Lithium supplement positive electrode, preparation method thereof and lithium ion battery

Abstract

The invention relates to the technical field of energy storage batteries, in particular to a lithium supplementing positive electrode, a preparation method thereof and a lithium ion battery. The lithium supplementing positive electrode comprises a positive electrode current collector and a lithium supplementing layer arranged on at least one side of the positive electrode current collector; the lithium supplementing layer comprises an inorganic lithium supplementing layer, an organic lithium supplementing layer and an interface layer arranged between the inorganic lithium supplementing layer and the organic lithium supplementing layer; preferably, the lithium supplementing layer comprises an inorganic lithium supplementing layer, an interface layer and an organic lithium supplementing layer from the position close to the current collector to the position away from the current collector. Through gradient structure design, interface layer optimization and sequential regulation and control of the organic lithium supplementing layer and the inorganic lithium supplementing layer, comprehensive breakthrough is achieved on core indexes such as the first effect, the cycle life (100 weeks capacity retention rate, the gas production rate, the interface impedance and the ion diffusion coefficient).

Description

Technical Field

[0001] This invention relates to the field of energy storage battery technology, and in particular to a lithium-ion cathode, its preparation method, and a lithium-ion battery. Background Technology

[0002] With the iterative development of high-energy-density lithium-ion battery technology, positive electrode lithium replenishment materials, as the core components for compensating for the loss of active lithium at the electrode interface, have become the key to breaking through the bottleneck of battery energy density and cycle life through performance optimization.

[0003] Current mainstream inorganic lithium supplements (such as Li5FeO4) exhibit excellent thermodynamic stability, but their high lithium release energy barrier (>3.5 eV) limits their initial lithium compensation efficiency, making it difficult to meet the requirements of high first-efficiency systems. Organic lithium supplements (such as Li2C2O2) can achieve lithium release efficiency at 3.8 V (vs. Li / Li). + It decomposes at low voltages, but has defects such as irreversible gas production (CO2, C2H2, etc.) and loose SEI membrane structure.

[0004] Existing technologies attempt to balance performance contradictions by combining composite lithium replenishers with interface modifiers. However, the mismatch in interfacial charge transport between heterogeneous materials and the discontinuous lithium-ion diffusion path lead to industrialization bottlenecks such as insufficient initial efficiency improvement, accelerated cycle capacity decay, and failure of gas generation suppression. Against this backdrop, developing novel lithium replenisher architectures with functional decoupling characteristics to achieve a synergistic improvement in lithium compensation efficiency and interfacial stability has become a crucial breakthrough for advancing the industrialization of next-generation high-energy-density batteries. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and defects of the prior art and to provide a lithium-ion cathode, its preparation method, and a lithium-ion battery.

[0006] To achieve the above objectives, this application adopts the following solution:

[0007] A lithium-supplemented positive electrode includes a positive electrode current collector and a lithium-supplemented layer disposed on at least one side of the positive electrode current collector; the lithium-supplemented layer includes an inorganic lithium-supplemented layer, an organic lithium-supplemented layer, and an interface layer disposed between the inorganic lithium-supplemented layer and the organic lithium-supplemented layer.

[0008] Preferably, the lithium replenishment layer comprises an inorganic lithium replenishment layer, an interface layer, and an organic lithium replenishment layer from the vicinity of the current collector to the distance from the current collector.

[0009] Preferably, the inorganic lithium-supplementing layer density is 3.4-6.8 mg / cm³. 2 Interfacial layer density: 0.03-0.173 mg / cm³ 2 Organic lithium supplementation layer density: 1.7-2.72 mg / cm³2 .

[0010] Preferably, the thickness of the inorganic lithium replenishment layer is 5-20 μm; the thickness of the organic lithium replenishment layer is 2-9 μm.

[0011] Preferably, the thickness ratio of the inorganic lithium replenishment layer to the organic lithium replenishment layer is 1:(0.13-1); more preferably, it is 1:(0.4-0.5).

[0012] Preferably, the interfacial lithium supplement agent in the interface layer is 0.3%-5% of the total amount of inorganic and organic lithium supplement agents in the inorganic and organic lithium supplement layers; more preferably, it is 3%.

[0013] Preferably, the inorganic lithium replenishment layer includes an inorganic lithium replenishment agent, a positive electrode conductive agent, and a positive electrode binder;

[0014] Preferably, the inorganic lithium supplement is Li5FeO4, Li2MnO3, Li2NiO2, Li2O, or Li 4+x At least one of V₂O₅; X = -2, 0, 2;

[0015] Preferably, the mass ratio of inorganic lithium supplement, positive electrode conductive agent and positive electrode binder is (90-95):(1-5):(1-5); more preferably 92:5:3.

[0016] Preferably, the interface layer includes an interface lithium replenishing agent, a positive electrode conductive agent, and a positive electrode binder;

[0017] Preferably, the interfacial lithium supplement includes at least one of LiBOB, LiTFSI, LiF, or Li3PO4;

[0018] Preferably, the mass ratio of the interfacial lithium supplement, the positive electrode conductive agent and the positive electrode binder is (80-85):(5-10):(5-10); more preferably, it is 85:8:7.

