Bilayer Negative Electrode Coating to Mitigate Lithium Plating
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Solution Overview
Problem
Secondary batteries face challenges with lithium plating at the negative electrode, leading to safety issues due to insufficient lithiation capacity, which can result in separator puncture and battery short circuits, compromising safety performance and energy density.
Innovation Solution
A negative electrode plate is designed with a bilayer coating of active materials, where the second active material layer has higher lithiation and delithiation potentials than the first active material layer, strategically applied to reduce lithium plating risks without compromising energy density, enhancing safety and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the energy density of the secondary battery is improved, then the battery capacity increases, but lithium plating phenomenon occurs at the negative electrode due to insufficient lithiation capacity
Solution Approach 1:
The patent applies local quality by coating the second active material layer selectively at specific positions on the negative electrode plate where lithium plating is prone to occur, rather than uniformly across the entire electrode. This localized treatment addresses the insufficient lithiation capacity problem at critical areas while maintaining the overall energy density of the battery.
Solution Approach 2:
The patent uses composite materials by combining two different active materials with distinct lithiation potentials. The first active material layer provides the base lithiation capacity, while the second active material layer with higher lithiation potential is added to prevent lithium plating, creating a composite structure that balances capacity and safety.
2Reliability
If the second active material layer is coated to prevent lithium plating, then the safety performance improves, but the energy density may be reduced
Solution Approach 1:
By applying the second active material layer only at specific positions where lithium plating is prone to occur rather than uniformly across the entire negative electrode, the patent minimizes the amount of additional material added. This localized approach improves safety performance while reducing the impact on energy density compared to a full-coating approach.
3Reliability
If the lithiation capacity of the negative electrode is increased to prevent lithium plating, then the safety improves, but the battery mass increases
Solution Approach 1:
The patent increases lithiation capacity locally only at positions where lithium plating is prone to occur, rather than uniformly increasing the capacity across the entire negative electrode. This selective local enhancement achieves the safety improvement needed to prevent lithium plating while minimizing the additional mass added to the battery.
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 bilayer coating effectively mitigates lithium plating, improves safety performance, extends battery life, and maintains energy density by ensuring lithium ions are intercalated and locked, preventing dendrite formation and separator puncture.
Implementation Method 1
lithium from the positive electrode material can be first intercalated into the second active material
Implementation Method 2
the non-deintercalated lithium ions will fail to be reduced and generate lithium dendrite. That is, the second active material can enrich and lock lithium ions
Data Source
AI summary
A negative electrode plate includes a current collector; a first active material layer arranged on at least one surface of the current collector; and a second active material layer arranged on a surface of the first active material layer away from the current collector; wherein the first active material layer comprises a first active material, the second active material layer comprises a second active material, and the second active material has a lithiation potential and a delithiation potential higher than those of the first active material.