CN115954480A - Sodium-ion battery positive electrode material, preparation method thereof, pole piece and sodium-ion battery - Google Patents
Sodium-ion battery positive electrode material, preparation method thereof, pole piece and sodium-ion battery Download PDFInfo
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Abstract
The invention discloses a sodium-ion battery positive electrode material, a preparation method thereof, a pole piece and a sodium-ion battery, and belongs to the technical field of sodium-ion batteries. The positive electrode material of the sodium-ion battery has a core-shell structure, wherein the core is formed by active material particles, and the shell is formed by functional material particles; the active material has the chemical formula of Na x Ni y Me z O 2 Wherein Me comprises at least one of iron, copper, cobalt, aluminum, magnesium, zirconium and titanium, and x>Y & lt 0.5 & lt 1, y + z =1, and the values of x, y and z satisfy the formula charge balance; active material particlesThe particle size of (A) is micron-sized; the functional material particles comprise metal oxide particles and fluorinated graphene particles, and the particle size of the functional material particles is in a nanometer level. The positive electrode material of the sodium-ion battery has better cycle performance, rate capability and safety performance. The preparation method is simple and easy to operate. The method can be used for preparing the positive pole piece and further used for preparing the sodium-ion battery with excellent performance.
Description
Technical Field
The invention relates to the technical field of sodium-ion batteries, in particular to a sodium-ion battery positive electrode material, a preparation method thereof, a pole piece and a sodium-ion battery.
Background
The sodium ion battery has a wide application prospect in the fields of low-speed two-wheel vehicles, four-wheel vehicles and energy storage due to the cost advantage, the working principle of the sodium ion battery is similar to that of the lithium ion battery, and the sodium ion battery realizes the storage and release of energy by utilizing the reversible embedding and releasing of the sodium ion between a positive electrode and a negative electrode.
When the sodium ion battery is in high temperature, puncture, abuse or bad external environment, the diaphragm is thermally contracted, the battery is easy to be internally short-circuited, the electrolyte is decomposed to generate gas and heat, the anode loses oxygen and other side reactions, and the oxygen released by the anode losing oxygen provides a combustion condition, so that the explosion or combustion of the battery is caused.
The existing sodium ion battery needs to be improved in the aspects of cyclicity, rate capability and safety.
In view of this, the invention is particularly proposed.
Disclosure of Invention
One of the objectives of the present invention is to provide a positive electrode material for sodium ion battery, which has better cycle performance, rate capability and safety performance.
The invention also aims to provide a preparation method of the positive electrode material of the sodium-ion battery.
The invention also aims to provide a pole piece which is prepared from the raw materials comprising the positive pole material of the sodium-ion battery.
The fourth purpose of the invention is to provide a sodium-ion battery, the raw materials of which comprise the positive electrode material or the pole piece of the sodium-ion battery.
The application can be realized as follows:
in a first aspect, the present application provides a positive electrode material for a sodium ion battery, the positive electrode material for a sodium ion battery has a core-shell structure, wherein an inner core is formed by active material particles, and an outer shell is formed by functional material particles;
the active material has the chemical formula of Na x Ni y Me z O 2 Wherein Me comprises at least one of iron, copper, cobalt, aluminum, magnesium, zirconium and titanium, and x>Y & lt 0.5 & lt 1, y + z =1, and the values of x, y and z satisfy the formula charge balance; the particle size of the active material particles is micron-sized;
the functional material particles comprise metal oxide particles and fluorinated graphene particles, and the particle size of the functional material particles is in a nanometer level.
In an alternative embodiment, the weight ratio of functional material particles to active material particles is 1.
In an alternative embodiment, the functional material particles are primary particles and the active material particles are secondary particles.
In an alternative embodiment, the active material particles include first nickel-based oxide particles and second nickel-based oxide particles, the first nickel-based oxide particles having a particle size larger than that of the second nickel-based oxide particles; and the nickel content of the first nickel-based oxide particles is greater than the nickel content of the second nickel-based oxide particles.
In an alternative embodiment, the first nickel-based oxide has the formula Na x Ni y1 Me z O 2 Y1 is more than or equal to 0.75 and less than 1; the second nickel-based oxide has a chemical formula of Na x Ni y2 Me z O 2 ，0. 5≤y2＜0.75。
In an alternative embodiment, the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles is 50 to 80.
In an alternative embodiment, D of the first nickel-based oxide 50 10-100 μm, D of a second nickel-based oxide 50 Is 5-50 μm.
