A composite lithium supplementing material, a lithium supplementing positive electrode and a lithium ion battery

Abstract

The application discloses a kind of composite lithium supplement material, lithium supplement positive and lithium ion battery.The composite lithium supplement material of the application at least includes lithium supplement material, and at least one of sodium supplement / magnesium supplement / zinc supplement material.The above-mentioned composite lithium supplement scheme, in addition to because lithium source can improve capacity and cycle life by additional addition, further improve battery life, also can improve SEI composition by sodium supplement / magnesium supplement / zinc supplement material, improve its stability, reduce cycle attenuation rate, further improve battery life, and sodium supplement / magnesium supplement / zinc supplement material is relatively lower in price lithium supplement material, can further reduce cost.Finally, the above-mentioned positive lithium supplement + sodium supplement / magnesium supplement / zinc supplement composite mode can improve battery capacity, improve battery life, and has extremely wide application prospect in secondary battery field.

Description

Technical Field

[0001] This invention relates to the field of secondary battery materials technology, and in particular to a composite lithium replenishment material, a lithium replenishment cathode, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in products such as 3C (computers, communications, and consumer electronics), electric vehicles, and power tools due to their numerous advantages, including high energy density, long cycle life, and no memory effect. However, during the first charge and discharge cycle, the electrolyte decomposes on the negative electrode surface, forming a solid electrolyte interphase (SEI) film. This permanently consumes some lithium ions from the positive electrode, resulting in a lower coulombic efficiency (ICE) during the first cycle, thus reducing the battery's capacity and energy density. Furthermore, during cyclic storage, the consumption of active lithium also leads to capacity decay, further reducing battery life.

[0003] In related technologies, the above problems can be solved by adding additional active lithium. Currently, there are two main methods: positive electrode lithium replenishment and negative electrode lithium replenishment. Negative electrode lithium replenishment is less commonly used due to its lower safety profile, while positive electrode lithium replenishment is more prevalent. However, simply replenishing the positive electrode of a lithium-ion battery also has shortcomings: since one reason for cycle capacity decay is the consumption of active lithium during SEI reforming, simply replenishing the positive electrode cannot improve SEI stability or reduce the rate of active lithium consumption; on the other hand, because lithium resources are relatively expensive, replenishment inevitably increases the battery's production cost.

[0004] Therefore, it is of great significance to address the problems of current cathode lithium replenishment materials, such as their inability to improve SEI stability and excessive cost, and to provide a composite lithium replenishment material that can improve SEI stability and reduce cycle decay rate. Summary of the Invention

[0005] This invention aims to address at least one of the technical problems existing in the prior art. To this end, this invention proposes a composite lithium replenishment material, a lithium replenishment cathode, and a lithium-ion battery, aiming to solve the problems of current cathode lithium replenishment materials, such as their inability to improve SEI stability and excessively high cost.

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

[0007] The composite lithium replenishment material according to embodiments of the present invention has at least the following beneficial effects: The present invention proposes a composite lithium replenishment material, comprising at least a lithium replenishment material and at least one of sodium / magnesium / zinc replenishment materials. Besides improving capacity and cycle life due to the additional addition of a lithium source, thereby improving cell lifespan, the above-mentioned composite lithium replenishment scheme can also improve the composition of the SEI (Sediment Electrode Ion) by adding sodium / magnesium / zinc replenishment materials, enhancing its stability, reducing the cycle decay rate, and further improving cell lifespan. Moreover, sodium / magnesium / zinc replenishment materials are relatively cheaper than lithium replenishment materials, further reducing costs. Ultimately, the above-mentioned lithium replenishment + composite sodium / magnesium / zinc replenishment method can improve cell capacity and battery life, and has extremely broad application prospects in the field of rechargeable batteries.

[0008] In some embodiments of the present invention, the lithium supplement material A includes Li x M y N z Where 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 replenishing material A includes one or more of Li5FeO4, Li2O, Li2O2, Li3N, LiN3, Li2S, LiF, Li2C4O4, Li2C2O4, Li2C3O5, Li2C6O6, and Li2N4O2. More preferably, the lithium replenishing material A can be an inorganic lithium replenishing material Li5FeO4 or Li2O, or an organic lithium replenishing material Li2C2O4.

