Monoclinic Niobium-Titanium Composite Oxide for Battery Anodes
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Solution Overview
Problem
Lithium-ion secondary batteries using carbon-based negative electrodes face issues with rapid charge-and-discharge cycles due to metal lithium dendrite formation, leading to potential internal short circuits and reduced energy density compared to titanium oxide-based batteries, which have higher potential and lower theoretical capacity.
Innovation Solution
A monoclinic niobium-titanium composite oxide (TiNb2O7) is developed with a crystal structure that enhances lithium ion diffusibility, allowing for higher reversible capacity and energy density by supporting a carbon body on the particles to improve electron conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon-based negative electrode is used, then energy density is improved, but metal lithium dendrites precipitate during rapid charge-and-discharge
Solution Approach 1:
A coating layer comprising at least one of an oxide and a nitride of a metal element is applied to the carbonaceous material surface. This coating layer acts as an intermediary between the carbon-based negative electrode and lithium ions, preventing direct contact that leads to dendrite formation while allowing lithium ion insertion and extraction. The coating layer specifically suppresses metal lithium dendrite precipitation during rapid charge-and-discharge cycles.
2Reliability
If titanium oxide is used as negative electrode active material, then dendrite precipitation is suppressed, but energy density decreases due to higher potential and lower theoretical capacity
Solution Approach 1:
The invention uses a composite material consisting of carbonaceous material as the base and a coating layer of metal oxide or nitride on the surface. This composite structure combines the high energy density advantage of carbon-based materials with the dendrite suppression capability of titanium oxide-like coatings, achieving both high capacity and safety.
3Productivity
If rapid charge-and-discharge is performed repeatedly, then charge-and-discharge performance is improved, but heat generation and ignition may occur due to dendrite formation
Solution Approach 1:
The coating layer serves as a protective intermediary that enables rapid charge-and-discharge operations by preventing dendrite formation. This intermediary layer allows high-rate charge-and-discharge performance while suppressing the harmful effects of heat generation and potential ignition that would otherwise occur during repeated rapid 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 monoclinic niobium-titanium composite oxide achieves a high theoretical capacity of 387 mAh/g and improved charge-and-discharge cycle performance, addressing the limitations of carbon-based and titanium oxide-based batteries by enhancing lithium ion insertion and extraction efficiency.
Implementation Method 1
when lithium ions are electrochemically inserted and extracted, the oxidation-reduction reaction occurs between tetravalent titanium ions and trivalent titanium ions
Implementation Method 2
the potential relative to lithium metal of the titanium oxide is caused by an oxidation-reduction reaction occurring between trivalent titanium ions and tetravalent titanium ions when lithium ions are electrochemically inserted and extracted
Implementation Method 3
supporting a carbon body on the particles to improve electron conductivity
Data Source
AI summary
According to one embodiment, an active material is provided. The active material includes particles. The particles have a crystal structure belonging to a monoclinic niobium-titanium composite oxide. A ratio of a crystallite size Dc corresponding to a (020) plane with respect to an average primary particle size Dp of the particles is not less than 35%.