SiOx Carbon Composite Negative Electrode for Lithium Ion Battery Cycle Durability
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Solution Overview
Problem
Lithium ion secondary batteries using a negative electrode with SiOx and carbon materials face challenges in achieving sufficient cycle durability when combined with a solid solution positive electrode active material, leading to performance issues.
Innovation Solution
A lithium ion secondary battery design incorporating a negative electrode active material layer with a mixture of SiOx and carbon, and a positive electrode active material layer with a solid solution composition, along with an electrolytic solution containing 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide and lithium difluorophosphate, to enhance cycle durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si material is used for negative electrode to achieve high capacity, then energy density is improved, but cycle durability deteriorates due to large volumetric change
Solution Approach 1:
The patent uses a composite negative electrode material consisting of SiOx particles (where x is 0 to 2) combined with carbon material. The SiOx provides high capacity through lithium alloying reactions while the carbon component accommodates volume expansion and maintains structural integrity during cycling, thus achieving both high energy density and good cycle durability.
Solution Approach 2:
The patent modifies the composition parameter of the negative electrode by using SiOx with variable oxygen content (x = 0 to 2) instead of pure Si. This parameter change allows optimization of the balance between capacity and volume stability, as the oxygen content can be adjusted to control the degree of volume expansion during lithium alloying.
2Quantity of substance
If SiOx and carbon materials are combined in negative electrode, then energy density is improved, but cycle durability is insufficient when combined with solid solution positive electrode active material
Solution Approach 1:
The patent optimizes the composition ratio between SiOx and carbon materials in the negative electrode, and matches it with a solid solution positive electrode active material having specific compositional parameters. This coordinated parameter optimization ensures that the electrochemical reactions are balanced, preventing premature failure while maintaining high energy density.
3Reliability
If carbon graphite-based material is used for negative electrode, then charge and discharge cycle life is improved, but theoretical capacity cannot be ensured
Solution Approach 1:
The patent creates a composite negative electrode material combining SiOx (providing high theoretical capacity through lithium alloying) with carbon material (providing structural stability and long cycle life). This composite structure allows the system to achieve both high capacity and excellent cycle durability, overcoming the limitations of using either material alone.
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 battery exhibits improved cycle durability and high energy density, making it suitable for vehicle applications while maintaining high initial capacity and long-term reliability.
Implementation Method 1
when 1 mol of Si absorbs and desorbs 4.4 mol of lithium ions in accordance with the reaction formula (A) and a reversible capacity component of Li22Si5(= Li4.4Si) with a theoretical capacity of 4200 mAh/g is generated
Implementation Method 2
a separator impregnated with an electrolytic solution
Data Source
Figure 1
Figure 2~3
AI summary
To provide a means capable of further improving cycle durability in an electrical device such as a lithium ion secondary battery containing a positive electrode using a solid solution positive electrode active material. An electrical device has a power generating element containing a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on a surface of a positive electrode current collector, a negative electrode in which a negative electrode active material layer containing a negative electrode active material is formed on a surface of a negative electrode current collector, and a separator impregnated with an electrolytic solution. The negative electrode active material layer contains a negative electrode active material represented by formula (1). The positive electrode active material layer contains a positive electrode active material (solid solution positive electrode active material) represented by formula (2). As the solid solution positive electrode active material contained in the positive electrode active material layer, a material having a composition represented by formula (3) as a basic structure is used. The electrolytic solution contains a predetermined additive.