阅读说明：本技术 二次电池、多功能隔膜及制备方法 (Secondary battery, multifunctional diaphragm and preparation method ) 是由 赵泽泉 钟澄 胡文彬 宋永江 刘丝靓 于 2021-08-23 设计创作，主要内容包括：本发明公开了二次电池、多功能隔膜及制备方法,二次电池包括多功能隔膜,该多功能隔膜成分主要由主导电剂、副导电剂、辅助剂、保水剂、粘结剂构成,并采用物理辊压法制备成膜。本发明多功能隔膜在二次电池中能够有效发挥多种功能以提升电池的循环寿命、日历寿命：1)抑制二次电池中锌负极普遍存在的形变、枝晶生长、活性物质脱落等问题；2)该多功能隔膜由于具备导电特性,可以成为锌负极的延伸,增加电极有效导电网络的面积；3)该多功能隔膜由于具备强保水性,抑制半开放体系下的电池普遍存在的电解液流失严重问题；4)抑制电池的析氢反应,对于锌镍电池而言,还可以有效复合电池内部析出的氧气防止负极过度氧复合。(The invention discloses a secondary battery, a multifunctional diaphragm and a preparation method thereof, wherein the secondary battery comprises the multifunctional diaphragm, the components of the multifunctional diaphragm mainly comprise a main conductive agent, an auxiliary agent, a water-retaining agent and an adhesive, and a physical rolling method is adopted to prepare a film. The multifunctional diaphragm of the invention can effectively play a plurality of functions in the secondary battery to improve the cycle life and the calendar life of the battery: 1) the problems of deformation, dendritic crystal growth, active substance shedding and the like commonly existing in a zinc cathode in a secondary battery are inhibited; 2) the multifunctional diaphragm can be an extension of a zinc cathode due to the conductive property, so that the area of an effective conductive network of the electrode is increased; 3) the multifunctional diaphragm has strong water retention property, so that the serious problem of electrolyte loss commonly existing in batteries under a semi-open system is inhibited; 4) the hydrogen evolution reaction of the battery is inhibited, and for the zinc-nickel battery, the oxygen evolved in the battery can be effectively compounded to prevent the excessive oxygen recombination of the negative electrode.)

1. The utility model provides a secondary battery, includes anodal, negative pole, electrolyte and is located the multi-functional diaphragm between anodal and negative pole, its characterized in that, the multi-functional diaphragm comprises conducting layer and insulating layer, the conducting layer of multi-functional diaphragm pastes on the reaction face of negative pole, and the conducting layer covers the reaction face completely, negative pole and conducting layer are wrapped up so that negative pole and anodal are insulating by the insulating layer of multi-functional diaphragm, the insulating layer is ordinary battery diaphragm, the conducting layer essential element includes:

a main conductive agent, bismuth powder;

secondary conductive agent, zinc powder;

water-retaining agent, potassium polyacrylate;

adjuvant, fumed alumina;

adhesive, polytetrafluoroethylene;

the main conductive agent, the water-retaining agent and the auxiliary agent do not react with the electrolyte chemically, and the mass ratio of the main conductive agent to the auxiliary conductive agent to the water-retaining agent to the auxiliary agent to the binder is (5-8): (5-8): (2-3): (1-3): (1-2), wherein the secondary battery is a secondary zinc-based battery, a secondary lead-acid battery or a secondary nickel-hydrogen battery.

2. The secondary battery according to claim 1, characterized in that: the mass ratio of the main conductive agent to the auxiliary conductive agent to the water-retaining agent to the auxiliary agent to the adhesive is 7: 5: 3: 3: 2.

3. the secondary battery according to claim 1, characterized in that: the thickness of the conducting layer is 0.02-0.4 mm.

4. The secondary battery according to claim 1, wherein the general battery separator is a glass fiber separator, a filter paper, a polyethylene separator, a polypropylene separator.

5. A multifunctional diaphragm suitable for a secondary battery is characterized by consisting of a conductive layer and an insulating layer, wherein the insulating layer is a common battery diaphragm, and the conductive layer mainly comprises the following components:

a main conductive agent, bismuth powder;

secondary conductive agent, zinc powder;

water-retaining agent, potassium polyacrylate;

adjuvant, fumed alumina;

adhesive, polytetrafluoroethylene;

the bismuth powder, the potassium polyacrylate and the fumed alumina do not react with the electrolyte chemically, and the mass ratio of the main conductive agent to the auxiliary conductive agent to the water retaining agent to the auxiliary agent to the binder is (5-8): (5-8): (2-3): (1-3): (1-2).

