WO2015027826A1 - 锂离子电池正极材料及其制备方法 - Google Patents

锂离子电池正极材料及其制备方法 Download PDF

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WO2015027826A1
WO2015027826A1 PCT/CN2014/084459 CN2014084459W WO2015027826A1 WO 2015027826 A1 WO2015027826 A1 WO 2015027826A1 CN 2014084459 W CN2014084459 W CN 2014084459W WO 2015027826 A1 WO2015027826 A1 WO 2015027826A1
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source
positive electrode
electrode material
ion battery
lithium ion
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French (fr)
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宋阜
林建雄
谢能建
杨金洪
钱文连
何向明
高剑
王莉
李建军
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清华大学
厦门钨业股份有限公司
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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

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  • the invention relates to a lithium ion battery cathode material and a preparation method thereof.
  • spinel LiMn 2 O 4 has received extensive attention due to its low cost, non-toxicity, high energy density, etc., but LiMn 2 O 4 has poor cycle performance and poor high temperature performance. defect.
  • spinel lithium nickel manganese oxide LiNi 0.5 Mn 1.5 O 4 has received extensive attention due to its excellent performance (theoretical capacity 146.7 mAh/g, discharge platform voltage 4.7 V vs Li/Li + ).
  • LiM x Mn 2 ⁇ x O 4 is liable to cause oxidative decomposition of the electrolyte due to high pressure during the cycle.
  • the appearance of Li x Ni 1-x O impurity phase is likely to occur due to oxygen deficiency, resulting in serious phase change during charge and discharge.
  • the electrochemical performance deteriorates.
  • a lithium ion battery cathode material having a chemical formula of Li x Ni 0.5-y Mg y Mn 1.5 O 4 , 0.95 ⁇ x ⁇ 1.05, and 0.01 ⁇ y ⁇ 0.04.
  • a method for preparing a positive electrode material for a lithium ion battery comprising: respectively providing a nickel (Ni) source, a manganese (Mn) source, and a magnesium (Mg) source soluble in a liquid phase solvent; And a manganese source and a magnesium source are dissolved in the liquid phase solvent to form a mixed solution containing Ni + , Mn 2+ and Mg 2+ , wherein the nickel source, the manganese source and the magnesium source are in accordance with Ni:Mn:Mg
  • the molar concentration ratio is (0.5-y): 1.5:z mixed, and 0.01 ⁇ y ⁇ 0.04, z>y; a precipitant is added to the mixed solution to make the Ni + , Mn 2+ and Mg 2+ Precipitating to obtain a coprecipitate; separating and purifying the coprecipitate from the mixed solution to obtain a precursor Ni (0.5-y)/2 Mg y/2 Mn 0.75 CO 3 , sintering the precursor to obtain a precursor oxide
  • the lithium ion battery cathode material of the present invention and the preparation method thereof can replace Ni by adding an excess of Mg, and achieve atomic mixing of Mg, Ni and Mn by a coprecipitation method, thereby effectively avoiding Li
  • the appearance of 1-x Ni x O heterophase improves cycle performance.
  • the structural stability of the positive electrode material can be improved.
  • the particle size of the positive electrode material of the lithium ion battery is controllable.
  • the preparation method of the positive electrode material of the lithium ion battery has the characteristics of simple method and low cost.
  • FIG. 1 is a flow chart of a method for preparing a positive electrode material for a lithium ion battery according to an embodiment of the present invention.
  • Examples 1-2 and Comparative Examples 1-2 of the present invention are an X-ray diffraction (XRD) spectrum of a positive electrode material synthesized in Examples 1-2 and Comparative Examples 1-2 of the present invention.
  • XRD X-ray diffraction
  • Fig. 3 is a partial enlarged view of Fig. 2;
  • Example 4 is a scanning electron microscope (SEM) image of a positive electrode material LiNi 0.48 Mg 0.02 Mn 1.5 O 4 synthesized in Example 1 of the present invention.
  • Fig. 5 is a graph showing the rate discharge curve of the positive electrode material LiNi 0.48 Mg 0.02 Mn 1.5 O 4 synthesized in Example 1 of the present invention at different current densities.
  • an embodiment of the present invention provides a method for preparing a cathode material for a lithium ion battery, which includes the following steps:
  • S1 providing a nickel (Ni) source, a manganese (Mn) source, and a magnesium (Mg) source soluble in a liquid phase solvent;
  • the nickel source, the manganese source, and the magnesium source are all soluble in the liquid phase solvent.
