A lithium ion battery positive electrode material and preparation method thereof and lithium ion battery

Abstract

The present invention provides a lithium-ion battery positive electrode material, a preparation method thereof, and a lithium-ion battery. The lithium-ion battery positive electrode material comprises a substrate and a coating layer. The substrate comprises a non-metallic doping element and a metal doping element, and the coating layer comprises lithium sulfate, a non-metallic coating element, and a metal coating element. The non-metallic doping element in the substrate is derived from a non-metallic sulfide dopant, and the metal doping element is derived from a metal sulfide dopant and / or a metal sulfate dopant. The sulfur in the lithium sulfate is derived from the non-metallic sulfide dopant and the metal sulfide dopant and / or the metal sulfate dopant. The present invention uses lithium sulfate in the coating layer to suppress the destruction of the material surface crystal structure during the water washing process and the generation of NiO inactive substances. Simultaneously, the doping and coating elements stabilize the lattice oxygen and oxygen framework structure, thereby improving the material's capacity and cycle performance while ensuring safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a lithium ion battery positive electrode material and a preparation method thereof and a lithium ion battery. Background Art

[0002] A lithium-ion battery is a secondary chemical battery (i.e., a rechargeable chemical battery) whose positive and negative electrodes are composed of two different materials, allowing lithium ions to reversibly embed and de-embedding. During charging, lithium ions are released from the positive electrode and embedded into the lattice of the negative electrode through the electrolyte, leaving the positive electrode in a high-potential, lithium-deficient state and the negative electrode in a low-potential, lithium-rich state. The opposite occurs during discharge. As a result, lithium-ion batteries offer high voltage, high specific energy and power, long cycle life, low self-discharge, no memory effect, and are environmentally friendly, earning them the reputation of being a green new energy product.

[0003] The ternary cathode material is modified from LiNiO2. Due to the obvious synergistic effect between Ni, Co and Mn (Al), the performance of NCM (nickel cobalt manganese material) / NCA (nickel cobalt aluminum material) is better than that of single component layered cathode materials and is considered to be one of the most promising cathode materials. The three elements of nickel, cobalt and manganese have different effects on the electrochemical properties of the material. Generally speaking, the presence of Ni helps to improve the capacity, but too high a content of Ni will cause the Li + This produces a mixing effect, leading to deterioration in cycling and rate performance. Co effectively stabilizes the layered structure of the ternary material and inhibits cation mixing, enhancing the material's electronic conductivity and improving cycling performance. The presence of Mn reduces costs and improves the material's structural stability and safety, while excessive Mn content reduces the material's specific capacity. Aluminum doping, on the other hand, enhances the material's structural stability and safety, further improving its cycling stability.

[0004] Ternary cathode materials have certain advantages in storage, power performance, etc. However, there are still some urgent problems to be solved in ternary cathode materials. The first is that there is still Ni in the ternary cathode materials. 2+ Occupy Li + The phenomenon of position leads to capacity loss during the charge and discharge process. Secondly, the microstructure of the ternary positive electrode material will change during the water washing process, generating a new NiQ-like phase, and the surface structure is unstable. A new resistance layer is generated on the surface of the primary particles during the charge and discharge process, resulting in poor cycle performance.

[0005] In the existing technology, the ternary cathode materials are doped with high-valent elements or main element Al, and the radial growth direction of the precursor is controlled to improve the material's cycle performance and capacity at the same time. However, the refinement of primary particles will lead to the deterioration of the material's high-temperature cycle performance, thermal stability and other safety performance. Therefore, at this stage, the ternary cathode materials are still facing the challenge of Ni 2+ Occupy Li+ There is a problem of NiO phase.

