Lithium ion battery positive electrode material, preparation method thereof and lithium ion battery

Abstract

The 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 matrix and a coating layer, the matrix comprises a non-metal doping element and a metal doping element, and the coating layer comprises lithium sulfate, a non-metal coating element and a metal coating element; a non-metal doping element in the matrix is derived from a non-metal sulfide doping agent, and a metal doping element is derived from a metal sulfide doping agent and / or a metal sulfate doping agent; the sulfur in the lithium sulfate is derived from the non-metal sulfide dopant, as well as a metal sulfide dopant and / or a metal sulfate dopant. The lithium sulfate in the coating layer inhibits the damage to the crystal structure on the surface of the material in the washing process and the generation of NiO inactive substances, and the doped and coated elements stabilize the lattice oxygen and oxygen frame structure, so that the capacity and cycle performance of the material can be improved while the safety performance is ensured.

Description

Technical Field

[0001] The 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] Lithium-ion battery is a secondary chemical battery (i.e., rechargeable chemical battery), whose positive and negative electrodes are composed of two different substances, which can be used for reversible insertion and extraction of lithium ions. During the charging process of lithium-ion battery, lithium ions are extracted from the positive electrode and embedded in the lattice of the negative electrode through the electrolyte, so that the positive electrode is in a high-potential lithium-poor state, and the negative electrode is in a low-potential lithium-rich state; the opposite is true during discharge. Therefore, lithium-ion batteries have the characteristics of high voltage, high specific energy, high specific power, long cycle life, low self-discharge, no memory effect, and environmental friendliness, and are called green new energy products.

[0003] The ternary cathode material is LiNiO 2 Modified, 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 positive electrode materials, and is considered to be one of the most promising positive electrode 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 will interact with Li + The mixing effect is generated, resulting in deterioration of the cycle performance and rate performance. Co can effectively stabilize the layered structure of the ternary material and inhibit cation mixing, thereby improving the electronic conductivity of the material and improving the cycle performance. The presence of Mn can reduce costs, improve the structural stability and safety of the material, while too high a Mn content will reduce the material's gram capacity. Aluminum doping will enhance the material's structural stability and safety, thereby improving the material's cycle 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. The surface structure is unstable, and 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 prior art, the ternary cathode materials are doped with high-valent elements or the main element Al, and the radial growth direction of the ternary materials is regulated in the precursor process to improve the cycling performance of the materials and increase the capacity at the same time. However, the refinement of primary particles will lead to the deterioration of the high-temperature cycling performance, thermal stability and other safety performance of the materials. Therefore, at this stage, the ternary cathode materials are still facing the challenge of Ni2+ Occupy Li + There is a problem with the 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 generation of NiO inactive substances during the water washing process, and provide battery capacity and cycle performance. Summary of the invention

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

[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 positive electrode material for a lithium ion battery, the positive electrode material for a lithium ion battery comprising a substrate and a coating layer on the surface of the substrate, the substrate comprising a layered oxide material, the substrate further comprising a non-metallic doping element and a metal doping element, the coating layer comprising 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 and a second sulfide, wherein the first sulfide includes the non-metallic sulfide dopant, and the second sulfide 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 element 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 element. That is, the present invention forms Li in situ on the surface of the positive electrode material through the sulfur in the above dopant. 2 SO 4 The protective layer inhibits the destruction of the surface crystal structure of the positive electrode material during the water washing process and reduces the residual alkali of the material. At the same time, the doping of non-metallic elements and metal elements is realized. Among them, the metal doping elements are used to stabilize the lattice oxygen and oxygen framework structure, and prevent the lattice oxygen from being in the form of gaseous O 2The 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 the effect of water washing on the material, that is, to gradually transform the surface NiO rock salt phase into a layered structure, thereby improving the cycle performance and capacity of the material.

[0013] Preferably, the non-metal coating element in the coating layer is derived from a non-metal 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 originates 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, 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 each independently include B 2 S 3 , SeS 2 or SiS 2 Any one 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 or a combination of at least two of B, Se or Si.

