WO2023071912A1 - 补锂添加剂及其制备方法和应用 - Google Patents

补锂添加剂及其制备方法和应用 Download PDF

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WO2023071912A1
WO2023071912A1 PCT/CN2022/126438 CN2022126438W WO2023071912A1 WO 2023071912 A1 WO2023071912 A1 WO 2023071912A1 CN 2022126438 W CN2022126438 W CN 2022126438W WO 2023071912 A1 WO2023071912 A1 WO 2023071912A1
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Prior art keywords
lithium
encapsulation layer
additive
core body
layer
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PCT/CN2022/126438
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English (en)
French (fr)
Inventor
钟泽钦
万远鑫
孔令涌
赵中可
朱成奔
钟文
裴现一男
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深圳市德方创域新能源科技有限公司
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Priority to EP22871038.0A priority Critical patent/EP4231385A1/en
Priority to US18/038,917 priority patent/US20240208837A1/en
Publication of WO2023071912A1 publication Critical patent/WO2023071912A1/zh

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Definitions

  • the application belongs to the field of secondary batteries, and in particular relates to a lithium supplement additive and its preparation method and application.
  • Lithium-ion batteries are considered to be the most promising due to their high operating voltage and energy density, relatively small self-discharge level, no memory effect, no pollution from heavy metal elements such as lead and cadmium, and long cycle life. one of the energy sources.
  • the surface of the negative electrode is usually accompanied by the formation of a solid electrolyte film SEI film.
  • This process consumes a large amount of Li + , which means that the Li + part released from the positive electrode material is irreversibly consumed, corresponding to the reversible charge of the battery cell. Lower specific capacity.
  • Anode materials, especially silicon-based anode materials will further consume Li + , resulting in loss of lithium in cathode materials, reducing the first Coulombic efficiency and battery capacity of the battery. For example, in a lithium-ion battery system using a graphite negative electrode, about 10% of the lithium source will be consumed for the first charge.
  • anode materials with high specific capacity such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide), and amorphous carbon anodes
  • the consumption of lithium sources in the cathode will be further aggravated.
  • lithium-rich iron-based materials reported publicly is as high as 867mAh/g
  • the operating voltage window is consistent with conventional lithium-ion batteries, and basically does not participate in the electrochemical process in the later stage. It is a lithium-supplementing additive with broad prospects.
  • Li 5 FeO 4 it is prepared by a sol-gel method. This material is used as a lithium ion battery positive electrode lithium supplement material and has the characteristics of large charge capacity and small discharge capacity.
  • the carbon source is used for gas-phase coating to isolate the external environment, and the contact between lithium ferrite and water in the air is relieved to improve the stability of the material; however, the coating layer is always It is difficult to completely isolate the contact with water in the air, resulting in material deterioration and failure. Moreover, residual alkali still exists in the coating layer or between the interface with the lithium ferrite core body, which makes it difficult to process.
  • the purpose of this application is to overcome the above-mentioned deficiencies in the prior art, to provide a lithium supplement additive and a preparation method thereof, to solve the problem that the existing lithium supplement additive is unstable in lithium supplement or the content of residual alkali is high, which leads to unsatisfactory lithium supplement effect and processability. technical problem.
  • Another object of the present application is to provide an electrode sheet and a secondary battery containing the electrode sheet, so as to solve the technical problems of unsatisfactory initial Coulombic efficiency and battery capacity of existing secondary batteries.
  • the first aspect of the present application provides a lithium supplement additive.
  • the lithium supplement additive of the present application includes a core body and a functional encapsulation layer coated on the core body.
  • the core body includes a lithium supplement material, and lithium carbonate is dispersed between the interface between the functional encapsulation layer and the core body or/and in the functional encapsulation layer.
  • lithium carbonate accounts for 0.2-1.5wt% of the mass of the functional encapsulation layer.
  • lithium carbonate accounts for 0.5-1.5wt% of the mass of the functional encapsulation layer.
  • the content of lithium carbonate between the interface between the functional encapsulation layer and the core body and/or in the surface layer of the functional encapsulation layer in contact with the core body is greater than that in the surface layer away from the core body.
  • the lithium-supplementing material includes at least one element of lithium-rich transition metal oxide, Li w A, Li 1+x+y Al x M y N z Ti 2-xyz (PO 4 ) 3 metallic lithium; wherein, 0 ⁇ w ⁇ 5, A is at least one element of C, N, O, P, S, F, B, Se, N is at least one of Si, Ge, Sn, M is selected from Sc, Ga , at least one of Y, La, at least one of 0 ⁇ y ⁇ 0.5, 0 ⁇ z ⁇ 0.5, and 0 ⁇ x+y ⁇ 0.5.
  • Li w A Li 1+x+y Al x M y N z Ti 2-xyz (PO 4 ) 3 metallic lithium
  • A is at least one element of C, N, O, P, S, F, B, Se
  • N is at least one of Si, Ge, Sn
  • M is selected from Sc, Ga , at least one of Y, La, at least one of 0 ⁇ y ⁇ 0.5, 0 ⁇ z ⁇ 0.5
  • the lithium-supplementing materials include Li 2 MnO 2 , Li 6 MnO 4 , aLiFeO 2 bLi 2 O cM x O y , Li 6 CoO 4 , Li 2 NiO 2 , Li 4 SiO 4 , Li 2 S, At least one of Li 3 N, Li 8 SnO 6 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ; wherein, in the chemical formula aLiFeO 2 ⁇ bLi 2 O ⁇ cM x O y , a+b ⁇ 0.98, c ⁇ 0.02, 1.8 ⁇ b/a ⁇ 2.1, 1 ⁇ y/x ⁇ 2.5, M is at least one of Ni, Co, Mn, Ti, Al, Cu, V, Zr.
  • the particle diameter of the nuclei may be 50nm-10 ⁇ m.
  • the functional encapsulation layer includes a hydrophobic encapsulation layer.
  • the hydrophobic encapsulation layer includes a conductive coating layer, and lithium carbonate is distributed in the conductive carbon coating layer and the contact interface with the core body.
  • the particle size of the lithium-supplementing additive is 0.2 ⁇ m ⁇ D50 ⁇ 10 ⁇ m, D10/D50 ⁇ 0.3, and D90/D50 ⁇ 2.
  • the specific surface area of the lithium-supplementing additive is 0.5 ⁇ BET ⁇ 20m 2 /g.
  • the resistivity of the lithium supplement additive is 1.0-500 ⁇ /cm.
  • the second aspect of the present application provides the preparation method of the lithium supplement additive of the present application.
  • the preparation method of the present application lithium supplement additive comprises the steps:
  • the first A precursor of a core material includes a precursor of a first lithium-supplementing material
  • a second core material comprising a second lithium supplement material is provided, and a second functional encapsulation layer covering the second core material is formed on the surface of the second core material; and then the second core material is carried out in an environment containing a second carbon source.
  • the second heat treatment generates lithium carbonate in the second functional encapsulation layer to obtain the lithium supplement additive.
  • first carbon source and/or the second carbon source include carbon dioxide, C 1 -C 4 alcohols, C 1 -C 4 ethers, C 1 -C 4 ketones, C 1 -C 4 at least one of the hydrocarbon compounds.
  • the temperature of the first sintering treatment is 450°C-1000°C, and the time is 0.5-10h.
  • the first sintering treatment is to raise the temperature to 450°C-1000°C at a rate of 100-500°C/h.
  • the temperature of the first heat treatment and/or the second heat treatment is 400-800° C., and the time is 2-10 hours.
  • the third aspect of the present application provides an electrode sheet.
  • the electrode sheet of the present application includes a current collector and an electrode active layer bonded to the surface of the current collector.
  • the lithium supplement additive prepared by the preparation method.
  • a secondary battery in a fourth aspect of the present application, includes a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet or the negative electrode sheet is an electrode sheet.
  • the nuclei contained in the lithium-replenishing additive of this application contain lithium-replenishing materials, so the lithium-replenishing additive of this application can provide abundant lithium, so that it can be used as a "sacrifice agent" during the first cycle of charging, and all lithium ions can be charged as much as possible at one time. Released to replenish the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the first efficiency and overall electrochemical performance of the battery.
  • the lithium supplement additive of the present application disperses lithium carbonate between the functional encapsulation layer and the core body interface or/and in the functional encapsulation layer in the functional encapsulation layer, which plays a synergistic effect with the functional encapsulation layer, and can Effectively improve the effect of the functional encapsulation layer on the nuclei, so that the nuclei are isolated from moisture and carbon dioxide in the outside world, ensuring the stability of the nuclei, thereby ensuring the lithium supplementation effect of the lithium supplement additive and the stability of lithium supplementation, and making the functional
  • the residual alkali content in the encapsulation layer is low, which endows the lithium supplement additive of the present application with excellent processing performance.
  • the preparation method of the lithium-supplementing additive of the present application can effectively prepare a lithium-supplementing additive with a core-shell structure, and can enable the functional encapsulation layer to effectively cover the core body containing the lithium-supplementing material, and make the residual alkali content contained in the prepared lithium-supplementing additive
  • the content of residual alkali is low or can be eliminated, and lithium carbonate is contained, and the prepared functional encapsulation layer is dense, so that the prepared lithium supplement additive has excellent lithium supplement effect, stable lithium supplement performance and good processability.
  • the preparation method of the lithium-supplementing additive can ensure that the prepared lithium-supplementing additive is stable in structure and electrochemical performance, has high efficiency, and saves production costs.
  • the electrode sheet of this application contains the lithium supplement additive of this application, the components contained in the electrode active layer of the electrode sheet of this application are uniformly dispersed, and the film quality is high, which endows the electrode sheet of this application with excellent electrochemical performance.
  • the contained lithium supplement additive can be used as a lithium source and as a "sacrifice agent" during the first cycle of charging to supplement the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode, thereby maintaining the battery system.
  • the abundance of lithium ions improves the first efficiency of the battery and the overall electrochemical performance.
  • the lithium ion battery of the present application has excellent first-time Coulombic efficiency, battery capacity and cycle performance, long service life, and stable electrochemical performance.
  • Fig. 1 is the structural representation of the lithium supplement additive of the embodiment of the present application.
  • Figure 2 is a schematic structural view of the functional encapsulation layer contained in the lithium supplement additive shown in Figure 1 including a hydrophobic encapsulation layer;
  • Figure 3 is a schematic structural view of the functional encapsulation layer contained in the lithium supplement additive shown in Figure 1 including a hydrophobic encapsulation layer and an electronic conductor encapsulation layer;
  • Figure 4 is a schematic structural view of the functional encapsulation layer contained in the lithium supplement additive shown in Figure 1 including a hydrophobic encapsulation layer and an ion conductor encapsulation layer;
  • Fig. 5 is a schematic structural diagram of the functional encapsulation layer contained in the lithium supplement additive shown in Fig. 1 including a hydrophobic encapsulation layer, an electronic conductor encapsulation layer and an ionic conductor encapsulation layer;
  • Fig. 6 is a schematic flow diagram of a preparation method of a lithium supplement additive in an embodiment of the present application.
  • Fig. 7 is a schematic flow chart of another preparation method of the lithium supplement additive in the embodiment of the present application.
  • Fig. 8 is the electron micrograph of supplementary lithium additive in embodiment 1;
  • Fig. 9 is the electron micrograph of the lithium supplement additive in embodiment 5.
  • Fig. 10 is the electron micrograph of supplementary lithium additive in comparative example 1;
  • Fig. 11 is the X-ray diffraction pattern of lithium supplement additive in embodiment 5.
  • FIG. 12 is an X-ray diffraction pattern of the lithium-supplementing additive in Comparative Example 1.
  • the term "and/or” describes the association relationship of associated objects, indicating that there may be three relationships, for example, A and/or B may mean: A exists alone, A and B exist simultaneously, and B exists alone Condition. Among them, A and B can be singular or plural.
  • the character "/" generally indicates that the contextual objects are an "or" relationship.
  • At least one means one or more, and “multiple” means two or more.
  • At least one of the following” or similar expressions refer to any combination of these items, including any combination of single or plural items.
