Phosphorus-containing tellurium-containing lithium-rich manganese-based positive electrode material and preparation method and application thereof

Abstract

The invention discloses a phosphorus-containing tellurium-containing lithium-rich manganese-based positive electrode material as well as a preparation method and application thereof. The chemical formula of the phosphorus-containing tellurium-containing lithium-rich manganese-based positive electrode material is Li < 1 + delta > MnaNibCocTexPyO2, wherein delta is more than or equal to 0 and less than or equal to 0.2, a is more than or equal to 0.4 and less than or equal to 0.6, b is more than or equal to 0.1 and less than or equal to 0.2, c is more than or equal to 0.1 and less than or equal to 0.2, and 1lt is 0; x is less than or equal to 0.01, 0lt; y < = 0.05, and 4a + 2b + 3c + 6x + 5y = 3-delta. The lithium-rich manganese-based positive electrode material is spherical secondary particles and is prepared by a method of high-temperature solid-phase sintering after carbonate / hydroxide coprecipitation, a Li3PO4 fast ion conductor is introduced to the surfaces of the lithium-rich manganese-based positive electrode primary particles, interface reaction and lattice oxygen release are inhibited, the lattice stabilization effect brought by Te < 6 + > is cooperated, and the lithium-rich manganese-based positive electrode material is obtained. And synchronous improvement of energy density, rate capability and cycling stability is realized. The phosphorus-containing tellurium-containing lithium-rich manganese-based positive electrode material is applied to a lithium ion battery, has high energy density and excellent rate capability and cycling stability, and is easy for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and in particular to a phosphorus-containing, tellurium-containing, lithium-rich manganese-based positive electrode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used in 3C digital products due to their advantages such as long cycle life, high energy density, high safety and low cost. They are currently the preferred energy storage device for promoting the electrification of transportation. Further improvements in their energy density and cycle life will also provide possibilities for their application in renewable energy storage such as wind and light. Therefore, the development of high-capacity lithium-ion battery technology will provide an important driving force for the green transformation of energy supply and energy consumption. Lithium-ion batteries usually include positive electrodes, negative electrodes, separators, and electrolytes. Compared with high-specific-capacity negative electrode materials, positive electrode materials are the main factor limiting the specific capacity and energy density of the battery system. Traditional positive electrode materials commonly used in lithium-ion batteries, such as LiCoO2, LiMn2O4, LiFePO4, and LiNi x Co y Mn 1-x-y O2、LiNi x Co y Al 1-x-y O2, etc., their theoretical specific capacity is lower than 200mAh / g, and their energy density is lower than 800Wh / kg, which makes it difficult to meet the requirements of power battery specific capacity and energy density.

[0003] Unlike the single-electron redox reaction that occurs in traditional positive electrode materials, lithium-rich manganese-based positive electrode materials (i.e., xLi2MnO3·(1-x)LiMO2, M=Mn,Ni,Co) can achieve a specific capacity exceeding 250mAh / g and a high energy density of nearly 1000Wh / kg due to the anion redox brought about by the Li-O-Li configuration, and have great application potential in energy storage batteries. However, the redox of lattice oxygen is often accompanied by the irreversible release of lattice oxygen, the irreversible migration of transition metal ions, and the continuous spinel phase transition, which leads to severe capacity decay and voltage decay. In addition, due to the poor conductivity of the Li2MnO3 component itself, the rate performance of the lithium-rich positive electrode is also poor. In order to promote the commercialization of lithium-rich manganese-based positive electrodes and give full play to their advantages of high specific capacity and high energy density, it is necessary to explore a lithium-rich manganese-based positive electrode material with good rate performance and strong cycling stability.

