Silicon-Graphite Negative Electrode Structure for Fast-Charging Lifespan
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium secondary batteries face limitations in energy density, rapid charging performance, and lifespan due to the use of graphite as a negative electrode active material, which has low electrical capacity and slow lithium insertion reaction rates, leading to long charging times and reduced efficiency.
Innovation Solution
A negative electrode comprising a two-layer structure with a first carbon-based negative electrode active layer and a second carbon-based negative electrode active layer, incorporating silicon-based active materials, optimized through specific orientation indices and particle sizes, and a manufacturing process involving magnetic field application to enhance adhesion and lithium transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If graphite is used as negative electrode active material, then the battery structure is simple and manufacturing is easy, but the lithium insertion reaction speed is slow and rapid charging performance is limited
Solution Approach 1:
The patent uses a composite negative electrode structure combining graphite particles (providing structural stability and ease of manufacture) with silicon particles (providing high capacity and improved lithium insertion speed). The composite material achieves both manufacturing simplicity and enhanced rapid charging performance by leveraging the complementary properties of different materials.
2Quantity of substance
If silicon is used as negative electrode active material to increase capacity, then the energy density is improved, but the volume expansion during charging and discharging is large and lifespan is reduced
Solution Approach 1:
The patent embeds silicon particles inside graphite particles or nests them together in a composite structure. The graphite outer layer constrains the silicon inner particles, preventing excessive volume expansion during lithium insertion/extraction cycles. This nested configuration allows silicon to provide high capacity while graphite maintains structural integrity, thus improving both energy density and lifespan.
Solution Approach 2:
The graphite component acts as a flexible constraint shell around silicon particles, accommodating the volume changes of silicon during charging and discharging without causing structural failure. This flexible constraint mechanism prevents particle pulverization and maintains electrode integrity over many cycles, thereby extending battery lifespan.
3Reliability
If the negative electrode active layer adhesion to current collector is improved, then the electrode durability is enhanced, but the manufacturing process complexity increases
Solution Approach 1:
The patent optimizes parameters such as the orientation index of graphite particles (controlling their alignment angle relative to the current collector) and the particle size distribution of the composite material. By adjusting these parameters, the adhesion between the active layer and current collector is enhanced through improved mechanical interlocking and contact area, achieving better durability without requiring complex additional manufacturing steps.
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 provides high charge and discharge capacity, excellent adhesion to the current collector, and improved lifespan, enabling rapid charging and discharge performance even at standard conditions, reducing charging time and maintaining battery safety.
Implementation Method 1
silicon has been found to be capable of reversibly adsorbing and releasing large amounts of lithium through compound formation reaction with lithium
Implementation Method 2
when graphite is used as a negative electrode active material, the insertion reaction of lithium ions proceeds at a slow speed
Implementation Method 3
a manufacturing process involving magnetic field application to enhance adhesion and lithium transport
Data Source
AI summary
A negative electrode for a lithium secondary battery may include a negative electrode having a silicon-based negative electrode active material with a predetermined content in a first negative electrode active layer in contact with a negative electrode current collector. By controlling an orientation index (O.I1st) of a first negative electrode active layer and a ratio of the orientation index (O.I1st /O.I2nd) of the first negative electrode active layer to the second negative electrode active layer to a predetermined range, the negative electrode for a lithium secondary battery has the characteristics of not only high charge and discharge capacity but also excellent adhesion between the negative electrode current collector and the negative electrode active layer. In addition, the lithium secondary battery including the negative electrode has excellent lifespan characteristics, has excellent output characteristics, and can be charged in a short time even at a 1C-rate.