High-Voltage Li-Ion Electrolyte Additives for Cathode Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-voltage, high-capacity lithium-ion battery cathodes degrade organic electrolytes, leading to capacity fade and impedance rise, which limits energy density and charging/discharging efficiency, and current additives' mechanisms are not fully understood.
Innovation Solution
A method involving the use of specific electrolyte additives, such as (R3SiO)3P, which are aged in a solution with a lithium salt in a non-aqueous solvent at 20-30°C for 5-10 days to form an aged electrolyte, reducing impedance and improving cathode surface protection without affecting capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-voltage, high-capacity cathode materials are used to increase energy density, then the energy density of the battery is improved, but the organic electrolyte degrades due to reactions with the energized cathode
Solution Approach 1:
The patent introduces electrolyte additives (phosphites, phosphates, borates, boroxanes) as intermediary substances that mediate between the high-voltage cathode and the organic electrolyte. These additives preferentially react with the cathode surface to form protective interphases, preventing direct contact and reaction between the cathode and electrolyte, thus protecting the electrolyte from degradation while enabling high-voltage operation
Solution Approach 2:
The patent applies preliminary action by having the electrolyte additives pre-react with the cathode surface during initial cycles to form stable protective films before the electrolyte can undergo harmful degradation reactions. This preliminary formation process creates a barrier that prevents subsequent electrolyte decomposition during normal battery operation
2Reliability
If electrolyte additives are used to protect the cathode surface, then capacity fade is reduced, but the mechanism of action is not fully understood and multiple additives may be needed
Solution Approach 1:
The patent identifies a universal class of electrolyte additives (phosphites, phosphates, borates, boroxanes with specific molecular structures) that can all perform the same protective function on cathode surfaces. These compounds share common structural features (P(OR)3, OP(OR)3, B(OR)3, or c-B3O3(OR)3 groups) that enable them to universally form protective films on high-voltage cathodes, reducing the need for complex multi-component formulations
3Object-affected harmful factors
If HF scavenging additives are used to remove corrosive HF, then cathode corrosion is reduced, but further hydrolysis of PF6- is facilitated by shifting hydrolytic equilibria
Solution Approach 1:
The patent converts the harmful effect of HF generation into a beneficial process by designing additives that undergo controlled hydrolysis to scavenge HF. The additives intentionally react with water to produce HF, which then reacts with the additive to form stable fluoro compounds, effectively removing HF from the system while the byproducts remain stable and non-corrosive
Solution Approach 2:
The electrolyte additives serve as intermediary substances that mediate between HF and the cathode material. Instead of allowing HF to directly corrode the cathode, the additives intercept HF through hydrolysis and acidolysis reactions, forming stable intermediates that prevent cathode degradation while the reaction products remain stable in the 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 method prevents excessive impedance increases and improves coulombic efficiency, providing a protective film on positive electrode oxide surfaces, enhancing the performance of lithium-ion batteries.
Implementation Method 1
In LiPF6 containing electrolytes, TMSPi undergoes extensive solvolysis, yielding numerous reaction products
Implementation Method 2
electrochemically subjecting the electrochemical cell to formation cycling (e.g., to form a solid electrolyte interface (SEI) on the anode thereof)
Data Source
AI summary
This invention relates to an electrolyte composition for a lithium ion battery comprising a lithium salt in a non-aqueous solvent containing an additive comprising a compound of formula R3SiOP(O)nF2; wherein each R independently is a hydrocarbyl group; and n is 0 or 1; and wherein the additive is substantially free from (R3SiO)3P(O)n and (R3SiO)2P(O)nF. Electrochemical cells and batteries also are described.