WO2024000337A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

Info

Publication number
WO2024000337A1
WO2024000337A1 PCT/CN2022/102578 CN2022102578W WO2024000337A1 WO 2024000337 A1 WO2024000337 A1 WO 2024000337A1 CN 2022102578 W CN2022102578 W CN 2022102578W WO 2024000337 A1 WO2024000337 A1 WO 2024000337A1
Authority
WO
WIPO (PCT)
Prior art keywords
active material
powder
material layer
electrochemical device
mass percentage
Prior art date
Application number
PCT/CN2022/102578
Other languages
English (en)
French (fr)
Inventor
袁国霞
郎野
徐磊敏
Original Assignee
宁德新能源科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宁德新能源科技有限公司 filed Critical 宁德新能源科技有限公司
Priority to PCT/CN2022/102578 priority Critical patent/WO2024000337A1/zh
Priority to CN202280060044.6A priority patent/CN117941100A/zh
Publication of WO2024000337A1 publication Critical patent/WO2024000337A1/zh

Links

Images

Classifications

    • 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
    • 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
    • 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
    • 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 electrochemical technology, and specifically relates to an electrochemical device and an electronic device.
  • Electrochemical devices such as lithium-ion batteries are widely used in all aspects of today's life due to their advantages such as high operating voltage, long cycle life, environmental protection, and light weight.
  • lithium-ion batteries have developed rapidly in the fields of new energy vehicles and large-scale energy storage.
  • materials such as lithium iron phosphate have excellent They are widely used in cathode materials due to their excellent cycle performance and safety performance.
  • materials such as lithium iron phosphate have much lower energy density, resulting in reduced cruising range of new energy vehicles. Therefore, further research is needed. Research on cathode active materials that improve battery energy density and cycle performance.
  • the purpose of this application is to provide an electrochemical device and an electronic device, aiming to improve the discharge specific capacity of the electrochemical device, make it have higher energy density, and improve its cycle performance.
  • a first aspect of the present application provides an electrochemical device, including: a positive electrode, a negative electrode and an electrolyte.
  • the positive electrode includes a positive active material layer, and the positive active material layer includes a first powder and a second powder, wherein, After the electrochemical device is fully charged, the X-ray diffraction analysis pattern of the positive electrode active material layer has a first diffraction peak at a diffraction angle 2 ⁇ of 17.3° to 19.3°, and a first diffraction peak at a diffraction angle 2 ⁇ of 19.8° to 21.8°.
  • the position has a second diffraction peak, the first powder includes iron element, and the second powder includes manganese element.
  • the first diffraction peak is the diffraction peak corresponding to the second powder
  • the second diffraction peak is the diffraction peak corresponding to the first powder.
  • the second powder with the first diffraction peak can provide a higher gram capacity
  • the first powder with the second diffraction peak can provide good structural stability and charge and discharge reversibility.
  • the two powders It can exert a good synergistic effect in the cathode active material layer, so that the cathode active material layer has high gram capacity, better structural stability and charge and discharge reversibility, improve the discharge specific capacity and energy density of the electrochemical device and improve its cycle performance .
  • the peak intensity I A of the first diffraction peak and the peak intensity I B of the second diffraction peak satisfy: 0 ⁇ I A /I B ⁇ 0.3, preferably, 0.05 ⁇ I A / IB ⁇ 0.25.
  • the peak intensity IA of the first diffraction peak and the peak intensity IB of the second diffraction peak satisfy the above relationship, it means that the structure and content of the second powder satisfy a certain relationship with the structure and content of the first powder. At this time, the structure and content of the second powder satisfy a certain relationship.
  • the second powder and the first powder have better synergy, ensuring ion transmission inside the electrochemical device and improving electrical performance, effectively increasing the discharge specific capacity of the electrochemical device and improving its cycle performance, making it have higher energy density.
  • the mass percentage content of manganese element ⁇ Mn and the mass percentage content of iron element ⁇ Fe satisfy: 0.01% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30% , preferably, 0.05% ⁇ Mn / ⁇ Fe ⁇ 25 %.
  • the electrochemical device has a higher Discharge specific capacity, ⁇ Mn / ⁇ Fe within the above range, can effectively improve the cycle performance of the electrochemical device and increase its discharge specific capacity, making it have a higher energy density.
  • the second powder has a stepped morphology.
  • the second powder with a stepped morphology can better combine with the first powder with an olivine structure, improving the uniformity of the positive active material layer and conducive to the absorption of active ions. Embedding and extracting further enhance the discharge specific capacity of the electrochemical device, making it have a higher energy density.
  • the second powder includes element M, wherein the element M includes at least one of Al, Ti, Cr, Ce, Nb, Y, and Mg.
  • element M can improve the stability of the manganese-oxygen bond, inhibit the dissolution of manganese, and further improve the cycle performance of the electrochemical device; at the same time, element M can also improve the detachability of the second powder.
  • the content of embedded active ions further increases the discharge specific capacity of the electrochemical device, making it have a higher energy density.
  • the mass percentage content ⁇ M of the element M and the mass percentage content ⁇ Mn of the manganese element satisfy: 0.01% ⁇ M / ⁇ Mn ⁇ 4%, preferably, 0.02% ⁇ ⁇ M / ⁇ Mn ⁇ 3.5 %.
  • the ratio of the mass percentage ⁇ M of element M to the mass percentage ⁇ Mn of manganese element is within an appropriate range, which is conducive to further improving the stability of the manganese-oxygen bond and inhibiting the dissolution of manganese element; it is also conducive to making the second powder
  • the content of deintercalable active ions in the body is within a suitable range, further improving the discharge specific capacity of the electrochemical device and improving the cycle performance of the electrochemical device, so that the electrochemical device has a higher energy density.
  • the compacted density of the positive active material layer is 2.0g/cm 3 to 2.8g/cm 3 , preferably 2.2g/cm 3 to 2.6g/cm 3 . Controlling the compaction density of the positive active material layer within an appropriate range is conducive to further improving the cycle performance of the electrochemical device and increasing its specific discharge capacity.
  • the single-sided coating weight of the positive active material layer is 100 mg/1540.25mm 2 to 500mg/1540.25mm 2 , preferably 150mg/1540.25mm 2 to 450mg/1540.25mm 2 . Controlling the single-sided coating weight of the positive active material layer within an appropriate range is conducive to further improving the cycle performance of the electrochemical device and increasing its specific discharge capacity.
  • the electrolyte contains additives, and the additives include at least one of unsaturated carbonate and sulfur-oxygen double bond-containing compounds; based on the quality of the electrolyte, the mass of the additive is The content is 0.01% to 5%.
  • the additive can decompose on the surface of the positive electrode to form an interface protective film, improve the oxidation resistance of the positive electrode active material, and further improve the cycle performance of the electrochemical device; the additive can also be used on the negative electrode active material.
  • the formation of a dense and stable interface film on the surface of the material helps to reduce the ion transmission resistance at the negative electrode interface and further improves the cycle performance of the electrochemical device.
  • the mass percentage of additives in the electrolyte is within an appropriate range, which can effectively improve the cycle performance of the electrochemical device.
  • the unsaturated carbonate includes at least one of vinylene carbonate and ethylene ethylene carbonate;
  • the sulfur-oxygen double bond-containing compound includes at least one of 1,3-propane sultone, propylene sultone and vinylene sulfate;
  • the mass percentage of the additive is 0.05% to 4% based on the mass of the electrolyte.
  • a second aspect of the present application provides an electronic device, which includes the electrochemical device of the first aspect of the present application.
  • the positive active material layer includes a first powder and a second powder.
  • the X-ray diffraction analysis pattern of the positive active material layer has a diffraction angle 2 ⁇ of 17.3° to 19.3°.
  • the first powder includes iron element
  • the second powder includes manganese element.
  • the second powder with the first diffraction peak can provide a higher gram capacity, and the first powder with the second diffraction peak can provide good structural stability and charge and discharge reversibility.
  • the two powders are used in the positive electrode.
  • a good synergistic effect can be exerted in the active material layer, so that the cathode active material layer has high gram capacity, excellent structural stability and charge and discharge reversibility, improves the specific discharge capacity and energy density of the electrochemical device, and improves its cycle performance.
  • Figure 1 is an X-ray diffraction spectrum of the positive electrode active material layer of Example 1.
  • FIG. 2 is an enlarged view of the X-ray diffraction spectrum of the positive electrode active material layer of Example 1.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if the items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • lithium iron phosphate As the cathode material, due to the poor conductivity of lithium iron phosphate, in order to obtain a lithium-ion battery with high capacity, it is generally achieved by reducing the particle size of lithium iron phosphate. However, the particle size of lithium iron phosphate is small. The particle size makes the lithium iron phosphate material less dense, resulting in a lower battery energy density.
  • the inventors have effectively improved the discharge specific capacity of the cathode material and the compaction density of the cathode plate through extensive research, thereby significantly improving the energy density and cycle performance of the electrochemical device.
  • a first aspect of the embodiments of the present application provides an electrochemical device, including any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy.
  • an electrochemical reaction occurs to convert chemical energy into electrical energy.
  • Specific examples thereof include but are not limited to lithium-ion batteries or sodium-ion batteries.
  • the electrochemical device in this application includes: a positive electrode, a negative electrode and an electrolyte.
  • the positive electrode includes a positive active material layer, and the positive active material layer includes a first powder and a second powder, wherein the electrochemical device is After full discharge, the X-ray diffraction analysis pattern of the positive electrode active material layer has a first diffraction peak at a position where the diffraction angle 2 ⁇ is 17.3° to 19.3°, and a second diffraction peak at a position where the diffraction angle 2 ⁇ is 19.8° to 21.8°. peak.
  • a fully discharged electrochemical device refers to charging the electrochemical device at a constant current of 0.2C to 3.65V, then charging at a constant voltage to a current of 0.05C, leaving it for 5 minutes, and then discharging at a constant current of 0.2C to 2.5V. , after two cycles according to the above charge and discharge process, the obtained electrochemical device is in a fully discharged state.
  • the X-ray diffraction analysis pattern of the positive electrode active material layer has the first diffraction peak at the position where the diffraction angle 2 ⁇ is 17.3° to 19.3°, and has the third diffraction peak at the position where the diffraction angle 2 ⁇ is 19.8° to 21.8°.
  • Two diffraction peaks wherein the first diffraction peak is the diffraction peak corresponding to the second powder, and the second diffraction peak is the diffraction peak corresponding to the first powder.
  • the second powder with the first diffraction peak can provide a higher gram capacity, and the first powder with the second diffraction peak can provide good structural stability and charge and discharge reversibility.
  • the two powders can exert a good synergistic effect in the positive active material layer, so that the positive active material layer has high gram capacity, better structural stability and charge and discharge reversibility, improve the discharge specific capacity of the electrochemical device, and make it have higher energy. density, and improve its cycle performance.
