Silicon-Carbon Pre-Lithiated Anode with SEI-Forming Nanolayer
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Solution Overview
Problem
Current pre-lithium methods for lithium-ion batteries, such as adding lithium-rich oxides to cathode electrodes and pressing lithium sources onto anode electrodes, face limitations in reducing irreversibility and achieving continuous lithium replenishment, leading to reduced energy and power density, and increased risk of thermal runaway due to volume expansion of silicon-based anode materials.
Innovation Solution
A silicon-carbon pre-lithium composite anode material is created by nanoizing silicon, adding carbon and polymer for homogenization, mixing with pre-lithium nanomaterials, and sintering to form a composite with a stable pre-lithium nanolayer that forms a solid electrolyte interface and provides lithium replenishment and buffer space for volume expansion, enhancing cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-lithium processing is performed by adding lithium-rich oxides to cathode electrode or pressing lithium source onto anode electrode, then the lifetime is improved by reducing initial irreversibility, but the method generates by-products with low conductivity on the surface and has limited ability to reduce irreversibility
Solution Approach 1:
The patent uses a composite anode structure consisting of silicon particles embedded in a carbon matrix, with the carbon material serving multiple functions: conducting electricity, accommodating silicon expansion, and preventing direct contact between silicon and electrolyte that would form harmful by-products. This composite approach resolves the contradiction by maintaining reliability through silicon's high capacity while using carbon to eliminate the harmful low-conductivity surface by-products.
2Reliability
If one-time replenishment pre-lithium processing is performed, then the loss of active lithium caused by first charge is improved, but most pre-lithium materials exist as inert substance reducing overall energy density and power density
Solution Approach 1:
The carbon matrix in the silicon-carbon composite performs multiple functions simultaneously: it acts as a conductive network, provides structural support, accommodates volume expansion, and serves as a reservoir for reversible lithium storage. This multi-functionality allows the anode to maintain high energy density while continuously replenishing lithium, eliminating the need for inert pre-lithium materials that would reduce density.
Solution Approach 2:
The patent changes the functional role of carbon from a simple binder to an active lithium storage component. By designing the carbon matrix with appropriate porosity and surface area, it can reversibly host lithium ions during cycling, transforming it from a passive structural element to an active participant in lithium replenishment, thereby maintaining high energy density.
3Reliability
If lithium source is pre-stored on anode electrode to achieve continuous replenishment, then continuous lithium replenishment during cycles is improved, but there is great risk of thermal runaway during first charging process
Solution Approach 1:
The silicon-carbon composite is prepared in advance with the carbon matrix already structured to accommodate silicon expansion and provide conductive pathways. This preliminary structuring eliminates the need for aggressive pre-lithiation treatments during battery assembly, allowing the battery to be safely assembled in a standard state and then activated through normal charging cycles, thereby avoiding thermal runaway risks associated with pre-stored lithium sources.
4Quantity of substance
If silicon-based anode electrode active material is used, then high specific capacity is achieved, but volume expansion during charge and discharge process causes repeated solid electrolyte interface formation and consumes lithium
Solution Approach 1:
The carbon matrix acts as a flexible shell surrounding the silicon particles, accommodating their volume expansion and contraction during lithium insertion and extraction. This flexible carbon shell maintains structural integrity while allowing silicon to expand up to 300% in volume, preventing particle disintegration and maintaining electrical contact, thereby preserving high specific capacity over many cycles.
Solution Approach 2:
The silicon-carbon composite structure combines the high capacity of silicon with the volume stability and conductivity of carbon. The carbon component forms a stable framework that prevents silicon from undergoing harmful phase transformations and maintains continuous electrical pathways, resolving the contradiction between achieving high specific capacity and maintaining compositional stability 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 high cycle stability with Faraday efficiency over 90%, effectively addressing the limitations of existing pre-lithium methods by providing continuous lithium replenishment and reducing stress on silicon materials.
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
sintering the silicon-carbon pre-lithium composite precursor to obtain the silicon-carbon pre-lithium composite anode material
Data Source
AI summary
A method of making a silicon-carbon pre-lithium composite anode material is provided. 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.