  • the nickel source, the manganese source and the magnesium source are one of a nitrate, a sulfate, a formate, a hydrochloride, an acetate and a citrate of Ni, Mn and Mg.
  • the liquid phase solvent is a solvent which is easy to evaporate and does not react with the nickel source, the manganese source, and the magnesium source, and the liquid phase solvent may be one or more of water, ethanol, acetone, and propanol, preferably. For water or ethanol.
  • step S2 since precipitates such as magnesium carbonate and magnesium oxalate are slightly soluble in water, magnesium is easily lost during the course of the reaction and during the subsequent washing. Therefore, the addition of an excessive amount of Mg is more advantageous for the formation of a positive electrode material.
  • the total concentration of the Ni + , Mn 2+ , and Mg 2+ in the mixed solution is 0.8 mol/L or more and 3 mol/L or less.
  • the total concentration of Mn 2+ and Mg 2+ facilitate control of the reaction pH range subsequent coprecipitation, and facilitate control of the nucleation rate during the subsequent addition of a precipitating agent and the like. More preferably, the total concentration of the Ni + , Mn 2+ , and Mg 2+ is 1.0 mol/L or more and 2.0 mol/L or less.
  • step S2 by dissolving the nickel source, the manganese source and the magnesium source in the liquid phase solvent, the nickel source, the manganese source and the magnesium source can be atomically mixed, thereby avoiding segregation, agglomeration and different mixing of the solid phase mixing. The problem of large differences in batch stability.
  • the precipitating agent may form an anion in the liquid phase solvent, and the anion may simultaneously react with Ni + , Mn 2+ , and Mg 2+ to form a precipitate insoluble in the liquid phase solvent.
  • the liquid phase, containing the precipitating agent may be CO 3 2-, C 2 O 4 2- and OH - at least one water-soluble substances, such as sodium hydroxide (NaOH), Potassium hydroxide (KOH), sodium carbonate (Na 2 CO 3 ), potassium carbonate (K 2 CO 3 ), sodium oxalate (Na 2 C 2 O 4 ), potassium oxalate (K 2 C 2 O 4 ), oxalic acid (H)
  • 2 C 2 O 4 ) and ammonium oxalate ((NH 4 ) 2 C 2 O 4 ).
  • sodium carbonate is used as a precipitating agent, and the precipitating agent is used, and it is not necessary to add any form of complexing agent such as ammonia water, and it is not necessary to add a shielding gas, and the pollution is small and the cost is low.
  • step S3 may include: formulating the precipitant into a precipitant solution, and uniformly mixing the precipitant solution with the liquid phase solution.
  • the method of mixing may be to drip the precipitant solution into the mixed solution by dropwise addition. During the dropwise addition, stirring may be continued. After the precipitating agent solution is completely added dropwise, it may be stirred for another 4 to 6 hours to sufficiently precipitate Ni + , Mn 2+ and Mg 2+ . Further, the precipitant solution and the mixed solution may be uniformly dropped into a reactor at the same time, and stirring is continued to sufficiently precipitate Ni + , Mn 2+ and Mg 2+ .
  • the amount of the precipitant added can be determined according to the pH value of the reaction system, and generally slightly higher than the metering ratio is more favorable for the complete precipitation of Ni + , Mn 2+ and Mg 2+ . It can be understood that for different nickel sources, manganese sources and magnesium sources, the pH of the mixed solution, the reaction temperature, the stirring speed after the addition of the precipitating agent, and the use of reducing gas protection can be controlled during the coprecipitation. The obtained Ni, Mn, and Mg atoms in the coprecipitate were uniformly mixed.
  • the pH of the mixed solution to which the precipitant is added is controlled to be 8.0 to 8.5, and the reaction temperature is 45 to 50 °C.
  • the coprecipitate may be separated from the liquid phase by a filtration method to obtain the precursor.
  • the precursor may be further washed with deionized water and dried at about 100 ° C for 12 to 18 hours.
  • the precursor has the characteristics of loose structure and large specific surface, thereby facilitating the full diffusion of Li from the void during the subsequent sintering process, thereby making the distribution of Li more uniform.
  • the precursor may be sintered in a sintering furnace in an air atmosphere.
  • the sintering temperature is 450 ° C to 750 ° C, the precursor may be completely decomposed, and the MnO 2 impurity phase may be avoided.
  • oxide precursor having the formula: Ni (0.5-y) / 2 Mg y / 2 Mn 0.75 O.
  • the temperature profile of the sintering may be set to: from room temperature to 450 to 750 ° C; the heating rate may be 3 to 5 ° C / min; and the holding time is set to 4 to 8 hours.
