A gradient doping modified cation disordered lithium-rich rock salt positive electrode material and its preparation method and application

Abstract

The present application relates to the field of lithium batteries, and discloses a gradient doped modified cation disordered lithium-rich rock salt positive electrode material, and its preparation method and application. The positive electrode material described in the present application is doped with ions that have strong interactions with lattice oxygen in steps on the basis of the cation disordered lithium-rich rock salt structure material, so that the doped ions show a trend of increasing concentration from the center to the surface in the material particles. The interaction between the ions and the lattice oxygen is stronger than that of manganese ions and transition metal ions, which can optimize the unit cell parameters of the cation disordered lithium-rich rock salt structure material, regulate the overlap between the 3d energy band of Mn and the 2p energy band of O, inhibit the charge compensation of oxygen and the migration of lattice oxygen, and improve the Mn 4+ / Mn 3+ The stability of the ions ultimately achieves the effect of alleviating the voltage decay of the cation disordered lithium-rich rock salt structure material during the charge and discharge cycle without affecting the initial capacity.

Description

Technical Field

[0001] The present application relates to the field of lithium batteries, and specifically to a gradient-doped modified cation disordered lithium-rich rock salt positive electrode material, and a preparation method and application thereof. Background Art

[0002] Cationic disordered lithium-rich rock salt structure cathode materials have attracted extensive attention in the industry due to their ultra-high specific capacity and energy density as well as the rich element reserves in the earth's crust. The reason for this type of ultra-high specific capacity is that in addition to the basic capacity provided by transition metals, lattice oxygen also participates in redox during the charge and discharge process to provide additional capacity. Among the cationic disordered lithium-rich rock salt materials reported so far, manganese-based materials (such as Li 1.2 Mn 0.4 Ti 0.4 O 2 ) has the advantages of simple preparation, high energy density, and abundant manganese resources, and is considered to be a high-energy-density lithium-ion positive electrode material with great development prospects.

[0003] However, the voltage of the cation disordered lithium-rich rock salt structure material will decay with the increase of the number of charge and discharge cycles. Under normal circumstances, the voltage can decrease by more than 30% after 50 charge and discharge cycles, which will seriously affect the actual energy density and service life of the material, and also seriously affect its commercial application prospects. The study found that the lattice oxygen in the material, especially the lattice oxygen in the shallow surface of the particles, migrated, resulting in the instability of manganese ions, Mn 4+ / Mn 3+ Ion pair Mn 3+ / Mn 2+ conversion, resulting in a voltage drop. Therefore, inhibiting the migration of lattice oxygen in the shallow surface layer of particles is an effective means to alleviate the voltage decay of disordered lithium-rich materials. Doping with ions that have strong interactions with lattice oxygen can effectively inhibit lattice oxygen migration, but ordinary doping is bulk doping. Although it can alleviate voltage decay to a certain extent, it will also limit the redox degree of lattice oxygen inside the particles, resulting in a decrease in initial capacity. Therefore, it is necessary to develop a new modification method to alleviate the voltage decay problem of manganese-based cation disordered lithium-rich rock salt positive electrode materials during the charge and discharge cycle without affecting the initial capacity. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a gradient doped modified cation disordered lithium-rich rock salt positive electrode material and a preparation method thereof, so that the positive electrode material can alleviate the voltage decay problem during the battery charge and discharge cycle without affecting the initial capacity, that is, significantly improve the voltage retention rate during the charge and discharge cycle;

[0005] Another object of the present application is to provide a positive electrode sheet and a lithium battery based on the above-mentioned positive electrode material.

[0006] In order to solve the above-mentioned technical problems / achieve the above-mentioned purposes or at least partially solve the above-mentioned technical problems / achieve the above-mentioned purposes, as the first aspect of the present application, a gradient doping-modified cation disordered lithium-rich rock salt positive electrode material is provided, comprising a cation disordered lithium-rich rock salt structural material and doping ions having a strong interaction with lattice oxygen, wherein the concentration of the doping ions in the cation disordered lithium-rich rock salt structural material particles gradually increases from the center to the surface.