[0010] In some embodiments of the present invention, the composite supplement material B includes A. a B b C c Where 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 supplement material B includes a sodium supplement material, which includes one or more of Na5FeO4, Na2O, Na2O2, Na3N, NaN3, Na2S, NaF, Na2C2O4, Na2C3O5, Na2C4O4, Na2C6O6, and Na2N4O2; preferably, the sodium supplement material can be Na5FeO4 or Na2O.

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

[0013] In some embodiments of the present invention, the composite supplement material B includes a zinc supplement material, which 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 can be ZnS or ZnCo2O4.

[0014] In a second aspect, the present invention provides an electrode comprising the aforementioned composite lithium-filling material.

[0015] The electrode sheet according to embodiments of the present invention has at least the following beneficial effects: The electrode sheet provided by the present invention additionally incorporates a composite lithium replenishment material, which includes at least a lithium replenishment material and at least one of sodium / magnesium / zinc replenishment materials. Besides improving capacity and cycle life due to the additional addition of the lithium source, thereby improving cell life, the above-mentioned composite lithium replenishment scheme can also improve the composition of the SEI (Sediment Electrode Ion) by adding sodium / magnesium / zinc materials, thereby increasing its stability, reducing the cycle decay rate, and further improving cell life. Moreover, sodium / magnesium / zinc replenishment materials are relatively cheaper than lithium replenishment materials, which can further reduce costs. Ultimately, the above-mentioned lithium replenishment electrode sheet can improve cell capacity and battery life, and has extremely broad application prospects in the field of rechargeable batteries.

[0016] A third aspect of the present invention provides a lithium-supplementing cathode, comprising a cathode current collector and a cathode material disposed on at least one side surface of the cathode current collector, wherein the cathode material comprises a cathode active material, a binder, a conductive agent, and the aforementioned composite lithium-supplementing material.

[0017] The lithium-supplemented cathode according to embodiments of the present invention has at least the following beneficial effects: The lithium-supplemented cathode provided by the present invention adds a composite lithium-supplementing material to the cathode material. This material includes at least a lithium-supplementing material and at least one of sodium, magnesium, or zinc supplementing materials. Besides improving capacity and cycle life due to the additional addition of a lithium source, thus improving cell life, the above-mentioned composite lithium-supplementing cathode scheme can also improve the composition of the SEI (Sediment Electrode Ion) by adding sodium, magnesium, or zinc supplementing materials, thereby improving its stability, reducing the cycle decay rate, and further improving cell life. Moreover, sodium, magnesium, or zinc supplementing materials are relatively cheaper than lithium supplementing materials, which can further reduce costs. Ultimately, the above-mentioned lithium-supplemented cathode can improve cell capacity and battery life, and has extremely broad application prospects in the field of rechargeable batteries.

[0018] In some embodiments of the present invention, the lithium supplement material A includes Li x M y N z Where 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 replenishing material A includes one or more of Li5FeO4, Li2O, Li2O2, Li3N, LiN3, Li2S, LiF, Li2C4O4, Li2C2O4, Li2C3O5, Li2C6O6, and Li2N4O2. More preferably, the lithium replenishing material A can be an inorganic lithium replenishing material Li5FeO4 or Li2O, or an organic lithium replenishing material Li2C2O4.

[0020] In some embodiments of the present invention, the composite supplement material B includes A. a B b C c Where 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 supplement material B includes a sodium supplement material, which includes one or more of Na5FeO4, Na2O, Na2O2, Na3N, NaN3, Na2S, NaF, Na2C2O4, Na2C3O5, Na2C4O4, Na2C6O6, and Na2N4O2; preferably, the sodium supplement material can be Na5FeO4 or Na2O.

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

[0023] In some embodiments of the present invention, the composite supplement material B includes a zinc supplement material, which 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 can 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 supplementation 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 in the cathode material satisfies 0 < W ≤ 10%, preferably 0.8% ≤ W ≤ 8%.