[0019] Preferably, the organic lithium replenishing layer includes an organic lithium replenishing agent, a positive electrode conductive agent, and a positive electrode binder;

[0020] Preferably, the organic lithium supplement is at least one of Li2C2O2, C6H5Li, and Li2C4O4;

[0021] The organic lithium replenishment layer comprises an organic lithium replenishment agent, a positive electrode conductive agent, and a positive electrode binder in a mass ratio of (85-90):(5-10):(1-5); preferably 88:8:4.

[0022] The present invention also includes a method for preparing the aforementioned lithium-added cathode, comprising the following steps:

[0023] 1) Prepare inorganic lithium replenishment slurry, interfacial lithium replenishment slurry and organic lithium replenishment slurry respectively;

[0024] 2) Using a layered coating process, an inorganic lithium replenishing slurry is sequentially coated onto the positive electrode current collector to obtain an inorganic lithium replenishing layer, an interface lithium replenishing slurry is sprayed onto the positive electrode current collector to obtain an interface layer, and an organic lithium replenishing slurry is coated onto the positive electrode current collector to obtain an organic lithium replenishing layer; or, an organic lithium replenishing slurry is sequentially coated onto the positive electrode current collector and dried to obtain an organic lithium replenishing layer, an interface lithium replenishing slurry is sprayed onto the positive electrode current collector to obtain an interface layer, and an inorganic lithium replenishing slurry is coated onto the positive electrode current collector to obtain an inorganic lithium replenishing layer.

[0025] 3) After drying, rolling and gradient activation, a lithium-supplemented positive electrode is formed.

[0026] Preferably, in step 1), the inorganic lithium replenishing slurry solvent is NMP, with a solid content of 55% and a viscosity of 3500±100 mPa·s;

[0027] Preferably, the solvent for the interfacial lithium replenishment slurry is NMP, with a solid content of 50% and a viscosity of 1000±200 mPa·s.

[0028] Preferably, the organic lithium supplementing slurry solvent is NMP, with a solid content of 45% and a viscosity of 1200±50 mPa·s.

[0029] Preferably, the density of the organic lithium-supplementing layer is 3.4-6.8 mg / cm³. 2 Interfacial layer density: 0.03-0.173 mg / cm³ 2 Organic lithium supplementation layer density: 1.7-2.72 mg / cm³ 2 ;

[0030] Preferably, the thickness ratio of the inorganic lithium replenishment layer to the organic lithium replenishment layer is 1:(0.13-1); more preferably, it is 1:(0.4-0.5).

[0031] Preferably, the interfacial lithium supplement agent in the interface layer is 0.3%-5% of the total amount of inorganic and organic lithium supplement agents in the inorganic and organic lithium supplement layers; more preferably, it is 3%.

[0032] Preferably, the drying temperature in step 3) is 60-100℃; more preferably 85℃.

[0033] Preferably, the compacted density after rolling is 3.4 ± 0.1 g / cm³. 3 ;

[0034] Preferably, the gradient activation step in step 3) is as follows: place the electrode in a low temperature environment of -30℃ to -50℃ for 6-24h, and then place the electrode in an ambient temperature of 15-40℃ to restore it to room temperature for 12-48h.

[0035] Preferably, the electrode is placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to restore room temperature for 24 hours.

[0036] The present invention also includes a lithium-ion battery, comprising the aforementioned lithium-filled positive electrode, negative electrode sheet, and separator.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] This patent achieves significant technical effects in terms of first-time efficiency improvement, cycle life extension, gas generation suppression, interface impedance reduction, and process compatibility through the synergistic innovation of "gradient lithium replenishment structure (inorganic lithium replenishment layer - interface layer - organic lithium replenishment layer) + optimized thickness ratio (the thickness ratio of inorganic lithium replenishment layer to organic lithium replenishment layer is 1:0.4-0.5) + independent interface layer design".

[0039] Specifically as follows:

[0040] 1. Significantly improved initial efficiency, breaking through industry bottlenecks in lithium source utilization.

[0041] Traditional mechanical mixed lithium replenishment (Comparative Example 1) suffers from the density difference between inorganic and organic lithium replenishing agents (Li5FeO4 4.3 g / cm³). 3 vsLi2C2O2 2.1g / cm 3 This results in low lithium release efficiency, with an initial efficiency of only 83.8%. Due to functional coupling (the contradiction between lithium replenishment and SEI film formation), the initial efficiency of monolayer lithium replenishment (comparative examples 2-3) is further reduced to 76.2%-84.3%.

[0042] This patent uses a gradient structure to physically isolate the two phases (an inorganic lithium replenishment layer as the bottom layer and an organic lithium replenishment layer as the top layer), and introduces an interface layer to fill the pores and reduce the lithium release energy barrier, thereby improving the initial efficiency to 95.1% (Example 1). This is 13.5% higher than the traditional mechanical mixing scheme (83.8%) and 12.8% higher than the single-layer Li5FeO4 (84.3%), achieving an industry-leading lithium source utilization rate.

[0043] 2. The cycle life is significantly extended, and the capacity decay rate is reduced.

[0044] The conventional mixed lithium replenishment (Comparative Example 1) had a capacity retention of only 65.8% after 100 weeks due to interfacial side reactions and increased porosity (28.5%); the gradient structure without interfacial agent (Comparative Example 4) had a capacity retention of 78.4% due to the loose SEI film.

