Two-Step Electrolyte Injection for High-Nickel Battery Interfaces
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Solution Overview
Problem
High-nickel lithium-ion batteries experience severe oxidative decomposition of conventional electrolytic solutions at the positive electrode interface, leading to gas production during high-temperature storage, which is mitigated by adding film-forming additives but results in increased impedance and deterioration of cycle performance due to the negative electrode interface being affected.
Innovation Solution
A two-step electrolytic solution injection method where a negative electrode film-forming additive is first introduced to form a solid electrolyte interphase (SEI) film on the graphite surface, followed by a positive electrode film-forming additive during high-voltage charging, forming a cathode electrolyte interphase (CEI) to inactivate surface active sites and balance high-temperature and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If film-forming additives are added to the electrolytic solution to mitigate oxidative decomposition at the positive electrode interface, then gas production during high-temperature storage is reduced, but impedance increases and cycle performance deteriorates due to the negative electrode interface being affected
Solution Approach 1:
The electrolytic solution is divided into two separate injection stages: first injection contains only negative electrode film-forming additive (VC, 0.5-2.0 wt%), second injection contains positive electrode film-forming additive (PS and SN, each 0.1-0.5 wt%). This segmentation allows each additive to act selectively on its target electrode interface without cross-interference, resolving the contradiction between reducing gas production and maintaining cycle performance
Solution Approach 2:
The negative electrode film-forming additive (VC) is introduced in the first injection to form a protective SEI film on the graphite surface before the positive electrode additives are introduced. This preliminary action protects the negative electrode interface from subsequent additive deposition, preventing impedance increase and cycle performance deterioration while still allowing the positive electrode additives to mitigate gas production
2Ease of operation
If conventional electrolytic solution is used in high-nickel lithium-ion batteries, then the battery can operate, but severe oxidative decomposition occurs at the positive electrode interface leading to gas production during high-temperature storage
Solution Approach 1:
Film-forming additives (VC for negative electrode, PS and SN for positive electrode) are introduced to change the chemical composition parameters of the electrolytic solution. These additives modify the interface chemistry at both electrodes, creating protective films that prevent oxidative decomposition and gas production while maintaining battery operability
Solution Approach 2:
The film-forming additives act as intermediary substances between the electrolytic solution and the electrode interfaces. VC mediates the interaction at the negative electrode by forming a stable SEI film, while PS and SN mediate at the positive electrode by forming protective CEI films, thereby preventing direct harmful oxidative decomposition reactions
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 approach effectively reduces gas production and maintains dynamic performance by isolating the negative electrode from the electrolytic solution and modifying the electrode interfaces, thereby enhancing the high-temperature and cycle performance of high-nickel lithium-ion batteries.
Implementation Method 1
a solid electrolyte interphase (SEI) film is formed on the surface of the graphite through a formation process
Implementation Method 2
a fine cathode electrolyte interphase (CEI) film is formed during a first high-voltage charging of the battery cell and testing of the nominal capacity
Data Source
AI summary
The present invention relates to the field of batteries. Provided are a secondary battery and a method for electrolyte injection. In the secondary battery, a positive electrode active material of a positive tab comprises a high-nickel ternary positive electrode material. An electrolyte is formed from an electrolyte S1 injected at a first injection and an electrolyte S2 injected at a second injection. A film-forming additive in the electrolyte S1 is a film-forming additive for a negative electrode. A film-forming additive in the electrolyte S2 is a film-forming additive for a positive electrode. In the secondary battery, the film-forming additive for a negative electrode is added during the first electrolyte injection, and formation processing is performed to form a good SEI at a graphite surface. Next, the film-forming additive for a positive electrode is added during the second electrolyte injection, thereby forming a dense CEI to passivate an active site at a surface of a high-nickel material, and accordingly attaining a balance between high temperature performance and kinetic performance of a high-nickel secondary battery. The electrolyte injection method is simple and can be implemented easily by adding a second electrolyte injection process to an existing process.