CN115064674A - High-rate long-cycle ternary cathode material, and preparation method and application thereof - Google Patents

Abstract

The invention provides a high-rate and long-cycle ternary positive electrode material, a preparation method and application thereof. The high-rate and long-cycle ternary positive electrode material includes a ternary positive electrode material matrix and a coating layer coated on the surface of the ternary positive electrode material matrix; the chemical formula of the ternary positive electrode material matrix is LiNi _x Co _y Mn _{1- x-y} O ₂ , wherein 0<x<1, 0<y<1; the chemical formula of the coating layer is Nam Ni _n Mn _{1-n O 2} , wherein 0.3<m<1.0, 0.3<n< 0.95. The preparation method is simple, and it is easy to realize large-scale production. The prepared ternary positive electrode material is used as a positive electrode material for a lithium ion battery, which can effectively stabilize the electrode/electrolyte interface, reduce the growth of DCR, improve the cycle and rate performance of the material, and can also It effectively isolates the direct contact between the electrode material and the electrolyte, and reduces the DCR growth of the battery during the cycle.

Description

A high-rate long-cycle ternary cathode material, its preparation method and application

technical field

The invention relates to the technical field of lithium ion battery electrode materials, in particular to a high-rate and long-cycle ternary positive electrode material, a preparation method and application thereof.

Background technique

Due to the guidance and promotion of the national new energy policy, lithium-ion batteries have been rapidly applied and promoted in the fields of 3C, power batteries, aerospace and power tools. In the field of electric vehicles, the cycle life and rate performance of batteries are two important indicators for evaluating the performance of batteries and materials. Among them, the cathode material in the battery system is the decisive factor. In the existing cathode material system, ternary materials are widely used due to their advantages of high specific energy density and good cycle performance. As we all know, with the charging and discharging of the battery, the electrochemical performance of the positive electrode material in the battery will be greatly attenuated, mainly from the following factors: (1) During the continuous charging and discharging process, the electrode/electrolyte The interfacial reaction leads to the continuous increase of the DCR of the battery, which affects the electrochemical performance of the electrode material; (2) the interfacial coating layer is corroded by HF in the electrolyte, and new interfaces are continuously formed, which further deteriorates the capacity and cycle performance of the battery.

In order to improve the interfacial stability of the battery, currently, the primary sintered material is coated and secondary by the use of inert nano inorganic oxides (such as alumina, magnesia, titania, and zinc oxide) by means of a solid-phase mixed coating method. sintering. However, the solid-phase hybrid coating method has the following shortcomings: (1) The coating layer formed is usually distributed in the form of dots or islands, the thickness of the interface is not uniform and the coverage is incomplete, and the electrochemical performance of the battery is not good under extreme conditions of use. (2) The conventional nano-oxide coating layer has a loose structure and is easy to react with HF to form a new exposed interface, leading to the dissolution of transition metals, causing continuous structural deterioration and performance degradation of the interface, thereby reducing the cycle of the material. performance and rate capability.

For example, CN108767246A adopts the solid-phase mixed coating method to coat the inorganic oxides such as alumina, magnesia, titania and zirconia on the surface of the ternary positive electrode material respectively. The obtained product has a good layered structure and can be charged and discharged for the first time. The mass specific capacity can reach 200mAh/g, and the capacity decay after 50 cycles is small. However, the rate performance of the product is poor, and further optimization is needed for the capacity fading of longer cycles.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a high rate and long cycle ternary positive electrode material, its preparation method and application. The high-rate and long-cycle ternary cathode material can effectively stabilize the electrode/electrolyte interface, reduce the corrosion and structural damage of the material interface, reduce the growth of DCR, and improve the cycle and rate performance of the material as a cathode material for a lithium ion battery.

In a first aspect, the present invention provides a high-rate and long-cycle ternary positive electrode material, comprising a ternary positive electrode material matrix and a coating layer coated on the surface of the ternary positive electrode material matrix;

The chemical formula of the ternary cathode material matrix is LiNi _x Co _y Mn _1-xy O ₂ , wherein 0<x<1, 0<y<1; the chemical formula of the coating layer is _{Nam Ni n Mn 1- n} O ₂ , where 0.3<m<1.0 and 0.3<n<0.95.

Preferably, the mass ratio of the coating layer to the ternary cathode material matrix is (0.0001-0.02):1.

