Composite lithium supplementing material, lithium supplementing positive electrode and lithium ion battery

Abstract

The invention discloses a composite lithium supplementing material, a lithium supplementing positive electrode and a lithium ion battery. The composite lithium supplementing material provided by the invention at least comprises at least one of a lithium supplementing material and a sodium / magnesium / zinc supplementing material. According to the composite lithium supplementing scheme, the capacity can be improved, the cycle life can be prolonged and the service life of the battery cell can be prolonged due to the additional addition of the lithium source, besides, the composition of SEI can be improved by supplementing sodium / magnesium / zinc materials, the stability is improved, the cycle attenuation rate is reduced, and the service life of the battery cell is further prolonged; and the price of the sodium / magnesium / zinc supplementing material is lower than that of the lithium supplementing material, so that the cost can be further reduced. Finally, the above mode of positive electrode lithium supplement and composite sodium / magnesium / zinc supplement can improve the capacity of the battery cell and improve the service life of the battery, and has an extremely wide application prospect in the field of secondary batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary battery materials, and in particular to a composite lithium supplement material, a lithium supplement positive electrode and a lithium ion battery. Background Art

[0002] Lithium-ion batteries are widely used in 3C, electric vehicles, power tools and other products due to their many advantages such as high energy density, long cycle life and no memory effect. However, during the first charge and discharge process of lithium-ion batteries, the electrolyte will be reduced and decomposed on the surface of the negative electrode to form a solid electrolyte interface (SEI), which will permanently consume some lithium ions from the positive electrode, resulting in a low coulombic efficiency (ICE) of the first cycle, reducing the capacity and energy density of lithium-ion batteries. On the other hand, during the cycle storage of the battery, the consumption of active lithium will also cause the battery capacity to decay, further reducing the battery life.

[0003] In the related art, in order to solve the above problems, it can be solved by additionally supplementing active lithium. At present, there are mainly two ways of replenishing lithium at the positive electrode and replenishing lithium at the negative electrode. Among them, replenishing lithium at the negative electrode is less used due to low safety and other reasons, while replenishing lithium at the positive electrode is more commonly used. However, simply replenishing lithium at the positive electrode of lithium-ion batteries also has shortcomings: given that one of the reasons for the decay of cyclic capacity is the consumption of active lithium by SEI reforming and repair, simply replenishing lithium at the positive electrode cannot improve the stability of SEI and cannot reduce the consumption rate of active lithium; on the other hand, since lithium resources are relatively expensive, replenishing lithium will inevitably increase the production cost of the battery.

[0004] Therefore, it is of great significance to solve the problems of the current positive electrode lithium supplement materials, such as the inability to improve the stability of SEI and the high cost, and to provide a composite lithium supplement material that can improve the stability of SEI and reduce the cycle attenuation rate. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a composite lithium supplement material, a lithium supplement positive electrode and a lithium ion battery, aiming to solve the problems of the current positive electrode lithium supplement material that cannot improve the stability of SEI and the high cost.

[0006] In a first aspect of the present invention, a composite lithium supplement material is proposed, which includes a lithium supplement material A and a composite supplement material B; the composite supplement material B includes at least one of a sodium supplement material, a magnesium supplement material, and a zinc supplement material; the mass ratio of the lithium supplement material A to the composite supplement material B is (0.8~8):(0.1~5).

[0007] The composite lithium supplement material according to the embodiment of the present invention has at least the following beneficial effects: The present invention proposes a composite lithium supplement material, which at least includes a lithium supplement material and at least one of a sodium supplement / magnesium supplement / zinc supplement material. In addition to improving the capacity and cycle life, thereby improving the life of the battery cell, the above-mentioned composite lithium supplement scheme can also improve the composition of SEI through sodium supplement / magnesium supplement / zinc supplement materials, improve its stability, reduce the cycle attenuation rate, and further improve the life of the battery cell. Moreover, the sodium supplement / magnesium supplement / zinc supplement materials are cheaper than lithium supplement materials, which can further reduce costs. Finally, the above-mentioned lithium supplement + composite sodium supplement / magnesium supplement / zinc supplement method can increase the capacity of the battery cell and improve the battery life, and has extremely broad application prospects in the field of secondary batteries.

