Silicon-Anode Lithium Battery Cathode Mix for Crack and Gas Control
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Solution Overview
Problem
Lithium secondary batteries using silicon-based negative electrodes face issues with resistance, cracking, and gas generation due to high voltage exposure, especially when using single-particle positive electrode active materials alone, which affect capacity and cycle characteristics.
Innovation Solution
A lithium secondary battery design incorporating a mixture of secondary particle and single-particle positive electrode active materials, with optimized weight ratios and composition, including a silicon-based negative electrode and a positive electrode active material layer with specific content ratios, to address these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode is used to increase capacity, then energy density is improved, but resistance and cracking occur due to volume expansion
Solution Approach 1:
The patent applies the nesting principle by placing silicon-based active material particles inside a porous carbonaceous material shell, forming a core-shell structure. The silicon core provides high capacity while the carbonaceous shell accommodates volume expansion and prevents cracking, effectively nesting the problematic material within a protective structure.
Solution Approach 2:
The patent uses a porous carbonaceous material shell as a flexible container that can accommodate the volume expansion of silicon during lithium insertion. The shell acts as a buffer that flexes with the silicon core, preventing structural failure and maintaining electrical conductivity throughout charge-discharge cycles.
2Quantity of substance
If single-particle positive electrode active material is used alone, then capacity is improved, but gas generation increases due to high voltage exposure
Solution Approach 1:
The patent applies composite materials by combining single-particle positive electrode active material with porous carbonaceous material. This composite structure allows the single-particle material to provide high capacity while the carbonaceous component suppresses gas generation, creating a material system where the harmful effects of one component are mitigated by the other.
Solution Approach 2:
The porous carbonaceous material acts as an intermediary between the single-particle positive electrode active material and the electrolyte, mediating the high voltage exposure. The carbonaceous layer provides a buffer that reduces direct high-voltage stress on the active material, thereby suppressing gas generation while maintaining electrochemical performance.
3Speed
If thin film negative electrode active material layer is formed to reduce diffusion distance, then charging rate is improved, but conductivity decreases
Solution Approach 1:
The patent uses porous carbonaceous material that provides a three-dimensional conductive network within the thin film structure. The porous structure maintains short diffusion paths for lithium ions while the carbonaceous material ensures adequate electrical conductivity throughout the electrode, solving the conductivity problem inherent in thin film designs.
Solution Approach 2:
The patent applies local quality by creating regions of different properties within the thin film electrode. The porous carbonaceous material provides localized conductivity enhancement at critical interfaces and throughout the film structure, ensuring that electron transport is maintained even where the film thickness minimizes ion diffusion distance.
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 battery achieves high capacity, energy density, and rapid charging performance while reducing resistance and cracking, and minimizing gas generation, thereby enhancing overall battery performance.
Implementation Method 1
The negative electrode includes a negative electrode active material for intercalating and deintercalating lithium ions coming from the positive electrode
Implementation Method 2
During charging, lithium moving from the positive electrode to the negative electrode reacts with the electrolyte to form a kind of passivation film, that is, a solid electrolyte interface (SEI) on a surface of the negative electrode. The SEI inhibits migration of electrons required for the reaction of the negative electrode with the electrolyte to prevent decomposition of the electrolyte
Data Source
AI summary
The present application relates to a lithium secondary battery, including comprising: a positive electrode, a silicon-based negative electrode, a separator provided between the positive electrode and the negative electrode, and an electrolyte. In the secondary battery according to the present application, the weight ratio of the silicon-based active material and the single-particle positive electrode active material is adjusted to solve the resistance problem, the cracking in high-voltage cells, and the gas generation issues.