Lithium-rich manganese-based material containing ferroelectric heterojunction coating as well as preparation method and application of lithium-rich manganese-based material

Abstract

The invention provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating as well as a preparation method and application, the lithium-rich manganese-based material comprises a lithium-rich manganese-based matrix and the ferroelectric heterojunction coating, the chemical general formula of the lithium-rich manganese-based matrix is LixMnaNibCo1-a-bO2, 1 < = x < = 1.5, 0.55 < = a < = 0.8, and 0.1 < = b < = 0.2; the ferroelectric heterojunction coating comprises an M1-cNcTO3 material, 0.05 < = c < = 0.2, M, N and T are selected from any one or a combination of at least two of Mg, Fe, Mo, Pb, Y, Ru, Sn, W, Nb, Ti, Ce, V, Al, La, Cr or Bi, and M, N and T are selected from different metal elements. The lithium ion transmission kinetics is enhanced by utilizing the spontaneous polarization and piezoelectric effect of the coating, the compatibility of the coating and a matrix interface is optimized, the lattice oxygen loss and transition metal dissolution are inhibited, and the performance of the material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries are currently the mainstream energy storage technology, and the performance of their cathode materials directly affects the battery's energy density and cycle life. Lithium-rich manganese-based cathode materials (LMR, with the general formula xLi2MnO3·(1-x)LiMO2) have attracted much attention due to their high specific capacity (>250mAh / g) and low cost. However, they suffer from issues such as irreversible lattice oxygen loss, transition metal dissolution, and structural phase transitions, which can lead to poor battery cycling stability and severe voltage decay. In existing technologies, methods such as doping and coating are commonly used to improve the performance of lithium-rich manganese-based cathode materials.

[0003] For example, CN117594783A discloses a layered composite lithium-rich manganese-based cathode material, its preparation method, and application. Through modification, a single-crystal lithium-rich manganese-based cathode material coated with an oxygen ion conductor is obtained, exhibiting good particle dispersion and significantly improved electrochemical performance. However, under high voltage conditions, the use of a non-metallic ion conductor coating is prone to damage or loose bonding, and the oxygen ions in the cathode material may react adversely with the solvent in the electrolyte or the anode material.

[0004] Although applying a protective layer on the surface of lithium-rich manganese-based materials can isolate the active material from the electrolyte, inhibit the precipitation of lattice oxygen and Mn dissolution, and effectively improve the initial coulombic efficiency and cycle stability of lithium-ion batteries, under high voltage conditions, the coating is prone to damage, excessive thickness or unevenness, and insufficient conductivity, which leads to limited lithium ion transport kinetics and affects the battery's rate performance.

[0005] Based on the above research, the optimization of the high-voltage system of lithium-rich manganese-based materials has not yet achieved ideal results. The bonding between the coatings is not tight or the thickness is improperly controlled, and it is still difficult to effectively inhibit HF corrosion and side reactions of the electrolyte. Summary of the Invention

[0006] The purpose of the present invention is to provide a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, a preparation method and an application. The lithium-rich manganese-based material is coated with a ferroelectric heterojunction coating, and the spontaneous polarization and piezoelectric effect of the coating are utilized to enhance the lithium ion transfer kinetics. The compatibility of the coating with the interface of the lithium-rich manganese-based substrate is also optimized, lattice oxygen loss and transition metal dissolution are suppressed, structural stability is improved, and the cycle life and rate performance of the lithium-rich manganese-based material are improved.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, wherein the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate, wherein the chemical formula of the lithium-rich manganese-based substrate is Li x Mn a Ni b Co 1-a-b O2, where 1≤x≤1.5, 0.55≤a≤0.8, 0.1≤b≤0.2;

[0009] The ferroelectric heterojunction coating includes M 1-c N c TO3 material, wherein 0.05≤c≤0.2, M, N and T are independently selected from any one or a combination of at least two of Mg, Fe, Mo, Pb, Ba, Sr, Hf, Pt, Zr, Cu, Ge, Y, Ru, Sn, W, Nb, Ti, Ce, V, Al, La, Cr or Bi, and M, N and T are selected from different metal elements.

[0010] The present invention adopts heterojunction interface design, wherein the ferroelectric heterojunction coating is coated with a lithium-rich manganese-based substrate, and the M 1-c N c In TO3 materials, N ions and M ions partially replace the transition metal layer, which increases the M 1-c N c The room temperature ferroelectricity of TO3 material, and the coating forms a chemically bonded interface with the lithium-rich manganese-based substrate, which inhibits the crack propagation caused by cyclic stress and promotes the migration of lithium ions. Therefore, the ferroelectric heterojunction coating provided by the present invention enhances the lithium ion transfer kinetics through spontaneous polarization and piezoelectric effect, optimizes the interface compatibility between the coating and the substrate, and improves the cycle life and rate performance of the battery.

