Preparation method of high-voltage manganese-based lithium ion battery positive electrode material co-modified by lanthanum and tetraethyl orthosilicate

Abstract

The application discloses a preparation method of a high-voltage manganese-based lithium ion battery positive electrode material modified by lanthanum and tetraethyl silicate, and comprises the following steps: weighing the high-voltage manganese-based positive electrode material and a lanthanum-containing compound, dispersing them in a solvent and mixing them uniformly, heating and stirring the mixed solution until the solvent is completely volatilized to obtain a powder material, and then performing high-temperature calcination treatment on the powder material to form an inorganic oxide coating and obtain the lanthanum-modified high-voltage manganese-based positive electrode material; weighing the tetraethyl silicate, dispersing the tetraethyl silicate in a solvent and mixing them uniformly; weighing the lanthanum-modified high-voltage manganese-based positive electrode material, dispersing the material in the tetraethyl silicate solution and mixing them uniformly, heating and stirring the mixed solution, volatilizing the solvent, and forming a high-molecular polymer polysiloxane on the surface of the material by hydrolysis of the tetraethyl silicate, so that the high-voltage manganese-based lithium ion battery has improved coulomb efficiency and rate performance, and the capacity attenuation problem is relieved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery preparation technology, and relates to a method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate. Background Technology

[0002] The rapid advancement of automotive electrification and clean energy storage has led to an explosive growth in demand for lithium-ion batteries, a key new energy technology. However, current lithium-ion battery production heavily relies on scarce resources like nickel and cobalt, making the development of abundant and high-performance alternative cathode materials for lithium-ion batteries an inevitable choice. High-voltage spinel-type LiNi 0.5 Mn 1.5 O4 (LNMO) is a cathode material with great research and application prospects. Its theoretical capacity is 147 mAh / g, its theoretical energy density is 650 Wh / kg, and it has a high operating voltage of 4.7V. Its application in energy storage devices for electric vehicles, hybrid vehicles and other high-power devices is very promising. From an industrialization perspective, it has the following obvious advantages: (1) my country's manganese reserves are 133 times that of nickel and 2000 times that of cobalt, resulting in raw material prices that are only 7% and 1.4% of those of nickel and cobalt, respectively. (2) The volumetric energy density and mass energy density of LNMO are 1.7 and 1.2 times that of lithium iron phosphate (LFP), respectively, and the unit watt-hour cost is only 85% of that of LFP. (3) LNMO has a three-dimensional lithium-ion transport channel, which ensures that it still has high lithium-ion kinetics even at micron-sized grains.

[0003] However, the high operating voltage of LNMO inevitably leads to electrolyte oxidation and decomposition. This decomposition produces substances like hydrofluoric acid, which continuously corrode the surface of the cathode material, resulting in transition metal dissolution and surface structure distortion. Transition metals deposit on the anode surface, disrupting the electrolyte interface and causing a sharp increase in battery internal resistance and significant consumption of active lithium. Ultimately, this leads to problems such as capacity decay, low coulombic efficiency, and poor rate performance in high-voltage LNMO batteries, severely hindering their industrial application. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate. The method employs the synergistic modification of inorganic lanthanum compounds and organic compound tetraethyl silicate, thereby improving the coulombic efficiency and rate performance of the high-voltage manganese-based lithium-ion battery and alleviating the capacity decay problem.

[0005] The technical solution adopted in this invention is a method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate, comprising the following steps: Step 1: Weigh the high-voltage manganese-based cathode material and the lanthanum-containing compound, disperse them in a solvent and mix them evenly. The molar ratio of the high-voltage manganese-based cathode material to lanthanum atoms is 100: 0.1~1. Step 2: Heat and stir the well-mixed solution until the solvent evaporates completely to obtain powder material, then calcine it at high temperature to form an inorganic oxide coating, thus obtaining lanthanum-modified high-voltage manganese-based cathode material; Step 3: Weigh out tetraethyl silicate and disperse it in the solvent, then mix thoroughly. Step 4: Weigh out the lanthanum-modified high-voltage manganese-based cathode material and disperse it in the solution of step 3 and mix it evenly. The mass ratio of the lanthanum-modified high-voltage manganese-based cathode material to tetraethyl silicate is 100: 1~5. Step 5: Heat and stir the well-mixed solution to evaporate the solvent. The high molecular polymer polysiloxane formed by the hydrolysis of tetraethyl silicate completely coats the surface of the material, resulting in a high-voltage manganese-based cathode material modified by lanthanum and tetraethyl silicate.

[0006] Furthermore, in step 1, the dispersing solvent is deionized water or anhydrous ethanol.

[0007] Furthermore, in step 1, the high-voltage manganese-based cathode material and the lanthanum-containing compound are dispersed in a solvent and mixed evenly to obtain a homogeneous solution with a total concentration of 0.5~1 mol / L.