  • “at least one (one) of a, b, or c”, or “at least one (one) of a, b, and c” can mean: a, b, c, a-b ( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.
  • sequence numbers of the above-mentioned processes do not mean the order of execution, and some or all steps may be executed in parallel or sequentially, and the execution order of each process shall be based on its functions and The internal logic is determined and should not constitute any limitation to the implementation process of the embodiment of the present application.
  • the weight of the relevant components mentioned in the description of the embodiments of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the various components.
  • the scaling up or down of the content of the fraction is within the scope disclosed in the description of the embodiments of the present application.
  • the mass described in the description of the embodiments of the present application may be ⁇ g, mg, g, kg and other well-known mass units in the chemical industry.
  • first and second are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features.
  • first XX can also be called the second XX
  • second XX can also be called the first XX.
  • a feature defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • the embodiment of the present application provides a lithium supplement additive.
  • the lithium-replenishing additive of the embodiment of the present application includes a core body and a functional encapsulation layer coated on the core body, that is, the lithium-replenishing additive of the embodiment of the present application has a core-shell structure, as in the embodiment, the lithium-replenishing additive of the embodiment of the present application
  • the structure is shown in FIGS. 1 to 5 , including a core body 10 and a functional encapsulation layer 20 covering the core body 10 .
  • the core body 10 includes a lithium supplement material, that is, in the lithium supplement additive in the embodiment of the present application, the core body 10 is a lithium source for lithium supplementation.
  • the core body 10 is rich in lithium, thereby ensuring that the lithium supplement additive in the embodiment of the present application can provide abundant lithium, which is added to the electrode as an additive, so that it can be used as a "sacrifice agent" during the first cycle of charging, as much as possible. All the lithium ions contained in the lithium supplement additive are released to supplement the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode.
  • the lithium-replenishing material contained in the core body 10 may be a conventional lithium-replenishing material, or a newly developed lithium-replenishing material.
  • the lithium supplement material may be a ternary lithium supplement material or a binary lithium supplement material.
  • the lithium supplement material can but not only include at least one of lithium-rich transition metal oxides, Li w A, Li 1+x+y Al x M y N z Ti 2-xyz (PO 4 ) 3 ; wherein, 0 ⁇ w ⁇ 5, A is at least one element of C, N, O, P, S, F, B, Se, N is selected from at least one of Si, Ge, Sn, M is selected from Sc, Ga, At least one of Y and La, at least one of 0 ⁇ y ⁇ 0.5, 0 ⁇ z ⁇ 0.5, and 0 ⁇ x+y ⁇ 0.5.
  • Li w A Li 1+x+y Al x M y N z Ti 2-xyz (PO 4 ) 3 ; wherein, 0 ⁇ w ⁇ 5, A is at least one element of C, N, O, P, S, F, B, Se, N is selected from at least one of Si, Ge, Sn, M is selected from Sc, Ga, At least one of Y and La, at least one of 0 ⁇ y
  • the lithium-supplementing material may but not only include chemical formulas of Li 2 MnO 2 , Li 6 MnO 4 , aLiFeO 2 bLi 2 O cM x O y , Li 6 CoO 4 , Li 2 NiO 2 , Li 4 At least one of SiO 4 , Li 2 S, Li 3 N, Li 8 SnO 6 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 .
  • the lithium-replenishing material of the core body 10 may be a negative electrode lithium-replenishing material or a positive electrode lithium-replenishing material.
  • the lithium supplement additive in the embodiment of the present application is a positive electrode lithium supplement additive.
  • the lithium supplement additive of the embodiment of the present application is a negative electrode lithium supplement additive, specifically such as a metal lithium micropowder core body and a cladding layer doped with lithium carbonate after passivation, then the cladding layer doped with lithium carbonate
  • metallic lithium is the lithium supplement material for the core body 10
  • the coating layer doped with lithium carbonate can be used as the functional encapsulation layer 20 or as a layer structure of the functional encapsulation layer 20.
  • the core body 10 may be at least one of primary particles and secondary particles, and specifically may be at least one of primary particles and secondary particles formed of lithium-supplementing materials contained in the core body 10 .
  • the particle diameter of the core body 10 may be 50nm-15 ⁇ m, further 50nm-10 ⁇ m.
  • the particle size of the primary particle is that the particle size distribution of the nucleus 10 is 50nm-5 ⁇ m; when the nucleus 10 is a secondary particle, the secondary particle size is the nucleus 10
  • the particle size distribution is 200nm-15 ⁇ m, further 200nm-10 ⁇ m.
  • secondary particles refer to agglomerated particles formed by aggregating more than one primary particle.
  • the core body 10 By controlling the particle size, shape and particle size of the core body 10, on the basis of its ability to provide abundant lithium ions, it also improves the processability of the lithium supplement additive in the preparation of lithium battery slurry, wherein the smaller primary particles The path can also extract more lithium.
  • the lithium-supplementing material contained in the core body 10 in the above-mentioned embodiments is rich in lithium, it is unstable when it encounters water and carbon dioxide, and it is easy to react with water and carbon dioxide, which leads to the lithium-supplementing material in the embodiments of the present application.
  • the lithium supplement effect of the additive is reduced.
  • lithium supplement materials are generally rich in residual alkali formed due to processing, and these residual alkalis will further reduce their processing performance. For example, the viscosity of the slurry containing the above lithium supplement materials will increase sharply, and the gel will lose fluidity rapidly. , so that subsequent processing cannot be performed.
  • the functional encapsulation layer 20 contained in the lithium-supplementing additive in the above-mentioned embodiments is coated on the core body 10 to form a complete coating layer, and in functional Lithium carbonate is dispersed between the interface between the encapsulation layer 20 and the core body 10 or/in the functional encapsulation layer 20 . Therefore, in the presence of lithium carbonate, the functional encapsulation layer 20 can effectively protect the core body 10, so that the core body 10, specifically the lithium supplement material, is isolated from moisture and carbon dioxide in the outside world.
  • the lithium carbonate and the functional encapsulation layer 20 play a synergistic effect, which can effectively improve the effect of the functional encapsulation layer 20 on the core body 10, so that the core body 10 is isolated from moisture and carbon dioxide in the outside world, ensuring the stability of the core body 10 So as to ensure the lithium-supplementing effect and the stability of lithium-supplementing additives, and stimulate the gram capacity of lithium-supplementing additives.
  • lithium carbonate accounts for 0.2-1.5wt% of the mass of the functional encapsulation layer 20.
  • the content of lithium carbonate is 0.5-1.5wt%, specifically 0.2wt%, 0.5wt%, 0.6wt% %, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt% and other typical but non-limiting contents.
  • the content of lithium carbonate to further reduce the content of residual alkali in the lithium-supplementing additive, especially the content of residual alkali in the functional encapsulation layer 20, to further improve the processing performance of the lithium-supplementing additive in the embodiment of the present application, and at the same time improve the performance of the present application.
  • the lithium supplementation stability and lithium supplementation effect of the lithium supplementation additive and the improvement of the conductivity of the functional encapsulation layer 20 stimulate the gram capacity of the lithium supplementation additive.
  • lithium carbonate may be mainly or only distributed between the interface of the functional encapsulation layer 20 and the core body 10 , or may be mainly distributed in the functional encapsulation layer 20 . In the embodiment of the present application, more lithium carbonate is mainly distributed between the interface of the functional encapsulation layer 20 and the core body 10 , while the distribution spreads in the functional encapsulation layer 20 .
  • the content of lithium carbonate between the functional encapsulation layer 20 and the core body 10 interface and/or in the surface layer of the functional encapsulation layer 20 in contact with the core body 10 of the functional encapsulation layer 20 is greater than that away from the core body 10 content in the surface layer (that is, the outer layer of the functional encapsulation layer 20).
  • the distribution characteristics of lithium carbonate in the functional encapsulation layer 20 are that the content of lithium carbonate gradually decreases from the surface of the functional encapsulation layer 20 close to the core body 10 to its outer surface, that is, the content of lithium carbonate is gradually reduced by the functional encapsulation layer.
  • lithium carbonate In the direction from the inner surface to the outer surface, lithium carbonate is distributed in a diffuse manner, and its content gradually decreases.
  • the distribution characteristics of the lithium carbonate can effectively reduce the content of residual alkali in the lithium supplement additive, and improve the effect of insulating the water vapor and carbon dioxide of the functional encapsulation layer 20 coating the core body 10, and improve the lithium supplement stability and the lithium supplement additive of the lithium supplement additive. Lithium supplementation effect.
  • the material of the functional encapsulation layer 20 can be a material capable of at least insulating moisture and carbon dioxide.
  • the functional encapsulation layer 20 includes a hydrophobic encapsulation layer, and its material is such as At least one of ceramics, carbon materials, oxides, and the like may be included.
  • the functional encapsulation layer 20 may also be a composite layer structure.
  • the hydrophobic encapsulation layer includes a conductive carbon coating layer, and lithium carbonate is distributed in the conductive carbon coating layer and on the contact interface with the core body 10 .
  • the functional encapsulation layer 20 covers the surface of the core body 10, the lithium-supplementing material contained in the core body 10 needs to pass through the functional encapsulation layer 20 during the lithium ion extraction process when the lithium ion is delithiated for the first time.
  • the electrochemical properties and thickness of the functional encapsulation layer 20 will also affect the extraction and migration efficiency of lithium ions. Therefore, the functional encapsulation layer 20 ideally has good ion conductivity properties on the basis of insulating moisture and carbon dioxide and other unfavorable factors.
  • the functional encapsulation layer 20 may include an ionic conductor encapsulation layer.
  • the functional encapsulation layer 20 covering the surface of the core body 10, during or after the lithium supplementation additive completes the lithium supplementation process, its conductivity will also affect the electrochemical performance of the battery such as the rate and first effect. Therefore, the functional The permanent encapsulation layer 20 can ideally also have good electronic conductivity properties on the basis of insulating moisture and carbon dioxide and other unfavorable factors.
  • the functional encapsulation layer 20 may comprise an electronic conductor encapsulation layer.
  • the functional encapsulation layer 20 contained in the lithium supplement additive may include at least one of a hydrophobic encapsulation layer, an ionic conductor encapsulation layer, and an electronic conductor encapsulation layer. Then lithium carbonate can be dispersed in at least one layer of the hydrophobic encapsulation layer, the ion conductor encapsulation layer, and the electron conductor encapsulation layer, specifically, it can be mainly distributed in the cladding layer close to the core body 10 .
  • the functional encapsulation layer 20 has at least the following structure:
  • the functional encapsulation layer 20 includes a hydrophobic encapsulation layer 21 .
  • the functional encapsulation layer 20 includes a hydrophobic encapsulation layer 21 covering the core 10 and an electronic conductor encapsulation layer 22 covering the outer surface of the hydrophobic encapsulation layer 21 .
  • the functional encapsulation layer 20 includes a hydrophobic encapsulation layer 21 covering the core body 10 and an ion conductor encapsulation layer 23 covering the outer surface of the hydrophobic encapsulation layer 21 .
  • the functional encapsulation layer 20 includes a hydrophobic encapsulation layer 21 covering the core body 10 and an electronic conductor encapsulation layer 22 and an ion conductor encapsulation layer encapsulating the outer surface of the hydrophobic encapsulation layer 21. Layer 23.
  • the functional encapsulation layer may also be a composite structural layer formed by other combinations of hydrophobic encapsulation layer, ionic conductor encapsulation layer, and electronic conductor encapsulation layer.
  • the electronic conductor encapsulation layer 22 added in the above-mentioned functional encapsulation layer 20 can enhance the electronic conductivity of the functional encapsulation layer 20, thereby enhancing the electronic conductivity of the lithium supplement additive, which is conducive to reducing the internal impedance of the electrode; 10
  • the electronic conductor encapsulation layer 22 can also be used for secondary use, playing an auxiliary role as a conductive agent inside the electrode.
  • the electronic conductor encapsulation layer 22 Based on the effect of the electronic conductor encapsulation layer 22, based on the effect of the electronic conductor encapsulation layer 22, when the functional encapsulation 20 only contained the electronic conductor encapsulation layer 22, the electronic conductor encapsulation layer 22 should have a dense structure and be fully covered;
  • the permanent package 20 includes at least an electronic conductor package layer 22 and an ion conductor package layer 23, the electronic conductor package layer 22 can be a non-full covering layer structure, or a non-dense structure, but the electronic conductor package layer 22 and the ion conductor package layer 23 constitute The composite cladding layer should have harmful components such as moisture and carbon dioxide.