[0007] Optionally, the molar ratio of the cationic disordered lithium-rich rock salt structure material to the doping ions is 1:0.001-0.05.

[0008] Further optionally, the doping ions include W 6+ , Nb 5+ 、V 5+ One or more of the following.

[0009] Further optionally, the chemical formula of the cationic disordered lithium-rich rock salt structure material is Li a Mn 0.4 M b O 2 , wherein M represents a transition metal, 1.1≤a≤1.3, b=(2.8-a) / m, and m is the valence of the transition metal M; more specifically, the transition metal includes one or more of Ta, Zr and Ti.

[0010] As a second aspect of the present application, a method for preparing the positive electrode material is provided, comprising:

[0011] According to the atomic ratio of the cationic disordered lithium-rich rock salt structure material chemical formula, a manganese source raw material, a transition metal source raw material and an excess of a lithium source raw material are weighed, wet-milled, and an ion additive containing doping ions is added twice or more during the wet-milling process, and dried after the wet-milling is completed to obtain a precursor material;

[0012] After the precursor material is calcined, the positive electrode material is obtained.

[0013] Optionally, the ionic additive includes WO 3 , Nb 2 O 5 、V 2 O 5 One or more of the following.

[0014] Optionally, the preparation method further comprises adding chloride as a grinding aid during the wet grinding process.

[0015] As the third aspect of the present application, based on the excellent performance of the positive electrode material described in the present application, its application in the preparation of positive electrode sheets or lithium batteries is proposed.

[0016] As a fourth aspect of the present application, a positive electrode plate is provided, comprising a current collector, a conductive agent, a binder and the positive electrode material described in the present application.

[0017] As a fifth aspect of the present application, a lithium battery is provided, comprising a negative electrode plate, an electrolyte, a separator and the positive electrode plate described in the present application.

[0018] Compared with the existing cation disordered lithium-rich rock salt structure materials, the positive electrode material described in the present application has at least the following beneficial effects:

[0019] (1) The lattice of the cationic disordered lithium-rich rock salt structure material is modified by using ionic additives, forming a concentration gradient effect from the center to the surface inside the material particles, effectively inhibiting the migration of lattice oxygen and increasing the Mn 4+ / Mn 3+ The stability of ions effectively alleviates the voltage decay of materials without reducing the initial capacity;

[0020] (2) The addition of chloride grinding aid in the present application can enhance the grinding effect of the cationic disordered lithium-rich material and reduce the particle size; on the other hand, 6+ 、V 5+ and Nb 5+ The plasma entering the interior of the lattice has a promoting effect;

[0021] (3) The application scheme is simple and easy to operate, the process conditions are green and mild, and it has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The doping ions that have strong interactions with lattice oxygen are shown in Figure 2. 1.2 Ti 0.4 Mn 0.4 O 2 Schematic diagram of gradient doping effect;

[0023] Figure 2 The figure shows the locking effect of doping ions that have strong interactions with lattice oxygen on lattice oxygen. The red balls represent lattice oxygen atoms, and the central gray balls represent doping ions. The doping ions lock lattice oxygen through strong chemical bonds (such as WO, VO, Nb-O, etc.) to inhibit its migration.

[0024] Figure 3 The EDX spectrum of the positive electrode material particles prepared in Example 1 is shown; wherein AE represents five sampling points from the near surface to the center of the positive electrode material. DETAILED DESCRIPTION

[0025] The present application discloses a gradient doped modified cationic disordered lithium-rich rock salt positive electrode material and its preparation method and application. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It should be pointed out in particular that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in this application. The products, applications and methods of this application have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention.

