Pre-Lithiated Silicon Anodes for Low-Decay Li-Ion Cycling
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Solution Overview
Problem
Electrochemical apparatuses, such as lithium-ion batteries, face continuous capacity decay and low first-cycle efficiency due to issues with silicon-based negative electrode active substances, which experience poor cycling performance and volume swelling, leading to rapid electrolyte consumption and reduced cycling capacity.
Innovation Solution
Excess lithiation is performed on the negative electrode active substance, compensating for lithium loss during the initial intercalation process and reserving excess lithium to alleviate capacity decay, thereby improving cycling performance and first-cycle efficiency without compromising energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active substances are used to improve capacity, then energy density is improved, but cycling performance deteriorates due to volume swelling and rapid electrolyte consumption
Solution Approach 1:
The patent applies preliminary action by performing excess lithiation on the negative electrode active substance before the battery enters the cycling stage. This pre-treatment process reserves excess lithium in the negative electrode, which compensates for lithium consumption during subsequent cycling, thereby improving cycling performance while maintaining high capacity
Solution Approach 2:
The patent changes the parameter of lithium content in the negative electrode by controlling the lithiation degree. By adjusting the lithiation parameter to create a lithium-rich state initially, the battery achieves better cycling stability without sacrificing the high capacity benefits of silicon-based materials
2Reliability
If excess lithiation is performed to reserve lithium and improve cycling performance, then cycling performance is improved, but energy density may be compromised due to additional lithium consumption
Solution Approach 1:
The patent applies partial or excessive action by performing excess lithiation beyond the stoichiometric requirement. This excessive lithiation reserves sufficient lithium to compensate for consumption during cycling, ensuring cycling performance improvement while the excess amount is optimized to minimize impact on energy density
3Quantity of substance
If conventional lithiation is used to maintain energy density, then energy density is maintained, but first-cycle efficiency is low due to lithium loss in initial intercalation
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the negative electrode before battery assembly. This preliminary lithium addition ensures that when the battery undergoes its first charge-discharge cycle, there is sufficient lithium available for efficient intercalation, thereby improving first-cycle efficiency without requiring additional lithium compensation later
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 method enhances the cycling performance and first-cycle efficiency of electrochemical apparatuses by maintaining lithium reserves, reducing capacity decay, and maintaining energy density, as demonstrated by increased capacity retention rates and stable energy density across multiple cycles.
Implementation Method 1
loss of active lithium in an initial lithium-intercalation process
Implementation Method 2
excess lithiation is performed on an electrochemical apparatus
Data Source
AI summary
An electrochemical apparatus includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate, where the negative electrode plate includes a negative electrode current collector and a negative electrode active substance layer disposed on the negative electrode current collector, where the electrochemical apparatus has a first capacity a in the unit of mAh, the first capacity a is greater than 0, and the first capacity a represents a capacity when a battery that is prepared using the negative electrode plate and a lithium plate as a counter electrode of the negative electrode plate is charged to 2.0 V after the electrochemical apparatus has been discharged from a 100% state of charge (SOC) to 2.5 V.