Multi-element lithium supplement agent, preparation method thereof, positive pole piece and lithium ion battery

Abstract

The invention provides a multi-element lithium supplement agent and a preparation method thereof, a positive pole piece and a lithium ion battery, the multi-element lithium supplement agent comprises an inner core, a first coating layer and a second coating layer, the inner core comprises lithium-rich lithium aluminum ferrite, the first coating layer comprises lithium-rich lithium manganate, and the second coating layer comprises lithium-rich lithium nickelate; the chemical general formula of the multi-element lithium supplement agent is LixFeaAlbMncNidOy, 0.1 < = d / (a + b) < = 0.9, 0.62 < = a < = 0.96, 0.04 < = b < = 0.38, 0.005 < = c / (a + b) < = 0.02, 5a + 5b + 2c + 2d < = x < = 5.5 a + 5.5 b + 2.1 c + 2.1 d, and y = (x + 3a + 3b + 4c + 2d) / 2. Iron and aluminum are adopted as main elements, and lithium-rich lithium manganate and lithium-rich lithium nickelate are coated at the same time, so that the stability of the lithium supplementing agent can be improved, gas production can be reduced, the ionic conductivity can be improved, and the capacity exertion of the lithium supplementing agent can be promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a multi-element lithium supplementing agent, a preparation method thereof, a positive pole piece and a lithium ion battery. BACKGROUND

[0002] In a lithium ion battery, a complex SEI film (solid electrolyte interface film) is generated on the surface of a carbon negative electrode or a carbon-silicon negative electrode. The SEI film has a loose structure, a large and uneven thickness, and can cause the initial efficiency of the battery to decrease. In addition, during the use of the battery, the SEI film is often shed and re-generated, which can consume a large amount of lithium. In order to compensate for the loss of active lithium and enable the capacity of the positive electrode material to be fully utilized, lithium supplementing needs to be performed.

[0003] Currently, a commonly used lithium supplementing agent is lithium-rich lithium iron oxide Li5FeO4 (referred to as LFO), which has a very high theoretical capacity and an irreversible lithium supplementing capacity of more than 700 mAh / g. However, the lithium-rich lithium iron oxide lithium supplementing agent also has problems of poor ionic and electronic conductivity, poor capacity development, and continuous gas production during charging and subsequent cycles of the lithium-rich lithium iron oxide lithium supplementing agent.

[0004] Based on the above research, it is necessary to provide a lithium supplementing agent that has a high lithium supplementing capacity, excellent ionic and electronic conductivity, and low gas production. SUMMARY

[0005] The application aims to provide a multi-element lithium supplementing agent, a preparation method thereof, a positive pole piece and a lithium ion battery. The multi-element lithium supplementing agent uses iron and aluminum as main elements of the lithium supplementing agent, and simultaneously coats lithium-rich lithium manganate and lithium-rich lithium nickelate, so that the stability of a traditional lithium-rich lithium iron oxide lithium supplementing agent can be improved, gas production can be reduced, ionic conductivity can be improved, and the capacity development of the lithium supplementing agent can be promoted.

[0006] To achieve the application purpose, the following technical solutions are used in the application.

[0007] In a first aspect, the application provides a multi-element lithium supplementing agent, which includes a core, a first coating layer on the surface of the core, and a second coating layer on the surface of the first coating layer away from the core.

[0008] The core includes lithium-rich lithium aluminum iron oxide, the first coating layer includes lithium-rich lithium manganate, and the second coating layer includes lithium-rich lithium nickelate.

[0009] The chemical general formula of the multi-element lithium supplementing agent is Li x Fe a Al b Mn c Ni d O ywherein, 0.1≤d / (a+b)≤0.9, 0.62≤a≤0.96, 0.04≤b≤0.38, 0.005≤c / (a+b)≤0.02, 5a+5b+2c+2d≤x≤5.5a+5.5b+2.1c+2.1d, y=(x+3a+3b+4c+2d) / 2.