[0026] In the first aspect of the present application, a gradient doped modified cation disordered lithium-rich rock salt positive electrode material is provided, wherein the doping ions having strong interactions with lattice oxygen are gradient doped into the cation disordered lithium-rich rock salt structural material, and the doping ion concentration in the particle gradually increases from the center to the surface, effectively inhibiting the migration of lattice oxygen and increasing the Mn 4+ / Mn 3+ The stability of ions effectively alleviates the voltage decay problem of cation disordered lithium-rich rock salt structure materials during the charge and discharge cycle, while leaving the initial capacity unaffected; Figure 1 The doping ions that have strong interactions with lattice oxygen are shown in Figure 2. 1.2 Ti 0.4 Mn 0.4 O 2 Schematic diagram of gradient doping effect; Figure 2 Shown is a schematic diagram of the locking effect of doped ions that have strong interactions with lattice oxygen on lattice oxygen.

[0027] In certain embodiments of the present application, the molar ratio of the cationic disordered lithium-rich rock salt structure material and the doping ions having a strong interaction with lattice oxygen is 1:0.001-0.05; in other embodiments of the present application, the ratio between the two is 1:0.01, 1:0.02 or 1:0.04.

[0028] In certain embodiments of the present application, the ions having strong interactions with lattice oxygen include W 6+ , Nb 5+ 、V 5+ One or more of the following.

[0029] In certain embodiments of the present application, the cationic disordered lithium-rich rock salt structure material has a chemical formula of Li a Mn 0.4 M b O 2, wherein M represents a transition metal, 1.1≤a≤1.3, b=(2.8-a) / m, and m is the valence of the transition metal M; in some other embodiments of the present application, the transition metal includes one or more of Ta, Zr and Ti; more specifically, the cationic disordered lithium-rich rock salt structure material has a chemical formula of Li 1.2 Ti 0.4 Mn 0.4 O 2 , Li 1.2 Mn 0.4 Zr 0.4 O 2 or Li 1.3 Mn 0.4 Ta 0.3 O 2 .

[0030] In a second aspect of the present application, a method for preparing the positive electrode material is provided, comprising:

[0031] According to the atomic ratio of the chemical formula of the cationic disordered lithium-rich rock salt structure material, a manganese source raw material, a transition metal source raw material and an excess of a lithium source raw material are weighed and wet-milled. During the wet-milling process, an ion additive containing doping ions is added twice or more. After the wet-milling is completed, the material is dried to obtain a precursor material.

[0032] After the precursor material is calcined, the positive electrode material is obtained. In certain embodiments of the present application, the cationic disordered lithium-rich rock salt structure material has a chemical formula of Li 1.2 Ti 0.4 Mn 0.4 O 2 The manganese source raw materials, transition metal titanium source raw materials and lithium source raw materials are Mn 2 O 3 、TiO 2 and Li 2 CO 3 ; The excess lithium source material is usually 10% in excess.

[0033] In some embodiments of the present application, the wet grinding can use a commonly used organic solvent as a wet grinding solvent, such as methanol, ethanol, etc., the solid-liquid ratio can be 1:1, and the wet grinding (ball milling) is 4-12h; in some other embodiments of the present application, KCl and / or CaCl are added 2 As grinding aids, the particles can be made smaller, the grinding time can be shortened, and the ions that have strong interactions with the lattice oxygen can be promoted to enter the lattice. In some other embodiments of the present application, the amount of the grinding aid is Li 1.2 Mn 0.4 Ti 0.4 O 2The material molar fraction is 0.5%-2%, for example 1%, 2%.

[0034] In certain embodiments of the present application, the ionic additive is divided into n equal parts according to the number of additions n, for example, divided into 3 equal parts, and added in 3 times during the wet grinding process; in other embodiments of the present application, at the time point of each addition of the ionic additive, the wet grinding time is divided into n+1 equal parts according to the number of additions n, for example, if it is added in 3 times, the wet grinding time is divided into 4 equal parts, and the 3 time points of adding the ionic additive are respectively at 1 / 4t, 1 / 2t and 3 / 4t of the wet grinding, and t represents the time of wet grinding.