[0008] Furthermore, in step 1, the lanthanum-containing compound is at least one of lanthanum nitrate and lanthanum acetate.

[0009] Furthermore, in step 2, the heating temperature is 65~90℃, the stirring speed is 100~150 rpm, and the calcination is carried out at 500~800℃ for 1~3 hours.

[0010] Furthermore, in step 5, the heating temperature is 50~90℃ and the stirring speed is 100~300 rpm.

[0011] Furthermore, in step 1, the high-voltage manganese-based cathode material is a spinel-structured material, Li + It occupies a tetrahedral site.

[0012] Furthermore, in step 1, the preparation method of the high-voltage manganese-based cathode material is as follows: Step S1: Powder materials are prepared by co-precipitation of lithium-containing compounds, nickel-containing compounds, and manganese-containing compounds; Step S2: The obtained powder is subjected to multiple heating and calcination steps to obtain a high-voltage manganese-based cathode material.

[0013] Furthermore, in step S2, the heating and calcination are carried out in multiple steps: calcining at 400~500℃ for 2~5 hours, calcining at 700~1000℃ for 1~2 hours, and calcining at 600~800℃ for 8~12 hours in sequence.

[0014] Furthermore, in step 2, the inorganic oxide coating is LaTMO3, and TM is Ni and Mn.

[0015] The beneficial effects of this invention are: 1. By controlling the chemical composition of the high-voltage manganese-based material, an inorganic oxide LaTMO3 (TM=Ni,Mn) coating layer and a polymer polysiloxane coating layer are sequentially formed on the material surface. The inorganic oxide coating is firmly bonded to the high-voltage manganese-based cathode material through high-temperature calcination, while the polymer coating is formed by hydrolysis at low temperature without heating. Its flexible nature allows it to completely coat the surface of the high-voltage manganese-based cathode material.

[0016] 2. Modification with inorganic lanthanum compounds can form a single-atom-thick coating layer on the surface that integrates with the epitaxially grown grains, thereby introducing stronger La-O bonds, stabilizing lattice oxygen in the material, suppressing lattice distortion, and preventing its transformation from the cubic phase to the tetragonal phase, which would otherwise result in an unstable tetrahedral structure in the crystal. Secondly, it can avoid the Jahn-Teller distortion effect, stabilize the electrode material structure, increase three-dimensional channels, increase ionic conductivity, suppress the dissolution of transition metals, and enhance structural stability and safety.

[0017] 3. The organic compound tetraethyl silicate readily hydrolyzes to form polysiloxanes, which contain an ethyl functional group. This polysiloxane can suppress side reactions between high-voltage manganese-based cathode materials and the electrolyte, neutralize HF produced by the electrolyte, protect the electrode material, prevent the dissolution of transition metals, and improve Li... + The migration rate of lanthanum ions is increased, the potential difference at the interface layer is reduced, the interfacial impedance of the electrode electrolyte is lowered, and the material structure is stabilized. In addition, lanthanum ions have a large ionic radius and a high coordination number, which can form interfacial coordination with polysiloxanes, further improving the surface layer stability and thus improving the cycle life of the battery.

[0018] 4. It can effectively solve the problems of low coulombic efficiency in the first cycle, rapid capacity decay during cycling, and poor rate performance of high-voltage materials. By reducing the side reactions between the active material and the electrolyte, the interfacial impedance between the electrode and electrolyte is reduced, improving the initial capacity and capacity retention during cycling. By suppressing the formation of the cathode electrolyte interface (CEI), the stability of the special layered structure of the two-phase mixture of high-voltage materials during cycling is enhanced, reducing the release of lattice oxygen and the migration of transition metal cations, thereby improving both the initial coulombic efficiency and the rate performance and cycling stability. 5. Lanthanum and tetraethyl orthosilicate are introduced after the preparation of high-voltage manganese-based cathode materials. Compared with simple simultaneous introduction, the polysiloxane polymer formed by the hydrolysis of tetraethyl orthosilicate on the surface of high-voltage manganese-based cathode materials has good ductility and can spread on the surface of high-voltage manganese-based cathode materials, thereby achieving the effect of completely coating the high-voltage manganese-based cathode material particles and improving its coating coverage. This avoids the influence of modifying ions or their compounds on the formation and growth of cathode material grains, which is conducive to the formation of cathode materials with larger grain size and better crystallinity. 6. Compared with the common two-step calcination preparation method, this invention adds a pre-calcination process of heating at 700-1000℃ for 1-2 hours in the preparation of high-voltage manganese-based cathode materials. The two-step calcination preparation method consists of precursor synthesis (removing impurities such as carbon, nitrogen, and hydrogen from the material) and morphology control of the material. This invention, after synthesizing the precursor, adds a pre-calcination process, which can shape the material, control grain growth and size, and facilitate further control of its crystal phase composition and grain structure during subsequent calcination.

