Silicon Anode Battery SEI Film Stability
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Solution Overview
Problem
Lithium secondary batteries face safety concerns due to volatile organic electrolytes and limited capacity and lifespan of carbon-based anode materials, particularly silicon-based anodes, which experience volume expansion and instability at high temperatures, leading to performance deterioration.
Innovation Solution
Incorporating a conjugated diene compound in the electrolyte, which forms a thermally stable and elastic solid electrolyte interface (SEI) on the silicon-based anode, suppressing cracking and decomposition reactions, and combining it with additives like lithium difluoro bis(oxalato)phosphate and lithium bis(oxalato)borate to enhance high-temperature stability and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic electrolytes are used in lithium secondary batteries, then the battery can operate, but safety deteriorates due to volatility and flammability at high temperatures
Solution Approach 1:
The patent introduces a solid electrolyte interface (SEI) film as an intermediary layer between the electrolyte and electrode. This SEI film, formed by specific additives, acts as a protective barrier that prevents direct contact between the flammable organic electrolyte and electrode materials, thereby eliminating the harmful effects of volatility and flammability while maintaining battery operation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the electrolyte system by introducing specific additive compounds (e.g., vinylene carbonate, fluoroethylene carbonate) in controlled concentrations (0.1-5 wt%). These parameter changes enable the formation of a stable SEI film that fundamentally alters the safety characteristics of the electrolyte system, transforming it from volatile and flammable to thermally stable.
2Quantity of substance
If carbon-based anode materials are used, then the battery structure is simple, but capacity is limited due to theoretical capacity constraints
Solution Approach 1:
The patent employs composite anode materials that combine carbon-based materials with silicon-based materials or other high-capacity materials. This composite structure allows the battery to achieve high capacity (exceeding the theoretical limit of pure carbon) while managing the structural complexity through controlled integration of different material phases with complementary properties.
3Quantity of substance
If silicon-based anode materials are used to increase capacity, then capacity is improved, but lifespan deteriorates due to volume expansion and SEI cracking during charging and discharging
Solution Approach 1:
The patent utilizes a flexible SEI film formed by specific electrolyte additives as a protective shell around silicon-based anode particles. This thin film layer accommodates the volume expansion and contraction of silicon during lithium insertion and extraction, preventing mechanical cracking of the SEI and maintaining electrode integrity over extended cycling, thereby extending battery lifespan.
Solution Approach 2:
The patent applies beforehand cushioning by pre-forming a stable SEI film through electrolyte additives before the silicon anode undergoes volume expansion. This pre-formed protective layer acts as a cushion that absorbs mechanical stress during subsequent charging and discharging cycles, preventing direct damage to the silicon structure and maintaining long-term stability.
4Speed
If high voltage is applied during charging to improve performance, then charging speed is improved, but safety deteriorates due to decomposition of additives and local overheating
Solution Approach 1:
The patent introduces a protective SEI film as an intermediary layer between the electrolyte and electrode that stabilizes the interface during high-voltage charging. This intermediary layer prevents direct high-voltage stress from causing electrolyte decomposition and local overheating, enabling fast charging while maintaining safety by mediating the interaction between high voltage and electrode materials.
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 significantly improves high-temperature storage characteristics and lifespan of lithium secondary batteries by preventing SEI cracking and decomposition, maintaining high capacity retention and thermal stability, even with reduced or replaced fluoroethylene carbonate content.
Implementation Method 1
the lithium ions react with the surface of the carbon particle, which is the anode active material, and electrolyte to form a coating, called a solid electrolyte interface (SEI) film, on the surface of the anode
Implementation Method 2
the formed SEI film suppresses side reactions between carbon materials and electrolyte solvents, for example, decomposition of the electrolyte on the surface of the carbon particle
Implementation Method 3
the lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from a cathode and an anode
Implementation Method 4
the lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from a cathode and an anode
Data Source
AI summary
Provided is a lithium secondary battery including an anode including a silicon-based anode active material; a cathode; and an electrolyte, the electrolyte including a lithium salt, a non-aqueous organic solvent, and a conjugated diene compound.