6. The method of preparing the multifunctional membrane of claim 5, comprising the steps of:

step 1, weighing and preparing a main conductive agent, an auxiliary conductive agent, a water-retaining agent, an auxiliary agent and an adhesive in proportion;

step 2, mixing the main conductive agent, the auxiliary conductive agent, the water-retaining agent and the auxiliary agent, putting the mixture into a mortar, fully mixing the powder by mechanical stirring and grinding, and uniformly dispersing the components to obtain mixed powder;

step 3, adding a binder and a proper amount of battery electrolyte into the mixed powder, and fully stirring to form soft and elastic powder balls;

step 4, tabletting the powder dough by using a roller press to form a film so as to form a conductive layer, wherein drying is not needed after preparation;

and 5, stacking the conducting layer and the insulating layer together, rolling to form the multifunctional diaphragm, and directly assembling the battery or sealing for later use.

Technical Field

The invention belongs to the technical field of battery materials, and particularly relates to a secondary battery, a multifunctional diaphragm and a preparation method of the multifunctional diaphragm.

Background

The battery technology mainly used for energy storage at present mainly uses a lithium battery and a lead-acid battery, compared with the problems of large potential safety hazard and high cost of a lithium ion battery, the lead-acid battery has the advantages of intrinsic safety, low cost and the like as a representative of a water-based battery, and is widely applied. The common diaphragm of the secondary battery at present mainly comprises glass fiber, filter paper and polypropylene diaphragm, but the components of the diaphragm are single, and the diaphragm only can achieve the function of simply and physically insulating the positive electrode and the negative electrode. Currently, research is focused on improving the traditional diaphragm, such as a modified diaphragm obtained by modifying a phosphate or sulfonate compound on the basis of the traditional diaphragm. These modified separators are intended to improve the hydrophilicity, porosity, ionic conductivity, etc. of the separator, but their functions are still relatively simple, and they cannot fully suppress the problems commonly existing in secondary batteries, such as dendrite growth, deformation, active material falling off, electrolyte volatilization, severe side reactions (hydrogen evolution reaction, oxygen evolution reaction), etc. of the negative electrode.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a multifunctional diaphragm which is simple in preparation process and can effectively prolong the calendar life and the cycle life of a battery in a secondary battery, a preparation method of the multifunctional diaphragm and the secondary battery.

In order to solve the technical problems, the invention adopts the technical scheme that:

the invention provides a multifunctional diaphragm suitable for a secondary battery, which is formed by compounding a conducting layer and an insulating layer, wherein the multifunctional diaphragm mainly comprises the conducting layer and the insulating layer, the conducting layer has multiple functions to improve the performance of the battery, and the conducting layer comprises the following components:

(1) the water-retaining agent is used for increasing the water-retaining property of the diaphragm, and usually, organic or inorganic powder containing hydrophilic groups is selected as the water-retaining agent, and the selected water-retaining agent cannot react with electrolyte chemically. Such as potassium Polyacrylate (PAAK), sodium polyacrylate, polyvinyl alcohol, preferably potassium Polyacrylate (PAAK).

(2) A main conductive agent for increasing the conductivity of the separator and improving the hydrogen evolution overpotential of the negative electrode, and a conductive non-zinc-based metal or non-metal powder such as graphite, activated carbon, or Sn powder is included in the selection range of the main conductive agent. The main conductive agent is preferably metal powder with high hydrogen evolution overpotential, and the selected main conductive agent is required to be incapable of chemical reaction with the electrolyte, for example, metal bismuth (Bi) can be selected.

(3) And a secondary conductive agent for increasing the conductivity of the separator, increasing the amount of the active material of the negative electrode, and allowing oxygen recombination, wherein the conductive metal powder having the same element as the active material of the positive and negative electrodes of the battery is selected from the secondary conductive agent, and the secondary conductive agent is preferably a metal powder which is easily subjected to oxidation-reduction reaction and has the same composition as the negative electrode active material, such as zinc powder (Zn).

