Aluminum-boron co-doped ternary positive electrode material and its preparation method and application

Abstract

The present invention provides an aluminum-boron co-doped ternary cathode material, wherein the raw materials for preparing the ternary cathode material include a precursor, a lithium source, an aluminum source, and a boron source; the chemical formula of the ternary cathode material is Li(Ni x Co y Mn z ) 1‑b‑c Al b B c O2, wherein 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1; 0<b≤0.015, 0<c≤0.015, and 0<b+c≤0.03. The present invention dopes an appropriate amount of Al and B into the positive electrode material, and defines a specific Al / B doping sequence and doping amount. After modification, the obtained positive electrode material has excellent electrochemical properties, effectively improving the discharge capacity, cycle performance and rate performance of the battery. In particular, within the high voltage range of 2.75-4.5V, it has excellent cycle performance and rate performance. The process of the present invention is simple and easy to control, with a high output ratio, which is conducive to the promotion and application of large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of battery positive electrode materials, and in particular to an aluminum-boron co-doped ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] Since the birth of lithium-ion batteries (LIBs) in the 1990s, they have attracted widespread attention due to their ultra-high energy density and excellent long-cycle cycle stability. In particular, lithium-ion batteries have an irreplaceable and prominent position in electronic devices, electric vehicles (EVs) and energy storage systems. As an important power source for electric vehicles, the most important research direction for lithium-ion batteries is to increase the specific energy density, increase their cycle performance and safety stability, and reduce costs. Therefore, the current priority is to develop efficient, sustainable, and low-cost batteries. In lithium-ion batteries, the most important component that determines battery performance is the positive electrode material. Among the many positive electrode materials, nickel-cobalt-manganese / lithium aluminate ternary positive electrode materials (LiNi x Co y Mn 1–x–y O2 / LiNi x Co y Al 1–x–y High hopes are being placed on high-nickel NCM / NCA materials, particularly high-nickel NCM / NCA (0.5 ≤ x < 1). While the discharge capacity of this type of material increases with increasing nickel content, cycling performance decreases accordingly. While increasing nickel content significantly boosts capacity, it also introduces a host of new challenges, primarily surface and bulk issues, such as residual alkali on the surface, transition metal dissolution, and cation mixing.

[0003] In order to improve the electrochemical properties of NCM ternary materials and meet market demand, the following methods are mainly used for modification: (1) Doping modification. Transition metal ions and other non-metallic ions are introduced into the lattice of NCM ternary materials to improve the electronic conductivity and ionic conductivity of the materials, thereby enhancing the stability of the ternary material structure; (2) Coating modification. A thinner metal oxide layer is coated on the surface of the material to reduce the occurrence of side reactions, that is, under high state of charge (SOC), the special coating protective layer generated reduces the direct contact area between the material and the electrolyte, prevents the corrosion of the electrolyte on the material, reduces the occurrence of side reactions such as oxygen release, prolongs its cycle life and improves the stability of the material; (3) Structural design. Structural design of the material and changes the element distribution inside the material can effectively improve the stability and safety of the battery during cycling.

[0004] While coating is effective in resolving surface issues, its effect on the crystal structure is very limited. Bulk structure is also key to material performance, so doping modification is necessary to further enhance material performance. Doping with a specific single element can significantly improve electrochemical performance, especially when two or more elements are co-doped, where interactions occur, leading to a significant performance leap. Changing the doping order or doping amount of two or more elements can also lead to different effects on the material.

[0005] Chinese patent CN110112403A discloses a high-capacity lithium nickel cobalt manganese oxide cathode material and its preparation method. The material comprises a precursor, an aluminum-doped body, a boron-doped body, a coating, and a lithium source. By coating the material surface with a layer of silicon dioxide and doping the bulk of the material with boron and aluminum, the structural stability of the lithium nickel cobalt manganese oxide during cycling is effectively improved. However, the high number of doping elements can easily interfere with each other, affecting the material's performance.

