Bisfluorophosphite Electrolyte Stabilizes Nickel Cathode
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Solution Overview
Problem
Lithium nickel-based transition metal oxide cathode active materials in lithium secondary batteries suffer from stability issues at high temperatures, including swelling and rapid chemical degradation, which limits their commercialization and cycle life.
Innovation Solution
An electrolyte comprising a lithium salt, a nonaqueous organic solvent, and a bisfluorophosphite multicyclic compound, along with additional additives such as oxalatoborate-based and sulfinyl group-containing compounds, is used to stabilize the cathode structure and prevent electrolyte oxidation, thereby minimizing thickness increase and maintaining high temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel-based transition metal oxide is used as cathode active material to achieve higher capacity, then battery capacity is improved, but stability at high temperature deteriorates due to swelling and rapid chemical degradation
Solution Approach 1:
A coating layer comprising at least one of a metal oxide and a metal phosphate is formed on the surface of the lithium nickel-based transition metal oxide cathode active material. This coating layer acts as an intermediary barrier between the cathode material and the electrolyte, preventing direct harmful interactions while allowing lithium ion transport, thereby improving high-temperature stability without sacrificing capacity
Solution Approach 2:
The surface composition and structure of the cathode active material are modified by forming a coating layer with different chemical properties (metal oxide or metal phosphate). This parameter change in surface chemistry reduces chemical reactivity at high temperatures while maintaining electrochemical performance
2Quantity of substance
If lithium nickel-based transition metal oxide is used to increase capacity, then energy density is improved, but cycle life deteriorates due to rapid deterioration of cycle characteristics
Solution Approach 1:
The coating layer of metal oxide or metal phosphate serves as a protective intermediary that prevents direct contact between the reactive lithium nickel-based cathode material and the electrolyte. This intermediary layer stabilizes the electrode-electrolyte interface, reducing side reactions and structural degradation during cycling, thereby extending cycle life
Solution Approach 2:
The coating layer is formed in advance on the cathode active material surface before battery assembly and initial charging. This preliminary protective action prevents harmful reactions during storage and initial cycles, establishing a stable interface that maintains performance over extended cycling
3Productivity
If conventional organic electrolyte is used to achieve good ionic conductivity, then charge-discharge performance is improved, but safety deteriorates due to high flammability and volatility
Solution Approach 1:
The coating layer on the cathode acts as an intermediary barrier that prevents direct contact between the conventional organic electrolyte and the electrode materials. This intermediary layer suppresses harmful side reactions and prevents electrolyte decomposition that could lead to gas generation and thermal runaway, thereby improving safety while maintaining the benefits of conventional electrolytes
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 electrolyte significantly reduces the thickness increase rate and improves capacity retention and recovery rates, enhancing the battery's stability and life characteristics at high temperatures while maintaining efficient charge-discharge performance.
Implementation Method 1
the bisfluorophosphite multicyclic compound is coordinately bonded to the transition metal of the cathode to further stabilize the structure of the cathode
Implementation Method 2
a solution to improve life characteristics and stability at a high temperature of a battery by adding vinylene carbonate, vinyl ethylene carbonate, or the like which is known in the art as an electrolyte additive to form the SEI film
Implementation Method 3
The lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from a cathode and an anode
Implementation Method 4
The lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from a cathode and an anode
Data Source
AI summary
Provided are an electrolyte for a secondary battery including a lithium salt, a nonaqueous organic solvent, and a bisfluorophosphite multicyclic compound, and a lithium secondary battery including the electrolyte.