CN111799454B - High-nickel layered material with niobium-containing nano surface layer and preparation method thereof - Google Patents

Abstract

A high-nickel layered electrode material with a nano surface layer containing Nb comprises Nb ⁵⁺ Gradient doped sublayer and LiNbO ₃ /T‑Nb ₂ O ₅ A composite surface coating layer; the LiNbO ₃ /T‑Nb ₂ O ₅ The composite surface coating layer is made of LiNbO ₃ And T-Nb ₂ O ₅ Two compounds of LiNbO ₃ /T‑Nb ₂ O ₅ The structure of the composite surface coating layer is structure (a) and/or (b), wherein structure (a) is T-Nb ₂ O ₅ Coated with LiNbO ₅ Structure (b) is T-Nb ₂ O ₅ And LiNbO ₃ Mixing occurs in the same layer; the Nb ⁵⁺ Nb in gradient doped layer ⁵⁺ Gradually decreases from the particle surface inwards; the LiNbO ₃ /T‑Nb ₂ O ₅ In the composite surface coating layer, T-Nb ₂ O ₅ The mass percentage of (B) is 1-99%. The electrode material is prepared by constructing Nb ⁵⁺ Gradient doped subsurface layer and T-Nb ₂ O ₅ /LiNbO ₅ The composite surface coating layer effectively relieves the problems of unstable surface structure and residual active lithium ion surface, inhibits the reaction of active materials and organic electrolyte, and obviously enhances the structural stability and the thermal stability of the materials, thereby obviously improving the multiplying power, the circulation and the safety performance of the battery.

Description

A kind of high nickel layered material with niobium-containing nanometer surface layer and preparation method thereof

technical field

The invention relates to a high-nickel layered material with a niobium-containing nanometer surface layer and a preparation method thereof, belonging to the field of lithium battery electrode materials.

Background technique

High-nickel layered transition metal oxide cathode material (LiNi _1-x M _x O ₂ , where M=Co, Mn, Al, etc., 0.6≤1-x≤1) has high energy density, low cost and relatively safe Due to its advantages, it has been used in many fields such as electric vehicle power batteries and power tool batteries, and has become one of the most promising cathode materials for lithium-ion batteries.

However, high-nickel layered cathode materials still have inherent key technical problems that need to be solved urgently. The first is the surface structure transformation and oxygen release reaction caused by cation mixing. The nickel content on the surface of high-nickel layered materials is high. When charged to a higher voltage (>4.3V), Ni ²⁺ is oxidized to Ni ⁴⁺ , Ni ⁴⁺ has strong oxidizing property and is easy to react with organic electrolytes, and the transition from Ni ^{4+ →} Ni ²⁺ occurs; while Ni ²⁺ is similar to Li ⁺ ion radius, and it is easy to migrate from the transition metal layer to the lithium layer, resulting in " Cation mixing”, causing the transformation of the surface structure from layered → spinel-like → rock-salt phase. The structural transformation starts from the surface layer and gradually “spreads” to the core region, resulting in the degradation of rate performance and cycling stability. At the same time of structural transformation, oxygen is released from the lattice on the surface of the material. Under high temperature and high voltage, the reaction between the released oxygen and the organic electrolyte is intensified to generate CO ₂ , CO and other gases; ” and other unexpected situations, or encountering an “open flame”, the rapidly released gas reacts violently with the flammable organic electrolyte, causing combustion or even explosion, causing the phenomenon of “thermal runaway”, which seriously affects the safety of the battery.

Another key technical problem of high-nickel layered materials is the residual lithium on the surface. In the preparation of high-nickel layered materials, in order to suppress cation mixing and achieve the ideal stoichiometric ratio and performance, an excess of lithium is required. Excess lithium remains on the surface of the material and easily reacts with _CO2 and water vapor in the air to form _LiOH and _Li2CO3 surface lithium impurities. And the higher the nickel content in the electrode material, the more serious the lithium residual problem. The residual lithium is alkaline, which leads to the high pH value of the material. During the mixing process, it reacts with the solvent in the binder - nitrogen methyl pyrrolidone (NMP), resulting in a gel phenomenon, which makes it difficult to mix the positive electrode. In addition, during the long-cycle cycle, Li ₂ CO ₃ can react with the organic electrolyte to generate CO ₂ , O ₂ and other gases, resulting in the phenomenon of "flatulence", which seriously affects the performance of the battery. Since _LiOH and Li2CO3 are lithium inert phases, they hinder the transport _of lithium ions and electrons at the interface between the cathode and the electrolyte, which affects the rate capability of the material.