[0008] In some embodiments of the present invention, the lithium supplement material A comprises Li x M y N z , wherein 0<x<10, 0≤y≤10, 0≤z≤20, and y+z>0; M is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, and Mo, and N is selected from at least one of C, O, S, N, F, and P.

[0009] In some embodiments of the present invention, the lithium supplement material A includes one or more of Li5FeO4, Li2O, Li2O2, Li3N, LiN3, Li2S, LiF, Li2C4O4, Li2C2O4, Li2C3O5, Li2C6O6, and Li2N4O2. More preferably, the lithium supplement material A can be an inorganic lithium supplement material Li5FeO4, Li2O, or an organic lithium supplement material Li2C2O4.

[0010] In some embodiments of the present invention, the composite supplementary material B comprises A a B b C c , wherein 0<a<10, 0≤b≤10, 0≤c≤20, and b+c>0; A is selected from at least one of Na, Mg, and Zn, B is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, Mo, Ti, Al, and Ag, and C is selected from at least one of C, O, S, N, F, and P.

[0011] In some embodiments of the present invention, the composite supplementary material B includes a sodium-supplementing material, and the sodium-supplementing material includes one or more of Na5FeO4, Na2O, Na2O2, Na3N, NaN3, Na2S, NaF, Na2C2O4, Na2C3O5, Na2C4O4, Na2C6O6, and Na2N4O2; preferably, the sodium-supplementing material may be Na5FeO4 or Na2O.

[0012] In some embodiments of the present invention, the composite supplementary material B includes a magnesium supplement material, and the magnesium supplement material includes one or more of Mg2Mo6S8, MgS, MgMn2O4, MgMn2S4, MgCo2O4, MgNiO2, MgNi2S4, MgAl2O4, MgFe2O4, MgTiO3, and Mg3(PO4)2. Preferably, the magnesium supplement material may be Mg2Mo6S8 or MgS.

[0013] In some embodiments of the present invention, the composite supplementary material B includes a zinc supplement material, and the zinc supplement material includes one or more of ZnO, ZnCo2O4, ZnMn2O4, ZnFe2O4, ZnTiO3, ZnS, Zn3(PO4)2, ZnAl2O4, ZnNiO2, ZnV2O4, ZnMoO4, ZnCuO, and ZnAgVO4. Preferably, the zinc supplement material may be ZnS or ZnCo2O4.

[0014] A second aspect of the present invention provides a pole piece comprising the above-mentioned composite lithium supplement material.

[0015] The pole piece according to the embodiment of the present invention has at least the following beneficial effects: the pole piece provided by the present invention has additionally added a composite lithium supplement material, which at least includes a lithium supplement material and at least one of a sodium supplement / magnesium supplement / zinc supplement material. In addition to improving the capacity and cycle life, thereby improving the life of the battery cell, the above-mentioned composite lithium supplement scheme can also improve the composition of SEI through sodium supplement / magnesium supplement / zinc supplement materials, improve its stability, reduce the cycle attenuation rate, and further improve the life of the battery cell. Moreover, the sodium supplement / magnesium supplement / zinc supplement materials are cheaper than lithium supplement materials, which can further reduce costs. Finally, the above-mentioned lithium supplement pole piece can increase the capacity of the battery cell, improve the battery life, and has extremely broad application prospects in the field of secondary batteries.

[0016] In a third aspect of the present invention, a lithium-supplementing positive electrode is proposed, comprising a positive electrode current collector and a positive electrode material disposed on at least one side of the positive electrode current collector, wherein the positive electrode material comprises a positive electrode active substance, a binder, a conductive agent and the above-mentioned composite lithium-supplementing material.

[0017] The lithium-supplemented positive electrode of the pole piece according to the embodiment of the present invention has at least the following beneficial effects: the lithium-supplemented positive electrode provided by the present invention has a composite lithium-supplementing material additionally added to the positive electrode material, and the material at least includes a lithium-supplementing material and at least one of a sodium-supplementing / magnesium-supplementing / zinc-supplementing material. In addition to improving the capacity and cycle life and thus improving the life of the battery cell due to the additional addition of a lithium source, the above-mentioned positive electrode composite lithium-supplementing scheme can also improve the composition of SEI through sodium-supplementing / magnesium-supplementing / zinc-supplementing materials, improve its stability, reduce the cycle attenuation rate, and further improve the life of the battery cell. Moreover, the sodium-supplementing / magnesium-supplementing / zinc-supplementing materials are cheaper than lithium-supplementing materials, which can further reduce costs. Finally, the above-mentioned lithium-supplementing positive electrode can increase the capacity of the battery cell, improve the battery life, and has extremely broad application prospects in the field of secondary batteries.