[0035] In certain embodiments of the present application, the ionic additive includes WO 3 , Nb 2 O 5 、V 2 O 5 One or more of the above; in some other embodiments of the present application, the amount of the ionic additive is 0.1%-5% of the molar fraction of the cationic disordered lithium-rich rock salt structure material, for example 0.5%, 1%, 1.5%, 2%.

[0036] In certain embodiments of the present application, the calcination is performed at 700-1000°C for 8-16h; wherein the temperature may be 700°C, 800°C, 900°C or 1000°C, and the calcination time may be 8h, 10h, 12h or 16h.

[0037] In the third aspect of the present application, compared with conventional non-gradient doping modification schemes and non-modification schemes, under the premise of not affecting the initial capacity, the voltage retention rate of the lithium battery composed of the positive electrode material of the present application is above 90% after 50 cycles, while the voltage retention rate of other schemes is lower than 90%, and the non-gradient doping modification scheme will lead to a decrease in initial capacity. Based on this excellent performance, its application in the preparation of positive electrode sheets or lithium batteries is proposed.

[0038] In a fourth aspect of the present application, a positive electrode plate is provided, comprising a current collector, a conductive agent, a binder and the positive electrode material described in the present application.

[0039] In certain embodiments of the present application, the positive electrode plate includes a current collector and a slurry coated on the current collector; wherein the current collector can be selected from a metal foil with good conductivity, such as aluminum foil; the slurry includes the positive electrode material described in the present application, as well as a binder and a conductive agent, the binder, the conductive agent and their amounts are selected according to conventional methods, and the present application does not make specific restrictions, for example, the binder is polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC), etc., the conductive agent is conductive carbon black (SP), acetylene black, etc., the solvent is N-methylpyrrolidone (NMP), deionized water, etc., and the positive electrode material: conductive agent: binder = 7:2:1.

[0040] In a fifth aspect of the present application, a lithium battery is provided, comprising a negative electrode plate, an electrolyte, a separator and the positive electrode plate described in the present application.

[0041] In certain embodiments of the present application, the lithium-ion battery is a full battery, a soft-pack battery, a Swagelok battery, or a button battery.

[0042] In certain embodiments of the present application, the negative electrode is a metal lithium sheet; the diaphragm is a glass fiber diaphragm; the electrolyte is 1.0-1.5 mol / L LiPF 6 The solution is an electrolyte, such as LiPF with ethylene carbonate (EC) and dimethyl carbonate (DMC) as solvents in a volume ratio of 1:1. 6 of electrolyte.

[0043] In each group of comparative experiments provided in this application, unless otherwise specified, other experimental conditions, materials, etc. are kept consistent except for the differences indicated in each group, so as to provide comparability. In addition, all materials used in this application can be purchased through commercial channels.

[0044] The following further describes a gradient doping-modified cationic disordered lithium-rich rock salt positive electrode material provided in the present application, as well as its preparation method and application.

[0045] Embodiment 1:

[0046] (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 molLi 2 CO 3 , and then grind it evenly and place it in a high-energy ball mill. Add ethanol at a liquid-solid ratio of 1:1, and add 0.001 mol KCl as an auxiliary agent for ball milling. 3 , and divided into 3 equal parts for later use. Add 1 part of WO to the ball mill at the 2nd, 4th, and 6th hour of ball milling. 3After ball milling for 8 hours, the precursor material was obtained after drying. 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and W 6+ The molar ratio of WO is 1:0.01, that is, 3 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O 2 The molar fraction of structural materials is 1%; KCl accounts for 1% of Li 1.2 Ti 0.4 Mn 0.4 O 2 The mole fraction of structural materials is 1%;

[0047] (2) The above precursor was placed in a tube furnace and calcined at 900°C for 10 hours, and then ground to obtain a gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0048] Five test points were selected from the core to the near surface of the prepared positive electrode material for ion doping concentration detection. The EDX images are shown in Figure 3 , Figure 3 It shows that the ion doping concentration near the surface is higher than that in the core, and the ion doping concentration gradually increases from the center to the surface.