(4) The auxiliary agent is used as a support, and is selected from oxides which are not easily oxidized and reduced, have a low density, are easily formed into a film, and have water-absorbing properties, and are required to be chemically unreactive with an electrolyte, such as Bi₂O₃、SiO₂Preferably vapor phase alumina (Al)₂O₃）。

(5) The binder, which is intended to bond the components of the separator, should be chosen from a polymeric emulsion with stable properties, strong bonding power and moderate resistance, such as Polytetrafluoroethylene (PTFE), (polyvinylidene fluoride) PVDF, preferably Polytetrafluoroethylene (PTFE).

The insulating layer mainly plays an insulating role and adopts common battery diaphragms, such as glass fiber diaphragms, filter paper, polyethylene diaphragms and polypropylene diaphragms.

The invention also provides a preparation method of the multifunctional diaphragm, which comprises the following specific processes:

(1) mixing a main conductive agent, an auxiliary conductive agent, a water-retaining agent, an auxiliary agent and a binder according to a certain proportion, such as (5-8): (5-8): (2-3): (1-3): (1-2) weighing and preparing materials, wherein the optimal proportion is 7: 5: 3: 3: 2, then placing the components except the binder into a mortar, and fully mixing the powder through mechanical stirring and grinding to uniformly disperse the components;

(2) adding a binder and a proper amount of battery electrolyte into the mixed powder in the step (1), and fully stirring to form soft and elastic powder dough;

(3) tabletting the powder dough by using a roller press to form a film so as to form a conductive layer, wherein the thickness of the conductive layer is 0.02-0.4 mm, and the preferred thickness is 0.04 mm;

(4) after the preparation is finished, drying is not needed, the conducting layer and the insulating layer are stacked together, and the multifunctional diaphragm is formed after rolling, and can be directly assembled into a battery or sealed for standby.

The invention further provides a secondary battery comprising the multifunctional diaphragm, which comprises a positive electrode, a negative electrode, electrolyte and the multifunctional diaphragm positioned between the positive electrode and the negative electrode, wherein a conductive layer of the multifunctional diaphragm is attached to a reaction surface of the negative electrode, the conductive layer completely covers the reaction surface, and the negative electrode and the conductive layer are wrapped by an insulating layer of the multifunctional diaphragm to insulate the negative electrode from the positive electrode. The secondary battery can be a secondary zinc-based battery, or a secondary lead-acid battery, or a secondary nickel-hydrogen battery. The method for assembling the multifunctional separator in the secondary battery is as follows: placing the prepared conductive layer of the multifunctional diaphragm on the reaction surface of the cathode, and completely covering the reaction surface; at this time, an insulating layer is disposed on the outer periphery of the conductive layer for insulating the positive and negative electrodes, and the assembly of the battery is schematically shown in fig. 1.

After the technical scheme is adopted, compared with the prior art, the invention has the following beneficial effects.

The multifunctional diaphragm mainly comprises a main conductive agent, an auxiliary agent, a water-retaining agent and an adhesive, and is prepared into a film by adopting a physical rolling method, and the obtained multifunctional diaphragm can effectively play multiple functions in a secondary battery so as to improve the cycle life and the calendar life of the battery:

1) the problems of deformation, dendritic crystal growth, active substance shedding and the like commonly existing in a zinc cathode in a secondary battery are inhibited;

2) the multifunctional diaphragm can be an extension of a zinc cathode due to the conductive property, so that the area of an effective conductive network of the electrode is increased;

3) the multifunctional diaphragm has strong water retention property, so that the serious problem of electrolyte loss commonly existing in a secondary battery under a semi-open system is inhibited;

4) the hydrogen evolution reaction of the secondary battery is inhibited, and for the zinc-nickel battery, the oxygen evolved in the battery can be effectively compounded to prevent the excessive oxygen recombination of the negative electrode.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention to its proper form. It is obvious that the drawings in the following description are only some embodiments, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:

FIG. 1 is a schematic view of the assembly of a multi-functional separator of one embodiment of the invention in a battery;

FIG. 2 is a battery cycling curve according to one embodiment of the present invention;

FIG. 3 is a photograph of a negative scan after testing in accordance with one embodiment of the present invention;

FIG. 4 is a high temperature float test curve according to an embodiment of the present invention;

fig. 5 is a photograph of a negative electrode after a high temperature float-charge test in accordance with an embodiment of the present invention.

