LiFSI and TMSPa Additives for Stable SEI in Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in enhancing low temperature output properties and lifespan due to non-uniform solid electrolyte interface (SEI) membrane formation and decomposition issues with existing liquid electrolytes, particularly at high temperatures.
Innovation Solution
A non-aqueous liquid electrolyte comprising lithium bis(fluorosulfonyl)imide (LiFSI) and trimethylsilyl phosphate (TMSPa) additives, combined with a lithium-nickel-manganese-cobalt-based oxide positive electrode active material, forms a stable SEI membrane, improving output and lifespan properties by preventing decomposition and oxidation reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid electrolyte additive is added to improve low temperature output property, then the SEI membrane formation is enhanced, but the positive electrode surface is decomposed at high temperature and oxidation reactions occur
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by introducing specific additives (cyclic carboxylate and chain carboxylate) with controlled concentrations (0.01-5 wt% and 0.01-1 wt% respectively). This parameter optimization allows the electrolyte to form stable SEI membranes at low temperatures while preventing high-temperature decomposition reactions, thus resolving the contradiction between low-temperature performance and high-temperature stability
Solution Approach 2:
The carboxylate additives act as intermediary substances that mediate between the electrolyte and electrode surfaces. They facilitate uniform SEI membrane formation at low temperatures through controlled decomposition, while at high temperatures they form protective layers that prevent further decomposition of the positive electrode surface, thus serving as a protective mediator in both temperature regimes
2Productivity
If existing liquid electrolytes are used to form SEI membrane, then charge and discharge reactions are enabled, but the SEI membrane is non-uniform and lifespan property deteriorates
Solution Approach 1:
The patent employs preliminary action by having the carboxylate additives perform initial SEI membrane formation during early charging cycles. This preliminary SEI layer serves as a stable foundation that prevents subsequent electrolyte decomposition and electrode degradation, thereby enabling sustained charge-discharge cycles and extending battery lifespan while maintaining productivity
3Power
If liquid electrolyte additive is used to enhance output property, then ion conduction is improved, but irreversible capacity increases and output property declines over time
Solution Approach 1:
The patent optimizes the concentration parameters of carboxylate additives within specific ranges (cyclic carboxylate: 0.01-5 wt%, chain carboxylate: 0.01-1 wt%) to achieve the right balance between ion conduction enhancement and irreversible capacity reduction. This precise parameter control ensures sufficient output property while minimizing electrolyte decomposition and capacity loss over time
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 solution effectively enhances low temperature output, high temperature stability, and lifespan of lithium secondary batteries by forming a thin, efficient SEI membrane, reducing irreversible capacity and corrosion, and maintaining superior performance after high temperature storage.
Implementation Method 1
A secondary battery is manufactured by applying the active material on a current collector to proper thickness and length or applying the active material itself in a film form, and winding or laminating the result with a separator, which is an insulator, to form an electrode group, then placing the result in a can or a container similar thereto, and then injecting a liquid electrolyte thereto.
Implementation Method 2
This ion tunnel solvates lithium ions and performs a role of preventing the collapse of the carbon negative electrode structure by high molecular weight organic solvents of a liquid electrolyte moving together being co-intercalated to the carbon negative electrode.
Implementation Method 3
even when a liquid electrode additive is comprised but the amounts of the additive added are not adjusted to required amounts, there has been a problem in that a positive electrode surface is decomposed in a high temperature reaction due to the liquid electrolyte additive, or the liquid electrolyte causes an oxidation reaction
Implementation Method 4
Such a lithium secondary battery experiences charge and discharge while repeating intercalation and deintercalation of lithium ions from a lithium metal oxide of a positive electrode to a graphite electrode of a negative electrode.
Data Source
AI summary
The present disclosure provides a lithium secondary battery comprising a non-aqueous liquid electrolyte comprising lithium bis(fluorosulfonyl)imide (LiFSI) and a trimethylsilyl phosphate (TMSPa) additive, a positive electrode comprising a lithium-nickel-manganese-cobalt-based oxide as a positive electrode active material, a negative electrode and a separator.The non-aqueous liquid electrolyte for a lithium secondary battery of the present disclosure is capable of forming a solid SEI membrane in the negative electrode when initially charging a lithium secondary battery comprising the same, is capable of improving an output property of the lithium secondary battery, and is also capable of enhancing an output property and a capacity property after high temperature storage.