Cathode material, preparation method and application thereof, cathode sheet and application thereof, lithium ion battery

Abstract

The application relates to the field of lithium ion battery positive electrode materials, and discloses a positive electrode material, a preparation method and application thereof, a positive electrode sheet and application thereof, and a lithium ion battery. The positive electrode material contains a phosphate phase. Compared with a positive electrode material without the phosphate phase, the positive electrode material has a 2theta of a (003) diffraction peak obtained by XRD (003) The 2theta of the (104) diffraction peak is offset to a small angle by 0.01-0.2 degrees. (104) The 2theta of the (104) diffraction peak is offset to a small angle by 0.01-0.15 degrees. The positive electrode material contains a phosphate phase in a bulk phase, and the positive electrode material has a special structure when tested by XRD, so that the structure stability of a lithium ion battery containing the positive electrode material is improved during charging and discharging, and the safety performance is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion battery cathode materials, in particular to a cathode material, a preparation method and application thereof, a cathode sheet and application thereof, and a lithium ion battery. BACKGROUND

[0002] With the increasing requirements of new energy vehicle market on the endurance mileage and safety of electric vehicles, developing lithium ion batteries with high energy density and high safety has become the focus of industry development. Increasing the nickel content of multi-element materials can effectively improve the energy density of the battery, but as the nickel content increases, the charge and discharge depth increases, the structural stability of the cathode material deteriorates, and the cycle performance and safety performance gradually deteriorate, causing the current industrialization progress of cathode materials with ultra-high nickel content to be hindered. In order to improve the safety performance of the ultra-high nickel cathode material, a structure-stable coating layer can usually be constructed on the surface to alleviate the collapse of the material surface structure during the charging and discharging process.

[0003] CN105940535A discloses that a phosphate coating is formed on the outer surface of the cathode material, which can react with lithium by-products on the outer surface to reduce the lithium by-products, thereby reducing the lithium by-products and preventing swelling and impedance film formation caused by the lithium by-products. However, the adhesion between the surface coating layer and the substrate is usually weak, and the coating layer is easy to fall off during the cycle process. Moreover, for the internal interface of the substrate, especially for the secondary spherical morphology agglomerate sample, the grain boundary position between the primary particles in the particles is difficult to protect, and the electrolyte gradually penetrates during the charging and discharging cycle process, causing side reactions at the grain boundary position, which seriously affects the battery cycle and safety. SUMMARY

[0004] The purpose of the present application is to overcome the problem that the existing lithium ion battery cannot balance the high energy density and high safety performance during the current development process, and to provide a cathode material, a preparation method and application thereof, a cathode sheet and application thereof, and a lithium ion battery. The cathode material contains a phosphate phase in the bulk phase, and the cathode material exhibits a special structure when tested by XRD, thereby improving the structural stability of the lithium ion battery containing the cathode material during the charging and discharging process, and greatly improving the safety performance.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a cathode material, characterized in that the cathode material contains a phosphate phase, and the 2θ of the (003) diffraction peak obtained by XRD of the cathode material is 0.01°-0.2° smaller than that of a cathode material without a phosphate phase. (003) The 2θ of the (104) diffraction peak is 0.01°-0.2° smaller than that of a cathode material without a phosphate phase. (104) The 2θ of the (104) diffraction peak is 0.01°-0.15° smaller than that of a cathode material without a phosphate phase.

[0006] The second aspect of the present application provides a preparation method of a positive electrode material, characterized in that the preparation method comprises:

[0007] (1) a mixed salt solution is prepared by mixing a nickel salt, a cobalt salt and an M salt according to a molar ratio of n(Ni):n(Co):n(M)=(1-x-y-z-m):x:y; a doping element G solution is prepared by mixing a doping element G; a P solution is prepared by dissolving a phosphate in deionized water; a complexing agent solution is prepared by mixing a complexing agent; and a precipitant solution is prepared by mixing a precipitant;

[0008] (2) the mixed salt solution, the precipitant solution, the P solution, the complexing agent solution and optionally the doping element G solution are added into a reaction kettle to perform a co-precipitation reaction, and a positive electrode material precursor is obtained through aging, filtration, washing and drying;

[0009] (3) the positive electrode material precursor, a Li source and optionally a compound containing the doping element G are mixed and sintered to obtain the positive electrode material;

[0010] wherein the amount of the mixed salt solution and the P solution satisfies 0mol%<n(P) / [n(Ni)+n(Co)+n(M)]<2mol%.

[0011] The third aspect of the present application provides a positive electrode material prepared by the above preparation method.

[0012] The fourth aspect of the present application provides a positive electrode tab, characterized in that the positive electrode tab comprises the above positive electrode material.

[0013] The fifth aspect of the present application provides an application of the above positive electrode material or positive electrode tab in a lithium ion battery.

[0014] The sixth aspect of the present application provides a lithium ion battery, characterized in that the lithium ion battery comprises the above positive electrode material or positive electrode tab.

[0015] Through the above technical solutions, the positive electrode material, the preparation method and application thereof and the lithium ion battery provided by the present application have the following beneficial effects:

[0016] In the present application, the positive electrode material contains a phosphate phase in the bulk phase, and the positive electrode material presents a special crystal structure when tested by XRD, so that the structural stability of the positive electrode material is significantly improved, and the cycle performance and safety performance of the lithium ion battery containing the positive electrode material are greatly improved.

[0017] Further, the phosphate phase of the positive electrode material provided by the present application is gradiently distributed, preferably, the phosphate phase is gradiently distributed along the direction from the center to the surface of the positive electrode material particle, wherein the phosphate is tightly connected with the positive electrode material through a tight chemical bond, thereby affecting the cell parameter of the positive electrode material, so that the XRD diffraction peak is offset to a certain extent, the special structure can effectively prevent the irreversible conversion of the positive electrode material to rock salt phase and spinel phase at high SOC, and affect the composition and thickness of the CEI film formed by the surface layer and the electrolyte, thereby improving the coulomb efficiency, cycle stability and safety of the positive electrode material.