Preferably, the thickness of the coating layer is 5-50 nm.

Preferably, the particle size of the ternary cathode material matrix is 4-15 μm.

In a second aspect, the present invention provides a method for preparing the high-rate long-cycle ternary positive electrode material, comprising the following steps:

(1) Mixing the ternary cathode material matrix with sodium salt to obtain a bottom liquid;

(2) After adding an aqueous solution containing nickel element and manganese element to the bottom liquid for in-situ coating and precipitation, drying and sintering are performed in sequence to obtain the ternary positive electrode material.

Preferably, the sodium salt includes sodium carbonate.

Preferably, the mass ratio of the ternary cathode material matrix, sodium salt, nickel element and manganese element is 1:(0.002-0.5):(0.001-1.0):(0.001-1.0).

Preferably, the addition rate of the aqueous solution containing nickel and manganese elements is 0.4-0.6 mL/min, preferably 0.5 mL/min.

Preferably, the sintering temperature is 200˜800° C., and the sintering time is 5˜30 h.

In a third aspect, the present invention provides a lithium ion battery, comprising the high-rate long-cycle ternary positive electrode material or the high-rate long-cycle ternary positive electrode material prepared by the preparation method.

Compared with the prior art, the beneficial effects of the present invention are:

(1) In the present invention, a dense and electrochemically active Nam Ni _n Mn _{1-n O 2} coating layer is covered on the surface of the ternary positive electrode material by the liquid phase in-situ coating technology, which is used as the positive electrode of the lithium ion battery. When the material is used, on the one hand, it can effectively stabilize the electrode/electrolyte interface, reduce the corrosion and structural damage of the material interface, reduce the DCR growth, and improve the cycle and rate performance of the material; on the other hand, it can effectively isolate the direct contact between the electrode material and the electrolyte. , significantly improving the interfacial defects due to HF corrosion and reducing the DCR growth of the battery during cycling;

(2) The Na _m Ni _n Mn _1-n O ₂ coating layer has very good electrochemical activity, and the exchange of Na ions and ions occurs during the first cycle, which realizes the electrochemical activation of the interface layer and avoids conventional high The internal resistance of the oxide coating layer increases the battery resistance, and the coating layer has high strength, which can remain intact during the electrode rolling process;

(3) The preparation method provided by the present invention is simple and easy to realize large-scale production.

Description of drawings

Fig. 1 is the SEM image of the ternary positive electrode material obtained in Example 1;

FIG. 2 is a comparison diagram of the cycle performance of the ternary cathode materials obtained in Example 1-2 and Comparative Example 1-2 at 25°C;

FIG. 3 is a comparison chart of the rate performance of the ternary cathode materials obtained in Example 1-2 and Comparative Example 1-2.

Detailed ways

All raw materials involved in the present invention are not particularly limited in their sources, and can be purchased from the market or prepared according to conventional preparation methods well known to those skilled in the art.

The invention provides a high-rate and long-cycle ternary positive electrode material, which comprises a ternary positive electrode material matrix and a coating layer coated on the surface of the ternary positive electrode material matrix;

The chemical formula of the ternary cathode material matrix is LiNi _x Co _y Mn _1-xy O ₂ , wherein 0<x<1, 0<y<1; the chemical formula of the coating layer is _{Nam Ni n Mn 1- n} O ₂ , where 0.3<m<1.0 and 0.3<n<0.95.

In the present invention, a layer of Nam Ni _n Mn _{1-n O 2} coating layer with dense structure and electrochemical activity is coated on the surface of the ternary positive electrode material substrate through the liquid phase in-situ coating technology, and on the one hand, the electrode can be effectively stabilized / Electrolyte interface, reduce the corrosion and structural damage of the material interface, reduce the DCR growth, and improve the cycle and rate performance of the material; on the other hand, it can effectively isolate the direct contact between the electrode material and the electrolyte, and significantly improve the interface defects caused by HF corrosion. , reducing the DCR growth of the battery during cycling. In addition, the Nam Ni _n Mn _{1-n O 2} coating layer has very good electrochemical activity, and the exchange of Na ions and ions occurs during the first cycle, which realizes the electrochemical activation of the interface layer and avoids the conventional high internal The resistance of the battery increases due to the resistive oxide coating layer, and the coating layer has high strength and can remain intact during the electrode rolling process.

