Phosphoric Acid Electrolyte Additives for High-Temperature Li-Ion Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high-temperature storage characteristics and lifetime due to side reactions and instability of the SEI layer, particularly with high-voltage nickel-based positive electrodes, leading to increased resistance and capacity deterioration.
Innovation Solution
Incorporating a phosphoric acid-based additive with a specific structure into the non-aqueous electrolyte solution to form a film on the electrodes, suppressing side reactions and enhancing the stability of the SEI layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-voltage nickel-based positive electrode is used to increase energy density, then capacity is improved, but electrochemical side reactions increase and SEI layer stability deteriorates
Solution Approach 1:
The phosphoric acid-based compound acts as an intermediary substance that mediates between the high-voltage nickel-based positive electrode and the electrolyte. It forms a protective interface layer that prevents direct harmful interactions while allowing lithium ion transport, thus resolving the contradiction between achieving high capacity and maintaining SEI layer stability.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by introducing phosphoric acid-based compounds with specific molecular structures (containing P=O and P-OH groups). This parameter change transforms the interface properties, enabling stable SEI layer formation on high-voltage nickel electrodes without sacrificing capacity.
2Quantity of substance
If high-voltage nickel-based positive electrode is used to increase energy density, then capacity is improved, but resistance increases due to decomposition reactions
Solution Approach 1:
The phosphoric acid-based compound serves as a protective intermediary that forms a stable interface layer between the electrode and electrolyte. This layer prevents decomposition reactions that would otherwise generate resistance, while still permitting efficient lithium ion conduction to maintain high capacity.
Solution Approach 2:
The invention converts the potentially harmful high reactivity of nickel-based electrodes into a benefit by using phosphoric acid-based compounds that preferentially react with the electrode surface to form a protective layer. This layer then prevents further harmful decomposition reactions, effectively converting the initial harmful effect into a protective mechanism.
3Reliability
If conventional electrolyte additives are used to form SEI layer, then surface protection is improved, but high-temperature storage characteristics deteriorate
Solution Approach 1:
The invention changes the chemical parameters of the electrolyte additive by using phosphoric acid-based compounds with specific structural features (P=O and P-OH groups). These parameter changes enable the formation of an SEI layer with enhanced thermal stability, simultaneously improving surface protection and high-temperature storage characteristics.
Solution Approach 2:
The phosphoric acid-based compound creates a composite interface structure combining organic and inorganic components. This composite SEI layer exhibits superior thermal stability compared to conventional organic-only additives, resolving the contradiction between surface protection and high-temperature performance.
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 phosphoric acid-based additive effectively improves the durability and high-temperature storage characteristics of lithium secondary batteries by reducing decomposition reactions and maintaining capacity retention, as evidenced by improved capacity retention, resistance, and volume stability during high-temperature storage.
Implementation Method 1
highly reactive lithium ions react with electrolytes to create compounds such as Li2CO3, Li2O, LiOH, and LiF, and these compounds form a solid electrolyte interface (SEI) layer on the electrode surface
Implementation Method 2
incorporating, as an additive to the non-aqueous electrolyte solution for the lithium secondary battery, a phosphoric acid-based additive having a specific structure with excellent conductivity capable of forming a film that can effectively suppress side reactions
Data Source
AI summary
Provided is a non-aqueous electrolyte solution for a lithium secondary battery containing a lithium salt, an organic solvent and a phosphoric acid-based additive of Formula 1 below, which significantly improves the high temperature stability of the lithium secondary battery:wherein R is described herein.