Lithium replenishment materials, positive electrodes, electrochemical devices and power consuming devices

Abstract

This disclosure provides LiFe 1-x M x O4 and Li5Fe 1-x M x and a cladding layer disposed on the surface of O4. 1-x M x In O4, M is at least one of Ni, Mn, Ru, Cr, Cu, Nb, Al, Mg, Ca, Ga, Ti, and Mo, and 0≦x≦0.2. The cladding layer includes zinc oxide doped with M′ or a zinc oxide-based composite oxide doped with M′, where M′ is an ion capable of forming a substitution solid solution with zinc oxide or a zinc oxide-based composite oxide.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This disclosure claims priority to and benefit of Chinese Patent Application No. 202211739170.2, filed with the State Intellectual Property Office on December 30, 2022, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to the field of electrochemical technology, and in particular to lithium replenishment materials, positive electrodes, electrochemical devices, and power consuming devices. [Background technology]

[0003] During the initial charge of a lithium-ion battery, a solid electrolyte interphase (commonly referred to as an SEI film) forms on the surface of the negative electrode. As a result, the active lithium in the positive electrode is consumed, resulting in low initial efficiency of the lithium-ion battery. The irreversible capacity loss of the most widely used graphite negative electrode can be up to 10%. For silicon- and tin-based negative electrodes with high specific capacities, the irreversible capacity loss can be up to 30% or more, significantly reducing the energy density of the lithium-ion battery. Therefore, the initial efficiency and cycling performance of lithium-ion batteries are usually improved by using lithium replenishment methods. Current lithium replenishment materials suffer from low lithium replenishment efficiency, poor chemical stability, and / or poor conductivity. Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure is intended to solve at least one of the technical problems in the prior art to some extent. Accordingly, the present disclosure provides a lithium replenishment material, a positive electrode, an electrochemical device, and a power consuming device. [Means for solving the problem]

[0005] In particular, the first aspect of the present disclosure is a LiFe 1-x M x O4 and Li5Fe 1-x M x The present invention provides a lithium replenishment material comprising a clad layer disposed on the surface of LiFeO4. The clad layer includes ZnO or a ZnO composite oxide doped with M' ions, the M' ions being capable of forming a substitutional solid solution with the ZnO or the ZnO composite oxide. 1-x M x In O4, M is at least one of Ni, Mn, Ru, Cr, Cu, Nb, Al, Mg, Ca, Ga, Ti, or Mo. 1-x M x In O4, 0≦x≦0.2.

[0006] A second aspect of the present disclosure provides a positive electrode comprising a positive electrode current collector and a positive electrode material layer, the positive electrode material layer comprising a positive electrode active material and the lithium supplement material provided in the first aspect of the present disclosure.

[0007] A third aspect of the present disclosure provides an electrochemical device comprising the positive electrode provided in the second aspect of the present disclosure.

[0008] A fourth aspect of the present disclosure provides a power consuming device comprising the electrochemical apparatus provided in the third aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following clearly describes the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only a part, not all, of the embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0010] Li5Fe 1-x M x Each molecule of O4 contains four Li +It has a high specific capacity and has the potential to efficiently replenish lithium in electrochemical devices. 1-x M x O4 is highly susceptible to degradation in air, easily reacting with carbon dioxide and water in the air to form lithium hydroxide and lithium carbonate on the surface. The formation of alkaline compounds on the surface not only affects the homogenization process (easily forming a jelly-like texture, which affects subsequent coating), but also causes capacity loss, deterioration of cycle performance, and poor battery consistency. Furthermore, Li5Fe 1-x M x The conductivity of O4 is low, and Li5Fe 1-x M x The result is that the capacity of O4 cannot be fully utilized and a slower charge rate needs to be used during decomposition. 1-x M x The cladding of semiconducting oxide on the surface of O4 is Li5Fe 1-x M x It is possible to form a dense oxide on the surface of O4, and Li5Fe 1-x M x The stability of O4 can be improved to some extent. However, Li5Fe 1-x M x The overall conductivity of the material obtained by cladding only semiconductor oxide on the surface of LiFeO4 is still insufficient. 1-x M x Li5Fe in air when cladded on the surface of O4 1-x M x The stability of O4 can be improved, and a material with improved conductivity can be obtained. However, the excess cladding layer reduces the content of effective lithium replenishment material in the material, thereby affecting the lithium replenishment ability of the material.

[0011] An embodiment of the present disclosure is LiFe 1-x M x O4 and Li5Fe 1-x M xand a clad layer disposed on the surface of O4. The clad layer includes zinc oxide (ZnO) doped with M' or a zinc oxide (ZnO)-based composite oxide doped with M', where M' is an ion capable of forming a substitution solid solution with ZnO or a ZnO-based composite oxide. 1-x M x In O4, M is at least one of Ni, Mn, Ru, Cr, Cu, Nb, Al, Mg, Ca, Ga, Ti, and Mo. 1-x M x In O4, 0≦x≦0.2.