In the present invention, the mass ratio of the coating layer to the ternary cathode material matrix is preferably (0.0001-0.02):1, and may be 0.0001:1, 0.0005:1, 0.001:1, 0.005:1, 0.01:1 , 0.015:1 or 0.02:1, etc., other point values within the above numerical range can be selected, and will not be repeated here.

In the present invention, the thickness of the coating layer is preferably 5-50 nm. If the thickness of the coating layer is less than 5 nm, it may cause that the coating layer cannot effectively perform the function of isolating the electrode/electrolyte interface reaction. If the thickness of the layer exceeds 50 nm, it will lead to the instability of the phase interface of the material, which is not conducive to the optimal electrochemical performance of the material.

The thickness of the coating layer can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, etc. Other values within the above numerical range can be selected, and they will not be listed here. Repeat.

In the present invention, the particle size of the ternary cathode material matrix is 4-15 μm, which can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc.

The present invention also provides a preparation method of the high-rate long-cycle ternary positive electrode material, comprising the following steps:

(1) Mixing the ternary cathode material matrix with sodium salt to obtain a bottom liquid;

(2) After adding an aqueous solution containing nickel element and manganese element to the bottom liquid for in-situ coating and precipitation, drying and sintering are performed in sequence to obtain the ternary positive electrode material.

In the present invention, the ternary cathode material matrix can be prepared according to conventional methods well known to those skilled in the art. Exemplarily, the ternary cathode material matrix can be prepared according to the following method:

After uniformly mixing the ternary cathode material matrix precursor and the lithium source, sintering can be performed in an atmosphere of oxygen and/or air.

The chemical formula of the ternary cathode material matrix precursor is Ni _x Co _y Mn _1-xy (OH) ₂ , wherein 0<x<1, 0<y<1. The sintering temperature is preferably 400-1000° C., and the sintering time is preferably 8-30 h.

The sintering temperature may be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, and the like.

The sintering time can be 8h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h or 30h, etc.

Other point values within the above-mentioned numerical range can be selected, which will not be repeated here.

In the present invention, the sintering preferably further includes jaw crushing and pulverization, so that the particle size of the ternary cathode material matrix obtained after pulverization is 4-15 μm.

In the present invention, in step (1), the ternary positive electrode material is preferably mixed with sodium carbonate to obtain a bottom liquid. Among them, sodium carbonate can be used as a precipitant to precipitate the added nickel and manganese elements.

In the present invention, the mass ratio of the ternary cathode material matrix, sodium salt, nickel element and manganese element is 1:(0.002～0.5):(0.001～1.0):(0.001～1.0), which can be 1:0.002 :0.001:0.001, 1:0.01:0.001:0.001, 1:0.2:0.5:0.5, 1:0.3:0.02:0.5, 1:0.1:0.03:0.4, 1:0.02:0.01:0.01, 1:0.2:0.1 :0.1 or 1:0.05:1:1, etc., other point values within the above range can be selected, and will not be repeated here.

The aqueous solution containing nickel element and manganese element can be prepared according to a conventional method well known to those skilled in the art, by dissolving soluble nickel salt and manganese salt in water. In the present invention, preferably, the soluble nickel salt and the manganese salt are added to the aqueous solution in sequence, and after they are completely dissolved, they are allowed to stand for 12-20 hours. The standing time is more than 12 hours to ensure that the nickel element and the manganese element are uniformly dispersed in the aqueous solution.

The described aqueous solution containing nickel element and manganese element can adopt the conventional filling method well known to those skilled in the art. In the present invention, preferably a peristaltic pump is used for filling, so as to effectively control the speed at which nickel and manganese elements are introduced into the bottom liquid and ensure the inclusion of The thickness of the coating is 5-50 nm. The addition rate of the aqueous solution containing nickel element and manganese element is preferably 0.4-0.6 mL/min, more preferably 0.5 mL/min.

The addition rate can be 0.4mL/min, 0.45mL/min, 0.5mL/min, 0.55mL/min or 0.6mL/min, etc. Other values within the above range of values can be selected, which will not be omitted here. Repeat them one by one.

The present invention has no particular limitation on the drying method. In the present invention, the product obtained after in-situ coating and precipitation is preferably dried at 80° C. for 5 hours in a rotary evaporator.

