WO2018014165A1 - 钠离子电池极片，其制备方法及含有该极片的钠离子电池 - Google Patents

钠离子电池极片，其制备方法及含有该极片的钠离子电池 Download PDF

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WO2018014165A1
WO2018014165A1 PCT/CN2016/090329 CN2016090329W WO2018014165A1 WO 2018014165 A1 WO2018014165 A1 WO 2018014165A1 CN 2016090329 W CN2016090329 W CN 2016090329W WO 2018014165 A1 WO2018014165 A1 WO 2018014165A1
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sodium
pole piece
ion battery
sodium ion
initial
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PCT/CN2016/090329
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English (en)
French (fr)
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梁成都
王莹
郭永胜
李晓燕
罗莉
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宁德时代新能源科技股份有限公司
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Priority to CN201680087757.6A priority Critical patent/CN109565037B/zh
Priority to PCT/CN2016/090329 priority patent/WO2018014165A1/zh
Publication of WO2018014165A1 publication Critical patent/WO2018014165A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of secondary batteries, and in particular to a sodium ion battery pole piece, a preparation method thereof, and a sodium ion battery including the pole piece.
  • Lithium-ion batteries which are advanced rechargeable secondary batteries, have been widely used in consumer electronics and energy vehicles.
  • lithium-ion batteries still face safety concerns, high cost of raw materials, and shortage of global lithium resources.
  • These problems have largely restricted the development of lithium-ion batteries, especially in large-scale energy storage. Therefore, the development of a resource-rich, low-cost Xi'an battery system is an inevitable solution to the future application of large-scale energy storage systems.
  • the sodium element is in the same family as lithium, the electrochemical properties are similar, and the electrode TV is relatively close.
  • the sodium resources in the world are very rich, 2.64%, far higher than 0.006% of lithium, and the refining cost is lower. If a sodium ion battery with excellent performance and low cost is developed, it will have a greater competitive advantage in mass storage than a lithium ion battery.
  • the radius of sodium ions is larger than the radius of lithium ions. It is more difficult to insert and remove sodium ions in the positive anode material than lithium ions in the same crystal structure material. During the charging and discharging process, some sodium ions remain in the anode and cannot escape smoothly. At the same time, in the first charge and discharge process, the SEI film is formed at the anode, and the sodium ion is further consumed, so that the first charge and discharge coulombic of the sodium ion battery is low. Taking carbon materials as an example, graphite materials have a good application in lithium ion batteries, and their first charge and discharge performance can reach about 94 to 95%.
  • the sodium ion of the same material cannot be smoothly inserted and removed, and it is difficult to apply it in a sodium ion battery.
  • the hard carbon material can smoothly insert and dissociate the sodium ions.
  • the charge and discharge efficiency is low, and it is difficult to achieve 90%. Therefore, it is necessary to find a suitable method to improve the coulombic efficiency of sodium ion batteries and improve their electrochemical performance.
  • the primary object of the present application is to provide a sodium ion battery pole piece.
  • a second object of the present application is to provide a method for preparing the sodium ion battery pole piece.
  • a third object of the present application is to provide a sodium ion battery containing the pole piece.
  • the present application relates to a sodium ion battery pole piece comprising a sodium sheet, a current collector, and a membrane attached to the current collector, the current collector and the diaphragm forming an initial pole piece,
  • the sodium sheet is disposed on the initial pole piece.
  • the sodium flakes are bonded to the initial pole piece by cold pressing.
  • the sodium sheet has a thickness of from 1 ⁇ m to 500 ⁇ m, preferably from 5 ⁇ m to 100 ⁇ m.
  • the width of the sodium sheet is a
  • the width of the initial pole piece is b, a ⁇ b; preferably, 80% b ⁇ a ⁇ b; more preferably, 80% b ⁇ a ⁇ 98% b .
  • the sodium sheet is disposed in the middle of the initial sodium sheet.
  • the current collector is one selected from the group consisting of aluminum foil, copper foil, stainless steel foil, porous aluminum foil, porous copper foil, and porous stainless steel foil.
  • the initial pole piece comprises an initial anode pole piece and an initial cathode pole piece.
  • the sodium content of the sodium flakes is compatible with the sodium supplementation capacity of the initial anode pole piece.
  • the diaphragm of the initial anode pole piece contains an anode active material, a binder and a conductive agent;
  • the anode active material is selected from the group consisting of carbon materials, alloy materials, over-plated metal oxides, over-plated metal sulfides, At least one of a phosphorus-based material or a titanate material;
  • the film of the initial cathode pole piece contains a cathode active material, a binder, and a conductive agent;
  • the cathode active material is selected from the group consisting of a layered structural material, a tunnel type At least one of an oxide material, a polyanionic material, or a blue sapphire
  • the alloy material is selected from an alloy material composed of at least two of Si, Ge, Sn, Pb, and Sb; the over-metallized oxide and the over-plated metal sulfide have a chemical formula of M1 x N y Wherein M1 is selected from at least one of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, and N is selected from O or S; and the phosphorus-based material is selected from the group consisting of red phosphorus, white phosphorus, and black phosphorus.
  • the titanate material is at least one selected from the group consisting of Na 2 Ti 3 O 7 , Na 2 Ti 6 O 13 , Na 4 Ti 5 O 12 , Li 4 Ti 5 O 12 , and NaTi 2 (PO 4 ) 3
  • the layered structural material and the tunnel-type oxide material each have a chemical formula of Na x M 2 O 2 , and M 2 is at least one selected from the group consisting of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu;
  • the polyanionic material is selected from at least one of NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM3PO 4 F or Na 3 (VO x ) 2 (PO 4 ) 2 F 3-2x
  • M3 is selected from the group consisting of V and Fe.
  • the present application further relates to a method for preparing the sodium ion battery pole piece, comprising at least the steps of: preparing an initial pole piece, and covering the surface of the film of the initial pole piece in a dry environment, that is, the method Sodium ion battery pole piece.
  • the sodium sheet is covered on the surface of the diaphragm of the initial pole piece and then cold pressed.
  • the cold pressing pressure is 0.01 to 1.5 MPa; preferably, the pressure is 0.2 to 1.0 MPa.
  • the initial pole piece is prepared by uniformly stirring the active material, the conductive agent, the binder and the solvent to obtain a slurry, coating the slurry on the current collector, drying, and initializing after cold pressing.
  • the present application also relates to a sodium ion battery, comprising a positive electrode tab, a negative pole tab, a separator interposed between the positive pole tab and the negative pole tab, and an electrolyte, wherein the positive pole tab And/or the negative pole piece is the sodium ion battery pole piece of the present application.
  • the sodium ion battery pole piece of the present application can improve the first coulombic efficiency of the active material in the pole piece and reduce the loss of cathode sodium ion during the first charge and discharge process.
  • the sodium ion battery pole piece of the present application can also be supplemented by the method of pre-supplementing sodium.
  • the sodium ions in the sodium-rich pole piece penetrate the anode material in the anode material, so that sodium ions are more easily deintercalated in the anode material during charge and discharge, thereby improving the capacity retention rate of the battery.