[0010] The present application adopts lithium-rich lithium aluminum ferrite as the inner core, that is, introducing aluminum element into lithium-rich lithium ferrite, and the aluminum element exists as a main element (confirmed from the chemical formula of the multi-element lithium supplementing agent), improving the stability of the material and reducing the gas production of the residual after lithium supplementing; then coating a layer of lithium-rich lithium manganese oxide (Li2MnO3) on the surface of the lithium-rich lithium aluminum ferrite, compared with the Mn element doped into the inner core, the coated lithium-rich lithium manganese oxide can protect the interface and stabilize the lattice oxygen, and continuously supplement lithium during the battery cycle process; finally, coating lithium-rich lithium nickel oxide (Li2NiO2) on the surface of the lithium-rich lithium manganese oxide, improving the ion conductivity of the material, promoting the capacity of the material, and further protecting the lithium-rich lithium aluminum ferrite and improving the gas production problem, therefore, the multi-element lithium supplementing agent provided by the present application has high structural stability, ion conductivity, lithium supplementing capacity and low gas production through mutual cooperation in multiple aspects.

[0011] The chemical formula of the multi-element lithium supplementing agent is Li x Fe a Al b Mn c Ni d O y wherein, 0.1≤d / (a+b)≤0.9, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, 0.62≤a≤0.96 (preferably 0.62≤a≤0.80), for example, it can be 0.62, 0.65, 0.70, 0.75, 0.80, 0.90 or 0.96, 0.04≤b≤0.38 (preferably 0.2≤b≤0.38), for example, it can be 0.04, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.38, 0.005≤c / (a+b)≤0.02, for example, it can be 0.005, 0.01, 0.015 or 0.02, 5a+5b+2c+2d≤x≤5.5a+5.5b+2.1c+2.1d, for example, it can be 5.1a+5.2b+2.05c+2.05d, 5.3a+5.3b+2.05c+2.05d or 5.5a+5.5b+2.1c+2.1d, y=(x+3a+3b+4c+2d) / 2, but not limited to the listed values, other values not listed in the value range are also applicable.

[0012] The multi-element lithium supplementing agent adopts a specific chemical formula, i.e., the elements are preferably in a specific range, wherein if the Al element is too little, the material stability decreases, if the Al element is too much, the Fe element is relatively reduced, then the material internal resistance is too large, the conductivity is too poor, the lithium supplementing capacity is affected, if the Mn element is too little, the content of the lithium-rich lithium manganate coating layer is too little, then the effect of stabilizing the lattice oxygen is affected, if the Mn element is too much, the content of the lithium manganate coating layer is too much, then the capacity of the whole lithium supplementing agent system is affected, if the Ni element is too little, the content of the lithium-rich lithium nickelate coating layer is too little, then the coating is uneven, the conductivity is limitedly improved and the system gas production cannot be effectively reduced, and if the Ni element is too much, the content of the lithium-rich lithium nickelate is too much, then the capacity of the whole lithium supplementing agent system is affected.

[0013] Preferably, in the core, the content of the iron element gradually decreases from the core to the surface of the core.

[0014] Preferably, in the core, the content of the aluminum element gradually increases from the core to the surface of the core.

[0015] In the core, the iron element and the aluminum element are gradiently distributed, wherein the content of the iron element gradually decreases and the content of the Al element gradually increases from the core to the surface of the core, which can improve the stability of the surface lattice and the air stability of the material.

[0016] In the second aspect, the application provides a preparation method of the multi-element lithium supplementing agent according to the first aspect, and the preparation method comprises the following steps:

[0017] (1) mixing and primary sintering of an iron-aluminum-manganese oxide precursor material and a first lithium source to obtain a primary sintered material;

[0018] The iron-aluminum-manganese oxide precursor material comprises an iron-aluminum oxide and a manganese oxide coated on the surface of the iron-aluminum oxide;

[0019] (2) mixing and secondary sintering of the primary sintered material, a nickel source and a second lithium source to obtain the multi-element lithium supplementing agent.

[0020] In the application, the manganese oxide is coated in the precursor stage, and the lithium-rich lithium nickelate is coated in situ after the primary sintering, i.e., the first coating layer and the second coating layer are both obtained by in-situ coating, the coating layer is uniformly and controllably distributed, and the coating effect is better than that of the traditional coating method.

[0021] Preferably, the method for preparing the iron-aluminum-manganese oxide precursor material in step (1) comprises the following steps:

[0022] performing a first coprecipitation reaction on the iron source solution, the aluminum source solution, the precipitant solution and the complexing agent solution to obtain an iron-aluminum hydroxide;

[0023] carrying out a second co-precipitation reaction on the manganese source solution, the precipitant solution and the complexing agent solution to obtain the hydroxide precursor material;

[0024] then carrying out a heat treatment on the hydroxide precursor material to obtain the iron-aluminum-manganese oxide precursor material.