  • the electronic conductor packaging layer 22 has a thickness of 1-100 nm, further 1-50 nm, and further 2-20 nm. In other embodiments, the mass content of the electronic conductor encapsulation layer 22 in the lithium supplement additive is 0.1-30%, further 0.1-10%, more preferably 0.5-5%.
  • the material of the electronic conductor encapsulation layer 22 includes at least one of carbon material and conductive oxide.
  • the carbon material includes at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, graphene, and the like.
  • the conductive oxide may include at least one of In 2 O 3 , ZnO, and SnO 2 .
  • the above-mentioned ionic conductor encapsulation layer 23 can enhance the ionic conductivity of the functional encapsulation 20, thereby enhancing the ionic conductivity of the lithium-supplementing additive, which is conducive to the outward transport of lithium ions from the nucleus; at the same time, when the nucleus 10 acts as After the "victim" releases lithium ions, the ion conductor encapsulation layer 23 can also be used for secondary use, and plays an auxiliary role in enhancing ion transmission inside the electrode.
  • the ionic conductor encapsulation layer 23 should have a compact structure and be fully covered; when the functional encapsulation 20 at least includes the ionic conductor encapsulation layer 23 and electronic conductor encapsulation layer 22, the ion conductor encapsulation layer 23 is a non-full covering layer structure, also can be a non-dense structure, but the composite cladding layer that the ion conductor encapsulation layer 23 and the electronic conductor encapsulation layer 22 constitutes should have the ability to isolate water parts and harmful components such as carbon dioxide.
  • the thickness of the ion conductor packaging layer 23 is 1-200 nm, further 1-50 nm, and further 2-20 nm.
  • the material of the ion conductor encapsulation layer 23 includes at least one of perovskite type, NASICON type and garnet type.
  • the perovskite type includes Li 3x La 2/3-x TiO 3 (LLTO), specifically Li 0.5 La 0.5 TiO 3 , Li 0.33 La 0.57 TiO 3 , Li 0.29 La 0.57 TiO 3 , Li 0.33 Ba At least one of 0.25 La 0.39 TiO 3 , (Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.0103 , Li 0.5 La 0.5 Ti 0.95 Zr 0.05 O 3 , etc., NASICON type such as but not only Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP), garnet type including Li 7 La 3 Zr 2 O 12 (LLZO), Li 6 ⁇ 4 La 3 Zr 1 ⁇ 4 Ta 0 ⁇ 6 O 12 , Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 at least one of the By adjusting the thickness and material of the ion conductor encapsulation layer 23, its ion conductivity can be further improved.
  • LLTO Li 3x La 2/3-x TiO 3
  • the functional encapsulation layer 20 it is also possible to include other layer structures on the outer surface of the functional encapsulation layer 20 as required, such as but not only covering layers such as conductive organic substances, such as in the above-mentioned electronic conductor encapsulation layer 22 and ionic conductor encapsulation layer 23. At least one layer of the composite cladding layer structure.
  • other coating layers include a conductive organic coating layer, the conductive organic coating layer is coated on the outer surfaces of the electronic conductor packaging layer 22 and the ion conductor packaging layer 23 .
  • the particle size of the lithium-supplementing additives in the embodiments of the present application basically satisfies: 0.2 ⁇ m ⁇ D50 ⁇ 10 ⁇ m, further 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m; D10/D50 ⁇ 0.3, D90/D50 ⁇ 2.
  • the specific surface area of the lithium supplement additive can be controlled to be 0.5 ⁇ BET ⁇ 20m 2 /g. Therefore, the particle size of the lithium-supplementing additive in the embodiment of the present application is controllable and uniform, and the surface, that is, the coating layer, is dense.
  • the embodiment of the present application also provides the preparation method of the above lithium supplement additive.
  • the process flow of a preparation method of the lithium supplement additive in the embodiment of the present application is shown in Figure 6, including the following steps:
  • S01 Perform a first mixing process on the first core material precursor or the first core material and the first functional encapsulation layer precursor to form a first mixture;
  • the composite is subjected to a first heat treatment in an environment containing a first carbon source, and lithium carbonate is generated in the first functional encapsulation layer to obtain a lithium supplement additive.
  • the first core material precursor in step S01 is a precursor for forming the first core material.
  • the first nuclei material is the material contained in the nuclei 10 of the lithium-supplementing additive in the embodiment of the above application. Therefore, the precursor of the first core material is the precursor of the lithium supplement material contained in the core body 10 of the lithium supplement additive in the embodiment of the above application (this specification is defined as the precursor of the first lithium supplement material), the first core material It also includes the lithium-replenishing material contained in the lithium-replenishing additive core body 10 of the above-mentioned application embodiment.
  • the precursor of the first functional encapsulation layer in step S01 is the material used to form the functional encapsulation layer 20 contained in the lithium-supplementing additive in the above application example. Therefore, the type of the precursor of the first functional encapsulation layer can be selected according to the material of the first functional encapsulation layer.
  • step S01 the types of the first core material precursor or the core material and the first functional encapsulation layer precursor material in step S01 will not be repeated here.
  • the first sintering treatment in step S02 when the first mixture contains the precursor of the first nucleus material, is to make the precursor of the first nucleus material in the first mixture generate the first nucleus material, then it must Generate the lithium supplement material contained in the core body 10 contained in the lithium supplement additive of the above application embodiment. At the same time, the precursor of the first functional encapsulation layer generates the functional encapsulation layer 20 contained in the lithium-supplementing additive in the embodiment of the above application.
  • the temperature of the first sintering treatment is 450°C-1000°C, and the first sintering treatment at this temperature can fully react the first core material precursor and/or the first functional encapsulation layer precursor to form a core material And/or the material of the first functional encapsulation layer, such as controlling the time of the first sintering treatment to be 0.5-10h.
  • the first sintering treatment may be performed at a rate of 100-500°C/h to 450°C-1000°C.
  • the first functional encapsulation layer contained in the prepared lithium-supplementing additive is a composite layer structure, such as the composite layer structure shown in Figure 3 to Figure 5, the corresponding step can be formed in situ according to the above steps S01 and S02.
  • the composite layer structure formed by the coating layer of each precursor coats the composite lithium supplementary material of the core body 10, and then the composite lithium supplementary material is sintered again.
  • chemical deposition or physical deposition can also be used to sequentially form the layer structure contained in the composite layer structure on the surface of the core body 10 .
  • the protective atmosphere may be an atmosphere formed by any protective gas including nitrogen, argon, nitrogen-argon mixed gas, nitrogen-hydrogen mixed gas, and argon-hydrogen mixed gas.
  • the protective atmosphere can effectively ensure that the first sintering process The stability of the crystal structure and electrochemical performance of the formed complex.
  • step S03 the first heat treatment is performed on the compound in step S03, so that the first carbon source can chemically react with the residual alkali contained in the compound in step S02 and the first carbon source during the heat treatment to form
  • the products include lithium carbonate. Therefore, the temperature of the first heat treatment is at least a temperature that can ensure that lithium carbonate can be generated. As in the embodiment, the temperature of the first heat treatment can be 400-800° C. and the time is 2-10 hours.
  • the first carbon source can fully react with the residual alkali contained in the compound, reduce the content of residual alkali, and at least include lithium carbonate in the generated product to volatilize carbonic acid Lithium applies for the role of lithium carbonate contained in the lithium supplement additive as described above.
  • the first carbon source includes carbon dioxide, C 1 -C 4 alcohols, C 1 -C 4 ethers, C 1 -C 4 ketones, C 1 -C 4 hydrocarbon compounds at least one of .
  • These types of first carbon sources are capable of providing carbon and reacting with the residual base in the complex.
  • these first carbon sources can effectively form a gaseous state, and can effectively enter the cladding layer of the composite during the heat treatment process, fully react with the residual alkali contained in the composite to generate lithium carbonate, and reduce the residual alkali of the composite. content.
  • step S03 other layer structures can be further formed on the outer surface of the first functional encapsulation layer after the heat treatment in step S03 according to the needs. , such as forming a composite coating layer structure with at least one of the above-mentioned electronic conductor packaging layer 22 and ion conductor packaging layer 23 .
  • other coating layers include a conductive organic coating layer
  • the conductive organic coating layer is coated on the outer surfaces of the electronic conductor packaging layer 22 and the ion conductor packaging layer 23 .
  • the formation method can also be formed by in-situ mixing treatment, spray drying and other methods.
  • step S05 The product in step S05 is subjected to a second heat treatment in an environment containing a second carbon source to generate lithium carbonate in the second functional encapsulation layer to obtain a lithium supplement additive.
  • the second core body material in step S04 is the material of the core body 10 of the lithium supplementary additive of the above text application embodiment
  • the second lithium supplementary material is the supplementary material contained in the core body 10 of the lithium supplementary additive of the above text application embodiment lithium material.
  • the second functional encapsulation layer formed in step S05 is also the functional encapsulation layer 20 contained in the lithium-supplementing additive in the embodiment of the above application. In order to save space, the types of the second lithium-supplementing material and the second core material in step S04 and the second functional encapsulation layer formed in step S05 will not be repeated here.
  • the method of forming the second functional encapsulation layer in step S05 can be formed by in-situ coating method, chemical vapor deposition method or physical vapor deposition method.
  • the formed second functional encapsulation layer structure can be formed according to the structure of the functional encapsulation layer 20 contained in the lithium-supplementing additive of the above-mentioned application embodiment, such as the composite cladding layer structure shown in Figure 3 to Figure 5, can be in order Each layer structure is sequentially formed.
  • step S06 the compound in step S05 is subjected to a second heat treatment, so that the second carbon source can form the compound contained in the second functional encapsulation layer and the core material formed in step S05 during the heat treatment.
  • the residual alkali reacts chemically with the second carbon source, and the products generated include lithium carbonate. Therefore, the temperature of the second heat treatment is at least able to ensure the temperature that can generate lithium carbonate, the condition of the second heat treatment can be the same as or different from the condition of the first heat treatment above, as in an embodiment, the temperature of the second heat treatment can be 400- 800°C, the time is 2-10h.
  • the second carbon source can fully react with the residual alkali contained in the complex formed in step S05, reduce the content of residual alkali, and at least include lithium carbonate in the generated product , apply the effect of lithium carbonate contained in the lithium supplement additive with volatile lithium carbonate as above text.
  • the type of the second carbon source may be the same as or different from the type of the first carbon source above, as in a specific embodiment, the second carbon source includes carbon dioxide, C 1 -C 4 alcohols, C 1 -C 4 ethers At least one of C 1 -C 4 ketones, C 1 -C 4 hydrocarbon compounds.
  • These types of second carbon sources can provide carbon and react with the residual alkali in the complex formed in step S05.
  • these second carbon sources can effectively form a gaseous state, and can effectively enter the cladding layer of the composite during the heat treatment process, fully react with the residual alkali contained in the composite to generate lithium carbonate, and reduce the residual alkali of the composite. content.
  • step S06 other layer structures can be further formed on the outer surface of the second functional encapsulation layer after the heat treatment in step S05 according to the needs. , such as forming a composite coating layer structure with at least one of the above-mentioned electronic conductor packaging layer 22 and ion conductor packaging layer 23 .
  • other coating layers include a conductive organic coating layer
  • the conductive organic coating layer is coated on the outer surfaces of the electronic conductor packaging layer 22 and the ion conductor packaging layer 23 .
  • the formation method can also be formed by in-situ mixing treatment, spray drying and other methods.
  • the preparation method of the above-mentioned lithium-supplementing additive can effectively prepare the lithium-supplementing additive of the above-mentioned application example with a core-shell structure, specifically to prepare a functional encapsulation layer containing lithium carbonate to effectively coat the core body containing the lithium-supplementing material, endowing the prepared
  • the lithium supplement additive has low residual alkali content or eliminates residual alkali, and improves the compactness of the functional encapsulation layer. It has the excellent lithium supplement effect, stable lithium supplement performance and good processing performance of the above-mentioned application example lithium supplement additive, and can also pass Control the materials and process conditions of the core body and functional encapsulation layer to optimize the related performance of the lithium supplement additive prepared.
