WO2024040838A1 - 电池正极材料、钠离子电池和用电设备 - Google Patents

电池正极材料、钠离子电池和用电设备 Download PDF

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WO2024040838A1
WO2024040838A1 PCT/CN2022/143301 CN2022143301W WO2024040838A1 WO 2024040838 A1 WO2024040838 A1 WO 2024040838A1 CN 2022143301 W CN2022143301 W CN 2022143301W WO 2024040838 A1 WO2024040838 A1 WO 2024040838A1
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battery
particle
cathode material
positive electrode
sodium
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PCT/CN2022/143301
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English (en)
French (fr)
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邓常健
安黎
张耀
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欣旺达电子股份有限公司
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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

  • This application belongs to the field of batteries, and particularly relates to a battery cathode material, a sodium-ion battery and electrical equipment.
  • Secondary batteries especially sodium-ion batteries, not only have the advantages of abundant sodium resources, wide distribution, low cost, no development bottlenecks, environmental friendliness and compatibility with existing lithium-ion battery production equipment, but also have good power characteristics, wide range of Advantages include temperature range adaptability, safety performance and no over-discharge issues.
  • the surface Na of the cathode material used in sodium-ion batteries easily reacts with carbon dioxide and water in the air to generate alkaline sodium hydroxide and sodium carbonate, which increases the surface alkalinity of the cathode material. Therefore, when the cathode material is homogenized, it causes The structure of the adhesive PVDF changes in a highly alkaline environment and the slurry gels, which is not conducive to the coating process.
  • the high alkalinity on the surface of the battery cathode material will increase the irreversible capacity loss of the battery, worsen the battery cycle performance, and also cause battery Flatulence. Therefore, the problem of reducing residual alkali on the surface of battery cathode materials needs to be solved urgently.
  • This application provides a battery cathode material, a sodium-ion battery and electrical equipment, aiming to solve the problem of high residual alkalinity on the surface of existing battery cathode materials, causing slurry gelation and deterioration of electrochemical performance.
  • the chemical formula of the battery cathode material includes Na x TMO 2 , where 0.9 ⁇ x ⁇ 1.1, and TM is a transition metal;
  • the sodium content on the side of the particle outer area of the battery positive electrode material close to the inner area of the particle is greater than the sodium content on the surface of the particle;
  • the inner area of the particle refers to the range from the center of the particle to the 90% radius in the direction from the center of the particle to the surface of the particle. area;
  • the particle outer area refers to the area within the range of 90% radius to the particle surface.
  • the sodium content in the inner region of the particle is evenly distributed, and the sodium content in the inner region of the particle is greater than the sodium content in the outer region of the particle.
  • the sodium content in the inner region of the particle of the battery positive electrode material is denoted as A
  • the sodium content in the outer region of the particle is denoted as a, then 1 ⁇ A/a ⁇ 1.5 is satisfied.
  • the crystal structure space group of the battery cathode material is composed of one or more of R-3m, R3m, P63/mmc and P63mc.
  • the secondary particles of the battery cathode material include spherical structures and spherical-like particles.
  • the particle size Dv50 of the battery cathode material is 1 to 20 ⁇ m, and the Dv99 is 10 ⁇ m to 30 ⁇ m.
  • the specific surface area of the battery cathode material is 0.005 m 2 /g ⁇ 10 m 2 /g.
  • the tap density of the battery cathode material is 1g/cm 3 to 3g/cm 3 and the compacted density is 2g/cm 3 to 4g/cm 3 .
  • TM is selected from at least one of Mn, Fe, Ni, Li, Cu, Zn, Co and Ti.
  • This application also provides a sodium-ion battery, which includes the above-mentioned battery cathode material.
  • This application also provides an electrical device, which includes the above-mentioned sodium ion battery, and the sodium ion battery serves as the power supply for the electrical device.
  • Figure 1 shows an SEM surface morphology image of a battery cathode material according to an embodiment of the present application.
  • Figure 2 shows the distribution trend diagram of sodium in the cathode material of the battery in Example 1 of the present application.
  • Figure 3 shows the 100 cycle retention rate curves of the cathode materials of Example 1 and Comparative Example 1 of the present application.
  • the surface of the battery cathode material has higher energy sodium.
  • sodium reacts with oxygen and water in the air to form sodium hydroxide and carbonic acid.
  • Alkaline compounds such as sodium cause the surface alkalinity of the battery cathode material to increase.
  • slurry gel appears, which is not conducive to coating.
  • the surface alkalinity The formation of chemical compounds consumes active sodium, increases the irreversible capacity loss of the battery, and worsens the cycle performance of the battery.