  • the preparation method of the sodium ion battery pole piece of the present application is not only easy to operate, but also has a short production cycle and high efficiency, and can also achieve the effect of quantitatively controlling sodium supplementation.
  • Example 1 is a graph showing the capacity retention ratios of the sodium ion batteries of Example 1 and Comparative Example 1.
  • the present application proposes a sodium ion battery pole piece, the sodium ion battery pole piece includes a current collector, a diaphragm attached to the current collector, and a sodium piece, and the current collector and the diaphragm form an initial pole piece.
  • the sodium piece is placed on the initial pole piece.
  • the sodium sheet is provided in the sodium ion battery pole piece of the present application in order to pre-supplement the anode.
  • One of the aims is to improve the first coulombic efficiency of the active material in the initial anode pole piece during the formation process of the battery preparation process, and reduce During the first charge and discharge process, the sodium ion in the cathode material is due to the irreversible sodium ion capacity of the material itself and the loss of the cathode sodium ion during the formation of the SEI film.
  • the second purpose is to open the path of sodium ions in the anode material to make the charge and discharge. During the process, sodium ions are more easily deintercalated in the anode material, thereby increasing the capacity retention of the battery.
  • the sodium source for sodium supplementation is a sodium plate having a uniform thickness, thereby achieving uniform sodium supplementation for the anode.
  • the surface of the sodium sheet is prepared with a passivation layer in the production process, and the deterioration reaction does not occur in a dry environment (the humidity in the air is less than 5%), and the passivation layer may be an oxide film or a nitride film.
  • the sodium piece is cold pressed to the initial pole piece. That is, in the present application, the sodium sheet is bonded to the membrane by cold pressing using a sodium sheet. After cold pressing, the sodium sheet is bonded to the initial pole piece to increase the contact between the sodium sheet and the active material of the diaphragm, so as to facilitate the subsequent processes of the bare cell core.
  • the pre-doped sodium treatment of the positive anode material by the electrolysis method and the steaming method can improve the first charge and discharge efficiency of the sodium ion battery, but the steaming method needs to be operated at a high temperature, possibly for the binder in the pole piece, etc.
  • the cold compression method of the present application is not only easy to operate, but also has a short production cycle and high efficiency, and can also achieve the effect of quantitatively controlling sodium supplementation.
  • the initial pole piece comprises an initial anode pole piece or an initial cathode pole piece.
  • the sodium ion battery pole piece of the present application may be an anode pole piece or a cathode pole piece.
  • a cathode pole piece containing a sodium sheet is referred to as a cathode sodium-rich pole piece
  • an anode pole piece containing a sodium sheet is referred to as an anode sodium-rich pole piece.
  • the anode-rich sodium plate can increase the contact between the sodium sheet and the anode active material, so that the anode active material can quickly absorb the sodium in the sodium sheet to achieve the effect of pre-supplementing sodium.
  • the anode sodium-rich pole piece or the cathode sodium-rich pole piece can achieve the pre-supplementing effect on the sodium ion battery.
  • the sodium content of the sodium piece is compatible with the sodium supplement capacity of the initial anode piece.
  • the present application can accurately supplement the anode with sodium by the sodium content in the sodium tablet.
  • sodium content in the present application means the capacity of sodium in the sodium tablet for sodium supplementation.
  • sodium supplementation capacity of the initial anode electrode piece in the present application means that the sodium-rich anode electrode piece has an increased pole piece capacity after the first effect is increased by the method of pre-supplementing the sodium electrode.
  • the meaning of "adapted" in the present application includes the case where the sodium content of the sodium flake is completely consistent with the sodium supplemental capacity of the initial pole piece of the anode, and also includes the case where the sodium content of the sodium flake is greater than or less than the sodium supplemental capacity of the initial pole piece. .
  • the sodium content of the sodium tablet is equal to the sodium supplement capacity of the anode pole piece, it is a total sodium supplement.
  • the sodium content of the sodium tablet is greater than the sodium supplement capacity of the anode pole piece, it is super-supplemented sodium.
  • the sodium content is less than the sodium supplement capacity of the initial pole piece of the anode, it is under-supplemented.
  • the thickness of the sodium sheet is from 1 ⁇ m to 500 ⁇ m, preferably from 5 ⁇ m to 100 ⁇ m.
  • the sodium supplement capacity of the initial anode sheet is controlled by the thickness of the sodium sheet.
  • the width of the sodium piece is a, and the width of the initial pole piece is b, a ⁇ b.
  • the width of the sodium sheet is less than or equal to the width of the initial pole piece.
  • metal sodium may come through the separator to contact the other active material, thereby causing a danger of short circuit. Since the sodium flakes have a certain ductility, it is preferred that the sodium flakes have a width smaller than the width of the initial pole flakes.
  • the relationship between the width of the sodium sheet and the width of the initial pole piece is: 80% b ⁇ a ⁇ b; when the width of the sodium sheet is less than 80% of the width of the pole piece, in a short time The pole piece cannot be completely diffused, affecting the sodium supplementation effect at the edge of the pole piece, resulting in uneven sodium supplementation.
  • the width of the sodium piece and the width of the initial pole piece The relationship is: 80% b ⁇ a ⁇ 98% b; considering that the pole piece is formed into a battery core by lamination or winding, the pressure is applied in the process of top side sealing or molding of the subsequent process, and the material of the sodium piece is soft. There will be some deformation and extension. If the difference between the width of the sodium sheet and the width of the initial pole piece is too small, a local micro short circuit may occur before the formation process in the process, and the cell survival rate during the preparation process is lowered, so that a ⁇ 98% b is further preferable.
  • the relationship between the width of the sodium sheet and the width of the initial pole piece is: 90% b ⁇ a ⁇ 98% b.
  • the sodium piece is disposed in the middle of the initial sodium piece, that is, a blank area is formed on both sides in the width direction of the initial pole piece.
  • the current collector is selected from one of aluminum foil, copper foil, stainless steel foil, porous aluminum foil, porous copper foil, and porous stainless steel foil.
  • the initial anode pole piece diaphragm contains an anode active material, a binder and a conductive agent;
  • the anode active material is selected from the group consisting of carbon materials, alloy materials, overplated metal oxides, At least one of metal sulfide, phosphorus-based material or titanate material;
  • the cathode of the initial cathode pole piece contains a cathode active material, a binder and a conductive agent;
  • the cathode active material is selected from the group consisting of layered structural materials, At least one of a tunnel type oxide material, a polyanionic material, or a blue sapphire.
  • the alloy material is selected from the group consisting of alloy materials composed of at least two of Si, Ge, Sn, Pb, and Sb;
  • the overplated metal oxide and the overplated metal sulfide have a chemical formula of M1 x N y , wherein M1 is at least one selected from the group consisting of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V, and N is selected from the group consisting of at least one selected from the group consisting of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V. O or S;
  • the phosphorus-based material is selected from at least one of red phosphorus, white phosphorus, and black phosphorus;
  • the titanate material is at least one selected from the group consisting of Na 2 Ti 3 O 7 , Na 2 Ti 6 O 13 , Na 4 Ti 5 O 12 , Li 4 Ti 5 O 12 , and NaTi 2 (PO 4 ) 3 ;
  • the layered structural material and the tunnel-type oxide material have a chemical formula of Na x M 2 O 2 , and M 2 is at least one selected from the group consisting of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu;
  • the polyanionic material is selected from at least one of NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM3PO 4 F or Na 3 (VO x ) 2 (PO 4 ) 2 F 3-2x , and M3 is selected from the group consisting of V and Fe. At least one of Mn and Ni, 0 ⁇ x ⁇ 1; the chemical formula of the Bruce blue material is Na x M4Fe(CN) 6 , and M4 is at least one selected from the group consisting of Ni, Cu, Fe, Mn, Co, and Zn. Kind.