  • the first powder includes iron element
  • the second powder includes manganese element
  • the first powder in the positive active material layer includes an olivine structure, which has a relatively stable structure and has a small volume change during the charge and discharge process of the electrochemical device, that is, the insertion and extraction of active ions such as lithium ions has a negative impact on The structure of the first powder has little influence, and it has good charge and discharge reversibility.
  • the second powder in the positive active material layer has a higher gram capacity, which enables the electrochemical device to have a higher specific discharge capacity.
  • the electrochemical device of the present application can give full play to the synergistic effect between the first powder and the second powder in the positive active material layer.
  • the active lithium in the second powder is released from it, and part of the Active lithium can be deposited on the negative electrode, which can effectively compensate for the irreversible loss of active lithium caused by repairing the SEI film on the surface of the negative electrode active material.
  • the remaining active lithium can be embedded into the first powder, effectively improving the cycle performance of the electrochemical device.
  • the peak intensity I A of the first diffraction peak and the peak intensity I B of the second diffraction peak satisfy: 0 ⁇ I A / IB ⁇ 0.3.
  • the peak intensity I A of the first diffraction peak and the peak intensity I B of the second diffraction peak satisfy: 0.05 ⁇ I A /I B ⁇ 0.3, 0.1 ⁇ I A /I B ⁇ 0.3, 0.15 ⁇ I A /I B ⁇ 0.3, 0.2 ⁇ I A /I B ⁇ 0.3, 0.25 ⁇ I A /I B ⁇ 0.3, 0.05 ⁇ I A /I B ⁇ 0.25, 0.1 ⁇ I A /I B ⁇ 0.25 , 0.15 ⁇ I A /I B ⁇ 0.25, 0.2 ⁇ I A /I B ⁇ 0.25, 0.05 ⁇ I A /I B ⁇ 0.2, 0.1 ⁇ I A /I B ⁇ 0.2, 0.15 ⁇ I A /I B ⁇ 0.2 , 0.05 ⁇ I A /I B ⁇ 0.15 ⁇ I A
  • the ratio of the peak intensity I A of the first diffraction peak to the peak intensity I B of the second diffraction peak is related to the structure and content of the second powder and the structure and content of the first powder.
  • the peak intensity I A of the first diffraction peak and the peak intensity I B of the second diffraction peak satisfy the above relationship, it means that the structure and content of the second powder satisfy a certain relationship with the structure and content of the first powder.
  • the second powder has better synergy with the first powder.
  • the active lithium in the second powder can not only effectively compensate for the loss of surface active lithium of the negative active material, but also can be efficiently embedded into the first powder to ensure the battery life.
  • the ion transport inside the chemical device and the improvement of electrical properties can effectively improve the discharge specific capacity of the electrochemical device and improve its cycle performance.
  • the X-ray diffraction analysis pattern of the positive electrode active material layer and the peak intensity of the first diffraction peak and the second diffraction peak have meanings known in the art, and can be tested using methods known in the art. For example, charge a lithium-ion battery to 3.65V at a constant current of 0.2C, then charge at a constant voltage until the current is 0.05C, let it sit for 5 minutes, then discharge it at a constant current of 0.2C to 2.5V, and cycle for two cycles according to the above charging and discharging process ( At this time, the battery is fully discharged).
  • the mass percentage content of manganese element ⁇ Mn and the mass percentage content of iron element ⁇ Fe satisfy: 0.01% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%.
  • the mass percentage of manganese element ⁇ Mn and the mass percentage of iron element ⁇ Fe satisfy: 0.05% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 0.1% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 0.5% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 1% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 5% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 10% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 15% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 20% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 25% ⁇ ⁇ Mn / ⁇ Fe ⁇ 30%, 0.05% ⁇ ⁇ Mn / ⁇ Fe ⁇
  • the mass percentage content of manganese element ⁇ Mn and the mass percentage content of iron element ⁇ Fe respectively represent the mass percentage contents of the second powder and the first powder in the cathode active material layer.
  • the higher the mass percentage content of manganese element ⁇ Mn the higher the mass percentage content of the second powder in the positive active material layer.
  • the electrochemical device has a higher discharge specific capacity. Without intending to be bound by any theory, the inventors found that since the active lithium in the second powder will be detached and deposited to the negative electrode during the cycle of the electrochemical device, the loss of active lithium on the surface of the negative electrode active material is compensated.
  • the positive electrode When the positive electrode is active When the mass percentage of the second powder in the material layer is higher, it can provide more active lithium that can be extracted, which can not only effectively compensate for the loss of active lithium on the surface of the negative active material, but also enable sufficient active lithium recovery. Embedding in the first powder ensures the transmission of active ions, effectively improves the cycle capacity retention rate of the electrochemical device, and improves its cycle performance.
  • the inventor also found that the mass percentage of the second powder should not be too high compared to the first powder.
  • the mass percentage of the second powder is too high, , the amount of lithium it can provide for extraction and compensation will be too much.
  • it exceeds the amount of lithium that can be reintercalated by the positive active material layer the internal resistance will increase and the discharge specific capacity of the electrochemical device will be reduced. Therefore, by controlling the mass percentage of the second powder and the first powder in the cathode active material layer, that is, the mass percentage of manganese element ⁇ Mn and the mass percentage of iron element ⁇ Fe , within the above range , can effectively improve the cycle performance of the electrochemical device and increase its discharge specific capacity, making it have a higher energy density.
  • the second powder has a stepped morphology.
  • the second powder with a stepped morphology can be better combined with the first powder including an olivine structure, improving the uniformity of the positive active material layer and conducive to the absorption of active ions. Intercalation and extraction can further improve the discharge specific capacity of the electrochemical device, making it have a higher energy density.
  • the morphology of the second powder can be measured by the following method: dismantle the lithium-ion battery to obtain the positive electrode piece, dry the positive electrode piece, and use liquid nitrogen to brittle the dried positive electrode piece, and then Using a scanning electron microscope (SEM) to observe the cross section of the positive electrode piece (ie, the cross section in the thickness direction of the positive active material layer), the morphology of the second powder can be observed and analyzed.
  • the second powder includes element M, wherein the element M includes at least one of Al, Ti, Cr, Ce, Nb, Y, and Mg. After element M is added to the second powder, element M can improve the stability of manganese-oxygen bonds.
  • the improvement in the stability of manganese-oxygen bonds can inhibit the dissolution of manganese and further improve the cycle performance of the electrochemical device; at the same time, element M can also Increase the deintercalable lithium content in the second powder so that there is enough lithium in the second powder to deintercalate to compensate for the loss of active lithium on the surface of the negative active material, and at the same time there is still enough active lithium to be embedded back into the positive active material.
  • the discharge specific capacity of the electrochemical device is further improved, making it have a higher energy density.
  • SEM scanning electron microscope
  • the mass percentage ⁇ M of the element M and the mass percentage ⁇ Mn of the manganese element satisfy: 0.01% ⁇ ⁇ M / ⁇ Mn ⁇ 4% .
  • the mass percentage ⁇ M of the element M and the mass percentage ⁇ Mn of the manganese element satisfy: 0.05% ⁇ ⁇ M / ⁇ Mn ⁇ 4%, 0.1% ⁇ ⁇ M / ⁇ Mn ⁇ 4%, 0.5 % ⁇ M / ⁇ Mn ⁇ 4%, 1% ⁇ M / ⁇ Mn ⁇ 4%, 1.5% ⁇ M/ ⁇ Mn ⁇ 4%, 2% ⁇ M/ ⁇ Mn ⁇ 4 % , 2.5 % ⁇ ⁇ M / ⁇ Mn ⁇ 4%, 3% ⁇ ⁇ M / ⁇ Mn ⁇ 4%, 3.5% ⁇ ⁇ M / ⁇ Mn ⁇ 4%, 0.05% ⁇ ⁇ M / ⁇ Mn ⁇ 3.5%, 0.1%
  • the ratio of the mass percentage ⁇ M of element M to the mass percentage ⁇ Mn of manganese element is within an appropriate range, which is conducive to further improving the stability of the manganese-oxygen bond and inhibiting the dissolution of manganese element; it is also conducive to making the second powder
  • the content of deintercalable lithium in the body is within a suitable range, so that there is enough lithium in the second powder to compensate for the loss of active lithium on the surface of the negative active material, and there is also enough active lithium to be embedded back into the positive active material layer. , further improving the discharge specific capacity of the electrochemical device, making it have a higher energy density, and improving the cycle performance of the electrochemical device.
  • the compacted density of the positive active material layer is 2.0g/cm 3 to 2.8g/cm 3 , for example, the compacted density of the positive active material layer is 2.1g/cm 3 , 2.2g/cm 3 , 2.3g/cm 3 , 2.4g/cm 3 , 2.5g/cm 3 , 2.6g/cm 3 , 2.7g/cm 3 or within the range composed of any of the above values.
  • the positive active material layer has a compacted density of 2.2g/cm 3 to 2.6g/cm 3 .
  • the single-sided coating weight of the positive active material layer is 100 mg/1540.25mm 2 to 500 mg/1540.25mm 2 .
  • the single-sided coating weight of the positive active material layer is 100mg/1540.25mm 2 , 150mg/1540.25mm 2 , 200mg/1540.25mm 2 , 250mg/1540.25mm 2 , 3100mg/1540.25mm 2 , 350mg/1540.25mm 2 , 400mg/1540.25mm 2 , 450mg/1540.25mm 2 , 500mg/1540.25mm 2 or within the range of any of the above values.
  • the single-sided coating weight of the positive active material layer is 150 mg/1540.25mm 2 to 450 mg/1540.25mm 2 .
  • the contact between the cathode active materials can be closer, which can increase the compaction density of the cathode active material layer, thereby enabling the electrochemical device to have higher energy Density, controlling the single-sided coating weight and compaction density of the positive active material layer within an appropriate range is conducive to the migration of electrons and active ions, thereby further improving the cycle performance of the electrochemical device and increasing its discharge specific capacity.
  • the compacted density and single-sided coating weight of the positive active material layer have meanings known in the art, and can be tested using methods known in the art. For example, cut the dried positive electrode sheet into 5 pieces with an area of 1540.25mm2 , measure the thickness of the positive electrode piece with a multimeter, record it as d0cm, and use a scraper to scrape off the positive electrode active material layer in the positive electrode piece.
  • the compacted density of the positive electrode active material layer is the average of the compacted density of the positive electrode active material layer among the five positive electrode pieces cut out above.
  • the single-sided coating weight of the positive electrode active material layer is the average mass of the positive electrode active material layer among the five positive electrode pieces cut out above.
  • the first powder includes but is not limited to lithium iron phosphate, a composite material of lithium iron phosphate and carbon.
  • the second powder can be prepared as follows: place MnOOH in a corundum crucible, and heat it to 500°C at a heating rate of 5°C/min in an air atmosphere. And keep the temperature at constant temperature for 1 hour to obtain anhydrous Mn 3 O 4 . Weigh anhydrous Mn 3 O 4 and LiOH at a molar ratio of Li:Mn of 1.05:1. At the same time, add nano-Cr 2 O 3 at an element mass ratio of Cr:Mn of 0.008:1, and use sand grinding equipment. Mix evenly to obtain a mixture precursor.
  • the precursor was placed in a corundum crucible, nitrogen was introduced at a rate of 2m 3 /h, the temperature was raised to 940°C at a heating rate of 5°C/min and maintained at a constant temperature for 10 hours, and then naturally cooled to room temperature to obtain a second powder containing manganese element. body.
  • Mn 3 O 4 can also be replaced by MnO 2 , and the ratio with LiOH is corrected according to the Mn content.
  • the cathode active material layer optionally further includes a conductive agent and a binder.
  • a conductive agent includes, but is not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • binders include, but are not limited to, styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA).
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVB polyvinyl butyral
