Positive electrode mixture for lithium ion secondary battery, method for producing positive electrode mixture for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

Abstract

To provide a cathode composite material, a manufacturing method of the same, a cathode, and a lithium ion secondary battery.SOLUTION: A cathode composite material contains: a cathode base material of which a Mg element is doped; and a fluoride that is a fluoride existed in a dot shape onto a front surface of the cathode base material, and contains MgF2. By the cathode composite material, a method for manufacturing the cathode composite material, a cathode containing the cathode composite material, and a lithium ion secondary battery of the present invention, corrosion of the cathode base material due to an electrolyte in the lithium ion secondary battery can be effectively prevented, and can hold larger lithium ion channels. Without an influence to a capacity and an initial resistance of the lithium ion secondary battery, a cycle performance of the lithium ion secondary battery is improved, and an increase of a resistance of the lithium ion secondary battery can be reduced.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion secondary batteries, and in particular to a cathode mixture, a method for producing the cathode mixture, and a cathode and a lithium ion secondary battery including the cathode mixture. [Background technology]

[0002] In recent years, with the continuous development of electronic technology, people's demand for battery devices to support the energy supply of electronic devices has also been constantly increasing. Today, there is a demand for batteries that can store more electricity and output higher power. Traditional lead-acid batteries and nickel-metal hydride batteries are no longer able to meet the demands of new electronic products, such as mobile devices like smartphones and stationary devices like energy storage systems. For this reason, lithium-ion batteries have attracted widespread attention. During the development of lithium-ion batteries, their capacity and performance have been effectively improved.

[0003] A lithium ion secondary battery comprises a positive electrode containing a positive electrode material, a negative electrode, and an electrolyte. The arrangement of the positive electrode material has a significant effect on the performance of the lithium ion secondary battery. Various studies have been conducted on the arrangement of the positive electrode material. Prior art discloses treating a positive electrode precursor to coat the surface of a substrate with one or more of Co2O3, BO3, Al2O3, and Al(OH)3. However, such a method increases the initial electrochemical reaction resistance of the material and also requires a high temperature for coating, resulting in higher energy consumption. Prior art also discloses LiNi 0.8 Co 0.1 Mn 0.1 Chemical composition is M for O2 x It is disclosed that a coating of pyrophosphate of P2O7 is used, where M is one or more of Ti, Na, K, Cu, Mg, Al, Zn, and Ca, but the coating obtained by this method has poor electronic and ionic conductivity, which increases the resistance of the positive electrode material and thereby reduces the rate performance.

[0004] The positive electrode materials in the prior art cannot effectively improve the cycling and resistance increase of lithium-ion secondary batteries, so there is a need to develop new positive electrode mixtures, methods for manufacturing the positive electrode mixtures, and positive electrodes and lithium-ion secondary batteries containing the positive electrode mixtures. Summary of the Invention [Problem to be solved by the invention]

[0005] The main objective of the present invention is to provide a positive electrode composite, a method for manufacturing the positive electrode composite, and a positive electrode and a lithium ion secondary battery including the positive electrode composite, in order to solve the problem in the prior art that positive electrode materials are difficult to effectively improve the cycle life and resistance increase of lithium ion secondary batteries. [Means for solving the problem]

[0006] In order to achieve the above object, according to one aspect of the present invention, there is provided a positive electrode composite, which includes a positive electrode base material doped with Mg element and a fluoride present in a dotted form on a surface of the positive electrode base material, the fluoride including MgF.

[0007] Furthermore, in the positive electrode mixture, the fluoride further includes one or more of LiF, AlF3, NH4F, MnF4, TiF3, ZrF4, SrF3, and MoF5.

[0008] Furthermore, in the positive electrode mixture, the doping concentration of Mg element is in the range of 0.05 wt% to 4.00 wt%, and preferably in the range of 0.30 wt% to 1.00 wt%, based on the weight of the positive electrode substrate.

[0009] Furthermore, in the positive electrode mixture, the amount of elemental fluorine in the positive electrode mixture is in the range of 0.03 wt% to 0.60 wt%, and preferably in the range of 0.06 wt% to 0.30 wt%.

[0010] Furthermore, in the positive electrode composite, the positive electrode substrate has the general formula LiNix Co y M (1-x-y) O2 high nickel positive electrode material, wherein M is one or two selected from Al and Mn, and x≧0.6, 0 <y<0.4である。 Furthermore, in the positive electrode mixture, the Mg element exhibits a gradient distribution within the particles of the positive electrode substrate, and the concentration of the Mg element gradually decreases from the inside of the particle toward the outside of the particle.

[0011] According to another aspect of the present invention, there is provided a method for producing a cathode composite, the method including: step S1 mixing a cathode material precursor, lithium hydroxide, and magnesium oxide to obtain a first mixture, followed by sintering the first mixture at a first temperature for a first time to obtain a sintered product; and step S2 mixing a fluoride and the sintered product to obtain a second mixture, followed by calcining the second mixture at a second temperature for a second time.

[0012] Furthermore, in the method for producing the positive electrode composite, in step S1, the first temperature is in the range of 650° C. to 780° C., and the first time is in the range of 6 hours to 24 hours.

[0013] Furthermore, in the method for producing the positive electrode composite, in step S2, the second temperature is in the range of 200° C. to 350° C., and the second time is in the range of 2 hours to 8 hours.

[0014] Further, in the method for producing the cathode composite described above, the fluoride includes one or more of MgF2, LiF, AlF3, NH4F, MnF4, TiF3, ZrF4, SrF3, and MoF5.