[0011] The general chemical formula of the lithium-rich manganese-based matrix is ​​Li x Mn a Ni b Co 1-a-b O2, wherein 1≤x≤1.5, for example, it can be 1, 1.1, 1.2, 1.3, 1.4 or 1.5, 0.55≤a≤0.8, for example, it can be 0.55, 0.6, 0.7, or 0.8, 0.1≤b≤0.2, for example, it can be 0.1, 0.15 or 0.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] The ferroelectric heterojunction coating includes M 1-c N cTO3 material, wherein 0.05≤c≤0.2, for example, it can be 0.05, 0.1, 0.15 or 0.2, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] The M of the present invention 1-c N c TO3 material is a doped material, in which N is a doped metal ion such as doped Y 3+ If the doped N ions are too few, the oxygen vacancies will be reduced, which will hinder the conduction of lithium ions. If the doped N ions are too many, the material structure stability will decrease and the energy storage capacity will be reduced.

[0014] Preferably, the M is selected from any one or a combination of at least two of Pb, Ba, Sr, Bi, La, Hf, Pt or Nb, the N is selected from any one or a combination of at least two of Y, Mg, Sn, W, Ce, V or Cr, and the T is selected from any one or a combination of at least two of Ti, Zr, Fe, Ru, Mo, Ge, Cu or Al.

[0015] Preferably, the M 1-c N c TO3 materials include Pb 1-c Y c TiO3 material.

[0016] M of the present invention 1-c N c The preferred material for TO3 is Pb 1-c Y c Compared with materials composed of other metal ions, TiO3 materials can improve the structural stability and cycle life of the materials.

[0017] Preferably, the ferroelectric heterojunction coating comprises a first coating located on the surface of the lithium-rich manganese-based substrate, and a second coating on the surface of the first coating, wherein the first coating comprises a porous M 1-c N c TO3 coating, the second coating includes dense M 1-c N c TO3 coating.

[0018] The ferroelectric heterojunction coating of the present invention is preferably a porous layer and a dense layer, wherein the porous layer is conducive to the insertion and removal of lithium ions while playing the role of a ferroelectric heterojunction coating, and the dense layer can effectively protect the base material and prevent the dissolution of manganese ions while playing the role of a ferroelectric heterojunction coating.

[0019] Preferably, the mass ratio of the first coating layer to the second coating layer is 1:(0.5-2), for example, it can be 1:0.5, 1:1, 1:1.5 or 1:2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] The mass ratio of the first coating layer to the second coating layer of the present invention will affect the performance of the ferroelectric heterojunction coating layer, which is beneficial to improving the comprehensive performance of the lithium-rich manganese-based material.

[0021] Preferably, in the lithium-manganese-rich based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 0.5-10wt%, for example, it can be 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3-10wt%.

[0022] In the lithium-rich manganese-based material of the present invention, if the content of the ferroelectric heterojunction coating is too little, the role of the ferroelectric heterojunction coating cannot be effectively exerted. If the content of the ferroelectric heterojunction coating is too much, an excessively thick interface layer will be formed, which will hinder the Li + diffusion.

[0023] Preferably, the particle size D50 of the lithium-rich manganese-based matrix is ​​3-10 μm, for example, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the thickness of the ferroelectric heterojunction coating is 100-500 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm or 500 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] In a second aspect, the present invention provides a method for preparing the lithium-rich manganese-based material containing the ferroelectric heterojunction coating according to the first aspect, the preparation method comprising the following steps:

[0026] The lithium-rich manganese-based matrix and M 1-c N c The TO3 materials are mixed and calcined to obtain the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0027] Preferably, the lithium-rich manganese-based matrix and M 1-c N c The mixing and calcination of TO3 materials include the following steps:

[0028] According to the formula, lithium-rich manganese-based matrix, M 1-cN c After the TO3 material, pore-forming agent and deionized water are mixed, dried and ground, they are calcined once to obtain a burnt material;

[0029] According to the formula, the burning material, M 1-c N c The TO3 material and deionized water are mixed, dried, and ground, and then calcined twice to obtain the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0030] The present invention prepares porous M in the presence of a pore-forming agent. 1-c N c TO3 coating, dense M was prepared in the absence of pore forming agent 1-c N c TO3 coating.

[0031] Preferably, the pore former comprises ammonium carbonate and / or ammonium bicarbonate.

[0032] Preferably, the amount of the pore-forming agent added is 1-c N c 15-35wt% of TO3 material can be, for example, 15wt%, 20wt%, 25wt%, 30wt% or 35wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the primary calcination temperature is 700-900°C, for example, 700°C, 800°C or 900°C, and the time is 3-12h, for example, 3h, 5h, 7h, 9h, 11h or 12h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the secondary calcination temperature is 700-900°C, for example, 700°C, 800°C or 900°C, and the time is 3-12h, for example, 3h, 5h, 7h, 9h, 11h or 12h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] The invention ensures that the coating is uniform and closely combined with the lithium-rich manganese-based substrate through multi-step calcination.

