Negative Electrode Lithium Supplement Layer for First Coulomb Efficiency
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Solution Overview
Problem
Existing lithium ion battery cells face issues with low first Coulomb efficiency, cycle performance, and storage performance due to lithium ion loss during the battery formation process, leading to risks such as lithium precipitation and short circuits.
Innovation Solution
A lithium supplement layer is arranged on a portion of the negative electrode current collector, creating a voltage difference that allows lithium ions to embed slowly into the electrode active material, preventing over-embedding and enhancing the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium ion battery cells are formed with conventional negative electrode structure, then manufacturing process is simple, but first Coulomb efficiency is low and lithium ion loss occurs during formation process
Solution Approach 1:
The negative electrode is divided into two functional portions: a first portion (exposed end extending beyond positive electrode) and a second portion (arranged corresponding to positive electrode). The lithium supplement layer is selectively applied only to the first portion, creating distinct functional zones that address lithium ion loss while maintaining structural clarity and manufacturing feasibility.
Solution Approach 2:
The lithium supplement layer is applied locally only to the first portion of the negative electrode that extends beyond the positive electrode, rather than uniformly across the entire negative electrode. This localized application targets the specific area where lithium ion loss occurs during formation, improving first Coulomb efficiency while minimizing additional complexity.
2Reliability
If lithium supplement layer is added to improve first Coulomb efficiency, then lithium ion migration is stabilized, but device structure becomes more complex
Solution Approach 1:
The lithium supplement layer is pre-applied to the first portion of the negative electrode before battery formation. This preliminary lithium supplementation ensures that lithium ions are available in advance to compensate for losses during the formation process, stabilizing lithium ion migration and improving cycle performance without requiring complex real-time control mechanisms.
3Reliability
If conventional negative electrode structure is used, then manufacturing is simple, but lithium precipitation and short circuit risks occur
Solution Approach 1:
The lithium supplement layer is selectively applied to the first portion of the negative electrode, creating a localized lithium reservoir that prevents lithium precipitation and short circuits without requiring complex modifications to the overall manufacturing process. This local enhancement maintains ease of manufacture while significantly improving storage performance and safety.
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 lithium supplement layer improves first Coulomb efficiency, cycle performance, and storage performance by stabilizing lithium ion migration, reducing the risk of lithium deposition and ensuring safety.
Implementation Method 1
the standard electrode potential of lithium relative to hydrogen in the lithium supplement layer is less than the standard electrode potential of the first portion relative to hydrogen, and there is a voltage difference between the lithium supplement layer and the first portion. After the battery cell is injected with the electrolyte, an electrical circuit is formed between the lithium supplement layer and the first portion due to the contact between the lithium supplement layer and the first portion, which is equivalent to a short circuit state, the lithium in the lithium supplement layer will lose electrons and become free-moving lithium ions
Implementation Method 2
the lithium in the lithium supplement layer will lose electrons and become free-moving lithium ions which will be embedded into the first portion, and then the lithium will be diffused and embedded to the second portion at a slow speed
Data Source
AI summary
Provided are a battery cell, a battery and an electric device. The battery cell includes a positive electrode plate and a negative electrode plate, the negative electrode plate includes a negative electrode current collector, a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, and a lithium supplement layer, wherein the negative electrode active material layer includes a first portion and a second portion connected with the first portion, the first portion exceeds the positive electrode plate, the second portion is arranged corresponding to the positive electrode plate, and the lithium supplement layer is arranged on at least part of a surface of the first portion away from the negative electrode current collector. The negative electrode plate of the present application can improve the first Coulomb efficiency, cycle performance and storage performance of the battery cell.