Ternary positive electrode material with low gas evolution and high capacity

Abstract

Positive electrode material comprising a substrate, wherein the formula of the substrate is Li x Ni y Co z M k Me p O r A m is where 0.95 ≤ x ≤ 1.05, 0.50 ≤ y ≤ 0.95, 0 ≤ z ≤ 0.2, 0 ≤ k ≤ 0.4, 0 ≤ p ≤ 0.05, 1 ≤ r ≤ 2, 0 ≤ m ≤ 2, m + r ≤ 2, M is selected from Mn and / or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb, and A is selected from one or more of N, F, S and Cl; wherein a coating layer is arranged on the substrate, the coating layer comprising a coating element selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P; and where the absorption of nickel leaching product per unit mass of the positive electrode material is w ≤ 0.7.

Description

[0001] The present disclosure claims priority from Chinese patent application No. CN201910578176.8, filed on June 28, 2019, entitled “TERNARY POSITIVE ELECTRODE MATERIAL WITH LOW GAS EVOLUTION AND HIGH CAPACITY”, and is hereby incorporated in its entirety by reference. TECHNICAL AREA

[0002] The present disclosure relates to the field of electrochemistry and in particular to a ternary positive electrode material with low gas evolution and high capacity, as well as an electrochemical energy storage device. BACKGROUND

[0003] In light of the worsening energy crisis and environmental problems, the development of new green energy sources is becoming increasingly important. Due to their advantages, such as high specific energy, application across a wide temperature range, low self-discharge rate, long lifespan, good safety performance, and environmental compatibility, lithium-ion batteries are being used in various sectors. Lithium-ion batteries intended to serve as vehicle energy systems and replace conventional diesel engines are being tested gradually worldwide. However, lithium iron phosphate (LiFePO4) and a ternary material with a low nickel content (LiNi) are still being developed. 1 / 3 Co 1 / 3 Mn 1 / 3The energy density of ternary positive electrode materials (O2) currently in common use is limited by the material properties themselves and cannot fully meet the energy density requirements of traction batteries with regard to the positive electrode material in lithium-ion batteries. Increasing the nickel content of a high-nickel ternary positive electrode material can improve the energy density of batteries. Therefore, high-nickel ternary positive electrode materials are one of the main research areas in the field of traction batteries. However, the increased nickel content apparently exacerbates the direct side reactions between the active material of the positive electrode and an electrolyte solution and significantly degrades the gas evolution performance at high temperatures, which is one of the obstacles to the commercial mass production of batteries.

[0004] Regarding the material, the most important methods for improving gas evolution performance at high temperatures currently all lead to varying degrees of performance loss in the battery cells. For example, the reversible capacity per gram of active material decreases, and the cycle performance deteriorates. SUMMARY

[0005] In view of the disadvantages of the prior art, the present disclosure is intended to provide a ternary positive electrode material with low gas evolution and high capacity to solve the problems of the prior art.

[0006] To achieve the above-mentioned and other related objectives, the present disclosure provides a positive electrode material containing a substrate, wherein the formula of the substrate is Li x Ni y Co z M k Me p O r A mis where 0.95 ≤ x ≤ 1.05, 0.50 ≤ y ≤ 0.95, 0 ≤ z ≤ 0.2, 0 ≤ k ≤ 0.4, 0 ≤ p ≤ 0.05, 1 ≤ r ≤ 2, 0 ≤ m ≤ 2, m + r ≤ 2, M is selected from Mn and / or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb, and A is selected from one or more of N, F, S and Cl; A coating layer is arranged on a surface of the substrate, wherein the coating layer contains a coating element selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P; and the absorption of nickel leaching product per unit mass of the positive electrode material is w ≤ 0.7.

[0007] According to another aspect, the present disclosure provides an electrochemical energy storage device that contains the positive electrode material according to the present disclosure.

[0008] Compared to the prior art, the present disclosure offers the following advantageous effects:

[0009] The positive electrode material of the present disclosure exhibits good crystal structure stability and surface inertness. The absorption of nickel leaching product in the positive electrode material is relatively low, so that side reactions between the positive electrode material and an electrolyte solution can be effectively prevented, thereby optimizing cycle performance, improving thermal stability, and reducing gas evolution. DESCRIPTION OF THE EXECUTION FORMS

[0010] The lithium-ion battery of the present disclosure and a method for its manufacture are described in detail below.

[0011] A first aspect of the present disclosure provides a positive electrode material containing a substrate, wherein the formula of the substrate is Lix Ni y Co z M k Me p O r A m is, where 0.95 < x ≤ 1.05, 0.50 ≤ y ≤ 0.95, 0 ≤ z ≤ 0.2, 0 ≤ k ≤ 0.4, 0 ≤ p ≤ 0.05, 1 ≤ r ≤ 2, 0 ≤ m ≤ 2, m + r ≤ 2, M is selected from Mn and / or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb, and A is selected from one or more of N, F, S and Cl; a coating layer is arranged on the substrate, the coating layer containing a coating element selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P; and the absorption of nickel leaching product per unit mass of the positive electrode material is w ≤ 0.7.

[0012] In one embodiment of the present disclosure, a method for determining the absorption w of nickel leaching product per unit mass of the positive electrode material may typically include: introducing the unit mass of the positive electrode material into a suitable solution and measuring the absorption of the resulting leaching product under a defined wavelength range.In a specific embodiment of the present disclosure, a method for determining the absorption w of nickel leaching product per unit mass of the positive electrode material may in particular include the following steps: immersing 1 g of the positive electrode material in 10 ml of ethanol solution having a pH of about 8 to 11 and a dimethylglyoxime concentration of 10 g / l for 24 hours; removing 5 ml of supernatant and diluting to 10 ml of leaching product by adding deionized water; and measuring the absorption of the leaching product in a range of 430 nm to 570 nm using a UV / VIS spectrophotometer.

[0013] A higher relative nickel content in a ternary material typically indicates a greater capacity per gram of the ternary material and contributes to increasing the energy density of the electrochemical energy storage device. However, an increase in the relative nickel content can lead to numerous negative effects on the overall performance of the electrochemical energy storage device. For example, if the relative nickel content in the ternary material is relatively high, the layered structure of the ternary material can break down due to the mixing of nickel. 2+ and Li + together, thereby deintercalating Li +The removal of the ternary material becomes more difficult, ultimately leading to a deterioration in the cycle performance of the electrochemical energy storage device. As another example, an increase in the relative Ni content in the ternary material also reduces the thermal decomposition temperature of the ternary material, resulting in increased heat release and a deterioration of the thermal stability of the ternary material. As the relative Ni content in the ternary material increases, the amount of Ni also decreases. 4+This occurs in cases of high oxidizability. When the electrolyte solution comes into contact with the ternary material, further side reactions occur between the electrolyte solution and the ternary material, and the ternary material releases oxygen to maintain charge equilibrium. This not only destroys the crystal structure of the ternary material but also increases the swelling of the electrochemical energy storage device and degrades its storage performance.Thanks to extensive research, the researchers of this application have found that contact between the electrolyte solution and the material can be avoided to a certain extent by doping and surface-coating the positive electrode material in a high nickel substrate to keep the absorption of nickel leaching product of the positive electrode material within a suitable range, thereby optimizing cycle performance, improving thermal stability, reducing the extent of side reactions and decreasing gas evolution.

[0014] In some embodiments of the present disclosure, the absorption of the nickel element per unit mass of the positive electrode material can be w ≤ 0.7, w ≤ 0.6, w ≤ 0.5, w ≤ 0.4, w ≤ 0.3, or w ≤ 0.2. In the present disclosure, an absorption w of nickel leaching product per unit mass of the positive electrode material greater than 0.7 indicates that the nickel element can readily leach from the particles of the positive electrode material. In this case, side reactions between the surface of the positive electrode material and the electrolyte solution readily occur, causing a lithium-ion battery using the positive electrode material to generate excessive amounts of gas. A lower absorption of nickel leaching product per unit mass of the positive electrode material indicates greater stability of the crystal structure, particularly the surface crystal structure, of the positive electrode material.

