porosity and conductivity test results

By comparing the separators A1, A2, A3, A4, A5 and the comparative example separator AC3, the liquid absorption rate, the porosity and the conductivity of the hydrophilic separator of the invention are obviously higher than those of a commercial hydrophilic PP microporous membrane under the condition of the same pore diameter, and the hydrophilic high polymer material is shown to greatly improve the absorption capacity and the ion conducting capacity of the microporous membrane to an aqueous electrolyte.

Comparing the separators a5, a6, a7 and A8, it can be found that as the pore size of the microporous membrane increases, the liquid absorption rate, porosity and ionic conductivity thereof increase. When the pore diameter of the microporous membrane is 1.2 mu m, the imbibition rate is close to that of a commercial PET non-woven fabric membrane, and the porosity and the ionic conductivity are higher than those of the PET non-woven fabric membrane.

While increased pore size is beneficial for liquid uptake and conductivity, increased membrane pore size increases the risk of electrode particles passing through the membrane causing cell shorting. Separators AC1 and AC2 are fiber-type separators, and exhibit excellent liquid absorption rate due to their high porosity, but since such separators have too large pore diameter, they are often used in combination with microporous membranes, since they are likely to cause short circuits in batteries. The diaphragms A9, A10 and AC4 are composite films formed by compounding microporous films and non-woven fabrics, so that the liquid absorption performance of the microporous films is improved to a certain degree, and the risk of easy short circuit of the non-woven fabrics is further reduced.

In order to embody the pore diameter, pore uniformity and porosity degree of the microporous structure of the separator of the present invention, the surface morphologies of the above-mentioned a1, a2, a5 and AC3 separators were characterized by a scanning electron microscope, and the results are shown in fig. 1.

As can be seen from fig. 1, the separators a1, a2, a5, AC3 are microporous structures integrated with the base material, and pores having an average diameter of 0.1 to 0.2 μm are distributed therebetween, and the uniformity of pore diameters is good, so that such separators have excellent barrier ability. The pores of the separators a1, a2, a5 were circular, and the distribution area of the substrate around the pores was small, so that the separators exhibited high porosity. The pores of the separator AC3 exhibit directionality, which is an effect of the mechanical stretching film formation method, and many substrate regions still exist around the pores, so the porosity of the separator is low. In the separator AC1, a fiber spinning structure was found to be disordered, pores formed by fibers being interlaced with each other were used as micropores, the sizes of the pores were varied, and macropores having a diameter of 10 μm were present, and when such a nonwoven fabric film was used as a separator, some fine particles could pass through the pores, causing a short circuit of the battery.

4. The test of the dendritic crystal penetration resistance performance of the hydrophilic diaphragm

The zinc dendrite penetration resistance of the hydrophilic membrane of the invention was tested using a Zn/Zn symmetric cell. Specifically, two zinc foil disks with the diameter of 13mm are cut, the separator is selected from A1-A8 and AC1-AC4 and is cut into disks with the diameter of 19mm, and 2mol/L zinc methylsulfonate aqueous solution is used as electrolyte to assemble the button cell. The assembled battery is heated at normal temperature at 2mA/cm²And 10mAh/cm²The current density and the electric quantity of the battery are subjected to constant current charge and discharge tests, the battery is judged whether to be short-circuited or not by observing the voltage of the battery after circulating for a certain number of times, the time of the short circuit is recorded, and the result is shown in a table 2:

TABLE 2A 1-A8 and AC1-AC4 results of battery short circuit tests of hydrophilic separator assembly

From table 2, it can be derived: the growth of zinc dendrites cannot be inhibited under high current density and electric quantity by a non-woven fabric membrane, a glass fiber membrane, a hydrophilic PP microporous membrane and a composite membrane thereof, the cycle time is not more than 9 hours, and the cycle time of the hydrophilic microporous membrane using the invention is more than 100 hours. Wherein, the cycle time of the batteries adopting the cellulose acetate microporous membrane, the cellulose nitrate microporous membrane and the mixed cellulose microporous membrane with the pore diameter of 0.2 mu m is over 2000h, and the excellent dendritic crystal penetration resistance is shown. On the other hand, by comparing the Zn/Zn symmetrical batteries assembled by the separators a5 to A8, it can be found that the separator with a smaller pore size is more advantageous in resisting dendrites under the same material condition, while the separator with a pore size larger than 0.45 μm is easily punctured by dendrites to cause short circuit.

