Lithium Battery Electrolyte Additive for High-Temperature Output Retention
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high temperature output and lifespan due to the high reactivity and unstable crystal structure of Ni-rich Ni—Co—Mn based oxide positive electrodes and the volume changes and interfacial instability of silicon-graphite negative electrodes, leading to safety and performance issues.
Innovation Solution
An electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, solvent, and functional additives such as (4-(1H-1,2,4-triazol-1-yl)phenyl)(fluorosulfonyl)sulfamoyl fluoride, vinylene carbonate, and lithium difluorophosphate, which form a flexible film on the positive electrode and a LiF-based solid electrolyte interphase on the negative electrode, enhancing stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-rich Ni-Co-Mn based oxide is used to increase positive electrode capacity, then energy density is improved, but interfacial reactivity increases and crystal structure stability deteriorates
Solution Approach 1:
A coating layer comprising fluorinated cyclic carbonate and fluorinated chain carbonate is introduced as an intermediary between the Ni-rich positive electrode and the electrolyte solution. This coating layer acts as a protective barrier that reduces interfacial reactivity between Ni4+ and the electrolyte, preventing oxidative decomposition and metal elution, while maintaining the high capacity characteristics of the Ni-rich electrode material.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte solution by incorporating specific fluorinated cyclic carbonate (10-40 vol%) and fluorinated chain carbonate (5-30 vol%) components. These parameter changes in the electrolyte composition enable the formation of a stable coating layer on the positive electrode, which suppresses interfacial reactions and improves cycle stability without sacrificing capacity.
2Quantity of substance
If Ni content is increased to achieve high capacity, then energy density is improved, but oxidative decomposition of electrolyte solution increases
Solution Approach 1:
The fluorinated cyclic carbonate and fluorinated chain carbonate form a protective coating layer that serves as an intermediary barrier, preventing direct contact between the high-Ni content positive electrode and the electrolyte solution. This coating layer effectively blocks the oxidative decomposition pathway while allowing lithium ion transport, thus eliminating the harmful electrolyte decomposition effect.
3Quantity of substance
If silicon-graphite negative electrode is used to increase capacity, then energy density is improved, but volume change increases and interfacial stability deteriorates
Solution Approach 1:
Vinylene carbonate (VC) is introduced as an intermediary substance that forms a stable solid electrolyte interphase (SEI) layer on the silicon-graphite negative electrode. This SEI layer acts as a protective intermediary that accommodates the volume expansion and contraction of silicon during charging and discharging cycles, maintaining interfacial stability and preventing direct reaction between silicon and the electrolyte solution.
Solution Approach 2:
The SEI layer formed by vinylene carbonate acts as a flexible thin film that can accommodate the greater than 300% lattice volume expansion of silicon during charging. This flexible film structure maintains integrity during volume changes, preventing electrode disintegration and maintaining interfacial stability throughout cycling.
4Quantity of substance
If silicon content is increased to improve negative electrode capacity, then energy density is improved, but SEI coverage decreases and mechanical strength deteriorates
Solution Approach 1:
The patent combines fluorinated cyclic carbonate and fluorinated chain carbonate in the electrolyte solution to form a composite coating layer on the positive electrode. Similarly, vinylene carbonate is combined with the fluorinated carbonates to form a composite SEI layer on the negative electrode. These merged components create synergistic effects that produce coating layers with enhanced mechanical strength and cohesive properties.
Solution Approach 2:
The coating layer on the positive electrode is formed as a composite material comprising fluorinated cyclic carbonate and fluorinated chain carbonate components. This composite structure provides both flexibility to accommodate volume changes and mechanical strength to maintain structural integrity during cycling, resolving the contradiction between capacity and strength.
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 solution improves the capacity retention rate and output characteristics of lithium secondary batteries, maintaining 80% capacity after 100 cycles and 70% after 200 cycles at high temperature, while reducing cell resistance and improving stability.
Implementation Method 1
the functional additive may include a first electrode film additive, which is (4-(1H-1,2,4-triazol-1-yl)phenyl)(fluorosulfonyl)sulfamoyl fluoride
Implementation Method 2
form a flexible film on the positive electrode
Implementation Method 3
form a LiF-based solid electrolyte interphase on the negative electrode
Data Source
AI summary
Disclosed are an electrolyte solution for a lithium secondary battery capable of improving the output and lifespan characteristics at high temperature of a lithium secondary battery, and a lithium secondary battery including the same. An electrolyte solution for a lithium secondary battery includes a lithium salt, a solvent, and a functional additive, and in particular, the functional additive includes (4-(1H-1,2,4-triazol-1-yl)phenyl)(fluorosulfonyl)sulfamoyl fluoride.