[0012] In the embodiment of the present disclosure, "LiFe 1-x M x O4 and Li5Fe 1-x M x and a cladding layer disposed on the surface of O4 can be understood as follows: LiFe 1-x M x The cladding layer containing ZnO or ZnO-based composite oxides doped with M' ions is Li5Fe 1-x M x The M' ions in the cladding layer are arranged on the surface of the O4 particles, and form a solid solution with ZnO or a ZnO-based composite oxide. The cladding layer is composed of Li5Fe 1-x M x The O4 particles can inhibit the chemical reaction between carbon dioxide and water in the air, preventing the reaction between the lithium replenishment material and the external environment, thereby improving the stability of the lithium replenishment material and its overall conductivity.When the lithium replenishment material is used in electrochemical devices such as lithium ion batteries, the formation time can be significantly shortened, the initial coulomb efficiency and cycle performance of the battery can be significantly improved, and the battery's consistency can be improved.

[0013] In the embodiments of the present disclosure, ZnO doped with M' ions can be understood as a composite oxide formed by M' and Zn. In the composite oxide, part or all of M' forms a substitutional solid solution with ZnO. A ZnO-based composite oxide doped with M' can be understood as a composite oxide formed by M', Zn, and another element. In the composite oxide, part or all of M' forms a substitutional solid solution with the ZnO-based composite oxide. The M' ions can be understood as ions capable of forming a substitutional solid solution with ZnO, and include, but are not limited to, any one or more of tetravalent ions of elements such as silicon (Si), germanium (Ge), titanium (Ti), zirconium (Zr), molybdenum (Mo), and tin (Sn), and trivalent ions of elements such as aluminum (Al), molybdenum (Mo), titanium (Ti), gallium (Ga), indium (In), and yttrium (Y).

[0014] In the embodiment of the present disclosure, "LiFe 1-x M x The cladding layer placed on the surface of O4 is Li5Fe 1-x M x The surface of O4 may be partially clad, or Li5Fe 1-x M x The entire surface of O may be clad. In some embodiments of the present disclosure, the cladding layer is LiFe 1-x M x The entire surface of O4 is clad, which can better prevent the reaction between the lithium-supplemented material and the external environment, and improve the stability and conductivity of the lithium-supplemented material.

[0015] In some embodiments of the present disclosure, LiFe 1-x M xThe x in O4 satisfies 0≦x≦0.1. The x satisfies 0≦x≦0.1 so that the capacity of the lithium supplementary material can be balanced. On the one hand, the electronic conductivity of the material is improved so that the capacity of the material is fully utilized. On the other hand, the content of effective substances is not significantly reduced, and the capacity of the material is not reduced.

[0016] In some embodiments of the present disclosure, LiFe 1-x M x O4 is Li5FeO4.

[0017] In some embodiments of the present disclosure, M' is Si 4+ , Ge 4+ , Ti 4+ , Zr 4+ , Mo 4+ , Sn 4+ , Al 3+ , Mo 3+ , Ti 3+ , Ga 3+ , In 3+ , and Y 3+ In this case, the M' ions can better form a substitution solid solution with ZnO, improving the conductive performance of the lithium-supplemented material.

[0018] In some embodiments of the present disclosure, M' is Zr 4+ , Mo 3+ , Ti 3+ , Ga 3+ , and Al 3+ At least one of Zr 4+ , Mo 3+ , Ti 3+ , or Ga 3+ The ionic radius of Zn 2+ The ionic radius of Al is close to that of Al, which can better introduce impurity defects. 3+ Zn 2+ High doping rates can be achieved to improve the solid solubility, thereby achieving higher carrier concentrations and improving the conduction performance of the lithium-supplemented material. 3+ The cost of Al is low. 3+ is also a good choice.

[0019] In some embodiments of the present disclosure, the ZnO-based composite oxide is a composite oxide formed of ZnO and at least one of SnO, ZrO2, and BO3. The composite oxide formed of ZnO and at least one of SnO, ZrO2, and BO3 can improve the stability and conductivity of the lithium-supplemented material.

[0020] In some embodiments of the present disclosure, in M'-doped ZnO or M'-doped ZnO-based composite oxide, the amount of substance of M' accounts for 1 mol% to 5 mol% of the total amount of substance of non-oxygen elements. In other words, the molar content of M' is 1% to 5% by using the total molar amount of non-oxygen elements in M'-doped ZnO or M'-doped ZnO-based composite oxide as reference. In M'-doped ZnO, the non-oxygen elements can be understood as M' and Zn, and the total amount of substance of non-oxygen elements can be understood as the total amount of substance of M' and Zn. In M'-doped ZnO-based composite oxide, the non-oxygen elements can be understood as M', Zn, and other non-oxygen elements such as Sn, B, and Zr in the composite oxide. When the content of M' is within this range, the carrier concentration in the cladding layer can be maintained within an appropriate range, thereby enabling the cladding layer to be formed as Li5Fe 1-x M x This ensures that the chemical reaction between O4 and carbon dioxide and water in the air can be better inhibited, and the conductive performance of the lithium-supplemented material can be further improved. In the M'-doped ZnO or M'-doped ZnO-based composite oxide, the percentage of the amount of substance of M' relative to the total amount of substance of non-oxygen elements can be, for example, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4 mol%, 4.5 mol%, and 5 mol%.

