Polymer-Coated Graphite Anode for Low Solvent Co-Intercalation
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Solution Overview
Problem
Existing graphite-based negative electrode materials in lithium-ion batteries suffer from poor compatibility with electrolyte solutions, leading to irreversible consumption of lithium ions and low initial coulombic efficiency due to co-intercalation of electrolyte solvents and lithium ions, which affects the electrochemical performance.
Innovation Solution
A negative electrode material with a specific polymer coating layer that forms a protective layer containing Li3N during lithium intercalation, reducing side reactions and improving ionic conductivity, while a moderate polymerization degree and chemical bonding enhance the bonding force between the coating and the graphite core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite negative electrode materials are used, then good conductivity and low cost are achieved, but poor compatibility with electrolyte solutions causes co-intercalation of electrolyte solvents and lithium ions, resulting in irreversible consumption of lithium ions and low initial coulombic efficiency
Solution Approach 1:
A polymer coating layer is introduced as an intermediary between the graphite negative electrode material and the electrolyte solution. This coating layer prevents direct contact between the electrolyte and graphite surface, thereby blocking the harmful co-intercalation of electrolyte solvents and lithium ions into the graphite layers, while still allowing lithium ion insertion/extraction. The polymer coating acts as a protective mediator that resolves the compatibility issue between graphite and electrolyte.
Solution Approach 2:
The negative electrode is constructed as a composite material system consisting of a polymer coating layer combined with graphite particles. The polymer component provides protection against electrolyte co-intercalation, while the graphite component maintains good conductivity and lithium ion intercalation capability. This composite structure combines the advantages of both materials to achieve high initial coulombic efficiency while retaining graphite's beneficial properties.
2Reliability
If a polymer coating layer is formed on graphite, then compatibility with electrolyte solution improves and initial coulombic efficiency increases, but the complexity of material preparation increases
Solution Approach 1:
The polymer coating layer is formed on the graphite particles before assembly into the battery electrode structure. This preliminary coating action ensures that the graphite particles are pre-protected against electrolyte co-intercalation, and the coating is applied uniformly to all particles before they are mixed with other electrode components, simplifying the overall preparation process.
Solution Approach 2:
The polymer coating layer is designed to automatically form a protective structure that self-regulates lithium ion insertion. The coating material inherently provides the necessary protection against electrolyte co-intercalation while allowing lithium ion transport, eliminating the need for additional complex control mechanisms or post-treatment steps to achieve the desired performance.
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 polymer-coated graphite core reduces lithium ion consumption and enhances the initial coulombic efficiency and cycle performance of the battery by minimizing interface reactions and improving ionic conductivity.
Implementation Method 1
the polymer in the coating layer preferentially undergoes a reduction reaction with an electrolyte solution component, and the C—N bond is broken and further forms compound Li3N
Implementation Method 2
the unsaturated bond undergoes a self-polymerization reaction to form a polymer network
Implementation Method 3
the carboxyl group and other functional groups are capable of undergoing a dehydration reaction with a hydroxy group and other groups on a surface of the graphite to form chemical bonds
Data Source
AI summary
A negative electrode material, a negative electrode plate and a secondary battery are provided. The negative electrode material includes an inner core and a coating layer arranged on at least a part of a surface of the inner core, the coating layer includes a polymer, an infrared spectrum of the negative electrode material has a first characteristic peak, a second characteristic peak and a third characteristic peak in a wave number range of 1320±10 cm−1 to 1880±10 cm−1, a peak area ratio of the first characteristic peak to the third characteristic peak is Z, and the Z is 0.35 to 0.8.