  • the present application provides a method for preparing the above-mentioned sodium ion battery pole piece, which comprises at least the following steps:
  • the initial pole piece is prepared, and in a dry environment, the sodium piece is covered on the surface of the initial pole piece to obtain a sodium ion battery pole piece.
  • the sodium sheet is covered on the surface of the initial pole piece and then subjected to a cold pressing process; the contact between the sodium sheet and the active material of the diaphragm can be increased, and the ion is caused by the two solid phases.
  • the transfer is slower, which increases the rate of absorption of the sodium tablets.
  • a dry environment means that the humidity in the air in the environment is less than 5%.
  • the pressure at the time of cold pressing is 0.01 to 1.5 MPa; preferably, the pressure is 0.2 to 1.0 MPa.
  • the pressure is controlled at 1.5.
  • Mpa is used to ensure the appearance of the pole piece.
  • the pressure is controlled at 0.2 to 1.0 MPa to ensure the cold pressing effect.
  • the initial pole piece is prepared by uniformly stirring the active material, the conductive agent, the binder and the solvent to obtain a slurry, coating the slurry on the current collector, and drying. After cold pressing, an initial pole piece was obtained in which the slurry coated on the current collector became a film after drying and cold pressing.
  • the initial electrode sheet is prepared to cover the sodium-rich pole piece of the sodium sheet for 1 to 10 minutes.
  • the present application provides a sodium ion battery comprising a positive electrode tab, a negative pole tab, a separator interposed between the positive pole tab and the negative pole tab, and an electrolyte, wherein the positive pole tab And/or the negative pole piece is the sodium ion battery pole piece of the present application.
  • the positive electrode tab or the negative electrode tab is the sodium ion battery pole piece of the present application.
  • the steps are as follows: forming the positive pole piece, the negative electrode initial pole piece and the separator of the present application into a bare cell by winding or laminating, or passing the positive electrode pole piece, the negative electrode piece and the separator of the present application through The wound or laminated piece is made into a bare cell; then the bare cell is placed in the battery package to be top-side sealed, then the electrolyte is injected, and then the sodium ion battery is prepared by a process of standing, shaping, and forming.
  • Preparing the initial anode pole piece preparing the slurry by uniformly mixing the anode active material, the binder and the conductive agent with a solvent at a mass ratio of 88:10:2; wherein the binder is PAA, and the conductive agent is Conductive carbon black, the solvent is water.
  • the slurry is coated on a copper current collector, the coating weight is 100mg / 1540mm 2 , the pole piece is dried, cold pressed, and stripped to obtain a sodium ion battery anode pole piece, the width of the pole piece is b;
  • preparing a sodium-rich anode pole piece in a dry environment, a certain thickness, a width of the sodium sheet is covered on the surface of the initial pole piece (ie, the cold pressure is zero), to obtain a sodium-rich anode pole piece; Or the initial pole piece coated with the sodium piece is subjected to cold pressing, and a certain pressure is applied to obtain a sodium-rich anode electrode piece. The time at which the initial pole piece was prepared as a sodium-rich pole piece was also recorded.
  • Preparing the initial cathode pole piece preparing the slurry by uniformly mixing the cathode active material, the binder and the conductive agent with a solvent at a mass ratio of 88:10:2, wherein the binder is PVDF, and the conductive agent is Conductive carbon black, the solvent is N-methylpyrrolidone (NMP); the slurry is coated on an aluminum current collector, the coating weight is 0.33g/1540mm 2 , and the pole piece is dried, cold pressed, and stripped to obtain sodium. Ion battery anode pole piece, the pole piece is cut into a width b;
  • a sodium-rich cathode pole piece in a dry environment, a sodium piece having a thickness of 10 ⁇ m and a width a is covered on the surface of the initial pole piece (ie, the cold pressing pressure is zero), and a sodium-rich anode pole piece is obtained; Or the initial pole piece coated with the sodium piece is subjected to cold pressing, and a certain pressure is applied to obtain a sodium-rich anode electrode piece. The time at which the initial pole piece was prepared as a sodium-rich pole piece was also recorded.
  • the cathode pole piece, the anode pole piece and the separator of the sodium ion battery are made into a bare cell through the lamination; then the cell is placed in the aluminum plastic film package, and then subjected to a top side sealing process, then the electrolyte is injected, and then passed through
  • the sodium ion battery is prepared by a process of standing, shaping, and forming.
  • the sodium-rich pole pieces 1 to 16 and the initial pole pieces 1 to 6 were prepared according to the above preparation methods, and the specific parameters are shown in Table 1:
  • the sodium-rich pole piece of Comparative Example 1 was subjected to an evaporation method.
  • the specific process conditions were as follows: evaporation of the metal sodium layer onto the anode initial film by vapor deposition, the thickness of the plating layer was 10 ⁇ m, and the width of the plate was controlled by a baffle plate of 150 mm, that is, plating and The above embodiment 1 is the same.
  • the time for evaporating an equal amount of Na layer was 30 min, and the vacuum time was 150 min before and after.
  • the preparation time from the initial pole piece to the sodium-rich pole piece was about 180 min.
  • the sodium-rich pole piece of Comparative Example 2 was electroplated.
  • the specific process conditions were as follows: electroplating equipment was used to electrolyze the metal sodium layer onto the initial film, the electrolyte was sodium hexafluorophosphate, and the thickness of the coating was 10 ⁇ m, and the width was controlled by the baffle. The thickness was 150 mm, that is, the plating layer was the same as in the above Example 1.
  • the time for plating the equal amount of Na layer is about 20 min, and the electrolysis condition time is about 10 min before and after, and the preparation end time from the initial pole piece to the sodium-rich pole piece is about 30 min.
  • the sodium ion battery was prepared according to the foregoing method using the pole pieces in Tables 1 and 2, as shown in Table 3:
  • the first coulombic efficiency the sodium ion battery sodium battery 1 to 16 and the sodium ion battery of the sodium ion battery 1 to 7 were subjected to a constant current charge and discharge test at 25 ° C, and the charging and discharging steps were: constant current charging at a rate of 0.7 C The voltage is 4.0V, and then charged at a constant voltage of 4.0V until the current is 0.05C. At this time, the sodium ion battery reaches the full charge state, then it is left to stand for 5min; the constant current discharge is 0.5V rate to the voltage of 1.5V, and then it is allowed to stand. 5min; a cycle of charge and discharge. The secondary discharge capacity and the first charge capacity were measured in accordance with this method.
  • First Coulomb efficiency initial discharge capacity / first charge capacity ⁇ 100%.