[0006] Based on the above research, it is necessary to provide a lithium-ion battery positive electrode material, which can inhibit the destruction of the crystal structure on the surface of the material and the production of NiO inactive substances during the water washing process, and improve the battery capacity and cycle performance. Summary of the Invention

[0007] The present invention aims to provide a lithium-ion battery positive electrode material, a preparation method thereof, and a lithium-ion battery. The lithium-ion battery positive electrode material, through the lithium sulfate in the coating layer, suppresses the destruction of the crystal structure on the surface of the material during the water washing process and the generation of NiO inactive substances. At the same time, through the doping and coating elements, the lattice oxygen and oxygen framework structure are stabilized, and the introduction of sulfur-containing substances that affect the safety performance of the material is avoided. While ensuring the safety performance, the capacity and cycle performance of the material can be improved.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a lithium-ion battery positive electrode material, comprising a substrate and a coating layer on the surface of the substrate, wherein the substrate comprises a layered oxide material, the substrate further comprises a non-metallic doping element and a metal doping element, and the coating layer comprises lithium sulfate, a non-metallic coating element, and a metal coating element;

[0010] The non-metallic doping element in the matrix is derived from a non-metallic sulfide dopant, and the metal doping element in the matrix is derived from a metal sulfide dopant and / or a metal sulfate dopant;

[0011] The sulfur in the lithium sulfate is derived from a first sulfide-containing material and a second sulfide-containing material. The first sulfide-containing material includes the non-metallic sulfide dopant, and the second sulfide-containing material includes the metal sulfide dopant and / or the metal sulfate dopant.

[0012] The sulfur in the lithium sulfate of the present invention and the non-metallic doping elements in the matrix are derived from the same non-metallic sulfide dopant, and are also derived from the same metal sulfide dopant and / or metal sulfate dopant as the metal doping elements. That is, the present invention forms an in-situ Li2SO4 protective layer on the surface of the positive electrode material through the sulfur in the above-mentioned dopant, thereby inhibiting the damage to the surface crystal structure of the positive electrode material during the water washing process, reducing the residual alkali of the material, and realizing the doping of non-metallic elements and metal elements at the same time. Among them, the metal doping elements are used to stabilize the lattice oxygen and oxygen framework structure, prevent the lattice oxygen from being lost in the form of gaseous O2, and improve the structural stability and safety performance of the positive electrode material. The non-metallic doping elements act as structural stabilizers to further improve the stability of the material. In addition, the coating layer of the present invention also includes non-metallic coating elements and metal coating elements, which are used to repair the surface of the positive electrode material and repair the effects of water washing on the material, that is, gradually transforming the surface NiO-like rock salt phase into a layered structure, thereby improving the cycle performance and capacity of the material.

[0013] Preferably, the non-metallic coating element in the coating layer is derived from a non-metallic coating agent, and the metal coating element in the coating layer is derived from a metal coating agent.

[0014] Preferably, the non-metal coating agent includes a non-metal sulfide coating agent and / or a non-metal oxide coating agent.

[0015] Preferably, the metal coating agent includes any one of a metal sulfide coating agent, a metal sulfate coating agent or a metal oxide coating agent, or a combination of at least two of them.

[0016] Preferably, when the non-metallic coating agent includes a non-metallic sulfide coating agent and the metal coating agent includes a metal sulfide coating agent and / or a metal sulfate coating agent, the sulfur in the lithium sulfate is derived from a first sulfide, a second sulfide, a third sulfide and a fourth sulfide, the first sulfide includes the non-metallic sulfide dopant, the second sulfide includes the metal sulfide dopant and / or the metal sulfate dopant, the third sulfide includes the non-metallic sulfide coating agent, and the fourth sulfide includes the metal sulfide coating agent and / or the metal sulfate coating agent.

[0017] The metal coating elements and non-metal coating elements in the coating layer of the present invention are preferably derived from sulfur-containing substances. While achieving the coating of metal elements and non-metal elements, the sulfur can also be further generated into a lithium sulfate protective layer to reduce residual alkali. At this time, the sulfur in the lithium sulfate is derived from the first sulfide, the second sulfide, the third sulfide and the fourth sulfide.

[0018] Preferably, the non-metallic sulfide dopant and the non-metallic sulfide coating agent independently include any one of B2S3, SeS2 or SiS2 or a combination of at least two of them, that is, the non-metallic doping element and the non-metallic coating element of the present invention independently include any one of B, Se or Si or a combination of at least two of them.

[0019] Preferably, the metal sulfide dopant and the metal sulfide coating agent independently include any one or a combination of at least two of MoS2, CeS, Na2S, Al2S3, K2S, Na2S or CuS.