[0004] Methods to improve the cycle stability of lithium-rich manganese-based positive electrodes mainly include surface modification and bulk doping. Surface modification is limited to the surface of particles. Common surface coatings are often oxides, phosphates, fluorides, etc. that are not electrochemically active. While inhibiting the side reactions on the electrode surface and the spinel phase transition on the surface, it will lead to a loss of specific capacity. Moreover, it does not change the structure and composition of the electrode particles, and is not conducive to the improvement of rate performance. For example, Zhang et al. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 surface coated with Mg2TiO4, the cycle capacity at 0.1C decreased from about 290mAh / g to about 270mAh / g, and the capacity retention rate at 2C increased, but the specific capacity was only about 160mAh / g (Adv.Mater.2020,32,2000496). In contrast, bulk doping provides more structural possibilities. Part of the metal ions in the transition metal layer of the lithium-rich manganese-based positive electrode are replaced by Te 6+ , can be achieved with the help of TeO 6- The stronger Te-O bond in the octahedron stabilizes the lattice O, inhibits irreversible anion redox, and at the same time expands the interplanar spacing of the Li layer and improves the ionic conductivity. For example, Meng et al. synthesized a Li 1.2 [Mn 0.56 Ni 0.16 Co 0.08 ] 1-x Te x The positive electrode material of O2 (x = 0.05) has a discharge capacity of 271.6 mAh / g (2.5-4.6 V) at 0.1C and a discharge capacity of 191.2 mAh / g (2.5-4.6 V) at 0.5C. The capacity retention rate after 100 cycles is 84.3%, which is improved compared with the original sample (J. Electrochem. Soc. 2017, 164 (12), A2594-A2602). However, too high Te content will greatly reduce the theoretical specific capacity of the positive electrode, but fail to fully demonstrate the Te content in the lattice. 6+ Furthermore, a single Te 6+ Doping will inhibit grain growth, which helps to improve rate performance, but the increase in interface side reactions caused by the reduction in particle size will have a negative impact on cycle stability. 6+ In order to overcome the role of lithium-rich manganese-based cathode materials with good rate performance and strong cycle stability, it is still a problem to be broken through. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a phosphorus- and tellurium-containing lithium-rich manganese-based cathode material with high energy density, good rate performance, and strong cycling stability. By introducing Li3PO4 fast ion conductor on the surface of the primary particles of the lithium-rich manganese-based cathode, the interfacial reaction and the release of lattice oxygen are inhibited, and the lattice stabilization effect brought by Te is synergistically utilized to simultaneously improve the energy density, rate performance, and cycling stability. 6+ The lattice stabilization effect brought by Te is utilized to simultaneously improve the energy density, rate performance, and cycling stability.

[0006] Another objective of the present invention is to provide a preparation method for the above-mentioned cathode material.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A phosphorus- and tellurium-containing lithium-rich manganese-based cathode material, with the chemical formula Li 1+δ Mn a Ni b Co c Te x P y O2, where 0 ≤ δ ≤ 0.2, 0.4 ≤ a ≤ 0.6, 0.1 ≤ b ≤ 0.2, 0.1 ≤ c ≤ 0.2, 0 < x ≤ 0.01, 0 < y ≤ 0.05, and 4a + 2b + 3c + 6x + 5y = 3 - δ; the lithium-rich manganese-based cathode material is spherical secondary particles, Te is distributed in the primary particle matrix phase, and P exists in the form of Li3PO4 in the surface layer of the primary particles.

[0009] Preferably, 0.165 ≤ δ < 0.176, 0.512 ≤ a < 0.529, 0.127 < b ≤ 0.142, 0.126 ≤ c ≤ 0.128, 0 < x ≤ 0.00772, 0.01 ≤ y ≤ 0.02; the lithium-rich manganese-based cathode material is spherical secondary particles with a particle size within 5 - 10 microns.

[0010] The above-mentioned lithium-rich manganese-based cathode material is prepared by the method of high-temperature solid-phase sintering after carbonate / hydroxide coprecipitation. The specific preparation method includes the following steps:

[0011] 1) Prepare a spherical carbonate / hydroxide precursor material with uniform distribution of P and Te by the method of liquid-phase coprecipitation.

[0012] According to the chemical formula Li 1+δ Mn a Ni b Co c Te x P yAccording to the stoichiometric ratio shown in FIG02, a compound containing Mn, Ni, and Co elements and telluric acid (when the tellurium source includes telluric acid) are first prepared into a solution of a certain concentration, which is recorded as solution A; a tellurium source other than telluric acid (if telluric acid is used as the tellurium source, telluric acid is added to solution A), a phosphorus source, a carbonate / hydroxide precipitant, and a complexing agent are prepared into a mixed solution, which is recorded as solution B; the above-mentioned solution A and solution B are respectively added dropwise to the reactor at a certain drop rate, and the mixture is continuously stirred under controlled temperature, pH and suitable atmosphere (operate in air when a carbonate precipitant is used, and operate in an inert atmosphere such as argon when a hydroxide precipitant is used) to obtain a precipitate through reaction. The precipitate is washed and dried to obtain a phosphorus- and tellurium-containing precursor material.

