Li-Ion Battery Positive Electrode Buffer Layer Design
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Solution Overview
Problem
Existing Li-ion battery technologies face challenges in improving safety performance without compromising energy density and cycle life, particularly in low State Of Charge (SOC) conditions and large capacity batteries used in electric vehicles, as well as increased internal resistance and polarization issues.
Innovation Solution
A positive electrode design featuring a first active material layer, a carbon-based buffer layer, and a second active material layer on the current collector, where the buffer layer is strategically positioned between the first and second active material layers, enhancing safety and cycle performance by reducing polarization and internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with high safety are mixed in the slurry in high proportion, then safety performance is improved, but energy density is greatly reduced
Solution Approach 1:
The positive electrode is segmented into three distinct layers: a first active material layer, a buffer layer, and a second active material layer. This segmentation allows different materials to be positioned strategically - high safety materials in the buffer layer and high energy density materials in the active material layers - thereby resolving the contradiction between safety and energy density.
Solution Approach 2:
Different regions of the positive electrode are assigned different material compositions and functions. The buffer layer contains high safety materials, while the first and second active material layers contain high energy density materials. This local differentiation allows the battery to achieve both high safety performance and high energy density simultaneously.
2Reliability
If materials with high safety are mixed in the slurry in high proportion, then safety performance is improved, but internal resistance increases in low SOC conditions
Solution Approach 1:
By segmenting the electrode structure into distinct layers, high safety materials are concentrated in the buffer layer rather than being distributed throughout. This allows high energy density materials to dominate the active material layers, maintaining low internal resistance while the buffer layer provides safety protection.
3Reliability
If another active material layer is coated after the first active material layer, then safety performance is improved, but polarization increases and cycle performance deteriorates
Solution Approach 1:
The buffer layer acts as an intermediary between the first and second active material layers. It provides mechanical cushioning that accommodates expansion and contraction differences during cycling, preventing interface damage and maintaining stable electrical contact. This intermediary layer resolves the contradiction by protecting the electrode structure while enabling the safety benefits of multiple material layers.
Solution Approach 2:
The buffer layer is positioned beforehand between the active material layers to provide cushioning protection. This preemptive cushioning prevents damage from expansion differences before they occur during cycling, thereby maintaining cycle performance while enabling the use of multiple active material layers for enhanced safety.
Data Source
AI summary
The present application relates to a positive electrode and a Li-ion battery including the positive electrode, the positive electrode comprises a positive electrode current collector and a first active material layer including a first positive electrode active material arranged on the positive electrode current collector, a buffer layer including a carbon material and a binder, and a second active material layer including a second positive electrode active material, the buffer layer is arranged between the first active material layer and the second active material layer. The positive electrode provided by the present application, when applied to the lithium battery, not only can improve the safety performance of the Li-ion battery, but also improve the cycle performance of the Li-ion battery.