[0018] Further, in the preparation method of the positive electrode material provided by the present application, the phosphate is introduced in situ during the preparation of the precursor, in particular, the addition amount, addition time and speed of the phosphate are controlled, so that the prepared positive electrode material contains a special phosphate phase in the bulk phase, and then the doping and sintering process in the later stage are controlled, and the coating and post-treatment process are controlled, so that the prepared positive electrode material has a suitable bulk phase structure and surface ion and electron transport channel, thereby ensuring good short-term and long-term performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the P element distribution profile of the positive electrode material of Example 1;

[0020] Figure 2 is the DSC of the positive electrode plate containing the positive electrode material of Example 1 and Comparative Example 1 after activation. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values should be considered to be an approximation within the context of the range or value. The endpoints of the ranges of values and the values within the range of values are not to be construed as limiting the range of values. It is specifically contemplated that each and every value within the range achieves at least the minimum range.

[0022] The first aspect of the present application provides a positive electrode material, characterized in that the positive electrode material contains a phosphate phase, and the (003) diffraction peak of the positive electrode material obtained by XRD has a 2θ (003) offset to a small angle of 0.01°-0.2°, and the (104) diffraction peak has a 2θ (104) offset to a small angle of 0.01°-0.15°.

[0023] In this invention, the bulk phase of the cathode material contains a phosphate phase, and the cathode material exhibits a special crystal structure when tested by XRD, which significantly improves the structural stability of the cathode material, thereby greatly improving the cycle performance and safety performance of the lithium-ion battery containing the cathode material.

[0024] In particular, when the 2θ of the (003) diffraction peak (003) And the 2θ of the (104) diffraction peak (104) Within the aforementioned range, shifting to a small angle allows the phosphate phase in the cathode material to stabilize the layered structure of the cathode material, effectively preventing the collapse of the layered structure under high charge state and the transformation to other rock salt phases, thus delaying the structural failure of the cathode material.

[0025] In this invention, the positive electrode material is obtained by XRD with a 2θ peak of (003) diffraction. (003) The 2θ of the (104) diffraction peak is 18-19°. (104) It is 44-45°.

[0026] Furthermore, when the cathode material is subjected to XRD, the 2θ peak of the (003) diffraction peak is obtained. (003) Shifting to a smaller angle of 0.02°-0.08°, the 2θ of the (104) diffraction peak (104) When the angle shifts to a smaller angle of 0.01°-0.05°, the overall performance of the cathode material is even better.

[0027] According to the present invention, the cell parameter a of the (103) diffraction peak obtained by XRD of the cathode material is 0.285-0.290 nm and the cell parameter c is 1.41-1.43 nm.

[0028] In this invention, the cell parameters a and c obtained by XRD of the cathode material satisfy the above-mentioned range, indicating that the cathode material has a complete hexagonal layered structure and a wide lithium-ion channel, thereby greatly improving the cycle performance and safety performance of the lithium-ion battery containing the cathode material.

[0029] Furthermore, the cathode material was subjected to XRD to obtain the 2θ of the (103) diffraction peak. (103) For every small angular shift of 0.01°, the cell parameter a decreases by 0.0004 nm, and the cell parameter c increases by 0.0007 nm.

[0030] According to the present invention, the phosphate phase is containing PO4. 3- Spinel phase.

[0031] Furthermore, based on the total molar amount of the cathode material, and using n(PO4) 3- The molar content of the phosphate phase is calculated to be 0 mol%. <n(PO43- ) 2 mol%.

[0032] In the present application, when the molar content of the phosphate phase in the positive electrode material satisfies the above range, there are enough phosphate groups in the bulk phase of the positive electrode material to anchor the material structure and maintain the structural stability, thereby greatly improving the cycle performance and safety performance of the lithium ion battery containing the positive electrode material; if the content of the phosphate phase is too high, it will affect the capacity of the material.

[0033] Further, the molar content of the phosphate phase satisfies 0.01 mol% ≤ n(PO4 3- ) 1.5 mol% based on the total molar amount of the positive electrode material. 3-

[0034] In a preferred embodiment of the present application, the content of the phosphate phase in the positive electrode material is gradiently distributed along the direction from the center to the surface of the positive electrode material particles.

[0035] In the present application, the gradiently distributed phosphate phase can further improve the structural stability of the positive electrode material, thereby further improving the cycle performance and safety performance of the lithium ion battery containing the positive electrode material.

[0036] Further, when the change rate of the molar content of the phosphate phase along the direction from the center to the surface of the positive electrode material particles is 0.01-1 mol% / μm, preferably 0.01-0.5 mol% / μm, the chemical bonds in the phosphate phase are more stable, which can inhibit the loss of anions and maintain the stability of the layered structure of the positive electrode material.

[0037] According to the present application, the positive electrode material comprises single-crystal large particles and / or secondary particles formed by agglomeration of primary particles.

[0038] According to the present application, the composition of the positive electrode material is shown in Formula I:

[0039] Li e (Ni 1-x-y-z-m Co x M y G z H m )O (4-3n) / 2 (PO4) n Formula I;

[0040] wherein 0.9 ≤ e ≤ 1.3, x ≤ (1-x-y-z-m), y ≤ (1-x-y-z-m), 0.5 ≤ 1-x-y-z-m < 1, 0 ≤ y < 0.2, 0 ≤ z < 0.05, 0 ≤ m < 0.05, 0 < n ≤ 0.01, y and z are not 0 at the same time; ​

[0041] M is selected from Al and / or Mn, G is selected from at least one element in Groups IIA- IIIA of Periods 2-5, and H is selected from at least one element of B, Mg, Ca, Sr, Y, Ti, V, Cr, Fe, Cu, Zr, W, Nb, and Al.

