WO2024114184A1 - 一种高安全长循环钠离子电池 - Google Patents

一种高安全长循环钠离子电池 Download PDF

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WO2024114184A1
WO2024114184A1 PCT/CN2023/126274 CN2023126274W WO2024114184A1 WO 2024114184 A1 WO2024114184 A1 WO 2024114184A1 CN 2023126274 W CN2023126274 W CN 2023126274W WO 2024114184 A1 WO2024114184 A1 WO 2024114184A1
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negative electrode
sodium
ion battery
electrolyte
capacity
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PCT/CN2023/126274
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English (en)
French (fr)
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刘中波
刘杨
敖小虎
张强强
郑仲天
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深圳新宙邦科技股份有限公司
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    • 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 new energy storage technology, and in particular to a high-safety, long-cycle sodium ion battery.
  • lithium-ion batteries have been widely used.
  • Sodium-ion batteries have similar principles and structures to lithium-ion batteries, but compared with lithium batteries, sodium-ion batteries have wide resources, low costs, small fluctuations, a wider temperature range and higher safety performance. These characteristics have become favorable factors for sodium-ion batteries to replace lithium-ion batteries.
  • sodium-ion batteries With the continuous advancement of sodium-ion battery technology, sodium-ion batteries will occupy an important position in my country's energy system, especially in the field of energy storage, and have broad growth space. The development of high-performance, low-cost sodium-ion batteries is the decisive factor in determining whether they can be industrialized.
  • the present application aims to solve at least one of the technical problems in the related art to a certain extent.
  • the present application embodiment provides a high-safety long-cycle sodium ion battery, including a positive electrode, a negative electrode and an electrolyte, wherein:
  • the electrolyte includes a fluoroether solvent, the molecular formula of the fluoroether solvent is: FxCnH2n + 1- xOCmH2m +1 , wherein x/(2n+1) ⁇ 80%, n/m>1.5, 4 ⁇ n ⁇ 10, 1 ⁇ m ⁇ 5, and the mass percentage C% of the fluoroether in the electrolyte is 7% ⁇ C% ⁇ 30%; and
  • the compaction density D of the negative electrode is 0.85-1.00 g/cm 3 .
  • the mass content C% of the fluoroether in the electrolyte and the compaction density D of the negative electrode satisfy: 7 ⁇ C/D ⁇ 35.
  • the mass content C% of the fluoroether in the electrolyte and the compaction density D of the negative electrode satisfy: 10 ⁇ C/D ⁇ 31.
  • the fluoroether solvent is selected from at least one of 2,2,3,3,4,4,5,5-octafluoropentyl methyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl ethyl ether, 2,2,3,3,4,4,5-heptafluoropentyl methyl ether, 2,2,3,4,4,5,5-heptafluoropentyl ethyl ether, 3,3,4,4,5,5-hexafluoropentyl methyl ether, 3,3,4,4,5,5-hexafluoropentyl ethyl ether, 2,2,3,3,4,4-hexafluorobutyl methyl ether, 2,2,3,3,4,4-hexafluoropentyl methyl ether or 2,2,3,3,4,4-hexafluorobutyl ethyl ether.
  • the fluoroether solvent includes one or more of 2,2,3,3,4,4,5,5-octafluoropentyl ethyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl methyl ether, and 2,3,3,4,4,5,5-heptafluoropentyl methyl ether.
  • the electrolyte further includes an auxiliary solvent
  • the auxiliary solvent includes at least one of C3-C5 carbonates, C2-C6 carboxylates, and C4-C10 ethers, wherein:
  • the C3-C5 carbonates include cyclic carbonates or chain carbonates having 3-5 carbon atoms;
  • the C2-C6 carboxylic acid ester includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and propyl propionate;
  • the C4-C10 ethers include cyclic ethers or chain ethers having 4 to 10 carbon atoms.
  • the cyclic carbonate includes at least one of ethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, propylene carbonate, ⁇ -butyrolactone, and butylene carbonate;
  • the chain carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate.
  • the cyclic ether includes at least one of 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran;
  • the chain ether includes at least one of dimethoxymethane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether.
  • the electrolyte includes an electrolyte salt
  • the electrolyte salt includes at least one of sodium perchlorate (NaClO 4 ), sodium tetrafluoroborate (NaBF 4 ), sodium hexafluorophosphate (NaPF 6 ), sodium trifluoroacetate (CF 3 COONa), sodium tetraphenylborate (NaB(C 6 H 5 ) 4 ), sodium trifluoromethylsulfonate (NaSO 3 CF 3 ), sodium bis(fluorosulfonyl)imide (Na[(FSO 2 ) 2 N]) or sodium bis(trifluoromethylsulfonyl)imide (Na[(CF 3 SO 2 ) 2 N]).
  • the electrolyte further comprises an additive, wherein the additive comprises a fluorocarbonate.
  • the fluorocarbonate comprises at least one of fluoroethylene carbonate (FEC) or bisfluoroethylene carbonate (DFEC), and the mass percentage of the fluorocarbonate in the electrolyte is 1-5%.
  • the positive electrode includes a positive electrode active material, and the positive electrode active material is selected from at least one of layered metal oxides, polyanion compounds, Prussian compounds, phosphate compounds, and sulfate compounds, wherein:
  • the chemical formula of the layered metal oxide is Na x M y O z , 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 1 ⁇ z ⁇ 2, M is selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V;
  • the molecular formula of the Prussian compound is Na x M[M′(CN) 6 ] y ⁇ zH 2 O, where M and M′ are transition metals, 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20;
  • the chemical formula of the phosphate compound is Na 3 (MO 1-x PO 4 ) 2 F 1+2x , 0 ⁇ x ⁇ 1, M is at least one selected from Al, V, Ge, Fe, Ga; and
  • the chemical formula of the sulfate compound is Na2M ( SO4 ) 2 ⁇ 2H2O , where M is at least one selected from Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.
  • the Prussian compound is at least one of NaxMn [Fe(CN) 6 ] y ⁇ zH2O (0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20) or NaxFe [Fe(CN) 6 ] y ⁇ zH2O (0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20).
  • the phosphate compound is at least one of Na 3 (VPO 4 ) 2 F 3 or Na 3 (VOPO 4 ) 2 F; or, the chemical formula of the phosphate compound is Na 2 MPO 4 F, where M is selected from at least one of Fe and Mn.
  • the phosphate compound is at least one of Na 2 FePO 4 F or Na 2 MnPO 4 F.
  • the negative electrode includes a negative electrode active material and a conductive agent
  • the negative electrode active material includes at least one of hard carbon or soft carbon
  • the particle size of the negative electrode active material satisfies 4 ⁇ m ⁇ d 50 ⁇ 8 ⁇ m
  • the mass percentage of the conductive agent is 1% to 5%.
  • the inventors found in the study that by controlling the platform area capacity and the slope area capacity ratio of the negative electrode material used in the battery to meet 0.66 ⁇ A/B ⁇ 2.34, it is possible to ensure that the capacity of the negative electrode is fully utilized, stabilize the positive and negative electrode capacity release ratio, and enable the Na + deintercalated from the positive electrode to be fully embedded in the negative electrode, preventing Na + from precipitating at the negative electrode, effectively inhibiting the occurrence of sodium precipitation, and improving the battery's cycle performance and rate performance.
  • the embodiment of the present application uses a fluoroether as a co-solvent in the electrolyte, and the fluoroether solvent can participate in the solvation structure of the ions, affecting the composition of the interface film SEI and CEI, improving the film quality, and improving the interface stability between the electrode material and the electrolyte, thereby improving the battery's cycle performance.
  • the inventors also found in the study that the addition of the fluoroether solvent of the embodiment of the present application will cause the wettability of the electrolyte to decrease. Based on this, the inventors further found that controlling the compaction density of the negative electrode to 0.85-1.00g/ cm3 can greatly improve the wetting effect of the negative electrode.
  • the negative electrode While ensuring that the battery has sufficient energy density, the negative electrode has excellent wettability, shortens the wetting time of battery production, and is conducive to improving the film forming effect during battery activation.
  • the embodiment of the present application effectively improves the performance of the sodium ion battery by controlling the ratio of the platform area capacity to the slope area capacity of the negative electrode, adding a specific fluoroether solvent to the electrolyte, and controlling the compaction density of the negative electrode, especially greatly improving the rate performance and cycle performance, and no sodium precipitation occurs.
