Lithium Battery Negative Electrode Orientation for Low Internal Resistance
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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, where the conductive agent has specific size and orientation characteristics, including a Degree of Divergence (DD) value of 24 or greater, to facilitate lithium ion movement and prevent resistance increase, while also including a magnetic field orientation to enhance material alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive agents are used in the negative electrode, then the electrode structure is simple, but DC internal resistance increases and high-rate cycle-life characteristics deteriorate
Solution Approach 1:
The patent uses a composite conductive agent system combining fiber-shaped conductive agents (length 1-200 μm) and particle-shaped conductive agents (long diameter 1-20 μm) to create a multi-functional conductive network. This composite approach improves high-rate cycle-life characteristics by establishing both point-contact and line-contact conductive pathways, reducing DC internal resistance while maintaining reasonable electrode structure complexity
Solution Approach 2:
The patent optimizes specific parameters of the conductive agents including fiber length (1-200 μm), particle diameter (1-20 μm), and their area ratio (50-300% relative to carbon negative active material). These parameter adjustments create an optimal conductive network density that reduces internal resistance and improves cycle-life without excessive structural complexity
2Reliability
If carbon negative active material is oriented to improve lithium ion movement, then high-rate cycle-life characteristics improve, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary magnetic field orientation to the carbon negative active material during the electrode manufacturing process. By pre-orienting the carbon material in a magnetic field before assembly, the electrode achieves improved lithium ion movement and high-rate cycle-life characteristics without requiring complex post-manufacturing processing steps
Solution Approach 2:
The patent replaces mechanical orientation methods with magnetic field orientation for aligning the carbon negative active material. This substitution simplifies the manufacturing process by using a non-contact magnetic field application rather than complex mechanical alignment systems, thereby improving reliability while maintaining ease of manufacture
3Reliability
If conductive agent amount is increased to reduce resistance, then DC internal resistance decreases, but energy density deteriorates due to volume occupation
Solution Approach 1:
The patent employs a composite conductive agent system with fiber-shaped agents (1-200 μm length) and particle-shaped agents (1-20 μm diameter) that creates an efficient conductive network at low concentrations. The fiber agents provide extended conductive pathways while particle agents fill gaps, achieving effective resistance reduction with minimal volume occupation, thus maintaining energy density
Solution Approach 2:
The patent applies conductive agents strategically at critical locations where conductivity is most needed, such as at the interfaces between carbon negative active material particles and within the matrix structure. This localized application reduces overall conductive agent content while effectively lowering DC internal resistance, preserving energy density by minimizing volume occupied by non-active material
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, improves high-rate cycle-life characteristics, and enhances energy density by ensuring proper orientation of the carbon negative active material, thereby improving battery performance and safety by facilitating heat dissipation.
Implementation Method 1
facilitate lithium ion movement and prevent resistance increase
Implementation Method 2
including a magnetic field orientation to enhance material alignment
Implementation Method 3
improving battery performance and safety by facilitating heat dissipation
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:DD (Degree 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.