[0025] Preferably, the flow rate of the iron source solution is gradually reduced.

[0026] Preferably, the flow rate of the aluminum source solution is gradually increased.

[0027] Preferably, in the iron-aluminum hydroxide, the molar ratio of iron element and aluminum element in the core is m:(1-m), and the molar ratio of iron element and aluminum element on the surface is n:(1-n), wherein 0.96≤m≤1, for example, it can be 0.96, 0.97, 0.98, 0.99 or 1, 0.30≤n≤0.50, for example, it can be 0.30, 0.35, 0.4, 0.45 or 0.5, but not limited to the listed values, other values not listed in the value range are also applicable.

[0028] Preferably, the pH of the first co-precipitation reaction and the second co-precipitation reaction is independently 9.5-11.5, for example, it can be 9.5, 10.0, 10.5, 11.0 or 11.5, but not limited to the listed values, other values not listed in the value range are also applicable.

[0029] Preferably, the concentration of the complexing agent in the system of the first co-precipitation reaction and the system of the second co-precipitation reaction is 2-4 mol / L, for example, it can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L, but not limited to the listed values, other values not listed in the value range are also applicable.

[0030] Preferably, the temperature of the first co-precipitation reaction is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but not limited to the listed values, other values not listed in the value range are also applicable, and the temperature of the second co-precipitation reaction is 30-45℃, for example, it can be 30℃, 35℃, 40℃ or 45℃, but not limited to the listed values, other values not listed in the value range are also applicable.

[0031] Preferably, the temperature of the heat treatment is 120-250℃, for example, it can be 120℃, 150℃, 220℃ or 250℃, the time is 1-2h, for example, it can be 1h, 1.25h, 1.5h, 1.75h or 2h, and the heat treatment is carried out in an air atmosphere or an oxygen atmosphere.

[0032] The iron-aluminum-manganese oxide precursor material and the first lithium source are mixed according to the formula amount of the chemical general formula of the multi-element lithium supplementing agent.

[0033] Preferably, the first sintering in step (1) includes pre-sintering at 400-550℃, for example, 400℃, 450℃, 500℃ or 550℃, for 5-40h, for example, 5h, 10h, 15h, 20h, 25h, 30h, 35h or 40h, and then continuing sintering at 700-850℃, for example, 700℃, 750℃, 800℃ or 850℃, for 5-15h, for example, 5h, 7.5h, 10h, 12.5h or 15h, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0034] The nickel source and the second lithium source are mixed according to the formula amount of the chemical general formula of the multi-element lithium supplementing agent, and further preferably, the molar ratio of lithium in the second lithium source to nickel in the nickel source in step (2) is (2-2.1):1, for example, 2:1, 2.05:1 or 2.1:1, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0035] Preferably, the second sintering in step (2) is performed at a temperature of 400-650℃, for example, 400℃, 450℃, 500℃, 550℃, 600℃ or 650℃, for a time of 5-15h, for example, 5h, 7.5h, 10h, 12.5h or 15h, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0036] Preferably, the total mass of the nickel source and the second lithium source is 10%-50% of the mass of the first sintered material, for example, 10%, 20%, 30%, 40% or 50%, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] In a third aspect, the present application provides a positive electrode sheet, which comprises the multi-element lithium supplementing agent according to the first aspect.

[0038] In a fourth aspect, the present application provides a lithium ion battery, which comprises the positive electrode sheet according to the second aspect.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] The present application adopts lithium-rich lithium aluminum iron oxide as the core, that is, introduces aluminum element into lithium-rich lithium iron oxide, and the aluminum element exists as a main element (confirmed from the chemical formula of the multi-element lithium supplementing agent), improves the stability of the material, and reduces the gas production of the residual after lithium supplementing; then a layer of lithium-rich lithium manganese oxide is coated on the surface of the lithium-rich lithium aluminum iron oxide, the crystal lattice oxygen on the surface of the material is stabilized, the stability of the material is improved, and the lithium can be continuously supplemented; finally, lithium-rich lithium nickel oxide is coated on the surface of the lithium-rich lithium manganese oxide, the ion conductivity of the material is improved, the capacity of the material is promoted, and the lithium-rich lithium aluminum iron oxide is further protected, and the gas production problem is improved, therefore, the multi-element lithium supplementing agent provided by the present application has high structural stability, ion conductivity, lithium supplementing capacity and low gas production through mutual cooperation in multiple aspects. DETAILED DESCRIPTION