[0045] In this patent, the lithium phosphate interface layer forms a LiF / Li3PO4 composite SEI film (Rsei = 5.8Ω), which inhibits electrolyte decomposition. The interface impedance growth rate is only 0.010Ω / week (Example 1), and the capacity retention rate after 100 weeks reaches 91.2% (Example 1), which is 38.6% higher than the traditional hybrid scheme (65.8%) and 16.3% higher than the gradient structure without interface agent (78.4%), and the cycle life is significantly extended.

[0046] 3. Excellent gas production suppression effect and significantly improved safety.

[0047] Traditional organic lithium supplements (Li2C2O2) decomposed and produced severe gas (5.1 mL / Ah in Comparative Example 3), mechanical mixed lithium supplementation (Comparative Example 1) caused gas production to be aggravated due to stratification (18.9 mL / Ah), and commercial interface agents (Comparative Example 5) had limited inhibitory effect (11.5 mL / Ah).

[0048] This patent isolates the two phases through a gradient structure and introduces an interface layer (3%) to fill the interface pores (porosity 19.5%), blocking the gas generation channels of organic lithium supplementation agent decomposition. The gas generation is reduced to 0.15 mL / Ah (Example 1), which is 99.2% lower than the traditional mechanical mixing scheme (18.9 mL / Ah) and 98.7% lower than commercial interface agents (11.5 mL / Ah), significantly improving battery safety.

[0049] 4. Significantly reduced interfacial impedance and improved ion transport efficiency.

[0050] Traditional mixed lithium replenishment (Comparative Example 1) suffers from large interfacial gaps and high pore tortuosity, with Rsei = 35.7 Ω and Rct = 78.9 Ω, resulting in a lithium-ion diffusion coefficient of only 0.5 × 10⁻⁻¹. 10 cm 2 / s; The gradient structure without interfacial agent (Comparative Example 4) has poor interfacial contact, Rsei = 21.3Ω, diffusion coefficient 1×10- 10 cm 2 / s.

[0051] In this patent, the interface layer serves as an ion-conducting medium, reducing the interfacial contact impedance (Rsei = 5.8Ω) and constructing a three-dimensional ion transport network (Li). + Diffusion coefficient 3.5 × 10 -10 cm 2 / s (Example 1), which improves upon traditional hybrid schemes by 600% and upon interface-free gradient structures by 250%, significantly optimizing ion transport efficiency.

[0052] 5. Strong process compatibility and controllable mass production costs.

[0053] This patent employs a layered coating process (current collector → inorganic lithium replenishment layer → interface layer → organic lithium replenishment layer), which is fully compatible with existing lithium battery production line equipment (coating machine, twin-roll press) and requires no additional modifications; the interface agent dosage is only 0.05-0.3 mg / cm³. 2 (Corresponding to 0.5-3wt%), the material cost is reduced by approximately 40% compared to commercial LiBOB interface agents (according to market research, the unit price of Li3PO4 is approximately 60% of that of LiBOB). Experimental data show that the overall manufacturing cost of Example 1 is only 5% higher than that of traditional hybrid solutions, but the performance improvement is significant, demonstrating potential for large-scale industrialization.

[0054] In summary, this patent, through gradient structure design, interface layer optimization, and sequential control of organic and inorganic lithium replenishment layers, achieves significant improvements in initial efficiency (95.1%), cycle life (91.2% capacity retention after 100 cycles), gas production (0.15 mL / Ah), interfacial impedance (Rsei = 5.8 Ω), and ion diffusion coefficient (3.5 × 10⁻⁶). -10 cm 2 Achieving comprehensive breakthroughs in core indicators such as ( / s), the performance is improved by 38.6%-600% compared to traditional solutions, while taking into account process compatibility and cost controllability, providing key technical support for the long life, high safety and low cost mass production of high energy density lithium-ion batteries. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the gradient lithium replenishment structure of the present invention;

[0056] Figure 2 This is a SEM image from an embodiment of the present invention. Detailed Implementation

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0058] Example 1: A method for preparing a lithium-added cathode, comprising the following steps:

[0059] 1) Prepare inorganic lithium replenishment slurry, interfacial lithium replenishment slurry and organic lithium replenishment slurry respectively;

[0060] Li5FeO4, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 92:5:3, and NMP solvent was added to prepare an inorganic lithium supplementation slurry (solid content 55%, 3500±100mPa·s).

[0061] Li2C2O2, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 88:8:4, and NMP solvent was added to prepare an organic lithium supplementation slurry (solid content 45%, 1200±50mPa·s).

[0062] Lithium phosphate nanoparticles (50-200nm), conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 85:8:7, and NMP solvent was added to prepare an interfacial lithium supplementation slurry (solid content 50%, 1000±200mPa·s).