[0015] Furthermore, in the method for producing the positive electrode mixture, the amount of magnesium oxide is in the range of 0.10 wt% to 5.00 wt%, and preferably in the range of 0.50 wt% to 1.50 wt%, based on the weight of the positive electrode material precursor.

[0016] Furthermore, in the method for producing the positive electrode mixture, the amount of fluoride is in the range of 0.05 wt% to 1.00 wt%, and preferably in the range of 0.10 wt% to 0.50 wt%, based on the weight of the positive electrode material precursor.

[0017] Furthermore, in the method for producing the positive electrode mixture, the sintering or calcination is carried out in an air atmosphere or an oxygen atmosphere.

[0018] Furthermore, in the method for producing the positive electrode composite described above, in step S2, the fluoride and the sintered product are mixed in a ball mill for 10 min to 60 min, and the rotation speed of the ball mill is within a range of 250 r / min to 300 r / min.

[0019] Furthermore, in the method for producing the positive electrode mixture, the positive electrode material precursor is a compound represented by the general formula Ni x Co y Mn (1-x-y) (OH)2 or Ni x Co y Al (1-x-y) (OH) (3-x-y) The material includes the following materials, where 0.8≦x<1 and 0.01≦y<0.2.

[0020] Furthermore, in the method for producing the positive electrode composite, the method further includes a step of crushing the calcined product obtained in step S2 to obtain a crushed product, and then sieving the crushed product preferably using a sieve with a mesh size of 150 to 350.

[0021] According to another aspect of the present invention, there is provided a lithium ion secondary battery positive electrode, the lithium ion secondary battery positive electrode including the above-described positive electrode mixture.

[0022] According to another aspect of the present invention, a lithium ion secondary battery is provided, the lithium ion secondary battery including a positive electrode, a negative electrode, and a separator, and the positive electrode includes the above-described positive electrode mixture. [Effects of the Invention]

[0023] The positive electrode composite, the method for producing the positive electrode composite, and the positive electrode and lithium ion secondary battery including the positive electrode composite of the present invention can effectively prevent the positive electrode substrate in the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery. [Brief explanation of the drawings]

[0024] [Figure 1] 1 shows a schematic diagram of the formation of MgF2 in the calcination process of step S2. [Figure 2] 1 shows a schematic diagram of fluoride present in the form of dots on the surface of a positive electrode substrate. [Figure 3] 1 shows a scanning electron microscope photograph of the positive electrode mixture produced in Example 1. [Figure 4] 1 shows the results of XPS analysis of the positive electrode mixture produced in Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] It should be noted that, where not inconsistent, the embodiments and features in the embodiments in this application can be combined with each other. The present invention will be described in detail below in conjunction with the examples. The following examples are for illustrative purposes only and do not constitute limitations on the protection scope of the present invention.

[0026] As described in the background art, it is difficult for the positive electrode materials in the prior art to effectively improve the cycle life and resistance increase of lithium-ion secondary batteries. Regarding the problems in the prior art, one exemplary embodiment of the present invention provides a positive electrode mixture, which includes a positive electrode substrate doped with Mg element and a fluoride dot-like fluoride present on the surface of the positive electrode substrate, the fluoride including MgF2.

[0027] Fluoride has a high band gap, can maintain stable performance in the electrolyte of a lithium ion secondary battery, and has good ionic conductivity. Furthermore, the fluoride exists on the surface of the positive electrode substrate in the form of dotted semi-coatings rather than fully coated, which can reserve more lithium ion channels without significantly changing the capacity and initial resistance of the lithium ion secondary battery. The fluoride dotted on the surface of the positive electrode substrate protects the positive electrode substrate during the charge and discharge process of the lithium ion secondary battery, preventing the positive electrode substrate from being corroded by the electrolyte, thereby exhibiting low resistance increase and good cycle performance.

[0028] Because magnesium fluoride (MgF2) is an electronically conductive insulator, using it to fully coat the positive electrode substrate increases the material's electronic resistivity and inhibits lithium ion insertion and release, adversely affecting the high-power discharge performance of lithium-ion secondary batteries. Fluorides, including MgF2, exist on the surface of the positive electrode substrate in the form of dotted semi-coatings, which can reserve a sufficiently large active contact area and prevent the material's electronic conductivity and ion insertion channels from being affected, achieving a balanced performance effect.

[0029] The cathode composite of the present invention comprises a cathode substrate doped with Mg and a fluoride containing MgF2 present on the surface of the cathode substrate in a dotted pattern. This improves the cycle retention and post-cycle resistance of lithium-ion secondary batteries without significantly changing the initial resistance of the material, without affecting the capacity or efficiency of the lithium-ion secondary battery, and with minimal change in the residual lithium content after coating. The doping with Mg stabilizes the crystal structure, improving cycle performance and thermal stability. In addition to the above effects, the present invention also uses Mg and F to form MgF2 on the surface, which provides surface protection.

[0030] In the positive electrode composite of the present invention, the positive electrode substrate is doped with Mg element, and the dotted fluoride is present on the surface of the positive electrode substrate, which can effectively prevent the positive electrode substrate of the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, thereby improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0031] In some embodiments of the present invention, in order to more effectively prevent corrosion of the positive electrode substrate in the lithium ion secondary battery by the electrolyte, more effectively improve the cycle performance of the lithium ion secondary battery, and more effectively reduce resistance increase in the lithium ion secondary battery, the fluoride in the positive electrode composite further includes one or more of LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5. Specifically, the fluoride may include one of LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5 in combination with MgF2, or the fluoride may include one of LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5 in combination with MgF2.