  • FIG1 is a voltage-capacity curve of the negative electrode in the sodium ion battery provided in an embodiment of the present application in a buckle test.
  • FIG. 2 is a photograph of a sodium precipitation test of the sodium ion battery prepared in Example 1.
  • FIG3 is a sodium precipitation test photograph of the sodium ion battery prepared in Comparative Example 1.
  • a high-safety, long-cycle sodium-ion battery comprises a positive electrode, a negative electrode and an electrolyte, wherein:
  • the electrolyte includes a fluoroether solvent, the molecular formula of the fluoroether solvent is: FxCnH2n + 1- xOCmH2m +1 , wherein x/(2n+1) ⁇ 80%, n/m>1.5, 4 ⁇ n ⁇ 10, 1 ⁇ m ⁇ 5, and the mass percentage C% of the fluoroether in the electrolyte is 7% ⁇ C% ⁇ 30%; and
  • the compaction density D of the negative electrode is 0.85-1.00 g/cm 3 .
  • the compaction density D of the negative electrode can be 0.85g/ cm3 , 0.86g/ cm3 , 0.87g/cm3, 0.88g/ cm3 , 0.89g/ cm3 , 0.90g/ cm3 , 0.91g/cm3, 0.92g/ cm3 , 0.93g/ cm3 , 0.94g/ cm3 , 0.95g/ cm3 , 0.96g/ cm3 , 0.97g/ cm3 , 0.98g/ cm3 , 0.99g/ cm3 , or 1.00g/ cm3 .
  • the compaction density of the negative electrode is greater than 1.00 g/cm 3 , the negative electrode wettability will be poor, affecting the film formation effect and deteriorating the cycle and rate performance; if the compaction density of the negative electrode is less than 0.85 g/cm 3 , the overall energy density of the battery will be reduced and the battery capacity will be affected.
  • the mass content C% of the fluoroether in the electrolyte and the compaction density D of the negative electrode satisfy: 7 ⁇ C/D ⁇ 35.
  • the C/D of the mass content C% of the fluoroether in the electrolyte and the compaction density D of the negative electrode can be: 7.5, 8, 9, 10, 12, 15, 18, 20, 22, 24, 26, 28, 30, 31, 33, or 35.
  • the mass content C% of the fluoroether in the electrolyte and the compaction density D of the negative electrode satisfy: 10 ⁇ C/D ⁇ 31.
  • the battery by controlling the ratio of the fluoroether solvent content in the electrolyte to the compacted density of the negative electrode, the battery within the range of the requirements of the embodiment of the present application can ensure that the battery has sufficient wettability, solve the problem of poor battery wettability caused by the high viscosity of the fluoroether, ensure the battery capacity while improving the film stability of the electrolyte and the electrode material properties, promoting circulation performance.
  • the A/B values of the slope area capacity A and the platform area capacity B corresponding to the discharge capacity curve of the negative electrode for the power-on test can be 0.66, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, and 2.34.
  • the slope region capacity A and the platform region capacity B corresponding to the discharge capacity curve of the negative electrode subjected to the power-off test satisfy: 0.81 ⁇ A/B ⁇ 1.63.
  • the ratio of the slope area capacity A and the platform area capacity B corresponding to the discharge capacity curve of the negative electrode for the power-on test is further controlled to be 0.81-1.63, while ensuring that there is no sodium precipitation, the cycle performance and rate performance of the sodium ion battery are further improved.
  • the fluoroether solvent is selected from one or more of 2,2,3,3,4,4,5,5-octafluoropentyl methyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl ethyl ether, 2,3,3,4,4,5,5-heptafluoropentyl methyl ether, 2,3,3,4,4,5,5-heptafluoropentyl ethyl ether, 2,2,3,3,4,4,5-heptafluoropentyl methyl ether, 2,2,3,4,4,5,5-heptafluoropentyl ethyl ether, 3,3,4,4,5,5-hexafluoropentyl methyl ether, 3,3,4,4,5,5-hexafluoropentyl ethyl ether, 2,2,3,3,4,4-hexafluorobutyl methyl ether, 2,2,3,3,4,4-hexafluoropentyl methyl ether and 2,2,3,3,4,4,4,5,5-
  • the fluoroether solvent includes one or more of 2,2,3,3,4,4,5,5-octafluoropentyl ethyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl methyl ether, and 2,3,3,4,4,5,5-heptafluoropentyl methyl ether.
  • the mass percentage of the fluoroether solvent in the electrolyte can be 7%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%.
  • Fluoroether solvents are added to the electrolyte, which can partially replace the solvents of conventional electrolytes such as EMC, form co-solvents with other solvents, participate in the solvation structure of ions, affect the formation of SEI and CEI, and improve the interface stability between electrode materials and electrolytes.
  • the embodiment of the present application controls the mass content of the fluoroether solvent in the electrolyte to be 7-30%. If the content of the fluoroether solvent is too low, the conductivity of the electrolyte will be too low; if the content of the fluoroether solvent is too high, it will make it difficult to dissolve the electrolyte salt.
  • the electrolyte further includes an auxiliary solvent
  • the auxiliary solvent includes at least one of C3-C5 carbonates, C2-C6 carboxylates, and C4-C10 ethers.
  • the C3-C5 carbonate includes a cyclic carbonate or a chain carbonate having a carbon number of 3 to 5.
  • the cyclic carbonate includes at least one of ethylene carbonate, vinylene carbonate, vinylethylene carbonate, propylene carbonate, ⁇ -butyrolactone, and butylene carbonate;
  • the chain carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate.
  • the C2-C6 carboxylic acid ester includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and propyl propionate.
  • the C4-C10 ether includes a cyclic ether or a chain ether having a carbon number of 4 to 10.
  • the cyclic ether includes at least one of 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran;
  • the chain ether includes at least one of dimethoxymethane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether.
  • solvents other than fluoroether compounds there is no particular limitation on solvents other than fluoroether compounds, and any solvent commonly used in sodium ion batteries can be applied to the present application.
  • the electrolyte includes an electrolyte salt
  • the electrolyte salt includes at least one of sodium perchlorate (NaClO 4 ), sodium tetrafluoroborate (NaBF 4 ), sodium hexafluorophosphate (NaPF 6 ), sodium trifluoroacetate (CF 3 COONa), sodium tetraphenylborate (NaB(C 6 H 5 ) 4 ), sodium trifluoromethylsulfonate (NaSO 3 CF 3 ), sodium bis(fluorosulfonyl)imide (Na[(FSO 2 ) 2 N]) or sodium bis(trifluoromethylsulfonyl)imide (Na[(CF 3 SO 2 ) 2 N]).
  • electrolyte salt there is no particular limitation on the electrolyte salt, and any electrolyte salt commonly used in sodium ion batteries can be applied to the present application.
  • the electrolyte further includes an additive, and the additive includes a fluorocarbonate.
  • the fluorocarbonate includes at least one of fluoroethylene carbonate (FEC) or bisfluoroethylene carbonate (DFEC); the mass percentage of the fluorocarbonate in the electrolyte is 1-5%.
  • the electrolyte may further include an additive fluorocarbonate, which can further improve the film quality and help improve the battery performance.
  • the positive electrode includes a positive electrode active material, and the positive electrode active material is selected from at least one of layered metal oxides, polyanion compounds, Prussian compounds, phosphate compounds, and sulfate compounds.
  • the chemical formula of the layered metal oxide is NaxMyOz , 0 ⁇ x ⁇ 1 , 0 ⁇ y ⁇ 1, 1 ⁇ z ⁇ 2 , and M is selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.
  • the molecular formula of the Prussian compound is Na x M [M' (CN) 6 ] y ⁇ zH 2 O, M and M' are transition metals, 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20.
  • the Prussian compound is at least one of Na x Mn [Fe (CN) 6 ] y ⁇ zH 2 O (0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20) or Na x Fe [Fe (CN) 6 ] y ⁇ zH 2 O (0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 20).
  • the chemical formula of the phosphate compound is Na 3 (MO 1-x PO 4 ) 2 F 1+2x , 0 ⁇ x ⁇ 1, and M is selected from at least one of Al, V, Ge, Fe, and Ga.
  • the phosphate compound is at least one of Na 3 (VPO 4 ) 2 F 3 or Na 3 (VOPO 4 ) 2 F; or, the chemical formula of the phosphate compound is Na 2 MPO 4 F, and M is selected from at least one of Fe and Mn.