[0049] Embodiment 2:

[0050] (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 mol Li 2 CO 3 After grinding evenly, place it in a high-energy ball mill, add ethanol at a liquid-solid ratio of 1:1, and add 0.001 mol KCl as an auxiliary agent for ball milling. In addition, weigh 0.0005 mol Nb 2 O 5 , divided into 3 equal parts for later use. Add 1 part of Nb to the ball mill at the 3rd, 6th and 9th hours of ball milling. 2 O 5 After ball milling for 12 hours, the precursor material was obtained after drying. 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and Nb 5+ The molar ratio of Nb is 1:0.01, that is, 2 O5 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O 2 The molar fraction of structural materials is 0.5%; KCl accounts for Li 1.2 Ti 0.4 Mn 0.4 O 2 The mole fraction of structural materials is 1%;

[0051] (2) The above precursor was placed in a tube furnace and calcined at 1000°C for 10 hours, and then ground to obtain a gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0052] The positive electrode material prepared in this embodiment was subjected to EDX detection in the manner of Example 1. The results showed that the doping ion concentration showed a gradient distribution characteristic of gradually increasing from the center to the surface, which was similar to the EDX figure of Example 1.

[0053] Embodiment 3:

[0054] (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 mol Li 2 CO 3 After grinding evenly, place it in a high-energy ball mill, add ethanol at a liquid-to-solid ratio of 1:1, and add 0.001 mol CaCl 2 The additive was ball milled. In addition, 0.002 mol V 2 O 5 , and divided into 3 equal parts for later use. Add 1 part of V to the ball mill at 1.5, 3, and 4.5 hours of ball milling. 2 O 5 After ball milling for 6 hours, the precursor material was obtained after drying. 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and V 5+ The molar ratio of V 2 O 5 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O 2 The molar fraction of structural materials is 2%; CaCl 2 Occupy 1.2 Ti 0.4 Mn0.4 O 2 The mole fraction of structural materials is 1%;

[0055] (2) The above precursor was placed in a tube furnace and calcined at 700°C for 16 hours, and then ground to obtain a gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0056] The positive electrode material prepared in this embodiment was subjected to EDX detection in the manner of Example 1. The results showed that the doping ion concentration showed a gradient distribution characteristic of gradually increasing from the center to the surface, which was similar to the EDX figure of Example 1.

[0057] Embodiment 4:

[0058] (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 mol Li 2 CO 3 After grinding evenly, place it in a high-energy ball mill, add ethanol at a liquid-to-solid ratio of 1:1, and add 0.002 mol KCl as an auxiliary agent for ball milling. In addition, weigh 0.0005 mol Nb 2 O 5 and 0.0015mol V 2 O 5 The ion dopant was divided into 3 equal parts for standby use. One part of the ion dopant was added to the ball mill at the 1st, 2nd and 3rd hour of ball milling. After ball milling for 4 hours, the precursor material was obtained after drying. 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and V 5+ The molar ratio of V 2 O 5 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O 2 The molar fraction of structural materials is 1.5%, Li 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and Nb 5+ The molar ratio of Nb is 1:0.01, that is, 2 O 5 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O2 The molar fraction of structural materials is 0.5%; KCl accounts for Li 1.2 Ti 0.4 Mn 0.4 O 2 The mole fraction of structural materials is 2%;

[0059] (2) The above precursor was placed in a tube furnace and calcined at 900°C for 12 hours, and then ground to obtain a gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0060] The positive electrode material prepared in this embodiment was subjected to EDX detection in the manner of Example 1. The results showed that the doping ion concentration showed a gradient distribution characteristic of gradually increasing from the center to the surface, which was similar to the EDX figure of Example 1.