Ion doping is one of the effective means to suppress cation mixing. The main doping ions include metal ions such as Al ³⁺ , Ti ⁴⁺ , Mg ²⁺ and Zr ⁴⁺ , as well as PO ₄ ^3- , BO ₄ ^5- /BO ₃ ^3- and other non-metal ions. The main function of ion doping is to suppress cation mixing, improve ionic and electronic conductance, and fix lattice oxygen. Nevertheless, single ion doping is often unable to effectively remove the surface lithium residues, and cannot effectively avoid the occurrence of surface side reactions.

Water washing can remove most of the lithium residues on the surface of high-nickel materials. However, a large amount of water rinsing may "wash out" the lithium in the inner layer of the material, which affects the electrochemical and storage performance of the material. Direct heating in a pure oxygen atmosphere can also remove the surface lithium residues. However, the thermal decomposition products of the lithium residues exist in the form of _Li2O , which is easy to react with water vapor and _CO2 again when exposed to air to generate LiOH and Li. ₂ CO ₃ .

The surface coating isolates the active material from the organic electrolyte and inhibits surface side reactions, which can significantly improve the cycling stability and safety of the material. However, traditional lithium inert cladding materials such as Al ₂ O ₃ , AlF ₃ , MgO, AlPO ₄ , etc., have very low ionic conductivities, which may cause a decrease in rate capability. Lithium conductive coatings, such as Li ₃ PO ₄ , Li ₂ SiO ₃ , Li ₂ O 2B ₂ O ₃ , etc., have high ionic conductivity, which not only acts as a physical protective layer, but also does not reduce the material's performance. rate performance. Although lithium conductive coating has many advantages, the active lithium source is still introduced in the preparation process, and there is still the problem of removing active lithium residues.

Therefore, for high-nickel layered materials, a single coating or doping effect is limited, which often cannot solve the problems of unstable surface structure and lithium residues at the same time. A novel material structure design and preparation method is required to solve the above problems at the same time.

SUMMARY OF THE INVENTION

Existing research results show that Nb ⁵⁺ doped layered transition metal oxide cathode material can inhibit cation mixing and significantly improve the rate and cycle stability of the material; LiNbO ₃ coating modified cathode material, due to its high Lithium-ion conductivity ensures that the rate capability of the material is not degraded while effectively isolating the organic electrolyte. Therefore, the construction of Nb ⁵⁺ doping and /LiNbO ₃ structures will have synergistic effects and significantly improve the rate, cycling and safety performance.

T-Nb ₂ O ₅ (T-phase niobium oxide) has a special lithium ion transport channel, and has excellent rate performance, which is comparable to the most excellent solid-state electrolytes. At present, T-phase niobium oxide has been used as a high-rate anode material for lithium batteries. Using T-Nb ₂ O ₅ as the niobium source, while constructing the Nb ⁵⁺ doped/LiNbO ₃ coating, the excess niobium source (T-Nb ₂ O ₅ ) remains on the surface of the material, which can continue to serve as a physical protective layer without reducing the rate capability of the material.

The invention solves the problems of unstable surface structure and residual lithium on the surface of the high-nickel layered positive electrode material by constructing a composite niobium-containing nanoscale surface layer on the surface of the high-nickel layered material.