  • EVA ethylene-vinyl acetate copolymer
  • PVA polyvinyl alcohol
  • the positive electrode is a positive electrode sheet
  • the positive electrode sheet further includes a positive electrode current collector
  • the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or porous metal plate, for example, a foil or porous plate made of metals such as aluminum, copper, nickel, titanium, silver, or alloys thereof.
  • the positive electrode current collector is aluminum foil.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive active material layer is disposed on both surfaces of the positive current collector, if the parameters of the positive active material layer on either surface meet the parameter range of this application, it is considered to fall within the protection scope of this application.
  • the positive electrode sheet can be prepared according to conventional methods in the art. Usually, the first powder, the second powder and the optional conductive agent and binder are dispersed in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry, and the positive electrode slurry is coated Covered on the positive electrode current collector, the positive electrode piece is obtained through drying, cold pressing and other processes.
  • NMP N-methylpyrrolidone
  • the positive electrode sheet of the present application does not exclude other positive active materials besides the first powder and the second powder.
  • the specific types of other positive electrode active materials are not subject to specific restrictions and can be selected according to needs.
  • other positive active materials include, but are not limited to, at least one of lithium manganese phosphate, composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, composite materials of lithium iron manganese phosphate and carbon, and their respective modified compounds. .
  • the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive active material layer.
  • the positive electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. ).
  • the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode active material layer.
  • the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode.
  • the electrolyte contains additives, and the additives include at least one of unsaturated carbonate and sulfur-oxygen double bond-containing compounds.
  • the additives include, but are not limited to, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3- At least one of propane sultone (PS) and propenyl-1,3-sultone (PES).
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • DTD vinyl sulfate
  • ES vinyl sulfite
  • PS propane sultone
  • PES propenyl-1,3-sultone
  • the additive When the additive is added to the electrolyte of the present application, the additive can decompose on the surface of the cathode to form an interface protective film, improve the oxidation resistance of the cathode active material layer, stabilize the structure of the cathode active material, and reduce the gap between the cathode active material layer and the electrolyte.
  • the side reaction effect further improves the cycle performance of the electrochemical device; the additive can also form a dense and stable interface film on the surface of the negative electrode active material, which helps to reduce the ion transmission impedance of the negative electrode interface and can also further improve the electrochemical device. cycle performance.
  • the mass percentage of the additive is 0.01% to 5% based on the mass of the electrolyte.
  • the mass percentage of the additive is 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 4% or any of the above values. within the composition range.
  • the mass percentage of the additive is 0.5% to 3%.
  • the mass percentage of additives in the electrolyte is within a suitable range, which helps to form an interface protective film of suitable thickness on the surface of the material. It also has lower impedance, which is beneficial to improving the cycle performance of the electrochemical device. If the mass percentage of the additive is too small, the interface protective film will be insufficiently formed, affecting the performance of the electrochemical device; if the mass percentage of the additive is too high, the impedance of the electrolyte will increase and the migration of active ions will occur. The rate decreases, affecting the cycle performance of the electrochemical device.
  • the electrolyte also includes organic solvents, lithium salts, and optional other optional electrolyte additives.
  • organic solvents, lithium salts, and other optional electrolyte additives are not specifically limited. , you can choose according to your needs.
  • the lithium salts include, but are not limited to, LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate) , LiFSI (lithium bisfluoromethanesulfonimide), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium triflate), LiDFOB (lithium difluoroxalate borate), LiBOB (lithium dioxalate borate) ), LiPO 2 F 2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlor
  • the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid Dimethyl ester (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate Ester (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), Methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS)
  • EC ethylene carbon
  • the other optional electrolyte additives may include electrolyte additives that can improve certain properties of the battery, such as electrolyte additives that improve battery overcharge performance, electrolyte additives that improve battery high or low temperature performance, etc. .
  • the electrolyte solution can be prepared according to conventional methods in the art.
  • organic solvents, lithium salts, additives, and other optional electrolyte additives can be mixed evenly to obtain an electrolyte.
  • the negative electrode is a negative electrode sheet.
  • the negative electrode sheet may be a metal lithium sheet, or may be an electrode sheet including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the negative active material layer typically includes a negative active material and optional conductive agents, binders, and thickeners.
  • the material, composition and manufacturing method of the negative electrode piece used in this application may include any technology known in the art.
  • negative active material includes, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn- At least one of O alloy, Sn, SnO, SnO 2 , spinel structure Li 4 Ti 5 O 12 , and Li-Al alloy.
  • MCMB mesophase microcarbon beads
  • the conductive agent includes, but is not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • binder includes, but are not limited to, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin (Water- Based on acrylic resin) and at least one of carboxymethyl cellulose.
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVB polyvinyl butyral
  • water-based acrylic resin Water- Based on acrylic resin
  • thickeners include, but are not limited to, sodium carboxymethyl cellulose (CMC).
  • the present application is not limited to the above materials.
  • the negative electrode sheet of the present application can also use other well-known materials that can be used as negative active materials, conductive agents, binders and thickeners.
  • the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • a metal foil or porous metal plate can be used as the negative electrode current collector.
  • the negative electrode current collector is copper foil.
  • the negative electrode piece can be prepared according to conventional methods in the art. Usually, the negative active material and optional conductive agent, binder and thickener are dispersed in a solvent, which can be N-methylpyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry, and the negative electrode slurry is The material is coated on the negative electrode current collector, and the negative electrode piece is obtained through processes such as drying and cold pressing.
  • a solvent which can be N-methylpyrrolidone (NMP) or deionized water
  • the negative electrode sheet of the present application does not exclude other additional functional layers in addition to the negative active material layer.
  • the negative electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. composition).
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative active material layer.
  • the electrochemical device further includes an isolation membrane.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece, and mainly functions to prevent the positive and negative electrodes from short-circuiting, and at the same time, allows active ions to pass through.
  • the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation film.
  • a second aspect of the embodiment of the present application provides an electronic device, which includes the electrochemical device of the first aspect of the embodiment of the present application, wherein the electrochemical device can be used as a power source in the electronic device.
  • the electronic device of the present application is not particularly limited and may be used in any electronic device known in the art.
  • electronic devices may include, but are not limited to, laptop computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders , LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the precursor was placed in a corundum crucible, nitrogen was introduced at a rate of 2 m 3 /h, the temperature was raised to 940°C at a heating rate of 5°C/min and maintained at a constant temperature for 10 hours, and then naturally cooled to room temperature to obtain the second powder.
  • the powder surface has a ladder structure with a width of 600nm to 700nm.
  • a positive electrode piece with a coating thickness of 65 ⁇ m coated with a positive electrode active material layer on one side was obtained.
  • Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides.
  • a negative electrode slurry was obtained, in which the solid content of the negative electrode slurry was 70wt%.
  • the negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil with a thickness of 10 ⁇ m, and the copper foil is dried at 85°C to obtain a negative electrode with a coating thickness of 63 ⁇ m coated with a negative active material layer on one side. Extreme piece.
  • the chain carbonate DEC and the cyclic carbonate EC are mixed at a mass ratio of 2:1 to obtain a base solvent, and then the lithium salt LiPF 6 is added to the base solvent to dissolve and mix evenly to obtain an electrolyte. Among them, based on the mass of the electrolyte, the mass percentage of LiPF 6 is 12.5%. Then add a certain content of additives (at least one of VC, VEC, DTD, PS or PES) to the electrolyte.
  • the coating slurry is evenly coated on one surface of a PP film (provided by Celgard Company) with a thickness of 5 ⁇ m, and dried at 85°C to obtain a single-sided coated isolation film with a coating thickness of 5 ⁇ m. Repeat the above steps on the other surface of the isolation film to obtain an isolation film coated on both sides. Then after drying and cold pressing, the isolation film is obtained.
  • a PP film provided by Celgard Company
  • the positive electrode piece, isolation film and negative electrode piece prepared above are stacked in order, so that the isolation film is between the positive electrode piece and the negative electrode piece to play an isolation role, and the electrode assembly is obtained by winding.
  • the electrode assembly is placed in an aluminum-plastic film packaging bag, dried and then injected with electrolyte. After vacuum packaging, standing, formation, degassing, trimming and other processes, a lithium-ion battery is obtained.
  • the preparation method of the lithium-ion battery is similar to Example 1, except that the relevant parameters in the preparation process of the positive electrode plate and the electrolyte are adjusted.
  • the specific parameters are shown in Table 1. "/" indicates that the corresponding component is not added.
  • the capacity of the second cycle is D0; disassemble the battery, take out the positive electrode piece, soak the positive electrode piece in DMC (dimethyl carbonate) for 30 minutes, remove the electrolyte and by-products on the surface of the positive electrode piece, and then put it in a fume hood After drying for 4 hours, the pole piece is fired into powder at 400°C in a vacuum, and the mass is weighed as m1.
  • Cycle capacity retention rate of lithium-ion battery (%) D1/D01 ⁇ 100%.
  • Tables 1 to 4 give the performance test results of Examples 1 to 38 and Comparative Examples 1 to 3.
  • Figure 1 is the X-ray diffraction spectrum of the positive active material layer of Example 1.
  • the positive active material layer has a first diffraction peak at a position of 17.3° to 19.3° and a first diffraction peak at a position of 19.8 to 21.8°. Has a second diffraction peak. It can be seen from the test results in Table 1 that adding the second powder to the positive active material layer can significantly increase the discharge specific capacity of the lithium-ion battery; and through the synergistic effect between the second powder and the first powder, it can It effectively compensates for the loss of surface active lithium in the negative active material, effectively improves the energy density and cycle capacity retention rate of lithium-ion batteries, and improves the cycle performance of lithium-ion batteries.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

