WO2024104240A1 - 一种中高熵层状富锂正极氧化物及其制备方法 - Google Patents

一种中高熵层状富锂正极氧化物及其制备方法 Download PDF

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WO2024104240A1
WO2024104240A1 PCT/CN2023/130595 CN2023130595W WO2024104240A1 WO 2024104240 A1 WO2024104240 A1 WO 2024104240A1 CN 2023130595 W CN2023130595 W CN 2023130595W WO 2024104240 A1 WO2024104240 A1 WO 2024104240A1
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entropy
lithium
medium
positive electrode
layered lithium
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PCT/CN2023/130595
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French (fr)
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孙俊良
蔡国鸿
刘毅丁
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北京大学
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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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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

Definitions

  • the present application relates to the technical field of lithium-ion batteries, and in particular to a medium-high entropy layered lithium-rich positive electrode oxide and a preparation method thereof.
  • Lithium-ion batteries are currently the most widely used energy storage devices, and are used in many fields such as portable devices, grid energy storage, and electric vehicles. With the development of science and technology, people's demand for high-energy-density lithium-ion batteries is becoming increasingly strong.
  • Layered lithium-rich cathode oxide Li 1+x TM 1-x O 2 is a highly potential high-specific-capacity (>250mAh g -1 ) cathode material. In the voltage range of 2.0-4.8V, not only does the transition metal cation undergo redox to contribute capacity, but it also activates oxygen anions to participate in the redox process and contribute additional capacity. However, this type of layered lithium-rich cathode material still has the following problems:
  • the purpose of the present application is to provide a medium-high entropy layered lithium-rich positive electrode oxide and a preparation method thereof to solve the problems raised in the background technology.
  • a medium-high entropy layered lithium-rich positive electrode oxide wherein the chemical formula of the medium-high entropy layered lithium-rich positive electrode oxide is Li 1+x Ni 1-xyz Mn y M z O 2 ,
  • the value range of x, y, and z is: 0.1 ⁇ x ⁇ 0.2, 0.3 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.3, 0.2 ⁇ 1-x-y-z ⁇ 0.35;
  • M is one or more of Co, Al, Ti, Zr, Nb, Mo and W; wherein the configuration entropy S config ⁇ 1.0R of the medium-high entropy layered lithium-rich cathode oxide;
  • S config ⁇ 1.5R When the configuration entropy S config ⁇ 1.5R is satisfied, it is high entropy; when it satisfies 1.0R ⁇ S config ⁇ 1.5R, it is medium entropy; when it satisfies S config ⁇ 1.0R, it is low entropy.
  • the medium-high entropy layered lithium-rich positive electrode oxide is Li 1.15 Ni 0.35 Mn 0.3 Co 0.05 Al 0.05 Ti 0.05 Mo 0.05 O 2 , Li 1.2 Ni 0.3 Mn 0.4 Ti 0.05 Mo 0.05 O 2 , Li 1.15 Ni 0.25 Mn 0.3 Co 0.1 Al 0.1 Ti 0.05 Mo 0.05 O 2 or Li 1.2 Ni 0.3 Mn 0.3 Co 0.05 Al 0.05 Ti 0.05 Mo 0.05 O 2 .
  • the present application also proposes a method for preparing a medium-high entropy layered lithium-rich positive electrode oxide, which comprises the following steps:
  • the soluble salt of lithium is one or more of lithium nitrate and lithium acetate;
  • the soluble salt of nickel is nickel acetate and/or nickel nitrate
  • the soluble salt of manganese is acetate and/or nitrate of manganese.
  • the cobalt source and aluminum source in the soluble salt of element M are one or more mixtures of acetate and nitrate;
  • the titanium source is ammonium titanium oxalate
  • the zirconium source is zirconium oxalate
  • the niobium source is ammonium niobium oxalate
  • the molybdenum source is ammonium molybdate
  • the tungsten source is ammonium tungstate.
  • the molar concentration of the soluble salt of lithium in the clear solution 1 is in excess of 5%.
  • step S02 the molar ratio of the citric acid monohydrate to the metal ions in the clear solution 1 is 1:1.
  • the low-temperature pre-sintering and high-temperature sintering are both heated at a heating rate of 5°C/min.