[0019] Preferably, the metal sulfide dopant and the metal sulfide coating agent each independently include MoS 2 , CeS, Na2 S, Al 2 S 3 , K 2 S, Na 2 Any one or a combination of at least two of S or CuS.

[0020] Preferably, the metal sulfate dopant and the metal sulfate coating agent each independently include Al 2 (SO 4 ) 3 .

[0021] That is, the metal doping element and the metal coating element of the present invention each 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 first-fired, washed, dried material for preparing the positive electrode material of the lithium-ion battery satisfies the following relationship: the absolute value of (Li 2 CO 3 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 unlisted values within the numerical range are equally applicable.

[0023] The surface residual alkali of the first-fired, washed, dried material of the present invention satisfies the above relationship, indicating that the non-metal sulfide dopant, and the 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 or a combination of at least two of NCA (nickel-cobalt-aluminum material), NCMA (nickel-cobalt-manganese-aluminum material) or NCM (nickel-cobalt-manganese material). Among them, 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 equally applicable.

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

[0026] Preferably, in the lithium-ion battery positive electrode material, the content of the metal doping 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 unlisted values ​​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 by the doping + coating element). The present invention preferably contains non-metallic doping elements and metal doping elements within a specific range, which can ensure the amount of lithium sulfate in the coating layer, reduce the residual alkali value, inhibit the damage of water washing to the material, and ensure (Li 2 CO 3 The absolute value of LiOH content (LiOH content) / LiOH content is in the range of 0.3-5, while ensuring the effective doping of metal elements and non-metal elements; however, if the doping amount of non-metallic doping elements and metal doping elements is too much, 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 unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, in the lithium-ion battery positive electrode material, the content of aluminum element 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 unlisted values ​​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, and 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 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 positive electrode material for a lithium-ion battery.

[0035] The present invention adds the first sulfide and the second sulfide during the first calcination, so that the sulfur therein forms lithium sulfate in situ, which can inhibit the destruction of the crystal structure of the material surface during the water washing process and reduce the residual alkali. At the same time, metal elements and non-metal elements are added to the matrix to improve the structural stability and stabilize the lattice oxygen and oxygen framework structure during the water washing process. The present invention coats the non-metal coating agent and the metal coating agent during the second calcination to further repair the water-washed surface, that is, the surface NiO-like rock salt phase is gradually transformed 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 that the non-metallic doping element content in the lithium ion battery positive electrode material is 0.05wt%-0.5wt%, the metal doping element content is 0.06wt%-0.6wt%, the non-metallic coating element content is 0.05wt%-0.5wt%, and the metal coating element content is 0.06wt%-0.6wt%.

[0037] Preferably, the primary sintering temperature in step (1) is 650°C-750°C, for example, 650°C, 700°C or 750°C, and the sintering 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) comprises 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, wherein the lithium ion battery comprises 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 element 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 element. That is, the present invention forms Li in situ on the surface of the positive electrode material through the sulfur in the above dopant. 2 SO 4 The protective layer inhibits the destruction of the surface crystal structure of the positive electrode material during the water washing process and reduces the residual alkali of the material. At the same time, the doping of non-metallic elements and metal elements is realized. Among them, the metal doping elements are used to stabilize the lattice oxygen and oxygen framework structure, and prevent the lattice oxygen from being in the form of gaseous O 2 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 the effect of water washing on the material, that is, to gradually transform the surface NiO 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 It is the Dq / Dv diagram (differential capacity curve diagram) of the battery prepared with 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 specific implementation methods. It should be understood by those skilled in the art that the embodiments are only 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 positive electrode material for a lithium-ion battery, the positive electrode material for a lithium-ion battery comprising a substrate and a coating layer on the surface of the substrate, the substrate comprising an NCA material, the substrate further comprising a non-metallic doping element (specifically B) and a metal doping element (specifically Mo), the coating layer comprising 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 B 2 S 3 ), the metal doping element in the matrix is ​​derived from the metal sulfide dopant (specifically MoS 2 The non-metal coating element in the coating layer is derived from a non-metal sulfide coating agent (specifically B 2 S 3 ), the metal coating element in the coating layer is derived from a metal sulfide coating agent (specifically MoS 2 );