[0019] 7. High-voltage manganese-based cathode materials are composed of inexpensive transition metal elements such as nickel and manganese, resulting in lower raw material costs compared to cobalt-containing cathode materials. The preparation process is relatively simple, requiring less equipment and time. The resulting lithium-ion battery materials exhibit good practical performance and safety, making them suitable for large-scale industrialization.

[0020] 8. Assembling a lithium-ion battery (i.e., a half-cell) with metallic lithium as the negative electrode and the prepared material as the positive electrode can be used to test the specific capacity and impedance of the electrode materials, providing an objective reference value that reflects the superior electrochemical performance of the battery materials. Assembling a lithium-ion battery (i.e., a full cell) with commercial graphite material (mesophase carbon graphite microspheres) as the negative electrode and the prepared material as the positive electrode can be used to test the degree of matching between the materials and the rest of the battery (electrochemical and mechanical performance). Factors affecting battery capacity and performance, such as electrode thickness, excess material, and impedance, need to be considered, and this method better reflects the battery's performance in practical everyday applications. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a cycling curve of a lithium-ion battery (with metallic lithium as the negative electrode and the prepared material as the positive electrode) assembled from the high-voltage manganese-based positive electrode material prepared in Example 1 of the present invention at a current density of 735 mAh / g.

[0023] Figure 2 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 0.1% lanthanum in Example 2 of the present invention at a current density of 735 mAh / g.

[0024] Figure 3 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 3% tetraethyl silicate by mass in Example 3 of the present invention at a current density of 735 mAh / g.

[0025] Figure 4 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 0.1% lanthanum and 1% tetraethyl silicate in Example 4 of the present invention at a current density of 735 mAh / g.

[0026] Figure 5 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 0.5% lanthanum and 3% tetraethyl silicate in Example 5 of the present invention at a current density of 735 mAh / g.

[0027] Figure 6 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 1% lanthanum and 5% tetraethyl silicate in Example 6 of the present invention at a current density of 735 mAh / g.

[0028] Figure 7 This is a cycling curve of a lithium-ion battery (with lithium metal as the negative electrode and the prepared material as the positive electrode) assembled from a high-voltage manganese-based positive electrode material modified with 0.1% lanthanum and 1% tetraethyl silicate by a modified calcination process in Example 7 of the present invention, at a current density of 735 mAh / g.

[0029] Figure 8 This is a comparison graph of the cycling curves of lithium-ion batteries assembled from the materials prepared in Examples 1-4 of this invention (with metallic lithium as the negative electrode and the prepared materials as the positive electrode) at a current density of 735 mAh / g.

[0030] Figure 9This is a comparison graph of the cycling curves of lithium-ion batteries (with metallic lithium as the negative electrode and the prepared materials as the positive electrode) assembled from the materials prepared in Examples 1, 4 to 6 of this invention at a current density of 735 mAh / g.

[0031] Figure 10 This is a comparison graph of the cycling curves of lithium-ion batteries assembled from the materials prepared in Examples 4 and 7 of this invention (with metallic lithium as the negative electrode and the prepared materials as the positive electrode) at a current density of 735 mAh / g.

[0032] Figure 11 The graph shows the cycling curves of lithium-ion batteries assembled from the materials prepared in Examples 1-4 of this invention (using commercial graphite material as the negative electrode and the prepared material as the positive electrode) activated for 5 cycles at a current density of 29.4 mAh / g and then cycled at a current density of 294 mAh / g.

[0033] Figure 12 The graph shows a comparison of the cycling curves of lithium-ion batteries assembled from the materials prepared in Examples 1, 4-6 of this invention (using commercial graphite material as the negative electrode and the prepared material as the positive electrode), activated for 5 cycles at a current density of 29.4 mAh / g, and then cycled at a current density of 294 mAh / g.

[0034] Figure 13 The graph shows a comparison of the cycling curves of lithium-ion batteries assembled from the materials prepared in Examples 4 and 7 of this invention (using commercial graphite material as the negative electrode and the prepared material as the positive electrode) after activation for 5 cycles at a current density of 29.4 mAh / g and then cycling at a current density of 294 mAh / g. Detailed Implementation

[0035] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1, Preparation of chemical formula LiNi 0.5 Mn 1.5 The high-voltage manganese-based cathode material for O4 is prepared according to the following steps: Step S1: Weigh 10.712g of lithium acetate dihydrate, 12.442g of nickel acetate tetrahydrate, and 36.764g of manganese acetate tetrahydrate and dissolve them in 1000mL of deionized water to obtain a homogeneous solution A with a total concentration of 0.1mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then, dissolve 31.518g of oxalic acid dihydrate in 2500mL of ethanol to obtain a homogeneous solution B with a total concentration of 0.1mol / L. The ratio of the total amount of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Add solution A dropwise to solution B at a rate of 0.5mL per second, allowing the metal ions to precipitate with the oxalic acid and disperse uniformly in the solution. Heat and stir at 100℃ and 100 rpm until the ethanol and water are completely evaporated to obtain oxalate precipitate powder.