[0006] In summary, how to prepare a ternary positive electrode material with excellent electrochemical properties, simple preparation process, stable and easy-to-control process is still the current research focus. Summary of the Invention

[0007] In view of the above problems, the present invention provides an aluminum-boron co-doped ternary cathode material, wherein the raw materials for preparing the ternary cathode material include a precursor, a lithium source, an aluminum source, and a boron source; the chemical formula of the ternary cathode material is Li(Ni x Co y Mn z ) 1-b-c Al b B cO2, wherein 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1; 0<b≤0.015, 0<c≤0.015, and 0<b+c≤0.03. For example, x may be 0.75, 0.8, 0.85, 0.9, 0.95, etc., for example, y may be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, etc., for example, z may be 0.05, 0.1, 0.15, etc., for example, b may be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, etc. For example, c can be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, etc., but are not limited to the listed values. Other values ​​not listed in this numerical range are also applicable. More preferably, 0.001 < b ≤ 0.008, 0.001 < c ≤ 0.008, and 0.002 < b + c ≤ 0.016.

[0008] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0009] A second aspect of the present invention provides a method for preparing the ternary cathode material, comprising the following steps:

[0010] Step S1: Precursor preparation: nickel source, cobalt source, and manganese source are weighed and mixed to form a salt solution. The salt solution, precipitant, and complexing agent are added to a reactor and reacted at 40-60° C. to obtain a solid-liquid mixture. The solid-liquid mixture is filtered and dried to obtain a precursor.

[0011] Step S2: Mix the precursor with a lithium source, add an aluminum source, and perform a first calcination to obtain a sintered product A; add a boron source, and perform a second calcination to obtain a sintered product B, and grind the sintered product B into powder to obtain the ternary positive electrode material.

[0012] Preferably, the chemical formula of the precursor is Ni x Co y Mn z(OH)2, wherein 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1. For example, x may be 0.75, 0.8, 0.85, 0.9, 0.95, etc., for example, y may be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, etc., for example, z may be 0.05, 0.1, 0.15, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. More preferably, 0.8≤x≤0.95, 0.02≤y≤0.06, 0.02≤z≤0.15, and x+y+z=1.

[0013] Ni is used in the present invention x Co y Mn z (OH)2 is used as a precursor, and a high-nickel, low-cobalt ternary positive electrode material is used to increase the battery's electrical capacity and reduce the cobalt content in the battery, thereby reducing the battery's material cost.

[0014] Preferably, in step S1, the nickel source is one of NiSO4·6H2O and Ni(CH3COO)2·4H2O; the cobalt source is one of CoSO4·7H2O and Co(CH3COO)2·4H2O; and the manganese source is one of MnSO4·H2O, MnCO3 and Co(CH3COO)2·4H2O.

[0015] Preferably, in step S1, the molar ratio of nickel in the nickel source, cobalt in the cobalt source, and manganese in the manganese source is 7-9.8:0.1-1:0.1-2. More preferably, the molar ratio of nickel, cobalt, and manganese is 8-9.5:0.1-0.6:0.1-1.5.

[0016] Preferably, in step S1, the precipitant is a 0.5-10 mol / L NaOH solution; and the complexing agent is a 0.05-3 mol / L ammonia solution.

[0017] More preferably, the concentration of the NaOH solution is 1 to 5 mol / L, and the concentration of the ammonia solution is 0.1 to 2 mol / L.

[0018] Preferably, the concentration ratio of the salt solution, precipitant, and complexing agent in step S1 is 1:0.8-1.2:0.02-0.05. Examples include 1:0.8:0.02, 1:0.9:0.03, 1:1:0.04, and 1:1.1:0.05, but are not limited to these values. Other values ​​not listed within this range are also applicable. More preferably, the concentration ratio of the salt solution, precipitant, and complexing agent is 1:1:0.3.

[0019] By controlling the ratio of salt solution, precipitant and complexing agent in the reaction, controlling the addition rate, controlling the pH during the reaction to 11-12, and coordinating stirring to ensure efficient and stable reaction, the obtained precursor has uniform particle size and stable performance, and is easier to use as a matrix for aluminum-boron doped ternary positive electrode materials. The inventors found in the experiment that although accelerating the feed amount can shorten the reaction time, if the feed rate is too fast, it will lead to uneven reaction, resulting in uneven particle size in the obtained precursor, affecting the further aluminum-boron doping effect, thereby affecting its battery performance as a positive electrode material. If the pH is too large or too small, it will also affect the growth reaction of the precursor. If the pH is too small or the reaction is too slow, the precursor particle size will be smaller, and problems such as uneven reaction will occur, which will cause the material to show a decline in electrochemical performance due to charge and discharge during use.