[0021] In some embodiments of the present disclosure, in M'-doped ZnO or M'-doped ZnO-based composite oxide, the amount of substance of M' accounts for 2 mol % to 3 mol % of the total amount of substance of non-oxygen elements.

[0022] In some embodiments of the present disclosure, the lithium supplement material has a median particle size D50 of 7 μm to 13 μm. When the D50 of the lithium supplement material is within this range, the lithium supplement material can have better conductivity, promote uniform dispersion of the lithium supplement material, and improve lithium supplement efficiency. The specific median particle size D50 of the lithium supplement material can be, for example, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or 13 μm.

[0023] In some embodiments of the present disclosure, the D90 of the lithium supplemented material is 30 μm or less. When the D90 of the lithium supplemented material is within this range, the lithium supplemented material can have better conductivity, promote uniform dispersion of the lithium supplemented material, and improve lithium supplementation efficiency. The D90 of the lithium supplemented material can be, for example, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm.

[0024] The test method for the above D50 and D90 includes performing a laser particle size test on a material in accordance with GB / T19077-2016 Particle Size Analysis - Laser Diffraction Method to obtain a particle size distribution curve of the material, and reading the corresponding particle sizes obtained when the cumulative volume distribution percentage of the material reaches 50% and 90% from the curve, i.e., obtaining D50 and D90.

[0025] In some embodiments of the present disclosure, the content of M'-doped ZnO or M'-doped ZnO-based composite oxide in the lithium supplement material is 1 wt% to 6 wt%. In other words, the mass content of the composite oxide containing M' and Zn is 1 wt% to 6 wt% by using the total mass of the lithium supplement material as reference. When the mass of the composite oxide containing M' and Zn is within this range, the conductivity and air stability of the lithium supplement material can be improved, and excessive reduction in the content of the effective lithium supplement material can be avoided, thereby avoiding an impact on the capacity of the lithium supplement material.

[0026] The present disclosure further provides a positive electrode comprising a positive electrode current collector and a positive electrode material layer. The positive electrode material layer comprises a positive electrode active material and the lithium supplement material provided in the present disclosure. The lithium supplement material provided in the present disclosure has good stability and conductivity, so the positive electrode active material comprises the lithium supplement material. When the positive electrode is used in an electrochemical device, such as a lithium-ion battery, the initial coulomb efficiency and cycle performance of the battery can be significantly improved, and the battery has good consistency.

[0027] In the positive electrode of the present disclosure, the positive electrode material layer can be a single layer or multiple layers.

[0028] When the positive electrode material layer is a single layer, the lithium supplementary material is mixed with the positive electrode active material in the positive electrode material layer. It should be noted that in addition to the lithium supplementary material and the positive electrode active material, the positive electrode material layer may further include some necessary auxiliary materials, such as a conductive agent and an adhesive, based on requirements. In the case of a solid-state battery system, the positive electrode material layer may not include an adhesive, but includes a solid electrolyte. This is not particularly limited in this specification.

[0029] When the positive electrode material layer has multiple layers, the positive electrode material layer may include a lithium supplementary layer and a positive electrode active material layer, where the lithium supplementary layer includes the lithium supplementary material provided in the present disclosure, and the positive electrode active material layer includes a positive electrode active material. It should be noted that in addition to the lithium supplementary material provided in the present disclosure, the lithium supplementary layer may further include some necessary auxiliary materials, such as a conductive agent and an adhesive, based on requirements. This is not particularly limited herein. In addition to the positive electrode active material, the positive electrode active material layer may further include some necessary auxiliary materials, such as a conductive agent and an adhesive, based on requirements. In the case of a solid-state battery system, the lithium supplementary layer and the positive electrode active material layer may not include an adhesive, but include a solid electrolyte. Furthermore, the positive electrode active material layer may further include a certain amount of lithium supplementary material based on requirements. This is not particularly limited herein.

[0030] The positive electrode active material is a material that can reversibly release and incorporate active ions. In some embodiments of the present disclosure, the positive electrode active material includes one or more of a lithium transition metal oxide and a lithium-containing phosphate. In some embodiments of the present disclosure, the positive electrode active material can include, but is not limited to, one or more of a lithium monoxide (e.g., lithium cobalt oxide, lithium manganese oxide, or lithium nickel oxide), a lithium binary oxide (e.g., lithium nickel manganese oxide or lithium nickel cobalt oxide), a lithium ternary oxide (e.g., lithium nickel cobalt manganate ternary material or lithium nickel cobalt aluminate ternary material), and a lithium-containing phosphate (e.g., lithium iron phosphate or lithium manganese iron phosphate).