The invention discloses a high nickel layered electrode material with a niobium-containing nanometer surface layer, comprising a subsurface layer doped with Nb ⁵⁺ gradient and a LiNbO ₃ /T-Nb ₂ O ₅ composite surface coating layer; the The LiNbO ₃ /T-Nb ₂ O ₅ composite surface coating layer is composed of two compounds, LiNbO ₃ and T-Nb ₂ O ₅ , and the structure of the LiNbO ₃ /T-Nb ₂ O ₅ composite surface coating layer is the structure ( a) and/or (b), wherein the structure (a) is that T-Nb ₂ O ₅ is coated on the surface of LiNbO ₅ , and the structure (b) is that T-Nb ₂ O ₅ and LiNbO ₃ are mixed in the same layer; The concentration of Nb ⁵⁺ in the Nb ⁵⁺ gradient doping layer gradually decreases from the particle surface inward.

The structures (a) and (b) of the LiNbO ₃ /T-Nb ₂ O ₅ composite surface cladding layer appear randomly because LiOH/Li ₂ CO ₃ lithium residues are distributed on the surface of the material, but they are not on the surface of the electrode material. The distribution is not uniform. After coating T-Nb ₂ O ₅ , during the heat treatment, T-Nb ₂ O ₅ reacts with LiOH/Li ₂ CO ₃ to form LiNbO ₃ , and the unreacted remains on the surface. Therefore, T- The amount of Nb ₂ O ₅ remaining depends on the residual amount of LiOH/Li ₂ CO ₃ and the amount of T-Nb ₂ O ₅ added.

The thickness of the LiNbO ₃ /T-Nb ₂ O ₅ composite surface coating layer is 1-50 nm, preferably 5-10 nm.

In the LiNbO ₃ /T-Nb ₂ O ₅ composite surface coating layer, the mass percentage of T-Nb ₂ O ₅ is 1-99%, preferably 3-50%, more preferably 5-20%.

The mass ratio of the T-Nb ₂ O ₅ /LiNbO ₃ composite surface coating layer to the high nickel layered positive electrode material LiNi _x M _1-x O ₂ is 0.1%-5%, preferably 0.5-2%;

For high-nickel layered materials, due to the preparation process and the material itself, the surface of the base material LiNi _x M _1-x O ₂ will contain LiOH/Li ₂ CO ₃ lithium residues. The larger the x value, the higher the lithium residue. After LiNi _x M _1-x O ₂ is coated with T-Nb ₂ O ₅ , it can be reacted with LiOH/Li ₂ CO ₃ after medium temperature heat treatment (about 500-600 ℃) to generate LiNbO ₃ , and The unreacted T-Nb ₂ O ₅ remains on the surface of the material to form a LiNbO ₃ /T-Nb ₂ O ₅ composite structure. The reaction mechanism is as follows:

Li ₂ CO ₃ +Nb ₂ O ₅ →2LiNbO ₃ +CO ₂

2LiOH+Nb ₂ O ₅ →2LiNbO ₃ +H ₂ O

Since LiOH/Li ₂ CO ₃ does not completely cover the surface of the material, in areas without lithium residues, LiNbO ₃ may not appear after T-Nb ₂ O ₅ coating and heat treatment, so T-Nb may appear _The case where _2O5 and _LiNbO3 are in the same layer. The thickness of the Nb ⁵⁺ gradient-doped subsurface layer is 10-200 nm, preferably 20-100 nm;

A preparation method of a high-nickel layered electrode material with a niobium-containing nanometer surface layer, comprising the following steps:

(1) Mix the lithium source and the transition metal precursor in proportion, add a dispersant, and mix by ball milling; in terms of the moles of lithium and transition metal, the ratio of the lithium source to the transition metal precursor described in step (1) is: 1.05-1.15, preferably 1.08-1.10;

(2) step (1) the product after ball milling and mixing is heat-treated under an oxidizing atmosphere to obtain a high-nickel positive electrode material with lithium residues on the surface;

(3) coating the nano-T-Nb ₂ O ₅ on the surface of the high-nickel positive electrode material with lithium residues on the surface obtained by sintering in step (2), to obtain a high-nickel layered positive electrode material coated with nano-T-Nb ₂ O ₅ ;

(4) The high-nickel layered positive electrode material coated with nano-T-Nb ₂ O ₅ obtained in step (3) is calcined at 450-600° C. for 2-12 h to obtain a high-nickel layered electrode material with a niobium-containing nano-surface layer .

