Secondary Battery Conductive Network for High Energy Density
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high energy density and rate performance while maintaining a compact size, due to the limitations of conductive additives like carbon black and graphene, which often result in high contact resistance and aggregation issues.
Innovation Solution
A method involving a specific mixing ratio of graphene and carbon black as conductive additives, where the weight of carbon black is optimized to be between 1.5 to 20 times that of graphene, forming a highly conductive network to increase active material proportion and electrode density, thereby enhancing capacity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used as conductive additive, then electron conductivity is improved, but contact resistance increases and aggregation occurs
Solution Approach 1:
The patent uses a composite conductive additive system combining carbon black (first carbon material) with graphene or carbon nanotubes (second carbon material). This composite approach leverages the high conductivity of carbon black while using graphene/carbon nanotubes to form a conductive network that reduces contact resistance and prevents aggregation, thereby resolving the technical contradiction between improving conductivity and eliminating harmful aggregation effects.
Solution Approach 2:
The patent applies different carbon materials at different locations and functions within the electrode: carbon black provides bulk conductivity in the active material matrix, while graphene or carbon nanotubes form a conductive network at critical interfaces and contact points. This local differentiation optimizes conductivity where needed while minimizing aggregation issues.
2Use of energy by moving object
If high-capacity secondary batteries are used, then energy density is improved, but device weight increases
Solution Approach 1:
The patent optimizes the composition ratios of conductive additives (carbon black:graphene/carbon nanotubes in specific weight ratios) to maximize energy density while controlling weight. By precisely controlling the amounts and types of conductive materials, the patent achieves high capacity electrodes with minimized unnecessary mass, resolving the contradiction between energy density and weight.
3Reliability
If conductive additive amount is increased, then electron conductivity is improved, but active material proportion decreases
Solution Approach 1:
The patent employs a composite conductive additive system where graphene or carbon nanotubes form an efficient conductive network at lower concentrations compared to traditional carbon black alone. This allows achieving the same or better conductivity with less total conductive additive, thereby maintaining higher active material proportion in the electrode.
Solution Approach 2:
Graphene or carbon nanotubes act as intermediary conductive elements that bridge active material particles more efficiently than carbon black alone. Their high aspect ratio and superior conductivity create effective conductive pathways with smaller amounts, reducing the overall conductive additive requirement while maintaining electron conductivity.
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 results in a secondary battery with improved energy density, rate performance, and cycle stability, enabling a vehicle to achieve a driving range of 500 km or longer per charge without increasing the battery weight, and allows for fast charging capabilities.
Implementation Method 1
forming a highly conductive network to increase active material proportion and electrode density, thereby enhancing capacity and cycle performance
Data Source
AI summary
An active material layer that has a high filling rate and a higher density and is formed using a small amount of conductive additive is provided. A positive electrode active material layer includes a first carbon material and a second carbon material, which is more likely to aggregate than the first carbon material, and mixing is performed such that the weight of the second carbon material is more than or equal to 1.5 times and less than or equal to 20 times that of the first carbon material, thereby preventing the aggregation of the second carbon material and the aggregation of the first carbon material and reducing the proportion of the aggregated portions.