[0015] In the positive electrode material provided in the embodiments of the present disclosure, a theoretical specific surface area BET1 of the positive electrode material and an actual specific surface area BET2 of the positive electrode material can typically satisfy the following: 0.3≤(BET2−BET1) / BET1≤5.5; where BET1 = 6 / (ρ × D v 50); ρ is the actual density of the positive electrode material, measured in g / cm² 3 ; and D v50 is a particle size of the positive electrode material below a cumulative volume distribution percentage of 50%, measured in µm. The actual specific surface area BET2 of the positive electrode material can be measured by the N2 adsorption method. Details can be found in GB / T19587-2004. (BET2 - BET1) / BET1 represents a degree of deviation between the theoretical specific surface area and the actual specific surface area of ​​the positive electrode material, thus allowing the degree of unevenness on the surface of the positive electrode material to be measured.Since material uniformity is one of the factors influencing the BET2 of the positive electrode material, controlling the degree of deviation between the theoretical and actual specific surface area of ​​the positive electrode material within a defined range can indicate relatively good grain size and morphological uniformity. The coated positive electrode material exhibits a relatively flat surface and fewer concave and convex structures, and therefore has a relatively small contact area with the electrolyte solution. All these measures help to prevent the leaching of the nickel element from the positive electrode material while simultaneously ensuring good lithium ion transfer between secondary particles, thus achieving a balance between gas evolution at high temperatures and the kinetics.

[0016] In the positive electrode material provided in the embodiments of the present disclosure, the substrate can contain secondary particles consisting of primary particles. The secondary particles have a D v 50 from 5 µm to 18 µm, and the particle size of the primary particles can range from 0.1 µm to 1.0 µm. The D v 50 is a particle size of the sample below a cumulative volume distribution percentage that reaches 50%. In particular, the D v50 of the secondary particles are 5 µm to 18 µm, 5 µm to 6 µm, 6 µm to 7 µm, 7 µm to 8 µm, 8 µm to 9 µm, 9 µm to 10 µm, 10 µm to 11 µm, 11 µm to 12 µm, 12 µm to 13 µm, 13 µm to 14 µm, 14 µm to 15 µm, 15 µm to 16 µm, 16 µm to 17 µm or 17 µm to 18 µm and preferably 8 to 15 µm. The particle size of the primary particles can range from 0.1 µm to 1 µm, 0.1 µm to 0.9 µm, 0.2 µm to 0.8 µm, or 0.2 µm to 0.5 µm. For a ternary material with a relatively high nickel content, a relatively large amount of powder with a small particle size has a greater influence on the residual lithium content and gas evolution of the active material of the positive electrode. Therefore, controlling the D v 50 of the primary particles and of the secondary particles of the ternary material with high nickel content Li x Ni y Co z M k Me p O r A m with a secondary particle morphology or Li x Ni y Coz M k Me p O r A m Applying a coating layer to a surface within defined areas can be an effective means of solving the gas formation problem. If the substrate contains secondary particles composed of primary particles, the actual specific surface area BET2 of the positive electrode material can be 0.1 m². 2 / g up to 1.0 m 2 / g, 0.1 m 2 / g up to 0.2 m 2 / g, 0.2 m 2 / g up to 0.3 m 2 / g, 0.3 m 2 / g up to 0.4 m 2 / g, 0.4 m 2 / g up to 0.5 m 2 / g, 0.5 m 2 / g up to 0.6 m 2 / g, 0.6 m 2 / g up to 0.7 m 2 / g, 0.7 m 2 / g up to 0.8 m 2 / g, 0.8 m 2 / g up to 0.9 m 2 / g or 0.9 m 2 / g up to 1.0 m 2The surface area of ​​the positive electrode material can be reduced by a certain amount per gram. A suitable specific surface area of ​​the positive electrode material can reduce the contact area between the electrolyte solution and the active material of the positive electrode, thus helping to prevent side reactions and avoid exacerbating swelling of the electrochemical energy storage device due to corrosion of the electrolyte solution and damage to the crystal structure of the active material of the positive electrode. Such a specific surface area of ​​the positive electrode material can also help to achieve relatively strong adhesion of the binder and the conductive agent to the active material of the positive electrode with fewer auxiliary materials when mixing a positive electrode paste, thereby helping to increase the energy density of the electrochemical energy storage device.

[0017] In the positive electrode material provided in the embodiments of the present disclosure, the substrate can contain single-crystal or single-crystal-like particles. If the substrate consists of single-crystal or single-crystal-like particles, the particle size D can be v 50 of the substrate 1 µm to 6 µm, 1 µm to 2 µm, 2 µm to 3 µm, 3 µm to 4 µm, 4 µm to 5 µm or 5 µm to 6 µm, and preferably the particle size D v 50 of the substrate 2 µm to 5 µm. The single-crystal or single-crystal-like particles typically refer to a positive electrode material whose particle morphology is formed by a single complete particle or an aggregate of fewer than ten particles. If the positive electrode material contains single-crystal or single-crystal-like particles, the actual specific surface area BET2 of the positive electrode material can be 0.5 m². 2 / g up to 1.5 m 2 / g, 0.5 m2 / g up to 0.6 m 2 / g, 0.6 m 2 / g up to 0.7 m 2 / g, 0.7 m 2 / g up to 0.8 m 2 / g, 0.8 m 2 / g up to 0.9 m 2 / g, 0.9 m 2 / g up to 1.0 m 2 / g, 1.0 m 2 / g up to 1.1 m 2 / g, 1.1 m 2 / g up to 1.2 m 2 / g, 1.2 m 2 / g up to 1.3 m 2 / g or 1.3 m 2 / g up to 1.4 m 2 / g or 1.4 m 2 / g up to 1.5 m 2 / g. In the embodiments of the present disclosure, if the positive electrode material contains the above-mentioned single-crystal or single-crystal-like particles, whose particle sizes and BETs are within the above-mentioned ranges, the positive electrode material has a more integral surface and internal crystal structure as well as a smaller contact area with the electrolyte solution, which helps to reduce the leaching of the nickel element from the particle surface.

[0018] In the positive electrode material provided in the embodiments of the present disclosure, a coating element content per volume unit Mv in the positive electrode material of 0.4 mg / cm³ can be achieved. 3 up to 15 mg / cm² 3 , 0.4 mg / cm² 3 up to 0.6 mg / cm² 3 , 0.6 mg / cm² 3 up to 0.8 mg / cm² 3 , 0.8 mg / cm² 3 up to 1 mg / cm² 3 , 1 mg / cm 3 up to 2 mg / cm² 3 , 2 mg / cm 3 up to 4 mg / cm² 3 , 4 mg / cm 3 up to 6 mg / cm² 3 , 6 mg / cm 3 up to 8 mg / cm² 3 , 8 mg / cm 3 up to 10 mg / cm² 3 or 10 mg / cm² 3 up to 15 mg / cm² 3 The amount is preferably 0.8 mg / cm². 3 up to 10 mg / cm² 3The coating element content can generally be adjusted to ensure that, even with varying volume-based particle size distributions, a balance is achieved between surface modification and polarization of the positive electrode material. This effectively reduces the gas formation problem in high-capacity batteries and optimizes their cycle and rate performance. The coating element is typically present in the coating layer in the form of an oxide.For example, the coating layer may contain one or more oxides of the aforementioned coating elements or a lithium-containing oxide of the aforementioned coating element and the lithium element, and may in particular, but not limited to, contain one or more of aluminium oxide, zirconium oxide, zinc oxide, titanium oxide, silicon oxide, tin oxide, tungsten oxide, yttrium oxide, cobalt oxide, barium oxide, phosphorus oxide, boron oxide and lithium aluminium oxide, lithium zirconium oxide, lithium zinc oxide, lithium magnesium oxide, lithium tungsten oxide, lithium yttrium oxide, lithium cobalt oxide, lithium barium oxide, lithium phosphorus oxide and lithium boron oxide.