  • the lithium source may be a lithium salt or lithium hydroxide, and the lithium salt may be soluble in water, ethanol or acetone or the like in order to facilitate subsequent wet mixing.
  • the lithium salt may be one or more of lithium nitrate, lithium chloride, lithium sulfate, lithium dihydrogen phosphate, lithium acetate, lithium carbonate, and is not limited to the ones listed. Since lithium generates a small amount of loss during the sintering process, excessive lithium can be added to compensate for the loss of lithium during the sintering process.
  • the lithium source and the precursor oxide are mixed in a molar concentration ratio of Li:(Ni+Mn+Mg) of (0.95-1.05):2.
  • the lithium source and the precursor oxide are mixed in a molar concentration ratio of Li:(Ni+Mn+Mg) of (1.01-1.05):2.
  • the material can achieve a more uniform mixing and the particle breakage is small. Therefore, it is more advantageous to uniformly mix the lithium source with the precursor oxide by wet mixing.
  • the precursor oxide and the lithium source are added to ethanol, and the wet mixture is mixed for about 4 hours; then dried at about 100 ° C; the mixed powder is placed in an air atmosphere sintering furnace. Sintering; after the furnace is cooled, the material is taken out to obtain a cathode material of a lithium ion battery, which has the formula: Li x Ni 0.5-y Mg y Mn 1.5 O 4 .
  • the sintering temperature is 700-900 ° C, which is beneficial to avoid the generation of the heterophase in the generated positive electrode material, and is also beneficial to avoid the lattice defect of the positive electrode material caused by partial lithium loss or the spinel structure of the positive electrode material.
  • the decrease in order is beneficial to improve the capacity, cycle life and rate performance of the lithium ion battery.
  • the temperature profile of the sintering may be set to: room temperature is raised to 700 to 900 ° C; the heating rate is 3 to 5 ° C / min; and the holding time is set to 12 to 20 hours.
  • the invention may further comprise: grinding the material obtained after cooling in step S5, and specifically, grinding method such as breaking, ball milling, jet milling or the like may be used.
  • the method further includes sieving the ground material to remove a part of the material agglomerated by the sintering, and is more advantageous for obtaining a pure phase of Li x Ni 0.5-y Mg y Mn 1.5 O 4 .
  • the nucleation rate and the growth rate can also be controlled by controlling the flow rate of the feed liquid and the solid content in the reaction tank, so that the particle size of the positive electrode material of the lithium ion battery can be controlled.
  • the particle size is controlled in the range of 5-20 ⁇ m.
  • the lithium source is lithium carbonate (Li 2 CO 3 )
  • the nickel source, the magnesium source, and the manganese source are respectively nickel sulfate, magnesium sulfate, and manganese sulfate
  • the liquid solvent is deionized water.
  • the precipitating agent is an aqueous solution of sodium carbonate.
  • nickel sulfate, manganese sulfate and magnesium sulfate are respectively weighed according to a molar ratio of Ni:Mn:Mg of nickel source, manganese source and magnesium source of 0.24:0.75:0.016; the nickel sulfate, magnesium sulfate and sulfuric acid are respectively weighed
  • Manganese is added to deionized water to form a mixed solution containing Ni + , Mn 2+ and Mg 2+ ; sodium monocarbonate solution and the mixed solution are added dropwise to the reaction kettle at a certain speed, and stirred to form a coprecipitate during the reaction.
  • This embodiment is basically the same as the first embodiment except that the molar ratio of Ni:Mn:Mg in the nickel source, manganese source and magnesium source is 0.23:0.75:0.031.
  • This embodiment is basically the same as the first embodiment except that no magnesium source is added.
  • NiO, MnO 2 , MgO, Li 2 CO 3 were weighed according to the molar ratio of Ni:Mn:Mg:Li of 0.24:0.75:0.01:0.5175, and the mixture was wet-mixed with ethanol as the medium for 4 hours.
  • the mixed powder is sintered in an air atmosphere sintering furnace, and the sintering temperature curve is set to: from room temperature to 850 ° C, the heating rate is 5 ° C / min, reaching After 850 ° C, the temperature was kept for 16 hours; after the furnace was cooled, the material was taken out, ground and passed through a 200 mesh screen to obtain LiNi 0.48 Mg 0.02 Mn 1.5 O 4 .
  • the positive electrode material of Example 1-2 does not have a diffraction peak of the Li 1-x Ni x O phase, while the positive electrode material of Comparative Example 1-2 contains Li.