In an alternative embodiment, the metal oxide has the formula TM a O b A, b satisfy stoichiometric balance; it is composed ofWherein TM comprises at least one of titanium, aluminum, lithium, silver, bismuth, copper, chromium, zinc, cadmium, gallium, zirconium, tin, iron, cobalt, nickel, vanadium, magnesium, calcium, barium, tungsten, and niobium.
In an alternative embodiment, the metal oxide comprises at least one of titanium oxide, aluminum oxide, iron oxide, bismuth oxide, gallium oxide, vanadium oxide, and tungsten oxide.
In an alternative embodiment, the weight ratio of metal oxide particles to fluorinated graphene particles is from 40 to 20.
In an alternative embodiment, D of the functional material particles 50 Is 20-300nm.
In a second aspect, the present application provides a method for preparing a positive electrode material for a sodium-ion battery according to any one of the preceding embodiments, comprising the steps of: the functional material particles are stacked or coated on the surface of the inner core formed of the active material particles.
In a third aspect, the present application provides a pole piece, wherein the raw material for preparing the pole piece comprises the positive electrode material of the sodium-ion battery in any one of the foregoing embodiments.
In a fourth aspect, the present application provides a sodium-ion battery, wherein the raw material for preparing the sodium-ion battery comprises the positive electrode material of the sodium-ion battery of any one of the foregoing embodiments or the pole piece of the foregoing embodiments.
The beneficial effect of this application includes:
according to the method, the sodium ion battery anode material with the core-shell structure is obtained by stacking or coating nanoscale functional materials (metal oxide and fluorinated graphene) on the surface of an active material.
The metal oxide in the functional material has high thermal conductivity, high strength and high temperature resistance, and when the functional material is used as a coating or stacking material, when the battery is subjected to safety tests such as short circuit, acupuncture and the like, a short circuit point firstly acts on coating particles, and the characteristics of high safety and large short circuit resistance can be fully utilized to buffer and weaken short circuit current, so that the function of safety protection is achieved, and the purpose of remarkably improving the safety performance of the sodium ion battery is achieved. In addition, the high extensibility and electronic insulation properties of the metal oxide can play a role in wrapping the active material, and can further reduce the thermal runaway hazard, thereby improving the needling safety of the battery.
The fluorinated graphene is used in the functional material, and has a unique crystal structure, good stability and corrosion resistance, high mechanical strength, good biocompatibility and the like, on one hand, the fluorine element contained in the fluorinated graphene can stabilize an interface, the stability of the material is improved, and the cyclicity is improved, on the other hand, the existence of the fluorine element can make the possibility that oxygen atoms escape from the surface of the graphene difficult, namely, when the nickel-containing compound and the electrolyte are subjected to thermal runaway, oxygen can be generated (the oxygen is an important influence factor for aggravation of the thermal runaway), the fluorinated graphene is positioned on the surface, the oxygen escape can be prevented, the harm is prevented from being further aggravated, and therefore, the safety of the battery is improved.
The obtained positive electrode material of the sodium-ion battery has better cycle performance, rate capability and safety performance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is an SEM image of the positive electrode material of the sodium ion battery provided in example 1 of the present application.
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 of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following provides a sodium ion battery positive electrode material, a preparation method thereof, a pole piece and a sodium ion battery.
The application provides a positive electrode material of a sodium-ion battery, which has a core-shell structure, wherein the core is formed by active material particles, and the shell is formed by functional material particles.
The chemical formula of the active material is Na x Ni y Me z O 2 Wherein Me comprises at least one of iron, copper, cobalt, aluminum, magnesium, zirconium and titanium, and x>Y & lt 0.5 & lt 1, y + z =1, and the values of x, y and z satisfy the formula charge balance; the particle size of the active material particles is in the micron order.
Illustratively, the active material may include Na 2/3 [Ni 1/3 Ti 2/3 ]O 2 、Na[Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 、Na[Ni 1/3 Co 1/ 3 Mn 1/3 ]O 2 、Na 2/3 [Ni 0.6 Co 0.4 ]O 2 Or Na [ Ni ] 0.5 Fe 0.5 ]O 2 And so on.
In some preferred embodiments, the active material particles include first nickel-based oxide particles and second nickel-based oxide particles, wherein the first nickel-based oxide particles have a particle size larger than that of the second nickel-based oxide particles; and the nickel content of the first nickel-based oxide particles is greater than the nickel content of the second nickel-based oxide particles.
The first nickel-based oxide particles are mainly used for providing capacity, and the second nickel-based oxide particles are mainly used for obtaining a better compacting effect.