  • the phosphate compound is at least one of Na 2 FePO 4 F or Na 2 MnPO 4 F;
  • the chemical formula of the sulfate compound is Na2M ( SO4 ) 2 ⁇ 2H2O , where M is selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.
  • the positive electrode active material in the positive electrode is preferably selected, which can cooperate with the additives used in the embodiments of the present application to form a film, improve the film formation quality, and help further improve the performance of the battery.
  • the negative electrode includes a negative electrode active material and a conductive agent
  • the negative electrode active material includes at least one of hard carbon or soft carbon
  • the particle size of the negative electrode active material satisfies 4 ⁇ m ⁇ d 50 ⁇ 8 ⁇ m
  • the mass percentage of the conductive agent is 1% to 5%.
  • the particle size of the negative electrode active material may be 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, or 8 ⁇ m.
  • the mass percentage of the conductive agent in the negative electrode can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.
  • the slope region capacity A and the platform region capacity B are obtained by performing a button half-cell test on the negative electrode, which is specifically performed in the following steps (1) to (2).
  • the negative electrode was tested. First, it was discharged to 0 V at a current density of 0.1 C, with a voltage range of 0-1.5 V, to obtain a discharge capacity of 1. After standing for 10 min, it was charged to 1.5 V at a current density of 0.1 C, to obtain a charge capacity of 2.
  • step (1) the discharge and charge curves of the negative electrode can be obtained.
  • the voltage-capacity curve when discharged to 0 V is the platform area and slope area curve in the embodiment of the present application, see Figure 1.
  • the method for regulating the slope zone capacity and the platform zone capacity in the negative electrode charge test is as follows: by controlling the particle size of the negative electrode active material particles in the negative electrode of the sodium ion battery of the embodiment of the present application, the amount of the conductive agent in the negative electrode, and the amount of the negative electrode film-forming additive in the electrolyte, the ratio (A/B) of the slope zone capacity A and the platform zone capacity B can be controlled.
  • the particle size of the negative electrode active material satisfies 4 ⁇ m ⁇ d 50 ⁇ 8 ⁇ m
  • the mass content of the conductive agent in the negative electrode plate is 1% to 5%
  • the mass content of the negative electrode film-forming additive in the electrolyte is 1% to 5%
  • Table 1 The relationship between the particle size d 50 of the negative electrode active material, the amount of the conductive agent in the negative electrode, and the amount of the negative electrode film-forming additive in the electrolyte and A/B can be summarized in Table 1.
  • the fluoroether solvents in the examples of the present application can be prepared by the preparation methods of fluoroethers disclosed in the prior art.
  • the synthesis method of the fluoroethers in the embodiments of the present application can be to use the corresponding alcohol to react with an alcohol reagent or other alkylating reagent in NMP solvent under the catalysis of NaOH to produce the corresponding ether.
  • Example 1 2,2,3,3,4,4,5,5-octafluoro-1-pentanol was reacted with ethanol in NMP solvent under the catalysis of NaOH to obtain 2,2,3,3,4,4,5,5-octafluoropentyl ethyl ether.
  • electrolyte 9 wt % of electrolyte salt NaPF 6 , 14 wt % of fluoroether solvent 2,2,3,3,4,4,5,5-octafluoropentylethyl ether, 76 wt % of auxiliary solvent (a mixed solvent of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) in a mass ratio of 20:10:70), and 1 wt % of negative electrode film-forming additive fluoroethylene carbonate FEC were mixed uniformly to obtain an electrolyte.
  • auxiliary solvent a mixed solvent of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) in a mass ratio of 20:10:70
  • EMC ethyl methyl carbonate
  • the negative electrode active material hard carbon (d 50 is 4.5 ⁇ m), the conductive agent carbon black, the solvent water, and the binder sodium carboxymethyl cellulose are mixed evenly to obtain a negative electrode slurry, and the negative electrode slurry is coated on the current collector. After coating, drying, and rolling, a negative electrode sheet is obtained, wherein the mass content of the conductive agent in the negative electrode is 5%.
  • the compacted density of the negative electrode is 1.0 g/cm 3 .
  • a PP separator is placed between the positive electrode sheet and the negative electrode sheet prepared above, and then the sandwich structure consisting of the positive electrode sheet, the negative electrode sheet and the separator is wound, and then the wound body is flattened and placed in an aluminum foil packaging bag, and vacuum baked at 75°C for 48 hours to obtain a battery cell to be injected with liquid; the electrolyte prepared above is injected into the battery cell through the injection hole, and the amount of electrolyte must be guaranteed to fill the gaps in the battery cell, and the sodium ion battery is encapsulated.
  • Examples 2 to 26 are used to illustrate the sodium ion battery disclosed in the present application, and include most of the operating steps in Example 1, except that:
  • Comparative Examples 1 to 9 are used to compare and illustrate the sodium ion battery disclosed in the present application, including most of the operating steps in Example 1, except that:
  • the sodium ion battery prepared above was subjected to the first efficiency and cyclic charge and discharge tests in the voltage range of 1.5 to 3.95 V, and the charge and discharge capacity of the first formation and capacity distribution of the battery and the capacity retention rate after 200 cycles were recorded.
  • the specific steps are as follows (1) to (4).
  • the capacity C2 released by the sodium ion battery when discharged from 3.95V to 1.5V at a rate of 4C and the capacity C1 released by the battery when discharged from 3.95V to 1.5V at a rate of 0.2C during the initial activation stage are measured.
  • the calculation formula is as follows:
  • the sodium ion battery was placed in a constant temperature environment of 25°C, charged at a constant current of 0.5C to 3.95V, then charged at a constant voltage until the current dropped to 0.03C, and then discharged at a constant current of 1C to 1.5V. This cycle was repeated, and the discharge capacity of the first cycle and the discharge capacity of the last cycle were recorded.
  • the capacity retention rate of 25°C cycle is calculated as follows:
  • Capacity retention rate (%) discharge capacity of the last cycle/discharge capacity of the first cycle ⁇ 100%.
  • the sodium ion battery was placed in a constant temperature environment of 45°C, charged at a constant current of 0.5C to 3.95V, then charged at a constant voltage until the current dropped to 0.03C, and then discharged at a constant current of 1C to 1.5V. This cycle was repeated for 200 times, and the discharge capacity and battery volume of the first cycle, as well as the discharge capacity and battery volume of the 200th cycle were recorded.
  • the capacity retention rate of 45°C cycle is calculated as follows:
  • Capacity retention rate (%) discharge capacity at the last cycle/discharge capacity at the 200th cycle ⁇ 100%.
  • the sodium ion battery was charged at a constant current of 1C and a constant voltage of 3.95V, and then charged at 0.03C and discharged at 1C/1.5V. Afterwards, after 50 cycles, the battery was disassembled to evaluate the effect of the sodium ion battery on inhibiting sodium precipitation at the negative electrode.
  • the discharge capacity curves of the negative electrodes of the batteries prepared in Examples 1-7 of the present application are
  • the capacity A in the slope area and the capacity B in the platform area corresponding to the line both satisfy the relationship: 0.66 ⁇ A/B ⁇ 2.34, which can make the capacity of the negative electrode fully utilized, and the Na + deintercalated from the positive electrode can be fully embedded in the negative electrode, effectively preventing the precipitation of Na + at the negative electrode.
  • No sodium precipitation occurs in Examples 1-7, and they have excellent cycle performance and rate performance.
  • the 4C rate discharge capacity ratio can reach more than 87%, the capacity retention rate after 200 cycles at room temperature can reach more than 92%, and the capacity retention rate after 200 cycles at high temperature is more than 90.5%.
  • the ratio A/B of the capacity A in the slope area of the negative electrode in the buckle test to the capacity B in the platform area is too large, resulting in too low a release of the negative electrode material capacity, leading to sodium precipitation in the whole battery, as shown in Figure 3, and deteriorating the cycle performance of the battery, increasing the safety risk of the battery, and the capacity retention rate of 200 cycles of high-temperature cycles is only 83.2%, while the rate performance is also seriously reduced, and the 4C rate discharge capacity ratio is reduced to 65.0%.