[0018] In some embodiments of the present invention, the lithium supplement material A comprises Li x M y N z , wherein 0<x<10, 0≤y≤10, 0≤z≤20, and y+z>0; M is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, and Mo, and N is selected from at least one of C, O, S, N, F, and P.

[0019] In some embodiments of the present invention, the lithium supplement material A includes one or more of Li5FeO4, Li2O, Li2O2, Li3N, LiN3, Li2S, LiF, Li2C4O4, Li2C2O4, Li2C3O5, Li2C6O6, and Li2N4O2. More preferably, the lithium supplement material A can be an inorganic lithium supplement material Li5FeO4, Li2O, or an organic lithium supplement material Li2C2O4.

[0020] In some embodiments of the present invention, the composite supplementary material B comprises A a B b C c , wherein 0<a<10, 0≤b≤10, 0≤c≤20, and b+c>0; A is selected from at least one of Na, Mg, and Zn, B is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, Mo, Ti, Al, and Ag, and C is selected from at least one of O, S, N, F, and P

[0021] In some embodiments of the present invention, the composite supplementary material B includes a sodium-supplementing material, and the sodium-supplementing material includes one or more of Na5FeO4, Na2O, Na2O2, Na3N, NaN3, Na2S, NaF, Na2C2O4, Na2C3O5, Na2C4O4, Na2C6O6, and Na2N4O2; preferably, the sodium-supplementing material may be Na5FeO4 or Na2O.

[0022] In some embodiments of the present invention, the composite supplementary material B includes a magnesium supplement material, and the magnesium supplement material includes one or more of Mg2Mo6S8, MgS, MgMn2O4, MgMn2S4, MgCo2O4, MgNiO2, MgNi2S4, MgAl2O4, MgFe2O4, MgTiO3, and Mg3(PO4)2. Preferably, the magnesium supplement material may be Mg2Mo6S8 or MgS.

[0023] In some embodiments of the present invention, the composite supplementary material B includes a zinc supplement material, and the zinc supplement material includes one or more of ZnO, ZnCo2O4, ZnMn2O4, ZnFe2O4, ZnTiO3, ZnS, Zn3(PO4)2, ZnAl2O4, ZnNiO2, ZnV2O4, ZnMoO4, ZnCuO, and ZnAgVO4. Preferably, the zinc supplement material may be ZnS or ZnCo2O4.

[0024] In some embodiments of the present invention, the mass ratio of the positive electrode active material to the composite lithium supplement material is (75-98): (0.8-10).

[0025] In some embodiments of the present invention, the mass percentage W of the composite lithium supplement material to the positive electrode material satisfies 0<W≤10%, preferably 0.8%≤W≤8%.

[0026] In some embodiments of the present invention, the lithium supplement material A accounts for a mass percentage W of the positive electrode material. A Satisfy 0<W A <10%, preferably 0.8%≤W A In some embodiments of the present invention, the composite supplementary material B accounts for a mass percentage of W of the positive electrode material. B Satisfy 0<W B <5%, preferably 0<W B ≤3%. The composite supplementary material B only participates in the formation of the first SEI (increasing capacity) and improves the stability of SEI. The amount used is small, and excessive materials cannot be used. In particular, when the composite supplementary material B is a magnesium supplementary material, a good effect can be achieved when the addition amount is low.

[0027] In some embodiments of the present invention, the preparation method of the composite lithium supplement material is not limited, as long as it can play the lithium supplement function in the positive electrode sheet. For example, the lithium supplement material A and the composite supplement material B can be added to the positive electrode slurry and directly coated and rolled into a positive electrode sheet. The lithium supplement material A and the composite supplement material B can also be sprayed onto the surface of the positive electrode sheet or coated on the isolation film.

[0028] In some embodiments of the present invention, taking the composite lithium supplement material, positive electrode active material, conductive agent and binder as a whole, the mass percentage of each component is: positive electrode active material 75% to 98%, conductive agent 1% to 10%, binder 1% to 10%, composite lithium supplement material 0.8% to 10%.

