Lithium-Ion Electrode Salt Coating for Capacity Loss Reduction
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Solution Overview
Problem
Lithium-ion accumulators face significant irreversible capacity loss during the first charge due to the formation of a passivation layer on the negative electrode, leading to reduced energy density and cyclability, as existing techniques either lose lithium ions from the active material or cause structural disruptions with sacrificial salts.
Innovation Solution
A method involving the deposition of a lithium salt on the surface of the positive electrode before assembly, allowing its decomposition to provide lithium ions for passivation layer formation on the negative electrode during the first charge, thereby minimizing capacity loss and maintaining the internal structure of the positive electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sacrificial salt is introduced directly into the ink comprising the ingredients of the positive electrode, then lithium ions are provided for passivation layer formation, but porosity increases and internal resistance increases
Solution Approach 1:
The patent divides the sacrificial salt into separate components: the positive electrode ink contains the active material and binder, while the sacrificial salt is applied separately as a coating on the positive electrode surface. This segmentation prevents the salt from being randomly distributed within the electrode bulk, thereby avoiding excessive porosity and internal resistance while still providing the necessary lithium ions for passivation layer formation.
2Quantity of substance
If sacrificial salt is distributed randomly in the positive electrode, then lithium ions are available for passivation, but structural organization is disrupted and porosity increases
Solution Approach 1:
The sacrificial salt is applied to the positive electrode surface before assembly into the battery. This preliminary action allows the salt to be positioned strategically on the electrode surface where it can dissolve during initial charging cycles and release lithium ions for passivation layer formation, without disrupting the internal structural organization of the electrode during manufacturing processes like calendering.
3Strength
If minimum porosity is maintained to withstand mechanical stress, then structural integrity is preserved, but lithium ion supply for passivation layer formation is insufficient
Solution Approach 1:
The patent applies the sacrificial salt locally on the positive electrode surface rather than mixing it throughout the entire electrode. This local application ensures that the salt is concentrated in specific areas where it can effectively provide lithium ions for passivation layer formation, while the bulk electrode structure maintains its mechanical integrity and appropriate porosity levels.
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 reduces irreversible capacity loss to zero, maintains the structural organization of the positive electrode, and allows for precise control of lithium ion distribution, enhancing the energy density and cyclability of the lithium-ion battery.
Implementation Method 1
a step of forming a passivation layer on the surface of the negative electrode with the lithium ions resulting from the decomposition of the lithium salt by applying a first charge to the aforementioned assembly
Implementation Method 2
the lithium removed from the negative electrode in the ionic form Li + during the discharge of the accumulator
Implementation Method 3
During the first charging cycle of the battery, when the active material of the negative electrode is brought to a lithium insertion potential, part of the lithium will react with the electrolyte on the surface of the grains of active material of the negative electrode to form a passivation layer on its surface
Data Source
Figure 1
AI summary
The invention deals with a method of preparing a lithium-ion accumulator comprising a positive electrode and a negative electrode which are disposed on either side of an electrolyte, said positive electrode comprising, as active material, a lithium-based material, said method comprising the following steps: a) a step of depositing lithium salt on the surface of the positive electrode, before placement in the accumulator; b) a step of assembling the positive electrode, the negative electrode and the electrolyte; and c) a step of forming a passivation layer on the surface of the negative electrode with the lithium ions arising from the decomposition of the lithium salt by applying a first charge to the abovementioned assembly.