Acrylate Electrolyte Additives for SEI Layer Control
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Solution Overview
Problem
Lithium secondary batteries face degradation during repeated charge/discharge cycles, particularly due to the formation of a solid electrolyte interface (SEI) layer that can lead to increased electric resistance and reduced capacity density.
Innovation Solution
A non-aqueous electrolyte comprising a combination of a first acrylate compound with one or two acryl groups and a second acrylate compound with three or more acryl groups, along with an electrolyte salt and organic solvent, is used to form an SEI layer that maintains passivation while minimizing resistance and capacity drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an acrylate compound with more acryl groups is used to form SEI layer, then the passivation effect and density of SEI layer increase, but the electric resistance increases significantly
Solution Approach 1:
The patent changes the parameter of acryl group number from a single high value to a distribution including zero, one, two, or three acryl groups. This parameter modification allows the SEI layer to achieve passivation while controlling electric resistance by including compounds with fewer acryl groups that form less resistant interfaces.
Solution Approach 2:
The patent creates a composite SEI layer by combining reduced forms of multiple acrylate compounds with different acryl group counts (0-3 groups). This composite approach integrates the high passivation effect of multi-acryl compounds with the lower resistance characteristics of single or zero-acryl compounds, achieving both protection and conductivity.
2Quantity of substance
If the capacity density of the battery is increased, then the energy storage capability improves, but the degradation during charge/discharge cycles becomes more serious
Solution Approach 1:
The patent applies prior cushioning by forming a protective SEI layer on the anode before significant degradation can occur. This SEI layer, composed of reduced acrylate compounds, acts as a cushion that prevents direct contact between the electrolyte and anode, thereby protecting the high-capacity electrode materials from decomposition during repeated charge/discharge cycles.
3Device complexity
If a single acrylate compound is used as electrolyte additive, then the formulation is simple, but the SEI layer properties cannot be optimized for both low resistance and high passivation
Solution Approach 1:
The patent employs composite materials by combining multiple acrylate compounds with different acryl group numbers (0-3 groups) in the electrolyte. This composite electrolyte formulation creates a multi-component SEI layer that integrates the beneficial properties of each compound: high passivation from multi-acryl compounds and low resistance from single or zero-acryl compounds.
Solution Approach 2:
The patent applies local quality by allowing different regions of the SEI layer to be formed from different acrylate compounds. The SEI layer comprises reduced forms of acrylate compounds distributed throughout, with compounds containing zero, one, two, or three acryl groups contributing different local properties that collectively optimize overall SEI performance.
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 combined acrylate compounds enhance the lifespan and thermal stability of lithium secondary batteries by forming an SEI layer with optimal passivation properties, maintaining initial capacity and improving high-temperature performance.
Implementation Method 1
the use of an acrylic compound having at least three acryl groups as an additive for an electrolyte in a lithium secondary battery leads to formation of a solid electrolyte interface (SEI) layer via reduction at an anode
Data Source
AI summary
Disclosed is an electrode comprising a coating layer formed partially or totally on a surface thereof, the coating layer comprising: (i) a reduced form of a first acrylate compound having one or two acryl groups; and (ii) a reduced form of a second acrylate compound having three or more acryl groups. Further, disclosed in an electrochemical device comprising a cathode, an anode, a separator and a non-aqueous electrolyte, wherein the cathode and/or the anode is the above electrode.