  • the present application also provides the use of the medium-high entropy layered lithium-rich positive electrode oxide described in the above technical scheme or the medium-high entropy layered lithium-rich positive electrode oxide prepared by the preparation method described in the above technical scheme in lithium-ion batteries.
  • the method of preparing medium-entropy/high-entropy layered lithium-rich cathode materials by multi-element doping has achieved a higher discharge specific capacity at 2.0-4.5V.
  • the additional capacity beyond the theoretical capacity of metal cations can be attributed to the capacity contribution of oxygen anions.
  • the increase in configurational entropy reduces the activation voltage of oxygen anions, reducing their charge cutoff voltage from 4.8V to 4.5V, and improving their compatibility with the electrolyte;
  • the medium-to-high entropy layered lithium-rich cathode material prepared in this application has better structural stability.
  • the multi-element distribution reduces the degree of local order in the structure, inhibits the migration of transition elements and the accompanying adverse structural phase changes during the cycle, and therefore has a slower voltage decay. It also increases the system configuration entropy to reduce the activation voltage of oxygen anions in the layered lithium-rich cathode, thereby obtaining a higher discharge specific capacity at 4.5V.
  • FIG1 is a powder X-ray diffraction comparison diagram of low entropy, medium entropy and high entropy layered lithium-rich positive electrodes in Example 1.
  • FIG. 2 is a charge and discharge curve diagram of the low entropy, medium entropy and high entropy layered lithium-rich positive electrodes in Example 1 at 20 mA g -1 in the voltage range of 2.0-4.5 V.
  • FIG3 is a cycle curve diagram of low entropy, medium entropy and high entropy layered lithium-rich cathodes in Example 1 at 200 mA g -1 in the voltage range of 2.0-4.5 V.
  • FIG. 4 is a graph showing the voltage range of 2.0-4.5 V for low entropy, medium entropy and high entropy layered lithium-rich cathodes in Example 1. Cyclic voltammetry curve at 0.1 mV/s.
  • the process of preparing high entropy layered lithium-rich cathode material Li 1.15 Ni 0.35 Mn 0.3 Co 0.05 Al 0.05 Ti 0.05 Mo 0.05 O 2 by citric acid combustion method includes the following steps:
  • lithium acetate dihydrate (0.0120 mol), nickel acetate tetrahydrate (0.0035 mol), manganese acetate tetrahydrate (0.003 mol), cobalt acetate tetrahydrate (0.0005 mol), aluminum nitrate nonahydrate (0.0005 mol), ammonium titanium oxalate (0.0005 mol), and ammonium molybdate (containing Mo 0.0005 mol) were dissolved in 40 mL of deionized water in sequence to obtain a clear solution 1, in which the molar concentration of the lithium salt was 5% in excess;
  • S04 The gel obtained in S03 was heated at 300°C for 2-3h to fully burn the organic matter to obtain a brown-black fluffy powder. After being fully ground, it was placed in an alumina crucible, which was then placed in a muffle furnace. In an air atmosphere, it was heated to 500°C at a heating rate of 5°C/min and pre-sintered at low temperature for 3h. Subsequently , it was heated to 900°C at a heating rate of 5°C/min and sintered at high temperature for 12h.
  • the layered lithium-rich positive electrode oxide Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2 was obtained by naturally cooling the powder .
  • a citric acid combustion method is also provided to prepare a low-entropy layered lithium-rich cathode material Li 1.2 Ni 0.2 Mn 0.6 O 2 and a medium-entropy layered lithium-rich cathode material Li 1.2 Ni 0.3 Mn 0.4 Ti 0.05 Mo 0.05 O 2 ; the method comprises the following steps:
  • lithium acetate dihydrate (0.0120 mol), lithium acetate tetrahydrate Nickel acetate (0.0030 mol), manganese acetate tetrahydrate (0.0040 mol), ammonium titanium oxalate (0.0005 mol), and ammonium molybdate (containing Mo 0.0005 mol) were dissolved in 40 mL of deionized water to obtain a clear solution B1, in which the molar concentration of lithium salt was 5% excess;
  • S04 The gels A3 and B3 obtained in S03 were heated at 300°C for 2-3h to fully burn the organic matter to obtain brown-black fluffy powder. After being fully ground, they were placed in an alumina crucible, placed in a muffle furnace, and heated to 500°C in an air atmosphere at a heating rate of 5°C/min for low-temperature pre-sintering for 3h. Subsequently, they were heated to 900°C at a heating rate of 5°C/min for high-temperature sintering for 12h.