In reference, the first nickel-based oxide may have a chemical formula of Na x Ni y1 Me z O 2 Y1 is more than or equal to 0.75 and less than 1; the second nickel-based oxide may have a chemical formula of Na x Ni y2 Me z O 2 ，0. 5≤y2＜0.75。
For reference, the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles is 50 to 80, such as 50.
If the number of the first nickel-based oxide particles is too small, the capacity of the whole battery is not improved; if the number of the first nickel-based oxide particles is too large, it is not favorable to obtain excellent compacting effect and safety performance.
For reference, D of the first nickel-based oxide 50 May be 10 to 100. Mu.m, such as 10 μm, 20 μm, 50 μm, 80 μm or 100 μm, etc., or may be any other value within the range of 10 to 100. Mu.m.
D of the second nickel-based oxide 50 May be 5 to 50 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, and may be any other value within the range of 5 to 50 μm.
Setting the particle diameters of the first nickel-based oxide and the second nickel-based oxide within the above ranges allows the both to have the best compounding effect.
The functional material particles used in the present application include metal oxide particles and fluorinated graphene (CF) particles, and the particle size of the functional material particles is in the nanometer order.
The functional material particles are mainly used to be stacked or coated on the surface of the active material to form a shell structure.
The metal oxide in the functional material has high thermal conductivity, high strength and high temperature resistance, and when the metal oxide is used as a coating or stacking material and can be used for safety tests such as short circuit, acupuncture and the like of a battery, a short circuit point firstly acts on coating particles, the characteristics of high safety and large short circuit resistance can be fully utilized, and the short circuit current is buffered and weakened, so that the effect of safety protection is achieved, and the purpose of remarkably improving the safety performance of the sodium ion battery is achieved. In addition, the high extensibility and electronic insulation properties of the metal oxide can play a role in wrapping the active material, and can further reduce the thermal runaway hazard, thereby improving the needling safety of the battery.
For reference, the metal oxide has the formula TM a O b A, b satisfy stoichiometric balance; wherein TM comprises at least one of titanium, aluminum, lithium, silver, bismuth, copper, chromium, zinc, cadmium, gallium, zirconium, tin, iron, cobalt, nickel, vanadium, magnesium, calcium, barium, tungsten, and niobium.
In some preferred embodiments, the metal oxide comprises at least one of titanium oxide, aluminum oxide, iron oxide, bismuth oxide, gallium oxide, vanadium oxide, and tungsten oxide to provide better buffering and attenuation of short circuit current.
The fluorinated graphene is used in the functional material, and has a unique crystal structure, good stability and corrosion resistance, high mechanical strength, good biocompatibility and the like, on one hand, the fluorine element contained in the fluorinated graphene can stabilize an interface, the stability of the material is improved, and the cyclicity is improved, on the other hand, the existence of the fluorine element can make the possibility that oxygen atoms escape from the surface of the graphene difficult, namely, when the nickel-containing compound and the electrolyte are subjected to thermal runaway, oxygen can be generated (the oxygen is an important influence factor for aggravation of the thermal runaway), the fluorinated graphene is positioned on the surface, the oxygen escape can be prevented, the harm is prevented from being further aggravated, and therefore, the safety of the battery is improved.
For reference, the weight ratio of the metal oxide particles to the fluorinated graphene particles may be 40.
If the dosage of the metal oxide particles is too low, the safety effect cannot be achieved; if the amount of the metal oxide particles used is too high, the capacity of the entire battery is affected.
In the present application, D of the functional material particles 50 Can be 20-300nm, such as 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm or 300nm, etc., or any other value within 20-300nm.
The weight ratio of functional material particles to active material particles may be 1.
If the dosage of the functional material particles is too low, the effect of improving the safety of the sodium-ion battery cannot be effectively achieved; if the amount of the functional material particles is too high, the capacity of the battery as a whole is affected.
In this application, above-mentioned functional material granule is primary particle, the active material granule is secondary particle, primary particle structural stability is good, easily do the high compaction, and primary particle specific surface area is big, difficult dispersion, the quantity can not be too much, otherwise can consume too much viscose, influence battery capacity, the active material selects for secondary particle size distribution evenly, the dynamic property is better, in a word, primary particle structural stability, specific surface area is big, secondary particle size is even, the dynamic property is excellent, the functional material of primary particle easily the cladding is on active material's surface, contact electrolyte stabilizes active material's structure, the circulation and the security performance of battery are improved.
In the present application, the primary particles of the nanoscale metal oxide and the fluorinated graphene are partially or completely stacked on the outer layers of the first nickel-based oxide and the second nickel-based oxide to form the porous coating layer, so that the core-shell structure including the micron-sized nickel-based oxide particles as the core and the nanoscale metal oxide and fluorinated graphene particles as the shell is formed.