[0020] Preferably, the metal sulfate dopant and the metal sulfate capping agent each independently comprise Al2(SO4)3.

[0021] That is, the metal doping element and the metal coating element in the present invention independently include any one or a combination of at least two of Mo, Ce, Na, Al, K, Na or Cu.

[0022] Preferably, the surface residual alkali of the water-washed and dried material used to prepare the lithium-ion battery positive electrode material satisfies the following relationship: the absolute value of (Li2CO3 content-LiOH content) / LiOH content is 0.3-5, for example, it can be 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0023] The residual alkali on the surface of the water-washed and dried material of the present invention satisfies the above relationship, indicating that the non-metallic sulfide dopant, metal sulfide dopant and / or metal sulfate dopant introduced in the present invention can effectively reduce the residual alkali.

[0024] Preferably, the layered oxide material includes any one of NCA (nickel-cobalt-aluminum material), NCMA (nickel-cobalt-manganese-aluminum material) or NCM (nickel-cobalt-manganese material) or a combination of at least two thereof, wherein the nickel ion content in the layered oxide material accounts for 80 mol%-99 mol% of the total metal ion content, for example, it can be 80 mol%, 85 mol%, 90 mol%, 95 mol% or 99 mol%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0025] Preferably, the content of the non-metallic doping element in the lithium-ion battery positive electrode material is 0.05wt%-0.5wt%, for example, it can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0026] Preferably, the content of the metal doping element in the lithium-ion battery positive electrode material is 0.06wt%-0.6wt%, for example, it can be 0.06wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0027] The present invention does not specifically limit the content of lithium sulfate. Since it is generated in situ, its content is determined by the content of the doping element (or determined by the doping + coating element). The present invention preferably contains non-metallic doping elements and metal doping elements within a specific range to ensure the amount of lithium sulfate in the coating layer, reduce the residual alkali value, inhibit damage to the material caused by water washing, ensure that the absolute value of (Li2CO3 content - LiOH content) / LiOH content is within the range of 0.3-5, and ensure effective doping of metal elements and non-metallic elements. However, if the doping amount of non-metallic doping elements and metal doping elements is too high, excessive sulfur will be introduced, affecting the safety of the material.

[0028] Preferably, in the lithium-ion battery positive electrode material, the content of the non-metallic coating element is 0.05wt%-0.5wt%, for example, it can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0029] Preferably, in the lithium-ion battery positive electrode material, the content of the metal coating element is 0.06wt%-0.6wt%, for example, it can be 0.06wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0030] Preferably, the content of aluminum in the lithium-ion battery positive electrode material is 0.5wt%-2.5wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2.0wt% or 2.5wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0031] In a second aspect, the present invention provides a method for preparing the positive electrode material for a lithium-ion battery as described in the first aspect, the preparation method comprising the following steps:

[0032] (1) mixing a positive electrode precursor, a lithium source, a first sulfide-containing material, and a second sulfide-containing material and sintering them once to obtain a sintered material, washing and drying the sintered material to obtain a sintered washed and dried material;

[0033] The first sulfide-containing material includes a non-metallic sulfide dopant, and the second sulfide-containing material includes a metal sulfide dopant and / or the metal sulfate dopant;

[0034] (2) The water-washed and dried material, the non-metallic coating agent and the metal coating agent in step (1) are mixed and subjected to secondary sintering to obtain the lithium-ion battery positive electrode material.

[0035] The present invention adds a first sulfide and a second sulfide during the first calcination, so that the sulfur therein forms lithium sulfate in situ, which can inhibit the damage to the crystal structure of the material surface during the water washing process and reduce residual alkali. At the same time, metal elements and non-metallic elements are incorporated into the matrix, thereby improving structural stability and stabilizing the lattice oxygen and oxygen framework structure during the water washing process. The present invention coats a non-metallic coating agent and a metal coating agent during the second calcination to further repair the water-washed surface, that is, gradually transforming the surface NiO-like rock salt phase into a layered structure, thereby improving the cycle performance and capacity of the material.

[0036] The present invention prepares the lithium ion battery positive electrode material according to the formula ratio of the non-metallic doping element in the lithium ion battery positive electrode material to 0.05wt%-0.5wt%, the metal doping element content to 0.06wt%-0.6wt%, the non-metallic coating element content to 0.05wt%-0.5wt%, and the metal coating element content to 0.06wt%-0.6wt%.