[0032] In some embodiments of the present invention, the doping concentration of Mg element in the positive electrode composite is in the range of 0.05 wt% to 4.00 wt%, preferably 0.30 wt% to 1.00 wt%, based on the weight of the positive electrode substrate. By controlling the doping concentration of Mg element within this range, the cycle performance of the lithium ion secondary battery can be significantly improved, the increase in resistance of the lithium ion secondary battery can be significantly reduced, and the stability and safety of the lithium ion secondary battery can be improved without affecting the capacity and initial resistance of the lithium ion secondary battery. If the doping concentration of Mg element is too low, it may not perform its function, and if the doping concentration of Mg element is too high, it may result in a decrease in capacity.

[0033] Specifically, the doping concentration of Mg element is 0.05 wt% to 4.00 wt%, 0.10 wt% to 3.80 wt%, 0.15 wt% to 3.60 wt%, 0.20 wt% to 3.40 wt%, 0.25 wt% to 3.20 wt%, 0.30 wt% to 3.00 wt%, 0.35 wt% to 2.80 wt%, 0.40 wt% to 2.60 wt%, 0.45 wt% to 2.40 wt%, It may be in the range of 0.50 wt% to 2.20 wt%, 0.55 wt% to 2.00 wt%, 0.60 wt% to 1.80 wt%, 0.65 wt% to 1.60 wt%, 0.70 wt% to 1.40 wt%, 0.75 wt% to 1.20 wt%, 0.80 wt% to 1.00 wt%, 0.40 wt% to 0.90 wt%, 0.50 wt% to 0.80 wt%, or 0.60 wt% to 0.70 wt%.

[0034] In some embodiments of the present invention, the amount of elemental fluorine in the positive electrode composite is in the range of 0.03 wt% to 0.60 wt%, preferably in the range of 0.06 wt% to 0.30 wt%. By controlling the amount of elemental fluorine within this range, the cycle performance of the lithium ion secondary battery can be significantly improved, the resistance increase of the lithium ion secondary battery can be significantly reduced, and the stability and safety of the lithium ion secondary battery can be improved without affecting the capacity and initial resistance of the lithium ion secondary battery. If the amount of elemental fluorine added is too small, it may not fulfill its function. If the amount of elemental fluorine added is too large, the initial resistance may be increased.

[0035] Specifically, the amount of elemental fluorine in the positive electrode composite may be within a range of 0.03 wt% to 0.60 wt%, 0.08 wt% to 0.55 wt%, 0.13 wt% to 0.50 wt%, 0.18 wt% to 0.45 wt%, 0.23 wt% to 0.40 wt%, 0.28 wt% to 0.35 wt%, 0.06 wt% to 0.30 wt%, 0.11 wt% to 0.25 wt%, or 0.16 wt% to 0.20 wt%.

[0036] The positive electrode substrate in the present invention can use ordinary positive electrode active materials in this field. Preferably, in some embodiments of the present invention, the positive electrode substrate may be a lithium-containing compound. Examples of such lithium-containing compounds include, for example, lithium-transition metal composite oxides such as lithium nickelate (LiNiO2).

[0037] In some embodiments of the present invention, in the above positive electrode composite, the positive electrode substrate has a general formula of LiNi x Co y M (1-x-y) O2, a high-nickel positive electrode material, provided that M is one or two selected from Al and Mn, x≧0.6, and 0<y<0.4. Preferably, in the above positive electrode composite, the positive electrode substrate is the high-nickel positive electrode material of the above general formula.

[0038] When the positive electrode substrate contains the high-nickel positive electrode material of the above general formula, by doping the positive electrode substrate containing the high-nickel positive electrode material with Mg element, and by the fluoride existing in dot form on the surface of the positive electrode substrate containing the high-nickel positive electrode material, the positive electrode composite of the present invention can more effectively prevent the positive electrode substrate containing the high-nickel positive electrode material in the lithium-ion secondary battery from being corroded by the electrolyte, can retain more lithium-ion channels, improve the cycle performance of the lithium-ion secondary battery better without affecting the capacity and initial resistance of the lithium-ion secondary battery, further reduce the increase in the resistance of the lithium-ion secondary battery, solve the problem of the increase in the initial resistance due to the coating of the positive electrode substrate containing the high-nickel positive electrode material, and solve the problem that the increase in the resistance after cycling is too high when using the positive electrode substrate containing the high-nickel positive electrode material as the positive electrode material of the lithium-ion battery.

[0039] In some embodiments of the present invention, the Mg element in the positive electrode composite has a gradient distribution within the particles of the positive electrode substrate, and the Mg element concentration gradually decreases from the inside to the outside of the particle. The presence of the Mg element on the surface of the positive electrode substrate increases the initial resistance, and the gradient concentration distribution allows a small amount of Mg to be present on the surface of the positive electrode substrate in the form of MgF2, which minimizes the impact on the initial resistance.

[0040] In another exemplary embodiment of the present invention, a method for manufacturing a cathode composite is provided, the method including: a step S1 of mixing a cathode material precursor, lithium hydroxide, and magnesium oxide to obtain a first mixture, followed by sintering the first mixture at a first temperature for a first time to obtain a sintered product; and a step S2 of mixing a fluoride and the sintered product to obtain a second mixture, followed by calcining the second mixture at a second temperature for a second time.

[0041] The method for producing a positive electrode composite of the present invention involves doping a positive electrode substrate with Mg through a sintering process in step S1, and then dry-coating the surface of the positive electrode substrate with fluoride through a calcination process in step S2. The fluoride reacts with the Mg doped into the positive electrode substrate to produce MgF2, forming fluoride-containing MgF2 dots on the surface of the positive electrode substrate. This solves the problem of the prior art, in which positive electrode materials are unable to effectively improve the cycle life and resistance increase of lithium-ion secondary batteries. Figure 1 shows a schematic diagram of the formation of MgF2 during the calcination process in step S2. Figure 2 shows a schematic diagram of the fluoride dots on the surface of the positive electrode substrate.

