Carbon Layer Current Collector for High Power Lithium Battery
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Solution Overview
Problem
Lithium rechargeable batteries face challenges in achieving high-rate capability, power density, and cycle-life characteristics due to limitations in current electrode designs, particularly with the use of sulfur-based positive active materials which increase internal resistance.
Innovation Solution
A positive electrode for lithium rechargeable batteries is designed with a carbon layer on a substrate, featuring a carbon-based material like artificial or natural graphite, with a specific loading level and thickness to enhance binding properties and reduce internal resistance, paired with a lithiated intercalation compound as the positive active material, and a carbon-based negative electrode with a binder to improve conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sulfur-based positive active materials are used, then energy density is improved, but internal resistance increases
Solution Approach 1:
A carbon layer is introduced as an intermediary between the sulfur-based positive active material and the current collector. This carbon layer mediates the electrical connection, providing a conductive pathway that reduces internal resistance while preserving the high energy density benefits of sulfur-based materials.
Solution Approach 2:
The patent employs a composite structure combining carbon-based materials (graphite, carbon black, acetylene black) with sulfur-based positive active materials. This composite approach creates a synergistic effect where the carbon component enhances electrical conductivity and reduces internal resistance, while the sulfur component maintains high energy density.
2Reliability
If carbon layer loading level is increased, then conductivity is improved, but weight increases
Solution Approach 1:
The patent optimizes the carbon layer loading level within a specific range of 0.5-3 g/m2. By precisely controlling this parameter, the invention achieves the necessary conductivity improvement while minimizing the weight penalty. The optimal loading level balances electrical performance with weight constraints.
Solution Approach 2:
The carbon layer is applied selectively on the current collector surface where it is most needed for electrical conductivity. This localized application ensures that conductivity is improved at the critical interface between the current collector and active material, without unnecessarily increasing the overall battery weight through excessive carbon distribution.
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 improved high-rate capability, power density, and extended cycle-life characteristics, making the battery suitable for high-power applications such as automotive use, while avoiding issues associated with sulfur-based compounds.
Implementation Method 1
the carbon layer has a loading level of 0.5 g/m2 to 3 g/m2... improved high-rate capability, power density, and extended cycle-life characteristics
Implementation Method 2
a positive active material layer disposed on the current collector... The positive active material layer may include a positive active material that reversibly intercalates and deintercalates lithium ions
Data Source
AI summary
Disclosed are a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the positive electrode includes a current collector including a carbon layer disposed on a substrate; and a positive active material layer disposed on the current collector, wherein the carbon layer has a loading level of 0.5 g/m2 to 3 g/m2. The effects of the carbon layer include improving the high power characteristics and the power density by decreasing the internal resistance of an electrode, and to improve the power density by providing uniform current to the positive electrode. The carbon layer may have a thickness of about 1 μm to about 2 μm. The carbon layer may include a carbon-based material of artificial graphite, natural graphite, carbon black, acetylene black, ketjen black, denka black, or combinations thereof.