Layered Negative Electrode Structure for Fast-Charging Secondary Batteries
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving both high energy density and fast charging capability due to the trade-off between coating weight and active material distribution, leading to energy density loss and poor kinetic performance.
Innovation Solution
A secondary battery design featuring multiple electrode plate layers, where a negative electrode with a small lithium deintercalation potential slope is used as a lower layer for high energy density and a layer with a large lithium deintercalation potential slope is used as an upper layer for fast charging, optimizing the terminal potential slopes and thickness ratios to enhance both energy density and kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the coating weight is reduced to improve fast charging capability, then the fast charging performance is improved, but the energy density is significantly reduced
Solution Approach 1:
The electrode plate is divided into multiple layers with different active materials. The first layer (closer to current collector) uses active material with small lithium deintercalation potential slope for high energy density, while the second layer (farther from current collector) uses active material with large lithium deintercalation potential slope for fast charging capability. This segmentation allows each layer to specialize in one function, resolving the contradiction between energy density and fast charging performance.
Solution Approach 2:
Different regions of the electrode plate are assigned different active materials with specific properties. The first active material layer has properties optimized for energy density (small potential slope), while the second active material layer has properties optimized for fast charging (large potential slope). This local differentiation of material properties enables simultaneous optimization of both contradictory requirements in different locations.
2Quantity of substance
If the coating weight is increased to increase energy density, then the energy density is improved, but the fast charging capability is degraded due to large thickness and long active ion transport path
Solution Approach 1:
The thick electrode plate is segmented into multiple layers, where the first layer provides the bulk of the active material for high energy density, while the second layer facilitates fast ion transport to and from the current collector. This segmentation allows the electrode to maintain large thickness for energy density while avoiding the fast charging degradation that would normally result from such thickness.
Solution Approach 2:
The first active material layer acts as an intermediary between the current collector and the second active material layer. It provides a transition zone that maintains electrical continuity and facilitates ion transport, allowing the second layer to be optimized for fast charging while the overall structure maintains high energy density through the combined effect of both layers.
3Device complexity
If a single layer electrode plate design is used, then the structure is simple, but it is challenging to achieve both high energy density and fast charging capability
Solution Approach 1:
The electrode plate is segmented into multiple functional layers, each with specific active materials optimized for different performance aspects. This segmentation provides the versatility needed to simultaneously achieve high energy density and fast charging capability, while the layered structure remains relatively simple to manufacture and assemble.
Solution Approach 2:
The multi-layer electrode plate design creates a universal structure that can simultaneously perform multiple functions: energy storage (high energy density) and fast ion transport (fast charging capability). Each layer contributes to both functions to some degree, making the overall structure adaptable and versatile in meeting multiple performance requirements simultaneously.
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
This design allows for high energy density and excellent fast charging capability while minimizing energy density loss, improving the overall performance of the secondary battery.
Implementation Method 1
a first button battery using lithium plate as a negative electrode and the first active material as a positive material of a positive electrode experiences a charge and discharge test; a terminal potential slope of a lithium deintercalation curve of the first button battery is denoted as Sa
Implementation Method 2
a second button battery using lithium plate as a negative electrode and the second active material as a positive material of a positive electrode experiences a charge and discharge test; a terminal potential slope of a lithium deintercalation curve of the second button battery is denoted as Sb
Data Source
Figure 1~2
AI summary
A secondary battery in this application includes a negative electrode. The negative electrode includes a current collector and a negative electrode active material layer provided on the current collector. The negative electrode active material layer includes a first active material layer and a second active material layer. The first active material layer is provided between the current collector and the second active material layer. The first active material layer includes a first active material. A first button battery using lithium plate as a negative electrode and the first active material as a positive material of a positive electrode experiences a charge and discharge test; a terminal potential slope of a lithium deintercalation curve of the first button battery is denoted as Sa; the second active material layer includes a second active material; a second button battery using lithium plate as a negative electrode and the second active material as a positive material of a positive electrode experiences a charge and discharge test; a terminal potential slope of a lithium deintercalation curve of the second button battery is denoted as Sb; and Sa<Sb; where 2 mAh•g-1/V≤Sa≤7 mAh•g-1/V, and 5 mAh•g-1/V≤Sb≤14 mAh•g-1/V.