Li-ion Battery Cathode Composite with Glassy Coating
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Solution Overview
Problem
Cathode materials for Li-ion batteries that can be charged to high voltages are often reactive with the electrolyte, leading to accelerated capacity loss and impedance build-up, which shortens the battery's life.
Innovation Solution
A composite cathode material comprising a base active material of Li1+y(Nia—COb—Mnc—Yd)O2 coated with a glassy phase containing Li2O, B2O3, and LiX, where the coating is ion-conductive and stable at high voltages, minimizing adverse reactions with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cathode materials are charged to high voltages (>4.2V) to achieve high capacity, then the lithium removal per unit weight increases, but the cathode material becomes reactive towards the electrolyte resulting in surface reactions that damage the cathode material and consume electrolyte
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the cathode material (Li1+y(NiCoMn)O2) forms the core and a protective coating layer is applied on the surface. This composite structure allows the core to provide high capacity through high voltage charging while the coating shell protects against electrolyte reactions, resolving the contradiction between high lithium removal and material stability.
Solution Approach 2:
The protective coating layer acts as an intermediary between the cathode material and the electrolyte. This intermediate layer prevents direct contact and harmful reactions between the reactive cathode surface and the electrolyte, while still allowing lithium ion transport, thus enabling high voltage operation without sacrificing stability.
2Reliability
If a coating layer is applied to improve stability at high voltages, then the cathode material stability improves, but the coating layer may be insulating and not lithium ion conductive which negatively affects performance
Solution Approach 1:
The patent applies parameter changes by carefully controlling the composition and thickness of the coating layer. By adjusting the coating parameters (composition ratios, layer thickness), the material achieves optimal balance between stability and lithium ion conductivity, transforming the coating from a potentially insulating layer to a functional protective layer that maintains high ion transport.
3Quantity of substance
If surface reactions occur at high voltages, then capacity is increased, but impedance builds up and capacity loss accelerates greatly shortening battery life
Solution Approach 1:
The protective coating layer provides preliminary anti-action by preventing harmful surface reactions before they can occur. The coating is applied in advance to create a protective barrier that stops electrolyte decomposition and cathode material degradation at high voltages, thereby preventing impedance buildup and capacity loss that would otherwise occur during cycling.
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 composite material achieves high capacity and extended cycle life at high voltages by providing a stable, ion-conductive coating that reduces capacity loss and impedance, enhancing the performance and longevity of Li-ion batteries.
Implementation Method 1
a coating on the base active material comprised of a glassy phase containing the components Li2O, B2O3 and LiX in which LiX is at least one of Li2F2, Li2Cl2 and Li2SO4
Data Source
AI summary
Disclosed herein is a composite for the cathode of Li-ion battery comprising: a base active material represented by Li1+y(Nia—COb—Mnc—Yd)O2 wherein Y is at least one selected from Mg, Zn, Al, Ga, Cu, B, Zr, and Ti, y is 0 to 0.5, a is 0.1 to 0.6, b is 0.05 to 0.5, c is 0.25 to 0.8, d is 0 to 0.02, and the sum of a, b, c and d is 1; and a coating on the base active material comprised of a glassy phase containing the components Li2O, B2O3 and LiX in which LiX is at least one of Li2F2, Li2Cl2 and Li2SO4, relative to the total amount of the glassy phase, the mole percent of Li2O is 43% to 75%, the mole percent of B2O3 is 25% to 57%, the mole percent of LiX is from more than 0% to 20%, and the sum of the mole percents of Li2O, B2O3 and LiX is 100%.