[0036] Preferably, the lithium-rich manganese-based matrix, M 1-c N c TO3 material, pore forming agent and deionized water are mixed, and the first burning material, M 1-c N cThe mixing time of TO3 material and deionized water is 20-120 minutes, for example, 20 minutes, 50 minutes, 100 minutes or 120 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the atmospheres of the primary calcination and the secondary calcination respectively and independently include any one of nitrogen, oxygen, air or hydrogen, or a combination of at least two of them.

[0038] Preferably, the method for preparing the lithium-rich manganese-based matrix comprises the following steps:

[0039] The lithium-rich manganese-based precursor and the lithium source are mixed and sintered to obtain the lithium-rich manganese-based matrix.

[0040] Preferably, the sintering atmosphere includes any one of nitrogen, oxygen, air or hydrogen, or a combination of at least two of them.

[0041] Preferably, the sintering includes first sintering at 400-550°C, for example, 400°C, 450°C, 500°C or 550°C, for 2-9.5h, for example, 2h, 4h, 6h, 8h or 9.5h, and then heating to 800-1050°C, for example, 800°C, 900°C, 1000°C or 1050°C, for 12-24h, for example, 12h, 15h, 20h or 24h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the lithium source includes any one of lithium hydroxide, lithium carbonate, lithium sulfate or lithium nitrate, or a combination of at least two thereof.

[0043] Preferably, the molar ratio of lithium ions in the lithium source to the total metal ions in the lithium-rich manganese-based precursor is (1-1.5):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the method for preparing the lithium-rich manganese-based precursor comprises the following steps:

[0045] The nickel salt solution, manganese salt solution, cobalt salt solution, precipitant solution and complexing agent solution are subjected to coprecipitation reaction, aging, filtering, washing, drying and sieving to obtain the lithium-rich manganese-based precursor.

[0046] Preferably, the concentrations of the nickel salt solution, manganese salt solution and cobalt salt solution are independently 30-100 g / L, for example, 30 g / L, 50 g / L, 70 g / L, 80 g / L or 100 g / L, and the feed flow rates are independently 5-15 L / h, for example, 5 L / h, 10 L / h or 15 L / h, but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the metal salts in the nickel salt solution, the manganese salt solution and the cobalt salt solution independently include any one of nitrate, chloride, sulfate or acetate, or a combination of at least two of them.

[0048] Preferably, the concentration of the precipitant solution is 20-40 wt%, for example, 20 wt%, 30 wt% or 40 wt%, and the feed flow rate is 2-4 L / h, for example, 2 L / h, 3 L / h or 4 L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the precipitant solution comprises any one of sodium hydroxide, ammonium bicarbonate, sodium carbonate or ammonium oxalate, or a combination of at least two thereof.

[0050] Preferably, the concentration of the complexing agent solution is 5-20wt%, for example, 5wt%, 10wt%, 15wt% or 20wt%, and the feed flow rate is 0.1-1.0L / h, for example, 0.1L / h, 0.3L / h, 0.5L / h, 0.7L / h, 0.9L / h or 1.0L / h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Preferably, the complexing agent solution comprises any one of citric acid, ethylenediaminetetraacetic acid, ammonia water or ammonium chloride, or a combination of at least two thereof.

[0052] Preferably, the temperature of the coprecipitation reaction is 40-68°C, for example, 40°C, 50°C, 60°C or 68°C, the pH is 9-11.5, for example, 9, 10, 11 or 11.5, and the total alkali concentration is 10-20 g / L, for example, 10 g / L, 15 g / L or 20 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] Preferably, the rotation speed of the coprecipitation reaction is 100-350 r / min, for example, 100 r / min, 200 r / min, 300 r / min or 350 r / min, and the time is 40-160 h, for example, 40 h, 100 h or 160, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the aging temperature is 40-70°C, for example, 40°C, 50°C, 60°C or 70°C, and the aging time is 2-10h, for example, 2h, 4h, 6h, 8h or 10h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, the washing comprises sequentially performing alkaline washing and water washing, wherein the alkaline washing is performed with sodium hydroxide solution for 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times, and then washed with hot water for 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the drying temperature is 100-200°C, for example, 100°C, 150°C or 200°C, and the drying time is 10-36h, for example, 10h, 20h, 30h or 36h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] Preferably, the preparation of the M 1-c N c The TO3 material method includes the following steps:

[0058] The mixed salt solution, citric acid and ethylene glycol are mixed and heated to form a gel, and the gel is dried and then heat-treated to obtain the M 1-c N c TO3 material;

[0059] The mixed salt solution includes formulated amounts of M ions, N ions and T ions.

[0060] The M salt, N salt and T salt in the mixed salt solution are selected from any one of nitrate, chloride, sulfate or acetate, or a combination of at least two thereof.

[0061] Preferably, the total metal ion concentration of the mixed salt solution is 0.2-1.0 g / L, for example, 0.2 g / L, 0.4 g / L, 0.6 g / L, 0.8 g / L or 1.0 g / L, but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] Preferably, the heating temperature is 50-80°C, for example, 50°C, 60°C, 70°C or 80°C, and the heating time is 10-60min, for example, 10min, 30min, 50min or 60min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] Preferably, the heat treatment temperature is 500-700°C, for example, 500°C, 600°C or 700°C, the time is 1-5h, for example, 1h, 2h, 3h, 4h or 5h, and the atmosphere includes any one of air, nitrogen, hydrogen or oxygen or a combination of at least two of them.

