Secondary Battery Safety Coating for Lithium Dendrite Suppression
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Solution Overview
Problem
Lithium dendrite growth during charge-and-discharge cycles in secondary batteries reduces energy density, cycle performance, and safety, posing a significant challenge for their widespread application in mobile devices and electric vehicles.
Innovation Solution
A secondary battery design incorporating a negative electrode plate and separator with a safety coating, where the charge and discharge capacity ratios of the electrodes are optimized (0.45≤Nc/Pc<1 and 0.45≤Nd/Pd<1), and the safety coating is applied to the negative electrode plate or separator, reducing lithium dendrite formation and enhancing energy density and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the energy density of the secondary battery is increased, then the cycle performance and safety performance deteriorate due to lithium dendrite growth
Solution Approach 1:
A safety coating layer is introduced as an intermediary between the negative electrode plate and the separator. This coating layer acts as a mediator that suppresses lithium dendrite growth while allowing lithium ion transport, thereby resolving the contradiction between increasing energy density and maintaining cycle/safety performance
Solution Approach 2:
The charge capacity ratio of the negative electrode to positive electrode is optimized to 0.45≤Nc/Pc<1, which changes the electrochemical parameters of the battery system. This parameter adjustment prevents excessive lithium ion deposition on the negative electrode, thereby suppressing dendrite formation while maintaining high energy density
2Use of energy by moving object
If the charge capacity ratio Nc/Pc is increased to improve energy density, then lithium dendrite formation increases and safety performance deteriorates
Solution Approach 1:
The safety coating is applied preliminarily to the negative electrode plate or separator before battery operation. This preliminary protective layer prevents lithium dendrites from forming and penetrating into the separator, countering the harmful effect before it can occur
Solution Approach 2:
The safety coating serves as an intermediary layer that modifies the interface between the negative electrode and electrolyte/separator. It mediates lithium ion deposition behavior, promoting uniform plating and preventing dendrite formation even at high charge capacity ratios
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 increases energy density while maintaining good cycle and safety performance by reducing lithium dendrite growth, thereby improving the battery's performance and longevity.
Implementation Method 1
the safety coating is disposed on a surface of the negative film layer. In this way, formed lithium dendrites are reduced effectively, and the probability of the lithium dendrites piercing the separator and directly contacting the positive electrode plate is also reduced
Implementation Method 2
a separator located between the negative electrode plate and the positive electrode plate
Data Source
AI summary
A secondary battery, a battery module, a battery pack, and an electrical device are provided. The secondary battery includes a negative electrode plate, a positive electrode plate, and a separator located between the negative electrode plate and the positive electrode plate. The negative electrode plate or the separator includes a safety coating. A negative electrode charge capacity Nc and a positive electrode charge capacity Pc of the secondary battery satisfy: 0.45≤Nc/Pc<1, and/or, a negative electrode discharge capacity Nd and a positive electrode discharge capacity Pd of the secondary battery satisfy: 0.45≤Nd/Pd<1. By setting the values of Nc/Pc and/or Nd/Pd and disposing the safety coating in the secondary battery, this application achieves good cycle performance and safety performance while maintaining a high energy density of the secondary battery.