[0041] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0042] Embodiment 1

[0043] The present embodiment provides a multi-element lithium supplementing agent, the chemical formula of the multi-element lithium supplementing agent is Li 5.74 Fe 0.8 Al 0.2 Mn 0.01 Ni 0.2 O 4.59 ; the multi-element lithium supplementing agent comprises a core, a first coating layer on the surface of the core, and a second coating layer on the surface of the first coating layer away from the core;

[0044] The core comprises lithium-rich lithium aluminum iron oxide, and from the core to the surface of the core, the content of iron element gradually decreases, and the content of aluminum element gradually increases; the first coating layer comprises lithium-rich lithium manganese oxide, and the second coating layer comprises lithium-rich lithium nickel oxide;

[0045] The preparation method of the multi-element lithium supplementing agent comprises the following steps:

[0046] (1) a first co-precipitation reaction is carried out on a ferric nitrate solution, an aluminum sulfate solution, a sodium hydroxide solution and a citric acid solution at a pH of 10.5, a temperature of 70°C and a system complexing agent concentration of 3 mol / L, wherein the flow rate of the ferric nitrate solution gradually decreases, and the flow rate of the aluminum sulfate solution gradually increases, to obtain iron aluminum hydroxide, and in the iron aluminum hydroxide, the molar ratio of core iron element to aluminum element is m:(1-m), and the molar ratio of surface iron element to aluminum element is n:(1-n), wherein m=0.98 and n=0.38;

[0047] Then continue to carry out the second co-precipitation reaction of the manganese sulfate solution, the sodium hydroxide solution and the citric acid solution at a pH of 10.5, a temperature of 35℃ and a system complexing agent concentration of 3 mol / L, and by controlling the amount of the manganese sulfate solution, a hydroxide precursor material is obtained with a Mn / (Fe+Al) element molar ratio = 0.01, and the hydroxide precursor material is heat-treated in an oxygen atmosphere at a temperature of 180℃ for 2h to obtain the iron aluminum manganese oxide precursor material;

[0048] (2) The iron aluminum manganese oxide precursor material and anhydrous lithium hydroxide are mixed according to the formula amount, and the mixed material is pre-fired at 500℃ for 20h, and then sintered at 800℃ for 10h to obtain a fired material;

[0049] (3) Lithium oxide and nickel oxide are mixed according to a Li element / Ni element molar ratio of 2.05, the mixed material is added to the fired material of step (1) according to the formula amount, mixed uniformly, and then sintered at a temperature of 550℃ for 10h in a nitrogen atmosphere to obtain the multi-element lithium supplement agent.

[0050] Example 2

[0051] The present embodiment provides a multi-element lithium supplement agent, and the chemical formula of the multi-element lithium supplement agent is Li 7.04 Fe 0.8 Al 0.2 Mn 0.02 NiO 6.06 ; the multi-element lithium supplement agent comprises a core, a first coating layer on the surface of the core, and a second coating layer on the surface of the first coating layer away from the core;

[0052] The core comprises lithium-rich lithium aluminum iron oxide, and from the core to the surface of the core, the content of iron elements gradually decreases and the content of aluminum elements gradually increases; the first coating layer comprises lithium-rich lithium manganese oxide, and the second coating layer comprises lithium-rich lithium nickel oxide;

[0053] The preparation method of the multi-element lithium supplement agent comprises the following steps:

[0054] (1) An iron nitrate solution, an aluminum sulfate solution, a sodium hydroxide solution and a citric acid solution are subjected to a first co-precipitation reaction at a pH of 9.5, a temperature of 80℃ and a system complexing agent concentration of 4 mol / L, wherein the flow rate of the iron nitrate solution gradually decreases and the flow rate of the aluminum sulfate solution gradually increases to obtain iron aluminum hydroxide, and in the iron aluminum hydroxide, the molar ratio of core iron elements and aluminum elements is m:(1-m), and the molar ratio of surface iron elements and aluminum elements is n:(1-n), wherein m=0.96 and n=0.36;