FIG. 6 is an electron microscope image of a multifunctional membrane in operation according to an embodiment of the invention.

In the figure: 1-a conductive layer of a multifunctional diaphragm, 2-a cathode, and 3-an insulating layer of the multifunctional diaphragm.

It should be noted that the drawings and the description are not intended to limit the scope of the inventive concept in any way, but to illustrate it by a person skilled in the art with reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

(1) bi powder with the granularity of 100 nm, eight-hundred-mesh Zn powder, potassium polyacrylate particles and gas phase Al₂O₃60 wt.% aqueous PTFE solution in a 7: 5: 3: 3: 2, weighing and preparing materials, then placing the components except the PTFE aqueous solution into a mortar, and fully mixing the powder and uniformly dispersing the components through mechanical stirring and grinding;

(2) adding a PTFE aqueous solution and a proper amount of electrolyte for a zinc-nickel battery (30 wt.% KOH solution) into the mixed powder, and fully stirring to form soft and elastic powder dough; the added electrolyte for the zinc-nickel battery can be as follows: in the step (1), 0.3 mL of electrolyte is correspondingly added to every 0.7gBi powder.

(3) Tabletting the powder dough into a film by using a roller press, wherein the film thickness is 0.04 mm, and cutting the film into 100 x 80 mm for later use or cutting the film according to the requirement; in the process of pressing the die, a plurality of times of rolling are adopted, the thickness is gradually reduced in each time of rolling, and the thickness can be according to 0.4mm → 0.2 mm → 0.1 mm → 0.08 mm → 0.04 mm, so that the structural damage of the film caused by one-time pressing due to too thin thickness can be avoided. The cut film is a conductive layer, then the conductive layer and the insulating layer are stacked together, and the multifunctional diaphragm is formed after rolling. The thickness of the insulating layer (common battery diaphragm) can be generally 30-80 um, and the insulating layer is selected according to requirements. The thickness of the insulating layer (ordinary battery separator) in this example was 35 um.

(4) The multifunctional diaphragm is assembled into a secondary zinc-nickel battery according to the 'assembly method of the multifunctional diaphragm in the secondary battery' in the invention, the cathode of the zinc-nickel battery is a ZnO powder cathode, and the anode is Ni (OH)₂A powder anode, namely activating the assembled zinc-nickel battery and preparing for testing;

(5) the zinc-nickel battery assembled with the multifunctional diaphragm is subjected to charge-discharge cycle test under the test conditions of multiplying power of 4C and discharge depth of 70% to monitor the voltage change of the zinc-nickel battery. After 800 cycles of the zinc-nickel battery, as shown in fig. 2, the voltage is still as high as 1.3V, and the discharge voltage platform is stable with little fluctuation.

(6) The battery with 900 residual circles is disassembled, the negative electrode morphology is observed by using a scanning electron microscope, as shown in fig. 3, the appearance of the negative electrode surface is spherical, the acicular morphology does not appear, the surface particles are uniformly and compactly distributed, and the obvious deformation and the falling of active substances do not exist, so that the multifunctional diaphragm effectively inhibits the negative electrode deformation, the growth of dendrites, the falling of the active substances and other problems, the reason is that the conductivity of the multifunctional diaphragm can be uniform, the current density on the electrode surface is uniform, and the generation of the dendrites is inhibited.

(7) And (3) preparing the zinc-nickel battery assembled with the multifunctional diaphragm again according to the steps (1) to (4), putting the zinc-nickel battery in a 60 ℃ oven, fully charging the zinc-nickel battery, continuously carrying out constant-voltage floating charging on the zinc-nickel battery at 1.8V, and discharging at intervals of one week under the test conditions of the multiplying power of 1C and the discharge depth of 100%. The high temperature float charge test was carried out for more than 20 days under the above conditions, and the voltage change was monitored. As shown in FIG. 4, in the high-temperature float charge test of the zinc-nickel battery, the voltage is still higher than 1.4V, and the stable descending speed of the discharge voltage platform is slower. In addition, the charging current generated during the float charge is small, mostly below 0A, which is beneficial for the positive electrode to generate less oxygen and reduce the formation of zinc dendrites.