[0013] Preferably, in the solution A, the compound containing the Mn element as a manganese source can be selected from one or more manganese salts such as MnSO4, Mn(CH3COO)2, and Mn(NO3)2; the compound containing the Ni element as a nickel source can be selected from one or more nickel salts such as NiSO4, Ni(CH3COO)2, and Ni(NO3)2; the compound containing the Co element as a cobalt source can be selected from one or more cobalt salts such as CoSO4, Co(CH3COO)2, and Co(NO3)2; and the compound containing the Te element as a tellurium source can be selected from one or more compounds such as telluric acid (H6TeO6), sodium tellurate (Na6TeO6), and sodium tellurite (NaTeO3). The total concentration of transition metal elements in the solution A is 1 to 5 mol / L.

[0014] In the solution B, the compound serving as a phosphorus source contains pyrophosphate, which can be selected from one or more of sodium pyrophosphate (Na4P2O7), potassium pyrophosphate (K4P2O7), sodium acid pyrophosphate (Na2H2P2O7), potassium acid pyrophosphate (K2H2P2O7), etc.; the precipitant is a carbonate and / or hydroxide, which can be selected from one or more of NaOH, NaHCO3, Na2CO3, KOH, KHCO3, K2CO3, etc., and the total concentration of the precipitant is 2 to 10 mol / L; the complexing agent can be selected from ammonia water or oxalic acid, and its concentration is 0 to 1 mol / L.

[0015] Preferably, the dropwise addition rate of solution A and solution B is set to 10-50 mL / h, the reaction is completed in 30-50 h, the pH is set to 6-8, and the temperature is set to 50-60° C. After the reaction is completed, the precipitate is washed several times with deionized water and then dried in a forced air drying oven at 100° C. for 12-20 h.

[0016] 2) After the carbonate / hydroxide precursor material and the lithium source are uniformly mixed, they are sintered at high temperature in air or an oxidizing atmosphere.

[0017] Preferably, the lithium source can be selected from one or more of Li2CO3, LiOH, lithium acetate, lithium oxalate, and lithium nitrate, and the excess is 0-5%. The precursor material and the lithium source are ground evenly in a mortar, and the temperature is raised to 200-600°C at a rate of 1-5°C / min. After pre-sintering for 2-6 hours, the temperature is raised to 700-900°C at a rate of 1-5°C / min, and the sintering is continued for 10-20 hours.

[0018] The third object of the present invention is to provide a lithium-ion battery comprising the above-mentioned phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is made of the above-mentioned phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) By doping Te 6+ Regulate the nucleation rate, limit the growth of primary particles in the cathode material, and shorten the Li + Diffusion path, while TeO 6- The octahedron widens the interplanar spacing of the Li layer, improves the ionic conductivity, and thus improves the rate performance; using Te 6+ The strong chemical bond between the material and the lattice oxygen inhibits the bonding and irreversible release of lattice oxygen, improving the lattice stability and thus achieving better cycle stability. At the same time, the incorporation of pyrophosphate in the precursor forms a fast ion conductor Li3PO4 on the surface of the primary particles, which is beneficial to the rapid deintercalation of lithium ions during charge and discharge, and acts as a protective layer to inhibit the occurrence of side reactions at the electrode-electrolyte interface. As a result, the modified lithium-rich manganese-based cathode material has high energy density while also having excellent rate performance and cycle stability. This phosphorus- and tellurium-containing lithium-rich manganese-based cathode material has a discharge capacity of 308.91mAh / g at a current density of 20mA / g, and a discharge capacity of 250.67mAh / g in the 2-4.6V voltage window at a current density of 200mA / g. The capacity retention rate after 200 cycles is 97.7%, and it still has a capacity of 234.21mAh / g after the cycle ends.

[0021] 2) By co-precipitating tellurates, pyrophosphates, and carbonates / hydroxides, the problem of uneven element distribution caused by excessive nucleation rate of a single component is avoided, ensuring uniform distribution of the doping elements.

[0022] 3) The preparation of this phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material by co-precipitation meets the requirements of commercial production and is easy to produce on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the phosphorus-containing, tellurium-containing, lithium-rich manganese-based positive electrode material prepared based on Example 1.