[0019] In the positive electrode material provided in the embodiments of the present disclosure, the coating layer can include an inner coating layer. The inner coating layer can be located within the substrate and can be situated on the surfaces of at least some primary particles. The inner coating layer contains a coating element, wherein the coating element of the inner coating layer is selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, and P. In the positive electrode material, the substrate contains secondary particles that consist of primary particles. Therefore, at least one section of the coating layer can be located between the primary particles that are located within the secondary particles, that is, on the surfaces of at least some primary particles within the secondary particles.This section of the coating layer can be considered the inner coating layer. The inner coating layer may contain an oxide of the coating element. More precisely, at least one section of the coating element may be present in the inner coating layer in the form of its oxide or lithium-containing oxide and may, in particular, but not limited to, contain one or more of the following: aluminum oxide, zirconium oxide, zinc oxide, titanium oxide, silicon oxide, tin oxide, tungsten oxide, yttrium oxide, cobalt oxide, barium oxide, phosphorus oxide, boron oxide, lithium aluminum oxide, lithium zirconium oxide, lithium zinc oxide, lithium magnesium oxide, lithium tungsten oxide, lithium yttrium oxide, lithium cobalt oxide, lithium barium oxide, lithium phosphorus oxide, and lithium boron oxide.Since a secondary particle is formed by the dense packing of several primary particles, the volume of the secondary particles can swell or shrink during the cycle, thereby increasing the gaps between the primary particles inside the secondary particles and exposing a large portion of the uncoated, fresh surface. This creates a risk of side reactions with the electrolyte solution. In the embodiments described in the present disclosure, although the secondary particles are provided with coating layers on their surfaces, a coating is applied to the surfaces of at least one section of the primary particles or to the grain boundaries between adjacent primary particles. This increases the internal density of the secondary particles, improves the force acting between the inner primary particles, and further reduces the gas formation problem during the cycle.

[0020] In the positive electrode material provided in the embodiments of the present disclosure, the coating layer can include an outer coating layer. The outer coating layer can be located on the surfaces of the secondary particles and / or on a surface of the substrate. The outer coating layer contains a coating element, wherein the coating element of the outer coating layer is selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, and P. In the positive electrode material, the substrate contains secondary particles consisting of primary particles, wherein at least a portion of the coating layer can be located on the surfaces of the secondary particles, and the coating element can be distributed in the oxide coating layer on the surfaces of the secondary particles. The outer coating layer can contain an oxide of the coating element.More precisely, at least one section of the coating element in the inner coating layer can be present in the form of its oxide or lithium-containing oxide and can, in particular, but not limited to, contain one or more of the following: aluminum oxide, zirconium oxide, zinc oxide, titanium oxide, silicon oxide, tin oxide, tungsten oxide, yttrium oxide, cobalt oxide, barium oxide, phosphorus oxide, boron oxide, lithium aluminum oxide, lithium zirconium oxide, lithium zinc oxide, lithium magnesium oxide, lithium tungsten oxide, lithium yttrium oxide, lithium cobalt oxide, lithium barium oxide, lithium phosphorus oxide, and lithium boron oxide. In the case of positive electrode material, the outer coating layer is a part that primarily serves to reduce the contact area between the substrate and the electrolyte solution.The existence of the outer coating layer allows the surface of the high nickel-content positive electrode material to be effectively modified and the side reactions between the positive electrode material and the electrolyte solution to be reduced, thereby effectively preventing gas evolution in the battery.

[0021] In the positive electrode material provided in the embodiments of the present disclosure, the coating layer can contain at least two of the aforementioned coating elements or, more precisely, an oxide formed from at least two of the aforementioned coating elements, thereby improving the stability of the adhesion of the coating layer to the substrate surface. In this way, the coating layer can provide a certain degree of ionic conductivity and electronic conductivity, thereby reducing the influence of the coating layer on the polarization of the positive electrode material.

[0022] In the positive electrode material provided in the embodiments of the present disclosure, the outer coating layer can comprise a continuous and / or discontinuous coating layer. A continuous coating layer can provide relatively complete protection for the substrate surface, which contributes to stabilizing the surface structure of the positive electrode material, inhibiting the amount of nickel leached from the positive electrode material, and preventing side reactions with the electrolyte solution. However, the continuous coating layer must exhibit good electronic and ionic conductivity to avoid increasing the impedance of an electrode sheet and deteriorating the battery kinetics.A discontinuous coating layer is advantageous because it reduces the proportion of the coating layer on the substrate surface and thus provides more ion transfer channels, but contributes less to improving the structural stability of the substrate surface than a continuous coating layer. In a preferred embodiment of the present disclosure, the outer coating layer can comprise a continuous first coating layer and a discontinuous second coating layer, a composite form of the two. The second coating layer can be located on the surface of the first coating layer or can be located between the first coating layer and the substrate.In a preferred embodiment of the present disclosure, the area of ​​a single cell of the discontinuous second coating layer is typically smaller than the area of ​​a single cell of the first coating layer. In a further preferred embodiment of the present disclosure, the second coating layer and the first coating layer can contain different coating elements in the outer coating layer, such that the coating substance of the discontinuous coating layer and the coating substance of the continuous coating layer differ at least partially.

[0023] In the positive electrode material provided in the embodiments of the present disclosure, the coating element contained in the outer coating layer can constitute 60 wt.% or more, 70 wt.% or more, 80 wt.% or more, The coating element may constitute 90 wt.% or more, or preferably 80 wt.% to 98 wt.% of the total mass of the coating element in the positive electrode material. Since, in the embodiments described in this disclosure, the surfaces of the secondary particles are the first to come into contact with the electrolyte solution and their relative surface areas are larger, the coating element is distributed mainly on the surfaces of the secondary particles. If the proportion of the mass distributed on the surfaces of the secondary particles to the total mass of the coating element in the active material of the positive electrode exceeds a certain value, the surface modification of the high-nickel positive electrode material is relatively stronger, and the effect on inhibiting gas evolution in the battery is also improved.

[0024] In the positive electrode material provided in the embodiments of the present disclosure, the substrate is a lithium transition metal oxide with a relatively high nickel content. In the formula of the substrate, y preferably satisfies 0.50 ≤ y ≤ 0.90 and more preferably 0.70 ≤ y ≤ 0.90, z preferably satisfies 0 ≤ z ≤ 0.15 and more preferably 0.05 ≤ z ≤ 0.15, k preferably satisfies 0 ≤ k ≤ 0.2 and more preferably 0.05 ≤ k ≤ 0.2, and p preferably satisfies 0 ≤ p ≤ 0.03 and more preferably 0 ≤ p ≤ 0.025. In particular, the formula of the substrate Li x Ni y Co z M k Me p O r A m , without being limited to, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0,3 Co 0,2 Mn 0,3 O2, LiNi 0,3 Co 0,25 Mn 0,23 O2, LiNi 0,55 CO0, 15 Mn 0,3 O2, LiNi 0,33 Co 0,1 Mn 0,35 O2, LiNi 0,55 Co0,03 Mn 0,4 O2, LiNi 0,6 Co 0,2 Mn 0,2 O2, LiNi 0,63 Co 0,13 Mn 0,2 O2, LiNi 0,63 Co 0,12 Mn 0,23 O2, LiNi 0,63 Co 0,1 Mn 0,23 O2, LiNi 0,63 Co 0,03 Mn 0,3 O2, LiNi 0,75 Co 0,1 Mn 0‚15 O2, LiNi 0,8 Co 0,1 Mn 0,1 O2, LiNi 0,83 Co 0,03 Mn 0,1 O2, LiNi 0,88 Co 0,03 Mn 0,07 O2, LiNi 0,9 Co 0,05 Mn 0,05 Containing O2 or the like, or it may be a substance formed by partial substitution and modification of these substances with a doping element Me and / or a doping element A.