  • the low-entropy layered lithium-rich positive electrode material Li 1.2 Ni 0.2 Mn 0.6 O 2 and the medium-entropy layered lithium-rich positive electrode material Li 1.2 Ni 0.3 Mn 0.4 Ti 0.05 Mo 0.05 O 2 were obtained by natural cooling.
  • the low-entropy, medium-entropy and high-entropy layered lithium-rich positive electrode oxides prepared in this embodiment are respectively mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1 to prepare slurry and then coated to form positive electrode sheets.
  • a is the low entropy layered lithium-rich cathode oxide Li 1.2 Ni 0.2 Mn 0.6 O 2 in Example 1;
  • b is the medium entropy layered lithium-rich cathode oxide Li 1.2 Ni 0.3 Mn 0.4 Ti 0.05 Mo 0.05 O 2 in Example 1;
  • c is the high entropy layered lithium-rich positive electrode oxide Li 1.15 Ni 0.35 Mn 0.3 Co 0.05 Al 0.05 Ti 0.05 Mo 0.05 O 2 in Example 1.
  • the discharge specific capacities of the low-entropy, medium-entropy, and high-entropy lithium-rich cathodes are 119 mAh g -1 , 182 mAh g -1 , and 183 mAh g -1 , respectively.
  • the discharge specific capacities of the low-entropy, medium-entropy, and high-entropy lithium-rich cathodes are 90 mAh g -1 , 143 mAh g -1 , and 152 mAh g -1 , respectively.
  • the capacity is maintained at The rates are 91.3%, 88.1%, and 85.5% respectively, and the voltage decays are 1.81mV/cycle, 0.81mV/cycle, and 0.32mV/cycle.
  • the theoretical capacity contributed by metal cations in low-entropy, medium-entropy and high-entropy lithium-rich cathodes was calculated to be 126 mAh g -1 , 154 mAh g -1 and 181 mAh g -1 , respectively.
  • the voltages corresponding to low-entropy, medium-entropy and high-entropy lithium-rich cathodes are 4.47 V, 4.26 V and 4.21 V, respectively.
  • the cyclic voltammetry curves show that the medium-entropy lithium-rich cathode and the high-entropy lithium-rich cathode have an oxidation peak at around 4.3 V, corresponding to the oxidation process of oxygen anions, which is not present in the low-entropy lithium-rich cathode.
  • the process of preparing high entropy layered lithium-rich cathode material Li 1.15 Ni 0.25 Mn 0.3 Co 0.1 Al 0.1 Ti 0.05 Mo 0.05 O 2 by citric acid combustion method includes the following steps:
  • S04 The gel obtained in S03 was heated at 300°C for 2-3h to fully burn the organic matter to obtain a brown-black fluffy powder. After being fully ground, it was placed in an alumina crucible and placed in a muffle furnace. In an air atmosphere, it was heated to 450°C at a heating rate of 5°C/min and pre-sintered at low temperature for 3h . Then , it was continued to be heated to 900°C at a heating rate of 5°C/min and sintered at high temperature for 12h .
  • the layered lithium-rich positive electrode oxide Li1.15Ni0.25Mn0.3Co0.1Al0.1Ti0.05Mo0.05O2 was obtained by natural cooling .
  • the high entropy layered lithium-rich positive electrode oxide prepared in this example was mixed with the conductive agent acetylene black and the binder PVDF in a mass ratio of 8:1:1 to prepare a slurry and then coated to form a positive electrode sheet.
  • the constant current charge and discharge test was carried out at a current density of 20mA g -1 , and its discharge specific capacity was 185mAh g -1 , and at a current density of 200mA g -1 , its discharge specific capacity was 138mAh g -1 , and after 100 cycles, the capacity retention rate was 87.6%, and the voltage decay was 0.63mV/cycle.