  • sodium carbonate will decompose into carbon dioxide gas, causing the battery to swell and pose safety risks.
  • this application provides a battery cathode material, a sodium ion battery and electrical equipment.
  • one embodiment of the present application provides a battery cathode material whose general chemical formula includes Na x TMO 2 , where 0.9 ⁇ x ⁇ 1.1, and TM includes transition metals;
  • the sodium content on the side of the particle outer area of the battery positive electrode material close to the inner area of the particle is greater than the sodium content on the surface of the particle;
  • the inner area of the particle refers to the range from the center of the particle to the 90% radius in the direction from the center of the particle to the surface of the particle. area;
  • the particle outer area refers to the area within the range of 90% radius to the particle surface.
  • the sodium content on the side of the outer region of the particle of the battery cathode material close to the inner region of the particle is greater than the sodium content on the surface of the particle
  • the sodium content on the surface of the battery cathode material is lower because the exposure of the battery cathode material to The content of alkaline substances generated when air is used to avoid the phenomenon of slurry gel in the battery cathode material during the homogenization process, and avoid the loss of battery capacity, deterioration of battery cycle performance and battery bloating due to the presence of excessive alkaline substances. consequences, thereby improving the specific capacity, cycle life and safety performance of the battery.
  • the sodium content in the inner region of the particles is evenly distributed, and the sodium content in the inner region of the particles is greater than the sodium in the outer region of the particles.
  • content; the sodium content in the inner region of the particle of the battery positive electrode material is recorded as A, and the sodium content in the outer area of the particle is recorded as a, then 1 ⁇ A/a ⁇ 1.5 is satisfied.
  • battery cathode materials with a lower pH value can be obtained.
  • the pH range is between 11.3 and 11.6. Within this range, gelation of the slurry during the pulping process will not occur.
  • the sodium content on the surface of the battery cathode material is not as low as possible. When the sodium content on the surface is too low, it will cause the conductivity of the battery cathode material to deteriorate. It will also cause the sodium ion migration rate to decrease during the charge and discharge process, which is not conducive to battery capacity. It is also not conducive to the fast charging performance of the battery. Therefore, in another embodiment, the sodium content on the surface of the battery cathode material accounts for 8% to 20% of the total sodium content of the battery cathode material. When the surface sodium content is less than 10%, the conductivity and ion conductivity of the battery cathode material will decrease. When the surface sodium content is higher than 20%, the PH of the battery cathode material will be too high and the slurry will gel seriously, causing the battery to Electrochemical performance deteriorates.
  • the crystal structure space group of the battery cathode material is composed of one or more of R-3m, R3m, P63/mmc and P63mc.
  • the existence of the above space group can increase the concentration of sodium ions in the battery cathode material.
  • the deintercalation rate can also improve the interlayer stability of battery cathode materials.
  • the crystal structure of the battery cathode material can be obtained by XRD (X-ray diffraction) analysis.
  • the secondary particles of the battery cathode material have a spherical structure, and the particle size Dv50 is 1 ⁇ m to 20 ⁇ m, for example, it can be 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 12 ⁇ m, 15 ⁇ m, or 20 ⁇ m; and the Dv99 is 10 ⁇ m to 30 ⁇ m, for example. 10 ⁇ m, 15 ⁇ m, 18 ⁇ m, 25 ⁇ m, 30 ⁇ m. If the particle size Dv50 of the battery positive electrode material is too small, the specific surface area will be too large, which will lead to the occurrence of too many side reactions and cause the battery cycle performance to decrease.
  • the specific surface area of the battery cathode material is 0.005m 2 /g ⁇ 10m 2 /g, for example, it can be 0.005m 2 /g, 0.5m 2 /g, 2m 2 /g, 5m 2 /g, 8m 2 /g, 10m 2 /g. Battery cathode materials within this specific surface area range have excellent electrochemical charge-discharge performance and cycle performance.
  • the tap density of the battery cathode material is 1g/cm 3 to 3g/cm 3
  • the compacted density is 2g/cm 3 to 4g/cm 3 .
  • the battery can have a higher gram capacity, while also ensuring that the positive electrode plate has appropriate porosity, ensuring the liquid retention capacity of the positive electrode plate, and avoiding capacity loss during battery cycling. The phenomenon of rapid attenuation and increased internal resistance.
  • the true density of the battery cathode material is 2g/cm 3 to 4g/cm 3 .
  • TM in NaxTMO2 in the chemical formula of the cathode material may be selected from at least one of Mn, Fe, Ni, Li, Cu, Zn, Co and Ti.