[0061] Embodiment 5:

[0062] (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 mol Li 2 CO 3 , and add 0.0005molNb 2 O 5 and 0.001mol WO 3 After grinding evenly, place it in a high-energy ball mill, add ethanol at a liquid-to-solid ratio of 1:1, and add 0.001 mol KCl and 0.001 mol CaCl 2 The precursor material was obtained after mechanical ball milling for 6 hours and drying. 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and Nb 5+ The molar ratio of Nb is 1:0.01, that is, 2 O 5 Ionic additives account for Li 1.2 Ti 0.4 Mn 0.4 O 2 The molar fraction of structural materials is 0.5%, Li 1.2 Ti 0.4 Mn 0.4 O 2 Structural Materials and W 6+ The molar ratio of WO is 1:0.01, that is, 3 Ionic additives account for Li 1.2 Ti 0.4Mn 0.4 O 2 The molar fraction of structural materials is 1%; KCl and CaCl 2 Respectively 1.2 Ti 0.4 Mn 0.4 O 2 The mole fractions of structural materials are 1% and 1%;

[0063] (2) The above precursor was placed in a tube furnace, calcined at 800°C for 8 hours, and ground to obtain gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0064] The positive electrode material prepared in this embodiment was subjected to EDX detection in the manner of Example 1. The results showed that the doping ion concentration showed a gradient distribution characteristic of gradually increasing from the center to the surface, which was similar to the EDX figure of Example 1.

[0065] Comparative Example 1:

[0066] Undoped Li 1.2 Ti 0.4 Mn 0.4 O 2 :(1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 molLi 2 CO 3 After being evenly ground, it is placed in a high-energy ball mill, and ethanol is added at a liquid-to-solid ratio of 1:1. At the same time, 0.001 mol of KCl additive is added. The precursor material is obtained after mechanical ball milling for 8 hours and drying.

[0067] (2) The above precursor was placed in a tube furnace and calcined at 900°C for 10 hours, and then ground to obtain Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0068] Comparative Example 2:

[0069] Non-gradient doping modification of Li 1.2 Ti 0.4 Mn 0.4 O 2 Materials: (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 molLi2 CO 3 , and then grind it evenly and place it in a high-energy ball mill. Add ethanol at a liquid-to-solid ratio of 1:1, and add 0.001 mol KCl as an auxiliary agent for ball milling. 3 , added into the ball mill before the start of ball milling, after ball milling for 8 hours, the precursor material is obtained after drying.

[0070] (2) The above precursor was placed in a tube furnace and calcined at 900°C for 10 hours, and then ground to obtain non-gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0071] Comparative Example 3:

[0072] Gradient doping modification of Li without adding grinding aids 1.2 Ti 0.4 Mn 0.4 O 2 Materials: (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO 2 and 0.066 mol Li 2 CO 3 After grinding evenly, place it in a high-energy ball mill and add ethanol at a liquid-solid ratio of 1:1 for ball milling. 2 O 5 and 0.0015mol V 2 O 5 The ion dopant was divided into 3 equal parts for standby use. One part of the ion dopant was added to the ball mill at the 1st, 2nd and 3rd hour of ball milling. After ball milling for 4 hours, the precursor material was obtained after drying.

[0073] (2) The above precursor was placed in a tube furnace and calcined at 900°C for 12 hours, and then ground to obtain a gradient ion-doped modified Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0074] Comparative Example 4:

[0075] Al gradient doping modification of Li 1.2 Ti 0.4 Mn 0.4 O 2 Materials: (1) Weigh 0.02 mol Mn 2 O 3 , 0.04 mol TiO2 and 0.066 molLi 2 CO 3 , and then grind it evenly and place it in a high-energy ball mill. Add ethanol at a liquid-solid ratio of 1:1, and add 0.001 mol KCl as an auxiliary agent for ball milling. 2 O 3 , and divided into 3 equal parts for later use. Add 1 part of Al to the ball mill at the 2nd, 4th, and 6th hour of ball milling. 2 O 3 After ball milling for 8 h, the precursor material was obtained after drying.

[0076] (2) The precursor was placed in a tube furnace and calcined at 900°C for 10 hours, and then ground to obtain Al-gradient doped Li 1.2 Ti 0.4 Mn 0.4 O 2 Material.