Correspondingly, the application also provides a preparation method of the sodium-ion battery cathode material, which comprises the following steps: the functional material particles are stacked or coated on the surface of the inner core formed of the active material particles.
For reference, the active material particles and the functional material particles may be fused in a mechanical fusion machine by a high speed (e.g., rotating speed may be 4600 rpm, and time may be 2 hours) mechanical fusion method, so that the functional material particles are stacked or coated on the surface of the active material.
In some alternative embodiments, the first nickel-based oxide and the second nickel-based oxide may be mechanically fused with the graphene fluoride and the metal oxide in a mechanical fusion machine, so that the graphene fluoride and the metal oxide are deposited on the surface of the first nickel-based oxide and the second nickel-based oxide to form a coating layer.
The thickness of the coating layer is preferably not more than 1 μm.
In addition, the application also provides a pole piece, and the preparation raw materials of the pole piece comprise the positive pole material of the sodium-ion battery.
For reference, the positive electrode material of the sodium-ion battery, a conductive agent and a binder may be dispersed in a solvent to obtain a positive electrode active slurry; and then coating the positive active slurry on an aluminum foil and performing vacuum drying to obtain the positive pole piece.
Illustratively, the conductive agent may be acetylene black, the binder may be polyvinyl fluoride, and the solvent may be N-methylpyrrolidone.
It should be noted that, the dosage relationship of the positive electrode material, the conductive agent and the binder of the sodium ion battery can refer to the related prior art, and will not be described and limited herein.
Further, the application also provides a sodium ion battery, and the preparation raw materials of the sodium ion battery comprise the positive electrode material or the pole piece of the sodium ion battery.
For reference, the sodium secondary battery can be obtained by winding a positive electrode sheet, a separator, and a negative electrode sheet to obtain a core, and then loading the core into a case and injecting an electrolyte.
Illustratively, the negative electrode plate can be sodium metal after polishing, the separator can be Celgard 3000, and the electrolyte can be NaPF with 0.25mol/L 6 。
It should be noted that, during the specific operation, other methods and raw materials (such as conductive agent, binder, solvent, negative electrode sheet, separator or electrode solution) can be used to prepare the positive electrode sheet and the sodium ion battery according to the actual situation and the requirement.
The features and properties of the present invention are described in further detail below with reference to examples.
The active materials referred to in the following examples were all purchased from new materials of the gagagaku, anhui, specifically synthesized by the prior art solid phase or liquid phase methods. Fluorinated graphene is commercially available (Allatin, CAS number 1034343-98-0).
Example 1
The embodiment provides a sodium-ion battery, which is prepared by the following method:
s1: and preparing the positive electrode material of the sodium-ion battery.
The active material particles (secondary particles of the first nickel-based oxide and the second nickel-based oxide) and the functional material particles (primary particles of the fluorinated graphene and the metal oxide) were mechanically fused (4600 rpm, 2 hours) in a mechanical fusion machine, and the primary particles of the fluorinated graphene and the metal oxide were deposited on the surfaces of the secondary particles of the first nickel-based oxide and the second nickel-based oxide.
Wherein the weight ratio of the active material particles to the functional material particles is 95.
The first nickel-based oxide has a chemical formula of NaNi 0.83 Co 0.12 Mn 0.05 O 2 D of the first nickel-based oxide particles 50 Is 50 μm. The second nickel-based oxide has a chemical formula of NaNi 0.55 Co 0.1 Mn 0.35 O 2 D of second nickel-based oxide particles 50 And was 25 μm. The chemical formula of the fluorinated graphene is CF, the metal oxide is aluminum oxide, aluminum oxide particles and D of the fluorinated graphene particles 50 Are all 150nm.
The SEM image of the obtained positive electrode material for sodium ion battery is shown in fig. 1. As can be seen from fig. 1: there are active materials of different sizes and a large number of nano-functional material particles on the surface of the active material.
S2: and preparing the positive pole piece.
The positive electrode material of the sodium-ion battery, a conductive agent and a binder are dispersed in a solvent according to the mass percentage of 96%, 1.5% and 2.5% respectively to obtain positive electrode active slurry. And coating the positive active slurry on an aluminum foil and carrying out vacuum drying to obtain the positive pole piece.
The conductive agent is acetylene black, the binder is polyvinyl fluoride, and the solvent is N-methylpyrrolidone.
S3: and (5) preparing the sodium ion battery.
And winding the positive pole piece, the diaphragm and the negative pole piece to obtain a pole core, and filling the pole core into a shell and injecting electrolyte to obtain the sodium secondary battery.