  • the process of preparing high entropy layered lithium-rich cathode material Li 1.2 Ni 0.3 Mn 0.3 Co 0.05 Al 0.05 Ti 0.05 Mo 0.05 O 2 by citric acid combustion method includes the following steps:
  • lithium acetate dihydrate (0.0126 mol), nickel acetate tetrahydrate (0.003 mol), manganese acetate tetrahydrate (0.003 mol), cobalt acetate tetrahydrate (0.0005 mol), aluminum nitrate nonahydrate (0.0005 mol), ammonium titanium oxalate (0.0005 mol), and ammonium molybdate (containing Mo 0.0005 mol) were dissolved in 40 mL of deionized water in sequence to obtain a clear solution 1, in which the molar concentration of the lithium salt was 5% in excess;
  • S04 The gel obtained in S03 is heated at 300°C for 2-3h to fully burn the organic matter to obtain a brown-black fluffy powder. After being fully ground, it is placed in an alumina crucible and placed in a muffle furnace. In an air atmosphere, it is heated to 500°C at a heating rate of 5°C/min and pre-sintered at low temperature for 3h. Then , it is continued to be heated to 800°C at a heating rate of 5°C/min and sintered at high temperature for 12h.
  • the layered lithium - rich positive electrode oxide Li1.2Ni0.3Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2 is obtained by naturally cooling .
  • the high entropy layered lithium-rich positive electrode oxide prepared in this example was mixed with a conductive agent, acetylene black, and a binder, PVDF, in a mass ratio of 8:1:1 to form a slurry, which was then coated to form a positive electrode sheet.
  • the medium-entropy/high-entropy layered lithium-rich positive electrode materials prepared in the above three examples have higher discharge specific capacity, better capacity retention rate and lower voltage decay rate in the voltage range of 2.0-4.5V.

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Abstract

公开了一种中高熵层状富锂正极氧化物的制备方法，涉及锂离子电池技术领域，该方法包括：将锂、镍和锰的可溶性盐与几种M元素的可溶性盐溶解于去离子水中；将一水柠檬酸溶解于其中并搅拌，使柠檬酸与金属离子发生水解和缩合反应，得到凝胶；将凝胶加热，使有机物充分燃烧，得到蓬松粉体，烧结，自然降温即获得中熵/高熵层状富锂正极氧化物。制备的中熵/高熵层状富锂正极材料具有更好的结构稳定性，多元素分布降低了结构中存在的局域有序程度，抑制了循环过程中发生的过渡元素迁移以及伴随的不利结构相变，因此具有更缓慢的电压衰退,还增加体系构型熵降低层状富锂正极中氧阴离子激活电压，在4.5V下获得更高的放电比容量。

