WO2021159618A1 - 一种高功率型的锂离子电池用正极材料及其制备方法 - Google Patents

一种高功率型的锂离子电池用正极材料及其制备方法 Download PDF

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WO2021159618A1
WO2021159618A1 PCT/CN2020/089850 CN2020089850W WO2021159618A1 WO 2021159618 A1 WO2021159618 A1 WO 2021159618A1 CN 2020089850 W CN2020089850 W CN 2020089850W WO 2021159618 A1 WO2021159618 A1 WO 2021159618A1
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precursor
positive electrode
electrode material
particles
solution
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PCT/CN2020/089850
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English (en)
French (fr)
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郭忻
胡海诗
胡志兵
黄承焕
张海艳
周友元
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湖南长远锂科股份有限公司
金驰能源材料有限公司
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Priority to JP2021531385A priority Critical patent/JP7241875B2/ja
Priority to EP20904305.8A priority patent/EP3893298A4/en
Priority to US17/311,465 priority patent/US20220102717A1/en
Publication of WO2021159618A1 publication Critical patent/WO2021159618A1/zh

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Definitions

  • the invention belongs to the technical field of lithium ion batteries, and in particular relates to a high-power positive electrode material for lithium ion batteries and a preparation method thereof.
  • Hybrid electric vehicles have the advantages of lightness and convenience, high specific energy, high specific power, high efficiency and environmental protection, and are recognized as the first choice for automotive power batteries in the future.
  • Hybrid electric vehicles have both internal combustion engine and power battery as the driving system, which requires high power performance of the power battery. Therefore, the development of high-output lithium-ion batteries is eagerly anticipated.
  • the positive electrode material with a hollow structure has a loose and porous surface and a large specific surface area, which can enhance the contact between the positive electrode material and the electrolyte, provide a strong support for the high-current discharge of the battery, and thus can improve the power performance of the battery.
  • template method and inner core oxidation method:
  • the first method is to add a template agent (for example, carbon microspheres) to the base solution of the precursor synthesis as the substrate for crystal growth, and then adopt a certain method to remove the template agent in the subsequent process to obtain a hollow material.
  • a template agent for example, carbon microspheres
  • the introduction and removal of template agents will increase the cost of materials and the difficulty of process control, especially the synthesis cost of precursors and the difficulty of process control.
  • the second method is the inner core oxidation method, in which an oxidizing atmosphere (such as air atmosphere) is used in the nucleation and core growth stages, and an inert gas atmosphere (such as nitrogen) is used in the shell growth stage.
  • an oxidizing atmosphere such as air atmosphere
  • an inert gas atmosphere such as nitrogen
  • This method prepares the precursor core once The particles are very small and the core is loose. Hollow cathode materials can also be obtained after sintering.
  • the principle of this method is to oxidize Mn 2+ to Mn 3+ in an oxidizing atmosphere during the nucleation and core growth stages, which reduces the crystallinity of the precursor, so that the primary particles of the core are arranged loosely and the size is refined.
  • the method is only suitable for cathode materials containing a certain amount of Mn (for example , z ⁇ 0.1 in Li a Ni x Co y Mn z O 2 ), and is not suitable for materials that do not contain Mn or have a very low Mn content (such as nickel, cobalt, aluminum ternary materials) ).
  • the obtained precursor has poor crystallinity and low tap density, and at the same time, the content of impurities Na and S in the precursor will increase.
  • the hollow cathode material due to the difference in the internal and external structure of the precursor, it is easy to collapse during the sintering process. And because this material has a hollow structure, its tap density and compaction density are low, and the particle strength is not high. When the pole piece is rolled, the positive electrode material is easily broken, which will destroy the original structure of the material and affect the material's performance. Electrical performance. At the same time, due to the large specific surface area of the material, although it is conducive to the increase of its output power, the contact area between the material and the electrolyte increases, and the side reaction increases, which leads to the deterioration of the cycle performance.
  • the technical problem to be solved by the present invention is to overcome the shortcomings and deficiencies mentioned in the above background art, and provide a hollow microsphere structure lithium ion battery cathode material with excellent rate performance and cycle performance and a preparation method thereof, and a method for preparing the same. Electrodes and lithium-ion batteries prepared from materials.
  • the average particle size of the secondary particles is 0.1 ⁇ m-40 ⁇ m, the specific surface area is 0.1 m 2 /g-15.0 m 2 /g; the particle size of the primary particles is 0.1 ⁇ m-3.5 ⁇ m; the ratio of the thickness of the shell part of the secondary particles to the particle size of the secondary particles is 1%-49%; the positive electrode material also includes doping elements, which are Al, Zr, Mg, W, Ti, Y, La, One or more of B and Sr, and the mass percentage of the doping element in the positive electrode material is 0.01 wt% to 2 wt%.
  • the positive electrode material with micron-sized hollow microsphere structure has a low thermal expansion coefficient, a high specific surface area, uniform particle size, and a small particle size distribution range.
  • it is beneficial to the diffusion of lithium ions.
  • After being prepared into a positive electrode sheet Can effectively increase the contact area with the electrolyte, facilitate the transmission of electrons and the intercalation/deintercalation of Li ions, the compression of buffer materials and the volume change during charging and discharging, which can effectively improve the rate and cycle performance of the positive electrode material. Improving the output performance and safety of power batteries is of great significance to improving the driving performance and safety performance of electric vehicles.
  • the present invention also provides a method for preparing the above-mentioned cathode material for lithium ion batteries, which includes the following steps:
  • the Ni x Co y M z (OH) 2 precursor is synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth phase and the shell growth phase. In the nucleation and core growth phase, no complexing agent is used. Or use a low-concentration complexing agent; in the shell growth stage, use a complexing agent with a higher concentration than the nucleation and core growth stages; the center of the obtained precursor is composed of tiny particles, and the shell is composed of smaller particles
  • the composition of larger large particles, the particle composition of the center part and the outer part is Ni x Co y M z (OH) 2 ;
  • step (1) The precursor obtained in step (1) is uniformly mixed with the lithium salt, and then sintered to obtain the Li a Ni x Co y M z O 2 cathode material.
  • the operation of synthesizing the Ni x Co y M z (OH) 2 precursor by the co-precipitation method specifically includes the following steps: a metal salt solution containing Ni, Co, and M , Alkaline solution and ammonia solution were added to the reaction kettle with bottom liquid to react.
  • the reaction temperature was 40°C-60°C
  • the stirring speed was 100r/min-1000r/min
  • the pH value of the reaction system was controlled at 8-13
  • the reactor is continuously filled with nitrogen;
  • the ammonium ion concentration of the reaction system is controlled to be 0g/L-15g/L during the nucleation and kernel growth stages of the precursor, and the ammonium ion concentration of the reaction system is controlled during the shell growth stage It is 5g/L-40g/L, and the ammonium ion concentration in the shell growth stage is higher than the ammonium ion concentration in the nucleation stage and the kernel growth stage;
  • the precipitate obtained by the reaction is separated by solid-liquid separation, aging, washing and drying Then, the Ni x Co y M z (OH) 2 precursor can be obtained.
  • the ammonium ion concentration of the reaction system is controlled to be 7g/L-15g/L in the nucleation and kernel growth stages of the precursor, and the ammonium ion concentration of the reaction system is controlled to be 30g/L-40g/L in the shell growth stage. .
  • Ni(OH) 2 , Co(OH) 2 , Mn(OH) 2 phase separation which makes the precursor product internal
  • the distribution of elements is not uniform, thereby reducing the electrical properties of the final product.
  • a complexing agent is added, and its function is mainly to form free complex metal ions with Ni 2+ , Co 2+ and Mn 2+ to appropriately reduce the precipitation rate , So that the three elements can produce uniform co-precipitation, prevent phase separation, and a large number of studies have shown that the presence of complexing agents can effectively improve the crystallinity of the product, and is very important for the formation of dense spherical hydroxide.
  • no complexing agent is used or a lower concentration of complexing agent is used (ammonium ion concentration is 0g/L-15g/L, more preferably 7g/L-15g/L).
  • the primary particles are relatively small and loose.