  • Sodium deposition The samples of sodium ion batteries 1 to 16 and the comparative sodium ion batteries 1 to 7 were charged to 4.0 V at a rate of 0.7 C, and then charged at a constant voltage of 4.0 V to a current of 0.05 C, and at full charge. In the state, the battery core is disassembled to observe the sodium supplementation effect of different sodium sheets or processes and the influence on the cross section and appearance of the pole piece.
  • Cyclic performance The sodium ion battery 1 and the sodium ion battery of the comparative sodium ion battery 1 were subjected to a constant current charge and discharge test at 25 ° C, and the charging and discharging steps were: constant current charging at a rate of 0.7 C to a voltage of 4.0 V, and then 4.0V constant voltage charging to current is 0.05C, at this time, the sodium ion battery reaches full charge state, then it is left to stand for 5min; it is discharged at a constant current of 0.5C to 1.5V, and then left for 5min; it is a cycle charging and discharging process. . 50 charge and discharge cycles were performed, and the capacity retention rate of each cycle was calculated.
  • the capacity retention ratio of the sodium ion battery 1 and the comparative sodium ion battery 1 sodium ion battery is shown in FIG.
  • Contrast sodium ion battery 15 88.5%
  • Sodium ion battery 16 91.0% Contrast sodium ion battery 1
  • Contrast sodium ion battery 2 70.1% Contrast sodium ion battery 3 75.3% Contrast sodium ion battery 4 62.7% Contrast sodium ion battery 5
  • Contrast sodium ion battery 6 91.0% Contrast sodium ion battery 7 90.8%
  • the sodium ion battery 4 has a portion of sodium remaining on the edge of the pole piece, and the remaining small amount of sodium has exceeded the width of the initial diaphragm. This is because after the initial film is coated with sodium, there is a process of cold pressing, and in the top side sealing and shaping process of the subsequent process, a certain pressure is applied to the cell because the sodium piece is soft and its ductility
  • the initial width of the sodium flakes is equal to that of the pole pieces, resulting in a portion of the sodium exceeding the initial pole piece width, which is prone to sodium dendrites and pierce the membrane during subsequent cycles. Or cause local micro-short circuit, causing certain damage to the cycle performance. Therefore, in the preferred technical solution of the present application, the technical solution of a ⁇ 98% b is selected to avoid the occurrence of the above problems;
  • the edge of the pole piece is obviously insufficient in sodium supplementation, and the first effect of the sodium ion battery 5 is significantly lower than that of the sodium ion battery 1, the difference is that the ratio of the width of the sodium piece to the initial pole piece is different. Therefore, when the width of the sodium sheet is less than 80% of the width of the initial pole piece, sodium in the edge region may not be diffused in a short time, and there is a tendency for the pole piece to be uneven in sodium. Therefore, preferred in the present application In the technical solution, the technical solution of 80b% ⁇ a can be used to avoid the above problems;
  • the present application more preferably ranges from 90b% ⁇ a ⁇ 98% b.