[0037] Preferably, the temperature of the primary sintering in step (1) is 650°C-750°C, for example, 650°C, 700°C or 750°C, and the time is 7h-30h, for example, 7h, 10h, 15h, 20h, 25h or 30h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0038] Preferably, the positive electrode precursor in step (1) comprises a nickel cobalt hydroxide precursor, and an aluminum source is added when the positive electrode precursor, the lithium source, the first sulfide-containing material, and the second sulfide-containing material are mixed. Preferably, the aluminum source comprises any one of Al hydroxide, Al sulfide, Al chloride, or Al oxide, or a combination of at least two thereof.

[0039] Preferably, the particle size D50 of the positive electrode precursor in step (1) is 2 μm-20 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm or 20 μm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0040] Preferably, the lithium source in step (1) includes lithium carbonate and / or lithium hydroxide.

[0041] Preferably, the ratio of the molar amount of Li in the lithium source in step (1) to the total molar amount of metal ions in the positive electrode precursor is (1.04-1.3):1, for example, it can be 1.04:1, 1.1:1, 1.2:1 or 1.3:1, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0042] Preferably, the temperature of the secondary sintering in step (2) is 250°C-700°C, for example, it can be 250°C, 300°C, 400°C, 500°C, 600°C or 700°C, and the time is 3h-15h, for example, it can be 3h, 5h, 7h, 9h, 11h, 13h or 15h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0043] In a third aspect, the present invention provides a lithium-ion battery, comprising the lithium-ion battery positive electrode material as described in the first aspect.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The sulfur in the lithium sulfate of the present invention and the non-metallic doping elements in the matrix are derived from the same non-metallic sulfide dopant, and are also derived from the same metal sulfide dopant and / or metal sulfate dopant as the metal doping elements. That is, the present invention forms an in-situ Li2SO4 protective layer on the surface of the positive electrode material through the sulfur in the above-mentioned dopant, thereby inhibiting the damage to the surface crystal structure of the positive electrode material during the water washing process, reducing the residual alkali of the material, and realizing the doping of non-metallic elements and metal elements at the same time. Among them, the metal doping elements are used to stabilize the lattice oxygen and oxygen framework structure, prevent the lattice oxygen from being lost in the form of gaseous O2, and improve the structural stability and safety performance of the positive electrode material. The non-metallic doping elements act as structural stabilizers to further improve the stability of the material. In addition, the coating layer of the present invention also includes non-metallic coating elements and metal coating elements, which are used to repair the surface of the positive electrode material and repair the effects of water washing on the material, that is, gradually transforming the surface NiO-like rock salt phase into a layered structure, thereby improving the cycle performance and capacity of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 1 is a Dq / Dv diagram (differential capacity curve diagram) of batteries prepared using the lithium-ion battery positive electrode materials described in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] This embodiment provides a lithium-ion battery positive electrode material, comprising a substrate and a coating layer on the surface of the substrate, wherein the substrate comprises an NCA material, the substrate further comprises a non-metallic doping element (specifically B) and a metal doping element (specifically Mo), and the coating layer comprises lithium sulfate, a non-metallic coating element (specifically B), and a metal coating element (specifically Mo);

[0050] The non-metallic doping element in the matrix is derived from a non-metallic sulfide dopant (specifically B2S3), and the metal doping element in the matrix is derived from a metal sulfide dopant (specifically MoS2); the non-metallic coating element in the coating layer is derived from a non-metallic sulfide coating agent (specifically B2S3), and the metal coating element in the coating layer is derived from a metal sulfide coating agent (specifically MoS2);

[0051] The non-metallic doping elements in the matrix are derived from non-metallic sulfide dopants, metal sulfide dopants, non-metallic sulfide coating agents and metal sulfide coating agents;

[0052] In the lithium-ion battery positive electrode material, the content of non-metallic doping elements is 0.25wt%, the content of metal doping elements is 0.3wt%, the content of non-metallic coating elements is 0.25wt%, and the content of metal coating elements is 0.3wt%;