  • a higher concentration of complexing agent is used (ammonium ion concentration is 5g/L-40g/L, more preferably 30g/L-40g/L), the resulting primary particles are more than core particles, The primary particles are slightly coarser and the resulting shell layer is denser.
  • the core particles will shrink toward the outer shell, thereby forming a positive electrode material with a hollow structure.
  • the end of the nucleation and kernel growth stage is based on the particle size control.
  • the ammonium ion concentration can be increased to start the shell growth stage until the particles grow to the target particle size.
  • the present invention realizes the differentiation of the inner core and outer shell of the precursor by adjusting the concentration of ammonium ion in the different reaction stages of the precursor. It does not need to introduce new raw materials such as template agent, and has a wide range of applications. It is not only suitable for Mn-containing materials, but also suitable for Materials that do not contain Mn, such as nickel, cobalt, and aluminum. At the same time, because nitrogen protection has been used during the synthesis process, the crystallinity and tap density of the precursor are significantly better than the core oxidation method, and the content of impurities Na and S is relatively low.
  • the cost of precursor synthesis can be reduced, and the volatilization of ammonia in the reaction system is also reduced, thereby reducing environmental pollution.
  • the reaction temperature in the nucleation, core growth stage, and shell growth stage is set to 40°C-60°C. Under high temperature conditions higher than 60°C, Mn 2+ in an alkaline environment is more likely to be oxidized, which seals the equipment. The higher the requirements for the flow rate of the inert gas and inert gas, this will increase the cost of equipment and the amount of inert gas used, and the required energy consumption will be higher, thereby increasing the production cost of the precursor.
  • the metal salt solution is one or more of sulfate solution, nitrate solution, chloride solution, acetate solution and metaaluminate solution, and the total metal ion concentration in the metal salt solution is 0.05 mol /L-3mol/L;
  • the alkali solution is sodium hydroxide solution, the concentration of the alkali solution is 1mol/L-10mol/L; the ammonium ion concentration of the ammonia solution is 3mol/L-6mol/L; the tiny particles in the center The diameter is less than 0.3 ⁇ m, and the large particle diameter of the outer shell is ⁇ 0.3 ⁇ m.
  • the amount of lithium salt added is based on the molar ratio of Li to Ni+Co+M of 0.96-1.35, and the lithium salt is one of lithium carbonate, lithium hydroxide, lithium oxalate and lithium acetate.
  • the oxide of the doping element is also added, the doping element is one or more of Al, Zr, Mg, W, Ti, Y, La, B and Sr ,
  • the mass percentage of the doping element in the positive electrode material is 0.01wt%-2wt%.
  • the sintering temperature is 500° C.-1000° C.
  • the sintering time is 6-24 h
  • the sintering atmosphere is air and/or oxygen.
  • a multi-stage temperature-controlled sintering method is used in the sintering process. First, keep it at 500-700°C for 5-6h, then increase the temperature to 810-1000°C for 8-10h, and then reduce the temperature to 700-750°C for 5-6h. -8h.
  • the present invention improves and adjusts the sintering process, adopts a multi-stage temperature control sintering method, and sets a heat preservation process in the cooling stage, which is beneficial to the stability of the hollow structure and causes the internal particles of the material to shrink from the inside to the outside. Oxygen diffuses from the outside to the inside to form a uniform and stable hollow cathode material.
  • a higher lithium content is conducive to the formation of a hollow structure. This is because a higher lithium content increases the reaction activity of the precursor with lithium ions, and promotes the outward diffusion of the central particles to react with lithium. In turn, it is easier to form a hollow morphology.
  • the contact area with the electrolyte is increased, which is beneficial to increase its output power and shorten the distance of lithium ion diffusion, but at the same time, there are also increased side reactions with the electrolyte, which leads to poor cycle performance. risk.
  • the commonly used method to improve the cycle performance is surface coating, but the surface coating is bound to reduce the specific surface area of the material, which conflicts with the design of the material of the present invention.
  • the present invention can increase the particle strength of the material by doping the corresponding element during the sintering process of the positive electrode material, which can prevent the particles from breaking during the pole piece rolling process and improve the material Processing performance; It can also prevent structural instability caused by the side reaction of the material due to the large surface area and the electrolyte, and improve the cycle stability of the material.
  • the technical principles of preparing the hollow microsphere structure are: 1) During the synthesis of the precursor, the ammonium ion concentration is adjusted to achieve the difference between the inner core and the outer shell of the precursor, so that the particle size in the center of the precursor is smaller and Loose, the particle size of the outer shell is slightly larger and dense; 2) Using the difference between the precursor core and outer shell particles, during the sintering process, through the control of the sintering process (temperature control and time control), the particles shrink from the inside to the outside, and oxygen Diffusion from the outside to the inside to form a spherical granular material with a hollow morphology inside; 3) Doping elements during the sintering process to improve particle strength and cycle characteristics.
  • the present invention also provides an electrode and a lithium ion battery (a lithium ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte).
  • a lithium ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte.
  • the active material of the electrode and the lithium ion battery includes the above-mentioned positive electrode material, and the positive electrode material in the electrode The mass content is 50-99.9%.
  • the cathode material for lithium ion batteries of the present invention has a hollow microsphere structure, uniform particle size, loose and porous surface, high specific surface area, can increase the reaction area with electrolyte, shorten the distance of lithium ion diffusion, and have a high Rate performance and excellent cycle performance.
  • the preparation method of the positive electrode material of the present invention has simple process, low cost, industrial production, good material consistency, regular particle shape, small particle size distribution range, and stable material structure.
  • the electrode and lithium ion battery of the present invention adopt the above-mentioned positive electrode material, have good performance such as high cycle characteristics, low resistance, high output power, high safety, and are of great significance to improving the driving performance and safety performance of electric vehicles.
  • Figure 1 is a schematic cross-sectional view of the positive electrode material of the present invention (A is the thickness of the shell part, D is the particle size of the secondary particles);
  • Example 2 is a cross-sectional electron micrograph of the cathode material obtained in Example 2;
  • FIG. 3 is an electron micrograph of the cathode material obtained in Comparative Example 3;
  • FIG. 5 is a diagram showing the discharge specific capacity of the positive electrode material obtained in Comparative Example 3 at different rates.
  • the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.
  • a positive electrode material for lithium ion batteries of the present invention is Li 1.2 Ni 0.6 Co 0.2 Mn 0.2 O 2 .
  • the shell part is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • the Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 precursor is synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth stages and the shell growth stage.
  • the specific operations include: first use nickel, cobalt, and manganese To prepare a mixed metal salt solution with a total metal ion concentration of 2mol/L, the molar ratio of nickel, cobalt and manganese is 6:2:2, and a sodium hydroxide solution with a concentration of 2mol/L and an ammonium ion concentration of 6mol /L ammonia solution, pure water is used as the bottom liquid in the reactor, the pH in the bottom liquid of the reactor is adjusted to 12.0 with sodium hydroxide, the ammonium ion concentration is adjusted to 7g/L, and then the metal salt solution and hydroxide are mixed The sodium solution and aqueous ammonia solution are fed into the reactor through a metering pump for reaction.
  • the reaction temperature is 55°C
  • the speed is 500r/min
  • the pH of the reactor is controlled at 10.5-12.0
  • nitrogen is continuously introduced into the reactor
  • the ammonium ion concentration in the reaction system is controlled at 7g/L.
  • the ammonium ion concentration of the reaction system is adjusted to 35g/L, and the shell grows until the particle size grows to 5.5 ⁇ m;
  • a Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 precursor is obtained.
  • the average particle size of the precursor is 5.5 ⁇ m
  • the thickness of the shell part is about 2 ⁇ m
  • the precursor is composed of a center part composed of fine particles and an outer part composed of particles larger than the fine particles.
  • the physical and chemical properties of the cathode material Li 1.2 Ni 0.6 Co 0.2 Mn 0.2 O 2 were tested.
  • the cathode material has a specific surface area of 1.08 m 2 /g and an average particle size of 5.5 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM results that the positive electrode material is hollow microsphere secondary particles, and the shell part is formed by sintering and agglomerating primary particles, and the shell part has a thickness of about 2.0 ⁇ m.