[0063] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0064] Li5FeO4 slurry (inorganic lithium supplementation slurry) was uniformly coated onto an aluminum foil current collector, with an electrode areal density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0065] Lithium phosphate slurry (lithium phosphate added at 3% of the total mass of Li5FeO4 and Li2C2O2, the same below) was sprayed onto the Li5FeO4 inorganic lithium supplementation layer, with an areal density of 0.173 mg / cm³. 2 Dry the coating layer to obtain the interface layer;

[0066] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The coating layer is dried to obtain an organic lithium replenishment layer;

[0067] The drying temperature is 85℃, and the drying time is 45 minutes;

[0068] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0069] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0070] Example 2:

[0071] The difference between Example 2 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0072] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0073] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 5.1 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0074] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.173 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0075] Li₂C₂O₂ slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode surface density of 0.68 mg / cm². 2 The organic lithium replenishment layer is obtained by drying the coating layer;

[0076] The drying temperature is 85℃, and the drying time is 45 minutes;

[0077] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0078] The coated composite electrode was rolled, and after rolling, the thickness of the Li5FeO4 inorganic lithium-supplementing layer was 15 μm, and the thickness of the Li2C2O2 organic lithium-supplementing layer was 9 μm (thickness ratio 1:0.6), with a compaction density of 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0079] Example 3

[0080] The difference between Example 3 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0081] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0082] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 5.1 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0083] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.173 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0084] Li₂C₂O₂ slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode surface density of 0.68 mg / cm². 2 Dry the coating layer onto the organic lithium replenishment layer;

[0085] The drying temperature is 85℃, and the drying time is 45 minutes;

[0086] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0087] The coated composite electrode was rolled, resulting in a Li5FeO4 inorganic lithium-replenishing layer thickness of 15 μm and a Li2C2O2 organic lithium-replenishing layer thickness of 2 μm (thickness ratio 1:0.13). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0088] Example 4

[0089] The difference between Example 4 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0090] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0091] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 6.8 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0092] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.255 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0093] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium replenishment layer is obtained by drying the coating layer;

[0094] The drying temperature is 85℃, and the drying time is 45 minutes;

[0095] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0096] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 20 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.25). The compaction density was 3.4 ± 0.1 g / cm³. 3The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0097] Example 5

[0098] The difference between Example 5 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0099] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0100] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 1.7 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0101] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.102 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0102] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium replenishment layer is obtained by drying the coating layer;

[0103] The drying temperature is 85℃, and the drying time is 45 minutes;

[0104] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0105] The coated composite electrode was rolled, resulting in a Li5FeO4 inorganic lithium-replenishing layer thickness of 5 μm and a Li2C2O2 organic lithium-replenishing layer thickness of 5 μm (thickness ratio 1:1). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0106] Example 6

[0107] The difference between Example 6 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0108] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0109] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 6.8 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0110] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.286 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0111] Li₂C₂O₂ slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 2.72 mg / cm². 2 The organic lithium-replenishing layer is obtained by drying the coating layer.

[0112] The drying temperature is 85℃, and the drying time is 45 minutes;

[0113] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0114] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 20 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 8 μm (thickness ratio 1:0.4). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0115] Example 7

[0116] The difference between Example 7 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0117] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0118] Li2C2O2 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 1.7 mg / cm³. 2 The organic lithium replenishment layer is obtained by drying the coating layer;

[0119] A lithium phosphate slurry (3% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.153 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0120] Li5FeO4 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer.

[0121] The drying temperature is 85℃, and the drying time is 45 minutes;

[0122] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0123] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0124] Example 8

[0125] The difference between Example 8 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0126] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0127] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0128] Lithium phosphate slurry (0.3% addition) was sprayed onto the Li5FeO4 inorganic lithium-supplementing layer, with an areal density of 0.018 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0129] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium replenishment layer is obtained by drying the coating layer;

[0130] The drying temperature is 85℃, and the drying time is 45 minutes;

[0131] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0132] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0133] Example 9

[0134] The difference between Example 9 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0135] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0136] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0137] A lithium phosphate slurry (0.5% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.03 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0138] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium-replenishing layer is obtained by drying the coating layer.

[0139] The drying temperature is 85℃, and the drying time is 45 minutes;

[0140] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0141] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0142] Example 9

[0143] The difference between Example 9 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0144] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0145] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0146] A lithium phosphate slurry (1.5% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.08 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0147] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium-replenishing layer is obtained by drying the coating layer.

[0148] The drying temperature is 85℃, and the drying time is 45 minutes;

[0149] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0150] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0151] Example 11

[0152] The difference between Example 11 and Example 1 lies in steps 2) and 3), specifically including the following steps:

[0153] 2) A layered coating process is adopted, in which inorganic lithium replenishment slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishment layer, an interface lithium replenishment slurry is sprayed to obtain an interface layer, and an organic lithium replenishment slurry is coated to obtain an organic lithium replenishment layer.

[0154] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 The inorganic lithium replenishment layer is obtained by drying the coating layer;

[0155] A lithium phosphate slurry (5% addition) was sprayed onto an inorganic lithium-supplementing layer of Li5FeO4, with an areal density of 0.255 mg / cm³. 2 The interface layer is obtained by drying the coating layer;

[0156] Li2C2O2 slurry was uniformly coated onto a lithium phosphate coating, resulting in an electrode areal density of 1.7 mg / cm³. 2 The organic lithium-replenishing layer is obtained by drying the coating layer.