[0042] The key technical point of the present invention is that the doped Mg reacts with fluoride during the calcination process to generate MgF2, and the fluoride exists on the surface of the positive electrode substrate in the form of dotted semi-coating, without significantly increasing the initial resistance of the lithium ion secondary battery. Fluoride, especially metal fluoride, has a very high band gap and is less likely to react with the electrolyte in the lithium ion secondary battery, thus protecting the positive electrode substrate.

[0043] In addition, the method for producing the cathode composite of the present invention involves dry semi-coating of the cathode substrate in dots, which simplifies the overall production process, requires low coating temperatures, and is highly economical.

[0044] In the positive electrode composite prepared by the method of the present invention, the fluoride has a high band gap, can maintain stable performance in the electrolyte of a lithium ion secondary battery, and has good ionic conductivity. Furthermore, the fluoride is present on the surface of the positive electrode substrate in the form of dotted semi-coatings rather than fully coated, which can reserve more lithium ion channels and cause no significant change in the capacity and initial resistance of the lithium ion secondary battery. The fluoride present in dotted form on the surface of the positive electrode substrate protects the positive electrode substrate during the charge and discharge process of the lithium ion secondary battery, preventing corrosion of the positive electrode substrate by the electrolyte, thereby exhibiting low resistance increase and good cycle performance.

[0045] In the cathode composite prepared by the method of the present invention, the cathode substrate is doped with Mg element, and the dotted fluoride is present on the surface of the cathode substrate, which can effectively prevent the cathode substrate of the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, thereby improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0046] In some embodiments of the present invention, in the method for producing the cathode composite, in step S1, the first temperature is in the range of 650°C to 780°C, and the first time is in the range of 6 hours to 24 hours. Preferably, the first temperature is in the range of 660°C to 760°C, and the first time is in the range of 7 hours to 20 hours. More preferably, the first temperature is in the range of 670°C to 740°C, and the first time is in the range of 8 hours to 16 hours. Most preferably, the first temperature is in the range of 680°C to 720°C, and the first time is in the range of 8 hours to 12 hours. By controlling the first temperature and the first time in step S1 within the above ranges, the cathode substrate can be doped with Mg element very well, resulting in a good Mg doping effect, which can improve the cycle performance of the lithium-ion secondary battery and reduce the increase in resistance of the lithium-ion secondary battery.

[0047] In some embodiments of the present invention, in step S2 of the method for producing a cathode composite, the second temperature is in a range of 200°C to 350°C, and the second time is in a range of 2 hours to 8 hours, preferably the second temperature is in a range of 250°C to 340°C, and the second time is in a range of 3 hours to 7 hours, more preferably the second temperature is in a range of 270°C to 320°C, and the second time is in a range of 4 hours to 6 hours, even more preferably the second temperature is in a range of 280°C to 310°C, and the second time is in a range of 4 hours to 5 hours, and most preferably the second temperature is in a range of 290°C to 300°C, and the second time is in a range of 4 hours to 5 hours. By controlling the second temperature and the second time in step S2 within the above ranges, the fluoride can react very well with the Mg doped in the positive electrode substrate to generate MgF2, thereby achieving a good dot-shaped semi-coating effect, which can improve the cycle performance of the lithium ion secondary battery and reduce the increase in resistance of the lithium ion secondary battery.

[0048] In some embodiments of the present invention, in order to more effectively prevent corrosion of the positive electrode substrate in a lithium ion secondary battery by an electrolyte, more effectively improve the cycle performance of the lithium ion secondary battery, and more effectively reduce the resistance increase of the lithium ion secondary battery, the fluoride in the method for producing the positive electrode composite includes one or more of MgF2, LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5. When the fluoride added in step S2 includes one or more of LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5, a substitution reaction occurs between the fluoride and the Mg doped in the positive electrode substrate in step S2 to produce MgF2, and the finally obtained positive electrode composite includes a combination of MgF2 and one or more of LiF, AlF3, NHF, MnF4, TiF3, ZrF4, SrF3, and MoF5 present in the form of dots on the surface of the positive electrode substrate.

[0049] In some embodiments of the present invention, in the method for preparing the cathode composite, the amount of magnesium oxide is in the range of 0.10 wt % to 5.00 wt %, preferably 0.50 wt % to 1.50 wt %, based on the weight of the cathode material precursor. By controlling the amount of magnesium oxide added in step S1 within this range, the cycle performance of the lithium ion secondary battery can be significantly improved, the increase in resistance of the lithium ion secondary battery can be significantly reduced, and the stability and safety of the lithium ion secondary battery can be improved without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0050] Specifically, the amount of magnesium oxide is 0.10 wt% to 5.00 wt%, 0.15 wt% to 4.80 wt%, 0.20 wt% to 4.60 wt%, 0.25 wt% to 4.40 wt%, 0.30 wt% to 4.20 wt%, 0.35 wt% to 4.00 wt%, 0.40 wt% or more, based on the weight of the positive electrode material precursor. ~3.80wt%, 0.45wt%~3.60wt%, 0.50wt%~3.40wt%, 0.55wt%~3.20wt%, 0.60wt%~3. 00wt%, 0.65wt% to 2.80wt%, 0.70wt% to 2.60wt%, 0.75wt% to 2.40wt%, 0.80wt% to 2.20wt %, 0.85wt% to 2.00wt%, 0.90wt% to 1.80wt%, 0.95wt% to 1.60wt%, 1.00wt% to 1.40wt%, 1 .05wt% to 1.20wt%, 1.10wt% to 1.30wt%, 0.50wt% to 1.50wt%, 0.50wt% to 1.40wt%, 0.50w % to 1.30 wt%, 0.50 wt% to 1.20 wt%, 0.50 wt% to 1.10 wt%, 0.50 wt% to 1.00 wt%, 0.50 wt% to 0.90 wt%, 0.50 wt% to 0.80 wt%, 0.50 wt% to 0.70 wt%, or 0.50 wt% to 0.60 wt%.