  • the above-mentioned metal elements can increase the specific capacity of the battery cathode material or improve the stability of the battery cathode material.
  • the battery cathode material mentioned above in this application can be obtained through the following steps:
  • the Na-TM oxide can be obtained by thoroughly mixing the sodium salt and the TM metal oxide and then calcining.
  • the sodium salt can be sodium citrate, sodium hydroxide, sodium nitrate, or sodium carbonate.
  • the above-mentioned organic solvent can be ethanol or propanol, and the molybdenum salt is ammonium molybdate tetrahydrate.
  • the pH value of the dispersion is controlled between 8 and 10, and ammonia water can be used to adjust the pH of the dispersion.
  • the calcining temperature is 700 to 1000°C and the time is 6 to 24 hours. After the calcining is completed, the calcined product can be cleaned with an alcohol solution to remove the Na 2 MoO 4 impurities present in the calcined product and then dried. Finally, pure battery cathode material is obtained.
  • the battery cathode material precursor is a molybdenum salt evenly wrapped in Na-TM oxide.
  • the molybdenum salt is converted into molybdenum trioxide.
  • the molybdenum oxide reacts with the sodium element on the surface of the Na-TM oxide, and the sodium element inside the Na-TM oxide migrates to the surface under high temperature conditions, thereby obtaining a battery cathode material with low surface sodium content.
  • This application also provides a sodium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet includes the above-mentioned battery positive electrode material.
  • the sodium-ion battery containing the battery cathode material of the present application has higher specific capacity, cycleability and lower gas production.
  • This application also provides an electrical device, which includes the above-mentioned sodium ion battery, and the sodium ion battery serves as the power supply for the electrical device.
  • the battery cathode material, conductive carbon black and binder PVDF prepared in step 1) Disperse the battery cathode material, conductive carbon black and binder PVDF prepared in step 1) into the solvent NMP and mix evenly to obtain a cathode slurry (the weight ratio of the cathode material, conductive carbon black and binder PVDF is 96 :2:2); the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting, and cutting, the positive electrode piece is obtained.
  • the compacted density of the positive electrode piece is 3g/cm 3 .
  • Preparation of sodium-ion battery stack the positive electrode sheet, isolation film and negative electrode sheet in sequence.
  • the isolation film is made of PP/PE/PP composite film, and then rolled into a battery core and put into the battery shell, through the top side Seal and inject the electrolyte (the electrolyte is prepared by: mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) at a mass ratio of 30:40:30 to obtain a non-aqueous solution.
  • Organic solvent Dissolve 1 mol/L NaPF6 in the above-mentioned non-aqueous organic solvent, mix evenly to obtain electrolyte) and other processes to make a sodium ion battery.
  • Example 2 The same as Example 1, except that during the preparation process of the battery cathode material, the raw material NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was replaced with NaNi 0.33 Co 0.33 Ti 0.33 O.
  • Example 3 is the same as Example 1, except that during the preparation process of the battery cathode material, the raw material NaNi 0.33 Fe 0.33 Mn 0.33 O 2 is replaced by NaNi 0.5 Zn 0.5 O 2 .
  • Example 2 The same as Example 1, except that during the preparation process of the battery cathode material, the raw material NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was replaced with NaNi 0.7 Co 0.1 Cu 0.2 O 2 .
  • Example 2 The same as Example 1, except that in the preparation process of the battery cathode material, NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was used with a Dv5 of 1 ⁇ m.
  • Example 2 The same as Example 1, except that in the preparation process of the battery cathode material, NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was used with a Dv5 of 5 ⁇ m.
  • Example 2 The same as Example 1, except that in the preparation process of the battery cathode material, NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was used with a Dv5 of 12 ⁇ m.
  • Example 2 The same as Example 1, except that in the preparation process of the battery cathode material, the Dv5 of NaNi 0.33 Fe 0.33 Mn 0.33 O 2 is 15 ⁇ m.
  • Example 2 The same as Example 1, except that during the preparation process of the battery cathode material, NaNi 0.33 Fe 0.33 Mn 0.33 O 2 was used with a Dv5 of 20 ⁇ m.
  • Example 2 It is the same as Example 1, except that the calcination temperature is 700°C, and the A/a of the battery cathode material is 0.8.
  • Example 2 The same as Example 1, but the difference is that the calcination temperature is 750°C, and the A/a of the battery cathode material is 1.1.
  • Example 2 It is the same as Example 1, except that the calcination temperature is 850°C, and the A/a of the battery cathode material is 1.5.
  • Example 2 The same as Example 1, but the difference is that the calcination temperature is 1000°C, and the A/a of the battery cathode material is 1.8.
