Silicon Anode Interface Layer for High-Temperature Li-Ion Storage
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Solution Overview
Problem
Lithium-ion batteries with silicon-based negative electrodes face issues such as volume expansion, damage to the solid electrolyte interface film, and poor high-temperature storage performance due to the alloying of silicon and lithium during charging, leading to decomposition and lithium precipitation.
Innovation Solution
A lithium-ion battery design incorporating a silicon-based negative electrode with a phosphorus-containing inactive material layer formed on its surface, using a compound represented by structural formula 1 in the non-aqueous electrolyte, which regulates the mass content, thickness, and mass density to form a protective layer that prevents further decomposition, reduces impedance growth, and minimizes lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to increase energy density, then the theoretical specific capacity is improved (4200 mAh/g vs graphite 372 mAh/g), but the volume expansion reaches up to 300% during alloying with lithium, destroying the solid electrolyte interface film
Solution Approach 1:
The patent applies preliminary action by forming a phosphorus-containing inactive material layer on the silicon-based negative electrode surface before the battery operates. This layer is created through adding a phosphorus-containing compound to the non-aqueous electrolyte, which reacts with silicon during battery formation to pre-establish a protective interface that prevents subsequent film destruction during lithium alloying
Solution Approach 2:
The patent uses an intermediary approach by introducing a phosphorus-containing compound as a mediator between silicon and lithium. This compound forms a phosphorus-containing inactive material layer that acts as an intermediate protective barrier, allowing lithium alloying to proceed while preventing direct contact that would destroy the solid electrolyte interface film
2Quantity of substance
If silicon-based negative electrode is used to achieve high energy density, then the capacity is improved, but the high-temperature storage performance deteriorates due to continuous interface film decomposition and lithium precipitation
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable phosphorus-containing inactive material layer during battery formation before high-temperature storage occurs. This pre-established protective layer has high thermal stability and prevents the decomposition reactions that would otherwise occur at elevated temperatures, thereby maintaining battery reliability during storage
Solution Approach 2:
The patent uses parameter changes by modifying the chemical composition parameters of the electrolyte (adding phosphorus-containing compound at specific concentrations of 0.1%-1.5%) and controlling the thickness parameter of the formed protective layer (30-100 nm). These parameter adjustments create a interface layer with optimized stability properties that resist high-temperature degradation
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 the battery's energy density and high-temperature storage capacity retention by protecting the electrode from further damage, reducing impedance growth, and preventing lithium precipitation, thereby improving overall performance.
Implementation Method 1
the additive comprises a compound represented by structural formula 1... a phosphorus-containing inactive material layer is formed on a surface of the negative electrode material layer
Data Source
AI summary
A lithium-ion battery, comprising a positive electrode, a negative electrode and a non-aqueous electrolyte. The negative electrode comprises a negative electrode material layer containing a silicon-based material, and a phosphorus-containing inactive material layer is formed on the surface of the negative electrode material layer. The non-aqueous electrolyte includes a lithium salt, an organic solvent and an additive of the compound represented by structural formula 1, where n is 0 or 1, X is selected from formula 2 or formula 3, R1 and R2 are each independently selected from H, halogen, an unsubstituted or halogen-substituted hydrocarbon group with 1-5 carbon atoms, formula 4, formula 5, and formula 6, and at least one sulfur atom is present in X, R1 or R2.