  • the electrical performance of the cathode material was evaluated using a 2032 button battery.
  • the initial discharge capacity at 1C was 165mAh/g.
  • the rate performance of this sample was better, with 2C/1C at 97.81%, 5C/1C at 93.44%, and 10C/1C at 90.65%.
  • a positive electrode material for lithium ion batteries of the present invention is Li 1.08 Ni 0.9 Co 0.08 Al 0.02 O 2 , as shown in Figure 1.
  • the positive electrode material is a secondary particle with a hollow microsphere structure.
  • the shell part is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • Ni 0.9 Co 0.08 Al 0.02 (OH) 2 precursor is synthesized by co-precipitation method.
  • the synthesis of the precursor includes nucleation and core growth stages and shell growth stages.
  • the specific operations include: firstly use sulfuric acid containing nickel and cobalt.
  • the reaction temperature is 55 °C, rotation speed 450r/min, the pH of the reactor is controlled at 10.0-11.5, the reactor is continuously fed with nitrogen, and the flow ratio of the mixed metal salt solution and the metaaluminate solution solution is controlled to make the metal molar ratio of nickel, cobalt and aluminum 90 :8:2;
  • the ammonium ion concentration in the reaction system is controlled at 10g/L. After the material particle size grows to 2 ⁇ m, then the ammonium ion concentration in the reaction system is adjusted to 30g/L for shell growth.
  • Ni 0.9 Co 0.08 Al 0.02 (OH) 2 precursor is obtained.
  • the average particle size of the precursor is 9.0 ⁇ m
  • the thickness of the outer shell part is about 3.5 ⁇ m, and the precursor is composed of a center part composed of fine particles and an outer shell part composed of particles larger than the fine particles.
  • the physical and chemical properties of the cathode material Li 1.08 Ni 0.9 Co 0.08 Al 0.02 O 2 were tested.
  • the cathode material has a specific surface area of 0.76 m 2 /g and an average particle size of 9.0 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM results (as shown in Figure 2) that the positive electrode material is hollow microsphere secondary particles.
  • the electrical performance of this cathode material was evaluated using a 2032 button battery. Its 1C initial discharge specific capacity was 192mAh/g. The sample rate performance was better, 2C/1C was 97.09%, 5C/1C was 92.68%, and 10C/1C was 90.00%.
  • a cathode material for lithium ion batteries is Li 1.25 Ni 1/3 Co 1/3 Mn 1/3 O 2.
  • the cathode material is a secondary particle with a hollow microsphere structure.
  • the shell part of the secondary particles is formed by agglomeration of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • the Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 precursor is synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth stages and the shell growth stage.
  • the specific operations include: first use Sulfate containing nickel, cobalt, and manganese, prepare a mixed metal salt solution with a total metal ion concentration of 2mol/L, the molar ratio of nickel, cobalt, and manganese is 1:1:1, prepare a sodium hydroxide solution with a concentration of 2mol/L and An ammonia solution with an ammonium ion concentration of 5 mol/L, with pure water as the bottom liquid in the reactor, and sodium hydroxide to adjust the pH in the bottom liquid of the reactor to 11.0, without adding ammonia water (ensure that the ammonium ion concentration is 0), Then pass the mixed metal salt solution and sodium hydroxide solution into the reaction kettle through a metering pump for reaction.
  • the reaction temperature is 50°C
  • the speed is 500r/min
  • the pH of the reaction kettle is controlled at 9.5-11.0
  • the reaction kettle continues Blow in nitrogen; do not add ammonia in the nucleation and kernel growth stages, wait until the particle size of the material grows to 1.6 ⁇ m, then pour in ammonia, control the ammonium concentration of the reaction system at 10g/L, and grow the shell until the particle size grows to 4.0 ⁇ m;
  • a precursor of Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 is obtained.
  • the average particle size of the precursor is 4 ⁇ m.
  • the thickness of the outer shell part is about 1.2 ⁇ m, and the precursor is composed of a center part composed of fine particles and an outer shell part composed of particles larger than the fine particles.
  • the sintering process includes a heating platform, a high temperature platform and a cooling platform. The temperature is first kept at 600°C for 6h, then heated to 900°C for 8h, and then cooled to 700°C for 5h.
  • the sintering atmosphere is After the sintering is completed, the material is sieved after being cooled to room temperature to obtain a cathode material Li 1.25 Ni 1/3 Co 1/3 Mn 1/3 O 2 with a Zr-doped hollow microsphere structure.
  • the physical and chemical properties of the cathode material Li 1.25 Ni 1/3 Co 1/3 Mn 1/3 O 2 were tested.
  • the specific surface area of the cathode material was 2.13m 2 /g, and the average particle size of the secondary particles was about 4.5 ⁇ m.
  • the particle size is 0.1 ⁇ m-2 ⁇ m. SEM observation and cross-sectional SEM observation were performed on the material (see Figure 3 and Figure 4).
  • the material has a secondary spherical structure with uniform particle size.
  • the positive electrode material is a secondary particle with a hollow microsphere structure, and its outer shell is formed by sintering and agglomerating primary particles, and the thickness of the outer shell is about 1.2 ⁇ m.
  • the electrical performance of the positive electrode material was evaluated using a 2032-type button battery, and the results are shown in FIG. 5. Its 1C initial discharge specific capacity is 147.7mAh/g, and the rate performance of this sample is better, 2C/1C is 98.24%, 5C/1C is 94.85%, and 10C/1C is 90.66%.
  • a positive electrode material for lithium ion batteries The chemical formula of the positive electrode material is Li 1.1 Ni 0.4 Co 0.3 Mn 0.3 O 2. As shown in Figure 1, the positive electrode material is a secondary particle with a hollow microsphere structure. It is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • the Ni 0.4 Co 0.3 Mn 0.3 (OH) 2 precursor was synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth stages and the shell growth stage.
  • the specific operations include: first use nickel, cobalt, and manganese To prepare a mixed metal salt solution with a total metal ion concentration of 2mol/L, the molar ratio of nickel, cobalt and manganese is 4:3:3, and a sodium hydroxide solution with a concentration of 4mol/L and an ammonium ion concentration of 5mol /L ammonia solution, pure water is used as the bottom liquid in the reactor, the pH in the bottom liquid of the reactor is adjusted to 13.0 with sodium hydroxide, and ammonia water is not passed (ensure that the ammonium ion concentration is 0), and then mix the metal salt solution , Sodium hydroxide solution is fed into the reactor through a metering pump for reaction.
  • the reaction temperature is 45°C
  • the speed is 600r/min
  • the pH of the reactor is controlled at 9.5-13.0
  • nitrogen is continuously introduced into the reactor;
  • the nucleus and inner core growth stage do not enter ammonia water.
  • the ammonium concentration of the reaction system is adjusted to 15g/L
  • the shell grows until the particle size grows to 3.8 ⁇ m.
  • a Ni 0.4 Co 0.3 Mn 0.3 (OH) 2 precursor is obtained.
  • the average particle size of the precursor is 3.8 ⁇ m
  • the thickness of the shell part is about 1.5 ⁇ m
  • the precursor is composed of a center part composed of fine particles and an outer part composed of particles larger than the fine particles.
  • the physical and chemical properties of the positive electrode material Li 1.1 Ni 0.4 Co 0.3 Mn 0.3 O 2 were tested.
  • the positive electrode material has a specific surface area of 0.65 m 2 /g and an average particle size of 4.0 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM results that the positive electrode material is a secondary particle with a hollow microsphere structure.
  • the electrical performance of the positive electrode material was evaluated using a 2032 button battery.
  • the initial discharge capacity at 1C was 152mAh/g.
  • the rate performance of this sample was better.
  • 2C/1C was 98.00%
  • 5C/1C was 94.24%
  • 10C/1C was 91.37%.
  • a positive electrode material for lithium-ion batteries The chemical formula of the positive electrode material is Li 1.2 Ni 0.6 Co 0.2 Mn 0.2 O 2 , as shown in Figure 1.
  • the positive electrode material is a secondary particle with a hollow microsphere structure. The outer shell of the secondary particle It is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • the Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 precursor is synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth stages and the shell growth stage.