[0064] Preferably, the M 1-c N c The average particle size of the TO3 material is 10-50 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0065] In a third aspect, the present invention provides a lithium-ion battery, comprising the lithium-rich manganese-based material containing the ferroelectric heterojunction coating as described in the first aspect.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) The ferroelectric heterojunction coating provided by the present invention can enhance the lithium ion transport kinetics through spontaneous polarization and piezoelectric effect, optimize the interface compatibility between the coating and the substrate, and improve the cycle life and rate performance of the battery.

[0068] (2) The lithium-rich manganese-based material containing a ferroelectric heterojunction coating described in the present invention comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating. The coating material can effectively block the lithium-rich manganese-based substrate from contacting the electrolyte, thereby avoiding the dissolution of Mn and reducing the occurrence of side reactions when the reaction material contacts the electrolyte. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0070] Example 1

[0071] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, wherein the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate. The chemical formula of the lithium-rich manganese-based substrate is Li 1.3 Mn 0.75 Ni 0.17 Co 0.08 O2, ferroelectric heterojunction coating including Pb 0.85 Y 0.15 TiO3;

[0072] In the lithium-rich manganese-based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 5 wt %; the particle size D50 of the lithium-rich manganese-based matrix is ​​8.5 μm; and the thickness of the ferroelectric heterojunction coating is 400 nm;

[0073] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises the following steps:

[0074] (1) Prepare high-purity manganese chloride (MnCl2·4H2O), nickel chloride (NiCl2·6H2O) and cobalt chloride (CoCl2·6H2O) as raw materials, accurately weigh manganese chloride, nickel chloride and cobalt chloride in turn, and mix them according to the set molar ratio n(CoCl2·6H2O). 2+ ):n(Ni 2+ ):n(Mn 2+ )=0.75:0.17:0.08 for weighing;

[0075] Under constant temperature and stirring conditions, the three chloride salts were gradually added to an appropriate amount of deionized water to prepare a manganese chloride solution, a nickel chloride solution, and a cobalt chloride solution with a concentration of 50 g / L, respectively;

[0076] Sodium carbonate is selected as the precipitant, and the sodium carbonate is prepared into a sodium carbonate solution with a mass fraction of 30%;

[0077] The complexing agent is ammonia water, which is prepared into an ammonia solution with a mass fraction of 13%;

[0078] The reactor was started and preheated to stabilize the reactor temperature at 62°C. The reactor was filled with nitrogen and kept sealed. The stirring system was turned on and the reactor speed was set to 300 rpm to ensure uniform mixing of the reaction system and prevent agglomeration or uneven growth of the precipitated particles. The following five solutions were simultaneously pumped into the reactor at the set feed flow rates: manganese chloride solution, nickel chloride solution, cobalt chloride solution, ammonium carbonate solution, and ammonia solution. The feed flow rates were set to 8.5 L / h, 8.5 L / h, 8.5 L / h, 3 L / h, and 0.75 L / h, respectively.

[0079] During the entire coprecipitation reaction process, the pH value of the reaction solution was monitored in real time by an online pH monitoring system and maintained in the range of 10.9-11.2. The total alkali concentration was strictly controlled at 14.0-15.0 g / L. The reaction lasted for 95 hours. During this period, a laser particle size analyzer was used to monitor the particle size distribution in real time. The reaction was immediately stopped after the D50 of the lithium-rich manganese-based precursor particles reached 8.0 μm.

[0080] (2) The lithium-rich manganese-based precursor particles obtained in step (1) are aged for 5.5 hours at a temperature of 60°C. After aging, they are washed with alkali and water, washed with a liquid alkali solution for 3 times, and then washed with hot water for 5 times, dried at 160°C for 18 hours, and sieved to remove iron. The lithium-rich manganese-based precursor powder is evenly mixed with lithium carbonate in a molar ratio of lithium content to transition metal of 1.3:1, and sintered in an air atmosphere using a two-step heating strategy. First, the precursor particles are heated to 475°C and maintained for 4.5 hours, and then the temperature is continuously raised to 920°C and kept constant for 16 hours to obtain a lithium-rich manganese-based matrix.

[0081] (3) Lead nitrate, yttrium nitrate, and titanium nitrate were accurately weighed in a molar ratio of Pb:Y:Ti=0.85:0.15:1, dissolved in ethanol, and prepared into a mixed solution with a concentration of 0.5 g / L. 50 mL of ethylene glycol and 10 mL of citric acid were added, stirred for 30 min, and heated in a water bath at 65°C to form a gel. Subsequently, the dried gel was placed in an atmosphere furnace and calcined at 600°C for 2 h while passing flowing air to obtain Pb 2+ with an average particle size of 25 nm. 0.85 Y 0.15 TiO3 powder.

