Lithium-Ion Battery Electrolyte Composition for Cathode Dissolution Control
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Solution Overview
Problem
Lithium-ion batteries exhibit poor cycling performance due to the dissolution of metal and non-metal elements in the positive electrode active material, which migrate to the negative electrode and deteriorate the solid electrolyte interphase film, leading to structural instability and reduced cycle life.
Innovation Solution
Incorporating a high content of lithium hexafluorophosphate in the electrolyte to form a protective lithium fluoride layer on the positive electrode active material, combined with elements like Ti and Zr in the positive electrode active material, and using specific additives in the electrolyte to bind with migrating metal ions, along with optimizing the composition of the negative electrode active material to enhance structural stability and SEI film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If element M (Ti or Zr) is added to improve structural stability, then crystal structure stability is enhanced, but metal ions dissolve and migrate to the negative electrode causing SEI film damage
Solution Approach 1:
Lithium hexafluorophosphate acts as an intermediary substance in the electrolyte that forms a protective interface layer between the positive electrode active material and the electrolyte, preventing direct contact and reducing metal ion dissolution while maintaining structural stability
Solution Approach 2:
The mass proportion of lithium hexafluorophosphate is optimized to 15%-20% to achieve the best balance between forming sufficient protective layer and maintaining electrolyte performance, thereby reducing metal ion dissolution without compromising crystal structure stability
2Quantity of substance
If high nickel content is used in positive electrode active material, then capacity is improved, but structural stability deteriorates leading to poor cycling performance
Solution Approach 1:
The positive electrode active material uses a composite composition with specific ratios of lithium, nickel, cobalt, manganese, and element M (Ti or Zr), creating a multi-element composite structure that leverages the high capacity of nickel while the other elements provide structural stability and prevent degradation
3Object-generated harmful factors
If lithium hexafluorophosphate content is increased to form protective layer, then element dissolution is reduced, but electrolyte composition complexity increases
Solution Approach 1:
The concentration of lithium hexafluorophosphate is precisely controlled within 15%-20% mass proportion, which is sufficient to form an effective protective layer while avoiding excessive complexity in electrolyte formulation and maintaining manufacturability
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 proposed solution significantly improves the cycling performance of lithium-ion batteries by mitigating element dissolution, stabilizing the positive electrode structure, and enhancing the integrity of the SEI film, thereby extending the battery's cycle life and power performance.
Implementation Method 1
The high content of lithium hexafluorophosphate can form a protective layer primarily composed of lithium fluoride LiF on the surface of the positive electrode active material
Implementation Method 2
there is a risk of dissolution of both metal and non-metal elements in the positive electrode active material
Implementation Method 3
These dissolved metal and non-metal elements can migrate through the electrolyte to the surface of the negative electrode plate
Implementation Method 4
The first additive contains fluoride ions and boron ions, and the fluoride ions and boron ions have a strong ability of binding with the above metal ions
Data Source
AI summary
This application relates to a lithium-ion battery, a battery, and an electric apparatus. The lithium-ion battery includes an electrolyte and a positive electrode plate. The electrolyte includes lithium salt, the lithium salt includes lithium hexafluorophosphate, and a mass proportion of the lithium hexafluorophosphate relative to a total mass of the electrolyte is 15% to 20%. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material. This application can improve cycling performance of the lithium-ion battery.