Modified negative electrode, full cell and preparation method

Abstract

This invention relates to the field of battery technology, and in particular to a modified negative electrode, a full cell, and a preparation method thereof. The modified negative electrode includes a negative electrode and a ceramic layer coated on the surface of the negative electrode; the ceramic layer includes a fast ion conductor, ceramic particles, and a binder. The ceramic layer of this invention employs a composition of a fast ion conductor, hollow ceramic particles, and a binder. The hollow ceramic particles provide mechanical strength and buffer space, the fast ion conductor provides an ultrafast lithium-ion transport channel, and the composite ceramic layer, incorporating the fast ion conductor and ceramic particles, provides the core requirements for stable mechanical support, stress buffering, and ion conduction at the silicon-doped negative electrode interface. This significantly improves the effectiveness of reducing interface wrinkles on the negative electrode sheet after formation, maintaining the integrity of the electrode structure between the coating and the current collector, and the active material particles.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a modified negative electrode, a full cell, and a method for preparing them. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, are widely used in portable electronic devices, electric vehicles, grid energy storage, and other fields, and have become an indispensable energy storage device in the global energy transition. The negative electrode, as the core component of a lithium-ion battery, undertakes the crucial task of lithium-ion insertion and extraction. Its performance directly determines the battery's core indicators such as energy density, cycle stability, charge / discharge rate, and safety performance, and is one of the key bottlenecks restricting further improvements in lithium-ion battery performance.

[0003] Currently, commercial lithium-ion battery anodes primarily use graphite-based materials, which offer advantages such as structural stability and low cost. However, their theoretical capacity is limited (only about 372 mAh / g), making it difficult to meet the growing market demands for long-range electric vehicles and high-capacity energy storage systems. To overcome this limitation, novel high-capacity anode materials such as silicon-carbon have been extensively studied. Their theoretical capacity is far higher than that of graphite, but they experience significant volume expansion and contraction during charging and discharging, which can easily lead to electrode structure collapse and active material shedding, resulting in rapid battery capacity decay and severely impacting battery cycle life.

[0004] In addition, the traditional negative electrode surface is prone to side reactions with the electrolyte, producing an unstable solid electrolyte interphase (SEI) film. This not only increases interfacial impedance and reduces lithium-ion transport efficiency, but may also cause safety hazards such as battery thermal runaway, further restricting the overall performance and application promotion of lithium-ion 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 modified negative electrode, a full cell, and a preparation method thereof.

[0006] To achieve the above objectives, this application adopts the following solution: A modified negative electrode includes a negative electrode and a ceramic layer coated on the surface of the negative electrode; the ceramic layer includes a fast ion conductor, hollow ceramic particles, and a binder.

[0007] The fast ion conductor includes at least one or any mixture of LLTO, LLZO, or LATP; preferably, the fast ion conductor has a D50 of 100-500 nm and a particle size distribution coefficient of <0.8.

[0008] The hollow ceramic particles are at least one of hollow alumina, hollow silicon dioxide, or hollow zirconium oxide; preferably hollow alumina; particle size D50 = 1~3 μm, wall thickness 100~200 nm.

[0009] The adhesive includes a lithium polymer adhesive and a conventional adhesive; preferably, the lithium polymer adhesive is at least one of PAA-Li, CMC-Li, or Li-Nafion; the conventional adhesive is at least one of sodium methyl cellulose (CMC), styrene-butadiene rubber (SBR) emulsion, or polyacrylic acid (PAA); preferably, the ratio of the lithium polymer adhesive to the conventional adhesive is 4:(1-3); more preferably, it is 4:1.5; preferably, the adhesive is a mixture of CMC-Li, PAA-Li, and SBR; the ratio of the three is 1:3:1.5.

[0010] The thickness of the ceramic layer is 1~2 μm.

[0011] The mass ratio of fast ion conductor, ceramic particles and binder is (60-80):(15-35):(2-15).

