Sodium-Ion Battery Electrolyte Additives for Stable SEI and CEI Films
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Solution Overview
Problem
Sodium-ion batteries face issues with poor cycle performance, high-temperature storage, and gas expansion due to unstable SEI and CEI films, which are not effectively repaired, affecting long cycle and high-temperature performance.
Innovation Solution
A sodium-ion battery design with specific additives in the electrolyte, including a sodium salt and an organic additive, controlled within certain ratios relative to the carbon material's surface area, to form stable SEI and CEI films, reducing side reactions and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a common additive is added to the electrolyte to form an SEI film on the negative electrode, then the negative electrode deposition quality is improved, but the additive is depleted and the SEI film becomes unstable, affecting long cycle performance
Solution Approach 1:
The patent introduces a preliminary protection mechanism by adding a specific amount of sodium salt additive (0.01-3% by mass) that reacts first to form a stable foundation layer on the negative electrode surface. This preliminary action creates a stable SEI film structure that prevents subsequent electrolyte decomposition, thereby resolving the contradiction between initial deposition quality and long-term cycle stability
Solution Approach 2:
The patent uses sodium salt additives (such as NaBOB, NaDFOB, NaDFOP, or NaPO2F2) as intermediary substances that mediate between the negative electrode and the organic additive. These intermediaries form a stable SEI film structure that prevents direct contact between the electrolyte and electrode, reducing continuous dissolution and improving both deposition quality and cycle performance
2Manufacturing precision
If the additive is depleted during formation, then the SEI film is formed, but the CEI film cannot be effectively formed or repaired on the positive electrode, affecting high-temperature performance
Solution Approach 1:
The patent applies preliminary action by pre-introducing sodium salt additives that remain partially unreacted after formation, creating a reservoir of protective substances. These remaining additives continuously repair and maintain both SEI and CEI films during cycling and high-temperature storage, preventing film degradation and ensuring long-term reliability
Solution Approach 2:
The sodium salt additives act as intermediaries that facilitate the formation of stable CEI films on the positive electrode. By controlling the additive amount and composition, the patent enables these intermediaries to protect both electrodes, with the CEI film formation being particularly crucial for high-temperature performance and gas suppression
3Reliability
If more additive is added to improve film stability, then the SEI and CEI films are stabilized, but the cost and complexity of the electrolyte formulation increases
Solution Approach 1:
The patent optimizes the parameters of electrolyte formulation by precisely controlling the sodium salt additive content (0.01-3% by mass) and its ratio to the negative electrode surface area (e/a: 0.01-3.5). This parameter optimization achieves film stability without excessive additive amounts, balancing performance improvement with formulation simplicity and cost-effectiveness
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
Improves cycle performance, high- and low-temperature storage, and reduces gas generation by stabilizing the SEI and CEI films, enhancing the battery's electrochemical performance.
Implementation Method 1
The sodium salt additive may react with the negative electrode earlier than the organic additive, to passivate a surface of the negative electrode, so that film formation quality of the organic additive on the surface of the negative electrode is improved
Implementation Method 2
A common additive in the electrolyte forms an SEI (Solid Electrolyte Interphase, solid electrolyte interface) film at a stage of formation or capacity grading to cover a surface of a hard carbon negative electrode
Implementation Method 3
the additive is almost depleted at this stage. However, the SEI film of the sodium-ion battery has poor stability, and the SEI film cannot be effectively repaired subsequently
Data Source
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AI summary
A sodium-ion battery, a preparation method for the sodium-ion battery, and a power consumption device including the sodium-ion battery are disclosed. The sodium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a carbon material, and a specific surface area of the carbon material is a in a unit of m2/g. The electrolyte includes an electrolyte salt, an organic solvent, and an additive, the additive includes a sodium salt additive and an organic additive, a mass percentage of the sodium salt additive in the electrolyte is e in a unit of %, a numerical ratio of e to a satisfies: 0.01≤e/a≤3.5, a mass percentage of the organic additive in the electrolyte is f in a unit of %, and a numerical ratio of f to a satisfies: 0.05≤f/a≤10. In the sodium-ion battery, a proper amount of the additive required in the electrolyte is determined based on physicochemical properties of an electrode material, and an appropriate amount of sodium salt additive and an appropriate amount of organic additive are added to the electrolyte, to better improve battery performance.