Non-aqueous Electrolyte Passivation for Li-Ion Cycle Stability
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Solution Overview
Problem
Lithium ion batteries face challenges with cycle performance and high-temperature storage performance, particularly due to the instability of the positive electrode under high voltage and oxidative decomposition of the electrolyte, which leads to capacity attenuation and gas expansion.
Innovation Solution
A non-aqueous electrolyte comprising compounds A and B, specifically designed to form passivation films on both positive and negative electrodes, reducing side reactions and improving stability and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the working voltage of lithium ion battery is increased to improve energy density, then the energy density is improved, but the crystal structure of the positive electrode becomes unstable and collapses during charging and discharging, resulting in deterioration of performance
Solution Approach 1:
The patent introduces compound A (maleic anhydride copolymer) as an intermediary substance that mediates between the high-voltage positive electrode and the electrolyte. This compound forms a protective interface layer that stabilizes the crystal structure of the positive electrode during charging and discharging, preventing collapse while allowing lithium ion transport, thus resolving the contradiction between high energy density and cycle stability
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding compound A at specific concentrations (0.1-5% by mass). This parameter change transforms the electrolyte's properties to enable it to form stable passivation films on the positive electrode surface, which maintains structural stability under high voltage conditions while preserving high energy density
2Use of energy by moving object
If the working voltage of lithium ion battery is increased to improve energy density, then the energy density is improved, but the surface of the positive electrode undergoes oxidative decomposition of the electrolyte, causing gas expansion and deterioration of battery performance
Solution Approach 1:
Compound A acts as an intermediary that preferentially reacts with the positive electrode surface to form a stable protective film, preventing direct contact between the electrolyte and the high-voltage electrode surface. This intermediary layer suppresses oxidative decomposition reactions that would otherwise generate gas, thus resolving the contradiction between high energy density and gas expansion
Solution Approach 2:
The patent applies preliminary anti-action by having compound A form a protective passivation film on the positive electrode surface before electrolyte decomposition can occur. This pre-formed protective layer prevents the harmful oxidative reactions that lead to gas expansion, allowing the battery to operate at high voltages without suffering from electrolyte decomposition
3Reliability
If additive maleic anhydride copolymer is used to improve cycle performance at high voltage, then the cycle performance is improved, but the attenuation in subsequent cycles accelerates and gas expansion occurs during long-term high-temperature storage
Solution Approach 1:
The patent creates a composite electrolyte system combining compound A (maleic anhydride copolymer) with compound B (a fluorinated cyclic carbonate compound). This composite approach leverages the synergistic effects of both compounds: compound A provides initial passivation and cycle stability, while compound B suppresses high-temperature storage degradation and gas expansion, resolving the contradiction between cycle performance and storage stability
Solution Approach 2:
The patent applies local quality by having different compounds perform different functions at different locations and conditions: compound A primarily acts on the positive electrode surface to improve cycle performance, while compound B provides broader stabilization including suppression of high-temperature storage degradation. This differentiated functional assignment resolves the contradiction between cycle enhancement and storage stability
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 electrolyte enhances cycle stability and high-temperature storage performance by forming effective passivation films, reducing impedance and maintaining battery capacity and performance over extended cycles and high-temperature storage.
Implementation Method 1
specifically designed to form passivation films on both positive and negative electrodes
Implementation Method 2
reducing impedance and maintaining battery capacity and performance
Data Source
AI summary
In order to solve the problem of insufficient cycle performance and high-temperature storage performance of the existing non-aqueous electrolyte for lithium ion battery containing maleic anhydride copolymer, the application provides a non-aqueous electrolyte for lithium ion battery. The non-aqueous electrolyte for lithium ion battery comprises a compound A represented by formula I and a compound B represented by formula II,In formula I, R7 and R8 are independently selected from one of hydrogen atom, halogen atom, —O—R9 or aryl, wherein n is a positive integer and R9 is a C1-C4 alkyl group; In formula II, R1, R2, R3, R4, R5 and R6 are each independently selected from one of hydrogen atom, fluorine atom and C1-C5 group. The non-aqueous electrolyte for lithium ion battery provided by the invention can improve the cycle stability and high-temperature storage performance of the battery through the effections of compound A and compound B.