[0051] In some embodiments of the present invention, in the method for preparing the cathode composite, the amount of fluoride is in the range of 0.05 wt% to 1.00 wt%, preferably 0.10 wt% to 0.50 wt%, based on the weight of the cathode material precursor. By controlling the amount of fluoride added in step S2 within this range, the cycle performance of the lithium ion secondary battery can be significantly improved, the increase in resistance of the lithium ion secondary battery can be significantly reduced, and the stability and safety of the lithium ion secondary battery can be improved without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0052] Specifically, the amount of fluoride may be within the range of 0.05 wt % to 1.00 wt %, 0.10 wt % to 0.90 wt %, 0.15 wt % to 0.80 wt %, 0.20 wt % to 0.70 wt %, 0.25 wt % to 0.60 wt %, 0.30 wt % to 0.50 wt %, 0.35 wt % to 0.40 wt %, 0.10 wt % to 0.50 wt %, 0.10 wt % to 0.45 wt %, 0.15 wt % to 0.40 wt %, 0.20 wt % to 0.35 wt %, or 0.25 wt % to 0.30 wt %, based on the weight of the cathode material precursor.

[0053] In some embodiments of the present invention, in the method for producing the cathode composite, sintering or calcining is performed in an air or oxygen atmosphere. Specifically, the first mixture is sintered in an air or oxygen atmosphere, or the second mixture is calcined in an air or oxygen atmosphere. The second mixture can be calcined in a roasting furnace or continuous kiln. If the cathode substrate contains a high-nickel cathode material, it is best to sinter it in a pure oxygen atmosphere; otherwise, defects in the crystal structure may be present. If the sintering atmosphere does not contain oxygen during the production of the cathode composite, defects in the crystal structure of the cathode substrate are likely to occur. However, because the sintering temperature during the production of the cathode composite is low, a pure oxygen atmosphere is not necessarily required, but an oxygen or air atmosphere is required.

[0054] In some embodiments of the present invention, in the method for producing the cathode composite, the fluoride and the sintered product may be mixed in step S2 using a ball mill or a high-speed dry mixer. In some embodiments of the present invention, the fluoride and the sintered product are mixed in a ball mill for 10 to 60 minutes, and the rotation speed of the ball mill is within a range of 250 to 300 r / min. The ball mill contains agate balls of different particle sizes, which allows the materials to be thoroughly mixed. By controlling the mixing time and the rotation speed of the ball mill within the above ranges in step S2, it is possible to ensure that the fluoride and the sintered product are thoroughly and uniformly mixed.

[0055] In some embodiments of the present invention, the method for producing the cathode composite may use a cathode material precursor that is conventional in the art. Preferably, the cathode material precursor has the general formula: x Co y Mn (1-x-y) (OH)2 or Ni x Co y Al (1-x-y) (OH) (3-x-y) where x is a positive electrode material having a cation bond, y is a positive electrode material having a cation bond, and y is a positive electrode material having a cation bond. The positive electrode material of the present invention comprises a material having the formula (x, y) above, where x is a positive electrode material having a cation bond, and y is a positive electrode material having a cation bond. The positive electrode material of the present invention can more effectively prevent the high-nickel positive electrode material positive electrode substrate in a lithium-ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels. This improves the cycle performance of the lithium-ion secondary battery without affecting the capacity and initial resistance of the lithium-ion secondary battery, and further reduces the increase in resistance of the lithium-ion secondary battery. This solves the problem of the increase in initial resistance due to coating of the high-nickel positive electrode material positive electrode substrate, and also solves the problem of excessive increase in resistance after cycling when the high-nickel positive electrode material positive electrode substrate is used as the positive electrode material for a lithium-ion battery.

[0056] In some embodiments of the present invention, the method for producing the positive electrode mixture further includes crushing the calcined product obtained in step S2 to obtain a crushed product, and then sieving the crushed product, preferably using a 150 to 350 mesh sieve. The presence of large particles can affect the subsequent preparation and application of a positive electrode paste and the preparation of an electrode sheet. Sieving can remove large particles. This step allows a positive electrode mixture with an appropriate particle size to be obtained.

[0057] In another exemplary embodiment of the present invention, a positive electrode for a lithium ion secondary battery is provided, the positive electrode for the lithium ion secondary battery comprising the above-described positive electrode mixture. Because the positive electrode for the lithium ion secondary battery of the present invention comprises the above-described positive electrode mixture, it can effectively prevent the positive electrode substrate of the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0058] In another exemplary embodiment of the present invention, a lithium ion secondary battery is provided, the lithium ion secondary battery including a positive electrode, a negative electrode, and a separator, the positive electrode including the above-described positive electrode mixture. Because the lithium ion secondary battery of the present invention includes the above-described positive electrode mixture, it can effectively prevent the positive electrode substrate of the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0059] The positive electrode of the present invention includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode mixture. The positive electrode active material layer is formed on two surfaces of the positive electrode current collector. The positive electrode current collector can be a metal foil such as aluminum foil, nickel foil, or stainless steel foil. The negative electrode of the present invention includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material. The negative electrode active material layer is formed on two surfaces of the negative electrode current collector. The negative electrode current collector can be a metal foil such as copper (Cu) foil, nickel foil, or stainless steel foil.