[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, Al with D50 of 13.5 μm 2 O 3 , B 2 S 3 and MoS 2 High-speed mixing (in the formula, the Al content is 0.7wt%, the Ni 0.96 Co 0.04 (OH) 2 Precursor and Al 2 O 3The ratio of the total molar amount of metal ions in the mixture to the molar amount of LiOH is 1:1.08), the mixing speed is 1000 rpm / min, and after mixing for 20 minutes, the first mixed material is placed in a muffle furnace, and sintered at 700°C for 28 hours in an oxygen atmosphere, and the material is taken out after naturally cooling to room temperature, and is crushed and sieved to obtain a first-burned semi-finished product, and the first-burned semi-finished product is washed, filtered, and dried to obtain a first-burned water-washed and dried material;

[0055] (2) According to the formula, the washed and dried material in step (1) is washed with water, and the 2 S 3 and MoS 2 The mixture is mixed to obtain a second mixed material, and the second mixed material is sintered in an oxygen atmosphere and secondary sintered 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 positive electrode material for a lithium-ion battery, the positive electrode material for a lithium-ion battery comprising a substrate and a coating layer on the surface of the substrate, the substrate comprising an NCA material, the substrate further comprising a non-metallic doping element (specifically Se) and a metal doping element (specifically Ce), the coating layer comprising 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 SeS 2 ), the metal doping element in the matrix is ​​derived from a metal sulfide dopant (specifically CeS); the non-metal coating element in the coating layer is derived from a non-metal sulfide coating agent (specifically SeS 2 ), 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) 2Precursor, LiOH, Al with D50 of 13.5 μm 2 O 3 , SeS 2 and CeS are mixed at high speed (in the formula, the Al content is 1.5wt%, the Ni 0.96 Co 0.04 (OH) 2 Precursor and Al 2 O 3 The ratio of the total molar amount of metal ions in the mixture 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, and the material is taken out after naturally cooling to room temperature, and is crushed and sieved to obtain a first-burned semi-finished product, and the first-burned semi-finished product is washed, filtered, and dried to obtain a first-burned water-washed and dried material;

[0063] (2) According to the formula, the washed and dried material and SeS 2 and CeS to obtain a second mixed material, wherein the second mixed material is sintered in an oxygen atmosphere and secondary sintered 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 positive electrode material for a lithium-ion battery, the positive electrode material for a lithium-ion battery comprising a substrate and a coating layer on the surface of the substrate, the substrate comprising an NCA material, the substrate further comprising a non-metallic doping element (specifically B) and a metal doping element (specifically Mo), the coating layer comprising 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 B 2 S 3 ), the metal doping element in the matrix is ​​derived from the metal sulfide dopant (specifically MoS 2 The non-metal coating element in the coating layer is derived from a non-metal sulfide coating agent (specifically B 2 S 3 ), the metal coating element in the coating layer is derived from a metal sulfide coating agent (specifically MoS 2 );

[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, Al with D50 of 13.5 μm 2 O 3 , B 2 S 3 and MoS 2 High-speed mixing (in the formula, the Al content is 2wt%, the Ni 0.96 Co 0.04 (OH) 2 Precursor and Al 2 O 3 The ratio of the total molar amount of metal ions in the mixture to the molar amount of LiOH is 1:1.08), the mixing speed is 1000 rpm / min, and after mixing for 20 minutes, the first mixed material is placed in a muffle furnace, and sintered at 750°C for 10 hours in an oxygen atmosphere, and the material is taken out after naturally cooling to room temperature, and is crushed and sieved to obtain a first-burned semi-finished product, and the first-burned semi-finished product is washed, filtered, and dried to obtain a first-burned water-washed and dried material;

[0071] (2) According to the formula, the washed and dried material in step (1) is washed with water, and the 2 S 3 and MoS 2 The mixture is mixed to obtain a second mixed material, and the second mixed material is sintered in an oxygen atmosphere and secondary sintered 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. In addition to the preparation method of the positive electrode material for a lithium ion battery, the B 2 S 3 Replace with B of equal mass 2 O 3 Except for this, the rest are the same as in Example 1.