  • the specific operations include: first use nickel, cobalt, and manganese To prepare a mixed metal salt solution with a total metal ion concentration of 2mol/L, the molar ratio of nickel, cobalt and manganese is 6:2:2, and a sodium hydroxide solution with a concentration of 2mol/L and an ammonium ion concentration of 6mol /L of ammonia solution.
  • Pure water is used as the bottom liquid in the reactor, the pH in the bottom liquid of the reactor is adjusted to 12.0 with sodium hydroxide, the ammonium ion concentration is adjusted to 0g/L, and then the mixed metal salt solution, sodium hydroxide solution, and ammonia solution are passed through The metering pump is fed into the reactor for reaction.
  • the reaction temperature is 55°C
  • the speed is 500r/min
  • the pH of the reactor is controlled at 10.5-12.0
  • nitrogen is continuously fed into the reactor; wait until the particle size of the material grows to 1.5 ⁇ m
  • the ammonium concentration of the reaction system is adjusted to 25g/L
  • the shell grows until the particle size grows to 5.5 ⁇ m
  • the precipitate obtained by the reaction is solid-liquid separated, aged, washed and dried to obtain Ni 0.6 Co 0.2 Mn A 0.2 (OH) 2 precursor with an average particle diameter of 5.5 ⁇ m and a thickness of about 2 ⁇ m in the outer shell part.
  • the precursor is composed of a center part composed of fine particles and an outer shell part composed of particles larger than the fine particles.
  • the physical and chemical properties of the positive electrode material Li 1.2 Ni 0.6 Co 0.2 Mn 0.2 O 2 were tested.
  • the positive electrode material has a specific surface area of 0.88 m 2 /g and an average particle size of 6.0 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM result that the positive electrode material is hollow microsphere secondary particles.
  • the electrical performance of the cathode material was evaluated using a 2032 button battery. Its 1C initial discharge specific capacity was 163mAh/g, and the rate performance of this sample was better, with 2C/1C being 92.16%, 5C/1C being 88.06%, and 10C/1C being 86.42%.
  • a positive electrode material for lithium-ion batteries The chemical formula of the positive electrode material is Li 1.08 Ni 0.9 Co 0.08 Al 0.02 O 2. As shown in Figure 1, the positive electrode material is a secondary particle with a hollow microsphere structure. The outer shell of the secondary particle It is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • Ni 0.9 Co 0.08 Al 0.02 (OH) 2 precursor is synthesized by co-precipitation method.
  • the synthesis of the precursor includes nucleation and core growth stages and shell growth stages.
  • the specific operations include: firstly use sulfuric acid containing nickel and cobalt.
  • the reaction temperature is 55 °C, rotation speed 450r/min, the pH of the reactor is controlled at 10.0-11.5, the reactor is continuously fed with nitrogen, and the flow ratio of the mixed metal salt solution and the metaaluminate solution solution is controlled to make the metal molar ratio of nickel, cobalt and aluminum 90 :8:2;
  • the particle size of the material grows to 2 ⁇ m
  • the ammonium concentration of the reaction system is adjusted to 25g/L, and the shell grows until the particle size grows to 9.0 ⁇ m;
  • the precipitate obtained by the reaction is separated, aged and washed by solid-liquid And after drying, a Ni 0.9 Co 0.08 Al 0.02 (OH) 2 precursor is obtained.
  • the average particle size of the precursor is 9.0 ⁇ m, and the thickness of the shell part is about 3.5 ⁇ m.
  • the shell part is composed of small particles and large particles.
  • the physical and chemical properties of the cathode material Li 1.08 Ni 0.9 Co 0.08 Al 0.02 O 2 were tested.
  • the cathode material has a specific surface area of 0.5 m 2 /g and an average particle size of 9.0 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM results that the positive electrode material is hollow microsphere secondary particles, and the shell part is formed by sintering and agglomerating primary particles, and the shell part has a thickness of about 4 ⁇ m.
  • the electrical performance of this cathode material was evaluated using a 2032 button battery.
  • the initial discharge capacity at 1C was 188mAh/g.
  • the rate performance of this sample was better, with 2C/1C at 90.89%, 5C/1C at 87.43%, and 10C/1C at 85.24%.
  • a positive electrode material for lithium ion batteries of the present invention the chemical formula of the positive electrode material is Li 1.1 Ni 0.5 Co 0.3 Mn 0.2 O 2 , as shown in Figure 1, the positive electrode material is secondary particles with a hollow microsphere structure. The shell part is made up of several primary particles.
  • the preparation method of the positive electrode material includes the following steps:
  • the Ni 0.5 Co 0.3 Mn 0.2 (OH) 2 precursor is synthesized by the co-precipitation method.
  • the synthesis of the precursor includes the nucleation and core growth stages and the shell growth stage.
  • the specific operations include: first use nickel, cobalt, and manganese To prepare a mixed metal salt solution with a total metal ion concentration of 2mol/L, the molar ratio of nickel, cobalt and manganese is 5:3:2, and a sodium hydroxide solution with a concentration of 2mol/L and an ammonium ion concentration of 5mol /L ammonia solution, pure water is used as the bottom liquid in the reactor, the pH in the bottom liquid of the reactor is adjusted to 12.0 with sodium hydroxide, the ammonium concentration is adjusted to 3g/L, and then the metal salt solution and sodium hydroxide are mixed The solution and aqueous ammonia solution are fed into the reactor through a metering pump for reaction.
  • the reaction temperature is 55°C
  • the speed is 400r/min
  • the pH of the reactor is controlled at 10.0-12.0
  • nitrogen is continuously fed into the reactor
  • the ammonia concentration in the reaction system is controlled at 3g/L, after the particle size of the material grows to 2.5 ⁇ m, then the ammonium concentration of the reaction system is adjusted to 25g/L, and the shell grows until the particle size grows to 4.5 ⁇ m;
  • a Ni 0.5 Co 0.3 Mn 0.2 (OH) 2 precursor is obtained.
  • the average particle size of the precursor is 4.5 ⁇ m
  • the thickness of the shell part is about 1 ⁇ m.
  • the precursor is composed of a center part composed of fine particles and an outer part composed of particles larger than the fine particles.
  • the physical and chemical properties of the positive electrode material Li 1.1 Ni 0.5 Co 0.3 Mn 0.2 O 2 were tested.
  • the positive electrode material has a specific surface area of 1.89 m 2 /g and an average particle size of 4.5 ⁇ m.
  • SEM observation and cross-sectional SEM observation of the material were carried out. From the results of the electron microscope, it can be seen that the material has a secondary spherical structure and the particle size is uniform. It can be seen from the cross-sectional SEM results that the positive electrode material is a secondary particle with a hollow microsphere structure.
  • the electrical performance of the cathode material was evaluated using a 2032 button battery.
  • the initial discharge specific capacity at 1C was 158.6mAh/g.
  • the rate performance of the sample was better, with 2C/1C being 99.02%, 5C/1C being 95.66%, and 10C/1C being It is 92.13%.