Description

一种中高熵层状富锂正极氧化物及其制备方法
本申请要求于2022年11月14日提交中国专利局、申请号为202211421676.9、发明名称为“一种中高熵层状富锂正极氧化物及其制备方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池技术领域，具体是一种中高熵层状富锂正极氧化物及其制备方法。
背景技术
锂离子电池是目前最广泛使用的储能器件，应用于便携式设备、电网储能、电动汽车等诸多领域。随着科学技术的发展，人们对高能量密度锂离子电池的需求也日益强烈。层状富锂正极氧化物Li1+xTM1-xO2是一种极具潜力的高比容量(＞250mAh g-1)正极材料，在2.0-4.8V的电压区间内，不仅有过渡金属阳离子发生氧化还原贡献容量，而且会激活氧阴离子参与氧化还原过程，贡献额外的容量。然而这类层状富锂正极材料目前仍然存在以下问题：
(1)在4.5V之前基本为过渡金属阳离子贡献容量，而氧阴离子参与氧化需要更高激活电压(通常为4.5-4.8V)，但这个过程一般伴随着不可逆的氧释放，氧气进攻电解液并在正极与电解液的界面处发生副反应，无论是高压还是氧释放都使得富锂正极材料与传统EC/DMC电解液的兼容性差，具有安全隐患；
(2)层状富锂正极材料随着Li+脱出与氧空位的产生，容易诱发过渡金属原子迁移重排，最终发生从层状→尖晶石→岩盐相的不可逆结构相变，伴随着过渡金属的价态还原，多次充放电之后出现明显的电压衰退。
目前大多数的改性策略都聚焦于表面包覆修饰或者体相单掺杂，这些努力在一定程度上减缓了副反应的发生以及相转变过程，但是依然要在高电压下(≥4.6V)才能实现较高容量。
发明内容
本申请的目的在于提供一种中高熵层状富锂正极氧化物及其制备方法，以解决背景技术中提出的问题。
为实现上述目的，本申请提供如下技术方案：
一种中高熵层状富锂正极氧化物，所述中高熵层状富锂正极氧化物的化学式为Li1+xNi1-x-y-zMnyMzO2，
式中，式中x,y,z的取值范围是：0.1≤x≤0.2，0.3≤y≤0.6，0≤z≤0.3，0.2≤1-x-y-z≤0.35；
M为Co、Al、Ti、Zr、Nb、Mo和W元素中的一种或几种；其中，所述中高熵层状富锂正极氧化物的构型熵Sconfig≥1.0R；
当满足构型熵Sconfig≥1.5R时为高熵，当满足1.0R≤Sconfig＜1.5R时为中熵，当满足Sconfig＜1.0R时为低熵。
优选的，所述中高熵层状富锂正极氧化物为Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2、Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2、Li1.15Ni0.25Mn0.3Co0.1Al0.1Ti0.05Mo0.05O2或Li1.2Ni0.3Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2。
本申请实施例还提出了一种中高熵层状富锂正极氧化物的制备方法，该制备方法包括以下步骤：
S01：将锂的可溶性盐、镍的可溶性盐和锰的可溶性盐与几种M元素的可溶性盐溶解于去离子水中，得到澄清溶液一；
S02：将螯合剂一水柠檬酸溶解于所述澄清溶液一中，充分搅拌，得到澄清溶液二；
S03：将所述澄清溶液二在70℃水浴加热搅拌2-3h，使柠檬酸与金属离子充分发生水解、缩合反应，得到凝胶；
S04：将所述凝胶在300℃加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，将所述蓬松粉体充分研磨后置于氧化铝坩埚中，在空气或氧气气氛中，先在450-500℃低温预烧3h，随后继续升温到800-900℃高温烧结12h，自然降温，得到所述中高熵层状富锂正极氧化物。
在上述技术方案的基础上，本申请还提供以下可选技术方案：
优选的，所述锂的可溶性盐为硝酸锂和乙酸锂中的一种或多种；
或所述锂的可溶性盐替换为氢氧化锂。
优选的，所述镍的可溶性盐为镍的乙酸盐和/或镍的硝酸盐；
所述锰的可溶性盐为锰的乙酸盐和/或硝酸盐。
优选的，M元素的可溶性盐中钴源和铝源为乙酸盐、硝酸盐中的一种或多种混合物；钛源为草酸钛铵，锆源为草酸锆，铌源为草酸铌铵，钼源为钼酸铵，钨源为钨酸铵。
优选的，所述澄清溶液一中锂的可溶性盐的摩尔浓度过量5％。
优选的，所述步骤S02中，所述一水柠檬酸与所述澄清溶液一中的金属离子的摩尔比为1:1。