[0060] The negative electrode active material layer contains one or more negative electrode materials capable of inserting and releasing lithium ions as the negative electrode active material, and may contain other materials, such as a negative electrode binder and / or a negative electrode conductive agent, if necessary. The negative electrode active material may be selected from one or more of lithium metal, lithium alloy, carbon material, silicon or tin, and oxides thereof.

[0061] The separator of the present invention is used to separate the positive electrode and the negative electrode in a battery, to allow lithium ions to pass through, and to prevent short-circuiting of current due to contact between the positive electrode and the negative electrode. The separator is, for example, a porous film formed from a synthetic resin or ceramic, or may be a laminated film formed by laminating two or more types of porous films. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene.

[0062] In an embodiment of the present invention, when a lithium ion secondary battery is charged, for example, lithium ions are released from the positive electrode and inserted into the negative electrode by the electrolyte impregnated in the separator, and when the lithium ion secondary battery is discharged, for example, lithium ions are released from the negative electrode and inserted into the positive electrode by the electrolyte impregnated in the separator.

[0063] The present application will be described in more detail below in conjunction with specific examples, but these examples should not be construed as limiting the scope of protection sought by the present application.

[0064] Example 1 In step S1, 100 g of the positive electrode material precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 27 g of LiOH, and 0.5 g of magnesium oxide were weighed out, and the positive electrode material precursor, LiOH, and magnesium oxide were uniformly mixed and sintered at 680°C for 8 hours in a pure oxygen atmosphere to obtain a sintered product doped with Mg.

[0065] In step S2, 0.3 g of MgF2 is weighed out as a coating material. The coating material and the sintered product obtained in step S1 are added to a mixer and mixed uniformly. The mixer rotation speed is 300 r / min, and the mixing time is 30 minutes. The mixed material is placed in a roasting furnace and calcined at 300°C for 4 hours under oxygen gas. The calcined product is removed and crushed using a crusher, and then sieved using a 200-mesh sieve to obtain a positive electrode composite.

[0066] In step S3, 90 g of the positive electrode composite produced in the above steps, 5 g of conductive carbon black as a conductive agent, and 5 g of polyvinylidene fluoride (PVDF) as a binder were weighed out to prepare an electrode sheet. A half cell was also produced using the electrode sheet, and the results are shown in Table 1.

[0067] Example 2 In step S1, 100 g of the positive electrode material precursor Ni 0.8 Co 0.1 Mn 0.1 Instead of (OH)2, 100g of the cathode material precursor Ni 0.8 Co 0.15 Al 0.05 A half-cell was fabricated using the same method as in Example 1, except that (OH)2 was used.

[0068] Example 3 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of LiF was used as the coating material instead of 0.3 g of MgF2.

[0069] Example 4 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of AlF3 was used as the coating material instead of 0.3 g of MgF2.

[0070] Example 5 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of TiF3 was used as the coating material instead of 0.3 g of MgF2.

[0071] Example 6 A half-cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of ZrF4 was used as the coating material instead of 0.3 g of MgF2.

[0072] Example 7 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of SrF3 was used as the coating material instead of 0.3 g of MgF2.

[0073] Example 8 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of MoF5 was used as the coating material instead of 0.3 g of MgF2.

[0074] Example 9 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of NH4F was used as the coating material instead of 0.3 g of MgF2.

[0075] Example 10 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.3 g of MnF4 was used as the coating material instead of 0.3 g of MgF2.

[0076] Example 11 A half-cell was produced in the same manner as in Example 1, except that in step S2, calcination was carried out at 250°C for 4 hours instead of at 300°C for 4 hours.

[0077] Example 12 A half-cell was produced in the same manner as in Example 1, except that in step S2, calcination was carried out at 350°C for 4 hours instead of at 300°C for 4 hours.

[0078] Example 13 A half cell was produced in the same manner as in Example 1, except that in step S2, 0.05 g of MgF2 was used as the coating material instead of 0.3 g of MgF2.

[0079] Example 14 A half cell was produced in the same manner as in Example 1, except that in step S2, 1.0 g of MgF2 was used as the coating material instead of 0.3 g of MgF2.

[0080] Example 15 A half cell was fabricated in the same manner as in Example 1, except that in step S1, 0.1 g of magnesium oxide was used instead of 0.5 g of magnesium oxide.

[0081] Example 16 A half cell was fabricated using the same method as in Example 1, except that in step S1, 1.5 g of magnesium oxide was used instead of 0.5 g of magnesium oxide.

[0082] Example 17 A half cell was fabricated using the same method as in Example 1, except that in step S1, 5.0 g of magnesium oxide was used instead of 0.5 g of magnesium oxide.

[0083] Example 18 A half-cell was fabricated using the same method as in Example 1, except that in step S1, sintering was performed at 650°C for 6 hours instead of at 680°C for 8 hours.

[0084] Example 19 A half-cell was fabricated using the same method as in Example 1, except that in step S1, sintering was performed at 780°C for 24 hours instead of at 680°C for 8 hours.

[0085] (Comparative Example 1) 100g of cathode precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 27 g of LiOH, and 0.5 g of magnesium oxide were weighed out, and the cathode material precursor, LiOH, and magnesium oxide were uniformly mixed and sintered at 680°C for 8 h in a pure oxygen atmosphere to obtain an Mg-doped cathode material.