[0020] Preferably, the pH during the reaction in step S1 is 11-12.

[0021] Preferably, in step S1, the addition rate of the salt solution and the precipitant is 0.1 to 3 ml / min, and the addition rate of the complexing agent is 0.01 to 2 ml / min.

[0022] Preferably, in step S1, stirring is performed while feeding, and the stirring rate is 300 to 600 rpm.

[0023] The reaction requires a specific stirring rate. The inventors have found that stirring rates that are too fast or too slow can result in poor precursor performance, affecting the battery performance of the resulting cathode material. The inventors analyzed that excessive stirring rates may cause shearing, resulting in uneven precursor particle size, affecting its performance, and may also cause machine instability, affecting product production and use. Excessively low stirring rates may lead to excessive local concentrations of the reaction raw materials, reducing material reliability.

[0024] Preferably, in step S1, the drying temperature is 100-130° C. and the drying time is 6-10 hours.

[0025] Further preferably, in step S1, after the solid-liquid mixture is dried, it is passed through a 300-mesh sieve to obtain a precursor. The sieving process is performed to remove impurities and improve the homogeneity of the precursor.

[0026] Preferably, in step S2, the lithium source is LiOH·H2O or Li2CO3 or a mixture of the two.

[0027] More preferably, the molar ratio of the precursor to the lithium source is 1:1.05 to 1.08. Since lithium loss may occur during calcination, the content of the lithium source is set to be relatively high in the present invention.

[0028] Preferably, in step S2, the aluminum in the aluminum source is 0-1.5% of the molar amount of the precursor and is not equal to 0; the boron in the boron source is 0-1.5% of the molar amount of the precursor and is not equal to 0. Examples include 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc., but are not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable. Preferably, the aluminum in the aluminum source is 0.1%-0.8% of the molar amount of the precursor; the boron in the boron source is 0.1%-0.8% of the molar amount of the precursor. More preferably, the aluminum in the aluminum source is 0.5% of the molar amount of the precursor; the boron in the boron source is 0.5% of the molar amount of the precursor.

[0029] In the present invention, by doping the positive electrode material with an appropriate amount of Al and B, the obtained positive electrode material has excellent electrochemical properties, effectively improves the discharge capacity of the battery, and improves its cycle performance and rate performance. The inventor analyzed that due to the doping of aluminum and boron, radially arranged primary particles are generated inside the material, and the primary particles are arranged radially, so that the entire positive electrode particles shrink uniformly, thereby eliminating local stress concentration and minimizing microcracks. Thereby solving the problem that the longitudinal stress inside the spherical particles is too large and the particles are easily damaged during the battery cycle, and effectively improving the cycle performance and rate performance of the material. However, if the Al and B content is too high, it will affect the battery performance of the material. This may be because when the Al and B content is too high, the layered structure of the matrix material will be destroyed, and it does not participate in the chemical reaction. Too much doping will hinder the insertion and extraction of lithium ions.

[0030] Preferably, in step S2, the aluminum source is one of Al2O3 and Al(OH)3.

[0031] Preferably, the specific steps of the first calcination in step S2 are: placing a mixture of the precursor, lithium source, and aluminum source in a sintering furnace, heating it to 450-550°C in an oxygen environment, keeping it warm for 5-10 hours, cooling it down and taking it out to obtain a sintered product A; the heating rate is 2-7°C / min.

[0032] Preferably, in step S2, the boron source is B2O3.

[0033] Preferably, the specific steps of the second calcination in step S2 are: grinding the sintered product A, adding a boron source, heating to 700°C to 800°C, keeping warm for 10 to 30 hours, cooling and taking out to obtain a sintered product B; the heating rate is 2 to 7°C / min.

[0034] The inventors discovered in experiments that during aluminum-boron doping, Al-O bonds form more easily due to the BO bond energy of 809 kJ / mol, compared to the Al-O bond energy of 542 kJ / mol. Al preferentially combines with O, creating a potential energy barrier inside the particle that hinders further ingress of B, forcing it to remain outside the particle. In particular, excessive aluminum content can interfere with boron doping. Interference between the two elements can lead to poor doping results, impacting the material's electrochemical performance.

