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CN-122025539-A - Negative electrode piece and lithium secondary battery comprising same

CN122025539ACN 122025539 ACN122025539 ACN 122025539ACN-122025539-A

Abstract

The invention discloses a negative electrode plate and a lithium secondary battery comprising the same, belonging to the technical field of lithium batteries, wherein the negative electrode plate comprises a negative electrode substrate plate and an artificial SEI layer positioned on the surface of the negative electrode substrate plate, the artificial SEI layer comprises lithium fluoride, a boron-containing inorganic phase and a phosphorus-containing inorganic phase, wherein the boron-containing inorganic phase is selected from lithium borate and the like, the phosphorus-containing inorganic phase is selected from lithium phosphate and the like, the average thickness of the artificial SEI layer is 6-12 nm, the preparation method comprises the steps of slurry coating and densification treatment under inert atmosphere, and the problems of easy falling off, high impedance and the like of the traditional artificial film layer are effectively solved by matching with the unique densification treatment, so that the cycle life, the storage performance and the multiplying power performance of the lithium secondary battery are greatly improved.

Inventors

  • WANG KAI
  • ZHANG KAI

Assignees

  • 江苏睿恩新能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260226

Claims (10)

  1. 1. The negative electrode plate is characterized by comprising a current collector and a negative electrode active material layer arranged on at least one side of the current collector, wherein an artificial SEI layer is arranged on at least part of the surface of the negative electrode active material layer, and the average thickness of the artificial SEI layer is 6-12 nm.
  2. 2. The negative electrode sheet of claim 1, wherein the artificial SEI layer has a dry film surface density of 0.0015 to 0.0030mg/cm 2 .
  3. 3. The negative electrode tab of claim 1, wherein the negative electrode tab has a compacted density of 1.2-1.7 g/cm 3 .
  4. 4. The negative electrode tab of claim 1, wherein the artificial SEI layer comprises LiF, a boron-containing inorganic phase, and a phosphorus-containing inorganic phase.
  5. 5. The negative electrode sheet according to claim 4, wherein the inorganic phase containing boron is one or more selected from the group consisting of lithium metaborate, lithium borate and lithium tetraborate, and the inorganic phase containing phosphorus is one or more selected from the group consisting of lithium phosphate, lithium difluorophosphate and lithium pyrophosphate.
  6. 6. The negative electrode sheet according to claim 4, wherein in the artificial SEI layer, the mass ratio of LiF, the inorganic phase containing phosphorus to the inorganic phase containing boron satisfies the following relationship, liF: inorganic phase containing phosphorus=50 to 70:15 to 20:15 to 30.
  7. 7. The negative electrode sheet according to claim 1, wherein the artificial SEI layer further comprises an auxiliary binder and a dispersing agent, the auxiliary binder is selected from one or more of polyvinylidene fluoride, polyacrylic acid and salts thereof, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyvinyl alcohol, and the dispersing agent is selected from polyvinylpyrrolidone.
  8. 8. The negative electrode tab of claim 1, wherein the negative electrode active material layer comprises a negative electrode active material selected from one or more of graphite, hard carbon, soft carbon, a silicon oxygen material, a silicon carbon material, a silicon-based alloy material, a negative electrode binder, and a conductive agent.
  9. 9. The negative electrode tab of claim 8, wherein the negative electrode active material comprises a composite system of graphite and a silicon-based material, wherein the mass fraction of the silicon-based material is 0-20wt%.
  10. 10. A lithium secondary battery comprising the negative electrode tab of any one of claims 1 to 9.

Description

Negative electrode piece and lithium secondary battery comprising same Technical Field The invention relates to the technical field of lithium batteries, in particular to a negative electrode plate and a lithium secondary battery comprising the same. Background With the rapid development of mobile electronic devices, electric vehicles and large-scale energy storage systems, the market has placed increasingly stringent demands on the energy density, cycle life and safety of lithium secondary batteries. The performance of a lithium secondary battery largely depends on the characteristics of electrode materials and the interface properties between electrodes and an electrolyte. On the negative electrode side of a lithium secondary battery, whether the lithium secondary battery is a traditional graphite material or a novel silicon-based negative electrode material with higher theoretical specific capacity, electrolyte is subjected to reductive decomposition on the surface of the negative electrode in the first charging process of the battery, so that a layer of solid electrolyte interface film (Solid Electrolyte Interphase, SEI film for short) is formed. The SEI film is critical to the performance of the battery, and the ideal SEI film should have good electronic insulation and ion conductivity and be capable of preventing continuous decomposition of electrolyte, thereby maintaining stable circulation of the battery. However, in practical applications, naturally-formed SEI films often have problems of uneven components, loose structure, insufficient mechanical strength, and the like. Particularly, during long-term charge and discharge cycles of a battery, the natural SEI film is easily broken and regenerated along with volume expansion and contraction of the anode active material, so that an active lithium source is continuously consumed, an electrolyte is gradually dried, and finally rapid decay of the battery capacity and rapid increase of internal resistance are caused. In order to improve this problem, a method of constructing an artificial modification layer (i.e., an artificial SEI layer) on the surface of a negative electrode is generally employed in the prior art, for example, by introducing an inorganic compound layer, a polymer layer, or an organic-inorganic composite layer on the surface of the negative electrode by means of physical coating or chemical deposition, etc., in an attempt to enhance the stability of the interface. Although various negative electrode interface modification schemes have been proposed in the prior art, the practical application effect still needs to be further improved. The existing surface modification layer is difficult to combine excellent ion transmission capability and enough mechanical stability, for example, although part of the modification layer can provide certain physical barrier, the interface impedance of a battery is obviously increased to influence the rate performance, and the other part of the modification layer is insufficient in structure retention capability in a long-cycle process, so that the situation that a coating is fallen off or fails easily occurs, and the requirements of a high-performance lithium secondary battery on long service life and high stability cannot be met. Therefore, how to develop a technical scheme capable of effectively improving the comprehensive performance of the anode interface is still a problem to be solved in the current field. Disclosure of Invention In order to solve the defects in the prior art, the invention aims to provide a negative electrode plate and a lithium secondary battery comprising the same, and the invention combines high ion conductivity and excellent mechanical toughness by constructing a multi-component synergistic densification artificial SEI layer, thereby effectively inhibiting interface side reaction and material volume expansion. In order to achieve the above purpose, the present invention adopts the following technical scheme: in a first aspect, the present invention provides a negative electrode tab. The negative electrode plate comprises a current collector and a negative electrode active material layer arranged on at least one side of the current collector, wherein at least part of the surface of the negative electrode active material layer is provided with an artificial SEI layer. In some embodiments of the present invention, the artificial SEI layer has an average thickness of 6-12 nm. Too thin an artificial SEI layer may not provide sufficient protection, resulting in insignificant improvement in cycle stability, while too thick may hinder the transmission of lithium ions, increasing battery resistance. In some embodiments of the invention, the artificial SEI layer has a dry film areal density of 0.0015 to 0.0030mg/cm 2. The areal density range helps to avoid excessive loss of battery energy density while ensuring SEI layer continuity. In some embodiments of the invention, the negative electr