一种电化学装置和电子装置，电化学装置包括正极、负极和电解液，正极包括正极活性材料层，正极活性材料层包括第一粉体和第二粉体，其中，电化学装置经满放后，正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰。电化学装置同时具备高的放电比容量及长的循环寿命。

Description

电化学装置和电子装置 技术领域
本申请属于电化学技术领域，具体涉及一种电化学装置和电子装置。
背景技术
电化学装置如锂离子电池因工作电压高、循环寿命长、绿色环保、质轻等优点，广泛应用在如今生活的各个方面。近年来，锂离子电池更是在新能源汽车和大规模储能领域得到了迅猛发展。随着新能源汽车普及速度的不断加快，更长的续航里程需求对电池的能量密度、循环性能等提出了更高的要求，如在目前的锂离子电池中，磷酸铁锂等材料因具有优异的循环性能和安全性能而被广泛应用于正极材料，但是，磷酸铁锂等材料相比于镍钴锰三元材料，能量密度要低很多，造成新能源汽车的续航时里程减少，因此需进一步研究提高电池能量密度和循环性能的正极活性材料。
发明内容
本申请的目的在于提供一种电化学装置和电子装置，旨在提高电化学装置的放电比容量，使其具有较高的能量密度，和提升其循环性能。
本申请第一方面提供一种电化学装置，包括：正极、负极和电解液，所述正极包括正极活性材料层，所述正极活性材料层包括第一粉体和第二粉体，其中，所述电化学装置经满放后，所述正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰，所述第一粉体包括铁元素，所述第二粉体包括锰元素。第一衍射峰为第二粉体对应的衍射峰，第二衍射峰为第一粉体对应的衍射峰。具有所述第一衍射峰的第二粉体可提供较高的克容量，而具有所述第二衍射峰的第一粉体可提供良好的结构稳定性以及充放电可逆性，两种粉体在正极活性材料层中可发挥良好的协同效应，使正极活性材料层具有高克容量、较优结构稳定性和充放电可逆性，提高电化学装置的放电比容量及能量密度和提升其循环性能。
在本申请任意实施方式中，所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0<I A/I B≤0.3，优选地，0.05≤I A/I B≤0.25。当第一衍射峰的峰强IA与第二衍射峰的峰强I B满足上述关系式时，表明第二粉体的结构及含量和第一粉体的结构及含量满足一定关系，此时第二粉体与第一粉体具有更优的协同作用，保证电化学装置内部的离子传输以及提高电性能，有效提高电化学装置的放电比容量及提升其循环性能，使其具有较高的能量密度。
在本申请任意实施方式中，基于所述正极活性材料层的质量，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.01％≤ω Mn/ω Fe≤30％，优选地，0.05％≤ω Mn/ω Fe≤25％。锰元素的质量百分含量ω Mn越高，说明正极活性材料中第二粉体的质量百分含量较高，基于第二粉体具有较高的克容量，此时电化学装置具有较高的放电比容量，ω Mn/ω Fe在上述范围内，能够有效提升电化学装置的循环性能和提高其放电比容量，使其具有较高的能量密度。
在本申请任意实施方式中，所述第二粉体具有阶梯状形貌。在正极活性材料层中，具有阶梯状形貌的第二粉体能够与具有橄榄石结构的所述第一粉体进行更好的复合，提升正极活性材料层的均匀性，有利于活性离子的嵌入和脱出，进一步提升电化学装置的放电比容量，使其具有较高的能量密度。
在本申请任意实施方式中，所述第二粉体包含元素M，其中，所述元素M包括Al、Ti、Cr、Ce、Nb、Y及Mg中的至少一种。向第二粉体中添加元素M后，元素M可提升锰氧键的稳定性，抑制锰的溶出，进一步提升电化学装置的循环性能；同时，元素M也可以提高第二粉体中可脱嵌的活性离子的含量，进一步提升电化学装置的放电比容量，使其具有较高的能量密度。
在本申请任意实施方式中，基于所述第二粉体的质量，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.01％<ω M/ω Mn≤4％，优选地，0.02％<ω M/ω Mn≤3.5％。元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn之比在合适范围内，有利于进一步提升锰氧键的稳定性，抑制锰元素的溶出；还有利于使第二粉体中可脱嵌的活性离子的含量处于合适范围，进一步提高电化学装置的放电比容量和提升电化学装置的循环性能，使电化学装置具有较高的能量密度。
在本申请任意实施方式中，所述正极活性材料层的压实密度为2.0g/cm 3至2.8g/cm 3，优选为2.2g/cm 3至2.6g/cm 3。将正极活性材料层的压实密度控制在合适的范围内，有利于进一步提升电化学装置的循环性能和提高其放电比容量。
在本申请任意实施方式中，所述正极活性材料层的单面涂布重量为100mg/1540.25mm 2至500mg/1540.25mm 2，优选为150mg/1540.25mm 2至450mg/1540.25mm 2。将正极活性材料层的的单面涂布重量控制在合适的范围内，有利于进一步提升电化学装置的循环性能和提高其放电比容量。
在本申请任意实施方式中，所述电解液包含添加剂，所述添加剂包括不饱和碳酸酯及含硫氧双键化合物中的至少一种；基于所述电解液的质量，所述添加剂的质量百分含量为0.01％至5％。本申请电解液中添加所述添加剂时，所述添加剂可在正极表面分解形成界面保护膜，提高正极活性材料的抗氧化性，进一步提升电化学装置的循环性能；所述添加剂也可在负极活性材料表面形成致密稳定的界面膜，有助于降低负极界面的离子传输阻抗，也可进一步提升电化学装置的循环性能。电解液中添加剂的质量百分含量在合适范围内，可有效提升电化学装置的循环性能。
在本申请任意实施方式中，所述不饱和碳酸酯包括碳酸亚乙烯酯和碳酸乙烯亚乙酯中的至少一种；
在本申请任意实施方式中，所述含硫氧双键化合物包括1,3-丙磺酸内酯、丙烯磺酸内酯及硫酸亚乙烯酯中的至少一种；
在本申请任意实施方式中，基于所述电解液的质量，所述添加剂的质量百分含量为0.05％至4％。
本申请第二方面提供一种电子设备，其包括本申请第一方面的电化学装置。
本申请中，正极活性材料层包括第一粉体和第二粉体，其中，电化学装置经满放后，正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰，第一粉体包括铁元素，第二粉体包括锰元素。具有第一衍射峰的第二粉体可提供较高的克容量，而具有所述第二衍射峰的第一粉体可提供良好的结构稳定性以及充放电可逆性，两种粉体在正极活性材料层中可发挥良好的协同效应，使正极活性材料层具有高克容量、较优结构稳定性和充放电可逆性，提高电化学装置的放电比容量及能量密度和提升其循环性能。
附图说明
图1是实施例1的正极活性材料层的X射线衍射谱。
图2是实施例1的正极活性材料层的X射线衍射谱放大图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合实施例对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。在此所描述的有关实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。基于本申请提供的技术方案及所给出的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
在现有的以磷酸铁锂作为正极材料的锂离子电池中，因磷酸铁锂的导电性差，为获得具有高容量的锂离子电池，一般通过减少磷酸铁锂的粒径实现，但是，较小的粒径使得磷酸铁锂材料的压密较小，造成电池能量密度降低。
为了解决上述问题，发明人通过大量研究有效提高了正极材料的放电比容量和正极极片压实密度，实现显著提升电化学装置的能量密度和循环性能。
电化学装置
本申请实施方式的第一方面提供了一种电化学装置，包括其中发生电化学反应以将化学能与电能互相转化的任何装置，它的具体实例包括但不限于锂离子电池或钠离子电池。
本申请中的电化学装置包括：正极、负极和电解液，所述正极包括正极活性材料层，所述正极活性材料层包括第一粉体和第二粉体，其中，所述电化学装置经满放后，所述正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰。
本申请中，满放态的电化学装置指将电化学装置以0.2C恒流充电至3.65V，然后恒压充电至电流为0.05C，静置5min，然后以0.2C恒流放电至2.5V，按照上述充放电过程循环两次后，得到的电化学装置即为满放态。
本申请的电化学装置中，正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰，其中，第一衍射峰为第二粉体对应的衍射峰，第二衍射峰为第一粉体对应的衍射峰。具有所述第一衍射峰的第二粉体可提供较高的克容量，而具有所述第二衍射峰的第一粉体可提供良好的结构稳定性以及充放电可逆性，两种粉体在正极活性材料层中可发挥良好的协同效应，使正极活性材料层具有高克容量、较优结构稳定性和充放电可逆性，提高电化学装置的放电比容量，使其具有较高的能量密度，和提升其循环性能。
本申请的电化学装置中，第一粉体包括铁元素，第二粉体包括锰元素。本申请中，正极活性材料层中的第一粉体包括橄榄石结构，其结构较稳定，在电化学装置的充放电过程中，体积变化较小，即活性离子如锂离子的嵌入和脱出对第一粉体的结构影响较小，其具有良好的充放电可逆性。正极活性材料层中的第二粉体具有较高的克容量，可使电化学装置具有较高的放电比容量。本申请的电化学装置能够充分发挥正极活性材料层中 第一粉体和第二粉体之间的协同效应，在电化学装置充放电过程中，第二粉体中的活性锂从中脱出，一部分活性锂可沉积在负极，能够有效补偿负极活性材料表面因修补SEI膜造成的活性锂的不可逆损失，其余的活性锂能够嵌入至第一粉体中，有效提升电化学装置的循环性能。
在一些实施方式中，所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0<I A/I B≤0.3。例如，所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0.05≤I A/I B≤0.3，0.1≤I A/I B≤0.3，0.15≤I A/I B≤0.3，0.2≤I A/I B≤0.3，0.25≤I A/I B≤0.3，0.05≤I A/I B≤0.25，0.1≤I A/I B≤0.25，0.15≤I A/I B≤0.25，0.2≤I A/I B≤0.25，0.05≤I A/I B≤0.2，0.1≤I A/I B≤0.2，0.15≤I A/I B≤0.2，0.05≤I A/I B≤0.15或0.05≤I A/I B≤0.1。优选地，所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0.05≤I A/I B≤0.25。
本申请中，第一衍射峰的峰强I A和第二衍射峰的峰强I B的比值与第二粉体的结构及含量和第一粉体的结构及含量相关联。当第一衍射峰的峰强I A与第二衍射峰的峰强I B满足上述关系式时，表明第二粉体的结构及含量和第一粉体的结构及含量满足一定关系，此时第二粉体与第一粉体具有更优的协同作用，第二粉体中的活性锂既能有效补偿负极活性材料表面活性锂的损失，又能够高效嵌入至第一粉体中，保证电化学装置内部的离子传输以及提高电性能，有效提高电化学装置的放电比容量和提升其循环性能。
本申请中，正极活性材料层的X射线衍射分析图谱及第一衍射峰与第二衍射峰的峰强为本领域公知的含义，可采用本领域已知的方法测试。例如，将锂离子电池以0.2C恒流充电至3.65V，然后恒压充电至电流为0.05C，静置5min，然后以0.2C恒流放电至2.5V，按照上述充放电过程循环两圈(此时电池为满放态)，完成后，拆解锂离子电池，取出正极极片，将正极极片浸泡在碳酸二甲酯(DMC)中30分钟，去除正极极片表面的电解液及副产物，然后在通风橱中干燥4小时，用刮刀将干燥后的正极活性材料层刮下，得到正极活性材料层粉末。将正极活性材料层粉末放置在XRD测试仪器(型号布鲁克D8)样品台中，使用2°/min的扫描速率，扫描角度范围10°至90°，得到XRD衍射图，在XRD衍射图中计算正极活性材料第一衍射峰、第二衍射峰的峰位与峰强，得到I A/I B。