[0031] Adhesives and conductive agents are conventional choices in the battery field. For example, the adhesive may be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin (e.g., polyethylene, polypropylene, or polystyrene), sodium carboxymethyl cellulose (CMC), sodium alginate, etc. The conductive agent may be at least one of carbon black (e.g., acetylene black or ketjen black), carbon nanotubes (CNT), graphene, carbon fiber, graphite, etc. Furthermore, the positive electrode current collector may include, but is not limited to, metal film materials and foam metal mesh, specifically aluminum foil, carbon-coated aluminum foil, etc.

[0032] In some embodiments of the present disclosure, the content of the lithium supplementary material in the positive electrode layer is 1 wt % to 5 wt %. In other words, the mass content of the lithium supplementary material is 1 wt % to 5 wt % by using the total mass of the positive electrode layer as a reference. When the content of the lithium supplementary material in the positive electrode layer is within this range, it can be ensured that there is enough lithium supplementary material to replenish lithium, and the reduction in the content of the active material caused by the introduction of excess lithium supplementary material can be avoided, thereby improving the initial coulomb efficiency and cycle performance of the battery as a whole.

[0033] In some embodiments of the present disclosure, the active cathode material includes at least one of lithium iron phosphate, a ternary material, lithium manganate, and lithium cobaltate.

[0034] The present disclosure further provides an electrochemical device comprising a positive electrode according to the present disclosure.

[0035] Electrochemical devices in the present disclosure can include any device in which an electrochemical reaction occurs, and specific examples of electrochemical devices include, but are not limited to, primary batteries, secondary batteries, and capacitors. Optionally, the electrochemical device can be a lithium-ion secondary battery.

[0036] In some embodiments of the present disclosure, a lithium-ion secondary battery includes a positive electrode, a negative electrode, a partition wall disposed between the positive and negative electrodes, and an electrolyte. In the present disclosure, the negative electrode is a conventional option in the battery field. For example, the negative electrode includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector. The negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, mesocarbon microbeads (MCMB), silicon-carbon composites, silicon oxide, silicon alloys, lithium titanate, etc. The negative electrode current collector may include, but is not limited to, a metal film material, a foam metal mesh, etc., and may specifically be copper foil, etc. The partition wall is used to separate the positive and negative electrodes and maintain insulation between them. The partition wall, positive and negative electrodes, and the electrode together form the battery's electrode core. The electrode core is housed in a battery housing. The separator may be a separator commonly used in batteries, such as a polymer separator, a nonwoven separator, or a polymer / inorganic composite separator, including, but not limited to, a monolayer PP (polypropylene) film, a monolayer PE (polyethylene) film, a two-layer PP / PE separator, a two-layer PP / PP separator, and a three-layer PP / PE / PP separator. An electrolyte is injected into the battery housing, and the electrolyte is the medium through which lithium ions are transferred between the positive and negative plates. The specific composition of the electrolyte is a conventional choice in the battery field, and is not limited herein.

[0037] In some embodiments of the present disclosure, a method for preparing a lithium-ion secondary battery includes sequentially stacking a positive electrode, a partition wall, and a negative electrode to form a pole core, housing the pole core in a battery casing, injecting an electrolyte, and then sealing the battery casing to obtain a lithium-ion battery.

[0038] In some embodiments of the present disclosure, the lithium ion secondary battery includes a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode of the present disclosure. The specific composition of the negative electrode and the solid electrolyte is a conventional choice in the battery field and is not limited herein.

[0039] The present disclosure further provides a power consuming device that includes an electrochemical device provided herein.

[0040] Power consuming devices in the present disclosure include, but are not limited to, energy storage devices, vehicles, or electronic products. [Example]

[0041] The present invention will now be described in more detail with reference to examples.

[0042] Example 1 A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. Al(NO3)3·9H2O is added to the Zn(CH3COO)2·2H2O solution and stirred until completely dissolved, resulting in a mixed solution containing Zn and Al ions. In the mixed solution, the molar content of Al ions is 3 mol% relative to the total amount of Zn and Al ions. A 0.8 mol / L NaHCO3 solution is added dropwise to the mixed solution containing Zn and Al ions while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued to completely precipitate the carbonate. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then fired in an oxidizing atmosphere at a high temperature of 900 to 1200°C to obtain ZnO doped with Al ions. In the ZnO doped with Al ions, the molar content of Al ions is 3 mol% relative to the total amount of Zn ions and Al ions.

[0043] Lithium oxalate, iron oxide, and the above Al ion-doped ZnO are mixed and ground to obtain a precursor, which is then dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a Li5FeO4 positive electrode lithium supplement material coated with Al ion-doped ZnO, which is designated as M1. In M1, the mass content of Al ion-doped ZnO is 5 wt%.