  • Example 2 The same as Example 1, except that the cold pressing pressure was adjusted during the preparation process of the positive electrode piece, so that the compacted density of the positive electrode piece was 1 g/cm 3 .
  • Example 2 It is the same as Example 1, except that the cold pressing pressure is adjusted during the preparation process of the positive electrode piece, so that the compacted density of the positive electrode piece is 2g/cm 3 .
  • Example 2 It is the same as Example 1, except that the cold pressing pressure is adjusted during the preparation process of the positive electrode piece, so that the compacted density of the positive electrode piece is 4g/cm 3 .
  • Example 2 It is the same as Example 1, except that the cold pressing pressure is adjusted during the preparation process of the positive electrode piece, so that the compacted density of the positive electrode piece is 6g/cm 3 .
  • the cathode material provided is NaNi 0.33 Fe 0.33 Mn 0.33 O 2 .
  • the sodium content on the side of the outer region of the particle close to the inner region of the particle of the positive electrode material of the battery is less than the sodium content on the surface of the particle.
  • the positive electrode material was made into a sodium ion battery, and the battery manufacturing method was the same as in Example 1.
  • the battery material with low surface sodium content provided by the present application has a lower pH value, that is, its alkalinity is low.
  • the surface sodium content is low, the battery capacity can be increased, the battery cycle life can be improved, and the battery gas production can also be reduced.
  • the capacity fading rate of Comparative Example 1 is significantly greater than the cycle capacity fading rate of Example 1.
  • the specific surface area of the battery cathode material increases, the gas production rate of the battery will increase accordingly. This is because the effective area where the electrolyte and the battery cathode material can react increases. , thereby increasing the occurrence of side reactions and causing gas production.
  • the specific surface area of the battery cathode material is too small or too large, it will cause the battery cycle performance and battery gram capacity to decay.
  • the specific surface area of the battery cathode material is preferably 0.5 ⁇ 8m 2 /g.