在一些实施方式中，基于所述正极活性材料的质量，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.01％≤ω Mn/ω Fe≤30％。例如，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.05％≤ω Mn/ω Fe≤30％，0.1％≤ω Mn/ω Fe≤30％，0.5％≤ω Mn/ω Fe≤30％，1％≤ω Mn/ω Fe≤30％，5％≤ω Mn/ω Fe≤30％，10％≤ω Mn/ω Fe≤30％，15％≤ω Mn/ω Fe≤30％，20％≤ω Mn/ω Fe≤30％，25％≤ω Mn/ω Fe≤30％，0.05％≤ω Mn/ω Fe≤25％，0.1％≤ω Mn/ω Fe≤25％，0.5％≤ω Mn/ω Fe≤25％，1％≤ω Mn/ω Fe≤25％，5％≤ω Mn/ω Fe≤25％，10％≤ω Mn/ω Fe≤25％，15％≤ω Mn/ω Fe≤25％，20％≤ω Mn/ω Fe≤25％，0.05％≤ω Mn/ω Fe≤20％，0.1％≤ω Mn/ω Fe≤20％，0.5％≤ω Mn/ω Fe≤20％，1％≤ω Mn/ω Fe≤20％，5％≤ω Mn/ω Fe≤20％，10％≤ω Mn/ω Fe≤20％，15％≤ω Mn/ω Fe≤20％，0.05％≤ω Mn/ω Fe≤15％，0.1％≤ω Mn/ω Fe≤15％，0.5％≤ω Mn/ω Fe≤15％，1％≤ω Mn/ω Fe≤15％，5％≤ω Mn/ω Fe≤15％，10％≤ω Mn/ω Fe≤15％， 0.05％≤ω Mn/ω Fe≤10％，0.1％≤ω Mn/ω Fe≤10％，0.5％≤ω Mn/ω Fe≤10％，1％≤ω Mn/ω Fe≤10％，5％≤ω Mn/ω Fe≤10％，0.05％≤ω Mn/ω Fe≤5％，0.1％≤ω Mn/ω Fe≤5％，0.5％≤ω Mn/ω Fe≤5％，1％≤ω Mn/ω Fe≤5％，0.05％≤ω Mn/ω Fe≤1％，0.1％≤ω Mn/ω Fe≤1％或0.05％≤ω Mn/ω Fe≤0.1％。优选地，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.05％≤ω Mn/ω Fe≤25％。
本申请中，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe分别代表第二粉体与第一粉体在正极活性材料层中的质量百分含量。锰元素的质量百分含量ω Mn越高，说明正极活性材料层中第二粉体的质量百分含量较高，基于第二粉体具有较高的克容量，此时电化学装置具有较高的放电比容量。并非意在受限于任何理论，发明人发现，由于第二粉体中的活性锂在电化学装置的循环过程中会脱出并沉积到负极，补偿负极活性材料表面活性锂的损失，当正极活性材料层中第二粉体的质量百分含量较高时，其能够提供的可脱出的活性锂较多，不仅能够有效补偿负极活性材料表面活性锂的损失，还使得能够有足够的活性锂回嵌入第一粉体中，保证活性离子的传输，有效提高电化学装置的循环容量保持率，提升其循环性能。
并非意在受限于任何理论，发明人还发现，与第一粉体相比，第二粉体的质量百分含量也不应太高，当第二粉体的质量百分含量太高时，其能够提供的可脱出及补偿的锂就会太多，当其多于正极活性材料层可回嵌的锂的量时，导致内阻增大，会降低电化学装置的放电比容量。因此，通过将第二粉体与第一粉体在正极活性材料层中的质量百分含量，即锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe控制在上述范围内，能够有效提升电化学装置的循环性能和提高其放电比容量，使其具有较高的能量密度。
在一些实施方式中，所述第二粉体具有阶梯状形貌。在正极活性材料层中，具有阶梯状形貌的第二粉体能够与包括橄榄石结构的所述第一粉体进行更好的复合，提升正极活性材料层的均匀性，有利于活性离子的嵌入和脱出，可进一步提高电化学装置的放电比容量，使其具有较高的能量密度。
本申请中，第二粉体的形貌可通过如下方法测量：拆解锂离子电池得到正极极片，将正极极片进行烘干，将烘干后的正极极片使用液氮脆断，然后使用扫描电子显微镜(SEM)观察正极极片的截面(即正极活性材料层厚度方向的截面)，可观察分析第二粉体的形貌。在一些实施方式中，所述第二粉体包含元素M，其中，所述元素M包括Al、Ti、Cr、Ce、Nb、Y及Mg中的至少一种。向第二粉体中添加元素M后，元素M可提升锰氧键的稳定性，锰氧键稳定性的提升可抑制锰的溶出，进一步提升电化学装置的循环性能；同时，元素M也可以提高第二粉体中可脱嵌的锂的含量，使第二粉体中有足够的锂能够脱出而补偿负极活性材料表面活性锂的损失，同时仍有足够的活性锂能够回嵌入正极活性材料层中，进一步提升电化学装置的放电比容量，使其具有较高的能量密度。
拆解锂离子电池得到正极极片，将正极极片进行烘干，将烘干后的正极极片使用液氮脆断得到截面，然后使用扫描电子显微镜(SEM)观察正极极片的截面(即正极活性材料层厚度方向的截面)，可观察分析第二粉体，使用元素分析仪(EDS)分析第二粉 体中M元素的种类和含量以及Mn元素的含量。
在一些实施方式中，基于所述第二粉体的质量，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.01％<ω M/ω Mn≤4％。例如，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.05％≤ω M/ω Mn≤4％，0.1％≤ω M/ω Mn≤4％，0.5％≤ω M/ω Mn≤4％，1％≤ω M/ω Mn≤4％，1.5％≤ω M/ω Mn≤4％，2％≤ω M/ω Mn≤4％，2.5％≤ω M/ω Mn≤4％，3％≤ω M/ω Mn≤4％，3.5％≤ω M/ω Mn≤4％，0.05％≤ω M/ω Mn≤3.5％，0.1％≤ω M/ω Mn≤3.5％，0.5％≤ω M/ω Mn≤3.5％，1％≤ω M/ω Mn≤3.5％，1.5％≤ω M/ω Mn≤3.5％，2％≤ω M/ω Mn≤3.5％，2.5％≤ω M/ω Mn≤3.5％，3％≤ω M/ω Mn≤3.5％，0.05％≤ω M/ω Mn≤3％，0.1％≤ω M/ω Mn≤3％，0.5％≤ω M/ω Mn≤3％，1％≤ω M/ω Mn≤3％，1.5％≤ω M/ω Mn≤3％，2％≤ω M/ω Mn≤3％，2.5％≤ω M/ω Mn≤3％，0.05％≤ω M/ω Mn≤2.5％，0.1％≤ω M/ω Mn≤2.5％，0.5％≤ω M/ω Mn≤2.5％，1％≤ω M/ω Mn≤2.5％，1.5％≤ω M/ω Mn≤2.5％，2％≤ω M/ω Mn≤2.5％，0.05％≤ω M/ω Mn≤2％，0.1％≤ω M/ω Mn≤2％，0.5％≤ω M/ω Mn≤2％，1％≤ω M/ω Mn≤2％，1.5％≤ω M/ω Mn≤2％，0.05％≤ω M/ω Mn≤1.5％，0.1％≤ω M/ω Mn≤1.5％，0.5％≤ω M/ω Mn≤1.5％，1％≤ω M/ω Mn≤1.5％，0.05％≤ω M/ω Mn≤1％，0.1％≤ω M/ω Mn≤1％，0.5％≤ω M/ω Mn≤1％。优选地，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.02％<ω M/ω Mn≤3.5％。
元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn之比在合适范围内，有利于进一步提升锰氧键的稳定性，抑制锰元素的溶出；还有利于使第二粉体中可脱嵌的锂的含量处于合适范围，既能够使第二粉体中有足够的锂补偿负极活性材料表面活性锂的损失，还能有足够的活性锂能够回嵌入正极活性材料层中，进一步提高电化学装置的放电比容量，使其具有较高的能量密度，和提升电化学装置的循环性能。
在一在一些实施方式中，所述正极活性材料层的压实密度为2.0g/cm 3至2.8g/cm 3，例如，所述正极活性材料层的压实密度为2.1g/cm 3，2.2g/cm 3，2.3g/cm 3，2.4g/cm 3，2.5g/cm 3，2.6g/cm 3，2.7g/cm 3或处于以上任何数值所组成的范围内。优选地，所述正极活性材料层的压实密度为2.2g/cm 3至2.6g/cm 3。
在一些实施方式中，所述正极活性材料层的单面涂布重量为100mg/1540.25mm 2至500mg/1540.25mm 2。例如，所述正极活性材料层的单面涂布重量为100mg/1540.25mm 2，150mg/1540.25mm 2，200mg/1540.25mm 2，250mg/1540.25mm 2，3100mg/1540.25mm 2，350mg/1540.25mm 2，400mg/1540.25mm 2，450mg/1540.25mm 2，500mg/1540.25mm 2或处于以上任何数值所组成的范围内。优选地，所述正极活性材料层的单面涂布重量为150mg/1540.25mm 2至450mg/1540.25mm 2。
本申请正极活性材料层中加入阶梯状形貌的第二粉体之后，正极活性材料间的接触可更紧密，能够提升正极活性材料层的压实密度，从而使电化学装置具有较高的能量密度，将正极活性材料层的单面涂布重量及压实密度控制在合适的范围内，有利于电子和活性离子的迁移，从而进一步提升电化学装置的循环性能和提高其放电比容量。
本申请中，正极活性材料层的压实密度和单面涂布重量为本领域公知的含义，可 采用本领域已知的方法测试。例如，将烘干的正极极片裁切面积为1540.25mm 2的极片5片，通过万分尺分别测量正极极片的厚度，记为d0cm，用刮刀刮下正极极片中的正极活性材料层，通过天平称量正极活性材料层的质量，记为m(mg)，即为正极活性材料层1540.25mm 2面积上的质量；通过万分尺测量去除正极活性材料层的正极集流体厚度记为dcm，按照下式计算正极活性材料层的压实密度：压实密度P＝m/[154.025×(d0-d)]。正极活性材料层的压实密度为上述裁切得到的5片正极极片中正极活性材料层压实密度的平均值。正极活性材料层的单面涂布重量为上述裁切得到的5片正极极片中正极活性材料层质量的平均值。
在一些实施方式中，所述第一粉体包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料。
在一些实施方式中，作为示例，所述第二粉体可以采用如下所示的方法进行制备：将MnOOH放置在刚玉坩埚中，在空气气氛下，以5℃/min的升温速率升温至500℃并保持恒温1h，得到无水Mn 3O 4。将无水Mn 3O 4与LiOH按照Li:Mn摩尔为1.05:1的比例进行称取，同时按照Cr:Mn以元素质量比为0.008:1的比例加入纳米Cr 2O 3，使用砂磨设备混合均匀，得到混合物前驱体。将前驱体放置在刚玉坩埚中，以2m 3/h的速度通入氮气，以5℃/min的升温速率升温至940℃并保持恒温10h，自然冷却至室温，得到包括锰元素的第二粉体。其中，Mn 3O 4也可使用MnO 2代替，同时根据Mn含量修正与LiOH的配比。
在一些实施方式中，所述正极活性材料层还可选地包括导电剂和粘结剂。导电剂和粘结剂的具体种类均不受到具体的限制，可根据需求进行选择。作为示例，导电剂包括但不限于导电石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。作为示例，粘结剂包括但不限于丁苯橡胶(SBR)、水性丙烯酸树脂(Water based acrylic resin)、羧甲基纤维素(CMC)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、乙烯-醋酸乙烯酯共聚物(EVA)及聚乙烯醇(PVA)中的至少一种。
本申请中，所述正极为正极极片，所述正极极片还包括正极集流体，所述正极活性材料层设置于所述正极集流体的至少一个表面上。
在一些实施方式中，所述正极集流体可以采用金属箔材或多孔金属板，例如使用铝、铜、镍、钛、银等金属或它们的合金的箔材或多孔板。作为示例，所述正极集流体为铝箔。
在一些实施方式中，正极集流体具有在自身厚度方向相对的两个表面，正极活性材料层设置于正极集流体所述两个相对表面中的任意一者或两者上。当正极活性材料层设置在正极集流体两个表面上时，其中任意一个表面上的正极活性材料层的参数满足本申请的参数范围，即认为落入本申请的保护范围内。
正极极片可以按照本领域常规方法制备。通常将第一粉体、第二粉体及可选的导电剂和粘结剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)，形成均匀的正极浆 料，将正极浆料涂覆在正极集流体上，经烘干、冷压等工序得到正极极片。
本申请的正极极片并不排除除了第一粉体和第二粉体之外的其他正极活性材料。其他正极活性材料的具体种类不受到具体的限制，可根据需求进行选择。作为示例，其他正极活性材料包括但不限于磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的至少一种。
本申请的正极极片并不排除除了正极活性材料层之外的其他附加功能层。例如，在一些实施方式中，本申请的正极极片还包括夹在正极集流体和正极活性材料层之间、设置于正极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的正极极片还包括覆盖在正极活性材料层表面的保护层。
本申请中，所述电解液在正极和负极之间起到传导活性离子的作用。
在一些实施方式中，所述电解液包含添加剂，所述添加剂包括不饱和碳酸酯及含硫氧双键化合物中的至少一种。
作为示例，所述添加剂包括但不限于碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、硫酸乙烯酯(DTD)、硫酸丙烯酯、亚硫酸乙烯酯(ES)、1,3-丙烷磺酸内酯(PS)、丙烯基-1,3-磺酸内酯(PES)中的至少一种。
本申请电解液中添加所述添加剂时，所述添加剂可在正极表面分解形成界面保护膜，提高正极活性材料层的抗氧化性，达到稳定正极活性材料结构及减少正极活性材料层与电解液间的副反应的效果，进一步提升电化学装置的循环性能；所述添加剂也可在负极活性材料表面形成致密稳定的界面膜，有助于降低负极界面的离子传输阻抗，也可进一步提升电化学装置的循环性能。
