LiVOPO4 Cathode Material for High Voltage Lithium Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries using conventional phosphate-based positive electrode materials like LiVOPO4 face challenges in achieving sufficient discharge capacity and rate characteristics due to limitations in charging/discharging voltage and intercalation/deintercalation processes.
Innovation Solution
A positive electrode active material with a chemical formula LiVOPO4 is developed, featuring an orthorhombic crystal system and a specific range of tetravalent V content (27.7-28.2 mass %), which facilitates easy intercalation and deintercalation of Li, enhancing discharge capacity and rate characteristics through structural distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiVOPO4 is used as positive electrode material to achieve high charging/discharging voltage of 4 volts, then voltage is improved, but discharge capacity and rate characteristic are insufficient
Solution Approach 1:
The patent changes the oxidation state parameter of vanadium from the conventional +5 state to a mixed state containing +4 state vanadium (27.7-28.2 mass%). This parameter change in the chemical composition enables both high voltage (4V) operation and sufficient discharge capacity by creating a more favorable electronic structure for lithium ion intercalation while maintaining the high voltage characteristic of LiVOPO4
2Use of energy by moving object
If LiVOPO4 is used to achieve high charging/discharging voltage, then voltage is improved, but rate characteristic is insufficient
Solution Approach 1:
The patent modifies the oxidation state parameter of vanadium to include +4 state vanadium content (27.7-28.2 mass%), which changes the electronic structure and conductivity of the material. This parameter change enables faster lithium ion transport kinetics, improving rate characteristic while maintaining the high voltage of 4V charging/discharging
3Reliability
If conventional phosphate-based materials like LiFePO4 are used to achieve high thermal stability, then safety is improved, but energy density is low due to charging/discharging voltage as low as 3.5 volts
Solution Approach 1:
The patent changes the chemical composition parameter by replacing Fe with V in the phosphate structure, and specifically controlling the vanadium oxidation state to include +4 state (27.7-28.2 mass%). This compositional parameter change increases the charging/discharging voltage from 3.5V to 4V, thereby increasing energy density while the phosphate structure maintains thermal stability
Data Source
AI summary
A positive electrode active material contains a compound represented by a chemical formula LiVOPO4. A crystal system of the compound is an orthorhombic system, and the amount of tetravalent V of the compound is 27.7 mass % or more and 28.2 mass % or less.