[0053] The preparation method of the lithium ion battery positive electrode material comprises the following steps:

[0054] (1) According to the formula, Ni 0.96 Co 0.04 (OH)2 precursor, LiOH, Al2O3 with D50 of 13.5μm, B2S3 and MoS2 were mixed at high speed (the Al content in the formula was 0.7wt%, the Ni 0.96 Co 0.04 The ratio of the total molar amount of metal ions in the (OH)2 precursor and Al2O3 to the molar amount of LiOH is 1:1.08), the mixing speed is 1000 rpm, and after mixing for 20 minutes, the obtained first mixed material is placed in a muffle furnace and sintered at 700°C for 28 hours in an oxygen atmosphere. After naturally cooling to room temperature, the material is taken out, crushed and sieved to obtain a first-fired semi-finished product, and the first-fired semi-finished product is washed, filtered, and dried to obtain a first-fired water-washed and dried material;

[0055] (2) According to the formula, the water-washed and dried material described in step (1), B2S3 and MoS2 are mixed to obtain a second mixed material, and the second mixed material is sintered in an oxygen atmosphere and sintered for a second time at a temperature of 550°C for 10 hours to obtain the lithium-ion battery positive electrode material.

[0056] Example 2

[0057] This embodiment provides a lithium-ion battery positive electrode material, comprising a substrate and a coating layer on the surface of the substrate, wherein the substrate comprises an NCA material, the substrate further comprises a non-metallic doping element (specifically Se) and a metal doping element (specifically Ce), and the coating layer comprises lithium sulfate, a non-metallic coating element (specifically Se), and a metal coating element (specifically Ce);

[0058] The non-metallic doping element in the matrix is derived from a non-metallic sulfide dopant (specifically SeS2), and the metal doping element in the matrix is derived from a metal sulfide dopant (specifically CeS); the non-metallic coating element in the coating layer is derived from a non-metallic sulfide coating agent (specifically SeS2), and the metal coating element in the coating layer is derived from a metal sulfide coating agent (specifically CeS);

[0059] The non-metallic doping elements in the matrix are derived from non-metallic sulfide dopants, metal sulfide dopants, non-metallic sulfide coating agents and metal sulfide coating agents;

[0060] In the lithium-ion battery positive electrode material, the content of non-metallic doping elements is 0.05wt%, the content of metal doping elements is 0.6wt%, the content of non-metallic coating elements is 0.5wt%, and the content of metal coating elements is 0.06wt%;

[0061] The preparation method of the lithium ion battery positive electrode material comprises the following steps:

[0062] (1) According to the formula, Ni 0.96 Co 0.04 (OH)2 precursor, LiOH, Al2O3 with D50 of 13.5μm, SeS2 and CeS are mixed at high speed (in the formula, the Al content is 1.5wt%, the Ni 0.96 Co 0.04 The ratio of the total molar amount of metal ions in the (OH)2 precursor and Al2O3 to the molar amount of LiOH is 1:1.1), the mixing speed is 1000 rpm, and after mixing for 20 minutes, the first mixed material is placed in a muffle furnace and sintered at 650°C for 30 hours in an oxygen atmosphere. After naturally cooling to room temperature, the material is taken out, crushed and sieved to obtain a first-fired semi-finished product, and the first-fired semi-finished product is washed, filtered, and dried to obtain a first-fired water-washed and dried material;

[0063] (2) According to the formula, the water-washed and dried material of step (1), SeS2 and CeS are mixed to obtain a second mixed material. The second mixed material is sintered in an oxygen atmosphere and sintered for a second time at a temperature of 700°C for 3 hours to obtain the lithium-ion battery positive electrode material.