The Nb ⁵⁺ gradient doped sub-surface layer is formed by diffusing part of the Nb ⁵⁺ of the cladding layer into the material surface layer through heat treatment after coating T-Nb ₂ O ₅ . The concentration of Nb ⁵⁺ decreases gradually from the particle surface inwards.

Preferably, the type of the dispersant in step (1) is one of water and ethanol.

Preferably, the lithium source in step (1) is one of Li ₂ CO ₃ and LiOH, preferably LiOH; the transition metal precursor in step (1) is Ni _x M _1-x (OH) ₂ or Ni _x M _1-x CO ₃ , wherein M is one or a combination of Co, Mn and Al, x is 0.01-0.4, preferably x is 0.1-0.4, preferably the transition metal precursor is Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ , Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ , Ni _0.9 Co _0.05 Mn _0.05 (OH) ₂ and Ni _0.6 Co _0.2 Mn _0.2 CO ₃ and One of Ni _0.8 Co _0.15 Al _0.05 (OH) ₂ .

Preferably, the oxidizing atmosphere in step (2) is O ₂ or air, preferably an oxygen atmosphere; the temperature of the heat treatment is 750-900° C., and the heat treatment time is 10-25 hours.

Preferably, the mass percentage of lithium residual (LiOH+Li ₂ CO ₃ ) in the high-nickel positive electrode material with lithium residual on the surface in step (2) is 0.1%-1%.

Preferably, in step (2), the high-nickel positive electrode material with lithium residues on the surface has the molecular formula of LiNi _1-x M _x O ₂ , wherein M is one or a combination of Co, Mn, and Al, and x is 0.01-0.4, preferably x is 0.1-0.4, and the preferred high nickel positive electrode materials are LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.7 Co _0.15 Mn _0.15 O ₂ , LiNi _0.9 Co One of _0.05 Mn _0.05 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

Preferably, the particle size of the nano T-Nb ₂ O ₅ in step (3) is <100 nm, preferably 10-30 nm.

Preferably, the coating method in step (3) is one of ball milling, solid-phase fusion, and ultrasonic vibration liquid-phase coating, preferably solid-phase fusion.

beneficial technical effect

The invention effectively relieves the problems of unstable surface structure and residual active lithium ions on the surface of the high-nickel positive electrode material by constructing a Nb ⁵⁺ gradient doped subsurface layer and a T-Nb ₂ O ₅ /LiNbO ₅ composite surface coating layer. , inhibiting the reaction between the active material and the organic electrolyte, significantly enhancing the structural stability and thermal stability of the material, thus significantly improving the rate, cycle and safety performance of the battery.

Instruction drawings

Fig. 1 is the structure (a) schematic diagram of LiNbO ₃ and T-Nb ₂ O ₅ composite surface coating layer;

Fig. 2 is the structure (b) schematic diagram of LiNbO ₃ and T-Nb ₂ O ₅ composite surface coating layer;

Fig. 3 is a scanning electron microscope photograph of a high-nickel layered material with Nb surface gradient doping/LiNbO ₃ and T-Nb ₂ O ₅ composite coating;

Detailed ways

The present invention is further illustrated by the following examples

Example 1

500 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was mixed with 141 g of LiOH (Li:TM=1.08), 100 mL of deionized water was added as a dispersant, and the mixing time was 30 min by ball milling at 200 rpm. The mixed lithium sample was placed in a vacuum drying oven, dried at 110 °C for 4 h until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 900 °C for 12 h to obtain a high nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). 500 g of sintered product NCM622 was mixed with 5 g of T-Nb ₂ O ₅ with a particle size of 30 nm (T-Nb ₂ O ₅ /NCM=1wt%), and was placed in a solid-phase fusion machine for 30 min. The mixed product was taken out and heat-treated at a high temperature of 500 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM622-Nb1-SF.