  • the diffraction peak of the 1-x Ni x O phase It can be seen that the formation of the Li 1-x Ni x O impurity phase in the LiNi 0.5-x Mg x Mn 1.5 O cathode material can be effectively avoided by the coprecipitation method of the present invention and by adding an excessive amount of Mg.
  • the prepared positive electrode material particles have a relatively smooth surface, a well-defined boundary, a small particle size, and a high degree of crystal development.
  • LiNi 0.48 Mg 0.02 Mn 1.5 O 4 , LiNi 0.46 Mg 0.04 Mn 1.5 O 4 , LiNi 0.5 Mn 1.5 O 4 and LiNi 0.48 Mg 0.02 Mn 1.5 O 4 were respectively used as positive electrode materials for battery performance test, and it was found that the positive electrode material of the present invention has Good cycle stability.
  • the positive electrode of the test cell includes the following components:
  • the components were thoroughly stirred and mixed to form a slurry, which was applied to the surface of the aluminum foil current collector, and then vacuum dried at 120 ° C for 24 hours.
  • the lithium metal plate was used as the negative electrode, and the Celgard 2400 microporous polypropylene film was used as the separator.
  • the electrolyte was composed of 1 mol/L LiPF6/EC+DMC+DEC (1:1:1 volume ratio) and CR2032 was formed in the argon atmosphere glove box.
  • the button cell battery was tested for battery performance in the range of 3.0V to 4.95V after standing at room temperature for a period of time. The test results are shown in Table 1:
  • the positive electrode material prepared by the method of the present invention has a high specific capacity and cycle retention ratio in a voltage range of 3.0 V to 4.95 V. This is because the present invention can reduce Li 1-x Ni x O by adding an excess amount of Mg, preferably adding 40-70% of Mg beyond the stoichiometric ratio, and achieving atomic mixing of Mg, Ni, and Mn by a coprecipitation method. Phase, improve cycle performance.