  • the ratio A/B of the capacity A in the slope area of the negative electrode in the buckle test to the capacity B in the platform area is too small, which also causes the negative electrode material capacity to be released too low, resulting in sodium precipitation, and deteriorating the cycle performance and rate performance of the battery, the 4C rate discharge capacity ratio is reduced to 68.0%, and the capacity retention rate of 200 cycles of high-temperature cycles is reduced to 81.90.
  • the content of fluoroether in the electrolyte is controlled at 7-30%, and the compaction density of the negative electrode is controlled at 0.85-1.00 g/cm 3 .
  • the prepared batteries have excellent rate performance and cycle performance.
  • the 4C rate discharge capacity ratio can reach more than 85%, the capacity retention rate after 200 cycles at room temperature can reach more than 92.5%, and the capacity retention rate after 200 cycles at high temperature can reach more than 91%.
  • the compaction density of the negative electrode in the sodium ion battery is relatively low, only 0.75 g/cm 3 .
  • the addition of fluoroether will lead to poor wettability.
  • the use of a negative electrode with a lower compaction density cannot make up for the decrease in wettability caused by fluoroether, and cannot effectively improve the wettability, which is not conducive to improving the performance of the sodium ion battery.
  • the capacity retention rate after 200 cycles of high-temperature cycling drops to 81.6%.
  • Comparative Example 4 the compaction density of the negative electrode in the sodium ion battery is relatively high, reaching 1.2 g/cm 3 , which will cause poor wettability of the negative electrode, affecting the film forming effect, thereby deteriorating the performance of the battery.
  • the capacity retention rate of the battery prepared in Comparative Example 4 drops to 76.5% after 200 cycles at room temperature, and drops to 74.3% after 200 cycles at high temperature.
  • the fluoroether solvent added to the electrolyte is 2,2,3,3,3-pentafluoropropyl methyl ether, and the n value is only 3, which does not meet the requirements of the embodiments of the present application for fluoroether solvents.
  • the ionic conductivity, rate performance and cycle performance of the prepared battery are greatly reduced.
  • the electrolyte conductivity at 25°C is only 5.29 mS/cm, the 4C rate discharge capacity ratio is reduced to 78.9%, the capacity retention rate after 200 cycles at room temperature is reduced to 77.9%, and the capacity retention rate after 200 cycles at high temperature is reduced to 76.8%.
  • the fluoroether solvent added to the electrolyte is 1,1,2,2,3,3,4,4,5-nonafluorobutyl methyl ether.
  • the ionic conductivity, rate performance and cycle performance of the battery prepared in Comparative Example 9 all show a significant decrease.
  • the electrolyte conductivity at 25°C is only 5.46 mS/cm, the 4C rate discharge capacity ratio is reduced to 79.8%, the capacity retention rate after 200 cycles at room temperature is reduced to 76.9%, and the capacity retention rate after 200 cycles at high temperature is reduced to 75.3%.
  • the sodium ion batteries prepared in Examples 1-26 can be The ratio A/B of the capacity in the slope area and the capacity in the platform area corresponding to the discharge capacity curve of the negative electrode in the buckle test is in the range of 0.66-2.34, which provides sufficient negative electrode capacity release, effectively suppresses the sodium precipitation phenomenon, and at the same time improves the cycle performance and rate performance of the battery, thereby improving the safety performance of the battery.
  • the embodiment of the present application uses a specific fluoroether solvent as a co-solvent in the electrolyte, which can improve the conductivity, electrochemical and thermal stability of the electrolyte.
  • the fluoroether solvent can participate in the formation of CEI and SEI films, reduce the occurrence of side reactions, improve the film quality, and thus improve the interface stability.