  • the battery cathode material provided by this application has a lower sodium content on the surface of the battery cathode material because the sodium content on the side close to the inner area of the particle in the particle outer region of the battery cathode material is greater than the sodium content on the particle surface.
  • the content of alkaline substances generated when the battery cathode material is exposed to the air thereby preventing the slurry gelation of the battery cathode material during the homogenization process, and avoiding the loss of battery capacity and battery cycle due to the presence of excessive alkaline substances. Performance deterioration and the consequences of battery bloating, thereby increasing the battery's specific capacity, cycle life and improving battery safety performance.
  • the sodium content on the surface of the battery cathode material is relatively high. Low, which reduces the content of alkaline substances generated when the battery cathode material is exposed to the air, thus avoiding the phenomenon of slurry gel in the battery cathode material during the homogenization process, and avoiding the loss of battery capacity due to the presence of excessive alkaline substances. loss, deterioration of battery cycle performance and battery bloating, thereby increasing the battery's specific capacity, cycle life and improving battery safety performance.

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Abstract

本申请提供一种电池正极材料、钠离子电池以及用电设备，其中电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量；颗粒内部区域指在颗粒中心到颗粒表面方向上，颗粒中心至90％半径范围内的区域；颗粒外部区域指90％半径至颗粒表面范围内的区域。由于电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量，使得电池正极材料表面钠含量较低，降低了电池正极材料暴露在空气时所生成的碱性物质含量，避免电池正极材料在匀浆过程中出现浆料凝胶的现象，避免过多碱性物质的存在导致电池容量损失、电池循环性能恶化及电池胀气，进而提高了电池的比容量、循环使用寿命以及提高电池的安全性能。

Description

电池正极材料、钠离子电池和用电设备 技术领域
本申请属于电池领域，特别涉及一种电池正极材料、钠离子电池和用电设备。
背景技术
二次电池，特别是钠离子电池，不仅具有钠资源储量丰富、分布广泛、成本低廉、无发展瓶颈、环境友好和兼容锂离子电池现有生产设备的优势，还具有较好的功率特性、宽温度范围适应性、安全性能和无过放电问题等优势。但是，钠离子电池采用的正极材料由于表面Na容易与空气中的二氧化碳和水反应生成碱性的氢氧化钠和碳酸钠，使得正极材料表面碱性升高，因而正极材料在匀浆时，引起粘接剂PVDF在高碱性环境下结构改变，浆料凝胶，不利于涂布工艺，同时电池正极材料表面的高碱性会增加电池的不可逆容量损失，恶化电池循环性能，还会引起电池胀气。因此降低电池正极材料表面残碱的问题亟需解决。
发明内容
本申请提供一种电池正极材料、钠离子电池和用电设备旨在解决现有电池正极材料表面残碱性高，引起浆料凝胶，电化学性能恶化的问题。
基于上述问题，本申请提供了一种电池正极材料，该电池正极材料化学通式包括Na xTMO 2，其中0.9＜x＜1.1，TM为过渡金属；
所述电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量；所述颗粒内部区域指在颗粒中心到颗粒表面方向上，颗粒中心至90％半径范围内的区域；所述颗粒外部区域指90％半径至颗粒表面范围内的区域。