[0042] In the present application, the positive electrode material contains doping element G and coating element H, and specific types of doping element G and coating element H are selected, so that different bonds are formed between transition metals and different doping coating elements in the positive electrode material, and thus the battery prepared from the positive electrode material has high initial charge-discharge capacity and excellent cycle performance.

[0043] Further, 0.95≤e≤1.1, 0.53≤1-x-y-z-m<0.99, 0<y<0.15, 0<z<0.03, 0<m<0.03, and 0<n≤0.008.

[0044] Further, G is selected from at least one element of Al, Mg, Ca, Sr, Zr, Nb, and Mo, and H is selected from at least one element of B, Zr, Nb, Al, and Y.

[0045] The second aspect of the present application provides a preparation method of a positive electrode material, characterized in that the preparation method comprises:

[0046] (1) a nickel salt, a cobalt salt, and a M salt are prepared into a mixed salt solution according to a molar ratio of n(Ni):n(Co):n(M)=(1-x-y-z-m):x:y; a doping element G is prepared into a doping element G solution; a phosphate salt is dissolved in deionized water to prepare a P solution; a complexing agent is prepared into a complexing agent solution; and a precipitating agent is prepared into a precipitating agent solution;

[0047] (2) the mixed salt solution, the precipitating agent solution, the P solution, the complexing agent solution, and optionally the doping element G solution are added into a reaction kettle to perform a co-precipitation reaction, and a positive electrode material precursor is obtained through aging, filtration, washing, and drying;

[0048] (3) the positive electrode material precursor, a Li source, and optionally a compound containing the doping element G are mixed and sintered to obtain the positive electrode material.

[0049] The amount of the mixed salt solution and the P solution is such that 0mol%<n(P) / [n(Ni)+n(Co)+n(M)]<2mol%.

[0050] In the present application, by introducing phosphate in-situ during the preparation of the precursor, the prepared positive electrode material contains special phosphate phase in the bulk phase, and through the control of the doping and sintering process and the control of the coating and post-processing process, the positive electrode material with special XRD diffraction peak in the first aspect of the present application is prepared, specifically, the positive electrode material has suitable bulk phase structure and surface ion and electron transmission channel, ensuring good short-term and long-term performance, and when the positive electrode material is used in a lithium ion battery, the cycle performance and safety performance of the lithium ion battery can be significantly improved.

[0051] Further, the amount of the mixture salt solution and the P solution is such that 0.01 mol% ≤ n(P) / [n(Ni)+n(Co)+n(M)] ≤ 1.5 mol%.

[0052] According to the present application, in the co-precipitation reaction process, the initial speed of the P solution added to the reaction kettle ranges from 0 to 0.6 L / h, and the acceleration rate ranges from 0 to 1 L / h 2 .

[0053] In the present application, when the initial speed and acceleration of the P solution added to the reaction kettle meet the above ranges, a distributed, preferably gradient-distributed, phosphate phase can be constructed in the bulk phase of the prepared positive electrode material, the phosphate group effectively anchors the oxygen ions and transition metal ions in the bulk phase of the positive electrode material, maintains the structural stability of the positive electrode material during charging and discharging, and further improves the cycle performance and safety of the lithium ion battery containing the positive electrode material.

[0054] Further, in the co-precipitation reaction process, the initial speed of the P solution added to the reaction kettle ranges from 0.01 to 0.5 L / h, and the acceleration rate ranges from 0.01 to 0.5 L / h 2 .

[0055] In a preferred embodiment of the present application, after the P solution is added to the complexing agent solution to form a composite complexing agent solution, the composite complexing agent is added to the reaction kettle for co-precipitation reaction.

[0056] According to the present application, in the co-precipitation reaction process, the initial speed of the P solution added to the complexing agent solution ranges from 0 to 0.6 L / h, and the acceleration rate ranges from 0 to 1 L / h 2 .

[0057] Further, in the co-precipitation reaction process, the initial speed of the P solution added to the complexing agent solution ranges from 0.01 to 0.5 L / h, and the acceleration rate ranges from 0.01 to 0.5 L / h 2 .

[0058] In the present application, the type of nickel salt and cobalt salt is not particularly limited, and can be a conventional nickel salt and cobalt salt in the art, for example, the nickel salt is selected from at least one of nickel sulfate, nickel nitrate and nickel chloride; and the cobalt salt is selected from at least one of cobalt sulfate, cobalt nitrate and cobalt chloride.

[0059] In the present application, the type of complexing agent and precipitant is not particularly limited, and a conventional complexing agent and precipitant in the art can be used, for example, the precipitant is an alkali solution, preferably a sodium hydroxide solution; and the complexing agent is ammonia water.

[0060] According to the present application, the phosphate salt is selected from at least one of phosphoric acid, monammonium phosphate, diammonium phosphate and ammonium phosphate.

[0061] Further, the M salt is selected from an Al salt and / or a Mn salt, more preferably, the Al salt is selected from at least one of aluminum sulfate, aluminum nitrate and aluminum chloride; and the Mn salt is selected from at least one of manganese sulfate, manganese nitrate and manganese chloride.

[0062] According to the present application, the time of the co-precipitation reaction is 10-100 h, and the temperature of the co-precipitation reaction is 30-100℃.

[0063] In the present application, when the time and temperature of the co-precipitation reaction are controlled to meet the above range, the co-precipitation reaction is more uniform and stable, and the prepared precursor has higher sphericity and density, so that the subsequently prepared cathode material has excellent electrochemical performance.

[0064] Further, the time of the co-precipitation reaction is 15-80 h, and the temperature of the co-precipitation reaction is 40-70℃.

[0065] According to the present application, the co-precipitation reaction is carried out in the presence of nitrogen and / or oxygen.

[0066] In the present application, preferably, the pH of the co-precipitation reaction is controlled to be 8-13.