[0035] The inventor unexpectedly discovered that when the aluminum in the aluminum source is 0.1%-0.8% of the molar weight of the precursor; the boron in the boron source is 0.1%-0.8% of the molar weight of the precursor, and the aluminum doping is performed first and then the boron doping, the obtained positive electrode material has the best battery performance, especially excellent cycle performance and rate performance under high voltage conditions. The inventor analyzed that it may be because during the charge and discharge cycle of the high nickel material, especially under high voltage, the material is subjected to excessive stress in the longitudinal direction, which easily produces vacancies and poor reversibility, resulting in poor cycle performance of the material, and the nickel-rich material will produce a large amount of unstable Ni during the charge process. 4+ , which will lead to capacity decay. In addition, the continuous appearance of Ni-O phases on the particle surface and excessive Li / Ni disorder have a negative impact on electrochemical performance, which is particularly serious on the particle surface, hindering the normal transport of lithium ions to a certain extent. At this time, by doping with Al and B, the material is prevented from generating vacancies in the longitudinal direction due to excessive stress, avoiding particle damage, enhancing its stability and improving cycle performance. At the same time, under high voltage, the electrolyte is more likely to decompose, leading to corrosion of the material. At this time, the Al that is doped first enters the interior of the layered structure, supporting the layered structure and preventing its structural collapse; while the B that remains on the outside of the particle forms a protective effect on the particle surface. The Al doping level still cannot be too high, otherwise it will interfere with the B doping. If the B doping level is too high, it will cause a decrease in the relative content of active materials, affecting the insertion and extraction of lithium ions, and in turn leading to poor charge and discharge performance of the material.

[0036] Preferably, the preparation method of the ternary positive electrode material specifically comprises the following steps:

[0037] Step S1: Preparation of precursor: nickel source, cobalt source and manganese source are weighed in molar ratio and mixed to form a salt solution. 0-100 ml of base liquid is first added to the reactor, and the salt solution, precipitant and complexing agent are added to the reactor. The pH is controlled to be 11-12 and the stirring rate is 300-600 rpm. The reaction is carried out at 40-60 ° C to obtain a solid-liquid mixture. The solid-liquid mixture is filtered, dried and passed through a 300 mesh sieve to obtain a precursor. The chemical formula of the precursor is Ni x Co y Mn z(OH)2, where 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1;

[0038] Step S2: Mix the precursor and the lithium source in a molar ratio, add the aluminum source, place the mixture in a sintering furnace, heat it to 450-550°C in an oxygen environment, keep it warm for 5-10 hours, cool it down and take it out to obtain a sintered product A, and the heating rate is 2-7°C / min; grind the sintered product A, add the boron source, heat it to 700-800°C, keep it warm for 10-30 hours, cool it down and take it out to obtain a sintered product B, and the heating rate is 2-7°C / min; grind the sintered product B into powder to obtain the ternary positive electrode material, the chemical formula of the ternary positive electrode material is Li(Ni x Co y Mn z ) 1-b-c Al b B c O2, where 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1; 0<b≤0.015, 0<c≤0.015, and 0<b+c≤0.03.

[0039] Preferably, the ternary cathode material is a spherical particle. More preferably, the particle size of the ternary cathode material is 5 to 15 μm.

[0040] Another aspect of the present invention provides an application of an aluminum-boron co-doped ternary positive electrode material in a lithium-ion battery.

[0041] Beneficial effects:

[0042] (1) The present invention dopes the positive electrode material with appropriate amounts of Al and B, and defines a specific Al / B doping sequence and doping amount. After modification, the resulting positive electrode material has excellent electrochemical properties, effectively improving the battery's discharge capacity, cycle performance, and rate performance. In particular, it exhibits excellent cycle performance and rate performance within the high voltage range of 2.75-4.5V.