[0082] (4) According to the formula, the lithium-rich manganese-based matrix of step (2) and the Pb 0.85 Y 0.15 The TiO3 powder was mixed and dispersed in deionized water, and ultrasonically treated for 60 minutes. The uniformly mixed material was then placed in an atmosphere furnace and calcined at a high temperature of 800°C for 12 hours while flowing air to promote the solid-phase diffusion of the metal elements, thereby obtaining the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0083] Example 2

[0084] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, wherein the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate. The chemical formula of the lithium-rich manganese-based substrate is Li 1.3 Mn 0.8 Ni 0.1 Co 0.1 O2, ferroelectric heterojunction coating including Pb 0.8 Y 0.2 TiO3;

[0085] In the lithium-rich manganese-based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 10 wt %; the particle size D50 of the lithium-rich manganese-based matrix is ​​10 μm; and the thickness of the ferroelectric heterojunction coating is 100 nm;

[0086] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises the following steps:

[0087] (1) Prepare high-purity manganese chloride (MnCl2·4H2O), nickel chloride (NiCl2·6H2O) and cobalt chloride (CoCl2·6H2O) as raw materials, accurately weigh manganese chloride, nickel chloride and cobalt chloride in turn, and mix them according to the set molar ratio n(CoCl2·6H2O). 2+ ):n(Ni 2+ ):n(Mn 2+ )=0.8:0.1:0.1 for weighing;

[0088] Under constant temperature and stirring conditions, the three chloride salts were gradually added to an appropriate amount of deionized water to prepare a manganese chloride solution, a nickel chloride solution, and a cobalt chloride solution with a concentration of 100 g / L, respectively;

[0089] Sodium carbonate is selected as the precipitant, and the sodium carbonate is prepared into a sodium carbonate solution with a mass fraction of 40%;

[0090] The complexing agent is ammonia water, which is prepared into an ammonia solution with a mass fraction of 20%;

[0091] The reactor was started and preheated to stabilize the reactor temperature at 45°C. The reactor was filled with nitrogen and kept sealed. The stirring system was turned on and the reactor speed was set to 350 rpm to ensure uniform mixing of the reaction system and prevent agglomeration or uneven growth of precipitated particles. The following five solutions were simultaneously pumped into the reactor at the set feed flow rates: manganese chloride solution, nickel chloride solution, cobalt chloride solution, ammonium carbonate solution, and ammonia solution. The feed flow rates were set to 5 L / h, 5 L / h, 5 L / h, 4 L / h, and 1 L / h, respectively.

[0092] During the entire co-precipitation reaction process, the pH value of the reaction solution was monitored in real time by an online pH monitoring system and maintained in the range of 11.2-11.5. The total alkali concentration was strictly controlled at 18-20 g / L. The reaction lasted for 160 hours. During this period, a laser particle size analyzer was used to monitor the particle size distribution in real time. The reaction was immediately stopped after the D50 of the lithium-rich manganese-based precursor particles reached 9.5 μm.

[0093] (2) The lithium-rich manganese-based precursor particles obtained in step (1) are aged for 10 hours at a temperature of 40°C. After aging, they are washed with alkali and water, washed twice with a liquid alkali solution, and then washed twice with hot water, dried at 200°C for 10 hours, and sieved to remove iron. The lithium-rich manganese-based precursor powder is evenly mixed with lithium carbonate in a molar ratio of lithium content to transition metal of 1.3:1, and sintered in an air atmosphere using a two-step heating strategy. First, the precursor particles are heated to 400°C and maintained for 9.5 hours, and then the temperature is continuously raised to 800°C and kept constant for 24 hours to obtain a lithium-rich manganese-based matrix.

[0094] (3) Lead nitrate, yttrium nitrate, and titanium nitrate were accurately weighed in a molar ratio of Pb:Y:Ti=0.8:0.2:1, dissolved in ethanol, and prepared into a mixed solution with a concentration of 1 g / L. 50 mL of ethylene glycol and 10 mL of citric acid were added, stirred for 60 min, and heated in a water bath at 50°C to form a gel. Subsequently, the dried gel was placed in an atmosphere furnace and calcined at 700°C for 1 h while passing flowing air to obtain Pb with an average particle size of 50 nm. 0.8 Y 0.2 TiO3 powder.

[0095] (4) According to the formula, the lithium-rich manganese-based matrix of step (2) and the Pb 0.8 Y 0.2 The TiO3 powder was mixed and dispersed in deionized water, and ultrasonically treated for 10 minutes. The uniformly mixed material was then placed in an atmosphere furnace and calcined at a high temperature of 700°C for 24 hours while flowing air to promote the solid-phase diffusion of the metal elements, thereby obtaining the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0096] Example 3

[0097] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, wherein the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate. The chemical formula of the lithium-rich manganese-based substrate is Li 1.3 Mn 0.75 Ni 0.17 Co 0.08 O2, ferroelectric heterojunction coating including Pb 0.9 Y 0.1 TiO3;