[0026] In some embodiments of the present invention, the lithium replenishment material A accounts for W% of the mass percentage of the cathode material. A Satisfying 0 < W A <10%, preferably 0.8% ≤ W A ≤8%. In some embodiments of the present invention, the composite supplementary material B accounts for W% of the mass percentage of the positive electrode material. B Satisfying 0 < W B <5%, preferably 0 < W B ≤3%. Composite supplement B only participates in the formation of the first SEI layer (improving capacity) and enhances SEI stability. The dosage is small; excessive amounts cannot be utilized. Especially when composite supplement B is a magnesium supplement, a low addition amount can achieve excellent results.

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

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

[0029] In some embodiments of the present invention, the positive electrode active material includes LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiMnPO4, LiFePO4, and 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 selected from acetylene black, graphene, graphylene, carbon nanotubes, carbon fibers, and conductive carbon black. The present invention does not have special requirements for the conductive agent; conventional conductive agents in the art can be used, such as conductive carbon black or carbon nanotubes.

[0031] In some embodiments of the present invention, the adhesive includes at least one selected from polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and PAA-type adhesives. The present invention does not have special requirements for the adhesive; conventional adhesives in the art can be used.

[0032] In some embodiments of the present invention, the positive current collector may be aluminum foil, composite aluminum foil or other common current collectors, and the present invention does not limit it.

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

[0034] In a fourth aspect, the present invention provides a lithium-ion battery comprising the above-described lithium-replenishing positive electrode, separator, electrolyte, and negative electrode.

[0035] Since the lithium-ion battery adopts all the technical solutions of the lithium-filled cathode described in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments. That is, it has good specific capacity and cycle life, improves SEI stability, reduces cycle decay rate, increases cell capacity, improves battery life, and reduces cost, thus having extremely broad application prospects.

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

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

[0038] In some embodiments of the present invention, the negative electrode is selected from silicon negative electrodes or silicon-carbon negative electrodes, and the composite supplementary material B includes at least a magnesium supplementary material. Particularly for silicon negative electrodes, a low amount of magnesium supplementary material can achieve good results.

[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; 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-filling positive electrode and the negative electrode, and the electrolyte wets the lithium-filling positive electrode, the negative electrode and the separator.

[0041] In some embodiments of the present invention, the diaphragm is made of 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 multilayer structure formed by stacking the above materials, 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 perform the basic function of a diaphragm, it is acceptable.

[0042] In some embodiments of the present invention, the electrolyte comprises an electrolyte salt and an organic solvent. The electrolyte salt comprises lithium hexafluorophosphate. The organic solvent comprises at least one of carbonate solvents and carboxylic acid ester solvents.

[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 carboxylic acid ester solvent includes propyl propionate (PP).

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

[0046] In some embodiments of the present invention, the electrolyte in the lithium-ion battery has a retention capacity of 6.05–9.65 g / 5 Ah. Specifically, it can be 7.2–7.95 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] In a fifth aspect, the present invention provides an application of the above-described lithium-ion battery in an energy storage device, an electrical appliance, or an electronic device. Detailed Implementation

[0049] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0050] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. Unless otherwise stated, the various reaction or operation steps may be performed sequentially or not. Preferably, the reaction methods in this invention are performed sequentially.

[0052] Unless otherwise specified in the following examples, the techniques or conditions described in the literature in this field or in accordance with the product instructions shall apply. All reagents or instruments without a specified manufacturer are commercially available conventional products.

[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), lithium supplement material Li5FeO4, sodium supplement material Na2C2O4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 90:3:2:3:2. The mixture was then coated onto the positive electrode current collector Al foil, 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, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5. The mixture is then coated onto the negative electrode current collector Cu foil, and after drying, cold pressing, and slitting, the negative electrode sheet is obtained.

[0059] (3) Preparation of the separating membrane

[0060] Polyethylene (PE) porous polymer film is used as the separator.