优选的，所述低温预烧和高温烧结均是以5℃/min的升温速率加热。
本申请还提供了上述技术方案所述中高熵层状富锂正极氧化物或上述技术方案所述制备方法制备得到的中高熵层状富锂正极氧化物在锂离子电池中的应用。
相较于现有技术，本申请的有益效果如下：
1、采用多元素掺杂制备中熵/高熵层状富锂正极材料的方法，在2.0-4.5V获得了更高的放电比容量，超出金属阳离子理论容量的额外容量可归因于氧阴离子参与的容量贡献。构型熵增加降低了氧阴离子的激活电压，将其充电截止电压从4.8V降低到4.5V，提高了其与电解液的兼容性；
2、本申请制备的中高熵层状富锂正极材料具有更好的结构稳定性，多元素分布降低了结构中存在的局域有序程度，抑制了循环过程中发生的过渡元素迁移以及伴随的不利结构相变，因此具有更缓慢的电压衰退，还增加体系构型熵降低层状富锂正极中氧阴离子激活电压，在4.5V下获得更高的放电比容量。
附图说明
图1是实施例1中低熵、中熵与高熵层状富锂正极的粉末X射线衍射对比图。
图2是实施例1中低熵、中熵和高熵层状富锂正极在2.0-4.5V电压范围内20mAg-1下的充放电曲线图。
图3是实施例1中低熵、中熵和高熵层状富锂正极在2.0-4.5V电压范围内200mA g-1下的循环曲线图。
图4是实施例1中低熵、中熵和高熵层状富锂正极在2.0-4.5V电压范围 内0.1mV/s下的循环伏安曲线图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。本申请所列举的各实施例仅用以说明本申请，并非用以限制本申请的范围。对本申请所作的任何显而易知的修饰或变更都不脱离本申请的精神与范围。
实施例1
采用柠檬酸燃烧法制备高熵层状富锂正极材料Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2的流程包括如下步骤：
S01：将二水乙酸锂(0.0120mol)、四水乙酸镍(0.0035mol)、四水乙酸锰(0.003mol)、四水乙酸钴(0.0005mol)、九水硝酸铝(0.0005mol)、草酸钛铵(0.0005mol)、钼酸铵(含Mo 0.0005mol)依次溶解于40mL去离子水中，得到澄清溶液一，其中，锂盐的摩尔浓度过量5％；
S02：将螯合剂一水柠檬酸(0.0205mol)溶解于澄清溶液一中，充分搅拌后得到澄清溶液二，其中，一水柠檬酸与金属离子摩尔比为1:1；
S03：将澄清溶液二在70℃温度下水浴加热搅拌2-3h，使柠檬酸与金属充分发生水解、缩合反应，得到凝胶；
S04：将S03中得到的凝胶在300℃下加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，充分研磨后置于氧化铝坩埚中，放置于马弗炉中，在空气气氛中，以5℃/min的升温速率加热到500℃下低温预烧3h，随后继续以5℃/min的升温速率加热到900℃高温烧结12h，自然降温即获得层状富锂正极氧化物Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2。
在本实施例中，还提供一种采用柠檬酸燃烧法，该方法制备了低熵层状富锂正极材料Li1.2Ni0.2Mn0.6O2与中熵层状富锂正极材料Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2；包括以下步骤：
S01：对于Li1.2Ni0.2Mn0.6O2，将二水乙酸锂(0.0120mol)、四水乙酸镍(0.0020mol)、四水乙酸锰(0.0060mol)依次溶解于40mL去离子水中，得到澄清溶液A1，其中，锂盐的摩尔浓度过量5％；
对于Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2，将二水乙酸锂(0.0120mol)、四水 乙酸镍(0.0030mol)、四水乙酸锰(0.0040mol)、草酸钛铵(0.0005mol)、钼酸铵(含Mo 0.0005mol)依次溶解于40mL去离子水中，得到澄清溶液B1，其中，锂盐的摩尔浓度过量5％；
S02：将螯合剂一水柠檬酸(0.0205mol)分别溶解于澄清溶液A1和B1中，充分搅拌后得到澄清溶液A2和B21，其中，一水柠檬酸与金属离子摩尔比为1:1；
S03：将澄清溶液A2和B2分别在70℃温度下水浴加热搅拌2-3h，使柠檬酸与金属充分发生水解、缩合反应，分别得到凝胶A3和B3；