[0067] According to the present application, the doping element G is selected from at least one element in the group of IVA-VA in the 2nd-5th period.

[0068] In the present application, the doping element G can be introduced in the co-precipitation reaction in step (2) or in the sintering process in step (3), and the amount of the doping element G solution added in step (2) and / or the amount of the doping element G added in step (3) is not particularly limited, as long as the amount of the doping element G is 5000 ppm or less, preferably 0-3000 ppm, based on the total weight of the cathode material precursor.

[0069] In the present application, when the amount of the doping element G meets the above range, the material structure can be effectively stabilized, the lithium ion transmission channel can be widened, and the proportion of active elements in the material is not excessively affected, thereby improving the cycle performance and safety of the ion battery containing the positive electrode material without sacrificing the capacity.

[0070] According to the present application, the sintering conditions include that the sintering temperature is 650-900℃ and the sintering time is 6-30h.

[0071] In the present application, when the sintering conditions meet the above range, the lithiumated crystal of the positive electrode material is more sufficient, and the construction of the layered structure is more complete, thereby making the positive electrode material have excellent electrochemical comprehensive performance.

[0072] Further, the sintering conditions include that the sintering temperature is 700-890℃ and the sintering time is 8-25h.

[0073] According to the present application, the amount of the Li source is such that 0.9≤[n(Li)] / [n(Ni)+n(Co)+n(M)]≤1.3, preferably 0.95≤[n(Li)] / [n(Ni)+n(Co)+n(M)]≤1.2.

[0074] In the present application, the positive electrode material can contain or not contain a coating layer. When containing a coating layer, the product obtained after sintering in step (3) is used as a matrix, and the positive electrode material with a coating layer is obtained after heat treatment of the coating layer. Those skilled in the art can understand that, if the positive electrode material does not have a coating layer, the preparation process is completed after step (3); if it has a coating layer, the preparation process needs to include a heat treatment process.

[0075] Specifically, when containing a coating layer, the preparation method of the positive electrode material according to the present application further comprises:

[0076] Mixing the product after sintering in step (3) with a compound containing a coating element H, and performing heat treatment to obtain the positive electrode material.

[0077] According to the present application, the compound containing the coating element H is selected from compounds containing at least one element of B, Mg, Ca, Sr, Y, Ti, V, Cr, Fe, Cu, Zr, W, Nb and Al.

[0078] In the present application, using the compound containing the above special kind of element as a coating agent can make the coating element in the coating agent and the residual alkali on the surface further react to generate lithium metal oxide, form a coating layer on the material surface, stabilize the structure of the material surface, and improve the cycle performance.

[0079] Further, the compound containing the coating element H is selected from a compound containing at least one of B, Al, Zr, Nb and Y.

[0080] According to the present application, the compound containing the coating element H is used in an amount such that the amount of the coating element H is 5000 ppm or less, based on the total weight of the first sintering material.

[0081] In the present application, when the amount of the coating element H satisfies the above range, the transition metal and the doping element on the surface can be bonded to each other, the crystal structure is stabilized, and at the same time, the proper amount of addition is ensured not to block the entry and exit of lithium ions on the surface of the material, and the first capacity of the material is effectively ensured.

[0082] Further, the compound containing the coating element H is used in an amount such that the amount of the coating element H is 0-3000 ppm, based on the total weight of the first sintering material.

[0083] According to the present application, the heat treatment conditions include that the heat treatment temperature is 200-500℃, and the heat treatment time is 5-18h.

[0084] In the present application, under the above conditions, the coating element and the surface atoms of the product after sintering in step (3) as the substrate can achieve close chemical bonding, so that the coating layer and the substrate are organically integrated, and the cycle stability of the positive electrode material and the battery is improved.

[0085] Further, the heat treatment conditions include that the heat treatment temperature is 300-480℃, and the heat treatment time is 5-12h.

[0086] In a preferred embodiment of the present application, step (2) comprises the following steps:

[0087] S1, the mixed salt solution, the precipitant solution, the complexing agent solution and optionally the doping element G solution are added into a reaction kettle to perform a first co-precipitation reaction;

[0088] S2, the P solution or the complexing agent solution containing the P solution is added into the reaction kettle to perform a second co-precipitation reaction, and the positive electrode material precursor is obtained through aging, filtration, washing and drying.

[0089] In the present application, by controlling the timing of adding the P solution or the complexing agent solution containing the P solution, a positive electrode material containing a gradient distribution of phosphate phases can be prepared, so that the structural stability of the positive electrode material is significantly improved, and finally the cycle performance and safety of the lithium ion battery containing the positive electrode material are significantly improved.

[0090] In this invention, there are no particular limitations on the amount of complexing agent solution added in step S1 and the amount of complexing agent solution introduced in the form of a composite complexing agent solution in step S2, as long as the total amount of complexing agent solution is controlled to meet the requirements.

[0091] According to the present invention, the time for the first coprecipitation reaction is 2-10 h, and the temperature for the first coprecipitation reaction is 30-100 °C.

[0092] According to the present invention, the second coprecipitation reaction takes 8-25 hours and the temperature of the second coprecipitation reaction is 30-100°C.

[0093] In this invention, the first coprecipitation reaction and the second coprecipitation reaction together constitute the coprecipitation reaction described above.

[0094] In one specific embodiment of the present invention, the positive electrode material is prepared according to the following steps:

[0095] (I) Prepare a mixed salt solution by mixing nickel salt, cobalt salt, and M salt in a molar ratio of n(Ni):n(Co):n(M) = (1-xyzm):x:y; prepare a solution by dissolving dopant element G in deionized water to prepare a P solution; prepare a complexing agent solution by preparing a complexing agent solution; prepare a precipitant solution by preparing a precipitant solution.

