Lithium Secondary Battery Electrolyte Balance for Silicon Anodes
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high energy density and long service life due to material selection and combination issues, particularly with silicon-based negative electrodes, which can lead to efficiency deterioration and reduced service life.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with a lithium composite transition metal compound containing nickel and cobalt, a mixed negative electrode active material of silicon-based and carbon-based materials, and an electrolyte with fluoroethylene carbonate, where the efficiency constants and electrolyte content satisfy a specific equation to balance performance and extend service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used in the negative electrode to increase capacity, then energy density is improved, but service life deteriorates due to efficiency deterioration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content of fluoroethylene carbonate in the electrolyte and adjusting the efficiency constants of electrode materials to satisfy a specific mathematical relationship. This optimization of chemical composition parameters enables the battery to achieve high energy density while maintaining long service life by balancing the electrochemical efficiency between positive and negative electrodes.
Solution Approach 2:
The patent uses composite materials by combining silicon-based active material with carbon-based active material in the negative electrode, and lithium composite transition metal compound containing multiple metals in the positive electrode. This composite approach allows the battery to achieve high energy density while the carbon component and optimized electrolyte composition mitigate the service life deterioration caused by silicon expansion and side reactions.
2Productivity
If electrode active material composition is changed to improve battery performance, then some performance is improved, but other performance deteriorates
Solution Approach 1:
The patent resolves performance imbalance by changing parameters including the efficiency constants (a and b) of electrode materials and the fluoroethylene carbonate content (c) in the electrolyte, which must satisfy the relationship [(b/a)×100−c]≤95. This mathematical constraint ensures that improvements in one performance metric do not cause deterioration in other metrics by maintaining proper electrochemical balance between electrodes.
Solution Approach 2:
The patent implements feedback control through the efficiency constant relationship, where the performance of positive and negative electrodes is continuously balanced. By requiring that [(b/a)×100−c]≤95, the system automatically adjusts the relative efficiency of both electrodes, preventing one electrode from being over-optimized at the expense of the other, thus maintaining overall battery performance balance.
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 configuration enhances energy density, improves charging and discharging efficiency, and extends the battery's service life by protecting silicon-based compounds and optimizing the electrolyte's role in reducing side reactions.
Implementation Method 1
fluoroethylene carbonate helps form a film that protects a silicon-based compound
Implementation Method 2
the electrolyte includes fluoroethylene carbonate
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a separator, a negative electrode, and an electrolyte, in which the positive electrode includes a lithium composite transition metal compound including nickel (Ni) and cobalt (Co), the negative electrode includes a mixed negative electrode active material of a silicon-based active material and a carbon-based active material, the electrolyte includes fluoroethylene carbonate, and the efficiency constants of the mixed negative electrode active material and the lithium composite transition metal compound and the part by weight of the fluoroethylene carbonate satisfy a specific Equation.