(8) And disassembling the battery with 900 residual circles, and observing the macroscopic morphology of the negative electrode, as shown in fig. 5. After a high-temperature test for one month, the surface of the negative electrode is still relatively wet, which shows that the diaphragm has extremely strong water-retaining property; the area of the white zinc oxide on the surface of the negative electrode is small, which shows that the diaphragm effectively isolates and absorbs the oxygen precipitated by the nickel positive electrode in the charging process, and avoids the composite oxidation of the large-area zinc negative electrode by excessive oxygen. The larger area of the gray black zinc on the surface of the cathode indicates that the diaphragm also effectively inhibits the loss and dissolution of the cathode active material caused by the hydrogen evolution reaction of the zinc cathode. FIG. 6 is an electron microscope image during operation, from which it can be seen that the separator (PCL, darker color) is clearly separated from the cathode (PCL periphery, lighter color); the left side is that the diaphragm is pasted on the reaction surface of the negative electrode, 200 circles of circulation can be carried out, the black (dark color) part and the gray (light color) part are obviously layered, and the diaphragm (PLC, black dark color) is arranged above the negative electrode (gray light color); the right separator is sandwiched between the cathodes, i.e., both sides of the separator are sandwiched by the cathodes, and RS1100 is also very obviously layered. The phenomenon of the separation of the diaphragm and the negative electrode is that in the electrochemical reaction, the negative electrode participates in the reaction, but the diaphragm is inert, does not participate in the reaction and does not have the characteristics of the negative electrode, and the separation is more and more obvious along with the increase of the time of the negative electrode participating in the reaction. Due to the conductivity of the separator, the surface conductivity of the battery is increased, namely the battery takes the form shown in fig. 6, and the performance of the battery is improved.

Additional experiments:

effect of the experimental multifunctional diaphragm in the lead-acid battery: based on the ratio of the multifunctional diaphragm in the embodiment 1, the (1) to (3) are the same as the embodiment 1, the lead-acid battery is only applied in the step (4), the negative electrode of the lead-acid battery is lead, the positive electrode of the lead-acid battery is lead dioxide, and the assembled lead-acid battery is tested after being activated. The test result shows that the lead-acid battery is a water-system battery, the water solution is used as electrolyte, the diaphragm can be concluded to be effective for the battery, and the diaphragm can block the growth of dendritic crystals.

Effect of the experimental multifunctional diaphragm in the nickel-metal hydride battery: based on the ratio of the separator in example 1, (1) to (3) were the same as in example 1, and only in step (4) was used a nickel-metal hydride battery having a negative electrode made of lithium hydride and a positive electrode made of Ni (OH)₂And testing the assembled nickel-metal hydride battery after activation. The test result shows that the nickel-metal hydride battery plays a role in isolating and absorbing oxygen, the nickel-metal hydride battery can generate oxygen, and the multifunctional diaphragm can isolate the oxygen.

Through the experiments of three batteries, namely a zinc-based battery, a lead-acid battery and a nickel-metal hydride battery, the diaphragm can effectively inhibit the growth of dendritic crystals in the zinc-based battery and the lead-acid battery, and the reason is that the conductivity of the diaphragm can homogenize the current density on the surface of an electrode so as to inhibit the generation of the dendritic crystals, but the diaphragm is inert and does not participate in electrochemical reaction; in a nickel-metal hydride battery, the separator can exclude oxygen.

Example 2:

this embodiment differs from embodiment 1 described above in that: the proportion of each component in the step (1).

