Lithium-Ion Battery Formation Using Sacrificial Salt
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Solution Overview
Problem
Lithium-ion batteries experience significant irreversible capacity loss during the formation of the Solid Electrolyte Interphase (SEI) layer, leading to reduced energy density and shorter lifespan, particularly due to lithium consumption at the positive electrode during the first charging cycle.
Innovation Solution
A method for forming a lithium-ion battery cell with a positive electrode material having a porosity rate of 20-35% and incorporating a sacrificial salt, such as lithium oxalate, which oxidizes during the first charging cycle to produce pre-lithium ions that compensate for capacity loss, while maintaining controlled porosity to avoid performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial salt is added to the positive electrode to compensate for irreversible lithium consumption, then the energy density and lifespan are improved, but the oxidation potential of the sacrificial salt must be controlled to avoid structural instability
Solution Approach 1:
The patent changes the oxidation potential parameter of the sacrificial salt by selecting specific compounds (Li2C2O4, Li2C3O5, Li2C4O6, LiN3) with oxidation potentials between 4.5-5.5V. This parameter optimization allows the sacrificial salt to effectively compensate for lithium consumption during SEI formation while avoiding the harmful effect of excessive oxidation potential that would cause positive electrode structure instability.
2Quantity of substance
If the porosity of the positive electrode is increased to accommodate sacrificial salt, then the sacrificial salt can be effectively incorporated, but excessive porosity degrades battery performance
Solution Approach 1:
The patent utilizes porous electrode structures with controlled porosity ratios between 20-35% to effectively incorporate sacrificial salt particles. This controlled porosity allows sufficient space for the sacrificial salt (3-10% by weight) while maintaining adequate electrical conductivity and preventing performance degradation that would occur with excessive porosity.
3Reliability
If additives are introduced into the electrolyte to improve SEI quality, then the cell lifespan is extended, but lithium is consumed from the positive electrode impacting initial capacity
Solution Approach 1:
The patent applies preliminary action by incorporating sacrificial salt into the positive electrode before battery assembly. During the first charging cycle, the sacrificial salt oxidizes and releases lithium ions in advance, which then compensate for the lithium consumed by SEI formation on the negative electrode. This preliminary lithium release ensures that the negative electrode receives sufficient lithium despite additive consumption, maintaining both initial capacity and extended lifespan.
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 approach significantly reduces capacity loss during the first charging cycle, thereby increasing the battery's service life and maintaining performance by optimizing the SEI formation and internal resistance.
Implementation Method 1
A sacrificial salt can also be added to the positive electrode... it oxidizes at too high a potential
Implementation Method 2
thermodynamic reactions are initiated during the cell's first charging cycle, and the initial exchange of lithium ions between the electrodes takes place
Implementation Method 3
This layer is essential for the proper functioning of the Li-ion battery because it not only conducts lithium ions very effectively but also prevents the catalytic decomposition of the solvent
Implementation Method 4
when the cell assembly is complete and the electrolyte is impregnated within the cell
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for forming a cell of a lithium-ion battery comprising a material for a positive electrode having a pore ratio of between 20 and 35% and comprising at least one sacrificial salt, a material for a negative electrode, a separator and an electrolyte, comprising the following successive steps: (a) heating the cell to a temperature T of between 30 and 45°C; and (b) charging the cell to a potential lower than or equal to 4.8 V, preferably between 4.6 and 4.8 V, even more preferably between 4.7 and 4.8 V.