[0024] Figure 2 This is the XRD result of the phosphorus-containing, tellurium-containing, lithium-rich manganese-based positive electrode material prepared based on Example 1.

[0025] Figure 3 These are the charge and discharge curves of the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material prepared based on Example 1 and the original lithium-rich manganese-based positive electrode material prepared based on Comparative Example 1.

[0026] Figure 4 This is a comparison chart of the rate performance of the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material prepared based on Example 1 and the original lithium-rich manganese-based positive electrode material prepared based on Comparative Example 1.

[0027] Figure 5 This is a comparison chart of the cycle performance of the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material prepared based on Example 1 and the original lithium-rich manganese-based positive electrode material prepared based on Comparative Example 1.

[0028] Figure 6 This is a comparison chart of the cycle performance of the tellurium-containing lithium-rich manganese-based positive electrode material prepared based on Comparative Example 2 and the original lithium-rich manganese-based positive electrode material prepared based on Comparative Example 1. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the examples, but is not limited thereto. Any modification or equivalent substitution of the technical solution of the present invention, without departing from the spirit and scope of the technical solution of the present invention, should be covered by the protection of the present invention. Experimental methods for which specific conditions are not specified in the examples are generally carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise defined, all professional and scientific terms used have the same meanings as those familiar to those skilled in the art.

[0030] In all examples, the electrochemical performance of the prepared positive electrode materials was tested by assembling button batteries. The button batteries used were 2032 type, which were assembled from a battery case, a positive electrode, a negative electrode, a separator, an electrolyte, a gasket, and a spring. The specific battery preparation and assembly process is as follows:

[0031] 1) Preparation of positive electrode sheet: Weigh 80 mg of positive electrode material, 10 mg of conductive agent (Super P), and 10 mg of binder (PVDF) in a mass ratio of 80:10:10, add an appropriate amount of NMP as a solvent to the powder, and mix evenly in a homogenizer. Use a scraper to apply the mixed slurry on aluminum foil to form a film, place it in a blast drying oven, and dry it at 100 ° C for 2-6 hours to remove NMP. Then, cut the dried aluminum foil coated with the slurry into discs with a diameter of 14 mm, weigh them, put them in a vacuum drying oven, and dry them at 110 ° C overnight. Finally, transfer them to a glove box with a water and oxygen content of less than 0.1 ppm.

[0032] 2) Assembly of button cells: The positive electrode is the electrode prepared in step 1), the negative electrode is a lithium sheet, the brand and model of the separator is Celgard2400, and the high-voltage electrolyte is purchased from Dongguan Shanshan Battery Materials Co., Ltd., with a ratio of 1M LiPF6 dissolved in a solvent of EC:DEC=3:7, and 5% FEC as an additive.

[0033] Example 1

[0034] Phosphorus-containing and tellurium-containing lithium-rich manganese-based positive electrode material Li 1.17 Mn 0.517 Ni 0.136 Co 0.128 Te 0.0039 P 0.0158 The specific steps for the preparation of O2 are as follows:

[0035] 1) According to the stoichiometric ratios in the chemical formula, 220.37 g of manganese sulfate tetrahydrate, 90.18 g of nickel sulfate hexahydrate, 90.96 g of cobalt sulfate heptahydrate, and 2.25 g of telluric acid were weighed and dissolved in 1 L of deionized water to prepare Solution A with a total ion concentration of 2 mol / L. 207.74 g of sodium carbonate and 5.32 g of sodium pyrophosphate were weighed and dissolved in 1 L of deionized water to prepare Solution B with a total ion concentration of 2 mol / L. 15 mL of industrial ammonia was added to Solution B as a complexing agent. Solution B was dripped into a continuously stirred reactor at a rate of 30 mL / h. The drip rate of Solution A was controlled to maintain a constant pH of 7.7 during the reaction. The reaction temperature was controlled at 55°C, and the reactor was stirred at 2100 rpm. After the reaction, the stirring speed was adjusted to 1200 rpm and the mixture was aged for 14 hours. After washing the precipitate in the reactor six times by suction filtration, the pink precipitate was placed in a forced air drying oven and dried at 100° C. for 12 h.

[0036] 2) Take 1.5 g of the dried precursor powder, grind it with 0.71 g of lithium carbonate in a mortar according to the stoichiometric ratio in the chemical formula, mix well and place it in a tube furnace. Under an air atmosphere, heat it to 500 ° C at 5 ° C / min and keep it at this temperature for 5 h to complete pre-sintering; heat it to 850 ° C at 5 ° C / min and keep it at this temperature for 12 h to complete sintering; finally, cool it to room temperature with the furnace to obtain the target product.