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Abstract

本发明公开了一种高功率型的锂离子电池用正极材料，该正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成，颗粒大小均匀，表面疏松多孔，比表面积高，且得到的颗粒形状规则，材料结构稳定，拥有较高的倍率性能和优异的循环性能。本发明还公开了该正极材料的制备方法，包括如下步骤：(1)采用共沉淀法合成Ni xCo yM z(OH) 2前驱体，前驱体的中心部由微小粒子组成，外壳部由粒径比该微小粒子更大的大粒子组成；(2)将前驱体与锂盐混合均匀，混合时加入掺杂元素的氧化物，然后进行烧结，得到Li aNi xCo yM zO 2正极材料。该制备方法的工艺简单，成本低廉，可工业化生产。

Description

一种高功率型的锂离子电池用正极材料及其制备方法 技术领域
本发明属于锂离子电池技术领域，尤其涉及一种高功率型的锂离子电池用正极材料及其制备方法。
背景技术
近年来，新能源汽车得到了蓬勃的发展。为满足节能减排的需求及传统汽车向新能源汽车的平稳过渡，混合动力汽车(HEV)不失为当下最优的选择。锂离子电池具有轻巧方便、比能量高、比功率高、高效环保等优点，已是公认的未来汽车动力电池的首选。混合动力汽车同时拥有内燃机和动力电池作为驱动系统，这对动力电池的功率性能要求较高。因此高输出功率的锂离子电池的开发被寄予了热切期待。
为了使电池具有高循环特性、低电阻、高输出功率等良好性能，针对作为正极活性物质的锂复合氧化物而言，需要形成具有均匀且适度粒径、并且比表面积大的正极材料粒子。中空型结构的正极材料，表面疏松多孔，比表面积大，能增强正极材料和电解液的接触，为电池大电流放电提供强有力的支撑，从而能够提升电池的功率性能。目前制备中空型正极材料的方法主要有模板法与内核氧化法两种：
第一种方法是在前驱体合成的底液中添加模板剂(例如碳微球)作为晶体生长的基体，在后续过程中再采取一定方式除去模板剂，从而得到中空型材料。但是，模板剂的引入与除去会增加材料的成本与工艺控制难度，尤其是前驱体的合成成本与工艺控制难度。
第二种方法是内核氧化法，在成核及内核生长阶段采用氧化性的氛围(例如空气氛围)，在外壳生长阶段采用惰性气体氛围(例如氮气)，这种方法制备得到的前驱体内核一次颗粒十分细小，内核疏松，烧结后也能得到中空型正极材料。该方法原理是在成核及内核生长阶段，利用氧化性的气氛将Mn 2+氧化成Mn 3+，降低了前驱体的结晶性，从而使内核一次颗粒排布疏松、尺寸细化，但是该方法仅适用于含有一定量Mn(例如Li aNi xCo yMn zO 2中z≥0.1)的正极材料，不适用于不含Mn或Mn含量很低的材料(例如镍钴铝三元材料)。同时由于合成过程中的氧化作用，得到的前驱体结晶性很差，振实密度很低，同时会增加前驱体中杂质Na、S的含量。
此外，在中空型正极材料的合成过程中，因前驱体存在内外结构差异，在烧结过程中易产生扁塌。且由于此种材料为中空结构，其振实密度及压实密度较低，粒子强度不高，在极片辊压时正极材料容易碎裂，这将破坏材料原有的结构并影响到材料的电性能。同时，由于 材料比表面积较大，虽有利于其输出功率的提高，但材料与电解液接触面积增大，副反应增加而导致循环性能变差。
发明内容
本发明所要解决的技术问题是，克服以上背景技术中提到的不足和缺陷，提供一种倍率性能和循环性能优异的中空微球结构锂离子电池用正极材料及其制备方法，以及由该正极材料制备得到的电极和锂离子电池。
为解决上述技术问题，本发明提出的技术方案为：
一种高功率型的锂离子电池用正极材料，正极材料的化学式为Li aNi xCo yM zO 2，其中，0.96≤a≤1.35，0.3≤x≤1，0≤y≤0.4，0≤z≤0.4，x+y+z＝1，M为Mn、Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种；正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
上述的锂离子电池用正极材料，优选的，二次颗粒的平均粒径为0.1μm-40μm，比表面积为0.1m 2/g-15.0m 2/g；一次颗粒的粒径为0.1μm-3.5μm；二次颗粒的外壳部分厚度与二次颗粒粒径的比值为1％-49％；正极材料还包括掺杂元素，掺杂元素为Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种，该掺杂元素在正极材料中所占质量百分比为0.01wt％-2wt％。
微米级中空微球结构的正极材料具有较低的热膨胀系数、较高的比表面积，颗粒大小均匀，粒径分布范围较小，在烧结过程中，有利于锂离子的扩散，制备成正极片后，能够有效地增大与电解液的接触面积，有利于电子的传输以及Li离子的嵌入/脱嵌，缓冲材料压制以及充放电过程中的体积变化，可以有效提高正极材料的倍率以及循环性能，改善动力电池的输出性能和安全性，对提高电动汽车的行驶性能和安全性能意义重大。
基于一个总的发明构思，本发明还提供一种上述的锂离子电池用正极材料的制备方法，包括如下步骤：
(1)采用共沉淀法合成Ni xCo yM z(OH) 2前驱体，前驱体的合成包括成核及内核生长阶段和外壳生长阶段，在成核及内核生长阶段，不使用络合剂或者使用低浓度的络合剂；在外壳生长阶段，使用浓度高于成核及内核生长阶段的络合剂；得到的前驱体的中心部由微小粒子组成，外壳部由粒径比该微小粒子更大的大粒子组成，中心部及外壳部的粒子成分均是Ni xCo yM z(OH) 2；
(2)将步骤(1)得到的前驱体与锂盐混合均匀，然后进行烧结，得到Li aNi xCo yM zO 2正极材料。
上述的制备方法，优选的，步骤(1)中，采用共沉淀法合成Ni xCo yM z(OH) 2前驱体的操作，具体包括如下步骤：将含有Ni、Co、M的金属盐溶液、碱溶液、氨水溶液分别加入到具 有底液的反应釜中进行反应，反应过程中，反应温度为40℃-60℃，搅拌转速为100r/min-1000r/min，反应体系的pH值控制在8-13，反应釜内持续通入氮气；在前驱体的成核及内核生长阶段控制反应体系的铵根离子浓度为0g/L-15g/L，外壳生长阶段控制反应体系的铵根离子浓度为5g/L-40g/L，且外壳生长阶段的铵根离子浓度要高于成核阶段及内核生长阶段的铵根离子浓度；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即可得到Ni xCo yM z(OH) 2前驱体。
更优选的，在前驱体的成核及内核生长阶段控制反应体系的铵根离子浓度为7g/L-15g/L，外壳生长阶段控制反应体系的铵根离子浓度为30g/L-40g/L。
传统制备工艺中不添加络合剂，合成的产品振实密度极低，BET极高，这不仅极大的降低了材料的能量密度，而且给前驱体的后处理提出了极高的要求，低振实高BET的产品，烘干后极易发生团聚，当前主流的陈化与烘干工艺无法满足要求，难以大规模量产；不添加络合剂，前驱体的结晶性差，产品Na、S等杂质含量高，会对烧结过程以及正极材料的电性能产生较大的负面影响，还会产生Ni(OH) 2、Co(OH) 2、Mn(OH) 2分相，使得前驱体产品内部元素分布不均匀，从而降低最终产品的电性能。而本发明在Ni、Co、Mn三元素共沉淀过程中，添加了络合剂，其作用主要是与Ni 2+、Co 2+与Mn 2+形成游离的络合金属离子，适当降低沉淀速率，使三元素能产生均匀的共沉淀，防止产生相分离，而且大量的研究表明，络合剂的存在能有效提高产物的结晶性，而且对形成致密的球形氢氧化物至关重要。
在成核及内核生长过程，不使用络合剂或者使用较低浓度的络合剂(铵根离子浓度为0g/L-15g/L，更优选为7g/L-15g/L)，所生成的一次颗粒较为细小且疏松。在外壳生长过程，使用较高浓度的络合剂(铵根离子浓度为5g/L-40g/L，更优选为30g/L-40g/L)，所生成的一次颗粒较内核颗粒来说，一次颗粒稍微粗大，得到的壳层较为致密。在正极材料烧结过程中，由于内核的一次粒子较小且疏松，反应活性较大，随着烧结的进行，内核粒子会向外壳方向收缩，从而形成具有中空结构的正极材料。
成核及内核生长阶段的结束是以粒度控制为准，当内核粒度达到预定要求，即可将铵根离子浓度上调，开始外壳生长阶段，直至颗粒生长至目标粒度即可。
本发明通过在前驱体的不同反应阶段调整铵根离子浓度实现前驱体内核与外壳的差异化，不需要引入模板剂等新的原材料，而且适用范围广，不仅适用于含Mn材料，也适用于镍钴铝等不含Mn的材料。同时，由于合成过程中一直采用氮气保护，前驱体的结晶度和振实密度要明显优于内核氧化法，杂质Na、S的含量相对较低。另外，由于在内核及内核生长阶段，没有使用氨水或者仅使用少量的氨水，可以降低前驱体合成的成本，同时也降低了反应体系中氨水的挥发量，减少了环境污染。此外，将成核及内核生长阶段、外壳生长阶段的反应温 度设置为40℃-60℃，在高于60℃的高温度条件下，碱性环境中的Mn 2+更容易氧化，对设备的密封性、惰性气体的流量要求更高，这会增加设备成本以及惰性气体的使用量，所需的能耗较高，从而增加前驱体生产成本。
更优选的，金属盐溶液为硫酸盐溶液、硝酸盐溶液、氯化盐溶液、醋酸盐溶液和偏铝酸盐溶液中的一种或多种，金属盐溶液中总金属离子浓度为0.05mol/L-3mol/L；碱溶液为氢氧化钠溶液，碱溶液的浓度为1mol/L-10mol/L；氨水溶液的铵根离子浓度为3mol/L-6mol/L；中心部的微小粒子粒径＜0.3μm，外壳部的大粒子粒径≥0.3μm。