Example 2

10 g of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ was mixed with 2.85 g of LiOH (Li:TM=1.10), 2 mL of ethanol was added as a dispersant, and the ball was milled at 200 rpm for 30 min. The product after mixing lithium was put into a vacuum drying oven, dried at 110 °C for 4 hours, until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 750 °C for 15 hours to obtain a high-nickel ternary material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811). 10 g of sintered product NCM811 was mixed with 0.2 g of T-Nb ₂ O ₅ with a particle size of 20 nm (T-Nb ₂ O ₅ /NCM=2wt%), and 2 mL of water was added as a dispersant, and ball milled for 30 min. The mixed product was taken out and heat-treated at a high temperature of 500 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM811-Nb2.

Example 3

10 g of Ni _0.8 Co _0.15 Al _0.05 (OH) ₂ was mixed with 2.87 g of LiOH (Li:TM=1.10), and 2 mL of water was added as a dispersant, and ball milled at 200 rpm for 30 min. The product after mixing lithium was put into a vacuum drying _oven , and dried at 110 °C for 4 hours until the dispersant was completely _volatilized . _0.05 O ₂ (NCA). 10 g of sintered NCA was mixed with 0.2 g of T-Nb ₂ O ₅ with a particle size of 30 nm (T-Nb ₂ O ₅ /NCM=2wt%), and 2 mL of water was added as a dispersant, and ball milled for 30 min. The mixed product was taken out and heat-treated at a high temperature of 550 °C for 6 h in an oxygen atmosphere to obtain the final product, which was named NCA-Nb2.

Comparative Example 1

10 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was mixed with 2.82 g of LiOH (Li:TM=1.08), 2 mL of deionized water was added as a dispersant, and ball milled at 200 rpm for 30 min. The product after mixing lithium was put into a vacuum drying oven, dried at 110 °C for 4 hours until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 900 °C for 12 hours to obtain a high nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). In Comparative Example 1, the niobium-containing nano-surface layer was not supported, and other steps were the same as those in Example 1.

Comparative Example 2

10 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was mixed with 2.82 g of LiOH (Li:TM=1.08), and 2 mL of deionized water was added as a dispersant, and the mixing time was 30 min at 200 rpm. The product after mixing lithium was put into a vacuum drying oven, dried at 110 °C for 4 hours until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 900 °C for 12 hours to obtain a high nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). 10g of sintered product NCM622 was mixed with 0.1g of H-Nb ₂ O ₅ (H-Nb ₂ O ₅ /NCM=1wt%) with a particle size of 30nm, and 2mL of water was added as a dispersant, and the mixture was ball milled for 30min. The mixed product was taken out and heat-treated at a high temperature of 500 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM622-Nb1-H. In Comparative Example 2, H-Nb ₂ O ₅ was used as the coating material, and other steps were the same as those in Example 1.

Comparative Example 3

10 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was mixed with 2.82 g of LiOH (Li:TM=1.08), and 2 mL of deionized water was added as a dispersant, and the mixing time was 30 min at 200 rpm. The product mixed with lithium was placed in a vacuum drying oven, dried at 110 °C for 4 hours until the dispersant was completely volatilized, and the dried mixture was heat treated at a high temperature of 900 °C for 12 hours to obtain a high nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). 10g of sintered product NCM622 was mixed with 0.1g of T-Nb ₂ O ₅ (T-Nb ₂ O ₅ /NCM=1wt%) with a particle size of 30nm, and 2mL of water was added as a dispersant, and the mixture was ball milled for 30min. The mixed product was taken out and heat-treated at a high temperature of 400 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM622-Nb1-400. In Comparative Example 3, the cladding sintering temperature was 400° C., and other steps were the same as those in Example 1.

Comparative Example 4

10 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ was mixed with 2.82 g of LiOH (Li:TM=1.08), and 2 mL of deionized water was added as a dispersant, and the mixing time was 30 min at 200 rpm. The product mixed with lithium was placed in a vacuum drying oven and dried at 110°C for 4 hours until the dispersant was completely volatilized. The dried mixture was heat-treated at a high temperature of 900 °C for 12 h to obtain a high-nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). 10g of sintered product NCM622 was mixed with 0.1g of T-Nb ₂ O ₅ (T-Nb ₂ O ₅ /NCM=1wt%) with a particle size of 30nm, and 2mL of water was added as a dispersant, and the mixture was ball milled for 30min. The mixed product was taken out and heat-treated at a high temperature of 700 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM622-Nb1-700. In Comparative Example 3, the cladding and sintering temperature was 700° C., and other steps were the same as those in Example 1.