[0012] The negative electrode includes a negative electrode current collector and a negative electrode active layer coated on the negative electrode current collector; Preferably, the negative electrode active layer comprises a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (95-96):(1-1.5):(1.5-3.5). Preferably, the negative electrode active material is graphite or silicon carbide; the negative electrode conductive agent is at least one of conductive carbon black SP or aqueous single-walled carbon nanotubes (CNTs). Preferably, the negative electrode binder includes a lithium polymer binder and a conventional binder; preferably, the lithium polymer binder is at least one of PAA-Li, CMC-Li, or Li-Nafion; the conventional binder is at least one of sodium methyl cellulose (CMC), styrene-butadiene rubber (SBR) emulsion, or polyacrylic acid (PAA); preferably, the ratio of the lithium polymer binder to the conventional binder is 4:(1-3); more preferably, it is 4:1.5; preferably, the binder is a mixture of CMC-Li, PAA-Li, and SBR; the ratio of the three is 1:3:1.5.

[0013] The present invention also includes a method for preparing the modified negative electrode, comprising the following steps: mixing fast ion conductor, ceramic particles and binder to prepare a ceramic layer slurry, coating the ceramic layer slurry onto the surface of the negative electrode, and drying to obtain the modified negative electrode; preferably, the baking temperature is 100-120℃ and the coating speed is 3-8m / min.

[0014] The present invention also includes a full battery comprising the modified negative electrode, positive electrode, and separator; preferably, the positive electrode comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; preferably, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (96-97):(0.5-1.5):(1-2.5). Preferably, the positive electrode active material is a high-nickel ternary material; the positive electrode conductive agent is at least one of conductive carbon black SP and oily single-walled carbon nanotubes CNT; and the positive electrode binder is PVDF.

[0015] The present invention also includes a method for preparing the full battery, comprising the following steps: stacking a positive electrode, a modified negative electrode and a separator in a "Z" shape to obtain a bare cell, and then performing welding, encapsulation, electrolyte injection, formation, capacity testing and aging to obtain a full battery.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The ceramic layer of the present invention adopts a composition of fast ion conductor, hollow ceramic particles and binder. The hollow ceramic particles provide mechanical strength and buffer space, the fast ion conductor provides an ultrafast lithium ion transport channel, and the composite ceramic layer of ceramic particles mixed with fast ion conductor provides the core requirements of mechanical support, stress buffering and ion conduction for stable silicon-doped anode interface. It has a significant effect on improving the interface wrinkles of the anode sheet after formation, maintaining the integrity of the electrode structure between the coating and the current collector and active material particles. The construction of the composite ceramic layer significantly reduces the consumption caused by the formation of a thick and unstable SEI between the silicon anode and the electrolyte during the first charge and discharge cycle, thus improving the initial coulombic efficiency. The stable interface reduces continuous lithium consumption caused by repeated SEI rupture / regeneration during cycling. The stable interface inhibits electrolyte decomposition and silicon pulverization, significantly improving cycle stability; the formation of a stable and uniform thin-layer SEI reduces ion migration resistance, lowers voltage polarization during charge and discharge, and makes the voltage plateau more stable. Furthermore, both the ceramic particles and the fast ion conductor are ceramic materials, which are high-temperature resistant and non-flammable, enhancing the thermal stability of the electrode structure and reducing the risk of thermal runaway. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process of the full battery of the present invention. Detailed Implementation

[0018] 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.

[0019] Example 1: Preparation of a full cell ( Figure 1 (The flowchart is shown below), specifically including the following steps: S1. Preparation of the positive electrode: The high-nickel ternary positive electrode material is mixed with conductive agent SP, conductive agent oily single-walled carbon nanotubes (CNT), and binder PVDF in a certain ratio (96.5%:1.0%:0.5%:2.0%) to prepare the positive electrode slurry; the positive electrode slurry is coated, rolled, and die-cut to obtain the positive electrode. S2. Preparation of silicon-doped anode: Anode graphite, silicon carbide, conductive agent SP, conductive agent water-based single-walled carbon nanotubes (CNTs), binder CMC-Li, binder PAA-Li, and binder SBR are mixed in a certain proportion (64.89%: 27.81%: 1.5%: 0.3%: 1.0%: 3.0%: 1.5%) to prepare anode slurry; the anode slurry is then coated and rolled to obtain silicon-doped anode. S3. Preparation of modified negative electrode: 1. Preparation of ceramic slurry: Hollow Al2O3 (D50=2um, wall thickness 150nm) and LLTO (particle size D50=300nm, particle size distribution coefficient 0.5) are mixed in a certain proportion in a CMC-Li, PAA-Li, SBR binder (1:3:1.5) system, wherein the mass ratio of LLTO, Al2O3 and binder is 70:25:5, to prepare a composite ceramic slurry; 2. Composite ceramic layer coating: The composite ceramic slurry is coated onto the silicon-doped anode surface using a micro-gravure coating machine to a thickness of 2 μm, with a baking temperature of 110℃ and a coating speed of 5 m / min; the anode roll coated with the composite ceramic layer is then rolled and die-cut to obtain the modified anode. S4. Preparation of full cell: The positive electrode, modified negative electrode and separator are stacked in a "Z" shape to obtain bare cell. After welding, encapsulation, liquid injection, formation, capacity testing and aging, the full cell is obtained. S5. Full Cell Test: After the full cell is off the production line, disassemble it to confirm that the fully charged interface is wrinkle-free, and perform EIS electrochemical impedance spectroscopy test at 50% charge state (frequency range 0.01Hz~100kHz, voltage perturbation 5mV, charge transfer impedance Rct: 30 mΩ·cm). 2 Bulk impedance Rs: 12mΩ·cm 2 Cyclic performance test (1C CCCV charging, 1C DC discharging, 1500 cycles @ 80% SOH), hot box test (160℃ 30min, with clamps, passed).

