Secondary Battery Electrolyte Additives for Stable SEI and Low Gas
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Solution Overview
Problem
Secondary batteries face challenges in balancing safety performance and cycle performance while maintaining a high utilization rate of the electrolytic solution, as the carbonate solvent in the electrolyte is prone to decomposition, leading to gas production and performance degradation.
Innovation Solution
A secondary battery design incorporating a negative electrode plate with a boron-containing lithium salt and an ester additive, forming a solid electrolyte interface film, which regulates the discharge capacity, gas production, and reduction potential to ensure a stable SEI film, reducing solvent decomposition and enhancing ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the carbonate solvent in the electrolytic solution is used to ensure high capacity and long service life, then the utilization rate of the electrolytic solution is improved, but the carbonate solvent is prone to decomposition leading to gas production and safety performance degradation
Solution Approach 1:
The boron-containing lithium salt acts as an intermediary substance between the carbonate solvent and the negative electrode active material. It forms a stable SEI film that prevents direct contact and decomposition reactions between the carbonate solvent and electrode material, thereby reducing gas production while maintaining electrolyte utilization rate.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolytic solution by introducing boron-containing lithium salts with specific reduction potentials (0.8-2.0V vs Li+/Li). This parameter change modifies the decomposition behavior of the carbonate solvent, shifting from direct decomposition to controlled film formation, thus reducing gas production while maintaining high utilization rate.
2Duration of action of moving object
If the electrolytic solution is designed to achieve high discharge capacity, then the cycle performance is improved, but gas production increases leading to internal pressure buildup and safety issues
Solution Approach 1:
The invention converts the potentially harmful decomposition of carbonate solvent into a beneficial process by controlling it to form a protective SEI film through boron-containing lithium salts. The film formation process, which would normally be considered a side reaction causing gas production, is instead harnessed to create a stable interface that enhances cycle performance while minimizing harmful gas accumulation.
Solution Approach 2:
The boron-containing lithium salts create a localized stable SEI film at the electrode-electrolyte interface. This local quality change ensures that the decomposition reactions are confined to a controlled region, forming a protective layer that prevents further decomposition and gas production in the bulk electrolyte, thus maintaining cycle performance while reducing overall gas production.
3Reliability
If the reduction potential of the first additive is adjusted to form a stable SEI film, then the safety performance is improved, but the complexity of electrolyte composition increases
Solution Approach 1:
The boron-containing lithium salts serve multiple functions simultaneously: they act as electrolyte components providing ionic conductivity, serve as film-forming agents creating stable SEI layers, and function as decomposition inhibitors preventing carbonate solvent breakdown. This multi-functionality reduces the need for separate additives, thereby improving safety performance without significantly increasing electrolyte composition complexity.
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 stabilizes the SEI film, improves cycle performance, ensures safe internal pressure, and maintains a high utilization rate of the electrolytic solution by controlling gas production and solvent decomposition.
Implementation Method 1
the first additive comprising a boron-containing lithium salt and an ester additive, which are configured to form a solid electrolyte interface film on the surface of the negative electrode active material
Implementation Method 2
it is possible to ensure that metal ions migrate smoothly, so as to ensure cycle performance of the secondary battery
Implementation Method 3
decomposition degree of the carbonate solvent in the electrolytic solution is small so that its gas production is within the controllable range
Data Source
AI summary
The present application provides a secondary battery, a battery module, a battery pack, and an electrical device. The secondary battery includes a positive electrode plate, a negative electrode plate comprising a negative electrode active material; and an electrolytic solution including a first additive and a carbonate solvent, and the first additive including a boron-containing lithium salt and an ester additive, which are configured to form a solid electrolyte interface film on the surface of the negative electrode active material, wherein a discharge capacity of the secondary battery is denoted as B1 in Ah, a change in amount of gas production of the secondary battery is denoted as B2 in mL, a mass of the electrolytic solution is denoted as C in g, a reduction potential of the first additive relative to lithium metal is denoted as D.