[0098] In the lithium-rich manganese-based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 3 wt %; the particle size D50 of the lithium-rich manganese-based matrix is ​​5 μm; and the thickness of the ferroelectric heterojunction coating is 500 nm;

[0099] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises the following steps:

[0100] (1) Prepare high-purity manganese chloride (MnCl2·4H2O), nickel chloride (NiCl2·6H2O) and cobalt chloride (CoCl2·6H2O) as raw materials, accurately weigh manganese chloride, nickel chloride and cobalt chloride in turn, and mix them according to the set molar ratio n(CoCl2·6H2O). 2+ ):n(Ni 2+ ):n(Mn 2+ )=0.75:0.17:0.08 for weighing;

[0101] Under constant temperature and stirring conditions, the three chloride salts were gradually added to an appropriate amount of deionized water to prepare a manganese chloride solution, a nickel chloride solution, and a cobalt chloride solution with a concentration of 50 g / L, respectively;

[0102] Sodium carbonate is selected as the precipitant, and the sodium carbonate is prepared into a sodium carbonate solution with a mass fraction of 20%;

[0103] The complexing agent is ammonia water, which is prepared into an ammonia solution with a mass fraction of 5%;

[0104] The reactor was started and preheated to stabilize the reactor temperature at 68°C. The reactor was filled with nitrogen and kept sealed. The stirring system was turned on and the reactor speed was set to 200 rpm to ensure uniform mixing of the reaction system and prevent agglomeration or uneven growth of precipitated particles. The following five solutions were simultaneously pumped into the reactor at the set feed flow rates: manganese chloride solution, nickel chloride solution, cobalt chloride solution, ammonium carbonate solution, and ammonia solution. The feed flow rates were set to 15 L / h, 15 L / h, 15 L / h, 2 L / h, and 0.2 L / h, respectively.

[0105] During the entire coprecipitation reaction process, the pH value of the reaction solution was monitored in real time by an online pH monitoring system and maintained in the range of 10.5-10.6. The total alkali concentration was strictly controlled at 15.0-17.0 g / L. The reaction lasted for 40 hours. During this period, a laser particle size analyzer was used to monitor the particle size distribution in real time. The reaction was immediately stopped after the D50 of the lithium-rich manganese-based precursor particles reached 4.5 μm.

[0106] (2) The lithium-rich manganese-based precursor particles obtained in step (1) are aged for 5.5 hours at a temperature of 60°C. After aging, they are washed with alkali and water, washed with a liquid alkali solution for 3 times, and then washed with hot water for 5 times, dried at 160°C for 18 hours, and sieved to remove iron. The lithium-rich manganese-based precursor powder and lithium carbonate are uniformly mixed in a ratio of lithium content to transition metal of 1.3:1, and sintered in an air atmosphere using a two-step heating strategy. First, the precursor particles are heated to 550°C and maintained for 2.5 hours, and then the temperature is continued to be raised to 1050°C and kept constant for 12 hours to obtain a lithium-rich manganese-based matrix.

[0107] (3) Lead nitrate, yttrium nitrate, and titanium nitrate were accurately weighed in a molar ratio of Pb:Y:Ti=0.9:0.1:1, dissolved in ethanol, and prepared into a mixed solution with a concentration of 1 g / L. 50 mL of ethylene glycol and 10 mL of citric acid were added, stirred for 20 min, and heated in a water bath at 80°C to form a gel. Subsequently, the dried gel was placed in an atmosphere furnace and calcined at 800°C for 1 h while passing flowing air to obtain Pb 2+ with an average particle size of 10 nm. 0.9 Y 0.1 TiO3 powder.

[0108] (4) According to the formula, the lithium-rich manganese-based matrix of step (2) and the Pb 0.9 Y 0.1 The TiO3 powder was mixed and dispersed in deionized water, and ultrasonically treated for 60 minutes. The uniformly mixed material was then placed in an atmosphere furnace and calcined at a high temperature of 900°C for 6 hours while flowing air to promote the solid-phase diffusion of the metal elements, thereby obtaining the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0109] Example 4

[0110] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating, wherein the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate. The chemical formula of the lithium-rich manganese-based substrate is Li 1.3 Mn 0.75 Ni 0.17 Co 0.08 O2, ferroelectric heterojunction coating including Pb 0.85 Y 0.15 TiO3, the ferroelectric heterojunction coating comprises a first coating on the surface of a lithium manganese-based substrate and a second coating on the surface of the first coating, the first coating comprising porous Pb 0.85 Y 0.15 TiO3 material, the second coating layer includes dense Pb 0.85 Y 0.15TiO3 material, the mass ratio of the first coating layer to the second coating layer is 1:1;

[0111] In the lithium-rich manganese-based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 5 wt %; the particle size D50 of the lithium-rich manganese-based matrix is ​​8.5 μm; and the thickness of the ferroelectric heterojunction coating is 400 nm;

[0112] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises the following steps:

[0113] Steps (1) to (3) are the same as in Example 1;