[0044] M1 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M1-lithium iron phosphate mixed positive electrode material.

[0045] Example 2 A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. Al(NO3)3·9H2O is added to the Zn(CH3COO)2·2H2O solution and stirred until completely dissolved, resulting in a mixed solution containing Zn and Al ions. In the mixed solution, the molar content of Al ions is 5 mol% relative to the total amount of Zn and Al ions. A 0.8 mol / L NaHCO3 solution is added dropwise to the mixed solution containing Zn and Al ions while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued to completely precipitate the carbonate. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then fired in an oxidizing atmosphere at a high temperature of 900 to 1200°C to obtain ZnO doped with Al ions. In the ZnO doped with Al ions, the molar content of Al ions is 5 mol% relative to the total amount of Zn ions and Al ions.

[0046] Lithium oxalate, iron oxide, and the above Al ion-doped ZnO are mixed and ground to obtain a precursor, which is then dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a Li5FeO4 positive electrode lithium supplement material coated with Al ion-doped ZnO, which is designated as M2. In M2, the mass content of Al ion-doped ZnO is 5 wt%.

[0047] M2 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M2-lithium iron phosphate mixed positive electrode material.

[0048] Example 3 A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. Zr(NO3)4·3H2O is added to the Zn(CH3COO)2·2H2O solution and stirred until completely dissolved, resulting in a mixed solution containing Zn and Zr ions. In the mixed solution, the molar content of Zr ions is 3 mol% relative to the total amount of Zn and Zr ions. A 0.8 mol / L NaHCO3 solution is added dropwise to the mixed solution containing Zn and Zr ions while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued to completely precipitate the carbonate. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then fired in an oxidizing atmosphere at a high temperature of 900°C to 1200°C to obtain ZnO doped with Zr ions. In the ZnO doped with Zr ions, the molar content of Zr ions is 3 mol% relative to the total amount of Zn ions and Zr ions.

[0049] Lithium oxalate, iron oxide, and the above Zr ion-doped ZnO are mixed and ground to obtain a precursor, which is dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a Li5FeO4 positive electrode lithium supplement material coated with Zr ion-doped ZnO, which is designated as M3. In M3, the mass content of Zr ion-doped ZnO is 5 wt%.

[0050] M3 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M3-lithium iron phosphate mixed positive electrode material.

[0051] Example 4 A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. Ge(NO3)4 is added to the Zn(CH3COO)2·2H2O solution and stirred until completely dissolved, resulting in a mixed solution containing Zn and Ge ions. In the mixed solution, the molar content of Ge ions is 2 mol% relative to the total amount of Zn and Ge ions. A 0.8 mol / L NaHCO3 solution is added dropwise to the mixed solution containing Zn and Ge ions while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued to completely precipitate the carbonate. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then fired in an oxidizing atmosphere at a high temperature of 900 to 1200°C to obtain ZnO doped with Ge ions. In the ZnO doped with Ge ions, the molar content of Ge ions is 3 mol% relative to the total amount of Zn ions and Ge ions.

[0052] Lithium oxalate, iron oxide, and the above-mentioned Ge ion-doped ZnO are mixed and pulverized to obtain a precursor, which is dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a LiFeO positive electrode lithium supplement material coated with Ge ion-doped ZnO, which is designated as M4. In M4, the mass content of Ge ion-doped ZnO is 5 wt%.

[0053] M4 is mixed with lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain M4-lithium iron phosphate mixed positive electrode material.

[0054] Example 5 A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. Al(NO3)3·9H2O is added to the Zn(CH3COO)2·2H2O solution and stirred until completely dissolved, resulting in a mixed solution containing Zn and Al ions. In the mixed solution, the molar content of Al ions is 3 mol% relative to the total amount of Zn and Al ions. A 0.8 mol / L NaHCO3 solution is added dropwise to the mixed solution containing Zn and Al ions while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued to completely precipitate the carbonate. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then fired in an oxidizing atmosphere at a high temperature of 900 to 1200°C to obtain ZnO doped with Al ions. In the ZnO doped with Al ions, the molar content of Al ions is 3 mol% relative to the total amount of Zn ions and Al ions.

[0055] Lithium oxalate, iron oxide, and the above Al ion-doped ZnO are mixed and ground to obtain a precursor, which is then dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a Li5FeO4 positive electrode lithium supplement material coated with Al ion-doped ZnO, which is designated as M5. In M5, the mass content of Al ion-doped ZnO is 2 wt%.

[0056] M5 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M5-lithium iron phosphate mixed positive electrode material.

[0057] Example 6 Example 6 differs from Example 1 only in that the amount of Al(NO3)3·9H2O added is adjusted so that the molar content of Al ions in the resulting Al ion-doped ZnO is 0.5 mol%.

[0058] The obtained positive electrode lithium supplement material M6 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M6-lithium iron phosphate mixed positive electrode material.