[0029] In some embodiments of the present invention, the positive electrode active material includes LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiMnPO4, LiFePO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.85 Co 0.15 Al 0.05 At least one of O2.

[0030] In some embodiments of the present invention, the conductive agent includes at least one of acetylene black, graphene, graphyne, carbon nanotubes, carbon fibers, and conductive carbon black. The present invention has no special requirements for the conductive agent, and any conventional conductive agent in the art can be used, such as conductive carbon black or carbon nanotubes.

[0031] In some embodiments of the present invention, the binder includes at least one of polyvinylidene fluoride PVDF, sodium carboxymethyl cellulose CMC, styrene butadiene rubber SBR, and PAA-based binders. The present invention has no special requirements for the binder, and any conventional binder in the art can be used.

[0032] In some embodiments of the present invention, the positive electrode current collector may be aluminum foil, composite aluminum foil or other common current collectors, which is not limited herein.

[0033] In some embodiments of the present invention, the initial state of the positive electrode sheet or the battery cell as a whole should contain at least one lithium supplement material A and at least one of the sodium supplement / magnesium supplement / zinc supplement materials (B); during the actual use of the battery cell, the positive electrode sheet can still detect the above-mentioned substance residues (which cannot be completely decomposed) and residual products of the substance reaction (such as LiFeO2 residual from the Li5FeO4 reaction).

[0034] In a fourth aspect of the present invention, a lithium-ion battery is provided, comprising the above-mentioned lithium-supplementing positive electrode, a separator, an electrolyte and a negative electrode.

[0035] Since the lithium-ion battery adopts all the technical solutions of the lithium-supplementing positive electrode of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, that is, it has good gram capacity and cycle life, improves the stability of SEI, reduces the cycle attenuation rate, increases the cell capacity, improves the battery life, and reduces the cost, and has extremely broad application prospects.

[0036] In some embodiments of the present invention, the negative electrode is selected from a graphite negative electrode, a silicon negative electrode or a silicon-carbon negative electrode.

[0037] In some embodiments of the present invention, the negative electrode is selected from a graphite negative electrode, and the composite supplementary material B includes at least one of a sodium supplementary material or a magnesium supplementary material.

[0038] In some embodiments of the present invention, the negative electrode is selected from a silicon negative electrode or a silicon-carbon negative electrode, and the composite supplementary material B at least includes a magnesium supplementary material. In particular, for a silicon negative electrode, a good effect can be achieved when the amount of magnesium supplementary material added is relatively low.

[0039] In some embodiments of the present invention, the negative electrode is preferably a silicon-carbon negative electrode. On the one hand, the carbon material can serve as a matrix to ensure the conductivity of the electrode material, and on the other hand, it can also buffer the volume expansion of the silicon material to a certain extent.

[0040] In some embodiments of the present invention, the separator is disposed between the lithium-supplemented positive electrode and the negative electrode, and the electrolyte infiltrates the lithium-supplemented positive electrode, the negative electrode and the separator.

[0041] In some embodiments of the present invention, the material of the diaphragm includes at least one of polyethylene, polypropylene and polyvinylidene fluoride. In actual production, the material and structure of the diaphragm are not strictly limited, for example, it can be a multi-layer structure formed by stacking the above materials, or a single-layer structure formed by mixing the above materials, or a single-layer structure formed by a single material; as long as it can play the basic role of the diaphragm.

[0042] In some embodiments of the present invention, the electrolyte includes an electrolyte salt and an organic solvent. The electrolyte salt includes lithium hexafluorophosphate. The organic solvent includes at least one of a carbonate solvent and a carboxylate solvent.

[0043] In some embodiments of the present invention, the carbonate solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC).

[0044] In some embodiments of the present invention, the carboxylate solvent includes propyl propionate (PP).

[0045] In some embodiments of the present invention, in the electrolyte solution, the concentration of the electrolyte salt is 0.8 to 1.5 mol / L.

[0046] In some embodiments of the present invention, in the lithium-ion battery, the electrolyte has a retention capacity of 6.05 to 9.65 g / 5 Ah, for example, 7.2 to 7.95 g / 5 Ah.

[0047] In some embodiments of the present invention, the conductive agent, binder, current collector, etc. used to prepare the negative electrode are all conventional materials in the art and will not be described in detail here.