  • the structural stability of the positive electrode material is improved, and the positive electrode material is improved at a high voltage and a high temperature. Cycle stability energy.

Abstract

一种锂离子电池正极材料及其制备方法，该正极材料化学通式为LixNi0.5-yMgyMn1.5O4，0.95≤ｘ≤1.05，0.01＜y≤0.04。该正极材料制备方法包括：将一镍源、一锰源及一镁源溶于一液相溶剂中形成一含有Ni+、Mn2+、及Mg2+的混合溶液，其中，所述镍源、锰源及镁源按Ni：Mn：Mg的摩尔浓度比为（0.5-y）：1.5：z混合，且z＞y；在所述混合溶液中加入沉淀剂，使所述Ni+、Mn2+及Mg2+共沉淀，得到一共沉淀物；分离提纯该共沉淀物得到一前驱体，烧结该前驱体，得到一前驱体氧化物，以及；将所述前驱体氧化物与一锂源均匀混合后进行烧结，得到所述正极材料。

Description

锂离子电池正极材料及其制备方法 技术领域
本发明涉及一种锂离子电池正极材料及其制备方法。
背景技术
在锂离子电池诸多正极材料中，尖晶石LiMn2O4以其低成本、无毒、高能量密度等特点受到了广泛的关注，但LiMn2O4存在着循环性能差和高温性能差等缺陷。目前，为克服所述缺陷，研究者采用其它元素部分取代Mn形成LiMxMn2−xO4 (M= Co, Cr, Ni, Fe, Cu等)来改善锂离子电池的性能。其中，尖晶石镍锰酸锂LiNi0.5Mn1.5O4以其优异的性能（理论容量146.7mAh/g，放电平台电压4.7V vs Li/Li+）受到广泛关注。但是，LiMxMn2−xO4在循环过程中容易因高压导致电解液的氧化分解。此外，在合成LiMxMn2−xO4的过程中，当温度高于600℃时，容易出现氧缺陷造成LixNi1-xO杂相的出现，导致充放电过程中相变严重，电化学性能恶化。
发明内容
有鉴于此，确有必要提供一种能抑制LixNi1-xO杂相的锂离子电池正极材料及其制备方法。
一种锂离子电池正极材料，该正极材料的化学通式为LixNi0.5-yMgyMn1.5O4，0.95≤x≤1.05，0.01<y≤0.04。
一种锂离子电池正极材料的制备方法，其包括：分别提供可溶于一液相溶剂的一镍(Ni)源、一锰(Mn)源及一镁(Mg)源；将所述镍源、锰源及镁源溶于所述液相溶剂中形成一含有Ni+、Mn2+及Mg2+的混合溶液，其中，所述镍源、锰源和镁源按照Ni:Mn:Mg的摩尔浓度比为(0.5-y):1.5:z混合，且0.01<y≤0.04，z>y；在所述混合溶液中加入沉淀剂，使所述Ni+、Mn2+及Mg2+共沉淀，得到一共沉淀物；从所述混合溶液中分离提纯该共沉淀物得到前驱体Ni(0.5-y)/2Mgy/2Mn0.75CO3，烧结该前驱体，得到前驱体氧化物Ni(0.5-y)/2Mgy/2Mn0.75O；将该前驱体氧化物与一锂源均匀混合后进行烧结，得到正极材料LixNi0.5- y MgyMn1.5O4，其中，0.95≤x≤1.05。
相较于现有技术，本发明的锂离子电池正极材料及其制备方法，通过加入过量的Mg部分取代Ni，且通过共沉淀法实现Mg、Ni、Mn原子级别的混合，从而可以有效避免Li1-xNixO杂相的出现，提高循环性能。另外，在锂离子电池反应过程中，由于取代部分Ni离子的Mg离子不参加氧化还原反应，故，可以提高该正极材料的结构稳定性。此外，该锂离子电池正极材料的粒径大小可控。该锂离子电池正极材料的制备方法还具有方法简单，成本低廉等特点。
 附图说明
图1是本发明实施例的锂离子电池正极材料制备方法流程图。
图2是本发明实施例1-2及对比例1-2合成的正极材料的X射线衍射(XRD)谱图。
图3是图2的局部放大图。
图4是本发明实施例1合成的正极材料LiNi0.48Mg0.02Mn1.5O4的扫描电镜 (SEM)图。
图5是本发明实施例1合成的正极材料LiNi0.48Mg0.02Mn1.5O4在不同电流密度下的倍率放电曲线。
具体实施方式
以下将结合附图详细说明本发明实施例锂离子电池正极材料及其制备方法。
请参阅图1，本发明实施例提供一种锂离子电池正极材料的制备方法，其包括以下步骤：
S1：提供可溶于一液相溶剂的一镍（Ni）源、一锰（Mn）源及一镁（Mg）源；
