Artificial SEI Cathode Material for Lithium Battery ESR Reduction
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Solution Overview
Problem
Conventional lithium-ion batteries suffer from irreversible capacity loss due to solvent decomposition and passive film formation on the cathode surface, leading to high impedance and reduced battery efficiency.
Innovation Solution
An artificial SEI cathode material is developed, comprising a conductive polymer/carbon composite encapsulating the cathode material, which forms a stable solid electrolyte interface (SEI) around the cathode, reducing equivalent series resistance (ESR) and enhancing electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cathode material is used without artificial SEI coating, then the battery structure is simple and manufacturing is easier, but irreversible capacity loss occurs due to solvent decomposition and passive film formation, leading to high impedance and reduced battery efficiency
Solution Approach 1:
The conductive polymer/carbon composite is applied to the cathode material surface before battery operation to preemptively form a protective artificial SEI layer. This preliminary coating prevents solvent decomposition and passive film formation during initial charging cycles, eliminating the harmful effects that would otherwise occur naturally during battery operation.
Solution Approach 2:
The invention converts the naturally occurring harmful passive film formation into a beneficial protective layer by using conductive polymer/carbon composite to create an artificial SEI that performs the protective function while maintaining electrical conductivity. The harmful effect of surface passivation is transformed into a beneficial stable interface that reduces impedance.
2Reliability
If conductive polymer/carbon composite is applied to form artificial SEI, then ESR is reduced and electrochemical properties are enhanced, but the amount of additional material increases device complexity
Solution Approach 1:
The invention optimizes the composition parameters of the conductive polymer/carbon composite, specifically maintaining carbon material content at no more than 25% by weight of the composite and the composite itself at no more than 5% by weight of the total cathode material. These parameter optimizations achieve the desired electrochemical performance while minimizing the amount of additional material required.
Solution Approach 2:
The invention uses a composite material system combining conductive polymer and carbon material in specific ratios to achieve synergistic effects. The conductive polymer provides the SEI-forming capability while the carbon material enhances conductivity, creating a composite that delivers superior electrochemical performance with minimal loading.
3Reliability
If high carbon material content is used in conductive polymer/carbon composite, then electrical conductivity is improved, but the weight percentage exceeds the optimal range for effective SEI formation
Solution Approach 1:
The invention precisely controls the carbon material content parameter within the range of no more than 25% by weight of the conductive polymer/carbon composite and no more than 5% by weight of the total cathode material. This parameter optimization balances electrical conductivity requirements with the need to maintain effective SEI formation characteristics.
Solution Approach 2:
The invention applies different material compositions to different functional requirements: the conductive polymer component provides SEI formation capability while the carbon material component (at controlled low concentrations) provides localized conductivity enhancement. This local quality differentiation optimizes both conductivity and SEI formation without requiring high overall carbon content.
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 artificial SEI cathode material significantly reduces ESR, improves discharge capacity, and extends cycle lifetime, enabling faster charging and discharging while maintaining high capacity retention over multiple cycles.
Implementation Method 1
a conductive polymer/carbon composite encapsulating the cathode material and forming a solid electrolyte interface (SEI) around the cathode
Implementation Method 2
improved electrochemical properties such as a low ESR
Implementation Method 3
materials in which lithium intercalation/de-intercalation reversibly occurs as the cathode and anode active materials
Implementation Method 4
The batteries produce and store electric energy by a redox reaction when the lithium ions are intercalated into and de-intercalated from the cathode electrode and the anode electrode
Data Source
Figure 1A~1B
Figure 2
Figure 3(A)~3(B)
AI summary
Disclosed herein is an artificial solid electrolyte interface (SEI) cathode material for use in a rechargeable battery, particularly a lithium battery. The artificial SEI cathode material includes in its structure, a cathode material, and a conductive polymer/carbon composite encapsulating the cathode material for forming an artificial solid electrolyte interface (SEI) around the cathode in the secondary battery, in which the conductive polymer/carbon composite is no more than 5％by weight of that of the artificial cathode material. Also provided herein is a lithium secondary battery including a cathode formed from the artificial SEI cathode material that renders the lithium secondary battery a reduced level of equivalent series resistance (ESR), an enhanced level of capacitance, and a long cycle life-time.