[0086] An electrode sheet was prepared by weighing out 90 g of the positive electrode material obtained by the above process, 5 g of conductive carbon black as a conductive agent, and 5 g of polyvinylidene fluoride (PVDF) as a binder. A half cell was prepared using the electrode sheet, and the results are shown in Table 1.

[0087] (Comparative Example 2) A half-cell was fabricated using the same method as in Example 1, except that in step S1, sintering was performed at 800°C for 8 hours instead of at 680°C for 8 hours.

[0088] (Comparative Example 3) In step S1, 100 g of the positive electrode material precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and 27 g of LiOH were weighed out, and the positive electrode material precursor and LiOH were uniformly mixed and sintered at 680°C for 8 hours in a pure oxygen atmosphere to obtain a sintered product.

[0089] In step S2, 0.3 g of MgF2 is weighed out as a coating material. The coating material and the sintered product obtained in step S1 are added to a mixer and mixed uniformly. The mixer rotation speed is 300 r / min, and the mixing time is 30 minutes. The mixed material is placed in a roasting furnace and calcined at 300°C for 4 hours under oxygen gas. The calcined product is removed and crushed using a crusher, and then sieved using a 200-mesh sieve to obtain a positive electrode composite.

[0090] In step S3, 90 g of the positive electrode composite produced in the above steps, 5 g of conductive carbon black as a conductive agent, and 5 g of polyvinylidene fluoride (PVDF) as a binder were weighed out to prepare an electrode sheet. A half cell was fabricated using the electrode sheet, and the results are shown in Table 1.

[0091] Comparative Example 4 In step S1, 100 g of the positive electrode material precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 27 g of LiOH, and 0.5 g of magnesium oxide were weighed out, and the cathode material precursor, LiOH, and magnesium oxide were uniformly mixed and sintered at 680°C for 8 hours in a pure oxygen atmosphere to obtain a sintered product doped with Mg.

[0092] In step S2, 0.3 g of MgF2 is weighed out as a coating material, and the coating material is dissolved in 30 mL of water. The resulting aqueous solution and the sintered product obtained in step S1 are added to a mixer and mixed uniformly at a mixer speed of 300 r / min for 30 minutes. After filtering and drying, the mixed material is placed in a roasting furnace and calcined at 300°C for 4 hours under oxygen gas. The calcined product is removed and crushed using a crusher, and then sieved using a 200-mesh sieve to obtain a positive electrode composite.

[0093] In step S3, 90 g of the positive electrode composite produced in the above steps, 5 g of conductive carbon black as a conductive agent, and 5 g of polyvinylidene fluoride (PVDF) as a binder were weighed out to prepare an electrode sheet. A half cell was fabricated using the electrode sheet, and the results are shown in Table 1.

[0094] Battery performance testing Charge-discharge and resistance tests were performed on the half-cells of Examples 1 to 19 and Comparative Examples 1 to 4 at voltages between 2.0 V and 4.25 V. The half-cells of the above Examples and Comparative Examples were first subjected to a single 0.1 C charge-discharge test at 23°C to determine the initial discharge capacity and initial resistance of the battery. Subsequently, a 1 C charge-5 C discharge cycle test was performed 100 times at 60°C to determine the capacity retention and post-cycle resistance increase factor of the battery. The experimental results are shown in Table 1 and Figures 3 and 4 below. Figure 4 specifically shows the spectrum of the 2p electron orbital of Mg element. The MgF2 fitting curve and MgO fitting curve can be clearly seen in Figure 4. It is necessary to subtract the background curve before fitting.

[0095] [Table 1]

[0096] As can be seen from the above test results, the above embodiments of the present invention achieve the following technical effects.

[0097] Comparing the results of Examples 1 to 19 with Comparative Example 1 reveals that the batteries in Examples 1 to 19, in which dotted fluoride is present on the surface of the positive electrode substrate, have a lower resistance increase factor and a significantly higher capacity retention rate after 100 cycles than Comparative Example 1, in which no fluoride is present on the surface of the positive electrode substrate. In particular, comparing Comparative Example 1 with Examples 1 and 3 to 14, in which the conditions for step S1 are identical, reveals that the batteries in Examples 1 and 3 to 14, in which dotted fluoride is present on the surface of the positive electrode substrate, have a lower resistance increase factor and a significantly higher capacity retention rate after 100 cycles than Comparative Example 1, in which no fluoride is present on the surface of the positive electrode substrate. Furthermore, it is reasonable that the initial resistance in some Examples is slightly higher than the initial resistance in the Comparative Examples due to the coating.

[0098] By comparing the results of Example 1 and Comparative Example 2, it can be seen that the battery in Example 1 of the present invention has a significantly lower resistance increase factor and a significantly higher capacity retention rate after 100 cycles compared to Comparative Example 2, which has a relatively high sintering temperature in step S1, but there is no change in the first charge capacity and initial resistance of the battery.

[0099] By comparing the results of Examples 1 to 19 with those of Comparative Example 3, it can be seen that the batteries in Examples 1 to 19, in which the positive electrode substrate was doped with Mg element, had a lower resistance increase factor and a significantly higher capacity retention rate after 100 cycles compared to Comparative Example 3, in which the positive electrode substrate was not doped with Mg element.

[0100] By comparing the results of Example 1 and Comparative Example 4, it can be seen that the battery in Example 1, which is subjected to the dry dot-shaped semi-coating of the present invention, has a significantly lower resistance increase factor, a significantly higher capacity retention rate after 100 cycles, a higher first charge capacity, and a lower initial resistance than the battery in Comparative Example 4, which is subjected to the wet full-coating.

[0101] By comparing the results of Examples 1 and 16 with those of Examples 15 and 17, it can be seen that when the amount of magnesium oxide is within the range of 0.50 wt % to 1.50 wt % relative to the weight of the positive electrode material precursor, the resistance increase factor can be further reduced and the capacity retention rate after 100 cycles can be further improved.