[0157] The drying temperature is 85℃, and the drying time is 45 minutes;

[0158] 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed;

[0159] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0160] Example 12: A method for preparing a lithium-added cathode, comprising the following steps:

[0161] Li5FeO4 + lithium phosphate (3% of the total mass of Li5FeO4 and Li2C2O2), conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 92:5:3, and NMP solvent was added to prepare a positive electrode slurry (solid content 55%, 3500±100mPa·s).

[0162] Li2C2O2, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 88:8:4, and NMP solvent was added to prepare a positive electrode slurry (solid content 45%, 1200±50mPa·s).

[0163] A slurry of Li5FeO4 + lithium phosphate (3% of the total mass of Li5FeO4 and Li2C2O2) was uniformly coated onto an aluminum foil current collector, resulting in an electrode areal density of 3.4 mg / cm³. 2 Dry the coating layer; uniformly coat the Li2C2O2 slurry onto the Li5FeO4+lithium phosphate (3%) coating, with an electrode surface density of 1.7 mg / cm³. 2 Dry the coating layer at a temperature of 85℃ for 45 minutes.

[0164] The coated composite electrode was compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-replenishing layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-replenishing layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0165] Example 13: A method for preparing a lithium-added cathode, comprising the following steps:

[0166] Li5FeO4, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 92:5:3, and NMP solvent was added to prepare a positive electrode slurry (solid content 55%, 3500±100mPa·s).

[0167] Li2C2O2 + lithium phosphate (3%), conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 88:8:4, and NMP solvent was added to prepare a positive electrode slurry (solid content 45%, 1200±50mPa·s).

[0168] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 Dry the coating layer; uniformly coat the lithium phosphate coating with a slurry of Li2C2O2 + lithium phosphate (3% of the total mass of Li5FeO4 and Li2C2O2), resulting in an electrode surface density of 1.7 mg / cm³. 2 The coating layer was dried at 85℃ for 45 minutes. The coated composite electrode was then compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-filling layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-filling layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0169] Comparative Example 1

[0170] Li5FeO4 + Li2C2O2 (mass ratio 3:1) and conductive agent (Super P) were added to a high-speed mixer at a mass ratio of 92:8 and dry-mixed at 2000 rpm for 20 minutes. The dry-mixed powder and binder (PVDF) were then uniformly mixed at a mass ratio of 93:7, and NMP solvent was added to prepare a positive electrode slurry (solid content 50%, 2500±100 mPa·s). The slurry was uniformly coated onto an aluminum foil current collector, and the electrode surface density was 9.5 mg / cm³. 2 The coating layer was dried at 85℃ for 45 minutes. The coated composite electrode was then rolled to a thickness of 60μm and a compaction density of 3.4±0.1g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a mechanically mixed lithium-added electrode.

[0171] Comparative Example 2

[0172] Li5FeO4, conductive agent (Super P), and binder (PVDF) were uniformly mixed at a mass ratio of 92:5:3, and NMP solvent was added to prepare a positive electrode slurry (solid content 55%, 3500±100 mPa·s). The Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, and the electrode surface density was 5.1 mg / cm³. 2The coating layer was dried at 85℃ for 45 minutes. The coated electrode was then rolled to a thickness of 15μm and a compaction density of 3.4±0.1g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a single-layer Li5FeO4 lithium supplementation electrode.

[0173] Comparative Example 3

[0174] Li₂C₂O₂, conductive agent (Super P), and binder (PVDF) were uniformly mixed at a mass ratio of 88:8:4, and NMP solvent was added to prepare a positive electrode slurry (solid content 45%, 1200±50 mPa·s). The Li₂C₂O₂ slurry was uniformly coated onto an aluminum foil current collector, with an electrode areal density of 5.1 mg / cm². 2 The coating layer was dried at 85℃ for 45 minutes. The coated electrode was then rolled to a thickness of 15μm and a compaction density of 3.4±0.1g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a single-layer Li2C2O2 lithium supplementary electrode.

[0175] Comparative Example 4

[0176] Li5FeO4, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 92:5:3, and NMP solvent was added to prepare a positive electrode slurry (solid content 55%, 3500±100mPa·s).

[0177] Li2C2O2, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 88:8:4, and NMP solvent was added to prepare a positive electrode slurry (solid content 45%, 1200±50mPa·s).

[0178] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 Dry the coating layer; uniformly coat the Li2C2O2 slurry onto the Li5FeO4 coating, with an electrode surface density of 1.7 mg / cm³. 2 The coating layer was dried at 85℃ for 45 minutes. The coated composite electrode was then compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-filling layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-filling layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a lithium-added electrode without a lithium phosphate interface layer.

[0179] Comparative Example 5

[0180] Li5FeO4, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 92:5:3, and NMP solvent was added to prepare a positive electrode slurry (solid content 55%, 3500±100mPa·s).

[0181] Li2C2O2, conductive agent (Super P), and binder (PVDF) were uniformly mixed in a mass ratio of 88:8:4, and NMP solvent was added to prepare a positive electrode slurry (solid content 45%, 1200±50mPa·s).