Wherein the negative pole piece is polished sodium metal, the diaphragm is Celgard 3000, and the electrolyte is 0.25mol/L NaPF 6 。
Example 2
This example differs from example 1 in that: the weight ratio of active material particles to functional material particles was 99.
Example 3
This example differs from example 1 in that: the weight ratio of active material particles to functional material particles was 90.
Example 4
The present example differs from example 1 in that: the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles was 80.
Example 5
This example differs from example 1 in that: the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles is 50.
Example 6
This example differs from example 1 in that: the weight ratio of fluorinated graphene particles to metal oxide particles was 60.
Example 7
This example differs from example 1 in that: the weight ratio of fluorinated graphene particles to metal oxide particles was 80.
Example 8
This example differs from example 1 in that: d of first nickel-based oxide particles 50 15 μm, D of second nickel-based oxide particles 50 Is 5 μm.
Example 9
The present example differs from example 1 in that: d of first nickel-based oxide particles 50 D of 100 μm, second nickel-based oxide particles 50 Is 50 μm.
Example 10
D of alumina particles 50 20nm, D of fluorinated graphene particles 50 Is 300nm.
Example 11
This example differs from example 1 in that: the metal oxide is titanium oxide.
Example 12
This example differs from example 1 in that: the first nickel-based oxide has a chemical formula of NaNi 0.75 Co 0.15 Mn 0.1 O 2 The second nickel-based oxide has a chemical formula of NaNi 0.55 Co 0.15 Mn 0.3 O 2 。
Comparative example 1
The present comparative example differs from comparative example 1 in that: the weight ratio of active material particles to functional material particles was 99.5.
Comparative example 2
The present comparative example differs from comparative example 1 in that: the weight ratio of active material particles to functional material particles was 85.
Comparative example 3
The comparative example differs from comparative example 1 in that: the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles was 40.
Comparative example 4
The comparative example differs from comparative example 1 in that: the weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles is 90.
Comparative example 5
The comparative example differs from comparative example 1 in that: the weight ratio of fluorinated graphene particles to metal oxide particles is 50.
Comparative example 6
The present comparative example differs from comparative example 1 in that: the weight ratio of fluorinated graphene particles to metal oxide particles is 90.
Comparative example 7
The comparative example differs from comparative example 1 in that: d of first nickel-based oxide particles 50 25 μm, D of second nickel-based oxide particles 50 And 25 μm.
Comparative example 8
The present comparative example differs from comparative example 1 in that: d of first nickel-based oxide particles 50 25 μm, D of second nickel-based oxide particles 50 Is 50 μm.
Comparative example 9
The comparative example differs from comparative example 1 in that: the functional material does not contain fluorinated graphene, and the portion is filled with metal oxide particles.
Comparative example 10
The present comparative example differs from comparative example 1 in that: the functional material contains no metal oxide particles, and the portion is filled with fluorinated graphene.
Comparative example 11
The present comparative example differs from comparative example 1 in that: the active material particles are only the first nickel-based oxide particles.
Comparative example 12
The comparative example differs from comparative example 1 in that: the active material particles are only the second nickel-based oxide particles.
Comparative example 13
The present comparative example differs from comparative example 1 in that: functional material particles and active material particles of the positive electrode material of the sodium-ion battery do not form a core-shell structure between the functional material particles and the active material particles through a high-speed mechanical method.
Test example 1
The gram capacity, the positive mass energy density, the first efficiency, the first discharge capacity, the capacity retention rate/cycle expansion rate of 1000T cycle, the positive plate extension rate, the gas generation test and the needle punching test of the positive plate of the sodium-ion battery prepared in the examples 1 to 12 and the comparative examples 1 to 13 are shown in the table 1 and the table 2.
The testing process of the gram capacity and the energy density of the anode comprises the following steps: charging the battery at a constant current and a constant voltage of 1/3C at 25 ℃ until the cutoff current of 4.0V is 0.05C, standing for 15min, and then discharging at a constant current of 1/3C to 2.0V to obtain the discharge capacity and the average discharge voltage of 1/3C, wherein the gram capacity is 1/3C of the discharge capacity divided by the weight of the positive electrode active material, and the energy density is the gram capacity multiplied by the average discharge voltage.
The sodium ion batteries prepared in examples 1 to 12 and comparative examples 1 to 13 were subjected to a positive plate elongation test, according to the following method: the positive plate was cut into strips of 15mm wide and 100mm and fixed on a universal stretcher, and the elongation of the positive plate was recorded when the plate was stretch broken using a stretching speed of 10 mm/s.