S04：将S03中得到的凝胶A3和B3在300℃下加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，充分研磨后置于氧化铝坩埚中，放置于马弗炉中，在空气气氛中，以5℃/min的升温速率加热到500℃下低温预烧3h，随后继续以5℃/min的升温速率加热到900℃高温烧结12h，自然降温即分别获得低熵层状富锂正极材料Li1.2Ni0.2Mn0.6O2与中熵层状富锂正极材料Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2。
本实施例制备得到的低熵、中熵和高熵层状富锂正极氧化物分别与导电剂乙炔黑、粘结剂PVDF按照质量比8:1:1调配浆料后涂布制成正极片。
参阅附图1-图4，对本实施例制备得到的低熵、中熵和高熵层状富锂正极氧化物的测试如下：其中，在附图1-4中：
a为实施例1中的低熵层状富锂正极氧化物Li1.2Ni0.2Mn0.6O2；
b为实施例1中的中熵层状富锂正极氧化物Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2；
c为实施例1中的高熵层状富锂正极氧化物Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2。
在2.0-4.5V的电压范围下，分别以20mAg-1的电流密度进行恒电流充放电测试和以200mAg-1的电流密度进行稳定性测试。
在20mAg-1的电流密度下，低熵、中熵、高熵富锂正极的放电比容量分别为119mAhg-1、182mAh g-1、183mAh g-1。
在200mAg-1的电流密度下，低熵、中熵、高熵富锂正极的放电比容量分别为90mAhg-1，143mAh g-1，152mAh g-1，100圈循环之后容量保持 率分别为91.3％、88.1％、85.5％，电压衰退为1.81mV/cycle、0.81mV/cycle、0.32mV/cycle。
计算低熵、中熵和高熵富锂正极中金属阳离子贡献的理论容量分别为126mAh g-1，154mAh g-1和181mAh g-1。充电过程中达到上述理论容量时低熵、中熵和高熵富锂正极所对应的电压分别是4.47V，4.26V和4.21V。循环伏安曲线显示，中熵富锂正极与高熵富锂正极在4.3V左右存在一个氧化峰，对应于氧阴离子的氧化过程，这是低熵富锂正极所没有的。
实施例2
柠檬酸燃烧法制备高熵层状富锂正极材料Li1.15Ni0.25Mn0.3Co0.1Al0.1Ti0.05Mo0.05O2的流程包括如下步骤：
S01：将二水乙酸锂(0.0120mol)、四水乙酸镍(0.0025mol)、四水乙酸锰(0.003mol)、四水乙酸钴(0.001mol)、九水硝酸铝(0.001mol)、草酸钛铵(0.0005mol)、钼酸铵(含Mo 0.0005mol)依次溶解于40mL去离子水中，得到澄清溶液一，其中，锂盐的摩尔浓度过量5％；
S02：将螯合剂一水柠檬酸(0.0205mol)溶解于澄清溶液一中，充分搅拌后得到澄清溶液二，其中，一水柠檬酸与金属离子摩尔比为1:1；
S03：将澄清溶液二在70℃温度下水浴加热搅拌2-3h，使柠檬酸与金属充分发生水解、缩合反应，得到凝胶；
S04：将S03中得到的凝胶在300℃下加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，充分研磨后置于氧化铝坩埚中，放置于马弗炉中，在空气气氛中，以5℃/min的升温速率加热到450℃下低温预烧3h，随后继续以5℃/min的升温速率加热到900℃高温烧结12h，自然降温即获得层状富锂正极氧化物Li1.15Ni0.25Mn0.3Co0.1Al0.1Ti0.05Mo0.05O2。
本实例制备得到的高熵层状富锂正极氧化物与导电剂乙炔黑、粘结剂PVDF按照质量比8:1:1调配浆料后涂布制成正极片。在2.0-4.5V的电压范围下，以20mA g-1的电流密度进行恒电流充放电测试，其放电比容量为185mAh g-1，在200mA g-1的电流密度下其放电比容量为138mAh g-1，100圈循环之后容量保持率87.6％，电压衰退为0.63mV/cycle。
实施例3
柠檬酸燃烧法制备高熵层状富锂正极材料Li1.2Ni0.3Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2的流程包括如下步骤：
S01：将二水乙酸锂(0.0126mol)、四水乙酸镍(0.003mol)、四水乙酸锰(0.003mol)、四水乙酸钴(0.0005mol)、九水硝酸铝(0.0005mol)、草酸钛铵(0.0005mol)、钼酸铵(含Mo 0.0005mol)依次溶解于40mL去离子水中，得到澄清溶液一，其中，锂盐的摩尔浓度过量5％；
S02：将螯合剂一水柠檬酸(0.0206mol)溶解于澄清溶液一中，充分搅拌后得到澄清溶液二，其中，一水柠檬酸与金属离子摩尔比为1:1；
S03：将澄清溶液二在70℃温度下水浴加热搅拌2-3h，使柠檬酸与金属充分发生水解、缩合反应，得到凝胶；
