Double-Layer Silicon Anode Structure for Uniform Pre-Lithiation
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Solution Overview
Problem
Lithium secondary batteries using silicon-based compounds as negative electrode active materials face challenges such as rapid volume expansion during charging, which disrupts the conductive path and leads to capacity degradation, as well as uneven lithium ion charging and surface degradation, resulting in reduced service life.
Innovation Solution
A negative electrode for lithium secondary batteries is designed with a double layer active material structure, where the first layer consists of SiOx and the second layer includes a silicon-based and carbon-based active material mixture, with a specific pre-lithiation ratio adjusted to optimize capacity and service life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based compound is used as a negative electrode active material to increase capacity, then the discharge capacity is improved, but the volume rapidly expands during charging which disconnects the conductive path and deteriorates battery characteristics
Solution Approach 1:
A thin film coating layer is applied to the surface of the silicon-based active material particles. This coating layer acts as a protective shell that accommodates volume expansion during charging while maintaining structural integrity and preventing conductive path disconnection. The coating layer is designed to be flexible enough to handle the expansion stress while remaining thin enough to maintain high capacity.
Solution Approach 2:
The negative electrode is designed as a composite structure combining silicon-based active material with other materials that have complementary properties. This composite approach allows the electrode to benefit from the high capacity of silicon while the other materials provide structural stability and maintain conductive pathways during volume changes.
2Quantity of substance
If the proportion of silicon-based active material is increased to achieve high-density energy battery, then the capacity is improved, but pre-lithiation becomes concentrated on the surface causing heterogeneous pre-lithiation and damaging the silicon-based active material
Solution Approach 1:
The pre-lithiation process is designed to create different lithium distribution characteristics in different regions of the electrode. By controlling the pre-lithiation conditions, lithium is preferentially deposited in specific areas to compensate for expected volume expansion in those regions, rather than uniform distribution across the entire surface. This localized approach prevents heterogeneous pre-lithiation damage.
Solution Approach 2:
A controlled pre-lithiation step is performed before the main charging cycles. This preliminary action introduces a specific amount of lithium into the electrode structure in advance, creating buffer capacity that compensates for the volume expansion that will occur during subsequent charging. This preliminary lithium insertion prevents excessive stress and heterogeneous distribution during normal operation.
3Quantity of substance
If silicon-based compound is used as negative electrode active material, then the capacity characteristics are excellent, but the volume expansion during charging disconnects the conductive path
Solution Approach 1:
An intermediary coating layer is introduced between the silicon-based active material and the conductive network. This coating layer acts as a mediator that accommodates volume expansion while maintaining the conductive pathway. The coating material is selected to provide both mechanical flexibility for volume changes and electrical conductivity for maintaining the conductive path.
Solution Approach 2:
A flexible coating shell is applied to the silicon-based particles that can expand and contract with the underlying active material during charging cycles. This flexible shell maintains the structural integrity of the particle and preserves the conductive path connectivity even as the particle volume changes significantly.
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 double layer structure effectively prevents electrode surface degradation and enhances uniformity during pre-lithiation, leading to improved capacity retention and extended service life of the lithium secondary battery.
Implementation Method 1
The negative electrode includes a negative electrode active material for intercalating and deintercalating lithium ions from the positive electrode
Implementation Method 2
studies have been actively conducted on a field of electricity generation and electricity storage using an electrochemical reaction
Implementation Method 3
the volume rapidly expands during the charging process to disconnect the conductive path
Data Source
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AI summary
A negative electrode for a lithium secondary battery, a method for preparing a negative electrode for a lithium secondary battery, and a lithium secondary battery including the negative electrode. The negative electrode for a lithium secondary battery includes a negative electrode current collector layer, a first negative electrode active material layer on one surface or both surfaces of the negative electrode current collector layer, and a second negative electrode active material layer on a surface opposite to a surface of the first negative electrode active material layer facing the negative electrode current collector layer. The second negative electrode active material layer satisfies the following Equation 1: 0.5 ≤ B/A ≤ 2, wherein A is a discharge capacity of the second negative electrode active material layer, and B means a capacity of pre-lithiation lithium.