Example b1

A cell comprising a hydrophilic separator whose electrolyte was assembled using a 2mol/L aqueous solution of zinc methanesulfonate and a mixed cellulose membrane of cellulose acetate and cellulose nitrate having a pore size of 0.2 μm, a thickness of 0.12mm and a porosity of 79%, the cell comprising a hydrophilic separator described in example B1 being designated B1.

Example b2

A cell comprising a hydrophilic separator whose electrolyte was assembled using a 2mol/L aqueous solution of zinc trifluoromethanesulfonate, a mixed cellulose film of cellulose acetate and cellulose nitrate having a pore size of 0.2 μm, a thickness of 0.12mm and a porosity of 79%, a Zn/Zn symmetric cell, said cell comprising a hydrophilic separator of example B2 being designated B2.

Example b3

A cell comprising a hydrophilic separator whose electrolyte is a mixture of 2mol/L aqueous zinc sulphate and 0.2% wt cetyltrimethylammonium bromide, the separator using a mixed cellulose membrane of cellulose acetate and cellulose nitrate of 0.2 μm pore size, 0.12mm thickness and 79% porosity, assembled into a Zn/Zn symmetric cell, the cell comprising a hydrophilic separator described in example B3 being designated B3.

Example b4

A cell comprising a hydrophilic separator whose electrolyte is a mixture of 2mol/L aqueous zinc sulphate and 0.2% wt sodium dodecylbenzenesulfonate, the separator using a mixed cellulose film of cellulose acetate and cellulose nitrate of 0.2 μm pore size, 0.12mm thickness and 79% porosity, assembled into a Zn/Zn symmetric cell, the cell comprising a hydrophilic separator described in example B4 being designated B4.

Comparative example bc1

In contrast to example b1, a Zn/Zn symmetrical cell was assembled using 2mol/L zinc sulphate in water, the cell containing a hydrophilic separator described in example BC1 being designated BC 1.

Comparative example bc2

In contrast to example b1, a Zn/Zn symmetric cell was assembled using AGM glass fiber membrane as separator, and the cell containing a hydrophilic separator described in example BC2 was designated BC 2.

Comparative example bc3

In contrast to example b1, the separator was assembled into a Zn/Zn symmetrical cell using a hydrophilic PP microporous membrane with a pore size of 0.2 μm, the cell containing the hydrophilic separator described in example BC3 was designated BC 3.

The assembled B1-B4 and BC1-BC3 batteries are subjected to constant current charge and discharge tests at normal temperature at current density and electric quantity of 2mA/cm2 and 10mAh/cm2, and the short-circuit time of the batteries is observed. The results of the test for judging whether the battery is short-circuited by observing the battery voltage after the battery is cycled for a certain number of times are shown in table 3.

TABLE 3B 1-B4 and BC1-BC3 cell short circuit results

As can be seen from table 3: the diaphragm made of cellulose acetate and cellulose nitrate mixed cellulose is short-circuited in a short time after being matched with a zinc sulfate solution, the cycle time of the battery is remarkably prolonged when the diaphragm is matched with the electrolyte provided by the invention, and particularly the cycle time can exceed 2000 hours under the condition that the electrolyte is zinc methylsulfonate and zinc trifluoromethanesulfonate. After a small amount of surfactant cetyl trimethyl ammonium bromide and sodium dodecyl benzene sulfonate are added into the zinc sulfate electrolyte, the circulation time is prolonged to more than 500 h. The above results indicate that the dendrite penetration resistance effect of the Zn/Zn symmetric battery is related to the combination of the separator and the electrolyte, and is a property generated when the separator and the electrolyte are specifically matched with each other, and therefore, the growth of zinc dendrites can be effectively inhibited and the battery short circuit can be prevented by adjusting the combination of the separator and the electrolyte in the secondary aqueous zinc-based battery.

