Silicon Anode Fluoride Additive Stress Relaxation
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Solution Overview
Problem
Lithium ion secondary batteries with graphite anodes face limitations in capacity due to the expansion and shrinkage of the anode active material layer during charge and discharge, leading to reduced cycle characteristics and potential battery swelling.
Innovation Solution
Incorporating a fluoride of an alkali metal or alkali earth metal into the anode active material layer, along with oxygen and specific metal elements like iron, cobalt, or nickel, to prevent expansion and improve contact characteristics between the anode active material layer and the current collector, thereby enhancing cycle life and preventing battery swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used for the anode active material layer to increase battery capacity, then the battery capacity is improved, but the anode active material layer is intensely expanded and shrunk during charge and discharge, leading to pulverization and reduced cycle characteristics
Solution Approach 1:
The invention changes the chemical composition parameters of the anode active material layer by incorporating fluorides of alkali metals or alkaline earth metals along with silicon and oxygen. This compositional modification allows the material to achieve high capacity while maintaining structural stability during charge-discharge cycles, preventing pulverization and improving cycle characteristics.
Solution Approach 2:
The invention creates a composite anode active material layer combining silicon, fluoride compounds, and oxygen-containing compounds. This composite structure leverages the high capacity of silicon while the fluoride and oxygen components provide structural stability and prevent excessive expansion, resolving the contradiction between capacity and cycle life.
2Quantity of substance
If the anode active material layer is greatly expanded during charge and discharge, then the battery capacity is improved, but the battery becomes swollen and the anode active material layer separates from the current collector
Solution Approach 1:
By modifying the chemical composition to include fluorides and oxygen-containing compounds, the invention changes the expansion characteristics of the anode material. This allows the material to accommodate lithium ions effectively while maintaining dimensional stability, preventing battery swelling and maintaining good contact with the current collector during cycling.
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 use of fluorides and oxygen in the anode active material layer relaxes internal stress, prevents separation from the current collector, and promotes the formation of a protective coat, resulting in improved battery characteristics such as increased capacity retention and reduced swelling.
Implementation Method 1
the anode active material layer therein contains at least one selected from the group consisting of a fluoride of an alkali metal and a fluoride of an alkali earth metal... expansion of the anode active material layer is prevented to relax the internal stress
Implementation Method 2
formation of coat is promoted by the fluoride contained in the anode active material layer, and formation of new coat due to deposition is prevented
Data Source
AI summary
An anode capable of preventing expansion of an anode active material layer and a battery using it are provided. The anode includes an anode current collector, and an anode active material layer containing silicon (Si) as an element, wherein the anode active material layer therein contains at least one selected from the group consisting of a fluoride of an alkali metal and a fluoride of an alkali earth metal.