  • the preparation method of the lithium-supplementing additive can ensure that the prepared lithium-supplementing additive is stable in structure and electrochemical performance, has high efficiency, and saves production costs.
  • the embodiment of the present application further provides an electrode sheet.
  • the electrode sheet of the embodiment of the present application includes a current collector and an electrode active layer bonded to the surface of the current collector, and the electrode active layer is doped with the lithium-supplementing additive in the embodiment of the above application. Since the electrode sheet of the embodiment of the present application contains the above-mentioned lithium-replenishing additive of the embodiment of the present application, during the charging and discharging process, the lithium-replenishing additive contained in the electrode sheet plays the above role, and can be used as a lithium source during the first cycle of charging.
  • the "sacrificing agent" is first consumed to supplement the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode, so as to maintain the abundance of lithium ions in the battery system and improve the first efficiency and overall electrochemical performance of the battery.
  • the electrode sheet may be a conventional electrode sheet of a secondary battery, such as including a current collector and an electrode active layer bonded on the surface of the current collector.
  • the mass content of the lithium-supplementing additive in the above application example contained in the electrode active layer may be 0.1-20wt%; preferably, 0.1-8wt%.
  • the electrode active layer includes, in addition to the lithium-supplementing additive, also includes an electrode active material, a binding agent and a conductive agent, wherein the binding agent can be a commonly used electrode binding agent, such as polyvinylidene chloride, soluble polytetrafluoroethylene One of ethylene, styrene-butadiene rubber, hydroxypropylmethylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives one or more species.
  • the conductive agent may be a commonly used conductive agent, such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotube.
  • the electrode active material can be selected according to the type of electrode such as positive electrode and negative electrode, and the corresponding positive electrode active material or negative electrode active material can be selected.
  • the positive electrode active material includes lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadium phosphate, lithium titanate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate. one or more.
  • the type of the above-mentioned lithium-replenishing additive should be compatible with the type of the electrode active material, such as when the electrode active material is a positive electrode active material, then the above-mentioned lithium-replenishing additive should be suitable for use as a positive electrode lithium-replenishing additive;
  • the electrode active material is a negative electrode active material, then the above-mentioned lithium-replenishing additive should be suitable for use as a negative electrode lithium-replenishing additive.
  • the preparation process of the electrode sheet can be as follows: mixing the electrode active material, lithium supplement additive, conductive agent and binder to obtain the electrode slurry, coating the electrode slurry on the current collector, drying, rolling, molding
  • the positive electrode sheet is prepared by cutting and other steps.
  • the embodiment of the present application further provides a secondary battery.
  • the secondary battery of the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, and of course other necessary or auxiliary components.
  • the positive electrode sheet and/or the negative electrode sheet are the positive electrode sheet and/or the negative electrode sheet of the above-mentioned embodiment of the present application, that is, the positive electrode active layer contained in the positive electrode sheet contains the lithium supplementation additive of the above-mentioned application example.
  • the negative electrode sheet may also contain the lithium-supplementing additive in the above-mentioned application examples in the negative electrode active layer.
  • the secondary battery of the embodiment of the present application contains the above-mentioned lithium-replenishing additive in the embodiment of the application, based on the excellent lithium-replenishing performance of the lithium-replenishing additive in the above-mentioned embodiment of the application or further has ion conductivity and/or electronic conductivity, this application is endowed with EXAMPLE
  • the secondary battery has excellent initial Coulombic efficiency, battery capacity and cycle performance, long service life and stable electrochemical performance.
  • the lithium-supplementing additive comprises LiFeO 2 ⁇ 1.99Li 2 O lithium-supplementing material nuclei and a dense carbon layer covering the nuclei.
  • the average particle size of the nuclei is 500nm
  • the thickness of the dense carbon layer is 40nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 9.4 m 2 /g
  • the measured resistivity is 400 ⁇ /cm.
  • the lithium supplement additive comprises LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 lithium supplement material nucleus and a dense carbon layer covering the nucleus.
  • the average particle size of the nuclei is 800nm
  • the thickness of the dense carbon layer is 100nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 5.2 m 2 /g
  • the measured resistivity is 300 ⁇ /cm.
  • the lithium-supplementing additive comprises LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.01CuO lithium-replenishing material nuclei and a dense carbon layer covering the nuclei.
  • the average particle size of the nuclei is 200nm
  • the thickness of the dense carbon layer is 100nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 15 m 2 /g
  • the measured resistivity is 52 ⁇ /cm.
  • the lithium supplement additive comprises LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 lithium supplement material nucleus and a dense carbon layer covering the nucleus.
  • the average particle size of the nuclei is 1.2 ⁇ m
  • the thickness of the dense carbon layer is 45 nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 5.2 m 2 /g
  • the measured resistivity is 253 ⁇ /cm.
  • the lithium-supplementing additive comprises LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01CuO lithium-supplementing material nuclei and a dense carbon layer covering the nuclei.
  • the average particle size of the nuclei is 2 ⁇ m
  • the thickness of the dense carbon layer is 150 nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 4.1 m 2 /g
  • the measured resistivity is 130 ⁇ /cm.
  • the lithium supplement additive comprises LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01MnO lithium supplement material nucleus and a dense carbon layer covering the nucleus.
  • the average particle size of the nuclei is 750nm
  • the thickness of the dense carbon layer is 80nm
  • lithium carbonate is dispersed in the dense carbon layer
  • the specific surface area is 6.7m 2 /g
  • the measured resistivity is 290 ⁇ /cm.
  • the crushed powder is prevented from passing nitrogen protection in the rotary furnace, the temperature is raised to 700°C at a heating rate of 200°C/h, 1L/min ethanol and 20L/min 80% Vol N 2 /CO 2 are kept for 5 hours, and the temperature is cooled to obtain carbonic acid Lithium & carbon coated LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.01MnO 2 powder.
  • the lithium supplement additive includes LiFeO 2 ⁇ 1.99Li 2 O lithium supplement material without carbon coating layer.
  • the preparation method of this comparative example lithium supplement additive comprises the steps:
  • the lithium-supplementing additive comprises Fe(NO 3 ) 3 .9H 2 O, LiNO 3 lithium-supplementing material nuclei and a dense carbon layer covering the nuclei. Lithium carbonate is not contained in the dense carbon layer.
  • the preparation method of this comparative example lithium supplement additive comprises the steps:
  • the lithium-supplementing additive comprises Fe(NO 3 ) 3 ⁇ 9H 2 O, LiNO 3 , Al(NO 3 ) 3 lithium-supplementing material nuclei and a dense carbon layer covering the nuclei. Lithium carbonate is not contained in the dense carbon layer.
  • the preparation method of this comparative example lithium supplement additive comprises the steps:
  • the lithium supplement additive comprises LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 lithium supplement material nucleus and a lithium carbonate layer covering the nucleus.
  • the preparation method of this comparative example lithium supplement additive comprises the steps:
  • lithium-replenishing additives provided by the above-mentioned Examples 1 to 6 and the lithium-replenishing additives provided by the comparative examples were assembled into positive electrodes and lithium-ion batteries according to the following methods:
  • Negative electrode lithium metal sheet
  • Electrolyte Ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3:7, and LiPF 6 is added to form an electrolyte.
  • the concentration of LiPF 6 is 1mol/L;
  • Lithium-ion battery assembly Assemble the lithium-ion battery in an inert atmosphere glove box according to the assembly sequence of lithium metal sheet-diaphragm-electrolyte-positive electrode sheet.
  • the lithium-supplementing additives provided in the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 3 were analyzed by scanning electron microscope respectively, wherein the electron microscope photos of Example 1, Example 5 and Comparative Example 1 are shown in Fig. 8 and Fig. 9. As shown in Figure 10.
  • the in-situ carbon-coated lithium-rich iron-based lithium supplement additive in Example 1 has many non-standard particles and the interface is relatively rough. It can be seen from FIG. 9 that the surface of the lithium-rich iron-based lithium-supplementing additive in Example 5 is relatively smooth. It is found from Figure 10 that the interface of the uncoated lithium-rich iron-based lithium supplement additive is also relatively rough. Therefore, after the secondary coating treatment, the surface quality of the lithium-supplementing additive can be effectively improved, and the insulation effect can be improved.
  • Example 1 to 6 and Comparative Examples 1 to 3 were subjected to XRD analysis respectively, wherein the XRDs of Example 5 and Comparative Example 1 are shown in Figure 10 and Figure 11 respectively.
  • the lithium-rich iron-based lithium-supplementing material provided in Example 5 has not only the main peak of Li 5 FeO 4 , but also some diffraction peaks of lithium carbonate. It can be seen from Fig. 12 that the lithium-rich iron-based lithium supplement material provided in Comparative Example 1 is mainly Li 5 FeO 4 , without lithium carbonate.
  • the XRD figure of other embodiment 1 to embodiment 4, embodiment 6 also all confirms the existence of lithium carbonate.
  • ICP Inductively coupled Plasma
  • the prepared positive electrode slurry does not appear jelly phenomenon and is easy to coat.
  • the positive electrode can have a higher initial gram capacity and a lower initial efficiency, thereby compensating for the decrease in energy density caused by the irreversible loss of lithium in the negative electrode for the first time.
  • Example 1 and Comparative Example 2 it can be seen from Example 1 and Comparative Example 2 that the lithium carbonate and carbon composite coating layer has better electrochemical stability, good processability, and more active lithium available for extraction than a single single-layer coating;
  • Example 2 From Example 2, Example 4 and Comparative Example 3, it can be seen that the carbon layer with a high loading capacity not only occupies the active material content, but also cannot completely cover and isolate the reaction with water, resulting in reduced processability.
  • the unfavorable factors such as coating and water isolation can be further improved, and the processing performance and the stability of lithium supplementation can be significantly improved.
  • Example 2 Example 4 and Comparative Example 4 that lithium carbonate can effectively coat lithium carbonate and carbon composite layer, which can further improve unfavorable factors such as coating and water isolation, and can significantly improve the processing performance and the stability of lithium supplementation.
  • lithium carbonate is an insulator, a certain thickness of lithium carbonate increases the polarization resistance, resulting in poor kinetics of lithium ions, which affects the normal extraction of lithium ions.

