Lithium Battery Negative Electrode Composition for Expansion Control
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining high-rate cycle-life characteristics and energy density due to increased DC internal resistance and electrode expansion during charge and discharge, which are not adequately addressed by existing technologies.
Innovation Solution
A negative electrode is designed with a carbon negative active material and a conductive agent having specific properties, including a Degree of Divergence (DD) value of 24 or greater, optimized through magnetic field orientation and composition, to enhance lithium ion movement and prevent resistance increases, thereby improving cycle life and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive agents are used in the negative electrode, then the electrode structure is simple and easy to manufacture, but the DC internal resistance increases during charge and discharge, reducing high-rate cycle-life characteristics
Solution Approach 1:
The patent employs a composite conductive agent system combining fiber-shaped conductive agents (length 1-200 μm) and particle-shaped conductive agents (long diameter 1-20 μm) with specific DD values (24-70). This composite approach creates a synergistic conductive network that maintains low DC internal resistance during charge-discharge cycles, thereby improving high-rate cycle-life characteristics without excessive complexity
Solution Approach 2:
The patent optimizes specific parameters of the conductive agents including fiber length (1-200 μm), particle diameter (1-20 μm), DD value (24-70), specific external surface area (4-1500 m2/g), and aspect ratio (10-3000). These parameter optimizations enable the conductive agent system to maintain effective conductivity during electrode expansion and contraction, resolving the contradiction between reliability and complexity
2Reliability
If the conductive agent has high specific external surface area and aspect ratio, then the electrical conductivity and lithium ion movement are enhanced, but the manufacturing precision and control difficulty increase
Solution Approach 1:
The patent defines specific parameter ranges for conductive agents: fiber length (1-200 μm), particle diameter (1-20 μm), DD value (24-70), specific external surface area (4-1500 m2/g), and aspect ratio (10-3000). These optimized parameter ranges achieve effective conductivity while remaining manufacturable with conventional precision controls
Solution Approach 2:
The patent applies different conductive agent properties to different regions and functions within the electrode. The conductive agents with specific surface areas and aspect ratios are optimized for their particular roles in creating conductive networks, ensuring that each component's local properties contribute maximally to overall electrical conductivity without requiring extreme manufacturing precision across all parameters
3Quantity of substance
If the negative active material layer has high carbon content, then the energy density is improved, but the electrode expansion during charge and discharge increases, reducing cycle life
Solution Approach 1:
The patent uses a composite conductive agent system (fiber-shaped + particle-shaped) that maintains structural stability during electrode expansion. The combination of different shapes and sizes creates a flexible conductive network that accommodates volume changes while maintaining electrical connectivity, allowing high carbon content for energy density without sacrificing cycle life
Solution Approach 2:
The conductive agents act as intermediary materials between the carbon negative active material particles, maintaining structural integrity and electrical connectivity during expansion and contraction. This intermediary network allows the electrode to tolerate higher carbon content for improved energy density while preventing structural degradation that would reduce cycle life
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 effectively suppresses DC internal resistance and electrode expansion, enhancing high-rate cycle-life characteristics and energy density while preventing thermal runaway, thus improving the overall performance of rechargeable lithium batteries.
Implementation Method 1
the conductive agent includes at least one of a fiber-shaped conductive agent having a average length of about 1 μm to about 200 μm and a particle-shaped conductive agent having a average long diameter of about 1 μm to about 20 μm
Implementation Method 2
optimized through magnetic field orientation and composition
Data Source
AI summary
A negative electrode and a rechargeable lithium battery, the negative electrode including a current collector; and a negative active material layer on at least one surface of the current collector, the negative active material layer including a carbon negative active material and a conductive agent, wherein the conductive agent includes at least one of a fiber-shaped conductive agent having a average length of about 1 µm to about 200 µm and a particle-shaped conductive agent having a average long diameter of about 1 µm to about 20 µm, and a DD (Degree of Divergence) value defined by Equation 1 is about 24 or greater:DDDegree of Divergence = Ia/Itotal * 100[Equation 1]wherein, in Equation 1, Ia is a sum of peak intensities at non-planar angles measured by XRD using a CuKα ray, and Itotal is a sum of peak intensity at all angles measured by XRD using a CuKα ray.