  • the compaction density of the negative electrode active material is controlled, which makes up for the decrease in wettability caused by the addition of the fluoroether solvent, improves the battery wettability, shortens the infiltration time of the battery production, and at the same time, by controlling the compaction density of the negative electrode, the film quality can be improved during the battery activation process, which is conducive to suppressing the occurrence of the sodium precipitation phenomenon and improving the performance of the battery.
  • the sodium ion battery of the embodiment of the present application can have a capacity retention rate of up to 96.5% after 200 cycles of high-temperature cycling, a 4C rate discharge capacity ratio of up to 91%, and no sodium precipitation occurs, thus having excellent performance.
  • the terms “one embodiment”, “some embodiments”, “example”, “specific example”, or “some examples” etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application.
  • the schematic representations of the above terms do not necessarily refer to the same embodiment or example.
  • the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
  • those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

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Abstract

公开了一种高安全长循环钠离子电池，包括正极、负极和电解液，其中，所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34；所述电解液包括氟醚溶剂，所述氟醚溶剂的分子式为:FxCnH2n+1-xOCmH2m+1，其中，x/(2n+1)＜80％，n/m>1.5，4≤n≤10，1≤m≤5，所述电解液中氟醚的质量百分含量C％为7％≤C％≤30％；和所述负极的压实密度D为0.85-1.00g/cm3。

Description

一种高安全长循环钠离子电池
相关申请的交叉引用
本申请要求在2022年11月29日在中国提交的中国专利申请号2022115106925的优先权，其全部内容通过引用并入本文。
技术领域
本申请涉及新能源储能技术领域，具体涉及一种高安全长循环钠离子电池。
背景技术
在新能源储能技术中，锂离子电池已被广泛应用。钠离子电池与锂离子电池具有类似的原理和结构，但与锂电池相比，钠离子电池资源广、成本低且波动小，具有较宽的温区和较高的安全性能，这些特点成为钠离子电池替代锂离子电池的有利因素，随着钠离子电池技术的不断进步，钠离子电池将在我国能源体系占据重要席位，尤其在储能领域具备广阔的成长空间。发展高性能、低成本的钠离子电池是决定其是否能够产业化的决定性因素。
目前的钠离子电池，易发生析钠现象，同时存在着循环性能不足以及倍率放电能力差的问题，因此，有必要对钠离子电池进行研究改进。
发明内容
本申请是基于发明人对以下事实和问题的发现和认识做出的：目前钠离子电池普遍存在循环性能差和倍率性能不足的问题，因此，有必要对钠离子电池进行深入研究，抑制析钠发生，以改善钠离子电池的循环性能和倍率性能。
本申请旨在至少在一定程度上解决相关技术中的技术问题之一。为此，本申请实施例提供了一种高安全长循环钠离子电池，包括正极、负极和电解液，其中，
所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34，其中，斜坡区容量A为扣电测试0.1-3.0V电压区间的容量释放占比，平台区容量B为扣电测试0.1-0V电压区间的容量释放占比，A+B＝1；
所述电解液包括氟醚溶剂，所述氟醚溶剂的分子式为:FxCnH2n+1-xOCmH2m+1，其中，x/(2n+1)＜80％，n/m>1.5，4≤n≤10，1≤m≤5，所述电解液中氟醚的质量百分含量C％为7％≤C％≤30％；和
所述负极的压实密度D为0.85-1.00g/cm3。
在一些实施例中，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：7＜ C/D＜35。
在一些实施例中，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：10≤C/D≤31。
在一些实施例中，0.81≤A/B≤1.63。
在一些实施例中，所述氟醚溶剂选自2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,2,3,3,4,4,5-七氟戊基甲基醚、2,2,3,4,4,5,5-七氟戊基乙基醚、3,3,4,4,5,5-六氟戊基甲基醚、3,3,4,4,5,5-六氟戊基乙基醚、2,2,3,3,4,4-六氟丁基甲基醚、2,2,3,3,4,4-六氟戊基甲基醚或2,2,3,3,4,4-六氟丁基乙基醚中的至少一种。
在一些实施例中，所述氟醚溶剂包括2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,3,3,4,4,5,5-七氟戊基甲基醚一种或多种。
在一些实施例中，所述电解液中还包括辅助溶剂，所述辅助溶剂包括C3～C5的碳酸酯、C2～C6的羧酸酯、C4～C10的醚中的至少一种，其中，
所述C3～C5的碳酸酯包括碳原子数为3～5的环状碳酸酯或链状碳酸酯；
所述C2～C6的羧酸酯包括乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯、丙酸丙酯中的至少一种；和
所述C4～C10的醚包括碳原子数为4～10的环状醚或链状醚。
在一些实施例中，所述环状碳酸酯包括碳酸乙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、碳酸丙烯酯、γ-丁内酯、碳酸亚丁酯中的至少一种；所述链状碳酸酯包括碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯中的至少一种。
在一些实施例中，所述环状醚包括1,3-二氧戊烷、1,4-二氧惡烷、四氢呋喃、2-甲基四氢呋喃，2-三氟甲基四氢呋喃中的至少一种；所述链状醚包括二甲氧基甲烷、1,2-二甲氧基乙烷、二甘醇二甲醚中的至少一种。
在一些实施例中，所述电解液中包括电解质盐，所述电解质盐包括高氯酸钠(NaClO4)、四氟硼酸钠(NaBF4)、六氟磷酸钠(NaPF6)、三氟乙酸钠(CF3COONa)、四苯硼酸钠(NaB(C6H5)4)、三氟甲基磺酸钠(NaSO3CF3)、双(氟磺酰)亚胺钠(Na[(FSO2)2N])或双(三氟甲基磺酰)亚胺钠(Na[(CF3SO2)2N])中的至少一种。
在一些实施例中，所述电解液还包括添加剂，所述添加剂包括氟代碳酸酯。在一些实施例中，所述氟代碳酸酯包括氟代碳酸乙烯酯(FEC)或双氟代碳酸乙烯酯(DFEC)中的至少一种，所述电解液中所述氟代碳酸酯的质量百分含量为1-5％。
在一些实施例中，所述正极包括正极活性物质，所述正极活性物质选自层状金属氧化物、聚阴离子化合物、普鲁士类化合物、磷酸盐化合物、硫酸盐化合物中的至少一种，其中，
所述层状金属氧化物的化学式为NaxMyOz，0＜x≤1，0＜y≤1，1＜z≤2，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种；
所述普鲁士类化合物的分子式为NaxM[M′(CN)6]y·zH2O，M和M′为过渡金属，0<x≤2，0<y≤1，0<z≤20；
所述磷酸盐化合物的化学式为Na3(MO1-xPO4)2F1+2x，0≤x≤1，M选自Al、V、Ge、Fe、Ga中的至少一种；和
所述硫酸盐化合物的化学式为Na2M(SO4)2·2H2O，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种。
在一些实施例中，所述层状金属氧化物为NaNimFenMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)或NaNimConMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)中的至少一种。
在一些实施例中，所述普鲁士类化合物为NaxMn[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)或NaxFe[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)中的至少一种。
在一些实施例中，所述磷酸盐化合物为Na3(VPO4)2F3或Na3(VOPO4)2F中的至少一种；或者，所述磷酸盐化合物的化学式为Na2MPO4F，M选自Fe、Mn中的至少一种，优选地，所述磷酸盐化合物为Na2FePO4F或Na2MnPO4F中的至少一种。
在一些实施例中，所述负极包括负极活性物质和导电剂，所述负极活性物质包括硬碳或软碳中的至少一种；所述负极活性物质的粒径满足4μm≤d50≤8μm；所述负极中，所述导电剂的质量百分含量为1％～5％。