S2：将所述镍源、锰源和镁源溶于所述液相溶剂中形成一含有Ni+，Mn2+，及Mg2+的混合溶液，其中，所述镍源、锰源和镁源按照Ni:Mn:Mg的摩尔浓度比为(0.5-y):1.5:z混合，且0.01<y≤0.04，z>y；
S3：在所述混合溶液中加入一沉淀剂，使所述Ni+，Mn2+及Mg2+共沉淀，得到一共沉淀物；
S4: 从所述混合溶液中分离提纯所述共沉淀物得到一前驱体Ni(0.5-y)/2Mgy/2Mn0.75CO3，烧结该前驱体，得到一前驱体氧化物Ni(0.5-y)/2Mgy/2Mn0.75O；以及
S5：将该前驱体氧化物与一锂源均匀混合后进行烧结，得到正极材料LixNi0.5- yMgyMn1.5O4，其中，0.95≤x≤1.05。
在步骤S1中，所述镍源、锰源和镁源均能溶于所述液相溶剂。优选的，所述镍源、锰源和镁源为Ni、Mn及Mg的硝酸盐、硫酸盐、甲酸盐、盐酸盐、醋酸盐以及柠檬酸盐中的一种。所述液相溶剂为易于蒸发、且不与所述镍源、锰源、镁源反应的溶剂，所述液相溶剂可为水、乙醇、丙酮及丙醇中的一种或多种，优选为水或乙醇。
在步骤S2中，由于碳酸镁、草酸镁等沉淀物微溶于水，在反应过程中及后期的洗涤过程中镁容易缺失。故，加入过量的Mg更有利于正极材料的形成。优选地，1.4y≤z≤1.7y。更优选地，1.5y≤z≤1.6y。另外，在步骤S2中，优选地，在所述混合溶液中，所述Ni+、Mn2+以及Mg2+的总浓度大于等于0.8mol/L且小于等于3mol/L。通过控制Ni+、Mn2+以及Mg2+的总浓度，有利于后续共沉淀反应中pH值范围的控制，且有利于控制后续加入沉淀剂时的成核速度等。更优选地，所述Ni+、Mn2+以及Mg2+的总浓度大于等于1.0mol/L且小于等于2.0mol/L。在步骤S2中，通过使镍源、锰源及镁源溶解在液相溶剂中，可以使镍源、锰源及镁源达到原子级混合，从而避免了固相混合的偏析、团聚以及不同混合批次稳定性差异较大的问题。
在步骤S3中，所述沉淀剂可以在所述液相溶剂中形成阴离子，且该阴离子可同时与Ni+、Mn2+及Mg2+反应生成不溶于所述液相溶剂的沉淀。例如，当液相溶剂为水时，该沉淀剂可以是含CO3 2-、C2O4 2-及OH-中至少一种的可溶于水的物质，如氢氧化钠(NaOH)、氢氧化钾(KOH)、碳酸钠(Na2CO3)、碳酸钾(K2CO3)、草酸钠(Na2C2O4)、草酸钾(K2C2O4)、草酸(H2C2O4)和草酸铵((NH4)2C2O4)中的一种或多种。优选地，采用碳酸钠作为沉淀剂，采用该沉淀剂，不需要加入氨水等任何形式的络合剂，也不需要加入保护气体，污染少，成本低。
具体地，步骤S3可包括：将该沉淀剂配制成沉淀剂溶液，并将该沉淀剂溶液与所述液相溶液均匀混合。该混合的方法可以是通过滴加的方式将沉淀剂溶液滴入所述混合溶液中。在滴加的过程中可以不断搅拌，待沉淀剂溶液滴加完全后，可再搅拌4至6小时，使Ni+、Mn2+及Mg2+充分沉淀。另外，还可将沉淀剂溶液与所述混合溶液同时均匀地滴入一反应器中，并不断搅拌使Ni+、Mn2+及Mg2+充分沉淀。沉淀剂的加入量可根据反应体系的pH值来确定，一般略高于计量比更有利于Ni+、Mn2+及Mg2+充分沉淀。可以理解，对于不同的镍源、锰源和镁源，在所述共沉淀的过程中可以通过控制混合溶液的pH值、反应温度、沉淀剂加入后的搅拌速度以及使用还原气体保护等方法来使获得的所述共沉淀物中Ni、Mn及Mg原子均匀地混合。优选地，加入沉淀剂的混合溶液的pH值控制在8.0-8.5，反应温度45℃-50℃。
在步骤S4中，所述共沉淀物可以通过过滤的方法与液相分离，从而获得所述前驱体。另外，可以进一步包括用去离子水清洗该前驱体，并在100℃左右条件下干燥所述前驱体12～18小时。所述前驱体具有结构松散、比表面较大等特点，从而有利于在后面烧结的过程中使Li从空隙中充分扩散进入，进而使Li的分布更加均匀。
所述前驱体可以置于空气氛围的烧结炉中烧结，优选地，所述烧结温度为450℃～750℃，可使所述前驱体完全分解，且避免出现MnO2杂相。有利于烧结后得到纯相的前驱体氧化物，其通式为：Ni(0.5-y)/2Mgy/2Mn0.75O。具体地，烧结的温度曲线可以设定为：由室温升温至450～750℃；升温速率可以为3～5℃/min；保温时间设定为4～8个小时。
在步骤S5中，所述锂源可为一锂盐或氢氧化锂，为了有利于后续的湿法混合，所述锂盐可溶于水、乙醇或丙酮等。优选的，所述锂盐可为硝酸锂、氯化锂、硫酸锂、磷酸二氢锂、醋酸锂、碳酸锂中的一种或多种，且并不限于该所列举的几种。由于在烧结过程中锂会产生少量的损耗，故，加入过量的锂可以用来补偿在烧结过程中锂的损耗。具体地，所述锂源与所述前驱体氧化物按照Li :(Ni+Mn+Mg)的摩尔浓度比为（0.95-1.05）:2混合。优选地，所述锂源与所述前驱体氧化物按照Li:(Ni+Mn+Mg)的摩尔浓度比为（1.01-1.05）:2混合。