[0064] Example 3

[0065] This embodiment provides a lithium-ion battery positive electrode material, comprising a substrate and a coating layer on the surface of the substrate, wherein the substrate comprises an NCA material, the substrate further comprises a non-metallic doping element (specifically B) and a metal doping element (specifically Mo), and the coating layer comprises lithium sulfate, a non-metallic coating element (specifically B), and a metal coating element (specifically Mo);

[0066] The non-metallic doping element in the matrix is derived from a non-metallic sulfide dopant (specifically B2S3), and the metal doping element in the matrix is derived from a metal sulfide dopant (specifically MoS2); the non-metallic coating element in the coating layer is derived from a non-metallic sulfide coating agent (specifically B2S3), and the metal coating element in the coating layer is derived from a metal sulfide coating agent (specifically MoS2);

[0067] The non-metallic doping elements in the matrix are derived from non-metallic sulfide dopants, metal sulfide dopants, non-metallic sulfide coating agents and metal sulfide coating agents;

[0068] In the lithium-ion battery positive electrode material, the content of non-metallic doping elements is 0.5wt%, the content of metal doping elements is 0.06wt%, the content of non-metallic coating elements is 0.05wt%, and the content of metal coating elements is 0.6wt%;

[0069] The preparation method of the lithium ion battery positive electrode material comprises the following steps:

[0070] (1) According to the formula, Ni 0.96 Co 0.04 (OH)2 precursor, LiOH, Al2O3 with D50 of 13.5μm, B2S3 and MoS2 are mixed at high speed (in the formula, the Al content is 2wt%, the Ni 0.96 Co 0.04The ratio of the total molar amount of metal ions in the (OH)2 precursor and Al2O3 to the molar amount of LiOH is 1:1.08), the mixing speed is 1000 rpm, and after mixing for 20 minutes, the obtained first mixed material is placed in a muffle furnace and sintered at 750°C for 10 hours in an oxygen atmosphere. After naturally cooling to room temperature, the material is taken out, crushed and sieved to obtain a first-fired semi-finished product, and the first-fired semi-finished product is washed, filtered, and dried to obtain a first-fired water-washed and dried material;

[0071] (2) According to the formula, the water-washed and dried material of step (1), B2S3 and MoS2 are mixed to obtain a second mixed material, and the second mixed material is sintered in an oxygen atmosphere and sintered for a second time at a temperature of 400°C for 15 hours to obtain the lithium-ion battery positive electrode material.

[0072] Example 4

[0073] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that of embodiment 1 except that in its preparation method, the mass of B2S3 in step (2) is replaced by B2O3.

[0074] Example 5

[0075] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that of embodiment 1 except that in its preparation method, the mass of MoS2 in step (2) is replaced by MoO3.

[0076] Example 6

[0077] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that the content of the non-metallic doping element is 0.03 wt %.

[0078] Example 7

[0079] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that of Example 1 except that the content of the non-metallic doping element is 0.7 wt %.

[0080] Example 8

[0081] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that of Embodiment 1 except that the content of the metal doping element is 0.04 wt %.

[0082] Example 9

[0083] This embodiment provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that the content of the metal doping element is 0.7 wt %.

[0084] Comparative Example 1

[0085] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in the preparation method thereof, B2S3 and MoS2 are not added during the mixing in step (1), thereby causing the adaptability of the positive electrode material for a lithium-ion battery to change.

[0086] Comparative Example 2

[0087] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in its preparation method, the mass of B2S3 and the like in step (1) is replaced by MoS2 to change the adaptability of the positive electrode material for a lithium-ion battery.

[0088] Comparative Example 3

[0089] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in the preparation method thereof, the mass of the MoS2 in step (1) is replaced by B2S3 to change the adaptability of the positive electrode material for a lithium-ion battery.

[0090] Comparative Example 4

[0091] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in its preparation method, the mass of B2S3 in step (1) is replaced by B2O3 to change the adaptability of the positive electrode material for a lithium-ion battery.

[0092] Comparative Example 5

[0093] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in the preparation method thereof, the mass of the MoS2 in step (1) is replaced by MoO3 to change the adaptability of the positive electrode material for a lithium-ion battery.

[0094] Comparative Example 6

[0095] This comparative example provides a positive electrode material for a lithium-ion battery. The positive electrode material for a lithium-ion battery is the same as that in Example 1 except that in the preparation method thereof, B2S3 and MoS2 are not added during the mixing in step (2), thereby causing the adaptability of the positive electrode material for a lithium-ion battery to change.

