Positive Electrode Crack Ratio Control for Silicon Pre-Lithiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The rapid volume change of silicon-based active material particles in lithium secondary batteries during cycling leads to a decrease in battery lifetime due to excessive heat generation and ignition risks during pre-lithiation processes.
Innovation Solution
A positive electrode with a controlled crack ratio of 5.0% to 14.2% is achieved by transferring a lithium metal layer onto the positive electrode active material layer and rolling it, allowing lithium ions to intercalate into the positive electrode, thereby reducing the available region of the negative electrode and minimizing volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If lithium metal is transferred to the negative electrode for pre-lithiation, then the available region of the negative electrode is reduced and volume change is minimized, but excessive heat is generated due to alloy reaction between lithium and silicon
Solution Approach 1:
A polymer layer is introduced as an intermediary between the lithium metal layer and the silicon-based active material particle. This polymer layer allows lithium ions to be supplied to the negative electrode while preventing direct contact and alloy reaction between lithium metal and silicon, thereby reducing heat generation while maintaining the pre-lithiation effect
Solution Approach 2:
The harmful alloy reaction between lithium metal and silicon is separated by removing the direct contact interface. The polymer layer extracts the heat-generating reaction pathway while preserving the beneficial lithium ion supply function
2Duration of action of stationary object
If lithium metal is transferred to the negative electrode for pre-lithiation, then the lifetime of the battery is improved, but the possibility of ignition due to reaction between lithium and moisture increases
Solution Approach 1:
The polymer layer serves as a protective intermediary that prevents direct exposure of lithium metal to moisture in the environment. This barrier layer maintains the stability of lithium metal while allowing controlled lithium ion supply to the negative electrode, thereby extending battery lifetime without increasing ignition risk
3Productivity
If the reaction area between lithium and silicon-based active material is increased during notching and punching, then pre-lithiation effect is enhanced, but the possibility of ignition is further increased
Solution Approach 1:
The polymer layer is applied across the entire surface including notched and punched regions, ensuring that increased reaction area does not lead to increased ignition risk. The intermediary layer allows lithium ion supply to be enhanced in these high-surface-area regions while preventing direct lithium-silicon contact that would cause ignition
4Quantity of substance
If pre-lithiated silicon-based active material particles are used, then capacity is improved, but the possibility of ignition caused by pre-lithiated particles exists
Solution Approach 1:
The polymer layer remains on the surface of pre-lithiated silicon-based active material particles, allowing them to provide high capacity while the polymer barrier prevents direct exposure to moisture and environment that would cause ignition. The intermediary layer enables safe use of high-capacity pre-lithiated particles
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
This method enhances battery life by reducing ignition risks and increasing capacity without excessive heat generation, while maintaining efficient lithium utilization.
Implementation Method 1
lithium ions intercalated into the negative electrode in advance
Implementation Method 2
excessive heat is generated due to an alloy reaction between lithium and silicon
Data Source
AI summary
A positive electrode, a method of preparing the same, and a lithium secondary battery including the positive electrode are provided. The positive electrode includes a positive electrode active material layer including a positive electrode active material, wherein a crack ratio of a surface portion of the positive electrode active material layer, which is derived from Equation 1, CR=(CA)/[(PA)+(CA)], is in a range of 5.0% to 14.2%, wherein CR is a crack ratio (%), CA is an area of a crack region, PA is an area of a particle region, and the surface portion of the positive electrode active material layer refers to a region up to 20 μm in a depth direction from a surface of the positive electrode active material layer.