In the present invention, the sintering temperature is preferably 200-800° C., and the sintering time is preferably 5-30 h.

The sintering temperature can be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C, and the like.

The sintering time can be 5h, 10h, 15h, 20h, 25h or 30h, etc.

Other point values within the above-mentioned numerical range can be selected, which will not be repeated here.

The preparation method provided by the invention is simple and easy to carry out large-scale production.

The present invention also provides a lithium ion battery, comprising the high-rate long-cycle ternary positive electrode material or the high-rate long-cycle ternary positive electrode material prepared by the preparation method.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In order to further illustrate the present invention, the following examples are used for detailed description. The sources of the raw materials used in the following examples of the present invention are not particularly limited, and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

Example 1

This embodiment provides a ternary positive electrode material whose chemical formula is LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Na _2/3 Ni _1/3 Mn _2/3 O ₂ , and the preparation method is as follows:

(1) After uniformly mixing the Ni _0.6 Co _0.1 Mn _0.3 (OH) ₂ precursor with a particle size of 4 μm and lithium hydroxide according to the ratio of Li/(Ni+Mn) molar ratio of 1.04, under the oxygen atmosphere of the box furnace, Sintering at 940°C for 15h, the rollers (upper spacing 15cm, lower spacing 5cm) are crushed to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ , a ternary cathode primary sintered material;

(2) get 1g of nickel acetate and 0.492g of manganese acetate and add it to 60mL of pure water, stir for 1h to dissolve, and let stand for 12h to obtain a water coating solution containing nickel and manganese elements;

(3) Take 25g of the ternary positive electrode primary sintered material obtained in step (1) and add it to a 0.01mol/L sodium carbonate solution to form a 200mL bottom liquid. Introduce the water coating liquid of 100 °C into the bottom liquid, transfer it to a rotary evaporator after the precipitation is complete, dry at 80 °C for 5 h, and process to obtain a pre-coated product;

(4) The pre-coated product was sintered at 450° C. for 20 hours in an air atmosphere to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Na _2/3 Ni _1/3 Mn _2/3 O ₂ ternary cathode material .

Scanning electron microscope was used to characterize the morphology of the ternary cathode material obtained in Example 1. The results are shown in Figure 1. It can be seen that there is an obvious coating layer structure on the surface of the ternary cathode material, and the coating layer is relatively uniform , the overall coating effect is good.

Example 2

This embodiment provides a ternary positive electrode material whose chemical formula is LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Na _1/3 Ni _2/3 Mn _1/3 O ₂ , and the preparation method is as follows:

(1) After uniformly mixing the Ni _0.6 Co _0.1 Mn _0.3 (OH) ₂ precursor with a particle size of 4 μm and lithium hydroxide according to the ratio of Li/(Ni+Mn) molar ratio of 1.04, under the oxygen atmosphere of the box furnace, Sintering at 940°C for 15h, crushed by rollers (upper spacing 15cm, lower spacing 5cm) to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ , a ternary cathode primary sintered material;

(2) get 1g of nickel acetate and 0.492g of manganese acetate and add it to 100mL of pure water, stir for 1h to dissolve, and let stand for 12h to obtain a water coating solution containing nickel and manganese;

(3) Take 20g of the ternary cathode primary sintered material obtained in step (1) and add it to a 0.01mol/L sodium carbonate solution to configure a bottom liquid of 200mL. The above-mentioned nickel- and manganese-containing elements are mixed with a peristaltic pump (0.5mL/min). Introduce the water coating liquid into the bottom liquid, transfer it to a rotary evaporator after the precipitation is complete, and dry it at 80 °C for 5 hours to obtain a pre-coated product;

(4) The pre-coated product was sintered at 450° C. for 20 hours in an air atmosphere to obtain a LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Na _1/3 Ni _2/3 Mn _1/3 O ₂ material.