[0020] S6. Electrode Physicochemical Tests: Test the adhesion between the silicon-doped negative electrode and the current collector after rolling (45gf / 42mm); Disassemble and analyze the cycled battery, test the cross-sectional SEM of the negative electrode before and after cycling, and observe the integrity of the coating, the absence of peeling between the coating and the current collector, and the absence of internal cracks. Example 2: The difference between Example 2 and Example 1 is that the ratio of LLTO, Al2O3 and binder is 60:35:5.

[0021] Example 3: The difference between Example 3 and Example 1 is that the ratio of LLTO, Al2O3 and binder is 80:15:5.

[0022] Example 4: The difference between Example 4 and Example 1 is that the ratio of LLTO, Al2O3 and binder is 72:26:2.

[0023] Example 5: The difference between Example 5 and Example 1 is that the ratio of LLTO, Al2O3 and binder is 62.5:22.5:15.

[0024] Example 6: The difference between Example 6 and Example 1 is that the ceramic layer thickness is 1 μm.

[0025] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that a common negative electrode is used, that is, no ceramic layer is added to the surface.

[0026] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the ceramic layer does not contain hollow Al2O3, and the ratio of LLTO to binder is 95:5.

[0027] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the ceramic layer contains ordinary alumina Al2O3, LLTO, and the ratio of LLTO, Al2O3 and binder is 70:25:5. Based on the comparison of the fully charged interface state after formation, EIS charge transfer impedance Rct and bulk impedance Rs at 50% SOC, cycle performance, and thermal chamber test data of Examples 1-6 and Comparative Examples 1-2, as detailed in Table 1, Example 1 is the optimal solution. The batteries of Examples 1-6 were disassembled and analyzed after cycling. SEM images of the negative electrode cross-section were performed before and after cycling to observe the integrity of the coating, the absence of peeling between the coating and the current collector, and the absence of internal cracks. Table 1

[0028] Compared to Example 1, Example 2 has a reduced LLTO ratio, resulting in poorer uniformity of the continuous conductive agent and binder network in the coating layer, increased impedance, and worse adhesion and cycle performance. Example 3, compared to Example 1, has an increased LLTO ratio, resulting in better uniformity of the continuous conductive agent and binder network in the coating layer, reduced impedance, and slightly worse adhesion and cycle performance. Example 4, compared to Example 1, has increased LLTO and hollow Al2O3 ratios, and a reduced binder ratio, resulting in poor uniformity of the binder network in the coating layer, reduced impedance, but the electrode coating is easily peeled off, and cycle performance deteriorates. Example 5, compared to Example 1, has reduced LLTO and hollow Al2O3 ratios, and an increased binder ratio, resulting in agglomerated binder network in the coating layer, increased impedance, increased battery polarization, and slightly better cycle performance. Example 6, compared to Example 1, has a ceramic layer thickness of 1 μm, reduced impedance, and comparable electrode adhesion and cycle performance. Compared to Example 1, Comparative Example 1 uses a conventional negative electrode, i.e., no additional ceramic layer is added to the surface. This shortens the lithium-ion transport channel, significantly reduces battery impedance, increases polarization, and worsens cycle performance and thermal stability. Compared to Example 1, Comparative Example 2 does not contain hollow Al2O3 in the ceramic layer, and the ratio of LLTO to binder is 95:5. This results in poorer mechanical properties of the electrode structure, increased side reactions, and worse cycle performance and thermal stability. Compared to the examples, Comparative Example 3 contains a composite ceramic coating of ordinary solid alumina Al2O3 and LLTO in the ceramic layer. Ordinary alumina is an ion insulator, which will block ion channels, forcing ions to detour and increasing interfacial impedance. The volume expansion stress directly acts on the brittle coating, easily leading to cracking and peeling. The electrolyte continues to have side reactions, resulting in rapid capacity decay and poor cycle performance. 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. 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.