[0037] The prepared phosphorus-containing and tellurium-containing lithium-rich manganese-based positive electrode material Li 1.17 Mn 0.517 Ni 0.136 Co 0.128 Te 0.0039 P 0.0158 The scanning electron microscope image of O2 is as follows Figure 1As shown in Figure 2, the particle size distribution is uniform and the sphericity is high. From the XRD results, we can see the diffraction peak of the surface Li3PO4 layer, such as Figure 2 As shown, the existence of the fast ion conductor surface layer is proved.

[0038] The phosphorus-containing and tellurium-containing lithium-rich manganese-based cathode material Li 1.17 Mn 0.517 Ni 0.136 Co 0.128 Te 0.0039 P 0.0158 O2 was assembled into button cells for low rate charge and discharge test. Under constant temperature of 30℃, the cells were activated by 0.1C (20mA / g) and 2-4.5V charge and discharge (such as Figure 3 In Example 1, after 2-4.5V), the capacity measured at 0.1C (20mA / g) is 308.91mAh / g, and its charge-discharge curve is as follows Figure 3 As shown in Example 1 2-4.8V, it shows a very high capacity.

[0039] The phosphorus-containing and tellurium-containing lithium-rich manganese-based cathode material Li 1.17 Mn 0.517 Ni 0.136 Co 0.128 Te 0.0039 P 0.0158 O2 was assembled into button cells for rate performance testing. At a constant temperature of 30°C, after activation by 0.1C (20mA / g) 2-4.5V charge and discharge, five charge and discharge cycles were performed at 0.2C, 0.5C, 1C, 2C, and 5C, respectively. The discharge capacities in the first cycle were 294.05mAh / g, 273.22mAh / g, 250.67mAh / g, 221.47mAh / g, and 163.69mAh / g, respectively. Figure 4 As shown in Example 1, good rate performance is exhibited.

[0040] The phosphorus-containing and tellurium-containing lithium-rich manganese-based cathode material Li 1.17 Mn 0.517 Ni 0.136 Co 0.128 Te 0.0039 P 0.0158 O2 was assembled into a button cell for cycle performance testing. Under constant temperature conditions of 30°C, after activation by one cycle at 0.1C 2-4.5V / 2-4.8V and ten cycles at 1C 2-4.8V, it was cycled for 200 cycles at 1C 2-4.8V. The capacity retention rate was 97.7%, and the discharge capacity at the 200th cycle was still 234.21mAh / g. Figure 5 As shown in Example 1.

[0041] Comparative Example 1

[0042] Original lithium-rich manganese-based cathode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The preparation of O2 differs from that of Example 1 in that P and Te are not doped. The specific steps are as follows:

[0043] 1) According to the stoichiometric ratios in the chemical formula, 228.14 g of manganese sulfate tetrahydrate, 85.43 g of nickel sulfate hexahydrate, and 91.29 g of cobalt sulfate heptahydrate were weighed and dissolved in 1 L of deionized water to prepare Solution A with a total ion concentration of 2 mol / L. 211.98 g of sodium carbonate was weighed and dissolved in 1 L of deionized water to prepare Solution B with a total ion concentration of 2 mol / L. 15 mL of industrial ammonia was added to Solution B as a complexing agent. Solution B was dripped into a continuously stirred reactor at a rate of 30 mL / h. The drip rate of Solution A was controlled to maintain a constant pH of 7.7 during the reaction. The reaction temperature was controlled at 55°C, and the reactor stirring speed was 2100 rpm. After the reaction, the stirring speed was adjusted to 1200 rpm and the mixture was aged for 14 hours. The precipitate in the reactor was washed six times by suction filtration, and the pink precipitate was dried in a forced air drying oven at 100°C for 12 hours.

[0044] 2) Take 1.5g of the dried precursor powder, grind it with 0.715g of lithium carbonate in a mortar according to the stoichiometric ratio in the chemical formula, mix well and place it in a tube furnace. Under an air atmosphere, heat it to 500°C at 5°C / min and keep it at that temperature for 5 hours to complete pre-sintering; heat it to 850°C at 5°C / min and keep it at that temperature for 12 hours to complete sintering; finally, cool it to room temperature with the furnace to obtain the target product.

