Positive Electrode Polymer Electrolyte for Low-Porosity Solid Batteries
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Solution Overview
Problem
Conventional all-solid state batteries face issues of poor interfacial contact and high porosity at the positive electrode, leading to reduced cycling performance and energy density.
Innovation Solution
A positive electrode piece comprising a positive-electrode current collector coated with a positive-electrode active material, conductive agent, and a polymer electrolyte containing specific polymers and lithium salt, which forms a lithium-conducting network with low porosity and improved interfacial contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional all-solid electrolyte is used in positive electrode, then solid state battery structure is formed, but interfacial contact impedance becomes excessively high
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte by transitioning from solid-state to gel-state, and specifically develops a polymer electrolyte with optimized lithium salt content (5-20 mass%) and specific molecular structure (Formula 1), which reduces interfacial impedance while maintaining structural integrity
Solution Approach 2:
The patent creates a composite gel electrolyte system combining polymer matrix with lithium salts (LiPF6, LiBF4, LiTFSI) and organic carbonates, forming a composite material that exhibits both mechanical stability and ionic conductivity, resolving the contradiction between structural support and low interfacial impedance
2Reliability
If positive electrode active material, conductive agent, binder and solid electrolyte are uniformly mixed and coated, then electrode structure is formed, but porosity becomes high affecting cycling performance
Solution Approach 1:
The patent optimizes the composition parameters of the electrode slurry, specifically controlling the content of polymer electrolyte (3-28 mass%), lithium salt (5-20 mass%), conductive agent (2-15 mass%), and binder (0-10 mass%), which results in reduced porosity and improved cycling performance
Solution Approach 2:
The patent applies different functional materials in specific regions and proportions within the electrode layer, with the polymer electrolyte providing local ionic conduction pathways and the conductive agent providing electronic conduction networks, creating a heterogeneous structure with optimized local properties that reduces overall porosity
3Use of energy by moving object
If high energy density battery system is designed, then energy density increases, but safety problems such as leakage, fire, and explosion occur
Solution Approach 1:
The patent changes the state of the electrolyte from liquid to gel, which fundamentally alters the safety profile by eliminating leakage risks while maintaining high ionic conductivity, and the gel structure provides thermal stability that prevents fire and explosion even at high energy densities
Solution Approach 2:
The gel electrolyte acts as an intermediary between the high-energy active materials and the external environment, providing a stable medium that enables high energy density while simultaneously preventing harmful effects through its gel structure that suppresses thermal runaway and chemical reactions
4Ease of manufacture
If polymer electrolyte is used in solid state battery, then processability improves, but room-temperature conductivity becomes low
Solution Approach 1:
The patent creates a composite gel electrolyte combining polymer matrix with lithium salts and organic carbonates, where the lithium salts and carbonate additives provide ionic conduction pathways that compensate for the inherently low conductivity of pure polymers at room temperature, while maintaining the processability advantages of polymer-based systems
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 enhances lithium ion transmission, reduces internal resistance, and improves energy density and cycling performance of the battery.
Implementation Method 1
the polymer electrolyte includes a polymer and a lithium salt... enhances lithium ion and electron transmission
Implementation Method 2
the positive-electrode active material layer includes a positive-electrode active material, a conductive agent and a polymer electrolyte... enhances lithium ion and electron transmission
Data Source
AI summary
A positive electrode piece and a secondary battery including the same. By selecting a type of polymer electrolyte prepared from a polymer different from that in the prior art as the solid electrolyte in the positive electrode piece, the solid electrolyte have both a bonding function and a lithium conduction function, may replace a binder and a solid electrolytes in an existing electrode piece, can effectively improve and enhance the lithium ion transmission performance, and reduce the internal resistance of the battery. Meanwhile, the positive electrode piece including the solid electrolyte has a low porosity, below about 5%, which greatly reduces voids and holes in the positive electrode piece, increases the content of the positive-electrode active material in unit volume, improves the transmission of lithium ions and electrons, and effectively improves the energy density, cycling performance and rate performance of the battery.