[0096] (II) Under stirring conditions of 200-800 rpm and in a nitrogen and / or air atmosphere, the complexing agent solution and the precipitant solution are added to the reactor. After adjusting the pH of the reactor to 10-13, the mixed salt solution, the precipitant solution, the complexing agent solution and the optional dopant element G solution are added to the reactor. The first coprecipitation reaction is carried out under the conditions of controlling the temperature at 50-80℃ and the pH at 10-13 for 2-10 hours.

[0097] (III) Dispense the P solution at a rate of 0.01-0.5 L / h 2 The complexing agent solution is added at an initial velocity of 0-2 L / h with an acceleration of [unspecified value] to form a composite complexing agent solution. This composite complexing agent solution is then added to a reaction vessel, and a second coprecipitation reaction is carried out under controlled conditions of 50-80℃ and pH 10-13 for 8-25 hours. After the second coprecipitation, the material is aged, filtered, washed, and dried to obtain the cathode material precursor.

[0098] (IV) The cathode material precursor, Li source, and optionally a compound containing doped element G are mixed and sintered;

[0099] (V) The product sintered in step (IV) is mixed with a compound containing coating element H and subjected to heat treatment to obtain the cathode material;

[0100] The amount of the mixed salt solution and the P solution is such that 0 mol% < n(P) / [n(Ni)+n(Co)+n(M)] < 2 mol%, preferably 0.01 mol% ≤ n(P) / [n(Ni)+n(Co)+n(M)] ≤ 1.5 mol%.

[0101] The third aspect of the present application provides a positive electrode material prepared by the above preparation method.

[0102] The fourth aspect of the present application provides a positive electrode tab, characterized in that the positive electrode tab comprises the above positive electrode material.

[0103] According to the present application, the exothermic peak temperature of the positive electrode tab measured by DSC is greater than or equal to 205℃, preferably 205-300℃, under 100% SOC state.

[0104] In the present application, the exothermic peak temperature of the positive electrode tab measured by DSC is greater than or equal to 205℃, under 100% SOC state, indicating that the thermal stability of the positive electrode material provided by the present application is significantly better than that of conventional positive electrode materials, and has a higher thermal decomposition temperature during the working process of the lithium ion battery, reduces oxygen release, and significantly improves the safety performance of the lithium ion battery containing the positive electrode material.

[0105] Further, the exothermic peak temperature of the positive electrode material measured by DSC is 205-300℃, preferably 210-300℃, under 100% SOC state.

[0106] The fifth aspect of the present application provides an application of the above positive electrode material or positive electrode tab in a lithium ion battery.

[0107] The sixth aspect of the present application provides a lithium ion battery, characterized in that the lithium ion battery comprises the above positive electrode material or positive electrode tab.

[0108] The present application will be described in detail below through examples.

[0109] (1) X-ray diffraction test

[0110] An XRD diffractometer (SmartLab 9KV) is used to measure the sample, a Cu Ka radiation source is used, a small-angle test is performed by step scanning, and the diffraction pattern including the 003 peak and the 104 peak is tested. First, add an excess amount of material in the glass sample holder, press slightly and scrape the surface under the LED light, set the parameters, select the test category, and adjust the BB light path. Open the hatch, place the sample on the sample stage, click the "Execute" button to test, save the data, and complete the test.

[0111] (4) Morphology of the cathode material

[0112] The morphology of the cathode material was tested by SEM. First, the cathode material was embedded and treated, and then was put into an ion grinder to be thinned to obtain a cross-section sample of the ion ground particles. Finally, the cross-section sample was fixed on a scanning electron microscope sample stage for scanning electron microscope analysis.

[0113] (5) Battery performance test

[0114] The preparation method of the button cell was as follows: the cathode material, acetylene black and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95%:2.5%:2.5%, coated on an aluminum foil and dried, and then pressed into a cathode sheet with a diameter of 12 mm and a thickness of 120 μm under a pressure of 100 MPa. The cathode sheet was then placed in a vacuum drying oven and dried at 120°C for 12 h. The negative electrode used was a Li metal sheet with a diameter of 17 mm and a thickness of 1 mm; the separator used was a polyethylene porous film with a thickness of 25 μm, the surface of which was coated with a titanium aluminum lithium phosphate ceramic layer; and the electrolyte used was an equal amount of a mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC). The cathode sheet, the separator, the negative electrode sheet and the electrolyte were assembled into a 2025 type button cell in an Ar glove box with water content and oxygen content less than 5 ppm.

[0115] After the button cell was made, it was placed for 2 h, and after the open circuit voltage was stabilized, the cathode was charged at a current density of 0.1C to a cutoff voltage of 4.3V, and then constant voltage charged for 30 min, and then discharged to a cutoff voltage of 3V at the same current density; the same process was repeated once, and the battery at this time was used as an activated battery.

[0116] The cycle performance test was as follows: the activated battery was used, and the capacity retention rate was measured after 50 cycles at a current density of 1C (200 mA / g) in a voltage range of 3-4.3V at a temperature of 45°C.

[0117] The thermal stability test was as follows: the activated battery was used, and the cathode sheet was obtained by charging to 4.3V and disassembling the battery. The electrolyte was naturally dried, and the cathode sheet was placed in a DSC instrument and tested at a rate of 5°C / min under an oxygen atmosphere to obtain the temperature corresponding to the exothermic peak.

[0118] The raw materials used in the examples and comparative examples were commercially available.

[0119] Example 1

[0120] (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were added to water in a molar ratio of nickel sulfate:cobalt sulfate:manganese sulfate = 90:5:5 to prepare a 2 mol / L mixed salt solution. A 10 mol / L ammonia solution was prepared as complexing agent 1. Ammonium dihydrogen phosphate was prepared into a 2 mol / L phosphate solution with a molar ratio P / (Ni+Co+Mn) = 0.2 mol%. A 4 mol / L sodium hydroxide aqueous solution was prepared as a precipitant.