[0025] For the positive electrode material provided in the embodiments of the present disclosure, reference may be made to GBT 9725-2007, Chemical reagent - General rule for potentiometry titration, for a method for measuring the residual lithium on the surface of the positive electrode material. The Li₂CO₃ content contained in the residual lithium on the surface of the positive electrode material (that is, the mass of Li₂CO₃ contained in the residual lithium on the surface of the positive electrode material relative to the total mass of the positive electrode material) is generally less than 3000 ppm. Preferably, the Li₂CO₃ content contained in the residual lithium on the surface of the positive electrode material is less than 2000 ppm.The LiOH content contained in the residual lithium on the surface of the positive electrode material (that is, the mass of LiOH contained in the residual lithium on the surface of the positive electrode material relative to the total mass of the positive electrode material) is less than 5000 ppm. Preferably, the LiOH content contained in the residual lithium on the surface of the positive electrode material is less than 4000 ppm. In an actual manufacturing process of a ternary material, melting, decomposition, and volatilization losses of the lithium salt used as raw material can occur due to problems with potential impurities and the low melting point of the lithium salt used as raw material at relatively low temperatures. Therefore, in a process to manufacture the ternary material, an excessive amount of lithium salt is added to compensate for the lithium loss caused during sintering.The ternary material has active oxygen anions on its surface, which react with CO₂ and H₂O in the air to form carbonate. Meanwhile, lithium ions migrate from their initial position to the surface, forming Li₂CO₃ on the surface of the ternary material. This process is accompanied by deoxidation of the surface of the ternary material, resulting in a structurally distorted surface oxide layer. Furthermore, the addition of excessive amounts of lithium salt during the synthesis of the ternary material leads to Li oxides being the main products of the excess lithium salt calcined at high temperature. These Li oxides react with CO₂ and H₂O in the air to regenerate LiOH and Li₂CO₃, which remain on the surface of the ternary material, resulting in a relatively high pH value.Furthermore, during charging and discharging, Li₂CO₃, which remains on the surface of the ternary material, decomposes to produce CO₂. Since the CO₂ gas creates a pressure difference due to a temperature difference (especially if a reaction process is accompanied by a thermal reaction), the swelling of the electrochemical energy storage device is increased, thus degrading its storage performance. Applying a coating layer to the substrate surface can reduce the residual lithium content (such as LiOH or Li₂CO₃) on the surface of the active material of the positive electrode to a certain extent, thereby achieving the goal of improving the storage performance of the electrochemical energy storage device.Furthermore, providing a coating layer on the substrate surface can also reduce the likelihood of side reactions caused by direct contact between the substrate and the electrolyte solution, thereby further reducing the amount of oxygen released by the active material of the positive electrode for charge equalization during the charging and discharging process and mitigating the risks of a resulting breakdown of the crystal structure. In a preferred embodiment of the present disclosure, the amount of Li₂CO₃ contained on the surface of the positive electrode material obtained by providing a coating layer on the substrate surface (i.e., in the outer coating layer) is generally less than the amount of LiOH.On the surface of the positive electrode material, the residual lithium (LiOH, Li2O) is susceptible to reacting with moisture and CO2 in the air to produce, for example, Li2CO3. A higher amount of Li2CO3 indicates a stronger reaction, and the resulting gas formation problem in the battery is more severe.

[0026] A second aspect of the present disclosure provides a method for measuring the absorption of nickel leaching product per unit mass of a positive electrode material for the positive electrode material according to the first aspect of the present disclosure, including: (1) Preparation of a solution A comprising a colour developer, a colour enhancer and a principal solvent; (2) Immersion of the positive electrode material in solution A and, after standing, extraction of a clear solution B from the top; and (3) Measuring the absorbance of solution B or of a diluent of solution B using a UV / VIS spectrophotometer (ultraviolet-visible spectrophotometer).

[0027] The measurement result can serve as the absorption of the nickel leaching product of the positive electrode material.

[0028] In the method for measuring the absorption of the positive electrode material, the color developer is dimethylglyoxime. The main solvent may be one or more of ethanol, water, and acetone to provide a reaction medium in which the leached nickel can react with the color developer and form a complex. The color developer enhancer may, but is not limited to, one or more of ammonia, NaOH, KOH, and the like to provide a suitable pH for the reaction, thereby improving color development sensitivity and increasing the color development rate. The pH of solution A may be 8 to 11. After the positive electrode material has been fully immersed in contact with solution A, the clear solution B is drawn off from the top after standing. Solution B typically contains nickel dimethylglyoxime.The absorption of the nickel element of the positive electrode material is obtained by measuring the absorption of solution B or the diluent of solution B using a spectrophotometer. The wavelength range for the absorption test can be between 430 nm and 500 nm. For example, the absorption can be tested at a wavelength of 470 nm.

[0029] In a preferred embodiment of the present disclosure, the method for measuring the absorption of the nickel leaching product of the positive electrode material may in particular include the following steps: (1) Using dimethylglyoxime as a colour developing agent, ammonia as a colour developing enhancer and ethanol as the main solvent to assemble solution A, wherein the concentration of dimethylglyoxime in solution A is 10 g / l and the concentration of ammonia is 25 wt.% to 28 wt.%; (2) Add 1 g of the positive electrode material to 10 ml of solution A, shake, allow to stand for 24 hours, and then take 5 ml of the clear solution B from the top; and (3) Adding deionized water to solution B to obtain 10 ml of solution C and measuring the absorption of solution C at a wavelength of 470 nm using an ultraviolet visible spectrophotometer.

[0030] In the embodiments of the present disclosure, the absorption of the nickel leaching product of the positive electrode material, measured with an ultraviolet visible spectrophotometer, exhibits relatively high sensitivity and accuracy and can visually reflect the structural stability of the crystal structure, particularly the crystal surface, of the positive electrode material. The gas formation problem of the positive electrode material can be quickly detected without the need for long-term cycle testing of the battery. Specifically, when light strikes an atom or a molecular structure, the outer electrons of the atom selectively absorb electromagnetic waves of certain wavelengths, thus forming an atomic absorption spectrum. The electron energy level in the molecule undergoes a transition, resulting in an electronic spectrum in ultraviolet and visible light.By measuring the absorption of monochromatic light of different wavelengths by a specific substance, an absorption spectrum curve can be obtained, using the wavelength as the abscissa and the absorption as the ordinate. The wavelength at which the degree of light absorption is greatest is called the maximum absorption wavelength. At different concentrations of the substance, the light absorption curves exhibit the same shape and the same maximum absorption wavelength, except for the different absorption values. The application of absorption in the field of lithium batteries is also based on this principle. According to the law of light absorption (Lambert-Beer law), the light absorption of a solution depends on the solution concentration, the thickness of the liquid layer, and the wavelength of the incident light.If the wavelength of the incident light and the thickness of the liquid layer remain unchanged, the light absorption of the solution is solely dependent on the solution concentration. Materials with a high nickel content contain a large amount of nickel. If a battery cell made from such a material is stored in a fully charged state, the high oxidation of the material promotes the oxidation and decomposition of the electrolyte solution, producing a large amount of gas. Surface coating can, to a certain extent, prevent contact between the electrolyte solution and the material, thereby reducing the extent of side reactions and, in turn, mitigating the gas formation problem.Determining the gas evolution performance of high-nickel materials before manufacturing battery cells from the raw materials undoubtedly reduces evaluation costs and provides a fast and effective method for material selection. A solid exhibits a specific solubility in liquids. When the leaching rate of the material is reduced, the ion concentration in the solution decreases. Based on this principle, immersing the high-nickel material in a liquid and measuring the concentration of leached nickel reveals differences in the material's gas evolution.