[0102] By comparing the results of Example 1 with Examples 13 and 14, it can be seen that when the amount of fluoride is within the range of 0.10 wt% to 0.50 wt% relative to the weight of the positive electrode material precursor, it has a better effect in reducing the resistance increase factor and improving the capacity retention rate after 100 cycles.

[0103] As can be seen from the above battery performance test results, the cathode composite of the present invention, the method for preparing the cathode composite, and the cathode and lithium ion secondary battery including the cathode composite can effectively prevent the cathode substrate of the lithium ion secondary battery from being corroded by the electrolyte, and can reserve more lithium ion channels, improving the cycle performance of the lithium ion secondary battery and reducing the increase in resistance of the lithium ion secondary battery without affecting the capacity and initial resistance of the lithium ion secondary battery.

[0104] The above description is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. Those skilled in the art can make various modifications and changes to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. a positive electrode substrate doped with Mg element; The fluoride present in the form of dots on the surface of the positive electrode substrate is MgF ２ and a coating layer made of a fluoride containing The positive electrode substrate has the general formula LiNi ｘ Co ｙ M （１－ｘ－ｙ） O ２ wherein M is one or both of Al and Mn, x≧0.6, 0<y<0.4, and (1−x−y)≠0; A positive electrode mixture for a lithium ion secondary battery, characterized in that

2. The fluoride may further include LiF, AlF ３ , N.H. ４ F, MnF ４ , TiF ３ , ZrF ４ , SrF ３ and MoF ５ including one or more of The positive electrode mixture for a lithium ion secondary battery according to claim 1 .

3. The doping concentration of the Mg element is in the range of 0.05 wt % to 4.00 wt % based on the weight of the positive electrode substrate.

3. The positive electrode mixture for a lithium ion secondary battery according to claim 1 or 2.

4. The doping concentration of the Mg element is in the range of 0.30 wt % to 1.00 wt % based on the weight of the positive electrode substrate. The positive electrode mixture for a lithium ion secondary battery according to claim 3 .

5. The amount of fluorine element in the positive electrode mixture is in the range of 0.03 wt % to 0.60 wt %.

3. The positive electrode mixture for a lithium ion secondary battery according to claim 1 or 2.

6. The amount of fluorine element in the positive electrode mixture is in the range of 0.06 wt % to 0.30 wt %. The positive electrode mixture for a lithium ion secondary battery according to claim 5 .

7. the Mg element exhibits a gradient distribution within the particle of the positive electrode substrate, and the concentration of the Mg element gradually decreases from the inside of the particle to the outside of the particle; The Mg element outside the particles is present in the form of fluoride.

3. The positive electrode mixture for a lithium ion secondary battery according to claim 1 or 2.

8. Step S1: mixing a cathode material precursor, lithium hydroxide, and magnesium oxide to obtain a first mixture, and then sintering the first mixture at a first temperature for a first time to obtain a sintered product; A fluoride and the sintered product are mixed to obtain a second mixture, and then the second mixture is calcined at a second temperature for a second time, thereby forming a dot-like fluoride, such as MgF, on the surface of the sintered product obtained in step S1. ２ Step S2 of forming a coating layer made of a fluoride containing The positive electrode material precursor has the general formula Ni ｘ Co ｙ Mn （１－ｘ－ｙ） (OH) ２ or Ni ｘ Co ｙ Al （１－ｘ－ｙ） (OH) （３－ｘ－ｙ） wherein 0.8≦x<1, 0.01≦y<0.2, and (1−x−y)≠0; A method for producing a positive electrode mixture for a lithium ion secondary battery, comprising:

9. In the step S1, the first temperature is in the range of 650°C to 780°C, and the first time is in the range of 6 hours to 24 hours.

9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

10. In step S2, the second temperature is in the range of 200°C to 350°C, and the second time is in the range of 2 hours to 8 hours.

9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

11. The fluoride is MgF ２ , LiF, AlF ３ , N.H. ４ F, MnF ４ , TiF ３ , ZrF ４ , SrF ３ and MoF ５ including one or more of 9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

12. the amount of magnesium oxide is in the range of 0.10 wt % to 5.00 wt % based on the weight of the positive electrode material precursor; 9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

13. The amount of magnesium oxide is in the range of 0.50 wt % to 1.50 wt % based on the weight of the cathode material precursor.

13. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 12.

14. the amount of the fluoride is in the range of 0.05 wt % to 1.00 wt % based on the weight of the cathode material precursor; 9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

15. The amount of the fluoride is in the range of 0.10 wt % to 0.50 wt %, based on the weight of the cathode material precursor.

15. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 14.

16. The sintering or calcination is carried out in an air atmosphere or an oxygen atmosphere.

9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

17. In step S2, the fluoride and the sintered product are mixed in a ball mill for 10 min to 60 min, and the rotation speed of the ball mill is within a range of 250 r / min to 300 r / min.

9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

18. The method further includes crushing the calcined product obtained in step S2 to obtain a crushed product, and then sieving the crushed product using a 150 to 350 mesh sieve.

9. The method for producing a positive electrode mixture for a lithium ion secondary battery according to claim 8.

19. The positive electrode mixture for a lithium ion secondary battery according to claim 1 or 2, A positive electrode for a lithium ion secondary battery.

20. A positive electrode and a negative electrode; A lithium ion secondary battery comprising: The positive electrode comprises the positive electrode mixture for a lithium ion secondary battery according to claim 1 or 2. A lithium-ion secondary battery characterized by:

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