[0059] Example 7 Example 7 differs from Example 1 only in that the amount of Al(NO3)3·9H2O added is adjusted so that the molar content of Al ions in the resulting Al ion-doped ZnO is 7 mol%.

[0060] The obtained positive electrode lithium supplement material M7 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M7-lithium iron phosphate mixed positive electrode material.

[0061] Example 8 Example 8 differs from Example 1 only in that the amount of Al ion-doped ZnO added is adjusted so that the mass content of Al ion-doped ZnO in the resulting positive electrode lithium supplement material M8 is 0.6 wt %.

[0062] M8 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M8-lithium iron phosphate mixed positive electrode material.

[0063] Example 9 Example 9 differs from Example 1 only in that the amount of Al ion-doped ZnO added is adjusted so that the mass content of Al ion-doped ZnO in the resulting positive electrode lithium supplement material M9 is 8 wt %.

[0064] M9 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M9-lithium iron phosphate mixed positive electrode material.

[0065] Example 10 M1 is prepared according to the same method as in Example 1, and M1 is mixed with lithium iron phosphate positive electrode active material in a mass ratio of 1:99 to obtain M10-lithium iron phosphate mixed positive electrode material.

[0066] Example 11 M1 is prepared according to the same method as in Example 1, and M1 is mixed with lithium iron phosphate positive electrode active material in a mass ratio of 5:95 to obtain M11-lithium iron phosphate mixed positive electrode material.

[0067] Example 12 M1 is prepared according to the same method as in Example 1, and M1 is mixed with lithium iron phosphate positive electrode active material in a mass ratio of 0.5:99.5 to obtain M12-lithium iron phosphate mixed positive electrode material.

[0068] Example 13 Example 13 differs from Example 1 only in that Al(NO3)3·9H2O is replaced with Ti(Cl)3·4H2O aqueous solution to obtain ZnO doped with Ti ions.

[0069] The obtained positive electrode lithium supplement material M13 is mixed with a lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M13-lithium iron phosphate mixed positive electrode material.

[0070] Example 14 Example 14 differs from Example 1 only in that 0.5 mol / L Zn(CH3COO)2·2H2O solution is replaced with 0.25 mol / L Zn(CH3COO)2·2H2O solution and 0.25 mol / L SnSO4 aqueous solution to obtain Al ion-doped ZnO.SnO.

[0071] The obtained positive electrode lithium supplement material M14 is mixed with a lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M14-lithium iron phosphate mixed positive electrode material.

[0072] Example 15 The ZnO doped with Al ions is prepared in the same manner as in Example 1.

[0073] Lithium oxalate, iron oxide, manganese oxalate, and the above Al-ion doped ZnO were mixed to form Li5Fe 0.9 Mn 0.1 The precursor was obtained by mixing and grinding the elements in stoichiometric ratio in O4, drying the precursor, sintering it at a high temperature of 600 °C in an inert atmosphere, and cooling it to obtain Li5Fe coated with ZnO doped with Al ions. 0.9 Mn 0.1 An O4 positive electrode lithium supplement material is obtained, which is designated as M15, in which the mass content of Al ion-doped ZnO is 5 wt%.

[0074] M15 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain an M15-lithium iron phosphate mixed positive electrode material.

[0075] (Comparative Example 1) A 0.5 mol / L Zn(CH3COO)2·2H2O solution is prepared using deionized water as the solvent. A 0.8 mol / L NaHCO3 solution is added dropwise to the Zn(CH3COO)2·2H2O solution while stirring until the pH reaches the specified value of 7 (±0.5). At this point, the dropwise addition of the NaHCO3 solution is stopped, and stirring and aging are continued until the carbonate is completely precipitated. After the carbonate precipitation reaction is complete, the precipitate is vacuum filtered, washed with deionized water, and then dried in an oven at 80°C to obtain the precursor. The precursor is then calcined at high temperatures of 900°C to 1200°C in an oxidizing atmosphere to obtain ZnO.

[0076] Lithium oxalate, iron oxide, and the above ZnO are mixed and ground to obtain a precursor, which is then dried, sintered at a high temperature of 600°C in an inert atmosphere, and cooled to obtain a ZnO-coated LiFeO positive electrode lithium supplement material, designated PM1. In PM1, the mass content of ZnO is 5 wt%.

[0077] PM1 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain a PM1-lithium iron phosphate mixed positive electrode material.

[0078] (Comparative Example 2) The lithium supplement material PM1 is prepared according to the same method as in Comparative Example 1. Acetylene black is coated on the surface of PM1 to obtain PM2. PM2 comprises a Li5FeO4 matrix, a first clad layer, i.e., a ZnO layer, on the surface of the Li5FeO4 matrix, and a second clad layer, i.e., a carbon layer, on the surface of the first clad layer. In PM2, the mass content of ZnO is 3 wt% and the content of the carbon layer is 1.5%.

[0079] PM2 is mixed with the lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain a PM2-lithium iron phosphate mixed positive electrode material.