[0096] The lithium-ion battery positive electrode materials obtained in the above examples and comparative examples were prepared into positive electrode sheets, which were then prepared into button batteries with a metal lithium sheet, a polyethylene microporous separator, and LiPF6-EC / DMC (the volume ratio of EC to DMC was 1:1, EC was ethylene carbonate, and DMC was dimethyl carbonate). The button batteries were subjected to capacity tests (2.5V-4.25V, 0.2C), cycle tests (3.0V-4.5V, 0.5C / 1C), and DSC tests (0.1C charging to 4.3V). The test results are shown in Table 1. The Dq / Dv graphs of the batteries obtained in Example 1 and Comparative Example 1 are shown in Table 1. Figure 1 As shown by Figure 1 It can be seen that the non-metallic sulfide dopant and the metal sulfide dopant of the present invention can inhibit the harmful phase transition of H2-H3 during the water washing process, reduce the generation of inactive substances, and protect the surface of the material from being damaged; In addition, the residual alkali on the surface of the washed and dried material in step (1) of the above embodiment and comparative example satisfies the relationship: (Li2CO3 content-LiOH content) / LiOH content, as shown in Table 1:

[0097] Table 1

[0098]

[0099] From the above table we can see that:

[0100] (1) It can be seen from Examples 1-3 and Comparative Example 1 that the non-metallic sulfide dopant and the metal sulfide dopant of the present invention can form a lithium sulfate protective layer, reduce residual alkali, avoid damage to the material by water washing, and improve the safety of the material, so that the battery has a higher capacity, excellent cycle performance and a higher thermal decomposition temperature; It can be seen from Example 1 and Comparative Examples 2-3 that if the non-metallic sulfide dopant is replaced by a metal sulfide dopant and / or a metal sulfate dopant, or only contains a metal sulfide dopant and / or a metal sulfate dopant without adding a non-metallic sulfide dopant, the electrical performance is reduced, especially the capacity is significantly reduced. If the metal sulfide dopant and / or the metal sulfate dopant is replaced by a non-metallic sulfide dopant, or only contains a non-metallic sulfide dopant without adding a metal sulfide dopant and / or a metal sulfate dopant, the impact on the cycle and safety is more obvious.

[0101] (2) As can be seen from Example 1 and Comparative Examples 4-5, the dopants of the present invention are all sulfur-containing substances. Compared with oxygen-containing substances, they can not only form a lithium sulfate protective layer in situ, but S can also work synergistically with metal or non-metal elements, thereby reducing residual alkali and improving battery performance; As can be seen from Example 1 and Comparative Example 6, the present invention also contains coated metal elements and non-metal elements, thereby repairing the surface of the material and further improving the performance of the battery; As can be seen from Example 1 and Examples 4-5, the preferred coating agent of the present invention is a sulfur-containing substance, which can further generate a lithium sulfate protective layer, further reduce residual alkali, and improve the material structure stability and battery performance; As can be seen from Example 1 and Examples 6-9, the addition amount of the non-metallic sulfide dopant, metal sulfide dopant and / or metal sulfate dopant of the present invention will not only affect the doping amount of metal and non-metal elements, but also affect the amount of lithium sulfate, thereby affecting the battery performance.

[0102] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lithium-ion battery positive electrode material, characterized in that The lithium-ion battery positive electrode material includes a substrate and a coating layer on the surface of the substrate, the substrate includes a layered oxide material, the substrate also includes a non-metallic doping element and a metal doping element, and the coating layer includes lithium sulfate, a non-metallic coating element and a metal coating element; The non-metallic doping element in the matrix is derived from a non-metallic sulfide dopant, and the metal doping element in the matrix is derived from a metal sulfide dopant and / or a metal sulfate dopant; The sulfur in the lithium sulfate is derived from a first sulfide and a second sulfide, the first sulfide comprising the non-metallic sulfide dopant, and the second sulfide comprising the metal sulfide dopant and / or the metal sulfate dopant; the non-metallic sulfide dopant comprises any one of B2S3, SeS2 or SiS2, or a combination of at least two thereof; And / or, the metal sulfide dopant includes any one or a combination of at least two of MoS2, CeS, Al2S3, K2S, Na2S or CuS; and / or, the metal sulfate dopant comprises Al2(SO4)3; The surface residual alkali of the washed and dried material for preparing the lithium-ion battery positive electrode material satisfies the following relationship: the absolute value of (Li2CO3 content-LiOH content) / LiOH content is 0.3-5; The preparation method of the lithium ion battery positive electrode material comprises the following steps: (1) mixing a positive electrode precursor, a lithium source, a first sulfide-containing material, and a second sulfide-containing material and sintering them once to obtain a sintered material, washing and drying the sintered material to obtain a sintered washed and dried material; The first sulfide-containing material includes a non-metallic sulfide dopant, and the second sulfide-containing material includes a metal sulfide dopant and / or the metal sulfate dopant; (2) The water-washed and dried material, the non-metallic coating agent and the metal coating agent in step (1) are mixed and subjected to secondary sintering to obtain the lithium-ion battery positive electrode material.

