Composite Anode with Hard Carbon Coating for Lithium Dendrite Prevention
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Solution Overview
Problem
Lithium secondary batteries face challenges with lithium precipitation due to overvoltage, leading to safety issues and low energy density, as existing anode materials like graphite-based materials have limited differences in charge and discharge voltages, resulting in dendrite formation and micro short-circuits.
Innovation Solution
A lithium secondary battery anode comprising a combination of two anode active materials with different charge/discharge voltages and hardness, where the anode active material (A) with lower voltage and hardness is surface-coated with carbon, and the anode active material (B) with higher voltage and hardness is incorporated in a specific size ratio, preventing lithium precipitation and enhancing ionic and electric conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite-based material is used for anode, then Li charge/discharge is enabled, but Li dendrites are readily produced due to small voltage difference
Solution Approach 1:
The patent introduces a hard carbon material with a charge/discharge voltage of 0.2-0.5V, which is higher than the conventional graphite anode voltage of 0.05-0.2V. This parameter change in voltage creates a larger voltage difference between anode and cathode, reducing overvoltage and preventing Li dendrite formation during charging
Solution Approach 2:
The patent uses a composite anode structure consisting of hard carbon particles (0.2-0.5V) and graphite particles (0.05-0.2V). The hard carbon component prevents dendrite formation while the graphite component maintains high capacity, creating a composite material that combines the advantages of both materials
2Speed
If porosity is increased to improve Li ion mobility, then ion mobility increases, but electric contact decreases and energy density decreases
Solution Approach 1:
The patent optimizes the porosity parameter to a specific range of 20-40%, which balances Li ion mobility and electric contact. This controlled porosity allows sufficient ion transport while maintaining adequate electrical conductivity and energy density, resolving the trade-off between ion mobility and energy density
3Reliability
If graphite particles are used, then electrochemical reaction is enabled, but particles are crushed during rolling formation due to low hardness
Solution Approach 1:
The patent creates a composite anode system where hard carbon particles (with higher hardness) are combined with graphite particles. The hard carbon provides mechanical strength to withstand rolling formation pressure, while the graphite maintains excellent electrochemical Li insertion/extraction properties
Solution Approach 2:
The hard carbon material acts as a protective intermediary that absorbs mechanical stress during electrode fabrication, protecting the graphite particles from crushing while allowing the electrochemical reactions to proceed normally
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 solution effectively prevents lithium precipitation, improves ion and electric conductivity, and exhibits superior capacity and cycle characteristics by optimizing the porosity and rolling process of the anode, leading to enhanced battery performance.
Implementation Method 1
a lithium secondary battery uses lithium (Li), as can be seen from the name, and has high energy density and is light in weight... during charging, electricity is stored through transfer of Li ions from the cathode to the anode
Implementation Method 2
the hardness of the anode active material (B) is higher than that of the anode active material (A)... the anode active material (A) is surface-coated with carbon having a high hardness
Data Source
AI summary
Disclosed is an anode for secondary batteries comprising a combination of an anode active material having a relatively low charge/discharge voltage and a relatively low hardness (A) and an anode active material having a relatively high charge/discharge voltage and a relatively high hardness (B), wherein the anode active material (A) is surface-coated with carbon having a high hardness or a composite thereof, and a particle size of the anode active material (B) is smaller than a size of a space formed by the anode active materials (A) arranged in a four-coordination. The anode provides an electrode that prevents lithium precipitation caused by overvoltage, improves ionic conductivity as well as electric conductivity and exhibits superior capacity.