优选的，步骤(2)中，锂盐的添加量以Li与Ni+Co+M的摩尔比值为0.96-1.35为准，锂盐为碳酸锂、氢氧化锂、草酸锂和醋酸锂中的一种或多种；在前驱体与锂盐混合时还加入掺杂元素的氧化物，掺杂元素为Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种，该掺杂元素在正极材料中所占质量百分比为0.01wt％-2wt％。
优选的，步骤(2)中，烧结的温度为500℃-1000℃，烧结的时间为6-24h，烧结气氛为空气和/或氧气。
更优选的，在烧结过程中采用多段控温烧结的方式，先在500-700℃下保温5-6h，然后升温至810-1000℃下保温8-10h，再降温至700-750℃保温5-8h。
传统的制备方法，在中空型正极材料的合成过程中，因前驱体存在内外结构差异，在烧结过程中易产生扁塌。为了克服这一问题，本发明通过对烧结工艺进行改良与调整，采用多段控温烧结的方式，并在降温阶段设置一段保温过程，有利于中空结构的稳定，使材料内部粒子从内向外收缩，氧气从外向内扩散，形成均匀的稳定的中空型正极材料。此外，在烧结过程中，较高的配锂量有利于中空结构的形成，这是由于较高的锂含量会增加前驱体与锂离子的反应活性，促使中心部粒子向外扩散与锂反应，进而更容易形成中空的形貌。
由于正极材料的比表面积较大，与电解液接触面积增大，有利于其输出功率的提高，缩短锂离子扩散的距离，但同时也存在与电解液的副反应增加而导致循环性能变差的风险。常用的提高循环性能的手段为表面包覆，但是表面包覆势必降低材料的比表面积，这与本发明材料的设计相冲突。为了进一步提高正极材料的粒子强度及循环特性，本发明在正极材料烧结过程中，通过掺杂相应的元素，能提高材料的粒子强度，既能防止极片辊压过程中粒子破碎，提高材料的加工性能；又能防止材料因比表面大与电解液产生副反应而带来的结构不稳定化，提高了材料的循环稳定性。
总的来说，制备得到中空微球结构的技术原理在于：1)在前驱体合成过程中通过调整铵根离子浓度实现前驱体内核与外壳的差异化，使前驱体中心部粒子尺寸较小且疏松，外壳部粒子尺寸稍大且致密；2)利用前驱体内核与外壳粒子的差异，在烧结过程中，通过对烧结工 艺的控制(温度控制和时间控制)，使粒子由内向外收缩，氧气由外向内扩散，形成内部中空形貌的球形颗粒材料；3)在烧结过程中掺杂元素，提高粒子强度及循环特性。
基于一个总的发明构思，本发明还提供一种电极和锂离子电池(锂离子电池包括正极、负极、隔膜和电解液)，电极和锂离子电池的活性物质包括上述正极材料，电极中正极材料的质量含量为50-99.9％。
与现有技术相比，本发明的有益效果为：
1、本发明的锂离子电池用正极材料，呈中空微球结构，颗粒大小均匀，表面疏松多孔，比表面积高，能增加与电解液的反应面积，缩短锂离子扩散的距离，拥有较高的倍率性能和优异的循环性能。
2、本发明正极材料的制备方法，工艺简单，成本低廉，可工业化生产，且得到的材料一致性较好，颗粒形状规则且粒径分布范围较小，材料结构稳定。
3、本发明的电极及锂离子电池，采用上述正极材料，具有高循环特性、低电阻、高输出功率等良好性能，安全性高，对提高电动汽车的行驶性能和安全性能意义重大。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本发明的正极材料剖面示意图(A为外壳部分厚度，D为二次颗粒粒径)；
图2为实施例2得到的正极材料的剖面电镜图；
图3为对比实施例3得到的正极材料电镜图；
图4为对比实施例3得到的正极材料的剖面电镜图；
图5为对比实施例3得到的正极材料在不同倍率下的放电比容量图。
具体实施方式
为了便于理解本发明，下文将结合说明书附图和较佳的实施例对本发明做更全面、细致地描述，但本发明的保护范围并不限于以下具体实施例。
除非另有定义，下文中所使用的所有专业术语与本领域技术人员通常理解含义相同。本文中所使用的专业术语只是为了描述具体实施例的目的，并不是旨在限制本发明的保护范围。
除非另有特别说明，本发明中用到的各种原材料、试剂、仪器和设备等均可通过市场购买得到或者可通过现有方法制备得到。
实施例1：
一种本发明的锂离子电池用正极材料，正极材料的化学式为Li 1.2Ni 0.6Co 0.2Mn 0.2O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.6Co 0.2Mn 0.2(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴、锰的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴锰的摩尔比为6:2:2，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为6mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至12.0，铵根离子浓度调节至7g/L，再将混合金属盐溶液、氢氧化钠溶液、氨水溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度55℃，转速500r/min，反应釜pH控制在10.5-12.0，反应釜内持续通入氮气；在成核及内核生长阶段将反应体系中铵根离子浓度控制在7g/L，待材料粒度生长至1.5μm，然后将反应体系的铵根浓度调节至35g/L，进行外壳生长，直至粒度生长至5.5μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.6Co 0.2Mn 0.2(OH) 2前驱体，该前驱体平均粒径为5.5μm，其外壳部分厚度约2μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比1.20(Li与Ni+Co+Mn的摩尔比)称取适量上述前驱体及碳酸锂，按Mg占正极材料质量百分比为0.1wt％称取适量MgO，按Ti占正极材料比例为0.08wt％称取适量TiO 2，将上述物料混合均匀后在高温下进行烧结，先在700℃下保温6h，然后升温至850℃下保温10h，烧结气氛为氧气与空气混合，烧结完毕后待物料降温至室温后将其过筛处理，得到掺Mg和Ti的中空结构材料Li 1.2Ni 0.6Co 0.2Mn 0.2O 2。
对正极材料Li 1.2Ni 0.6Co 0.2Mn 0.2O 2进行物化性能检测，该正极材料比表面积为1.08m 2/g，平均粒径为5.5μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知，该正极材料为中空微球二次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约2.0μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为165mAh/g，该样品倍率性能较好，2C/1C为97.81％，5C/1C为93.44％，10C/1C为90.65％。
实施例2：
一种本发明的锂离子电池用正极材料，正极材料的化学式为Li 1.08Ni 0.9Co 0.08Al 0.02O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.9Co 0.08Al 0.02(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴的摩尔比为90:8，用铝的硫酸盐与过量氢氧化钠配制铝摩尔浓度为0.1mol/L偏铝酸盐溶液，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为5mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至11.5，铵根离子浓度调节至10g/L，再将混合金属盐溶液、偏铝酸盐溶液、氢氧化钠溶液、氨水溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度55℃，转速450r/min，反应釜pH控制在10.0-11.5，反应釜内持续通入氮气，控制混合金属盐溶液及偏铝酸盐溶液溶液的流量比，使镍钴铝的金属摩尔比为90:8:2；在成核及内核生长阶段将反应体系中铵根离子浓度控制在10g/L，待材料粒度生长至2μm，然后将反应体系的铵根浓度调节至30g/L，进行外壳生长，直至粒度生长至9.0μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.9Co 0.08Al 0.02(OH) 2前驱体，该前驱体平均粒径为9.0μm，其外壳部分厚度约3.5μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比1.08(Li与Ni+Co+Mn的摩尔比)称取适量上述前驱体及氢氧化锂，按Sr占正极材料质量百分比为0.2wt％称取适量SrCO 3，将上述物料混合均匀后在高温下进行烧结，直接升至710℃下保温12h，烧结气氛为氧气，烧结完毕后待物料降温至室温后将其过筛处理，得到掺Sr的中空结构材料Li 1.08Ni 0.9Co 0.08Al 0.02O 2。