[0031] A third aspect of the present disclosure provides a method for producing the positive electrode material according to the first aspect of the present disclosure, including: Providing a substrate; and Forming a coating layer on a surface of the substrate.

[0032] The method for producing the positive electrode material provided in the embodiment of the present disclosure may include: providing a substrate. The method for providing the substrate should be known to those skilled in the art and may, for example, include mixing the raw materials of the substrate and performing a sintering process to obtain the substrate. Those skilled in the art may select suitable raw materials and proportions based on the elemental composition of the substrate. For example, the raw materials of the substrate may include a ternary material precursor of nickel-cobalt-manganese and / or aluminum, a lithium source, a metal source, a metal source, an ammonium source, and the like, and the proportions of the raw materials are typically based on the proportions of the elements in the substrate. More specifically, the ternary material precursor may, without being limited to, Ni 1 / 3 CO 1 / 3 Mn 1 / 3(OH)2, Ni 0,3 What 0,2 Mn 0,3 (OH)2, Ni 0,5 What 0,25 Mn 0,25 (OH)2, Ni 0,55 What 0,15 Mn 0,3 (OH)2, Ni 0,33 What 0,1 Mn 0,35 (OH)2, Ni 0,55 What 0,05 Mn 0,4 (OH)2, Ni 0,6 What 0,2 Mn 0,2 (OH)2, Ni 0,65 What 0,15 Mn 0,2 (OH)2, Ni 0,65 What 0,12 Mn 0,23 (OH)2, Ni 0,65 What 0,1 Mn 0,25 (OH)2, Ni 0,65 What 0,05 Mn 0,3 (OH)2, Ni 0,73 What 0,1 Mn 0,13 (OH)2, Ni 0,8 What 0,1 Mn 0,1 (OH)2, Ni 0,88 What 0,55 Mn 0,07 (OH)2, 0.9Ni 0,8 Mn 0,2 (OH)2 0.1Al2(OH)3, 0.9Ni 0,9 Mn 0,1 (OH)2 0.1Al2(OH)3 and 0.9Ni 0,9 What 0,05 Mn 0,05(OH)₂·0.1Al₂(OH)₃. The lithium source may be a lithium-containing compound, and the lithium-containing compound may, but is not limited to, contain one or more of LiOH·H₂O, LiOH, Li₂CO₃, Li₂O, and the like. The metal source may typically be a compound containing the metal element, and the compound containing the metal element may be one or more of an oxide, a nitrate, and a carbonate containing at least one of the elements Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb. The ammonium source may be a compound containing the ammonium element, and the compound containing the ammonium element may be a salt containing the ammonium element, and may, but is not limited to, contain one or more of LiF, NaCl, NaBr, and the like. As another example, the sintering condition can be 800 °C at an oxygen concentration of ≥ 20 %.The particle morphology of the positive electrode material can be tailored by selecting a different ternary precursor and adjusting the synthesis process. For example, in the process for producing the ternary precursor, the particle size can be controlled by adjusting the reaction time, pH, and ammonia concentration during co-precipitation.

[0033] The method for producing the positive electrode material provided in the embodiment of the present disclosure may further include: forming a coating layer on a substrate. The method for forming the coating layer on the substrate surface should be known to those skilled in the art and may, for example, include: sintering the substrate under conditions in which a compound containing a coating element is present to form the coating layer on the substrate surface. Based on parameters such as the composition of the coating layer and the absorption of the nickel element of the positive electrode material, those skilled in the art can select the correct type, ratio, and sintering conditions for the compound containing the coating element.For example, the compound containing the coating element can be an oxide of the coating element, which may, in particular, but not limited to, contain one or more of A₂O₃, ZrO₂, Ba(NO₃)₂, ZnO, SnO₂, SiO₂, TiO₂, Co₂O₃, WO₃, Y₂O₃, H₃BO₃, and P₂O₅. As another example, the amount of the coating element used can be 0.01 wt.% to 0.5 wt.%, 0.01 wt.% to 0.05 wt.%, 0.05 wt.% to 0.1 wt.%, 0.1 wt.% to 0.2 wt.%, 0.2 wt.% to 0.3 wt.%, 0.3 wt.% to 0.4 wt.%, or 0.4 wt.% to 0.5 wt.% of the mass of the substrate. As another example, the sintering condition could be a high temperature of 200 °C to 700 °C, 200 °C to 300 °C, 300 °C to 400 °C, 400 °C to 500 °C, 500 °C to 600 °C or 600 °C to 700 °C.

[0034] A fourth aspect of the present disclosure provides an electrochemical energy storage device that includes the positive electrode material according to the first aspect of the present disclosure.

[0035] With regard to the electrochemical energy storage device provided in the embodiments of this disclosure, it should be noted that the electrochemical energy storage device can be a supercapacitor, a lithium-ion battery, a lithium-metal battery, or a sodium-ion battery. While the embodiments of this disclosure only describe embodiments in which the electrochemical energy storage device is a lithium-ion battery, this disclosure is not limited to such embodiments.

[0036] The lithium-ion battery provided in the embodiments of the present disclosure can comprise a positive electrode sheet, a negative electrode sheet, a separator arranged between the positive and negative electrode sheets, and an electrolyte solution, wherein the positive electrode sheet contains the active material of the positive electrode according to the first aspect of the present disclosure. The method for manufacturing the lithium-ion battery should be known to those skilled in the art. For example, the positive electrode sheet, the separator, and the negative electrode sheet can each be a layer, so that they can be cut to a target size and then stacked sequentially. The stack can be further wound to a target size to form a battery core, which can then be combined with an electrolyte solution to form a lithium-ion battery.

[0037] In the lithium-ion battery provided in the embodiments of the present disclosure, the positive electrode sheet typically comprises a positive current collector and a positive electrode material layer provided on the positive current collector, wherein the positive electrode material layer may comprise the positive electrode material according to the first aspect of the present disclosure, a binder, and a conductive agent. The person skilled in the art may select a suitable method for producing the positive electrode sheet, which may, for example, include the following steps: mixing the positive electrode material, the binder, and the conductive agent to form a paste, and applying the paste to the positive current collector.The binder typically contains a fluoropolymer-based binder, and water is generally a good solvent for this binder, meaning that the fluoropolymer-based binder usually exhibits good solubility in water. For example, the fluoropolymer-based binder may be a derivative containing, but not limited to, polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer, or the like, or their modified derivatives (e.g., carboxylic acid, acrylic, or acrylonitrile). Due to the binder's poor conductivity, the amount of binder used in the positive electrode material layer must not be too high in terms of its mass fraction. Preferably, the mass fraction of the binder in the active material layer of the positive electrode is less than or equal to 2 wt% to achieve a relatively low impedance of the electrode sheet.The conductive material of the positive electrode sheet can consist of various conductive materials suitable for practical (secondary) lithium-ion batteries and may, for example, but not limited to, include one or more of acetylene carbon black, conductive carbon black, vapor-grown carbon fibers (VGCF), carbon nanotubes (CNTs), Ketjen carbon black, and the like. The weight of the conductive material can be 1 wt.% to 10 wt.% of the total mass of the positive electrode material layer. Even more preferably, the weight ratio of the conductive material to the positive electrode substance in the positive electrode sheet is greater than or equal to 1.5:95.5.

[0038] In the lithium-ion battery provided in the embodiments of the present disclosure, the positive current collector of the positive electrode sheet can typically be a layer, and the positive current collector can typically be a structure or part capable of collecting current. The positive current collector can consist of a variety of materials suitable for use as the positive current collector of a prior art lithium-ion battery. For example, the positive current collector can, but is not limited to, a metal foil, and in particular can, but is not limited to, a copper foil, an aluminum foil, and the like.