Comparative Example 5

Mix 10 g of Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ with 2.82 g of LiOH (Li:TM=1.08), and add 2 mL of deionized water as a dispersant, and the mixing time is 30 min by ball milling at 200 rpm. . The mixed lithium sample was placed in a vacuum drying oven, dried at 110 °C for 4 h until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 900 °C for 12 h to obtain a high nickel ternary material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622). 10 g of sintered product NCM622 was mixed with 0.1 g of T-Nb ₂ O ₅ with a particle size of 30 nm (T-Nb ₂ O ₅ /NCM=1wt%), and 2 mL of water was added as a dispersant, and ball milled for 30 min. The mixed product was taken out and heat-treated at a high temperature of 500 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM622-Nb1-BM. The method of coating T-Nb ₂ O ₅ in Example 5 is different from that in Example 1.

Comparative Example 6

10 g of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ was mixed with 2.85 g of LiOH (Li:TM=1.10), 2 mL of ethanol was added as a dispersant, and the ball was milled at 200 rpm for 30 min. The product after mixing lithium was put into a vacuum drying oven, dried at 110 °C for 4 hours, until the dispersant was completely volatilized, and then the dried mixture was heat treated at a high temperature of 750 °C for 15 hours to obtain a high-nickel ternary material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811). 10 g of sintered product NCM811 was mixed with 0.2 g of T-Nb ₂ O ₅ with a particle size of 20 nm (T-Nb ₂ O ₅ /NCM=2wt%), and 2 mL of water was added as a dispersant, and ball milled for 30 min. The mixed product was taken out and heat-treated at a high temperature of 500 °C for 5 h in an oxygen atmosphere to obtain the final product, which was named NCM811-Nb2.

Comparative Example 7

10 g of Ni _0.8 Co _0.15 Al _0.05 (OH) ₂ was mixed with 2.87 g of LiOH (Li:TM=1.10), and 2 mL of deionized water was added as a dispersant, and ball milled at 200 rpm for 30 min. The product mixed with lithium was placed in a vacuum drying oven, dried at 110 °C for 4 hours, until the dispersant was completely volatilized, and the dried mixture was heat-treated at a high temperature of 750 °C for 15 hours in an oxygen atmosphere to obtain a high-nickel ternary material LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA).

Both Example 1 and Comparative Examples 1-5 were modified with LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622) as the matrix material, and the above examples and comparative examples were tested for electrode performance. The results are shown in Table 1.

Table 1 Performance of Examples and Comparative Examples with NCM622 as the Base Material

Both Example 2 and Comparative Example 6 were modified with LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) as the matrix material, and electrode performance tests were carried out on the above Examples and Comparative Examples, and the results are shown in Table 2.

Table 2 Performance comparison between Example 2 and Comparative Example 6 using NCM811 as the base material

Both Example 3 and Comparative Example 7 were modified with LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA) as the matrix material, and the electrode performance tests were carried out on the above Examples and Comparative Examples, and the results are shown in Table 3.

Table 3 Performance of Examples and Comparative Examples with NCA as the Base Material

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and these Modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (14)