[0037] Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4 was used and named LNMO1. The calcination conditions were 400℃ for 2 hours, 700℃ for 1 hour, and 600℃ for 8 hours.

[0038] Example 2, The preparation of lanthanum-modified high-voltage manganese-based cathode materials is carried out according to the following steps: Step S1: Weigh 6.895g lithium nitrate, 29.079g nickel nitrate hexahydrate, and 25.101g manganese nitrate tetrahydrate and dissolve them in 100mL deionized water to obtain a homogeneous solution A with a total concentration of 1mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then dissolve 31.518g oxalic acid dihydrate in 250mL ethanol to obtain a homogeneous solution B with a total concentration of 1mol / L. The total molar ratio of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Heat and stir at 150℃ and 200 rpm until a powder material is formed.

[0039] Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4 was calcined at 450℃ for 3 hours, at 900℃ for 2 hours, and at 700℃ for 10 hours, respectively.

[0040] The modified high-voltage manganese-based lithium-ion battery cathode material was prepared by modification with 0.1% lanthanum (i.e., the molar ratio of high-voltage manganese-based cathode material to lanthanum atoms was 100:0.1), specifically according to the following steps: Step 1: Weigh 2g of high-voltage manganese-based cathode material LiNi0.5 Mn 1.5 O4 and 6.92 mg of lanthanum acetate were dispersed in 21.9 mL of anhydrous ethanol and mixed thoroughly to obtain a homogeneous solution with a concentration of 0.5 mol / L.

[0041] Step 2: Heat and stir at 70℃ and 200 rpm until dry to obtain a powder material. Then calcine it at 500℃ for 2 hours to obtain a lanthanum-modified high-voltage manganese-based cathode material, named LNMO2.

[0042] Example 3, The preparation of a high-voltage manganese-based cathode material modified with tetraethyl silicate is carried out according to the following steps: Step S1: Weigh 12.796g of lithium sulfate monohydrate, 52.57g of nickel sulfate hexahydrate, and 44.612g of manganese sulfate tetrahydrate and dissolve them in 100mL of deionized water to obtain a homogeneous solution A with a total concentration of 2mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then dissolve 63.035g of oxalic acid dihydrate in 250mL of ethanol to obtain a homogeneous solution B with a total concentration of 2mol / L. The total molar ratio of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Heat and stir at 200℃ and 300 rpm until a powder material is formed.

[0043] Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4 was calcined at 500℃ for 5 hours, at 1000℃ for 1 hour, and at 800℃ for 12 hours, respectively.

[0044] And using a mass fraction of 3% (i.e., the mass of tetraethyl silicate is the same as that of high-voltage manganese-based cathode material LiNi) 0.5 Mn 1.5 To prepare a high-voltage manganese-based lithium-ion battery cathode material, the following steps were performed: (3% of O4) Tetraethyl silicate was used for modification. Step 1: Measure 32µL of tetraethyl silicate and disperse it in 14.4mL of anhydrous ethanol, mix well to obtain a homogeneous solution with a concentration of 0.01mol / L; Step 2: Weigh 1g of high-voltage manganese-based cathode material and disperse it in the solution from Step 1, mixing thoroughly. Step 3: Heat and stir at 80℃ and 200 rpm until dry to obtain a high-voltage manganese-based lithium-ion battery cathode material modified with tetraethyl silicate, named LNMO3.

[0045] Example 4, The preparation of a high-voltage manganese-based cathode material co-modified with lanthanum and tetraethyl silicate is carried out according to the following steps: Step S1: Weigh 21.424g of lithium acetate dihydrate, 24.884g of nickel acetate tetrahydrate, and 73.527g of manganese acetate tetrahydrate and dissolve them in 100mL of deionized water to obtain a homogeneous solution A with a total concentration of 2mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then dissolve 63.035g of oxalic acid dihydrate in 500mL of ethanol to obtain a homogeneous solution B with a total concentration of 1mol / L. The total molar ratio of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Heat and stir at 140℃ and 100 rpm until a powder material is formed. Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4 was calcined at 450℃ for 3 hours, at 900℃ for 2 hours, and at 700℃ for 12 hours.