The sodium ion batteries prepared in examples 1 to 12 and comparative examples 1 to 13 are subjected to formation and subsequent capacity test and gas production volume, and the first discharge efficiency of the battery cell is obtained through the test, and the formula is as follows: first discharge capacity/(formation capacity + first charge capacity).
The gas production volume test method refers to: the amount of gas can be obtained by testing the volume change of the battery core. The volume change can be measured according to the archimedes drainage method. And selecting high-purity light oil as a test solution, wherein the density of the light oil is rho. Light oil was filled in a beaker, which was placed on a balance and zeroed. The non-circulating cell was lifted using a thin wire, completely immersed in light oil and kept in balance, and the scale reading m1 was read. The cells were tested using the same procedure after 1000 weeks of the test cycle, and the scale reading m2 was read.
When the volume of the battery core expands by delta V during gas production, the value of delta V = (m 1-m 2)/rho; the specific gas production volume can be obtained through the formula.
The sodium ion batteries prepared in examples 1 to 12 and comparative examples 1 to 13 were charged at a constant current of 1C at a normal temperature of 25 ℃, the current was cut off at 0.05C, the batteries were left at rest for 10min, and the batteries were discharged at 0.7c, and were sequentially cycled 1000 times, and the capacity retention ratio (%) and the cycle expansion ratio (%) of 1000 cycles were calculated. The upper limit voltage of charging is 4.0V, and the qualified standard of the cycle performance test is as follows: the capacity retention rate is more than or equal to 80 percent after 1000 times, and the cyclic expansion thickness is less than or equal to 10 percent.
The needling test is that after the single cell is prepared according to the specification, a high temperature resistant steel needle (the conical angle of the needle point is 45-60 degrees, the surface of the needle is smooth and clean, and is free of rust, oxide layer and oil stain) with the diameter of 5-8 mm penetrates through the single cell at the speed of (25 +/-5) mm/s from the direction vertical to the pole plate of the storage battery, the penetrating position is preferably close to the geometric center of the needling surface, and the steel needle stays in the storage battery; the observation was carried out for 1h.
TABLE 1 test results
As can be seen from table 1: the batteries proposed in examples 1-12 possessed excellent gram capacity, positive electrode mass energy density, first-pass, and cycle performance.
Comparative example 1 compared to example 1: the content of the functional material particles is too low, so that higher gram capacity and energy density performance can be obtained, but the electronic conductivity of the pole piece is influenced, the cycle performance is restricted, and the expansion inhibiting capability of the battery is also influenced, so that the cycle and expansion rate performance is poor.
Comparative example 2 compared to example 1: the proportion content of the functional material particles is too high, and the content of the active material particles is too low, so that the energy density of the pole piece is low, but the electronic conductivity and the structural stability of the battery are good, and the battery can obtain excellent first effect, cycle performance and expansion rate.
Comparative example 3 compared to example 1: the content of the first nickel-based oxide particles is lower than that of the second nickel-based oxide particles, which affects the energy density of the final battery.
Comparative example 4 compared to example 1: the content of the first nickel-based oxide is far higher than that of the second nickel-based oxide, the battery obtains better energy density and gram capacity, but the expansion performance is poor due to the fact that the number of cycles is too high when the content of nickel is too high.
Comparative example 5 compared to example 1: the low content of the fluorinated graphene and the high content of the metal oxide particles affect the conductivity of the battery, so that the first effect and the cycle performance are achieved.
Comparative example 6 compared to example 1: the content of the fluorinated graphene is higher, and the content of the metal oxide particles is higher, so that the performance of the battery cycle expansion rate is poorer.
Comparative example 7 compared to example 1: if the first nickel-based oxide particles and the second nickel-based oxide particles have the same size, the compacted density may be low, which may affect the gram capacity, the positive electrode energy density, and the first discharge capacity of the battery.
Comparative example 8 compared to example 1: the size of the first nickel-based oxide particles is smaller than that of the second nickel-based oxide particles, which affects gram capacity, positive electrode energy density and first discharge capacity of the battery.
Comparative example 9 compared to example 1: the functional material does not contain fluorinated graphene, so that the electronic conductivity performance of the battery is poor, and the first efficiency and the cycle performance of the battery are influenced.
Comparative example 10 compared to example 1: the functional material does not contain metal oxide, so that the structure of the positive active material is easy to collapse in the battery cycle process, and the battery cycle expansion rate performance is poor.