[0182] Li5FeO4 slurry was uniformly coated onto an aluminum foil current collector, with an electrode surface density of 3.4 mg / cm³. 2 The coating layer was dried; a commercial LiBOB interface agent (3% addition) was sprayed onto the Li5FeO4 inorganic lithium-supplementing layer, with an areal density of 0.153 mg / cm³. 2 Dry the coating layer; uniformly coat the lithium phosphate coating with Li2C2O2 slurry, achieving an electrode surface density of 1.7 mg / cm³. 2 The coating layer was dried at 85℃ for 45 minutes. The coated composite electrode was then compacted. After compaction, the thickness of the Li5FeO4 inorganic lithium-filling layer was 10 μm, and the thickness of the Li2C2O2 organic lithium-filling layer was 5 μm (thickness ratio 1:0.5). The compaction density was 3.4 ± 0.1 g / cm³. 3 The electrode was placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to recover to room temperature for 24 hours to obtain a novel gradient lithium-supplemented electrode.

[0183] Cut the electrode sheets to the specified diameter (usually 18mm), weigh the electrode sheets, controlling the error within ±0.0050g, and vacuum dry to remove moisture. The water and oxygen content in the glove box must be <11ppm to prevent material oxidation or reaction. Stacking order: negative electrode shell → flat gasket + electrolyte → lithium sheet (surface passivation film needs to be scraped off) + electrolyte → separator (area must be larger than lithium sheet and electrode sheet) → positive electrode sheet + electrolyte → spring sheet → positive electrode shell; add 5-6 drops of electrolyte to ensure the separator is completely wetted; use an automatic sealing machine to apply pressure of about 50MPa to seal; after assembly, it needs to stand for 12 hours (30℃ environment) or overnight to ensure that the electrolyte fully wets the electrode sheets.

[0184] The formation test conditions were as follows: at room temperature of 25±2℃, charge and discharge were performed at a current density of 0.1C (charged to 4.3V, then constant voltage to 0.05C, discharge cutoff voltage 2.5V), and the first efficiency was calculated by the ratio of the first discharge capacity to the charge capacity. The cycle test conditions were as follows: at a high temperature of 45±2℃, cycled at a current density of 1C (charged to 4.3V, then constant voltage to 0.05C, discharge to 2.5V), and the capacity retention was calculated by the ratio of the discharge capacity in the 100th cycle to that in the 1st cycle.

[0185] Figure 2 Figure a shows the SEM image of Example 1. The image reveals a layered design for the electrode: a dense layer near the foil is Li5FeO4 (a high-lithium-content cathode material providing high ion conductivity), a middle layer is Li3PO4 (ensuring efficient lithium-ion transport), and an outer layer is Li2C2O2 (a loose, porous structure). Figure a shows the SEM image of the microstructure of the inorganic lithium-supplementing layer and the lithium phosphate interface layer in the gradient lithium-supplementing electrode. The densely packed circular particles correspond to the inorganic lithium-supplementing agent Li5FeO4, while lithium phosphate nanoparticles fill the gaps between the inorganic lithium-supplementing agent particles, reducing porosity (18.8% porosity in Example 1). The interface resistance of Example 1 is 7.5 Ω·cm. 2 Comparative Example 1 is 65 Ω·cm 2 The key roles of gradient stratification and interfacial agent filling in reducing ion transport resistance were verified. Figure b shows the SEM image of the microstructure of the organic lithium replenishment layer in the gradient lithium replenishment electrode. The dense particles on the electrode surface correspond to the tight packing of organic lithium replenishment agent Li2C2O2 particles without obvious gaps. This dense surface provides the basis for the uniform formation of the SEI film. In the early stage of cycling, a dense LiF / Li3PO4 composite SEI film is formed (the gas production rate in Example 1 is only 0.15 mL / Ah, which is significantly lower than the 5.1 mL / Ah of the traditional single-layer Li2C2O2).

[0186] Table 1 shows the differences between the different embodiments and comparative examples. Tables 2 and 3 show the comparison data of the coin cell cycle performance and EIS fitting of the embodiments and comparative examples, respectively. The table shows that: ① Thickness ratio optimization: 1:0.5 significantly reduces interfacial impedance and improves ion diffusion efficiency. A moderate thickness ratio balances the lithium source release efficiency of the inorganic layer with the density of the SEI film of the organic layer, reducing interfacial porosity and transport resistance, thereby reducing impedance and improving ion diffusion rate; ② Lithium phosphate content: 3% is the optimal interface, which can effectively fill interfacial pores and form a dense LiF / Li3PO4 composite SEI film, reducing charge transfer resistance (Rct) and improving ion diffusion rate; too low or too high content will lead to increased interfacial porosity or electrode embrittlement, degrading electrochemical performance; ③ Lithium replenishment layer sequence: Inorganic bottom layer-organic top layer is the key design of interfacial dynamics. The inorganic layer (Li5FeO4) directly contacts the current collector to stably release the lithium source and reduce interfacial polarization; the organic layer (Li2C2O2) as the top layer preferentially decomposes to form a dense SEI film, suppressing electrolyte side reactions. Reversing the order will lead to uneven lithium source release, loose SEI film structure, significantly increase interfacial impedance and reduce ion diffusion efficiency; ④ Lithium phosphate addition position: Independent interfacial layer is the core innovation for reducing impedance. Lithium phosphate needs to be sprayed as an independent interfacial layer between inorganic / organic layers in order to effectively bridge the two phases and reduce interfacial impedance; If mixed into the active layer (Li5FeO4 or Li2C2O2), it will hinder lithium source release and destroy the continuity of SEI film, resulting in a surge in impedance and performance degradation.

