Conductive Polymer-Coated Anodes for Low-Swelling Li-Ion Batteries
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Solution Overview
Problem
Secondary batteries experience volume expansion of the negative electrode active material, which affects their safety performance and electrochemical performance, including cycle life and capacity characteristics.
Innovation Solution
A composite negative electrode active material is developed with a conductive polymer layer on the surface of the negative electrode active material substrate, featuring specific cyclic voltammetry peaks, which provides flexibility and protects the substrate from direct contact with the electrolyte, sharing lithium storage current and reducing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a negative electrode active material substrate is used to achieve high capacity per gram, then the energy density is improved, but the volume expansion increases during charging and discharging
Solution Approach 1:
A conductive polymer coating layer is applied on the surface of the negative electrode active material substrate. This thin film layer accommodates volume changes during lithium ion intercalation and deintercalation, preventing cracking and maintaining structural integrity while allowing high capacity operation.
Solution Approach 2:
The invention creates a composite structure combining the negative electrode active material substrate with a conductive polymer coating layer. This composite material leverages the high capacity of the substrate while the polymer layer provides structural stability and reduces volume expansion effects.
2Quantity of substance
If the negative electrode active material undergoes volume expansion during charging and discharging, then the capacity per gram is maintained, but the cycle life is reduced
Solution Approach 1:
The conductive polymer coating layer is applied beforehand to cushion and accommodate volume expansion during subsequent charging and discharging cycles. This pre-applied protective layer prevents structural degradation and maintains capacity over extended cycling.
Solution Approach 2:
The flexible polymer coating layer dynamically expands and contracts with the substrate during cycling, maintaining continuous coverage and protection. This flexibility prevents cracking that would otherwise lead to capacity fade and reduced cycle life.
3Duration of action of stationary object
If a conductive polymer layer is coated on the negative electrode active material substrate to reduce volume expansion, then the cycle life is improved, but the initial coulombic efficiency decreases
Solution Approach 1:
The invention optimizes parameters including polymer layer thickness (5-50 nm), polymer-to-substrate mass ratio (1:95 to 10:90), and polymer molecular weight (10,000-1,000,000 g/mol) to balance protection benefits against initial efficiency losses.
Solution Approach 2:
The polymer coating is applied as a thin, uniform layer only on the surface of the substrate, providing localized protection where volume expansion occurs most intensely, while minimizing the overall mass of inactive material to preserve coulombic efficiency.
4Quantity of substance
If the negative electrode active material is used to achieve high energy density, then the capacity characteristics are improved, but the volume expansion affects safety performance
Solution Approach 1:
The conductive polymer coating acts as a flexible constraint layer that limits uncontrolled volume expansion of the high-capacity substrate. This prevents mechanical failure and safety issues while maintaining the energy density benefits of the active material.
Solution Approach 2:
The composite structure combines the high-energy-density substrate with the mechanically stable polymer matrix, creating a material that delivers high capacity while the polymer phase suppresses harmful volume expansion effects that would compromise safety.
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 composite material achieves low volume expansion, high capacity per gram, and high initial coulombic efficiency, resulting in a secondary battery with high energy density and long cycle life.
Implementation Method 1
the cyclic voltammetry curve of the composite negative electrode active material has an oxidation peak within a range of 3.2 V-3.6 V
Implementation Method 2
a reduction peak within a range of 2.1 V-2.6 V
Implementation Method 3
lithium ions are intercalated into and de-intercalated from an electrode active material
Data Source
AI summary
The present application provides a composite negative electrode active material and a preparation method therefor, a negative electrode plate comprising same, a secondary battery and a power consuming device. The composite negative electrode active material comprises a negative electrode active material substrate and a conductive polymer layer on the surface of the negative electrode active material substrate, wherein the cyclic voltammetry curve of the composite negative electrode active material has an oxidation peak within a range of 3.2 V-3.6 V and a reduction peak within a range of 2.1 V-2.6 V. The composite negative electrode active material provided by the present application can combine a low volume expansion, a high capacity per gram and a high initial coulombic efficiency, thus enabling a secondary battery to combine a low volume expansion, a high energy density and a long cycle life.