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Abstract

本申请公开了一种补锂添加剂及其制备方法和应用。本申请补锂添加剂包括核体和包覆于核体的功能性封装层，核体包括补锂材料，在功能性封装层与核体界面之间或/和功能性封装层中分散有碳酸锂。本申请补锂添加剂通过在功能性封装层与核体界面之间或/和功能性封装层中分散碳酸锂，其与功能性封装层起到增效作用，能够有效提高功能性封装层对核体的作用，使得核体与外界中的水分和二氧化碳隔离，保证核体的稳定性从而保证补锂添加剂的补锂效果和补锂的稳定性，而且使得功能性封装层中的残碱含量低，赋予本申请补锂添加剂优异的加工性能。补锂添加剂的制备方法能够保证制备的补锂添加剂结构和电化学性能稳定，而且效率高，节约生产成本。

Description

补锂添加剂及其制备方法和应用
本申请要求于2021年10月27日提交中国专利局，申请号为202111256908.5，申请名称为“补锂添加剂及其制备方法和应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于二次电池领域，具体涉及一种补锂添加剂及其制备方法和应用。
 背景技术
20世纪60、70年代的石油能源危机问题迫使人们去寻找新的可替代的新能源，随着人们对环境保护和能源危机意识的增强。锂离子电池因其具备较高的工作电压与能量密度、相对较小的自放电水平、无记忆效应、无铅镉等重金属元素污染、超长的循环寿命等优点，被认为是最具应用前景的能源之一。
锂离子电池在首次充电过程中，负极表面通常伴随着固态电解质膜SEI膜的形成，这个过程会消耗大量的Li +，意味着从正极材料脱出的Li +部分被不可逆消耗，对应电芯的可逆比容量降低。负极材料特别是硅基负极材料则会进一步消耗Li +，造成正极材料的锂损失，降低电池的首次库伦效率和电池容量。如在使用石墨负极的锂离子电池体系中，首次充电会消耗约10%的锂源。当采用高比容量的负极材料，例如合金类(硅、锡等)、氧化物类(氧化硅、氧化锡)和无定形碳负极时，正极锂源的消耗将进一步加剧。
为改善由于负极不可逆损耗引起的低库伦效率问题，除在负极材料、极片预锂化外，对正极进行补锂同样可以达到高能量密度的要求。如目前公开报道的富锂铁系材料理论容量高达867mAh/g，工作电压窗口与常规锂离子电池一致，且在后期基本不参与电化学过程，是一种具有广阔前景的补锂添加剂。在公开的另一份正极补锂材料Li 5FeO 4中，其采用溶胶凝胶法制备，该材料用作锂离子电池正极补锂材料具有充电容量大，放电容量小特点，然而该材料对环境适应性苛刻，表层残碱大不易加工。在公开的另一份碳包覆铁酸锂材料中，通过采用碳源进行气相包覆隔绝外界环境，缓解铁酸锂和空气中的水接触从而提高材料稳定性；尽管如此，包覆层始终难以彻底隔绝与空气中的水接触，导致材料变质失效。而且在包覆层中或与铁酸锂核体界面之间依然存在残碱，导致其不易加工。
技术问题
本申请的目的在于克服现有技术的上述不足，提供一种补锂添加剂及其制备方法，以解决现有补锂添加剂补锂不稳定或残碱含量高导致补锂效果和加工性不理想的技术问题。
本申请的另一目的在于提供一种电极片和含有该电极片的二次电池，以解决现有二次电池首次库伦效率和电池容量不理想的技术问题。
 技术解决方案
为了实现上述申请目的，本申请的第一方面，提供了一种补锂添加剂。本申请补锂添加剂包括核体和包覆于核体的功能性封装层，核体包括补锂材料，在功能性封装层与核体界面之间或/和功能性封装层中分散有碳酸锂。
进一步地，碳酸锂占功能性封装层质量的0.2-1.5wt%。
进一步地，碳酸锂占功能性封装层质量的0.5-1.5wt%。
进一步地，碳酸锂在功能性封装层与核体界面之间和/或在功能性封装层的与核体接触表层中含量大于背离核体的表层中含量。
进一步地，补锂材料包括富锂过渡金属氧化物、Li wA、Li 1+x+yAl xM yN zTi 2-x-y-z(PO 4) 3金属锂中的至少一种元素；其中，0＜w≤5，A为C、N、O、P、S、F、B、Se中的至少一种元素，N选自Si、Ge、Sn中的至少一种，M选自Sc、Ga、Y、La中的至少一种，0≤y≤0.5，0≤z≤0.5，0≤x+y≤0.5中的至少一种。
进一步地，补锂材料包括化学式为Li 2MnO 2、Li 6MnO 4、aLiFeO 2·bLi 2O·cM xO y、Li 6CoO 4、Li 2NiO 2、Li 4SiO 4、Li 2S、Li 3N、Li 8SnO 6、Li 1.3Al 0.3Ti 1.7(PO 4) 3中的至少一种；其中，化学式aLiFeO 2·bLi 2O·cM xO y中的a+b≥0.98，c≤0.02，1.8≤b/a≤2.1，1≤y/x≤2.5，M为Ni、Co、Mn、Ti、Al、Cu、V、Zr中的至少一种。
进一步地，核体的粒径可以为50nm -10μm。
进一步地，功能性封装层包括疏水性封装层。
更进一步地，疏水性封装层包括导电包覆层，碳酸锂分布在导电碳包覆层中和与核体接触界面。
进一步地，补锂添加剂的粒径为0.2μm≤D50≤10μm，D10/D50≥0.3，D90/D50≤2。
进一步地，补锂添加剂的比表面积为0.5≤BET≤20m 2/g。
进一步地，补锂添加剂的电阻率为1.0-500 Ω/cm。
本申请的第二方面，提供了本申请补锂添加剂的制备方法。本申请补锂添加剂的制备方法包括如下步骤：
将第一核体材料前驱体或第一核体材料与第一功能性封装层前驱体进行第一混合处理形成第一混合物；再于保护气氛中，将第一混合物进行第一烧结处理，得到第一功能性封装层包覆核体材料的复合物；然后于含第一碳源的环境中进行第一热处理，在第一功能性封装层中生成碳酸锂，得到补锂添加剂；其中，第一核体材料前驱体包括第一补锂材料前驱体；
或
提供包括第二补锂材料的第二核体材料，在第二核体材料表面形成包覆于第二核体材料的第二功能性封装层；再于含第二碳源的环境中进行第二热处理，在第二功能性封装层中生成碳酸锂，得到补锂添加剂。
进一步地，第一碳源和/或第二碳源包括二氧化碳、C 1-C 4的醇类、C 1-C 4的醚类、C 1-C 4的酮类、C 1-C 4的烃类化合物中的至少一种。
进一步地，第一烧结处理的温度为450℃-1000℃，时间为0.5-10h。
进一步地，第一烧结处理是以100-500℃/h的速率升温至450℃-1000℃。
进一步地，第一热处理和/或第二热处理的温度为400-800℃，时间为2-10h。
本申请的第三方面，提供了一种电极片，本申请电极片包括集流体和结合在集流体表面的电极活性层，电极活性层中掺杂有本申请补锂添加剂或由本申请补锂添加剂制备方法制备的补锂添加剂。
本申请的第四方面，提供了一种二次电池。本申请包括正极片和负极片，正极片或负极片为电极片。
与现有技术相比，本申请具有以下的技术效果：
本申请补锂添加剂所含的核体由于含有补锂材料，因此赋予本申请补锂添加剂能够提供丰富的锂，使得在首圈充电过程中作为“牺牲剂”，尽可能一次性将全部锂离子释放出来，用以补充负极形成SEI膜而消耗掉的不可逆的锂离子，从而保持电池体系内锂离子的充裕，提高电池首效和整体电化学性能。与此同时，本申请补锂添加剂通过在功能性封装层与核体界面之间或/和功能性封装层中功能性封装层中分散碳酸锂，其与功能性封装层起到增效作用，能够有效提高功能性封装层对核体的作用，使得核体与外界中的水分和二氧化碳隔离，保证核体的稳定性从而保证补锂添加剂的补锂效果和补锂的稳定性，而且使得功能性封装层中的残碱含量低，赋予本申请补锂添加剂优异的加工性能。
本申请补锂添加剂的制备方法能够有效制备具有核壳结构的补锂添加剂，而且能够使得功能性封装层有效包覆含补锂材料的核体，并使得制备的补锂添加剂所含残碱含量低或能够消除残碱含量，并含有碳酸锂，而且赋予制备的功能性封装层致密，从而使得制备的补锂添加剂补锂效果优异和补锂性能稳定以及良好的加工性能。另外，补锂添加剂的制备方法能够保证制备的补锂添加剂结构和电化学性能稳定，而且效率高，节约生产成本。
本申请电极片由于含有本申请补锂添加剂，因此，本申请电极片的电极活性层所含成分分散均匀，膜层质量高，赋予本申请极片优异的电化学性能。而且在充放电过程中，所含的补锂添加剂能够作为锂源在首圈充电过程中作为“牺牲剂”，用以补充负极形成SEI膜而消耗掉的不可逆的锂离子，从而保持电池体系内锂离子的充裕，提高电池首效和整体电化学性能。
本申请二次电池由于含有本申请电极片，因此，本申请锂离子电池具有优异的首次库伦效率和电池容量以及循环性能，寿命长，电化学性能稳定。
 附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请实施例补锂添加剂的结构示意图；
图2为图1所示补锂添加剂所含功能性封装层包括疏水性封装层的结构示意图；
图3为图1所示补锂添加剂所含功能性封装层包括疏水性封装层和电子导体封装层的结构示意图；
图4为图1所示补锂添加剂所含功能性封装层包括疏水性封装层和离子导体封装层的结构示意图；
图5为图1所示补锂添加剂所含功能性封装层包括疏水性封装层、电子导体封装层和离子导体封装层的结构示意图；
图6为本申请实施例补锂添加剂的一种制备方法的流程示意图；
图7为本申请实施例补锂添加剂的另一种制备方法的流程示意图；
图8为实施例1中补锂添加剂的电镜图；
图9为实施例5中补锂添加剂的电镜图；
图10为对比例1中补锂添加剂的电镜图；
图11为实施例5中补锂添加剂的X射线衍射图；
图12为对比例1中补锂添加剂的X射线衍射图。
 本发明的实施方式
为了使本申请要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请中，术语“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况。其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项（个）或复数项（个）的任意组合。例如，“ a,b,或c中的至少一项（个）”，或，“a,b,和c中的至少一项（个）”，均可以表示：a, b, c, a-b（即a和b）, a-c, b-c, 或a-b-c，其中a,b,c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。具体地，本申请实施例说明书中所述的质量可以是µg、mg、g、kg等化工领域公知的质量单位。
术语“第一”、“第二”仅用于描述目的，用来将目的如物质彼此区分开，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。例如，在不脱离本申请实施例范围的情况下，第一XX也可以被称为第二XX，类似地，第二XX也可以被称为第一XX。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。
第一方面，本申请实施例提供了一种补锂添加剂。本申请实施例补锂添加剂包括核体和包覆于核体的功能性封装层，也即是本申请实施例补锂添加剂为核壳结构，如实施例中，本申请实施例补锂添加剂的结构如图1至图5所示，包括核体10和包覆于核体10的功能性封装层20。
其中，核体10包括补锂材料，也即是在本申请实施例补锂添加剂中，核体10是为用于补锂的锂源。这样，核体10富含锂，从而保证本申请实施例补锂添加剂能够提供丰富的锂，其作为添加剂加入电极中，使得在首圈充电过程中作为“牺牲剂”，尽可能一次性将该补锂添加剂所含的全部锂离子释放出来，用以补充负极形成SEI膜而消耗掉的不可逆的锂离子。
同时，核体10所含的补锂材料可以是常规的补锂材料，也可以是新研发的补锂材料。如实施例中，补锂材料可以是三元补锂材料或二元补锂材料。如补锂材料可以但不仅仅包括富锂过渡金属氧化物、Li wA、Li 1+x+yAl xM yN zTi 2-x-y-z(PO 4) 3中的至少一种；其中，0＜w≤5，A为C、N、O、P、S、F、B、Se中的至少一种元素，N选自Si、Ge、Sn中的至少一种，M选自Sc、Ga、Y、La中的至少一种，0≤y≤0.5，0≤z≤0.5，0≤x+y≤0.5中的至少一种。在具体实施例中，补锂材料可以但不仅仅包括化学式为Li 2MnO 2、Li 6MnO 4、aLiFeO 2·bLi 2O·cM xO y、Li 6CoO 4、Li 2NiO 2、Li 4SiO 4、Li 2S、Li 3N、Li 8SnO 6、Li 1.3Al 0.3Ti 1.7(PO 4) 3中的至少一种。其中，化学式aLiFeO 2·bLi 2O·cM xO y中的a+b≥0.98，c≤0.02，1.8≤b/a≤2.1，1≤y/x≤2.5，M为Ni、Co、Mn、Ti、Al、Cu、V、Zr中的至少一种。该些补锂材料富含锂，能够在首圈充电过程中释放锂离子起到有效的补锂作用。另外，该核体10的补锂材料种类可以是负极补锂材料或正极补锂材料。当为正极补锂材料时，那么本申请实施例补锂添加剂为正极补锂添加剂。当为负极补锂材料时，那么本申请实施例补锂添加剂为负极补锂添加剂，具体如金属锂微粉核体和被钝化后掺杂碳酸锂的包覆层，那么掺杂碳酸锂的包覆层包覆金属锂微粉材料中，金属锂为核体10的补锂材料，掺杂碳酸锂的包覆层可以作为功能性封装层20或作为的功能性封装层20的一层结构。
