Graphite-Hard Carbon Negative Electrode for Low-Impedance Fast Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current commercial graphite negative electrodes in electrochemical apparatuses, such as lithium-ion batteries, face limitations in fast charge and discharge performance, rate performance, and cycling performance, necessitating an improvement in these aspects to meet the increasing demands of energy density and safety.
Innovation Solution
A negative electrode comprising a negative electrode current collector with a negative electrode active material layer made of a combination of graphite and hard carbon, where the mass ratio of hydrogen to carbon in both materials is optimized, along with specific compacted densities and particle sizes, to enhance the electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If commercial graphite is used as negative electrode material, then high efficiency and stable charge and discharge plateau are achieved, but fast charge and discharge performance and rate performance are limited
Solution Approach 1:
The patent uses a composite negative electrode material consisting of graphite and hard carbon. The graphite component provides stable charge and discharge plateau, while the hard carbon component enhances fast charge and discharge performance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent optimizes the local properties of the negative electrode by controlling the particle size distribution and morphology of graphite and hard carbon. The hard carbon with specific particle size and morphology is distributed within the graphite structure to locally enhance ion transport and electron conduction, improving rate performance while maintaining overall stability.
2Quantity of substance
If commercial graphite is used as negative electrode material, then high volumetric and mass energy densities are achieved, but cycling performance needs further improvement
Solution Approach 1:
The composite of graphite and hard carbon maintains the high energy density of graphite while the hard carbon component improves cycling performance through its structural stability and resistance to expansion/contraction during charge-discharge cycles.
Solution Approach 2:
The patent changes key parameters including the mass ratio of hard carbon to graphite (optimized at 5-20%), particle size distribution, and H/C ratio of hard carbon (optimized at 0.05-0.20) to simultaneously achieve high energy density and improved cycling performance.
Data Source
Figure 1~2
AI summary
A negative electrode includes: a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, where the negative electrode active material includes graphite and hard carbon. Based on a total mass of the hard carbon, a ratio of a mass of element hydrogen to a mass of element carbon in the hard carbon is Wi, and based on a total mass of the graphite, a ratio of a mass of element hydrogen to a mass of element carbon in the graphite is W2, a value of W1/W2 being within a range of 5 to 19. The electrochemical apparatus has reduced impedance and improved rate performance and cycling performance.