Lithium Phosphate Cathode Material with Carbon Coating for High Voltage Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with oxidation and decomposition of electrolytic solutions and gas generation at high voltages, leading to capacity degradation and safety concerns, particularly when using lithium phosphate compounds as cathode materials.
Innovation Solution
A cathode material comprising a combination of carbonaceous film-coated central particles and olivine structure primary particles, with a specific mass ratio and particle size distribution, is used to suppress oxidation and decomposition of electrolytic solutions, enhancing electron conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbonaceous film is coated on the surface of cathode active material particles to improve electron conductivity, then electron conductivity is enhanced, but oxidation and decomposition of electrolytic solution and gas generation occur at high voltages
Solution Approach 1:
The invention divides the cathode material into two distinct components: cathode material A with a carbonaceous film coating and cathode material B without such coating. This segmentation allows each component to perform its specialized function - material A provides electron conductivity while material B suppresses electrolyte decomposition - and their combined effect resolves the contradiction between conductivity enhancement and harmful side reactions
Solution Approach 2:
The invention applies different surface treatments to different portions of the cathode material. Specifically, only a portion of the cathode active material particles are coated with carbonaceous film, while the remaining particles remain uncoated. This local differentiation enables the coated particles to provide conductivity while the uncoated particles maintain stability with the electrolyte, thereby resolving the contradiction
2Use of energy by moving object
If high voltage is applied to achieve higher energy density, then battery capacity increases, but electrolytic solution decomposes and gas is generated
Solution Approach 1:
The invention introduces cathode material B (lithium phosphate compound without carbonaceous film coating) as an intermediary component that mediates the interaction between the cathode and electrolyte at high voltages. This material suppresses electrolyte oxidation and decomposition reactions, allowing the battery to operate at high voltages for increased energy density without suffering from electrolyte decomposition and gas generation
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 solution effectively reduces gas generation and maintains high capacity retention and safety, achieving excellent long-term cycle characteristics and stability in lithium-ion secondary batteries.
Implementation Method 1
a conductive carbon film is formed on the surface of the cathode active material, and it is possible to interpose carbon in the conductive carbon film as an electron-conductive substance
Implementation Method 2
cathode and an anode which have properties capable of reversibly intercalating and deintercalating lithium ions
Implementation Method 3
since oxygen is strongly bonded to phosphorus by means of covalent bonding, it is difficult for oxygen to be released from crystals, and stability is excellent
Data Source
AI summary
A cathode material for a lithium-ion secondary battery includes a cathode material A which includes central particles of a cathode active material represented by LixAyMzPO4 and a carbonaceous film with which surfaces of the central particles are coated and a cathode material B which is represented by LixAyMzPO4 and is made of primary particles of a cathode active material having an olivine structure.