Li-Ion Battery Electrolyte Additive for Silicon Anode Cycle Stability
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Solution Overview
Problem
Lithium-ion batteries with silicon-based negative electrodes face challenges due to volume expansion during lithiation and delithiation, leading to particle pulverization, loss of electrical contact, and unstable solid-electrolyte interface formation, resulting in capacity fading.
Innovation Solution
Incorporating (2-cyanoethyl)triethoxysilane as an electrolyte additive in combination with nickel-rich positive electroactive materials and silicon-based negative electroactive materials, along with a solvent mixture of ethylene carbonate and dimethyl carbonate, to enhance cycling stability and rate capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electroactive materials are used to increase specific capacity, then capacity capability is improved, but volume expansion during lithiation and delithiation causes particle pulverization and unstable solid-electrolyte interface formation
Solution Approach 1:
The electrolyte additive performs preliminary action by forming a stable solid-electrolyte interface layer on the silicon-based negative electrode before significant volume expansion occurs. This pre-formed protective interface prevents particle pulverization and maintains electrical contact during subsequent lithiation and delithiation cycles, enabling the high capacity silicon material to cycle reliably.
Solution Approach 2:
The electrolyte additive acts as an intermediary between the silicon-based negative electrode and the electrolyte solution. It forms an intermediate protective layer that mediates the interaction between silicon and electrolyte, preventing direct harmful reactions while allowing lithium ion transport, thus stabilizing the solid-electrolyte interface during silicon's volume expansion.
2Quantity of substance
If nickel-rich positive electroactive materials are used to improve capacity capability, then energy density is improved, but structural stability may be compromised
Solution Approach 1:
The electrolyte additive changes the chemical parameters at the electrode-electrolyte interface by forming a stable protective layer. This modifies the local chemical environment around the nickel-rich positive electrode, preventing detrimental reactions that would compromise structural stability while allowing the high-capacity nickel-rich material to function at improved energy density.
3Reliability
If electrolyte additives are added to improve cycling stability, then reliability is improved, but device complexity increases
Solution Approach 1:
The electrolyte additive improves reliability by creating local quality changes at the electrode surfaces where it forms protective solid-electrolyte interface layers. Rather than requiring complex modifications throughout the entire battery system, the additive acts locally at critical interfaces to prevent degradation, thus improving cycling stability with minimal increase in overall device complexity.
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 system improves capacity retention and cycling performance by forming robust electrolyte/electrode interfaces, leading to enhanced stability and rate capabilities in lithium-ion batteries.
Implementation Method 1
The electrolyte is suitable for conducting lithium ions between the electrodes
Implementation Method 2
forming robust electrolyte/electrode interfaces
Data Source
AI summary
An electrochemical cell includes a first porous electrode, a second porous electrode, and a separating layer disposed therebetween. The first porous electrode includes an electrolyte intermingled with a positive electroactive material represented by:LiM1xM2yM3zM4(1−x−y−z)O2 where M1 include nickel (Ni) and M2, M3, and M4 are transition metals independently selected from the group consisting of: manganese (Mn), cobalt (Co), aluminum (Al), iron (Fe), and combinations thereof and where 0.8≤x≤1, 0≤y≤1, and 0≤z≤1. The second porous electrode includes the electrolyte intermingled with a silicon-based negative electroactive material. The electrolyte includes greater than or equal to about 0.5 wt. % to less than or equal to about 2 wt. % of an electrolyte additive including (2-cyanoethyl)triethoxysilane (TEOSCN). The electrolyte also includes a lithium-containing salt and a solvent mixture including ethylene carbonate (EC) and dimethyl carbonate (DMC) in mass ratio of about 3:7.