Coated Cathode Materials With Phosphonate Additives for Stable Li-Ion Cells
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Solution Overview
Problem
Existing lithium ion batteries suffer from deterioration of electrochemical properties due to undesired reactions on the electrode surface, leading to increased cell resistance, reduced capacity, and gas generation, particularly at elevated temperatures.
Innovation Solution
The use of a partially coated cathode active material with transition metal oxides or lanthanide oxides, combined with an electrolyte composition containing silyl ester phosphonates, enhances electrochemical performance by improving capacity retention and reducing cell resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional additives and coatings are used to protect electrode surfaces, then some protection is provided, but electrochemical property deterioration still occurs due to unwanted reactions on electrode surfaces, leading to increased cell resistance, gas generation, and reduced capacity
Solution Approach 1:
The invention uses a composite coating system comprising both an inorganic oxide coating layer and an organic silyl ester phosphonate additive layer. The inorganic oxide coating (such as Al2O3, SiO2, TiO2, ZnO, or mixed oxides) provides a stable protective barrier, while the silyl ester phosphonate additive forms a complementary protective film that suppresses unwanted electrode surface reactions. This composite approach addresses the limitations of single-layer protection methods and significantly reduces cell resistance increase and gas generation during cycling.
Solution Approach 2:
The silyl ester phosphonate compounds act as intermediary substances that mediate between the electrolyte and the cathode active material surface. These compounds preferentially react with the cathode surface to form a protective interface layer that prevents direct contact between the electrolyte and reactive cathode materials, thereby suppressing unwanted side reactions, reducing gas generation, and maintaining electrochemical performance stability during cycling.
2Duration of action of stationary object
If electrode surfaces are protected to prevent reactions, then capacity retention improves, but lithium exchange during charging and discharging may be hindered
Solution Approach 1:
The protective coating system is designed to provide localized protection with specific functional properties. The inorganic oxide coating and silyl ester phosphonate layer create a protective interface that is selectively permeable - it blocks unwanted chemical reactions while allowing lithium ion transport. This localized functional differentiation enables simultaneous achievement of capacity retention and efficient lithium exchange without compromising either function.
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 combination results in electrochemical cells with improved capacity retention and reduced cell resistance during cycling, both at room temperature and elevated temperatures, while minimizing gas generation.
Implementation Method 1
the outer surface of said particulate cathode active material is at least partially coated with an oxide selected from transition metal oxides, lanthanide oxides, and oxides of metals and half metals of groups 2, 13, and 14 of the periodic system
Implementation Method 2
film forming additives which react during first charge/discharge cycle on the electrode surface thereby forming a film on the electrode to reduce direct contact between the electrolyte composition and the electrode active material
Implementation Method 3
organic carbonates, ethers, esters and ionic liquids are used as sufficiently polar solvents for solvating the conducting salt(s)
Data Source
AI summary
An electrochemical cell has a cathode active material selected from mixed lithium transition metal oxides containing Mn and at least one second transition metal; lithium intercalating mixed oxides containing Ni, Al and at least one second transition metal; and lithium metal phosphates, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from transition metal oxides, lanthanide oxides, and oxides of metals and half metals of groups 2, 13, and 14 of the periodic system; and an electrolyte composition containing at least one silyl ester phosphonate of formula (I)and at least one silyl ester phosphonate of formula (II)