1. A high-nickel laminated electrode material with nano surface layer containing Nb is composed of Nb ⁵⁺ Gradient doped sublayer and LiNbO ₃ /T-Nb ₂ O ₅ A composite surface coating layer; the LiNbO ₃ /T-Nb ₂ O ₅ The composite surface coating layer is made of LiNbO ₃ And T-Nb ₂ O ₅ Two compounds of LiNbO ₃ /T-Nb ₂ O ₅ The structure of the composite surface coating layer is structure (a) and/or (b), wherein structure (a) is T-Nb ₂ O ₅ Coated with LiNbO ₅ Surface of (a), structure (b) is T-Nb ₂ O ₅ And LiNbO ₃ Mixing occurs in the same layer; the Nb ⁵⁺ Gradient doped subsurface Nb ⁵⁺ Gradually decreases from the particle surface inwards; the LiNbO ₃ /T-Nb ₂ O ₅ In the composite surface coating layer, T-Nb ₂ O ₅ The mass percentage of (A) is 1-99%; the LiNbO ₃ /T-Nb ₂ O ₅ The thickness of the composite surface coating layer is 1-50nm; the Nb ⁵⁺ The thickness of the gradient doped sublayer is 10-200nm;

the preparation method of the high-nickel layered electrode material with the niobium-containing nano surface layer comprises the following steps:

(1) Mixing a lithium source and a transition metal precursor in proportion, adding a dispersing agent, and performing ball milling and mixing; the ratio of the lithium source to the transition metal precursor in the step (1) is 1.05-1.15 in terms of the number of moles of lithium and the transition metal;

(2) Carrying out heat treatment on the product obtained after ball milling and mixing in the step (1) in an oxidizing atmosphere to obtain a high-nickel anode material with lithium residues on the surface;

(3) Mixing nanometer T-Nb ₂ O ₅ Coating the surface of the high-nickel anode material which is obtained by sintering in the step (2) and has lithium residue on the surface to obtain nano T-Nb ₂ O ₅ A coated high nickel layered positive electrode material;

(4) The nano T-Nb obtained in the step (3) ₂ O ₅ And calcining the coated high-nickel layered positive electrode material at 450-550 ℃ for 2-12h to obtain the high-nickel layered electrode material with the niobium-containing nano surface layer.

2. The method of claim 1A polar material characterized in that said LiNbO ₃ /T-Nb ₂ O ₅ The thickness of the composite surface coating layer is 5-10nm.

3. The electrode material of claim 1, wherein the Nb is ⁵⁺ The thickness of the gradient doped sublayer is 20-100nm.

4. The electrode material of claim 1, wherein the ratio of the lithium source to the transition metal precursor in step (1) is from 1.08 to 1.10.

5. The electrode material as claimed in claim 1, wherein the dispersant used in the step (1) is one of water and ethanol.

6. The electrode material of claim 1, wherein in step (1) the lithium source is LiOH.

7. The electrode material according to claim 1, wherein the transition metal precursor in the step (1) is Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ 、Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ 、Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ 、Ni _0.9 Co _0.05 Mn _0.05 (OH) ₂ And Ni _0.6 Co _0.2 Mn _0.2 CO ₃ And Ni _0.8 Co _0.15 Al _0.05 (OH) ₂ One kind of (1).

8. The electrode material according to claim 1, wherein the oxidizing atmosphere in the step (2) is O ₂ Or air; the heat treatment temperature is 750-900 ℃, and the heat treatment time is 10-25 hours.

9. The electrode material as claimed in claim 1, wherein the oxidizing atmosphere in the step (2) is an oxygen atmosphere.

10. The electrode material according to claim 1, wherein the mass percentage of surface lithium remaining in the high nickel positive electrode material in the step (2) is 0.1% to 1%.

11. The electrode material of claim 1, wherein the high nickel positive electrode material of step (2) has the formula LiNi _1-x M _x O ₂ Wherein M is one or a combination of more of Co, mn and Al, and x is 0.01-0.4.

12. The electrode material of claim 1, wherein the high nickel positive electrode material in step (2) is LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.7 Co _0.15 Mn _0.15 O ₂ 、LiNi _0.9 Co _0.05 Mn _0.05 O ₂ And LiNi _0.8 Co _0.15 Al _0.05 O ₂ One kind of (1).

13. The electrode material of claim 1, wherein the nano-sized T-Nb used in step (3) is selected from the group consisting of ₂ O ₅ Has a particle size of less than 100nm.

14. The electrode material of claim 1, wherein the nano-T-Nb in step (3) ₂ O ₅ The particle diameter of (2) is 10-30nm.

Images