(1) Bi powder with the granularity of 100 nm, eight-hundred-mesh Zn powder, potassium polyacrylate particles and gas phase Al₂O₃60 wt.% aqueous PTFE solution in a weight ratio of 8: 7: 2: 1: 2, weighing and preparing materials, then placing the components except the PTFE aqueous solution into a mortar, and fully mixing the powder and uniformly dispersing the components through mechanical stirring and grinding;

the subsequent steps (2) to (8) correspond to those in example 1. In the test of charge-discharge circulation of the zinc-nickel battery assembled with the diaphragm in the step (5) under the test conditions of 4C multiplying power and 70% discharge depth, the sample begins to attenuate in a small range after 600 cycles of voltage circulation, the voltage drops to below 1.25V after 800 cycles of voltage circulation, and the discharge voltage platform shows a stable descending trend but has no obvious short circuit phenomenon. After the battery is disassembled after 800 cycles of circulation, the negative electrode particles are distributed more uniformly and have no obvious deformation. The voltage change was monitored according to the high temperature float test of step (7) of example 1. After the zinc-nickel sample is subjected to high-temperature float-charging test for 3 weeks, the voltage is still higher than 1.4V, and a relatively obvious decrease appears in the second week. The charging current generated in the floating charging process is small, and most of the time is below 0A.

Example 3:

this embodiment differs from embodiment 1 described above in that: the proportion of each component in the step (1).

(1) Bi powder with the granularity of 100 nm, eight-hundred-mesh Zn powder, potassium polyacrylate particles and gas phase Al₂O₃60 wt.% aqueous PTFE solution in a 5: 8: 2: 3: 2, weighing and preparing materials, then placing the components except the PTFE aqueous solution into a mortar, and fully mixing the powder and uniformly dispersing the components through mechanical stirring and grinding;

the subsequent steps (2) to (8) correspond to those in example 1.

In the test of charge-discharge circulation of the zinc-nickel battery assembled with the diaphragm in the step (5) under the test conditions of 4C multiplying power and 70% discharge depth, the sample voltage begins to attenuate in a small range after 290 cycles, the voltage drops to about 1.20V after 600 cycles, and the discharge voltage platform shows a stable descending trend but no obvious short circuit phenomenon. After the battery is disassembled after 600 cycles, no obvious dendritic crystal exists, and slight deformation exists. The voltage change was monitored according to the high temperature float test of step (7) of example 1. After the zinc-nickel sample is subjected to high-temperature floating charge test for 3 weeks, the voltage still reaches more than 1.4V, the charging current generated in the floating charge process is small, and most of the time is below 0A.

Comparative example 1:

adopting a glass fiber diaphragm to separate the anode and cathode of the battery, and assembling the battery into a secondary zinc-nickel battery, wherein the cathode of the zinc-nickel battery is a ZnO powder cathode, and the anode is Ni (OH)₂And (4) powder anode, and activating the assembled zinc-nickel battery to prepare for testing.

(1) The zinc-nickel battery provided with the diaphragm is subjected to charge-discharge cycle test under the test conditions of 4C multiplying power and 70% discharge depth to monitor the voltage change of the zinc-nickel battery. After the sample voltage is cycled for 200 circles, the voltage is sharply reduced to be below 0.5V, and the attenuation has obvious short-circuit characteristics. After the battery is left for 10 h after the test, the voltage of the battery continuously drops to 0V.

(2) And disassembling the battery with 900 residual rings, and observing the appearance of the negative electrode by using a scanning electron microscope. After disassembling the cell, significant dendrites penetrating the membrane were observed, and severe deformation occurred around the dendrites.

(3) And (3) placing the zinc-nickel battery in a 60 ℃ oven, continuously carrying out constant-voltage floating charge on the zinc-nickel battery at 1.8V after the zinc-nickel battery is fully charged, and discharging at intervals of one week under the test conditions of multiplying power of 1C and discharge depth of 100%. The high temperature float charge test was carried out for more than 20 days under the above conditions, and the voltage change was monitored. After the zinc-nickel sample is subjected to high-temperature floating charge test for 3 weeks, the voltage still reaches more than 1.4V, the charging current generated in the floating charge process is large, and most of the time is more than 10 mA, so that the continuous generation of oxygen of the anode and the formation of dendrites are easily activated.

Comparative example 2:

the anode and cathode of the battery are separated by a polypropylene diaphragm and assembled into a secondary zinc-nickel battery, wherein the cathode of the zinc-nickel battery is a ZnO powder cathode, and the anode is Ni (OH)₂And (4) powder anode, and activating the assembled zinc-nickel battery to prepare for testing.

(1) The zinc-nickel battery provided with the diaphragm is subjected to charge-discharge cycle test under the test conditions of 4C multiplying power and 70% discharge depth to monitor the voltage change of the zinc-nickel battery. After the voltage of the sample is cycled for 100 circles, the voltage is sharply reduced to be below 0.5V, and the attenuation has obvious short-circuit characteristics. After the battery is left for 10 h after the test, the voltage of the battery continuously drops to 0V.