[0055] Then continue to carry out a second co-precipitation reaction of the manganese sulfate solution, the sodium hydroxide solution and the citric acid solution at a pH of 9.5, a temperature of 30℃ and a system complexing agent concentration of 4 mol / L, so that the Mn / (Fe+Al) element molar ratio = 0.02 to obtain the hydroxide precursor material, and heat treat the hydroxide precursor material in an oxygen atmosphere at a temperature of 200℃ for 2h to obtain the iron-aluminum-manganese oxide precursor material;

[0056] (2) Mix the iron-aluminum-manganese oxide precursor material and anhydrous lithium hydroxide according to the formula amount, pre-burn the mixed material at 550℃ for 5h, and then sinter the material at 850℃ for 5h to obtain a first-burned material;

[0057] (3) Mix lithium oxide and nickel oxide according to a molar ratio of Li element / Ni element = 2, add the mixed material to the first-burned material according to the formula amount, mix uniformly, and then sinter the material in a nitrogen atmosphere at a temperature of 400℃ for 15h to obtain the multi-element lithium supplement agent.

[0058] Example 3

[0059] The present embodiment provides a multi-element lithium supplement agent, and the chemical formula of the multi-element lithium supplement agent is Li 5.75 Fe 0.62 Al 0.38 Mn 0.005 Ni 0.12 O 4.5 ; the multi-element lithium supplement agent comprises a core, a first coating layer on the surface of the core, and a second coating layer on the surface of the first coating layer away from the core;

[0060] The core comprises lithium-rich lithium aluminum iron oxide, and the content of iron element gradually decreases and the content of aluminum element gradually increases from the core to the surface of the core; the first coating layer comprises lithium-rich lithium manganese oxide, and the second coating layer comprises lithium-rich lithium nickel oxide;

[0061] The preparation method of the multi-element lithium supplement agent comprises the following steps:

[0062] (1) Carry out a first co-precipitation reaction of an iron nitrate solution, an aluminum sulfate solution, a sodium hydroxide solution and a citric acid solution at a pH of 11.5, a temperature of 50℃ and a system complexing agent concentration of 2 mol / L, wherein the flow rate of the iron nitrate solution gradually decreases and the flow rate of the aluminum sulfate solution gradually increases to obtain iron-aluminum hydroxide, and in the iron-aluminum hydroxide, the molar ratio of iron element and aluminum element in the core is m:(1-m), and the molar ratio of iron element and aluminum element on the surface is n:(1-n), wherein m=0.96 and n=0.72;

[0063] Then continue to carry out the second co-precipitation reaction of the manganese sulfate solution, the sodium hydroxide solution and the citric acid solution at a pH of 11.5, a temperature of 40℃ and a complexing agent concentration of 2 mol / L, so that the Mn / (Fe+Al) element molar ratio = 0.005 to obtain a hydroxide precursor material, and heat-treat the hydroxide precursor material in an oxygen atmosphere at a temperature of 250℃ for 1h to obtain an iron-aluminum-manganese oxide precursor material;

[0064] (2) Mix the iron-aluminum-manganese precursor material and anhydrous lithium hydroxide according to the formula amount, and pre-burn the mixed material at 400℃ for 40h, and then sinter the material at 700℃ for 15h to obtain a first-burned material;

[0065] (3) Mix lithium oxide and nickel oxide according to a molar ratio of Li element / Ni element = 2, add the mixed material to the first-burned material according to the formula amount, mix uniformly, and then sinter the material in a nitrogen atmosphere at a temperature of 650℃ for 5h to obtain the multi-element lithium supplement agent.

[0066] Example 4

[0067] The multi-element lithium supplement agent provided in this embodiment has a chemical formula of Li 5.74 Fe 0.9 Al 0.1 Mn 0.01 Ni 0.2 O 4.59 , and the rest are the same as in Example 1.

[0068] The preparation method of the multi-element lithium supplement agent in this embodiment is the same as in Example 1 except for the adaptive change in the formula amount according to the chemical formula.

[0069] Example 5

[0070] The multi-element lithium supplement agent provided in this embodiment has a chemical formula of Li 5.74 Fe 0.95 Al 0.05 Mn 0.01 Ni 0.2 O 4.59 , and the rest are the same as in Example 1.

[0071] The preparation method of the multi-element lithium supplement agent in this embodiment is the same as in Example 1 except for the adaptive change in the formula amount according to the chemical formula.