[0043] (2) The present invention uses a nickel-cobalt-manganese-based precursor and a high-nickel, low-cobalt ternary cathode material to increase the battery's specific capacity and reduce the cobalt content in the battery, thereby reducing the battery's material cost. Furthermore, the process of the present invention is simple and easy to control, with a high output ratio, which is conducive to the promotion and application of large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a SEM image of the high-nickel layered positive electrode material NCM9055-AB prepared in Example 1 of the present invention;

[0045] Figure 2This is a SEM image of the high-nickel layered positive electrode material NCM9055-A1B1 prepared in Example 2 of the present invention;

[0046] Figure 3 This is a SEM scanning electron microscope image of the high-nickel layered positive electrode material NCM9055 prepared in Comparative Example 1 of the present invention;

[0047] Figure 4 This is a SEM image of the high-nickel layered positive electrode material NCM9055-A prepared in Example 2 of the present invention;

[0048] Figure 5 This is a SEM image of the high-nickel layered positive electrode material NCM9055-B prepared in Example 3 of the present invention;

[0049] Figure 6 This is a SEM scanning electron microscope image of the high-nickel layered positive electrode material NCM9055-BA prepared in Comparative Example 4 of the present invention;

[0050] Figure 7 Cycling curves of the high-nickel layered cathode materials obtained in Examples 1-2 and Comparative Examples 1 to 4 of the present invention at a current of 1C (1C = 180 mAh / g);

[0051] Figure 8 The figure shows the rate performance curves of the high-nickel layered positive electrode materials obtained in Examples 1-2 and Comparative Examples 1 to 4 of the present invention at different rates. DETAILED DESCRIPTION

[0052] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0053] The following are typical but non-limiting examples of the present invention:

[0054] Example 1

[0055] On the one hand, this embodiment provides an aluminum-boron co-doped ternary cathode material, wherein the raw materials for preparing the ternary cathode material include a precursor, a lithium source, an aluminum source, and a boron source; the chemical formula of the ternary cathode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.99 Al 0.005 B 0.005 O2.

[0056] A second aspect of this embodiment provides a method for preparing a ternary positive electrode material, which specifically includes the following steps:

[0057] Step S1: Preparation of precursor: NiSO4·6H2O, CoSO4·7H2O, and MnSO4H2O were weighed in a molar ratio of 9:0.5:0.5, mixed, and then water was added to prepare a salt solution. Deionized water was added to the reactor as a base liquid, and 4 mol / L salt solution, 4 mol / L NaOH solution, and 1.2 mol / L ammonia water were added to the reactor (the addition rate of the salt solution and the precipitant was 0.4 ml / min, and the addition rate of the complexing agent was 0.08 ml / min). The pH was controlled to be 11-12 and the stirring rate was 500 rpm. The mixture was reacted at 50°C for 36 hours to obtain a solid-liquid mixture. The solid-liquid mixture was filtered and dried at a drying temperature of 110°C for 8 hours. After cooling, it was sieved through a 300-mesh sieve to obtain a precursor. The chemical formula of the precursor is (Ni 0.9 Co 0.05 Mn 0.05 (OH)2);

[0058] Step S2: The precursor is mixed with LiOH·H2O in a molar ratio of 1:1.05, 0.5% molAl (aluminum source is Al2O3) of the precursor is added, and the mixture is calcined in a tube furnace under an oxygen environment, heated to 500°C, kept warm for 8 hours, cooled and taken out to obtain a sintered product A, and the heating rate is 4°C / min; the sintered product A is ground and 0.5% molB (boron source is B2O3) of the precursor is added, the temperature is raised to 750°C, kept warm for 20 hours, cooled and taken out to obtain a sintered product B, and the heating rate is 4°C / min; the sintered product B is ground into powder to obtain the ternary positive electrode material, and the chemical formula of the ternary positive electrode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.99 Al 0.005 B 0.005 O2, denoted as NCM9055-AB.

[0059] Example 2

[0060] The embodiment provides an aluminum-boron co-doped ternary cathode material. The specific implementation method is the same as that of embodiment 1. The difference from embodiment 1 is that the specific steps of step S2 are:

[0061] The precursor was mixed with LiOH·H2O in a molar ratio of 1:1.05, 1% molAl (the aluminum source was Al2O3) of the precursor was added, and the mixture was calcined in a tube furnace under an oxygen environment, heated to 500°C, kept warm for 8 hours, cooled and taken out to obtain a sintered product A, and the heating rate was 4°C / min; the sintered product A was ground and 1% molB (the boron source was B2O3) of the precursor was added, heated to 750°C, kept warm for 20 hours, cooled and taken out to obtain a sintered product B, and the heating rate was 4°C / min; the sintered product B was ground into powder to obtain the ternary positive electrode material, and the chemical formula of the ternary positive electrode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.98 Al 0.01 B 0.01 O2, denoted as NCM9055-A1B1.