Example 3

This embodiment provides a ternary positive electrode material whose chemical formula is LiNi _0.65 Co _0.07 Mn _0.28 O ₂ @Na _1/3 Ni _2/3 Mn _1/3 O ₂ , and the preparation method is as follows:

(1) After the Ni _0.65 Co _0.07 Mn _0.28 (OH) ₂ precursor with a particle size of 10 μm and lithium hydroxide are uniformly mixed in a ratio of Li/(Ni+Mn) molar ratio of 1.04, in a box furnace oxygen atmosphere, Sintering at 940° C. for 15h, and crushing with rollers (upper spacing 15cm, lower spacing 5cm) to obtain ternary cathode primary sintered material LiNi _0.65 Co _0.07 Mn _0.28 O ₂ ;

(2) take 1g of nickel acetate and 0.985g of manganese acetate and add it to 80mL of pure water, stir for 1h to dissolve, and let stand for 12h to obtain a water coating solution containing nickel and manganese elements;

(3) take 20g of the ternary positive electrode primary sintered material obtained in step (1) and add it to a 0.12mol/L sodium carbonate solution to configure a bottom liquid of 220mL, and the above-mentioned nickel- and manganese-containing elements are mixed by a peristaltic pump (0.5mL/min). Introduce the water coating liquid of 100 °C into the bottom liquid, transfer it to a rotary evaporator after the precipitation is complete, dry at 80 °C for 5 h, and process to obtain a pre-coated product;

(4) The pre-coated product was sintered at 600° C. for 9 hours in an air atmosphere to obtain a LiNi _0.65 Co _0.07 Mn _0.28 O ₂ @Na _1/3 Ni _2/3 Mn _1/3 O ₂ material.

Example 4

This embodiment provides a ternary positive electrode material whose chemical formula is LiN _i0.8 Co _0.1 Mn _0.1 O ₂ @Na _2/3 Ni _0.6 Mn _0.4 O ₂ , and the preparation method is as follows:

(1) After uniformly mixing the Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ precursor with a particle size of 10 μm and lithium hydroxide according to the ratio of Li/(Ni+Mn) molar ratio of 1.04, under the oxygen atmosphere of the box furnace, After sintering at 750°C for 11h, the bipolar pair of rollers (upper spacing 15cm, lower spacing 5cm) were pulverized to obtain LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , a ternary cathode primary sintered material;

(2) get 1g of nickel acetate and 0.657g of manganese acetate and add it to 40mL of pure water, stir for 1h to dissolve, and let stand for 12h to obtain a water coating solution containing nickel and manganese;

(3) take 40g of the ternary cathode primary sintered material obtained in step (1) and add it to a 0.05mol/L sodium carbonate solution to configure a bottom liquid of 300mL, and the above-mentioned nickel and manganese elements are mixed with a peristaltic pump (0.5mL/min). Introduce the water coating liquid of 100 °C into the bottom liquid, transfer it to a rotary evaporator after the precipitation is complete, dry at 80 °C for 5 h, and process to obtain a pre-coated product;

(4) The pre-coated product was sintered at 550° C. for 8 hours in an air atmosphere to obtain a LiN _i0.8 Co _0.1 Mn _0.1 O ₂ @Na _2/3 Ni _0.6 Mn _0.4 O ₂ material.

Comparative Example 1

This comparative example provides a ternary positive electrode material (that is, the ternary positive electrode material is not modified) whose chemical formula is LiN _i0.6 Co _0.1 Mn _0.3 O ₂ , and its preparation method is as follows:

(1) After uniformly mixing the Ni _0.6 Co _0.1 Mn _0.3 (OH) ₂ precursor with a particle size of 4 μm and lithium hydroxide according to the ratio of Li/(Ni+Mn) molar ratio of 1.04, under the oxygen atmosphere of the box furnace, After sintering at 940°C for 15h, the bipolar pair of rollers (upper spacing 15cm, lower spacing 5cm) pulverized to obtain a ternary cathode primary sintered material;

(4) The ternary positive electrode primary-fired material was sintered at 450° C. for 15 hours in an air atmosphere to obtain a LiNi _0.6 Co _0.1 Mn _0.3 O ₂ ternary positive electrode material.

Comparative Example 2

This comparative example provides a ternary cathode material whose chemical formula is LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Al ₂ O ₃ , which is coated by a traditional dry method. The specific steps are as follows:

(1) After uniformly mixing the Ni _0.6 Co _0.1 Mn _0.3 (OH) ₂ precursor with a particle size of 4 μm and lithium hydroxide according to the ratio of Li/(Ni+Mn) molar ratio of 1.04, under the oxygen atmosphere of the box furnace, After sintering at 940°C for 15h, the bipolar pair of rollers (upper spacing 15cm, lower spacing 5cm) pulverized to obtain a ternary cathode primary sintered material;

(2) After taking 2.5Kg of the ternary cathode primary sintered material obtained in step (1) and mixing 8g of nano-alumina uniformly, sintered at 450°C for 15h in an air atmosphere of a box furnace to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @Al ₂ O ₃ ternary cathode material.