在一些实施方式中，基于所述电解液的质量，所述添加剂的质量百分含量为0.01％至5％。例如，添加剂的质量百分含量为0.05％，0.1％，0.5％，1％，1.5％，2％，2.5％，3％，3.5％，4％，4.5％，4％或处于以上任何数值所组成的范围内。优选地，所述添加剂的质量百分含量为0.5％至3％。
电解液中添加剂的质量百分含量在合适范围内，有助于材料表面形成合适厚度的界面保护膜，同时具有较低的阻抗，有利于提升电化学装置的循环性能。若添加剂的质量百分含量太少，则会使得界面保护膜成膜不足，影响电化学装置的性能；若添加剂的质量百分含量过高，则会使电解液的阻抗增加，活性离子的迁移速率下降，影响电化学装置的循环性能。
在一些实施方式中，所述电解液还包括有机溶剂、锂盐和可选的其他可选的电解液添加剂，有机溶剂、锂盐和其他可选的电解液添加剂的种类均不受到具体的限制，可根据需求进行选择。
在一些实施方式中，作为示例，所述锂盐包括但不限于LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟 草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的至少一种。上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。
在一些实施方式中，作为示例，所述有机溶剂包括但不限于碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的至少一种。上述有机溶剂可以单独使用一种，也可以同时使用两种或两种以上。可选地，上述有机溶剂同时使用两种或两种以上。
在一些实施方式中，所述其他可选的电解液添加剂可以包括能够改善电池某些性能的电解液添加剂，例如改善电池过充性能的电解液添加剂、改善电池高温或低温性能的电解液添加剂等。
电解液可以按照本领域常规的方法制备。例如，可以将有机溶剂、锂盐、添加剂、其他可选的电解液添加剂混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，将锂盐、添加剂、其他可选的电解液添加剂加入到有机溶剂中混合均匀，得到电解液；或者，先将锂盐加入有机溶剂中，然后再将添加剂、其他可选的电解液添加剂加入有机溶剂中混合均匀，得到电解液。
本申请中，所述负极为负极极片，负极极片可以是金属锂片，也可以是包括负极集流体及设置于负极集流体至少一个表面上的负极活性材料层的电极片。负极活性材料层通常包括负极活性材料以及可选的导电剂、粘结剂和增稠剂。
本申请中使用的负极极片的材料、构成和其制造方法可包括任何现有技术中公知的技术。
负极活性材料的具体种类不受到具体的限制，可根据需求进行选择。作为示例，负极活性材料包括但不限于天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳，软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的Li 4Ti 5O 12、Li-Al合金中的至少一种。
导电剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，导电剂包括但不限于导电石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
粘结剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，粘结剂包括但不限于丁苯橡胶(SBR)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、水性丙烯酸树脂(Water-based acrylic resin)及羧甲基纤维素中的至少一种。
增稠剂的具体种类不受到具体的限制，可根据需求进行选择。作为示例，增稠剂包括但不限于羧甲基纤维素钠(CMC)。
但本申请并不限定于上述材料，本申请的负极极片还可以使用可被用作负极活性材料、导电剂、粘结剂和增稠剂的其它公知材料。
在一些实施方式中，负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置于负极集流体所述两个相对表面中的任意一者或两者上。
负极集流体可以使用金属箔材或多孔金属板，例如使用铜、镍、钛、铁等金属或它们的合金的箔材或多孔板。作为示例，负极集流体为铜箔。
负极极片可以按照本领域常规方法制备。通常将负极活性材料及可选的导电剂，粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压等工序得到负极极片。
本申请的负极极片并不排除除了负极活性材料层之外的其他附加功能层。例如，在某些实施方式中，本申请的负极极片还包括夹在负极集流体和负极活性材料层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还包括覆盖在负极活性材料层表面的保护层。
本申请中，所述电化学装置还包括隔离膜。所述隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯、聚偏氟乙烯中的一种或几种，但不仅限于这些。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。
电子装置
本申请实施方式的第二方面提供了一种电子装置，其包括本申请实施方式第一方面的电化学装置，其中，所述电化学装置可在所述电子设备中作为电源使用。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施方式中，电子装置可以包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
下述实施例更具体地描述了本发明公开的内容，这些实施例仅仅用于阐述性说明，因为在本发明公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。
除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
第二粉体的制备
将MnOOH放置在刚玉坩埚中，在空气气氛下，以5℃/min的升温速率升温至500℃并保持恒温1h，得到无水Mn 3O 4。将无水Mn 3O 4与LiOH按照Li:Mn摩尔为1.05:1的比例进行称取，同时按照Cr:Mn以元素质量比为0.0213:1的比例加入纳米Cr 2O 3，使用砂磨设备混合均匀，得到混合物前驱体。将前驱体放置在刚玉坩埚中，以2m 3/h的速度通入氮气，以5℃/min的升温速率升温至940℃并保持恒温10h，自然冷却至室温，得到第二粉体，第二粉体表面具有宽度为600nm至700nm的阶梯结构。
正极极片的制备
将第一粉体磷酸铁锂、上述合成的第二粉体、导电剂Super P、粘结剂聚偏二氟乙烯按照质量比为88.32:7.68:2.4:1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系成均一状，获得正极浆料，其中正极浆料的固含量为70wt％。将正极浆料均匀涂覆于厚度为10μm的正极集流体铝箔的一个表面上，将铝箔在85℃下烘干，
得到涂层厚度为65μm的单面涂覆有正极活性材料层的正极极片。在铝箔的另一个表面上重复以上步骤，即得到双面涂布正极活性材料层的正极极片。然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4h，得到规格为74mm×867mm的正极极片。
负极极片的制备
将负极活性材料人造石墨、导电剂Super P、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按照质量比为96.4:1.5:0.5:1.6进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料，其中负极浆料的固含量为70wt％。将负极浆料均匀涂覆于厚度为10μm的负极集流体铜箔的一个表面上，将铜箔在85℃下烘干，得到涂层厚度为63μm的单面涂覆有负极活性材料层的负极极片。在铝箔的另一个表面上重复以上步骤，即得到双面涂布负极活性材料层的负极极片。然后经过冷压、裁片、分切后，在120℃的真空条件下干燥12h，得到规格为79mm×972mm的负极极片。
电解液的制备
将链状碳酸酯DEC和环状碳酸酯EC按照质量比2:1混合得到基础溶剂，然后向基础溶剂中加入锂盐LiPF 6溶解并混合均匀得到电解液。其中，基于电解液的质量，LiPF 6的质量百分含量为12.5％。再向电解液中加入一定含量的添加剂(VC、VEC、DTD、PS或PES中的至少一种)。
隔离膜的制备
将水性聚偏二氟乙烯、三氧化二铝、聚丙烯按照质量比为1:8:1混合，加入去离子水中，搅拌得到固含量为50wt％的涂层浆料。将涂层浆料均匀涂覆在厚度为5μm的PP薄膜(Celgard公司提供)的一个表面，在85℃下烘干，得到涂层厚度为5μm的单面涂覆有涂层的隔离膜。在隔离膜的另一个表面上重复以上步骤，即得到双面涂布涂层的隔离膜。然后经过烘干、冷压，得到隔离膜。
锂离子电池的制备
将上述制备得到的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片中间以起到隔离的作用，卷绕得到电极组件。将电极组件置于铝塑膜包装袋中，干燥后注入电解液，经过真空封装、静置、化成、脱气、切边等工序得到锂离子电池。
实施例2至38和对比例1至3
锂离子电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和电解液制备过程中的相关参数，具体参数详见表1，“/”表示未加入对应的组分。
测试部分
(1)锂离子电池的放电比容量测试
将锂离子电池以0.2C恒流充电至3.65V，然后恒压充电至电流为0.05C，静置5min，然后以0.2C恒流放电至2.5V，按照上述充放电过程，循环两圈，记录第二圈的容量为D0；拆解电池，取出正极极片，将正极极片浸泡在DMC(碳酸二甲酯)中30分钟，去除正极极片表面的电解液及副产物，然后在通风橱中干燥4小时，将极片真空中400℃烧成粉状，称取质量为m1。
锂离子电池的放电比容量＝D0/m1。
(2)锂离子电池的循环性能测试
将锂离子电池在25℃下以1C恒流充电至3.65V，然后恒压充电至电流为0.05C，静置5min，然后以1C恒流放电至2.5V，此为一圈充放电循环，并测试记录此时的放电容量为D01；按照上述充放电过程使锂离子电池进行3000圈循环，测试记录第3000圈循环的放电容量为D1。
锂离子电池的循环容量保持率(％)＝D1/D01×100％。
表1至表4给出实施例1至38和对比例1至3的性能测试结果。
表1
Figure PCTCN2022102578-appb-000001
Figure PCTCN2022102578-appb-000002
图1是实施例1的正极活性材料层的X射线衍射谱，从图1中可以看出，正极活性材料层在17.3°至19.3°的位置具有第一衍射峰，在19.8至21.8°的位置具有第二衍射峰。从表1的测试结果可知，在正极活性材料层中加入第二粉体后，能够显著提高锂离子电池的放电比容量；而且通过第二粉体与第一粉体之间的协同效应，能够有效补偿负极活性材料表面活性锂的损失，有效提高锂离子电池的能量密度和循环容量保持率，提升锂离子电池的循环性能。
表2
Figure PCTCN2022102578-appb-000003
从表2的测试结果还可知，通过向正极活性材料层中添加元素M，并将其含量控制在合适范围内，能够进一步提高锂离子电池的放电比容量及提升其循环性能。
表3
Figure PCTCN2022102578-appb-000004
从表3的测试结果还可知，通过对正极活性材料层的压实密度和单面涂布重量进行合理控制，能够进一步提高锂离子电池的能量密度和提升其循环性能，从而使锂离子电池能够具有高的放电比容量和长的循环寿命。
表4
  添加剂的种类 添加剂的含量(％) 25℃ 3000圈循环保持率(％)
实施例5 VC / 94.36
实施例27 VC 2.50 95.45
实施例28 VC 1.50 95.73
实施例29 VC 3.00 95.21
实施例30 VC 4.50 94.86
实施例31 VC 0.05 94.58
实施例32 VEC 1.50 95.35
实施例33 PS 1.50 95.57
实施例34 PES 1.50 95.78
实施例35 DTD 1.50 95.41
实施例36 VC+PES 1.00+0.50 96.32
实施例37 VC+DTD 1.00+1.50 95.86
实施例38 VC+PS 1.50+1.00 95.49
从表4的测试结果还可知，电解液包含添加剂时，有利于锂离子电池首圈充放电后形成更加均匀且具有低阻抗的界面保护膜，提高正极活性材料的抗氧化性，阻止电解液与正极活性材料层间的副反应，从而进一步提升锂离子电池的循环性能。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (10)