[0062] Comparative Example 1

[0063] This embodiment provides a ternary cathode material. The specific implementation method is the same as that of Example 1. The difference from Example 1 is that in step S2, no aluminum source and boron source are added. The chemical formula of the obtained ternary cathode material is LiNi 0.9 Co 0.05 Mn 0.05 O2, denoted as NCM9055.

[0064] Comparative Example 2

[0065] This embodiment provides a ternary cathode material. The specific implementation method is the same as that of Example 1. The difference from Example 1 is that the specific steps of step S2 are:

[0066] The precursor was mixed with LiOH·H2O in a molar ratio of 1:1.05, and 1.0% molAl (the aluminum source was Al2O3) of the precursor was added. The mixture was calcined in a tube furnace under an oxygen environment, heated to 500°C, kept warm for 8 hours, cooled and taken out to obtain a sintered product A, with a heating rate of 4°C / min; the sintered product A was ground, heated to 750°C, kept warm for 20 hours, cooled and taken out to obtain a sintered product B, with a heating rate of 4°C / min; the sintered product B was ground into powder to obtain the ternary positive electrode material, and the chemical formula of the ternary positive electrode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.99 Al 0.01 O2, denoted as NCM9055-A.

[0067] Comparative Example 3

[0068] This embodiment provides a ternary cathode material. The specific implementation method is the same as that of Example 1. The difference from Example 1 is that the specific steps of step S2 are:

[0069] The precursor was mixed with LiOH·H2O in a molar ratio of 1:1.05, 1% mol B (boron source was B2O3) of the precursor was added, and the mixture was calcined in a tube furnace under an oxygen environment, heated to 500°C, kept warm for 8 hours, cooled and taken out to obtain a sintered product A, and the heating rate was 4°C / min; the sintered product A was ground, heated to 750°C, kept warm for 20 hours, cooled and taken out to obtain a sintered product B, and the heating rate was 4°C / min; the sintered product B was ground into powder to obtain the ternary positive electrode material, and the chemical formula of the ternary positive electrode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.99 B 0.01 O2, denoted as NCM9055-B.

[0070] Comparative Example 4

[0071] This embodiment provides an aluminum-boron co-doped ternary cathode material. The specific implementation method is the same as that of Example 1. The difference from Example 1 is that the specific steps of step S2 are:

[0072] The precursor was mixed with LiOH·H2O in a molar ratio of 1:1.05, 0.5% molB (boron source is B2O3) of the precursor was added, and the mixture was calcined in a tube furnace under an oxygen environment, heated to 500°C, kept warm for 8 hours, cooled and taken out to obtain a sintered product A, and the heating rate was 4°C / min; the sintered product A was ground and 0.5% molAl (aluminum source is Al2O3) of the precursor was added, heated to 750°C, kept warm for 20 hours, cooled and taken out to obtain a sintered product B, and the heating rate was 4°C / min; the sintered product B was ground into powder to obtain the ternary positive electrode material, and the chemical formula of the ternary positive electrode material is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.99 B 0.005 Al 0.005 O2, denoted as NCM9055-BA.

[0073] Performance Testing

[0074] 1. Image Representation

[0075] The positive electrode materials of Example 1 and Comparative Examples 1-4 were subjected to SEM testing, and the SEM characterization images are shown as follows: Figure 1-5 As shown. Figure 1As can be seen, the ternary cathode material produced by the present invention is a quasi-spherical particle with good compactness. The surface primary particles are finer, resulting in a denser surface, which provides greater structural stability during cycling and reduces the formation of surface microcracks. However, this also makes lithium ion intercalation and deintercalation difficult in the initial stage, reducing the battery capacity.

[0076] 2. Electrochemical testing

[0077] The electrochemical performance of the high-nickel layered positive electrode materials of Example 1 and Comparative Examples 1 to 4 of the present invention was tested.