[0039] In the lithium-ion battery provided in the embodiments of the present disclosure, the negative electrode sheet typically includes a negative current collector and an active substance layer of the negative electrode provided on a surface of the negative current collector, and the active substance layer of the negative electrode typically contains an active substance of the negative electrode. The active substance of the negative electrode can consist of various materials suitable for use as the active substance of the negative electrode of a prior art lithium-ion battery.This can, for example, but is not limited to, include one or more of graphite, soft carbon, hard carbon, carbon fibers, mesophase carbon microspheres, silicon-based material, tin-based material, lithium titanate, or other metals that can alloy with lithium. The graphite can be selected from one or more types of synthetic graphite, natural graphite, and modified graphite. The silicon-based material can be selected from one or more types of elemental silicon, a silicon-oxygen compound, a silicon-carbon composite, and a silicon alloy. The tin-based material can be selected from one or more types of elemental tin, a tin-oxygen compound, and a tin alloy. The negative current collector is typically a structure or component capable of collecting current.The negative current collector can consist of a variety of materials suitable for use as the negative current collector of a lithium-ion battery in the prior art. For example, the negative current collector can contain, but is not limited to, a metal foil, and in particular, it can contain, but is not limited to, a copper foil and the like.

[0040] In the lithium-ion battery provided in the embodiments of the present disclosure, the separator can consist of various materials suitable for lithium-ion batteries in practice and can, for example, but not limited to, include one or more of polyethylene, polypropylene, polyvinylidene fluoride, Kevlar, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

[0041] In the lithium-ion battery provided in the embodiments of the present disclosure, the electrolyte solution can be various electrolyte solutions suitable for lithium-ion batteries. For example, the electrolyte solution typically contains an electrolyte and a solvent, and the electrolyte can typically contain a lithium salt. More specifically, the lithium salt can be an inorganic lithium salt and / or an organic lithium salt and can, in particular, but not limited to, contain one or more of LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), and LiBF2C2O4 (LiDFOB). As a further example, the concentration of the electrolyte can be in the range of 0.8 mol / l to 1.5 mol / l.The solvent may be various solvents suitable in the technology for the electrolyte solution of a lithium-ion battery, and the solvent of the electrolyte solution is typically a non-aqueous solvent, preferably an organic solvent, and may in particular, but not limited to, contain one or more of ethylene carbonate, propylene carbonate, butylene carbonate, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and the like, or halogenated derivatives thereof.

[0042] In general, a higher nickel content in a ternary material indicates a greater capacity per gram of the ternary material and is also more likely to contribute to an increase in the energy density of the electrochemical energy storage device. However, an increased nickel content apparently exacerbates direct side reactions between the active material of the positive electrode and the electrolyte solution, significantly degrading cycle performance. Researchers in this application found that a large amount of the nickel element still remains on the surface of the ternary material processed using a conventional coating method. Therefore, after the battery is fully charged, numerous side reactions can occur due to the contact between the high-valent nickel element on the material surface and the electrolyte solution, leading to degraded cycle performance.The positive electrode material in the embodiments of the present disclosure exhibits good crystal structure stability and surface inertness. The amount of nickel that can leach from the surface of the active substance of the positive electrode is relatively small, thereby effectively preventing side reactions between the positive electrode material and the electrolyte solution and thus improving the high-temperature cycling performance and the high-temperature storage performance of the ternary material.

[0043] The following describes embodiments of the present disclosure with reference to specific examples. A person skilled in the art can easily recognize further advantages and effects of the present disclosure from the content disclosed in this specification. This disclosure can also be implemented or applied according to other embodiments, and various modifications or changes to the details in the specification can be made based on different perspectives and applications without departing from the spirit of the present disclosure.

[0044] It should be noted that all process equipment or devices not specifically mentioned in the following examples are conventional devices or devices from the prior art.

[0045] Furthermore, it is understood that the one or more process steps mentioned in this disclosure do not preclude the possibility of further process steps before and after the combined steps, or the insertion of further process steps between these expressly mentioned steps, unless otherwise specified. It is also understood that the combination and connection relationship between one or more devices / assemblies mentioned in this disclosure does not preclude the possibility of further devices / assemblies before and after the combined devices / assemblies, or the insertion of further devices / assemblies between the two expressly mentioned devices / assemblies, unless otherwise specified.Furthermore, unless otherwise specified, the process step numbers are merely an aid to identifying the process steps and are not intended to restrict either the sequence of the process steps or the implementable scope of this disclosure. Any modification or adaptation of their relative relationships without substantial changes to the technical content shall also be considered to fall within the implementable scope of this disclosure. Example 1

[0046] (1) A specific manufacturing process for the positive electrode material is as follows: a. Production of a substrate precursor:

[0047] Nickel sulfate, manganese sulfate, and cobalt sulfate were combined in a molar ratio of 8:1:1 Ni:Co:Mn to obtain a solution with a concentration of 1 mol / L, and the precursor Ni 0,8 Co 0,1 Mn 0,1(OH)₂ of a large particle size lithium-nickel transition metal oxide A was prepared using the hydroxide co-precipitation process. In the process for preparing the precursor, the reaction time was 75 h to 125 h, the pH for co-precipitation was 7.5 to 8.5, and the ammonia concentration was 1 mol / l. b. Manufacturing process for a positive electrode material:

[0048] The ternary material precursor Ni 0,8 Co 0,1 Mn 0,1 (OH)₂ and LiOH·H₂O were mixed in a mixer, and the mixture was then sintered in an atmosphere furnace at 800 °C, followed by cooling and mechanical milling to obtain a substrate from the ternary material. The substrate for the positive electrode material and the additive aluminum oxide were enriched at 3.5 mg / cm². 3The coating element was mixed in a mixer, and then the resulting mixture was sintered in an atmosphere furnace at 450 °C to form a coating layer, and a finished positive electrode material was obtained.

[0049] The manufactured positive electrode material was subsequently used to produce a battery, employing the manufacturing process as described below. The performance of the manufactured battery was tested, with specific parameters listed in Table 1 and the test results in Table 2. (2) Production of a positive electrode sheet

[0050] Step 1: The aforementioned high-nickel positive electrode material, a polyvinylidene fluoride binder, and a carbon black conductive agent were mixed in a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) was added. The resulting mixture was stirred using a vacuum mixer until stable and homogeneous to obtain a positive electrode paste. The positive electrode paste was applied evenly to a 12 µm thick aluminum foil with a surface density of 0.1 mg / mm². 2 up to 0.3 mg / mm 2 applied.

[0051] Step 2: The coated electrode sheet was dried in an oven at 100 °C to 130 °C, then cold-pressed and cut to obtain the positive electrode sheet. (3) Production of a negative electrode sheet:

[0052] An active material for the negative electrode (graphite), a thickening agent (sodium carboxymethylcellulose), a binder (styrene-butadiene rubber), and a conductive agent (acetylene carbon black) were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred using a vacuum mixer to obtain a negative electrode paste. The negative electrode paste was uniformly coated with 0.05 mg / mm². 2 up to 0.15 mg / mm 2 The substance was applied to an 8 µm thick copper foil, which was then dried at room temperature and placed in an oven at 12 °C for 1 hour. The same process was applied to the reverse side of the electrode sheet, which was then cold-pressed and cut to create a negative electrode sheet. (4) Preparation of an electrolyte solution:

[0053] An organic solvent was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC, EMC, and DEC of 20:20:60. In a glovebox with an argon atmosphere and a water content of less than 10 ppm, the lithium salt LiPF6 was completely dissolved in the organic solvent to obtain a uniformly mixed electrolyte solution. The concentration of the lithium salt was 1 mol / L. (5) Production of a separator:

