Composite Positive Electrode for High-Temperature Li-Ion Cycling
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Solution Overview
Problem
Lithium-ion batteries suffer from irreversible capacity loss due to the consumption of active lithium in the formation and regeneration of the solid electrolyte interface (SEI) film, leading to a shorter cycle life, especially during high-temperature cycling.
Innovation Solution
The use of a positive electrode plate with a lithium manganese composite oxide and a lithium transition metal phosphate compound, characterized by specific XRD diffraction peaks, which provides structural stability and sufficient lithium sources for the SEI film, reducing structural damage and prolonging the high-temperature cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium transition metal phosphate compound with high initial coulombic efficiency is used, then initial coulombic efficiency is improved, but initial charge specific capacity is limited
Solution Approach 1:
The patent uses a composite positive electrode material comprising both lithium transition metal phosphate compound (olivine structure) and lithium manganese composite oxide (layered structure). The lithium manganese composite oxide supplements lithium ions to the system, compensating for the lithium consumption in SEI film formation and regeneration, thereby improving both initial charge specific capacity and maintaining high initial coulombic efficiency.
2Quantity of substance
If lithium manganese composite oxide with high initial charge specific capacity is used, then initial charge specific capacity is improved, but initial coulombic efficiency deteriorates
Solution Approach 1:
The composite material combines lithium manganese composite oxide (providing high initial charge specific capacity) with lithium transition metal phosphate compound (providing high initial coulombic efficiency). The two materials work synergistically, where the lithium transition metal phosphate compound's high efficiency characteristics help stabilize the overall electrochemical performance while the lithium manganese composite oxide provides sufficient lithium sources.
3Stability of the object's composition
If active lithium is intercalated back to high voltage range of lithium manganese composite oxide during initial discharge, then structural stability is improved, but active lithium is consumed in subsequent cycling
Solution Approach 1:
During initial discharge, active lithium is intentionally intercalated back to the high voltage range of lithium manganese composite oxide to stabilize its structure. In subsequent cycling, as active lithium is consumed, the stabilized structure releases lithium slowly, effectively recovering and maintaining lithium availability over extended cycling periods.
4Duration of action of stationary object
If sufficient lithium sources are provided for SEI film destruction and regeneration, then high-temperature cycle life is improved, but lithium consumption increases
Solution Approach 1:
The composite positive electrode material provides sufficient lithium sources through the lithium manganese composite oxide component, which has high lithium content. This enables the SEI film to undergo destruction and regeneration processes during initial cycling without causing excessive lithium consumption, thereby extending high-temperature cycle life while maintaining reasonable lithium utilization efficiency.
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 enhances the cycling performance and extends the high-temperature cycle life of lithium-ion batteries by stabilizing the structure and reducing lithium consumption, while maintaining air stability and compatibility with existing production processes.
Implementation Method 1
an XRD diffraction pattern of the positive electrode plate has a diffraction peak A1 of (003) crystal plane of the second material within a range of 18° to 20° and a diffraction peak C1 of (311) crystal plane of the first material within a range of 35° to 37°
Implementation Method 2
during the initial discharge of the electrochemical apparatus, part of active lithium is intercalated back to a high voltage range of the lithium manganese composite oxide with the layered crystal structure
Data Source
AI summary
An electrochemical apparatus, including a positive electrode plate, where the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first material and a second material; and in a fully charged state of the electrochemical apparatus, an XRD diffraction pattern of the positive electrode plate has a diffraction peak A1 of (003) crystal plane of the second material within a range of 18° to 20° and a diffraction peak C1 of (311) crystal plane of the first material within a range of 35° to 37°. The electrochemical apparatus can have prolonged high-temperature cycle life.