[0072] Example 6

[0073] The multi-element lithium supplement agent provided in this embodiment is the same as in Example 1 except that the content of iron and aluminum elements does not change from the core to the surface of the core.

[0074] The preparation method of the multi-element lithium supplementing agent in this embodiment is the same as that in Embodiment 1, except that the flow rates of the iron nitrate solution and the aluminum sulfate solution in step (1) are not changed, the flow rate ratio of the iron nitrate solution and the aluminum sulfate solution is always 8:2, and the adaptability of the iron-aluminum hydroxide is changed.

[0075] Comparative Example 1

[0076] This comparative example provides a multi-element lithium supplementing agent, the chemical formula of which is Li 5.74 Fe 0.55 Al 0.45 Mn 0.01 Ni 0.2 O 4.59 The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0077] The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0078] Comparative Example 2

[0079] This comparative example provides a multi-element lithium supplementing agent, the chemical formula of which is Li 5.74 FeMn 0.01 Ni 0.2 O 4.59 The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0080] The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0081] Comparative Example 3

[0082] This comparative example provides a multi-element lithium supplementing agent, the chemical formula of which is Li 5.915 Fe 0.7 Al 0.3 Mn 0.1 Ni 0.2 O 4.86 The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0083] The preparation method of the multi-element lithium supplementing agent in this comparative example is the same as that in Embodiment 1, except that the formula amount according to the chemical formula is adaptively changed.

[0084] Comparative Example 4

[0085] This comparative example provides a multi-element lithium supplementing agent, which is the same as that in Embodiment 1, except that it does not contain the first coating layer.

[0086] The preparation method of the multi-element lithium supplementing agent in the present comparative example is the same as that in Example 1 except that the second co-precipitation reaction in step (1) is not performed.

[0087] Comparative Example 5

[0088] The present comparative example provides a multi-element lithium supplementing agent which is the same as that in Example 1 except that the multi-element lithium supplementing agent does not contain a second coating layer and the chemical formula of the multi-element lithium supplementing agent is changed.

[0089] The preparation method of the multi-element lithium supplementing agent in the present comparative example is the same as that in Example 1 except that step (3) is not performed.

[0090] The multi-element lithium supplementing agents obtained in the above examples and comparative examples are tested for lithium supplementing capacity, gas production and ion conductivity by the following methods: (1) The lithium supplementing agents obtained in the examples and comparative examples are assembled into a coin cell and subjected to charge testing to obtain the specific charge capacity, i.e. the lithium supplementing capacity. The specific charge capacity is obtained by the following coin cell preparation method and charge testing conditions: the lithium supplementing agent, SP (conductive carbon black) and PVDF (polyvinylidene fluoride) are uniformly mixed (defoaming machine for 5 min) at a mass ratio of 85:10:5, the solid content of the slurry is 50%, and after uniform mixing, the slurry is coated, the surface density of the coating is 5 mg / cm 2 , and after drying the pole piece, a 12 mm grinding tool is used to punch the piece for standby assembly of the coin cell. After the coin cell is assembled, a blue charge-discharge tester is used for charge-discharge testing, and the specific charge capacity is recorded, i.e. the lithium supplementing capacity of the lithium supplementing agent, at 25°C, 0.05C rate charging to 4.4V, and then constant voltage charging until the current is ≤0.01C.

[0091] (2) The active material mass of the fully charged coin cell is recorded, electrolyte is injected at a liquid injection coefficient of 3.5 g / Ah, an aluminum plastic bag is used for packaging, and then the coin cell is stored at 60°C, and the gas production after 7 days of storage is recorded.

[0092] (3) The lithium supplementing agents in the examples and comparative examples are subjected to EIS testing to obtain the ion conductivity of the sample.

[0093] The test results are shown in Table 1:

[0094] Table 1

[0095]

[0096] From Table 1, it can be seen that:

[0097] It can be seen from examples 1-3 and comparative examples 1-2 that when too much Al is introduced into the core, the content of Fe decreases, thereby affecting the lithium supplement capacity, but when Al is not contained, the stability of the material is affected, and the gas production of the material is affected; it can be seen from examples 1-3 and comparative examples 3-4 that when the content of Mn is too high, the lithium supplement capacity of the material is also affected, but when Mn is not contained, that is, the material does not contain a lithium-rich lithium manganate coating layer, the gas production of the material increases; it can be seen from examples 1-3 and comparative example 5 that when the material does not contain a lithium nickelate coating layer, the ionic conductivity of the material decreases; it can be seen from examples 1 and 4-5 that when Al is added as a main element in the core, when the content of Al is too low, the effect of improving the stability of the material decreases, thereby affecting the performance of the material; it can be seen from examples 1 and 6 that the application preferably has a gradient change in the content of iron and aluminum, which can further improve the stability of the material and the lithium supplement capacity, and also reduce the gas production.