[0048] A fifth aspect of the present invention provides an application of the above-mentioned lithium-ion battery in an energy storage device, an electrical device or an electronic device. DETAILED DESCRIPTION

[0049] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0050] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0051] In the description of the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. Unless otherwise specified, each reaction or operation step may be performed in sequence or not. Preferably, the reaction method of the present invention is performed in sequence.

[0052] If no specific techniques or conditions are specified in the following examples, the techniques or conditions described in the literature in the art or the product instructions are used. All reagents or instruments without manufacturer specified are conventional products that can be purchased commercially.

[0053] Example 1

[0054] A lithium-ion secondary battery, LiFePO4-Gr system.

[0055] (1) Preparation of positive electrode sheet

[0056] The positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li5FeO4, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent system in a mass ratio of 90:3:2:3:2, and then coated on the positive electrode current collector Al foil, and then dried, cold pressed, and slit to obtain the positive electrode sheet.

[0057] (2) Preparation of negative electrode sheet

[0058] The negative electrode active material graphite Gr, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5, and then coated on the negative electrode current collector Cu foil, and dried, cold pressed, and slit to obtain the negative electrode sheet.

[0059] (3) Preparation of isolation membrane

[0060] A polyethylene (PE) porous polymer film is used as the isolation membrane.

[0061] (4) Preparation of electrolyte

[0062] A solution prepared by mixing lithium salt LiPF6 and non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC)) = 20:30:20:28:2, mass ratio) in a mass ratio of 8:92 is used as the electrolyte for lithium-ion secondary batteries.

[0063] (5) Preparation of lithium-ion secondary batteries

[0064] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, the separator is placed between the positive electrode sheet and the negative electrode sheet to play a role of safety isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in a packaging shell, the electrolyte is injected and packaged to obtain a lithium-ion secondary battery.

[0065] Example 2

[0066] The difference from Example 1 is that the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li5FeO4, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 89.5:3:2.5:3:2, and the rest is the same as Example 1 and will not be repeated.

[0067] Example 3

[0068] The difference from Example 1 is that the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li5FeO4, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 89.9:3.5:1.6:3:2, and the rest is the same as Example 1 and will not be repeated here.

[0069] Example 4

[0070] The difference from Example 1 is that the lithium supplement material Li5FeO4 is replaced by Li2NiO2. Since the content of Li in Li2NiO2 is lower, the content is increased to 4.0%, that is, the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li2NiO2, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 89:4:2:3:2. The rest is the same as Example 1 and will not be repeated.

[0071] Example 5

[0072] The difference from Example 1 is that the sodium supplement material Na2C2O4 is replaced by Na2NiO2. The rest is the same as Example 1 and will not be described again.

[0073] Example 6

[0074] The difference from Example 1 is that it does not contain sodium supplement material, but contains magnesium supplement material MgS of the same mass. The rest is the same as Example 1 and will not be described again.

[0075] Example 7

[0076] The difference from Example 1 is that it does not contain sodium supplement material, but contains zinc supplement material ZnNiO2 of the same mass. The rest is the same as Example 1 and will not be described again.

[0077] Example 8

[0078] The difference from Example 1 is that it contains magnesium-supplementing material MgS, and the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, lithium-supplementing material Li5FeO4, sodium-supplementing material Na2C2O4, magnesium-supplementing material MgS, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) is 90:3:1:1:3:2. The rest is the same as Example 1 and will not be repeated here.

[0079] Example 9

[0080] The difference from Example 1 is that it contains magnesium-supplementing material MgS and zinc-supplementing material ZnNiO2, and the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, lithium-supplementing material Li5FeO4, sodium-supplementing material Na2C2O4, magnesium-supplementing material MgS, zinc-supplementing material ZnNiO2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) is 90:3:1:0.5:0.5:3:2. The rest is the same as Example 1 and will not be repeated here.

[0081] Example 10

[0082] The difference from Example 1 is that the lithium ion secondary battery is a LiFePO4-Si system, the negative electrode active material is a mixture of graphite Gr and silicon Si, wherein the mass ratio of Gr to Si is 80:20.

[0083] Embodiment 11

[0084] The difference between Example 11 and Example 10 is that it does not contain sodium supplement material, but contains magnesium supplement material MgS of the same mass. The rest is the same as Example 10 and will not be described again.