[0114] (4) According to the formula, the lithium-rich manganese-based matrix of step (2) and the Pb 0.85 Y 0.15 TiO3 powder and ammonium carbonate were mixed and dispersed in deionized water (the amount of ammonium carbonate added was the amount of Pb 0.85 Y 0.15 TiO3 powder (20wt%), ultrasonic treatment for 60min, then the mixed material was placed in an atmosphere furnace and calcined at a high temperature of 800℃ for 6h to obtain a burnt material;

[0115] (5) According to the formula, the lithium-rich manganese-based matrix of step (2) and the Pb 0.85 Y 0.15 The TiO3 powders were mixed and dispersed in deionized water, and ultrasonically treated for 60 minutes. The uniformly mixed material was then placed in an atmosphere furnace and calcined at a high temperature of 800° C. for 6 hours to obtain the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

[0116] Example 5

[0117] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except that the content of the ferroelectric heterojunction coating is 13 wt %.

[0118] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0119] Example 6

[0120] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except that the content of the ferroelectric heterojunction coating is 1 wt %.

[0121] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0122] Example 7

[0123] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating includes Pb 0.7 Y 0.3 Except TiO3, the rest are the same as those in Example 4.

[0124] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0125] Example 8

[0126] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating includes Pb 0.95 Y 0.05 Except TiO3, the rest are the same as those in Example 4.

[0127] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0128] Example 9

[0129] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating includes Pb 0.8 Ce 0.2 Except TiO3, the rest are the same as those in Example 4.

[0130] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0131] Example 10

[0132] This embodiment provides a lithium-rich manganese-based material containing a ferroelectric heterojunction coating. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating includes Ba 0.8 Mg 0.2 Except for FeO3, the rest are the same as in Example 4.

[0133] The preparation method of the lithium-rich manganese-based material containing a ferroelectric heterojunction coating is the same as that of Example 4 except for the change in the formula amount.

[0134] Comparative Example 1

[0135] This comparative example provides a lithium-rich manganese-based material, which is the same as Example 1 except that the ferroelectric heterojunction coating includes PbTiO3;

[0136] The preparation method of the lithium-rich manganese-based material is the same as that of Example 1 except for the change in the formula amount.

[0137] Comparative Example 2

[0138] This comparative example provides a lithium-rich manganese-based material, which is the same as Example 1 except that it does not contain a ferroelectric heterojunction coating.

[0139] The preparation method of the lithium-rich manganese-based material is the same as that of Example 1 except that step (3) and step (4) are not performed.

[0140] The lithium-rich manganese-based materials obtained in the above examples and comparative examples were made into positive electrodes for lithium-ion batteries. A lithium metal sheet was then used as the negative electrode, Celgard 2400 was used as the separator, and an electrolyte containing 1 mol / L LiPF6 was used to assemble a CR2032 button cell. Electrochemical performance tests were then conducted under the following conditions: a voltage range of 2-4.8 V, a current density of 1 C, and 200 cycles. The test results are shown in Table 1.

[0141] Table 1

[0142]

[0143]

[0144] From Table 1 above, we can see that:

[0145] From Example 1 and Comparative Example 1, it can be seen that the coating material of the present invention is preferably doped with N metal ions such as Y 3+ , which can improve the room temperature ferroelectricity of the coating, thereby improving the migration of lithium ions and the performance of the battery; it can be seen from Example 1 and Comparative Example 2 that the setting of the ferroelectric heterojunction coating of the present invention can enhance the lithium ion transfer kinetics, optimize the interface compatibility between the coating and the lithium-rich manganese-based substrate, inhibit lattice oxygen loss and transition metal dissolution, and improve structural stability, thereby improving the performance of the battery; it can be seen from Example 1 and Example 4 that the ferroelectric heterojunction coating of the present invention is preferably divided into a porous layer and a dense layer, thereby further promoting the performance of the ferroelectric heterojunction coating and improving the performance of the battery; it can be seen from Example 4 and Examples 5-8 that the content of the ferroelectric heterojunction coating of the present invention and the amount of N ions doped in the coating material will affect the performance of the material, thereby affecting the performance of the battery; it can be seen from Example 4 and Examples 9-10 that the material of the ferroelectric heterojunction coating of the present invention will affect the performance of the battery.

[0146] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lithium-rich manganese-based material containing a ferroelectric heterojunction coating, characterized in that: The lithium-rich manganese-based material containing a ferroelectric heterojunction coating comprises a lithium-rich manganese-based substrate and a ferroelectric heterojunction coating on the surface of the lithium-rich manganese-based substrate. The general chemical formula of the lithium-rich manganese-based substrate is Li x Mn a Ni b Co 1-a-b O2, where 1≤x≤1.5, 0.55≤a≤0.8, 0.1≤b≤0.2; The ferroelectric heterojunction coating includes M 1-c N c TO3 material, wherein 0.05≤c≤0.2, M, N and T are independently selected from any one or a combination of at least two of Mg, Fe, Mo, Pb, Ba, Sr, Hf, Pt, Zr, Cu, Ge, Y, Ru, Sn, W, Nb, Ti, Ce, V, Al, La, Cr or Bi, and M, N and T are selected from different metal elements.

2. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating according to claim 1, characterized in that: The M is selected from any one or a combination of at least two of Pb, Ba, Sr, Bi, La, Hf, Pt or Nb, the N is selected from any one or a combination of at least two of Y, Mg, Sn, W, Ce, V or Cr, and the T is selected from any one or a combination of at least two of Ti, Zr, Fe, Ru, Mo, Ge, Cu or Al; Preferably, the M 1-c N c TO3 materials include Pb 1-c Y c TiO3 material; Preferably, the ferroelectric heterojunction coating comprises a first coating located on the surface of the lithium-rich manganese-based substrate, and a second coating on the surface of the first coating, wherein the first coating comprises a porous M 1-c N c TO3 coating, the second coating includes dense M 1-c N c TO3 coating; Preferably, the mass ratio of the first coating layer to the second coating layer is 1:(0.5-2).

3. The lithium-rich manganese-based material containing a ferroelectric heterojunction coating according to claim 1 or 2, characterized in that: In the lithium-rich manganese-based material containing the ferroelectric heterojunction coating, the content of the ferroelectric heterojunction coating is 0.5-10 wt %, preferably 3-10 wt %; Preferably, the particle size D50 of the lithium-rich manganese-based matrix is ​​3-10 μm; Preferably, the thickness of the ferroelectric heterojunction coating is 100-500 nm.

4. A method for preparing a lithium-rich manganese-based material containing a ferroelectric heterojunction coating according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The lithium-rich manganese-based matrix and M 1-c N c The TO3 materials are mixed and calcined to obtain the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

5. The preparation method according to claim 4, characterized in that The lithium-rich manganese-based matrix and M 1-c N c The mixing and calcination of TO3 materials include the following steps: According to the formula, the lithium-rich manganese-based matrix, M 1-c N c After the TO3 material, pore-forming agent and deionized water are mixed, dried and ground, they are calcined once to obtain a burnt material; According to the formula, the burning material, M 1-c N c The TO3 material and deionized water are mixed, dried, and ground, and then calcined twice to obtain the lithium-rich manganese-based material containing the ferroelectric heterojunction coating.

6. The preparation method according to claim 5, characterized in that The pore-forming agent includes ammonium carbonate and / or ammonium bicarbonate; Preferably, the amount of the pore-forming agent added is 1-c N c 15-35wt% of TO3 material; Preferably, the primary calcination temperature is 700-900°C and the time is 3-12h; Preferably, the secondary calcination is carried out at a temperature of 700-900° C. and for a time of 3-12 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that The method for preparing the lithium-rich manganese-based matrix comprises the following steps: Mixing and sintering a lithium-rich manganese-based precursor and a lithium source to obtain the lithium-rich manganese-based matrix; Preferably, the sintering atmosphere includes any one of nitrogen, oxygen, air or hydrogen, or a combination of at least two thereof; Preferably, the sintering comprises first maintaining the temperature at 400-550° C. for 2-9.5 hours, and then heating the temperature to 800-1050° C. and maintaining the temperature for 12-24 hours.

8. The preparation method according to claim 7, characterized in that The method for preparing the lithium-rich manganese-based precursor comprises the following steps: co-precipitating a nickel salt solution, a manganese salt solution, a cobalt salt solution, a precipitant solution, and a complexing agent solution, aging, filtering, washing, drying, and sieving to obtain the lithium-rich manganese-based precursor; Preferably, the concentrations of the nickel salt solution, manganese salt solution, and cobalt salt solution are independently 30-100 g / L, and the feed flow rates are independently 5-15 L / h; Preferably, the concentration of the precipitant solution is 20-40 wt %, and the feed flow rate is 2-4 L / h; Preferably, the concentration of the complexing agent solution is 5-20 wt %, and the feed flow rate is 0.1-1.0 L / h; Preferably, the coprecipitation reaction temperature is 40-68°C, the pH is 9-11.5, and the total alkali concentration is 10-20 g / L; Preferably, the coprecipitation reaction is carried out at a rotation speed of 100-350 r / min and for a time of 40-160 h.

9. The preparation method according to any one of claims 4 to 8, characterized in that Preparation of the M 1-c N c The TO3 material method includes the following steps: The mixed salt solution, citric acid and ethylene glycol are mixed and heated to form a gel, and the gel is dried and then heat-treated to obtain the M 1-c N c TO3 material; The mixed salt solution includes a formulated amount of M ions, N ions and T ions; Preferably, the total metal ion concentration of the mixed salt solution is 0.2-1.0 g / L; Preferably, the heating temperature is 50-80°C and the heating time is 10-60 minutes; Preferably, the heat treatment temperature is 500-700°C, the time is 1-5 hours, and the atmosphere includes any one of air, nitrogen, hydrogen or oxygen, or a combination of at least two thereof; Preferably, the M 1-c N c The average particle size of TO3 material is 10-50nm.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-rich manganese-based material containing the ferroelectric heterojunction coating according to any one of claims 1 to 3.

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