优选地，所述颗粒内部区域的钠含量分布均匀，所述颗粒内部区域的钠含量大于颗粒外部区域的钠含量。
优选地，所述电池正极材料的颗粒内部区域的钠含量记为A，颗粒外部区域的钠含量记为a，则满足1<A/a<1.5。
优选地，电池正极材料的晶体结构空间群由R-3m、R3m、P63/mmc和P63mc中的一种或多种组成。
优选地，电池正极材料的二次颗粒包括球形结构和类球形颗粒，所述 电池正极材料的粒径Dv50为1μm～20μm，Dv99为10μm～30μm。
优选地，电池正极材料的比表面积为0.005m 2/g～10m 2/g。
优选地，电池正极材料的振实密度为1g/cm 3～3g/cm 3，压实密度为2g/cm 3～4g/cm 3。
优选地，TM选自Mn、Fe、Ni、Li、Cu、Zn、Co和Ti中的至少一种。
本申请还提供一种钠离子电池，该钠离子电池包括上述的电池正极材料。
本申请还提供一种用电设备，该用电设备包括上述的钠离子电池，所述钠离子电池作为所述用电设备的供电电源。
附图说明
构成本申请的一部分的说明书附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定，在附图中：
图1示出了本申请一实施例电池正极材料的SEM表面形貌图。
图2示出了本申请实施例1电池正极材料中钠的分布趋势图。
图3示出了本申请实施例1和对比例1的正极材料100周循环保持率曲线。
具体实施方式
下述实施例中所使用的实验方法如无特殊说明，均为常规方法。
下述实施例中所用的材料、试剂等，如无特殊说明，均可从商业途径得到。
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本申请。
如本申请背景技术所分析的，现有技术中电池正极材料的表面由于具有较高能量的钠，在进行匀浆过程中，钠与空气中的氧气和水发生反应，形成氢氧化钠和碳酸钠等碱性化合物，导致电池正极材料表面碱性升高，在将电池正极材料进行匀浆过程中，出现浆料凝胶，不利于涂布，且在电池充放电充电状态下，表面的碱性化合物的形成消耗活性钠，增加了电池的不可逆容量损失，并会恶化电池的循环性能，另外碳酸钠会分解成二氧 化碳气体，引起电池膨胀，出现安全隐患。为了解决这些问题，本申请提供了一种电池正极材料、钠离子电池和用电设备。
参照图1，本申请一实施例提供一种电池正极材料，其化学通式包括Na xTMO 2，其中0.9＜x＜1.1，TM包括过渡金属；
所述电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量；所述颗粒内部区域指在颗粒中心到颗粒表面方向上，颗粒中心至90％半径范围内的区域；所述颗粒外部区域指90％半径至颗粒表面范围内的区域。
在本实施例中，由于电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量，使得电池正极材料表面钠含量较低，因为降低了电池正极材料暴露在空气时所生成的碱性物质含量，从而避免电池正极材料在匀浆过程中出现浆料凝胶的现象，并避免因为过多碱性物质的存在导致电池容量损失、电池循环性能恶化以及电池胀气的后果，进而提高了电池的比容量、循环使用寿命以及提高电池的安全性能。
在另一实施例中，为了进一步降低电池正极材料表面残碱量，同时充分发挥正极材料容量，所述颗粒内部区域的钠含量分布均匀，所述颗粒内部区域的钠含量大于颗粒外部区域的钠含量；所述电池正极材料的颗粒内部区域的钠含量记为A，颗粒外部区域的钠含量记为a，则满足1<A/a<1.5。在上述比值范围内，可以获得较低PH值的电池正极材料，其PH的范围在11.3～11.6之间，在该范围内不会引起制浆过程中浆料出现凝胶现象。
电池正极材料表面的钠含量并非越低越好，当表面的钠含量过低时，引起电池正极材料导电性能变差，还会导致在充放电过程中，钠离子迁移速率降低，不利于电池容量发挥，也不利于电池的快充性能。因此在另一实施例中，电池正极材料表面的钠含量占电池正极材料总钠含量的8％～20％。当表面钠含量低于10％时，引起电池正极材料导电性能、以及导离子性能下降，当表面钠含量高于20％时，出现电池正极材料PH过高，浆料凝胶严重，并导致电池电化学性能恶化。
在另一实施例中，电池正极材料的晶体结构空间群由R-3m、R3m、P63/mmc和P63mc中的一种或多种组成，上述空间群的存在能够提高钠离 子在电池正极材料中的脱嵌速率，还能够提高电池正极材料的层间稳定性。电池正极材料的晶体结构可由XRD(X射线衍射)分析得到。
在另一实施例中，电池正极材料的二次颗粒为球型结构，粒径Dv50为1μm～20μm，例如可以为1μm、5μm、8μm、12μm、15μm、20μm；Dv99为10μm～30μm，例如可以为10μm、15μm、18μm、25μm、30μm。若电池正极材料的粒径Dv50过小，引起比表面积过大，从而会导致过多副反应的发生，引起电池循环性能下降，若颗粒Dv50过大，钠离子在正极极片上的迁移路径过长，不利于电池的充放电速率，电池的循环性能也会受到影响。在另一实施例中，电池正极材料的比表面积为0.005m 2/g～10m 2/g，例如可以为0.005m 2/g、0.5m 2/g、2m 2/g、5m 2/g、8m 2/g、10m 2/g。在该比表面积范围内的电池正极材料具有较优的电化学充放电性能和循环性能。
在另一实施例中，电池正极材料的振实密度为1g/cm 3～3g/cm 3，压实密度为2g/cm 3～4g/cm 3。在上述振实和压实密度范围内，可使电池具有较高克容量的同时，还能保证正极极片具有合适的孔隙率，确保正极极片的保液能力，避免电池循环过程中出现容量衰减快，内阻增加的现象。在一些实施例中，电池正极材料的真密度为2g/cm 3～4g/cm 3。