根据本申请实施例提供的高安全长循环钠离子电池，发明人在研究中发现，通过控制电池所使用的负极材料的平台区容量与斜坡区容量比值满足0.66≤A/B≤2.34，能够保证负极的容量得到充分发挥，稳定正负极容量释放比，使得从正极脱嵌出的Na+能够全部嵌入负极，防止Na+在负极析出，有效抑制了析钠现象的发生，并且提升了电池的循环性能和倍率性能。同时，本申请实施例在电解液中采用了氟醚作为共溶剂，该氟醚溶剂能够参与到离子的溶剂化结构中，影响界面膜SEI和CEI的构成，改善了成膜质量，提升了电极材料与电解液的界面稳定性，从而提升了电池的循环性能。但是，发明人在研究中同时发现，在加入本申请实施例的氟醚溶剂后会导致电解液的浸润性出现下降，基于此，发明人进一步研究发现，将负极的压实密度控制为0.85-1.00g/cm3，可以很好的改善负极的浸润效果，在保证电池具有足够的能量密度的情况下，使负极具有极佳的浸润性，缩短了电池制作的浸润时间，并且在电池激活过程中有利于提高成膜效果。本申请实施例通过控制负极的平台区容量与斜坡区容量比值、在电解液中加入特定的氟醚溶剂以及控制负极的压实密度，有效提升了钠离子电池的性能，尤其是大幅改善了倍率性能和循环性能，并且无析钠现象发生。
附图说明
图1是本申请实施例提供的钠离子电池中的负极在扣电测试中的电压-容量曲线。
图2是实施例1制得的钠离子电池的析钠测试照片。
图3是对比例1制得的钠离子电池的析钠测试照片。
具体实施方式
下面详细描述本申请的实施例，所述实施例的示例在附图中示出。下面通过参考附图描述的实施例是示例性的，旨在用于解释本申请，而不能理解为对本申请的限制。
本申请实施例的一种高安全长循环钠离子电池，包括正极、负极和电解液，其中，
所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34，其中，斜坡区容量A为扣电测试0.1-3.0V电压区间的容量释放占比，平台区容量B为扣电测试0.1-0V电压区间的容量释放占比，A+B＝1，斜坡区容量A满足0.4≤A≤0.7，平台区容量B满足0.3≤B≤0.6；
所述电解液包括氟醚溶剂，所述氟醚溶剂的分子式为:FxCnH2n+1-xOCmH2m+1，其中，x/(2n+1)＜80％，n/m>1.5，4≤n≤10，1≤m≤5，所述电解液中氟醚的质量百分含量C％为7％≤C％≤30％；和
所述负极的压实密度D为0.85-1.00g/cm3。
在具体的实施例中，所述负极的压实密度D可以为0.85g/cm3、0.86g/cm3、0.87g/cm3、0.88g/cm3、0.89g/cm3、0.90g/cm3、0.91g/cm3、0.92g/cm3、0.93g/cm3、0.94g/cm3、0.95g/cm3、0.96g/cm3、0.97g/cm3、0.98g/cm3、0.99g/cm3、1.00g/cm3。负极的压实密度大于1.00g/cm3，会造成负极浸润性差，影响成膜效果，劣化循环和倍率性能；负极压实密度小于0.85g/cm3，会降低电池整体的能量密度，影响电池容量的发挥。
在具体的实施例中，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：7＜C/D＜35。
在具体的实施例中，所述电解液中氟醚质量含量C％和所述负极的压实密度D的C/D可以为：7.5、8、9、10、12、15、18、20、22、24、26、28、30、31、33、35。
在一些施例中，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：10≤C/D≤31。
本申请实施例中，通过控制电解液中氟醚溶剂含量和负极压实密度的比值，在满足本申请实施例要求范围内的电池，能够保证电池具有足够的浸润性，解决因氟醚粘度较大带来的电池浸润性差的问题，保证电池容量发挥的同时，改善电解液与电极材料的成膜稳定 性，促进循环性能。
在具体的实施例中，所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B的A/B值可以为0.66、0.7、0.8、0.9、1.0、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2.0、2.1、2.2、2.3、2.34。
发明人通过大量研究发现，当A/B小于0.66时，负极材料容量释放过低，导致全电池析钠，劣化电池的循环性能，增加电池的安全风险；当A/B大于2.34时，也会造成负极材料容量释放过低，导致全电池析钠，劣化循环性能，增加电池安全风险。
在一些实施例中，所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足：0.81≤A/B≤1.63。
本申请实施例中，进一步控制负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B的比值为0.81-1.63，在保证无钠析出的同时，进一步提高了钠离子电池的循环性能和倍率性能。
在具体的实施例中，所述氟醚溶剂选自2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,3,3,4,4,5,5-七氟戊基甲基醚、2,3,3,4,4,5,5-七氟戊基乙基醚、2,2,3,3,4,4,5-七氟戊基甲基醚、2,2,3,4,4,5,5-七氟戊基乙基醚、3,3,4,4,5,5-六氟戊基甲基醚、3,3,4,4,5,5-六氟戊基乙基醚、2,2,3,3,4,4-六氟丁基甲基醚、2,2,3,3,4,4-六氟戊基甲基醚和2,2,3,3,4,4-六氟丁基乙基醚中的一种或多种。
在一些实施例中，所述氟醚溶剂包括2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,3,3,4,4,5,5-七氟戊基甲基醚一种或多种。
进一步的，上述氟醚化合物的具体结构可以如下表所示：

在具体的实施例中，所述氟醚溶剂在所述电解液中的质量百分含量可以为7％、10％、12％、14％、16％、18％、20％、22％、24％、26％、28％、30％。
在电解液中加入氟醚溶剂，其能够部分取代EMC等常规电解液的溶剂，与其他溶剂形成共溶剂，参与到离子的溶剂化结构中，影响SEI和CEI的构成，提升电极材料与电解液的界面稳定性。本申请实施例控制电解液中氟醚溶剂的质量含量为7-30％，如果氟醚溶剂的含量过低，会使电解液的电导率过低；如果氟醚溶剂的含量过高，会导致电解质盐溶解困难。
在具体的实施例中，所述电解液中还包括辅助溶剂，所述辅助溶剂包括C3～C5的碳酸酯、C2～C6的羧酸酯、C4～C10的醚中的至少一种。
在一些实施例中，所述C3～C5的碳酸酯包括碳原子数为3～5的环状碳酸酯或链状碳酸酯。在一些实施例中，所述环状碳酸酯包括碳酸乙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、碳酸丙烯酯、γ-丁内酯、碳酸亚丁酯中的至少一种；所述链状碳酸酯包括碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯中的至少一种。
在一些实施例中，所述C2～C6的羧酸酯包括乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯、丙酸丙酯中的至少一种。
在一些实施例中，所述C4～C10的醚包括碳原子数为4～10的环状醚或链状醚。在一些实施例中，所述环状醚包括1,3-二氧戊烷、1,4-二氧惡烷、四氢呋喃、2-甲基四氢呋喃，2-三氟甲基四氢呋喃中的至少一种；所述链状醚包括二甲氧基甲烷、1,2-二甲氧基乙烷、二甘醇二甲醚中的至少一种。
本申请实施例中，对除了氟醚化合物以外的溶剂没有特别限制，钠离子电池中常用的溶剂均可以适用于本申请。
在具体的实施例中，所述电解液中包括电解质盐，所述电解质盐包括高氯酸钠(NaClO4)、四氟硼酸钠(NaBF4)、六氟磷酸钠(NaPF6)、三氟乙酸钠(CF3COONa)、四苯硼酸钠(NaB(C6H5)4)、三氟甲基磺酸钠(NaSO3CF3)、双(氟磺酰)亚胺钠(Na[(FSO2)2N])或双(三氟甲基磺酰)亚胺钠(Na[(CF3SO2)2N])中的至少一种。
本申请实施例中，对电解质盐没有特别限制，钠离子电池中常用的电解质盐均可以适用于本申请。
在具体的实施例中，所述电解液还包括添加剂，所述添加剂包括氟代碳酸酯。在一些实施例中，所述氟代碳酸酯包括氟代碳酸乙烯酯(FEC)或双氟代碳酸乙烯酯(DFEC)中的至少一种；所述电解液中所述氟代碳酸酯的质量百分含量为1-5％。本申请实施例中，电解液进步一还可以包括添加剂氟代碳酸酯，能够进一步提高成膜质量，有利于提升电池性能。
在具体的实施例中，所述正极包括正极活性物质，所述正极活性物质选自层状金属氧化物、聚阴离子化合物、普鲁士类化合物、磷酸盐化合物、硫酸盐化合物中的至少一种。
在一些实施例中，所述层状金属氧化物的化学式为NaxMyOz，0＜x≤1，0＜y≤1，1＜z≤2，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种。在一些实施例中，所述层状金属氧化物为NaNimFenMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)或NaNimConMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)中的至少一种。
在一些实施例中，所述普鲁士类化合物的分子式为NaxM[M′(CN)6]y·zH2O，M和M′为过渡金属，0<x≤2，0<y≤1，0<z≤20。在一些实施例中，所述普鲁士类化合物为NaxMn[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)或NaxFe[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)中的至少一种。
在一些实施例中，所述磷酸盐化合物的化学式为Na3(MO1-xPO4)2F1+2x，0≤x≤1，M选自Al、V、Ge、Fe、Ga中的至少一种。在一些实施例中，所述磷酸盐化合物为Na3(VPO4)2F3或Na3(VOPO4)2F中的至少一种；或者，所述磷酸盐化合物的化学式为Na2MPO4F，M选自Fe、Mn中的至少一种。在一些实施例中，所述磷酸盐化合物为Na2FePO4F或Na2MnPO4F中的至少一种；
