Silicon Anode Electrolyte for Low-Temperature Lithium-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries with graphite-based negative electrodes face limitations in low-temperature performance due to poor ionic transport and interfacial resistance, leading to significant polarization and early cut-off during charging/discharging.
Innovation Solution
A lithium-ion battery cell design featuring a silicon-based negative electrode with a non-aqueous electrolyte comprising a mixture of propylene carbonate, methyl ethyl carbonate, a lithium salt, and a mononitrile compound like butyronitrile, which improves low-temperature properties and cyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If graphite-based negative electrode is used, then battery structure is simple and manufacturing is easy, but low-temperature performance deteriorates due to poor ionic transport and interfacial resistance
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carbonate component (1,3-propanesultone) and optimizing the ratio of carbonate solvents (EC/DMC/EMC = 25/40/30 by volume). This parameter modification transforms the electrolyte's properties to reduce interfacial resistance and improve ionic transport at low temperatures, directly addressing the reliability issue while maintaining manufacturing simplicity
Solution Approach 2:
The patent creates a composite electrolyte system combining multiple carbonate solvents (ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate) with a cyclic carbonate (1,3-propanesultone) and lithium salt. This composite formulation synergistically improves low-temperature performance through enhanced ionic conductivity and reduced interfacial resistance, while the graphite electrode structure remains unchanged for manufacturing ease
2Ease of operation
If liquid electrolyte is used, then battery operation is simple, but low-temperature performance deteriorates due to poor ionic transport and high viscosity
Solution Approach 1:
The patent modifies the electrolyte's physical parameters by selecting carbonate solvents with appropriate viscosity characteristics and adding 1,3-propanesultone, which reduces overall electrolyte viscosity and improves ionic mobility at low temperatures. The EC/DMC/EMC ratio optimization specifically targets viscosity reduction while maintaining solvation capability
Solution Approach 2:
The patent enhances the local quality of the electrolyte at the electrode interface by introducing 1,3-propanesultone, which preferentially accumulates at the graphite-electrolyte interface to form a optimized SEI layer. This local modification reduces interfacial resistance without significantly altering the bulk electrolyte properties, maintaining ease of operation while improving low-temperature performance
3Quantity of substance
If graphite negative electrode is used, then theoretical capacity is 370 mAh/g, but practical capacity is limited to 320 mAh/g due to continuous capacity loss during cycling
Solution Approach 1:
The patent applies preliminary action by using 1,3-propanesultone to pre-form a stable and optimized solid electrolyte interface (SEI) layer on the graphite electrode during initial cycles. This pre-formed SEI layer prevents subsequent electrolyte decomposition and capacity loss, enabling the graphite electrode to achieve and maintain practical capacity closer to its theoretical maximum throughout cycling
Solution Approach 2:
The patent employs 1,3-propanesultone as a sacrificial additive that consumes during initial cycles to form a protective SEI layer. This disposable component irreversibly reacts to create a stable interface, sacrificing itself to prevent ongoing capacity loss and improve long-term cyclability
4Quantity of substance
If silicon-based negative electrode is used, then practical specific capacity increases to 3580 mAh/g, but electrode expansion and structural stability worsen
Solution Approach 1:
The patent introduces 1,3-propanesultone as an intermediary substance that mediates between the silicon electrode and the bulk electrolyte. This additive forms a stable interfacial layer that accommodates silicon expansion while maintaining electrical contact and preventing electrolyte degradation, thus enabling high capacity utilization without sacrificing structural stability
Solution Approach 2:
The patent modifies the interfacial chemical environment at the silicon electrode by introducing cyclic carbonate components that change the SEI formation parameters. This creates a more flexible and adherent interface layer that can accommodate the large volume changes of silicon during lithiation-delithiation, maintaining structural stability despite high capacity operation
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 enhances low-temperature performance by reducing resistance and improving charge reversibility, leading to better durability and cycling performance of the battery.
Implementation Method 1
an electrolyte disposed between said negative electrode and said positive electrode, said electrolyte comprising at least one lithium salt
Implementation Method 2
Lithium-ion batteries operate on the principle of insertion-de-insertion (or lithiation-delithiation) of lithium
Data Source
AI summary
The invention relates to an electrochemical cell for a lithium-ion battery including: a negative electrode including silicon as an active material; a positive electrode; and an electrolyte placed between said negative electrode and said positive electrode, said electrolyte including at least one lithium salt, at least one carbonate solvent, at least one mononitrile compound, and at least one compound having at least one of the following Formulas (I) and (II): Formulas (I) and (II), in which R1 and R2 are, independently from one another, H, Cl, or F, as long as R1 and R2 are not both H.