在一些实施例中，正极材料化学式中的Na xTMO 2中的TM可以选自Mn、Fe、Ni、Li、Cu、Zn、Co和Ti中的至少一种。上述金属元素可提高电池正极材料的比容量或者提高电池正极材料的稳定性。
在一实施例中，本申请上述的电池正极材料可以通过以下步骤获得：
S1、将Na-TM氧化物和钼盐反应分散于有机溶剂中，得到分散液；
S2、对所述分散液进行过滤，获得电池正极材料前驱体；
S3、对所述电池正极材料前驱体煅烧处理，得到所述电池正极材料。
上述步骤S1中Na-TM氧化物可以将钠盐和TM金属氧化物充分混合后，煅烧得到，其中，钠盐可以是柠檬酸钠、氢氧化钠、硝酸钠、碳酸钠。上述有机溶剂可以是乙醇、丙醇，钼盐为四水合钼酸铵。分散液的PH值控制在8～10之间，可利用氨水对分散液的PH进行调节。步骤S3中煅烧温度为700～1000℃，时间为6～24h，在煅烧完成之后，可利用醇类溶液对煅烧产物进行清洗，以清除煅烧产物中存在的Na 2MoO 4杂质，经过烘 干处理后得到纯净的电池正极材料。
在上述制备电池正极材料的过程中，电池正极材料前驱体是一种钼盐均匀包裹在Na-TM氧化物的物质，对电池正极材料前驱体煅烧过程中，钼盐转化为三氧化钼，三氧化钼又与Na-TM氧化物表面的钠元素进行反应，且在高温条件下Na-TM氧化物中内部的钠元素向表面发生迁移，从而得到具有表面钠含量低的电池正极材料。
本申请还提供一种钠离子电池，该钠离子电池包括正极极片、负极极片、隔膜以及电解液，其中正极极片包括上述电池正极材料。包含本申请的电池正极材料的钠离子电池具有较高的比容量、循环性以及较低的产气量。
本申请还提供一种用电设备，该用电设备包括上述的钠离子电池，钠离子电池作为用电设备的供电电源。
以下结合具体实施例对本申请作进一步详细描述，这些实施例不能理解为限制本申请所要求保护的范围。
实施例1
1)电池正极材料的制备：将原材料(NH 4) 6Mo 7O 24·4H 2O(四水合钼酸铵)和NaNi 0.33Fe 0.33Mn 0.33O 2(Dv50为10μm)放入浓度为4wt％的乙醇溶液中，用氨水调节PH至9，得到分散液。对分散液进行超声处理之后抽滤，得到电池正极材料前驱体。将得到的电池正极材料前驱体在800℃条件下煅烧10小时，冷却后利用乙醇溶液对煅烧产物进行清洗，烘干处理得到表面钠含量低的电池正极材料。所制备得到的电池正极材料的A/a为1.3，Dv50为10μm，比表面积为5m 2/g，含有的金属元素为Na、Ni、Fe和Mn。
2)正极极片的制备：
将步骤1)制备得到的电池正极材料、导电炭黑及粘结剂PVDF分散至溶剂NMP中进行混合均匀，得到正极浆料(其中正极材料、导电炭黑及粘结剂PVDF的重量比为96:2:2)；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压、分条、裁片后，得到正极极片，正极极片的压实密度为3g/cm 3。
3)负极极片的制备：
将负极活性物质石墨、导电炭黑、增稠剂CMC及粘结剂SBR按照重量比96:1:1:2分散于溶剂去离子水中进行混合均匀，得到负极浆料；将负极浆料均匀涂布于负极集流体铜箔上；经烘干、冷压、分条、裁片后，得到负极极片。
4)钠离子电池的制备：将正极极片、隔离膜及负极极片依次层叠设置，隔离膜采用PP/PE/PP复合薄膜，然后卷绕成电芯并装入电池外壳中，经顶侧封、注入电解液(电解液的制备方式为：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)以质量比30:40:30混合均匀，得到非水有机溶剂。将1mol/L的NaPF6溶解于上述非水有机溶剂中，混合均匀，得到电解液)等工序后，制成钠离子电池。
实施例2
与实施例1相同，不同的是，电池正极材料的制备过程中，将原料NaNi 0.33Fe 0.33Mn 0.33O 2替换成NaNi 0.33Co 0.33Ti 0.33O。
实施例3与实施例1相同，不同的是，电池正极材料的制备过程中，将原料NaNi 0.33Fe 0.33Mn 0.33O 2替换成NaNi 0.5Zn 0.5O 2。
实施例4
与实施例1相同，不同的是，电池正极材料的制备过程中，将原料NaNi 0.33Fe 0.33Mn 0.33O 2替换成NaNi 0.7Co 0.1Cu 0.2O 2。
实施例5
与实施例1相同，不同的是，电池正极材料的制备过程中，采用NaNi 0.33Fe 0.33Mn 0.33O 2的Dv5为1μm。
实施例6
与实施例1相同，不同的是，电池正极材料的制备过程中，采用NaNi 0.33Fe 0.33Mn 0.33O 2的Dv5为5μm。
实施例7
与实施例1相同，不同的是，电池正极材料的制备过程中，采用NaNi 0.33Fe 0.33Mn 0.33O 2的Dv5为12μm。
实施例8
与实施例1相同，不同的是，电池正极材料的制备过程中，采用 NaNi 0.33Fe 0.33Mn 0.33O 2的Dv5为15μm。
实施例9
与实施例1相同，不同的是，电池正极材料的制备过程中，采用NaNi 0.33Fe 0.33Mn 0.33O 2的Dv5为20μm。
实施例10
与实施例1相同，不同的是，煅烧温度为700℃，得到电池正极材料的A/a为0.8。
实施例11
与实施例1相同，不同的是，煅烧温度为750℃，得到电池正极材料的A/a为1.1。
实施例12
与实施例1相同，不同的是，煅烧温度为850℃，得到电池正极材料的A/a为1.5。
实施例13
与实施例1相同，不同的是，煅烧温度为1000℃，得到电池正极材料的A/a为1.8。
实施例14
与实施例1相同，不同的是，正极极片的制备过程中调节冷压压力，得到正极极片的压实密度为1g/cm 3。