  • the thickness of the sodium sheet should be controlled to be 1 to 500 ⁇ m, preferably 10 to 100 ⁇ m, in comparison with other sodium ion batteries.
  • the sodium supplementation effect can be achieved, and the pole piece of the sodium ion battery 14 in the fully charged state is disassembled, and no sodium is precipitated on the surface of the cathode anode, and the interface uniformity is good. It is indicated that the sodium supplementation method can also achieve the effect by using sodium-rich cathode pole piece, and there is no obvious side effect.
  • the sodium-rich pole piece of the sodium ion battery of the present application can effectively improve the first coulombic efficiency and cycle performance of the cell and improve its electrochemical performance.
  • the sodium-rich pole piece of the present application can achieve uniform sodium supplementation, and can accurately and simply control the amount of sodium supplementation.
  • the preparation process of the sodium-rich pole piece of the present application is simple, the environment is simple, the high temperature operation of the pole piece is not required or contact with other chemical preparations, the potential hazard to the pole piece is avoided, the cost is low, the operation is easy, and the industrial production is favorable.

Abstract

提供一种钠离子电池极片，其制备方法及含有该极片的钠离子电池。钠离子电池极片包括钠片、集流体以及附着于集流体上的膜片，集流体和膜片形成初始极片，钠片设置于初始极片上。电极极片可提高电池的首次库伦效率，减少在首次充放电过程中阴极材料中钠离子的损失，同时使在充放电过程中钠离子更容易在阳极材料中脱嵌，提高电池的容量保持率。制备方法易于操作、生产周期短、高效，可实现定量补钠。

Description

钠离子电池极片，其制备方法及含有该极片的钠离子电池 技术领域
本申请涉及二次电池领域，具体讲，涉及一种钠离子电池极片，其制备方法及含有该极片的钠离子电池。
背景技术
能源短缺和环境问题对大规模储能装置的开发和建设提出新的需求。作为先进的可充电二次电池的锂离子电池，已经广泛应用在消费类电子产品和能源汽车方面。然而，锂离子电池仍然面临安全隐患，原料成本昂贵以及全球锂资源短缺等问题。而这些问题在很大程度上制约了锂离子电池的发展基应用，尤其是在大规模储能方面。因此发展资源丰富、成本低廉的西安进电池体系，是解决未来大规模储能系统应用的必然出路。钠元素与锂同族，电化学性质相似，电极电视也比较接近。且钠元素在全球的资源非常丰富，为2.64％，远远高于锂元素的0.006％，且提炼成本较低。若开发出工作性能优良，成本低廉的钠离子电池，则其将拥有比锂离子电池电池在大规模储能方面具有更大的竞争优势。
然而，钠离子半径比锂离子半径大，钠离子在正阳极材料中嵌入和脱出比锂离子在同种晶体结构材料中更困难，在充放电过程中导致部分钠离子留在阳极而无法顺利脱出，同时在首次充放电过程中，在阳极形成SEI膜，对钠离子进一步消耗，造成钠离子电池的首次充放电库伦效率较低。以碳材料为例，石墨类材料在锂离子电池中具有较好的应用，其首次充放电性能可达到94～95％左右。而同类材料钠离子无法顺利的嵌入和脱出，很难在钠离子电池中应用。而硬碳材料可以使钠离子顺利的嵌入脱出，然而，其充放电效率较低，很难达到90％。因此需要寻找一种合适的方法提高钠离子电池的库伦效率，提高其电化学性能。
鉴于此，特提出本申请。
发明内容
本申请的首要发明目的在于提出一种钠离子电池极片。
本申请的第二发明目的在于提出该钠离子电池极片的制备方法。
本申请的第三发明目的在于提出含有该极片的钠离子电池。
为了完成本申请的目的，采用的技术方案为：
本申请涉及一种钠离子电池极片，所述钠离子电池极片包括钠片、集流体以及附着于所述集流体上的膜片，所述集流体和所述膜片形成初始极片，所述钠片设置于所述初始极片上。
优选的，所述钠片经冷压结合于所述初始极片上。
优选的，所述钠片的厚度为1μm～500μm，优选为5μm～100μm。
优选的，所述钠片的宽度为a，所述初始极片的宽度为b，a≤b；优选的，80％b≤a≤b；更优选的，80％b≤a≤98％b。
优选的，所述钠片设置于所述初始钠片的中部。
优选的，所述集流体选自铝箔、铜箔、不锈钢箔、多孔铝箔、多孔铜箔、多孔不锈钢箔中的一种。
优选的，所述初始极片包括初始阳极极片和初始阴极极片。
优选的，所述钠片的含钠量与所述初始阳极极片的补钠容量相适应。
优选的，所述初始阳极极片的膜片中含有阳极活性物质、粘结剂和导电剂；所述阳极活性物质选自碳材料、合金材料、过镀金属氧化物、过镀金属硫化物、磷基材料或钛酸盐材料中的至少一种；所述初始阴极极片的膜片中含有阴极活性物质、粘结剂和导电剂；所述阴极活性物质选自层状结构材料、隧道型氧化物材料、聚阴离子型材料或布鲁士蓝的至少一种
优选的，所述合金材料选自由Si、Ge、Sn、Pb和Sb中的至少两种组成的合金材料；所述过镀金属氧化物和所述过镀金属硫化物的化学式为M1xNy，其中M1选自Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V的至少一种，N选自O或S；所述磷基材料选自红磷、白磷、黑磷中的至少一种；所述钛酸盐材料选自Na2Ti3O7、Na2Ti6O13、Na4Ti5O12、Li4Ti5O12、NaTi2(PO4)3 的至少一种；所述层状结构材料和所述隧道型氧化物材料的化学式均为NaxM2O2，M2选自Ti、V、Mn、Co、Ni、Fe、Cr、Cu的至少一种；所述聚阴离子材料选自NaFePO4、Na3V2(PO4)3、NaM3PO4F或Na3(VOx)2(PO4)2F3-2x中的至少一种，M3选自V、Fe、Mn、Ni中的至少一种，0≤x≤1；所述布鲁士蓝材料的化学式为NaxM4Fe(CN)6，M4选自Ni、Cu、Fe、Mn、Co、Zn中的至少一种。
本申请还涉及该钠离子电池极片的制备方法，至少包括以下步骤：制备初始极片，在干燥环境中，将所述钠片覆盖于所述初始极片的膜片表面，即得所述钠离子电池极片。
优选的，将所述钠片覆盖于所述初始极片的膜片表面后进行冷压。
