Positive Electrode Composition for High-Voltage Electrolyte Stability
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Solution Overview
Problem
Conventional methods for suppressing the decomposition reaction of the liquid electrolyte in secondary batteries, such as forming a surface film on the positive electrode active material or adding phosphorus compounds to the electrolyte, are not sustainable in the long term, especially at higher upper limit voltages.
Innovation Solution
A positive electrode for secondary batteries is developed, comprising a positive electrode current collector and a positive electrode active material layer containing active material particles, a binder, and an organic phosphorus compound represented by a specific general formula. This organic phosphorus compound is solid at room temperature and enhances the stability of the positive electrode active material layer, even at high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the upper limit voltage is increased to improve battery capacity and performance, then the energy density and power output are improved, but the oxidative decomposition of the liquid electrolyte accelerates and the surface film stability deteriorates
Solution Approach 1:
An organic phosphorus compound is introduced as an intermediary substance between the liquid electrolyte and the positive electrode active material. This compound forms a stable surface film that acts as a protective barrier, preventing direct contact and oxidative decomposition reactions while allowing the battery to operate at high voltages above 4.3V
Solution Approach 2:
The invention changes the chemical composition parameters of the surface film by incorporating specific organic phosphorus compounds with defined molecular structures (where R1 and R2 are hydrogen or alkyl groups with 1-2 carbon atoms, and R3 is an alkyl group with 1-17 carbon atoms). This parameter change in film composition significantly improves oxidative resistance and stabilizes the electrolyte at high operating voltages
2Reliability
If a surface film is formed on the positive electrode active material to suppress electrolyte decomposition, then the electrolyte stability is improved, but the surface film is damaged by oxidative decomposition over time
Solution Approach 1:
The surface film is constructed as a composite material system incorporating organic phosphorus compounds with specific molecular structures. This composite composition provides both immediate protective function and long-term durability, maintaining film integrity and electrolyte stability even after extended operation at high voltages
Solution Approach 2:
The organic phosphorus compound is pre-applied to the positive electrode active material surface before battery operation begins. This preliminary action ensures that a stable, oxidation-resistant surface film is already in place to protect against electrolyte decomposition from the first charge-discharge cycle, preventing rather than merely responding to degradation
3Reliability
If phosphorus compounds are added to the liquid electrolyte to suppress decomposition reactions, then the chemical stability is improved, but the dissolution content is limited and the effect cannot be sustained
Solution Approach 1:
The invention extracts the phosphorus compound from the bulk liquid electrolyte environment and relocates it to the positive electrode active material surface. This extraction allows the phosphorus compound to function at much higher effective concentrations localized at the electrode surface, where it directly forms the protective surface film, without being limited by dissolution constraints in the bulk electrolyte
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 use of the organic phosphorus compound in the positive electrode active material layer effectively suppresses the oxidative decomposition of the liquid electrolyte, maintaining its stability even at high upper limit voltages, thereby ensuring sustainable battery performance.
Implementation Method 1
the oxidative decomposition of the liquid electrolyte
Data Source
AI summary
A positive electrode for a secondary battery including a positive electrode current collector, and a positive electrode active material layer supported on the positive electrode current collector, in which the positive electrode active material layer contains active material particles, a binder, and an organic phosphorus compound that is solid at room temperature. The organic phosphorus compound is, for example, selected from the group consisting of a phosphonic acid and a phosphonic acid ester each including an alkyl group having 1 to 17 carbon atoms.