Cyclic Sulfate Additive for Lithium Battery Voltage Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining open circuit voltage during storage in a charged state, with existing cyclic sulfate compounds causing a decrease in potential and affecting capacity retention.
Innovation Solution
A non-aqueous electrolyte solution containing a specific cyclic sulfate compound, represented by formula (I), is used to suppress the decrease in open circuit voltage and improve capacity retention, comprising a cyclic sulfate compound with specific structural groups and concentrations, along with electrolyte compounds like lithium difluorophosphate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cyclic sulfate compounds are added to the electrolyte solution, then capacity retention is improved, but open circuit voltage decreases during storage
Solution Approach 1:
The patent changes the chemical structure parameters of the cyclic sulfate compound by introducing specific substituents (R1-R6 groups) at defined positions on the dioxathiolane ring. This structural modification alters the compound's electrochemical properties, allowing it to form passivation films that preserve both capacity retention and open circuit voltage during storage, resolving the trade-off between these two performance parameters.
Solution Approach 2:
The patent creates a composite electrolyte system by combining the modified cyclic sulfate compound with specific solvents (cyclic carbonates, chain carbonates, cyclic carboxylic acid esters) and lithium salts. This composite formulation synergistically enhances both capacity retention and voltage stability during storage, overcoming the limitations of conventional single-additive approaches.
2Reliability
If passivation films are formed on the negative electrode to suppress solvent decomposition, then capacity retention improves, but battery resistance increases
Solution Approach 1:
The patent modifies the passivation film formation parameters by using a cyclic sulfate compound with specific substituent groups (R1-R6) that control the film's composition and structure. This results in a passivation film with optimized properties: sufficiently dense to prevent continuous solvent decomposition and maintain capacity retention, yet ionically conductive enough to limit resistance increase, achieving a balance between these conflicting requirements.
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 solution effectively maintains open circuit voltage and enhances capacity retention in lithium secondary batteries, improving their performance and storage characteristics.
Implementation Method 1
a reductive decomposition reaction of the electrolyte solution occurs at the surface of the negative electrode
Data Source
Figure 1
AI summary
A non-aqueous electrolyte solution containing a cyclic sulfate compound represented by formula (I) is provided, wherein in formula (I), R1 represents a group represented by formula (II) or a group represented by formula (III); R2 represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a group represented by formula (II), or a group represented by formula (III); and in formula (II), R3 represents a halogen atom, an alkyl group having from 1 to 6 carbon atoms, a halogenated alkyl group having from 1 to 6 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, or a group represented by formula (IV).