[0046] A high-voltage manganese-based lithium-ion battery cathode material was prepared by co-modification with 0.1% lanthanum and 1% tetraethyl silicate, specifically according to the following steps: Step 1: Weigh 2g of high-voltage manganese-based cathode material LiNi 0.5 Mn 1.5 O4 and 10 mg of lanthanum nitrate hexahydrate were dispersed in 11 mL of anhydrous ethanol and mixed evenly to obtain a homogeneous solution with a concentration of 1 mol / L. At this time, the metallic element lanthanum was distributed on the surface of the material in the form of ions. The molar ratio of high-voltage manganese-based cathode material to lanthanum atoms was 1000:1. Step 2: Heat and stir at 65℃ and 100 rpm until dry to evaporate the solvent and obtain powder material. Then calcine it at 700℃ for 1 hour to obtain lanthanum-modified high-voltage manganese-based cathode material.

[0047] Step 3: Measure 11 µL of tetraethyl silicate and disperse it in 24 mL of anhydrous ethanol, mix well to obtain a homogeneous solution with a concentration of 0.002 mol / L; Step 4: Weigh 1g of the lanthanum-modified high-voltage manganese-based cathode material prepared in Step 2 and disperse it in the solution in Step 3 and mix it evenly to obtain a uniform solution with a concentration of 0.23mol / L; the mass ratio of the lanthanum-modified high-voltage manganese-based cathode material to tetraethyl silicate is 100:1.

[0048] Step 5: Heat and stir at 80℃ and 100 rpm until dry, evaporate the solvent, and obtain a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate, named LNMO4.

[0049] Example 5, The preparation of a high-voltage manganese-based cathode material co-modified with lanthanum and tetraethyl silicate is carried out according to the following steps: Step S1: Weigh 3.448g of lithium nitrate, 14.5395g of nickel nitrate hexahydrate, and 12.5505g of manganese nitrate tetrahydrate and dissolve them in 500mL of deionized water to obtain a homogeneous solution A with a total concentration of 1mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then dissolve 15.759g of oxalic acid dihydrate in 250mL of ethanol to obtain a homogeneous solution B with a total concentration of 0.5mol / L. The total molar ratio of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Heat and stir at 160℃ and 150 rpm until a powder material is formed. Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4, calcined under the following conditions: calcined at 400℃ for 4 hours, calcined at 800℃ for 2 hours, and calcined at 800℃ for 8 hours.

[0050] The high-voltage manganese-based lithium-ion battery cathode material was prepared by co-modification with 0.5% lanthanum and 3% tetraethyl silicate, specifically according to the following steps: Step 1: Weigh 2g of high-voltage manganese-based cathode material LiNi 0.5 Mn 1.5 O4 and 50 mg of lanthanum nitrate hexahydrate were dispersed in 14.6 mL of anhydrous ethanol and mixed evenly to obtain a homogeneous solution with a concentration of 0.75 mol / L. The molar ratio of high-voltage manganese-based cathode material to lanthanum atoms was 1000:5. Step 2: Heat and stir at 90℃ and 150 rpm until dry to obtain powder material. Then calcine it at 500℃ for 1 hour to obtain lanthanum-modified high-voltage manganese-based cathode material.

[0051] Step 3: Measure 32µL of tetraethyl silicate and disperse it in 14.4mL of anhydrous ethanol, mix well to obtain a homogeneous solution with a concentration of 0.01mol / L; Step 4: Weigh 1g of the lanthanum-modified high-voltage manganese-based cathode material prepared in Step 2 and disperse it in the solution in Step 3. Mix it evenly to obtain a homogeneous solution with a concentration of 0.38mol / L. The mass ratio of the lanthanum-modified high-voltage manganese-based cathode material to tetraethyl silicate is 100:3.

[0052] Step 5: Heat and stir at 60℃ and 200 rpm until dry to obtain a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate, named LNMO5.

[0053] Example 6, The preparation of a high-voltage manganese-based cathode material co-modified with lanthanum and tetraethyl silicate is carried out according to the following steps: Step S1: Weigh 12.796g of lithium sulfate monohydrate, 52.57g of nickel sulfate hexahydrate, and 44.612g of manganese sulfate tetrahydrate and dissolve them in 200mL of deionized water to obtain a homogeneous solution A with a total concentration of 1mol / L, wherein the molar ratio of lithium, nickel, and manganese atoms is 2:1:3. Then dissolve 12.607g of oxalic acid dihydrate in 100mL of ethanol to obtain a homogeneous solution B with a total concentration of 1mol / L. The total molar ratio of lithium, nickel, and manganese atoms to oxalic acid is 120:101. Heat and stir at 120℃ and 150 rpm until a powder material is formed.

[0054] Step S2: Calcine the obtained powder material to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4, calcined at 400℃ for 2 hours, at 800℃ for 1 hour, and at 600℃ for 8 hours.