[0080] (Comparative Example 3) The carbon source (starch) is dispersed and mixed with the iron oxide. After the carbon source is uniformly dispersed, a layer of the carbon source solution is coated on the surface of the iron oxide under the action of a surfactant, and then sintered at 600°C for 10 hours to form a carbon layer on the surface of the iron oxide.

[0081] Using wet ball milling, the carbon-coated iron oxide was mixed with lithium oxalate in the stoichiometric ratio of lithium and iron in Li5FeO4, dried, and then sintered at 800 °C for 20 hours in an inert atmosphere and cooled to obtain the carbon-coated Li5FeO4.

[0082] The carbon-coated Li5FeO4 is added to a Zn(CH3COO)2 solution, and an ammonium hydroxide solution is slowly added to the mixture while stirring until the solution becomes a paste, forming an in situ zinc hydroxide precipitate on the carbon surface of the Li5FeO4. The Li5FeO4 material with the in situ zinc hydroxide precipitate formed on the carbon surface is sintered at 700°C for 9 hours in an inert atmosphere and cooled to obtain a Li5FeO4 composite lithium-supplemented material coated with two layers of carbon and zinc oxide, designated PM3.

[0083] PM3 includes a LiFeO matrix, a first cladding layer (i.e., a carbon layer) on the surface of the LiFeO matrix, and a second cladding layer (i.e., a zinc oxide layer) on the surface of the first cladding layer. In PM3, the mass of the carbon layer accounts for 1.5 wt% of PM3, and the mass of the zinc oxide layer accounts for 3 wt% of PM3.

[0084] PM3 is mixed with lithium iron phosphate positive electrode active material in a mass ratio of 3.5:96.5 to obtain PM3-lithium iron phosphate.

[0085] For Examples 1 to 13 and Comparative Examples 1 to 3, the particle size of the positive electrode lithium supplementary material was tested using a laser particle size analyzer (Mastersizer 3000), and the conductivity of the powder material was tested using a powder resistor (FT-301B, pressure 12 MPa). See Table 1 for the measurement data.

[0086] [Table 1]

[0087] The mixed positive electrode materials obtained in Examples 1 to 13 and Comparative Examples 1 to 3 were used separately, with acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the adhesive, and N-methylpyrrolidone (NMP) as the dispersant. The mixed positive electrode material, acetylene black, PVDF, and NMP were uniformly mixed in a mass ratio of mixed positive electrode material:acetylene black:PVDF:NMP=85:10:5:50, and then coated onto aluminum foil as a current collector. The mixture was then vacuum-dried in an oven at 120°C for 24 hours, tableted, and cut into positive electrode plates S1 to S13 and DS1 to DS3.

[0088] Graphite was used as the negative electrode material, styrene butadiene rubber (SBR) as the adhesive, sodium carboxymethylcellulose (CMC) as the thickener, and water (HO) as the dispersant. The graphite, SBR, CMC, and HO were uniformly mixed in a mass ratio of graphite:SBR:CMC:HO = 100:3:2:50 and then coated onto copper foil. The mixture was then dried in an oven at 90°C for 24 hours, and then tableted and cut into negative electrode plates.

[0089] Assemble test batteries in an argon-filled glove box by using positive electrode plates S1–S13 and DS1–DS3 as positive electrode plates, Celgard 2400 polypropylene porous membrane as a partition, and a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio of EC to DMC is 1:1) containing 1 mol / L LiPF6 as an electrolyte to obtain battery samples C1–C13 and DC1–DC3.

[0090] Electrochemical performance tests were conducted separately for battery samples C1 to C13 and DC1 to DC3. A charge / discharge cycle test was conducted on the batteries at 0.1 C using a LAND CT 2001C secondary battery performance detection device at a temperature of 25±1°C. The test procedure was as follows: 10 minutes of rest, 0.1 C constant current charge to 4.0 V, 10 minutes of rest, and 0.1 C constant current discharge to 2.0 V. The initial discharge capacity and initial charge capacity of the battery were recorded, and the initial efficiency was calculated as initial discharge capacity / initial charge capacity × 100%.

[0091] The batteries in the examples and comparative examples were subjected to a cycle performance test. The test conditions were as follows: a charge / discharge cycle test was performed on the batteries at 0.2 C using a LAND CT 2001C secondary battery performance detector under a temperature condition of 25±1°C. The test process was as follows: standing for 10 minutes; constant current charging at 0.2 C to 4.0 V and constant voltage charging to 0.05 C; standing for 10 minutes; and constant current discharging to 0 V. This constitutes one cycle. The cycle capacity retention rate = discharge capacity after 1000 cycles / initial cycle discharge capacity × 100%.

[0092] The measured initial and initial efficiencies of the battery samples are shown in Table 2.

