Electrolytic Solution Additives for Dense SEI in Lithium Metal Batteries
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Solution Overview
Problem
Lithium metal secondary batteries face challenges with safety and cycle performance due to irreversible electrolyte loss, lithium dendrite growth, and SEI film issues, which existing electrolytic solutions fail to adequately address.
Innovation Solution
An electrolytic solution containing a lithium salt, organic solvent, and a strong oxidizing inorganic salt additive with a specific formula (M1M2xOy) is used, where the additive reacts with lithium metal to form a dense SEI film, inhibiting electrolyte loss and dendrite growth, thereby enhancing cycle and safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as negative electrode material to achieve high specific energy, then energy density is improved, but safety performance and cycle performance deteriorate due to electrolyte loss and dendrite growth
Solution Approach 1:
The patent introduces a strong oxidizing inorganic salt additive as an intermediary substance that mediates between the lithium metal and the electrolyte. This additive preferentially reacts with lithium metal to form a protective oxide SEI film, preventing direct contact between the electrolyte and lithium metal, thereby reducing electrolyte loss and inhibiting dendrite growth while maintaining high specific energy
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by adding strong oxidizing inorganic salt additives (such as NH4VO3, KMnO4, Na2FeO4, LiCoO2, Na3VO4, NaVO3, K2Cr2O7, or NaCoO2) at specific concentrations (0.01-1 weight%). This parameter change transforms the electrolyte's interaction with lithium metal, leading to formation of a dense oxide SEI film that improves safety and cycle performance
2Ease of operation
If conventional electrolytic solution is used, then battery operation is simple, but electrolyte loss occurs irreversibly and lithium dendrites grow, reducing cycle life
Solution Approach 1:
The strong oxidizing inorganic salt additive performs preliminary action by preferentially reacting with lithium metal during initial charging cycles to form a dense oxide SEI film before the electrolyte can directly contact and decompose. This preliminary protective layer prevents subsequent electrolyte loss and dendrite growth, extending cycle life while maintaining ease of operation
Solution Approach 2:
The patent converts the harmful strong oxidizing property of the inorganic salt additive into a beneficial effect. The strong oxidizing capability, which could potentially damage battery components, is instead utilized to create a protective oxide SEI film on lithium metal surfaces, transforming a potential harm into a protective mechanism that extends cycle life
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 effectively reduces electrolyte loss, prevents lithium dendrite growth, and improves cycle performance by forming a dense, conductive oxide SEI film that can repair itself, ensuring stable battery operation and safety.
Implementation Method 1
a strong oxidizing inorganic salt additive is added to the electrolytic solution, the additive may take priority over the organic solvent to obtain an electron, and react with an active lithium metal to generate dense SEI film
Data Source
AI summary
An electrolytic solution includes a lithium salt, an organic solvent, and an additive. The additive is a salt with a formula of M1M2xOy. The M1 is selected from one or more of alkali metal element and NH4+. The M2 is selected from one or more of VB-VIII group elements in a fourth cycle of a periodic table of elements. x is in a range of 0.01-4, and y is in a range of 0.1-9.