Secondary Battery Anode Layout for SEI Lithium Compensation
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Solution Overview
Problem
Secondary batteries face challenges in increasing energy density due to irreversible capacity loss during the formation of a solid electrolyte interface (SEI) film on the negative electrode, leading to difficulties in compensating for lost active ions and maintaining cycling performance.
Innovation Solution
A secondary battery design featuring a positive electrode plate, a separator, and a negative electrode plate with a first and second negative electrode film layer, where the lithium source is stored in the peripheral region of the second negative electrode film layer, allowing for controlled lithium supplementation and diffusion to prevent loss during charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SEI film is formed on the negative electrode during first charge, then the negative electrode is protected, but active lithium ions are irreversibly consumed leading to capacity loss
Solution Approach 1:
A lithium source is pre-stored in the peripheral region of the negative electrode film layer before battery operation. This preliminary placement of lithium reserves enables subsequent compensation of active lithium loss without requiring external intervention during cycling.
Solution Approach 2:
The battery system uses its own internal lithium source stored in the peripheral region to compensate for lithium loss. The system serves itself by utilizing pre-stored lithium reserves to replenish active lithium ions consumed during SEI film formation and cycling, eliminating the need for external lithium supplementation.
2Quantity of substance
If lithium source is stored in the central region of the negative electrode, then lithium supplementation is available, but diffusion path is long causing lithium loss
Solution Approach 1:
The lithium source is specifically positioned in the peripheral region of the negative electrode film layer, creating a localized concentration gradient that optimizes lithium diffusion efficiency. This spatial differentiation ensures that lithium supplementation occurs where it is most needed while minimizing diffusion path length.
3Speed
If potential difference between first and second negative electrode film layers is large, then lithium diffusion is driven, but lithium intercalation into second layer occurs during charge
Solution Approach 1:
The system dynamically utilizes potential difference parameters to control lithium ion movement. During discharge, the potential difference drives lithium diffusion from the peripheral region to the first negative electrode film layer. During charge, the potential difference is managed to prevent excessive lithium intercalation into the second layer, optimizing lithium utilization.
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 enhances first-cycle coulombic efficiency, cycling performance, and storage performance by maintaining a small potential difference between the film layers, reducing lithium loss, and optimizing lithium supplementation efficiency.
Implementation Method 1
Li+ is produced by the lithium source under driving of the potential difference between the first negative electrode film layer and the second negative electrode film layer
Implementation Method 2
the Li+ ions diffuse slowly to the first negative electrode film layer
Implementation Method 3
after Li+ deintercalated from a positive electrode are intercalated into the first negative electrode film layer
Data Source
AI summary
Provided are a secondary battery and a battery module, battery pack, and electric apparatus containing such secondary battery. The secondary battery includes: a positive electrode plate including a positive electrode film layer; a separator; and a negative electrode plate. The negative electrode plate includes: a first negative electrode film layer, the first negative electrode film layer being provided opposite the positive electrode film layer with the separator therebetween; and a second negative electrode film layer, the second negative electrode film layer including a negative electrode film layer not provided opposite the positive electrode film layer, and the second negative electrode film layer including a central region and a peripheral region surrounding the central region, where a lithium source used for supplementing lithium to the first negative electrode film layer is stored in at least a portion of the peripheral region of the second negative electrode film layer.