S04：将S03中得到的凝胶在300℃下加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，充分研磨后置于氧化铝坩埚中，放置于马弗炉中，在空气气氛中，以5℃/min的升温速率加热到500℃下低温预烧3h，随后继续以5℃/min的升温速率加热到800℃高温烧结12h，自然降温即获得层状富锂正极氧化物Li1.2Ni0.3Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2。
本实例制备得到的高熵层状富锂正极氧化物与导电剂乙炔黑、粘结剂PVDF按照质量比8:1:1调配浆料后涂布制成正极片。
在2.0-4.5V的电压范围下，以20mA g-1的电流密度进行恒电流充放电测试，其放电比容量为188mAh g-1，在200mA g-1的电流密度下其放电比容量为136mAh g-1，100圈循环之后容量保持率81.6％，电压衰退为0.34mV/cycle。
由此可见，上述三个实例所制备得到的中熵/高熵层状富锂正极材料在2.0-4.5V的电压范围下均具有较高的放电比容量、较好的容量保持率以及较低的电压衰退速率。
以上所述仅是本申请的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本申请的保护范围。

Claims (10)

  1. 一种中高熵层状富锂正极氧化物，其特征在于，所述中高熵层状富锂正极氧化物的化学式为Li1+xNi1-x-y-zMnyMzO2，
    式中，式中x,y,z的取值范围是：0.1≤x≤0.2，0.3≤y≤0.6，0≤z≤0.3，0.2≤1-x-y-z≤0.35；
    M为Co、Al、Ti、Zr、Nb、Mo和W元素中的一种或几种；其中，所述中高熵层状富锂正极氧化物的构型熵Sconfig≥1.0R；
    当满足构型熵Sconfig≥1.5R时为高熵，当满足1.0R≤Sconfig＜1.5R时为中熵，当满足Sconfig＜1.0R时为低熵。
  2. 如权利要求1所述中高熵层状富锂正极氧化物，其特征在于，所述中高熵层状富锂正极氧化物为Li1.15Ni0.35Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2、Li1.2Ni0.3Mn0.4Ti0.05Mo0.05O2、Li1.15Ni0.25Mn0.3Co0.1Al0.1Ti0.05Mo0.05O2或Li1.2Ni0.3Mn0.3Co0.05Al0.05Ti0.05Mo0.05O2。
  3. 权利要求1或2所述的中高熵层状富锂正极氧化物的制备方法，其特征在于，包括以下步骤：
    S01：将锂的可溶性盐、镍的可溶性盐和锰的可溶性盐与几种M元素的可溶性盐溶解于去离子水中，得到澄清溶液一；
    S02：将螯合剂一水柠檬酸溶解于所述澄清溶液一中，充分搅拌，得到澄清溶液二；
    S03：将所述澄清溶液二在70℃水浴加热搅拌2-3h，使柠檬酸与金属离子充分发生水解、缩合反应，得到凝胶；
    S04：将所述凝胶在300℃加热2-3h，使有机物充分燃烧，得到棕黑色的蓬松粉体，将所述蓬松粉体充分研磨后置于氧化铝坩埚中，在空气或氧气气氛中，先在450-500℃低温预烧3h，随后继续升温到800-900℃高温烧结12h，自然降温，得到所述中高熵层状富锂正极氧化物。
  4. 根据权利要求3所述的制备方法，其特征在于，所述锂的可溶性盐为硝酸锂和乙酸锂中的一种或多种；
    或所述锂的可溶性盐替换为氢氧化锂。
  5. 根据权利要求3所述的制备方法，其特征在于，所述镍的可溶性盐为镍的乙酸盐和/或镍的硝酸盐；
    所述锰的可溶性盐为锰的乙酸盐和/或硝酸盐。
  6. 根据权利要求3所述的中高熵层状富锂正极氧化物的制备方法，其特征在于，M元素的可溶性盐中钴源和铝源为乙酸盐、硝酸盐中的一种或多种混合物；钛源为草酸钛铵，锆源为草酸锆，铌源为草酸铌铵，钼源为钼酸铵，钨源为钨酸铵。
  7. 根据权利要求3所述制备方法，其特征在于，所述澄清溶液一中锂的可溶性盐的摩尔浓度过量5％。
  8. 根据权利要求3所述的制备方法，其特征在于，所述步骤S02中，所述一水柠檬酸与所述澄清溶液一中的金属离子的摩尔比为1:1。
  9. 根据权利要求3所述的制备方法，其特征在于，所述低温预烧和高温烧结均是以5℃/min的升温速率加热。
  10. 权利要求1或2所述中高熵层状富锂正极氧化物或权利要求3～9任一项所述制备方法制备得到的中高熵层状富锂正极氧化物在锂离子电池中的应用。
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