NMC Cathode Composition Using Carbon Black-CNT Conductive Paths
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving small internal resistance, excellent output characteristics, and low-temperature performance due to issues with conductor distribution and aggregation when using carbon black with small particle diameter and long structure, as well as the need for high energy density and durability.
Innovation Solution
A positive electrode composition comprising lithium-nickel-cobalt-manganese complex oxide as the active material, combined with carbon black having a specific BET surface area and DBP absorption, and carbon nanotubes with a small fiber diameter, to create an effective conducting path and reduce conductor content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black with small particle diameter and long structure is used to improve electrical conduction properties, then electrical conduction properties are improved, but aggregation occurs due to entanglement of structures causing uneven distribution in the electrode
Solution Approach 1:
The patent combines carbon black with small particle diameter and long structure (DBP absorption 240-380 mL/100 g) with carbon nanotubes (average diameter 7-15 nm) to create a composite conductor system. The carbon nanotubes act as spacers that prevent aggregation of the carbon black structures, while both materials work together to provide excellent electrical conduction properties and uniform distribution in the electrode.
2Reliability
If carbon nanotubes with small fiber diameter are used to create conducting paths with smaller amount of conductor, then electrical conduction properties are improved, but the content of carbon black is reduced which affects electrolyte solution holding ability
Solution Approach 1:
The patent optimizes the specific parameters of carbon black (DBP absorption of 240-380 mL/100 g and BET specific surface area of 100-400 m²/g) to achieve the right balance. These parameter ranges ensure that sufficient carbon black content is maintained for electrolyte solution holding ability while still providing excellent electrical conduction when combined with carbon nanotubes.
3Use of energy by moving object
If conductor content is reduced to increase energy density, then energy density is improved, but electrical conduction properties deteriorate
Solution Approach 1:
The patent uses a composite conductor system combining carbon black and carbon nanotubes that provides superior electrical conduction properties at lower overall conductor content. The synergistic effect of the two materials allows for reduced conductor content (1-5 wt% of carbon black and 0.1-2 wt% of carbon nanotubes) while maintaining or improving electrical conduction, thereby increasing energy density.
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 results in a lithium-ion secondary battery with small internal resistance, excellent output and cycle characteristics, and improved low-temperature performance by optimizing the distribution and conductivity of the conductor materials.
Implementation Method 1
carbon black has a common structure in which primary particles in nearly a spherical shape are linked in a row, and such a structure of carbon black is called the structure. The length of the structure is generally indirectly evaluated using a DBP absorption as measured in accordance with JIS K6217-4, and the larger the DBP absorption is, the longer the structure is, and the more excellent the electrical conduction properties are.
Data Source
AI summary
According to various aspects of the present invention, a positive electrode composition for a lithium-ion secondary battery includes an active material capable of inserting and extracting lithium ions, and a conductor, wherein the active material is a lithium-nickel-cobalt-manganese complex oxide; the conductor is a carbon black and carbon nanotubes; the carbon black has a BET specific surface area of 100 to 400 m2/g, and a DBP absorption of 210 to 380 ml/100 g; and the carbon nanotubes have an average diameter of 7 to 15 nm.