实施例中，核体10可以是一次颗粒、二次颗粒中的至少一种，具体可以是核体10所含补锂材料形成的一次颗粒、二次颗粒中的至少一种。实施例中，核体10的粒径可以为50nm -15μm，进一步50nm -10μm。如当核体10为一次颗粒时，一次颗粒粒径也即是核体10的粒径分布为50nm-5μm；当核体10为二次颗粒时，二次颗粒粒径也即是核体10的粒径分布为200nm-15μm，进一步200nm -10μm。其中，二次颗粒是指由一颗以上的一次颗粒聚集而成的团聚颗粒。通过对核体10粒径形态和粒径控制，在其能够提供丰富的锂离子的基础上，还提高了补锂添加剂在锂电池浆料制备中的可加工性，其中，较小的一次粒径也可以脱出更多的锂。
另外，上述各实施例中的核体10所含的补锂材料虽然富含锂，但是其遇水和二氧化碳具有不稳定性，其易与水和二氧化碳发生反应，从而导致本申请实施例补锂添加剂的补锂效果降低。同时补锂材料一般还富含由于加工形成的残碱，该些残碱会进一步导致其加工性能的降低，如会导致含有上文补锂材料如浆料粘度剧增，迅速凝胶失去流动性，从而无法进行后续加工处理。因此，在上述各实施例中的核体10的基础上，上述各实施例中补锂添加剂所含的功能性封装层20包覆于核体10，形成完整的包覆层，且在功能性封装层20与核体10界面之间或/在功能性封装层20中分散有碳酸锂。因此，在碳酸锂的存在条件下，功能性封装层20能够有效起到保护核体10的作用，使得核体10具体是补锂材料与外界中的水分和二氧化碳隔离。由于碳酸锂的存在，至少有效降低了功能性封装层20中的残碱的含量或基本能够消除残碱的含量，从而有效避免残碱导致的加工难题，也即是使得本申请实施例补锂材料具有优异的加工性能。而且该碳酸锂与功能性封装层20起到增效作用，能够有效提高功能性封装层20对核体10的作用，使得核体10与外界中的水分和二氧化碳隔离，保证核体10的稳定性从而保证补锂添加剂的补锂效果和补锂的稳定性，并激发补锂添加剂的克容量发挥。
实施例中，碳酸锂占功能性封装层20质量的0.2-1.5wt%，在进一步实施例中，碳酸锂的含量为0.5-1.5wt%，具体可以是0.2 wt%、0.5 wt%、0.6 wt%、0.7 wt%、0.8 wt%、0.9 wt%、1 wt%、1.1wt%、1.2wt%、1.3wt%、1.4wt%、1.5wt%等典型但非限制性的含量。通过控制碳酸锂的含量以进一步降低补锂添加剂中残碱的含量，特别是功能性封装层20中残碱的含量，以进一步提高本申请实施例补锂添加剂的加工性能，同时提高本申请实施例补锂添加剂的补锂稳定性和补锂效果以及提高功能性封装层20的导电性，激发补锂添加剂的克容量发挥。
另外，碳酸锂可以主要或仅仅是分布在功能性封装层20与核体10界面之间，也可以是主要分布在功能性封装层20中。在本申请实施例中，更多的是碳酸锂主要分布在功能性封装层20与核体10的界面之间，同时分布扩展在功能性封装层20中。
实施例中，碳酸锂在功能性封装层20与核体10界面之间和/或在功能性封装层20的与核体10接触的功能性封装层20表层中碳酸锂含量大于背离核体10的表层（也即是功能性封装层20外表层）中含量。具体的是，碳酸锂在功能性封装层20中的分布特点是，功能性封装层20的靠近核体10的表面至其外表面方向，碳酸锂含量逐渐降低，也即是由功能性封装层20内表面至外表面的方向，碳酸锂呈扩散状分布，其含量逐渐降低。该碳酸锂的该分布特征，能够有效降低补锂添加剂中残碱的含量，且提高功能性封装层20包覆核体10的隔绝水汽和二氧化碳的作用，提高补锂添加剂的补锂稳定性和补锂效果。
基于功能性封装层20上述作用，功能性封装层20的材料可以是能够形成至少具有隔绝水份和二氧化碳作用的材料，如实施例中，功能性封装层20包括疏水性封装层，其材料如可以包括陶瓷、碳材料、氧化物等中的至少一种。功能性封装层20还可以是复合层结构。
如实施例中，疏水性封装层包括导电碳包覆层，碳酸锂分布在导电碳包覆层中和与核体10接触界面上。
进一步地，由于功能性封装层20是包覆核体10的表面，因此，核体10所含补锂材料在进行脱锂首次充电时的锂离子脱出过程中，需要经过功能性封装层20，那么功能性封装层20的电化学性能和厚度等还会影响到锂离子的脱出和迁移效率等。因此，功能性封装层20在具有隔绝水份和二氧化碳等不利因素的基础上，理想的还具有良好的离子导率特性。实施例中，功能性封装层20可以包括离子导体封装层。
另外，同样基于功能性封装层20包覆核体10的表面，补锂添加剂完成补锂作用过程中或之后，其导电性能还会影响到电池的倍率和首效等电化学性能，因此，功能性封装层20在具有隔绝水份和二氧化碳等不利因素的基础上，理想的还可以具有良好的电子导电特性。实施例中，功能性封装层20可以包括电子导体封装层。
因此，作为本申请实施例，补锂添加剂所含的功能性封装层20可以包括疏水性封装层、离子导体封装层、电子导体封装层中的至少一层。那么碳酸锂可以是分散在疏水性封装层、离子导体封装层、电子导体封装层中的至少一层中，具体的可以主要是分布在靠近核体10的包覆层中。可选地，功能性封装层20至少具有以下结构：
一实施例中，如图2所示，功能性封装层20包括疏水性封装层21。
另一实施例中，如图3所示，功能性封装层20包括包覆核体10的疏水性封装层21和包覆在疏水性封装层21外表面的电子导体封装层22。
另一实施例中，如图4所示，功能性封装层20包括包覆核体10的疏水性封装层21和包覆在疏水性封装层21外表面的离子导体封装层23。
另一实施例中，如图5所示，功能性封装层20包括包覆核体10的疏水性封装层21和包覆在疏水性封装层21外表面的电子导体封装层22和离子导体封装层23。
当然，该功能性封装层也可以是疏水性封装层、离子导体封装层、电子导体封装层的其他组合形成的复合结构层。
上述功能性封装层20中增设的电子导体封装层22能够增强功能性封装层20的电子电导率，从而增强补锂添加剂的电子电导率，有利于减小电极内部的阻抗；同时，在核体10作为“牺牲品”释放过程中和释放完毕之后，电子导体封装层22还可以进行二次利用，在电极内部起到导电剂的辅助作用。基于电子导体封装层22的作用，基于电子导体封装层22的作用，其当功能性封装20只含电子导体封装层22时，电子导体封装层22应该致密结构，且是全包覆；当功能性封装20至少包括电子导体封装层22与离子导体封装层23时，电子导体封装层22可以是非全包覆层结构，也可以是非致密结构，但是电子导体封装层22与离子导体封装层23构成的复合包覆层应该是具有隔绝水份和二氧化碳等有害成分的。
实施例中，电子导体封装层22的厚度为1-100nm，进一步为1-50nm，更进一步为2-20nm。另些实施例中，电子导体封装层22在补锂添加剂中的质量含量为0.1-30%，进一步为0.1-10%，更优选地0.5-5%。
实施例中，上述电子导体封装层22的材料包括碳材料、导电氧化物中的至少一种。具体实施例中，碳材料包括无定形碳、碳纳米管、石墨、炭黑、石墨烯等中的至少一种。具体实施例中，导电氧化物可以包括In 2O 3、ZnO、SnO 2中的至少一种。通过调节电子导体封装层22的厚度和材料，能够进一步提高其电子电导率。
实施例中，上述离子导体封装层23能够增强功能性封装20的离子电导率，从而增强补锂添加剂的离子电导率，有利于核体的锂离子向外输运；同时，当核体10作为“牺牲品”释放完锂离子之后，离子导体封装层23还可以进行二次利用，在电极内部起到增强离子传输的辅助作用。基于离子导体封装层23的作用，其当功能性封装20只含离子导体封装层23时，离子导体封装层23应该致密结构，且是全包覆；当功能性封装20至少包括离子导体封装层23与电子导体封装层22时，离子导体封装层23是非全包覆层结构，也可以是非致密结构，但是离子导体封装层23与电子导体封装层22构成的复合包覆层应该是具有隔绝水份和二氧化碳等有害成分的。实施例中，离子导体封装层23的厚度为1-200nm，进一步为1-50nm，更进一步为2-20nm。另一实施例中，离子导体封装层23的材料包括钙钛矿型、NASICON型、石榴石型中的至少一种。具体实施例中，钙钛矿型包括Li 3xLa 2/3-xTiO 3（LLTO），具体如Li 0.5La 0.5TiO 3、Li 0.33La 0.57TiO 3、Li 0.29La 0.57TiO 3、Li 0.33Ba 0.25La 0.39TiO 3、(Li 0.33La 0.56) 1.005Ti 0.99Al 0.0103、Li 0.5La 0.5Ti 0.95Zr 0.05O 3等中的至少一种，NASICON型如但不仅仅为Li 1.4Al 0.4Ti 1.6(PO 4) 3(LATP)，石榴石型包括 Li 7La 3Zr 2O 12（LLZO）、Li 6·4La 3Zr 1·4Ta 0·6O 12，Li 6.5La 3Zr 1.5Ta 0.5O 12中的至少一种。通过调节离子导体封装层23的厚度和材料，能够进一步提高其离子电导率。
另外，还可以根据需要，在功能性封装层20外表面还可以包括其他层结构，如可以但不仅仅包括导电有机物等包覆层，如与上述电子导体封装层22、离子导体封装层23中的至少一层构成复合包覆层结构。当其他包覆层包括导电有机物包覆层时，该导电有机物包覆层是包覆在电子导体封装层22、离子导体封装层23的外表面上。
基于上述各实施例，经检测，本申请实施例补锂添加剂的粒径基本满足：0.2μm≤D50≤10μm，进一步为1μm≤D50≤10μm；D10/D50≥0.3，D90/D50≤2。补锂添加剂的比表面积可以控制为0.5≤BET≤20m 2/g。因此，本申请实施例补锂添加剂粒径可控，均匀，而且表面也即是包覆层致密。
第二方面，本申请实施例还提供了上文补锂添加剂的制备方法。实施例中，本申请实施例补锂添加剂的一制备方法工艺流程如图6所示，包括以下步骤：
S01：将第一核体材料前驱体或第一核体材料与第一功能性封装层前驱体进行第一混合处理形成第一混合物；
S02：于保护气氛中，将第一混合物进行第一烧结处理，得到第一功能性封装层包覆核体材料的复合物；
S03：将复合物于含第一碳源环境中进行第一热处理，在第一功能性封装层中生成碳酸锂，得到补锂添加剂。
其中，步骤S01中的第一核体材料前驱体是形成第一核体材料的前驱体。而步骤S01中第一核体材料为上文本申请实施例补锂添加剂的核体10所含的材料。因此，第一核体材料前驱体是包括上文本申请实施例补锂添加剂核体10所含的补锂材料的前驱体（本说明书定义为第一补锂材料前驱体），第一核体材料也是包括上文本申请实施例补锂添加剂核体10所含的补锂材料。
步骤S01中的第一功能性封装层前驱体为形成上文本申请实施例补锂添加剂所含的功能性封装层20的材料。因此，该第一功能性封装层前驱体种类可以根据第一功能性封装层的材料而选择。
为了节约篇幅，在此不再对步骤S01中的第一核体材料前驱体或核体材料和第一功能性封装层前驱体材料种类做赘述。
步骤S02中的第一烧结处理处理，当第一混合物中含第一核体材料前驱体时，那么就是使得第一混合物中的第一核体材料前驱体生成第一核体材料，那么就必然生成有上文本申请实施例补锂添加剂所含核体10所含的补锂材料。同时第一功能性封装层前驱体生成上文本申请实施例补锂添加剂所含功能性封装层20。
实施例中，第一烧结处理的温度为450℃-1000℃，该温度的第一烧结处理能够使得第一核体材料前驱体和/或第一功能性封装层前驱体充分反应生成核体材料和/或第一功能性封装层材料，如控制第一烧结处理的时间为0.5-10h。
进一步实施例中，第一烧结处理可以是以100-500℃/h的速率升温至450℃-1000℃。通过对第一烧结处理的升温速率控制和调节，提高生成的补锂添加剂的包覆结构完整性和第一功能性封装层的致密性。
另外，当制备的补锂添加剂所含的第一功能性封装层为复合层结构时，如图3至图5所示的复合层结构时，可以按照上述步骤S01和步骤S02先原位形成对应各层前驱体包覆层形成的复合层结构包覆核体10的复合补锂材料，然后将该复合补锂材料进行再次烧结处理。当然，也可以采用化学沉积或物理沉积法在核体10表面依次形成复合层结构所含的层结构。
实施例中，保护气氛可以是由包括氮气、氩气、氮氩混合气、氮氢混合气、氩氢混合气中的任一种保护气体形成的气氛，该保护气氛能够有效保证第一烧结处理形成复合物的晶体结构和电化学性能的稳定性。
步骤S03中的，对步骤S03中的复合物进行第一热处理，使得第一碳源在热处理过程中，能够与步骤S02中的复合物所含的残碱与第一碳源发生化学反应，生成的产物包括碳酸锂。因此，第一热处理的温度至少是能够保证能够生成碳酸锂的温度，如实施例中，第一热处理的温度可以为400-800℃，时间为2-10h。通过对第一热处理的温度等条件控制，能够使得第一碳源能够充分与复合物所含的残碱进行充分反应，降低残碱的含量，并生成的产物中至少包括碳酸锂，以挥发碳酸锂如上文本申请补锂添加剂中所含碳酸锂的作用。