[0055] A high-voltage manganese-based lithium-ion battery cathode material was prepared by co-modification with 1% lanthanum and 5% tetraethyl silicate, specifically according to the following steps: Step 1: Weigh 1g of high-voltage manganese-based cathode material LiNi 0.5 Mn 1.5 O4 and 50 mg of lanthanum nitrate hexahydrate were dispersed in 10.9 mL of anhydrous ethanol and mixed evenly to obtain a homogeneous solution with a concentration of 0.5 mol / L. The molar ratio of high-voltage manganese-based cathode material to lanthanum atoms was 100:1. Step 2: Heat and stir at 90℃ and 150 rpm until dry to obtain powder material. Then calcine it at 800℃ for 3 hours to obtain lanthanum-modified high-voltage manganese-based cathode material.

[0056] Step 3: Measure 108µL of tetraethyl silicate and disperse it in 16mL of anhydrous ethanol, mix well to obtain a homogeneous solution with a concentration of 0.03mol / L; Step 4: Weigh 2g of the lanthanum-modified high-voltage manganese-based cathode material prepared in Step 2 and disperse it in the solution in Step 3. Mix it evenly to obtain a homogeneous solution with a concentration of 0.68mol / L. The mass ratio of the lanthanum-modified high-voltage manganese-based cathode material to tetraethyl silicate is 100:5.

[0057] Step 5: Heat and stir at 90℃ and 100 rpm until dry to obtain a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate, named LNMO6.

[0058] Example 7, The preparation of a high-voltage manganese-based cathode material co-modified with lanthanum and tetraethyl silicate is as follows: Step S2 only: The obtained powder material is calcined to obtain the high-voltage manganese-based cathode material LiNi. 0.5 Mn 1.5 O4 was used, and the calcination conditions were 450°C for 3 hours and 700°C for 12 hours. The remaining steps were the same as in Example 4, and a high-voltage manganese-based lithium-ion battery cathode material modified with lanthanum and tetraethyl silicate was obtained, named LNMO7.

[0059] The electrochemical cycling performance of Examples 1-7, such as Figures 1-7 As shown; a concentrated comparison of the electrochemical cycling performance of Examples 1-4, as follows. Figure 8 As shown, when the high-voltage manganese-based cathode material is modified with 0.1% lanthanum and 3% tetraethyl silicate, respectively, its discharge specific capacity and initial coulombic efficiency are significantly improved compared with the unmodified material. When the high-voltage manganese-based cathode material is modified with 0.1% lanthanum and 1% tetraethyl silicate, its cycle stability and capacity retention are significantly improved.

[0060] A concentrated comparison of the electrochemical cycling performance in Examples 1 and 4-6, such as... Figure 9 As shown, the performance of high-voltage manganese-based cathode materials varies when modified with different amounts of lanthanum and tetraethyl silicate, but all are superior to the unmodified high-voltage manganese-based cathode materials. Among them, the product obtained by co-modifying the high-voltage manganese-based cathode material with 0.1% lanthanum and 1% tetraethyl silicate exhibits the best electrochemical performance.

[0061] A concentrated comparison of the electrochemical cycling performance of Examples 4 and 7, such as... Figure 10As shown, the high-voltage manganese-based cathode material prepared by three-step calcination has significantly improved cycle stability and capacity retention, indicating that adding the pre-calcination process can indeed improve the physicochemical properties of the material.

[0062] From electrochemical cycle performance Figure 8 , 9 As can be seen from the data, Example 4 shows a significant improvement in specific capacity and cycle stability compared to Examples 2 and 3, which can increase the battery's capacity and lifespan. Simultaneously, the unique solid-liquid dual-layer coating of the material can stabilize the material's structure, suppress the Jahn-Teller distortion effect and material decomposition, ensuring battery safety and preventing spontaneous combustion, explosion, and other issues. However, Examples 5 and 6 show no significant improvement in electrochemical performance compared to Examples 2 and 3. This is because the modification ratio is too high, resulting in an excessively thick coating, which affects surface kinetics, hindering charge transfer and even causing segregation on the material surface, forming electrochemically inert oxides.

[0063] Figures 11-13 This is a comparison chart of the electrochemical cycle performance of lithium-ion batteries assembled using commercial graphite materials as the negative electrode and the materials prepared in Examples 1-7 as the positive electrode. The results reflected are more relevant to actual applications. Figures 11-13 In the study, modifying the calcination process and modifying with lanthanum and tetraethyl silicate both improved the discharge specific capacity, initial coulombic efficiency, and cycle stability of the high-voltage manganese-based cathode material. The product obtained by co-modifying the high-voltage manganese-based cathode material prepared by three-step calcination with 0.1% lanthanum and 1% tetraethyl silicate exhibited the best electrochemical performance. The first five cycles show cycle data at a discharge specific capacity of 29.4 mAh / g current density, while the data from the sixth cycle onwards shows cycle data at a discharge specific capacity of 294 mAh / g current density.