Comparative example 11 compared to example 1: the active material particles are only the first nickel-based oxide particles, so that the battery obtains higher gram capacity and anode energy density, and the expansion performance of the battery is influenced by the excessively high nickel content of the first nickel-based oxide particles.
Comparative example 12 compared to example 1: the active material particles are only the second nickel-based oxide particles, and the battery obtains lower gram capacity and positive electrode energy density.
Comparative example 13 compared to example 1: and a core-shell structure is not formed between the positive electrode materials, so that the performances of the battery are poorer than those of other examples and comparative examples.
To summarize: examples 1 to 12 are superior to comparative examples 1 to 2 in terms of gram capacity and energy density performance of the entire battery, but inferior in terms of cycle performance, first effect and cycle volume expansion rate performance, when the content of the functional material is too small, and in terms of electron conductivity and ion conductivity of the entire battery, but the lack of the active material leads to a lower capacity of the entire battery, when the content of the functional material is too large.
Examples 1 to 12, when the content of the metal oxide disappears or is lower, the cycle performance and the cycle expansion performance of the battery are inferior to those of comparative examples 6 and 10 because the structural stability of the active material is deteriorated during the cycle, affecting the cycle and the expansion rate.
In examples 1 to 12, when the content of the fluorinated graphene is disappeared or lower, the cycle performance and the first efficiency of the battery are poor, as compared with comparative examples 5 and 9, because the conductivity of the battery is deteriorated, and the cycle performance and the first efficiency of the entire battery are affected.
Examples 1 to 12, when the content of the first nickel-based oxide is excessively low, affect the gram capacity, the positive electrode energy density and the first discharge capacity of the battery as a whole, compared to comparative examples 3 to 4.
Examples 1-12 compared to comparative examples 7-9, when the size of the first nickel-based oxide particles was not greater than the size of the second nickel-based oxide particles, the compacted density of the pole piece was affected, thereby affecting the overall gram capacity, positive electrode energy density, and first discharge capacity.
Examples 1-12 compared to comparative examples 11-12, the active material particles achieved higher battery capacity for the first nickel-based oxide alone and slightly lower capacity performance for the second nickel-based oxide alone.
Comparative example 13 is inferior to examples 1 to 12 and comparative examples 1 to 12 in capacity performance, first effect and cycle performance, which indicates that the formation of a core-shell structure is an indispensable condition for obtaining the above excellent performance indexes.
TABLE 2
As can be seen from table 2:
comparing the comparative examples 6 and 10 with other comparative examples and examples: when the content of the metal oxide disappears or is low, the battery has poor extensibility performance and severe flatulence, and a needling experiment cannot be performed.
Comparative examples 5 and 9 are compared with other comparative examples and examples: when the content of the fluorinated graphene is disappeared or is lower, the escape of oxygen atoms is not blocked, and the battery has serious flatulence, so that the safety performance of the battery is influenced.
Comparative examples 4 and 11 are compared with other comparative examples and examples: when the active material is only the first nickel-based oxide or the content of the first nickel-based oxide is too high, the nickel content is too high, the consumed electrolyte is not uniform, sodium precipitation is easy to occur, and the needle punching experiment is difficult to pass.
The pole piece and the battery prepared in the comparative example 13 have poor ductility and severe flatulence, and cannot pass a needling test by 100%, which indicates that the core-shell structure formed by the material is an essential condition for obtaining the excellent safety performance index.
In summary, on one hand, the positive electrode material of the sodium-ion battery provided by the embodiment of the invention has high capacity, and the functional material has higher ionization degree and excellent electronic conductivity, so that the electrical property and the safety of the battery are improved. On the other hand, the first nickel-based oxide and the second nickel-based oxide can balance polarization, maintain polarization uniformity, improve circulation, and are beneficial to improving the elongation of the positive plate and improving the capacity retention rate. The preparation method is simple and easy to operate. The method can be used for preparing the positive pole piece and further used for preparing the sodium ion battery with excellent performance.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The positive electrode material of the sodium-ion battery is characterized by having a core-shell structure, wherein the core is formed by active material particles, and the shell is formed by functional material particles;
the chemical formula of the active material is Na x Ni y Me z O 2 Wherein Me comprises at least one of iron, copper, cobalt, aluminum, magnesium, zirconium and titanium, and x>0,0.5 < y < 1,y + z =1, and the values of x, y and z satisfy the charge balance of the chemical formula; the particle size of the active material particles is micron-sized;
the functional material particles comprise metal oxide particles and fluorinated graphene particles, and the particle size of the functional material particles is in a nanometer level.
2. The sodium-ion battery positive electrode material according to claim 1, wherein a weight ratio of the functional material particles to the active material particles is 1.