[0045] The original lithium-rich manganese-based cathode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 was assembled into a button cell for low rate charge and discharge test. At a constant temperature of 30℃, after activation by 0.1C (20mA / g) 2-4.5V charge and discharge, the capacity measured at 0.1C (20mA / g) was 294.54mAh / g. The charge and discharge curve is shown in the figure. Figure 3 Compared with the original sample, the phosphorus- and tellurium-containing lithium-rich manganese-based cathode material obtained in Example 1 exhibits more reversible cation redox and anion redox, thereby obtaining a higher capacity.

[0046] The original lithium-rich manganese-based cathode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13O2 was assembled into button cells for rate performance testing. At a constant temperature of 30°C, after activation by 0.1C (20mA / g) 2-4.5V charge and discharge, five charge and discharge cycles were performed at 0.2C, 0.5C, 1C, 2C, and 5C, respectively. The discharge capacities in the first cycle were 268.22mAh / g, 231.47mAh / g, 201.99mAh / g, 165.66mAh / g, and 119.08mAh / g, respectively. Figure 4 As shown in Comparative Example 1. Compared with the original sample, the rate performance of the phosphorus-containing, tellurium-containing, lithium-rich manganese-based positive electrode material obtained in Example 1 is significantly improved.

[0047] The original lithium-rich manganese-based cathode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 was assembled into a button cell for cycle performance testing. Under constant temperature conditions of 30°C, after activation by one cycle at 0.1C 2-4.5V / 2-4.8V and ten cycles at 1C 2-4.8V, it was cycled at 1C 2-4.8V for 200 cycles. The capacity retention rate was 82.2%, and the discharge capacity at the 200th cycle was only 197.75mAh / g. Figure 5 As shown in Comparative Example 1. Compared with the original sample, the phosphorus-containing, tellurium-containing, lithium-rich manganese-based positive electrode material obtained in Example 1 has obvious improvements in capacity and cycle stability.

[0048] Comparative Example 2

[0049] Tellurium-containing lithium-rich manganese-based cathode material Li 1.18 Mn 0.512 Ni 0.151 Co 0.15 Te 0.003 The preparation of O2 differs from that of Example 1 in that only Te is doped without P. The specific steps are as follows:

[0050] 1) According to the stoichiometric ratios in the chemical formula, 220.37 g of manganese sulfate tetrahydrate, 90.18 g of nickel sulfate hexahydrate, 90.96 g of cobalt sulfate heptahydrate, and 2.25 g of telluric acid were weighed and dissolved in 1 L of deionized water to prepare Solution A with a total ion concentration of 2 mol / L. 211.98 g of sodium carbonate were weighed and dissolved in 1 L of deionized water to prepare Solution B with a total ion concentration of 2 mol / L. 15 mL of industrial ammonia was added to Solution B as a complexing agent. Solution B was dripped into a continuously stirred reactor at a rate of 30 mL / h. The drip rate of Solution A was controlled to maintain a constant pH of 7.7 during the reaction. The reaction temperature was controlled at 55°C, and the reactor was stirred at 2100 rpm. After the reaction, the stirring speed was adjusted to 1200 rpm and the mixture was aged for 14 hours. After washing the precipitate in the reactor six times by suction filtration, the pink precipitate was placed in a forced air drying oven and dried at 100° C. for 12 h.

[0051] 2) Take 1.5g of the dried precursor powder, grind it with 0.705g of lithium carbonate in a mortar according to the stoichiometric ratio in the chemical formula, mix well and place it in a tube furnace. Under an air atmosphere, heat it to 500℃ at 5℃ / min and keep it at that temperature for 5h to complete pre-sintering; heat it to 850℃ at 5℃ / min and keep it at that temperature for 12h to complete sintering; finally, cool it to room temperature with the furnace to obtain the target product.

[0052] Tellurium-containing lithium-rich manganese-based cathode material Li 1.18 Mn 0.512 Ni 0.151 Co 0.15 Te 0.003 O2 was assembled into a button cell for cycle performance testing. Under constant temperature conditions of 30°C, after activation by one cycle at 0.1C 2-4.5V / 2-4.8V and ten cycles at 1C 2-4.8V, it was cycled at 1C 2-4.8V for 200 cycles. The capacity retention rate was 94.6%, and the discharge capacity at the 200th cycle was 233.11mAh / g. Figure 5 As shown in Comparative Example 2. Obviously, the introduction of Te element alone can also improve the rate performance and cycle performance, but the effect is slightly worse than that of Example 1. The phosphorus- and tellurium-containing cathode material in Example 1 is further modified with Li3PO4 on the surface to bring out the greater performance potential of the lithium-rich manganese-based cathode.