在具体实施例中，第一碳源包括二氧化碳、C 1-C 4的醇类、C 1-C 4的醚类、C 1-C 4的酮类、C 1-C 4的烃类化合物中的至少一种。该些种类的第一碳源能够提供碳，并与复合物中的残碱发生反应。另外，该些第一碳源能够有效形成气态，能够有效在热处理的过程中，进入复合物的包覆层中，与复合物所含的残碱进行充分反应生成碳酸锂，降低复合物残碱的含量。
另外，在步骤S03之后，还可以根据应有的需要，在步骤S03热处理后的第一功能性封装层外表面进一步形成其他层结构，如其他层结构可以但不仅仅包括导电有机物等包覆层，如与上述电子导体封装层22、离子导体封装层23中的至少一层构成复合包覆层结构。当其他包覆层包括导电有机物包覆层时，该导电有机物包覆层是包覆在电子导体封装层22、离子导体封装层23的外表面上。形成方法也可以采用原位混合处理、喷雾干燥等方法形成。
在另些实施例中，本申请实施例补锂添加剂的另一制备方法工艺流程如图7所示，包括以下步骤：
S04：提供包括第二补锂材料的第二核体材料；
S05：在第二核体材料表面形成包覆于第二核体材料的第二功能性封装层；
S06：将步骤S05中产物于含第二碳源环境中进行第二热处理，在第二功能性封装层中生成碳酸锂，得到补锂添加剂。
其中，步骤S04中的第二核体材料为上文本申请实施例补锂添加剂的核体10的材料，那么第二补锂材料为上文本申请实施例补锂添加剂的核体10所含的补锂材料。步骤S05中形成的第二功能性封装层也为上文本申请实施例补锂添加剂所含的功能性封装层20。为了节约篇幅，在此不再对步骤S04中的第二补锂材料和第二核体材料的种类以及步骤S05中形成的第二功能性封装层做赘述。
另外，步骤S05中形成第二功能性封装层的方法可以采用原位包覆法或化学气相沉积法或物理气相沉积法等形成。形成的第二功能性封装层结构可以按照上文本申请实施例补锂添加剂所含功能性封装层20的结构形成，如为图3至图5所示的复合包覆层结构时，可以按照顺序依次形成各层结构。
步骤S06中的，对步骤S05中的复合物进行第二热处理，使得第二碳源在热处理过程中，能够与步骤S05中形成的由第二功能性封装层和核体材料形成复合物所含的残碱与第二碳源发生化学反应，生成的产物包括碳酸锂。因此，第二热处理的温度至少是能够保证能够生成碳酸锂的温度，第二热处理的条件可以与上文第一热处理的条件相同或不同，如实施例中，第二热处理的温度可以为400-800℃，时间为2-10h。通过对第二热处理的温度等条件控制，能够使得第二碳源能够充分与步骤S05形成的复合物所含的残碱进行充分反应，降低残碱的含量，并生成的产物中至少包括碳酸锂，以挥发碳酸锂如上文本申请补锂添加剂中所含碳酸锂的作用。
第二碳源的种类可以与上文第一碳源的种类相同或不同，如在具体实施例中，第二碳源包括二氧化碳、C 1-C 4的醇类、C 1-C 4的醚类、C 1-C 4的酮类、C 1-C 4的烃类化合物中的至少一种。该些种类的第二碳源能够提供碳，并与步骤S05形成的复合物中的残碱发生反应。另外，该些第二碳源能够有效形成气态，能够有效在热处理的过程中，进入复合物的包覆层中，与复合物所含的残碱进行充分反应生成碳酸锂，降低复合物残碱的含量。
另外，在步骤S06之后，还可以根据应有的需要，在步骤S05热处理后的第二功能性封装层外表面进一步形成其他层结构，如其他层结构可以但不仅仅包括导电有机物等包覆层，如与上述电子导体封装层22、离子导体封装层23中的至少一层构成复合包覆层结构。当其他包覆层包括导电有机物包覆层时，该导电有机物包覆层是包覆在电子导体封装层22、离子导体封装层23的外表面上。形成方法也可以采用原位混合处理、喷雾干燥等方法形成。
因此，上述补锂添加剂的制备方法能够有效制备核壳结构的上文本申请实施例补锂添加剂，具体是制备含有碳酸锂的功能性封装层有效包覆含有补锂材料的核体，赋予制备的补锂添加剂残碱含量低或消除残碱，提高功能性封装层的致密性，具有上文本申请实施例补锂添加剂的优异补锂效果和补锂性能稳定以及良好的加工性能，而且还能够通过控制核体和功能性封装层的材料和工艺条件进行优化制备的补锂添加剂的相关性能。另外，补锂添加剂的制备方法能够保证制备的补锂添加剂结构和电化学性能稳定，而且效率高，节约生产成本。
第三方面，本申请实施例还提供了一种电极片。本申请实施例电极片包括集流体和结合在集流体表面的电极活性层，电极活性层中掺杂有上文本申请实施例补锂添加剂。由于本申请实施例电极片含有上述本申请实施例补锂添加剂，因此，在充放电过程中，电极片所含的补锂添加剂发挥上文作用，能够作为锂源在首圈充电过程中作为“牺牲剂”首先被消耗，用以补充负极形成SEI膜而消耗掉的不可逆的锂离子，从而保持电池体系内锂离子的充裕，提高电池首效和整体电化学性能。
其中，电极片可以是二次电池常规的电极片，如包括集流体和结合在集流体表面的电极活性层。
在一实施例中，电极活性层中所含上文本申请实施例补锂添加剂的质量含量可以为0.1-20wt%；优选地，0.1-8wt%。电极活性层包括除了该补锂添加剂之外，还包括电极活性材料、粘结剂和导电剂，其中，粘结剂可以是常用的电极粘结剂，如包括聚偏氯乙烯、可溶性聚四氟乙烯、丁苯橡胶、羟丙基甲基纤维素、甲基纤维素、羧甲基纤维素、聚乙烯醇、丙烯腈共聚物、海藻酸钠、壳聚糖和壳聚糖衍生物中的一种或多种。本申请实施方式中，导电剂可以是常用的导电剂，如包括石墨、碳黑、乙炔黑、石墨烯、碳纤维、C60和碳纳米管中的一种或多种。电极活性材料可以根据电极的种类如正极和负极的不同选择相应的正极活性材料或负极活性材料。其中，正极活性材料包括钴酸锂、锰酸锂、磷酸铁锂、磷酸钒锂，磷酸钒氧锂、氟代磷酸钒锂、钛酸锂、镍钴锰酸锂、镍钴铝酸锂中的一种或多种。那么此时，上述补锂添加剂的种类应该是与电极活性材料的种类相适配的，如当电极活性材料为正极活性材料时，那么上述补锂添加剂应该是适于作为正极补锂添加剂使用；当电极活性材料为负极活性材料时，那么上述补锂添加剂应该是适于作为负极补锂添加剂使用。
实施例中，电极片制备过程可以为：将电极活性材料、补锂添加剂、导电剂与粘结剂混合得到电极浆料，将电极浆料涂布在集流体上，经干燥、辊压、模切等步骤制备得到正极极片。
第四方面，本申请实施例还提供了一种二次电池。本申请实施例二次电池包括正极片、负极片、隔膜和电解质等必要的部件，当然还包括其他必要或辅助的部件。其中，正极片和/或负极片为上述本申请实施例正极片和/或负极片，也即是正极片所含的正极活性层中含有上文本申请实施例补锂添加剂。负极片也可以是在负极活性层中含有上文本申请实施例补锂添加剂。
由于本申请实施例二次电池中含有上文本申请实施例补锂添加剂，基于上文本申请实施例补锂添加剂所具有优异补锂性能或进一步具有离子传导性和/或电子传导性，赋予本申请实施例二次电池优异的首次库伦效率和电池容量以及循环性能，寿命长，电化学性能稳定。
以下通过多个具体实施例来举例说明本申请实施例补锂添加剂及其制备方法和应用等。
1. 补锂添加剂及其制备方法实施例：
实施例1
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为500nm，致密碳层的厚度为40nm，且在致密碳层中分散有碳酸锂，比表面积为9.4 m 2/g，测得电阻率为400 Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3以1：4.98的摩尔比加入到15wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在氮气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到原位碳包覆的LiFeO 2·1.99Li 2O粉体；
S3.将原位碳包覆的LiFeO 2·1.99Li 2O粉体放置回转炉中通80% Vol N 2/CO 2保护，以200℃/h升温速率升温至500℃保温1h，降温冷却得到碳酸锂掺杂的碳包覆LiFeO 2·1.99Li 2O粉体。
实施例2
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O·0.005Al 2O 3补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为800nm，致密碳层的厚度为100nm，且在致密碳层中分散有碳酸锂，比表面积为5.2 m 2/g，测得电阻率为300Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比加入到15wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在80%Vol N 2/CO 2中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到碳酸锂&碳复合包覆的LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体。
实施例3
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O·0.01CuO补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为200nm，致密碳层的厚度为100nm，且在致密碳层中分散有碳酸锂，比表面积15 m 2/g，测得电阻率为52 Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe 2O 3、LiOH、CuO以1：10.1：0.01的摩尔比充分混合均匀；
S2. 在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01CuO粉体；
S3. 将破碎得到粉末放置回转炉中通80% Vol N 2/CO 2保护，以200℃/h升温速率升温至900℃，加通1L/min乙炔保温0.5h，降温冷却得到碳酸锂&碳包覆LiFeO 2·1.99Li 2O·0.01CuO粉体。
实施例4
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O·0.005Al 2O 3补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为1.2μm，致密碳层的厚度为45nm，且在致密碳层中分散有碳酸锂，比表面积5.2m 2/g，测得电阻率为253 Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比加入到15wt%柠檬酸溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在空气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到原位碳包覆的LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体；
S3. 将破碎得到粉末放置回转炉中通氮气保护，以200℃/h升温速率升温至700℃，通1L/min乙炔和20L/min通80% Vol N 2/CO 2保护保温1h，降温冷却得到碳包覆LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体。
实施例5
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·2.025Li 2O·0.01CuO补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为2μm，致密碳层的厚度为150nm，且在致密碳层中分散有碳酸锂，比表面积4.1 m 2/g，测得电阻率为130 Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe 2O 3、LiOH、CuO以1：10.1：0.01的摩尔比充分混合均匀；
S2. 在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01CuO粉体；
S3. 将破碎得到粉末防止回转炉中通氮气保护，以200℃/h升温速率升温至900℃，通1L/min丙酮和20L/min通80% Vol N 2/CO 2保护保温2h，降温冷却得到碳酸锂&碳包覆LiFeO 2·1.99Li 2O·0.01CuO粉体。
实施例6
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·2.025Li 2O·0.01MnO补锂材料核体和包覆核体的致密碳层。其中，核体的平均粒径为750nm，致密碳层的厚度为80nm，且在致密碳层中分散有碳酸锂，比表面积6.7m 2/g，测得电阻率为290 Ω/cm。
本实施例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe 2O 3、LiOH、MnO 2以1：10.1：0.01的摩尔比充分混合均匀；
S2. 在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01MnO粉体；