[0187] Table 4 compares the interface resistance, porosity, and peel strength of the examples and comparative examples. From the table, it can be seen that "gradient delamination and lithium phosphate interface agent" significantly improve interface performance. ① Interface resistance: The gradient structure and lithium phosphate interface agent significantly reduce impedance; Example 1 shows only 7.5 Ω·cm. 2 Compared to traditional mechanical hybrid structures (Comparative Example 1, 65.0 Ω·cm), 2 The interfacial resistance was reduced by 88.5%, and the interfacial resistance of the mechanically mixed (Comparative Example 1), single-layer structure (Comparative Examples 2-3), and interface agent-free gradient structure (Comparative Example 4) were all >45 Ω·cm. 2This indicates that traditional structures suffer from high ion transport resistance due to layering or poor interfacial contact. This patent utilizes an "inorganic layer-lithium phosphate interface layer-organic layer" gradient structure, employing lithium phosphate nanoparticles to fill interfacial pores (porosity 18.8% in Example 1, 28.5% in Comparative Example 1), and constructs a three-dimensional ion transport network, reducing the contact resistance between the two phases. Secondly, porosity: the lithium phosphate interface agent effectively fills the pores, improving structural density, with porosity concentrated between 18.8-28.4%. Example 1 has only 18.8%, a 33.9% reduction compared to the traditional mechanically mixed structure (Comparative Example 1, 28.5%). The gradient structure without an interface agent (Comparative Example 4, porosity 24.5%) has significantly higher porosity than examples containing an interface agent (e.g., Example 8, 19.5%) due to the lack of lithium phosphate filling. The organic bottom layer-inorganic surface layer structure (Example 7, porosity 26.3%) has higher porosity than the optimal implementation because the lithium replenishment layer order is reversed and the interfacial pores are not effectively filled. For example, lithium phosphate nanoparticles are filled between the inorganic and organic layers through a spraying process, reducing the tortuosity of the pores (porosity of 18.8% in Example 1); ③ Peel strength: The low-temperature activation process strengthens the interfacial bonding force, with the peel strength concentrated between 9.8-17.5 N / m. The optimal example (Example 1) reaches 17.5 N / m, which is 42.3% higher than the traditional mechanical hybrid structure (Comparative Example 1, 12.3 N / m). Organic bottom layer-inorganic surface layer structure (Example 7, peel strength 9.8 N / m): due to the reversed order of the lithium replenishment layer, the interfacial bonding force is weak; Single layer structure (Comparative Example 3, peel strength 8.3 N / m): due to the lack of interfacial agent and gradient structure, the interfacial bonding force is the worst. This patent uses a low-temperature activation process of "-40℃ / 12h→25℃ / 24h" to induce lithium phosphate and lithium replenishment agent to undergo a pre-lithiation reaction and form chemical bonds, significantly improving the interfacial bonding force (peel strength of 17.2 N / m in Example 1) and inhibiting coating peeling during cycling.

[0188] Table 1

[0189]

[0190] Table 2. Comparison of Cyclic Performance Data for Button Cells

[0191]

[0192] Table 3. Comparison of EIS fitting data for button batteries

[0193]

[0194]

[0195] Table 4. Comparison of Electrode Interface Properties (Resistance, Porosity, Peel Strength)

[0196] Group Interface resistance (Ω-cm 2 )]]> Porosity (%) Peel strength (N / m) Example 1 7.5 18.8 17.5 Example 2 12.0 24.0 15.3 Example 3 15.0 28.0 13.8 Example 4 18.0 20.0 17.2 Example 5 22.0 22.0 14.2 Example 6 28.0 26.0 16.0 Example 7 28.7 26.3 9.8 Example 8 8.2 19.5 16.4 Example 9 18.7 21.3 14.8 Example 10 10.5 19.5 15.2 Example 11 15.8 22.8 13.6 Example 12 25.9 22.5 15.1 Example 13 29.8 28.4 11.2 Comparative Example 1 65.0 28.5 12.3 Comparative Example 2 45.3 24.7 12.5 Comparative Example 3 55.6 32.8 8.3 Comparative Example 4 55.6 24.5 12.3 Comparative Example 5 21.4 18.7 8.3

[0197] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0198] Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0199] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A lithium-added cathode, characterized in that, It includes a positive current collector and a lithium replenishment layer disposed on at least one side of the positive current collector; the lithium replenishment layer includes an inorganic lithium replenishment layer, an organic lithium replenishment layer, and an interface layer disposed between the inorganic lithium replenishment layer and the organic lithium replenishment layer.

2. The lithium-added cathode according to claim 1, characterized in that, The lithium replenishment layer, from near the current collector to far away from the current collector, includes an inorganic lithium replenishment layer, an interface layer, and an organic lithium replenishment layer.