  1. 一种电化学装置，包括：
    正极、负极和电解液，
    所述正极包括正极活性材料层，所述正极活性材料层包括第一粉体和第二粉体，
    其中，所述电化学装置经满放后，所述正极活性材料层的X射线衍射分析图谱在衍射角2θ为17.3°至19.3°的位置具有第一衍射峰，在衍射角2θ为19.8°至21.8°的位置具有第二衍射峰，
    所述第一粉体包括铁元素，所述第二粉体包括锰元素。
  2. 根据权利要求1所述的电化学装置，其中，所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0<I A/I B≤0.3。
  3. 根据权利要求1所述的电化学装置，其中，基于所述正极活性材料层的质量，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.01％≤ω Mn/ω Fe≤30％。
  4. 根据权利要求1所述的电化学装置，其中，所述第二粉体满足条件(1)至(2)中的至少一者：
    (1)所述第二粉体包含元素M，其中，所述元素M包括Al、Ti、Cr、Ce、Nb、Y及Mg中的至少一种；
    (2)所述第二粉体具有阶梯状形貌。
  5. 根据权利要求4所述的电化学装置，其中，基于所述第二粉体的质量，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.01％<ω M/ω Mn≤4％。
  6. 根据权利要求1所述的电化学装置，其中，所述正极活性材料层满足条件(3)至(4)中的至少一者：
    (3)所述正极活性材料层的压实密度为2.0g/cm 3至2.8g/cm 3；
    (4)所述正极活性材料层的单面涂布重量为100mg/1540.25mm 2至500mg/1540.25mm 2。
  7. 根据权利要求1所述的电化学装置，其中，所述电解液包含添加剂，所述添加剂包括不饱和碳酸酯及含硫氧双键化合物中的至少一种；
    基于所述电解液的质量，所述添加剂的质量百分含量为0.05％至5％。
  8. 根据权利要求7所述的电化学装置，其中，所述添加剂满足条件(5)至(6)中的至少一者：
    (5)所述不饱和碳酸酯包括碳酸亚乙烯酯和碳酸乙烯亚乙酯中的至少一种；
    (6)所述含硫氧双键化合物包括1,3-丙磺酸内酯、丙烯磺酸内酯及硫酸亚乙烯酯中的至少一种；
  9. 根据权利要求1-8中任一项所述的电化学装置，满足条件(7)至(12)中的至少一者：
    (7)所述第一衍射峰的峰强I A与所述第二衍射峰的峰强I B满足：0.05≤I A/I B≤0.25；
    (8)基于所述正极活性材料层的质量，锰元素的质量百分含量ω Mn与铁元素的质量百分含量ω Fe满足：0.05％≤ω Mn/ω Fe≤25％；
    (9)基于所述第二粉体的质量，所述元素M的质量百分含量ω M与锰元素的质量百分含量ω Mn满足：0.02％<ω M/ω Mn≤3.5％；
    (10)所述正极活性材料层的压实密度为2.2g/cm 3至2.6g/cm 3；
    (11)所述正极活性材料层的单面涂布重量为150mg/1540.25mm 2至450mg/1540.25mm 2；
    (12)基于所述电解液的质量，所述添加剂的质量百分含量为0.5％至3％。
  10. 一种电子装置，包括权利要求1-9中任一项所述的电化学装置。
PCT/CN2022/102578 2022-06-30 2022-06-30 电化学装置和电子装置 WO2024000337A1 (zh)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/CN2022/102578 WO2024000337A1 (zh) 2022-06-30 2022-06-30 电化学装置和电子装置
CN202280060044.6A CN117941100A (zh) 2022-06-30 2022-06-30 电化学装置和电子装置