优选的，所述冷压的压力为0.01～1.5Mpa；优选地，压力为0.2～1.0Mpa。
优选的，所述初始极片的制备方法为：将活性物质、导电剂、粘结剂和溶剂搅拌均匀得到浆料，将浆料涂覆在集流体上，经过烘干，冷压后得到初始极片，其中涂覆在集流体上的浆料在烘干冷压后成为膜片。
本申请还涉及一种钠离子电池，包括正极极片、负极极片、间隔于所述正极极片和所述负极极片之间的隔离膜以及电解液，其特征在于，所述正极极片和/或负极极片为本申请的钠离子电池极片。
本申请的技术方案至少具有以下有益的效果：
本申请的钠离子电池极片可提高极片中活性物质的首次库伦效率，减少在首次充放电过程中阴极钠离子的损失，本申请的钠离子电池极片还可通过预补钠的方式补入到富钠极片中的钠打通阳极材料中钠离子的路径，使在充放电过程中钠离子更容易在阳极材料中进行脱嵌，提高电池的容量保持率。
本申请的钠离子电池极片的制备方法不仅易于操作、生产周期短、高效，并且还可达到定量控制补钠的效果。
附图说明
图1为实施例1和对比例1钠离子电池的容量保持率对比图。
下面结合具体实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
具体实施方式
针对本申请的第一发明目的，本申请提出一种钠离子电池极片，钠离子电池极片包括集流体、附着于集流体上的膜片和钠片，集流体和膜片形成初始极片，钠片设置于初始极片上。本申请钠离子电池极片中设置钠片是为了对阳极进行预补钠，其目之一的是为了在电池制备过程的化成过程中提高初始阳极极片中活性物质的首次库伦效率，减少在首次充放电过程中对应阴极材料中钠离子因为材料本身的不可逆钠离子容量以及形成SEI膜过程中阴极钠离子的损失，其目的之二是为了打通阳极材料中钠离子的路径，使在充放电过程中钠离子更容易在阳极材料中进行脱嵌，从而提高电池的容量保持率。
本申请中补钠的钠源采用厚度均匀的钠片，从而实现针对阳极均匀的补钠。本申请中钠片表面在生产过程中制备有钝化层，在干燥环境内(空气中的湿度小于5％)不会发生变质反应，钝化层可为氧化膜或者氮化膜。
作为本申请钠离子电池极片的一种改进，钠片经冷压结合于初始极片上。即，本申请是采用钠片通过冷压的方式将钠片与膜片进行结合。经过冷压，将钠片结合于初始极片上，增加钠片与膜片活性物质的接触，便于后续裸电芯电芯等工序的进行。采用电解法、蒸渡法对正阳极材料进行预掺钠处理，虽然也可提高钠离子电池的首次充放电效率，但蒸渡法需要在高温下进行操作，可能对极片中粘结剂等高分子材料造成不良影响，而电解法可能因电解液引入其他的杂质，对电池性能可能存在影响，且其效率低，生产周期长，对生产设备要求高，操作困难，不利于大规模生产。而本申请采用冷压的方式则不仅易于操作、生产周期短、高效，并且还可达到定量控制补钠的效果。
作为本申请钠离子电池极片的一种改进，初始极片包括初始阳极极片或初始阴极极片。
本申请的钠离子电池极片可为阳极极片或阴极极片。为了描述的便利性，在本申请中，将含有钠片的阴极极片称为阴极富钠极片，将含有钠片的阳极极片称为阳极富钠极片。阳极富钠极片可增加钠片与阳极活性物质的接触，使阳极活性物质快速的吸收钠片中的钠，达到预补钠的效果。使用阴极富钠极片，在充放电过程中钠离子可以快速从阴极通过隔膜到达阳极，并且在阳极表面形成稳定的SEI膜，形成较好的阳极的截面。因此，阳极富钠极片或阴极富钠极片均可以实现对钠离子电池的预补钠效果。
作为本申请钠离子电池极片的一种改进，钠片的含钠量与初始阳极极片的补钠容量相适应。本申请可通过钠片中的含钠量对阳极精准的补钠。
其中，本申请中的“含钠量”的含义是指用于补钠的钠片中钠的容量。
本申请中的“初始阳极极片的补钠容量”的含义是指通过预补钠的方式后，富钠阳极极片比初始极片提高首效后增加的极片容量。
本申请中“相适应”的含义包括钠片的含钠量与阳极初始极片的补钠容量完全一致的情况，也包括钠片的含钠量大于或小于初始极片的补钠容量的情况。当钠片的含钠量与为阳极初始极片的补钠容量相等时为全补钠，当钠片的含钠量大于阳极初始极片的补钠容量时为过补钠，当钠片的含钠量小于阳极初始极片的补钠容量时为欠补钠。
作为本申请钠离子电池极片的一种改进，钠片的厚度为1μm～500μm，优选为5μm～100μm。当钠片的面积一定时，即通过对钠片厚度的来控制对初始阳极极片的补钠容量。
作为本申请钠离子电池极片的一种改进，钠片的宽度为a，初始极片的宽度为b，a≤b。钠片宽度小于或等于初始极片的宽度，当钠片宽度大于极片宽度时，可能出现金属钠穿过隔离膜与另一极活性物质接触，从而造成短路发生危险。由于钠片具有一定的延展性，因此优选钠片宽度小于初始极片的宽度。
作为本申请钠离子电池极片的一种改进，钠片宽度与初始极片宽度的关系为：80％b≤a≤b；当钠片宽度小于极片宽度的80％时，在短时间内极片无法完全扩散，影响极片边缘补钠效果，造成补钠不均匀。
作为本申请钠离子电池极片的一种改进，钠片宽度与初始极片宽度的 关系为：80％b≤a≤98％b；考虑到极片经过叠片或卷绕制备成电芯后，在后续工序的顶侧封或成型等工艺中受到压力，钠片材质较软，会有一定变形和延展。如果钠片宽度与初始极片的宽度差距过小，在加工过程中化成工序前可能出现局部微短路，降低制备过程中的电芯成活率，因此进一步优选a≤98％b。
作为本申请钠离子电池极片的一种改进，钠片宽度与初始极片宽度的关系为：90％b≤a≤98％b。
作为本申请钠离子电池极片的一种改进，钠片设置于初始钠片的中部，即沿初始极片宽度方向上的两侧形成空白区。
作为本申请钠离子电池极片的一种改进，集流体选自铝箔、铜箔、不锈钢箔、多孔铝箔、多孔铜箔、多孔不锈钢箔中的一种。
作为本申请钠离子电池极片的一种改进，初始阳极极片的膜片中含有阳极活性物质、粘结剂和导电剂；阳极活性物质选自碳材料、合金材料、过镀金属氧化物、过镀金属硫化物、磷基材料或钛酸盐材料中的至少一种；初始阴极极片的膜片中含有阴极活性物质、粘结剂和导电剂；阴极活性物质选自层状结构材料、隧道型氧化物材料、聚阴离子型材料或布鲁士蓝的至少一种。
作为本申请钠离子电池极片的一种改进，
合金材料选自由Si、Ge、Sn、Pb和Sb中的至少两种组成的合金材料；
过镀金属氧化物和所述过镀金属硫化物的化学式为M1xNy，其中M1选自Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V的至少一种，N选自O或S；
磷基材料选自红磷、白磷、黑磷中的至少一种；
钛酸盐材料选自Na2Ti3O7、Na2Ti6O13、Na4Ti5O12、Li4Ti5O12、NaTi2(PO4)3的至少一种；
层状结构材料和隧道型氧化物材料的化学式均为NaxM2O2，M2选自Ti、V、Mn、Co、Ni、Fe、Cr、Cu的至少一种；
聚阴离子材料选自NaFePO4、Na3V2(PO4)3、NaM3PO4F或Na3(VOx)2(PO4)2F3-2x中的至少一种，M3选自V、Fe、Mn、Ni中的至少一 种，0≤x≤1；布鲁士蓝材料的化学式为NaxM4Fe(CN)6，M4选自Ni、Cu、Fe、Mn、Co、Zn中的至少一种。
针对本申请的第二发明目的，本申请提出上述钠离子电池极片的制备方法，至少包括以下步骤：
制备初始极片，在干燥环境中，将钠片覆盖于初始极片的膜片表面，即得钠离子电池极片。
作为本申请制备方法的一种改进，将钠片覆盖于初始极片的膜片表面，再经过冷压工序；可以增加钠片与膜片活性物质的接触，改善其因为两种固相导致离子传递较慢，从而增快其对钠片的吸收速度。
在本申请中，干燥环境是指环境中空气中的湿度小于5％。
作为本申请制备方法的一种改进，冷压时的压力为0.01～1.5Mpa；优选地，压力为0.2～1.0Mpa。在冷压过程中，若压力过大，则可能导致初始极片变形，影响钠离子电池的制备过程，压力过小，则无法达到增加其贴合效果的目的，所以冷压压力应该控制在1.5Mpa一下以保证极片的外观良好性。优选地，压力控制在0.2～1.0Mpa，保证其冷压效果。
