Lithium Composite Negative Electrode with Uniform SEI Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium secondary batteries face challenges with irreversible capacity loss due to the formation of a Solid Electrolyte Interface (SEI) film on the carbon electrode, leading to reduced efficiency and cycle life, especially when using pre-lithiated carbon electrodes.
Innovation Solution
A method involving the preparation of pellets from a mixture of lithium metal and negative electrode active material, followed by immersion in an electrolyte containing specific SEI film-forming additives, and subsequent pulverization and drying to create a uniformly doped lithium composite negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode active material to increase capacity, then battery capacity increases, but volume expansion during alloying reaction occurs causing electrode deterioration
Solution Approach 1:
The silicon negative electrode active material is divided into fine particles with a maximum particle diameter of 0.6 μm or less. This segmentation prevents volume expansion from causing electrode deterioration by distributing the expansion stress across many small particles rather than a large continuous structure, while maintaining high battery capacity through increased surface area for lithium alloying reactions.
Solution Approach 2:
The silicon fine particles have a specific surface area of 0.5 m²/g or more, indicating a porous or highly surface-area structure. This porous structure accommodates volume expansion during lithium alloying while maintaining electrode integrity, and the high surface area provides more reaction sites for lithium insertion, increasing battery capacity.
2Reliability
If lithium oxide coating is applied to suppress electrolyte decomposition, then battery durability improves, but coating uniformity is difficult to achieve with conventional methods
Solution Approach 1:
The conventional mechanical coating method (doctor blade) is replaced with a chemical field method using a dip-coating process. The porous membrane filter acts as a medium through which the lithium oxide coating solution is drawn via capillary action, ensuring uniform coating thickness regardless of the substrate's surface geometry. This substitution of mechanical coating with capillary-driven chemical coating achieves consistent coating uniformity on silicon fine particles.
Solution Approach 2:
A porous membrane filter serves as an intermediary between the lithium oxide coating solution and the silicon fine particles. The filter's pore structure controls the coating solution flow and ensures uniform distribution of lithium oxide on the silicon particle surfaces, achieving coating uniformity that cannot be obtained by direct contact coating methods.
3Productivity
If silicon fine particles are used to increase surface area, then lithium alloying reaction efficiency improves, but particles aggregate making uniform coating difficult
Solution Approach 1:
The porous membrane filter acts as an intermediary that prevents aggregation of silicon fine particles during the coating process. The filter's pore structure maintains particle separation while allowing the coating solution to penetrate and coat each particle uniformly, preserving both the high surface area benefits and composition uniformity.
Solution Approach 2:
The porous membrane filter with controlled pore size prevents silicon fine particles from aggregating during coating. The porous structure allows the coating solution to reach individual particles while physically separating them, maintaining uniform particle dispersion and enabling efficient lithium alloying reactions across all particles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the initial efficiency and cycle life of lithium secondary batteries by ensuring uniform lithium doping and stable SEI film formation, thereby improving the battery's performance.
Implementation Method 1
applying a coating solution containing lithium oxide to the silicon fine particles in a state where the silicon fine particles are held by a porous membrane filter, thereby capillary penetrating the coating solution into the pores of the porous membrane filter
Implementation Method 2
silicon fine particles having a specific surface area of 0.5 m²/g or more, excellent lithium alloying reaction characteristics
Data Source
Figure 1~2
Figure 3
AI summary
A method for manufacturing negative electrode active material, of the present invention, comprises the steps of: manufacturing a pellet by extruding a mixture of lithium metal and negative electrode active material; immersing the pellet in an electrolyte comprising an SEI film-forming additive; and manufacturing the pellet into powder form by grinding, washing and drying same. A negative electrode and a lithium rechargeable battery, of the present invention, manufactured using the lithium-active material powder have an SEI film which is uniformly formed by having lithium uniformly doped in the negative electrode, and during initial charging, the SEI film is stably formed, and thus an effect is achieved whereby the initial efficiency of the lithium rechargeable battery is improved.