由于湿法混合下，物料能实现较均匀的混合，且颗粒破碎情况较小。故，通过湿法混合更有利于使所述锂源与所述前驱体氧化物均匀混合。具体地：将所述前驱体氧化物与所述锂源加入到乙醇中，进行湿法混合物料，混合时间为4h左右；然后在100℃左右烘干；将混合粉末置于空气氛围的烧结炉中烧结；随炉冷却后取出物料，得到锂离子电池正极材料，其通式为：LixNi0.5-yMgyMn1.5O4。优选地，所述烧结温度为700～900℃，有利于避免生成的正极材料中杂相的产生，也有利于避免部分锂损失所引起的正极材料晶格缺陷或正极材料的尖晶石结构有序度的降低，从而有利于提高锂离子电池的容量、循环寿命及倍率性能。具体地，所述烧结的温度曲线可设定为：室温升温至700～900℃；升温速率为3～5℃/min；保温时间设定为12～20个小时。
本发明还可以包括：将步骤S5中冷却后得到的所述物料进行研磨，具体的，可以采用鄂破、球磨、气流粉碎等研磨方法。还可进一步包括将上述研磨后的物料进行过筛处理，筛除部分因上述烧结而结块的物料，更有利于得到纯相的LixNi0.5-yMgyMn1.5O4。
在上述步骤S1-S5中，还可以通过控制料液流速、反应釜中固含量，控制形核速度与长大速度，从而使该锂离子电池正极材料的粒径大小可控。优选的，粒径大小的控制范围为5-20μm。
实施例一：制备LiNi0.48Mg0.02Mn1.5O4
本实施例中，所述锂源为碳酸锂（Li2CO3），所述镍源、镁源和锰源分别为硫酸镍，硫酸镁和硫酸亚锰，所述液相溶剂为去离子水，所述沉淀剂为碳酸钠的水溶液。首先，按照镍源、锰源和镁源中Ni:Mn:Mg的摩尔浓度比0.24：0.75：0.016分别称取硫酸镍、硫酸亚锰及硫酸镁；将所述硫酸镍、硫酸镁及硫酸亚锰加入去离子水中形成一含有Ni+、Mn2+以及Mg2+的混合溶液；将一碳酸钠溶液与所述混合溶液以一定速度滴加入反应釜中，搅拌形成共沉淀物，反应过程中控制pH值在8.0-8.5之间，并控制反应温度在45-50℃之间，确保所述Ni+、Mn2+以及Mg2+完全沉淀；过滤得到一共沉淀物；将所得的共沉淀物用去离子水清洗，并转入鼓风干燥箱在100℃条件下烘干8小时，得到前驱体Ni0.24Mg0.01Mn0.75CO3；将该前驱体Ni0.24Mg0.01Mn0.75CO3置于空气氛围的烧结炉中烧结，其中，烧结的温度曲线设定为：由室温升温至700℃，升温速率为5℃/min，到达700℃后保温6小时；随炉冷却后取出物料，得到前驱体氧化物Ni0.24Mg0.01Mn0.75O；按照Li:(Ni+Mn+Mg)的摩尔浓度比为1.035:2 的比例，分别称取Li2CO3和所述前驱体氧化物Ni0.24Mg0.01Mn0.75O加入到乙醇中混合4h，然后在100℃鼓风干燥箱中烘干得到一混合粉末；将所述混合粉末置于空气氛围的烧结炉中烧结，其中，烧结的温度曲线设定为：由室温升温至850℃，升温速率为5℃/min，到达850℃后保温16小时；最后，随炉冷却后取出物料，研磨、过200 目筛网，得到LiNi0.48Mg0.02Mn1.5O4。
实施例二 ：制备LiNi0.46Mg0.04Mn1.5O4
本实施例与所述实施例1基本相同，其区别在于：所述镍源、锰源和镁源中Ni:Mn:Mg的摩尔浓度比为0.23：0.75：0.031。
对比例一：制备LiNi0.5Mn1.5O4
本实施例与所述实施例1基本相同，其区别在于不添加镁源。
对比例二：LiNi0.48Mg0.02Mn1.5O4
按照Ni:Mn:Mg:Li的摩尔浓度比为0.24:0.75:0.01:0.5175的比例分别称取NiO、MnO2、MgO、Li2CO3，以乙醇为介质进行湿法混合，混合时间4小时；然后在100℃鼓风干燥箱中烘干；将混合粉末置于空气氛围的烧结炉中烧结，烧结的温度曲线设定为：由室温升温至850℃，升温速率为5℃/min，到达850℃后保温16小时；随炉冷却后取出物料，研磨、过200目筛网，得到LiNi0.48Mg0.02Mn1.5O4。
请参阅图2和3，从图中可以看出，实施例1-2中的正极材料并不存在Li1-xNixO相的衍射峰，而对比例1-2的正极材料却含有Li1-xNixO相的衍射峰。可见，采用本发明的共沉淀法，并通过加入过量的Mg可以有效避免LiNi0.5-xMgxMn1.5O正极材料中Li1-xNixO杂相的形成。
请一并参阅图4，由图中可以看出，制得的正极材料颗粒表面比较光滑，且边界分明，粒径较小，晶体发育度高。