[0064] In this embodiment of the invention, the mass of the high-voltage manganese-based cathode material and the lanthanum-containing compound is determined by the amount of lanthanum atoms in both materials. The molar ratio of the high-voltage manganese-based cathode material to lanthanum atoms is limited to determine the modification ratio of lanthanum on the high-voltage manganese-based cathode material. The concentration of the mixed solution is limited to ensure that the high-voltage manganese-based cathode material and lanthanum nitrate hexahydrate are completely dissolved in the solution and mixed uniformly.

[0065] In addition to the co-precipitation method described in Example 1, the high-voltage manganese-based cathode material in this invention can be prepared using other methods. The molecular formula of the high-voltage manganese-based cathode material is LiNi. 0.5 Mn 1.5 O4 is a spinel-structured material, Li +Occupying tetrahedral sites, the spinel-structured high-voltage manganese-based cathode material is more stable than layered lithium-rich manganese-based cathode materials. High-voltage manganese-based cathode materials possess a three-dimensional network crystal structure, exhibiting extremely high thermodynamic stability even in a fully delithiated state, reducing the possibility of thermal runaway. Simultaneously, the three-dimensional lithium-ion transport channels within the crystal structure enable high lithium-ion kinetics at the micron-scale grain size, resulting in excellent electrochemical performance over long cycles. The high-voltage manganese-based cathode material operates at a voltage as high as 4.7V, with a theoretical specific capacity of 147 mAh / g over long cycles. Furthermore, the cycle stability and capacity retention of the high-voltage manganese-based cathode material are significantly superior to those of lithium-rich manganese-based cathode materials. Especially in long cycles, the capacity of lithium-rich manganese-based cathode materials drops drastically to 0 mAh / g after 200 cycles, while the capacity of the high-voltage manganese-based cathode material remains nearly 80 mAh / g after 1000 cycles.

[0066] The coating formed between the inorganic oxide coating LaTMO3 (TM=Ni and Mn) and the high-voltage manganese-based cathode material through the solid-solid interface is uneven, making it difficult to completely coat the high-voltage manganese-based cathode material.

[0067] This invention employs two substances—an inorganic lanthanum compound and an organic compound tetraethyl silicate—to form a two-layer coating on the surface of a high-voltage manganese-based cathode material: an inorganic oxide LaTMO3 (TM = Ni and Mn) and a polymeric polysiloxane. The inorganic oxide coating is firmly bonded to the high-voltage manganese-based cathode material through high-temperature calcination, while the polymeric coating is formed through low-temperature hydrolysis without heating. Its flexible nature allows it to spread out well and completely coat the surface of the high-voltage manganese-based cathode material. The two layers are bonded together through the solid-liquid interface, preserving the advantages of each while maintaining the original structure of the high-voltage manganese-based material. The inorganic oxide layer and the high-voltage manganese-based material are bonded together by strong La-O bonds, forming a stable phase and maintaining structural stability. The inorganic coating has a granular structure, increasing the material's roughness and strengthening its adhesion to organic coatings. This also improves the structural and cycle stability of the high-voltage manganese-based cathode material. The polysiloxane polymer formed by the hydrolysis of tetraethyl silicate on the surface of the high-voltage manganese-based cathode material has good ductility and can spread across the surface, achieving complete coating of the high-voltage manganese-based cathode material particles and improving its coverage. The combination of rigidity and flexibility between inorganic oxides and polymers effectively suppresses the release of lattice oxygen, increases ionic conductivity, inhibits the dissolution of transition metals, reduces the interfacial potential difference, lowers the interfacial impedance of the electrode and electrolyte, and stabilizes the material structure. This improves both the capacity and cycle stability of the high-voltage manganese-based cathode material.

[0068] Lithium-ion batteries assembled with lithium metal as the negative electrode and the prepared material as the positive electrode (i.e., half-cells) can be used to test the specific capacity and impedance of the electrode materials, providing an objective reference value, and focusing on the study of the electrochemical performance of the battery materials. Lithium-ion batteries assembled with commercial graphite materials (mesophase carbon graphite microspheres) as the negative electrode and the prepared material as the positive electrode (i.e., full-cells) can be used to test the matching degree between the materials and the rest of the battery (electrochemical and mechanical properties). However, factors such as electrode thickness, excess material, and impedance, which affect battery capacity and performance, need to be considered, and this focuses on the study of battery manufacturing processes.

