Dual-Layer Lithium Battery Negative Electrode for Low-Temperature Charging
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Solution Overview
Problem
Rechargeable lithium batteries face issues with lithium metal precipitation during high-rate charging at low temperatures, leading to capacity loss and reduced cycle-life, which existing technologies have not adequately addressed.
Innovation Solution
A negative electrode for rechargeable lithium batteries is designed with a dual-layer structure, where the first layer consists of single particle graphite with a larger average diameter and higher specific surface area, and the second layer comprises secondary particles with smaller diameters, effectively suppressing lithium metal precipitation by improving bonding force and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-rate charging is performed at low temperature, then charging speed is improved, but lithium metal precipitation occurs leading to capacity loss and reduced cycle-life
Solution Approach 1:
The negative electrode active material is segmented into two distinct layers: a first layer containing larger particles (10-30 μm) and a second layer containing smaller particles (3-10 μm). This segmentation allows each layer to perform specialized functions - the first layer provides high capacity while the second layer suppresses lithium precipitation during high-rate charging, thereby resolving the contradiction between charging speed and cycle-life.
Solution Approach 2:
Different regions of the negative electrode are given different properties through the dual-layer structure. The first layer near the current collector has larger particles optimized for capacity, while the second layer at the surface has smaller particles optimized for suppressing lithium precipitation. This local differentiation allows the electrode to simultaneously achieve high capacity and high rate performance at low temperatures.
2Quantity of substance
If single particle graphite with larger diameter is used, then capacity is improved, but lithium metal precipitation occurs during high-rate charging
Solution Approach 1:
The graphite particles are segmented into two size categories arranged in layers: larger particles (10-30 μm) in the first layer provide high capacity, while smaller particles (3-10 μm) in the second layer suppress lithium precipitation. This segmentation resolves the contradiction by assigning different particle sizes to different functional roles within the same electrode.
Solution Approach 2:
The negative electrode uses a composite structure combining two types of graphite particles with different size characteristics. The composite of large and small particles creates synergistic effects where the small particles prevent lithium precipitation while the large particles contribute to high capacity, thereby resolving the contradiction between capacity and precipitation suppression.
3Object-generated harmful factors
If secondary particles with smaller diameter are used, then lithium metal precipitation is suppressed, but capacity is reduced
Solution Approach 1:
The electrode structure segments the particle size function: smaller particles (3-10 μm) in the second layer specifically suppress lithium precipitation, while larger particles (10-30 μm) in the first layer provide high capacity. This segmentation allows small particles to perform their precipitation-suppression function without limiting the overall capacity contribution from large particles.
Solution Approach 2:
The invention merges the advantages of both small and large particles into a single dual-layer electrode structure. The combination of small particles (for precipitation suppression) and large particles (for capacity) in specific layers creates a synergistic effect that achieves both precipitation suppression and high capacity simultaneously.
4Productivity
If dual-layer structure with different particle sizes is used, then charge/discharge efficiency is improved, but device complexity increases
Solution Approach 1:
The electrode is segmented into two functional layers with different particle size distributions, optimized for different aspects of performance. This segmentation improves charge/discharge efficiency by allowing each layer to perform its specialized function, while the segmentation itself provides a clear, systematic approach to manufacturing.
Solution Approach 2:
The invention changes the particle size parameter systematically across layers - the first layer uses particles of 10-30 μm while the second layer uses particles of 3-10 μm. This parameter change approach allows optimization of charge/discharge efficiency through controlled variation in particle size, while maintaining a relatively simple manufacturing process by using standard particle size ranges.
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 dual-layer structure effectively reduces lithium metal precipitation, enhances charge/discharge efficiency, and achieves high capacity and power characteristics, while maintaining high output performance even at low temperatures.
Implementation Method 1
improving bonding force and charge/discharge efficiency
Implementation Method 2
a positive electrode including an active material intercalating and deintercalating lithium ions, a negative electrode
Data Source
AI summary
A negative electrode for a rechargeable lithium battery which includes a current collector, a first negative electrode active material layer on one surface or both surfaces of the current collector; a second negative electrode active material layer on the first negative electrode active material layer is provided. The first negative electrode active material layer includes a first negative electrode active material, the first negative electrode active material includes graphite of single particles, the second negative electrode active material layer includes a second negative electrode active material, the second negative electrode active material includes graphite including secondary particles in which a plurality of primary particles are agglomerated (assembled), and an average particle diameter of the second negative electrode active material is smaller than an average particle diameter of the first negative electrode active material.