将LiNi0.48Mg0.02Mn1.5O4、LiNi0.46Mg0.04Mn1.5O4、LiNi0.5Mn1.5O4及LiNi0.48Mg0.02Mn1.5O4分别作为正极材料进行电池性能测试，发现本发明正极材料具有较好的循环稳定性。
该测试电池的正极包括以下组分：
Figure WO086-appb-I000001
将所述各组分充分搅拌混合形成一浆料，并涂覆于铝箔集流体表面，然后在120℃真空干燥24小时。以金属锂片为负极，Celgard 2400微孔聚丙烯膜为隔膜，以1mol/L LiPF6/EC+DMC+DEC（1:1:1体积比）为电解液，在氩气气氛手套箱中组成CR2032型纽扣电池，在室温下静置一段时间后在3.0V～4.95V范围内进行电池性能测试。测试结果如表1所示：
表1 不同样品的容量与循环性能
Figure WO086-appb-I000002
从表1可以看出，在3.0V～4.95V的电压范围内，采用本发明方法制备的正极材料具有较高的比容量和循环保持率。这是由于本发明通过加入过量的Mg，优选加入超出化学计量比40-70%的Mg，且通过共沉淀法实现Mg、Ni、Mn原子级别的混合，从而可以减少Li1-xNixO相，提高循环性能。另外，在锂离子电池反应过程中，由于取代正极材料中部分Ni离子的Mg离子不参加氧化还原反应，因此提高了该正极材料的结构稳定性，进而提高了该正极材料在高电压和高温下的循环稳定性能。
另外，本领域技术人员还可在本发明精神内作其它变化，当然这些依据本发明精神所作的变化，都应包含在本发明所要求保护的范围内。

Claims (10)

  1. 一种锂离子电池正极材料，其特征在于，该正极材料的化学通式为LixNi0.5-yMgyMn1.5O4，0.95≤x≤1.05，0.01<y≤0.04。
  2. 如权利要求1所述的锂离子电池正极材料，其特征在于，0.02y≤y≤0.03。
  3. 如权利要求1所述的锂离子电池正极材料，其特征在于，x=1，y=0.04或0.02。
  4. 如权利要求1所述的锂离子电池正极材料，其特征在于，所述正极材料的充放电电压范围为3.0V至4.95V。
  5. 一种锂离子电池正极材料的制备方法，包括：
    分别提供可溶于一液相溶剂的一镍（Ni）源、一锰（Mn）源及一镁（Mg）源；
    将所述镍源、锰源和镁源溶于所述液相溶剂中形成一含有Ni+、Mn2+、及Mg2+的混合溶液，其中，所述镍源、锰源和镁源按照Ni:Mn:Mg的摩尔浓度比为(0.5- y):1.5:z混合，且0.01<y≤0.04，z>y；
    在所述混合溶液中加入一沉淀剂，使所述Ni+，Mn2+及Mg2+共沉淀，得到一共沉淀物；
    从所述混合溶液中分离提纯所述共沉淀物得到一前驱体Ni(0.5-y)/2Mgy/2Mn0.75CO3，烧结该前驱体，得到一前驱体氧化物Ni(0.5-y)/2Mgy/2Mn0.75O，以及；
    将所述前驱体氧化物与一锂源均匀混合后进行烧结，得到正极材料LixNi0.5- y MgyMn1.5O4，其中，0.95≤x≤1.05。
  6. 如权利要求5所述的锂离子电池正极材料的制备方法，其特征在于，所述镍源、锰源及镁源为镍、锰和镁的硝酸盐、硫酸盐、甲酸盐、盐酸盐、醋酸盐以及柠檬酸盐中的一种。
  7. 如权利要求5所述的锂离子电池正极材料的制备方法，其特征在于，1.4y≤z≤1.7y。
  8. 如权利要求5所述的锂离子电池正极材料的制备方法，其特征在于，所述混合溶液中Ni+，Mn2+及Mg2+的浓度和大于等于0.8mol/L且小于等于3mol/L。
  9. 如权利要求5所述的锂离子电池正极材料的制备方法，其特征在于，所述锂源与所述前驱体氧化物按照Li:(Ni+Mn+Mg)的摩尔浓度比为(0.95-1.05):2混合。
  10. 如权利要求5所述的锂离子电池正极材料的制备方法，其特征在于，所述前驱体的烧结温度为450℃~750℃，烧结时间为4-8小时。
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CN114956200B (zh) * 2022-03-30 2023-11-14 湖南人文科技学院 一种正极材料的电化学性能调控方法
CN115304109A (zh) * 2022-08-12 2022-11-08 安徽格派新能源有限公司 一种掺杂型球形镍锰二元前驱体的制备方法及应用方法

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