Silicon-Carbon Negative Electrode Material for Lithium Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion batteries using silicon as the negative electrode material face issues of volume expansion, capacity fading, and low electrical conductivity due to uneven dispersion and surface fragmentation, leading to reduced cycle characteristics and performance.
Innovation Solution
A carbon-silicon negative electrode material and composite slurry are developed, comprising carbon nanotubes, silicon nanomaterials, and specific solvents, dispersants, and binders, which are uniformly mixed and processed to improve dispersion and conductivity, preventing volume expansion and enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the main material of the negative electrode to increase battery capacity, then the theoretical capacity increases significantly, but the volume expansion and contraction during charge and discharge cycles causes quick capacity fading and surface fragmentation
Solution Approach 1:
The patent uses a composite material system consisting of silicon nanomaterials (1-30 wt%), carbon material (1-30% of silicon amount), and conductive polymer (0.1-5 wt%). The carbon material and conductive polymer form a protective matrix that accommodates silicon's volume expansion (300-400%) during lithiation while maintaining structural integrity and electrical conductivity, thus preventing surface fragmentation and capacity fading.
Solution Approach 2:
The patent divides silicon into nanoscale particles (5-200 nm) to segment the bulk material. This nanosization reduces the absolute volume change per particle and shortens lithium diffusion paths, while the segmented structure prevents continuous surface cracking that would occur in bulk silicon, thereby improving cycle stability.
2Reliability
If silicon material is nanosized and mixed with carbon material to reduce volume expansion effect and improve electrical conductivity, then the electrical conductivity improves, but the nanosized silicon material and carbon material easily have uneven dispersion
Solution Approach 1:
The patent introduces conductive polymer (0.1-5 wt%) as an intermediary substance that mediates between nanosized silicon particles and carbon material. The conductive polymer forms a bonding matrix that uniformly distributes nanosized silicon throughout the carbon structure, preventing aggregation while maintaining continuous electrical conductivity pathways.
Solution Approach 2:
The patent controls the particle size of silicon nanomaterials within a specific range (5-200 nm) and adjusts the ratio of carbon material to silicon (1-30% of silicon amount). These parameter optimizations ensure that nanosized silicon disperses uniformly in the carbon matrix without excessive aggregation, achieving both good dispersion and electrical conductivity.
3Quantity of substance
If silicon is used as negative electrode material, then the theoretical capacity increases, but the large volume change causes fragmentation of the surface and generates new surface that induces decomposition reaction of electrolyte
Solution Approach 1:
The patent pre-coats silicon nanomaterials with carbon material and conductive polymer to create a protective buffer layer before silicon undergoes volume expansion. This beforehand cushioning layer accommodates the 300-400% volume change during lithiation, preventing direct contact between fresh silicon surfaces and electrolyte, thus avoiding electrolyte decomposition and coating film formation.
Solution Approach 2:
The composite structure of silicon-carbon-conductive polymer provides a stable outer surface that prevents electrolyte decomposition. The carbon and conductive polymer components form a chemically stable barrier that eliminates the harmful surface fragmentation effect while preserving silicon's high capacity benefits.
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
The solution achieves improved capacity, cycle retention, and electrical conductivity, thereby enhancing the performance and longevity of lithium ion batteries by ensuring uniform dispersion and reducing battery expansion.
Implementation Method 1
The carbon material and the silicon nanomaterial are uniformly mixed in the first solvent
Implementation Method 2
a conductive polymer coating the surface of the silicon nanomaterial... the electrical conductivity of the silicon material is also lower than that of the carbon material
Implementation Method 3
The carbon material comprises a carbon nanotube
Data Source
AI summary
A negative electrode material for a lithium ion battery comprises a carbon material, a silicon nanomaterial, and a first solvent. The carbon material comprises carbon nanotubes. The carbon material and the silicon nanomaterial are uniformly mixed in the first solvent. The weight percentage of the silicon nanomaterial is between 1% and 30%, and the amount of the carbon material is 1% to 30% of the amount of the silicon nanomaterial. A negative electrode composite slurry for a lithium ion battery comprises the negative electrode material and a graphite mixture material. The graphite mixture material comprises graphite and a second solvent. The graphite is uniformly mixed in the second solvent, and the weight percentage of the graphite is between 20% and 40%.