Comparative Example 3

This comparative example provides a ternary cathode material whose chemical formula is LiNi _0.65 Co _0.07 Mn _0.28 O ₂ @MnO ₂ , which is coated by a traditional dry method. The specific steps are as follows:

(1) After the Ni _0.65 Co _0.07 Mn _0.28 (OH) ₂ precursor with a particle size of 4 μm and lithium carbonate are uniformly mixed in a ratio of Li/(Ni+Mn) molar ratio of 1.05, in a box furnace under an oxygen atmosphere, in After sintering at 930°C for 15h, the bipolar pair of rollers (upper spacing 15cm, lower spacing 5cm) pulverized to obtain a ternary cathode primary sintered material;

(2) After taking 2.5Kg of the ternary cathode primary sintered material obtained in step (1) and mixing 10g of nano-manganese dioxide uniformly, sintered at 450 ℃ for 15h in a box furnace air atmosphere to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @MnO ₂ ternary cathode material.

Comparative Example 4

This comparative example provides a ternary cathode material whose chemical formula is LiNi _0.6 Co _0.2 Mn _0.2 O ₂ @TiO ₂ , which is coated by a traditional dry method. The specific steps are as follows:

(1) After uniformly mixing the Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ precursor with a particle size of 4 μm and lithium carbonate in a ratio of Li/(Ni+Mn) molar ratio of 1.05, in a box furnace under an oxygen atmosphere, the Sintered at 930°C for 15h, bipolar rollers (upper spacing 15cm, lower spacing 5cm), crushed to obtain ternary cathode primary sintered material;

(2) After taking 2.5Kg of the ternary cathode primary sintered material obtained in step (1) and mixing 10g of nano-titanium oxide uniformly, sintered at 450°C for 15h in an air atmosphere of a box furnace to obtain LiNi _0.6 Co _0.1 Mn _0.3 O ₂ @MnO ₂ ternary cathode material.

Performance Testing

A performance test is carried out for the ternary positive electrode materials obtained in Examples 1-4 and Comparative Examples 1-4, and the test method is as follows:

The prepared ternary positive electrode material is assembled into a button battery, wherein the electrode material: conductive carbon black=90:10wt%, the solvent is NMP, the surface density of the battery pole piece is 1.2mg/cm ² , and under the voltage of 2.8-4.4V, At 25°C and 55°C, charge and discharge at 0.1C/0.1C rate for 1 cycle, then charge and discharge at 0.1C/1C, 0.2C/1C, 0.5C/1C, 1C/1C rate, and then charge and discharge at 1C/1C rate. 1C magnification 50 laps test. The test results are shown in Table 1 below:

Table 1

It can be seen from the data in the above table that the capacity and retention performance of Comparative Examples 2-4 are not significantly improved compared with Comparative Example 1. It can be seen from the data of Examples 1-2 that the ternary cathode material modified by the coating of Nam Ni _n Mn _{1-n O 2} provided by the present invention has an increase of about 2mAh _/ g in charge and discharge capacity, and the Nam Ni _n The cycle performance and rate performance of the ternary cathode material modified by Mn _1-n O ₂ coating at 25 ° C and 55 ° C have been significantly improved, indicating that the preparation method provided in Examples 1-4 of the present invention provides coating modified ternary cathode materials. After the cathode material is used, an effective and stable interface layer can be formed, which can reduce the interface reaction of the electrode/electrolyte and significantly improve the electrochemical performance of the material.

For the ternary positive electrode materials obtained in Example 1-2 and Comparative Example 1-2, the cycle performance test at normal temperature of 25°C was carried out, and the test method was as follows:

The prepared ternary positive electrode material is assembled into a button battery, wherein the electrode material: conductive carbon black=90:10wt%, the solvent is NMP, the surface density of the battery pole piece is 1.2mg/cm ² , and under the voltage of 2.8-4.4V, At 25°C, charge and discharge for 1 cycle at a rate of 0.1C/0.1C, and then charge and discharge for 50 cycles at a rate of 1C/1C.