[0054] A 12 µm thick polypropylene membrane was chosen as the separator. (6) Manufacturing a battery:

[0055] The positive electrode sheet, separator, and negative electrode sheet were stacked sequentially, with the separator positioned between the positive and negative sheets to ensure separation. The stack was then coiled to form a square, exposed battery cell. This exposed cell was wrapped with an aluminum-plastic foil and baked at 80°C for dehydration. Following the steps of injecting the appropriate non-aqueous electrolyte solution, sealing, curing, hot and cold pressing, chemical conversion, clamping, and aging, a finished battery was obtained. Example 2

[0056] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was zirconium oxide and the coating element content was 4.6 mg / cm². 3 fraud. Example 3

[0057] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was titanium oxide and the coating element content was 4.3 mg / cm². 3 fraud. Example 4

[0058] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was phosphoric anhydride and the coating element content was 4.2 mg / cm². 3 fraud. Example 5

[0059] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was aluminum oxide and boron oxide, and the coating element content was 4.0 mg / cm². 3 fraud. Example 6

[0060] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was titanium oxide and boron oxide, and the coating element content was 3.8 mg / cm². 3 fraud. Example 7

[0061] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was boron oxide and the coating element content was 0.4 mg / cm². 3 fraud. Example 8

[0062] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was boron oxide and the coating element content was 0.8 mg / cm². 3 fraud. Example 9

[0063] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was boron oxide and the coating element content was 10 mg / cm². 3 fraud. Example 10

[0064] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was boron oxide and the coating element content was 15 mg / cm². 3 fraud. Example 11

[0065] Essentially the same as the manufacturing process for a positive electrode material in Example 7, except that the coating element content is 4.7 mg / cm². 3 fraud. Example 12

[0066] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the sintering temperature of the precursor and of LiOH was 900 °C, the resulting positive electrode material consisted of single-crystal particles, and D v 50 of the substrate was 6 µm; and the coating additive was boron oxide, and the coating element content was 4.2 mg / cm². 3 . Example 13

[0067] Essentially the same as the manufacturing process for a positive electrode material in Example 11, except that D v 50 of the substrate was 15 µm. Example 14

[0068] Essentially the same as the manufacturing process for a positive electrode material in Example 11, except that D v 50 of the substrate was 8 µm. Example 15

[0069] Essentially the same as the manufacturing process for a positive electrode material in Example 11, except that D v 50 of the substrate was 12 µm. Example 16

[0070] Essentially the same as the manufacturing process for a positive electrode material in Example 11, except that D v 50 of the substrate was 18 µm. Example 17

[0071] Essentially the same as the manufacturing process for a positive electrode material in Example 11, except that D v 50 of the substrate was 5 µm. Example 18

[0072] Essentially the same as the manufacturing process for a positive electrode material in Example 12, except that D v 50 of the substrate was 2 µm and the coating element content was 2.1 mg / cm². 3 fraud. Comparative example 1

[0073] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that no coating processing was carried out. Comparative example 2

[0074] Essentially the same as the manufacturing process for a positive electrode material in Example 1, except that the coating additive was magnesium oxide and the coating element content was 4.7 mg / cm². 3 fraud. Comparative example 3

[0075] Essentially the same as the manufacturing process for a positive electrode material in Comparative Example 1, except that the substrate is a positive electrode material made of single-crystal particles with D v 50 = 3.5 µm. Comparative example 4

[0076] Essentially the same as the manufacturing process for a positive electrode material in comparative example 3, except that the substrate was coated with magnesium oxide and the coating element content was 4.7 mg / cm². 3 fraud. Test method (1) Method for measuring the absorption of the nickel leaching product per unit mass of the positive electrode material: 1) Using dimethylglyoxime as a color developer, ammonia as a color development enhancer and ethanol as the main solvent to prepare solution A, wherein the concentration of dimethylglyoxime in solution A was 10 g / l and the concentration of ammonia was 25 to 28 wt%; 2) Add 1 g of the positive electrode material to 10 ml of solution A, shake, allow to stand for 24 hours, and then take 5 ml of the clear solution B from the top; and 3) Add water to solution B to obtain 10 ml of solution C and measure the absorption of solution C at a wavelength of 470 nm using an ultraviolet visible spectrophotometer. (2) Cycle performance test of the lithium-ion battery at 45 °C The battery was charged at a constant temperature of 45 °C at 1 C from 2.8 V to 4.2 V, then charged at a constant voltage of 4.2 V with a current of ≤ 0.05 mA, and after a 5-minute stand, discharged at 1 C to 2.8 V. The capacity was denoted as Dn (n = 0, 1, 2 ...). The preceding process was repeated until the capacity had decreased to 80% of the original capacity. A number of lithium-ion battery cycles were recorded. The test results for the examples and comparison examples are listed in Table 2. (3) Discharge capacity test of the lithium-ion battery The lithium-ion battery was charged at a constant temperature of 25 °C at 1 C from 2.8 V to 4.2 V, then charged at a constant voltage of 4.2 V to a current of ≤ 0.05 mA, and after a 5-minute stand, discharged at 1 C to 2.8 V. The capacity of the lithium-ion battery was recorded, and the specific results are listed in Table 2. (4) High-temperature gas evolution test of the battery: The battery was fully charged to 4.2 V at 1 C and then placed in a thermostat at 80 °C for 10 days. The battery's volume swelling rate was obtained by measuring the initial volume of the battery and the volume after a 10-day stand. Battery volume swelling rate (%) = (volume after standing for 10 days / initial volume - 1) × 100%. Table 1 Particle morphology coating layer Coating element content per unit volume Mv (µg / cm²) 3 ) D v 50(µm) (BET2 - BET1) / BET 1 BET2(m 2 / g) absorption Li2CO3 (ppm) LiOH(ppm) Example 1 Secondary particles Aluminum oxide 3,5 9 4,3 0,75 0,455 2315 3425 Example 2 Secondary particles Zirconium oxide 4,6 9 4,1 0,73 0,538 2585 3953 Example 3 Secondary particles titanium oxide 4,3 9 3,9 0,69 0,469 3684 4851 Example 4 Secondary particles Phosphorus oxide 4,2 9 4,5 0,78 0,653 2961 3976 Example 5 Secondary particles Discontinuous aluminum oxide coating layer + continuous boron oxide coating layer 4,0 9 3,8 0,68 0,209 1596 2854 Example 6 Secondary particles Discontinuous titanium oxide coating layer + continuous boron oxide coating layer 3,8 9 3,3 0,61 0,227 1984 2597 Example 7 Secondary particles boron oxide 0,4 9 5,5 0,92 0,683 2874 3512 Example 8 Secondary particles boron oxide 0,8 9 4,7 0,81 0,644 2850 3401 Example 9 Secondary particles boron oxide 10 9 2,0 0,42 0,502 2583 3195 Example 10 Secondary particles boron oxide 15 9 1,5 0,36 0,441 2256 3096 Example 11 Secondary particles boron oxide 4,7 9 3,5 0,64 0,613 2354 3451 Example 12 Single-crystal particles boron oxide 4,2 6 2,3 0,72 0,329 2234 3012 Example 13 Secondary particles boron oxide 4,7 15 4,6 0,48 0,286 2131 3588 Example 14 Secondary particles boron oxide 4,7 8 3,9 0,78 0,385 2554 3821 Example 15 Secondary particles boron oxide 4,7 12 4,5 0,59 0,43 2764 3353 Example 16 Secondary particles boron oxide 4,7 18 5,3 0,45 0,337 2481 3221 Example 17 Secondary particles boron oxide 4,7 5 0,8 0,46 0,432 2651 4231 Example 18 Single-crystal particles boron oxide 2,1 2 0,5 0,97 0,414 2134 3112 Comparative example 1 Secondary particles / / 9 3,2 0,6 0,7398 5452 4425 Comparative example 2 Secondary particles Magnesium oxide 4,7 9 2,5 0,5 0,711 2324 3821 Comparative example 3 Single-crystal particles / / 3,5 1,5 0,9 0,822 6479 5275 Comparative example 4 Single-crystal particles Magnesium oxide 4,7 3,5 1,0 0,74 0,79 3548 4673 Table 2 Capacity mAh / g Number of cycles in which the capacity drops to 80% at 45°C Volume swelling rate of the battery after storage at 80 °C Example 1 197 547 78% Example 2 196 553 71% Example 3 198 593 84% Example 4 197 502 87% Example 5 198 547 52% Example 6 196 559 55% Example 7 197 515 89% Example 8 196 529 91% Example 9 198 582 83% Example 10 198 567 78% Example 11 199 569 88% Example 12 193 1097 87% Example 13 194 489 56% Example 14 199 589 59% Example 15 195 563 72% Example 16 193 470 48% Example 17 201 591 47% Example 18 196 1196 85% Comparative example 1 197 364 189% Comparative example 2 198 489 164% Comparative example 3 196 990 197% Comparative example 4 196 1050 154%

