Silicon Negative Electrode Polymer Carbon Composite Coating
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Solution Overview
Problem
Lithium-ion batteries face issues with low cycle performance, poor deformation resistance, and high DC resistance due to the peeling of carbon coatings from silicon-based negative electrodes during battery cycling, leading to reduced conductivity and stability.
Innovation Solution
A negative electrode material is developed with a silicon-containing matrix coated with a composite layer of carbon and polymer, where the polymer interacts with the surface active groups of the matrix to improve conductivity and stability, ensuring a uniform polymer distribution that enhances cycle performance and deformation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon coating is applied to the silicon-based particles, then the conductivity is improved, but the carbon coating peels off during battery cycling due to expansion forces
Solution Approach 1:
The patent uses a composite coating structure consisting of an inner polymer layer and an outer carbon layer. The polymer layer (e.g., polyacrylic acid, polyacrylamide) bonds to the silicon-containing matrix through surface active groups, while the carbon layer provides conductivity. This composite structure prevents carbon peeling by anchoring it to the silicon matrix via the polymer intermediate layer, resolving the contradiction between conductivity and coating stability during cycling.
Solution Approach 2:
The polymer layer acts as an intermediary between the silicon-containing matrix and the carbon coating. It chemically bonds to the silicon matrix through surface active groups (e.g., carboxyl, hydroxyl, amino groups) and physically anchors the carbon layer, preventing direct carbon-silicon contact that would lead to peeling during volume expansion. This intermediary layer resolves the contradiction by providing both adhesion and structural integrity.
2Reliability
If the polymer layer is uniformly coated on the silicon-containing matrix, then the cycle performance is improved, but the manufacturing precision is difficult to control
Solution Approach 1:
The patent controls the coating process by adjusting parameters such as polymer concentration (0.1-10 wt%), crosslinking agent amount, pH value (3-9), and treatment temperature (20-80°C). These parameter optimizations ensure uniform polymer layer formation on the silicon-containing matrix surface, achieving both good cycle performance and controllable manufacturing precision.
Solution Approach 2:
The polymer solution spontaneously and uniformly coats the silicon-containing matrix surface through adsorption onto surface active groups, without requiring complex external coating equipment. This self-coating mechanism naturally produces uniform coverage, improving both cycle performance and manufacturing consistency while simplifying the manufacturing process.
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 improved negative electrode material exhibits enhanced cycle performance, deformation resistance, and reduced DC resistance when the temperature difference between the polymer and silicon-based particles' derivative thermogravimetric curves falls within a specific range, leading to more stable and efficient lithium-ion battery operation.
Implementation Method 1
selection of polymer materials that interact with a surface active group of the silicon-containing matrix can address a peeling issue of carbon materials in cycling
Implementation Method 2
Carbon coating can significantly improve conductivity of the silicon-based particles
Implementation Method 3
Carbon-coated materials in the prior art are likely to be peeled off due to a force generated by expansion of the silicon-containing matrix in a battery cycle process
Data Source
AI summary
A negative electrode material includes silicon-based particles. The silicon-based particles include a silicon-containing matrix and a polymer layer disposed on at least a portion of a surface of the silicon-containing matrix, and the polymer layer includes a carbon material and a polymer; when a thermogravimetric analysis is conducted at a temperature ranging from 0° C. to 800° C., a derivative thermogravimetric curve of the polymer in a free state has at least one characteristic peak, a temperature at the maximum characteristic peak of the at least one characteristic peak is Ti, a derivative thermogravimetric curve of the silicon-based particles has at least one characteristic peak, a temperature at the maximum characteristic peak of the at least one characteristic peak is T2, and T1-T2 is from 1.5° C. to 20° C. A lithium-ion battery prepared from the negative active material has improved cycle performance and deformation resistance, and reduced DC resistance.