SiO2 Nano-Composite Negative Material for Lithium Battery
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Solution Overview
Problem
Lithium rechargeable batteries face limitations in initial capacity, efficiency, and cycle-life due to irreversible reactions and mechanical deterioration of carbon-based and metal-based negative active materials.
Innovation Solution
A nano-composite material comprising a Si phase, a SiO2 phase, and a metal oxide phase with a specific formulation is developed, where the metal oxide has a negative Gibbs free energy, formed through mechanical alloying of SiO and a metal source material, to suppress initial irreversible reactions and enhance battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If graphite is used as negative active material, then discharge voltage and energy density are improved, but initial capacity and cycle-life are deteriorated due to low density and irreversible reactions
Solution Approach 1:
The patent uses a composite material consisting of SiO2 particles coated with a silane coupling agent and dispersed in a polymer matrix. This composite structure combines the high capacity of SiO2 with the stability and conductivity benefits of the silane coupling agent coating and polymer matrix, resolving the contradiction between achieving high discharge voltage/energy density and maintaining cycle-life reliability.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the negative active material by controlling the particle size, surface treatment with silane coupling agent, and polymer matrix composition. These parameter changes improve both the initial capacity and cycle-life characteristics while maintaining high discharge voltage, addressing the technical contradiction.
2Quantity of substance
If amorphous tin oxide is used as negative active material, then capacity per weight is improved, but initial irreversible capacity increases and material stability is deteriorated
Solution Approach 1:
The patent employs a composite structure where SiO2 particles are coated with silane coupling agent and embedded in a polymer matrix. This composite approach maintains high capacity per weight while the coating and matrix structure prevents material degradation and reduction to metal during charge-discharge cycles, resolving the stability issue.
Solution Approach 2:
The patent uses SiO2 as a stable, non-reducing material that maintains its composition throughout battery cycling, replacing materials like tin oxide that degrade over time. This ensures long-term material stability while maintaining high capacity characteristics.
3Reliability
If graphite is used as negative active material, then reversibility is improved, but energy density per unit volume is deteriorated due to low density
Solution Approach 1:
The patent creates a composite material where SiO2 particles provide high density and capacity, the silane coupling agent coating ensures good electrical conductivity and reversible lithium insertion/extraction, and the polymer matrix provides structural stability. This composite structure achieves both high energy density per unit volume and excellent reversibility.
Solution Approach 2:
The patent applies different functional properties to different parts of the composite material: SiO2 particles provide high density and capacity in the core, while the silane coupling agent coating provides conductivity and reversibility at the surface interface, and the polymer matrix provides structural support. This local quality differentiation resolves the contradiction between density and reversibility.
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 nano-composite material improves initial capacity, efficiency, and cycle-life characteristics by stabilizing the reaction with lithium, reducing volume expansion, and maintaining rate capability, while surface treatment with conductive materials further enhances electrical conductivity and battery performance.
Implementation Method 1
a metal oxide phase of the formulation MyO, where M is a metal with an oxidation number of x, a free energy of oxygen bond formation ranging from −900 kJ/mol to −2000 kJ/mol
Implementation Method 2
mechanically alloying a SiO source material and a metal (M) source material (where M has a free energy of oxygen bond formation ranging from −900 kJ/mol to −2000 kJ/mol) to obtain a nano-composite
Data Source
AI summary
An negative active material for a rechargeable lithium battery includes a nano-composite including a Si phase, a SiO2 phase, and a metal oxide phase of formulation MyO, where M is a metal with an oxidation number x, a free energy of oxygen-bond formation ranging from −900 kJ/mol to −2000 kJ/mol, x, and x·y=2. The negative active material for a rechargeable lithium battery according to the present invention can improve initial capacity, initial efficiency, and cycle-life characteristics by suppressing its initial irreversible reaction.