[0093] [Table 2]

[0094] From the data in Tables 1 and 2, it can be seen that in terms of the M' doping effect, the order is Example 1 > Example 3 > Example 13 > Example 4, i.e., Al > Zr > Ti > Ge. In terms of the M' doping amount, the order is Example 1 > Example 2 > Example 6 and Example 7, i.e., the optimal doping amount is 1 mol% to 5 mol%. In terms of the M'-doped ZnO cladding amount, the order is Example 1 > Example 8 and Example 9, i.e., the optimal cladding amount is 1 wt% to 6 wt%. This cladding amount can avoid a reduction in the effective lithium replenisher content due to an excessively large cladding amount, which affects the lithium replenishment capacity, or an excessively small cladding amount, which cannot achieve the corresponding cladding effect, resulting in incomplete utilization of the capacity and insufficient air stability of the lithium replenisher. In terms of particle size, the order is Example 1 > Example 5, which indicates that a D50 of 7 μm to 13 μm and a D90 of 30 μm or less are preferable. In terms of comparison between ZnO and ZnO composite oxide, Example 1>Example 14, that is, ZnO has a better effect than ZnO composite oxide. All of the above examples are superior to the three comparative examples.

[0095] The above description is merely an exemplary embodiment of the present disclosure. It should be noted that those skilled in the art can further make some improvements and modifications to the present disclosure without departing from the principle of the present disclosure, and the improvements and modifications shall fall within the protection scope of the present disclosure.

Claims

1. Li ５ Fe １－ｘ M ｘ O ４ And Li ５ Fe １－ｘ M ｘ O ４ and a cladding layer disposed on the surface of Li. ５ Fe １－ｘ M ｘ O ４ wherein M is at least one of Ni, Mn, Ru, Cr, Cu, Nb, Al, Mg, Ca, Ga, Ti, and Mo, and 0≦x≦0.2; the cladding layer comprises zinc oxide doped with M′ or a zinc oxide-based composite oxide doped with M′, and M′ is an ion capable of forming a substitution solid solution with the zinc oxide or the zinc oxide-based composite oxide.

2. Li ５ Fe １－ｘ M ｘ O ４ 2. The lithium replenishment material according to claim 1, wherein x satisfies 0≦x≦0.

1.

3. Li ５ Fe １－ｘ M ｘ O ４ But Li ５ FeO ４ 3. The lithium replenishment material according to claim 1 or 2, wherein:

4. M' is Si ４＋ , Ge ４＋ , Ti ４＋ , Zr ４＋ , Mo ４＋ , Sn ４＋ , Al ３＋ , Mo ３＋ , Ti ３＋ , Ga ３＋ , In ３＋ , and Y ３＋ 4. The lithium replenishment material according to claim 1, wherein the lithium replenishment material is at least one of:

5. M' is Zr ４＋ , Mo ３＋ , Ti ３＋ , Ga ３＋ , and Al ３＋ 5. The lithium replenishment material according to claim 1, wherein the lithium replenishment material is at least one of:

6. The zinc oxide-based composite oxide is SnO, ZrO ２ , and B ２ O ３ 6. The lithium replenishment material according to claim 1, which is a composite oxide formed by at least one of the above and ZnO.

7. 7. The lithium supplement material according to claim 1, wherein in the zinc oxide doped with M' or the zinc oxide-based composite oxide doped with M', the amount of substance of M' accounts for 1 mol% to 5 mol% of the total amount of substance of non-oxygen elements.

8. 8. The lithium supplement material according to claim 1, wherein in the zinc oxide doped with M' or the zinc oxide-based composite oxide doped with M', the amount of substance of M' accounts for 2 mol% to 3 mol% of the total amount of substance of non-oxygen elements.

9. 9. The lithium replenishment material according to any one of claims 1 to 8, wherein the lithium replenishment material has a D50 of 7 μm to 13 μm.

10. 10. The lithium replenishment material according to any one of claims 1 to 9, wherein the lithium replenishment material has a D90 of 30 μm or less.

11. 11. The lithium replenishment material according to claim 1, wherein the mass percentage of the M'-doped zinc oxide or the M'-doped zinc oxide-based composite oxide is 1% by weight to 6% by weight.

12. A positive electrode comprising a positive electrode current collector and a positive electrode material layer, the positive electrode material layer comprising a positive electrode active material and the lithium supplement material according to claim 1 .

13. 13. The positive electrode according to claim 12, wherein the content of the lithium supplementary material in the positive electrode material layer is 1% by weight to 5% by weight.

14. 14. The positive electrode of claim 12 or 13, wherein the positive electrode active material comprises one or more of a lithium transition metal oxide and a lithium-containing phosphate.

15. 15. The cathode of any one of claims 12-14, wherein the active cathode material comprises at least one of lithium iron phosphate, lithium nickel cobalt manganate ternary material, lithium nickel cobalt aluminate ternary material, lithium manganate, and lithium cobaltate.

16. 16. An electrochemical device comprising the positive electrode of any one of claims 12 to 15.

17. 17. A power consuming device comprising the electrochemical apparatus of claim 16.

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