Further, the B1 after cycle 100h and the BC2-BC4 after short circuit were disassembled, and the growth of dendrites on the surface of the zinc electrode was observed after cleaning, which is shown in table 4 and fig. 2.

TABLE 4B 1 and BC1-BC3 cell zinc cathode dendrite growth results

Battery with a battery cell	Observing dendrite time	Morphology of zinc cathode	Dendritic crystal growth
				B1	100h	Large and compact	Is free of
BC1	60h	Loose, porous	Is less
				BC2	30h	Small pieces and loose	Much more
BC3	3h	Partially flaky and loose	Much more

As can be seen from table 4 and fig. 2, when the cellulose acetate and cellulose nitrate mixed cellulose microporous membrane of the present invention is matched with zinc methanesulfonate electrolyte, the morphology of zinc deposition is a dense and large-sized sheet shape, which is parallel to the membrane direction, and there are no fine dendrites growing longitudinally, so that the membrane penetration probability is very low. After the cellulose acetate and cellulose nitrate mixed cellulose microporous membrane is matched with zinc sulfate electrolyte, the zinc deposition morphology of the battery is found to be a porous particle aggregate under a scanning electron microscope, the shape is irregular, and partial small-particle dendritic crystals appear, so that the risk of short circuit is generated. The cell assembled by adopting the zinc methanesulfonate electrolyte and the glass fiber membrane has the advantages that the zinc grows into small crystals under the observation of a scanning electron microscope, and the glass fiber membrane has low strength, so that most of the crystals are in a loose structure, and short circuit is easily caused. The battery assembled by the zinc methanesulfonate electrolyte and the hydrophilic PP microporous membrane finds that the surface of zinc evolves into partial flaky irregular accumulation from a scanning electron microscope image, and partial fine grains exist at the same time, so that the battery is rapidly disabled.

The influence of the combination of the hydrophilic diaphragm and the electrolyte on the polarization of the zinc cathode

The hydrophilic membrane and electrolyte combination also has an optimization effect on Zn dissolution/deposition, and is specifically shown in the reduction of the polarization overpotential of a Zn electrode.

The first charge and discharge curves of the battery of example b1 and the batteries of comparative examples bc1 and bc3 were selected and compared, and the results are shown in fig. 3. The Zn dissolution/deposition polarization overpotential of the combination of the mixed cellulose microporous membrane of the cellulose acetate and the cellulose nitrate and the zinc methylsulfonate electrolyte is 35mV, and the Zn dissolution/deposition polarization overpotential of the combination of the mixed cellulose microporous membrane of the cellulose acetate and the cellulose nitrate and the zinc sulfate electrolyte is 64mV which is almost twice of that of the zinc methylsulfonate electrolyte. The Zn dissolution/deposition polarization overpotential for the combination of hydrophilic PP microporous membrane and zinc methanesulfonate electrolyte was 81mV, which is much higher than the values for the combination of the present invention. The combination of the hydrophilic diaphragm and the electrolyte shows lower polarization overpotential, and can generate an enhancement effect on the electrochemical performance of a Zn cathode. Furthermore, the voltage-time graph of fig. 4 shows that the overpotential for the cell of example b1 is below 40mV and the stability is good over a 2000h cycle time, indicating uniform Zn dissolution/deposition.

The specific application of the invention, the effect of the combination of the diaphragm and the electrolyte on improving the charge and discharge performance and the cycle performance of the secondary water system zinc-based battery, is embodied by the following embodiment mode.

Example c1

Manganese dioxide is selected as a positive electrode active material, and a certain mass of the positive electrode active material, acetylene black and polytetrafluoroethylene are weighed according to the proportion of 85: 10: 5. Uniformly mixing the positive active material and acetylene black through a dry powder mixer, then sequentially adding polytetrafluoroethylene emulsion and ethanol solution to stir to obtain a mixture, taking out the mixture, repeatedly rolling the mixture in a roller press to form a continuous membrane, and removing ethanol and water in the membrane through drying to obtain the positive membrane, wherein the mass of the positive membrane per unit area is 600g/m²And pressing the positive diaphragm in a stainless steel net to obtain the positive pole piece.