[0077] The data in Table 1 and Table 2 indicate that in comparative examples 1 to 4, the absorption values ​​w of the nickel leaching product per unit mass of the positive electrode material were all above 0.7. This is because the ternary positive electrode materials with high nickel content were subject to a weak bond between the coating substance and the substrate, or to a coating layer with a less dense structure, or to excessively concave and convex structures in the powder particle morphology. Such absorption indicates that the nickel element could easily leach from the powder particles of the positive electrode material. When using such a positive electrode material in a lithium-ion battery, side reactions between the surfaces of the powder particles and the electrolyte solution readily occurred.Therefore, the lithium-ion battery with this positive electrode material produced excessive amounts of gas, causing its capacity to decrease rapidly during high-temperature cycles and its lifespan to be shortened.

[0078] In Examples 1 to 18, however, the absorption of the nickel leaching product of the positive electrode material did not exceed 0.7, as the overall influence of factors such as the coating substance of the positive electrode material, the relative coating content, and the surface morphology of the particles was adjusted. Since the absorption of nickel leaching product per unit mass of the positive electrode material was relatively low, the stability of the crystal structure, particularly the surface crystal structure, of the positive electrode material was greater. Therefore, the capacity per gram of positive electrode material measured during battery discharge was relatively high, the high-temperature cycle performance was good, and the volumetric swelling rate at high temperatures was effectively suppressed.In particular, controlling the degree of deviation between the theoretical and actual specific surface area of ​​the positive electrode material within a defined range ensured relatively good grain size and morphological uniformity of the positive electrode material. The coated positive electrode material had a relatively flat surface and fewer concave and convex structures, and therefore exhibited a relatively small contact area with the electrolyte solution. All these measures help to prevent the leaching of the nickel element from the positive electrode material while simultaneously ensuring good lithium ion transfer between secondary particles, thus achieving a balance between gas evolution at high temperatures and the kinetics.If the coating layer contained at least two of the aforementioned coating elements, the stability of its adhesion to the substrate surface could be improved, allowing the coating layer to provide some ionic and electronic conductivity, thereby mitigating its effects on the polarization of the positive electrode material. When a coating process was performed on the positive electrode material, a discontinuous outer coating layer could reduce the proportion of the coating layer on the substrate surface, thus preserving more ion transfer channels. However, this improved the structural stability of the substrate surface less than a continuous coating layer.By using a double-layer coating, high ionic conductivity could be achieved while simultaneously providing effective coating, and deterioration of battery performance due to excessive leaching of nickel from the cathode material during long-term cycles could be avoided.

[0079] In summary, this disclosure effectively overcomes various shortcomings of the prior art and is highly industrially applicable.

[0080] The foregoing embodiments merely illustrate the principles and effects of the present disclosure by way of example, but are not intended to limit this disclosure. Any person familiar with this technology may make modifications or changes to the above-mentioned embodiments without departing from the spirit or scope of the present disclosure. Therefore, any equivalent modifications or changes made by a person skilled in the art, without departing from the spirit or technical ideas of the present disclosure, remain within the scope of the claims of the present disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 201910578176.8

[0001]

Claims

[1] Positive electrode material comprising a substrate, wherein the formula of the substrate is Li x Ni y Co z M k Me p O r A m is where 0.95 ≤ x ≤ 1.05, 0.50 ≤ y ≤ 0.95, 0 ≤ z ≤ 0.2, 0 ≤ k ≤ 0.4, 0 ≤ p ≤ 0.05, 1 ≤ r ≤ 2, 0 ≤ m ≤ 2, m + r ≤ 2, M is selected from Mn and / or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb, and A is selected from one or more of N, F, S and Cl; wherein a coating layer is arranged on the substrate, the coating layer comprising a coating element selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P; and where the absorption of nickel leaching product per unit mass of the positive electrode material is w ≤ 0.

7. [2] Positive electrode material according to claim 1, wherein a theoretical specific surface area BET1 of the positive electrode material and an actual specific surface area BET2 of the positive electrode material satisfy the following: 0.3≤(BET2−BET1) / BET1≤5.5; where BET1 = 6 / (ρ × D v 50); ρ is the actual density of the positive electrode material, measured in g / cm³ 3 ; and D v 50 is a particle size of the positive electrode material below a cumulative volume distribution percentage of 50%, measured in µm. [3] Positive electrode material according to claim 1 or 2, wherein, if the substrate comprises secondary particles consisting of primary particles, the actual specific surface area BET2 of the positive electrode material is 0.1 m² 2 / g up to 1.0 m 2 / g is and D v 50 5 µm to 18 µm. [4] Positive electrode material according to claim 1 or 2, wherein the substrate comprises single-crystal or single-crystal-like particles, wherein the actual specific surface area BET2 of the positive electrode material is 0.5 m² 2 / g up to 1.5m 2 / g is and D v 50 1 µm to 6 µm. [5] Positive electrode material according to any one of claims 1 to 4, wherein a coating element content per unit volume Mv in the positive electrode material is 0.4 mg / cm³ 3 up to 15 mg / cm² 3 , preferably 0.8 mg / cm² 3 up to 10 mg / cm² 3 , amounts. [6] Positive electrode material according to any one of claims 1 to 5, wherein the coating layer comprises an inner coating layer, the inner coating layer is located on surfaces of at least some primary particles inside the substrate and the inner coating layer comprises a coating element, wherein the coating element of the inner coating layer is selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P. [7] Positive electrode material according to any one of claims 1 to 6, wherein the coating layer comprises an outer coating layer, the outer coating layer is located on a surface of the substrate and the outer coating layer comprises a coating element, wherein the coating element of the outer coating layer is selected from one or more of Al, Zr, Ba, Zn, Ti, Co, W, Y, Si, Sn, B and P. [8] Positive electrode material according to claim 7, wherein the outer coating layer comprises a continuous and / or discontinuous coating layer; the outer coating layer preferably comprises a continuous first coating layer and a discontinuous second coating layer; and the second coating layer and the first coating layer more preferably comprise different coating elements. [9] Positive electrode material according to claim 1, wherein in the molecular formula of the substrate 0.70 ≤ y ≤ 0.90, 0 ≤ z ≤ 0.15, 0 ≤ k ≤ 0.2 and 0 ≤ p ≤ 0.

03. [10] Positive electrode material according to claim 1, wherein the Li2CO3 content in the residual lithium on a surface of the positive electrode material is less than 3000 ppm and the LiOH content is less than 5000 ppm. [11] Positive electrode material according to claim 10, wherein the Li2CO3 content in the residual lithium on the surface of the positive electrode material is lower than the LiOH content. [12] Electrochemical energy storage device comprising the positive electrode material according to any one of claims 1 to 11.