Silicon-Based Negative Electrode with Sacrificial Positive Material
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Solution Overview
Problem
Lithium rechargeable batteries face challenges with low energy density and cycle life due to the use of graphite as a negative active material, which reacts with organic electrolytes and results in capacity loss and efficiency deterioration when used alone, and existing oxide materials do not adequately address these issues.
Innovation Solution
Incorporating a silicon-based negative active material and a sacrificial positive active material, such as lithium nickel oxides or lithium molybdenum oxides, in specific weight percentages, along with a non-aqueous electrolyte containing a lithium salt and organic solvent, to balance capacity and efficiency and improve cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as a negative active material, then the battery has high discharge voltage and excellent reversibility, but the battery exhibits low energy density per unit volume and capacity loss due to reaction with organic electrolyte
Solution Approach 1:
The patent employs a composite negative electrode structure combining graphite particles with void spaces filled by oxide material. This composite architecture allows graphite to provide reversibility while the oxide material increases volumetric capacity, achieving both high energy density and good cycle life through synergistic material combination
2Power
If graphite is used as a negative active material, then the battery has high discharge voltage, but the battery swells and capacity decreases due to reaction with organic electrolyte at high discharge voltage
Solution Approach 1:
The negative electrode is segmented into distinct functional zones: graphite particles providing voltage stability, void spaces accommodating volume changes, and oxide material enhancing capacity. This segmentation allows each component to address specific issues without compromising overall battery reliability
3Quantity of substance
If oxide negative active material is used to replace graphite, then the density and capacity in terms of energy density per unit volume may be improved, but sufficient cell performance is not realized
Solution Approach 1:
The patent merges the advantages of graphite (high discharge voltage and reversibility) with oxide materials (high density and volumetric capacity) in a unified electrode structure. The composite design ensures that oxide material improves energy density while graphite maintains cell performance and stability
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 combination of silicon-based and sacrificial positive active materials enhances the capacity and cycle-life of lithium rechargeable batteries while minimizing capacity loss and efficiency deterioration, achieving improved performance without significant volume expansion issues.
Implementation Method 1
The sacrificial positive active material may be adapted to deintercalate Li ions at a voltage from about 2.75 to about 4.3V
Implementation Method 2
a non-aqueous electrolyte may include a lithium salt and a non-aqueous organic solvent
Data Source
AI summary
A rechargeable lithium battery including a negative electrode including a silicon-based negative active material; a positive electrode including a positive active material including a sacrificial positive active material selected from lithium nickel oxides, lithium molybdenum oxides, and combinations thereof; and a non-aqueous electrolyte, is disclosed.