Claims

1. A lithium-rich manganese-based cathode material containing phosphorus and tellurium, with the chemical formula Li 1+δ Mn a Ni b Co c Te x P y O2, where 0 ≤ δ ≤ 0.2, 0.4 ≤ a ≤ 0.6, 0.1 ≤ b ≤ 0.2, 0.1 ≤ c ≤ 0.2, 0 < x ≤ 0.01, 0 < y ≤ 0.05, and 4a + 2b + 3c + 6x + 5y = 3 - δ; the lithium-rich manganese-based cathode material is spherical secondary particles, Te is distributed in the primary particle matrix phase, and P exists in the form of Li3PO4 on the surface layer of the primary particles.

2. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that 0.165≤δ<0.176,0.512≤a<0.529,0.127 <b≤0.142,0.126≤c≤0.128,0<x≤0.00772,0.01≤y≤0.02。 3. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The particle size of the lithium-rich manganese-based positive electrode material is 5 to 10 microns.

4. The method for preparing the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material according to any one of claims 1 to 3, comprising the following steps: 1) Liquid phase co-precipitation preparation of precursor materials: According to the chemical formula Li 1+δ Mn a Ni b Co c Te x P y A manganese source, a nickel source, and a cobalt source are prepared into a solution of a certain concentration in the stoichiometric ratio shown in O2, which is recorded as solution A. When the tellurium source includes telluric acid, telluric acid is added to solution A; a tellurium source other than telluric acid, a phosphorus source, a precipitant, and a complexing agent are prepared into a mixed solution, which is recorded as solution B, wherein the phosphorus source is pyrophosphate and the precipitant is carbonate and / or hydroxide; solution A and solution B are added dropwise to a reactor, and stirred continuously under conditions of controlling the temperature at 50-60°C and the pH at 6-8 to obtain a precipitate through reaction, and the precipitate is washed and dried to obtain a precursor material; 2) High-temperature solid-phase sintering: After the precursor material and the lithium source solid phase are evenly mixed, they are sintered at high temperature in air or an oxidizing atmosphere to obtain the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material.

5. The preparation method according to claim 4, wherein In solution A of step 1), the manganese source is selected from one or more of MnSO4, Mn(CH3COO)2, and Mn(NO3)2; the nickel source is selected from one or more of NiSO4, Ni(CH3COO)2, and Ni(NO3)2; the cobalt source is selected from one or more of CoSO4, Co(CH3COO)2, and Co(NO3)2; the tellurium source is selected from one or more of H6TeO6, Na6TeO6, and NaTeO3; the phosphorus source is selected from one or more of Na4P2O7, K4P2O7, Na2H2P2O7, and K2H2P2O7; and the total concentration of solution A in terms of transition metal elements is 1 to 5 mol / L.

6. The preparation method according to claim 4, wherein In solution B of step 1), the precipitant is selected from one or more of NaOH, NaHCO3, Na2CO3, KOH, KHCO3, and K2CO3, and the total concentration of the precipitant is 2 to 10 mol / L; the complexing agent is ammonia water or oxalic acid, and the concentration is 0 to 1 mol / L.

7. The preparation method according to claim 4, wherein In step 1), the dropwise addition rate of solution A and solution B is set to 10 to 50 mL / h, and the reaction is completed in 30 to 50 hours. When carbonate is used as a precipitant, the reaction is carried out in an air atmosphere, and when hydroxide is used as a precipitant, the reaction is carried out in an inert atmosphere.

8. The preparation method according to claim 4, wherein The lithium source in step 2) is selected from one or more of Li2CO3, LiOH, lithium acetate, lithium oxalate, and lithium nitrate.

9. The preparation method according to claim 4, wherein In step 2), the precursor material and the lithium source are ground uniformly, first heated to 200-600° C. for pre-sintering, and then heated to 700-900° C. for sintering.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The positive electrode is made of the phosphorus- and tellurium-containing lithium-rich manganese-based positive electrode material according to any one of claims 1 to 3.

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