[0121] (2) Set the stirring speed to 500 rpm and turn it on; simultaneously, purge the reactor with nitrogen for a certain period of time to ensure there is no air atmosphere inside the reactor. Add complexing agent 1 and sodium hydroxide solution to the reactor to adjust the bottom liquid, so that the pH value of the reactor is adjusted to 11.7. Use a metering pump to add the above-prepared mixed salt solution, sodium hydroxide solution and complexing agent 1 to the reactor. Control the reactor temperature at 60℃, and maintain the pH value at 11.8 during the reaction. After 2 hours of reaction, add phosphate solution at a rate of 0.5 L / h. 2 The compound complexing agent is added to the complexing agent 1 at an initial velocity of 0 L / h with an acceleration of 0 L / h to form a composite complexing agent. The addition rate of the composite complexing agent is controlled to be consistent with that of the complexing agent 1. After the reaction is completed, the material is aged. After aging, it is washed alternately with an alkaline solution at 75°C and pure water. Then the filter cake is dried and sieved to obtain a high-nickel cathode material precursor (Ni). 0.9 Co 0.05 Mn 0.05 (OH) 1.994 (PO4) 0.002 .

[0122] (3) The cathode material precursor and LiOH were dry-premixed at a molar ratio of 1:1.03. After premixing, Nb2O5 was used as a dopant, and the amount of Nb added was 3000 ppm based on the total weight of the cathode material precursor. The mixture was then dry-mixed together. The mixture was sintered at 765℃ for 20 h in an oxygen atmosphere to obtain the first sintered material.

[0123] (4) The first sintered material is further coated and heat-treated. The coating material is Y2O3. Based on the total weight of the first sintered material, the amount of Y is 1000 ppm. The above materials are mixed using a dry method. The heat treatment temperature is controlled at 350℃ and the heat treatment time is 12h. After the heat treatment is completed, the material is cooled and sieved to obtain the positive electrode material A1.

[0124] Figure 1 This is the cross-sectional P element distribution of the cathode material A1, composed of... Figure 1 It can be seen that the phosphate phase containing P element has a relatively uniform gradient distribution from the inside to the outside in the cross-section of cathode material A1.

[0125] Examples 2-4

[0126] The cathode material was prepared according to the method of Example 1, and the raw material ratio and specific process conditions are shown in Table 1. The cathode material A2-A4 was prepared.

[0127] Example 5

[0128] The cathode material was prepared according to the method of Example 1, except that: 2 mol / L aqueous solution of ammonium niobium oxalate was configured as an additive, and the niobium oxalate solution, the mixed salt aqueous solution, the aqueous sodium hydroxide solution and the complexing agent 1 were jointly added to the reaction kettle through the metering pump. In step (3), no dopant Nb2O5 was added.

[0129] The other raw material ratios and specific process conditions are shown in Table 1. The cathode material A5 was prepared.

[0130] Example 6

[0131] The cathode material was prepared according to the method of Example 1, and the raw material ratio and specific process conditions are shown in Table 1. The cathode material A6 was prepared.

[0132] Example 7

[0133] The cathode material was prepared according to the method of Example 1, except that:

[0134] In step (2), the phosphate solution was directly added to the reaction kettle at an acceleration of 0.5 L / h 2 , an initial speed of 0 L / h, without forming a complexing agent with the complexing agent 1 before being added to the reaction kettle.

[0135] The other raw material ratios and specific process conditions are shown in Table 1. The cathode material A7 was prepared.

[0136] Examples 8-11

[0137] The cathode material was prepared according to the method of Example 1, and the raw material ratio and specific process conditions are shown in Table 1. The cathode material A8-A11 was prepared.

[0138] Comparative Examples 1-3

[0139] The cathode material was prepared according to the method of Example 1, and the raw material ratio and specific process conditions are shown in Table 1. The cathode material D1-D3 was prepared.

[0140] Table 1

[0141]

[0142]

[0143] Table 1 (continued)

[0144]

[0145] Table 1 (continued)

[0146]

[0147]

[0148] Test Example

[0149] The compositions of the positive electrode materials prepared in the examples and comparative examples are shown in Table 2, and the XRD test results of the positive electrode materials are shown in Table 3.

[0150] Table 2

[0151] Composition Example 1 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 2 Li 1.03 (Ni 0.843 Co 0.089 Mn 0.059 Mo 0.003 Al 0.005 )O 0.9925 (PO4) 0.005 ]]> Example 3 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 4 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 5 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 6 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.988 (PO4) 0.008 ]]> Example 7 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 8 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 9 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 10 Li 1.03 (Ni 0.396 Co 0.297 Mn 0.0297 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Example 11 Li 1.03 (Ni 0.838 Co 0.094 Al 0.065 Nb 0.003 Y 0.001 )O 1.997 (PO4) 0.002 ]]> Comparative Example 1 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O2]]> Comparative Example 2 Li 1.03 (Ni 0.838 Co 0.094 Mn 0.065 Nb 0.003 Y 0.001 )O 0.97 (PO4) 0.02 ]]> Comparative Example 3 Li 1.03 (Ni 0.9 Co 0.05 Mn 0.05 )O2]]>

[0152] Table 3

[0153]

[0154]

[0155] Application Example

[0156] The positive electrode materials of the examples and comparative examples were used to prepare lithium ion batteries, and the preparation method was as follows: the non-aqueous electrolyte secondary battery composite nickel-cobalt-manganese multi-element positive electrode active material, acetylene black and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:3:2, coated on an aluminum foil and dried, and then pressed into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm under a pressure of 100 MPa, and then the positive electrode sheet was placed in a vacuum drying oven and dried at 120°C for 12 h.

[0157] The negative electrode used a Li metal sheet with a diameter of 17 mm and a thickness of 1 mm; the separator used a polyethylene porous film with a thickness of 25 μm; and the electrolyte used an equal amount of a mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC).

[0158] The performance of the lithium ion batteries was tested, and the results are shown in Table 4.