[0061] (4) Preparation of electrolyte

[0062] A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC)) in a mass ratio of 20:30:20:28:2, with 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, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrode assembly is then wound up to form the electrode assembly. The electrode assembly is placed in a packaging shell, electrolyte is injected, and the package is sealed 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. The rest is the same as in 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. The rest is the same as in Example 1 and will not be repeated.

[0069] Example 4

[0070] The difference from Example 1 is that the lithium supplement material Li5FeO4 is replaced with Li2NiO2. Since the Li content 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 in Example 1 and will not be repeated.

[0071] Example 5

[0072] The difference from Example 1 is that the sodium-supplementing material Na2C2O4 is replaced with Na2NiO2. Everything else is the same as in Example 1 and will not be repeated.

[0073] Example 6

[0074] The difference from Example 1 is that it does not contain sodium-supplementing material, but contains an equal mass of magnesium-supplementing material MgS. Everything else is the same as in Example 1 and will not be repeated.

[0075] Example 7

[0076] The difference from Example 1 is that it does not contain sodium-supplementing material, but contains an equal mass of zinc-supplementing material ZnNiO2. Everything else is the same as in Example 1 and will not be repeated.

[0077] Example 8

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

[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 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 in Example 1 and will not be repeated.

[0081] Example 10

[0082] The difference from Example 1 is that the lithium-ion secondary battery is a LiFePO4-Si system, and 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] Example 11

[0084] The difference between Example 11 and Example 10 is that Example 11 does not contain sodium-supplementing material, but contains an equal mass of magnesium-supplementing material MgS. The rest is the same as Example 10 and will not be repeated.

[0085] Comparative Example 1

[0086] The difference from Example 1 is that it does not contain sodium-supplementing materials. The mass ratio of the positive electrode active material lithium iron phosphate (LiFePO4), the lithium-supplementing material (Li5FeO4), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) is 92:3:3:2. The rest is the same as in Example 1 and will not be repeated.

[0087] Comparative Example 2

[0088] The difference from Example 1 is that the lithium supplement content is 11%, and 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 82:11:2:3:2. The rest is the same as in Example 1 and will not be repeated.

[0089] Comparative Example 3

[0090] The difference from Example 1 is that the sodium supplement content is 6%, and 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. The rest is the same as in Example 1 and will not be repeated.

[0091] Comparative Example 4

[0092] The difference from Example 1 is that the lithium supplement content is 7%, the sodium supplement content is 4%, and 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 84:7:4:3:2. The rest is the same as in Example 1 and will not be repeated.

[0093] Comparative Example 5

[0094] The difference from Example 1 is that it does not contain lithium supplementation material. The mass ratio of positive electrode active material lithium iron phosphate (LiFePO4), sodium supplementation material Na2C2O4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) is 93:2:3:2. The rest is the same as in Example 1 and will not be repeated.

[0095] Comparative Example 6

[0096] The difference from Example 1 is that it does not contain lithium-supplementing materials or sodium-supplementing materials. 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. The rest is the same as in 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 from the comparative example and the embodiment were taken and charged at a constant current rate of 0.1C at room temperature until the voltage reached 3.8V. They were then further charged at a constant voltage of 3.8V until the current dropped below 0.05C. Subsequently, they were discharged at a constant current rate of 0.1C until the voltage reached 2.0V.

[0106] Cyclic performance test

[0107] Five lithium-ion secondary batteries prepared in the comparative example and the embodiment were taken respectively. The lithium-ion secondary batteries were repeatedly charged and discharged through the following steps, and the cycle capacity retention rate of the lithium-ion secondary batteries was calculated: In an environment of 45°C, the first charge and discharge were performed. Constant current and constant voltage charging was performed at a charging current of 0.1C (i.e., the current value that completely discharges the theoretical capacity within 10 hours) until the upper limit voltage of 3.8V was reached. Then, constant current discharge was performed at a discharge current of 1C until the final voltage of 2.0V was reached. The discharge capacity of the first cycle was recorded. Then, 500 charge and discharge cycles were performed, and the discharge capacity of the 500th cycle was recorded.