S3. 将破碎得到粉末防止回转炉中通氮气保护，以200℃/h升温速率升温至700℃，通1L/min乙醇和20L/min 80% Vol N 2/CO 2保温5h，降温冷却得到碳酸锂&碳包覆LiFeO 2·1.99Li 2O·0.01MnO 2粉体。
对比例1
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O补锂材料，不含碳包覆层。
本对比例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3以1：4.98的摩尔比加入到15wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在空气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到LiFeO 2·1.99Li 2O粉体。
对比例2
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括Fe(NO 3) 3·9H 2O、LiNO 3补锂材料核体和包覆核体的致密碳层。在致密碳层中不含碳酸锂。
本对比例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3以1：4.98的摩尔比加入到15wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在氮气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到原位碳包覆的LiFeO 2·1.99Li 2O粉体。
对比例3
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3补锂材料核体和包覆核体的致密碳层。在致密碳层中不含碳酸锂。
本对比例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比加入到40wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在氮气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到原位碳包覆的LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体。
对比例4
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括LiFeO 2·1.99Li 2O·0.005Al 2O 3补锂材料核体和包覆核体的碳酸锂层。
本对比例补锂添加剂的制备方法包括如下步骤：
S1. 将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比加入到40wt%柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；
S2. 在空气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到原位碳包覆的LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体；以200℃/h升温速率升温至400℃，通20L/min 80% Vol N 2/CO 2保温1h，降温冷却得到碳酸锂包覆LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体。
2. 锂离子电池实施例：
将上述实施例1至实施例6提供的补锂添加剂和对比例提供的补锂添加剂分别按照如下方法组装成正极电极和锂离子电池：
正电极：将补锂添加剂与钴酸锂按照5∶95的质量比混合得到混合物，将混合物与聚偏氟乙烯和SP-Li以93∶3∶4的质量比混合球磨搅拌得到正极浆料，将正极浆料涂覆在铝箔表面，辊压后，110℃下真空干燥过夜，得到正极极片；
负极：锂金属片；
电解液：碳酸乙烯酯和碳酸甲乙酯以3:7的体积比混合，并加入LiPF 6，形成电解液，LiPF 6的浓度为1mol/L；
隔膜：聚丙烯微孔隔；
锂离子电池组装：按照锂金属片-隔膜-电解液-正极片的组装顺序在惰性气氛手套箱内组装锂离子电池。
3.相关性能测试
1.补锂添加剂的相关测试
1.1 补锂添加剂的电镜分析：
将上述实施例1至实施例6和对比例1至对比例3提供的补锂添加剂分别进行扫描电镜分析，其中，实施例1、实施例5和对比例1的电镜照片分别如图8、图9、图10所示。
由图8可以看出，实施例1的原位碳包覆富锂铁系补锂添加剂具有较多无规格颗粒，界面比较粗糙。由图9可以看出，实施例5的富锂铁系补锂添加剂表面比较光滑。由图10发现，未包覆的富锂铁系补锂添加剂界面同样比较粗糙。因此，经过二次包覆处理后，能够有效改善补锂添加剂表面质量，提高隔绝效果。
1.2 补锂添加剂的X射线衍射（XRD）表征：
将上述实施例1至实施例6和对比例1至对比例3提供的补锂添加剂分别进行XRD分析，其中，实施例5和对比例1的XRD分别如图10、图11所示。
由图11可以看出，实施例5提供的富锂铁系补锂材料具有除了主峰为Li 5FeO 4外，附带有部分的碳酸锂的衍射峰。由图12可以看出，对比例1提供的富锂铁系补锂材料主要为Li 5FeO 4，没有碳酸锂。其他实施例1至实施例4、实施例6的XRD图也均证实了碳酸锂的存在。
1.3 补锂添加剂核体中补锂材料中掺杂元素M的含量分析：
采用电感耦合等离子体(Inductively Coupled Plasma：ICP)发光分光法分别对将上述实施例1至实施例6和对比例1至对比例3提供的补锂添加剂中掺杂元素M的含量进行分析，测试结果请参阅表1，表1中掺杂元素M的y值即为补锂添加剂中掺杂元素M的含量。
2. 锂离子电池实施例：
将上述锂离子电池实施例中组装的各锂离子电池电化学性能进行测试，测试条件为：将装配好的电池在室温下放置24h后进行充放电测试，充放电电压为2.7V-4.3V，实施例1-4和对比例1-3的锂二次电池的电化学性能请参阅表1。
表1 实施例1-8和对比例1-3的富锂铁系补锂材料和锂离子电池的实验参数表
性能参数   实施组 掺杂元素M的y值 正极浆料状态 碳包覆量 (wt%) 首充克容量(mAh/g) 首效 (%)
LCO 0 正常 0 167.1 95.9
实施例1 0 正常 2.5 186.2 81.7
实施例2 0.01 正常 2.8 187.7 81.1
实施例3 0.01 正常 3.0 189.6 80.3
实施例4 0.005 正常 2.2 188.7 80.65
实施例5 0.01 正常 3.5 184.6 80.9
实施例6 0.01 正常 3.7 185.3 80.6
对比例1 0 果冻 0 170.3 87.7
对比例2 0.01 15min后果冻 2.3 180.2 82.8
对比例3 0.01 15min后果冻 10.8 181.2 83.9
对比例4 0.01 正常 0 175.2 89.2
从表1中可以看出，本申请实施例1-6的富锂铁系补锂材料包覆碳后，制备出的正极浆料不出现果冻现象，容易涂覆，并且将其添加到锂二次电池时，可以使正极具有更高的首次克容量发挥和更低的首次效率，从而补偿由于首次负极不可逆锂损耗导致的能量密度降低。
通过对比例的实验可以看出，对比例1的富锂铁系补锂材料未进行包覆，在正极浆料的制备过程中吸水导致形成果冻，不利于正极浆料的涂覆。
由实施例1和对比例2可以看出，碳酸锂与碳复合包覆层，相对单一单层包覆，电化学稳定性更加优异，加工性良好，且可供脱出的活性锂更多；
由实施例2、实施例4和对比例3可以看出，高负载量碳层，不仅占据活性物质含量，且并不能完好的包覆隔绝与水之间的反应，导致加工性降低。通过碳酸锂与碳复合包覆层，可以进一步提升包覆隔绝水等不利因素，能够显著提高加工性能和补锂的稳定性。
由实施例2、实施例4和对比例4可以看出，碳酸锂能够有效碳酸锂与碳复合包覆层，可以进一步提升包覆隔绝水等不利因素，能够显著提高加工性能和补锂的稳定性，但是将包覆层全部替换成碳酸锂时，由于碳酸锂为绝缘体，一定厚度的碳酸锂增加了极化阻抗，导致锂离子动力学较差，反而影响锂离子的正常脱出。
以上实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (14)

  1. 一种补锂添加剂，所述补锂添加剂包括核体和包覆于所述核体的功能性封装层，其特征在于：所述核体包括补锂材料，在所述功能性封装层与所述核体界面之间或/和所述功能性封装层中分散有碳酸锂。
  2. 根据权利要求1所述的补锂添加剂，其特征在于：所述碳酸锂占所述功能性封装层质量的0.2-1.5wt%；和/或
    所述碳酸锂在所述功能性封装层与所述核体界面之间和/或在所述功能性封装层的与所述核体接触表层中含量大于背离所述核体的表层中含量。
  3. 根据权利要求1或2所述的补锂添加剂，其特征在于：所述碳酸锂占所述功能性封装层质量的0.5-1.5wt%。
  4. 根据权利要求1-3任一项所述的补锂添加剂，其特征在于：所述补锂材料包括富锂过渡金属氧化物、Li wA、Li 1+x+yAl xM yN zTi 2-x-y-z(PO 4) 3金属锂中的至少一种元素；其中，0＜w≤5，A为C、N、O、P、S、F、B、Se中的至少一种元素，N选自Si、Ge、Sn中的至少一种，M选自Sc、Ga、Y、La中的至少一种，0≤y≤0.5，0≤z≤0.5，0≤x+y≤0.5中的至少一种。
  5. 根据权利要求1-4任一项所述的补锂添加剂，其特征在于：所述补锂材料包括Li 2MnO 2、Li 6MnO 4、aLiFeO 2·bLi 2O·cM xO y、Li 6CoO 4、Li 2NiO 2、Li 4SiO 4、Li 2S、Li 3N、Li 8SnO 6、Li 1.3Al 0.3Ti 1.7(PO 4) 3中的至少一种；其中，所述化学式aLiFeO 2·bLi 2O·cM xO y中的a+b≥0.98，c≤0.02，1.8≤b/a≤2.1，1≤y/x≤2.5，M为Ni、Co、Mn、Ti、Al、Cu、V、Zr中的至少一种。
  6. 根据权利要求1-4任一项所述的补锂添加剂，其特征在于：所述核体的粒径可以为50nm -10μm。
  7. 根据权利要求1-6任一项所述的补锂添加剂，其特征在于：所述功能性封装层包括疏水性封装层。
  8. 根据权利要求7所述的补锂添加剂，其特征在于：所述疏水性封装层包括导电碳包覆层，碳酸锂分布在所述导电碳包覆层中和与所述核体接触界面。
  9. 根据权利要求1-8任一项所述的补锂添加剂，其特征在于：所述补锂添加剂的粒径为0.2 μm≤D50≤10μm，D10/D50≥0.3，D90/D50≤2；和/或
    所述补锂添加剂的比表面积为0.5≤BET≤20m 2/g；和/或
    所述补锂添加剂的电阻率为1.0-500 Ω/cm。
  10. 一种补锂添加剂的制备方法，包括如下步骤：
    将第一核体材料前驱体或第一核体材料与第一功能性封装层前驱体进行第一混合处理形成第一混合物；再于保护气氛中，将所述第一混合物进行第一烧结处理，得到第一功能性封装层包覆核体材料的复合物；然后于含第一碳源的环境中进行第一热处理，在所述第一功能性封装层中生成碳酸锂，得到补锂添加剂；其中，所述第一核体材料前驱体包括第一补锂材料前驱体；
    或
    提供包括第二补锂材料的第二核体材料，在所述第二核体材料表面形成包覆于所述第二核体材料的第二功能性封装层；再于含第二碳源的环境中进行第二热处理，在所述第二功能性封装层中生成碳酸锂，得到补锂添加剂。
  11. 根据权利要求10所述的制备方法，其特征在于，所述第一碳源和/或第二碳源包括二氧化碳、C 1-C 4的醇类、C 1-C 4的醚类、C 1-C 4的酮类、C 1-C 4的烃类化合物中的至少一种。
  12. 根据权利要求10或11所述的制备方法，其特征在于，所述第一烧结处理的温度为450℃-1000℃，时间为0.5-10h；和/或
    所述第一烧结处理是以100-500℃/h的速率升温至450℃-1000℃；和/或
    所述第一热处理和/或第二热处理的温度为400-800℃，时间为2-10h。
  13. 一种电极片，包括集流体和结合在集流体表面的电极活性层，其特征在于：所述电极活性层中掺杂有权利要求1-9任一项所述的补锂添加剂或由权利要求10-12任一项所述的制备方法制备的补锂添加剂。
  14. 一种二次电池，包括正极片和负极片，其特征在于：所述正极片或负极片为权利要求13所述的电极片。
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CN116979051B (zh) * 2023-09-22 2023-12-01 深圳中芯能科技有限公司 锰系补锂添加剂及其制备方法和应用

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