Si-B-C Anode Material for High Capacity Batteries
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Solution Overview
Problem
Current secondary batteries with carbon-based anode active materials face limitations in achieving high capacity and superior cycle characteristics due to low energy density and poor hysteresis in charge and discharge cycles, while alloy materials like Si suffer from poor cycle characteristics due to expansion and pulverization during charge and discharge.
Innovation Solution
An anode active material containing silicon, boron, carbon, and one or more metal elements (cobalt, titanium, or iron) with specific mass percentage ranges, along with a reaction phase having a half-width diffraction peak of 1 degree or more, is used to enhance capacity and cycle characteristics by improving reactivity with electrode reactants and reducing electrolyte reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy materials like Si are used as anode active material, then capacity is improved, but cycle characteristics deteriorate due to expansion and pulverization
Solution Approach 1:
The patent uses a composite material system consisting of Si-B-C alloy particles combined with a specific binder material. This composite structure allows the Si-B-C alloy to provide high capacity while the binder material suppresses expansion and prevents pulverization during charge-discharge cycles, thereby maintaining good cycle characteristics
Solution Approach 2:
The patent optimizes the composition parameters of the Si-B-C alloy by controlling the Si content at 70-95 mass% and B content at 4.9-19.8 mass%, along with specific C content ranges. This parameter optimization ensures high capacity while maintaining structural stability to prevent pulverization and maintain cycle characteristics
2Reliability
If carbon material is used as anode active material, then cycle characteristics are favorable, but energy density is limited due to low capacity
Solution Approach 1:
The patent creates a composite anode system combining Si-B-C alloy particles with binder material. The Si-B-C alloy provides high capacity (overcoming carbon material limitations) while the binder material ensures structural integrity and favorable cycle characteristics, achieving both high capacity and good cycle performance simultaneously
3Quantity of substance
If Li-Al alloy or Sn alloy is used as anode active material, then capacity is improved, but cycle characteristics deteriorate due to pulverization
Solution Approach 1:
The patent employs a composite structure of Si-B-C alloy particles with binder material. This composite design provides high capacity from the alloy component while the binder material suppresses expansion and prevents pulverization, ensuring good cycle characteristics comparable to or better than Li-Al or Sn alloys
Solution Approach 2:
The patent optimizes the Si content at 70-95 mass% and B content at 4.9-19.8 mass% in the alloy, along with controlled C content. This parameter optimization achieves high capacity while maintaining structural stability to prevent pulverization, overcoming the cycle characteristic problems of Li-Al or Sn alloys
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 proposed anode active material achieves high capacity and superior cycle characteristics by optimizing the mass percentages of silicon, boron, carbon, and metal elements, ensuring smooth insertion and extraction of electrode reactants and reducing electrolyte reactivity, thereby improving battery performance.
Implementation Method 1
an anode active material which contains silicon, boron, carbon, and one or more of metal elements selected from the group consisting of cobalt, titanium and iron, as an element
Implementation Method 2
a reaction phase whose half-width of a diffraction peak obtained by X-ray diffraction is 1 degree or more is included
Data Source
AI summary
A secondary battery includes a cathode, an anode, and an electrolyte. The anode includes an anode active material containing silicon, boron, carbon, and one or more of metal elements selected from the group consisting of cobalt, titanium and iron. In the anode active material, a boron content is from 4.9 mass % to 19.8 mass % both inclusive, a carbon content is from 4.9 mass % to 19.8 mass % both inclusive, a total of the boron content and the carbon content is from 9.8 mass % to 29.8 mass % both inclusive, a ratio of a silicon content to the total of the silicon content and a content of the metal element is from 70 mass % to 95 mass % both inclusive. A reaction phase whose half-width of a diffraction peak obtained by X-ray diffraction is 1 degree or more is included and the anode active material is capable of reacting with an electrode reactant.