(2) And disassembling the battery with 900 residual rings, and observing the appearance of the negative electrode by using a scanning electron microscope. After disassembling the cell, significant dendrites penetrating the membrane were observed, and severe deformation occurred around the dendrites.

(3) And (3) placing the zinc-nickel battery in a 60 ℃ oven, continuously carrying out constant-voltage floating charge on the zinc-nickel battery at 1.8V after the zinc-nickel battery is fully charged, and discharging at intervals of one week under the test conditions of multiplying power of 1C and discharge depth of 100%. The high temperature float charge test was carried out for more than 20 days under the above conditions, and the voltage change was monitored. The zinc-nickel sample is discharged after being tested for 2 weeks by high-temperature floating charge, the cut-off voltage of 1.4V is achieved when the discharge capacity does not reach 100%, the charging current generated in the floating charge process is large, most of the time is more than 10 mA, and continuous generation of anode oxygen and formation of dendrite are easily activated.

Comparative example 3:

this comparative example differs from example 1 above in that: the components and the proportion of each component in the step (1).

(1) Replacing Bi powder with zinc oxide, and replacing gas-phase alumina with alumina powder, namely, zinc oxide powder, eight-hundred-mesh Zn powder, potassium polyacrylate particles, alumina powder, 60 wt.% of PTFE aqueous solution, and mixing the powder with the following components in percentage by weight: 5: 3: 3: 2, weighing and preparing materials, then placing the components except the PTFE aqueous solution into a mortar, and fully mixing the powder and uniformly dispersing the components through mechanical stirring and grinding;

the subsequent steps (2) to (8) correspond to those in example 1. In the test of charge-discharge circulation of the zinc-nickel battery assembled with the diaphragm in the step (5) under the test conditions of 4C multiplying power and 70% discharge depth, the sample voltage begins to attenuate in a small range after circulating for 220 circles, the voltage drops to below 1.20V after circulating for 350 circles, the discharge voltage platform shows a descending trend, and no obvious short circuit phenomenon occurs. After the battery is disassembled after the battery is circulated for 350 circles, the electrode is obviously deformed, and no dendritic crystal is formed. The voltage change was monitored according to the high temperature float test of step (7) of example 1. The voltage of the zinc-nickel sample still reaches more than 1.4V after 3 weeks of high-temperature float-charging test. The charging current generated in the floating charging process is moderate, and most of the time is about 5 mA.

The results of the tests of examples 1-3 and comparative examples 1-3 are statistically as follows:

as can be seen from the results in the table: in the best proportion in the embodiment 1, the Bi powder which does not participate in the electrochemical reaction in the diaphragm can play a role of a current collector in the later cycle stage of the battery, so that the conductive network of the battery is prolonged, the current density distribution on the surface of the negative electrode is uniform, and the guiding effect on zinc ions can be exerted by combining potassium polyacrylate and aluminum oxide, so that the negative electrode deformation and the formation of dendritic crystals are inhibited. In example 2, the ratio of potassium polyacrylate to fumed alumina was reduced, and the ability to suppress the negative electrode strain was slightly affected, and the voltage drop was more likely to occur than in example 1. In example 3, the ratio of Bi powder to potassium polyacrylate is reduced, which slightly affects the ability of suppressing the deformation of the negative electrode, and the relative area of the conductive network may be reduced, resulting in a decrease in the uniformity of the current density distribution on the surface of the negative electrode, which makes the cycle voltage more likely to be attenuated. The general battery separators of comparative examples 1 and 2 have no current density uniformizing ability and zinc ion guiding ability, and dendrite and deformation occur more easily from the thermodynamic viewpoint. The main conductive materials in comparative example 3, still Zn and charged ZnO, which are electrochemical in the cell, can be understood as simply thickening the zinc negative electrode, although raising the relative proportions of alumina and potassium polyacrylate to inhibit dendrite formation, the negative electrode surface current density tends to be non-uniform more easily in the later cycle period due to the absence of the electrochemically inert Bi conductive network, eventually leading to faster cell failure.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.