3. The lithium-filled cathode according to claim 1, characterized in that, Inorganic lithium-supplemented layer density: 3.4-6.8 mg / cm³ 2 Interfacial layer density: 0.03-0.173 mg / cm³ 2 Organic lithium supplementation layer density: 1.7-2.72 mg / cm³ 2 ; Preferably, the thickness of the inorganic lithium replenishment layer is 5-20 μm; the thickness of the organic lithium replenishment layer is 2-9 μm. Preferably, the thickness ratio of the inorganic lithium replenishment layer to the organic lithium replenishment layer is 1:(0.13-1); more preferably, it is 1:(0.4-0.5). Preferably, the interfacial lithium supplement agent in the interface layer is 0.3%-5% of the total amount of inorganic and organic lithium supplement agents in the inorganic and organic lithium supplement layers; more preferably, it is 3%.

4. The lithium-filled cathode according to claim 1, characterized in that, The inorganic lithium replenishment layer includes an inorganic lithium replenishment agent, a positive electrode conductive agent, and a positive electrode binder; Preferably, the inorganic lithium supplement is Li5FeO4, Li2MnO3, Li2NiO2, Li2O, or Li 4+x At least one of V2O5, X = -2, 0, 2; Preferably, the mass ratio of inorganic lithium supplement, positive electrode conductive agent and positive electrode binder is (90-95):(1-5):(1-5), and more preferably 92:5:3; Preferably, the interface layer includes an interface lithium replenishing agent, a positive electrode conductive agent, and a positive electrode binder; Preferably, the interfacial lithium supplement includes at least one of LiBOB, LiTFSI, LiF, or Li3PO4; Preferably, the mass ratio of the interfacial lithium replenishing agent, the positive electrode conductive agent, and the positive electrode binder is (80-85):(5-10):(5-10); more preferably, it is 85:8:

7. Preferably, the organic lithium replenishing layer includes an organic lithium replenishing agent, a positive electrode conductive agent, and a positive electrode binder; Preferably, the organic lithium supplement is at least one of Li2C2O2, C6H5Li, and Li2C4O4; Preferably, the organic lithium replenishing layer comprises an organic lithium replenishing agent, a positive electrode conductive agent, and a positive electrode binder in a mass ratio of (85-90):(5-10):(1-5); more preferably, it is 88:8:

4.

5. A method for preparing a lithium-added cathode according to any one of claims 1-4, characterized in that, Includes the following steps: 1) Prepare inorganic lithium replenishment slurry, interfacial lithium replenishment slurry and organic lithium replenishment slurry respectively; 2) A layered coating process is adopted, in which an inorganic lithium replenishing slurry is coated on the positive electrode current collector in sequence to obtain an inorganic lithium replenishing layer, an interface lithium replenishing slurry is sprayed on to obtain an interface layer, and an organic lithium replenishing slurry is coated and dried to obtain an organic lithium replenishing layer; or, an organic lithium replenishing slurry is coated on the positive electrode current collector in sequence and dried to obtain an organic lithium replenishing layer, an interface lithium replenishing slurry is sprayed on to obtain an interface layer, and an inorganic lithium replenishing slurry is coated to obtain an inorganic lithium replenishing layer. 3) After rolling and gradient activation, a lithium-supplemented positive electrode is formed.

6. The method for preparing the lithium-added cathode according to claim 5, characterized in that, In step 1), the inorganic lithium replenishment slurry uses NMP as the solvent, has a solid content of 55%, and a viscosity of 3500±100 mPa·s. Preferably, the solvent for the interfacial lithium replenishment slurry is NMP, with a solid content of 50% and a viscosity of 1000±200 mPa·s; Preferably, the organic lithium supplementing slurry solvent is NMP, with a solid content of 45% and a viscosity of 1200±50 mPa·s.

7. The method for preparing the lithium-added cathode according to claim 5 or 6, characterized in that, In step 2), the density of the inorganic lithium-supplementing layer is 3.4-6.8 mg / cm³. 2 Interfacial layer density: 0.03-0.173 mg / cm³ 2 Organic lithium supplementation layer density: 1.7-2.72 mg / cm³ 2 ; Preferably, the thickness ratio of the inorganic lithium replenishment layer to the organic lithium replenishment layer is 1:(0.13-1); more preferably, it is 1:(0.4-0.5). Preferably, the interfacial lithium supplement agent in the interface layer is 0.3%-5% of the total amount of inorganic and organic lithium supplement agents in the inorganic and organic lithium supplement layers; more preferably, it is 3%.

8. The method for preparing a lithium-added cathode according to any one of claims 5-7, characterized in that, The drying temperature in step 3) is 60-100℃; preferably 85℃. Preferably, the compacted density after rolling is 3.4 ± 0.1 g / cm³. 3 .

9. The method for preparing a lithium-added cathode according to any one of claims 5-8, characterized in that, Step 3) The gradient activation steps are as follows: place the electrode in a low temperature environment of -30℃ to -50℃ for 6-24h, and then place the electrode in an environment of 15-40℃ to restore room temperature for 12-48h. Preferably, the electrode is placed in a low-temperature environment of -40℃ for 12 hours, and then placed in an environment of 25℃ to restore room temperature for 24 hours.

10. A lithium-ion battery, characterized in that, Includes the lithium-filled positive electrode, negative electrode sheet, and separator as described in any one of claims 1-4.

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