Electrochemical Electrode Mass Balancing for Capacity and Durability
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Solution Overview
Problem
Existing electrochemical devices face a trade-off between achieving high capacity and high durability, making it difficult to optimize both characteristics simultaneously.
Innovation Solution
The electrochemical device is designed with a specific ratio of positive to negative electrode active material masses (Mp/Mn) ranging from 1.1 to 2.5, using non-graphitizable carbon for the negative electrode and a coating film containing lithium carbonate on the negative electrode surface to enhance durability, along with a balanced ratio of electrode active materials and specific surface areas to optimize capacity and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the positive electrode active material mass is increased to achieve high capacity, then the capacity is improved, but the durability deteriorates due to electrode deterioration
Solution Approach 1:
The invention optimizes the mass ratio parameter (Mp/Mn) of positive to negative electrode active materials within the specific range of 0.8 to 2.0. This parameter optimization balances the electrochemical reactions between electrodes, preventing excessive strain on the positive electrode while achieving high capacity, thereby resolving the contradiction between capacity improvement and durability maintenance
Solution Approach 2:
The invention employs non-graphitizable carbon as the negative electrode active material, which forms a composite structure with lithium carbonate coating. This composite material approach provides both high capacity and enhanced stability, allowing the negative electrode to withstand repeated lithium ion insertion/extraction cycles without significant deterioration, thus maintaining durability while achieving high capacity
2Quantity of substance
If the positive electrode active material mass is increased to achieve high capacity, then the capacity is improved, but the resistance increases due to unbalanced electrode reactions
Solution Approach 1:
The invention optimizes the mass ratio parameter (Mp/Mn) of positive to negative electrode active materials within the specific range of 0.8 to 2.0. This parameter optimization balances the electrochemical reactions between electrodes, preventing excessive strain on the positive electrode while achieving high capacity, thereby resolving the contradiction between capacity improvement and resistance reduction
Solution Approach 2:
The invention uses non-graphitizable carbon as the negative electrode material, which copies the desirable properties of graphite (high capacity, stability) while avoiding its drawbacks (layer structure issues, dendrite formation). This material selection enables balanced electrode reactions that reduce resistance while maintaining high capacity
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 configuration achieves both high capacity and high durability by balancing electrostatic capacitance and resistance, inhibiting negative electrode deterioration and maintaining excellent electrostatic capacitance characteristics.
Implementation Method 1
the positive electrode mixture layer contains a positive electrode active material reversibly doped with an anion
Implementation Method 2
the negative electrode mixture layer contains a negative electrode active material reversibly doped with lithium ions
Implementation Method 3
a coating film containing lithium carbonate is formed on a surface of the carbon material contained in the negative electrode layer
Data Source
AI summary
An electrochemical device includes a positive electrode, a negative electrode, and an electrolyte having lithium ion conductivity. The positive electrode includes a positive current collector and a positive electrode mixture layer supported on the positive current collector. The positive electrode mixture layer contains a positive electrode active material reversibly doped with an anion. The negative electrode includes a negative current collector and a negative electrode mixture layer supported on the negative current collector. The negative electrode mixture layer contains a negative electrode active material reversibly doped with lithium ions. The negative electrode active material contains non-graphitizable carbon. A ratio Mp/Mn of a mass Mp of the positive electrode active material supported on a unit area of the positive electrode to a mass Mn of the negative electrode active material supported on a unit area of the negative electrode is in a range from 1.1 to 2.5, inclusive.