作为本申请制备方法的一种改进，初始极片的制备方法为：将活性物质、导电剂、粘结剂和溶剂搅拌均匀得到浆料，将浆料涂覆在集流体上，经过烘干，冷压后得到初始极片，其中涂覆在集流体上的浆料在烘干冷压后成为膜片。
作为本申请制备方法的一种改进，将初始极片制备为覆盖有钠片的富钠极片的时间为1～10分钟。
针对本申请的第二发明目的，本申请提出一种钠离子电池，包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜以及电解液，其中，正极极片和/或负极极片为本申请的钠离子电池极片。
优选的，正极极片或负极极片为本申请的钠离子电池极片。
其步骤为：将本申请的正极极片、负极初始极片和隔离膜通过卷绕或叠片制成裸电芯，或者将正极初始极片、本申请的负极极片和隔离膜通过 卷绕或叠片制成裸电芯；然后将裸电芯装入电池包装壳中进行顶侧封，之后注入电解液，再经过静置，整形，化成等工艺制得钠离子电池。
为了使本发明的发明目的、技术方案及其有益技术效果更加清晰，以下实施例和对比例，对本发明进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅是为了解释本发明，并非为了限定本发明。本申请中所用原料均为市售原料。
制备例
(一)阳极极片
1、制备初始阳极极片：将阳极活性物质、粘结剂、导电剂按照质量比为88:10:2的比例与溶剂混合均匀制备成浆料；其中，粘结剂为PAA，导电剂为导电炭黑，溶剂为水。将浆料涂覆在铜集流体上，涂布重量为100mg/1540mm2，极片经过烘干、冷压、分条后得到钠离子电池阳极极片，将极片的宽度为b；
2、制备富钠阳极极片：在干燥环境中，将一定厚度、宽度为a的钠片覆盖于在初始极片的表面(即冷压压力为零的情况)，得到富钠阳极极片；或将覆有钠片的初始极片经过冷压，附加一定压力，得到富钠阳极极片。同时记录将初始极片制备为富钠极片的时间。
(二)阴极极片
1、制备初始阴极极片：将阴极活性物质、粘结剂、导电剂按照质量比为88:10:2的比例与溶剂混合均匀制备成浆料，其中，粘结剂为PVDF，导电剂为导电炭黑，溶剂为N-甲基吡咯烷酮(NMP)；将浆料涂覆在铝集流体上，涂布重量为0.33g/1540mm2，极片经过烘干、冷压、分条后得到钠离子电池阳极极片，将极片裁成宽度为b；
2、制备富钠阴极极片：在干燥环境中，将一定厚度10μm、宽度为a的钠片覆盖在初始极片的表面(即冷压压力为零的情况)，得到富钠阳极极片；或将覆有钠片的初始极片经过冷压，附加一定压力，得到富钠阳极极片。同时记录将初始极片制备为富钠极片的时间。
(三)钠离子电池的制备
将钠离子电池的阴极极片、阳极极片和隔离膜通过叠片制成裸电芯；然后将电芯装入铝塑膜包装中后，经过顶侧封工艺，之后注入电解液，再经过静置，整形，化成等工艺制得钠离子电池。
实施例
按上述制备方法分别制备富钠极片1～16、初始极片1～6，具体参数如表1所示：
表1：
Figure PCTCN2016090329-appb-000001
Figure PCTCN2016090329-appb-000002
对比例1的富钠极片采用蒸镀方法，具体工艺条件为：采用蒸镀将金属钠层蒸镀到阳极初始膜片上，镀层厚度为10μm，通过挡板控制宽度为150mm，即镀层与以上实施例1相同。蒸镀等量Na层的时间为30min，前后抽真空时间为150min，从初始极片到富钠极片制备结束时间约为180min。
对比例2的富钠极片采用电镀方法，具体工艺条件为：采用电镀设备将金属钠层电镀到初始膜片上，电解液为六氟磷酸钠，且镀层厚度为10μm，通过挡板控制宽度为150mm，即镀层与以上实施例1相同。电镀等量Na层的时间约为20min，前后达到电解条件时间约10min，从初始极片到富钠极片制备结束时间约为30min。
对比例1和2的具体参数如表2所示：
表2：
Figure PCTCN2016090329-appb-000003
采用表1和表2中的极片按照前述方法制备钠离子电池，具体如表3所示：
表3：钠离子电池中极片的组成
编号 阳极极片 阴极极片
钠离子电池1 富钠极片1 初始极片6
钠离子电池2 富钠极片2 初始极片6
钠离子电池3 富钠极片3 初始极片6
钠离子电池4 富钠极片4 初始极片6
钠离子电池5 富钠极片5 初始极片6
钠离子电池6 富钠极片6 初始极片6
钠离子电池7 富钠极片7 初始极片6
钠离子电池8 富钠极片8 初始极片6
钠离子电池9 富钠极片9 初始极片6
钠离子电池10 富钠极片10 初始极片6
钠离子电池11 富钠极片11 初始极片6
钠离子电池12 富钠极片12 初始极片6
钠离子电池13 富钠极片13 初始极片6
钠离子电池14 初始极片1 富钠极片14
钠离子电池15 初始极片1 富钠极片15
钠离子电池16 初始极片1 富钠极片16
对比钠离子电池1 初始极片1 初始极片6
对比钠离子电池2 初始极片2 初始极片6
对比钠离子电池3 初始极片3 初始极片6
对比钠离子电池4 初始极片4 初始极片6
对比钠离子电池5 初始极片1 初始极片5
对比钠离子电池6 富钠极片D1 初始极片6
对比钠离子电池7 富钠极片D2 初始极片6
实验例
性能测试：
首次库伦效率：将钠离子电池钠离子电池1～16以及对比钠离子电池1～7的钠离子电池在25℃下进行恒流充放电测试，其充放电步骤为：以0.7C倍率恒流充电至电压为4.0V，之后以4.0V恒压充电至电流为0.05C，此时钠离子电池达到满充状态，之后静置5min；以0.5C倍率恒流放电至电压为1.5V，再静置5min；为一个循环充放电过程。按照该方法测定次放电容量和首次充电容量。
首次库伦效率＝首次放电容量/首次充电容量×100％。
经测试、计算得到钠离子电池1～16以及对比钠离子电池1～7的钠 离子电池的首次库伦效率如表4所示。
析钠现象：将钠离子电池1～16和对比钠离子电池1～7的样品在0.7C的倍率下进行充电至4.0V，之后在4.0V恒压充电至电流为0.05C，并在满充状态下将电芯拆开，观察不同钠片或工艺的补钠效果及对极片截面和外观的影响。
循环性能：将钠离子电池1和对比钠离子电池1的钠离子电池在25℃下进行恒流充放电测试，其充放电步骤为：以0.7C倍率恒流充电至电压为4.0V，之后以4.0V恒压充电至电流为0.05C，此时钠离子电池达到满充状态，之后静置5min；以0.5C倍率恒流放电至电压为1.5V，再静置5min；为一个循环充放电过程。进行50个充放电循环，计算每个循环的容量保持率。
钠离子电池1和对比钠离子电池1钠离子电池的容量保持率如图1所示。
表4：
  库伦效率
钠离子电池1 90.6％
钠离子电池2 92.3％
钠离子电池3 93.1％
钠离子电池4 91.0％
钠离子电池5 87.6％
钠离子电池6 89.9％
钠离子电池7 90.3％
钠离子电池8 86.7％
钠离子电池9 88.2％
钠离子电池10 92.1％
钠离子电池11 85.7％
钠离子电池12 86.9％
钠离子电池13 82.3％
钠离子电池14 90.3％
钠离子电池15 88.5％
钠离子电池16 91.0％
对比钠离子电池1 80.2％
对比钠离子电池2 70.1％
对比钠离子电池3 75.3％
对比钠离子电池4 62.7％
对比钠离子电池5 81.2％
对比钠离子电池6 91.0％
对比钠离子电池7 90.8％
(一)比较钠离子电池1～16和对比钠离子电池1～5的首次库伦效率，可以发现：使用富钠极片的钠离子电池的首效均比对应的对比钠离子电池中的初始极片的首次库伦效率都明显提高，说明通过钠片对极片预嵌钠的富钠极片可以有效的提高钠离子电池的首次库伦效率，提高其电化学性能。
(二)比较钠离子电池1～5，其活性物质相同，因为钠片的厚度与宽度不相同而造成首次库伦效率略有不同。观察满充后极片，发现钠离子电池1～3的极片界面均一性良好，且无明显的析钠现象。
