Cathode Surface Treatment to Reduce Resistance and Gas Evolution
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Solution Overview
Problem
Lithium ion batteries face issues with capacity fade and gas evolution due to cell resistance increase, primarily caused by electrolyte decomposition, which leads to hazardous by-products and reduced cycling behavior.
Innovation Solution
A process involving the treatment of cathode active materials with oligomers bearing specific units, followed by application to a current collector and partial removal of solvent, to enhance cycling behavior and reduce capacity fade without forming hazardous by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cathode active materials are used without surface treatment, then the battery can be manufactured simply, but capacity fade and gas evolution occur due to cell resistance increase
Solution Approach 1:
The cathode active material is pre-treated with organometallic compounds before battery assembly. This preliminary surface treatment modifies the cathode material to reduce electrolyte decomposition and gas evolution during subsequent cycling, thereby improving reliability without adding operational complexity
Solution Approach 2:
Organometallic compounds are introduced as intermediary substances that form a protective interface between the cathode active material and the electrolyte. This intermediary layer prevents direct harmful interactions, reducing cell resistance increase and improving cycling behavior
2Reliability
If halosilanes are used for surface treatment, then cycling behavior improves, but hazardous by-products are formed due to halide oxidation or reduction
Solution Approach 1:
The halide component is extracted/removed from the surface treatment compound. Instead of using halosilanes, the invention employs organometallic compounds without halide leaving groups, thereby eliminating the source of hazardous by-products while maintaining the beneficial surface modification effects
Solution Approach 2:
The invention converts the potentially harmful halide-based surface treatment into a beneficial halide-free alternative. By using organometallic compounds without halides, the harmful oxidation or reduction reactions are prevented, transforming a harmful process into a safe and effective surface treatment
Data Source
AI summary
Process for making a cathode comprising the following steps (a) Providing a cathode active material selected from layered lithium transition metal oxides, lithiated spinels, lithium transition metal phosphate with olivine structure, and lithium nickel-cobalt aluminum oxides, (b) treating said cathode active material with an oligomer bearing units according to general formula (I a), wherein R1 are the same or different and selected from hydrogen and C1-C4-alkyl, aryl, and C4- C7-cycloalkyl, R2 and R3 are selected independently at each occurrence from phenyl and C1-C8-alkyl, C4-C7-cycloalkyl, C1-C8-haloalkyl, OPR1(0)-*, and -(CR9 2)P-Si(R2)2-* wherein one or more non-vicinal CR9 2 groups may be replaced by oxygen, R9 is selected independently at each occurrence from H and C1-C4-alkyl, and p is a variable from zero to 6, and wherein the overall majority of R2 and R3 is selected from C1-C8-alkyl, and, optionally, at least one of carbon in electrically conductive form and, optionally, a binder, c) applying a slurry of said treated cathode active material to a current collector, and d) at least partially removing solvent used in step (c).