[0085] Comparative Example 1

[0086] The difference from Example 1 is that no sodium supplement material is contained, the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 92:3:3:2, and the rest is the same as Example 1 and will not be repeated here.

[0087] Comparative Example 2

[0088] The difference from Example 1 is that the content of lithium supplement agent is 11%, the mass ratio of positive electrode active material lithium iron phosphate LiFePO4, lithium supplement material Li5FeO4, sodium supplement material Na2C2O4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) is 82:11:2:3:2, and the rest is the same as Example 1 and will not be repeated here.

[0089] Comparative Example 3

[0090] The difference from Example 1 is that the content of the sodium supplement is 6%, the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the lithium supplement material Li5FeO4, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 86:3:6:3:2, and the rest is the same as Example 1 and will not be repeated here.

[0091] Comparative Example 4

[0092] The difference from Example 1 is that the content of lithium supplement agent is 7%, the content of sodium supplement agent is 4%, the mass ratio of positive electrode active material lithium iron phosphate LiFePO4, lithium supplement material Li5FeO4, sodium supplement material Na2C2O4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) is 84:7:4:3:2, and the rest is the same as Example 1 and will not be repeated.

[0093] Comparative Example 5

[0094] The difference from Example 1 is that no lithium supplement material is contained, and the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the sodium supplement material Na2C2O4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 93:2:3:2. The rest is the same as Example 1 and will not be repeated here.

[0095] Comparative Example 6

[0096] The difference from Example 1 is that no lithium supplement material and sodium supplement material are contained, the mass ratio of the positive electrode active material lithium iron phosphate LiFePO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 95:3:2, and the rest is the same as Example 1 and will not be repeated.

[0097] Comparative Example 7

[0098] The difference from Comparative Example 6 is that the lithium ion secondary battery is a LiFePO4-Si system.

[0099] The materials and proportions of Examples 1-11 and Comparative Examples 1-7 are shown in Table 1:

[0100] Table 1

[0101]

[0102]

[0103] Performance Testing

[0104] Gram Capacity Test

[0105] Five lithium-ion secondary batteries in the comparative example and the example were taken, and charged at room temperature at a constant current of 0.1C until the voltage reached 3.8V, and further charged at a constant voltage of 3.8V until the current was lower than 0.05C. Then, they were discharged at a constant current of 0.1C until the voltage reached 2.0V.

[0106] Cyclic performance test

[0107] Take 5 lithium ion secondary batteries prepared in the comparative example and the example, and repeatedly charge and discharge the lithium ion secondary batteries through the following steps, and calculate the cycle capacity retention rate of the lithium ion secondary batteries: in an environment of 45°C, perform the first charge and discharge, perform constant current and constant voltage charging at a charging current of 0.1C (i.e., the current value at which the theoretical capacity is completely discharged within 10 hours) until the upper limit voltage is 3.8V, and then perform constant current discharge at a discharge current of 1C until the final voltage is 2.0V, and record the discharge capacity of the first cycle; then perform 500 charge and discharge cycles, and record the discharge capacity of the 500th cycle.

[0108] Cycle capacity retention rate C500=(discharge capacity at the 500th cycle / discharge capacity at the first cycle)×100%.

[0109] The test data is shown in Table 2:

[0110] Table 2

[0111]

[0112]

[0113] From Table 1 and Examples 1-3, it can be seen that different ratios of lithium-supplementing and sodium-supplementing materials within the scope of the present invention can also achieve similar effects; at the same time, Example 2 illustrates that further increasing the sodium-supplementing material cannot further increase the capacity and improve the lifespan.

[0114] It can be seen from Table 1, Example 1 and Examples 4-7 that one of the different lithium supplementation + sodium supplementation / magnesium supplementation / zinc supplementation materials can achieve similar effects.

[0115] It can be seen from Table 1, Example 1 and Examples 8-9 that supplementing lithium + sodium / magnesium / zinc materials together can achieve better results.

[0116] From Table 1, it can be seen from Example 1, Examples 10-11 and Comparative Example 7 that compared with the LiFePO4-Gr system, the first cycle of SEI formation at the Si negative electrode in the LiFePO4-Si system consumes more active Li and the battery capacity is lower. For the Si negative electrode, lithium supplementation and magnesium supplementation have better effects.