[0029] 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 modified negative electrode, characterized in that, It includes a negative electrode and a ceramic layer coated on the surface of the negative electrode; the ceramic layer includes a fast ion conductor, hollow ceramic particles, and a binder.

2. The modified negative electrode according to claim 1, characterized in that, The fast ion conductor includes at least one or any mixture of LLTO, LLZO, or LATP; preferably, the fast ion conductor has a D50 of 100-500 nm and a particle size distribution coefficient of <0.

8.

3. The modified negative electrode according to claim 1, characterized in that, The hollow ceramic particles are at least one of hollow alumina, hollow silicon dioxide, or hollow zirconium oxide; preferably hollow alumina; particle size D50 = 1~3 μm, wall thickness 100~200 nm.

4. The modified negative electrode according to claim 1, characterized in that, The adhesive includes a lithium polymer adhesive and a conventional adhesive; preferably, the lithium polymer adhesive is at least one of PAA-Li, CMC-Li, or Li-Nafion; the conventional adhesive is at least one of sodium methyl cellulose (CMC), styrene-butadiene rubber (SBR) emulsion, or polyacrylic acid (PAA); preferably, the ratio of the lithium polymer adhesive to the conventional adhesive is 4:(1-3); more preferably, it is 4:1.5; preferably, the adhesive is a mixture of CMC-Li, PAA-Li, and SBR; the ratio of the three is 1:3:1.

5.

5. The modified negative electrode according to claim 1, characterized in that, The thickness of the ceramic layer is 1~2 μm.

6. The modified negative electrode according to claim 1, characterized in that, The mass ratio of fast ion conductor, ceramic particles and binder is (60-80):(15-35):(2-15).

7. The modified negative electrode according to claim 1, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode active layer coated on the negative electrode current collector; Preferably, the negative electrode active layer comprises a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (95-96):(1-1.5):(1.5-3.5). Preferably, the negative electrode active material is graphite or silicon carbide; the negative electrode conductive agent is at least one of conductive carbon black SP or aqueous single-walled carbon nanotubes (CNTs). Preferably, the negative electrode binder includes a lithium polymer binder and a conventional binder; preferably, the lithium polymer binder is at least one of PAA-Li, CMC-Li, or Li-Nafion; the conventional binder is at least one of sodium methyl cellulose (CMC), styrene-butadiene rubber (SBR) emulsion, or polyacrylic acid (PAA); preferably, the ratio of the lithium polymer binder to the conventional binder is 4:(1-3); more preferably, it is 4:1.5; preferably, the binder is a mixture of CMC-Li, PAA-Li, and SBR; the ratio of the three is 1:3:1.

5.

8. A method for preparing the modified negative electrode according to any one of claims 1-7, characterized in that, The process includes the following steps: mixing fast ion conductors, ceramic particles and binders to prepare a ceramic layer slurry, coating the ceramic layer slurry onto the surface of the negative electrode, and drying to obtain a modified negative electrode; preferably, the baking temperature is 100-120℃ and the coating speed is 3-8m / min.

9. A full battery, characterized in that, The invention includes the modified negative electrode, positive electrode, and separator as described in any one of claims 1-7; preferably, the positive electrode includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; preferably, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (96-97):(0.5-1.5):(1-2.5). Preferably, the positive electrode active material is a high-nickel ternary material; the positive electrode conductive agent is at least one of conductive carbon black SP and oily single-walled carbon nanotubes CNT; and the positive electrode binder is PVDF.

10. A method for preparing a full cell according to claim 9, characterized in that, The process includes the following steps: stacking the positive electrode, modified negative electrode, and separator in a "Z" shape to obtain a bare cell, followed by welding, encapsulation, electrolyte injection, formation, capacity testing, and aging to obtain a full cell.

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