对正极材料Li 1.08Ni 0.9Co 0.08Al 0.02O 2进行物化性能检测，该正极材料比表面积为0.76m 2/g，平均粒径为9.0μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知(如图2)，该正极材料为中空微球二次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约3.5μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为192mAh/g，该样品倍率性能较好，2C/1C为97.09％，5C/1C为92.68％，10C/1C为90.00％。
对比实施例3：
一种锂离子电池用正极材料，正极材料的化学式为Li 1.25Ni 1/3Co 1/3Mn 1/3O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 1/3Co 1/3Mn 1/3(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴、锰的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴锰的摩尔比为1:1:1，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为5mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应 釜底液中pH调整至11.0，不添加氨水(保证铵根离子浓度为0)，再将混合金属盐溶液、氢氧化钠溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度50℃，转速500r/min，反应釜pH控制在9.5-11.0，反应釜内持续通入氮气；在成核及内核生长阶段不添加氨水，待材料粒度生长至1.6μm，然后通入氨水，将反应体系的铵根浓度控制在10g/L，进行外壳生长，直至粒度生长至4.0μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 1/3Co 1/3Mn 1/3(OH) 2前驱体，该前驱体平均粒径为4μm，其外壳部厚度约1.2μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比(Li与Ni+Co+Mn的摩尔比)1.25称取适量上述前驱体及碳酸锂，按Zr占正极材料质量百分比为0.5wt％称取适量ZrO 2，将上述物料混合均匀后，在高温下进行烧结，烧结工序包括升温平台、高温平台及降温平台，先在600℃下保温6h，然后升温至900℃下保温8h，再降温至700℃保温5h，烧结气氛为空气，烧结完毕后待物料降温至室温后将其过筛处理，得到掺Zr的中空微球结构的正极材料Li 1.25Ni 1/3Co 1/3Mn 1/3O 2。
对正极材料Li 1.25Ni 1/3Co 1/3Mn 1/3O 2进行物化性能检测，该正极材料比表面积为2.13m 2/g，二次颗粒的平均粒径约为4.5μm，一次颗粒的粒径为0.1μm-2μm。对该材料进行SEM观察和剖面SEM观察(见图3和图4)。
由图3可知，该材料呈二次球形结构，颗粒大小均匀。由图4可知，该正极材料为呈中空微球结构的二次颗粒，其外壳部分由一次颗粒烧结聚集而成，外壳部分的厚度约1.2μm。
采用2032型纽扣电池对该正极材料进行电性能评价，结果如图5所示。其1C初始放电比容量为147.7mAh/g，该样品倍率性能较好，2C/1C为98.24％，5C/1C为94.85％，10C/1C为90.66％。
对比实施例4：
一种锂离子电池用正极材料，正极材料的化学式为Li 1.1Ni 0.4Co 0.3Mn 0.3O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.4Co 0.3Mn 0.3(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴、锰的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴锰的摩尔比为4:3:3，配制浓度为4mol/L的氢氧化钠溶液与铵根离子浓度为5mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至13.0，不通入氨水(保证铵根离子浓度为0)，再将混合金属盐溶液、氢氧化钠溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度45℃，转速600r/min，反应釜pH控制在9.5-13.0，反应釜内持续通入氮气；在成核及内核生长阶段不通入氨水，待 材料粒度生长至0.8μm，然后将反应体系的铵根浓度调节至15g/L，进行外壳生长，直至粒度生长至3.8μm。反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.4Co 0.3Mn 0.3(OH) 2前驱体，该前驱体平均粒径为3.8μm，其外壳部分厚度约1.5μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比(Li与Ni+Co+Mn的摩尔比)1.10称取适量前驱体及碳酸锂，按Zr占正极材料质量百分比为0.3wt％称取适量ZrO 2，按B占正极材料比例为0.1wt％称取适量硼酸，将上述物料混合均匀后在高温下进行烧结，烧结工序包括升温平台、高温平台及降温平台，先在650℃下保温5h，然后升温至810℃下保温8h，再降温至700℃保温8h，烧结气氛为空气，烧结完毕后待物料降温至室温后将其过筛处理，得到掺Zr及B的中空微球结构的正极材料Li 1.1Ni 0.4Co 0.3Mn 0.3O 2。
对正极材料Li 1.1Ni 0.4Co 0.3Mn 0.3O 2进行物化性能检测，该正极材料比表面积为0.65m 2/g，平均粒径为4.0μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知，该正极材料为呈中空微球结构的二次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约1.5μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为152mAh/g，该样品倍率性能较好，2C/1C为98.00％，5C/1C为94.24％，10C/1C为91.37％。
对比实施例5：
一种锂离子电池用正极材料，正极材料的化学式为Li 1.2Ni 0.6Co 0.2Mn 0.2O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.6Co 0.2Mn 0.2(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴、锰的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴锰的摩尔比为6:2:2，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为6mol/L的氨水溶液。反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至12.0，铵根离子浓度调节至0g/L，再将混合金属盐溶液、氢氧化钠溶液、氨水溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度55℃，转速500r/min，反应釜pH控制在10.5-12.0，反应釜内持续通入氮气；待材料粒度生长至1.5μm，然后将反应体系的铵根浓度调节至25g/L，进行外壳生长，直至粒度生长至5.5μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.6Co 0.2Mn 0.2(OH) 2前驱体，该前驱体平均粒径为5.5μm，其外壳部分厚度约2μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比1.20(Li与Ni+Co+Mn的摩尔比)称取适量上述前驱体及碳酸锂，按Mg占正极材料质量百分比为0.1wt％称取适量MgO，按Ti占正极材料比例为0.08wt％称取适量TiO 2，将上述物料混合均匀后在高温下进行烧结，先在700℃下保温6h，然后升温至850℃下保温10h，烧结气氛为氧气与空气混合，烧结完毕后待物料降温至室温后将其过筛处理，得到掺Mg和Ti的中空结构材料Li 1.2Ni 0.6Co 0.2Mn 0.2O 2。
对正极材料Li 1.2Ni 0.6Co 0.2Mn 0.2O 2进行物化性能检测，该正极材料比表面积为0.88m 2/g，平均粒径为6.0μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知，该正极材料为中空微球二次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约2.5μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为163mAh/g，该样品倍率性能较好，2C/1C为92.16％，5C/1C为88.06％，10C/1C为86.42％。
对比实施例6：