在一些实施例中，所述硫酸盐化合物的化学式为Na2M(SO4)2·2H2O，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种。
本申请实施例中，优选了正极中的正极活性物质，能够与本申请实施例采用的添加剂协同成膜，提高成膜质量，有利于进一步提高电池的性能。
在具体实施例中，所述负极包括负极活性物质和导电剂，所述负极活性物质包括硬碳或软碳中的至少一种；所述负极活性物质的粒径满足4μm≤d50≤8μm；所述负极中，所述导电剂的质量百分含量为1％～5％。
在具体的实施例中，所述负极活性物质的粒径可以为4μm、4.5μm、5μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm。
在具体的实施例中，所述负极中导电剂的质量百分含量可以为1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％。
本申请实施例中，所述的斜坡区容量A和平台区容量B，是通过对负极进行扣式半电池测试获得。具体如下步骤(1)至(2)。
(1)使用蓝电(LAND)测试系统，测试负极，首先以0.1C的电流密度放电至0V，设置的电压范围为0-1.5V，得到放电容量1，静置10min，以0.1C的电流密度充电至1.5V，得到充电容量2。
(2)根据步骤(1)的程序可得到负极的放电和充电曲线，在放电时，以放电到0V时的电压-容量曲线为本申请实施例中的平台区和斜坡区曲线，参见图1。
本申请实施例中，采用上述方法对负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34，其中，斜坡区容量A为扣电测试0.1-3.0V电压区间的容量释放占比，平台区容量B为扣电测试0.1-0V电压区间的容量释放占比，A+B＝1。
本申请实施例中，负极扣电测试中斜坡区容量和平台区容量的调控方式为：通过控制本申请实施例的钠离子电池的负极中负极活性物质颗粒粒径、负极中导电剂的用量以及电解液中负极成膜添加剂的用量可以实现对斜坡区容量A和平台区容量B的比值(A/B)的控制。
其中，当负极活性材料的粒径满足4μm≤d50≤8μm，负极极片中导电剂的质量含量为1％～5％，且电解液中负极成膜添加剂的质量含量为1％～5％时，能够实现调控斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34。
发明人在试验的过程中发现，负极活性物质颗粒粒径、负极导电剂的用量以及电解液中负极成膜添加剂的用量与斜坡区容量A和平台区容量B的比值(A/B)的关系表现为：随着负极活性物质粒径和负极成膜添加剂用量的增大，负极表面缺陷和孔隙增加，A/B的比值增加；随着负极导电剂用量增大，钠离子更加容易嵌入负极，A/B的比值下降。负极活性物质颗粒粒径d50、负极中导电剂用量以及电解液中负极成膜添加剂的用量与A/B的关系总结可以参见表1。
表1
例如，通过控制负极活性材料颗粒粒径d50、负极导电剂的用量以及电解液中负极成膜添加剂的用量从而调控A/B的比值的示例可以参见表2。
表2
下面结合实施例和附图详细描述本申请。
本申请实施例中的氟醚溶剂可以采用现有技术公开的氟醚的制备方法制得。
实施例1
(1)氟醚的制备：本申请实施例的氟醚的合成方法可以是通过采用对应的醇，在NMP溶剂中，以NaOH催化下与醇类试剂或者其他烷基化试剂反应生产相应的醚。
以实施例1为例，使用2,2,3,3,4,4,5,5-八氟-1-戊醇，在NMP溶剂中，以NaOH催化下与乙醇反应，得到2,2,3,3,4,4,5,5-八氟戊基乙基醚。
(2)电解液的制备：将9wt％的电解质盐NaPF6、14wt％的氟醚溶剂2,2,3,3,4,4,5,5-八氟戊基乙基醚、76wt％的辅助溶剂(碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)按质量比为20：10：70的混合溶剂)、1wt％的负极成膜添加剂氟代碳酸乙烯酯FEC，混合均匀，得到电解液。
(3)正极的制备：将粘结剂聚偏氟乙烯、溶剂N-甲基吡咯烷酮、导电剂乙炔黑、正极活性物质NaNi1/3Fe1/3Mn1/3O2混合均匀，得到正极浆料，将正极浆料涂覆在集流体上，经过涂布、干燥、辊压工序制得正极片。
(4)负极的制备：将负极活性物质硬碳(d50为4.5μm)、导电剂炭黑、溶剂水、粘结剂羧甲基纤维素钠混合均匀，得到负极浆料，将负极浆料涂覆在集流体上，经过涂布、干燥、辊压工序制得负极片，其中负极中导电剂的质量含量为5％。负极的压实密度为1.0g/cm3。
(5)电池组装
在上述制备的正极片和负极片之间放置PP隔膜，然后将正极片、负极片和隔膜组成的三明治结构进行卷绕，再将卷绕体压扁后放入铝箔包装袋，在75℃下真空烘烤48h，得到待注液的电芯；将上述制备的电解液通过注液孔注入电芯中，电解液的量要保证充满电芯中的空隙，封装制得钠离子电池。
本实施例中的负极经过扣电测试后斜坡区容量与平台区容量的比值A/B＝0.66。
实施例2～26
实施例2～26用于说明本申请公开的钠离子电池，包括实施例1中大部分操作步骤，其不同之处在于：
实施例2～26所采用的氟醚溶剂及其含量、负极经过扣电测试后斜坡区容量与平台区容量的比值A/B、氟醚质量含量C％和所述负极的压实密度D的比值C/D如表3所示。
对比例1～9
对比例1～9用于对比说明本申请公开的钠离子电池，包括实施例1中大部分操作步骤，其不同之处在于：
对比例1～9所采用的氟醚溶剂及其含量、负极经过扣电测试后斜坡区容量与平台区容量的比值A/B、氟醚质量含量C％和所述负极的压实密度D的比值C/D如表4所示。
表3


表4
性能测试
对上述制备得到的钠离子电池，在电压范围1.5～3.95V进行首效和循环充放电测试，记录电池首圈化成和分容的充放电容量和循环200次的容量保持率。具体如下步骤(1)至(4)。
(1)4C倍率放电容量比
测量钠离子电池以4C倍率从3.95V放电至1.5V所释放出的容量C2以及电池在首次激活阶段以0.2C倍率从3.95V放电至1.5V所释放出的容量C1，计算公式如下：
4C倍率放电容量比＝C2/C1。
(2)常温循环性能测试
将钠离子电池置于25℃的恒温环境下，以0.5C的电流恒流充电至3.95V，再恒压充电至电流下降至0.03C，然后以1C的电流恒流放电至1.5V，如此循环，记录第1圈的放电容量和最后1圈的放电容量。
按下式计算25℃循环的容量保持率：
容量保持率(％)＝最后1圈的放电容量/第1圈的放电容量×100％。
(3)高温循环容量保持率
将钠离子电池置于45℃的恒温环境下，以0.5C的电流恒流充电至3.95V，再恒压充电至电流下降至0.03C，然后以1C的电流恒流放电至1.5V，如此循环200圈，记录第1圈的放电容量和电池体积、以及第200圈的放电容量和电池体积。
按下式计算45℃循环的容量保持率：
容量保持率(％)＝最后1圈的放电容量/第200圈的放电容量×100％。
(4)电池析钠现象测试
将钠离子电池在1C的恒定电流和3.95V的恒定电压下充电，然后经0.03C截止充电和1C/1.5V截止放电。之后，在50次循环后，将电池进行拆解，评价钠离子电池对于抑制负极析钠的效果。
实施例1～26和对比例1～9制得的电池的性能数据见表5-8，实施例1的析钠测试结果见图2，对比例1的析钠测试结果见图3。
表5
通过表5可以看出，本申请实施例1-7制得的电池，负极进行扣电测试的放电容量曲 线所对应的斜坡区容量A和平台区容量B均满足关系式：0.66≤A/B≤2.34，能够使负极的容量得到充分发挥，正极脱嵌出来的Na+能够全部嵌入负极，有效防止了Na+在负极析出，实施例1-7均无析钠现象发生，并且具有优异的循环性能和倍率性能，4C倍率放电容量比均可以都达到87％以上，常温循环200圈容量保持率可以达到92％以上，高温循环200圈容量保持率90.5％以上。
对比例1中，负极在扣电测试中的斜坡区容量A与平台区容量B的比值A/B过大，造成负极材料容量释放过低，导致全电池析钠，如图3所示，并且劣化了电池的循环性能，增加了电池的安全风险，高温循环200圈容量保持率仅为83.2％，同时倍率性能也严重下降，4C倍率放电容量比降至65.0％。对比例2中，负极在扣电测试中的斜坡区容量A与平台区容量B的比值A/B过小，同样地造成了负极材料容量释放过低，导致发生析钠现象，并且劣化了电池的循环性能和倍率性能，4C倍率放电容量比降至68.0％，高温循环200圈容量保持率降至81.90。
表6
通过表6可以看出，实施例8-17中，电解液中氟醚的含量控制在7-30％，同时负极的压实密度控制在0.85-1.00g/cm3，制得的电池均具有优异的倍率性能和循环性能，4C倍率放电容量比均可以都达到85％以上，常温循环200圈容量保持率可以达到92.5％以上，高温循环200圈容量保持率91％以上。
对比例3中，钠离子电池中负极的压实密度较低，仅为0.75g/cm3，氟醚的加入会导致浸润性能变差，而采用较低压实密度的负极不能弥补氟醚引起的浸润性的下降，无法有效改善浸润性，不利于改善钠离子电池的性能，高温循环200圈容量保持率降至81.6％。
对比例4中，钠离子电池中负极的压实密度较高，达到了1.2g/cm3，会造成负极的浸润性较差，影响成膜效果，从而劣化了电池的性能，对比例4制得的电池常温循环200圈容量保持率降至76.5％，高温循环200圈容量保持率降至74.3％。
对比例5中，电解液中不加入氟醚溶剂，在正负极侧形成的CEI和SEI膜的稳定性较差，在循环过程中电解液持续发生副反应，致使电解液和活性物质持续被消耗，造成电池性能劣化，电导率降至5.25mS/cm，4C倍率放电容量比降至79.8％，常温循环200圈容量保持率降至80.4％，高温循环200圈容量保持率降至79.2％。
对比例6中，电解液中加入的氟醚溶剂过少，氟醚无法有效参与成膜，不能对界面膜实现有效调控，电池性能改善不明显，电导率仅为5.89mS/cm，常温循环200圈容量保持率仅达到84.9％，高温循环200圈容量保持率仅达到82.6％。
对比例7中，电解液中加入了过多的氟醚溶剂，造成氟醚过度参与CEI和SEI膜的形成，使界面膜过厚并且不均匀，劣化了电池的循环性能，常温循环200圈容量保持率仅可以达到84.3％，高温循环200圈容量保持率仅可以达到83.1％。
