Porous Si/Cu Composite Electrode for Lithium Ion Battery
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Solution Overview
Problem
Silicon (Si) anode materials in lithium ion batteries face severe pulverization and shedding due to volumetric expansion during charge-discharge cycles, leading to reduced electrical conductivity and limited capacity, which existing methods like graphite coating or reduced loading density cannot effectively address.
Innovation Solution
A Si/Cu composite electrode with a porous structure is created through metallurgical bonding with a current collector using a method involving intensive mixing of Si, Cu, and Al powders, followed by sintering, diffusion welding, and chemical etching to form a porous Si/Cu composite electrode, where Si particles are embedded within a continuous porous Cu structure, acting as both a binder and conductive agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si loading density is increased to improve capacity, then total capacity increases, but pulverization and shedding worsen due to volumetric expansion
Solution Approach 1:
The patent employs a porous Cu matrix structure with controlled porosity (40-70%) that provides expansion space for Si particles during lithiation. The porous structure allows volumetric changes without causing pulverization, while maintaining electrical conductivity and mechanical integrity of the electrode.
Solution Approach 2:
The patent creates a composite structure where Si particles are embedded within a Cu matrix. This composite design combines the high capacity of Si with the structural stability and conductivity of Cu, preventing shedding while maintaining high Si loading density (up to 8.5 mg/cm²).
2Reliability
If graphite coating is applied to prevent pulverization, then electrode stability improves, but mass loading capacity of Si decreases
Solution Approach 1:
The patent removes the traditional graphite coating layer and replaces it with a Cu matrix structure that provides mechanical support and conductivity functions. This extraction of the graphite coating eliminates the barrier between Si and electrolyte while preventing pulverization through the Cu matrix's structural properties.
Solution Approach 2:
The patent changes the protective layer material from graphite to Cu, altering the protective mechanism from coating-based to matrix-based protection. This parameter change allows direct contact between Si and electrolyte for high capacity while Cu provides structural stability.
3Reliability
If Si loading density is reduced to prevent shedding, then electrode stability improves, but total capacity decreases
Solution Approach 1:
The Cu matrix performs multiple functions simultaneously: it provides mechanical support to prevent pulverization, maintains electrical conductivity, enables high Si loading density, and facilitates electron transmission. This multi-functionality allows high capacity without sacrificing stability.
4Reliability
If conventional coating methods are used, then pulverization is reduced, but electron transmission efficiency decreases due to additional layers
Solution Approach 1:
The patent merges the protective function and conductivity function into a single Cu matrix structure, eliminating the need for separate coating layers. The Cu matrix directly contacts Si particles and provides both mechanical protection and electrical conductivity pathways, reducing interfacial resistance.
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
This approach enhances the electrochemical performance by preventing pulverization, improving electron transmission, and increasing the reaction efficiency between Si and the electrolyte, resulting in higher capacity and cycle stability under high mass loading conditions.
Implementation Method 1
a stress caused by inhomogeneous volumetric expansion of Si (volume change can reach 270%)
Implementation Method 2
The pores inside the material can well accommodate the volume expansion of Si
Implementation Method 3
The surface of the material is covered by a C layer through a chemical vapor deposition method, and then the anode material is coated on the surface of a current collector by adding a conductive agent and a binder
Implementation Method 4
a current collector in metallurgical bonding with the bulk porous metal
Data Source
AI summary
The present disclosure discloses a porous structure Si/Cu composite electrode of a lithium ion battery and a preparation method thereof. The composite electrode comprises an active substance, a bulk porous Cu and a current collector, wherein the active substance Si is embedded into the bulk porous Cu, and the bulk porous Cu is in metallurgical bonding with the current collector and plays a dual role of “binder” and “conductive agent”, which not only relieves the pulverization and the shedding of the active substance Si particles but also improves electron transmission efficiency; and meanwhile, the porous structure increases the contact area between the active substance Si and electrolyte and increases the reaction efficiency of lithium insertion combination. The method of preparing the composite electrode comprises: with Si, Cu and Al powders as raw materials, preparing a Si—Cu—Al precursor alloy on the Cu current collector by powder metallurgy and diffusion welding technology; and removing Al element in the Si—Cu—Al precursor alloy by using a chemical de-alloying method to obtain a Si/Cu composite electrode with a porous-structure.