[0069] The existing technology 1 (CN 115353155 A, Preparation method of low-cobalt lithium-rich manganese-based cathode material) uses a sol-gel method, which has several problems: First, the metal alkoxides and organic solvents used in the raw materials are expensive and pose certain health risks; second, the entire sol-gel process takes a long time, often several days or weeks; third, the gel contains a large number of micropores, which will release a lot of gases and organic matter during the drying process, and cause shrinkage. In contrast, the co-precipitation method used in this invention uses inexpensive and pollution-free raw materials. It also allows for precise control of the content of each component, achieving uniform mixing at the molecular / atomic level. During the precipitation process, the purity, particle size, dispersibility, and phase composition of the resulting powder can be controlled by adjusting the precipitation conditions and the subsequent calcination regime of the precipitate. Furthermore, the sample has a low calcination temperature, stable performance, and good reproducibility. In the existing technology 1 (CN 115353155 A), lanthanum modification is achieved by forming a coating on the material surface through a solid-solid interface. The coating formed through the solid-solid interface is uneven and difficult to completely cover the material itself. In the process of preparing the material, phosphorus-containing compounds, lanthanum-containing compounds, and low-cobalt lithium-rich manganese-based cathode materials are simultaneously dispersed in a solvent. The resulting inorganic oxide coating will have complex components such as LaTMO3 (TM=Ni, Mn, Co) and lanthanum phosphorus compounds. It is not possible to take into account the effects of various materials at the same time, and it is difficult to improve the performance by coating with a flexible polysiloxane polymer layer.

[0070] The thickness and roughness of the inorganic oxide coating, as well as the coating thickness and uniformity of the polymer polyoxysilane coating, are related to the calcination process, the amount of lanthanum-containing compound and tetraethyl silicate, and the stirring temperature and rate during preparation. In the calcination process, increasing the calcination temperature can increase the particle size and coating roughness; performing multiple stages of calcination can control the size and morphology of the material. Changing the amount of lanthanum-containing compound and tetraethyl silicate can control the coating thickness. Too little amount cannot achieve complete coating of the material and thus stabilize its structure; too much amount results in an excessively thick coating, affecting its surface kinetics, thus hindering charge transfer, and even causing segregation on the material surface, forming electrochemically inert oxides. Changing the stirring temperature and rate during preparation ensures that the lanthanum-containing compound and tetraethyl silicate are fully and uniformly mixed with the main material, guaranteeing the uniformity of the coating formation.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate, characterized in that, Includes the following steps: Step 1: Weigh the high-voltage manganese-based cathode material and the lanthanum-containing compound, disperse them in a solvent and mix them evenly. The molar ratio of the high-voltage manganese-based cathode material to lanthanum atoms is 100: 0.1~1. Step 2: Heat and stir the well-mixed solution until the solvent evaporates completely to obtain powder material, then calcine it at high temperature to form an inorganic oxide coating, thus obtaining lanthanum-modified high-voltage manganese-based cathode material; Step 3: Weigh out tetraethyl silicate and disperse it in the solvent, then mix thoroughly. Step 4: Weigh out the lanthanum-modified high-voltage manganese-based cathode material and disperse it in the solution of step 3 and mix it evenly. The mass ratio of the lanthanum-modified high-voltage manganese-based cathode material to tetraethyl silicate is 100: 1~5. Step 5: Heat and stir the well-mixed solution to evaporate the solvent. The high molecular polymer polysiloxane formed by the hydrolysis of tetraethyl silicate completely coats the surface of the material, resulting in a high-voltage manganese-based cathode material modified by lanthanum and tetraethyl silicate.

2. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 1, the dispersing solvent is deionized water or anhydrous ethanol.

3. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 1, the high-voltage manganese-based cathode material and the lanthanum-containing compound are dispersed in a solvent and mixed evenly to obtain a homogeneous solution with a total concentration of 0.5~1 mol / L.

4. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 1, the lanthanum-containing compound is at least one of lanthanum nitrate and lanthanum acetate.

5. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 2, the heating temperature is 65~90℃, the stirring speed is 100~150 rpm, and the calcination is carried out at 500~800℃ for 1~3 hours.

6. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 5, the heating temperature is 50~90℃ and the stirring speed is 100~300 rpm.

7. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 1, the high-voltage manganese-based cathode material is a spinel structure material, Li + It occupies a tetrahedral site.

8. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 1, the preparation method of the high-voltage manganese-based cathode material is as follows: Step S1: Powder materials are prepared by co-precipitation of lithium-containing compounds, nickel-containing compounds, and manganese-containing compounds; Step S2: The obtained powder is subjected to multiple heating and calcination steps to obtain a high-voltage manganese-based cathode material.

9. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 8, characterized in that, In step S2, the heating and calcination are carried out in multiple steps: calcining at 400~500℃ for 2~5 hours, calcining at 700~1000℃ for 1~2 hours, and calcining at 600~800℃ for 8~12 hours in sequence.

10. The method for preparing a high-voltage manganese-based lithium-ion battery cathode material co-modified with lanthanum and tetraethyl silicate according to claim 1, characterized in that, In step 2, the inorganic oxide coating is LaTMO3, and TM is Ni and Mn.

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