[0078] The final product of the ternary positive electrode material obtained in Example 1 and Comparative Examples 1-4 was dissolved in N-methyl-2-pyrrolidone (NMP) with a binder (polyvinylidene fluoride (PVDF)) and a conductive agent (acetylene black, Super P) at a mass ratio of 8:1:1 and placed on a magnetic stirrer for 12 hours. The slurry was then coated on Al foil, the electrode sheet was dried, and then cut into circular pole pieces with a diameter of 14 mm. Afterwards, a half-cell was assembled in a glove box with an argon atmosphere, and the battery was left to stand in the glove box for 24 hours. Afterwards, the battery cycle performance and rate performance tests (1C = 180 mAh / g) were carried out, and charge and discharge cycles were carried out under test voltage conditions of 2.75 to 4.5 V to test the first discharge capacity, cycle discharge capacity, and capacity retention rate.

[0079] The test results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] The results show that after half-cell testing, the above-mentioned positive electrode material NCM9055-AB maintained a discharge capacity of 127mAh / g after 200 cycles at 1C in the voltage range of 2.75 to 4.5V. On the basis of a high discharge specific capacity, the capacity retention rate was 62.4%; in terms of rate performance, the 5C rate can reach 182mAh / g, with excellent rate performance and structural stability.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the invention. It should be noted that for those skilled in the art, under the technical enlightenment provided by the present invention, other equivalent improvements can be made, all of which can achieve the purpose of the present invention and should be considered as the scope of protection of the present invention.

Claims

1. An aluminum-boron co-doped ternary cathode material, characterized in that: The raw materials for preparing the ternary positive electrode material include a precursor, a lithium source, an aluminum source, and a boron source; the chemical formula of the ternary positive electrode material is Li(Ni x Co y Mn z ) 1-b-c Al b B c O2, where 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1; 0<b≤0.015, 0<c≤0.015, and 0<b+c≤0.03; The preparation method of the ternary positive electrode material comprises the following steps: Step S1: Precursor preparation: nickel source, cobalt source, and manganese source are weighed and mixed to form a salt solution. The salt solution, precipitant, and complexing agent are added to a reactor and reacted at 40-60° C. to obtain a solid-liquid mixture. The solid-liquid mixture is filtered and dried to obtain a precursor. Step S2: mixing the precursor with a lithium source, adding an aluminum source, and performing a first calcination to obtain a sintered product A; Adding a boron source and performing a second calcination to obtain a sintered product B, and grinding the sintered product B into powder to obtain the ternary positive electrode material; In step S1, the concentration ratio of the salt solution, the precipitant, and the complexing agent is 1:0.8-1.2:0.02-0.05; In step S2, the aluminum in the aluminum source is 0-1.5% of the molar amount of the precursor and is not equal to 0; the boron in the boron source is 0-1.5% of the molar amount of the precursor and is not equal to 0.

2. The aluminum-boron co-doped ternary cathode material according to claim 1, characterized in that: The chemical formula of the precursor is Ni x Co y Mn z (OH)2, wherein 0.7≤x≤0.98, 0.01≤y≤0.1, 0.01≤z≤0.2, and x+y+z=1.

3. The aluminum-boron co-doped ternary cathode material according to claim 1, characterized in that: In step S1, the nickel source is one of NiSO4·6H2O and Ni(CH3COO)2·4H2O; the cobalt source is one of CoSO4·7H2O and Co(CH3COO)2·4H2O; and the manganese source is one of MnSO4·H2O, MnCO3 and Co(CH3COO)2·4H2O.

4. The aluminum-boron co-doped ternary cathode material according to claim 1, characterized in that: In step S1, the precipitant is a 0.5-10 mol / L NaOH solution; and the complexing agent is a 0.05-3 mol / L ammonia solution.

5. The aluminum-boron co-doped ternary cathode material according to claim 1, characterized in that: The specific steps of the first calcination in step S2 are: placing the mixture of the precursor, lithium source and aluminum source in a sintering furnace, heating it to 450-550°C in an oxygen environment, keeping it warm for 5-10 hours, cooling it down and taking it out to obtain a sintered product A; the heating rate is 2-7°C / min.

6. The aluminum-boron co-doped ternary cathode material according to claim 1, characterized in that: The specific steps of the second calcination in step S2 are as follows: grinding the sintered product A, adding a boron source, heating to 700°C to 800°C, keeping the temperature for 10 to 30 hours, cooling and removing the product to obtain a sintered product B; The heating rate is 2-7°C / min.

7. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the aluminum-boron co-doped ternary positive electrode material according to any one of claims 1 to 6.

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