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

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

[0110] Table 2

[0111]

[0112]

[0113] As can be seen from Table 1 and Examples 1-3, similar effects can be achieved with different ratios of lithium-supplementing and sodium-supplementing materials within the scope of this invention; meanwhile, Example 2 illustrates that further increasing the sodium-supplementing material cannot further improve capacity and lifespan.

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

[0115] As shown in Table 1, Example 1, and Examples 8-9, supplementing with multiple materials such as lithium, sodium / magnesium / zinc supplements can achieve better results.

[0116] As shown in Table 1, Examples 1, 10-11, and Comparative Example 7, compared to the LiFePO4-Gr system, the LiFePO4-Si system requires more active Li to form SEI in the first cycle of the Si anode, resulting in a lower cell capacity. Furthermore, for the Si anode, lithium supplementation combined with magnesium supplementation yields better results.

[0117] As can be seen from Table 1, Example 1 and Comparative Examples 2-4, when the content of lithium and sodium supplementation agents is too high, the active material of the battery cell decreases, and the specific capacity of the battery cell deteriorates.

[0118] As shown in Table 1, Example 1, Comparative Examples 1 and 5-6, sodium supplementation alone can replenish the active Li consumed by the SEI and improve the SEI, thus improving the lifespan; however, the combination of lithium supplementation and sodium supplementation is better than either lithium supplementation alone or sodium supplementation alone, and is even better than no supplementation at all.

[0119] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that, It includes a lithium-filled positive electrode, a separator, an electrolyte, and a negative electrode; The lithium-supplementing cathode includes a cathode current collector and a cathode material disposed on at least one side surface of the cathode current collector, wherein the cathode material includes a composite lithium-supplementing material; The composite lithium replenishing material includes lithium replenishing material A and composite supplementing material B; the composite supplementing material B includes magnesium replenishing material, which includes one or more of Mg2Mo6S8, MgS, MgMn2O4, MgMn2S4, MgCo2O4, MgNiO2, MgNi2S4, MgAl2O4, MgFe2O4, MgTiO3, and Mg3(PO4)2; The mass ratio of the lithium supplement material A to the composite supplement material B is (0.8~8):(0.1~5); The negative electrode is selected from silicon negative electrodes or silicon-carbon negative electrodes.

2. The lithium-ion battery according to claim 1, characterized in that, The compound supplement material B also includes at least one of sodium supplement materials and zinc supplement materials.

3. The lithium-ion battery according to claim 2, 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 supplement material B includes A a B b C c Where 0 < a < 10, 0 ≤ b ≤ 10, 0 ≤ c ≤ 20, and b + c > 0; A is selected from at least one of Na 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.

4. The lithium-ion battery according to claim 2, characterized in that, The lithium replenishment material A includes one or more of the following: 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 zinc supplement material includes one or more of ZnO, ZnCo2O4, ZnMn2O4, ZnFe2O4, ZnTiO3, ZnS, Zn3(PO4)2, ZnAl2O4, ZnNiO2, ZnV2O4, ZnMoO4, ZnCuO, and ZnAgVO4.

5. The lithium-ion battery according to claim 1, characterized in that, The positive electrode material also includes a positive electrode active material, a binder, and a conductive agent.

6. The lithium-ion battery according to claim 1, characterized in that, The mass percentage W of the composite lithium supplement material in the cathode material satisfies 0 < W ≤ 10%.

7. The lithium-ion battery according to claim 6, characterized in that, The lithium supplementation material A accounts for W% of the mass percentage of the cathode material. A Satisfying 0 < W A <10%.

8. The lithium-ion battery according to claim 7, characterized in that, The lithium supplementation material A accounts for W% of the mass percentage of the cathode material. A Satisfying 0.8%≤W A ≤8%.

9. The lithium-ion battery according to claim 6, characterized in that, The composite supplementary material B accounts for W% of the mass percentage of the cathode material. B Satisfying 0 < W B <5%.

10. The lithium-ion battery according to claim 9, characterized in that, The composite supplementary material B accounts for W% of the mass percentage of the cathode material. B Satisfying 0 < W B ≤3%.

11. The application of a lithium-ion battery as described in any one of claims 1-10 in an energy storage device, an electrical appliance, or an electronic device.

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