Preformed Silicon Negative Electrode SEI Formation
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Solution Overview
Problem
Silicon-based negative electrodes in lithium-ion batteries suffer from high initial irreversible capacity loss and prolonged SEI formation time due to volume changes during lithiation and delithiation, leading to structural degradation, increased internal resistance, and reduced cycle stability.
Innovation Solution
A method involving the application of successive constant voltages between a silicon-based negative electrode precursor and a lithium-based counter electrode to preform the SEI, reducing initial irreversible capacity loss and shortening the SEI formation time, involving steps of providing the precursor, applying voltages of 1.2 V-1.8 V, 400 mV-800 mV, and 200 mV-390 mV for at least 35 minutes each, and obtaining the preformed electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrodes are used to increase energy density, then capacity is improved, but initial irreversible capacity loss increases significantly
Solution Approach 1:
The patent applies preliminary action by performing a pre-formation treatment before the electrode is put into service. The method involves applying a first constant voltage (1.2-1.8 V) for 1-24 hours to form an initial SEI layer, followed by a second constant voltage (400-800 mV) for 1-24 hours to complete SEI formation. This preliminary SEI formation reduces the initial irreversible capacity loss from 20-80% to below 10% while preserving the high capacity of silicon-based electrodes.
2Quantity of substance
If silicon-based negative electrodes are used to increase energy density, then capacity is improved, but SEI formation time is prolonged
Solution Approach 1:
The patent applies periodic action by dividing the SEI formation process into two distinct voltage stages. The first stage uses a higher voltage (1.2-1.8 V) for 1-24 hours to initiate SEI formation, then the voltage is reduced to a second stage (400-800 mV) for another 1-24 hours to complete formation. This staged approach accelerates SEI formation compared to conventional single-voltage methods, reducing total formation time while achieving complete SEI coverage.
3Quantity of substance
If silicon-containing negative electrode undergoes volume change during cycling, then lithiation and delithiation capacity is improved, but structural degradation occurs
Solution Approach 1:
The patent applies beforehand cushioning by forming a robust SEI layer through the two-stage voltage treatment before the electrode undergoes normal cycling. This pre-formed SEI layer acts as a protective cushion that accommodates the volume changes of silicon during lithiation and delithiation, preventing structural degradation and maintaining electrode integrity during capacity cycling.
4Quantity of substance
If high surface loading is applied to increase capacity, then energy density is improved, but electrode architecture preservation deteriorates
Solution Approach 1:
The patent applies preliminary action by forming a complete and stable SEI layer through the two-stage voltage treatment before high surface loading is applied. This pre-formed SEI layer provides structural support and protection, enabling the electrode to withstand high surface loading conditions while preserving architecture and maintaining energy density.
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 significantly reduces initial irreversible capacity loss and shortens the SEI formation time, enhancing the relative capacity and cycle stability of silicon-based negative electrodes, making them more suitable for lithium-ion batteries.
Implementation Method 1
a solid electrolyte interface (SEI), i.e., a boundary layer between the negative electrode and the electrolyte, is formed due to reductive decomposition of various electrolyte components such as solvents, additives, and impurities
Implementation Method 2
in the ideal case it has good ionic conductivity and at the same time has an electrically insulating effect. Due to its kinetically limiting effect, it largely suppresses further decomposition of the electrolyte
Implementation Method 3
the SEI protects the structure of the active material (graphite) from exfoliation, and thus protects the cell from significant capacity losses
Implementation Method 4
Applying at least three successive constant voltages of 1.2 V-1.8 V, 400 mV-800 mV, and 200 mV-390 mV, respectively, between the at least one silicon-based negative electrode precursor and the at least one lithium-based counter electrode for a period of at least 35 minutes in each case
Data Source
AI summary
The present invention relates to a method for manufacturing a silicon-based negative electrode, a method for manufacturing a lithium-ion battery from a preformed silicon-based negative electrode, and a lithium-ion battery thus obtained.