Battery Electrolyte Additives for High-Temperature Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high temperature performance due to the high reactivity and unstable crystal structure of Ni-rich Ni—Co—Mn based oxides and silicon-graphite negative electrodes, leading to reduced safety, lifespan, and instability.
Innovation Solution
An electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, solvent, and functional additives such as silver p-toluenesulfonate, vinylene carbonate, and lithium difluoro bis(oxalato) phosphate, which form a lithiophilic solid electrolyte interphase on the negative electrode, reducing interfacial reactivity and enhancing the insertion and deintercalation of lithium ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-rich Ni-Co-Mn based oxide is used to increase energy density, then capacity is improved, but interfacial reactivity increases and lifespan deteriorates
Solution Approach 1:
A coating layer comprising Li2SiO3, Li4SiO4, and/or Li2SiO2 is formed on the surface of the Ni-rich positive electrode material. This coating acts as an intermediary barrier that reduces interfacial reactivity between the high-Ni content material and the electrolyte, preventing oxidative decomposition and metal elution while maintaining high capacity. The coating layer specifically suppresses the harmful effects of Ni4+ reactivity without significantly reducing the electroactive Ni content.
Solution Approach 2:
The patent modifies the surface composition and structure of the positive electrode material by introducing a coating layer with specific chemical composition (Li2SiO3, Li4SiO4, and/or Li2SiO2). This parameter change at the surface level allows the bulk material to maintain high Ni content for capacity while the surface provides stability for lifespan.
2Quantity of substance
If positive electrode charging voltage is increased to achieve high capacity, then energy density is improved, but interfacial reactivity and oxidative decomposition increase
Solution Approach 1:
The coating layer of Li2SiO3, Li4SiO4, and/or Li2SiO2 serves as a protective intermediary that prevents direct contact between the high-voltage positive electrode material and the electrolyte. This barrier suppresses oxidative decomposition reactions that would otherwise occur at high charging voltages, enabling safe operation at elevated potentials for increased capacity.
3Quantity of substance
If silicon-graphite negative electrode is used to increase capacity, then energy density is improved, but volume change exceeds 300% and interfacial stability decreases
Solution Approach 1:
A coating layer is formed on the silicon-graphite negative electrode that acts as a flexible protective shell. This coating accommodates the >300% volume expansion of silicon during lithiation while maintaining interfacial stability. The coating prevents direct exposure of the silicon surface to the electrolyte, reducing formation of inactive chemical species and improving SEI coverage stability despite the large volume changes.
4Quantity of substance
If high Ni content material is used, then capacity is improved, but metal elution and gas generation increase reducing safety
Solution Approach 1:
The coating layer comprising Li2SiO3, Li4SiO4, and/or Li2SiO2 acts as a physical and chemical barrier that prevents metal elution from the high-Ni content positive electrode material. This intermediary layer traps potential eluting metals and prevents their migration to other components, thereby reducing gas generation and improving safety while maintaining high capacity.
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 battery's capacity retention rate and output characteristics at high temperatures, maintaining 88% capacity after 100 cycles and 80% after 200 cycles, while suppressing decomposition and metal deposition, thus enhancing the battery's lifespan and stability.
Implementation Method 1
form a lithiophilic solid electrolyte interphase on the negative electrode
Implementation Method 2
form a lithiophilic solid electrolyte interphase on the negative electrode, reducing interfacial reactivity
Implementation Method 3
enhancing the insertion and deintercalation of lithium ions
Data Source
AI summary
The present disclosure relates to 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, wherein the functional additive includes a first negative-electrode film additive, which is silver p-toluenesulfonate.