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/102578 WO2024000337A1 (zh) 2022-06-30 2022-06-30 电化学装置和电子装置

Publications (1)

Publication Number Publication Date
WO2024000337A1 true WO2024000337A1 (zh) 2024-01-04

Family

ID=89383503

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/102578 WO2024000337A1 (zh) 2022-06-30 2022-06-30 电化学装置和电子装置

Country Status (2)

Country Link
CN (1) CN117941100A (zh)
WO (1) WO2024000337A1 (zh)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1645654A (zh) * 2005-01-19 2005-07-27 天津大学 一种锂二次电池正极活性材料及其制备方法
US20100129715A1 (en) * 2007-03-22 2010-05-27 Sanyo Electric Co., Ltd. Nonaqueous electrolyte secondary battery
US20150214543A1 (en) * 2014-01-27 2015-07-30 Samsung Sdi Co., Ltd. Positive active material, lithium battery including the same, and method of manufacturing the positive active material
CN109638291A (zh) * 2018-12-27 2019-04-16 清远佳致新材料研究院有限公司 一种正极浆料、制备方法以及正极片和锂离子电池
JP2020167172A (ja) * 2020-06-24 2020-10-08 古河機械金属株式会社 リチウムイオン電池用正極活物質、正極材料、正極、およびリチウムイオン電池
CN113597693A (zh) * 2020-10-15 2021-11-02 宁德新能源科技有限公司 正极材料、电化学装置和电子设备

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1645654A (zh) * 2005-01-19 2005-07-27 天津大学 一种锂二次电池正极活性材料及其制备方法
US20100129715A1 (en) * 2007-03-22 2010-05-27 Sanyo Electric Co., Ltd. Nonaqueous electrolyte secondary battery
US20150214543A1 (en) * 2014-01-27 2015-07-30 Samsung Sdi Co., Ltd. Positive active material, lithium battery including the same, and method of manufacturing the positive active material
CN109638291A (zh) * 2018-12-27 2019-04-16 清远佳致新材料研究院有限公司 一种正极浆料、制备方法以及正极片和锂离子电池
JP2020167172A (ja) * 2020-06-24 2020-10-08 古河機械金属株式会社 リチウムイオン電池用正極活物質、正極材料、正極、およびリチウムイオン電池
CN113597693A (zh) * 2020-10-15 2021-11-02 宁德新能源科技有限公司 正极材料、电化学装置和电子设备

Also Published As

Publication number Publication date
CN117941100A (zh) 2024-04-26

Similar Documents

Publication Publication Date Title
WO2020187106A1 (en) Anode material, anode and electrochemical device comprising anode material
US20230282836A1 (en) Lithium metal negative electrode plate, electrochemical apparatus, and electronic device
US20200243907A1 (en) Electrolyte and electrochemical device
EP4120418B1 (en) Lithium-ion secondary battery, battery module, battery pack, and electrical device
WO2023015489A1 (zh) 一种电化学装置及电子装置
WO2023087213A1 (zh) 一种电池包及其用电装置
CN114824165B (zh) 负极极片、电化学装置及电子设备
WO2023070989A1 (zh) 电化学装置和包含其的电子装置
WO2022061582A1 (zh) 电解液、电化学装置及电子装置
CN108695487B (zh) 正极片及储能装置
EP4207385A2 (en) Electrochemical apparatus and electronic apparatus including same
CN117174873A (zh) 正极材料的制备方法、正极材料、正极极片、钠离子电池和用电装置
WO2022198651A1 (zh) 一种正极极片、包含该正极极片的电化学装置和电子装置
CN110364695B (zh) 锂离子电池
WO2024000336A1 (zh) 电化学装置和电子装置
WO2021088167A1 (zh) 正极及包含其的电化学装置和电子装置
WO2021128203A1 (zh) 一种电解液及电化学装置
WO2024000337A1 (zh) 电化学装置和电子装置
CN114400375A (zh) 电解液、电化学装置及电子装置
CN112368872A (zh) 一种电解液及电化学装置
WO2023225857A1 (zh) 电化学装置及电子设备
WO2023225849A1 (zh) 电化学装置及电子设备
US11837698B2 (en) Electrochemical device and electronic device
CN116053461B (zh) 电化学装置和包括其的电子装置
WO2024000477A1 (zh) 一种电化学装置及包含该电化学装置的电子装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22948451

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 202280060044.6

Country of ref document: CN