Silicon-Carbon Pre-Lithium Anode Composition for Stable SEI Formation
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Solution Overview
Problem
Current pre-lithium processing methods for lithium-ion batteries, which involve adding lithium-rich oxides to the anode electrode, face limitations in reducing irreversibility and enhancing energy density due to the formation of low-conductivity lithium oxide on silicon-based anode active materials, leading to inefficient lithium replenishment and increased risk of thermal runaway during charging.
Innovation Solution
A silicon-carbon pre-lithium composite anode material is created by nanoizing silicon materials, adding carbon and polymer for homogenization, mixing with pre-lithium nanomaterials, and sintering to form a composite structure with a stable pre-lithium nanolayer that reduces oxidation and volume expansion, while providing continuous lithium replenishment and improved cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-rich oxides are added to the anode electrode for pre-lithium processing, then the initial irreversibility is reduced, but low-conductivity lithium oxide forms on the silicon-based anode active material surface, limiting further improvement
Solution Approach 1:
The patent applies preliminary action by pre-storing lithium source materials (such as lithium metal thin films or lithium-rich compounds) on the anode electrode surface before battery operation. This pre-lithium layer is strategically positioned to compensate for lithium loss during subsequent charge-discharge cycles, particularly addressing the initial irreversibility issue without allowing harmful lithium oxide to form on the silicon surface
Solution Approach 2:
The patent uses an intermediary approach by introducing a dedicated lithium source layer as a mediator between the external environment and the silicon-based active material. This intermediary lithium layer provides lithium ions during cycling without directly exposing the silicon surface to conditions that would form low-conductivity lithium oxide, thus maintaining electrical conductivity while replenishing lithium
2Reliability
If one-time replenishment pre-lithium processing is performed, then the first activation loss is improved, but the pre-lithium materials exist as inert substances, reducing overall energy density and power density
Solution Approach 1:
The patent applies dynamics by designing a pre-lithium structure that transitions from a static inert layer to an active lithium source during battery operation. The pre-stored lithium materials are configured to dynamically release lithium ions during charge-discharge cycles, transforming from passive fillers into active participants in the electrochemical reactions, thereby maintaining energy density while providing continuous lithium replenishment
Solution Approach 2:
The patent utilizes parameter changes by controlling the composition, thickness, and chemical state of the pre-lithium layer to optimize both its initial protective function and its subsequent lithium-releasing capability. By adjusting parameters such as lithium content, material composition, and layer structure, the system achieves high Faraday efficiency (>90%) and specific capacity (>1600 mAh g-1) while maintaining acceptable energy density
3Reliability
If lithium source is pre-stored on the anode electrode, then continuous lithium replenishment is achieved, but the risk of thermal runaway during the first charging process increases
Solution Approach 1:
The patent applies local quality by creating spatially differentiated regions within the anode electrode structure. The pre-lithium materials are localized in specific zones (such as on the surface or in specific layers) rather than uniformly distributed throughout. This localized positioning allows controlled lithium release in specific regions during charging, reducing overall thermal runaway risk while maintaining continuous lithium replenishment capability where needed
Solution Approach 2:
The patent implements beforehand cushioning by designing the pre-lithium structure to absorb and mitigate potential thermal runaway effects before they can propagate. The pre-stored lithium materials are configured to act as a buffer, absorbing excess energy or stabilizing the electrode structure during the first charging process, thereby cushioning against thermal runaway while still providing the desired continuous lithium replenishment function
4Quantity of substance
If silicon-based anode electrode active material is used, then high specific capacity is achieved, but volume expansion occurs during charge and discharge, causing repeated solid electrolyte interface formation and lithium consumption
Solution Approach 1:
The patent applies the nested doll principle by embedding silicon-based active materials within a protective matrix or composite structure. The silicon particles are nested within a stable host material (such as carbon matrix or other accommodating structures) that provides structural support and accommodates volume expansion. This nested configuration allows the high-capacity silicon to expand and contract during cycling without compromising the overall electrode integrity or causing excessive solid electrolyte interface formation
Solution Approach 2:
The patent utilizes composite materials by combining silicon-based active materials with other materials that compensate for silicon's volume expansion issues. The composite structure integrates silicon particles with stable matrix materials, conductive additives, and binding agents to create a multi-functional anode electrode material that maintains high specific capacity while improving volume stability and reducing lithium consumption during cycling
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 silicon-carbon pre-lithium composite anode material achieves high specific capacity (>1600 mAh g-1) and Faraday efficiency (>90%) with enhanced cycle stability and reduced stress from lithium intercalation, effectively addressing the limitations of existing pre-lithium methods.
Implementation Method 1
the pre-lithium nanomaterials can form a stable solid electrolyte interface (SEI) film on the surface of the silicon-carbon composite
Implementation Method 2
forming a stable solid electrolyte interface (SEI) film on the surface of the silicon-carbon composite, and can replenish the lithium source during the battery cycle
Implementation Method 3
can replenish the lithium source during the battery cycle and can also provide the buffer space for the volume expansion of silicon materials
Data Source
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AI summary
The present application provides a method of making a silicon-carbon pre-lithium composite anode material. The method includes: nanoizing silicon materials to obtain nano-silicon particles, adding carbon materials and polymer into the nano-silicon particles for homogenization treatment to obtain a silicon-carbon composite; providing a pre-lithium nanomaterial; mixing the silicon-carbon composite and the pre-lithium nanomaterial to granulate to obtain a silicon-carbon pre-lithium composite precursor; and sintering the silicon-carbon pre-lithium composite precursor.