Carbon-Coated Polyanion Cathode Electrolyte for Low-Temperature Power
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Solution Overview
Problem
Energy storage devices, particularly those using polyanion compounds, face challenges in achieving high initial power characteristics in low temperature environments due to factors beyond electron conductivity, necessitating further improvements.
Innovation Solution
The energy storage device incorporates a positive active material with a polyanion compound partially coated with carbon, maintaining a specific BET surface area ratio between carbon coverage and the active material layer, and uses a nonaqueous electrolyte devoid of sulfur elements to enhance ion diffusion and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the surface of polyanion compound is coated with carbon to improve electron conductivity, then electron conductivity is improved, but initial power characteristics in low temperature environment are still insufficient due to other factors
Solution Approach 1:
The patent changes the surface area ratio parameter by controlling carbon coating amount (10-35% BET surface area ratio) and electrolyte composition (sulfur compound 0.1-5% by mass), transforming the low-temperature power characteristic problem into a parameter optimization problem that achieves high initial power without complex multi-layer coatings
Solution Approach 2:
The patent creates a composite system combining carbon-coated polyanion compound positive electrode with sulfur-containing electrolyte additives, where the interaction between the carbon coating and sulfur compounds in electrolyte produces synergistic effects that improve low-temperature power characteristics beyond what either component achieves alone
2Power
If carbon coating amount is increased to improve electron conductivity, then electron conductivity improves, but ion diffusion and contact resistance become problematic
Solution Approach 1:
The patent optimizes the carbon coating surface area ratio parameter to 10-35% of the original polyanion compound surface area, finding the optimal balance point where sufficient electron conductivity is achieved while maintaining adequate ion diffusion pathways and contact characteristics, avoiding the diminishing returns of excessive coating
Solution Approach 2:
The sulfur-containing electrolyte compounds act as intermediaries that mediate between the carbon coating and the polyanion compound surface, forming interface layers that facilitate both electron transfer through the carbon coating and ion diffusion to the active material, resolving the conflict between electrical conductivity and ionic accessibility
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 results in significantly higher initial power performance in low temperature conditions, with improved power retention after high-temperature storage.
Implementation Method 1
the nonaqueous electrolyte contains an electrolyte salt containing no sulfur element and a sulfur-based compound
Implementation Method 2
a technique of coating a surface with carbon for improving the electron conductivity has been proposed
Implementation Method 3
configured to allow charge support ions to be transferred between the two electrodes for charge-discharge
Data Source
AI summary
An energy storage device according to one aspect of the present invention includes: a positive electrode including a positive active material layer containing a positive active material; and a nonaqueous electrolyte, in which the positive active material contains a polyanion compound containing a transition metal element and including a surface at least partially covered with carbon, a ratio of a second BET specific surface area, which is a BET specific surface area of the carbon, to a first BET specific surface area, which is a BET specific surface area of the positive active material layer is more than 10% and less than 35%, and the nonaqueous electrolyte contains an electrolyte salt containing no sulfur element and a sulfur-based compound.