[0077] Experimental example:

[0078] The materials prepared in Examples 1-5 and Comparative Examples 1-4 were used as positive electrode active materials. They were weighed with acetylene black (conductive agent) and PVDF (binder) in a mass ratio of 7:2:1, ground in a mortar for a period of time, and then N-methylpyrrolidone (NMP) was added after uniform mixing. The grinding was continued to obtain a uniform black viscous slurry. The prepared slurry was placed on aluminum foil and coated with a scraper to form a film of uniform thickness. Metal lithium was used as the counter electrode, a glass fiber membrane was used as the diaphragm, and 1 mol / L LiPF 6 / EC:DMC (1:1) was used as the electrolyte and CR2032 button cells were assembled in an argon atmosphere glove box.

[0079] The average discharge voltage of the first cycle and the average discharge voltage after 50 cycles of the materials of Examples 1-5 and Comparative Examples 1-4 under the condition of 10 mA / g are shown in Table 1:

[0080] Table 1 Initial capacity, first cycle and average discharge voltage after 50 cycles of different samples

[0081]

[0082] It can be clearly seen from Table 1 that the button cell prepared by using the positive electrode material described in the present application has a voltage retention rate of more than 90% after 50 cycles at a rate of 10 mA / g, while the button cell composed of the positive electrode materials of Comparative Examples 1, 3, and 4 has a voltage retention rate of less than 85%. Although the button cell composed of the positive electrode material of Comparative Example 2 has a voltage retention rate of 89.7%, its initial capacity has decreased significantly. The above results show that the positive electrode material described in the present application uses ionic additives to modify the lattice of the cationic disordered lithium-rich rock salt structure material, effectively inhibiting the migration of lattice oxygen and increasing the Mn 4+ / Mn 3+ The stability of the ions does not affect the initial capacity, and is significantly better than other solutions in alleviating material voltage decay.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A gradient doped modified cation disordered lithium-rich rock salt cathode material, It is characterized in that The invention comprises a cation disordered lithium-rich rock salt structure material and doping ions having a strong interaction with lattice oxygen, wherein the concentration of the doping ions in the cation disordered lithium-rich rock salt structure material particles gradually increases from the center to the surface; the doping ions include W 6+ , Nb 5+ 、V 5+ One or more of the following; the chemical formula of the cation disordered lithium-rich rock salt structure material is Li a Mn 0.4 M b O 2 , wherein M represents a transition metal, 1.1≤a≤1.3, b=(2.8-a) / m, and m is the valence of the transition metal M.

2. The positive electrode material according to claim 1, It is characterized in that The molar ratio of the cationic disordered lithium-rich rock salt structural material to the doping ions is 1:0.001-0.

05.

3. The method for preparing the positive electrode material according to claim 1, It is characterized in that include: According to the atomic ratio of the cationic disordered lithium-rich rock salt structure material chemical formula, a manganese source raw material, a transition metal source raw material and an excess lithium source raw material are weighed, wet-milled, and an ion additive containing doping ions and chloride as a grinding aid are added twice or more during the wet-milling process, and dried after the wet-milling is completed to obtain a precursor material; After the precursor material is calcined, the positive electrode material is obtained; the doping ions include W 6+ , Nb 5+ 、V 5+ One or more of the above, the cationic disordered lithium-rich rock salt structure material has a chemical formula of Li a Mn 0.4 M b O 2 , wherein M represents a transition metal, 1.1≤a≤1.3, b=(2.8-a) / m, and m is the valence of the transition metal M.

4. The preparation method according to claim 3, It is characterized in that The ionic additive includes WO 3 , Nb 2 O 5 、V 2 O 5 One or more of the following.

5. Use of the positive electrode material according to any one of claims 1 to 2 in the preparation of positive electrode sheets or lithium batteries.

6. A positive electrode sheet, It is characterized in that The invention comprises a current collector, a conductive agent, a binder and the positive electrode material according to any one of claims 1 to 2.

7. A lithium battery, It is characterized in that It comprises a negative electrode sheet, an electrolyte, a separator and the positive electrode sheet as claimed in claim 6.

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