[0074] Example 5

[0075] This embodiment provides a positive electrode material for a lithium-ion battery. In addition to the preparation method of the positive electrode material for a lithium-ion battery, the MoS2 Replace with MoO of equal mass 3 Except for this, the rest are the same as in Example 1.

[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 of Embodiment 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 Embodiment 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 of Embodiment 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. In the preparation method of the positive electrode material for a lithium ion battery, B is not added during the mixing in step (1). 2 S 3 and MoS 2 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0086] Comparative Example 2

[0087] This comparative example provides a positive electrode material for a lithium ion battery. In addition to the preparation method of the positive electrode material for a lithium ion battery, the B 2 S 3 Replace with MoS with equal mass 2 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0088] Comparative Example 3

[0089] This comparative example provides a positive electrode material for a lithium-ion battery. In addition to the preparation method of the positive electrode material for a lithium-ion battery, the MoS2 Replace with B of equal mass 2 S 3 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0090] Comparative Example 4

[0091] This comparative example provides a positive electrode material for a lithium ion battery. In addition to the preparation method of the positive electrode material for a lithium ion battery, the B 2 S 3 Replace with B of equal mass 2 O 3 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0092] Comparative Example 5

[0093] This comparative example provides a positive electrode material for a lithium-ion battery. In addition to the preparation method of the positive electrode material for a lithium-ion battery, the MoS 2 Replace with MoO of equal mass 3 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0094] Comparative Example 6

[0095] This comparative example provides a positive electrode material for a lithium ion battery. In the preparation method of the positive electrode material for a lithium ion battery, B is not added during the mixing in step (2). 2 S 3 and MoS 2 , except that the adaptability of the positive electrode material of the lithium ion battery is changed, the rest is the same as Example 1.

[0096] The positive electrode materials of lithium ion batteries obtained in the above examples and comparative examples are prepared into positive electrode sheets, and then mixed with metal lithium sheets, polyethylene microporous diaphragms and LiPF 6 -EC / DMC (the volume ratio of EC to DMC is 1:1, EC is ethylene carbonate, and DMC is dimethyl carbonate) was prepared into a button battery, and the button battery was subjected to capacity test (2.5V-4.25V, 0.2C), cycle test (3.0V-4.5V, 0.5C / 1C) and DSC test (0.1C charging to 4.3V). The test results are shown in Table 1, wherein the Dq / Dv graphs of the batteries obtained in Example 1 and Comparative Example 1 are as shown in Table 1. Figure 1 As shown by Figure 1It can be seen that the non-metallic sulfide dopant and the metal sulfide dopant of the present invention can inhibit the harmful phase change 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: (Li 2 CO 3 The absolute value of LiOH content (LiOH content - LiOH content) / LiOH content is 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 cycle and safety are significantly affected.

[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-metal 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 implementation mode 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 are within the protection scope and disclosure scope of the present invention.

Claims

1. A positive electrode material for a lithium ion battery, characterized in that: The lithium-ion battery positive electrode material comprises 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; 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, wherein the first sulfide includes the non-metallic sulfide dopant, and the second sulfide includes the metal sulfide dopant and / or the metal sulfate dopant.

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 positive electrode material for lithium-ion batteries 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 dopant and the non-metallic sulfide coating agent independently include any one or a combination of at least two of B2S3, SeS2 or SiS2; And / or, 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; And / or, the metal sulfate dopant and the metal sulfate capping agent each independently include Al2(SO4)3.

5. The lithium ion battery positive electrode material according to any one of claims 1 to 4, characterized in that: The residual alkali on the surface 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; And / or, the layered oxide material includes any one of NCA, NCMA or NCM, or a combination of at least two thereof.

6. The positive electrode material for a lithium-ion battery according to any one of claims 1 to 4, characterized in that: In the lithium-ion battery positive electrode material, the content of non-metallic doping elements 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 positive electrode material for a lithium-ion battery 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-metal 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, and 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 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 positive electrode material for a lithium-ion battery.

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) 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; And / or, the secondary sintering in step (2) is performed at a temperature of 250° C. to 700° C. and for a time of 3 h to 15 h.

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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