3. The positive electrode material for sodium-ion batteries according to claim 2, wherein the functional material particles are primary particles and the active material particles are secondary particles.
4. The positive electrode material for sodium-ion batteries according to any one of claims 1 to 3, wherein the active material particles comprise first nickel-based oxide particles and second nickel-based oxide particles; the particle diameter of the first nickel-based oxide particles is larger than the particle diameter of the second nickel-based oxide particles; and the nickel content of the first nickel-based oxide particles is greater than the nickel content of the second nickel-based oxide particles;
the first nickel-based oxide has a chemical formula of Na x Ni y1 Me z O 2 Y1 is more than or equal to 0.75 and less than 1; the second nickel-based oxide has a chemical formula of Na x Ni y2 Me z O 2 ，0. 5≤y2＜0.75；
The weight ratio of the first nickel-based oxide particles to the second nickel-based oxide particles is 50 to 80;
d of the first nickel-based oxide 50 D of the second nickel-based oxide is 10 to 100 mu m 50 Is 5-50 μm.
5. The positive electrode material for sodium-ion battery according to any one of claims 1 to 3, wherein the metal oxide has the chemical formula of TM a O b A and b satisfy stoichiometric balance; wherein TM comprises at least one of titanium, aluminum, lithium, silver, bismuth, copper, chromium, zinc, cadmium, gallium, zirconium, tin, iron, cobalt, nickel, vanadium, magnesium, calcium, barium, tungsten, and niobium.
6. The sodium-ion battery positive electrode material according to claim 5, wherein the metal oxide comprises at least one of titanium oxide, aluminum oxide, iron oxide, bismuth oxide, gallium oxide, vanadium oxide, and tungsten oxide.
7. The sodium-ion battery positive electrode material according to any one of claims 1 to 3, wherein the weight ratio of the metal oxide particles to the fluorinated graphene particles is from 40 to 20; and/or D of the functional material particles 50 Is 20-300nm.
8. The method for preparing a positive electrode material for a sodium-ion battery according to any one of claims 1 to 7, comprising the steps of: stacking or coating the functional material particles on the surface of an inner core formed of the active material particles.
9. A pole piece, characterized in that the raw material for preparing the pole piece comprises the positive electrode material of the sodium-ion battery of any one of claims 1 to 7.
10. A sodium-ion battery, characterized in that the raw materials for preparing the sodium-ion battery comprise the positive electrode material of the sodium-ion battery as defined in any one of claims 1 to 7 or the pole piece as defined in claim 9.
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| US20200266426A1 (en) * | 2019-02-15 | 2020-08-20 | Nanotek Instruments, Inc. | Chemical-free production method of graphene-encapsulated electrode active material particles for battery applications |
| CN111933943A (en) * | 2020-08-10 | 2020-11-13 | 苏州科技大学 | Sodium ion battery Na with high energy density0.67Mn0.65Fe0.2Ni0.15O2Efficient and stable preparation method of anode material |
| CN113851652A (en) * | 2021-08-26 | 2021-12-28 | 蜂巢能源科技有限公司 | Modified cobalt-free positive electrode material of sodium ion battery, preparation method of modified cobalt-free positive electrode material and sodium ion battery |
| CN114744180A (en) * | 2022-05-17 | 2022-07-12 | 无锡钠科能源科技有限公司 | Composite coated positive electrode material of sodium-ion battery |
| CN115312781A (en) * | 2022-10-10 | 2022-11-08 | 苏州大学 | Sodium ion battery positive electrode material, preparation method thereof and sodium ion battery |
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| US20200266426A1 (en) * | 2019-02-15 | 2020-08-20 | Nanotek Instruments, Inc. | Chemical-free production method of graphene-encapsulated electrode active material particles for battery applications |
| CN111933943A (en) * | 2020-08-10 | 2020-11-13 | 苏州科技大学 | Sodium ion battery Na with high energy density0.67Mn0.65Fe0.2Ni0.15O2Efficient and stable preparation method of anode material |
| CN113851652A (en) * | 2021-08-26 | 2021-12-28 | 蜂巢能源科技有限公司 | Modified cobalt-free positive electrode material of sodium ion battery, preparation method of modified cobalt-free positive electrode material and sodium ion battery |
| CN114744180A (en) * | 2022-05-17 | 2022-07-12 | 无锡钠科能源科技有限公司 | Composite coated positive electrode material of sodium-ion battery |
| CN115312781A (en) * | 2022-10-10 | 2022-11-08 | 苏州大学 | Sodium ion battery positive electrode material, preparation method thereof and sodium ion battery |
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