Ether Electrolyte Additives for Stable Sodium-Metal Battery Interfaces
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Solution Overview
Problem
Sodium-ion secondary batteries face challenges due to lower energy density, volume expansion, and sodium metal's high reactivity, leading to reduced cyclic reversibility and safety issues, particularly with the formation of dendrites and violent reactions with the electrolyte.
Innovation Solution
An electrolyte system with ether organic solvent and additives like phosphite or borate additives forms a protective film on the positive electrode, suppressing oxidative decomposition and enhancing coulombic efficiency and cycling performance by forming a CEI film containing boron or phosphorus compounds, while using fluorinated alkyl ether additives on the negative electrode to reduce oxidative decomposition shuttling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sodium metal negative electrode is used to achieve high energy density, then energy density is improved, but chemical reactivity increases causing violent reactions with electrolyte
Solution Approach 1:
The patent introduces a protective film formed by phosphite or borate additives as an intermediary layer between the sodium metal negative electrode and the ether organic solvent electrolyte. This film acts as a mediator that prevents direct contact and violent chemical reactions while still allowing ion transport, thus maintaining high energy density while improving chemical stability and safety.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding specific phosphite or borate additives to the ether organic solvent system. These parameter changes alter the interfacial chemistry between the sodium metal and electrolyte, forming stable protective films that reduce chemical reactivity while preserving the high energy density characteristics of sodium metal negative electrodes.
2Reliability
If ether organic solvent is used in electrolyte to improve ion conductivity, then ion conductivity is improved, but oxidative decomposition occurs on positive electrode surface
Solution Approach 1:
The patent uses phosphite or borate additives as intermediary substances that form protective films on the positive electrode surface. These films act as mediators that prevent direct oxidative decomposition of the ether organic solvent while maintaining good ion conductivity, thus resolving the contradiction between ion conductivity and oxidative stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by introducing phosphite or borate additives, which alter the electrochemical window and stability parameters of the ether organic solvent system. This allows the electrolyte to maintain high ion conductivity while significantly reducing oxidative decomposition at the positive electrode.
3Reliability
If conventional electrolyte additives are used to form protective films, then electrode protection is improved, but sodium dendrite growth is not effectively suppressed
Solution Approach 1:
The patent changes the chemical nature of the protective film by using phosphite or borate additives instead of conventional additives. These parameter changes in film composition and structure create a more uniform and stable interface that effectively suppresses sodium dendrite growth while maintaining electrode protection and high coulombic efficiency.
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 solution improves the coulombic efficiency and cycling performance of sodium-ion secondary batteries by stabilizing the electrolyte interface, reducing oxidative decomposition, and enhancing the structural protection of the electrodes, thereby improving the battery's overall performance.
Implementation Method 1
the trivalent boron atom in the borate additive has an empty P-orbital, entirely exhibits Lewis acidity, can coordinate with anions to increase the transference number of lithium/sodium ions, and can also coordinate with oxygen atoms in the ether organic solvent molecules
Implementation Method 2
the first additive is relatively stable with respect to sodium metal and can preferentially undergo oxidative decomposition on a surface of an oxide positive electrode to form a CEI film containing a boron or phosphorus compound
Implementation Method 3
due to the extremely high chemical reactivity, sodium metal is prone to violent reactions with the electrolyte to form a solid electrolyte interface film
Data Source
Figure 1~3
Figure 4~6
AI summary
A secondary battery, an electrolyte, and an electric apparatus are provided. The secondary battery includes a positive electrode plate, an electrolyte, a separator, and a negative electrode current collector, where the electrolyte includes a non-aqueous solvent, an electrolytic salt, and an additive; the non-aqueous solvent includes an ether organic solvent; the additive includes a first additive; and the first additive includes one or more of a phosphite additive or a borate additive.