钠离子电池4的极片边缘有部分钠剩余，且剩余的少量钠部分地方已超出初始膜片的宽度。这是因为在初始膜片覆钠片后，有冷压的过程，且在后续工艺的顶侧封和整形过程中，均对电芯施加了一定的压力，因为钠片较软，其延展性较好，钠片的初始宽度与极片相等，导致部分钠超过初始极片宽度，这种电芯在后续循环过程中容易出现钠枝晶并刺穿隔膜。或造成局部的微短路，对循环性能造成一定损害。因此，在本申请优选的技术方案中，选用a≤98％b的技术方案，可避免以上问题的发生；
而钠离子电池5中的极片边缘地区明显补钠不足，且钠离子电池5的首效明显低于钠离子电池1，其差别在于钠片与初始极片的宽度比例不同。因此当钠片宽度小于初始极片宽度的80％以上时，可能导致边缘地区的钠无法在短时间扩散，具有极片补钠不均匀的趋势。因此，在本申请优选的 技术方案中，选用80b％≤a的技术方案，可避免以上问题的发生；
综上，本申请更优选90b％≤a≤98％b的范围。
(三)比较钠离子电池7～10，当钠片和活性物质相同时，在覆上钠片之后施加一定的压力比未施加压力(钠离子电池8)对极片的首效具有一定提高效果。这是由于增加压力可以提高钠片与初始膜片的接触，加快活性物质对钠的吸收。观察钠离子电池9的极片，虽然压力达到1.5Mpa时其首效有一定提高，但极片的部分区域发生明显变形的现象，极片的均一性下降。因此，如果压力继续增大会具有影响电芯循环性能的趋势。因此施加的压力应控制在在0.01～1.5Mpa；优选地，压力为0.2～1.0Mpa。
(四)比较钠离子电池11～13，发现当钠片厚度较大时，其首效虽然比初始极片增加，但是首效比钠离子电池10要低。比较其满充状态下的极片，发现钠离子电池12、13的极片表面仍然有部分钠产留，说明当钠片过厚时，电解液渗透较慢，对其吸收效果有一定影响。比较其他钠离子电池，钠片的厚度应该控制在1～500μm，优选的，厚度为10～100μm。
(四)比较钠离子电池14～16，采用阴极富钠极片，其首效也有明显提高，且达到预计补钠量。说明阳极补钠同样可以提高电芯首次充放电库伦效率。对比钠离子电池1，钠离子电池14与其阴阳极材料相同，而钠离子电池14的库伦效率与钠离子电池1的库伦效率相差不大，说明采用在阴极补钠或阳极补钠的效果并无明显区别，均可以达到补钠效果，拆开满充状态下的钠离子电池14的极片，阴极阳极表面均无明显钠析出，且界面均一性良好。说明采用富钠阴极极片的方式补钠同样可以达到效果，并无明显副作用。
(五)比较钠离子电池1与对比钠离子电池6～7，其对相同阳极的补钠量几乎相同，且首效并无明显区别，说明本发明中的钠片补钠可以与蒸镀或电解等化学方法同样控制其补钠量。并且对比制备相同补钠量的富钠极片的时间，本发明中包括将钠片覆与极片表面和冷压的过程需要5分钟左右时间，而同样含量的钠片蒸镀法和电镀法时间要更久。本申请中提供的富钠极片的工艺制备简单，节约时间成本的同时，可有效控制其补钠量。
(六)比较钠离子电池1与对比钠离子电池1的循环性能，本申请富 钠极片的电池的循环性能大大高于对比钠离子电池1。说明本申请通过对极片补钠，可打通阳极材料中钠离子的路径，使在充放电过程中钠离子更容易在阳极材料中进行脱嵌，从而提高电池的容量保持率。
综上所述，本申请的钠离子电池的富钠极片可以有效提高电芯的首次库伦效率和循环性能，改善其电化学性能。本申请的富钠极片可实现均匀的补钠，且可准确、简便的控制补钠量。本申请的富钠极片制备工艺过程简单，环境单纯，无需将极片高温作业或接触其他化学制剂，避免对极片带来潜在性的危害，并且成本低廉，易操作，有利于工业化生产。
根据上述说明书的揭示和教导，本申请所属领域的技术人员还可以对上述实施方式进行适当的变更和修改。因此，本申请并不局限于上面揭示和描述的具体实施方式，对本申请的一些修改和变更也应当落入本申请的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本申请构成任何限制。

Claims (15)

  1. 一种钠离子电池极片，其特征在于，所述钠离子电池极片包括钠片、集流体以及附着于所述集流体上的膜片，所述集流体和所述膜片形成初始极片，所述钠片设置于所述初始极片上。
  2. 根据权利要求1所述的钠离子电池极片，其特征在于，所述钠片经冷压结合于所述初始极片上。
  3. 根据权利要求1或2所述的钠离子电池极片，其特征在于，所述钠片的厚度为1μm～500μm，优选为5μm～100μm。
  4. 根据权利要求1～3任一权利要求所述的钠离子电池极片，其特征在于，所述钠片的宽度为a，所述初始极片的宽度为b，a≤b；优选的，80％b≤a≤b；更优选的，80％b≤a≤98％b。
  5. 根据权利要求1～4任一权利要求所述的钠离子电池极片，其特征在于，所述钠片设置于所述初始钠片的中部。
  6. 根据权利要求1所述的钠离子电池极片，其特征在于，所述集流体选自铝箔、铜箔、不锈钢箔、多孔铝箔、多孔铜箔、多孔不锈钢箔中的一种。
  7. 根据权利要求1所述的钠离子电池极片，其特征在于，所述初始极片包括初始阳极极片和初始阴极极片。
  8. 根据权利要求7所述的钠离子电池极片，其特征在于，所述钠片的含钠量与所述初始阳极极片的补钠容量相适应。
  9. 根据权利要求1所述的钠离子电池极片，其特征在于，所述初始阳极极片的膜片中含有阳极活性物质、粘结剂和导电剂；所述阳极活性物质选自碳材料、合金材料、过镀金属氧化物、过镀金属硫化物、磷基材料或钛酸盐材料中的至少一种；所述初始阴极极片的膜片中含有阴极活性物质、粘结剂和导电剂；所述阴极活性物质选自层状结构材料、隧道型氧化物材料、聚阴离子型材料或布鲁士蓝的至少一种
  10. 根据权利要求9所述的钠离子电池极片，其特征在于，所述合金材料选自由Si、Ge、Sn、Pb和Sb中的至少两种组成的合金材料；所述过 镀金属氧化物和所述过镀金属硫化物的化学式为M1xNy，其中M1选自Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V的至少一种，N选自O或S；所述磷基材料选自红磷、白磷、黑磷中的至少一种；所述钛酸盐材料选自Na2Ti3O7、Na2Ti6O13、Na4Ti5O12、Li4Ti5O12、NaTi2(PO4)3的至少一种；
    所述层状结构材料和所述隧道型氧化物材料的化学式均为NaxM2O2，M2选自Ti、V、Mn、Co、Ni、Fe、Cr、Cu的至少一种；所述聚阴离子材料选自NaFePO4、Na3V2(PO4)3、NaM3PO4F或Na3(VOx)2(PO4)2F3-2x中的至少一种，M3选自V、Fe、Mn、Ni中的至少一种，0≤x≤1；所述布鲁士蓝材料的化学式为NaxM4Fe(CN)6，M4选自Ni、Cu、Fe、Mn、Co、Zn中的至少一种。
  11. 一种如权利要求1～10任一权利要求所述的钠离子电池极片的制备方法，至少包括以下步骤：
    制备初始极片，在干燥环境中，将所述钠片覆盖于所述初始极片的膜片表面，即得所述钠离子电池极片。
  12. 根据权利要求11所述的制备方法，其特征在于，将所述钠片覆盖于所述初始极片的膜片表面后进行冷压。
  13. 根据权利要求12所述的制备方法，其特征在于，所述冷压的压力为0.01～1.5Mpa；优选地，压力为0.2～1.0Mpa。
  14. 根据权利要求11所述的制备方法，其特征在于，所述初始极片的制备方法为：将活性物质、导电剂、粘结剂和溶剂搅拌均匀得到浆料，将浆料涂覆在集流体上，经过烘干，冷压后得到初始极片，其中涂覆在集流体上的浆料在烘干冷压后成为膜片。
  15. 一种钠离子电池，包括正极极片、负极极片、间隔于所述正极极片和所述负极极片之间的隔离膜以及电解液，其特征在于，所述正极极片和/或负极极片为权利要求1～10任一权利要求所述的钠离子电池极片。
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