Titanium-Coated Cathode Material for Low-Temperature Li-Ion Output
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using existing positive or negative electrode active materials face challenges in reducing reaction resistance at low temperatures and suppressing resistance increase after repeated charging and discharging cycles.
Innovation Solution
A positive electrode active material is developed, comprising a lithium transition metal composite oxide core with a coating of titanium-containing compounds, including brookite type TiO2 and LiTi composite oxide, where at least part of the Ti is incorporated in a solid solution on the surface, enhancing lithium ion insertion/extraction and reducing reaction resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing positive electrode active materials are used, then the battery can operate normally, but the reaction resistance increases under low temperature environment and after repeated charging/discharging cycles
Solution Approach 1:
The patent applies composite materials by forming a coating layer containing TiO2 and LiTiO3 on the surface of the lithium transition metal composite oxide core. This composite structure combines the high capacity of the core material with the low temperature performance and structural stability of the titanium-based coating, resolving the contradiction between normal operation and low temperature resistance.
Solution Approach 2:
The patent changes the chemical and physical parameters of the electrode surface by incorporating Ti into the surface solid solution and forming specific titanium-containing compounds. This modifies the surface electrochemical properties, reducing reaction resistance at low temperatures while maintaining the bulk material's high capacity characteristics.
2Duration of action of stationary object
If existing positive electrode active materials are used, then the battery can be manufactured with standard materials, but the resistance increases after repeated charging and discharging cycles
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a protective coating layer on the electrode surface before cycling begins. This coating layer acts as a buffer that prevents direct degradation of the core material during initial cycles, cushioning against subsequent resistance increase and extending cycle life.
Solution Approach 2:
The composite structure of core and coating layers provides differential functionality where the coating layer specifically addresses cycle stability while the core maintains capacity, resolving the contradiction between manufacturability and long-term durability.
3Power
If a coating layer is formed on the core part, then the low temperature output characteristic improves, but the device complexity increases
Solution Approach 1:
The patent uses parameter changes by controlling the composition ratios (Li:Ti = 1:0.5 to 1:2) and formation conditions of the coating layer. This allows optimization of low temperature power output while keeping the coating structure relatively simple and compatible with existing manufacturing processes.
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
This configuration improves the low-temperature output characteristic and prevents the increase in resistance after cycling, resulting in a nonaqueous electrolyte secondary battery with enhanced performance.
Implementation Method 1
the brookite type TiO 2 having the effect of speeding up the insertion/extraction of Li ions
Implementation Method 2
at least part of Ti of the titanium-containing compound is incorporated in a solid solution in a surface of the core part
Data Source
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AI summary
The present disclosure provides a positive electrode active material which can impart an excellent low temperature output characteristic to a nonaqueous electrolyte secondary battery, and can suppress an increase in resistance after cycle charging and discharging. The positive electrode active material herein disclosed includes a core part including a lithium transition metal composite oxide, and a coating part including a titanium-containing compound on at least a partial surface of the core part. The coating part includes brookite type TiO2 and a lithium titanium (LiTi) composite oxide including lithium (Li) and titanium (Ti) as titanium-containing compounds, and at least part of titanium (Ti) of the titanium-containing compound is incorporated in a solid solution in the surface of the core part.