[0098] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any change or replacement within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A multi-element lithium supplement, characterized by, The multi-element lithium supplement agent comprises a core, a first coating layer on the surface of the core, and a second coating layer on the surface of the first coating layer away from the core; The core comprises lithium-rich lithium aluminum iron oxide, the first coating layer comprises lithium-rich lithium manganese oxide, and the second coating layer comprises lithium-rich lithium nickel oxide; The chemical general formula of the multi-element lithium supplementing agent is Li x Fe a Al b Mn c Ni d O y Wherein, 0.1≤d / (a+b)≤0.9, 0.62≤a≤0.96, 0.04≤b≤0.38, 0.005≤c / (a+b)≤0.02, 5a+5b+2c+2d≤x≤5.5a+5.5b+2.1c+2.1d, y=(x+3a+3b+4c+2d) / 2.

2. The multi-component lithium supplement of claim 1, wherein, 0.62≤a≤0.80, 0.2≤b≤0.38; And / or, in the core, the content of iron gradually decreases from the core to the surface of the core; And / or, in the core, the content of aluminum gradually increases from the core to the surface of the core.

3. A process for the preparation of a multi-component lithium supplement as claimed in claim 1 or 2, characterized in that The preparation method comprises the following steps: (1) mixing and primary sintering of an iron-aluminum-manganese oxide precursor material and a first lithium source to obtain a first sintered material; The iron-aluminum-manganese oxide precursor material comprises an iron-aluminum oxide and a manganese oxide coated on the surface of the iron-aluminum oxide; (2) mixing and secondary sintering of the first sintered material, a nickel source and a second lithium source to obtain the multi-element lithium supplement agent.

4. The production method according to claim 3, characterized by, The method for preparing the iron-aluminum-manganese oxide precursor material in step (1) comprises the following steps: carrying out a first coprecipitation reaction of an iron source solution, an aluminum source solution, a precipitant solution and a complexing agent solution to obtain an iron-aluminum hydroxide; carrying out a second coprecipitation reaction of a manganese source solution, a precipitant solution and a complexing agent solution to obtain a hydroxide precursor material; Then, heat treatment of the hydroxide precursor material to obtain the iron-aluminum-manganese oxide precursor material.

5. The preparation method according to claim 4, characterized in that, The flow rate of the iron source solution gradually decreases; And / or, the flow rate of the aluminum source solution gradually increases; And / or, in the iron-aluminum hydroxide, the molar ratio of iron and aluminum in the core is m:(1-m), and the molar ratio of iron and aluminum on the surface is n:(1-n), wherein 0.96≤m≤1 and 0.30≤n≤0.

50.

6. The production method according to claim 4 or 5, characterized by, The pH of the first coprecipitation reaction and the second coprecipitation reaction is independently 9.5-11.5; And / or, the concentration of the complexing agent in the system of the first coprecipitation reaction and the system of the second coprecipitation reaction is 2-4 mol / L; And / or, the temperature of the first coprecipitation reaction is 40-80℃, and the temperature of the second coprecipitation reaction is 30-45℃; And / or, the temperature of the heat treatment is 120-250℃, the time is 1-2h, and the heat treatment is carried out in an air atmosphere or an oxygen atmosphere.

7. The preparation method according to claim 3, characterized in that, The primary sintering in step (1) comprises pre-sintering at 400-550℃ for 5-40h, and then continuing sintering at 700-850℃ for 5-15h.

8. The preparation method according to claim 3, characterized in that, The molar ratio of lithium in the second lithium source and nickel in the nickel source in step (2) is (2-2.1):1; The temperature of the secondary sintering in step (2) is 400-650℃, and the time is 5-15h.

9. A positive electrode sheet characterized by comprising: The positive electrode tab comprises the multi-element lithium supplement agent according to claim 1 or 2.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises the positive electrode tab according to claim 9.

Images