实施例15
与实施例1相同，不同的是，正极极片的制备过程中调节冷压压力，得到正极极片的压实密度为2g/cm 3。
实施例16
与实施例1相同，不同的是，正极极片的制备过程中调节冷压压力，得到正极极片的压实密度为4g/cm 3。
实施例17
与实施例1相同，不同的是，正极极片的制备过程中调节冷压压力，得到正极极片的压实密度为6g/cm 3。
对比例1
提供的正极材料为NaNi 0.33Fe 0.33Mn 0.33O 2。该电池正极材料的颗粒外 部区域中靠近颗粒内部区域的一侧的钠含量小于颗粒表面的钠含量。将该正极材料制成钠离子电池，电池制作方式与实施例1相同。
将上述实施例1-17和对比例1所制备得到的电池正极材料的特征参数，以及制备得到的钠离子电池的测试数据记录在表1中，其中电池测试的具体方法为：
1)比容量的测试：将电池放置于新威充放电测试仪上，室温环境，0.33C充电至4.0V，0.33C放电至1.5V。放电容量即为比容量数值。
2)循环100圈容量保持率的测试：将电池放置于新威充放电测试仪上，室温环境，0.33C充电至4.0V，0.33C放电至1.5V。以此进行循环测试，一次充电、放电循环为一圈。每一圈的放电克容量与第一圈的放电克容量的比值，即为容量保持率。
3)体积膨胀的测试：通过电池体积膨胀率测试仪测试。
表1电池正极材料的特征和电池性能
Figure PCTCN2022143301-appb-000001
Figure PCTCN2022143301-appb-000002
根据表1中的实施例1-17与对比例1数据比较可见，本申请提供的表面钠含量低的电池材料具有较低的PH值，即其碱性低。当表面钠含量低时，能够提高电池容量，提高电池循环寿命，同时还可以降低电池产气。结合图3，对比例1的容量衰减率明显大于实施例1的循环容量衰减率。
根据表1实施例5～9的数据可见，随着电池正极材料的比表面积增大，电池的产气率就会随之增大，这是因为电解液和电池正极材料可反应的有效面积增加，从而增加副反应的发生，引起气体产出。然而当电池正极材料的比表面积过小或者过大，会引起电池循环性能和电池克容量的衰减，基于电池产气率、电池循环性能和电池克容量考虑，电池正极材料的比表面积优选为0.5～8m 2/g。
综上，本申请提供的电池正极材料，由于电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量，使得电池正极材料表面钠含量较低，因为降低了电池正极材料暴露在空气时所生成的碱性物质含量，从而避免电池正极材料在匀浆过程中出现浆料凝胶的现象，并避免因为过多碱性物质的存在导致电池容量损失、电池循环性能恶化以及电池胀气的后果，进而提高了电池的比容量、循环使用寿命以及提高电池的安全性能。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。
工业应用
本申请具有如下有益技术效果：
本申请提供的电池正极材料、钠离子电池和用电设备，由于电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量，使得电池正极材料表面钠含量较低，降低了电池正极材料暴露在空气时所生成的碱性物质含量，从而避免电池正极材料在匀浆过程中出现浆料凝胶的现象，并避免因为过多碱性物质的存在导致电池容量损失、电池循环性能恶化以及电池胀气的后果，进而提高了电池的比容量、循环使用寿命以及提高电池的安全性能。

Claims (10)

  1. 一种电池正极材料，其特征在于：所述电池正极材料的化学通式包括Na xTMO 2，其中0.9＜x＜1.1，TM包括过渡金属；
    所述电池正极材料的颗粒外部区域中靠近颗粒内部区域的一侧的钠含量大于颗粒表面的钠含量；所述颗粒内部区域指在颗粒中心到颗粒表面方向上，颗粒中心至90％半径范围内的区域；所述颗粒外部区域指90％半径至颗粒表面范围内的区域。
  2. 根据权利要求1所述的电池正极材料，其特征在于：所述颗粒内部区域的钠含量分布均匀，所述颗粒内部区域的钠含量大于颗粒外部区域的钠含量。
  3. 根据权利要求2所述的电池正极材料，其特征在于：所述电池正极材料的颗粒内部区域的钠含量记为A，颗粒外部区域的钠含量记为a，则满足1<A/a<1.5。
  4. 根据权利要求1所述的电池正极材料，其特征在于：所述电池正极材料的晶体结构空间群由R-3m、R3m、P63/mmc和P63mc中的一种或多种组成。
  5. 根据权利要求4所述的电池正极材料，其特征在于：所述电池正极材料的二次颗粒包括球形结构和类球形结构，所述电池正极材料的粒径Dv50为1μm～20μm，Dv99为10μm～30μm。
  6. 根据权利要求5所述的电池正极材料，其特征在于：所述电池正极材料的比表面积为0.005m 2/g～10m 2/g。
  7. 根据权利要求5所述的电池正极材料，其特征在于：所述电池正极材料的振实密度为1g/cm 3～3g/cm 3，压实密度为2g/cm 3～4g/cm 3。
  8. 根据权利要求1-7任一项所述的电池正极材料，其特征在于：TM选自Mn、Fe、Ni、Li、Cu、Zn、Co和Ti中的至少一种。
  9. 一种钠离子电池，其特征在于：其包括权利要求1-8中任一项所述电池正极材料。
  10. 一种用电设备，其特征在于：包括权利要求9所述钠离子电池，所述钠离子电池作为所述用电设备的供电电源。
PCT/CN2022/143301 2022-08-26 2022-12-29 电池正极材料、钠离子电池和用电设备 WO2024040838A1 (zh)

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