[0117] It can be seen from Table 1, Example 1 and Comparative Examples 2-4 that when the content of lithium supplement and sodium supplement is too high, the active material of the battery cell decreases, and the gram capacity of the battery cell will deteriorate.

[0118] From Table 1, Example 1 and Comparative Example 1, Comparative Examples 5-6, it can be seen that simple sodium supplementation can also replenish SEI to consume active Li and improve SEI, thereby improving life; but the method of composite lithium supplementation + sodium supplementation is better than simple lithium supplementation or simple sodium supplementation, and is better than no supplementation.

[0119] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A composite lithium supplement material, characterized in that: The composite lithium supplement material includes a lithium supplement material A and a composite supplement material B; the composite supplement material B includes at least one of a sodium supplement material, a magnesium supplement material, and a zinc supplement material; The mass ratio of the lithium supplement material A to the composite supplement material B is (0.8-8): (0.1-5).

2. The composite lithium supplement material according to claim 1, characterized in that: The lithium supplement material A includes Li x M y N z , wherein 0<x<10, 0≤y≤10, 0≤z≤20, and y+z>0; M is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, and Mo, and N is selected from at least one of C, O, S, N, F, and P; And / or, the composite supplementary material B comprises A a B b C c , wherein 0<a<10, 0≤b≤10, 0≤c≤20, and b+c>0; A is selected from at least one of Na, Mg, and Zn, B is selected from at least one of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Cr, V, Mo, Ti, Al, and Ag, and C is selected from at least one of C, O, S, N, F, and P.

3. The composite lithium supplement material according to claim 1, characterized in that: The lithium supplement material A includes one or more of Li5FeO4, Li2O, Li2O2, Li3N, LiN3, Li2S, LiF, Li2C4O4, Li2C2O4, Li2C3O5, Li2C6O6, and Li2N4O2; And / or, the sodium supplement material includes one or more of Na5FeO4, Na2O, Na2O2, Na3N, NaN3, Na2S, NaF, Na2C2O4, Na2C3O5, Na2C4O4, Na2C6O6, and Na2N4O2; And / or, the magnesium supplement material includes one or more of Mg2Mo6S8, MgS, MgMn2O4, MgMn2S4, MgCo2O4, MgNiO2, MgNi2S4, MgAl2O4, MgFe2O4, MgTiO3, and Mg3(PO4)2; And / or, the zinc supplement material includes one or more of ZnO, ZnCo2O4, ZnMn2O4, ZnFe2O4, ZnTiO3, ZnS, Zn3(PO4)2, ZnAl2O4, ZnNiO2, ZnV2O4, ZnMoO4, ZnCuO, and ZnAgVO4.

4. A pole piece, characterized in that: It comprises the composite lithium supplement material as described in any one of claims 1 to 3.

5. A lithium supplementing positive electrode, comprising a positive electrode current collector and a positive electrode material disposed on at least one side of the positive electrode current collector, characterized in that: The positive electrode material comprises a positive electrode active material, a binder, a conductive agent and the composite lithium supplement material according to any one of claims 1 to 3.

6. The lithium-supplemented positive electrode according to claim 5, characterized in that: The mass percentage W of the composite lithium supplement material to the positive electrode material satisfies 0<W≤10%; Preferably, the mass percentage of the lithium supplement material A in the positive electrode material is W A Satisfy 0<W A <10%, preferably 0.8%≤W A ≤8%; Preferably, the composite supplementary material B accounts for a mass percentage of W of the positive electrode material. B Satisfy 0<W B <5%, preferably 0<W B ≤3%.

7. A lithium ion battery, characterized in that: The invention comprises a lithium-supplementing positive electrode, a separator, an electrolyte and a negative electrode as described in any one of claims 5 to 6.

8. The lithium-ion battery according to claim 7, characterized in that: The negative electrode is selected from a graphite negative electrode, and the composite supplementary material B includes at least one of a sodium supplementary material or a magnesium supplementary material.

9. The lithium-ion battery according to claim 7, characterized in that: The negative electrode is selected from a silicon negative electrode or a silicon-carbon negative electrode, and the composite supplementary material B at least includes a magnesium supplementary material.

10. Use of the lithium ion battery according to any one of claims 7 to 9 in an energy storage device, an electrical device or an electronic device.

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