2. The lithium-ion battery positive electrode material according to claim 1, characterized in that The non-metallic coating element in the coating layer is derived from a non-metallic coating agent, and the metal coating element in the coating layer is derived from a metal coating agent; The non-metal coating agent includes a non-metal sulfide coating agent and / or a non-metal oxide coating agent; The metal coating agent includes any one of a metal sulfide coating agent, a metal sulfate coating agent or a metal oxide coating agent, or a combination of at least two of them.

3. The lithium-ion battery positive electrode material according to claim 2, characterized in that The non-metal coating agent includes a non-metal sulfide coating agent, and the metal coating agent includes a metal sulfide coating agent and / or a metal sulfate coating agent; The sulfur in the lithium sulfate is derived from a first sulfide, a second sulfide, a third sulfide and a fourth sulfide, wherein the first sulfide includes the non-metallic sulfide dopant, the second sulfide includes the metal sulfide dopant and / or the metal sulfate dopant, the third sulfide includes the non-metallic sulfide coating agent, and the fourth sulfide includes the metal sulfide coating agent and / or the metal sulfate coating agent.

4. The lithium-ion battery positive electrode material according to claim 3, characterized in that The non-metallic sulfide coating agent includes any one of B2S3, SeS2 or SiS2 or a combination of at least two; And / or, the metal sulfide coating agent includes any one or a combination of at least two of MoS2, CeS, Al2S3, K2S, Na2S or CuS; And / or, the metal sulfate coating agent includes Al2(SO4)3.

5. The lithium-ion battery positive electrode material according to any one of claims 1 to 4, characterized in that The layered oxide material includes any one of NCA, NCMA or NCM, or a combination of at least two of them.

6. The lithium-ion battery cathode material according to any one of claims 1 to 4, characterized in that In the lithium-ion battery positive electrode material, the content of the non-metallic doping element is 0.05wt%-0.5wt%; And / or, in the lithium-ion battery positive electrode material, the content of the metal doping element is 0.06wt%-0.6wt%.

7. The lithium-ion battery cathode material according to any one of claims 1 to 4, characterized in that In the lithium-ion battery positive electrode material, the content of the non-metallic coating element is 0.05wt%-0.5wt%; And / or, in the lithium-ion battery positive electrode material, the content of the metal coating element is 0.06wt%-0.6wt%.

8. A method for preparing a positive electrode material for a lithium-ion battery according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing a positive electrode precursor, a lithium source, a first sulfide-containing material, and a second sulfide-containing material and sintering them once to obtain a sintered material, washing and drying the sintered material to obtain a sintered washed and dried material; The first sulfide-containing material includes a non-metallic sulfide dopant, and the second sulfide-containing material includes a metal sulfide dopant and / or the metal sulfate dopant; (2) The water-washed and dried material, the non-metallic coating agent and the metal coating agent in step (1) are mixed and subjected to secondary sintering to obtain the lithium-ion battery positive electrode material.

9. The preparation method according to claim 8, characterized in that The primary sintering temperature in step (1) is 650°C-750°C and the sintering time is 7h-30h; And / or, the positive electrode precursor in step (1) includes a nickel cobalt hydroxide precursor, and an aluminum source is added when the positive electrode precursor, the lithium source, the first sulfide-containing material and the second sulfide-containing material are mixed; And / or, the secondary sintering in step (2) is performed at a temperature of 250°C-700°C and for a time of 3h-15h.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-ion battery positive electrode material according to any one of claims 1 to 7.

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