[0159] Table 4

[0160]

[0161]

[0162] As can be seen from Table 2 and Table 3, the lithium ion battery prepared by using the positive electrode material containing the phosphate phase, especially when the phosphate phase is distributed in a gradient, not only has high initial charge-discharge capacity, but also has high capacity retention rate. When the concentration gradient change rate of the phosphate phase (n(PO4 3- ) is small, the capacity is high, when the change rate is large, the capacity decreases, but the DSC temperature improves significantly. In Comparative Example 2, when the content of the phosphate phase (n(PO4 3- ) in the positive electrode material is too high and the concentration gradient change rate is too large, the material state is close to the core-shell structure, at this time, the transport channel of lithium ions is blocked, and the interface bonding between the phosphate phase and the matrix is poor, which causes the capacity and safety performance of the material to decrease sharply.

[0163] Figure 2 is the DSC graph of the positive electrode tab containing the positive electrode material of Example 1 and Comparative Example 1 after activation, and Figure 2 As can be seen, the DSC exothermic peak temperature of the positive electrode tab prepared by using the positive electrode material containing the phosphate phase after activation is significantly improved, and the exothermic amount is obviously reduced, which indicates that the thermal stability and safety performance of the positive electrode material containing the phosphate phase in Example 1 are significantly better than those of the conventional positive electrode material provided in Comparative Example 1.

[0164] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all belong to the protection scope of the present application.

Claims

1. A positive electrode material, characterized by, The positive electrode material comprises a phosphate phase, the 2theta of the (003) diffraction peak obtained by XRD of the positive electrode material is 43.5-44.5° （003） shifted to a small angle by 0.01°-0.2°, the 2theta of the (104) diffraction peak is 19.5-20.5° （104） shifted to a small angle by 0.01°-0.15°; The composition of the positive electrode material is shown as formula I: Li e (Ni 1-x-y-z-m Co x M y G z H m )O (4-3n) / 2 (PO4) n Formula I; 0.9≤e≤1.3, x≤(1-x-y-z-m), y≤(1-x-y-z-m), 0.838≤1-x-y-z-m<1, 0≤y<0.2, 0<z<0.05, 0≤m<0.05, 0<n≤0.01, and y and z are not 0 at the same time; M is selected from Al and / or Mn, G is selected from at least one element in Groups IIA-III A of Periods 2-5, and H is selected from at least one element of B, Mg, Ca, Sr, Y, Ti, V, Cr, Fe, Cu, Zr, W, Nb and Al; The content of the phosphate phase in the positive electrode material is gradiently distributed along the direction from the center to the surface of the positive electrode material particles. The change rate of the molar content of the phosphate phase along the direction from the center to the surface of the positive electrode material particles is 0.01-1 mol% / μm.

2. The positive electrode material of claim 1, wherein, the (003) diffraction peak of the positive electrode material obtained by XRD has a 2Θ （003） shifted to a small angle by 0.02°-0.08°, the 2Θ of the (104) diffraction peak （104） shifted to a small angle by 0.01°-0.05°.

3. The positive electrode material according to claim 1 or 2, wherein The cell parameters a and c of the (103) diffraction peak obtained by XRD of the positive electrode material are 0.285-0.290 nm and 1.41-1.43 nm respectively.

4. The positive electrode material according to claim 1 or 2, wherein The cathode material has a (103) diffraction peak at 2-theta obtained by XRD （103） With a 0.01° small-angle offset, the unit cell parameter a decreases by 0.0004 nm, and the unit cell parameter c increases by 0.0007 nm.

5. The positive electrode material according to claim 1 or 2, wherein The phosphate phase is PO4 3- Spinel phase; and / or, the molar content of the phosphate phase satisfies 0 mol% < n(PO4 3- ) < 2 mol%, based on the total moles of the positive electrode material. 3- and / or, the molar content of the phosphate phase satisfies 0 mol% < n(PO4 3- ) < 2 mol%, based on the total moles of the positive electrode material.

6. The cathode material of claim 5, wherein, The molar content of the phosphate phase satisfies 0.01 mol%≤ n(PO4 3- ) ≤ 1.5 mol% based on the total molar amount of the positive electrode material. The molar content of the phosphate phase satisfies 0.01 mol%≤ n(PO4 3- ) ≤ 1.5 mol% based on the total molar amount of the positive electrode material.

7. The positive electrode material according to claim 1 or 2, wherein The change rate of the molar content of the phosphate phase along the direction from the center to the surface of the positive electrode material particles is 0.01-0.5 mol% / μm.

8. The positive electrode material of claim 1 or 2, wherein, The positive electrode material comprises single-crystal large particles and / or secondary particles formed by agglomeration of primary particles; And / or, 0.95≤e≤1.1, 0.3≤1-x-y-z-m<0.99, 0<y<0.15, 0<z<0.03, 0<m<0.03, 0<n≤0.008; And / or, G is selected from at least one element of Al, Mg, Ca, Sr, Zr, Nb and Mo, and H is selected from at least one element of B, Zr, Nb, Al and Y.

9. A method of producing the positive electrode material according to any one of claims 1 to 8, characterized by, The preparation method comprises: (1) a mixed salt solution is prepared by mixing nickel salt, cobalt salt and M salt according to the molar ratio of n(Ni):n(Co):n(M)=(1-x-y-z-m):x:y; a doping element G solution is prepared by mixing doping element G; a P solution is prepared by dissolving phosphate in deionized water; a complexing agent solution is prepared by mixing a complexing agent; and a precipitant solution is prepared by mixing a precipitant; (2) the mixed salt solution, the precipitant solution, the P solution, the complexing agent solution and the doping element G solution are added into a reaction kettle to perform a co-precipitation reaction, and a positive electrode material precursor is obtained by aging, filtering, washing and drying; (3) the positive electrode material precursor, a Li source and a compound containing doping element G are mixed and sintered to obtain a first sintered material; (4) the first sintered material is mixed with a compound containing coating element H, and heat treatment is performed to obtain the positive electrode material; The amount of the mixed salt solution and the P solution is such that 0 mol%<n(P) / [n(Ni)+n(Co)+n(M)]<2 mol%; 0.9≤e≤1.3, x≤(1-x-y-z-m), y≤(1-x-y-z-m), 0.838≤1-x-y-z-m<1, 0≤y<0.2, 0<z<0.05, 0≤m<0.05, y and z are not 0 at the same time; The M salt is selected from Al salt and / or Mn salt; The doping element G is selected from at least one element in the group consisting of elements in the 2-5 period and the IIA-IIIA group.

