Silicon Anode Cohesion Structure for Capacity Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based compounds used in negative electrodes of lithium secondary batteries face issues with surface oxidation reactions leading to hydrogen gas generation and phase stability deterioration, posing explosion risks and capacity degradation due to electrode contraction and expansion during charge and discharge.
Innovation Solution
A negative electrode with a silicon-based active material layer having a cohesion strength ranging from 1 MPa to 20 MPa and a vertical resistance of 0.005 Ω to 0.3 Ω is developed, ensuring uniform cohesion and minimal resistance to maintain electrode connectivity and reduce capacity degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compounds are used as negative electrode active materials to increase capacity, then the battery capacity is improved, but surface oxidation reactions occur leading to hydrogen gas generation and phase stability deterioration
Solution Approach 1:
The patent applies composite materials by combining silicon-based compounds with graphite particles to form a negative electrode active material layer. The graphite component provides structural stability and prevents surface oxidation reactions, while the silicon-based compounds contribute high capacity. This composite structure resolves the contradiction by maintaining phase stability through graphite while achieving high capacity through silicon-based materials.
Solution Approach 2:
The patent uses an aqueous binder as an intermediary substance in the slurry composition, which contains silicon-based compounds, graphite particles, and the aqueous binder. The aqueous binder mediates between the silicon-based compounds and the current collector, preventing direct surface oxidation reactions while maintaining electrical connectivity and structural integrity during charge-discharge cycles.
2Quantity of substance
If silicon-based compounds are used to achieve high capacity, then the energy density is improved, but electrode contraction and expansion during charge and discharge cause internal network disconnection and capacity degradation
Solution Approach 1:
The composite structure of silicon-based compounds combined with graphite particles provides both high capacity and structural stability. The graphite component acts as a buffer that accommodates the contraction and expansion of silicon-based materials during charge-discharge cycles, preventing internal network disconnection and maintaining electrical connectivity throughout the electrode's lifespan.
Solution Approach 2:
The patent optimizes the composition parameters of the slurry, specifically controlling the ratios of silicon-based compounds to graphite particles and adjusting the aqueous binder content. By changing these parameters, the electrode structure achieves both high energy density and durability, allowing the electrode to maintain its integrity during repeated contraction and expansion cycles.
3Duration of action of stationary object
If the electrode structure is optimized for uniform cohesion strength, then capacity degradation is minimized, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes manufacturing parameters including slurry viscosity, coating speed, and drying temperature to achieve uniform cohesion strength throughout the electrode. By carefully controlling these parameters, the electrode maintains consistent mechanical properties that prevent capacity degradation while keeping manufacturing processes feasible and scalable.
Data Source
Figure 1~2
AI summary
The present application relates to an anode comprising an anode active material layer that includes a silicon-based active material, wherein, when the cohesion strength is measured at respective positions of 25%, 50% and 75% of the total thickness from a first surface of the anode active material layer on the basis of the total thickness T, which is the distance between the first surface and a second surface that face each other, the average of the measured cohesion strengths is 1 Mpa to 20 Mpa, the deviation of the measured cohesion strengths is 140% or less, and the vertical resistance is 0.005 Ω to 0.3 Ω.