一种锂离子电池用正极材料，正极材料的化学式为Li 1.08Ni 0.9Co 0.08Al 0.02O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.9Co 0.08Al 0.02(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴的摩尔比为90:8，用铝的硫酸盐与过量氢氧化钠配制铝摩尔浓度为0.1mol/L偏铝酸盐溶液，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为5mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至11.5，铵根离子浓度调节至0g/L，再将混合金属盐溶液、偏铝酸盐溶液、氢氧化钠溶液、氨水溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度55℃，转速450r/min，反应釜pH控制在10.0-11.5，反应釜内持续通入氮气，控制混合金属盐溶液及偏铝酸盐溶液溶液的流量比，使镍钴铝的金属摩尔比为90:8:2；待材料粒度生长至2μm，然后将反应体系的铵根浓度调节至25g/L，进行外壳生长，直至粒度生长至9.0μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.9Co 0.08Al 0.02(OH) 2前驱体，该前驱体平均粒径为9.0μm，其外壳部分厚度约3.5μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比1.08(Li与Ni+Co+Mn的摩尔比)称取适量上述前驱体及氢氧化锂，按Sr占正极材料质量百分比为0.2wt％称取适量SrCO 3，将上述物料混合均匀后在高温下进行烧结，直接升至710℃下保温12h，烧结气氛为氧气，烧结完毕后待物料降温至室温后将其 过筛处理，得到掺Sr的中空结构材料Li 1.08Ni 0.9Co 0.08Al 0.02O 2。
对正极材料Li 1.08Ni 0.9Co 0.08Al 0.02O 2进行物化性能检测，该正极材料比表面积为0.5m 2/g，平均粒径为9.0μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知，该正极材料为中空微球二次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约4μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为188mAh/g，该样品倍率性能较好，2C/1C为90.89％，5C/1C为87.43％，10C/1C为85.24％。
对比实施例7：
一种本发明的锂离子电池用正极材料，正极材料的化学式为Li 1.1Ni 0.5Co 0.3Mn 0.2O 2，如图1所示，正极材料为呈中空微球结构的二次颗粒，二次颗粒的外壳部分由若干一次颗粒聚集而成。
该正极材料的制备方法，包括如下步骤：
(1)利用共沉淀法合成Ni 0.5Co 0.3Mn 0.2(OH) 2前驱体，该前驱体的合成包括成核及内核生长阶段和外壳生长阶段，具体操作包括：首先用含有镍、钴、锰的硫酸盐，配制总金属离子浓度为2mol/L的混合金属盐溶液，镍钴锰的摩尔比为5:3:2，配制浓度为2mol/L的氢氧化钠溶液与铵根离子浓度为5mol/L的氨水溶液，反应釜中以纯水作为底液，用氢氧化钠将反应釜底液中pH调整至12.0，铵根浓度调节至3g/L，再将混合金属盐溶液、氢氧化钠溶液、氨水溶液通过计量泵通入到反应釜中进行反应，反应过程中，反应温度55℃，转速400r/min，反应釜pH控制在10.0-12.0，反应釜内持续通入氮气；在成核及内核生长阶段将反应体系中氨根浓度控制在3g/L，待材料粒度生长至2.5μm，然后将反应体系的铵根浓度调节至25g/L，进行外壳生长，直至粒度生长至4.5μm；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即得到Ni 0.5Co 0.3Mn 0.2(OH) 2前驱体，该前驱体平均粒径为4.5μm，其外壳部分厚度约1μm，该前驱体由微小粒子组成的中心部和比该微小粒子大的粒子组成的外壳部构成。
(2)按锂金属比(Li与Ni+Co+Mn的摩尔比)1.10称取适量上述前驱体及碳酸锂，按W占正极材料质量百分比为0.1wt％称取适量WO 3，将上述物料混合均匀后在高温下进行烧结，烧结工序包括升温平台、高温平台及降温平台，先在700℃下保温6h，然后升温至880℃下保温10h，再降温至750℃保温5h，烧结气氛为氧气与空气混合，烧结完毕后待物料降温至室温后将其过筛处理，得到掺W的中空微球结构的正极材料Li 1.1Ni 0.5Co 0.3Mn 0.2O 2。
对正极材料Li 1.1Ni 0.5Co 0.3Mn 0.2O 2进行物化性能检测，该正极材料比表面积为1.89m 2/g，平均粒径为4.5μm。对该材料进行SEM观察和剖面SEM观察，从电镜结果可知，该材料呈二次球形结构，颗粒大小均匀。通过剖面SEM结果可知，该正极材料为呈中空微球结构的二 次颗粒，其外壳部分由一次颗粒烧结聚集而成，其外壳部厚度约1μm。
采用2032型纽扣电池对该正极材料进行电性能评价，其1C初始放电比容量为158.6mAh/g，该样品倍率性能较好，2C/1C为99.02％，5C/1C为95.66％，10C/1C为92.13％。

Claims (10)

  1. 一种高功率型的锂离子电池用正极材料，其特征在于，所述正极材料的化学式为Li aNi xCo yM zO 2，其中，0.96≤a≤1.35，0.3≤x≤1，0≤y≤0.4，0≤z≤0.4，x+y+z＝1，M为Mn、Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种；所述正极材料为呈中空微球结构的二次颗粒，所述二次颗粒的外壳部分由若干一次颗粒聚集而成。
  2. 根据权利要求1所述的锂离子电池用正极材料，其特征在于，所述二次颗粒的平均粒径为0.1μm-40μm，比表面积为0.1m 2/g-15.0m 2/g；所述一次颗粒的粒径为0.1μm-3.5μm；所述二次颗粒的外壳部分厚度与二次颗粒粒径的比值为1％-49％。
  3. 根据权利要求1或2所述的锂离子电池用正极材料，其特征在于，所述正极材料还包括掺杂元素，所述掺杂元素为Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种，该掺杂元素在所述正极材料中所占质量百分比为0.01wt％-2wt％。
  4. 一种如权利要求1-3中任一项所述的锂离子电池用正极材料的制备方法，其特征在于，包括如下步骤：
    (1)采用共沉淀法合成Ni xCo yM z(OH) 2前驱体，所述前驱体的合成包括成核及内核生长阶段和外壳生长阶段，在所述成核及内核生长阶段，不使用络合剂或者使用低浓度的络合剂；在外壳生长阶段，使用浓度高于成核及内核生长阶段的络合剂；得到的前驱体的中心部由微小粒子组成，外壳部由粒径比该微小粒子更大的大粒子组成；
    (2)将所述步骤(1)得到的前驱体与锂盐混合均匀，然后进行烧结，得到Li aNi xCo yM zO 2正极材料。
  5. 根据权利要求4所述的制备方法，其特征在于，所述步骤(1)中，采用共沉淀法合成Ni xCo yM z(OH) 2前驱体的操作，具体包括如下步骤：将含有Ni、Co、M的金属盐溶液、碱溶液、氨水溶液分别加入到具有底液的反应釜中进行反应，反应过程中，反应温度为40℃-60℃，搅拌转速为100r/min-1000r/min，反应体系的pH值控制在8-13，反应釜内持续通入氮气；在前驱体的成核及内核生长阶段控制反应体系的铵根离子浓度为0g/L-15g/L，外壳生长阶段控制反应体系的铵根离子浓度为5g/L-40g/L，且外壳生长阶段的铵根离子浓度要高于成核阶段及内核生长阶段的铵根离子浓度；反应得到的沉淀经固液分离、陈化、洗涤以及烘干后，即可得到Ni xCo yM z(OH) 2前驱体。
  6. 根据权利要求5所述的制备方法，其特征在于，在前驱体的成核及内核生长阶段控制反应体系的铵根离子浓度为7g/L-15g/L，外壳生长阶段控制反应体系的铵根离子浓度为30g/L-40g/L。
  7. 根据权利要求5所述的制备方法，其特征在于，所述金属盐溶液为硫酸盐溶液、硝酸盐溶液、氯化盐溶液、醋酸盐溶液和偏铝酸盐溶液中的一种或多种，所述金属盐溶液中总金 属离子浓度为0.05mol/L-3mol/L；所述碱溶液为氢氧化钠溶液，所述碱溶液的浓度为1mol/L-10mol/L；所述氨水溶液的铵根离子浓度为3mol/L-6mol/L；所述中心部的微小粒子粒径＜0.3μm，外壳部的大粒子粒径≥0.3μm。
  8. 根据权利要求4所述的制备方法，其特征在于，所述步骤(2)中，锂盐的添加量以Li与Ni+Co+M的摩尔比值为0.96-1.35为准，所述锂盐为碳酸锂、氢氧化锂、草酸锂和醋酸锂中的一种或多种；在所述前驱体与锂盐混合时还加入掺杂元素的氧化物，所述掺杂元素为Al、Zr、Mg、W、Ti、Y、La、B和Sr中的一种或多种，该掺杂元素在所述正极材料中所占质量百分比为0.01wt％-2wt％。
  9. 根据权利要求4-8中任一项所述的制备方法，其特征在于，所述步骤(2)中，烧结的温度为500℃-1000℃，烧结的时间为6-24h，烧结气氛为空气或氧气，或氧气与空气混合。
  10. 根据权利要求9所述的制备方法，其特征在于，在烧结过程中采用多段控温烧结的方式，先在500-700℃下保温5-6h，然后升温至810-1000℃下保温8-10h，再降温至700-750℃保温5-8h。
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