Silicon Composite Battery Additive Stabilizes High-Temperature Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face performance deterioration and shortened cycle-life due to side reactions between silicon particles and electrolyte solutions, especially at high temperatures, leading to increased internal resistance and safety concerns.
Innovation Solution
Incorporating a compound represented by Chemical Formula 1, which includes a fluoro group or similar, as an additive in the electrolyte solution to form a solid electrolyte interface with the silicon composite, reducing gas generation and stabilizing lithium salts, thereby suppressing side reactions and improving battery stability and cycle-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiPF6 is used as lithium salt in the electrolyte solution, then high ionic conductivity is achieved, but decomposition occurs at high temperature generating HF and PFS which cause electrolyte depletion and safety issues
Solution Approach 1:
A cyclic carboxylate compound (e.g., lithium acetate, lithium propionate) is introduced as an intermediary substance to mediate between LiPF6 and the electrolyte solvent. This intermediary preferentially reacts with LiPF6 to form stable complexes, preventing direct decomposition of LiPF6 into harmful HF and PFS while maintaining ionic conductivity through the cyclic carboxylate's own dissociation.
Solution Approach 2:
The chemical environment parameters of the electrolyte solution are changed by adding cyclic carboxylate compounds with specific molecular structures and properties. These compounds have optimal dissociation constants and complexation abilities that alter the electrochemical stability window and decomposition behavior of the electrolyte system at high temperatures.
2Use of energy by moving object
If the voltage range is expanded to increase capacity, then energy density is improved, but oxidization of the electrolyte solution occurs causing performance deterioration
Solution Approach 1:
The cyclic carboxylate compound performs preliminary protective action by forming stable complexes with LiPF6 before high-voltage operation begins. This pre-formed complex is more resistant to oxidization at high voltages, preventing electrolyte decomposition and maintaining performance during extended charge-discharge cycles at elevated voltage ranges.
3Use of energy by moving object
If silicon particles are used as negative active material, then capacity is increased, but side reactions with electrolyte solution occur causing increased internal resistance
Solution Approach 1:
The cyclic carboxylate compound acts as a protective intermediary between silicon particles and the electrolyte solution. It forms a stable interfacial layer or complex at the silicon-electrolyte interface, preventing direct contact and side reactions between silicon and electrolyte components, thereby suppressing internal resistance increase while preserving high capacity.
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 additive significantly reduces internal resistance and enhances cycle-life characteristics of rechargeable lithium batteries, maintaining high capacity and stability even at high temperatures, by forming a stable interface with silicon particles and stabilizing lithium salts.
Implementation Method 1
Incorporating a compound represented by Chemical Formula 1, which includes a fluoro group or similar, as an additive in the electrolyte solution to form a solid electrolyte interface with the silicon composite
Implementation Method 2
stabilizing lithium salts, thereby suppressing side reactions and improving battery stability and cycle-life
Data Source
AI summary
A rechargeable lithium battery includes a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte solution including a non-aqueous organic solvent, a lithium salt, and an additive, wherein the negative active material includes a Si composite and the additive includes a compound represented by Chemical Formula 1.Details of Chemical Formula 1 are as described in the specification.