Silicon Oxide Carbon Negative Electrode for Battery Energy Density
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with negative electrodes composed of silicon oxide face challenges in maintaining high energy density and cycle characteristics due to volume expansion and contraction, leading to poor electrical contact and reduced charge/discharge efficiency.
Innovation Solution
A negative electrode comprising a silicon oxide (SiOx) and carbon material with a specific mass proportion (0.03≤y≤0.3) and a theoretical capacity density difference (ΔC) that ensures high initial efficiency and capacity retention, where the silicon oxide is coated with carbon to prevent reaction with lithium, thereby stabilizing the electrode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a material containing an element capable of alloying with lithium (such as Si, Sn, or Ge) is used as negative electrode active material to achieve high theoretical capacity density, then energy density is improved, but the crystal structure changes during lithium absorption causing volume expansion which leads to poor electrical contact and shorter charge/discharge cycle life
Solution Approach 1:
The patent applies the nesting principle by embedding silicon oxide particles within a porous carbon matrix structure. The carbon matrix acts as a container that accommodates the volume expansion of silicon oxide during lithium alloying, while maintaining the overall electrode structure integrity and electrical contact throughout charge/discharge cycles.
Solution Approach 2:
The patent uses composite materials by combining silicon oxide with porous carbon to create a hybrid negative electrode active material. This composite structure leverages the high capacity of silicon oxide while the carbon component provides structural stability, electrical conductivity, and accommodates volume changes, thereby resolving the contradiction between high capacity and cycle life.
2Quantity of substance
If a material containing an element capable of alloying with lithium is used to achieve high theoretical capacity density, then energy density is improved, but the material has large irreversible capacity causing low initial charge/discharge efficiency
Solution Approach 1:
The patent applies preliminary action by pre-doping lithium into the negative electrode during the manufacturing process. This pre-doping compensates for the irreversible capacity loss that occurs during the first charge cycle, ensuring that sufficient lithium is available from the beginning to achieve high initial charge/discharge efficiency while maintaining the high capacity benefits of silicon oxide.
3Quantity of substance
If silicon oxide content in the negative electrode material mixture layer is increased to improve capacity, then energy density is improved, but a buffer layer is required to suppress rapid reaction between silicon oxide and lithium which causes increase in internal resistance and reduction in energy density
Solution Approach 1:
The patent applies local quality by creating a porous carbon matrix with specific local structures that provide buffering capacity exactly where silicon oxide particles are located. The porous structure locally accommodates volume expansion and controls the reaction between silicon oxide and lithium, allowing high silicon oxide content without requiring additional buffer layers that would increase internal 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
The solution enhances the energy density and cycle characteristics of the battery while maintaining high initial charge/discharge efficiency, preventing the negative electrode from rapid capacity loss and ensuring reliable performance.
Implementation Method 1
the silicon oxide is coated with carbon to prevent reaction with lithium
Implementation Method 2
a material containing an element such as Si, Sn, or Ge capable of alloying with lithium
Data Source
AI summary
Provided is a negative electrode for a non-aqueous electrolyte secondary battery, capable of improving the energy density and the cycle characteristics of the battery without lowering the initial charge/discharge efficiency of the battery. This negative electrode includes a negative electrode active material including a silicon oxide represented by SiOx and carbon material. A proportion of a mass of the silicon oxide relative to a total mass of the silicon oxide and the carbon material: y satisfies 0.03≤y≤0.3. A difference between a theoretical capacity density of the negative electrode active material and a charge capacity density of the negative electrode active material when a cutoff voltage is 5 mV relative to lithium metal: ΔC (mAhg−1) satisfies L=ΔC/100 and 6y≤L≤12y+0.2.