表7
通过表7可以看出，实施例1、18-21中采用的氟醚溶剂结构式均满足FxCnH2n+1-xOCmH2m+1，其中，x/(2n+1)＜80％，n/m>1.5，4≤n≤10，1≤m≤5的要求，制得的电池均具有较好的倍率性能和循环性能，实现了电池倍率性能和循环性能的兼顾，4C倍率放电容量比均可以都达到84％以上，常温循环200圈容量保持率可以达到92％以上，高温循环200圈容量保持率91％以上。
对比例8中，电解液中加入的氟醚溶剂为2,2,3,3,3-五氟丙基甲醚，n值仅为3，不满足本申请实施例对氟醚溶剂的要求，制得的电池的离子电导率、倍率性能和循环性能均出现大幅下降，25℃电解液电导率仅为5.29mS/cm，4C倍率放电容量比降至78.9％，常温循环200圈容量保持率降至77.9％，高温循环200圈容量保持率降至76.8％。
对比例9中，电解液中加入的氟醚溶剂为1,1,2,2,3,3,4,4,5-九氟丁基甲醚，虽然n和m均满足本申请实施例对氟醚溶剂的要求，但F原子过多，x/(2n+1)＝100％，大于80％，不满足本申请实施例对氟醚溶剂的要求，对比例9制得的电池的离子电导率、倍率性能和循环性能均出现大幅下降，25℃电解液电导率仅为5.46mS/cm，4C倍率放电容量比降至79.8％，常温循环200圈容量保持率降至76.9％，高温循环200圈容量保持率降至75.3％。
表8
通过表8可以看出，实施例22-26中，采用了不同类型的负极材料、导电剂、负极成膜添加剂，制得的电池均具有较好的倍率性能和循环性能，并且无析钠现象，4C倍率放电容量比均可以都达到82％以上，常温循环200圈容量保持率可以达到91.5％以上，高温循环200圈容量保持率90％以上，说明不同类型的负极材料、导电剂、负极成膜添加剂均可以适用于本申请实施例的电池。
综上，通过表5-8可以看出，实施例1-26制得的钠离子电池，通过控制钠离子电池中 负极在扣电测试中的放电容量曲线对应的斜坡区容量和平台区容量的比值A/B在0.66-2.34的范围内，提供了足够的负极容量释放，有效抑制了析钠现象，同时使电池的循环性能和倍率性能得到提升，提高了电池的安全性能。本申请实施例在电解液中采用了特定的氟醚溶剂作为共溶剂，能够提升电解液的电导率以及电化学和热稳定性，氟醚溶剂能够参与CEI和SEI膜的形成，减少了副反应的发生，提高了成膜质量，进而提升了界面稳定性。并且，本申请实施例中，控制了负极活性材料的压实密度，弥补了氟醚溶剂的加入引起的浸润性的下降，改善了电池浸润性，缩短了电池制作的浸润时间，同时，通过控制负极的压实密度在电池激活的过程中能够提升成膜质量，有利于抑制析钠现象的发生，改善了电池的性能。本申请实施例的钠离子电池，高温循环200圈后容量保持率可以高达96.5％，4C倍率放电容量比可达91％，并且无析钠现象发生，具有优异的性能。
在本申请中，术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。
尽管上面已经示出和描述了本申请的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本申请的限制，本领域的普通技术人员在本申请的范围内可以对上述实施例进行变化、修改、替换和变型。

Claims (15)

  1. 一种高安全长循环钠离子电池，其特征在于，包括正极、负极和电解液，其中，
    所述负极进行扣电测试的放电容量曲线所对应的斜坡区容量A和平台区容量B满足关系式：0.66≤A/B≤2.34，其中，斜坡区容量A为扣电测试0.1-3.0V电压区间的容量释放占比，平台区容量B为扣电测试0.1-0V电压区间的容量释放占比，A+B＝1；
    所述电解液包括氟醚溶剂，所述氟醚溶剂的分子式为:FxCnH2n+1-xOCmH2m+1，其中，x/(2n+1)＜80％，n/m>1.5，4≤n≤10，1≤m≤5，所述电解液中氟醚的质量百分含量C％为7％≤C％≤30％；和
    所述负极的压实密度D为0.85-1.00g/cm3。
  2. 根据权利要求1所述的高安全长循环钠离子电池，其特征在于，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：7＜C/D＜35。
  3. 根据权利要求2所述的高安全长循环钠离子电池，其特征在于，所述电解液中氟醚质量含量C％和所述负极的压实密度D满足：10≤C/D≤31。
  4. 根据权利要求1至3中任一项所述的高安全长循环钠离子电池，其特征在于，0.81≤A/B≤1.63。
  5. 根据权利要求1至4中任一项所述的高安全长循环钠离子电池，其特征在于，所述氟醚溶剂选自2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,3,3,4,4,5,5-七氟戊基甲基醚、2,3,3,4,4,5,5-七氟戊基乙基醚、2,2,3,3,4,4,5-七氟戊基甲基醚、2,2,3,4,4,5,5-七氟戊基乙基醚、3,3,4,4,5,5-六氟戊基甲基醚、3,3,4,4,5,5-六氟戊基乙基醚、2,2,3,3,4,4-六氟丁基甲基醚、2,2,3,3,4,4-六氟戊基甲基醚和2,2,3,3,4,4-六氟丁基乙基醚中的一种或多种；
    优选地，所述氟醚溶剂包括2,2,3,3,4,4,5,5-八氟戊基乙基醚、2,2,3,3,4,4,5,5-八氟戊基甲基醚、2,3,3,4,4,5,5-七氟戊基甲基醚一种或多种。
  6. 根据权利要求1至5中任一项所述的高安全长循环钠离子电池，其特征在于，所述电解液中还包括辅助溶剂，所述辅助溶剂包括C3～C5的碳酸酯、C2～C6的羧酸酯、C4～C10的醚中的至少一种，其中，
    所述C3～C5的碳酸酯包括碳原子数为3～5的环状碳酸酯或链状碳酸酯；
    所述C2～C6的羧酸酯包括乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯、丙酸丙酯中的至少一种；和
    所述C4～C10的醚包括碳原子数为4～10的环状醚或链状醚。
  7. 根据权利要求6所述的高安全长循环钠离子电池，其特征在于，所述环状碳酸酯包 括碳酸乙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、碳酸丙烯酯、γ-丁内酯、碳酸亚丁酯中的至少一种；所述链状碳酸酯包括碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯中的至少一种。
  8. 根据权利要求6或7所述的高安全长循环钠离子电池，其特征在于，所述环状醚包括1,3-二氧戊烷、1,4-二氧惡烷、四氢呋喃、2-甲基四氢呋喃，2-三氟甲基四氢呋喃中的至少一种；所述链状醚包括二甲氧基甲烷、1,2-二甲氧基乙烷、二甘醇二甲醚中的至少一种。
  9. 根据权利要求1至8中任一项所述的高安全长循环钠离子电池，其特征在于，所述电解液中包括电解质盐，所述电解质盐包括高氯酸钠(NaClO4)、四氟硼酸钠(NaBF4)、六氟磷酸钠(NaPF6)、三氟乙酸钠(CF3COONa)、四苯硼酸钠(NaB(C6H5)4)、三氟甲基磺酸钠(NaSO3CF3)、双(氟磺酰)亚胺钠(Na[(FSO2)2N])或双(三氟甲基磺酰)亚胺钠(Na[(CF3SO2)2N])中的至少一种。
  10. 根据权利要求1至9中任一项所述的高安全长循环钠离子电池，其特征在于，所述电解液还包括添加剂，所述添加剂包括氟代碳酸酯，优选地，所述氟代碳酸酯包括氟代碳酸乙烯酯或双氟代碳酸乙烯酯中的至少一种，所述电解液中所述氟代碳酸酯的质量百分含量为1-5％。
  11. 根据权利要求1至10中任一项所述的高安全长循环钠离子电池，其特征在于，所述正极包括正极活性物质，所述正极活性物质选自层状金属氧化物、聚阴离子化合物、普鲁士类化合物、磷酸盐化合物、硫酸盐化合物中的至少一种，其中，
    所述层状金属氧化物的化学式为NaxMyOz，0＜x≤1，0＜y≤1，1＜z≤2，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种；
    所述普鲁士类化合物的分子式为NaxM[M′(CN)6]y·zH2O，M和M′为过渡金属，0<x≤2，0<y≤1，0<z≤20；
    所述磷酸盐化合物的化学式为Na3(MO1-xPO4)2F1+2x，0≤x≤1，M选自Al、V、Ge、Fe、Ga中的至少一种；和
    所述硫酸盐化合物的化学式为Na2M(SO4)2·2H2O，M选自Cr、Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的至少一种。
  12. 根据权利要求11所述的高安全长循环钠离子电池，其特征在于，所述层状金属氧化物为NaNimFenMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)或NaNimConMnpO2(m+n+p＝1，0≤m≤1，0≤n≤1，0≤p≤1)中的至少一种。
  13. 根据权利要求11或12所述的高安全长循环钠离子电池，其特征在于，所述普鲁士类化合物为NaxMn[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)或NaxFe[Fe(CN)6]y·zH2O(0＜x≤2，0＜y≤1，0＜z≤20)中的至少一种。
  14. 根据权利要求11至13中任一项所述的高安全长循环钠离子电池，其特征在于，所述磷酸盐化合物为Na3(VPO4)2F3或Na3(VOPO4)2F中的至少一种；或者，所述磷酸盐化合物的化学式为Na2MPO4F，M选自Fe、Mn中的至少一种，优选地，所述磷酸盐化合物为Na2FePO4F或Na2MnPO4F中的至少一种。
  15. 根据权利要求1至14中任一项所述的高安全长循环钠离子电池，其特征在于，所述负极包括负极活性物质和导电剂，所述负极活性物质包括硬碳或软碳中的至少一种；所述负极活性物质的粒径满足4μm≤d50≤8μm；所述负极中，所述导电剂的质量百分含量为1％～5％。
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