Cathode Active Material Coating for High-Voltage Li-Ion Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face challenges with side-reactions and solid electrolyte interface (SEI) film formation at high voltages, leading to reduced resistance and lifespan of positive electrode active materials.
Innovation Solution
A method involving the formation of a coating layer on lithium transition metal oxide particles using a mixture of a coating polymer and carbide, which is carbonized through heat-treatment, to enhance electrical conductivity and prevent mechanical breakage during high voltage charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high voltage charging condition (4.35 V or higher) is used to achieve higher energy density, then the energy density of the secondary battery is improved, but side-reactions with the electrolyte solution increase and solid electrolyte interface (SEI) film forms on the positive electrode active material surface, leading to resistance increase and lifespan deterioration
Solution Approach 1:
A coating layer comprising carbonized coating polymer and carbide is formed on the surface of the lithium transition metal oxide particles. This coating layer acts as an intermediary barrier between the positive electrode active material and the electrolyte solution, preventing direct contact and harmful side-reactions while allowing lithium ion intercalation and deintercalation, thus maintaining high voltage operation without excessive resistance increase or SEI film formation
Solution Approach 2:
The surface properties of the positive electrode active material are modified by coating with carbonized coating polymer and carbide. This changes the surface chemistry and morphology parameters, creating a stable interface that resists electrolyte decomposition and SEI film formation at high voltages, thereby enabling sustained high energy density operation without reliability degradation
2Reliability
If a coating layer is formed on the positive electrode active material to suppress side-reactions and SEI film formation, then the resistance and lifespan characteristics are improved, but the manufacturing process complexity increases
Solution Approach 1:
The coating process merges multiple functions into a single step: the coating polymer provides the base coating structure, while the carbide additive simultaneously contributes to conductivity enhancement and structural stability. This combined approach achieves comprehensive protection against side-reactions and SEI film formation without requiring multiple separate coating steps, thus limiting the increase in manufacturing complexity
Solution Approach 2:
The coating layer is formed as a composite material comprising carbonized coating polymer and carbide. This composite structure combines the protective properties of the polymer matrix with the conductive and structurally stable properties of the carbide particles, achieving superior performance in suppressing side-reactions and SEI film formation while maintaining a relatively simple single-step coating process
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 suppresses SEI film formation and side-reactions, improving the resistance and lifespan of the positive electrode active material, while ensuring uniform coating and reduced resistance increase.
Implementation Method 1
heat-treating the mixture to form a coating layer including a carbonized coating polymer and carbide on the surface of the lithium transition metal oxide particle
Data Source
AI summary
A positive electrode active material, a positive electrode including the same, and a lithium secondary batter including the same are disclosed herein. In some embodiments, the positive electrode active material includes a lithium transition metal oxide, and a coating layer formed on a surface of the lithium transition metal oxide particle, wherein the coating layer is formed in a film form, and the coating layer includes a carbonized coating polymer and carbide.