The positive electrode adopts the prepared positive electrode piece, the negative electrode adopts a zinc foil with the thickness of 20 mu m, the diaphragm adopts a cellulose acetate and cellulose nitrate mixed microporous membrane with the aperture of 0.2 mu m and the thickness of 0.12mm, and the electrolyte is 2mol/L zinc methanesulfonate and 0.1mol/L manganese acetate aqueous solution. The positive and negative electrode sheets were cut into 13mm diameter disks, the separator was cut into 19mm diameter disks, the above materials were fully immersed in an electrolyte, and then assembled into a battery, designated as C1.

Example c2

In contrast to example C1, a nitrocellulose membrane with a pore size of 0.2 μm and a thickness of 0.12mm was used as the separator, a 2mol/L aqueous solution of zinc trifluoromethanesulfonate was used as the electrolyte, and the assembled cell was designated as C2.

Example c3

In contrast to example C1, the diaphragm was a cellulose acetate membrane with a pore size of 0.2 μm and a thickness of 0.12mm, the electrolyte was zinc sulphate 2mol/L, manganese sulphate 0.1mol/L and cetyltrimethylammonium bromide 0.2% wt, and the assembled cell was designated C3.

Comparative example cc1

In contrast to example c1, a hydrophilic PP microporous membrane with a pore size of 0.2 μm and a thickness of 40 μm was used as the separator, and the cell was designated as CC 1.

Comparative example cc2

In contrast to example c1, the electrolyte used was 2mol/L zinc sulfate and 0.1mol/L manganese sulfate, and the cell was designated CC 2.

The cells C1-C3 and CC1-CC2 were subjected to constant current charge and discharge test at a current density of 50mA/g at room temperature, and the charge and discharge voltage ranged from 0.8V to 1.95V, and the results are shown in Table 5 and FIG. 5:

TABLE 5 result of charge and discharge test of batteries C1-C3, CC1 and CC2

As can be seen from table 5 and fig. 5, the battery using the commercial hydrophilic PP microporous film or the pure sulfate electrolyte cannot be continuously cycled at a higher discharge capacity per unit area, and the battery is rapidly short-circuited while having a lower specific discharge capacity.

The diaphragm and the electrolyte combination can realize more than 100 times of stable circulation for the water system zinc-manganese battery, and meanwhile, the discharge specific capacity is obviously improved. These enhancements result from the fact that the diaphragm of the present invention works in concert with the electrolyte to optimize the dissolution/deposition reaction of the Zn cathode, forcing Zn deposition to proceed in a regular manner, preventing zinc dendrites from occurring, and greatly avoiding internal short circuits.

The hydrophilic microporous separator of the present invention is significantly different from commercial hydrophilic PP microporous membranes. The polymer material of the diaphragm contains a large number of strong polar functional groups such as amide groups, ether groups, sulfone groups, carboxyl groups, hydroxyl groups, nitro groups and the like, so that the diaphragm has good hydrophilicity and liquid absorption performance. When the diaphragm is contacted with the metal zinc electrode, the difference of the surface energy of the diaphragm and the metal zinc electrode makes the diaphragm difficult to interact, when organic functional groups R-R' exist in the electrolyte, the interface gap between the diaphragm and the zinc electrode is eliminated, the functional groups in the diaphragm can interact with the metal zinc, the strong-polarity functional groups show negative charge, and when Zn in the electrolyte is reacted with the metal zinc electrode²⁺Can be attracted by functional groups or generate coordination during the migration in the micropores of the separator, and reduce Zn²⁺The hydration radius of the zinc oxide film reduces the energy barrier of the deposition of the zinc oxide film, drives the zinc crystal to grow into a larger size, and the zinc crystal grows in a platy parallel mode under the common guide of the organic functional group R-R' and the microporous film functional group, and the zinc crystal in the shape is not easy to pierce through a diaphragm, so that the short circuit of the battery is prevented, and the cycle performance of the battery is improved. At the same time, uniform Zn²⁺The deposition can prevent dendritic crystal growth caused by excessive local current and realize stripping-deposition with high volume density.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and additions can be made without departing from the method of the present invention, and these modifications and additions should also be regarded as the protection scope of the present invention.