Phosphoric Electrolyte Additive for Stable High-Voltage Li Batteries
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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 degradation.
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 additive acts as an intermediary substance between the high-voltage nickel-based positive electrode and the electrolyte. It forms a protective film on the electrode surface that mediates the interaction, preventing direct harmful reactions while allowing lithium ion transport. This resolves the contradiction by enabling the use of high-capacity nickel electrodes without suffering from their inherent instability and side reaction problems.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by introducing a phosphoric acid-based additive with specific molecular structure (containing P=O and P-OH groups). This parameter change in the electrolyte composition leads to the formation of a stable protective film on the positive electrode, thereby improving SEI layer stability while maintaining the high capacity benefits of nickel-based electrodes.
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 additive serves as a protective intermediary that forms a stable film on the positive electrode surface. This film prevents the decomposition of the electrolyte and subsequent generation of HF, thereby maintaining low resistance while allowing the high-capacity nickel electrode to function. The additive mediates between the electrode and electrolyte to prevent harmful resistance-increasing reactions.
Solution Approach 2:
The phosphoric acid-based additive converts the potentially harmful high-voltage environment into a beneficial stable interface. By utilizing the phosphoric acid groups that can form stable bonds, the invention transforms the aggressive high-voltage nickel electrode surface into a protected interface with stable resistance characteristics, effectively converting the harmful high-voltage condition into a beneficial stable operating state.
3Reliability
If high-temperature storage is performed, then battery performance is tested, but SEI layer disintegration occurs due to HF and PF5 generation
Solution Approach 1:
The phosphoric acid-based additive performs a preliminary protective action by forming a stable film on the positive electrode surface before high-temperature storage conditions can cause damage. This pre-formed protective layer prevents the generation of HF and PF5 during storage, thereby maintaining SEI layer integrity. The additive takes preliminary action to prevent the harmful chemical reactions that would otherwise occur during high-temperature storage.
Solution Approach 2:
The phosphoric acid-based additive acts as a thermal stability intermediary that remains stable at high temperatures while protecting the SEI layer. It forms a heat-resistant protective film that mediates between the high-temperature environment and the sensitive SEI layer, preventing disintegration. The additive's phosphoric acid groups provide thermal stability, allowing the battery to withstand high-temperature storage without SEI layer degradation.
4Reliability
If conventional electrolyte additives are used, then some protection is provided, but high-temperature storage characteristics and lifetime characteristics remain insufficient
Solution Approach 1:
The invention makes a significant parameter change in the electrolyte composition by introducing a phosphoric acid-based additive with specific molecular structure (containing P=O and P-OH groups in a 1:2 ratio). This compositional parameter change provides superior high-temperature storage characteristics and extended lifetime compared to conventional additives. The specific chemical parameters of the phosphoric acid-based additive enable it to form a more stable and durable protective film, thereby simultaneously improving both storage characteristics and lifetime.
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 additive significantly improves the durability and high-temperature storage characteristics of lithium secondary batteries by reducing decomposition reactions and maintaining capacity retention, as evidenced by capacity retention rate, resistance increase rate, and volume increase rate during high-temperature storage.
Implementation Method 1
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
Implementation Method 2
the lithium ions from the lithium-containing transition metal oxide used as the positive electrode are moved to and inserted into the carbon material negative electrode active material used as the negative electrode
Implementation Method 3
highly reactive lithium ions react with electrolytes to create compounds such as Li2CO3, Li2O, LiOH, and LiF
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, a non-aqueous electrolyte solution includes a lithium salt, an organic solvent, and a phosphoric acid-based additive represented by Formula 1 below, which improves the high temperature stability in a lithium secondary battery:wherein R is described herein.