10. The production method according to claim 9, wherein The amount of the mixed salt solution and the P solution is such that 0.01 mol%≤n(P) / [n(Ni)+n(Co)+n(M)]≤1.5 mol%.

11. The production method according to claim 9, wherein The initial speed of the P solution added into the reactor during the co-precipitation reaction is in the range of 0-0.6 L / h, and the acceleration rate is in the range of 0-1 L / h 2 .

12. The method of making according to claim 11, wherein, The initial speed of the P solution added to the reactor during the co-precipitation reaction is in the range of 0.01-0.5 L / h, and the acceleration rate is in the range of 0.01-0.5 L / h 2 .

13. The production method according to claim 9, wherein The P solution is added into the complexing agent solution to form a complexing agent solution, and then the complexing agent solution is added into a reactor to perform a co-precipitation reaction; and / or, the initial velocity of the P solution into the complexing agent solution is in the range of 0-0.6 L / h and the acceleration rate is in the range of 0-1 L / h 2 .

14. The production method according to claim 13, wherein The initial velocity of the P solution added to the complexing agent solution is in the range of 0.01-0.5 L / h, and the acceleration rate is in the range of 0.01-0.5 L / h 2 .

15. The method of manufacturing according to claim 9, wherein, The phosphate is selected from at least one of monobasic ammonium phosphate, dibasic ammonium phosphate and ammonium phosphate; And / or, the Al salt is selected from at least one of aluminum sulfate, aluminum nitrate and aluminum chloride; and the Mn salt is selected from at least one of manganese sulfate, manganese nitrate and manganese chloride; And / or, the amount of the doping element G solution in step (2) and the compound containing the doping element G in step (3) is such that the amount of the doping element G is 5000 ppm or less based on the total weight of the positive electrode material precursor; And / or, the amount of the Li source is such that 0.9≤[n(Li)] / [n(Ni)+n(Co)+n(M)]≤1.3; And / or, the compound containing the coating element H is selected from at least one of compounds containing B, Mg, Ca, Sr, Y, Ti, V, Cr, Fe, Cu, Zr, W, Nb and Al; And / or, the amount of the compound containing the coating element H is such that the amount of the coating element H is 5000 ppm or less based on the total weight of the first sintering material.

16. The method of manufacturing according to claim 15, wherein, The amount of the doping element G solution in step (2) and the compound containing the doping element G in step (3) is such that the amount of the doping element G is 0-3000 ppm based on the total weight of the positive electrode material precursor; And / or, the amount of the Li source is such that 0.95≤[n(Li)] / [n(Ni)+n(Co)+n(M)]≤1.2; And / or, the amount of the compound containing the coating element H is such that the amount of the coating element H is 0-3000 ppm based on the total weight of the first sintering material.

17. The method of making according to claim 9, wherein, The time of the co-precipitation reaction is 10-100 h; And / or, the temperature of the co-precipitation reaction is 30-100℃; And / or, the co-precipitation reaction is performed in the presence of nitrogen and / or oxygen; And / or, the sintering condition comprises that the sintering temperature is 650-900℃, and the sintering time is 6-30 h; And / or, the heat treatment condition comprises that the heat treatment temperature is 200-500℃, and the heat treatment time is 5-18 h.

18. The method of making according to claim 17, wherein, The time of the co-precipitation reaction is 15-80 h; And / or, the temperature of the co-precipitation reaction is 40-70℃; And / or, the sintering condition comprises that the sintering temperature is 700-890℃, and the sintering time is 8-25 h; And / or, the heat treatment condition comprises that the heat treatment temperature is 300-480℃, and the heat treatment time is 5-12 h.

19. The method of making according to claim 13, wherein, Step (2) comprises the following steps: S1, adding the mixed salt solution, the precipitant solution, the complexing agent solution and the doping element G solution into a reaction kettle to perform a first co-precipitation reaction; S2, adding the P solution or the complexing agent solution into the reaction kettle to perform a second co-precipitation reaction, and obtaining the positive electrode material precursor through aging, filtering, washing and drying.

20. The method of making according to claim 19, wherein, The first co-precipitation reaction is performed for 2-10 hours at a temperature of 30-100℃. And / or, the second co-precipitation reaction is performed for 8-25 hours at a temperature of 30-100℃.

21. The positive electrode material prepared by the preparation method of any one of claims 9-20.

22. A positive electrode sheet characterized by comprising: The positive electrode tab comprises the positive electrode material of any one of claims 1-8 and 21.

23. The cathode sheet of Claim 22, wherein, In a 100% SOC state, the exothermic peak temperature of the positive electrode tab measured by DSC is greater than or equal to 205℃.

24. The cathode sheet of either claim 22 or 23, wherein, In a 100% SOC state, the exothermic peak temperature of the positive electrode tab measured by DSC is 205-300℃.

25. The positive electrode material of any one of claims 1-8 and 21 or the positive electrode tab of any one of claims 22-24 is applied in a lithium ion battery.

26. A lithium-ion battery, characterized by, The lithium ion battery comprises the positive electrode material of any one of claims 1-8 and 21 or the positive electrode tab of any one of claims 22-24.

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