The test results are shown in Figure 2. It can be seen that the cyclability of the positive electrode material prepared by the preparation method provided in Example 1-2 is significantly better than that in Comparative Example 1-2, indicating that the coating modification method provided in this application is obviously better than Existing coating modification methods.

The ternary positive electrode materials obtained in Example 1-2 and Comparative Example 1-2 were tested for rate performance at 0.1C, 0.2C, 0.5C, 1C and 2C. The test method is as follows:

The prepared ternary positive electrode material is assembled into a button battery, wherein the electrode material: conductive carbon black=90:10wt%, the solvent is NMP, the surface density of the battery pole piece is 1.2mg/cm ² , and under the voltage of 2.8-4.4V, At 25℃, after 1 cycle of charge and discharge at the rate of 0.1C/0.1C, the charge and discharge tests were carried out at the rate of 0.1C/1C, 0.2C/1C, 0.5C/1C and 1C/1C respectively.

The test results are shown in Figure 3. It can be seen that the rate performance of the positive electrode material prepared by the preparation method provided in Example 1-2 is significantly better than that in Comparative Example 1-2, indicating that the coating modification method provided in this application is obviously better than Existing coating modification methods.

To sum up, the method for coating a modified ternary positive electrode material with _{Nam Ni n Mn 1-n} O ₂ provided by the present application is to coat the surface of the ternary positive electrode material with a dense layer of The structural and electrochemically active _{Nam Ni n Mn 1- n O 2 coating layer} can effectively stabilize the electrode/electrolyte interface, reduce the corrosion and structural damage of the material interface, reduce the growth of DCR, and improve the cycle and stability of the material. rate capability; on the other hand, the Nam Ni _n Mn _{1-n O 2} coating layer can effectively isolate the direct contact between the electrode material and the electrolyte, significantly improve the interface defects caused by HF corrosion, and reduce the DCR growth of the battery during cycling. , and the process is simple, the equipment has strong versatility, and it is easy to carry out large-scale production.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A high-magnification long-cycle ternary cathode material comprises a ternary cathode material matrix and a coating layer coated on the surface of the ternary cathode material matrix;

the chemical formula of the ternary cathode material matrix is LiNi _x Co _y Mn _1-x-y O ₂ Wherein x is more than 0 and less than 1, and y is more than 0 and less than 1;

the coatingThe layer has the chemical formula of Na _m Ni _n Mn _1-n O ₂ Wherein m is more than 0.3 and less than 1.0, and n is more than 0.3 and less than 0.95.

2. The high-rate long-cycle ternary cathode material according to claim 1, wherein the mass ratio of the coating layer to the ternary cathode material matrix is (0.0001-0.02): 1.

3. The high-rate long-cycle ternary cathode material according to claim 1, wherein the thickness of the coating layer is 5 to 50 nm.

4. The high-rate long-cycle ternary cathode material according to claim 1, wherein the particle size of the ternary cathode material matrix is 4-15 μm.

5. The preparation method of the high-rate long-cycle ternary cathode material according to any one of claims 1 to 4, comprising the following steps:

(1) mixing a ternary positive electrode material matrix with sodium salt to obtain a base solution;

(2) and adding an aqueous solution containing nickel and manganese into the base solution to carry out in-situ coating precipitation, and then sequentially carrying out drying and sintering treatment to obtain the ternary cathode material.

6. The method of claim 5, wherein the sodium salt comprises sodium carbonate.

7. The method according to claim 5, wherein the mass ratio of the ternary positive electrode material matrix to the sodium salt to the nickel element to the manganese element is 1 (0.002-0.5): 0.001-1.0.

8. The method according to claim 5, wherein the adding speed of the aqueous solution containing nickel and manganese elements is 0.4-0.6mL/min, preferably 0.5 mL/min.

9. The preparation method according to claim 5, wherein the sintering temperature is 200-800 ℃, and the sintering time is 5-30 h.

10. A lithium ion battery, which is characterized by comprising the high-rate long-cycle ternary cathode material of any one of claims 1 to 4 or the high-rate long-cycle ternary cathode material prepared by the preparation method of any one of claims 5 to 9.

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