Positive Electrode Mixture Layer Using Dual CNT Conductive Additives
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving high rate characteristics at ordinary and low temperatures, along with low internal resistance (DCR) at low temperatures, which are crucial for automotive applications in cold regions.
Innovation Solution
A conductive additive comprising carbon black and two specific types of carbon nanotubes with defined diameter and length ranges is used in the positive electrode mixture layer, enhancing electron conductivity and electrolyte solution retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Li4Ti5O12 particles are used as an electroconductive auxiliary agent in the positive electrode mixture, then lithium ion diffusivity and charge-discharge characteristics are improved, but internal stress during charge-discharge cycles increases leading to particle disintegration
Solution Approach 1:
The Li4Ti5O12 particles are divided into smaller secondary particles with a mean particle diameter of 0.03 µm or less. This segmentation reduces the path length for lithium ion diffusion, improving charge-discharge characteristics while reducing the magnitude of volume expansion and contraction during cycling, thereby maintaining particle integrity
Solution Approach 2:
The patent creates a composite structure where fine Li4Ti5O12 secondary particles are aggregated to form larger particles with a specific size distribution. This composite approach combines the high lithium ion diffusivity of ultra-fine particles with the structural stability of larger particles, resolving the contradiction between speed and strength
2Speed
If Li4Ti5O12 particles with mean particle diameter of 0.03 µm or less are used, then charge-discharge characteristics are further improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs a preliminary action by using a sol-gel method to pre-form uniform Li4Ti5O12 particles with controlled size distribution before electrode fabrication. This preliminary particle formation simplifies subsequent manufacturing steps while ensuring the desired fine particle characteristics for optimal charge-discharge performance
Solution Approach 2:
The patent changes the particle size parameter to a specific range (mean diameter ≤ 0.03 µm) and maintains a controlled size distribution. This parameter optimization achieves superior charge-discharge characteristics while the consistent size distribution simplifies processing and manufacturing compared to broader size distributions
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 lithium-ion secondary batteries with improved rate characteristics and reduced internal resistance at low temperatures, thereby increasing energy density and capacity retention.
Implementation Method 1
it has come to light by experimentation that, when Li4Ti5O12 particles are used as an electroconductive auxiliary agent in a positive electrode mixture, lithium ion diffusivity between positive and negative electrodes is improved and charge-discharge characteristics are thereby excellent
Implementation Method 2
when Li4Ti5O12 particles having a mean particle diameter of 0.03 µm or less (30 nm or less) are used, internal stress during charge-discharge cycles is reduced and particle disintegration is thereby prevented
Data Source
AI summary
A positive electrode mixture layer for a lithium-ion secondary battery providing a positive electrode mixture layer for a lithium-ion secondary battery suitable for producing a lithium-ion secondary battery with high rate characteristics at an ordinary temperature and low temperatures and low internal resistance (DCR) at low temperatures, characterized by including a positive electrode active material, a binder, and a conductive additive, in which the conductive additive includes carbon black, a carbon nanotube 1 having an average fiber diameter of 80 to 400 nm, and a carbon nanotube 2 having an average fiber diameter of 0.4 to 3.0 nm, the content rates of the carbon black, the carbon nanotube 1, and the carbon nanotube 2 in the conductive additive are 40 to 80% by mass, 10 to 50% by mass, and 1 to 30% by mass, respectively, and the content rate of the conductive additive in the positive electrode mixed layer is 0.1 to 5.0% by mass.